Effects of growth hormone administration on protein dynamics and substratemetabolism during 4 weeks of dietary restriction in obese women

OBJECTIVE Treatment of obesity with very low calorie diet (VLCD) is complic ated by protein loss. We evaluated the effects of coadministration of GH on protein turnover, substrate metabolism, and body composition in VLCD treat ed obesity. DESIGN AND PATIENTS Fifteen obese women underwent 4 weeks of very low calor ie diet (VLCD) in parallel with GH treatment (n = 7) or placebo (n = 8). MEASUREMENTS Protein metabolism and total glucose turnover were isotopicall y assayed. Plasma concentrations of amino acids were determined by an HPLC system. Estimated rates of lipid and glucose oxidation were obtained by ind irect calorimetry. Fat free mass was determined by DEXA-scan. RESULTS Protein breakdown decreased in both groups (tyrosine flux mu mol/h) : -12% +/- 3 (GH) vs. - 9% +/- 3 (placebo)). Phenylalanine degradation in r elation to phenylalanine concentration decreased by 9% in the GH group, whe reas an increase of 8% was observed in the placebo group (P = 0.1). Plasma concentrations of several amino acids were significantly decreased in the p lacebo group, while urea excretion decreased in the GH group. A decrease in FFM was found in placebo treated patients (2.14% +/- 1.9 (GH) vs. - 3.54% +/- 1.6 (placebo), P < 0.05). Rates of lipid oxidation tended to be increas ed by GH treatment (lipid oxidation (mg/minutes): 79.7 +/- 5.9 (GH) vs. 64. 6 +/- 5.9 (placebo), P = 0.1). CONCLUSION During dietary restriction GH primarily seems to conserve protei n by a reduced hepatic degradation of amino acids.