Endogenous Glucagon Regulation in Genetically Hyperlipemic Obese Rats

Glucagon concentration and regulation were examined in the Zucker rat, in which obesity and hyperlipemia are phenotypic expressions of an autosomal recessive gene. Using littermate animals which are phenotypically thin and normolipemic as controls, we observed reduced basal plasma glucagon levels in the obese lipemic rats. In response to fasting, obese lipemic animals inappropriately demonstrated a further reduction in plasma glucagon concentration. In response to pharmacologic glucagon stimulation (arginine), a subnormal rise in plasma glucagon concentration was observed in the obese, lipemic animals. Glucagon suppressibility with exogenous glucose remained intact. The reduced secretion of glucagon may be a consequence of the abnormal elevation in concentration of plasma insulin, free fatty acids, and glucose, which are characteristic of the obese, lipemic animal. A possible role of glucagon deficiency in the evolution or maintenance of the lipemic state is suggested.