Cafeteria diet-induced obesity is associated with a low spontaneous growth hormone secretion and normal plasma insulin-like growth factor-I concentrations

Abstract

Pituitary growth hormone (GH) secretion has been shown to be blunted in human and animal obesity. With respect to human obesity, cafeteria diet-induced obesity might be an appropriate model to study spontaneous GH secretion. In 6 cafeteria diet-overfed obese male Wistar rats and 6 control rats with chronically implanted catheters, GH levels were measured every 15 min over 6 h by standard RIA. A significantly lower GH secretion, reflected by the integrated GH concentration, was found in the obese rats (median 16.46, [range 10.55-19.13] ng/ml x 6 h vs 35.63 [range 21.90-41.50] ng/ml x 6 h, P < 0.05). The GH secretion in the obese rats was significantly negatively correlated with the body fat percentage, assessed by dual X-ray absorptiometry (Rho = -0.95, P < 0.05). Median plasma insulin-like growth factor-I (IGF-I) concentration was comparable between the two groups, while the median insulin concentration was significantly higher in the obese group (1.95 [range 1.76-3.55] ng/ml vs 1.21 [range 0.86-2.13] ng/ml, P < 0.05). No significant correlation existed between GH secretion and the plasma insulin concentration. In conclusion, cafeteria diet-induced obesity is associated with a low spontaneous GH secretion and normal plasma IGF-I concentration. The hyperinsulinemia present in this model probably explains the normal IGF-I concentrations, but not the GH hyposecretion.