Effects of dietary carbohydrate and energy intake on LAT1 protein expression in rat skeletal muscle

Abstract

Glucose has been reported to reduce the expression of L-type amino acid transporter 1 (LAT1) protein in C2C12 myocytes. We therefore hypothesized that increased dietary carbohydrate and energy intake would reduce LAT1 protein expression in rodent skeletal muscle. Here, we tested this hypothesis. In Experiment 1, to examine the effects of dietary carbohydrate intake, male Sprague Dawley (SD) rats were divided into low-carbohydrate (low-CHO) and high-carbohydrate (high-CHO) diet groups. Each group was fed a low-CHO (20% carbohydrate) or high-CHO (70% carbohydrate) diet, respectively. Total energy intakes of both groups were matched by pair feeding. In Experiment 2, to examine the effects of dietary energy intake, rats were divided into low-energy diet (fed 68% of ad libitum energy intake) and high-energy diet (ad libitum) groups. After 7 days of dietary manipulation, the lower leg muscles on one side were percutaneously stimulated and subjected to one acute bout of resistance exercise. The contralateral leg muscle served as an internal control. We collected gastrocnemius muscle 6 h after contraction. In both Experiments 1 and 2, when results were analyzed by two-way analysis of variance, no main effect of diet on LAT1 protein concentration was observed. Also, there was no main effect of resistance exercise, or no interaction between diet and exercise. These results do not support our hypothesis that increased dietary carbohydrate and energy intake reduce LAT1 protein expression in rodent skeletal muscle. Furthermore, it was shown that diet may not affect the effects of resistance exercise on LAT1 protein expression.