М.Ю.Швецов,ЧжэнАньтай,Л.В.Козловская,Н.А.Мухин

НИОнефрологииНИЦПервогоМГМУимениИ.М.Сеченова

КафедравнутреннихболезнейФакультетафундаментальной

медициныМГУимениМ.В.Ломоносова

Уромодулинкакновыибиомаркервоценкепрогрессированияхроническои

болезнипочек

Первичноеповреждение Олигонефрония Диффузный

нефросклероз

Этиотропнаяипатогенетическаятерапия

Нефропротективнаятерапия

Диализилитрансплантация

почки

По в р еждени е п о ч е к

Фун

кция

по

чек

ТПН

Стадия=Функция–Повреждение(активность)

Альбуминурия А0-1 А2 А3

Оптимальная или

незначительно повышенная

Высокая Очень высокая

<30 мг/г <3 мг/ммоль

30-300 мг/г 3-30

мг/ммоль

>300 мг/г >30

мг/ммоль

СКФ

, мл/мин

/1,7

3м2

С1 Высокая или оптимальная ≥90 Низкий Умеренный Высокий

С2 Незначительно снижена 60-89 Низкий Умеренный Высокий

С3а Умеренно снижена 45-59 Умеренный Высокий

Очень высокий

С3б Существенно снижена 30-44 Высокий

Очень высокий

Очень высокий

С4 Резко снижена 15-29 Очень высокий

Очень высокий

Очень высокий

С5 ТПН <15 Очень высокий

Очень высокий

Очень высокий

ImprovingGlobalOutcomes(KDIGO)CKDWorkGroup.KDIGO2012ClinicalPracVceGuidelinefortheEvaluaVonandManagementofChronicKidneyDisease.Kidneyinter.,Suppl.2013;3:1–150.

Альбуминурия А0-1 А2 А3

Оптимальная или

незначительно повышенная

Высокая Очень высокая

<30 мг/г <3 мг/ммоль

30-300 мг/г 3-30

мг/ммоль

>300 мг/г >30

мг/ммоль

СКФ

, мл/мин

/1,7

3м2

С1 Высокая или оптимальная ≥90 Низкий Умеренный Высокий

С2 Незначительно снижена 60-89 Низкий Умеренный Высокий

С3а Умеренно снижена 45-59 Умеренный Высокий

Очень высокий

С3б Существенно снижена 30-44 Высокий

Очень высокий

Очень высокий

С4 Резко снижена 15-29 Очень высокий

Очень высокий

Очень высокий

С5 ТПН <15 Очень высокий

Очень высокий

Очень высокий

Дисфун

кция

Повреждение

ImprovingGlobalOutcomes(KDIGO)CKDWorkGroup.KDIGO2012ClinicalPracVceGuidelinefortheEvaluaVonandManagementofChronicKidneyDisease.Kidneyinter.,Suppl.2013;3:1–150.

Оценкафункциипочек(СКФ)

•  ЦистатинC•  b-Traceprotein•  β2-микроглобулин

Повреждениетубулоинтерстиция

•  NGAL•  KIM-1•  NAG•  L-FABP…

Повреждениеклубочков

•  Подоцин•  Нефрин•  Подокаликсин…

FassedRG,VenuthurupalliSK,GobeGCetal.Biomarkersinchronickidneydisease:areview.KidneyInt2011;80:806–21.

• С-РБ,пентаксин-3,ФНО-α,ИЛ-18,ТИМП-1,CD14…

Воспаление

• Фибриноген,ТФР-бета,КоллагенIV…Фиброгенез

¨  Представительсемействалипокалинов,25kDa,ковалентносвязываетсясжелатиназойнейтрофилов,егосинтеззависитотактивацииNFκB,вбольшомколичествесинтезируетсявповрежденныхэпителиальныхклетках(вт.ч.впочечных).

¨  Отвечаетзаподдержаниеэпителиальногофенотипаклеток,участвуетвпроцессахпролиферацииидифференциации

¨  Полностьюфильтруется,значительнаяегочастьлокальновырабатываетсятубулоцитами

¨  Являетсямаркеромострогоповрежденияпочек

The aim of our study was to estimate urinary excretion of CA 9 as a marker of hypoxia, VEGF-A and NGAL as a marker of tubular injury in patients with CGN and their possible association with clinical activity of CGN and degree of GFR decrease.

NGAL is a member of the lipocalin protein family. It is a 23 kDa low molecular weight protein secreted by various types of human cells. Its physiologic role seems complex, implying cell growth and differentiation, a bacteriostatic immune effect and a role in cellular iron- transport pathways. Because of of its small size NGAL is freely filtered by the renal glomeruli without being reabsorbed. NGAL is also strongly expressed in renal tubules in animal models of renal ischemic injury. Later clinical studies demonstrated role of urinary and plasma NGAL as a new early and sensitive biomarker of acute kidney injury. Role of NGAL in chronic kidney disease is not clear yet. In our previous study we tested urinary NGAL as a marker of tubular injury in CGN and we had found its correlation with hypertension and proteinuria.

0

10

20

30

40

50

60

%бол

ьныхсуров

немNGAL

моч

и>15

нг/м

лP=0,011

М.Ю.Швецов,И.Н.Бобкова,ЧжэнАньтай,2010

¨  ВажныйестественныйструктурныйкомпонентБМК

¨  Патологическийкомпонентвнеклеточногоматриксапринефросклерозе

¨  Биомаркерповрежденияпочечныхклубочковприсахарномдиабете

S. Kado et al. 1 Diabetes Research and Clinical Practice 31 (1996) 103-108 105

NS

I P< 0.001 I

*7 1F-l .

z B 20. 1

t 3 : 15. !

8 i .

5 g 10.

,x x

i .

2 'C 5. .

3 i- P

Fig. 1. Urinary levels of type IV collagen in normal healthy controls, subjects with non-insulin-dependent diabetes melli- tus, and those with chronic glomerulonephritis. NIDDM, sub- jects with non-insulin-dependent diabetes mellitus; CGN, subjects with chronic glomerulonephritis; NS, not significant. The median values for each group are shown by horizontal bars.

were: 34.4 f 63.4, 6.5 + 7.7, and 280.8 + 392.7 mg/gCr, respectively. NIDDM subjects were divided into five subgroups according to their urinary level of albumin. As shown in

Fig. 2. Urinary levels of type IV collagen in normal healthy controls, and NIDDM subjects with various levels of albumin- uria. UALB, urinary albumin; NIDDM, patients with non-in- sulin-dependent diabetes mellitus.

Table 1 Correlation coefficients for the relations between urinary type IV collagen and other parameters in NIDDM subjects

Parameter Correlation coefficient P-vlaue

Age 0.23 Duration of diabetes 0.04 Plasma glucose 0.09 Fructosamine 0.14 H&c 0.21 Serum creatinine 0.05 Serum urea nitrogen 0.05 Serum total cholesterol 0.23 SBP 0.14 DBP 0.02 Urinary albumin 0.29 Urinary 0.54 G( 1 -microglobulin Urinary NAG 0.27 Serum type IV 0.22 collagen

0.01 NS NS NS 0.02 NS NS 0.01 NS NS 0.001 0.0001

0.003 0.02

SBP, systolic blood pressure; DBP, diastolic blood pressure; NAG, N-acetyl-p-D-glucosaminidase; NS, not significant.

Fig. 2, urinary level of type IV collagen was significantly higher in NIDDM subjects with urinary level of albumin < 10 mg/gCr (nor- moalbuminuria) than in normal controls. The urinary level of type IV coll- agen increased with increased urinary level of albumin in NIDDM subjects. There was a significant correlation between the urinary level of type IV collagen and albumin in NIDDM subjects (Table 1). There was no significant correlation between the urinary level of type IV collagen and the urinary level of albumin in normal controls and CGN subjects (data not shown).

The urinary level of type IV collagen was also significantly correlated with age, HbA,,, serum levels of total cholesterol and type IV collagen, urinary levels of a,-microglobulin, and NAG (Table 1).

The ratio of urinary type IV collagen to albumin were significantly lower in CGN sub- jects (2.7 + 2.7 x 10e6) than in NIDDM subjects (43.4 + 41.1 x 10W6) (Fig. 3). There was no significant difference in the ratios between NIDDM subjects and normal healthy controls (66.1 * 55.9 x 10W6).

S. Kado et al. 1 Diabetes Research and Clinical Practice 31 (1996) 103-108 105

NS

I P< 0.001 I

*7 1F-l .

z B 20. 1

t 3 : 15. !

8 i .

5 g 10.

,x x

i .

2 'C 5. .

3 i- P

Fig. 1. Urinary levels of type IV collagen in normal healthy controls, subjects with non-insulin-dependent diabetes melli- tus, and those with chronic glomerulonephritis. NIDDM, sub- jects with non-insulin-dependent diabetes mellitus; CGN, subjects with chronic glomerulonephritis; NS, not significant. The median values for each group are shown by horizontal bars.

were: 34.4 f 63.4, 6.5 + 7.7, and 280.8 + 392.7 mg/gCr, respectively. NIDDM subjects were divided into five subgroups according to their urinary level of albumin. As shown in

Fig. 2. Urinary levels of type IV collagen in normal healthy controls, and NIDDM subjects with various levels of albumin- uria. UALB, urinary albumin; NIDDM, patients with non-in- sulin-dependent diabetes mellitus.

Table 1 Correlation coefficients for the relations between urinary type IV collagen and other parameters in NIDDM subjects

Parameter Correlation coefficient P-vlaue

Age 0.23 Duration of diabetes 0.04 Plasma glucose 0.09 Fructosamine 0.14 H&c 0.21 Serum creatinine 0.05 Serum urea nitrogen 0.05 Serum total cholesterol 0.23 SBP 0.14 DBP 0.02 Urinary albumin 0.29 Urinary 0.54 G( 1 -microglobulin Urinary NAG 0.27 Serum type IV 0.22 collagen

0.01 NS NS NS 0.02 NS NS 0.01 NS NS 0.001 0.0001

0.003 0.02

SBP, systolic blood pressure; DBP, diastolic blood pressure; NAG, N-acetyl-p-D-glucosaminidase; NS, not significant.

Fig. 2, urinary level of type IV collagen was significantly higher in NIDDM subjects with urinary level of albumin < 10 mg/gCr (nor- moalbuminuria) than in normal controls. The urinary level of type IV coll- agen increased with increased urinary level of albumin in NIDDM subjects. There was a significant correlation between the urinary level of type IV collagen and albumin in NIDDM subjects (Table 1). There was no significant correlation between the urinary level of type IV collagen and the urinary level of albumin in normal controls and CGN subjects (data not shown).

The urinary level of type IV collagen was also significantly correlated with age, HbA,,, serum levels of total cholesterol and type IV collagen, urinary levels of a,-microglobulin, and NAG (Table 1).

The ratio of urinary type IV collagen to albumin were significantly lower in CGN sub- jects (2.7 + 2.7 x 10e6) than in NIDDM subjects (43.4 + 41.1 x 10W6) (Fig. 3). There was no significant difference in the ratios between NIDDM subjects and normal healthy controls (66.1 * 55.9 x 10W6).

