Microalgae polysaccharides ameliorates obesity in association with modulation of lipid metabolism and gut microbiota in high-fat-diet fed C57BL/6 mice

Microalgae are emerging as a good source of natural nutraceuticals and medicines. This study aims at evaluating the anti-obesity effects of two microalgae polysaccharides (CPS from Chlorella pyrenoidosa and SPS from Spirulina platensis) in high-fat diet (HFD)-induced obese C57BL/6 mice, with β-glucan as a positive control polysaccharide. CPS, SPS and β-glucan were daily administered intragastrically during 10-week HFD feeding, and conferred equally effective protection against overweight, energy imbalance, glucose tolerance impairment, systemic inflammation, dyslipidemia, and fat deposition in the liver and epididymal white adipose tissues. By western blotting analysis of CPT-1, PPARγ and SREBP-1c, those polysaccharides increased lipolysis and decreased lipogenesis in the liver. According to high-throughput sequencing of fecal 16S rRNA, CPS, SPS and β-glucan corrected the HFD-induced gut dysbiosis similarly by increasing beneficial bacteria especially Clostridia, Bacterioidia and Mollicutes and decreasing unfavorable bacteria especially Actinobacteria and Verrucomicrobia and, as revealed by PICRUSt functional analysis, they restored the HFD-induced perturbations in many gut bacterial enzymes and pathways involved in the metabolism of SCFAs, secondary bile acids and trimethylamine, implicating a possible anti-obesity mechanism through gut microbiome-mediated modulation of host lipid metabolism. Microalgae polysaccharides can thus serve as potent alternative food ingredients to improve disease conditions in obese patients.