Does exercise protect from coronary artery disease?

The effect of creatine supplementation on myocardial function, mitochondrial respiration and susceptibility to ischaemia/reperfusion injury in sedentary and exercised rats

AIM

To investigate the effects of dietary creatine supplementation alone and in combination with exercise on basal cardiac function, susceptibility to ischaemia/reperfusion injury and mitochondrial oxidative function. There has been an increase in the use of creatine supplementation among sports enthusiasts, and by clinicians as a therapeutic agent in muscular and neurological diseases. The effects of creatine have been studied extensively in skeletal muscle, but not in the myocardium.

METHODS

Male Wistar rats were swim-trained for 8 weeks, 5 days per week. Hearts were excised and either freeze-clamped for biochemical analysis or perfused on the isolated heart perfusion system to assess function and ischaemia/reperfusion tolerance. Mechanical function was documented in working heart and retrograde mode. The left coronary artery was ligated and infarct size determined. Mitochondrial oxidative capacity was quantified.

RESULTS

Aortic output recovery of hearts from the sedentary controls (CSed) was significantly higher than those from creatine-supplemented sedentary (CrSed), creatine-supplemented exercised (CrEx) as well as control exercised (CEx) groups. Ischaemic contracture of hearts from CrEx was significantly higher than that of CSed. There were no differences in infarct size and mitochondrial oxygen consumption.

CONCLUSION

This study suggests that creatine supplementation has no effects on basal cardiac function but reduces myocardial tolerance to ischaemia in hearts from exercise-trained animals, by increasing the ischaemic contracture and decreasing reperfusion aortic output. Exercise training alone also significantly decreased aortic output recovery. However, the exact mechanisms for these adverse myocardial effects are unknown and need further investigation.

Exercise and risk factors for arteriosclerosis in 42 married couples followed over four years

Forty-two married couples (30-69 years of age) were followed for 4 years with yearly measurements of risk factors for arteriosclerosis. Advice was given concerning relaxed, enjoyable exercise (mainly running at 10-13 km hr-1). Each person served as his own control by comparison of the first and the last yearly status. Both the group of women and the group of men significantly improved (two sided p less than 0.005) their maximum oxygen uptake, and reduced their blood glucose concentration (two-sided p less than 0.01). S-cholesterol (for the group of men) was reduced statistically significantly (two-sided p less than 0.01). At the first examination the groups of women and men with the lowest maximum oxygen uptake (group I) had higher average values for risk factors than the more active groups (group II). At the final examination almost all persons had improved their maximum oxygen uptake, so none of the other risk factor differences between groups I and II were statistically significant. Both the women and the men improved their well being and their health profile as evaluated in terms of risk factors for arteriosclerosis. Exhaustive exercise was not necessary for beneficial effects.