KadoS,AokiA,WadaSetal.UrinarytypeIVcollagenasamarkerforearlydiabeVcnephropathy.DiabetesResClinPract1996;31:103–8.

creatinine concentrations were !1.7mg/dl (!150 !mol/l) in all patients, andthe mean " SEM value for the RSC was113 " 3. The mean urine albumin excre-tion was 216 !g/mg creatinine, a valuefalling clearly within the microalbumin-uric range. Four patients had values #20!g/mg, and 10 patients had values in theovert proteinuric range ($350 !g/mg).The mean A:C ratio was 181.0 " 46.5 inpatients with type 1 diabetes and 228.9 "67.0 in patients with type 2 diabetes, andthe median A:C ratios were 79.2 and 93.6,respectively.

Urine excretion of collagen IV rangedfrom 6.8 to 52.8 ng/mg creatinine (mean20.9 ng/mg). The mean value for urinecollagen IV in 12 volunteers with albuminexcretion #10 !g/mg creatinine was 6.6ng/mg creatinine (range 4.3–12.8; intra-individual variability #9%). Collagen IVexcretion showed no significant correla-tion with albumin excretion (r % 0.12with analysis of 64 of 65 patients, exclud-ing an outlier with A:C ratio of 3,080) buthad a significant inverse correlation (r %&0.62) with RSC values (Fig. 1). In the 65patients studied, urine collagen IV did notcorrelate with HbA1c levels (r % &0.03).

Considering the data of Warram et al.(25), which suggest that a decline in RSCbegins to be detectable when A:C ratiosexceed 100 !g/mg, the patients in this

study were divided into two groups ac-cording to albumin excretion. Themean " SEM RSC in subjects with an A:Cratio !100 !g/mg was 115 " 4 and109 " 5 in patients with an A:C ratio$100 (P # 0.05). Urine collagen IVshowed a significant inverse correlationwith RSC values in patients with eitherlow (r % &0.73) or high (r % &0.53)albumin excretion (Fig. 2). In contrast,there was no significant correlation be-tween A:C ratios and RSC values, whetheranalyzed as all patients (Fig. 3) or sepa-rated into patients with low versus highalbumin excretion.

Using the approach of Warram et al.(28), who segmented microalbuminuricpatients into four groups according to

HbA1c levels in assessing risk for progres-sive disease, we evaluated albumin excre-tion and RSC values in our studypopulation similarly divided into groupsaccording to HbA1c. The mean A:C ratiowas lower in patients with HbA1c between5.1 and 5.9% (128 " 27; n % 21) andbetween 9.0 and 9.9% (98 " 21; n % 10)than in patients in the other two catego-ries of HbA1c values (330 " 175, n % 17,HbA1c 8.0–8.9%; and 278 " 65, n % 17;HbA1c 10–12.7%). However, the meanRSC value in patients with HbA1c $10%was significantly higher at 129 " 10 (P #0.05) than in patients with HbA1c levels inthe other three categories (108 " 4,104 " 3, and 109 " 8), suggesting thathyperfiltration in conjunction with poor

Figure 1—Correlation analysis in study population of urinary type IV collagen (ng/mg creati-nine) with A:C ratios (A: r % 0.12; NS when outlier at A:C ratio of 3,080 is excluded; r % 0.37, P %0.10 when outlier is included) and with RSC values (B: r % &0.62; P # 0.001).

Figure 2—Correlation analysis of urinary type IV collagen (ng/mg creatinine) with RSC valuesin patients with A:C ratios !100 "g/mg (A: r % &0.73) or $100 "g/mg (B: r % &0.53). Themean " SEM A:C ratios in these two groups were 54.2 " 45 and 392.7 " 95.7, respectively, andthe respective median values were 55.7 and 260.5.

Table 1—Clinical characteristics of the studypopulation

n 65Type 1 diabetes 18Type 2 diabetes 47

Age (years) 55.3 " 1.4(range 27–74)

Sex (male/female) 50/15Duration of diabetes

(years)16.6 " 4.3(range 5–35)

BMI 31.1 " 0.9(range 19.5–48.4)

Type 1 diabetes 27.6 " 1.4Type 2 diabetes 33.1 " 1.1

Fasting glucose (mmol/l) 11.8 " 0.8(range 5.4–21.9)

HbA1c (%) 8.90 " 0.24(range 5.4–12.7)

Urine A:C ratio (!g/mg) 215.6 " 50.0*(range 5.7–3,080)†

Serum creatinine(!mol/l)

78 " 2.4(range 44–150)

Data are means " SEM unless otherwise indicated.*Median 102.5; †log values of 0.7–3.49; 0.76–2.92,excluding the outlier.

Urinary collagen IV in diabetes

916 DIABETES CARE, VOLUME 24, NUMBER 5, MAY 2001

1/креатининсыв.Альбуминурия

CohenMP,LautenslagerGT,ShearmanCW.IncreasedcollagenIVexcreVonindiabetes.AmarkerofcompromisedfiltraVonfuncVon.DiabetesCare2001;24:914–8.

TominoY,SuzukiS,AzushimaCetal.AsianmulVcentertrialsonurinarytypeIVcollageninpaVentswithdiabeVcnephropathy.JClinLabAnal2001;15:188–92.

0

20

40

60

80

100

120

АУ<30 АУ30-299 АУ>300,Сыв.Кр.<1.1

АУ>300,Сыв.Кр.>1.2

ХПН

%бол

ьных

COL4<3.5μg/g·Cr COL4>3.5μg/g·Cr

N.Bulanov,A.Serova,P.lNovikov,S.Moiseev.ERA-EDTA53rdCongress,2016,MP143Conclusion

Results

Methods

Objectives

MP143 Clinical value of urinary biomarkers KIM-1, MCP-1 and type IV collagen in the assessment of kidney

involvement in patients with ANCA-associated vasculitides Nikolay Bulanov, Anna Serova, Pavel Novikov, Sergey Moiseev

I.M. Sechenov First Moscow State Medical University, Moscow, Russian Federation

Our aim was to evaluate diagnostic significance of urinary levels of kidney injury molecule-1 (KIM-1), monocyte chemoattractant protein-1 (MCP-1) and type IV collagen (collagen IV) in patients with ANCA-associated vasculitides.

Kidney involvement is common in ANCA-associated vasculitis (AAV), but early detection of glomerulonephritis often presents a challenge in clinical practice.

Contacts: nmbulanov@gmail.com; +79191002279

Twenty eight patients had active renal AAV (35.9%, group 1), 26 had active nonrenal AAV (33.3%, group 2) and 24 patients were in long-term remission (30.8%, group 3). Median urinary levels of all biomarkers in patients with active renal AAV were significantly higher than in active nonrenal AAV and remission (Table 1), and did not depend on age and nosological form of AAV. Urinary excretion of all molecules was comparable in patients with active nonrenal AAV and remission of AAV.

There was significant positive correlation between all studied biomarkers: rKIM-1-MCP-1=0.66; rKIM-1-CollagenIV=0.41; rMCP-1-CollagenIV=0.49 (p<0.05). Significant positive correlations were found between all urinary biomarkers and hematuria, proteinuria, serum creatinine and renal component of BVAS (Fig. 1).

Table 1. Urinary levels of KIM-1, MCP-1 and type IV collagen. All values are medians and IQR.

ROC-analysis showed that urinary MCP-1 ≥159 pg/mL identified renal involvement with sensitivity 89%, specificity 67% (AUC 0.80). KIM-1 ≥2283.3 pg/mL had similar sensitivity (92%) and lower specificity (58%), AUC 0.76. Collagen IV ≥3.09 mcg/L showed the worst sensitivity (57%), but the highest specificity (86%), AUC 0.76 (Fig. 2).

Urinary excretion of all biomarkers was significantly increased in active renal vasculitis. We suggest that MCP-1 and KIM-1 levels reflect local renal inflammation and elevated collagen IV level represents both glomerular basement membrane damage and activation of renal fibrogenesis. Therefore, these biomarkers allow to evaluate the prevalence of inflammation or fibrogenesis at the early stages of kidney involvement in AAV. Limited specificity or sensitivity of individual biomarkes may justify their combined use to identify active renal AAV.

We declare no conflicts of interest.

Figure 1. Correlation between urinary levels of MCP-1, KIM-1 and type IV collagen and traditional markers of kidney involvement.

Introduction

We enrolled in our study 78 patients with AAV (48 with granulomatosis with polyangiitis, 19 with microscopic polyangiitis, 11 with eosinophilic granulomatosis with polyangiitis), 32 male and 46 female, aged 55 (45; 61) yrs. AAV were diagnosed according to the Chapel-Hill (2012) and the ACR criteria.

To assess disease activity and kidney involvement we measured Birmingham Vasculitis Activity Score (3.0), proteinuria, hematuria, serum creatinine (SCr) and estimated GFR (CKD-EPI formula). Urinary excretion of KIM-1, MCP-1 and collagen IV was measured by ELISA.

Statistical analysis was performed using Statistica 7 (StatSoft).

Active renal AAV (1), n=28

Active non-renal AAV (2), n=26

Remission (3), n=24

p values

uKIM-1, pg/mL

3724.4 (3023.6; 5428.7)

1478.7 (1150.0; 2525.7)

1890.0 (1218.1; 3280.3)

р1-2=0.00001 р1-3=0.0009 р2-3=0.23

uMCP-1, pg/mL

407.4 (205.5; 795.2)

120.9 (49.9; 197.2)

124.3 (79.7; 335.3)

р1-2=0.00002 р1-3=0.00188 р2-3=0.49

uCollagenIV, mcg/L

3.88 (2.03; 7.06)

1.6 (1.23; 2.67)

1.68 (1.0; 2.59)

р1-2=0.00218 р1-3=0.0006 р2-3=0.76

Коллаген-IV, моча

0 20 40 60 80 100

0

20

40

60

80

100

100-Specificity

Sen

sitiv

ity

All p values <0.05

Figure 2. ROC-curve analysis. Collagen IV (0.76)

MCP-1 (AUC 0.80) KIM-1 (AUC 0.76)

COL4isthemostspecificbiomarkerforkidneyinvolmentinANCA-associatedvasculi�des

Оценкафункциипочек(СКФ)

•  ЦистатинC•  b-Traceprotein•  β2-микроглобулин

Повреждениетубулоинтерстиция

•  NGAL•  KIM-1•  NAG•  L-FABP

Повреждениеклубочков

•  Подоцин•  Нефрин•  Подокаликсин

FassedRG,VenuthurupalliSK,GobeGCetal.Biomarkersinchronickidneydisease:areview.KidneyInt2011;80:806–21.

• С-РБ,MCP-1,пентаксин-3,ФНО-α,ИЛ-18,ТИМП-1,CD14…

Воспаление

• Фибриноген,ТФР-бета,КоллагенIV…Фиброгенез

A.Bohleetal.PatholResPract.1990Feb;186(1):135-44.

