# Apolipoprotein A5 reduces clearance of VLDL by altering apolipoprotein E content

## TL;DR

Apolipoprotein A5 (APOA5) affects how the liver clears VLDL particles by changing their protein content, especially reducing APOE levels.

## Contribution

APOA5 modulates VLDL clearance by altering proteomic composition, particularly APOE, independent of LPL activity.

## Key findings

- APOA5 deletion reduces APOE and serum amyloid A1 in VLDL particles.
- APOA5 reintroduction restores normal VLDL proteome and hepatic uptake.
- APOA5 influences VLDL clearance through proteomic remodeling, not LPL activation.

## Abstract

Apolipoprotein A-V (APOA5) is a critical regulator of circulating triglyceride (TG) levels. Its deletion leads to elevated plasma TG concentrations by altering the metabolism of VLDL particles in vivo. One way APOA5 exerts its effects is through the modulation of LPL activity, specifically by disrupting inhibitory interactions between LPL and angiopoietin-like proteins (ANGPTLs). However, the impact of APOA5 on VLDL composition and its potential to alter VLDL metabolism in other ways remains poorly understood. To address this, we investigated the influence of APOA5 on the VLDL proteome, LPL activation, and hepatic remnant uptake. Using VLDL from Apoa5 KO and WT mice, we found no evidence that APOA5 directly enhances LPL activity in purified or plasma systems. However, VLDL from Apoa5 KO mice was cleared significantly more slowly by cultured hepatocytes. VLDL proteomics experiments from two independent laboratories identified altered contents of 23 proteins involved in lipoprotein metabolism, inflammation, and immune response in Apoa5 KO VLDL, including reductions in APOE and serum amyloid A1. Remarkably, reintroduction of recombinant mouse APOA5 to the KO plasma partially restored the WT VLDL proteome, including APOE, and normalized VLDL uptake by hepatocytes without altering LPL lipolysis. These findings reveal that APOA5 influences hepatic clearance of VLDL remnants by modulating particle composition, particularly APOE content. This study expands the functional scope of APOA5 in TG metabolism and underscores its role in VLDL remodeling and remnant clearance, offering new insights with implications for understanding hypertriglyceridemia and its roles in inflammation and immune response.