Researchers at Oregon State University in the US have found that a few organisms in the gut microbiome play a key role in type 2 diabetes, opening the door to possible probiotic treatments for a serious metabolic disease. The human gut microbiome features more than 10 trillion microbial cells from about 1,000 different bacterial species. Dysbiosis, or imbalance, in the microbiome is commonly associated with detrimental effects on a person's health.
According to study co-leader Andrey Morgun, the so-called 'western diet' - high in saturated fats and refined sugars - is one of the primary factors.
"But gut bacteria have an important role to play in modulating the effects of diet."
A key risk factor for type 2 diabetes is being overweight, often a result of a western diet in combination with low physical activity.
"Some studies suggest dysbiosis is caused by complex changes resulting from interactions of hundreds of different microbes," said Natalia Shulzhenko, an associate professor of biomedical sciences.
"However, our study and other studies suggest that individual members of the microbial community, altered by diet, might have a significant impact on the host."
Shulzhenko and Morgun used a new, data-driven, systems-biology approach called transkingdom network analysis to study host-microbe interactions under a western diet.
That allowed them to investigate whether individual members of the microbiota played a part in metabolic changes the diet induces in a host.
"The analysis pointed to specific microbes that potentially would affect the way a person metabolizes glucose and lipids," Morgun said.
The scientists identified four operational taxonomic units, or OTUs, that seemed to affect glucose metabolism; OTUs are a means of categorizing bacteria based on gene sequence similarity.
The identified OTUs corresponded to four bacterial species: Lactobacillus johnsonii, Lactobacillus gasseri, Romboutsia ilealis and Ruminococcus gnavus.
Checking the mouse results against data from an earlier human study, the scientists found correlations between human body mass index and abundance of the four bacteria - more of the improvers meant a better body mass index, more of the worseners was connected to a less healthy BMI.
"We found R. ilealis to be present in more than 80 per cent of obese patients, suggesting the microbe could be a prevalent pathobiont in overweight people," Shulzhenko said.
"Our study reveals potential probiotic strains for treatment of type 2 diabetes and obesity as well as insights into the mechanisms of their action," Morgun said in a paper published in Nature Communications.
"That means an opportunity to develop targeted therapies rather than attempting to restore 'healthy' microbiota in general."