Euphausia pacifica (North Pacific Krill): Review of Chemical Features and Potential Benefits of 8-HEPE against Metabolic Syndrome, Dyslipidemia, NAFLD, and Atherosclerosis

Abstract

Marine n-3 fatty acids are well known to have health benefits. Recently, krill oil, which contains phospholipids, has been in the spotlight as an n-3 PUFA-containing oil. Euphausia pacifica (E. pacifica), also called North Pacific krill, is a small, red crustacean similar to shrimp that flourishes in the North Pacific Ocean. E. pacifica oil contains 8-hydroxyeicosapentaenoic acid (8-HEPE) at a level more than 10 times higher than Euphausia superba oil. 8-HEPE can activate the transcription of peroxisome proliferator-activated receptor alpha (PPARα), PPARγ, and PPARδ to levels 10, 5, and 3 times greater than eicosapentaenoic acid, respectively. 8-HEPE has beneficial effects against metabolic syndrome (reduction in body weight gain, visceral fat area, amount of gonadal white adipose tissue, and gonadal adipocyte cell size), dyslipidemia (reduction in serum triacylglycerol and low-density lipoprotein cholesterol and induction of serum high-density lipoprotein cholesterol), atherosclerosis, and nonalcoholic fatty liver disease (reduction in triglyceride accumulation and hepatic steatosis in the liver) in mice. Further studies should focus on the beneficial effects of North Pacific krill oil products and 8-HEPE on human health.

Keywords: 8-HEPE; Euphausia pacifica; N-3 polyunsaturated fatty acids; nonalcoholic fatty liver disease.

Figure 1

(A) Photograph of Euphausia pacifica (E. pacifica), also called North Pacific krill. (B) The structural formula of 8-hydroxyeicosapentaenoic acid (8-HEPE).

Figure 2

(A) Representative computed tomography images of the abdomen (upper) and percentage changes in visceral fat area (lower) in mice fed an HFD only or an HFD with 8-HEPE. Visceral and subcutaneous fat areas are shown in red. Data are the mean ± SE obtained from eight mice for each group. (B) Blood sugar (BS) in apoE knock-out (apoE-KO) mice fed a WD only or WD with 8-HEPE. Data are the mean ± SE obtained from 10 mice for each group. An analysis of variance (ANOVA) with Dunnett’s test was used for the statistical analysis. HFD, high fat diet; 8-HEPE, 8-hydroxyeicosapentaenoic acid; WD, western diet.

Figure 3

Representative images of the aorta (left) stained with Sudan IV and percentage lesion area of atherosclerosis (right) in apoE-KO mice fed a Western diet (WD) only or a WD with 8-HEPE (WD + 8-HEPE). Data are the mean ± SE obtained from eight mice for each group. An analysis of variance (ANOVA) with Dunnett’s test was used for the statistical analysis. SD, standard diet; NS, not significant.

Figure 4

Potential beneficial effects of 8-HEPE against metabolic syndrome, dyslipidemia, NAFLD, and atherosclerosis. HFD, high-fat diet; WD, Western diet; apoE-KO, apolipoprotein E knock out; LDLR-KO, low-density lipoprotein receptor knock out; TAG, triacylglycerol; IL-6, interleukin 6; OxLDL, oxidized LDL; ABCA1, ATP-binding cassette transporter 1.