Previous research has shown that the gut microbiome may modulate host metabolic health including the development of type 2 diabetes. However, little is known regarding the role of the gut microbiome in the aetiology of gestational diabetes mellitus (GDM), which is defined as “any degree of glucose intolerance with onset or first recognition during pregnancy”.
A new study, led by Dr. Xiu Qiu from both the Division of Birth Cohort Study and the Department of Women and Children’s Health Care at the Guangzhou Medical University (China), has found a connection between gut microbiota and gestational diabetes.
The researchers compared the gut microbiota composition of 43 GDM patients and 81 healthy pregnant women through whole-metagenome shotgun sequencing of their faecal samples collected at 21-29 weeks of pregnancy. They explored the association between GDM and both composition and function of the gut microbiota.
When comparing gut microbiota between GDM patients and healthy pregnant women, significant differences were found. Although abundance at the phylum and class levels was similar between both cohort groups, at the genus level, GDM patients had a gut microbiota enriched in Parabacteroides, Megamonas, and Phascolarctobacterium, whereas healthy pregnant women were enriched in Ruminiclostridium, Roseburia, Eggerthella, Fusobacterium, Haemophilus, Mitsukella, and Aggregatibacter. Besides this, GDM patients were enriched in Bacteroides spp., Parabacteroides distasonis and the family Enterobacteriaceae -these shifts in gut microbiota composition have previously been reported as specific features of gut microbiota dysbiosis (here; here)-. Altogether these data suggest that GDM patients exhibit a gut microbiota dysbiosis.
When trying to identify GDM-related markers from gut microbiome, the distribution of metagenome linkage groups (MLGs) –defined as “a group of genetic material in a metagenome that is probably physically linked as a unit rather than being independently distributed”- in GDM patients was different from that in the control group. GDM-enriched MLGs of several bacteria belonging to the family Enterobacteriaceae were closely related and could have a role in GDM development. Specifically, the researchers found that the relative abundance of Enterobacteriaceae was positively associated with pre-pregnancy body mass index.
Furthermore, the ratios of the relative abundances of GDM-enriched MLGs to those of control-enriched MLGs were positively correlated with blood glucose levels during the second trimester of pregnancy. These results indicate that gut microbiota could affect blood glucose tolerance during pregnancy in GDM patients.
Finally, functional analysis showed a greater abundance of membrane transport and energy metabolism pathways in GDM patients, whereas the gut microbiome of healthy pregnant women was enriched the amino acid metabolic pathways. Besides this, the phosphotransferase system -which is responsible for transporting glucose and catalysing the uptake of carbohydrates- and lipopolysaccharide (LPS) biosynthesis -LPS is a known biomarker involved in microbial translocation that can stimulate inflammatory responses- were higher in GDM and were associated with glucose tolerance levels. According to the authors, “the increase abundance of these pathways may indicate gut environment of a GDM status may stimulate bacterial accelerated usage of glucose as energy”.
To sum up, this is the first study that explores the role of gut microbiota in GDM development. According to its results, new associations between gut microbiome and GDM status have been found. Further studies are needed to elucidate how gut microbiota composition may predict gestational diabetes risk.
Kuang YS, Lu JH, Li SH, et al. Connections between human gut microbiome and gestational diabetes mellitus. Gigascience. 2017. doi: 10.1093/gigascience/gix058