Does Glucagon Increase Plasma Free Fatty Acid Concentration in Humans with Normal Glucose Tolerance

To evaluate the effect of glucagon on regulation of plasma FFA concentration, continuous iv infusions of either somatostatin (S) or somatostatin (S) plus glucagon (G) were administered to 18 individuals with normal glucose tolerance. In 9 of these individuals there was no insulin replacement, whereas in the other 9 individuals enough insulin was infused to restore the insulin concentration to the basal level. Measurements were made of plasma glucose, insulin, G, and FFA concentrations as well as hepatic glucose production (Ra). The results indicated that plasma FFA concentrations were significantly lower when G was infused (S > S + G) regardless of whether insulin was infused. However, similar elevations of the plasma G concentration did lead to higher values of Ra and plasma glucose, although the basal concentration of plasma insulin decreased the increases in Ra and plasma glucose caused by G. The ability of a similar amount of insulin to lower plasma FFA concentrations was greater in magnitude than the...