Niacin lowers LDL primarily by inhibiting synthesis of which lipoprotein precursor?

• A. Chylomicrons
• B. LDL
• C. HDL
• D. VLDL

Answer: (D)

Niacin lowers LDL primarily by reducing hepatic production and secretion of VLDL, the lipoprotein that the liver packs with triglycerides. LDL is formed from VLDL as it circulates and is metabolized, so when VLDL synthesis drops, less LDL is produced downstream. Niacin accomplishes this by decreasing the influx of free fatty acids to the liver (from adipose tissue) and by limiting hepatic triglyceride synthesis needed for VLDL assembly. The result is lower circulating VLDL, which translates into reduced LDL levels. Chylomicrons and HDL aren’t the main players in this LDL-lowering pathway, and the primary effect here is on VLDL.