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

http://www.nytimes.com/library/national/science/051199sci-diet-drug.html

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