Intestinal disorders often occur in cancer patients, in association with body weight loss, and this alteration is commonly attributed to the chemotherapy. Here, using a mouse model of cancer cachexia induced by ectopic transplantation of C26 cancer cells, we discovered a profound alteration in the gut functions (gut permeability, epithelial turnover, gut immunity, microbial dysbiosis) independently of any chemotherapy. These alterations occurred independently of anorexia and were driven by interleukin 6. Gut dysfunction was found to be resistant to treatments with an anti-inflammatory bacterium (Faecalibacterium prausnitzii) or with gut peptides involved in intestinal cell renewal (teduglutide, a glucagon-like peptide 2 analogue). The translational value of our findings was evaluated in 152 colorectal and lung cancer patients with or without cachexia. The serum level of the lipopolysaccharide-binding protein, often presented as a reflection of the bacterial antigen load, was not only increased in cachectic mice and cancer patients, but also strongly correlated with the serum IL-6 level and predictive of death and cachexia occurrence in these patients. Altogether, our data highlight profound alterations of the intestinal homeostasis in cancer cachexia occurring independently of any chemotherapy and food intake reduction, with potential relevance in humans. In addition, we point out the lipopolysaccharide-binding protein as a new biomarker of cancer cachexia related to gut dysbiosis.

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.