Regulation of food intake

Food intake Regulation –Endocrine Adipose tissue Pancreas Liver Muscle –CNS

Critical area of study –Type II diabetes Obesity –Hormones involved in appetite regulation Interaction with insulin –Glucose uptake –Triglyceride metabolism

Endocrine factors Adipose tissue –Leptin –Adiponectin –Resistin GI tract –Ghrelin

Leptin Product of ob gene –16 kDa –No major similarity with other hormones

Produced by differentiated adipocytes –Acts on the CNS Hypothalamus Anorectic hormone –Appetite suppression –Acts on endocrine organs Pancreas Liver

Interaction with reproductive axis –Starvation Reduced leptin level Reduced reproductive efficiency –Suppression of HP-gonadal axis –Interaction between food intake and reproduction (detection of energy adequacy)

Mechanism of action –Leptin receptor Type I cytokine receptor –Several isoforms Found throughout body Leptin binding proteins

Mechanism of action –CNS Suppression of neuropeptide Y expression in brain –Suppression of appetite

Circulating leptin concentrations –Determined by body fat mass –Secretion regulated by nonhormonal and hormonal factors Stimulatory –Insulin –Glucocorticoids –Overeating Inhibitory –Fasting –cAMP –Beta receptor agonists

Clinical significance Hyperleptinemia –Human obesity Associated with body mass index Basal leptin concentrations –Positively correlated with insulin if a person is insulin-sensitive –Not influenced by age, basal glucose concentrations

Eating disorder –Anorexia nervosa and bulimia nervosa Leptin concentrations relfect BMI –Body fat content Weight maintenance –Leptin concentrations reflect body fat mass Weight loss/gain –Sensor of energy imbalance