Low incidence of spontaneous type 1 diabetes in non-obese diabetic mice raised on gluten-free diets is associated with changes in the intestinal microbiome - PubMed (original) (raw)
Low incidence of spontaneous type 1 diabetes in non-obese diabetic mice raised on gluten-free diets is associated with changes in the intestinal microbiome
Eric V Marietta et al. PLoS One. 2013.
Abstract
Human and animal studies strongly suggest that dietary gluten could play a causal role in the etiopathogenesis of type 1 diabetes (T1D). However, the mechanisms have not been elucidated. Recent reports indicate that the intestinal microbiome has a major influence on the incidence of T1D. Since diet is known to shape the composition of the intestinal microbiome, we investigated using non-obese diabetic (NOD) mice whether changes in the intestinal microbiome could be attributed to the pro- and anti-diabetogenic effects of gluten-containing and gluten-free diets, respectively. NOD mice were raised on gluten-containing chows (GCC) or gluten-free chows (GFC). The incidence of diabetes was determined by monitoring blood glucose levels biweekly using a glucometer. Intestinal microbiome composition was analyzed by sequencing 16S rRNA amplicons derived from fecal samples. First of all, GCC-fed NOD mice had the expected high incidence of hyperglycemia whereas NOD mice fed with a GFC had significantly reduced incidence of hyperglycemia. Secondly, when the fecal microbiomes were compared, Bifidobacterium, Tannerella, and Barnesiella species were increased (p = 0.03, 0.02, and 0.02, respectively) in the microbiome of GCC mice, where as Akkermansia species was increased (p = 0.02) in the intestinal microbiomes of NOD mice fed GFC. Thirdly, both of the gluten-free chows that were evaluated, either egg white based (EW-GFC) or casein based (C-GFC), significantly reduced the incidence of hyperglycemia. Interestingly, the gut microbiome from EW-GFC mice was similar to C-GFC mice. Finally, adding back gluten to the gluten-free diet reversed its anti-diabetogenic effect, reduced Akkermansia species and increased Bifidobacterium, Tannerella, and Barnesiella suggesting that the presence of gluten is directly responsible for the pro-diabetogenic effects of diets and it determines the gut microflora. Our novel study thus suggests that dietary gluten could modulate the incidence of T1D by changing the gut microbiome.
Conflict of interest statement
Competing Interests: The authors have declared that no competing interests exist.
Figures
Figure 1. Impact of dietary gluten upon the incidence of hyperglycemia and production of anti-insulin IgG in NOD Mice.
Blood glucose levels were measured once every two(gluten-containing) chow (N = 16), and the other that were weaned and maintained upon a gluten-free (casein-based) chow (N = 19). (A) Overall incidence of hyperglycemia. (B) The incidence of hyperglycemia in males and (C) females on the different diets. There were 8 Std-GCC males, 8 Std-GCC females, 8 C-GFC males, and 11 C-GFC females (D). p values are given in parenthesis. Anti-insulin IgG levels were evaluated in the standard (▪, N = 9) and casein-based (▴, N = 8) chow-fed NOD mice every 7 weeks for a total of three time points. P<0.05 for each time point.
Figure 2. Composition of the intestinal microbiomes in NOD mice on either a casein-based or standard chow.
NOD mice were weaned and maintained upon a casein-based gluten-free chow (black squares ▪, N = 5) or a standard gluten-containing chow (black inverted triangle ▾, n = 5). Stool was collected at 20 weeks of age. The microbiomes were evaluated using a multi-dimensional scale analysis as described in methods (Panel A). Richness was determined by observed Operational Taxonomic Units (OTU) (Panel B). Correspondence analysis (CA) plot shows the degree of correlation between specific OTUs and diet (Fig 2C). The black vectors point to the center of gravity of the samples where each OTU mostly occurs. The distance between the tip of the vector and the samples (dots) give an indication of the probability of OTU content in each sample. Green dots represent fecal samples from NOD mice on a casein-based chow; blue dots represent fecal samples from NOD mice on a standard chow. Percentages in parentheses in the CA plot axes describe the amount of variation explained by each axis.
Figure 3. Regulatory T lymphocytes and diet.
The distribution of regulatory (CD4+ CD25+ Foxp3+) was compared by FACS analysis between NOD mice on a casein-based or a standard chow. * p<0.05.
Figure 4. Reversal of the anti-diabetogenic effects of gluten-free chow by supplementation with gluten and overall effective of gluten-free chow on the incidence of hyperglycemia in NOD mice.
(A) Blood glucose levels were measured every two weeks for two cohorts of mice: mice that were weaned and maintained upon an egg white-based gluten-free (EW-GFC) chow (N = 19) and a casein-based gluten-free chow supplemented with gluten (GS-GFC) (N = 23). The overall incidence of hyperglycemia is depicted. (B) Diabetes incidence data from all diet groups were pooled and presented as gluten-free (both GFC-C and EW-GFC) (N = 51) and gluten-containing (standard GCC and GS-GFC) (N = 39) P<0.05 for each time point.
Figure 5. Effect of dietary gluten upon the composition of the intestinal microbiomes in NOD mice.
Microbiomes of mice on gluten free chows were compared with those of mice on gluten containing chows. For the gluten free chow derived microbiomes, microbiomes from five mice on an egg-white based gluten-free chow and five from a casein-based gluten-free chow were grouped together to make a total of 10 gluten-free chow mice (▾). For the microbiomes derived from mice on gluten containing chows, five were derived from mice on standard (gluten containing) chow and five were derived from mice on gluten-supplemented casein-based chow, making a total of 10 gluten associated microbiomes (•). These were evaluated using a multi-dimensional scale analysis (Fig 5A). Richness was determined by observed Operational Taxonomic Units (OTU) (Fig 5B).
Figure 6. Effect of Dietary Gluten Upon Specific OTU (Genus) Abundance.
A. Correspondence analysis (CA) plot shows the degree of correlation between specific OTUs and diet in all of the gluten-containing chows group (GCC) and gluten-free chows group (GFC) as in fig 5.
Figure 7. Effect of Dietary Gluten Upon Specific OTU (Genus) Abundance.
Mean relative abundance for each of 6 genera in all of the gluten-containing chows group (GCC) and gluten-free chows group (GFC) as in fig 5 are plotted in a box and whisker plot. The six genera plotted are A) Bacteroides, B) Akkermansia, C) Bifidobacterium, D) Tannerella, E) Barnesiella, F) Clostridiales. The respective p values are: A) 0.005843 B) 0.01783 C) 0.03615 D) 0.01761 E) 0.0234 and F) 0.0541.
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