Serum Hormone Levels and Tissue Metabolism in Pair-Fed Lean and Obese Zucker Rats[*]

Abstract

Obese Zucker rats were either pair-fed to their lean littermates or fed ad lib. to determine the effect of hyperphagia on serum hormone levels and tissue metabolism as indicated by enzyme activities and in vitro metabolite flux. Hyperphagia was shown to be non-essential for the elevation in serum insulin and suppression in serum growth hormone and prolactin in the genetically obese rat. It was also shown that the increased liver cell lipogenic rate was not dependent on hyperphagia in the obese rat and that adipose cell lipogenesis was not significantly altered in the pair-fed obese rat. The utilization of alanine for glucose synthesis in vitro was similar for both lean and obese rats, but its utilization for fatty acid synthesis was higher in the obese rat. Data is presented which suggest that the inhibitory effect of glucagon on liver lipogenesis is blunted in the obese rat.

Key words

Lipid Metabolism - Insulin - Growth Hormone - Prolactin - Enzymes

1 Authorized for publication on June 21, 1976 as paper no. 5108 in the journal series of the Pennsylvania Agriculture Experiment Station. Supported in part by NIH Grant No. HD 0709-04

1 Authorized for publication on June 21, 1976 as paper no. 5108 in the journal series of the Pennsylvania Agriculture Experiment Station. Supported in part by NIH Grant No. HD 0709-04