A Maternal Gluten-Free Diet Reduces Inflammation and Diabetes Incidence in the Offspring of NOD Mice
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Diabetes Volume 63, August 2014 2821
Camilla Hartmann Friis Hansen,1 Łukasz Krych,2 Karsten Buschard,3 Stine B. Metzdorff,1
Christine Nellemann,4 Lars H. Hansen,5 Dennis S. Nielsen,2 Hanne Frøkiær,1 Søren Skov,1
and Axel K. Hansen1
A Maternal Gluten-Free Diet
Reduces Inflammation and
Diabetes Incidence in the
Offspring of NOD Mice
Diabetes 2014;63:2821–2832 | DOI: 10.2337/db13-1612
Early-life interventions in the intestinal environment gluten-free (GF) diet decreased the incidence of diabetes
have previously been shown to influence diabetes in- from 64% to 15% when nonobese diabetic (NOD) mice
cidence. We therefore hypothesized that a gluten-free were fed a GF diet after weaning (1), and eating a GF diet
(GF) diet, known to decrease the incidence of type 1 decreased the incidence of diabetes to just 6% in the off-
PATHOPHYSIOLOGY
diabetes, would protect against the development of spring in two generations, which indicates that the inter-
diabetes when fed only during the pregnancy and lactation play between gut antigens and immune pathways leading
period. Pregnant nonobese diabetic (NOD) mice were to diabetes is particularly important in the preweaning
fed a GF or standard diet until all pups were weaned to period when insulitis starts to progress (2).
a standard diet. The early-life GF environment dramat- Accumulating evidence suggests that gut immune
ically decreased the incidence of diabetes and insulitis.
reactivity is skewed in human and murine diabetic
Gut microbiota analysis by 16S rRNA gene sequencing
patients. Studies in young human patients with T1D
revealed a pronounced difference between both moth-
have demonstrated increased numbers of interferon-g
ers and their offspring on different diets, characterized
by increased numbers of Akkermansia, Proteobacteria,
(IFN-g)–producing, interleukin (IL)-1a–producing, and
and TM7 in the GF diet group. In addition, pancreatic
IL-4–producing cells in the small intestinal lamina propria,
forkhead box P3 regulatory T cells were increased in reflecting T1D preceded by intestinal immune activation
GF-fed offspring, as were M2 macrophage gene markers (3). Similarly in NOD mice, a diabetes-promoting diet
and tight junction–related genes in the gut, while intesti- induced proinflammatory cytokines IFN-g and tumor ne-
nal gene expression of proinflammatory cytokines was crosis factor-a in the small intestinal lamina propria (4),
reduced. An increased proportion of T cells in the pan- and an antidiabetogenic diet decreased the high numbers
creas expressing the mucosal integrin a4b7 suggests of CD11b+CD11c+ dendritic cells (DCs) found in the colon
that the mechanism involves increased trafficking of lamina propria (5). Under germ-free conditions, reduced
gut-primed immune cells to the pancreas. In conclusion, expression of forkhead box P3 (FoxP3) in the ileum, colon,
a GF diet during fetal and early postnatal life reduces and the draining lymph node was associated with acceler-
the incidence of diabetes. The mechanism may involve ated development of insulitis in NOD mice (6), and, likewise
changes in gut microbiota and shifts to a less proinflam- in humans, Badami et al. (7) found that jejunal biopsy
matory immunological milieu in the gut and pancreas. samples from T1D patients showed reduced frequency of
CD4+CD25+FoxP3+CD1272 regulatory T cells (Tregs). The
Gluten has previously been shown to affect the devel- link between the gut and pancreas has also been empha-
opment of type 1 diabetes (T1D) in animal models. A sized in studies demonstrating that pancreatic islet T cells
1Department of Veterinary Disease Biology, Faculty of Health and Medical Sci- 5Department of Biology, Faculty of Science, University of Copenhagen, Copenha-
ences, University of Copenhagen, Frederiksberg, Denmark gen, Denmark
2Department of Food Science, Faculty of Science, University of Copenhagen,
Corresponding author: Camilla Hartmann Friis Hansen, camfriis@sund.ku.dk.
Frederiksberg, Denmark
3Bartholin Institute, Rigshospitalet, Copenhagen, Denmark Received 18 October 2013 and accepted 27 March 2014.
4Division of Toxicology and Risk Assessment, National Food Institute, Technical © 2014 by the American Diabetes Association. Readers may use this article as
University of Denmark, Søborg, Denmark long as the work is properly cited, the use is educational and not for profit, and
the work is not altered.
2822 Diabetes-Protective Diet Across Two Generations Diabetes Volume 63, August 2014
express gut homing receptor a4b7 integrin, which recog- at 4 weeks of age to the STD diet. Ten pups were killed
nizes mucosal addressin cell adhesion molecule-1 in the from each group at 4 weeks of age, and 10 mice from each
pancreas (8,9). group were killed at 10 weeks of age. The remaining 30
Failure in immune tolerance leading to pancreatic mice in each group were killed when a diagnosis of di-
b-cell depletion has been suggested to be regulated in abetes was made or at 30 weeks of age, when the study
part by gliadin-induced intestinal enteropathy and innate ended. Measurements of tail blood glucose levels were
immune responses (10,11). However, altered gut micro- made twice a week from 10 weeks of age, and a mouse
biota, previously demonstrated in GF-fed versus gluten- was considered to be diabetic when blood glucose levels
fed mice (12), might also contribute to modify intestinal exceeded 12 mmol/L on 2 consecutive days. The body
inflammation and development of autoimmune diabetes. weight of all offspring was monitored once a week.