30

mesangioproliferative glomerulonephritis, but also in the interstitial inflammation that complicates renal amyloidosis. The tubulo-interstitial inflammation of diabetic glomerulosclerosis is also characterized by T lymphocytes, macrophages, fibroblasts and fibrocytes.

As a result of investigations we have carried out over the past 12 years l • 2 • 3 , it has been possible to demonstrate that when the inflammatory processes occurring with the various glomerulopathies are accompanied by interstitial fibrosis, the excretory function of the kidney is impaired. These results also corroborate those of earlier work by Spuhler and Zollinger4 , Risdon et and Schainuck et a1. 6 • Moderately severe mesangioproliferative glomerulonephritis can be taken as an example. Here we found a significant correlation between the degree of widening of the renal cortical interstitium resulting from fibrotic processes and the serum creatinine level (Fig 1). As a result, the serum creatinine concentration in cases having the same degree of severity of mesangioproliferative glomerulonephritis may be normal in some and irreversibly elevated in others (Figs. 2a and b).

___

, n· II I __ ,·o.ne

Fig. 1. Correlation interstitium and mesangioproliferative interstitium

between the relative volume of the renal cortical the serum creatinine concentration in

glomerulonephritis. N normal width of the

It remains within the normal range as long as the inflammatory process is confined to the glomerulus. However, when the renal cortical interstitium is widened by an accompanying inflammatory process leading to fibrosis and the tubules are atrophic, the serum creatinine concentration becomes irreversibly elevated. What is true of mesangioproliferative glomerulonephritis also applies to all the other well-defined glomerulonephritides.

We have not, as yet, been able to detect any measurable decline in the glomerular filtration rate as a result of glomerular disease alone. This can be illustrated with the particularly impressive case of membranoproliferati ve glomerulonephritis type I shown in Figs. 3a and b: the glomeruli exhibit double contouring of the basement membrane, swelling of the endothelium and marked proliferation of the mesangial cells. In spite of these changes, the patient's serum creatinine concentration was 0.8 mg!\! and the creatinine clearance 120 ml/min - both within the normal range.

According to the results of our study, peri reticular renal amyloidosis, too, is accompanied by irreversible elevation of the serum creatinine concentration only when the renal cortical interstitium is widened by an inflammatory process that has led to tibrosis. If. on the other hand, the interstitium is not widened, there is no elevation of the serum creatinine level and no decline in creatinine clearance, even when the glomerular amyloidosis is very severe,·3.

Креатининсыв.,мг/дл

Отн.объеминтерстиция

R=0,7242

Нормальныйотн.объеминтерстиция,неизмененыеканальцы.Креатининсыв.0,8мг/дл

Выраженныйтубулоинтерстициальныйкомпонент.Креатининсыв.2,8мг/дл

Отн.объем

31

There is also clear evidence in the case of diabetic glomerulosclerosis that severe glomerular changes alone do not have a detrimental effect on the excretory function

a

b

Figs 2a and b. Moderately severe mesangioproliferative glomerulonephritis. a) The tubules are unremarkable and the interstitium is of normal width. Serum creatinine concentration: 0.8 mg%. b) The interstitium is widened. fibrosed and inflamed and the tubules are atrophic. Serum creatinine concentration: 2.8 mgt.

a b

Figs. 3a and b. a) membranoproliferative glomerulonephritis type I. showing mesangial cell proliferation and double contouring of the basement membrane. The surrounding tubules are unremarkable. Serum creatinine concentration: 0.8 mg%; creatinine clearance:120 ml/min. b) Glomerulus from a healthy kidney. Serum creatinine concentration: 1.0 mg%; creatinine clearance: 120 ml/min.

31

There is also clear evidence in the case of diabetic glomerulosclerosis that severe glomerular changes alone do not have a detrimental effect on the excretory function

a

b

Figs 2a and b. Moderately severe mesangioproliferative glomerulonephritis. a) The tubules are unremarkable and the interstitium is of normal width. Serum creatinine concentration: 0.8 mg%. b) The interstitium is widened. fibrosed and inflamed and the tubules are atrophic. Serum creatinine concentration: 2.8 mgt.

a b

Figs. 3a and b. a) membranoproliferative glomerulonephritis type I. showing mesangial cell proliferation and double contouring of the basement membrane. The surrounding tubules are unremarkable. Serum creatinine concentration: 0.8 mg%; creatinine clearance:120 ml/min. b) Glomerulus from a healthy kidney. Serum creatinine concentration: 1.0 mg%; creatinine clearance: 120 ml/min.

34

rig. 7. Section of the renal cortex in hypokalaemic nephropathy, showing obvious interstitial fibrosis and atrophy of the tubules. The glomeruli are not hyalinized, but the maximal urine osmolality is only 360 mosm; that is, the kidney is unable to concentrate the urine, despite the fact that the glomeruli are preserved. PAS reaction.

This can be illustrated with two examples. Firstly, mesangioproliferative glomerulonephritis (Fig. 8): for patients without tubulo-interstitial changes at the time of the biopsy, the lO-year kidney survival rate is 92%; if, on the other hand, there are signs of tubulo-interstitial fibrosis in addition to the glomerular changes at the time of biopsy, this falls to 65%.

III . 0

i !

.. 1 "0

.. 0

It

LONG-TERM PROGNOSIS OF MESANGIOPROUFERATIVE GN

IN RELATION TO INTERSTITIAL FIBROSIS (n. 456 I

80

80

.0

20

0 Follow - up " •• r.1

NORMAL INTERSTITIUM

INTERSTITIAL FIBROS ( 23" I

10

Fig. 8. Mesangioproliferati ve glomerulonephritis: Survey of the long-term prognosis of cases with interstitium of normal width and cases with a widened and inflamed interstitium at the time of biopsy.

Почечнаявыживаемость

Годынаблюдения

Норм.интерстиций

ТИФ

¨  Призаболеванияхпочекразнойприроды,втомчислегломерулярных(гломерулонефрит,диабетическаянефропатия),наблюдаетсяопережающееразвитиеинтерстициальногосклероза

¨  СкоростьпрогрессированияХПНсвязанасостепеньюинтерстициального,анеклубочковогосклероза

¨  Изолированноепоражениепочечныхклубочковдажепритяжелыхформахзаболеванийпочекнеприводиткразвитиюпочечнойнедостаточности

¨  Уровенькреатининанаходитсявобратнойзависимостиотплотностиперитубулярногокапиллярногорусла

¨  Связьмеждусклерозоминтерстиция,облитерациейперитубулярногокапиллярногоруслаинтерстицияиуровнемкреатининаотмечаетсяиприумереннойпротеинурии

Данные биопсий 2460 больных с ХГН, диабетической нефропатией и амилоидозом почек, 772 больных с сосудистыми нефропатиями, 72 больных с интерстициальным нефритом, A, Bohle, et al., 1996

32

of the kidney. Severe diabetic glomerulosclerosis can be accompanied by a normal serum creatinine concentration, but only when the renal cortical interstitium is not widened and the tubules are not atrophic. Even a minor degree of diabetic glomerulosclerosis can, on the other hand, be accompanied by an elevation of the serum creatinine concentration if the interstitium is widened and the tubules are atrophic. It is therefore not surprising that in diabetic glomerulosclerosis, as in the glomerulonephritides, a significant correlation is found between the relative volume of the renal interstitium and the serum creatinine concentration2 ,3,

However, it is not only the serum creatinine concentration that is affected b)' tubulo-interstitial processes accompanied by fibrosis: correlations with the more sensiti ve parameters inulin clearance and PAH clearance have also been found in mesangioproliferati ve glomerulonephritis and in other glomerulopathies. These findings also confirm results published by Risdon et aI." and Schainuck et al.". Their findings, obtained by semiquantitative methods, have received virtually no attention.

lie have also been able to demonstrate over the last few years that still more functions can be affected by tubulo-interstitial changes. In patients with mesangioproliferative glomerulonephritis whose maximum urine osmolality was measured at the time of renal biopsy, we were able to demonstrate a significant negative correlation between the width of the renal cortical interstitium and the maximum urinary concentrating ability of the kidney. In other words, the concentrating ability diminishes progressively as the renal cortical interstitium increases in width (Fig. 4). This correlation was also noted by both Risdon et al." and Schainuck et al." as a result of their semiquantitative investigations.

y

r' 20 ..

10

200 400 600

n·89 r-O.81

2p·0.0001

800 x

1000

Fig. 4. Correlation between the maximal urine osmolality and the relative volume of the cortical interstitium in cases of various glomerulopathies, mainly mesangioproliferative glomerulonephritis. A statistically significant negative correlation exists between these parameters; i.e., as the interstitium of the cortex increases in width, the maximal urine osmolality decreases significantly.

Similarly, correlations were also found between the urine osmolality and the cross-sectional area of the epithelium of the proximal tubules and of the distal tubules, that is, of the thick ascending limb of the loop of Henle (Fig. 5). In other words, the concentrating ability of the kidney diminishes as the cross-sectional area of the epithelium of these segments decreases. Furthermore, it was also evident that as the maximum concentrating ability of the kidney decreases, the glomerular filtration rate also falls (Fig. 6). This relationship is found in kidneys in which the glomeruli are not hyalinized but have a normal structure, as in the case of hypokalaeroic nephropathy illustrated in Fig. 7, where the urine osmolality was 360 mosro.

A.Bohleetal.PatholResPract.1990Feb;186(1):135-44.

Объеминтерстиция

Осмолярностьмочи,мосмоль/л

R=0,81

33

CORRELATION BETWEEN OSMOLALITY OF THE URINE AND EPITHELIAL AREA OF THE

PROXIMAL TUBULES RESP. EPITHEliAL AREA OF THE THICK SEGMENT OF LOOP OF HENLE

MEDULLA CORTEX

URINE THICK SEGMENT OF LOOP OF HENLE PROXIMAL TUBULES OSMOL (mosmol Il

1 : 9 • 1."'.

r ; 0,64

p : 0,0001

.. : . .' ....

. ..

. '

y : -;]23,6 • O,B

r = 0,7

p " 0.0001

63

800 1600

TUBULAR EPITHELIAL AREA wm")

Fig. 5. Correlation between the cross-sectional area of the epithelium of the proximal tubules and of the ascending limb of Henle's loop and the maximal urine osmolality. It is seen that as the area of these segments decreases, the maximal urine osmolality decreases significantly.

y CCreatinine ml/min/L73m2

100

• t·

.. . ... .. '" 50

. ..

. ..

..... : .. n=72

r o O.51 2p<Q0OO1

..

+ ___ ._2L.0_. ___ 6..L90 ___ ..:spoL:... __

7X

Fig. 6. Correlation between the maximal urine filtration rate in mesangioproliferative osmolality decreases, the glomerular significantly.

osmolality and the glomerular glomerulonephritis. As the

filtration rate decreases

Our investigations have also indicated that there is a correlation between tubulo-interstitial changes and blood pressure in various glomerulonephritides. Thus we found that in mesangioproliferative glomerulonephritis, chronic membranous glomerulonephritis, focal sclerosing glomerulonephritis and membranoproliferative glomerulonephritis type I, if the renal cortical interstitium is widened the blood pressure is always significantly higher than that found when the disease is confined to the glomeruli. Finally, we have been able to demonstrate in the past few years that the long-term prognosis of a wide range of glomerulonephritides is significantly worse when interstitial fibrosis is found at the time of the original renal biopsy.

