Glucose Tolerance during Moderate Alcohol Intake: Insights on Insulin Action from Glucose/Lactate Dynamics

Abstract

Moderate alcohol (ETOH) intake has been associated with a significant reduction in risk for infarction among general populations. In this study, we assessed the effects of low-dose ETOH (40 g over 3-h period as vodka) on the interaction between glucose (G), insulin, and lactate (L) during the insulin-modified frequently sampled iv glucose tolerance test (FSIGT) (0.3 U/kg body weight between 20-25 min) in eight normal volunteers. In the control (C) study, water was administered. An insulin-independent two-compartment model was used to describe G and L kinetics. Insulin sensitivity (S 1 ) was significantly higher in the ETOH study than in the C study (2.49 ± 0.52 vs. 0.92 ± 0.20 10 -4 min -1 μU -1 ml, C vs. ETOH; P = 0.0391). No significant differences were observed in G effectiveness (0.029 ± 0.004 vs. 0.033 ± 0.004 min -1 ). Blood L levels were higher during FSIGT when ETOH was administered [area under the curve (AUC), 201 ± 16 vs. 123 ± 23 mmol/liter in 240 min; P = 0.0001]. The dynamic analysis of blood L concentrations showed that ETOH also significantly decreased L clearance (0.0016 ± 0.0011 vs. 0.0029 ± 0.0002 min -1 ; P = 0.0156), whereas no difference was observed for the fractional conversion of the rate of G disappearance to L (0.0033 ± 0.0012 vs. 0.0031 ± 0.0005 min -1 ). ETOH decreased baseline plasma FFA concentration; AUC of FFA was markedly reduced with ETOH (65 ± 14 vs. 109 ± 17 mmol/liter in 240 min; P = 0.0063) and inversely correlated with S 1 (r = 0.693; P = 0.0029). The amount of C-peptide in 240 min as well as the amounts before and after insulin administration were not different between the two tests. We concluded that G and L kinetics derived from FSIGT shows that moderate ETOH intake: 1) improves insulin action; 2) decreases L clearance; and 3) does not affect β cell function. Because ETOH at moderate doses has a marked antilipolytic action, it might improve insulin action by improving substrate competition. The present findings suggest that moderate alcohol consumption in the diet should not be discouraged.