Attenuated aerobic exercise capacity in CD36 deficiency.

BACKGROUND: An important role of CD36 in muscle fatty acid (FA) uptake has been shown in CD36-knockout or CD36-overexpressed mice. FA is a predominant substrate in energy production during light exercise below the anaerobic threshold (AT). We studied whether aerobic exercise capacity in humans could be affected by CD36 deficiency. METHODS: We investigated the ventilatory threshold (VT) and serum FA changes in normal participants (n = 22) and participants with CD36 deficiency (n = 12) during pedalling on a cycle ergometer. RESULTS: In participants with CD36 deficiency, FA levels were not reduced at peak work rate, whereas FA levels decreased by about 50% in normal participants. Participants with CD36 deficiency showed significantly lower VT than normal participants. A significant correlation was observed between VT and percentage changes in FA at peak work rate. CONCLUSION: This study found reduced FA utilisation and an attenuated aerobic exercise capacity in CD36 deficiency, indicating that CD36-mediated FA oxidation is an important determinant for aerobic exercise capacity in humans.

Effect of ascorbate on serum lipids and urate metabolism during exhaustive training.

Physical activity is associated with beneficial changes in serum lipids, but exhaustive exercise has been suggested to increase oxidative stress. To test the effect of ascorbate (vitamin C) on serum lipids and the metabolism of urate, which is the most important intrinsic antioxidant, during exhaustive exercise, we performed a randomized, blinded, placebo-controlled study on eight male well-trained athletes. Subjects were randomly allocated to either a group given 1000 mg of ascorbate daily (n=4) or a placebo group (n=4). Fasting serum lipids and urate concentrations were measured before and after 3 weeks of training. Although serum low-density lipoprotein (LDL)-cholesterol levels decreased and high-density lipoprotein (HDL)-cholesterol levels increased significantly in the ascorbate group after the 3 weeks of training, serum LDL-cholesterol levels increased and HDL-cholesterol levels decreased significantly in the placebo group. Furthermore, serum urate levels were elevated significantly in the placebo group; however, these levels did not change in the ascorbate group. When compared with the placebo group, significantly higher serum HDL-cholesterol and lower serum LDL-cholesterol and urate levels were observed in the ascorbate group after training. In conclusion, our results suggested that ascorbate may contribute to the desirable changes in serum lipids during exhaustive training and suggest the significant association between ascorbate and urate under intense training.