The gastrointestinal tract houses a complex community of gut microbiota, and researchers have focused recent studies to learn more about the potential interplay between intestinal bacteria and diseases. Here are four mewly-discovered links between gut bacteria and human health.

1. Chronic fatigue syndrome/ Myalgic encephalomyelitis

Researchers from Columbia University’s Mailman School of Public Health have discovered that patients who suffer from myalgic encephalomyelitis/ chronic fatigue syndrome (ME/CFS) have abnormal levels of intestinal bacteria, unveiling a possible correlation between gut microbiome and the disease.

The team recruited 50 patients with ME/CFS and 50 healthy individuals, and tested the levels of bacterial species in the candidates’ faecal samples as well as the immune molecules in their blood. The team was also able to measure distinct differences between the ways bacteria break down food and transmit signals to the brain in healthy individuals and ME/CFS patients.

"Individuals with ME/CFS have a distinct mix of gut bacteria and related metabolic disturbances that may influence the severity of their disease," said researcher Dorottya Nagy-Szakal.

Faecalibacterium, Roseburia, Dorea, Coprococcus, Clostridium, Ruminococcus and Coprabacillus strains were strongly associated with ME/CFS, and the levels varied depending on the severity and symptoms experienced by patients.

"Our analysis suggests that we may be able to subtype patients with ME/CFS by analysing their fecal microbiome," said another researcher, Brent Williams. "Subtyping may provide clues to understanding differences in manifestations of disease."

2. Longevity and life expectancy

A five-week-old turquoise killifish is resplendent in vivid colours (above). At the age of twelve weeks, however, the colours have already begun to fade (below). Photo credit: Medical Xpress/ D.R.Valenzano
A five-week-old turquoise killifish is resplendent in vivid colours (above). At the age of twelve weeks, however, the colours have already begun to fade (below). Photo credit: Medical Xpress/ D.R.Valenzano

Gut microorganism may also have a significant effect on ageing according to researchers at the Max Planck Institute for Biology of Ageing in Cologne.

The team treated several 9.5-week-old killifish with antibiotics to clear out their intestinal bacteria and ‘transplanted’ intestinal flora from 6-week-old killifish – by placing them in a sterile aquarium containing the intestinal contents of the young fish – and observed that the older fish had a significantly longer lifespan than other fish that were only exposed to their own intestinal microbiota. The older killifish were also as agile and active as younger ones.

Interestingly, the killifish is a vertebrate and has gut microbiota similar in diversity and composition to that of humans, however, it remains unclear how intestinal microbes affect longevity.

"It is possible that an ageing immune system is less effective at protecting the microorganisms in the intestines, with the result that there is a higher prevalence of pathogens in older guts. The gut microbiota in a young organism could help to counter this and therefore support the immune system and prevent inflammation. This could lead to longer life expectancy and better health," said scientist Dario Riccardo Valenzano.

3. Cardiovascular diseases

Choline, an essential nutrient naturally found in red meat and egg yolks, may feed intestinal bacteria to produce a compound that increases the formation of blood clots, according to researchers from Cleveland Clinic.

The small study involving 18 patients on choline supplements found that choline increased the gut microbial production of trimethylamine N-oxide (TMAO), which enhances platelet function and had previously been identified as a strong predictor of heart disease.

"We previously showed gut microbial production of TMAO from dietary nutrients like choline, lecithin, and L-carnitine is linked to the development of cardiovascular diseases," said the team.

"The new study provides the first direct evidence in humans that consuming excess choline... raises both levels of the bacteria-produced compound, called TMAO and the tendency of platelets to clump together and form clots," added the American Heart Association.

The researchers reported that taking daily aspirin reduced the clotting effect, and also found that low doses of aspirin reduced choline supplement-dependent rise in TMAO levels.

"Although the mechanism for this result is unknown, aspirin has been reported to alter the composition of the gut microbial community,” they added.

4. Type 2 diabetes

A study by researchers from Finland has found that high serum concentrations of indole propionic acids – an intestinal bacteria metabolite, which production is boosted by a diet rich in fibre – are protective against type 2 diabetes.

The team analysed the serum metabolite profile of 200 individuals – all of whom were overweight and had impaired glucose tolerance, but either developed type 2 diabetes within the first five years or did not develop the disease within a 15-year follow-up – and discovered that a higher serum concentration of indolepropionic acid appeared to promote insulin secretion in pancreatic beta cells, which may inadvertently explain the protective effect of indolepropionic acid against diabetes.

The study also identified that a lower amount of dietary saturated fat yielded higher amounts of several new lipid metabolites, which, similar to indolepropionic acid, also seemed to protect against low-grade inflammation.

"Earlier studies, too, have linked intestinal bacteria with the risk of disease in overweight people,” said Kati Hanhineva, academy research fellow from the University of Eastern Finland.

“Our findings suggest that indolepropionic acid may be one factor that mediates the protective effect of diet and intestinal bacteria.” MIMS

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