In support of this, impaired oral tolerance to intestinal Histology
microbes was demonstrated in NOD mice (5), and the Hematoxylin-eosin–stained pancreas sections were evalu-
impact of microbes has also been verified in germ-free ated for insulitis score in a blinded fashion by two per-
(13), antibiotic-treated (14,15), and probiotic-treated di- sons. Lymphocytic infiltration was graded as follows: 0,
abetes-prone rodent models (16). It seems reasonable to no infiltration; 1, intact islets but with few mononuclear
assume that gluten and certain microbes have a synergistic cells surrounding the islets; 2, peri-insulitis; 3, islet in-
effect on the development of T1D, as was also recently filtration ,50%; and 4, islet infiltration .50%. Twenty-
suggested by Patrick et al. (17). Cytokine profiles of gut- five islets were scored for each nondiabetic mouse killed at
associated lymphoid tissue have revealed a strong associa- 10 and 30 weeks of age.
tion between intestinal IFN-g production and the incidence
of diabetes, especially in several gluten intervention stud- Gut Microbiota
ies (4,11,17–20). Also, type 1 T-helper cells proliferated Feces samples aseptically obtained from the mothers
specifically in the mesenteric lymph node (MLN) in re- during pregnancy and from the offspring at 4 and 10
sponse to wheat protein antigens (19). A GF diet was weeks of age when they were killed were analyzed by PCR
furthermore shown to reverse this shift in gut homeosta- amplification of the V3 region of the 16S rRNA gene foll-
sis toward an anti-inflammatory state with more trans- owed by denaturing gradient gel electrophoresis (DGGE)
forming growth factor-b (TGF-b)–producing T cells (18). as described previously (21). The resulting DGGE profiles
As early-life interventions in the intestinal environ- were analyzed using BioNumerics version 4.5 (Applied
ment can influence the incidence of diabetes, we hypoth- Maths, Sint-Martens-Latem, Belgium). The composition
esized that a GF diet exclusively fed to mice during of the prokaryotic community of feces samples from
gestation and lactation would be sufficient to protect the the mothers and the 4-week-old pups was determined
offspring from the development of diabetes even though using tag-encoded 454/FLX Titanium (Roche) pyrose-
they were weaned to a standard gluten-containing (STD) quencing of the V3 and V4 regions of the 16S rRNA
diet. We hypothesized that the dietary protective effect gene by the National High Throughput DNA Sequen-
would be partly mediated by a shift in the gut microbiota, cing Centre, University of Copenhagen, Copenhagen,
and that this shift is of imperative importance in the first Denmark (22), and was analyzed as described by Krych
period of life during which the immune system develops. et al. (23). An open source software package, Quantitative
Insight Into Microbial Ecology (QIIME version 1.7.0) was
RESEARCH DESIGN AND METHODS used to analyze the pyrosequencing data (National Cen-
ter for Biotechnology Information database accession
The experiment was performed in accordance with the
#PRJNA215143). Principal coordinate analysis (PCoA)
Council of Europe Convention European Treaty Series
was made using the jackknife_beta_diversity.py workflow
123 on the Protection of Vertebrate Animals used for
(the –e value: 2,000 sequences). The PCoA plot including
Experimental and Other Scientific Purposes, and the
bacterial taxa was drawn out with the make_3d_plots.py
Danish Animal Experimentation Act (LBK 1306 from 23
script based on the summary information of bacterial
November 2007). The study was approved by the Animal
phyla, and the differences in the taxa relative distribution
Experiments Inspectorate, Ministry of Justice, Denmark.
between categories were tested with Metastats (24)
Animals and Diet independently for both the phylum-level and the genus-
NOD/BomTac mice (Taconic, Hudson, NY) were fed ad level summarized taxa. The P value was calculated based
libitum either a GF modified Altromin diet or an STD on 1,000 permutations.
Altromin diet (Altromin, Lage, Germany), as described by Cell Isolation and Flow Cytometry
Funda et al. (1). The two groups were mated separately, Single-cell suspensions from spleen, MLN, and pancreatic
and their female offspring were group-housed (five mice/ lymph node (PLN) isolated from 4- and 10-week-old
cage) in our barrier-protected rodent facility (Faculty of offspring immediately upon their being killed, and flow
Health and Medical Sciences, University of Copenhagen, cytometric analyses of CD11b+CD11c+ DCs and T-cell
Frederiksberg, Denmark) under standard conditions in populations, including FoxP3+ Tregs, were performed as
open cages without filter lids. All offspring were weaned previously described (22). All antibodies were purchased
diabetes.diabetesjournals.org Hansen and Associates 2823
from eBiosciences (San Diego, CA). The analyses were per-
formed using an Accuri C6 flow cytometer (Accuri Cytom-
eters Inc., Ann Arbor, MI).
Quantitative PCR
Immediately after the mice were killed, 1-cm fragments of
the ileum and colon were placed in RNAlater (Ambion,
Austin, TX), after all luminal content was scraped out of
the gut. Homogenization, RNA isolation with MagMAX-
96 RNA Isolation Kit (Ambion), and cDNA synthesis using
the High-Capacity cDNA Reverse Transcriptase Kit (Ap-
plied Biosystems, Foster City, CA) were performed as
described previously (25). An inventoried TaqMan Mouse
Immune Array (Appled Biosystems) containing 90 TaqMan
gene expression assays of immune-related genes was used
to investigate ileal samples isolated at weaning, which were
analyzed as described previously (26). Actinb, Ocln, Tjp1,
Cldn8, Cldn15, Muc1, and Muc2 TaqMan gene expression
assays (Applied Biosystems) were used for quantitative
PCR (qPCR) analyses on ileum and colon cDNA isolated
at 4 weeks of age, and the data were analyzed as described
previously (25).
cDNA samples from the ileum and colon collected
at weaning were further analyzed for the presence of
Akkermansia muciniphila, which was quantified in dupli-
cate using the 7500 Fast Real-time PCR System (Applied
Biosystems), as previously described (27).
