Role of n-3 fatty acids in muscle loss and myosteatosis.

Image-based methods such as computed tomography for assessing body composition enables quantification of muscle mass and muscle density and reveals that low muscle mass and myosteatosis (fat infiltration into muscle) are common in people with cancer. Myosteatosis and low muscle mass have emerged as independent risk factors for mortality in cancer; however, the characteristics and pathogenesis of these features have not been resolved. Muscle depletion is associated with low plasma eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) in cancer and supplementation with n-3 fatty acids has been shown to ameliorate muscle loss and myosteatosis in clinical studies, suggesting a relationship between n-3 fatty acids and muscle health. Since the mechanisms by which n-3 fatty acids alter body composition in cancer remain unknown, related literature from other conditions associated with myosteatosis, such as insulin resistance and obesity is considered. In these noncancer conditions, it has been reported that n-3 fatty acids act by increasing insulin sensitivity, reducing inflammatory mediators, and altering adipokine profiles and transcription factors; therefore, the plausibility of these mechanisms of action in the neoplastic state are considered. The aim of this review is to summarize what is known about the effects of n-3 fatty acids with regards to muscle condition and to discuss potential mechanisms for effects of n-3 fatty acids on muscle health.