Leptin, secreted by adipocytes, reduces food intake primarily by acting on:

• A Ventromedial hypothalamic nucleus to stimulate NPY/AgRP neurons
• B Arcuate nucleus hypothalamic neurons expressing POMC/CART, increasing alpha-MSH to suppress appetite ✓
• C Vagal afferents in the gut wall, reducing gastric motility
• D Pituitary gland to increase TSH and GH secretion

Explanation

Leptin binds Ob-Rb receptors on arcuate nucleus POMC/CART neurons, stimulating alpha-MSH production, which acts on MC4R receptors in the paraventricular nucleus to reduce food intake; leptin also inhibits NPY/AgRP neurons. The ventromedial nucleus is a satiety centre but not the primary site of leptin action for appetite suppression. Leptin does not primarily act on vagal afferents or pituitary for appetite control.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

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