Introduction: A major complication of insulin resistant states is fasting dyslipidemia, a lipid profile characterized by elevated triglycerides, increased small dense LDL and low HDL-cholesterol. Recently, bile acid signaling has been suggested to improve hepatic insulin sensitivity and lipid accumulation through activation of the Takeda G protein-coupled receptor 5 (TGR5). Using CRISPR/CAS9 gene editing, and in collaboration with the Wang laboratory at Utah State University, we have developed a novel Tgr5-/- hamster model. As the role of TGR5 in regulating hepatic lipid and lipoprotein metabolism has not been explored, the present study was performed to characterize the fasting lipid profile of this model in normal and mild insulin resistant states and further examine bile acid signaling within these hamsters.
Methods/Results: Eight-week-old Tgr5+/+ and Tgr5-/- hamsters were fed a high fat, high fructose and low cholesterol (FFLC) diet for 6 weeks. Glucose tolerance and fasting plasma lipids were examined at baseline, and following 6-weeks of FFLC consumption. Unlike the Tgr5+/+ hamsters, who exhibited impaired glucose tolerance following 6-weeks of FFLC-feeding, Tgr5-/- hamsters did not. This alteration in glucose tolerance was not associated with any significant differences in body weight or food consumption, or hepatic triglyceride or cholesterol between genotypes. Lipoprotein profiling was performed via FPLC analysis. Preliminary results suggest that Tgr5-/- hamsters exhibit reduced VLDL-triglyceride and -cholesterol, and HDL-cholesterol. Finally, chow fed hamsters received intraduodenal injections of deoxycholic acid (DCA), a bile acid with a strong affinity for TGR5. DCA administration was associated with reduced VLDL-triglyceride secretion in Tgr5+/+ hamsters, an effect that was blunted in Tgr5-/- hamsters. The present research will set a framework to expand our knowledge of the role of TGR5 signaling in hepatic lipogenesis.
D.C.L. Alvares: None. S.S. Hoffman: None. K. Adeli: None.
Heart and Stroke Foundation of Canada