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TAXONOMY: PVC group -> Verrucomicrobia -> Verrucomicrobiae -> Verrucomicrobiales -> Akkermansiaceae -> Akkermansia -> Akkermansia muciniphila
Akkermansia muciniphila is a species of human intestinal mucin-degrading bacterium, the type species for a new genus, Akkermansia, proposed in 2004 by Muriel Derrien and others. Extensive research is being undertaken to understand its association with obesity, diabetes, and inflammation. A. muciniphila is a Gram-negative, strictly anaerobic, non-motile, non-spore-forming and oval-shaped. A. muciniphila is able to use mucin as its sole source of carbon and nitrogen, and is able to colonize the gastrointestinal tracts of a number of animal species. A. muciniphila is believed to have anti-inflammatory effects in humans, and studies have shown inverse relationships between A. muciniphila colonization and inflammatory conditions such as appendicitis or irritable bowel syndrome (IBS). In one study, reduced levels of A. muciniphila correlated with increased severity of appendicitis. In a separate study, IBS patients were found to have lower levels A. muciniphila in their intestinal tract than individuals without IBS. Researchers have discovered that A. muciniphila may be able to be used to combat obesity and type 2 diabetes. The study was carried out with mice, overfed to contain three times more fat than its lean cousin. The obese mice were then fed the bacteria, which were shown to reduce the fat burden of the mice by half without any change to the mice's diet. A study published in June 2015 showed an association between A. muciniphila abundance, insulin sensitivity and healthier metabolic status in overweight/obese adults. The healthier subjects were those with high A. muciniphila abundance and gut microbial richness. In addition, this study showed that having higher abundance of A. muciniphila at baseline was associated with greater clinical benefits after weight loss. The bacterium is naturally present in the human digestive tract at 3-5%, but has been seen to fall with obesity. It is thought that eating the bacterium increases the gut wall thickness, with the addition of mucin, which will block food from being absorbed by the body. The A. muciniphila genome analyses predict a large secretome with over 61 (11%) of proteins to be involved in the degradation of mucin. Metaomic data sets can easily be assessed for A. muciniphila as it is the single intestinal representatives of the deeply rooted Verrucomicrobia.
Proteome analyses from human fecal samples indicate that a high proportion of A. muciniphila mucus-degrading proteins are also expressed in vivo. In terms of host responses, it was shown that in the epithelial transcriptomes from gnotobiotic mice colonized with A. muciniphila; cecal colonization by A. muciniphila resulted in upregulation of genes involved in antigen presentation of leukocytes. In the colon, A. muciniphila induced multiple immune response-related pathways, involved in chemotaxis and complement cascade, parts of the innate immune response, but also in cell adhesion and the maturation of B and T cells. Finally, ileal colonization by A. muciniphila led to differential expression of genes involved in metabolic and signaling pathways, mainly via modulation of PPARα-dependent processes. These products can stimulate microbiota interactions and host response. Oligosaccharides and acetate stimulate growth and metabolic activity of bacteria that colonize close to the mucus layer. This may provide colonization resistance to pathogenic bacteria that have to cross the mucus layer to reach the intestinal cells. It is likely that during infection or inflammation the mucus layer gets damaged and the growth of Akkermansia spp. is automatically inhibited, causing an inhibition of microbes that coexist with Akkermansia spp.[PMC: 3401025] Enriched in type II diabetics.
This species has been identified as a resident in the human gastrointestinal tract based on the phylogenetic framework of its small subunit ribosomal RNA gene sequences.[PMC 4262072]
Ethanol exposure diminishes intestinal A. muciniphila abundance in both mice and humans and can be recovered in experimental alcoholic liver disease (ALD) by oral supplementation. A. muciniphila promotes intestinal barrier integrity and ameliorates experimental ALD. Patients with ALD might benefit from A. muciniphila supplementation.[PMID: 28550049] Identified as a 'core species' of the human gut microbiome. [PMID: 23222524]