Effect of 24-h food deprivation on lipoprotein composition and oleoyl-estrone content of lean and obese Zucker rats.

Background: Food deprivation induces the mobilization of fat reserves and, consequently, the transport of lipids in plasma. Zucker obese rats are grossly hyperlipidemic and do not use lipids as an efficient energy substrate. They also have lower circulating levels of acyl-estrone than expected because of their large fat stores.

Aim Of The Study: To measure the effect of 24 h food deprivation on hyperlipidemia and acyl-estrone distribution in plasma in Zucker obese rats.

Methods: The plasma lipoprotein distribution and composition of Zucker lean (Fa/?) and obese (fa/fa) rats was determined after 24 hours of food deprivation. Lipid classes: phospholipid, free and esterified cholesterol and triacylglycerols, and protein and total (mainly acyl-) estrone were also measured in total plasma and lipoprotein fractions.

Results: Food-deprived rats showed lower triacylglycerol levels than fed rats, but obese rats maintained high lipid levels, mainly in the VLDL fraction. The ratio of total plasma free-to-esterified cholesterol was lower in fed lean rats (0.29) than in the obese (0.61); the situation improved slightly after 24-h starvation, since the corresponding ratios were 0.30 and 0.41. Acyl estrone levels changed little with 24-h food deprivation. The chylomicra + VLDL total estrone compartment was essentially unchanged in lean and obese fed and starved groups, but the HDL pool decreased with food deprivation in the obese.

Conclusion: Short-term starvation helped to enhance the differences between lean and obese Zucker rats in the handling of lipoprotein lipids, the latter showing a marked impairment in their ability to dispose of circulating lipids. The different pace of plasma lipid utilization may compound the problems of cholesterol transfer, partly explaining the dyslipemia that characterizes this animal model of obesity. The differences in acyl-estrone distribution also indicate that fat mass is preserved more effectively in obese rats even after food deprivation.