Blue-Green Algae Inhibit the Development of Atherosclerotic Lesions in Apolipoprotein E Knockout Mice

Abstract

Hyperlipidemia and inflammation contribute to the development of atherosclerotic lesions. Our objective was to determine antiatherogenic effect of edible blue-green algae (BGA) species, that is, Nostoc commune var. sphaeroides Kützing (NO) and Spirulina platensis (SP), in apolipoprotein E knockout (ApoE(-/-)) mice, a well-established mouse model of atherosclerosis. Male ApoE(-/-) mice were fed a high-fat/high-cholesterol (HF/HC, 15% fat and 0.2% cholesterol by wt) control diet or a HF/HC diet supplemented with 5% (w/w) of NO or SP powder for 12 weeks. Plasma total cholesterol (TC) and triglycerides (TG) were measured, and livers were analyzed for histology and gene expression. Morphometric analysis for lesions and immunohistochemical analysis for CD68 were conducted in the aorta and the aortic root. NO supplementation significantly decreased plasma TC and TG, and liver TC, compared to control and SP groups. In the livers of NO-fed mice, less lipid droplets were present with a concomitant decrease in fatty acid synthase protein levels than the other groups. There was a significant increase in hepatic low-density lipoprotein receptor protein levels in SP-supplemented mice than in control and NO groups. Quantification of aortic lesions by en face analysis demonstrated that both NO and SP decreased aortic lesion development to a similar degree compared with control. While lesions in the aortic root were not significantly different between groups, the CD68-stained area in the aortic root was significantly lowered in BGA-fed mice than controls. In conclusion, both NO and SP supplementation decreased the development of atherosclerotic lesions, suggesting that they may be used as a natural product for atheroprotection.

Keywords: Nostoc commune var. sphaeroids kutzing; atherosclerosis; blue-green algae.

FIG. 1.

Effects of blue-green algae (BGA) supplementation on plasma total cholesterol (TC) and triglyceride (TG) concentrations at 6 and 12 weeks. Male ApoE^−/− mice were fed an atherogenic diet or atherogenic diet supplemented with 5% NO or 5% SP for 12 weeks. Plasma TC (A) and TG (B) levels were determined by an enzymatic analysis after 6 (left panel) or 12 (right panel) weeks on experimental diets. Horizontal lines are means, and groups with a different letter are significantly different (P < .05). Values are mean ± SEM. n = 10 for control, n = 12 for NO, and n = 14 for SP.

FIG. 2.

Effects of BGA supplementation on hepatic lipid metabolism of ApoE^−/− mice fed an atherogenic diet or atherogenic diet supplemented with 5% NO or 5% SP for 12 weeks. (A) liver weight. (B) liver TC content. (C) liver TG levels. Horizontal lines are means, and groups with a different letter are significantly different (P < .05).Values are mean ± SEM. n = 12 for NO and n = 14 for SP. (D) Representative liver sections stained with Hematoxylin and Eosin. 40× magnification. Bar = 20 μm. Color images available online at www.liebertpub.com/jmf

FIG. 3.

Antiatherogenic effects of BGA feeding in ApoE^−/− mice fed an atherogenic diet or atherogenic diet supplemented with 5% NO or 5% SP for 12 weeks. (A) Representative aortas stained with Oil red O for visualization at 5× magnification. (B) Aortic lesion area expressed as % of total lesion area over total aortic surface area. Horizontal lines are means, and groups with a different letter are significantly different (P < .05). (C) Representative aortic root sections stained with Oil Red O and counterstained with Hematoxylin and Eosin (upper panel). CD68 immunostaining (lower panel). Quantification of lesions (D) and CD68 (E) in the aortic root. Data represent as mean ± SEM, and bars with a different letter are significantly different (P < .05). n = 10 for control, n = 12 for NO, and n = 14 for SP.