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Biological functions of a blue-green alga, Nostoc commune var. sphaeroides Kützing (N. commune)
Abstract
Nostoc commune var. shproides Kützing (N. commune), a blue-green alga, has been used as a medicinal food for centuries, but many of its biological functions have not been elucidated. The primary objective of this study was to determine the effect of N. commune on inflammation and cholesterol metabolism, several risk factors of atherosclerosis. Anti-inflammatory functions of N. commune were assessed using RAW 264.7 macrophages, a murine macrophage cell line. Incubation with N. commune lipid extract reduced pro-inflammatory markers such as tumor necrosis factor α (TNFα), cyclooxygenase 2 (COX-2), interleukin-1β (IL-1β) and inducible nitric oxide synthase (iNOS) in a nuclear factor-kappa B (NF-κB) dependent manner ( P < 0.05). Contributing to its potential anti-antherogenic effect, N. commune reduced cholesterol biosynthesis in HepG2 cells, a human hepatoma cell line, by inhibiting the maturation of sterol regulatory element binding protein 2 (SREBP-2) and subsequently reducing the expression of its target genes, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) and low-density lipoprotein receptor (LDLR). To further substantiate the role of N. commune as an athero-protective compound, C57BL/J6 mice were fed the AIN-93M diet supplemented with 0 or 5% N. commune. N. commune-fed mice exhibited reduced plasma total cholesterol concentrations by ∼20% (P = 0.003) as well as reduced cholesterol absorption in coordination with increased fecal neutral sterol output (P < 0.05). The expression of cholesterol modulating genes, including SREBP-2 and HMGR, were significantly increased in mice fed N. commune ( P < 0.030), indicating that N. commune intake affected hepatic cholesterol metabolism. In addition, the effects of blue-green alga intake on intestinal microflora were explored. Consumption of N. commune, Spriluna platensis and Aphanizomenon flos-aquae altered the gastrointestinal microbiota population in mice, with N. commune having the most pronounced effect on host microbiota. These data elucidate the molecular mechanisms by which N. commune may regulate both cholesterol metabolism and inflammation, providing evidence for N. commune to be used as a dietary supplement to lower the risk of coronary heart disease.
Subject Area
Microbiology|Nutrition
Recommended Citation
Rasmussen, Heather E, "Biological functions of a blue-green alga, Nostoc commune var. sphaeroides Kützing (N. commune)" (2008). ETD collection for University of Nebraska-Lincoln. AAI3331442.
https://digitalcommons.unl.edu/dissertations/AAI3331442