Short and long-term effects of streptozotocin on dietary cholesterol absorption, plasma lipoproteins and liver lipoprotein receptors in RICO rats

Adult male genetically hypercholesterolemic RICO rats were studied 6 and 28 days after streptozotocin (STZ) administration together with untreated RIC O controls. The absorption coefficient of dietary cholesterol was determine d using dual-isotope blood ratio method. Plasma lipoproteins as well as fec al neutral sterols and bile acids were analysed at both experimental times Liver lipid parameters were measured and lipoprotein receptors (LDLr, SR-BI and HB2) were assayed by immunodetection. Six days after STZ administratio n, dietary cholesterol absorption was more efficient (+49%) in treated rats than in controls, and stayed higher (+ 68%) in the diabetic rats sacrifice d at day 28. Fecal neutral sterol elimination decreased soon after STZ admi nistration (by 35% at day 6), due to a higher cholesterol absorption coeffi cient, then increased to control level at day 28, due to installed diabetes -induced hyperphagia. Comparison of the lipoprotein profiles indicated that the concentration of HDLI, which is typically high in control Rico rats, f ell significantly in diabetic rats at both experimental times, whereas that of HDL2 increased only at day 28. In diabetic rats, an early and strong en hancement of the hepatic expression of SR-BI appeared at day 6 (+415%) and persisted at day 28, but at a lesser extent (+85%). The expression of LDLr and HB2 was unchanged at day 6, but was significantly modified at day 28 (140% for LDLr and - 50% for HB2). These data show that streptozotocin-induc ed diabetes in Rico rats results in modifications of the expression of live r lipoprotein receptors which can contribute to alterations of the lipoprot ein profile.