Площадьтубулярногоэпителия,мкм2

Осмоляр-ностьмочи,мосмоль/л

Прокс.канальцыВосх.сегм.п.Генле

0

10

20

30

40

безТИК сТИК0

200

400

600

800

1000

безТИК сТИК80859095100105110115

безТИК сТИК

Ссr,мл/мин

111± 6

93± 5

936± 45

639± 44

35± 4

23± 3

Uosmmax,мосм/кг

UNH4V/Ccr,ммоль/сут

p<0,05

М.Я.Ратнерисоавт.,1988

p<0,05 p<0,05

¨  Гликопротеинсмолекулярноймассой85-kDa,продуцируемыйтолстымсегментомвосходящегоотделапетлиГенлеиначальнойчастьюизвитогодистальногоканальца

¨  Состоитиз616аминокислотныхостатков,включая48цистеиновыхостатков,которыеформируютдисульфидныемостики

¨  Трансмембранныйпротеин,которыйсекретируетсявмочучерезпротеолитическоерасщеплениегликозилфосфатидилинозитольногоякоря

¨  Уздоровыхлицэкскретируетсяоколо20-70мгуромодулинавсутки

¨  Основныефункции:¡  ингибируетагрегациюкристалловкальция¡  связываетфимбрииIтипаEscherichiacoli,блокируяколонизацию

уротелиальныхклеток¡  модулируетклеточнуюадгезиюииммунныйответ

The fact that uromodulin is abun-dantly produced by TAL cells, whichplay a major role in sodium anddivalent cation handling and in urineconcentrating ability, and the asso-ciation of uromodulin with both raremonogenic diseases and common com-plex disorders suggest that it couldrepresent a valid biomarker of renaltubular function. Thus far, there isconflicting evidence about the potentialvalue of urinary levels of uromodulin inrelation to CKD. Early, small-sizedstudies suggested that reductions inestimated glomerular filtration rate(eGFR) are reflected by lower levels ofurinary uromodulin. A nested case–control study (n= 200) of incidentCKD (eGFR o60 ml/min per 1.73 m2)within the Framingham Heart Study(FHS) showed that elevated uromodu-lin concentrations precede the onset ofCKD and associate with a common riskvariant in the UMOD promoter region.5

More recently, a subanalysis including2948 individuals of the FHS didnot show a significant association ofuromodulin with eGFR.6

The study of Garimella andcolleagues7 (this issue) adds new ele-ments into the debate, by suggestingthat, in elderly ‘survivors’, low urinaryuromodulin concentrations in spot

urine identify people at risk of progres-sive kidney disease and mortality aboveand beyond established markers ofkidney disease. The study setting (theCardiovascular Health Study, including3406 people older than 65 years with amean age of 78 years at baseline in1996–1997) is interesting in that manyevents occur in elderly people, so thatrelatively modest sample sizes allowdetection of relevant effects. Theauthors investigated the association ofurinary uromodulin with eGFR andfour outcomes: end-stage renal disease,cardiovascular disease, heart failure, andall-cause mortality. They used eithera classic case–control design (rapideGFR decline, 430%) or a case–cohortdesign for the other outcomes. Between1996–1997 and 2005–2006, 192 partici-pants developed rapid eGFR decline and54 developed end-stage renal disease,and these were compared with controlsfrom the randomly selected subcohortof 958. Garimella et al.7 conclude that,in this population of older adults,higher concentrations of uromodulinin urine are associated with lower riskof progression of kidney disease andlower risk of mortality, adjustedfor baseline eGFR and the urinaryalbumin–creatinine ratio. They suggestthat the higher levels of uromodulin

may reflect a better tubular function ingeneral, which would limit progressionof kidney disease.

The study has many strengths, suchas the use of a cystatin C-basedequation, adjudicated outcomes, longduration of follow-up, central measure-ment of uromodulin, and a carefulepidemiological design including hardend points as well as sound statisticalanalyses. There are, however, severallimitations, the first being the lownumber of events for end-stage renaldisease, which leads to low precisionand lack of power. The second is the useof the concentration of uromodulin inspot urine without taking urinary crea-tinine into account in the main ana-lyses. We do not know under whichconditions the spot urines were taken,and indicators of urine concentration(such as osmolality or creatinine con-centration) are not provided. A thirdissue is the lack of information aboutparticipants’ characteristics by center.Considering the substantial inter-regional variations in urinary uromo-dulin levels,3 it would have been ofinterest to know whether uromodulinconcentrations varied across centers inthis study. Sample and methodologyissues are of central importance inmeasuring a complex secretory protein

5 µm XY

2Cl– Cl–Na+

3Na+

Ca2+Mg2+

K+

Na+ K+

K+2K+ROMK

UMOD

H2O

Luminal Basolateral

+ –

Cldns

NKCC2CIC–Kb

Barttin

Na/K–ATPase

Figure 1 |Uromodulin, a major secretory protein produced by the cells lining the thick ascending limb of the loop of Henle. Uromodulinis exclusively produced by the cells lining the thick ascending limb (TAL), a tubular segment involved in NaCl reabsorption, handling of divalentcations (Ca2+ and Mg2+), and urine concentration. Uromodulin is a glycosylphosphatidylinositol (GPI)-anchored glycoprotein that is targeted tothe apical membrane, cleaved by a protease, and assembled in the urine into polymers that form a gel-like structure. Interactions betweenuromodulin and the apical cotransporter NKCC2 and channel ROMK have been demonstrated. The right panels show the localization ofuromodulin at the apical membrane of TAL cells in the human kidney (immunoperoxidase staining); and the network of uromodulin filamentscovering a monolayer of primary cultured TAL cells obtained from mouse kidney (immunofluorescence staining, nuclear counterstain in blue;confocal microscopy imaging on the XY plane).

Kidney International (2015) 88 945

commentary

DevuystO,BochudM.Uromodulin,kidneyfunc�on,cardiovasculardisease,andmortality.KidneyInt2015;88:944–6.

receptor–ligand interaction. In uromodulin, these modulesare likely important for protein–protein interaction. The ZPdomain is found in a variety of extracellular eukaryoticproteins, such as sperm receptors ZP1 and ZP3 and tectorialmembrane components a- and b-tectorin, and is essential forprotein polymerization7 (Figure 1b). Indeed, uromodulin ismainly present in the urine as a high-molecular-weightpolymer (Mr 1–10! 106Da) that appears at the electronmicroscopy analysis as a matrix composed by fibrils, with awidth of about 100 A and an average length of 25,000 A.Depending on the ionic conditions, uromodulin matrices canform a gel-like structure that is water impermeable but allowsion movement.8

Timing and tissue specificity of expressionUromodulin is a kidney-specific protein that is exclusivelyexpressed by epithelial cells lining the thick ascending limb(TAL) of Henle’s loop.9 It is mainly located at the apicalplasma membrane,10 although localization at the basolateralside of TAL cells has also been reported.11 A basolateralrelease of uromodulin is suggested by studies on itstrafficking in transfected polarized epithelial cells and by itspresence at very low concentrations in the blood.12

The presence of uromodulin protein and transcript isdetected from embryonic day 16.5 in the developing mouse

kidney.13,14 In humans, the protein was detected fromgestational week 16 by immunohistochemistry analysis andfrom week 20 in the amniotic fluid.15 Its expression steadilyincreases with time and maturation of TAL tubules till afterbirth. Uromodulin is the most abundant transcript in matureTAL cells where it is produced at a very high rate.16 The half-lifeof the protein is rather short (about 9 h in rabbit and 16h inhumans)17 due to its high rate of secretion in the urine thatranges from 20 to 100mg/day in humans under physiologicalconditions.18 Uromodulin is released from the apical plasmamembrane of epithelial cells into the tubule lumen via aconserved proteolytic cleavage.19 Cleavage is necessary forprotein polymerization, as it releases an inhibitory motif thatprevents premature protein assembly,20 similarly to whatdescribed for ZP protein ZP3 (ref. 21) (Figure 1b). Interest-ingly, data from our studies in transfected MDCK cells20 andfrom urine peptidomes22 suggest the presence of an alternativecleavage distal to the inhibitory motif releasing monomericuromodulin. Little information is currently available on thepresence of a specific protease(s) involved in uromodulinexcretion in the urine and on how this is regulated.

Evolutionary conservationThe sequence and domain composition of uromodulin isvery similar to the one of glycoprotein 2, which is the major

a

23 31 148 198 287 334 585 640614GPI

I II III D8C ZP_N ZP_C

b

TAL tubularepithelial cell

Lumen

GPI anchoringProtein foldingN-glycosylation

N-glycanmaturation

PolymerizationUrinary excretionProteolysis

Figure 1 | Structure and maturation of uromodulin. (a) The predicted structure of uromodulin contains a leader peptide (predicted to becleaved at residue 23), three epidermal growth factor (EGF)-like domains (EGF-II and EGF-III are calcium binding), a central domain ofunknown function (named D8C as it contains eight conserved cysteines), a zona pellucida (ZP) domain, and a glycosylphosphatidylinositol(GPI)-anchoring site (predicted at position 614). The seven N-glycosylation sites are indicated. The high-mannose chain on residue Asn 274 isshown in red. (b) Model of uromodulin maturation, excretion, and polymerization. Uromodulin is synthesized in thick ascending limb (TAL)tubular epithelial cells. It is co-translationally inserted in the endoplasmic reticulum where GPI anchoring, formation of intramoleculardisulfide bonds, and N-glycosylation take place. In the Golgi, all glycan chains are modified, with the exception of the one on Asn 274 thatretains a high-mannose moiety. Uromodulin reaches the plasma membrane in a polymerization-incompetent conformation kept by theinteraction of two hydrophobic motifs (red), one within the ZP domain (internal hydrophobic patch) and one localized between the ZPdomain and the GPI-anchoring site (external hydrophobic patch). Proteolytic cleavage by a yet to be identified protease (scissors) releasesthe hydrophobic interaction, generating a polymerization-competent monomer that is assembled into polymeric filaments. The orientationof uromodulin monomers within a filament is hypothetical and deduced from structural data on ZP3 protein.94

Kidney International (2011) 80, 338–347 339

L Rampoldi et al.: Uromodulin and chronic diseases of the kidney m in i rev iew

RampoldiL,ScolariF,AmorosoAetal.Therediscoveryofuromodulin(Tamm-Horsfallprotein):fromtubulointersVValnephropathytochronickidneydisease.KidneyInt2011;80:338–47.

atrophy. As a rule, cysts are not present. Based on the strikingclinico-pathological resemblance and a strong linkage to thesame chromosomal interval, Dahan et al. suggested a possibleallelism between MCKD2 and FJHN [33]. In 2002, Hart et al.provided evidence that MCKD2 and FJHN arise from muta-tion of the UMOD gene and are allelic disorders [5]. Sincethen, FJHN and MCKD2 are collectively referred to UMOD-as-sociated kidney disease (UAKD). Mutations in the UMOD genewere also reported in two families affected by a variant ofGCKD (MIM 609886), resembling the UAKD phenotype [6,34]. Histology is similar to other UAKD except for the presenceof cystic dilatation of the Bowman’s space. GCKD is geneticallyheterogeneous, because it can be also found with mutation inthe hepatocyte nuclear factor 1-β gene (HNF 1-β) [35].

