Diverse Gut Bacteria May Ward Off Type 2 Diabetes

A diverse gut microbiome may be protective against type 2 diabetes, a new study suggested.

In a cross-sectional study of over 2,000 adults, higher Shannon index and richness, indicating alpha diversity, were associated with lower Homeostatic Model Assessment of Insulin Resistance (HOMA-IR; Shannon index -0.06, 95% CI -0.10 to -0.02, P=0.02; richness -0.07, 95% CI -0.11 to -0.03, P=0.03), reported Trudy Voortman, PhD, of Erasmus Medical Center in Rotterdam, the Netherlands, and colleagues.

In addition, greater richness of gut microbial alpha diversity was tied to a lower prevalence of type 2 diabetes (OR 0.93, 95% CI 0.88-0.99, P=0.04), they noted in JAMA Network Open.

That being said, beta diversity among the gut microbiome, measured using the Bray-Curtis dissimilarity matrix, was tied to insulin resistance.

The analysis included 2,166 participants from two Dutch population-based studies — the Rotterdam Study and the LifeLines-DEEP study. About 58% of each study population was comprised of men; average ages in the Rotterdam Study and the LifeLines-DEEP study were 62 and 45, respectively.

Gut microbiome data were assessed via stool samples, measured by the 16S ribosomal RNA method.

When looking more closely at gut bacteria, there were 12 specific types that were associated with insulin resistance and type 2 diabetes.

First, there were five taxa whose higher abundance was tied to lower prevalence of type 2 diabetes (all P<0.001):

• Clostridiaceae 1 (OR 0.51, 95% CI 0.41-0.65)
• Peptostreptococcaceae (OR 0.56, 95% CI 0.45-0.70)
• C sensu stricto 1 (OR 0.51, 95% CI 0.40-0.65)
• Intestinibacter (OR 0.60, 95% CI 0.48-0.76)
• Romboutsia (OR 0.55, 95% CI 0.44-0.70)

Building upon this, there were seven taxa whose greater abundance was associated with lower HOMA-IR (all P<0.001):

• Christensenellaceae (β = -0.08, 95% CI -0.12 to -0.03)
• Christensenellaceae R7 group (β = -0.07, 95% CI -0.12 to -0.03)
• Marvinbryantia (β = -0.07, 95% CI -0.11 to -0.03)
• Ruminococcaceae UCG005 (β = -0.09, 95% CI -0.13 to -0.05)
• Ruminococcaceae UCG008 (β = -0.07, 95% CI -0.11 to -0.03)
• Ruminococcaceae UCG010 (β = -0.08, 95% CI -0.12 to -0.04)
• Ruminococcaceae NK4A214 group (β = -0.09, 95% CI -0.13 to -0.05)

“All 12 [taxa] are known to be butyrate-producing bacteria,” Voortman’s group pointed out.

Although a few of these bacteria have already been linked to less insulin resistance in previous studies, the researchers made 10 novel identifications that further solidified butyrate-producing bacteria’s role in reducing diabetes risk.

“Of interest, some of these newly identified bacteria associated with type 2 diabetes have been previously reported in relation to obesity, which is closely associated with insulin resistance and development of type 2 diabetes,” they wrote.

They explained that butyrate is a short-chain fatty acid produced from the fermentation of dietary fiber — also known as a prebiotic.

Butyrate has been linked to a number of different benefits, the researchers noted, explaining how it’s been “suggested to induce beneficial metabolic effects through enhancement of mitochondrial activity, improvement of energy metabolism, activation of intestinal gluconeogenesis, and prevention of metabolic endotoxemia and inflammation via different routes of gene expression and hormone regulation.”

However, one limitation to this study was that neither stool butyrate concentrations nor circulating butyrate concentrations were directly measured. As a result, Voortman’s group recommended that future studies look directly at the relationship between butyrate-producing bacteria and diabetes risk.