Statistical Analysis
Figure 1—A: Cumulative diabetes incidence in female NOD off-
GraphPad Prism version 5.02 (GraphPad Software, San spring of mice fed an STD diet (n = 37, blue) or a GF diet (n = 36,
Diego, CA) was used for statistical analysis, and P values red). All offspring were weaned to an STD diet at 4 weeks of age and
,0.05 were considered to be significant. Cumulative di- were diagnosed as diabetic and killed when blood glucose levels
abetes incidence was calculated using the Kaplan-Meier exceeded 12 mmol/L on 2 consecutive days. Comparisons of the
two survival curves were tested by log-rank test, and the P value is
estimation, whereas statistical significance was evaluated shown. B: Average insulitis score for offspring of STD and GF diet–
by the log-rank test. Other differences were estimated fed NOD mice at 10 weeks of age that were weaned to an STD diet.
by two-tailed t test or one-way ANOVA test with Tukey C: Percentage of islets with a given score in 10-week-old offspring
post test. of STD diet–fed (n = 9) and GF diet–fed (n = 8) NOD mice. D:
Average insulitis score for nondiabetic offspring of STD and GF
diet–fed NOD mice at 30 weeks of age. E: Percentage of islets
RESULTS
with a given score in 30-week-old nondiabetic offspring of STD
A Maternal GF Diet Attenuates Diabetes in the diet–fed (n = 8) and GF diet–fed (n = 10) NOD mice. White, no
Offspring infiltration; light gray, few mononuclear cells infiltrated; gray, peri-
insulitis; dark gray, 50% islet infil-
In this study, it was demonstrated that feeding a GF diet tration. Error bars represent the SEM. *P < 0.05, **P < 0.01.
to pregnant NOD mice significantly reduced the cumu-
lative diabetes incidence (P , 0.01) and increased the
onset time (P , 0.01) in their offspring, even though all
pups were weaned to an STD diet at 4 weeks of age (Fig. GF Diet Leads to a Gut Microbiota Enriched in
1A). The diabetes incidence at 210 days was 51% (n = 37) Verrucomicrobia, Proteobacteria, and TM7 in Dams
in the offspring of STD diet–fed mice, and 22% (n = 36) and Offspring
in the offspring of GF diet–fed mice. Histological evalu- Gut microbiota analysis by DGGE demonstrated a differ-
ation of insulitis in pancreatic sections from nondiabetic ence in the fecal gut microbiota between the two groups
offspring revealed a significantly lower insulitis score in of pregnant NOD mice (Fig. 2A). ANOVA based on the
offspring of GF diet–fed mice compared with the off- first (X), second (Y), and third (Z) principal component
spring of STD diet–fed mice at both 10 weeks (P , (PC) revealed a significant difference in PC2 values (P ,
0.05; Fig. 1B and C) and 30 weeks of age (P , 0.05; 0.05), and a tendency to cluster in PC1 (P = 0.07) and PC3
Fig. 1D and E). No significant difference in body weight values (P = 0.08). The separate clustering on the PC anal-
gain was observed between the two groups of nondia- ysis plot was also evident in their offspring at weaning,
betic NOD mice within the observational period (data confirming that parental microbiomes altered by diet are
not shown). inheritable (28); significant differences in PC1 values (P ,
2824 Diabetes-Protective Diet Across Two Generations Diabetes Volume 63, August 2014 Figure 2—A: PC analysis plot based on DGGE profiles of 16S rRNA gene PCR–derived amplicons of feces samples collected from NOD offspring of mice fed an STD diet (n = 16, dark blue) or a GF diet (n = 16, red) at 4 weeks of age. STD diet–fed mothers (n = 6, light blue) and GF diet–fed mothers (n = 5, yellow) are also illustrated. B: PC analysis plot based on DGGE of feces collected from the two groups of offspring at 10 weeks of age, which were weaned to an STD diet at 4 weeks of age. ANOVA based on the X, Y, and Z PC analysis was used to compare the groups. C: PCoA plot of 16S rRNA gene tag–encoded pyrosequencing reads based on the weighted UniFrac distance matrix showing clustering of the two groups of offspring. The gray spherical coordinates indicating bacterial phyla are plotted as a weighted average of sample coordinates. The size of each sphere is proportional to the mean relative abundance among all plotted samples. D: The
diabetes.diabetesjournals.org Hansen and Associates 2825 Table 1—Phyla relative distribution in feces samples collected from 4-week-old offspring of STD diet–fed and GF diet–fed NOD mice Taxa STD diet mean abundance GF diet mean abundance P value* q value* Cyanobacteria 1.276 0.001 0.001 0.009 Verrucomicrobia 0.686 7.811 0.002 0.016 Proteobacteria 0.176 0.969 0.001 0.016 TM7 0.012 6.062 0.001 0.009 Firmicutes 54.510 49.030 0.501 1.000 Bacteroidetes 42.545 35.747 0.362 1.000 Deferribacteres 0.544 0.055 0.029 0.139 Tenericutes 0.057 0.007 0.195 0.669 Actinobacteria 0.005 0.000 0.086 0.407 *Values were calculated with Metastats using 1,000 permutations. 