UAKD is a rare disease. However, the true prevalence ofUADK is difficult to determine, because the condition is fre-quently underdiagnosed. The findings of slowly progressiverenal failure, non-significant urinalyses and unremarkable renalultrasounds make the correct diagnosis elusive. Families withUAKD have been reported from Europe, USA, Asia and Africa.A nationwide epidemiologic survey of UAKD conducted inAustria revealed a prevalence of 1.7 cases per million populationand 1 case per 1000 renal replacement therapy patients. Noother systematic study of the epidemiology of UAKD is avail-able. However, a prevalence of UADK of 1.52 and of 0.7 patientsper million population has been calculated in the Czech Repub-lic and in France (and Belgium), respectively [36]. In familiespresenting with symptoms fulfilling diagnostic criteria of FJHN/MCKD2, UMODmutations can be detected in 12–31% [37].

The renal clinical phenotype caused by UMOD mutation ischaracterized by dominant inheritance, CKD due to chronictubulointerstitial nephritis, hyperuricaemia, gout and, incon-stantly, renal cysts [5–7, 10]. More than 100 mutations in theUMOD gene have been described so far; the majority of re-ported UMOD mutations cluster in exons 4 and 5, resulting inthe replacement of cysteine residues and leading to misfolding

of the UMOD molecule [5–7, 10, 38] (Figure 1). The clinicalphenotype of UAKD and genotype–phenotype correlationshave been examined in two large cohorts of patients. In aFrench study, 37 UMOD mutations were identified in 109 pa-tients from 45 families. The majority of patients had hyperuri-caemia; gout was present in 75% of men and 50% of women.The median age at first gouty episode was 21 years. Cysts weredetected in 34% of patients. The median renal survival was54 years. Phenotype was not accurately predictive of UMODmutation and a high intrafamilial variability of renal survivalwas observed [37]. In a second series of 202 patients from74 families with 59 different UMOD mutations, median agesat onset of hyperuricaemia, gout and ESRD were 24, 40 and56 years, respectively. Men developed gout and ESRD signifi-cantly earlier than did women. The location of the mutationappeared to affect the progression of renal disease, because themedian age at ESRD development was lowest in patients withmutations in the EGF2 and EGF3 domains [39].

Several physiological aspects of UAKD, especially the puta-tive link between UMOD-mutated protein, renal salt wastingand uric acid handling remain enigmatic. Immunohistochem-istry analysis of renal biopsies of UAKD patients showed thepresence of large UMOD intracellular aggregates, colocalizingwith ER markers, in the cells lining the TAL [6, 7]. Differentcellular models revealed that mutant UMOD isoforms are de-fective in trafficking to the plasma membrane, being retainedin the ER [6, 7, 40]. A recent transgenic UAKD mouse modelrecapitulated most of the UAKD features, confirming that thekey primary event is ER accumulation of mutant UMOD inthe TAL cells, which precedes a progressive renal damage,characterized by tubulointerstitial fibrosis with inflammatorycell infiltration and tubule dilation [41]. Thus, UMOD muta-tions affect biosynthesis of the protein, leading to an aberrantintracellular trafficking, ER storage, abnormal UMOD expres-sion in the kidney and decreased urinary UMOD excretion. Asopposed to mice expressing mutant UMOD, mice lacking

F IGURE 1 : Structure of UMOD protein and summary of the published mutations associated with UADK. Upper panel: schematic representa-tion of the structure of the UMOD protein, showing a leader peptide, three epidermal growth factor EGF-like domains, a central domain namedD8C, a ZP domain and a glycosylphosphatidylinositol GPI-anchoring site. Glycosylation sites are represented as Y. Lower panel: summary of allUMOD mutations found with their corresponding functional domain and exon. A total of 113 mutations [5, 6, 42, 43, 44] have been reported todate. Most of UMODmutations are clustered in exons 4 (>80%) and 5 (>11%).

FULLREVIE

W

U r o m o d u l i n a n d d i s e a s e s 3

at University of A

berdeen on October 4, 2014

http://ndt.oxfordjournals.org/D

ownloaded from

ScolariF,IzziC,GhiggeriGM.Uromodulin:frommonogenictomulVfactorialdiseases.NephrolDialTranspl2014;0:1–7.

The term ‘familial hyperuricaemic nephropathy’ re-surfaced in a 1984 publication by Macdermot and colleaguesin which they demonstrated that purine metabolism was notinvolved in this condition and suggested there might be aproblem with tubular function—a far-sighted observation[8]. Studies generated by the Purine Laboratory at StThomas’ Hospital, London during the 1990s went a longway towards identifying some of the pathophysiology of thesyndrome, not all of which have withstood the test of time. Upto three generations of affected families were identified, de-scribed initially as ‘familial juvenile gouty nephropathy’ [9]and later as ‘familial juvenile hyperuricaemic nephropathy’[10] or FJHN. The overlapping confusion between the cysticdiseases persisted, with glomerulocystic disease of the kidney(GCKD) being identified as yet another variant which affectedchildren and adults [11], and this was subsequently neatlyclassified into three groups [12]. Genetic studies became thekey instruments in being able to distinguish between them;NPH1 was ultimately localised to chromosome 2 [13],MCKD1 to chromosome 1 [14] and MCKD2 to chromosome16 [15].

The final genetic breakthrough occurred in 2002 with thediscovery that mutations in the uromodulin gene (UMOD)were responsible for both FJHN and MCKD II [16], followedby a flurry of publications confirming this. The identity ofFJHN with MCKD type II was confirmed [17] and re-con-firmed, along with GCKD [18].

Nomenclature and classification

With the discovery of multiple genes causing a similar syn-drome, it became clear that the time-honoured FJHN was inneed of a more appropriate diagnostic term. Mutations in

UMOD were the most frequent mutations observed (in ap-proximately 40% of FJHN cases), leading to the proposal thatthe disease be referred to as ‘uromodulin-associated kidneydisease’ or UAKD [17].

The confusion is illustrated by the entries in the on-line database of inherited diseases OMIM (Table 1). Itbecame clear that UMOD mutations could account forless than half the cases of FJHN, and other mutationswere identified, namely mutations of the hepatocyte nu-clear factor 1β (HNF1β) gene [19] and the renin (REN)gene [20]. GCKD has also been described as a mani-festation of an HNF1β mutation [21]. The latest addi-tion to the list is the mucin 1 (MUC1) gene that hasbeen shown to be abnormal in MCKD1 [22].

Given that a phenotypic diagnosis could only be broad andnonspecific, combined with a variety of genetic mutationsinvolved, there was a crying need for an over-arching clinicalterm. The comprehensive term ‘autosomal dominanttubulointerstitial kidney disease’ or ADTKD, which seemssimple, practical and easy to understand, was suggested [23],and this has subsequently been adopted by a Kidney Disease:Improving Global Outcomes (KDIGO) consensus conference[24]. The participants of the consensus conference proposedthe following classification, depending on the mutation iden-tified (or not).

& ADTKD-UMOD& ADTKD-REN& ADTKD-MUC1& ADTKD-HNF1β& ADTKD-NOS (not otherwise specified)

The subject has been well summarised in a recent commen-tary [25].

Table 1 Nomenclature of uromodulin and its related mutations in the online database of inherited diseases (OMIM)

Name of disorder Abbreviation Mutant gene Cytogenetic location Phenotype Gene/locus

Hyperuricemic Nephropathy, Familial Juvenile, 1 HNFJ1 UMOD 16p12.3 162000 191845

Medullary cystic kidney disease type 2 MCKD2 UMOD 16p12.3 603860 191845

Glomerulocystic kidney disease GCKD UMOD 16p12.3 609886 191845

Hyperuricaemic nephropathy, Familial juvenile, 2 HNFJ2 REN 1q32.1 613092 179820

Renal tubular agenesis REN 1q32.1 267430 179820

Hyperuricaemic nephropathy, Familial juvenile, 3 HNFJ3 unknown 2p22.1-p21 614227 614227

Maturity onset diabetes of the young MODY HNF1b 17q12 125853 189907

Renal cysts and diabetes syndrome RCAD HNF1b 17q12 137920 189907

Medullary cystic kidney disease type 1 MCKD1 MUC1 1q22 174000 158340

Juvenile nephronophthisis type 1 NPHP1 NPHP1 2q13 256100 607100

Autosomal recessive polycystic kidney disease ARPKD FCYT 6p12.3-p12.2 263200 606702

UMOD, uromodulin; REN, renin; MUC1, mucin 1; NPHP1, nephronophthisis 1; FCYT, alternative name for PKHD1 (polycystic kidney and hepaticdisease 1 autosomal recessive)

Pediatr Nephrol

PediatrNephrol,Feb.2016.DOI10.1007/s00467-015-3308-y

The term ‘familial hyperuricaemic nephropathy’ re-surfaced in a 1984 publication by Macdermot and colleaguesin which they demonstrated that purine metabolism was notinvolved in this condition and suggested there might be aproblem with tubular function—a far-sighted observation[8]. Studies generated by the Purine Laboratory at StThomas’ Hospital, London during the 1990s went a longway towards identifying some of the pathophysiology of thesyndrome, not all of which have withstood the test of time. Upto three generations of affected families were identified, de-scribed initially as ‘familial juvenile gouty nephropathy’ [9]and later as ‘familial juvenile hyperuricaemic nephropathy’[10] or FJHN. The overlapping confusion between the cysticdiseases persisted, with glomerulocystic disease of the kidney(GCKD) being identified as yet another variant which affectedchildren and adults [11], and this was subsequently neatlyclassified into three groups [12]. Genetic studies became thekey instruments in being able to distinguish between them;NPH1 was ultimately localised to chromosome 2 [13],MCKD1 to chromosome 1 [14] and MCKD2 to chromosome16 [15].

The final genetic breakthrough occurred in 2002 with thediscovery that mutations in the uromodulin gene (UMOD)were responsible for both FJHN and MCKD II [16], followedby a flurry of publications confirming this. The identity ofFJHN with MCKD type II was confirmed [17] and re-con-firmed, along with GCKD [18].

Nomenclature and classification

With the discovery of multiple genes causing a similar syn-drome, it became clear that the time-honoured FJHN was inneed of a more appropriate diagnostic term. Mutations in

UMOD were the most frequent mutations observed (in ap-proximately 40% of FJHN cases), leading to the proposal thatthe disease be referred to as ‘uromodulin-associated kidneydisease’ or UAKD [17].

