ω3脂肪酸は高齢者の筋蛋白合成率を増加させるかも

ω3脂肪酸は高齢者の筋蛋白合成率を増加させるかもという論文を紹介します。

Smith GI, Atherton P, Reeds DN, Mohammed BS, Rankin D, Rennie MJ, Mittendorfer B. Dietary omega-3 fatty acid supplementation increases the rate of muscle protein synthesis in older adults: a randomized controlled trial. Am J Clin Nutr. 2010 Dec 15. [Epub ahead of print]

ω3脂肪酸は動物実験では筋蛋白同化を刺激する作用があるそうです。そこでサルコペニアの治療にω3脂肪酸が有効かもしれないということで、健常高齢者を対象に8週間、ω3脂肪酸もしくはコーンオイル（トウモロコシ）を投与して、筋蛋白合成率を比較したRCTです。

結果として、筋蛋白合成の基礎代謝率には変化がありませんでした。しかし、hyperaminoacidemia-hyperinsulinemia-induced increase in the rate of muscle protein synthesisは有意に増加したそうです。また、mTOR(Ser2448) (P = 0.08)とp70s6k(Thr389) (P < 0.01)のリン酸化反応が有意に増加したそうです。

この結果からω3脂肪酸は高齢者の筋蛋白合成率を増加させるという結論になっていますが、この結論は言い過ぎだと私は思います。また、実際の筋肉量を測定しているわけではありませんので、仮に結論が正しかったとしても、臨床で使用することはまだ不適切だと考えます。

ω3脂肪酸の使用を検討するのは、あくまで栄養障害の原因が前悪液質か悪液質と診断された場合のみと私は考えています。

Abstract
BACKGROUND: Loss of muscle mass with aging is a major public health concern. Omega-3 (n-3) fatty acids stimulate protein anabolism in animals and might therefore be useful for the treatment of sarcopenia. However, the effect of omega-3 fatty acids on human protein metabolism is unknown.

OBJECTIVE: The objective of this study was to evaluate the effect of omega-3 fatty acid supplementation on the rate of muscle protein synthesis in older adults.

DESIGN: Sixteen healthy, older adults were randomly assigned to receive either omega-3 fatty acids or corn oil for 8 wk. The rate of muscle protein synthesis and the phosphorylation of key elements of the anabolic signaling pathway were evaluated before and after supplementation during basal, postabsorptive conditions and during a hyperaminoacidemic-hyperinsulinemic clamp.

RESULTS: Corn oil supplementation had no effect on the muscle protein synthesis rate and the extent of anabolic signaling element phosphorylation in muscle. Omega-3 fatty acid supplementation had no effect on the basal rate of muscle protein synthesis (mean ± SEM: 0.051 ± 0.005 compared with 0.053 ± 0.008%/h before and after supplementation, respectively; P = 0.80) but augmented the hyperaminoacidemia-hyperinsulinemia-induced increase in the rate of muscle protein synthesis (from 0.009 ± 0.005%/h above basal values to 0.031 ± 0.003%/h above basal values; P < 0.01), which was accompanied by greater increases in muscle mTOR(Ser2448) (P = 0.08) and p70s6k(Thr389) (P < 0.01) phosphorylation.

CONCLUSION: Omega-3 fatty acids stimulate muscle protein synthesis in older adults and may be useful for the prevention and treatment of sarcopenia. This trial was registered at clinical trials.gov as NCT00794079.