0.05) and in PC3 values (P , 0.001) were evident between that the difference observed between the groups was ma- the two groups of offspring. However, how much of this inly due to a significantly expanded representation of the difference in microbiota is due to vertical transfer from bacterial phyla Verrucomicrobia, TM7, and Proteobacteria mothers to pups or to early ingestion of the GF diet by the in the mothers that were eating a GF diet and their pups pups is not known. Gut microbiota analysis of feces from compared with STD diet–fed mice (Fig. 2D). In addition, offspring at 10 weeks of age, 6 weeks after weaning to the the phylum Cyanobacteria was found in approximately STD diet, revealed no difference between the two groups half of the offspring of STD diet–fed mice, but in none of offspring (Fig. 2B). The influence of the diet and the of the offspring of GF diet–fed mice. The annotation of gut microbiota of the mothers on the gut microbiota of reads within the Verrucomicrobia represented one spe- the offspring was thus not permanent. cies, A. muciniphila, whereas the genus Proteus was respon- The differences in the fecal microbial composition sible for the difference evident in Proteobacteria phyla between the two groups of NOD mice and their offspring (Table 2). at 4 weeks of age were further corroborated by tag- qPCR analysis of Akkermansia in the ileum mucosal encoded 16S rRNA gene–based pyrosequencing. The raw layer at weaning revealed a higher abundance in the off- number of reads generated from all 39 fecal samples spring of GF diet–fed mice compared with STD diet–fed scored 1,332,137. Sequences that met all requirements mice (Fig. 2E; P , 0.001). A similar tendency was also of the quality control (minimum length 300 bp, quality evident in the colonic mucus layer (Fig. 2F; P = 0.06). score $25) and were free from chimeric reads yielded An Early GF Environment Increases Anti-Inflammatory 848,346, providing an average of 21,752 sequences per Immune Cells and Intestinally Primed T Cells in PLN sample (minimum 1,178 sequences, maximum 88,674 Both intestinal and pancreatic DCs have been reported to sequences, SD = 17,103 sequences), with a mean sequence play important roles in T1D, and especially the CD11b+ length of 458 bp (minimum 300 bp, maximum 470 bp). subset has been associated with both pathogenic and tol- One sample was discarded because of the low number of erogenic immunity to pancreatic islets. In this study, the reads (,1,000 reads). PCoA based on weighted UniFrac CD11b+CD11c+ DCs were less abundant among pancreatic distance metrics showed a clear separation of the two (P , 0.01), intestinal (P , 0.001), and systemic (P , 0.05) categories comprising GF diet–fed NOD mice and their lymphocyte populations in the offspring of GF diet–fed offspring, and STD diet–fed NOD mice with their off- mice compared with STD diet–fed offspring at the time spring. The proportion of the cumulative information de- of weaning (Fig. 3A). No differences in the overall propor- scribing the variance using the first two PCs reached 60% tion of CD11c+ DCs were observed, and no differences were (Fig. 2C). observed between the groups at 10 weeks of age. The most abundant phyla in both categories were The proportions of Tregs (CD4+FoxP3+) in the MLN Firmicutes and Bacteroidetes that constituted 50% and and spleen were similar in the offspring of GF diet–fed 40%, respectively (Table 1). Metastats analysis revealed and STD diet–fed mice, both at weaning and at 10 weeks relative distribution of bacterial phyla across samples. Bar charts represent the relative abundance of the seven major phyla across samples. Taxonomy assignation was based on the Greengenes reference database (version 12_10). E: qPCR analysis of A. muciniphila in ileum samples from 4-week-old NOD offspring of mice fed an STD diet (n = 8) or a GF diet (n = 8). F: qPCR analysis of A. muciniphila in ileum samples from 4-week-old NOD offspring of mice fed an STD diet (n = 9) or a GF diet (n = 9). The relative distribution of A. muciniphila within all bacteria is shown for each sample. All samples analyzed by qPCR were quantified in duplicate.
2826
Table 2—Significant differences in taxa among 4-week-old offspring of STD diet–fed and GF diet–fed NOD mice
STD diet mean GF diet mean
Phylum Class Order Family Genus abundance abundance P value* q value*
Firmicutes Clostridia Unclassified Unclassified Unclassified 0.460 1.818 0.001 0.011
Firmicutes Clostridia Unknown Unknown Unknown 0.128 1.616 0.001 0.011
Firmicutes Clostridia Clostridiales Unclassified Unclassified 0.096 0.358 0.001 0.011
Firmicutes Clostridia Clostridiales Halobacteriaceae Dehalobacterium 0.125 0.614 0.001 0.011
Firmicutes Clostridia Clostridiales Lachnospiraceae Roseburia 0.000 0.104 0.001 0.011
Firmicutes Clostridia Clostridiales Lachnospiraceae [Ruminococcus] 0.153 0.594 0.001 0.011
Diabetes-Protective Diet Across Two Generations
Firmicutes Clostridia Clostridiales Ruminococcaceae Unclassified 0.225 0.950 0.001 0.011
Firmicutes Clostridia Clostridiales Ruminococcaceae Unknown 0.289 1.446 0.003 0.026
Firmicutes Clostridia Clostridiales Ruminococcaceae Anaerotruncus 0.048 0.181 0.001 0.011
Firmicutes Clostridia Clostridiales Ruminococcaceae Oscillospira 5.844 11.871 0.006 0.049
Proteobacteria Gammaproteobacteria Enterobacteriales Enterobacteriaceae Proteus 0.000 0.187 0.002 0.020
TM7 TM7-3 CW040 F16 Unknown 0.012 6.057 0.001 0.011
Verrucomicrobia Verrucomicrobiae Verrucomicrobiales Verrucomicrobiaceae Akkermansia 0.686 7.809 0.003 0.026
Bacteroidetes Bacteroidia Bacteroidales [Paraprevotellaceae] [Prevotella] 1.918 0.012 0.001 0.011
Cyanobacteria 4C0d-2 YS2 Unknown Unknown 1.255 0.000 0.001 0.011
Firmicutes Bacilli Lactobacillales Lactobacillaceae Unknown 0.437 0.025 0.001 0.011
Firmicutes Clostridia Clostridiales Unknown Unknown 1.517 0.167 0.002 0.020
Firmicutes Clostridia Clostridiales Clostridiaceae Unclassified 0.964 0.001 0.001 0.011
Brackets indicate suggested but not verified names. Unclassified, inability to assign given operational taxonomic unit (OTU) into single taxonomic group; Unknown, absence of information
about given OTU in the database. *Values were calculated with Metastats using 1,000 permutations.