The confusion is illustrated by the entries in the on-line database of inherited diseases OMIM (Table 1). Itbecame clear that UMOD mutations could account forless than half the cases of FJHN, and other mutationswere identified, namely mutations of the hepatocyte nu-clear factor 1β (HNF1β) gene [19] and the renin (REN)gene [20]. GCKD has also been described as a mani-festation of an HNF1β mutation [21]. The latest addi-tion to the list is the mucin 1 (MUC1) gene that hasbeen shown to be abnormal in MCKD1 [22].

Given that a phenotypic diagnosis could only be broad andnonspecific, combined with a variety of genetic mutationsinvolved, there was a crying need for an over-arching clinicalterm. The comprehensive term ‘autosomal dominanttubulointerstitial kidney disease’ or ADTKD, which seemssimple, practical and easy to understand, was suggested [23],and this has subsequently been adopted by a Kidney Disease:Improving Global Outcomes (KDIGO) consensus conference[24]. The participants of the consensus conference proposedthe following classification, depending on the mutation iden-tified (or not).

& ADTKD-UMOD& ADTKD-REN& ADTKD-MUC1& ADTKD-HNF1β& ADTKD-NOS (not otherwise specified)

The subject has been well summarised in a recent commen-tary [25].

Table 1 Nomenclature of uromodulin and its related mutations in the online database of inherited diseases (OMIM)

Name of disorder Abbreviation Mutant gene Cytogenetic location Phenotype Gene/locus

Hyperuricemic Nephropathy, Familial Juvenile, 1 HNFJ1 UMOD 16p12.3 162000 191845

Medullary cystic kidney disease type 2 MCKD2 UMOD 16p12.3 603860 191845

Glomerulocystic kidney disease GCKD UMOD 16p12.3 609886 191845

Hyperuricaemic nephropathy, Familial juvenile, 2 HNFJ2 REN 1q32.1 613092 179820

Renal tubular agenesis REN 1q32.1 267430 179820

Hyperuricaemic nephropathy, Familial juvenile, 3 HNFJ3 unknown 2p22.1-p21 614227 614227

Maturity onset diabetes of the young MODY HNF1b 17q12 125853 189907

Renal cysts and diabetes syndrome RCAD HNF1b 17q12 137920 189907

Medullary cystic kidney disease type 1 MCKD1 MUC1 1q22 174000 158340

Juvenile nephronophthisis type 1 NPHP1 NPHP1 2q13 256100 607100

Autosomal recessive polycystic kidney disease ARPKD FCYT 6p12.3-p12.2 263200 606702

UMOD, uromodulin; REN, renin; MUC1, mucin 1; NPHP1, nephronophthisis 1; FCYT, alternative name for PKHD1 (polycystic kidney and hepaticdisease 1 autosomal recessive)

Pediatr Nephrol

PediatrNephrol,Feb.2016.DOI10.1007/s00467-015-3308-y

•  Гиперурикемическаянефропатия,семейнаяювенильная,1

•  Медуллярнаякистознаяболезньпочек,2тип•  Гломерулокистознаяболезньпочек

carrying mutations in SLC12A1, encoding the Na-K-2Cl co-transporter NKCC2, show no response to frusemide, whilepatients with KCNJ1 and CLCNKB mutations have a normalresponse [10], presumably because of a less severe defect insalt absorption. UMOD KO mice showed an attenuated re-sponse to frusemide administration, suggesting a defect inNaCl absorption along the TAL. The paradoxical response ofthe UAKD patient to frusemide suggests certainly the presenceof a residual function of the TAL. The authors interpretedtheir findings as the result of a hyper-activation of residualNKCC2, which in the early phase of the disease may be suffi-cient to ensure normal sodium and water balances at basal.The use of frusemide resulted in the disruption of this equilib-rium, with an exaggerated response, for a presumable lack ofadequate distal compensation acutely. This intriguing inter-pretation requires further studies to be confirmed.

The most important limitation of the study, as the authorsadmitted, is the low number of patients. The test has been con-ducted only in one patient, so no firm conclusionsmay bemade,as an underlying inter-individual variability may account forthe difference in the magnitude of the response. In addition,the opposite effect of frusemide in the patient compared withUMOD KO mice may depend on the impact of the geneticmutation on protein function. The majority of mutationsleading to human UAKD have been shown to affect pro-tein folding with ER retention [11]. Schaeffer et al. [12] haveshown that part of mutant UMOD escapes ER retention,reaches plasma membrane and is secreted in the urine, while inUMOD KO mice the protein is completely absent. The patient’smutation may potentially activate NKCC2, as a result of a gainof function mutation, thus explaining the exaggerated responseto frusemide. In fact, the reduced NKCC2 protein abundance inthe renal biopsy of UAKD patients has been shown only in thelate stage of the disease and may reflect general tissue derange-ment occurring during the late stage of kidney disease.

The authors explored further the function of the TAL byperforming the water restriction followed by the desmopressin(dDAVP) test. The patient showed a preserved response towater deprivation. Interestingly, dDAVP administration failedto induce a significant elevation of urine and plasma osmolal-ity in the patient. The mechanism underlying this defect hasnot been further investigated.

Urine concentration is the result of a combined function ofthe collecting duct (CD) and the TAL, in the presence of vaso-pressin (AVP) [13]. Endogenous or exogenous AVP enhanceswater absorption along the CD from the tubular fluid throughan increased water channel Aquaporin 2 (AQP2) proteinabundance on the apical membrane. The TAL contributes tothe urinary concentrating process by generating a medullaryosmotic gradient, through the active salt reabsorption.

The function of the CD as well as AVP plasma levels wereintact in an animal model resembling UAKD; conversely,histological lesions originating from the TAL could predict adysfunction of this segment leading to the loss of medullarhypertonicity [14]. The authors postulated that the blunted re-sponse to dDAVP could result from (i) a failure to generate theinterstitial osmotic gradient, because of the reduction of NaClabsorption and the reduced water impermeability of the TALand (ii) the lack of dDAVP-dependent NKCC2 stimulation, asobserved in UMOD KO mice [4]. Further studies are neededto better explore the mechanism underlying this defect inhumans.

In this paper, the patient had undergone dDAVP adminis-tration after 6 h of water restriction. In this condition, en-dogenous AVP is stimulated. To better evaluate the maximalresponse to dDAVP, it would be more appropriate to adminis-ter the drug after a water load, to suppress endogenous AVP.Then, measuring urine AQP2 and NKCC2 excretion may helpto confirm that the function of the CD is intact also in humansand that the NKCC2 response is blunted.

F IGURE 1 : UMOD regulates NKCC2 and ROMK function, presumably by modulating their turnover and NKCC2 phosphorylation.(A) Normal condition with phosphorylation of NKCC2 (+). (B) In the case of UMOD reduced expression: sub-apical accumulation of ROMKand NKCC2 with reduced NKCC2 phosphorylation.

INFOCUS

U r o m o d u l i n 159

at University of O

tago on October 15, 2015

http://ndt.oxfordjournals.org/D

ownloaded from

ZacchiaM,CapassoG.TheimportanceofuromodulinasregulatorofsaltreabsorpVonalongthethickascendinglimb.NephrolDialTransplant2015;30:158–60.

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ISSN 1561!6274. Нефрология. 2015. Том 19. №2.

В нефробиоптатах оценивалось общее число клубочков, рассчитывались доли (%) полностью склерозированных гломерул и клубочков с сегмен-тарным склерозом. Тяжесть повреждений мембран гломерулярных капилляров, состояние мезангия, интерстиция и канальцев оценивались полуколиче-ственно в баллах от 1 (отсутствие изменений) до 4 (значительная выраженность изменений) по систе-ме, разработанной в НИИ нефрологии ПСПбГМУ им. акад. И.П. Павлова. Функциональное состояние почек характеризо-

валось по величине расчетной скорости клубочко-вой фильтрации (рСКФ), вычисляемой на основе концентрации креатинина в сыворотке крови (Scr) по формулам CKD-EPI. При этом, концентрации креатинина в сыворотке крови и моче и белка в моче устанавливались с помощью стандартных лабораторных автоанализаторов. Концентрации Умо в сыворотке крови и моче измерялись иммуно-ферментным способом с использованием наборов

Human Uromodulin ELISA («BioVendor», Чехия). В моче вычислялось отношение концентраций: уромодулин/креатинин. У 20 пациентов было проведено суточное

мониторирование артериального давления (АД; «Кардиотехника-04-АД», «Инкарт», Россия).Статистическая обработка выполнялась c по-

мощью пакета прикладных программ STATISTICA 8.0. Поскольку статистическое распределение ряда изученных параметров существенно отличалось от нормального, в работе использовались только не-параметрические методы: коэффициент ранговой корреляции Спирмена и критерий Манна–Уитни для несопряженных совокупностей.

РЕЗУЛЬТАТЫКонцентрация Умо в моче оказалась значимо об-

ратно ассоциированной с выраженностью тубуляр-ной атрофии (рис. 1). Кроме того, мочевой уровень ТХБ обратно коррелировал с тяжестью мононуклеар-ной инфильтрации интерстиция (Rs=–0,37; р=0,05). В свою очередь концентрация Умо в сыворотке крови также была обратно связана с выраженностью атрофии канальцев (Rs=–0,39; р=0,038) и перива-скулярного фиброза стромы (Rs=–0,44; р=0,019). Интересно, что при наличии гиалиновых цилиндров (по данным морфологического исследования) в про-свете почечных канальцев сывороточный уровень ТХБ оказывался значимо ниже по сравнению с пациентами с отсутствием данного феномена (рис. 2). Сколько-нибудь отчетливых ассоциаций между концентрациями Умо в сыворотке крови или моче с повреждениями гломерул выявлено не было.Доказать наличие статистически существенной

связи между концентрациями Умо в сыворотке кро-ви и моче в данной когорте из 28 обследованных не удалось (Rs=0,29; р=0,14).Концентрации Умо как в сыворотке крови

(Rs=–0,45; р=0,045), так и моче (Rs=–0,49; р=0,028) была обратно связана с величиной среднего систо-лического артериального давления в дневные часы (срСАДд). В свою очередь, значения срСАДд прямо коррелировали с с тяжестью атрофии канальцев (Rs=0,50; р=0,026; рис. 3 и 4). Сывороточный уровень Умо был обратно ассо-

циирован с концентрацией креатинина (Rs=–0,64; р<0,001) и мочевины (Rs=–0,60; р<0,002) в сыво-ротке крови и прямо – с величиной рСКФ, оценен-ной по методу CKD-EPI на основе концентрации сывороточного креатинина (Rs=0,53; р=0,007). Обнаружить взаимосвязи концентраций Умо

ни в сыворотке крови, ни в моче с уровнем про-теинурии мы не смогли.

Рис. 1. Взаимосвязь между выраженностью атрофии каналь-цев и концентрацией уромодулина в моче (коэффициент ранговой корреляции Спирмена).

Рис. 2. Концентрация уромодулина в сыворотке крови в зави-симости от наличия гиалиновых цилиндров в просвете каналь-ца (1 – отсутствие цилиндров, n=22; 2 – наличие цилиндров, n=6). Критерий Манна–Уитни.

