Patients with type 2 diabetes (T2D) may have unique microbial profiles in the liver, plasma, and adipose tissue that are different from those observed in patients with obesity without T2D, according to study results published in Nature Metabolism. According to the investigators, these findings highlight new possible biomarkers and microbial targets for T2D in people with obesity.
The study involved analyses of tissue samples taken from the liver, mesenteric adipose tissue, omental adipose tissue, subcutaneous adiopse tissue, and plasma during bariatric surgery in individuals with severe obesity (mean age, 42±9 years; mean body mass index, 50.5 kg/m2). Mean fasting blood glucose was 145.95±66.67 mg/dL in the entire cohort, with significantly higher levels in patients with diabetes, as expected. In total, samples from 20 individuals with T2D and 20 without T2D matched for body mass index were used in the study. Using 16S ribosomal RNA gene-based bacterial quantification, researchers examined microbial signatures in the biopsied tissue samples.
The investigators identified a higher bacterial load in both the liver and omental adipose tissue in patients with diabetes compared with those without diabetes: an approximately 1000-fold higher 16S rRNA gene count was observed in tissue samples of participants with obesity and diabetes compared with negative controls. Patients with diabetes also had reduced microbial diversity in the mesenteric adipose tissue compared with patients without diabetes, with a higher abundance of gut colonizers. This finding may have been related to the characteristically lower gut microbiota diversity found in people with diabetes, which has been reported in previous research.
In analyzing site-specific beta diversity, the researchers found that compared with patients with obesity and no diabetes, patients with both obesity and T2D had higher mesenteric adipose tissue levels of Enterobacteriaceae, which have been linked to poorer glycemic control, and a lower abundance of certain Firmicutes, Bacteroidetes, and Deltaproteobacteria, which may be associated with better metabolic outcomes and leanness. Plasma samples from the individuals with T2D similarly had higher levels of Enterobacteriaceae than samples from negative controls.
The researchers commented that these differences in taxa found between T2D-positive and -negative plasma samples using 16S RNA gene counts “strongly point to a credible biological phenomenon.”
“It would be of major interest to identify bacteria or bacterial components that preserve glucose regulation in individuals with both normoglycemia and morbid obesity,” wrote the investigators, suggesting that further studies are needed to understand traits that are associated with bacterial translocation and how these tissue-specific bacterial components are related to T2D promotion or response.
Anhê FF, Jensen BAH, Varin TV, et al. Type 2 diabetes influences bacterial tissue compartmentalisation in human obesity. Nat Metab. 2020;2:233-242.