Spirulina Protects against Hepatic Inflammation in Aging: An Effect Related to the Modulation of the Gut Microbiota?

Abstract

Aging predisposes to hepatic dysfunction and inflammation that can contribute to the development of non-alcoholic fatty liver disease. Spirulina, a cyanobacterium used as a food additive or food supplement, has been shown to impact immune function. We have tested the potential hepatoprotective effect of a Spirulina in aged mice and to determine whether these effects can be related to a modulation of the gut microbiota. Old mice have been fed a standard diet supplemented with or without 5% Spirulina for six weeks. Among several changes of gut microbiota composition, an increase in Roseburia and Lactobacillus proportions occurs upon Spirulina treatment. Interestingly, parameters related to the innate immunity are upregulated in the small intestine of Spirulina-treated mice. Furthermore, the supplementation with Spirulina reduces several hepatic inflammatory and oxidative stress markers that are upregulated in old mice versus young mice. We conclude that the oral administration of a Spirulina is able to modulate the gut microbiota and to activate the immune system in the gut, a mechanism that may be involved in the improvement of the hepatic inflammation in aged mice. Those data open the way to new therapeutic tools in the management of immune alterations in aging, based on gut microbe-host interactions.

Keywords: Spirulina; aging; gut-liver axis; inflammaging; microbiota.

Figure 1

Non-metric dimensional scaling built on a Bray-Curtis distance matrix computed at the species level (A); Total bacteria measured by qPCR (B); Bacterial diversity deduced from the inverse Simpson Index (C); Bacterial richness deduced from the Chao1 Index (D); Bacterial evenness deduced from the Simpson Index (E). Old mice were fed a standard diet supplemented with or without Spirulina for six weeks and were compared to young mice fed a standard diet. Data of the whiskers plots show the minimum and maximum. Data with different superscript letters are significantly different at p < 0.05 (ANOVA).

Figure 2

Changes in microbial populations in the caecal content, assessed by 16S profiling (A–C) and qPCR (D–F). Relative abundances of bacterial phyla (A) and bacterial taxa accounting for more than 1%, at the family (B) and genus levels (C). qPCR analysis of Roseburia spp. (D) and Lactobacillus spp. (E) in the caecal content. Old mice were fed a standard diet supplemented with or without Spirulina for six weeks and were compared to young mice fed a standard diet.

Figure 3

Effect of Spirulina on the expression of antimicrobial peptides in the ileum. RegIIIγ encoded by Reg3g (A), phospholipase A2 group II encoded by Pla2g2 (B), α-defensins encoded by Defa (C), and lysozyme C encoded by Lys (D). Old mice were fed a standard diet supplemented with or without Spirulina for six weeks and were compared to young mice fed a standard diet. Data with different superscript letters are significantly different at p < 0.05 (ANOVA).

Figure 4

Expression of inflammatory markers in the jejunum (A), ileum (B), and colon (C). Old mice were fed a standard diet supplemented with or without Spirulina for six weeks and were compared to young mice fed a standard diet. Values are expressed as relative units with the mean of young mice values set at 1. * p < 0.05 versus young mice; ^§ p < 0.05 versus old-CT mice (ANOVA). IFNγ, interferon gamma; IL, interleukin; MCP1, monocyte chemotactic protein-1.

Figure 5

Expression of TLR2 (A) and TLR4 (B) in the ileum. Levels of TLR2 (C) and TLR4 (D) agonist activities in feces and in Spirulina, itself. Old mice were fed a standard diet supplemented with or without Spirulina for six weeks and were compared to young mice fed a standard diet. Data with different superscript letters are significantly different at p < 0.05 (ANOVA). TLR, toll like receptor.

Figure 6

Expression of inflammatory and oxidative markers in the liver. Old mice were fed a standard diet supplemented with or without Spirulina for six weeks and were compared to young mice fed a standard diet. Values are expressed as relative units with the mean of young mice values set at 1; * p < 0.05 versus young mice; ^§ p < 0.05 versus old-CT mice (ANOVA). COX2, cyclooxygenase 2; IFNγ, interferon gamma; IL, interleukin; LBP, lipopolysaccharide binding protein; MCP1, monocyte chemotactic protein-1; NADPHox, NADPH oxidase; TLR, toll like receptor; TNFα, tumor necrosis factor alpha.