Alterations of lipid kinetics and lipoprotein lipase activity in jaundiced tumor bearing rats

RESUMO

Obstructive jaundice is associated with high perioperative morbidity and mortality, and preoperative biliary decompression is still controversial. Profound alterations in intermediary metabolism have been observed with obstructive jaundice. To determine the effect of the common bile duct (CBD) obstruction on lipid metabolism in tumor-bearing animals, free fatty acid (FFA) and very low density lipoprotein-associated triglyceride (VLDL-TG) kinetics were assessed in 20 tumor bearing (subcutaneous MCA sarcoma) Fischer-344 rats, using an obstructive jaundice model. The animals were studied after chronic vascular catheterization, in an unanesthetized, undisturbed state. They were separated into 4 groups Normal controls (CTL), Tumor-bearing non-jaundiced rats (TBR), Non Tumor Bearing-Jaundiced (NTB-J), Tumor Bearing (tumor burden 1O per cent body weight)-Jaundiced (TBR-J). All rats were studied 7 days after CBD ligation, or at 1O per cent tumor burden. VLDL-TG and FFA kinetics were assessed by constant infusion of 3H-palmitate-labeled VLDL-TG, and l4C-palmitate bound to albumin, respectively. FFA rate of appearance (FFA-Ra) and clearance (FFA-CI), VLDL-TG rate of appearance (VLDL-TG-Ra) and clearance (VLDL-TG-CI) were determined at steady-states. Tumor burden signiricantly affects FFA-Ra and FFA-CI, as well as VLDL-TG-CI, while CBD ligation selectively affects VLDL-TG-Ra and VLDL-TG-CI. There was significant interaction between tumor burden and jaundice in FFA-Ra. CBD decompression increased significantly VLDL-TG-CI. We conclude that, in jaundiced tumor-bearing rats, tumor burden predominantly affects lipolysis, while CBD obstruction primarily affects triglyceride synthesis and clearance. Lipoprotein lipase (LPL) activity was also markedly decreased by the presence of jaundice and tumor burden, with the associated decrease in the clearance of VLDL-TG.