Metagenomics analysis of gut microbiota in response to diet intervention and gestational diabetes in overweight and obese women: a randomised, double-blind, placebo-controlled clinical trial.

OBJECTIVE: Gut microbiota and diet are known to contribute to human metabolism. We investigated whether the metagenomic gut microbiota composition and function changes over pregnancy are related to gestational diabetes mellitus (GDM) and can be modified by dietary supplements, fish oil and/or probiotics. DESIGN: The gut microbiota of 270 overweight/obese women participating in a mother-infant clinical study were analysed with metagenomics approach in early (mean gestational weeks 13.9) and late (gestational weeks 35.2) pregnancy. GDM was diagnosed with a 2 hour 75 g oral glucose tolerance test. RESULTS: Unlike women with GDM, women without GDM manifested changes in relative abundance of bacterial species over the pregnancy, particularly those receiving the fish oil + probiotics combination. The specific bacterial species or function did not predict the onset of GDM nor did it differ according to GDM status, except for the higher abundance of Ruminococcus obeum in late pregnancy in the combination group in women with GDM compared with women without GDM. In the combination group, weak decreases over the pregnancy were observed in basic bacterial housekeeping functions. CONCLUSIONS: The specific gut microbiota species do not contribute to GDM in overweight/obese women. Nevertheless, the GDM status may disturb maternal gut microbiota flexibility and thus limit the capacity of women with GDM to respond to diet, as evidenced by alterations in gut microbiota observed only in women without GDM. These findings may be important when considering the metabolic complications during pregnancy, but further studies with larger populations are called for to verify the findings.

Gut Microbiota Richness and Composition and Dietary Intake of Overweight Pregnant Women Are Related to Serum Zonulin Concentration, a Marker for Intestinal Permeability.

BACKGROUND: Increased intestinal permeability may precede adverse metabolic conditions. The extent to which the composition of the gut microbiota and diet contribute to intestinal permeability during pregnancy is unknown. OBJECTIVE: The aim was to investigate whether the gut microbiota and diet differ according to serum zonulin concentration, a marker of intestinal permeability, in overweight pregnant women. METHODS: This cross-sectional study included 100 overweight women [mean age: 29 y; median body mass index (in kg/m(2)): 30] in early pregnancy (<17 wk of gestation; median: 13 wk). Serum zonulin (primary outcome) was determined by using ELISA, gut microbiota by 16S ribosomal RNA sequencing, and dietary intake of macro- and micronutrients from 3-d food diaries. The Mann-Whitney U test was used for pairwise comparisons and linear regression and Spearman's nonparametric correlations for relations between serum zonulin and other outcome variables. RESULTS: Women were divided into "low" (<46.4 ng/mL) and "high" (≥46.4 ng/mL) serum zonulin groups on the basis of the median concentration of zonulin (46.4 ng/mL). The richness of the gut microbiota (Chao 1, observed species and phylogenetic diversity) was higher in the low zonulin group than in the high zonulin group (P = 0.01). The abundances of Bacteroidaceae and Veillonellaceae, Bacteroides and Blautia, and Blautia sp. were lower and of Faecalibacterium and Faecalibacterium prausnitzii higher (P < 0.05) in the low zonulin group than in the high zonulin group. Dietary quantitative intakes of n-3 (ω-3) polyunsaturated fatty acids (PUFAs), fiber, and a range of vitamins and minerals were higher (P < 0.05) in women in the low zonulin group than those in the high zonulin group. CONCLUSIONS: The richness and composition of the gut microbiota and the intake of n-3 PUFAs, fiber, and a range of vitamins and minerals in overweight pregnant women are associated with serum zonulin concentration. Modification of the gut microbiota and diet may beneficially affect intestinal permeability, leading to improved metabolic health of both the mother and fetus. This trial was registered at clinicaltrials.gov as NCT01922791.

Fermentable fibres condition colon microbiota and promote diabetogenesis in NOD mice.

AIMS/HYPOTHESIS: Gut microbiota (GM) and diet both appear to be important in the pathogenesis of type 1 diabetes. Fermentable fibres (FFs), of which there is an ample supply in natural, diabetes-promoting diets, are used by GM as a source of energy. Our aim was to determine whether FFs modify GM and diabetes incidence in the NOD mouse. METHODS: Female NOD mice were weaned to a semisynthetic diet and the effects of FF supplementation on diabetes incidence and insulitis were evaluated. Real-time quantitative PCR was employed to determine the effects imposed to gene transcripts in the colon and lymph nodes. Changes to GM were analysed by next-generation sequencing. RESULTS: NOD mice fed semisynthetic diets free from FFs were largely protected from diabetes while semisynthetic diets supplemented with the FFs pectin and xylan (PX) resulted in higher diabetes incidence. Semisynthetic diet free from FFs altered GM composition significantly; addition of PX changed the composition of the GM towards that found in natural-diet-fed mice and increased production of FF-derived short-chain fatty acid metabolites in the colon. The highly diabetogenic natural diet was associated with expression of proinflammatory and stress-related genes in the colon, while the semisynthetic diet free from FFs promoted Il4, Il22, Tgfß and Foxp3 transcripts in the colon and/or pancreatic lymph node. PX in the same diet counteracted these effects and promoted stress-related IL-18 activation in gut epithelial cells. 16S RNA sequencing revealed each diet to give rise to its particular GM composition, with different Firmicutes to Bacteroidetes ratios, and enrichment of mucin-degrading Ruminococcaceae following diabetes-protective FF-free diet. CONCLUSIONS/INTERPRETATION: FFs condition microbiota, affect colon homeostasis and are important components of natural, diabetes-promoting diets in NOD mice.