Hepatic microsomal triglyceride transfer protein gene expression in carbohydrate-induced hypertriglyceridemia

The microsomal triglyceride transfer protein (MTP) facilitates the assembly of very low density lipoproteins (VLDL). To investigate the effects of car bohydrate (CHO)-induced hypertriglyceridemia (HTG) on the hepatic expressio n of the MTP gene, Golden Syrian hamsters were fed fructose (FR) and sucros e (SUC) enriched diets. Changes in fasting plasma glucose (FPG), insulin, f ree fatty acids (FFA), TG, VLDL-TG and VLDL-protein were determined. Abunda nce of hepatic MTP-mRNA was compared to those of albumin (ALB)-mRNA and gly ceraldehyde 3-phosphate dehydrogenase (GAPDH)-mRNA. Hepatic secretion rates (SR) of VLDL-TG and VLDL-PR were assessed after intravenous Triton WR-1339 injection. Lipoprotein lipase (LpL) activity of the epididymal fat pads wa s determined. As compared to the control and SUC, FR increased plasma insul in (FR = 238+24, SUC = 115+/-17, control = 82+/-16 mu U/ml, p < 0.0001), FF A (FR = 1.93+/-0.24, SUC = 1.35+/-0.1, control = 1.47+/-0.13 mEq/L, p < 0.0 3) and TG (FR = 215+/-47, SUC = 93+/-7, control = 71+/-16 mg/dl, p < 0.01), without affecting FPG. There was no change in LpL activity. Fructose-feedi ng increased VLDL-TG-SR (FR = 2.95+/-0.26, SUC = 1.28+/-0.34, control = 2.1 8+/-0.26 mg/kg.wt/h(-1), p < 0.004), but not VLDL-protein-SR. MTP-mRNA abun dance did not change when compared to albumin mRNA, however FR-fed hamsters had lower MTP mRNA abundance when compared to GAPDH mRNA (FR = 0.96+/-0.13 , SUC = 1.15+/-0.14, control = 1.49+/-0.14 MTPGAPDH-mRNA, p < 0.05). The fi nding that PR-feeding increased VLDL-TG secretion without any increase in M TP mRNA proves that CHO-induced HTG can occur without an increase in hepati c MTP gene expression. (C) 1999 Elsevier Science Inc.