Hypertriglyceridemia and Hepatic Steatosis in Senescence-Accelerated Mouse Associate to Changes in Lipid-Related Gene Expression

Aged rodents show increasing plasma and tissue triglycerides, and reductions in liver peroxisome proliferator-activated receptor a (PPARa) and its target genes. We determined whether a similar situation is present in a model of accelerated aging, the senescence-accelerated prone (SAM-P8) mouse. Five-month-old SAM-P8 mice were hypertriglyceridemic, and exhibited hepatic steatosis and reduced fatty acid oxidation versus control 5-month-old senescence-accelerated resistant (SAM-R1) mice, with no differences in PPARa expression and binding activity; in fact, fenofibrate administration to SAM-P8 mice induced a clear PPARa-driven response. Complementary DNA (cDNA) microarray analysis (Affymetrix Mouse Genome 430A 2.0 GeneChip array), Western blot, and electrophoretic mobility shift assay (EMSA) experiments indicated, among other changes, a deficit in farnesoid X receptor (FXR) expression and binding activity in the livers of SAM-P8 mice with respect to SAM-R1 controls. Triglyceride accretion and a deficit in hepatic fatty acid oxidation, features of the aging process in mammals, associate to a deficit in hepatic FXR activity in the SAM-P8 mice. THE clustering of dyslipidemia, obesity, type II diabetes,and hypertension increases the incidence of cardio-vascular diseases among the elderly population (1). Th