Purpose of review: Protein anabolism is abnormal in human type 2 diabetes (T2DM). We review studies of anabolic stimuli that identify potential causes. If uncorrected, and combined with aging effects, they will compromise muscle function and mass. Knowing causes can guide studies of preventive and treatment measures.
Recent findings: T2DM accelerates age-related decreases in muscle mass. This could be related to insulin resistance of whole-body protein anabolism demonstrated in hyperglycemic obese men. In contrast, their protein anabolic response to hyperaminoacidemia suggested that ample amino acid administration, especially branched chain amino acids might overcome such insulin resistance. One study of chronic leucine supplementation in elderly T2DM patients did not increase muscle mass. However, they lacked sarcopenia and had adequate dietary protein intake, so may be atypical. Exercise induced similar increases in muscle protein synthesis, mass and strength in healthy and T2DM patients suggesting that physical activity might also overcome insulin resistance of protein anabolism.
Summary: Muscle protein anabolism in T2DM is resistant to the action of insulin but perhaps not to amino acid supply or exercise. Whether leucine supplementation improves muscle mass and function in persons with T2DM (especially elderly) with reduced protein intake or muscle mass needs to be determined.