Leptin and obesity

指導：周淑娥教授、洪偉珊助教組員： 57陳昱愷、 60陳重宇

Obesity• When people take in excessive energy-rich

molecules, they are converted to storage molecules.

• Order of storage: liver, muscle (glycogen) →adipose cells (fat)

• Order of expenditure ： liver → muscle, adipose cells

Oil drops

adipose cells

nucleus

Diseases• Obesity contributes to a number of healthy

problems, including the common type of diabetes, cancer of colon and breast, and cardiovascular disease.

D.Coleman’s experiment

• In 1973, scientists discovered that mice with mutant ob gene or db gene eat voraciously and grow much more than normal mice.

• To explore the roles of genes, Coleman surgically linked mice’s circulatory systems.

• In 1995, Jeffrey M. Friedman discover leptin and its role in regulating body weight.

• ob-deficient mice are injected with leptin and lose 30% weight.

ob-deficient mice do not produce leptin.• db-deficient mice are injected with leptin

and have no change.

db-deficient mice do not produce the receptor for leptin.

Result

Leptin

•Leptin (Greek leptos meaning thin) plays a key role in regulating energy intake and energy expenditure, including appetite and metabolism. •The gene is located on chromosome 7 in humans.

•It is manufactured primarily in the adipocytes of white adipose tissue, and the level of circulating leptin is directly proportional to the total amount of fat in the body.

• Leptin acts on receptors in the hypothalamus (1)counteracting the effects of neuropeptide Y (2) counteracting the effects of anandamid(3) promoting the synthesis of α-MSH, an

appetite suppressant.

• This inhibition is long-term.

The absence of leptin (or its receptor) leads to

uncontrolled food intake and resulting obesity.

function

Leptin resistance and obesity

• In general, obese people have an unusually high circulating concentration of leptin.

•These people are said to be resistant to the effects of leptin, in much the same way that people with type 2 diabetes are resistant to the effects of insulin.

Fructose and leptin resistance

•A study suggests that the consumption of high amounts of fructose causes leptin resistance and elevated triglycerides in rats.

Conclusion

• As of today, there are at least five genes and ten kinds of hormones associated with the regulation of body weight.

• Reducing the intake of calorie and increasing the consumption of calorie is still the only feasible way to lose weight.