Increased hepatic cholesterol synthesis in normal rats by cross-circulation with ileal bypassed partners

Aortic cross-circulation between Holtzman rat littermates was employed to investigate the possible role of a blood-borne factor from the small intestine in the regulation of hepatic cholesterol synthesis. Experimental pairs, consisting of a normal rat and a distal 50% small bowel excluded partner, demonstrated significantly increased combined hepatic cholesterol synthesis when compared to control pairs, consisting of two normal rats, both at 3 and 5 days following parabiosis. This difference was accounted for by increased hepatic cholesterol synthesis in the normal rat in each experimental pair. Neither weight loss nor differences in dietary intake contributed to this effect. Whole blood cholesterol in the common circulation of both experimental and control pairs was lowered; while hepatic cholesterol content was transiently increased, at 3 but not 5 days following parabiosis. Thus, the intestinal bypassed rat stimulates, or releases inhibition of, hepatic cholesterol synthesis in a non-bypassed parabiotic partner. The mechanism for this phenomenon has yet to be defined.