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The Gut Microbiome – Fad or The Future?

Which bacteria are colonising your gut is becoming increasingly important, Australian researchers say.

More and more evidence is suggesting the gut microbiota has a significant role in both the cause and the cure of a wide range of gastrointestinal and hepatic diseases and conditions.

According to a review in The Medical Journal of Australia, research shows that particular types of bacteria colonising the gut have been associated the development of inflammatory bowel disease (IBD), metabolic syndrome, non-alcoholic fatty liver disease (NAFLD), non-alcoholic steato-hepatitis (NASH), obesity and diabetes.

We know that the bowel starts to be colonised by bacteria in utero. The make-up of an individual’s gut microbiota then depends on factors such as mode of delivery, breast-feeding, diet, illness and exposure to antibiotics. By the age of three, the gut microbiota resembles that of an adult.

Observational studies have suggested a strong association between alterations in the microbiota because of environmental factors, and an increased risk of diseases. For instance, IBD was very rare in traditional Chinese populations, but studies have shown exposure to Western diets and medicines from a young age has increased the prevalence of this disease.

“Asian adults who migrate from countries of low prevalence to countries of high prevalence do not have an increased risk of developing IBD, but their children experience the IBD incidence of their new country of residence,” the review authors said.

Stronger evidence comes from studies into the exact nature of bacteria colonising the gut. It appears both the specific bacteria and the diversity of bacteria are important in disease pathogenesis.

“For example, the presence of Proteus species at the time of Crohn’s disease resection is associated with early disease recurrence, while the presence of Faecalibacterium prauznitzii is protective against recurrence,” they said.

Researchers have also found significant differences in the microbiota of people who develop severe alcoholic hepatitis and those who maintain normal hepatic function despite drinking the same amount of alcohol.

Most importantly in the investigation of the role of the gut microbiota, is the emerging evidence that by altering the bacterial colonies in the gut we can alter the course of the disease.

The classic example of this, of course, was the discovery of Helicobacter Pylori as the cause of peptic ulcer disease with treatment of this, dramatically changing health outcomes. But since then a lot of the research focus has been on faecal microbiota transplants (or poo transplants as they are commonly known). Mice studies have shown that a mouse will become fat if given a transplant of faecal bacteria from a fat donor mouse. Similarly, a similar result has been shown in a single trial of FMT from lean to obese humans, lowering triglyceride levels and increasing insulin sensitivity.

FMT has also been shown to be an effective therapy for recurrent C.difficile infection and in active ulcerative colitis. And while the application of FMT as a treatment continues to be explored, investigators are also looking at how the microbiota can be changed through dietary means and how this can be used therapeutically. While probiotics have not been shown to be effective in the majority of inflammatory diseases, an anti-inflammatory diet combined with liquid formulated enteral nutrition has shown some success in Crohn’s disease.

In short, the review authors suggest that the current interest in the gut microbiome is justified and has the potential to provide important therapeutic options in the future.

“Microbial manipulation is an effective therapy, likely to have broadening implications,” they concluded.

 

Reference

White LS, Van den Bogaerde J & Kamm M. The gut microbiota: cause and cure of gut diseases. Med J Aust. 2018 Oct 1; 209(7): 312-16. Available from: https://www.mja.com.au/journal/2018/209/7/gut-microbiota-cause-and-cure-gut-diseases doi: 10.5694/mja17.01067