Diabetes Volume 63, August 2014diabetes.diabetesjournals.org Hansen and Associates 2827 Figure 3—Flow cytometric analysis of cells isolated from PLN, MLN, and spleen. Percentages of CD11b+CD11c+ DCs (A) and FoxP3+CD4+ Tregs (B) isolated from 4-week-old offspring from GF diet–fed (n = 8) or STD diet–fed (n = 8) NOD mice. C and D: Representative flow cytometric dot plots illustrating the percentages of CD11b+CD11c+ DCs in MLN after gating on CD11c+ cells. E and F: Representative flow cytometric dot plots illustrating the percentages of FoxP3+CD4+ Tregs in PLN after gating on CD4+ T cells. Percentages of CD8+ T cells (G), CD4+ T cells (H), a4b7+CD8+ T cells (I), and a4b7+CD4+ T cells (J) isolated from 4-week-old offspring from GF diet–fed (n = 8) or STD diet– fed (n = 8) NOD mice are illustrated as indicated. K–N: Representative flow cytometric dot plots illustrating the percentages of a4b7+CD8+ and a4b7+CD4+ T cells in PLN after gating on CD8+ and CD4+ T cells, respectively, as indicated. Error bars represent the SEM. *P < 0.05, **P < 0.01, ***P < 0.001. of age, but, interestingly, a significantly higher proportion T cells in the MLN, PLN, and spleen were not different (P , 0.001) of these cells was evident in the PLN in the between the two groups either at weaning or at 10 weeks offspring of GF diet–fed mice compared with offspring of of age, except for a higher proportion (P , 0.001) of CD8 STD diet–fed mice at weaning, indicating a more anti-in- T cells in the PLN at weaning in the offspring of GF diet– flammatory local immune system due to an early GF en- fed mice compared with offspring of STD diet–fed mice vironment (Fig. 3B). The proportions of CD4 and CD8 (Fig. 3G and H). Furthermore, these CD8 T cells were
2828 Diabetes-Protective Diet Across Two Generations Diabetes Volume 63, August 2014
marked with gut-homing receptor a4b7 integrin, which is regulatory immunological activity, genes implicated in
induced when T cells are activated in the intestinal envi- immune cell migration, microbial recognition, and re-
ronment (Fig. 3I). Also on the CD4 T cells in PLN a higher sponse, as well as T-cell activation and signaling in the gut
proportion of cells (P , 0.01) was marked with a4b7 in were analyzed at weaning. Thirty-one of the 90 gene
the offspring of GF diet–fed mice compared with off- expressions analyzed were significantly altered between
spring of STD diet–fed mice (Fig. 3J). However, this dif- the two groups of offspring (Table 3). Of importance, the
ference in a4b7 integrin was evident only at weaning and early GF environment caused significantly less expression
not at 10 weeks of age. of several inflammatory mediators of insulitis such as
Intestinal Gene Expression Is Skewed Toward an Ifng, Il12b, and Il18 genes, and Prf1 and Gzmb genes for
Anti-Inflammatory Phenotype in Offspring of GF the cytolytic enzymes perforin-1 and granzyme B, respec-
Diet–Fed Mice tively. Interestingly, the Cd68 macrophage marker, the
To further explore how the early-life GF environ- Hmox1 gene for the heme oxygenase-1 enzyme, and the
ment affected gut homeostasis and the establishment of Stat6 gene involved in exerting IL-4 were more
Table 3—Relative gene expression of immune-related genes analyzed in an inventoried TaqMan Mouse Immune Array in ileal
samples collected from 4-week-old offspring of GF diet–fed and STD diet–fed NOD mice
RQ mean*
Gene Gene name [protein name] STD diet GF diet P value†
Signaling
C3 Complement component 3 [C3] 1.07 6 0.14 2.06 6 0.33 ,0.01
Col4a5 Procollagen, type IV, a5 [COL4a5] 1.06 6 0.16 2.63 6 0.66 ,0.05
Edn1 Endothelin 1 [EDN1] 1.28 6 0.39 6.65 6 1.12 ,0.001
Ikbkb Inhibitor of kB kinase b [IKKb] 1.03 6 0.09 1.51 6 0.17 ,0.05
Nfkb1 Nuclear factor of k light chain gene enhancer in 1.02 6 0.07 1.37 6 0.12 ,0.05
B-cells 1 [NFkB1]
Smad3 MAD homolog 3 (Drosophila) [SMAD3] 1.03 6 0.09 1.67 6 0.11 ,0.001
Smad7 MAD homolog 7 (Drosophila) [SMAD7] 1.03 6 0.09 1.64 6 0.16 ,0.01
Ski Sloan-Kettering viral oncogene homolog [SKI] 1.01 6 0.05 1.79 6 0.12 ,0.0001
Socs1 Suppressor of cytokine signaling 1 [SOCS1] 1.03 6 0.10 0.51 6 0.11 ,0.01
Socs2 Suppressor of cytokine signaling 2 [SOCS2] 1.02 6 0.07 1.89 6 0.17 ,0.001
Stat6 Signal transducer and activator of 1.02 6 0.07 1.66 6 0.11 ,0.001
transcription 6 [STAT6]
Cytokines/cytokine receptors
Fas Fas (TNF receptor superfamily member) [FAS] 1.02 6 0.07 1.50 6 0.16 ,0.05
Ifng IFN-g 3.13 6 1.63 0.29 6 0.22 ,0.01
Il10 IL-10 1.25 6 0.35 0.00 6 0.00 ,0.0001
Il12b IL-12b 3.42 6 1.55 0.85 6 0.80 ,0.05
