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.
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.
['Walton|R Grace|RG|', 'Dungan|Cory M|CM|', 'Long|Douglas E|DE|', 'Tuggle|S Craig|SC|', 'Kosmac|Kate|K|', 'Peck|Bailey D|BD|', 'Bush|Heather M|HM|', 'Villasante Tezanos|Alejandro G|AG|', 'McGwin|Gerald|G|', 'Windham|Samuel T|ST|', 'Ovalle|Fernando|F|', 'Bamman|Marcas M|MM|', 'Kern|Philip A|PA|', 'Peterson|Charlotte A|CA|0000-0001-9340-0705']
D000368:Aged D000369:Aged, 80 and over D001823:Body Composition D001835:Body Weight D002478:Cells, Cultured D004311:Double-Blind Method D015444:Exercise D005260:Female D005947:Glucose D006801:Humans D007004:Hypoglycemic Agents D008297:Male D008687:Metformin D008875:Middle Aged D053580:Muscle Strength D018482:Muscle, Skeletal D055070:Resistance Training D014057:Tomography, X-Ray Computed
aging muscle mass exercise-drug interaction strength training