Fecal microbiota present target for glucose tolerance assessment

SAN DIEGO — Gut microbiota varied in fecal samples of black men with a range of glucose tolerances, particularly between those with normoglycemia and prediabetes, according to research presented here.

A specific makeup of bacterial composition, alpha diversity and abundance could be associated with steady glycemic states, but further research is needed to determine causation between the gut bacteria and glucose tolerance shifts, according to the researchers.

“Our data showed that changes in the gut microbiota already occur in the early stages of diabetes development, known as impaired glucose tolerance or prediabetes,” Elena Barengolts, MD, of the University of Illinois College of Medicine at Chicago, said in a press conference. “The gut bacteria signature composition and abundance could be a useful tool in assessing a person’s risk for developing diabetes and obesity.”

Elena Barengolts

Barengolts, with Irina Ciubotaru, MD, PhD, and colleagues collected stool samples from 116 black men involved in a randomized controlled trial of vitamin D at the Jesse Brown VA Medical Center.

Based on changes in oral glucose tolerance test from baseline to 12 months, the men were categorized into four groups (Gr): stable normal glucose tolerance (Gr 1, n = 35); stable impaired fasting glucose or stable impaired glucose tolerance (Gr 2, n = 27); worsened glucose tolerance (Gr 3, n = 24); and improved glucose tolerance (Gr 4, n = 29).

The researchers analyzed microbiota DNA, extracted from stool collected at the end of the study, using high-throughput next-generation sequencing of microbial rRNA genes. Data were processed using established bioinformatics pipelines; the investigators examined composition, alpha diversity and abundance.

Significant bacterial composition differences were seen at the phylum level between Gr 1 and Gr 2 (P = .03), with a trend toward significance for Gr 1 vs. Gr 3 (P = .06) and Gr 1 vs. Gr 4 (P = .06).

With decreasing glycemic control, Bacteroidetes were higher and Firmicutes lower (Gr 1 vs. Gr 2 = 1.9 vs. 0.9, P = .01 and Gr 1 vs. Gr 3 = 1.9 vs. 1.1, P = .04), translating to a reduced ratio of Bacteroidetes-to-Firmicutes.

Proteobacteria dropped in Gr 2 and Gr 4 compared with Gr 1 (P = .01 for both), and similar significant differences were seen in microbiota at the family and genus levels.

Gr 2 had less Prevotella compared with Gr 1 (5.6 vs. 2.7, P = .05), and therefore a higher ratio of Bacteroides-to-Prevotella ratio, along with less Enterobacteriacea (P = .03). However, Gr 2 had more Ruminococcae (P = .01) and Veillonelacea (P = .02) than Gr 1. Akkermansia was notably more abundant in Gr 4 vs. Gr 1 (P = .04).

The possibility of therapeutically shifting microbiota to improve patient health represents yet another form of personalized and precision medicine, Barengolts explained. Researchers in China and Italy are currently conducting investigations into bacteria transplants, in addition to ongoing studies in the U.S., she said.

Less invasive options are already gaining ground as consumers learn more about the microbiome.

“Bacteria in a pill is very attractive. Probiotics are a booming business; just this year, it is expected that $42 billion will be spent on probiotics,” Barengolts said. “Functional foods promote the growth of healthy bacteria. The most boring prebiotic is barley, the most exciting prebiotic is chocolate.” – by Allegra Tiver

Reference:

Ciubotaru I, et al. Poster Board FRI-597. Presented at: The Endocrine Society Annual Meeting; March 5-8, 2015, San Diego.

Disclosure: Barengolts reports no relevant financial disclosures.