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 Willem de Vos. Extensive research is being undertaken to understand its association with obesity, diabetes, and inflammation.
Biology and Biochemistry.
"A. muciniphila" is a Gram-negative, strictly anaerobic, non-motile, non-spore-forming, oval-shaped bacterium. Its type strain is MucT (=ATCC BAA-835T =CIP 107961T). "A. muciniphila" is able to use mucin as its sole source of carbon and nitrogen, is culturable under anaerobic conditions on medium containing gastric mucin, and is able to colonize the gastrointestinal tracts of a number of animal species.
Recently, "A. muciniphila" strain Urmite became the first (evidently) unculturable bacterial strain to be sequenced in its entirety entirely from a human stool sample.
Human metabolism.
"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 inflammatory bowel disease (IBD). In one study, reduced levels of "A. muciniphila" correlated with increased severity of appendicitis. In a separate study, IBD patients were found to have lower levels "A. muciniphila" in their intestinal tract than individuals without IBD.
Researchers have discovered that "A. muciniphila" could be used to combat obesity and type 2 diabetes. The first study was carried out with mice, overfed to contain three times more fat than their 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. This effect was associated with a restoration of a proper gut barrier function, which means the absence of leakage of inflammatory bacterial compounds in the blood. Interestingly, in the same study, the authors found that if the bacteria was killed by very high temperature (autoclaving), the bacteria was unable to improve the metabolic response. 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.
In August 2015, additional research demonstrated that dietary fats influence the growth of "Akkermansia muciniphilia" relative to other bacterium in the dietary tract. Researchers conducted a study in which mice were fed diets which varied in fat composition but were otherwise identical: one group received lard, while the other received fish oil. After 11 weeks, the group receiving a fish oil diet had increased levels of "A. muciniphila" and bacterium of genus "Lactobacillus", while the group receiving a lard diet had decreased levels of "A. muciniphila" and "Lactobacillus". Additionally, fecal material from mice on the fish oil diet or the lard based diet was transplanted into a new group of mice which had their native gut flora eradicated by antibiotics. All of these mice were then fed a lard based diet. Despite receiving the same lard-based diet for 3 weeks, recipients of transplants from lard-fed donor mice showed increased levels of "Lactobacillus" and increased levels of inflammation, while recipients of transplants from fish oil-fed donors showed increased levels of "A. muciniphila" and decreased levels of inflammation. Researchers concluded that the increase in "A. muciniphila" corresponded to a reduction in inflammation, indicating a link between dietary fats, gut flora composition, and inflammation levels. In 2017, it was discovered that pasteurizing (70 °C 30min) the bacteria increased the beneficial effects of the bacteria by a mechanism likely associated with the presence of a protein present on the outer membrane of "Akkermansia muciniphila" and called Amuc_1100. Then in 2019, the same team of Belgian researchers from the UCLouvain tested for the first time in humans the impact of an oral supplementation with either "A. muciniphila" alive or pasteurized versus a placebo for 3 months. In this double-blind placebo-controlled proof-of-concept study, they found that the overweight or obese insulin resistant subjects displayed an improved metabolism with lower blood insulin, lower insulin resistance, lower inflammation and better cardiometabolic profile. More recently, they have linked this effect with the possible increased production of some endocannabinoids acting on the receptor PPAR-a.
Effects in cancer immunotherapy treatment.
One study looked at 249 patients with lung or kidney cancer, "A. muciniphila" was in 69% of patients that did respond compared with just a third of those who did not. Boosting levels of "A. muciniphila" in mice seemed to also boost their response to immunotherapy.
Effects in ALS in a mouse model.
Researchers discovered that a mouse model of Amyotrophic lateral sclerosis suffers from an abnormal gut microbiome, and that supplementing these mice with "Akkermansia muciniphila" improved their symptoms, slowed the progression of their disease, and increased their survival. Moreover, they found that "A. muciniphila" produce the vitamin nicotinamide, which when injected into the diseased mice improved their motor symptoms, although it did not increase their lifespan as the bacteria had. They also found lower levels of nicotinamide in the circulation and the cerebrospinal fluid (CSF) of a small sample human ALS patients compared to their family members, and lower levels of "A. muciniphila" in their stool. In addition, ALS patients with lower levels of nicotinamide in their blood tended to have worse symptoms than patients with higher levels.