Il15 IL-15 1.06 6 0.15 3.05 6 0.45 ,0.0001
Il17 IL-17 1.25 6 0.33 0.33 6 0.32 ,0.001
Il18 IL-18 1.03 6 0.09 0.20 6 0.02 ,0.0001
Chemokine/chemokine receptors
Ccr4 Chemokine (C-C motif) receptor 4 [CCR4] 1.72 6 0.37 0.15 6 0.04 ,0.01
Cxcl11 Chemokine (C-X-C motif) ligand 11 [I-TAC] 1.03 6 0.11 3.18 6 0.56 ,0.0001
Cell surface receptors
Cd34 CD34 antigen [CD34] 1.12 6 0.22 2.53 6 0.46 ,0.01
Cd38 CD38 antigen [CD38] 1.01 6 0.06 0.52 6 0.06 ,0.01
Cd3e CD3 antigen, ´ polypeptide [CD3e] 1.16 6 0.19 0.57 6 0.12 ,0.05
Cd68 CD68 antigen [CD68] 1.04 6 0.11 1.56 6 0.20 ,0.05
Cd8a CD8 antigen, a chain [CD8a] 1.19 6 0.23 0.49 6 0.10 ,0.05
Lrp2 LDL receptor–related protein 2 [LRP2] 1.39 6 0.29 4.16 6 0.67 ,0.01
Tfrc Transferrin receptor [TRFC] 1.02 6 0.08 1.38 6 0.11 ,0.05
Enzymes
Gzmb Granzyme B [CTLA1] 1.55 6 0.40 0.19 6 0.09 ,0.01
Hmox1 Heme oxygenase (decycling) 1 [HMOX1] 1.09 6 0.19 2.41 6 0.48 ,0.05
Nos2 Nitric oxide synthase 2, inducible, macrophage [NOS2] 1.05 6 0.12 0.15 6 0.04 ,0.0001
Prf1 Perforin 1 (pore-forming protein) [PRF1] 1.77 6 0.47 0.44 6 0.20 ,0.05
*Relative quantification was calculated by the comparative Ct method, where the expression of each gene is first normalized to the
expression of Actb. Comparative gene expression is calculated for the mean control group, and fold change (RQ) values are obtained,
with fold change = 1 for mean control. RQ values for genes more highly expressed compared with controls are marked in bold. †Only
genes that were significantly expressed differently (P , 0.05) between the two groups are included. Statistical analysis was performed
on dCt values [Ct(target) 2 Ct(reference)].diabetes.diabetesjournals.org Hansen and Associates 2829
profoundly expressed in the offspring of GF diet–fed mice
compared with STD diet–fed offspring, and they are all
characteristics of immunosuppressive M2 macrophages,
whereas the expression of the Nos2 (iNos) gene marker
of M1 macrophages was low. However, gene expressions
of intestinal cytokines Il10 and Il17, which have previ-
ously been associated with diabetes protection, were
lower in these mice similar to Socs1, an inhibitor of
IFN-g signaling and Smad7 and Ski, which are inhibitors
of the regulatory cytokine TGF-b signaling.
Expressions of T-cell marker genes such as Cd3e, Cd8a,
and Cd38 were also downregulated in the ileum, including
Ccr4 expression, which has been demonstrated on patho-
genic autoimmune T cells in NOD mice. Supportive of the
flow cytometry results, the CD34 gene expression, which
encodes a key molecule in T-cell trafficking to lymph
nodes, was higher in the offspring of GF diet–fed mice
compared with STD diet–fed offspring.
Expressions of Intestinal Tight Junction and Mucus-
Related Genes Are Elevated in the Gut at Weaning
To investigate whether the more anti-inflammatory gene
expression profile in the gut was associated with an
improved intestinal barrier at weaning, gene expressions
of tight junction and mucus components were analyzed in
Figure 4—Relative gene expression of Ocln (A), Tjp1 (B), Cldn8 (C),
the ileum and colon. The following tight junction Cldn15 (D), Muc1 (E), and Muc2 (F) in ileum and colon from 4-week-
component genes have been shown to be regulated in old offspring of GF diet–fed or STD diet–fed mice. Data were nor-
association with improved intestinal permeability assay malized to Actb and then to the mean control group, which was
defined as 1. All samples were quantified in duplicate (n = 8–9 per
results (29). Gene expressions of Ocln, which encodes group). Error bars represent the SEM. *P < 0.05, **P < 0.01.
occludin (P , 0.01; Fig. 4A), Tjp1, which encodes tight
junction protein 1 (P , 0.01; Fig. 4B), and Cldn15, which
encodes claudin-15 (P , 0.05; Fig. 4D), were elevated in
ilea from the offspring of GF diet–fed mice compared with insulitis than the nondiabetic STD mice, which indicates
those of STD diet–fed mice. Ocln (P , 0.05) gene expres- that the GF group is not just delayed in diabetes develop-
sion was also elevated in the colon together with a tendency ment, but is as far from diabetic as the nondiabetic con-
for higher expression of Muc1, which encodes a protein trol mice that usually do not develop diabetes; however,
that represents membrane-associated mucin (P = 0.06; a longer observational period would be necessary to fully
Fig. 4E). Conversely, colonic Muc2 expression representing clarify whether the mice are completely protected against
secreted mucin was lower (P , 0.05; Fig. 4F). diabetes.
