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