Characterization of the structure and analysis of the anti-oxidant effect of microalga Spirulina platensis polysaccharide on Caenorhabditis elegans mediated by modulating microRNAs and gut microbiota

The antioxidant activity of Spirulina platensis polysaccharide (SPP) was investigated in Caenorhabditis elegans. Nuclear magnetic resonance, Fourier-transform infrared, multi-angle laser light scattering, and GC–MS were used to identify the structural characteristics of SPP. It was composed of the →2)-α-L-Rhap-(1→, →4)-β-D-Manp-(1→, →6)-β-D-Glcp-(1→, →4)-β-Xylp-(1→, →3)-β-L-Araf-(1→, and →2)-β-L-Fucp-(1→, respectively. The modulation of gut microbiota in C. elegans was determined using 16S rRNA gene high-throughput sequencing. The malondialdehyde (MDA) content was significantly decreased, while the total superoxide dismutase (T-SOD) and reactive oxygen species (ROS) levels were improved after SPP supplementation. The cellular mitochondrial content and apoptosis were significantly down-regulated. The obvious increased levels of the DAF-16 and SKN-1 mRNAs were observed in the SPP-treated group, while the levels of miR-48 and miR-51 were significantly reduced. Moreover, SPP administration significantly increased the abundance of Flavobacterium, Achromobacter, Empedobacter, Anaerolinea, and Pseudoalteromonas of the intestinal flora. Based on these results, S. platensis polysaccharides may be used as a functional food to ameliorate diseases related to oxidative stress.