Circulating Ghrelin levels are decreased in human obesity

Ghrelin is a novel endogenous natural ligand for the growth hormone (GH) se cretagogue receptor that has recently been isolated from the rat stomach. G hrelin administration stimulates GH secretion but also causes weight gain b y increasing food intake and reducing fat utilization in rodents. To invest igate the possible involvement of ghrelin in the pathogenesis of human obes ity, we measured body composition (by dual X-ray absorption) as well as fas ting plasma ghrelin concentrations (radioimmunoassay) in 15 Caucasians (8 m en and 7 women, 31 +/- 9 years of age, 92 +/- 24 kg body wt, and 29 +/- 10% body fat, mean a SD) and 15 Pima Indians (8 men and 7 women, 33 +/- 5 year s of age, 97 +/- 29 kg body wt, and 30 +/- 8% body fat). Pasting plasma ghr elin was negatively correlated with percent body fat (r = -0.45; P = 0,01), fasting insulin (r = - 0.45; P = 0.01) and leptin (r = -0.38; P = 0.03) co ncentrations. Plasma ghrelin concentration was decreased in obese Cancasian s as compared with lean Caucasians (P < 0,01), Also, fasting plasma ghrelin was lower in Pima Indians, a population with a very high prevalence of obe sity, compared with Caucasians (87 <plus/minus> 28 vs. 129 +/- 34 fmol/ml; P < 0,01), This result did not change after adjustment for fasting plasma i nsulin concentration. There was no correlation between fasting plasma ghrel in and height. Prospective clinical studies are now needed to establish the role of ghrelin in the pathogenesis of human obesity.