Effects Of Metformin On Training Adaptations In Hyperglycemic Individuals With Metabolic Syndrome

Abstract

PURPOSE: To determine if chronic metformin use interferes with the improvements in insulin resistance and cardiorespiratory fitness of intense aerobic training in hyperglycemic metabolic syndrome individuals (MetS). METHODS: Sixty-three middle-aged (53 ± 7 y) MetS with obesity (BMI, 32.8 ± 4.5 kg·m-2) completed 16-weeks of supervised high intensity interval exercise-training (3 days·week-1, 43 min per session). Participants were either taking metformin (EXER+MET; n = 29) or free of any pharmacological treatment for their MetS factors (EXER; n = 34). Groups were similar in their initial cardiorespiratory fitness (VO2MAX), age, percent of women, BMI, and MetS deviation from normality (Z score). We measured the effects of exercise-training on fasting glucose and insulin concentrations, homeostasis model of insulin resistance (HOMA-IR), MetS Z score, VO2MAX, maximal fat oxidation during exercise (FOMAX) and maximal aerobic power output (POMAX). RESULTS: HOMA-IR decreased similarly in both groups with training (EXER+MET, -12.9%; EXER, -14.8%; P time = 0.023 and P time x group = 0.761). MetS Z score improved similarly in both groups with training (EXER+MET, -0.19 ± 0.49; EXER, -0.25 ± 0.25; P time < 0.001 and P time x group = 0.541). However, metformin use reduced by half VO2MAX improvements with training (i.e., EXER+MET 12.7%, 0.22 ± 0.27 L·min-1; EXER 25.3%, 0.44 ± 0.29 L·min-1, P time x group =0.002). FOMAX increased similarly in both groups (EXER+MET, -20.7%; EXER, 25.3%; P time < 0.001 and P time x group = 0.569). CONCLUSIONS: In summary chronic metformin treatment does not affect fasting insulin sensitivity improvements with aerobic exercise-training in hyperglycemic individuals with high cardiovascular risk (i.e., MetS). Although metformin use attenuates training VO2MAX improvements this does not preclude MetS improvements with training.