Interaction of free fatty acids and epinephrine in regulating hepatic glucose production in conscious dogs

Abstract

To determine the effects of an increase in lipolysis on the glycogenolytic effect of epinephrine (EPI), the catecholamine was infused portally into 18-h-fasted conscious dogs maintained on a pancreatic clamp in the presence [portal (Po)-EPI+FFA, n = 6] and absence (Po-EPI+SAL, n = 6) of peripheral Intralipid infusion. Control groups with high glucose (70% increase) and free fatty acid (FFA; 200% increase; HG+FFA, n = 6) and high glucose alone (HG+SAL, n = 6) were also included. Hepatic sinusoidal EPI levels were elevated (Δ568 ± 77 and Δ527 ± 37 pg/ml, respectively) in Po-EPI+SAL and EPI+FFA but remained basal in HG+FFA and HG+SAL. Arterial plasma FFA increased from 613 ± 73 to 1,633 ± 101 and 746 ± 112 to 1,898 ± 237 μmol/l in Po-EPI+FFA and HG+FFA but did not change in EPI+SAL or HG+SAL. Net hepatic glycogenolysis increased from 1.5 ± 0.3 to 3.1 ± 0.4 mg · kg−1 · min−1( P < 0.05) by 30 min in response to portal EPI but did not rise (1.8 ± 0.2 to 2.1 ± 0.3 mg · kg−1 · min−1) in response to Po-EPI+FFA. Net hepatic glycogenolysis decreased from 1.7 ± 0.2 to 0.9 ± 0.2 and 1.6 ± 0.2 to 0.7 ± 0.2 mg · kg−1 · min−1by 30 min in HG+FFA and HG+SAL. Hepatic gluconeogenic flux to glucose 6-phosphate increased from 0.6 ± 0.1 to 1.2 ± 0.1 mg · kg−1 · min−1( P < 0.05; by 3 h) and 0.7 ± 0.1 to 1.6 ± 0.1 mg · kg−1 · min−1( P < 0.05; at 90 min) in HG+FFA and Po-EPI+FFA. The gluconeogenic parameters remained unchanged in the Po-EPI+SAL and HG+SAL groups. In conclusion, increased FFA markedly changed the mechanism by which EPI stimulated hepatic glucose production, suggesting that its overall lipolytic effect may be important in determining its effect on the liver.