Acute hormonal changes following intravenous glucose challenge in lean and obese human subjects

To study the effects of rapid i.v. glucose bolus on insulin, leptin, ghrelin, peptide YY (PYY), free fatty acids (FFA), glucagon and glucagon-like peptide-1 (GLP-1) concentrations together with self-reported satiety ratings in lean and obese human subjects.

Twenty-five healthy subjects were recruited, 12 were lean (mean age = 26 years, BMI range = 19.8-23.9 kg/m(2)) and 13 were obese (mean age = 27 years, BMI range = 27.7-42.2 kg/m(2)). In two separate 55 min counter-balanced blinded sessions (separate days), subjects were administered an i.v. dose of 300 mg/kg glucose or saline. Blood concentrations of several feeding-related hormones were recorded at multiple time points, together with ratings of satiety and euphoria.

Greater increases in glucose concentrations were observed in the obese group compared to the lean group (p < 0.0001). In both lean and obese subjects, glucose injection induced a clear fall in the concentrations of FFA, ghrelin, glucagon and PYY (p < 0.0001) but not in the concentrations of leptin or GLP-1. Obese subjects showed positive correlations between satiety and glucose, but only at time points 30 min (r = 0.73, p = 0.005) and 55 min (r = 0.82, p = 0.0005).

The directions and the magnitudes of short-term hormonal changes after i.v. glucose challenge are the same in lean and moderately obese subjects. Possible short-term regulatory effects of leptin and GLP-1 can not be induced by acute energy load bypassing the GI-tract.