Update on APOA5 Genetics: Toward a Better Understanding of Its Physiological Impact

This review is intended to summarize the genetic studies published during the last 3 years that help us understand the physiology of apoAV and its clinical implications.

APOA5 is probably the gene with the strongest effect on triglyceride (TG) metabolism. APOA5 is almost exclusively expressed in the liver, and its product apoAV has a very low circulating concentration. New physiological roles of apoAV have been recently elucidated, such as control of chylomicron production in the intestine and TG accumulation in adipose tissue. The key role of APOA5 in TG metabolism has been largely shown through genetic studies in association with either severe or moderate hypertriglyceridemia. Studies suggest that APOA5 variants affect not only total TG concentrations but also the entire lipoprotein subclass distribution, shifting them toward atherogenic dyslipidemia in high-risk subjects. Environmental interactions and epigenetic factors are also crucial in regulating these processes. Delineation of the mechanisms involved in the transcriptional control of the gene, combined with determination of biological significance of the SNPs in the APOA5 locus, would help to fully understand the effect of APOA5 on TGs. In summary, APOA5 variants cause hypertriglyceridemia. In high cardiovascular risk patients (e.g., patients with metabolic syndrome or type 2 diabetes), APOA5 variants elevate TG levels and shift the entire lipoprotein subclass distribution toward atherogenic dyslipidemia. At a physiological level, apoAV seems to encompass more roles than those initially suggested after its discovery.