Which of the following correctly matches a gut-brain peptide with its principal pathway in appetite regulation?

• A. Peptide YY (PYY) increases appetite through the brainstem.
• B. Cholecystokinin (CCK) promotes hunger via the pancreas.
• C. Leptin stimulates appetite via the vagus nerve.
• D. Ghrelin stimulates appetite via the hypothalamus.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the role of gut-brain peptides in appetite regulation. These peptides are signaling molecules that communicate between the gastrointestinal system and the brain to regulate hunger and satiety.
2. Step 2: Analyze the function of each peptide mentioned in the problem. For example, Peptide YY (PYY) is known to reduce appetite, not increase it, by acting on the hypothalamus and brainstem. Cholecystokinin (CCK) reduces hunger by stimulating the vagus nerve and signaling satiety, not promoting hunger. Leptin, secreted by adipose tissue, suppresses appetite by acting on the hypothalamus, not stimulating it via the vagus nerve.
3. Step 3: Focus on the peptide Ghrelin. Ghrelin is often referred to as the 'hunger hormone' because it stimulates appetite. It is secreted by the stomach and acts on the hypothalamus to promote hunger.
4. Step 4: Match the correct pathway for Ghrelin. Ghrelin's primary pathway involves signaling to the hypothalamus, which is the brain region responsible for regulating hunger and energy balance.
5. Step 5: Conclude that the correct match is 'Ghrelin stimulates appetite via the hypothalamus,' as it aligns with the known biological function and pathway of this peptide.