Hyposomatotropism blunts lipolysis in abdominally obese women

Abdominal obesity is associated with reduced 24-h plasma GH concentrations. It is unclear whether hyposomatotropism in abdominally obese humans is compensated by up-regulation of GH receptor sensitivity or causes less biological effect in target tissues. We, therefore, determined the responsiveness of adipose tissue to the lipolytic action of GH in abdominally obese (OB) and normal weight (NW) postmenopausal women. An iv bolus of recombinant human GH or placebo was randomly administered to eight NW [body mass index (BMI): 22.2 ± 1.6 kg/m²] and eight abdominally OB (BMI: 32.1 ± 2.6 kg/m²) women. Lipolysis was measured by infusion of D5-glycerol and modeled as a function of plasma GH concentrations to describe adipose tissue responsiveness. Similar plasma GH concentration peaks (∼20 mU/liter) were achieved by GH injection in both groups. During placebo conditions, the average plasma GH level was significantly lower in OB compared with NW women (0.74 ± 0.52 vs. 2.08 ± 1.18 mU/liter, P = 0.023). Adipose tissue responsiveness, expressed as glycerol rate of appearance per kilogram of fat mass per unit plasma GH concentration was not different in both groups (NW: 1.06, OB: 0.68, P > 0.05). These results suggest that hyposomatotropism in abdominally obese individuals is not compensated by increased adipose tissue responsiveness to GH bio-action and, therefore, blunts lipolysis in these individuals.