Gut bacteria hold clues about type 2 diabetes
Published 25 Feb 2016
Changes in the types and activities of human gut bacteria could lead to earlier diagnoses of type 2 diabetes, according to a study of identical twins, findings of which are published in Genome Medicine.
Imbalances in the gut microbiota have been linked with a number of conditions, including type 2 diabetes.
However, previous studies have only compared healthy individuals with people already diagnosed with type 2 diabetes.
But changes in the microbiota may occur before type 2 diabetes becomes detectible by other means.
Curtis Huttenhower and colleagues - from the Broad Institute of Massachusetts Institute of Technology (MIT) and Harvard, as well as Seoul National University in South Korea - wanted to find out whether such early changes occur.
They set out to identify links between type 2 diabetes biomarkers, changes in gut microbiota and host genetics.
Identical twins offer unique research opportunities
Participants were 20 healthy identical Korean twins aged 30-48 years, who were already involved in the Healthy Twin Study, in South Korea.
As identical - or monozygotic - twins share the same genes, studying them enables scientists to investigate aspects of disease linked to the gut microbiome in isolation from genetic traits.
The researchers collected data such as age, height and weight, body mass index (BMI), fasting blood sugar (FBS) and details of diet and lifestyle.
They also took 36 fecal samples in order to study the microbial community structure.
Sixteen individuals provided one sample each at the start of the study and one each between 12-44 months later. Two pairs of twins, or four individuals, were only able to provide the first sample.
The sampling method made it possible to observe changes between individuals and over time.
None of the participants had a prior diagnosis of type 2 diabetes, but the types and levels of disease markers varied widely, from healthy to near-clinical.
This meant that the researchers could compare the functioning and composition of the microbiome at different stages before onset of type 2 diabetes.
Gut microbiota point to future type 2 diabetes
Changes were identified in both composition and function of the participants' gut microbiome.
They included a decrease in Akkermansia muciniphila (A. muciniphila), inversely associated with BMI. There were also functional changes relating to BMI, FBS and triglycerides that suggested oxidative stress due to immune activation or inflammation.
Similar changes have been seen before in patients with chronic type 2 diabetes and inflammatory bowel diseases.
One unexpected finding was that while twins had the same species of microorganisms living in their guts, the strains of the species were different.
Huttenhower says:
"It suggests that twins are initially colonized by the same bugs in infancy, due perhaps to shared environment or genetics and then retain those organisms long enough to begin to diverge through short-term evolution. If true, this can be studied directly in larger twin cohorts, and it would help us understand how the microbiome develops beyond diabetes alone in a wide variety of conditions."
The researchers hope that the methodology and findings will contribute to tracking changes that take place before and after type 2 diabetes becomes apparent.
They also speculate that microbial or immune responses play a causative role, although this was not a part of the current study.
Given the small sample size, the researchers suggest that larger cohorts should be examined to confirm the findings, but they hope that the methods used will be useful in future investigations.
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