Preferential Incorporation of Administered Eicosapentaenoic Acid Into Thin-Cap Atherosclerotic Plaques.

OBJECTIVE: n-3 polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have beneficial effects on atherosclerosis. Although specific salutary actions have been reported, the detailed distribution of n-3 polyunsaturated fatty acids in plaque and their relevance in disease progression are unclear. Our aim was to assess the pharmacodynamics of EPA and DHA and their metabolites in atherosclerotic plaques. Approach and Results: Apolipoprotein E-deficient (Apoe-/-) mice were fed a Western diet supplemented with EPA (1%, w/w) or DHA (1%, w/w) for 3 weeks. Imaging mass spectrometry analyses were performed in the aortic root and arch of the Apoe-/- mice to evaluate the distribution of EPA, DHA, their metabolites and the lipids containing EPA or DHA in the plaques. Liquid chromatography-mass spectrometry and histological analysis were also performed. The intima-media thickness of atherosclerotic plaque decreased in plaques containing free EPA and EPAs attached with several lipids. EPA was distributed more densely in the thin-cap plaques than in the thick-cap plaques, while DHA was more evenly distributed. In the aortic root, the distribution of total EPA level and cholesteryl esters containing EPA followed a concentration gradient from the vascular endothelium to the media. In the aortic arch, free EPA and 12-hydroxy-EPA colocalized with M2 macrophage. CONCLUSIONS: Administered EPA tends to be incorporated from the vascular lumen side and preferentially taken into the thin-cap plaque.

Metabolomic Analysis of Diet-Induced Obese Mice Supplemented with Eicosapentaenoic Acid.

Eicosapentaenoic acid (EPA) is an omega-3 fatty acid with anti-inflammatory effects. To determine the effects of EPA on metabolic pathways in obese adipose tissues and liver, mice were fed normal chow diet (NCD), high-fat diet (HFD), or 3% EPA-containing high fat diet (HFD+EPA) for 8 weeks. Metabolomic analysis was performed using epididymal adipose tissues (epi WAT) and liver. Metabolites that were specifically elevated in HFD+EPA, were assessed for their anti-inflammatory properties using RAW264.7 macrophage cells. Body and adipose tissue weights were significantly higher in HFD than NCD, and lower in HFD+EPA than HFD. Plasma insulin levels were significantly higher in HFD than NCD, and lower in HFD+EPA compared with HFD. Plasma monocyte chemotactic protein-1 (MCP-1) levels were higher in HFD than NCD, and tended to be lower in HFD+EPA than HFD. The levels of intermediate metabolites in the glycolytic pathways were lower in HFD compared with NCD and HFD+EPA in both epi WAT and liver, while intermediate metabolites of the TCA cycles were elevated in HFD and HFD+EPA compared with NCD in epi WAT. Among the metabolites in epi WAT, the levels of thiaproline, phenaceturic acid, and pipecolic acid were specifically elevated in HFD+EPA, but not in HFD or NCD. Treatment of RAW264.7 cells with thiaproline significantly ameliorated LPS-induced iNOS expression, while pipecolic acid inhibited LPS-induced IL-1ß expression. These results suggest that EPA normalizes glycolytic pathway intermediates in both epi WAT and liver, and induces metabolites with anti-inflammatory properties.

Eicosapentaenoic acid administration attenuates the pro-inflammatory properties of VLDL by decreasing its susceptibility to lipoprotein lipase in macrophages.

High level of plasma very low-density lipoprotein (VLDL) has been identified as a risk factor for coronary heart disease. Recent evidence suggests that excess VLDL induces inflammatory responses in macrophages and vascular endothelial cells. The Japan EPA Lipid Intervention Study (JELIS), a large scale clinical trial, demonstrated that highly purified eicosapentaenoic acid (EPA) prevented the onset of cardiovascular events in LDL-cholesterol independent fashion. In this study, we investigated the impact of EPA on pro-inflammatory properties of VLDL. Effects of VLDL prepared from mice fed 5% EPA diet for 1 week (EPA-VLDL) or mice fed normal diet (Ctrl-VLDL) on the mRNA expression of pro-inflammatory factors were examined in human THP-1 macrophages. Ctrl-VLDL increased mRNA expression of pro-inflammatory factors such as interleukin-1ß and tumor necrosis factor-α in macrophages. In contrast, the increases in pro-inflammatory factors by EPA-VLDL were lower than those by Ctrl-VLDL. Moreover, EPA-VLDL-treated macrophages had less triglyceride accumulation than Ctrl-VLDL-treated macrophages. Inhibition of lipoprotein lipase (LPL) appeared to suppress inflammation and triglyceride accumulation by Ctrl-VLDL suggesting that hydrolysis of VLDL is required for the pro-inflammatory properties of VLDL. Free fatty acid release from EPA-VLDL by macrophages and purified LPL was less than that from Ctrl-VLDL. Extracellular LPL mass was decreased by EPA-VLDL. Taken together, these findings indicate that the pro-inflammatory properties of VLDL were attenuated by EPA administration via decrease in susceptibility of VLDL to LPL. It appears possible that anti-inflammatory effects of EPA on VLDL contribute to the suppression of cardiovascular risk by EPA.

Cide-a and Cide-c are induced in the progression of hepatic steatosis and inhibited by eicosapentaenoic acid.

Cide-a and Cide-c belong to the cell death-inducing DNA fragmentation factor-alpha-like effector family. Recent evidences suggest that these proteins may be involved in lipid accumulation in liver and adipose tissues. We confirmed that in the high-fat/high-sucrose diet-induced murine model of hepatic steatosis, the expression levels of the Cide-a and Cide-c genes were markedly and time-dependently increased, but returned to normal levels following improvement of hepatic steatosis by eicosapentaenoic acid (EPA) administration. Levels of expression of the Cide-a and Cide-c genes correlated well with plasma ALT. EPA inhibited the promoter activity of the Cide-a gene in vitro. Sterol regulatory element-binding protein-1 (SREBP-1) markedly enhanced the promoter activity of Cide-a, and EPA inhibited the expression of Cide-a mRNA. SREBP-1 and EPA did not affect those of Cide-c. These findings indicate that Cide-a and Cide-c are closely involved in the progression of hepatic steatosis, and that EPA inhibits Cide-a gene expression through SREBP-1 regulation.