Effect of dietary glycemic index on substrate transporter gene expression in human skeletal muscle after exercise
I-S Cheng1, S-F Liao2, K-L Liu2, H-Y Liu2, C-L Wu2, C-Y Huang3, K Mallikarjuna4, R W Smith4 and C-H Kuo4
1. 1Department of Kinesiology, National Taichung University, Taichung, Taiwan, ROC
2. 2Department of Physical Medicine and Rehabilitation, Changhua Christian Hospital, Changhua, Taiwan, ROC
3. 3Graduate Institute of Basic Medical Science, China Medical University, Department of Health and Nutrition Biotechnology, Asia University, Taichung, Taiwan, ROC
4. 4Laboratory of Exercise Biochemistry and Graduate Institute of Exercise Sciences, Taipei Physical Education College, Taipei, Taiwan, ROC
Abstract
Background/Objectives:
Skeletal muscle plays important role in the regulation of whole-body metabolism. In skeletal muscle, uptakes of glucose and fatty acid from circulation are facilitated by transmembrane substrate transporters GLUT4 and FAT/CD36, respectively. The aim of this study was to determine the effect of dietary glycemic index (GI) on GLUT4 and FAT/CD36 gene expressions in human skeletal muscle after a single bout of exercise.
Subjects/Methods:
Eight male subjects completed a 60-min cycling exercise at 75% maximal oxygen consumption (VO2 max), and were immediately fed an isocaloric meal containing either high-GI (HGI) or low-GI (LGI) diets, with similar proportions of carbohydrate, fat and protein in a crossover design. Muscle samples from deep vastus lateralis were taken by needle biopsy immediately after exercise and 3 h after exercise.
Results:
After exercise, the HGI diet produced significantly greater glucose and insulin responses compared with the LGI diet, as indicated by the greater area under the curves. Both diets resulted in rapid reductions in plasma fatty acid and glycerol below fasting level. GLUT4 mRNA was downregulated by both HGI and LGI diets to a comparable extent, whereas GLUT4 protein levels were not changed during this short period. FAT/CD36 mRNA and protein levels were substantially decreased with the HGI diet below baseline, but not with the LGI diet.
Conclusion:
This study found a significant dietary GI effect on post-exercise FAT/CD36 gene expression in human skeletal muscle. This result implicates that the differences in dietary GI are sufficient to alter fat metabolism.
http://www.nature.com/ejcn/journal/v63/ ... 9100a.html" onclick="window.open(this.href);return false;
So basically, a meal with carbs that are high GI post workout will temporarily reduce one of the main proteins that deals with the body burning up circulating fat and LDL cholesterol. IMO another good reason to take your protein + carb shake PRE, and then eat a normal medium-low GI source of carbs PWO.
