It has been recently identified that Gram-negative, mucin-degrading bacteria, reside in the mucus layer and comprise of 3-5% of the gut microbiota (14). Studies show that the number of mucin degrading bacteria is inversely correlated with obesity and diabetes. While another study, a Chinese Metabolome-genome-wide association study (MGWAS) showed opposite result (15)(16). Everard et al recently presented a study, which suggested the protective function of A. muciniphila (17). This study found that there was a significant decrease in the concentration of A. muciniphila in genetic and dietary model of murine obesity but after prebiotic treatment concentration was restored to basal levels and improved metabolic function, gut integrity and metabolic endotoxemia. These studies suggest that A. muciniphila is able to influence glucose metabolism, TJ complex expression and improves intestinal barrier, but this study showed that only live bacteria can have a beneficial effect not the heat killed A muciniphila (18). This study showed that Akkermansia improve intestinal permeability by increasing mucus lay thickness, which have been confirmed by histopathological findings only. There are many other methods are available to measure the intestinal integrity, such as ussing chamber, LPS assay, labeled live bacteria and FD-4, (a fluorescein labelled dextran) method. These methods would help to get more detail information about Akkermansia and its impact on functional change in intestinal permeability. In another study published by same group, in this study author showed that either pasteurized A. muciniphila and membrane protein of A. muciniphila (Amuc1100) has impact to improve endotoxemia, reduced adiposity and improved gut barrier function in High fat diet (HFD) fed mice. The administration of pasteurized A. muciniphila or Amuc_1100* to mice with HFD-induced obesity, reduced LPS leakage and increased the expression of genes encoding tight-junction proteins in jejunal and ileal tissues, which supports author’s hypothesis that pasteurized A. muciniphila and Amuc_1100* alleviate metabolic endotoxemia by strengthening the gut barrier. Though This study showed the advantage of pasteurized A. muciniphila and Amuc1100 on intestinal barrier integrity, but this study lacks another bacterium (as a control) such as Lactobacillus plantarum (a good candidate of probiotic) to compare with A. muciniphila (live or pasteurized) because according to one study that that probiotic bacteria could partly or fully retain their beneficial effects even after pasteurization (19)(20). So, it could be better to compare both bacteria (live or pasteurized) together.
Both studies showed that A. muciniphila (live or pasteurized) and Amuc1100 improve intestinal permeability in HFD induced obesity. But there are some flaws in both studies, which I would like to point out here such as in both studies authors used conventionally raised animals model not the germ-free animals and only focused on Akkermansia only not the other gut bacteria and their response. In both studies they did not use appropriate method to measure the intestinal permeability, which can show functional change in intestinal barrier after Akkermansia (live or pasteurized) treatment.
Another interesting fact about Akkermansia are still somewhat controversial as, for example, one study, which demonstrated that presence of Akkermansia in well-defined gnotobiotic mouse model associated with a defined simplified human intestinal microbiota (SIHUMI) of eight bacterial species (Anaerostipes caccae, Bacteroides thetaiotaomicron, Bifidobacterium longum, Blautia producta, Clostridium ramosum, Escherichia coli and Lactobacillus plantarum ) infected with Salmonella typhymurium, disrupt mucus layer barrier, significantly increased histopathology scores and worsen the inflammatory response (21).
These three studies showed conflicting results about A muciniphila and its impact on intestinal barrier during obesity, which suggests that further studies and selection of suitable methods to measure the gut barrier and good study design may help to clarify the role of this bacterium.