Building muscle, browning fat and preventing obesity by inhibiting myostatin.

Robert & Arlene Kogod Center on Aging, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
Diabetologia (Impact Factor: 6.88). 11/2011; 55(1):13-7. DOI: 10.1007/s00125-011-2361-8
Source: PubMed

ABSTRACT The obesity epidemic is an overwhelming global health concern. Interventions to improve body weight and composition aim to restore balance between nutrient intake and energy expenditure. Myostatin, a powerful negative regulator of skeletal muscle mass, has emerged as a potential therapeutic target for obesity and type 2 diabetes mellitus because of the prominent role skeletal muscle plays in metabolic rate and insulin-mediated glucose disposal. In fact, inhibition of myostatin by genetic manipulation or pharmacological means leads to a hypermuscular and very lean build in mice. The resistance of myostatin-null mice to diet-induced obesity, fat mass accumulation and metabolic dysfunction has been presumed to be a result of their large skeletal muscle mass; however, in this issue of Diabetologia, Zhang et al. (doi: 10.1007/s00125-011-2304-4 ) provide evidence that myostatin inhibition also significantly impacts the phenotype of white adipose tissue (WAT). The authors reveal elevated expression of key metabolic genes of fatty acid transport and oxidation and, intriguingly, the presence of brown adipose tissue-like cells in WAT of myostatin-null mice. They also show that pharmacological inhibition of myostatin replicates several of the protective benefits conveyed by its genetic inactivation. Herein, these data, areas in need of further investigation and the evidence that implicates myostatin as a target for obesity and type 2 diabetes mellitus are discussed.

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    ABSTRACT: Background A sedentary lifestyle is an independent risk factor for cardiovascular disease and exercise has been shown to ameliorate this risk. Inactivity is associated with a loss of muscle mass, which is also reversed with isometric exercise training. The relationship between muscle mass and vascular function is poorly defined. The aims of the current study were to determine whether increasing muscle mass by genetic deletion of myostatin, a negative regulator of muscle growth, can influence vascular function in mesenteric arteries from obese db/db mice. Methods and Results Myostatin expression was elevated in skeletal muscle of obese mice and associated with reduced muscle mass (30% to 50%). Myostatin deletion increased muscle mass in lean (40% to 60%) and obese (80% to 115%) mice through increased muscle fiber size (P<0.05). Myostatin deletion decreased adipose tissue in lean mice, but not obese mice. Markers of insulin resistance and glucose tolerance were improved in obese myostatin knockout mice. Obese mice demonstrated an impaired endothelial vasodilation, compared to lean mice. This impairment was improved by superoxide dismutase mimic Tempol. Deletion of myostatin improved endothelial vasodilation in mesenteric arteries in obese, but not in lean, mice. This improvement was blunted by nitric oxide (NO) synthase inhibitor l‐NG‐nitroarginine methyl ester (l‐NAME). Prostacyclin (PGI2)‐ and endothelium‐derived hyperpolarizing factor (EDHF)‐mediated vasodilation were preserved in obese mice and unaffected by myostatin deletion. Reactive oxygen species) was elevated in the mesenteric endothelium of obese mice and down‐regulated by deletion of myostatin in obese mice. Impaired vasodilation in obese mice was improved by NADPH oxidase inhibitor (GKT136901). Treatment with sepiapterin, which increases levels of tetrahydrobiopterin, improved vasodilation in obese mice, an improvement blocked by l‐NAME. Conclusions Increasing muscle mass by genetic deletion of myostatin improves NO‐, but not PGI2‐ or EDHF‐mediated vasodilation in obese mice; this vasodilation improvement is mediated by down‐regulation of superoxide.
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