In agreement with this result, the ability of a low-
DISCUSSION protein diet to modify diabetes incidence was reported to
The importance of gluten for the development of auto- cause a significant drop in diabetes incidence from 86% in
immune diabetes was previously demonstrated in both control NOD mice to 63% in NOD mice when given only
NOD mice and BB rats, and it has become clear that during pregnancy and lactation (30). In contrast, wheat
disease-modulating interventions, including dietary or and barley protein deprivation only until weaning was
microbial antigen treatments, in these animal models demonstrated not to be sufficient to significantly delay
are particularly imperative in early life. To clarify whether diabetes development. However, in the gestational and
the effect of gluten could be prevented exclusively by preweaning period this diet was also supplemented with
limiting its exposure in the postnatal period, a two- fish oil and Vit D3, which in the same study (31) were
generation approach was used. Most importantly, the demonstrated to abrogate the protective effect of a wheat
diabetes incidence was significantly reduced in the off- and barley protein-free diet. Interestingly, it was also
spring of GF diet–fed NOD mice even though they were shown that accelerated diabetes was not completely
weaned to an STD diet. Thus, a GF diet during gestation reconstituted by supplementing the wheat and barley pro-
and lactation was protective later in life. The fact that we, tein-free diet with gliadin, which indicates that other di-
despite the low incidence of T1D in our facility, see a sig- etary or microbial antigens also mediate the protective
nificant difference in the GF group further substantiates effect. For example, the gut microbiota in GF diet–fed
the strong effect of this diet. The 30-week-old nondiabetic mice, which may not be altered by a pure gliadin supple-
offspring of GF diet–fed mice had a lower incidence of ment, is different from that in gluten-fed mice (12). A2830 Diabetes-Protective Diet Across Two Generations Diabetes Volume 63, August 2014
recent article (17) proposed cereal dietary antigens as a protected against the development of T1D later in life.
stronger T1D inducer than microbes. The authors Thus, its immune regulatory effect on, for example, Tregs
reported a similar protective effect on diabetes incidence at weaning in the prediabetic stage seems to have a long-
in BB rats that were fed a low-antigen hydrolyzed casein lasting impact on the capability of the immune system to
(HC) diet in both germ-free and specific pathogen–free protect against autoimmune attack on the b-cells.
(SPF) conditions. However, the HC diet was more pro- Interestingly, an early article (39) demonstrated that
tective in the germ-free than in the SPF condition, also adoptively transferred T cells from NOD mice on an HC
indicating a diabetes-promoting effect of the microbes. diet were unable to change the incidence of diabetes and
This was further supported by a low b-cell mass only in were presented with similar T-cell receptor–mediated pro-
the cereal-fed BB rats compared with the germ-free and liferative responses compared with controls. Considering
HC-fed BB rats. this, it was hypothesized that immune regulatory mecha-
In the current study, a distinct bacterial profile nisms in the pancreatic environment at weaning down-
enriched in especially Akkermansia, TM7, and Proteobac- regulate otherwise fully functional diabetogenic T-cell
teria was evident in both NOD mice fed a GF diet and in response in GF diet–fed NOD mice. In the current study,
their offspring at weaning. These taxonomic groups were this hypothesis was supported by increased proportions
also previously associated with protection against the de- of FoxP3+ Tregs in PLN and fewer CD11b+ DCs at wean-
velopment of autoimmune diabetes in NOD mice only ing, which also previously were modulated by an antidia-
when present before weaning (22), which is interesting betogenic diet (5). A similar anti-inflammatory immune
as Akkermansia has been demonstrated to modulate host profile has been observed in BALB/c mice receiving a GF
immune responses in monocolonized mice (32). In addi- diet in both pancreatic and gut-associated lymphoid tissue
tion, taxonomic differences between the gut microbiomes (18). The changes in the immune system were only found
of healthy and diabetic children were characterized by at weaning and not at 10 weeks of age. Thus, it seems that
mucin-degrading Akkermansia, which was more abundant changes in immunity later in life when insulitis is more
in control subjects than in case patients (33). As gluten progressive are not as critical as in postnatal life for the
has potential irritating effects in the small intestine where development of autoimmune diabetes, during which the
it is degraded, this might affect mucus production and insulitis process begins. This further indicates that the GF
barrier function. By leaving out gluten from the diet, diet, possibly through a change in the gut microbiota, may
the mucus production may increase, which in turn can have delayed the development of the adaptive immunity,
lead to an increase in the presence and metabolic activity but that the mice, independently of whether they develop
of specific bacterial strains, not least Akkermansia, which T1D or not, eventually develop a mature immune system.
