Effects of exercise training and/or high fat diet on lipid metabolism and carnitine concentrations in rats

Abstract

The effect of high fat diet and/or exercise on lipid metabolism and carnitine status was investigated in young Sprague-Dawley rats. The rats were fed an AIN-76 diet or a modified high-fat AIN-76 diet, supplemented with 20% corn oil, for 30 days. During the 30-day period half of the animals in each dietary group were exercised on a treadmill for 90 minutes per day. Lipid concentrations in both plasma and liver were determined, and carnitine concentrations were determined in plasma, liver, kidney, heart, and skeletal muscle. Exercised rats gained less weight than non-exercised rats during the study (135.7g vs. 119.4g and 134g vs. 119.1g for normal and high-fat diets groups, respectively). Plasma cholesterols, and liver triacylglycerol were significantly lower in exercised than non-exercised rats on either diet. Liver total lipids were lower in exercised rats but higher in rats fed the high fat diet. In liver tissue, carnitine concentrations were primarily increased by high fat diet. However, in kidney and skeletal muscle exercise resulted in higher concentrations of non-esterified, acyl, and total carnitine. High fat diet in skeletal muscle caused an increase in acyl and decrease in free carnitine concentrations without effecting total carnitine. This research demonstrates that, in rats, exercise is more important in reducing body weight gain than the fat content of the diet, and demonstrates a beneficial effect of exercise and detrimental effect of high fat diet on blood lipid parameters. This study also demonstrates that both high fat diet and exercise can increase tissue carnitine concentrations in an organ specific manner.