24-hour profiles of circulating ghrelin and peptide YY are inversely associated in normal weight premenopausal women.

Peptide YY (PYY) and ghrelin (GHR) may modulate one another's actions within the hypothalamus. Peripheral infusion of PYY in humans acutely suppresses circulating concentrations of GHR. Whether an association between PYY and GHR exists in the peripheral circulation of humans over 24h is unknown. The purpose of this study was to determine if circulating concentrations of PYY and GHR were significantly associated over 24h in humans. Participants (n=13) were normal weight, moderately active, women ages 18-24 yr. Blood samples were obtained q10 min for 24 h and assayed using RIA for total PYY and total GHR hourly from 0800 to 1000 h and 2000 to 0800 h and q20 min from 1000 to 2000 h. Dietary intake during the 24 h procedure was comprised of 55% carbohydrates, 30% fat, and 15% protein (three meals and a snack). Statistical analyses included linear mixed-effects modeling to test whether PYY predicted GHR concentrations over 24h. Participants weighed 57.0±1.5 kg and had 26.1±1.5% body fat (15.0±1.1 kg), 42.1±1.1 kg fat free mass, a BMI of 21.3±0.5 kg/m(2) and RMR of 1072±28 kcal/24 h. Visually, PYY and GHR exhibited an inverse association over nearly the entire 24h period. Statistically, circulating concentrations of 24 h PYY predicted 24 h GHR (ghrelin=1860.51-2.14*PYY; p=0.04). Circulating concentrations of PYY are inversely associated with GHR over 24 h. These data provide evidence that PYY may contribute to the modulation of the secretion of GHR in normal weight, premenopausal women over a 24 h period and supports similar inferences from experimental studies in animals and humans.