Original Research Effect of α-Lipoic Acid Combined With Creatine Monohydrate on Human Skeletal Muscle Creatine and Phosphagen Concentration
a-lipoic acid has been found to enhance glucose uptake into skeletal muscle in animal models. Studies have also found that the co-ingestion of carbohydrate along with creatine increases muscle creatine uptake by a process related to insulin-stimulated glucose disposal. The purpose of this study was to determine the effect of a-lipoic acid on human skeletal muscle creatine uptake by directly measuring intramuscular concentrations of creatine, phosphocreatine, and adenosine triphosphate when creatine monohydrate was co-ingested with a-lipoic acid. Muscle biopsies were acquired from the vastus lateralis m. of 16 male subjects (18–32 y) before and after the experimental intervention. After the initial biopsy, subjects ingested 20 g · d–1 of creatine monohydrate, 20 g · d–1 of creatine monohydrate + 100 g · d–1 of sucrose, or 20 g · d–1 of creatine monohydrate + 100 g · d–1 of sucrose + 1000 mg · d–1 of a-lipoic acid for 5 days. Subjects refrained from exercise and consumed the same balanced diet for 7 days. Body weight increased by 2.1% following the nutritional intervention, with no differences between the groups. There was a significant increase in total creatine concentration following creatine supplementation, with the group ingesting a-lipoic acid showing a significantly greater increase (p < .05) in phosphocreatine (87.6 >>> 106.2 mmol · kg–1 dry mass [dm]) and total creatine (137.8 >>> 156.8 mmol · kg–1 dm). These findings indicate that co-ingestion of a-lipoic acid with creatine and a small amount of sucrose can enhance muscle total creatine content as compared to the ingestion of creatine and sucrose or creatine alone.