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.
Biology and Biochemistry
A. muciniphila is a Gram-negative, strictly anaerobic, non-motile, non-spore-forming, oval-shaped bacterium. Its type strain is MucT. 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 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. 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 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. 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.
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.
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 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.