А.В.Смирнов,М.Хасун,И.Г.Каюковисоавт.,Нефрология.2015.Том19.No2.

А.В.Смирнов,М.Хасун,И.Г.Каюковисоавт.,Нефрология.2015.Том19.No2.

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ISSN 1561!6274. Нефрология. 2015. Том 19. №2.

ОБСУЖДЕНИЕВ литературе приводятся противоречивые све-

дения о роли уромодулина в развитии и прогресси-ровании повреждений почек. Существует немало данных о том, что Умо может играть протективную роль в отношении развития и прогрессирования заболеваний почек. Так, было обнаружено, что апоптоз клеток толстого восходящего отдела петли Генле может приводить к развитию ОПП [12]. Со-общалось также, что Умо предохраняет почки от ишемической травмы за счет уменьшения подавле-ния воспаления через влияние на TLR4-рецептор [13]. Кроме того, дефекты Умо могут вносить вклад в формирование нефрокальциноза и камнеобразо-вание [2, 14]. Мыши, нокаутные по гену Умо, ока-зались более подверженными к развитию инфекций мочевых путей [15]. Было также выявлено, что N-гликаны, переносимые Умо, играют решающую роль в защите от поражений мочевого тракта [16]. M.D. Saemann и соавт. [17] показали, что Умо обе-спечивает связь между активацией клеток системы врожденного иммунитета и системой адаптивного иммунитета за счет TLR4-зависимого механизма. Сообщалось, что у Умо-нокаутных мышей усилива-ется стресс-индуцированное мочеиспускание [18]. В свете представлений о нефропротекторной

роли Умо парадоксальными кажутся результаты ряда недавних проспективных популяционно-генетических исследований. Оказалось, что не-которые распространенные варианты однону-клеотидных полиморфизмов гена Умо (не путать с мутациями гена Умо, вызывающими болезни накопления уромодулина – авт.) четко ассоцииро-ваны с более высокой почечной экскрецией ТХБ и большей заболеваемостью и распространенностью ХБП [19–22]. Правда, в популяции пациентов с коронарной болезнью сердца было подтверждено, что у носителей минорного аллеля (ТТ) варианта однонуклеотидного полиморфизма rs12917707 действительно наблюдается меньшая концентрация Умо в моче. Однако сами мочевые уровни ТХБ не ассоциировались с заболеваемостью ХБП [23]. Ин-тересно также, что у реципиентов почечного транс-плантата, пересаженного от доноров-носителей минорного аллеля rs12917707, также отмечались меньшие уровни Умо в моче [20]. Наконец, очень любопытны данные, полученные при исследовании Исландской популяции. Они наводят на мысль о том, что высокая экскреция ТХБ с мочой, являясь фактором риска ХБП, одновременно препятствует камнеобразованию [22].Как бы ни были интересны приведенные выше

данные, ближе к предмету настоящего сообщения

находятся результаты исследований, пытавшихся связать уровни уромодулина с тяжестью повреж-дений почек у пациентов с нефропатиями. Таких работ в доступной нам литературе было обнаруже-но немного. J. Zhou и соавт. при обследовании па-циентов с IgA-нефропатией нашли, что у пациентов с большей выраженностью тубулярной атрофии/интерстициального фиброза отмечаются меньшие

Рис. 3. Уровень среднего систолического артериального дав-ления в дневные часы в зависимости от выраженности атро-фии канальцев и концентрации уромодулина в моче (UУмо).

Рис. 4. Уровень среднего систолического артериального давления в дневные часы в зависимости от выраженности атрофии канальцев и концентрации уромодулина в сыворотке крови (SУмо).

52

ISSN 1561!6274. Нефрология. 2015. Том 19. №2.

ОБСУЖДЕНИЕВ литературе приводятся противоречивые све-

дения о роли уромодулина в развитии и прогресси-ровании повреждений почек. Существует немало данных о том, что Умо может играть протективную роль в отношении развития и прогрессирования заболеваний почек. Так, было обнаружено, что апоптоз клеток толстого восходящего отдела петли Генле может приводить к развитию ОПП [12]. Со-общалось также, что Умо предохраняет почки от ишемической травмы за счет уменьшения подавле-ния воспаления через влияние на TLR4-рецептор [13]. Кроме того, дефекты Умо могут вносить вклад в формирование нефрокальциноза и камнеобразо-вание [2, 14]. Мыши, нокаутные по гену Умо, ока-зались более подверженными к развитию инфекций мочевых путей [15]. Было также выявлено, что N-гликаны, переносимые Умо, играют решающую роль в защите от поражений мочевого тракта [16]. M.D. Saemann и соавт. [17] показали, что Умо обе-спечивает связь между активацией клеток системы врожденного иммунитета и системой адаптивного иммунитета за счет TLR4-зависимого механизма. Сообщалось, что у Умо-нокаутных мышей усилива-ется стресс-индуцированное мочеиспускание [18]. В свете представлений о нефропротекторной

роли Умо парадоксальными кажутся результаты ряда недавних проспективных популяционно-генетических исследований. Оказалось, что не-которые распространенные варианты однону-клеотидных полиморфизмов гена Умо (не путать с мутациями гена Умо, вызывающими болезни накопления уромодулина – авт.) четко ассоцииро-ваны с более высокой почечной экскрецией ТХБ и большей заболеваемостью и распространенностью ХБП [19–22]. Правда, в популяции пациентов с коронарной болезнью сердца было подтверждено, что у носителей минорного аллеля (ТТ) варианта однонуклеотидного полиморфизма rs12917707 действительно наблюдается меньшая концентрация Умо в моче. Однако сами мочевые уровни ТХБ не ассоциировались с заболеваемостью ХБП [23]. Ин-тересно также, что у реципиентов почечного транс-плантата, пересаженного от доноров-носителей минорного аллеля rs12917707, также отмечались меньшие уровни Умо в моче [20]. Наконец, очень любопытны данные, полученные при исследовании Исландской популяции. Они наводят на мысль о том, что высокая экскреция ТХБ с мочой, являясь фактором риска ХБП, одновременно препятствует камнеобразованию [22].Как бы ни были интересны приведенные выше

данные, ближе к предмету настоящего сообщения

находятся результаты исследований, пытавшихся связать уровни уромодулина с тяжестью повреж-дений почек у пациентов с нефропатиями. Таких работ в доступной нам литературе было обнаруже-но немного. J. Zhou и соавт. при обследовании па-циентов с IgA-нефропатией нашли, что у пациентов с большей выраженностью тубулярной атрофии/интерстициального фиброза отмечаются меньшие

Рис. 3. Уровень среднего систолического артериального дав-ления в дневные часы в зависимости от выраженности атро-фии канальцев и концентрации уромодулина в моче (UУмо).

Рис. 4. Уровень среднего систолического артериального давления в дневные часы в зависимости от выраженности атрофии канальцев и концентрации уромодулина в сыворотке крови (SУмо).

Концентрацияуромодулинавмоче(UУмо).

Концентрацияуромодулинавсывороткекрови(SУмо).

B E T W E E N B E D S I D E A N D B E N C H

stroke; those who live long enough develop end-stage kidney disease that requires dialysis or kidney transplant to sustain life.

With the goal of elucidating genetic variants that substantially modify the risk of adult-onset CKD, four recently published studies reported single nucleotide polymorphisms (SNPs) in the UMOD gene promoter—the minor T allele at position –3,653 (rs12917707) was associated with a 20% reduction in CKD incidence4; the minor C allele at position –1,550 (rs4293393) was associated with bet-ter renal function in both incident people with CKD and controls in the US5, whereas the dominant T allele at this site was associ-ated with increased CKD risk in an Icelandic cohort6 and the minor G allele at position –1,617 (rs13333226) was associated with a lower risk of hypertension and with renal function in a European study7.

These recent findings provide a new win-dow of opportunity to probe further into the pathogenesis of CKD, with UMOD as a potential player. Could these minor genetic variants encode functionally altered proteins that modify the universal pathogenetic path-way for progressive CKD, irrespective of the primary etiology—characterized as chronic tubulointerstitial nephritis with interstitial inflammatory cells, matrix-producing myo-fibroblasts and destroyed renal parenchymal (tubules and pericapillary tubules) as the end result of fibrosis8? Two caveats need consider-ation. First, either loss of beneficial function of a normal UMOD or gain of harmful function of a variant protein are plausible mechanisms, and, second, UMOD may serve site-specific protective functions that might be selectively altered by a modified protein (Fig. 1).

An obvious open question is what happens to normal UMOD expression during the initia-tion and progression phases of CKD. Is pro-tein expression altered, misdirected or both? A better understanding of the function of native UMOD will help address these questions; pro-posed possibilities include apical membrane activities, such as endocytosis, signaling via interactions with co-receptors, ciliary func-tion and cell polarity; the formation of an api-cal surface gel-like water permeability barrier; and the inhibition of urinary stones (Fig. 1)3,9. Limited tissue studies suggest that UMOD may accumulate in the interstitium in dam-aged kidneys, caused either by ‘back-leaking’ from the urinary space through damaged tubu-lar cell tight junction or by shedding from the basolateral membrane of tubular cells. Once in the interstitium, UMOD might then promote inflammatory cell recruitment, activation or both, probably through engagement of Toll-like receptor 4, interactions with scavenger recep-

tors or cell surface lectins, and other receptor-ligand–dependent signaling pathways not yet discovered, such as the actions of an unknown specific leukocyte UMOD receptor3,9–11.

Studies in rats have shown how chronic injection of UMOD resulted in tubulointersti-tial nephritis characterized by immune com-plex formation and cell-mediated immune reactions, supporting an inflammatory effect within the interstitium12. As classical humoral immune mechanisms are not a common feature of CKD, a role for UMOD-specific antibodies in kidney fibrosis is unlikely. Within the interstitium, UMOD may also bind numerous ligands that could enhance interstitial fibrogenic responses as a result of increased extracellular matrix synthesis by activated (myo)fibroblasts, inadequate matrix degradation or both.

Tubular cell dysfunction and death are the primary structural correlates of renal func-tional decline in CKD. It is possible that UMOD expression protects positive tubules from irre-versible damage caused by apoptosis, necrosis or autophagy or enhances mitotic regeneration in the face of injury. In fact, although kidneys of UMOD-deficient mice seem to be normal, they are more susceptible to ischemia-induced acute

injury, suggesting that it serves a protective role in the face of damage10. Normally, UMOD is abundant in the apical tubular cell membrane where it is attached as a nonsignaling glyco-sylphosphatidylinositol (GPI)-anchored pro-tein, but it could also engage transmembrane co-receptors to activate classical intracellular signaling pathways.

Observations from people with UMOD mutations and CKD due to chronic tubuloint-erstitial disease have provided some functional insights—their kidney disease, described as a UMOD storage disease, is characterized by misfolding and aberrant trafficking of a mutant UMOD protein, resulting from pro-tein trapping in the endoplasmic reticulum (ER), which results in ER stress and tubular cell death13. This renal phenotype has been replicated in transgenic mice that express a mutant human UMOD gene14. Although the function of membrane-associated UMOD is unknown, marked reductions in its expression may also contribute to the renal phenotype by mechanisms yet to be discovered.

