Hepatic very low-density lipoprotein production pathway

The hepatic very low-density lipoprotein production pathway encompasses assembly, lipidation, maturation, and secretion of VLDL particles by hepatocytes to export endogenous triglycerides and cholesterol to peripheral tissues. VLDL assembly begins in the rough endoplasmic reticulum with co-translational translocation of apolipoprotein B-100 (ApoB-100) and initial lipidation mediated by microsomal triglyceride transfer protein (MTP), forming a pre-VLDL particle. A second lipidation step adds bulk triglycerides to generate mature VLDL; proteins such as TM6SF2 and others (CIDEB, PLTP, LPCAT3, TMEM41B) have been implicated in VLDL lipidation and assembly, with some steps occurring in ER or ER–Golgi compartments. Hepatically secreted VLDL is the core vehicle for endogenous triglyceride transport and contributes to downstream IDL and LDL formation during circulation through lipolysis and lipid exchange. VLDL secretion is strongly substrate-driven by hepatic fatty acid availability from de novo lipogenesis, cytosolic TG stores, lipoprotein-derived fatty acids, and plasma free fatty acids; nutritional and hormonal states (e.g., insulin resistance) channel fatty acids toward secretion, increasing VLDL output and hypertriglyceridemia. Regulatory inputs include S-adenosylmethionine–dependent signaling that activates mTORC1, enhances phosphatidylcholine synthesis via CCT, and stimulates VLDL particle synthesis and secretion; heterogeneity of VLDL secretion is linked to MASLD metabotypes with differing cardiovascular and liver cancer risks. Because this is a multi-protein pathway rather than a single molecular target, therapeutic interventions act on components (e.g., MTP) or on upstream substrate supply and signaling, with efficacy–safety trade-offs such as risk of hepatic steatosis when VLDL export is impaired.

Other names

Hepatic VLDL assembly and secretion pathwayEndogenous lipoprotein secretion pathway (hepatic)Very low-density lipoprotein biogenesis (liver)

MTP inhibition blocks initial lipid transfer to ApoB during co-translational translocation, reducing VLDL assembly. Reduction of hepatic fatty acid flux or de novo lipogenesis lowers substrate supply, decreasing VLDL output. Modulation of mTORC1–CCT–phosphatidylcholine synthesis can stimulate or reduce VLDL particle synthesis/secretion depending on pathway activation state.