Post-Prandial Glucose Levels Are Elevated by Metformin after High Intensity Exercise Training in Metabolic Syndrome.

Abstract

The clinical implications of metformin attenuating the insulin sensitizing effects of exercise are unclear. We tested the hypothesis that metformin would blunt reductions in post-prandial glucose in an exercise intensity-based manner in adults with metabolic syndrome (MetS) risk. In a double-blind trial, participants were randomized to low intensity exercise plus placebo (~55%VO2max 5d/wk, LoEx+PL, n=22) or metformin (2000mg/d, LoEx+Met, n=21) and high intensity exercise plus placebo (~85%VO2max 5d/wk, HiEx+PL, n=24) or metformin (HiEx+Met, n=24) for 16 weeks. A 120-min 75g oral glucose tolerance test was conducted pre- and post-treatment to assess early (0-30min), late (60-120min), and total (0-120min) phase glucose tolerance and circulating insulin (total area under the curve; tAUC). HiEx+Met increased 1-hr and 2-hr glucose by ~18-21mg/dl (P<0.04), and this was different from HiEx+PL (both, P=0.008). Late phase and total phase glucose tAUC was also higher after HiEx+Met versus HiEx+PL and LoEx+PL (both, P<0.02). Only total phase insulin tAUC was lower after HiEx+Met versus HiEx+PL and LoEx+PL (both, P<0.04). Increased metabolic insulin sensitivity related to reduced late and total phase glucose tAUC (both, P<0.04) after exercise training only. Metformin increased post-prandial glucose after high, but not low, intensity exercise training in adults with MetS risk.