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Aging Cell. 2019 Dec;18(6):e13039. doi: 10.1111/acel.13039. Epub 2019 Sep 26.

Metformin blunts muscle hypertrophy in response to progressive resistance exercise training in older adults: A randomized, double-blind, placebo-controlled, multicenter trial: The MASTERS trial.

Author information

1
Center for Muscle Biology, College of Health Sciences, University of Kentucky, Lexington, Kentucky.
2
UAB Center for Exercise Medicine, University of Alabama at Birmingham, Birmingham, Alabama.
3
Department of Biostatistics, College of Public Health, University of Kentucky, Lexington, Kentucky.
4
Department of Statistics, College of Arts & Sciences, University of Kentucky, Lexington, Kentucky.
5
Department of Epidemiology, School of Public Health, University of Alabama at Birmingham, Birmingham, Alabama.
6
Department of Surgery, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.
7
Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.
8
Department of Cell, Developmental & Integrative Biology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.
9
Division of Endocrinology, Department of Medicine, University of Kentucky, Lexington, Kentucky.

Abstract

Progressive resistance exercise training (PRT) is the most effective known intervention for combating aging skeletal muscle atrophy. However, the hypertrophic response to PRT is variable, and this may be due to muscle inflammation susceptibility. Metformin reduces inflammation, so we hypothesized that metformin would augment the muscle response to PRT in healthy women and men aged 65 and older. In a randomized, double-blind trial, participants received 1,700 mg/day metformin (N = 46) or placebo (N = 48) throughout the study, and all subjects performed 14 weeks of supervised PRT. Although responses to PRT varied, placebo gained more lean body mass (p = .003) and thigh muscle mass (p < .001) than metformin. CT scan showed that increases in thigh muscle area (p = .005) and density (p = .020) were greater in placebo versus metformin. There was a trend for blunted strength gains in metformin that did not reach statistical significance. Analyses of vastus lateralis muscle biopsies showed that metformin did not affect fiber hypertrophy, or increases in satellite cell or macrophage abundance with PRT. However, placebo had decreased type I fiber percentage while metformin did not (p = .007). Metformin led to an increase in AMPK signaling, and a trend for blunted increases in mTORC1 signaling in response to PRT. These results underscore the benefits of PRT in older adults, but metformin negatively impacts the hypertrophic response to resistance training in healthy older individuals. ClinicalTrials.gov Identifier: NCT02308228.

KEYWORDS:

aging; exercise-drug interaction; muscle mass; strength training

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