Lipoprotein lipase activities in exercise-trained rats isocalorically fed high or low fat diets

Abstract

Influences of exercise and changes in dietary carbohydrate and fat on tissue lipoprotein lipase (LPL) activities were studied in 40 female Sprague-Dawley rats. Rats were trained to run (n=20) on a treadmill 6 days/week, 60 minutes/day at 28 m/min on an 8° incline for 8 wk or remained sedentary (n=20). All rats were fed a control high carbohydrate diet (12% kcals fat) for 5 weeks and then one-half of the trained and nontrained groups were assigned to a high fat (HF) diet. The HF (73% kcals fat) fed rats were pair fed to be isocaloric and isonitrogenous with the animals receiving the control diet. Animals were fasted 12–14 hours before sacrifice. Feeding the HF diet increased body weight, fat pad weight and plasma TG levels, but had no effect on muscle weight or muscle TG content. Training at least doubled the LPL activivity of the red gastrocnemius muscle. The combination of HF feeding and exercise produced an elevation in the LPL activity of the red (135%) and white (80%) gastrocnemius muscles compared to control feeding and no exercise. The additive effect of the HF diet and exercise training also increased LPL activity of renal adipose tissue (43%) versus control feeding and no exercise. Feeding the HF diet reduced glycogen depletion in liver and skeletal muscle during exercise. This study demonstrates that skeletal muscle LPL activity is sensitive to the individual and combined effects of dietary fat and exercise.