Inhibition of the endocannabinoid system reverses obese phenotype in aged mice and partly restores skeletal muscle function

Sarcopenia, the age-related loss of skeletal muscle mass, is associated with lipid accumulation and anabolic resistance; phenom-ena also observed in obesity and worsen when obesity and aging are combined. The endocannabinoid system (ECS) is overacti-vated in obesity, but its role in aging obesity-related muscle dysfunction is unknown. The aims of this study were to evaluate the effect of inhibition of the ECS by rimonabant (RIM) on the metabolic alterations induced by a high-fat high-sucrose diet and on skeletal muscle mass/function in aged mice. Eighteen-month-old male mice were subjected to a control (CTL) or a high-fat high-sucrose (HFHS) diet for 24 weeks. Mice were administered with saline or RIM (10 mg/kg/day) for the last 4 weeks of the diet. Skeletal muscle function was evaluated by open-field, rotarod, and grip strength tests. Metabolic alterations in liver, adipose tissue, and skeletal muscle were investigated by quantitative RT-PCR. Body mass was higher in HFHS mice compared to CTL mice (48.0 +/- 1.5 vs. 33.5 +/- 0.7 g, P < 0.01), as a result of fat accumulation (34.8 +/- 1.0 vs. 16.7 +/- 0.8%, P < 0.01). RIM reduced body fat mass in both CTL (-16%, P < 0.05) and HFHS conditions (-40%, P < 0.01), without affecting hindlimb skeletal muscle mass. In HFHS mice, grip strength evolution was improved (-0.29 +/- 0.06 vs. -0.49 +/- 0.06 g/g lean mass, P < 0.05), and rotarod activity was increased by r-:::60% in response to RIM (45.9 +/- 6.3 vs. 28.5 +/- 4.6 cm, P < 0.05). Lipolysis and I3-oxidation genes were upreg-ulated in the liver as well as genes involved in adipose tissue browning. These results demonstrate that inhibition of the ECS induces metabolic changes in liver and adipose tissue associated with a reversion of the obese phenotype and that RIM is able to improve motor coordination and muscle strength in aged mice, without affecting skeletal muscle mass.NEW & NOTEWORTHY In 24-month-old mice submitted to high-fat high-sucrose-induced obesity, inhibition of the endocannabi-noid system by rimonabant reversed the obese phenotype by promoting adipose tissue browning and I3-oxidation in the liver but not in skeletal muscle. These metabolism modifications are associated with improved skeletal muscle function.