2型糖尿病の筋蛋白同化

2型糖尿病の筋蛋白同化のレビュー論文を紹介します。

Bassil MS, Gougeon R. Muscle protein anabolism in type 2 diabetes. Curr Opin Clin Nutr Metab Care. 2012 Nov 28. [Epub ahead of print]

2型糖尿病では筋蛋白同化の異常を認めます。加齢による筋萎縮を加速させます。これはインスリン抵抗性に関連していると思われます。一方、アミノ酸、特にBCAAの投与によってインスリン抵抗性を克服できるかもしれません。

高齢2型糖尿病患者に対するロイシン投与の先行研究では、筋肉量増加を認めませんでした。しかし、この研究ではサルコペニアではなく十分なタンパク質を摂取していたので、非定型な結果かもしれません。運動や身体活動も蛋白同化のインスリン抵抗性の克服に有効かもしれません。

糖尿病では筋障害による筋萎縮だけでなく、末梢神経障害による筋萎縮も合併しやすいです。また糖尿病性腎症で慢性腎不全となった場合、悪液質も合併することがあります。このように広義のサルコペニアの原因が多彩となるため、適切な評価と対応が求められます。

Abstract

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.