previously has been shown to grow on mucus proteins Lower intestinal gene expression of proinflammatory
(34). Minor fold-change differences were seen in tight cytokines and higher expression of anti-inflammatory M2
junction component gene expressions, which indicated macrophage markers, together with increased gut Cd3e,
that Akkermansia might be associated with an improved Cd8a expression were found in the offspring of GF diet–
intestinal barrier in both the ileum and colon, although fed mice. It is interesting that these findings were also
this link is purely speculative. The restoration of impaired seen in SPF BB rats fed an HC diet but not to the same
intestinal barrier and alleviated signs of gut epithelial extent as in the germ-free HC-fed BB rats (17). Thus, it
irritation such as colonic crypt hyperplasia have also pre- required the presence of microbes. M2 macrophages were
viously been shown in response to antidiabetogenic diets furthermore found to be associated with the microbiota-
in T1D rodent models (5,35). dependent sex difference observed in T1D development in
Not much is known about the role of TM7 in mam- NOD mice (40). The intestinal alterations found in the
malian health and disease, but in humans it is mainly offspring of GF diet–fed mice may therefore, also in this
associated with the oral cavity, where it has been associated experiment be a consequence of the altered microbiota in
with periodontitis (36,37). Furthermore, Kuehbacher et al. early life rather than the presence of cereal antigens. Al-
(38) suggested that TM7 members are involved in the though these data cannot be causally linked to the pan-
ethology of Crohn disease, although the mechanism creas, it was demonstrated that an early GF environment
remains unknown. A detailed examination of the influ- increased the trafficking of T cells with a mucosal pheno-
ence of the microbes from GF diet–fed NOD mice by type to PLN. It would be interesting to further investigate
transferring the microbiota to germ-free mice would be the regulatory properties of these T cells because a high
informative. It is striking that the effect on the microbial intestinal IL-15 level, as seen in the GF group, promotes
composition is only present as long as the mice are fed intestinal epithelial cell activation of noncytotoxic CD8
a GF diet. This indicates that the effect of the microbiota T cells with suppressor function (41). These cells have
is dependent on the diet and that this effect is especially nondetectable granzyme B, which was also expressed sig-
important during the development of the immune sys- nificantly lower in the GF group. This is further consistent
tem. Even more striking is the fact that even though with the prevalence of M2 anti-inflammatory macro-
the microbiota reverses after the introduction of gluten phages as these and Tregs seem to have a mutual ability
in the diet at weaning, the mice born by GF mothers are to promote the differentiation of one another, at leastdiabetes.diabetesjournals.org Hansen and Associates 2831
partly through the TGF-b pathway (42,43). It is possible 9. Yang XD, Sytwu HK, McDevitt HO, Michie SA. Involvement of beta 7 integrin
that any effect of bacterial or dietary antigens on pancre- and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in the de-
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dysfunction: the BB rat model. Horm Metab Res 2004;36:585–594
the tolerogenic gut environment.
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Whether the early ingestion of cereal antigens before non-obese diabetic mice fed a diet containing wheat. Diabetologia 2005;48:
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the early GF environment clearly attenuated diabetes preventive gluten-free diet decreases the number of caecal bacteria in non-obese
development in the NOD mice even though they were diabetic mice. Diabetes Metab Res Rev 2006;22:220–225
weaned to a gluten-containing diet, but the changes in gut 13. Wen L, Ley RE, Volchkov PY, et al. Innate immunity and intestinal microbiota
microbiota and immune system were no longer evident in the development of Type 1 diabetes. Nature 2008;455:1109–1113
later in life, from which we can conclude that the time and 14. Brugman S, Klatter FA, Visser JTJ, et al. Antibiotic treatment partially protects
the diet before weaning are of imperative importance for against type 1 diabetes in the Bio-Breeding diabetes-prone rat. Is the gut flora
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Funding. This work was carried out as part of the 3G Center—Gut, Grain & 16. Calcinaro F, Dionisi S, Marinaro M, et al. Oral probiotic administration in-
Greens; the 3G Center is supported by the Danish Council for Strategic Research. duces interleukin-10 production and prevents spontaneous autoimmune diabetes
This work was further funded by CHANCE (Chemometric Analysis Centre at the in the non-obese diabetic mouse. Diabetologia 2005;48:1565–1575
University of Copenhagen), the Center for Applied Laboratory Animal Research, 17. Patrick C, Wang GS, Lefebvre DE, et al. Promotion of autoimmune diabetes
and the Beckett Foundation. by cereal diet in the presence or absence of microbes associated with gut im-
Duality of Interest. No potential conflicts of interest relevant to this article mune activation, regulatory imbalance, and altered cathelicidin antimicrobial
were reported. peptide. Diabetes 2013;62:2036–2047
Author Contributions. C.H.F.H. conceived and designed the study, an- 18. Antvorskov JC, Fundova P, Buschard K, Funda DP. Dietary gluten alters the
alyzed histology, performed flow cytometry, contributed to the discussion, and balance of pro-inflammatory and anti-inflammatory cytokines in T cells of BALB/c
wrote the manuscript. Ł.K. analyzed the data, contributed to the discussion, and mice. Immunology 2013;138:23–33
wrote the manuscript. K.B. analyzed histology and contributed to the discussion. 19. Chakir H, Lefebvre DE, Wang H, Caraher E, Scott FW. Wheat protein-induced
S.B.M., C.N., and H.F. were involved in the analysis of gene expression data and proinflammatory T helper 1 bias in mesenteric lymph nodes of young diabetes-
contributed to the discussion. L.H.H. performed pyrosequencing and contributed prone rats. Diabetologia 2005;48:1576–1584
to the discussion. D.S.N. analyzed the data and contributed to the discussion. 20. Hoorfar J, Buschard K, Dagnaes-Hansen F. Prophylactic nutritional modi-
S.S. performed flow cytometry and contributed to the discussion. A.K.H. con- fication of the incidence of diabetes in autoimmune non-obese diabetic (NOD)
ceived and designed the study, contributed to the discussion, and wrote the mice. Br J Nutr 1993;69:597–607
manuscript. C.H.F.H. is the guarantor of this work and, as such, had full access 21. Hufeldt MR, Nielsen DS, Vogensen FK, Midtvedt T, Hansen AK. Variation in
to all the data in the study and takes responsibility for the integrity of the data and the gut microbiota of laboratory mice is related to both genetic and environmental
the accuracy of the data analysis. factors. Comp Med 2010;60:336–347
22. Hansen CH, Krych L, Nielsen DS, et al. Early life treatment with vancomycin
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