Abnormal fatty acid utilization by cultured cardiac cells from 7-day-old obese Zucker rats

Fatty acid utilization by muscle and nonmuscle heart cells in culture has been investigated in the 7-day-old Zucker rat to determine if this tissue could contribute to the lower energy expenditure reported in obese rats at the onset of obesity. The partitioning of oleate to oxidation and esterification products and the effect of genotype on this partitioning according to cell types were studied. Results showed that the fatty acid beta-oxidation and its esterification in neutral lipid was decreased by 30% in beating muscle cells from obese animals when compared with those from lean animals. In contrast, nonmuscle cells exhibited a decreased beta-oxidation alone. A similar fatty acid composition of the phospholipids was found in non-muscle cells of obese animals and their lean litter mates. In muscle cultures, palmitic and oleic acids are lower in cells of obese rats than in those of lean rats. The present study indicates that a defect in energy metabolism could be found in heart cells at the onset of obesity, suggesting that this defect is determined by intrinisic factor(s).