Abstract 1133: Docosahexaenoic Acid’s Impact On The HMG CoA Reductase Pathway: Endothelial Cell Growth State-dependency And Implications For Cardiovascular Health

Abstract

Docosahexaenoic acid (DHA), widely assumed to be atheroprotective, has recently faced scrutiny due to divergent findings in clinical trials studying omega-3 fatty acids and cardiovascular disease (CVD). Our prior work unveiled nuanced actions of DHA on endothelial cells, especially demonstrating its differential regulation of endothelial nitric oxide synthase in growing versus quiescent cells, which approximate the dysfunctional and healthy states in vivo , respectively. These findings led to the hypothesis that DHA benefits healthy endothelial cells but not dysfunctional ones. To elucidate novel pathways, RNA-seq was done on DHA-treated (20 or 125 μM for 8 h) and control human EA.hy926 cells in both states. The data were processed by the RSEM-STAR-DESeq2 pipeline. Differentially expressed genes (DEGs) were subjected to enrichment analysis with clusterProfiler. Genes selected from candidate enriched pathways were validated by Western blotting. Principal component analysis showed distinct groupings based on cell growth state and DHA concentration. DESeq2 identified 104 and 173 DEGs unique to growing and quiescent cells, respectively, at 20 μM DHA. Pathway analysis revealed significant enrichment for cholesterol biosynthesis-related terms of downregulated DEGs, including HMGCR , SREBF2 , and INSIG1 , in quiescent cells treated with 20 μM DHA, while SREBF1 was downregulated in both states. DHA also reduced HMGCR expression in human monocytes, concomitant with less cellular cholesterol content. Moreover, many genes associated with the Rho GTPase pathway, downstream of HMG CoA reductase (HMGCR), were downregulated by 20 μM DHA only in quiescent cells. These results attest to similarities between the effects of DHA and statins, inhibitors of HMGCR that address CVD via both cholesterol reduction and pleiotropic actions on Rho GTPase. Our study reveals that only quiescent endothelial cells respond positively to DHA. It pioneers a novel perspective that DHA should be targeted for CVD prevention in healthy people versus as a therapeutic for those with endothelial dysfunction. Further studies are required to validate the in vivo responses to DHA in healthy versus dysfunctional endothelium, and the optimal DHA dose to achieve maximal benefits.