Peroxisomal and mitochondrial palmitate oxidation in rat cardiac and skeletal muscles: Effects of diabetes, fasting and fat consumption

Abstract

Peroxisomal lipid metabolism in several tissues is altered under conditions in which there is a relative increase in the use of fatty acids for energy (eg. diabetes, fasting and high fat-feeding). The present study was undertaken to determine if these same conditions affect peroxisomal lipid metabolism in rat cardiac and skeletal muscle; catalase activity and mitochondrial palmitate oxidation were also measured. Rats were made diabetic by Streptozotocin injection; 4 weeks later peroxisomal palmitate oxidation capacity in vitro was elevated in heart and soleus, but not in two other skeletal muscles. Mitochondrial palmitate oxidation was significantly increased in heart by the diabetic condition. In fasted rats total peroxisomal palmitate oxidation capacity was decreased in cardiac and three skeletal muscles, whereas in rats fed a high fat (70% kcals lard) diet for 3 weeks, peroxisomal palmitate oxidation capacity was increased in psoas and soleus, but not in the heart or extensor digitorus longus. Muscle catalase activity was elevated in rats made diabetic, fasted or fed a high fat diet. The results support the concept that peroxisomal fatty acid oxidation in muscle participates in the overall regulation of lipid metabolism, but may not respond solely to the amount of fatty acid potentially available as substrate.