Oral administration of a Spirulina extract protects old mice against hepatic “ammaging”

Background & aims: Ageing predisposes to hepatic dysfunction and inflammation that can evolve to non-alcoholic fatty liver disease. Spirulina, a cyanobacterium used as a food additive or food supplement, has been shown to impact immune functions and to improve non-alcoholic steatohepatitis in obese mice. The aim of the present study was to test the potential hepatoprotective effects of Spirulina extract supplementation in aged mice and to determine whether these effects can be related to a modulation of the gut microbiota. Methods: Old mice of 24 months were fed a control diet supplemented with or without 5% Spirulina extract (Biores, Liège, Belgium) and were compared to young mice of 3 months during 6 weeks. Results: Combination of pyrosequencing and qPCR analyses of the 16S rRNA gene revealed a decrease in total bacteria and -among specific changes of gut microbiota composition,- an increase in Allobaculum, Blautia, Roseburia, and Lactobacillus populations by Spirulina treatment. Interestingly, parameters related to the innate immunity, especially T Regulatory cells (FoxP3), CD11b-dendritic cells, cytokines (IL6, IFN MCP-1) and antimicrobial peptides (Pla2g2, Reg3) were upregulated in the small intestine of Spirulina-treated mice. Aged mice exhibited inflammation and oxidative stress in the liver tissue as compared to young mice. The supplementation with Spirulina extract reduced several hepatic inflammatory and oxidative stress markers in old mice. Conclusions: Our study shows for the first time that the oral administration of a Spirulina is able to modulate the gut microbiota, to activate immune system in the gut, thereby improving hepatic inflammation in aged mice. Those data allow to envisagesuggest a new therapeutic tools in the management of immune and metabolic alterations in ageing, based on gut microbes-host interactions