Metformin attenuates metabolic insulin sensitivity and insulin-stimulated carbohydrate oxidation after high-intensity exercise training in adults at risk for metabolic syndrome
Abstract
Aims: Mixed evidence exists on whether metformin adds to or attenuates the insulin-sensitising effects of exercise. To date, no studies have tested whether metformin differentially impacts exercise training intensity-mediated insulin sensitivity. We tested the hypothesis that metformin would blunt metabolic insulin sensitivity and carbohydrate oxidation in an intensity-based manner among adults with metabolic syndrome (MetS) risk.
Materials and methods: In a double-blind, placebo-controlled trial, participants were randomised to low-intensity exercise plus placebo (~55% VO2max 5 days/week, LoEx + PL, n = 22) or metformin (2000 mg/day, LoEx + Met, n = 21) and high-intensity exercise plus placebo (~85% VO2max 5 days/week, HiEx + PL, n = 24) or metformin (HiEx + Met, n = 24) for 16 weeks. A 120-min euglycaemic-hyperinsulinemic clamp (40 mU/m2/min, 90 mg/dL) was conducted pre- and post-treatment to assess metabolic insulin sensitivity (M-value/insulin). Fasting and insulin-stimulated carbohydrate oxidation was also assessed using indirect calorimetry. Adipokines (leptin, high molecular weight (HWM), and total adiponectin) were measured at 0 and 120 min of the clamp. Aerobic fitness (VO2max) and body composition (DXA) were also analysed.
Results: HiEx + PL increased metabolic insulin sensitivity (p = 0.017) while HiEx + Met, LoEx + PL, or LoEx + Met did not. HiEx + PL also raised insulin-stimulated carbohydrate oxidation and decreased fat oxidation compared with LoEx + Met (both,…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 24 participants or records.
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