In a first-of-its-kind human trial, a team of researchers administered a specific strain of gut bacteria to overweight and obese volunteers to evaluate its benefits for cardiometabolic health. The study intriguingly discovered a pasteurized form of the bacteria conferred more benefits than the traditional live probiotic form.

Akkermansia muciniphila is species of gut bacteria receiving quite a bit of scientific attention for its purported beneficial health effects. As well as being one of the most abundant single gut bacteria species in the human microbiome, low levels of A. muciniphila have been associated with everything from obesity and diabetes to inflammatory bowel disease. It has even been suggested that A. muciniphila supplements could enhance the efficacy of certain cancer treatments.

To examine whether A. muciniphila actually functions as a therapeutic treatment in humans, a pilot study set out to explore the safety and tolerability of the bacteria in a small group of overweight or obese insulin-resistant subjects. Forty individuals were randomized into three different treatment groups receiving either a placebo, a live dose, or a pasteurized dose daily for a period of three months.

Being an initial proof-of-concept study the primary endpoint was to evaluate how safe the daily supplements were, and the trial was a complete success on this endpoint. There were no adverse events in either the live or the pasteurized groups, suggesting long-term supplementation of A. muciniphila to be relatively safe.

A variety of secondary outcomes following changes to several metabolic parameters revealed an interesting result. Those subjects receiving the pasteurized form of A. muciniphila displayed significant improvements to several insulin markers as well as a lowering in total blood cholesterol. Other improvements seen included a minor decrease in body weight, and a reduction in liver inflammation markers. But, those subjects receiving the live form of the bacteria did not display these same improvements, generally trending closer to the placebo group across most of these benchmarks.

This distinction between the effects of pasteurized and live A. muciniphila has previously been demonstrated in mouse studies, so the results here are not entirely unexpected. However, it is not clear exactly why the pasteurized bacteria confers more metabolic benefits than the live bacteria. It may be that the pasteurization process maintains enough active components of the bacteria to trigger a positive response, such as the cell-wall components and bacterial peptides, while inhibiting the bacteria's potential to replicate, which could interfere with these beneficial outcomes.

The researchers readily admit these results need to be verified in larger studies before any further conclusions can be generated, but this is undeniably an intriguing early pilot study. Ana Valdes, an expert in musculoskeletal genetics who did not participate in this particular study, suggests this is good quality research with impressive potential outcomes, but broader work is necessary to more consistently understand what could be generating these beneficial outcomes.

"Although the benefits of probiotic supplementation have been widely investigated, this is, to my knowledge the first time that a bacterial strain identified from microbiome studies has been isolated, cultured and then safely fed to humans," says Valdes. "If the beneficial effects on hepatic function or insulin resistance can be replicated and shown in a more consistent way then it may have important health implications."

The new study was published in the journal Nature Medicine.