Previous studies have suggested that the gut microbiome may be linked with development of type 2 diabetes mellitus (T2DM). However, these studies are restricted by small sample size, and due to insufficient evidence, its role in the development of T2DM remains uncertain. According to a population- based observational study from the Netherlands, more diverse gut bacteria (greater microbiome richness), particularly a larger abundance of 12 types of butyrate-producing bacteria, were linked with both less insulin resistance and less T2DM.
This study also identified a dozen types of bacteria that ferment dietary fiber (undigested carbohydrates) in the gut to produce butyrate, a short-chain fatty acid, which may play a role in protection against T2DM.
In the study recently published in JAMA Network Open, researchers Chen et al assessed the correlations of gut microbiome composition with insulin resistance and T2DM in a large, population-based setting controlling for various sociodemographic and lifestyle factors. The cross-sectional analysis included 2,166 participants from two Dutch population-based studies—the Rotterdam Study and the LifeLines-DEEP study. An estimated 58% of each study population was comprised of men; average ages in the Rotterdam Study and the LifeLines-DEEP study were 62 and 45 years, respectively.
The researchers noted, "The current study is the first, to our knowledge, to comprehensively investigate the associations between gut microbiome composition with type 2 diabetes in a large population-based sample for which we adjusted for a series of key confounders."
The study participants provided stool samples that were used to measure gut microbiome composition using the 16S ribosomal RNA method. They also had blood tests to measure glucose and insulin, and researchers collected other demographic and medical data. Chen and colleagues identified 126 (bacteria) genera in the gut microbiome in the Rotterdam study and 184 genera in the LifeLines Deep study. After correcting for age, gender, smoking, education, physical activity, alcohol intake, daily calories, body mass index, and use of lipid-lowering medication or proton pump inhibitors, higher microbiome diversity was associated with lower insulin resistance and a lower prevalence of T2DM.
The researchers observed that when looking more closely at gut bacteria, there were 12 specific types that were connected with insulin resistance and T2DM. They noted that a greater abundance of each of seven types of butyrate-producing bacteria—Christensenellaceae, Christensenellaceae R7 group, Marvinbryantia, Ruminococcaceae UCG005, Ruminococcaceae UCG008, Ruminococcaceae UCG010, and Ruminococcaceae NK4A214 group—was linked with lower insulin resistance after adjusting for confounders, such as diet and medications (all P <.001). They also noted that a higher abundance of each of five other types of butyrate-producing bacteria was linked with less T2DM (all P <.001).
Chen et al indicated that the study limitations include that gut microbiome composition was determined from stool (fecal) samples, whereas the actual composition fluctuates in different locations along the intestine, and the study also lacked information about butyrate concentrations in stool or blood.
The researchers concluded that in this cross-sectional study, higher microbiome α diversity, along with more butyrate-producing gut bacteria, was correlated with less T2DM and with lower insulin resistance among individuals without diabetes. The researchers also noted that these discoveries could assist in providing more insight into the etiology, pathogenesis, and prevention and treatment of T2DM. The groups recommended that future studies look directly at the relationship between butyrate-producing bacteria and diabetes risk.
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