非小細胞肺癌での骨格筋減少とn-3脂肪酸の関連

非小細胞肺癌での骨格筋減少とn-3脂肪酸の関連に関する論文を紹介します。

Rachel A. Murphy, et al: Skeletal Muscle Depletion Is Associated with Reduced Plasma (n-3) Fatty Acids in Non-Small Cell Lung Cancer Patients. J. Nutr. (July 14, 2010). doi:10.3945/jn.110.123521

結論としては、非小細胞肺癌患者では、サルコペニア（ここでは広義のサルコペニアで、悪液質による二次性サルコペニアの要素が大きいと考えます）の場合に、EPA、DHA、n-3脂肪酸の血中濃度が低いという関連を認めたということです。

EPA、DHA、n-3脂肪酸が少ないから骨格筋が減少するのかどうかの因果関係は断言できませんが、少ないために全身炎症が生じやすく、その結果サルコペニアになりやすい可能性はあります。

一方、悪液質による二次性サルコペニアだからEPA、DHA、n-3脂肪酸が少ないという可能性もあります。

悪液質による二次性サルコペニアでは、EPA、DHA、n-3脂肪酸を投与することで全身炎症が少なくなり、筋肉量をより保つことができる可能性があります。

Upwards of 50% of newly diagnosed advanced lung cancer patients have severe muscle wasting (sarcopenia). Supplementation with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in advanced cancer has been shown to attenuate lean tissue wasting. However, the relationship between muscle mass and plasma (n-3) fatty acids in the absence of supplementation is unclear. We aimed to determine how plasma phospholipid (n-3) fatty acids relate to sarcopenia and change in muscle mass in non-small cell lung cancer patients receiving chemotherapy. Computed tomography images were used to measure muscle mass. Patients were classified as sarcopenic or nonsarcopenic based on sex-specific cutpoints. Change in muscle mass during chemotherapy (2.5 mo) was calculated and patients were divided into quartiles based on the rate of muscle loss or gain. Patients with sarcopenia had lower plasma EPA (16.7 ± 2.1 µmol/L vs. 31.6 ± 4.4 µmol/L; P = 0.001), DHA (36.6 ± 4.0 µmol/L vs. 55.3 ± 4.0 µmol/L; P = 0.003), and (n-3) fatty acids (63.6 ± 5.6 µmol/L vs. 95.0 ± 7.7 µmol/L; P = 0.002) than nonsarcopenic patients. Patients with maximal muscle loss (mean –3.5 kg) had lower plasma EPA (12.2 ± 3.3 µmol/L vs. 35.0 ± 7.1 µmol/L; P = 0.03), DHA (26.9 ± 8.7 µmol/L vs. 59.6 ± 5.3 µmol/L; P = 0.01), and (n-3) fatty acids (57.8 ± 13.5 µmol/L vs. 104.6 ± 11.1 µmol/L; P = 0.005) compared with patients who were gaining muscle (mean +1 kg). Plasma (n-3) fatty acids are depleted in cancer patients with sarcopenia, which may contribute to accelerated rates of muscle loss.