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Séquenceur METAQUANT. © inra, BEAUCARDET William

Intestinal bacteria linked to type 2 diabetes

Type 2 diabetes (T2D) is the most widespread endocrine disorder in the world. It is known to be caused in part by genetic and environmental factors. INRA scientists working with Chinese teams on the MetaHIT* project have found evidence of a link between the presence of certain bacteria species in the human digestive tract and T2D. The results, published in the 26 September 2012 edition of Nature, offer new perspectives in research into the relationship between microbiota and human illnesses and the early diagnosis of T2D.

Updated on 03/06/2013
Published on 09/26/2012

Intestinal flora have become an important field of study in the area of human health. Until now, underlying genetic markers in T2D were analyzed using genome-wide association studies (1) involving the identification of genetic components in the human genome. Recently, though, studies have shown that the risk of developing T2D could also be linked to the bacterial genome (the metagenome) present in the human digestive tract.

Study conducted using METAQUANT sequencing platform. ©INRA/William Beaucardet. © inra, BEAUCARDET William
Study conducted using METAQUANT sequencing platform. ©INRA/William Beaucardet © inra, BEAUCARDET William
Working together with Chinese research teams, scientists at INRA Jouy-en-Josas examined which microbial species could be connected to T2D. They developed an experimental protocol for a large Metagenome-wide association study (MGWAS) to analyze the bacteria in the intestines of T2D patients. Microbial DNA extracted from stool samples from a total of 345 Chinese T2D patients and a non-diabetic control group were sequenced.

Researchers identified and confirmed the presence of approximately 60,000 genetic markers linked to T2D. Overall, T2D patients presented an imbalance in their intestinal flora (as seen in the presence or absence of the 60,000 identified genes) and significant differences in how different kinds of bacteria functioned in the tract. Some universal, butyrate-producing bacteria (which act as an anti-inflammatory) were less abundant in these patients. Several opportunistic pathogens were present in greater number, and certain microbial functions such as sulphate reduction and protection against oxidative stress were intensified. An additional study of another 23 patients confirmed that these intestinal markers can be used to effectively diagnose T2D.

These results are essential to understanding the link between the intestinal metagenome and T2D and other illnesses. New therapeutic approaches can also be developed if subsequent studies better explain the role played by gut flora in the appearance and development of this common disease.

(1) A genome-wide association study looks at a wide-range of genetic variations in the genome of various individuals of the same species to study links between those variations and different illnesses, among other things.

* http://www.international.inra.fr/press/metahit_bacteria_new_organ

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Junjie Qin et al. A Metagenome-Wide Association Study of gut microbiota in Type 2 Diabetes. Nature, 26 September 2012, DOI : 10.1038/nature1145