Publication:

補充八週共軛亞麻油酸對運動後人體骨骼肌肉肝醣合成的影響

共軛亞麻油酸(Conjugated Linoleic Acid, CLA)是一群含18個碳之共軛雙鍵不飽合脂肪酸。動物試驗指出CLA有增加游離脂肪酸氧化速率，降低身體脂肪的生理功能。這次研究探討補充八週CLA，在單次60分鐘75 % 最大攝氧量(VO2 max)腳踏車運動挑戰後，人體骨骼肌肌肉肝醣合成效果之影響。十二名健康男性受試者，在補充八週CLA前，接受單次60分鐘75 % VO2 max運動測試。緊接著，給予八週CLA補充劑(4 g/d)，然後再一次完成同樣強度單次運動挑戰。每次運動後立即給予等量碳水化合物補充(每公斤體重2克)。運動後立即進行第一次肌肉穿刺，並在碳水化合物補充後3小時內，每隔30分鐘進行血液採樣。最後，運動後第3小時進行第二次肌肉穿刺。另外，運動後恢復期3小時期間內第1、2、3小時，收集氣體樣本。研究結果顯示，CLA試驗血液葡萄糖、胰島素濃度曲線下面積皆明顯高於控制組(P<.05)。CLA試驗血漿甘油濃度在運動後0、30、60與180分鐘明顯低於控制組(P<.05)。CLA試驗血漿游離脂肪酸濃度在運動後0、30與180分鐘明顯低於控制組(P<.05)。補充CLA無顯著增加單一運動挑戰後0至3小時肌肉肝醣合成率。但是，補充CLA有利於減少單次運動期間肌肉肝醣損耗。另外，CLA增加GLUT4運動後0小時與3小時蛋白表現量(P<.05)，無法改變P-AKT、GS蛋白表現。氣體樣本顯示，補充八週CLA後，在運動恢復期間並不會改變呼吸交換率、脂肪氧化率、碳水化合物氧化率。這次研究顯示，規律運動習慣的健康男性，補充八週CLA後，有利降低60分鐘75 % VO2 max單次運動期間肌肉肝醣損耗。但是，補充CLA不利於運動恢復期間全身葡萄糖利用及胰島素敏感性增加。因此，這次試驗結果也沒證據可以支持補充八週CLA可以顯著增加人體運動後肌肉肝醣增補的效果。

Conjugated linoleic acid (CLA) is a group contained eighteen carbons and unsaturated fatty acids with two double bonds. CLA in animal studies enhanced fatty acid oxidation rate and reduced body fat. Purpose of this study was to demonstrate whether eight weeks oral CLA supplementation can increase glycogen synthesis in exercised human skeletal muscle. Twelve male subjects completed a single bout of exercise at 75% VO2 max for 60 minutes and accepted subsequently eight weeks oral CLA supplementation (4.0g/day). Immediately after eight weeks CLA supplementation, all subjects finished similarly a single bout of exercise challenge again. Subjects were asked to ingest a high carbohydrate meal immediately after cycling exercise (2g carbohydrate per body weight). Muscle samples were taken by needle biopsy immediately after exercise (0 h) and 3 h following exercise. Blood and gaseous samples were taken every 30 minutes till 3 h recovery after exercise. Lower responses were found in circulating non-esterify fatty acid (NEFA) and glycerol levels after 8 weeks CLA supplementation. Area under curve of glucose and insulin responses were higher response after CLA supplementation (P<.05). However, no significant increase in glycogen synthesis was shown after 8 weeks oral CLA supplementation in exercised human skeletal muscle. But CLA supplementation attenuate muscle glycogen depletion during the exercise challenge at 75% VO2 max for 60 minutes. In addition, GLUT4 protein expression was up-regulated by CLA supplementation but no similar finding on expressions of P-AKT and glycogen synthesis. No significant influence of respiratory exchange rate (RER), rates of fat and carbohydrate oxidation were found after 8 weeks supplementation based on evidence by gaseous exchange methods. The present study demonstrated that eight weeks oral CLA supplementation attenuated level of glycogen depletion during a single bout of exercise challenge. However, CLA supplementation cannot benefit on improve in whole body glucose uptake and insulin sensitivity. Therefore, there were no evidences to support that eight weeks oral CLA supplementation enhanced glycogen synthesis in exercised human skeletal muscle.