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

The effect of high fat diet and/or exercise on lipid metabolism and carniti ne 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% co rn oil, for 30 days. During the 30-day period half of the animals in each d ietary group were exercised on a treadmill far 90 minutes per day. Lipid co ncentrations in both plasma and liver were determined, and carnitine concen trations were determined in plasma, liver, kidney, heart, and skeletal musc le. Exercised rats gained less weight than non-exercised rats during the st udy (135.7g vs. 119.4g and 134g vs. 119.1g for normal and high-fat diets gr oups, respectively). plasma cholesterols, and liver triacylglycerol were si gnificantly lower in exercised than non-exercised rats on either diet. Live r total lipids were lower in exercised rats but higher in rats fed the high fat diet. In liver tissue, carnitine concentrations were primarily increas ed by high fat diet. However, in kidney and skeletal muscle exercise result ed in higher concentrations of non-esterified, acyl, and total carnitine. H igh fat diet in skeletal muscle caused an increase in acyl and decrease in free carnitine concentrations without effecting total carnitine. This resea rch demonstrates that, in rats, exercise is more important in reducing body weight gain than the fat content of the diet, and demonstrates a beneficia l effect of exercise and detrimental effect of high fat diet on blood lipid parameters. This study also demonstrates that both high fat diet and exerc ise can increase tissue carnitine concentrations in an organ specific manne r. (C) 1999 Elsevier Science Inc.