Physicochemical Characterization of a Polysaccharide from Green Microalga Chlorella pyrenoidosa and Its Hypolipidemic Activity via Gut Microbiota Regulation in Rats.

A bioactive polysaccharide from microalga Chlorella pyrenoidosa (CPP) was successively prepared via DEAE-52 and G-100 columns. Nuclear magnetic resonance analysis showed that the main glycosidic bonds were composed of 1,2-linked-α-l-Fucp, 1,4-linked-α-l-Rhap, 1,4-linked-ß-l-Araf, 1-linked-α-d-Glcp, 1,3-linked-ß-d-GlcpA, 1,4-linked-ß-d-Xylp, and 1,3,6-linked-ß-d-Manp. Its molecular weight was 5.63 × 106 Da. The hypolipidemic effect and intestinal flora regulation of CPP on diet-induced rats were evaluated through histopathology and biochemistry analyses. CPP could improve plasma and liver lipid metabolism and accelerate the metabolism of the cecal total bile acids and short-chain fatty acids. CPP has also upregulated the adenosine-monophosphate-activated protein kinase α and downregulated the acetyl-CoA carboxylase, sterol regulatory element-binding protein 1c, and ß-hydroxy ß-methylglutaryl-CoA expressions. Moreover, with the 16S rRNA gene sequencing, it was revealed that the composition of intestinal flora changed drastically after treatment, such as the bloom of Coprococcus_1, Lactobacillus, and Turicibacter, whereas there was a strong reduction of the [Ruminococcus]_gauvreauii_group. The above results illustrated that CPP might be served as an effective ingredient to ameliorate lipid metabolism disorders and intestinal flora in hyperlipidemia rats.

Anti-diabetic effect of oligosaccharides from seaweed Sargassum confusum via JNK-IRS1/PI3K signalling pathways and regulation of gut microbiota.

Brown seaweed Sargassum confusum (C. Agardh) has been used in traditional Chinese medicine to treat a variety of diseases. The aim of the present study was to evaluate the anti-diabetic effect of oligosaccharides from brown seaweed S. confusum (SCO). The anti-diabetic effect of SCO was evaluated in vivo using high-fat/high-sucrose fed hamsters. Molecular mechanisms of modulating gene expression of specific members of insulin signaling pathways were determined. The components of the intestinal microflora in diabetic animals were also analyzed by high-throughput 16S rRNA gene sequencing. And it was found that SCO had a sequence of sulfated anhydrogalactose and methyl sulfated galactoside units. Fasting blood glucose levels were significantly decreased after SCO administration. Histology showed that SCO could protect the cellular architecture of the liver. SCO could also significantly increase the relative abundance of Lactobacillus and Clostridium XIVa and decrease that of Allobaculum, Bacteroides and Clostridium IV. The active role of SCO in anti-diabetic effect was revealed by its regulation of insulin receptor substrate 1/phosphatidylinositol 3-kinase and c-Jun N-terminal kinase pathways. These results suggested that SCO might be used as a functional material to regulate gut microbiota in obese and diabetic individuals.

Polyunsaturated fatty acids from microalgae Spirulina platensis modulates lipid metabolism disorders and gut microbiota in high-fat diet rats.

Effects of Spirulina platensis 55% ethanol extract (SPL55) on lipid metabolism in high-fat diet-induced hyperlipidaemic rats were investigated. Ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry indicated that SPL55 was enriched with polyunsaturated fatty acids. Meanwhile, serum and liver lipid levels, including total triglyceride, total cholesterol, and low-density-lipoprotein cholesterol, were significantly decreased in hyperlipidaemic rats of SPL55. Analysis of tissue sections showed that SPL55 treatment could markedly inhibit hepatic lipid accumulation and steatosis. Moreover, SPL55 regulated the mRNA and protein expression levels of SREBP-1c, HMG-CoA, PEPCK, ACC, and AMPK genes involved in lipid metabolism. Furthermore, SPL55 led to decrease the abundances of Turicibacter, Clostridium_XlVa, and Romboutsia, which were positive correlation with lipid metabolism indicators, and has also enriched Alloprevotella, Prevotella, Porphyromonadaceae, and Barnesiella. These results provided evidence that SPL55 might be developed as a functional food to ameliorate lipid metabolic disorders and hyperlipidaemia.

Anti-diabetic activity of PUFAs-rich extracts of Chlorella pyrenoidosa and Spirulina platensis in rats.

The contributions to hypoglycemic function and gut microbiota regulation by water and ethanol extracts of the microalgae Chlorella pyrenoidosa and Spirulina platensis were determined. An ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry analysis indicated that most of the compounds in the 55% ethanol extracts of C. pyrenoidosa (CP55) and S. platensis (SP55) were polyunsaturated fatty acids. After an 8-week high-fat high-sucrose diet with C. pyrenoidosa and S. platensis supplementation, glucose tolerance was improved, and the composition of the gut microbiota was altered. The diversity of the gut bacterial community was evaluated using 16S rRNA gene pyrosequencing. C. pyrenoidosa supplementation increased the abundance of Ruminococcus, Parasutterella, and Erysipelotrichacea and decreased the abundance of Lactobacillus, Turicibacter, and Blautia; S. platensis supplementation increased the abundance of Oscillibacter, Parasutterella, and Alloprevotella and decreased the abundance of Turicibacter. Moreover, Erysipelotrichacea and Ruminococcus were uniquely increased in C. pyrenoidosa treatment groups. Thus, CP55 and SP55 may be developed as effective natural food materials for preventing diabetes, and Ruminococcus may play a vital role in the treatment of diabetes.

Regulatory Efficacy of the Polyunsaturated Fatty Acids from Microalgae Spirulina platensis on Lipid Metabolism and Gut Microbiota in High-Fat Diet Rats.

Ultra-high performance liquid chromatography coupled with photo-diode array detector and electrospray ionization-mass spectrometry was employed to analyze the major fatty acids in Spirulina platensis 95% ethanol extract (SPL95). The effects of SPL95 on hepatoprotection were evaluated, including liver tissue histopathology, liver, and serum biochemical analysis. The active principle of SPL95 revealed a hypolipidemic effect, as indicated by down-regulating the mRNA and protein levels of sterol regulatory element-binding transcription factor-1c, 3-hydroxy-3-methyl glutaryl coenzyme A reductase, acetyl CoA carboxylase pathway, and upregulating adenosine 5'-monophosphate-activated protein kinase-α in liver. SPL95 enriched the beneficial bacteria, including Prevotella, Alloprevotella, Porphyromonadaceae, Barnesiella, and Paraprevotella. Treatment with SPL95 led to a decrease in microbes, such as Turicibacter, Romboutsia, Phascolarctobacterium, Olsenella, and Clostridium XVIII, which were positively correlated with serum triglyceride, total cholesterol, and low-density-lipoprotein cholesterol levels, but negatively correlated with the serum high-density-lipoprotein cholesterol levels. These results provide evidence that the fatty acid from SPL95 may be used as a novel adjuvant therapy and functional food to regulate gut microbiota in obese and diabetic individuals.