UMOD also associates with cilia, lipid rafts and sodium transporters such as ROMK2 (ref. 15), highlighting the potential key role of these and other membrane functions. The fact that sev-

Loss of protective functions

Gain of damaging functions or mislocation

Basolateralmembrane

↑ Basolateral expression

↓ Apical membrane levels

Gel permeabilitybarrier

Protection from damage?

Urinary protein(UMOD)

Coreceptor

Lipid raft

GPI-anchored UMOD

Interstitial cellrecruitment

and activationInterstitial deposition

Protein misfolding

Tubularback-leak

Macrophage

Fibroblast

Deadcell

ERER stress

Epithelial cell death

Permeabilitybarrier

dysfunction

Extracellularmatrix

Nephron

DCT

TAHL

Fibrosis CKD

Uromodulin

Cilia

Figure 1 UMOD, normal and genetically determined variants, may actively participate in the pathogenesis of CKD. UMOD is normally expressed by epithelia of the TALH and the early distal tubule (DCT). Loss of protective UMOD activities might impair tubular recovery after injury, alter tubular transport function or enhance calcium crystal deposition. Gain of damaging functions or mislocation of UMOD may promote chronic interstitial fibrosis and irreversible nephron loss due to abnormal intracellular trafficking, leading to stress within the ER, tubular malfunction and eventual death. Abnormal interstitial UMOD deposition may recruit macrophages and myofibroblasts that promote scarring and irreversible kidney damage, the ultimate cause of all CKD. Disruption of the normal permeability barrier created by an apical UMOD gel could contribute to the CKD phenotype.

Mar

ina

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554 VOLUME 17 | NUMBER 5 | MAY 2011 NATURE MEDICINE

EddyAA.UMODulaVngrenalfibrosis.NatPublGr2011;17:553–5.

Теряетсвоизащитныесвойства

Проникаетвинтерстиций,индуцируявоспаление

1758      Risch et al.: Serum uromodulin and kidney function

view/j/cclm.2014.52.issue-12/issue-files/cclm.2014.52.issue-12.xml.

The diagnostic characteristics used for recognizing an eGFRCysC were calculated for creatinine, blood urea nitrogen, and the ratios of creatinine/uromodulin and blood urea nitrogen/uromodulin (see Supplemental Data, Figure 2). The AUCs of the different markers are shown in Table 1 of the Supplemental Data. The AUC of uromodulin was not significantly different from the AUCs of creatinine (p = 0.20) and blood urea nitrogen (p = 0.06). The AUCs of creatinine and blood urea nitrogen did not differ signifi-cantly (p = 0.41). Note that constructing the creatinine/uromodulin ratio revealed AUCs that were significantly higher than the AUCs of uromodulin (p = 0.03) and creati-nine (p = 0.004). Constructing the blood urea nitrogen/uro-modulin ratio also demonstrated a higher AUC than those from uromodulin or blood urea nitrogen alone. However, this difference was only significant for the AUC of blood urea nitrogen (p = 0.001) and not for uromodulin (p = 0.35).

DiscussionTo our knowledge, this study is, thus far, the largest to investigate serum uromodulin in individuals with different

levels of kidney function. In our cohort of elderly subjec-tively healthy participants, we demonstrated that serum uromodulin decreased with decreasing kidney function. As such, serum uromodulin behaved in an opposite manner to conventional kidney function serum retention markers. When defining CKD as decreased kidney function, our findings imply that reduced serum uromodulin reflects the presence of CKD. Our study, however, leaves open the ques-tion of whether higher serum uromodulin protects against CKD or whether decreased serum uromodulin is an instiga-tor or bystander of CKD [7]. Thus far, it can be hypothesized that low serum uromodulin may play a role in CKD.

To date, most studies referencing kidney function and uromodulin concentrations have concentrated on urinary uromodulin and its relationship with CKD and the eGFR [7, 28]. The association of serum uromodulin with markers of kidney function has rarely been investigated [4, 15, 29–31]. Uromodulin concentrations in urine are approxi-mately 1000-fold higher than those in serum [32]. No cir-cadian rhythm for the uromodulin serum concentrations could be detected [30]. The daily uromodulin variation in six healthy volunteers was lower in the serum than in the urine and ranged from 6% to 28% [4].

Little is known about the significance of uromodulin concentrations in the serum [7]. The existing studies all employ relatively low sample sizes (from n = 11 in [4] to n = 91

Figure 1 Relationship between serum uromodulin and (A) serum creatinine, (B) serum cystatin C, (C) blood urea nitrogen and (D) eGFRCysC.The relationship between the retention markers and serum uromodulin is of an inverse nature. The scatterplots suggest a hyperbolic relationship between the different markers, indicating a more than proportional increase in uromodulin concentrations with better kidney function.

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RischL,LhodaK,MeierDetal.TheserumuromodulinlevelisassociatedwithkidneyfuncVon.ClinChemLabMed2014;52:1755–61.

¨  изучитьмочевуюэкскрециюуромодулина,маркеровпочечногоповрежденияCOL4иNGALубольныххроническимгломерулонефритомвсопоставлениисизвестнымиклинико-лабораторнымифакторамирискаускоренногопрогрессированиязаболеваниядляоценкиеепрогностическогозначения.

11%

37%

11%

23%

5%13%

Морфологическаяхарактеристика

биопсированныхбольныхХГН,n=34

Мезангио-капиллярный

Мезангио-пролиферативный

ФСГС

Мембранознаянефропатия

Минимальныеизменения

Нефросклероз

М(95%CI)¨  Возраст,лет 36,5(28,0;55,0)¨  Длительность

ХБП,лет 9,6(7,0;12,2)¨  АДсист.,ммрт.ст. 130(126;134)¨  Числопрепаратов

длясниженияАД 1,4(1,2;1,6)¨  Иммуносупрес-

сивнаятерапия 53%

01020304050

<0,5 0,5-3,5 >3,5

%бол

ьных

Протеинурия,г/сут

0

20

40

60

80

1-2 3а 3б 4-5

%бол

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СтадииХБП

РаспределениебольныхпоуровнюпротеинурииистадиямХБП

Выраженный(>30%)тубулоинтерстициальныйфиброзвыявлену38%больных.

¡  Уромодулин(UMOD)–маркерфункциональногосостояниявосходящейчастипетлиГенле

¡  КоллагенIVтипа(COL4)–маркерфиброгенезавпочках

¡  Липокалин,ассоциированныйсжелатиназойнейтрофилов,(NGAL)–маркерповрежденияканальцевогоэпителияпочек

¨  Исследовалиутреннююпорциюмочи80больныхХГНметодомELISAсиспользованиеммоноклональныхантителкследующимантигенам:

01002003004005006007008009001000

0 50

Экскре

цияUMOD,мкг/гCr

UMOD

0

5

10

15

20

25

30

35

40

45

0 50

Экскре

цияCO

L4,м

кг/гCr

COL4

Медиана 28,8 2,29

(Квартили) (18,3,81,6) (1,53,3,19)

UMOD COL4 NGALВозраст -0,15 0,39 0,08ДлительностьХБП -0,43 0,25 0,12ДлительностьАГ -0,28 0,02 0,02САД -0,11 0,22 0,16ЧислопрепаратовдлясниженияАД

-0,07 0,20 0,06

Протеинурия -0,06 0,50 0,52СКФCKD-EPI 0,37 -0,36 -0,09Гемоглобин 0,12 -0,32 -0,27NGAL -0,08 0,50 –

é экскреции

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Повреждениеклубочков:

ПодоцитыБазальнаямембр.

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UMOD COL4 NGALВозраст -0,15 0,39 0,08ДлительностьХБП -0,43 0,25 0,12ДлительностьАГ -0,28 0,02 0,02САД -0,11 0,22 0,16ЧислопрепаратовдлясниженияАД

-0,07 0,20 0,06

Протеинурия -0,06 0,50 0,52СКФCKD-EPI 0,37 -0,36 -0,09Гемоглобин 0,12 -0,32 -0,27NGAL -0,08 0,50 –

8

0

13 13

0

2

4

6

8

10

12

14

Умеренныйнефросклероз

Выраженныйнефросклероз

ВысокаяэкскрецияUMOD

Умененнаяинизкаяэкскреция

р<0,05

*->50лет(м)или>55лет(ж),**-гемоглобин<130г/л(м)или<120г/л(ж)ПУ–протеинурия,НС–нефротическийсиндром,АГ–артериальнаягипертония

UMOD / COL4 Старший возраст*

ПУ ≥ 0,5 г/сут НС Тяжелая

АГСКФCKD-EPI < 60 ml/min/

1,73 m2 Анемия**

UMOD >82 мкг/г, COL4 <3,2 мкг/г, n = 15

13,3% 46,7% 26,7% 13,3% 13,3% 13,3%

UMOD >82 мкг/г, COL4 >3,2 мкг/г, n = 5

40,0% 80,0% 60,0% 20,0% 0,0% 0,0%

UMOD <82 мкг/г, COL4 <3,2 мкг/г, n = 44

18,2% 72,7% 22,7% 29,6% 31,8% 15,9%

UMOD <82 мкг/г, COL4 >3,2 мкг/г, n = 16

62,5% 100,0% 56,3% 56,3% 62,5% 62,5%

Χ2=13,65; р<0,01

Χ2=11,50; р<0,01

Χ2=7,99; р<0,05

Χ2=7,25; 0,05≤ р<0,1

Χ2=11,49; р<0,01

Χ2=15,76; р<0,001

COL4 >3,2 мкг/г

UMOD >82 мкг/г

UMOD <82 мкг/г

COL4 <3,2 мкг/г

UMOD >82 мкг/гCOL4 <3,2 мкг/г

COL4 >3,2 мкг/г

UMOD <82 мкг/гСамаяблагоприятнаягруппа

СамаяНЕблагоприятнаягруппа

Выраженноеповреждение,умеренноепрогрессирование

Умеренноеповреждение,ускоренноепрогрессирование

1.  УромодулинзанимаетуникальноеместосредибиомаркеровХБП:неявляясьмаркеромповрежденияпочек,онотражаетсостояниефенотипаканальцевогоэпителия,развитиетубулоинтерстициальногофиброза.

2.  Важнымидостоинствамиуромодулинакакбиомаркераявляютсяеговысокаяспецифичностьдляпочек(синтезируетсяисключительнотубулоцитамивосходящейчастипетлиГенлеиначальныхотделовдистальныхканальцев)ивысокаяпродукция(сопоставимасуровнемальбуминурииуздоровыхлюдей),чтоповышаетточностьегоопределениявмоче.

3.  Имеющиесяклиническиеданныесвидетельствуютосочетаниинизкойпродукцииуромодулинапочкамисоснижениемихфункциииразвитиемнефросклероза.Втожевремявысокаяегопродукциясвязанасблагоприятнымпрогнозомдажеупациентовсмассивнойпротеинурией.

4.  Необходимыпроспективныеисследования