E-Newsletter No. 31

Several hormones that affect appetite, satiety, and weight gain and loss have been identified. For example, insulin and leptin are long-term regulators: They are released from the pancreas and fat cells when the body's fat stores rise, and they exert sustained inhibition of food intake. In contrast, ghrelin [Refer to Newsletter No.27 for more information on ghrelin] (JW Jul 1 2002, p. 104, and N Engl J Med 2002; 346:1623, 1662) and cholecystokinin are short-term, food mediated hormones: Released from the gastrointestinal tract, ghrelin rises cyclically before meals and enhances appetite, whereas cholecystokinin rises after meal to suppress appetite. All of these hormones exert their effects by interacting with neurons in the hypothalamus. 

An international team identified another gut hormone, PYY3-36, which inhibits food intake in rats and mice and which acts through hypothalamic molecular signals and neural circuits (as do other appetite-related hormones). In a randomized crossover trial, 12 healthy, fasting, nonobese human volunteered received infusions of either PYY3-36 or saline and were served buffet meals. When the group received PYY3-36 food intake during the next 12 hours was about 30% less than when the group received saline. PYY3-36 had no effect on fluid intake, gastric emptying, or glucose, insulin, or leptin levels and did not lead to an increased sense of fullness. Thus, its effects on food intake were direct.

Comment: PYY3-36 is the latest hormone to be shown to play a major role in appetite and weight regulation. These findings establish its short-term effects in suppressing appetite. Much more work is needed to evaluate the long-term benefits and risks of using this hormone or its analogues as therapeutic agents.

Batterham RL et al. Gut hormonePYY3-36 physiologically inhibits food intake.
Nature 2002 Aug 8; 418:650-4.

Schwartz MW and Morton GJ. Keeping hunger at bay. Nature 2002 Aug 8; 418:595-7.

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