Objective: Sterol regulatory element-binding protein-1 (SREBP-1) is nutritionally regulated and is known to be a key transcription factor regulating lipogenic enzymes. The goal of this study was to evaluate the roles of SREBP-1 in dyslipidemia and atherosclerosis.
Methods and results: Transgenic mice that overexpress SREBP-1c in the liver and SREBP-1-deficient mice were crossed with low-density lipoprotein receptor (LDLR)-deficient mice, and the plasma lipids and atherosclerosis were analyzed. Hepatic SREBP-1c overexpression in LDLR-deficient mice caused postprandial hypertriglyceridemia, increased very-low-density lipoprotein (VLDL) cholesterol, and decreased high-density lipoprotein cholesterol in plasma, which resulted in accelerated aortic atheroma formation. Conversely, absence of SREBP-1 suppressed Western diet-induced hyperlipidemia in LDLR-deficient mice and ameliorated atherosclerosis. In contrast, bone marrow-specific SREBP-1 deficiency did not alter the development of atherosclerosis. The size of nascent VLDL particles secreted from the liver was increased in SREBP-1c transgenic mice and reduced in SREBP-1-deficient mice, accompanied by upregulation and downregulation of phospholipid transfer protein expression, respectively.
Conclusions: Hepatic SREBP-1c determines plasma triglycerides and remnant cholesterol and contributes to atherosclerosis in hyperlipidemic states. Hepatic SREBP-1c also regulates the size of nascent VLDL particles.