Characterization of the oral microbiome of medically controlled type-2 diabetes patients

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease that is becoming a significant global health care problem. Several studies have shown that people with diabetes are more susceptible to oral problems, such as periodontitis and, although the causes are still inconclusive, the oral microbiota seems to be an important factor in this interaction. This study aimed to characterize the oral microbiome of a sample representing T2DM patients from Portugal and exploit potential associations between some microorganisms and variables like teeth brushing, smoking habits, and nutrient intake. By sequencing the hypervariable regions V3-V4 of the 16S rRNA gene in 50 individuals belonging to a group of diabetes patients and a control group, we found a total of 233 taxa, from which only 65% were shared between both groups. No differences were found in terms of alpha and beta diversity between groups or habits categories. Also, there were no significant differences in the oral microbiome profiles of control and diabetes patients. Only the class Synergistia and the genus TG5, which are related to periodontitis, were statistically more frequent in the control group. This finding can be justified by the fact that these diabetic patients usually have their oral health under close medical control than an average healthy person, which in this study was represented by the control group. IMPORTANCEDiabetes has become a significant global health care issue as its incidence continues to increase exponentially, with type 2 diabetes being responsible for more than 90% of these cases. Portugal is one of the countries with a higher prevalence of diabetes in Europe. It has been reported that diabetic people have an increased risk of developing several health problems such as oral infections mostly caused by opportunistic pathogens. Some studies have pointed out a relationship between diabetes and oral microbiome. Therefore, the characterization of the microbial ecosystem of the mouth in reference groups is crucial to provide information to tackle oral health pathogen-borne conditions. In this study, we provide the first characterization of the oral microbiome of type 2 diabetes mellitus patients from Portugal, and therefore, contributing new data and knowledge to elucidate the relationship between diabetes and the oral microbiome.