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Aims/hypothesis: Impaired intestinal barrier function is observed in type 1 diabetes patients and animal models of the disease. Exposure to diabetogenic antigens from the intestinal milieu due to a compromised intestinal barrier is considered essential for induction of the autoimmune process leading to type 1 diabetes. Since a hydrolysed casein (HC) diet prevents autoimmune diabetes onset in diabetes-prone (DP)-BioBreeding (BB) rats, we studied the role of the HC diet on intestinal barrier function and, therefore, prevention of autoimmune diabetes onset in this animal model., Methods: DP-BB rats were fed the HC diet from weaning onwards and monitored for autoimmune diabetes development. Intestinal permeability was assessed in vivo by lactulose-mannitol test and ex vivo by measuring transepithelial electrical resistance (TEER). Levels of serum zonulin, a physiological tight junction modulator, were measured by ELISA. Ileal mRNA expression of Myo9b, Cldn1, Cldn2 and Ocln (which encode the tight junction-related proteins myosin IXb, claudin-1, claudin-2 and occludin) and Il-10, Tgf-ß (also known as Il10 and Tgfb, respectively, which encode regulatory cytokines) was analysed by quantitative PCR., Results: The HC diet reduced autoimmune diabetes by 50% in DP-BB rats. In DP-BB rats, prediabetic gut permeability negatively correlated with the moment of autoimmune diabetes onset. The improved intestinal barrier function that was induced by HC diet in DP-BB rats was visualised by decreasing lactulose:mannitol ratio, decreasing serum zonulin levels and increasing ileal TEER. The HC diet modified ileal mRNA expression of Myo9b, and Cldn1 and Cldn2, but left Ocln expression unaltered., Conclusions/interpretation: Improved intestinal barrier function might be an important intermediate in the prevention of autoimmune diabetes by the HC diet in DP-BB rats. Effects on tight junctions, ileal cytokines and zonulin production might be important mechanisms for this effect.

We have mapped and annotated the variable region of the immunoglobulin heavy (IGH) gene locus of the Brown Norway (BN) rat (assembly V3.4; Rat Genomic Sequence Consortium). In addition to known variable region genes, we found 12 novel previously unidentified functional IGHV genes and 1 novel functional IGHD gene. In total, the variable region of the rat IGH locus is composed of at least 353 unique IGHV genes, 21 IGHD genes, and 5 IGHJ genes, of which 131, 14, and 4 are potentially functional genes, respectively. Of all species studied so far, the rat seems to have the highest number of functional IGHV genes in the genome. Rat IGHV genes can be classified into 13 IGHV families based on nucleotide sequence identity. The variable region of the BN rat spans a total length of approximately 4.9 Mb and is organized in a typical translocon organization. Like the mouse, members of the various IGHV gene families are more or less grouped together on the genome, albeit some members of IGHV gene families are found intermingled with each other. In the rat, the largest IGHV gene families are IGHV1, IGHV2, and IGHV5. The overall conclusion is that the genomic organization of the variable region of the rat IGH locus is strikingly similar to that of the mouse, illustrating the close evolutionary relationship between these two species.

Aims/hypothesis: Accumulating data suggest that the gut immune system plays a role in the development of type 1 diabetes. The intestinal flora is essential for the development of the (gut) immune system and the establishment of tolerance. It has been reported that oral administration of food and bacterial antigens early in life suppresses later development of diabetes in the Bio-Breeding diabetes-prone (BB-DP) rat. This study was designed to investigate the possible relationship between the development of diabetes and the composition of intestinal flora., Materials and Methods: The intestinal flora of BB-DP rats, a rat model for type 1 diabetes, was characterised long before the clinical onset of diabetes by fluorescent in situ hybridisation. In a separate experiment, BB-DP rats were treated with antibiotics and the effect on diabetes incidence and level of insulitis was analysed., Results: We observed a difference in bacterial composition between rats that eventually did and those that did not develop diabetes. This difference was detectable long before clinical onset of the disease. Rats that did not develop diabetes at a later age displayed a lower amount of Bacteroides sp. Modulation of the intestinal flora through antibiotic treatment decreased the incidence and delayed the onset of diabetes. A combination of antibiotic treatment and a protective hydrolysed casein diet completely prevented diabetes in the BB-DP rat., Conclusions/interpretation: Our data suggest that the intestinal flora is involved in the development of type 1 diabetes. Factors influencing composition of the intestinal flora could be a target for therapeutic intervention.

Aims/hypothesis: Environmental factors such as diet and bacterial antigens play an important role in the onset of Type 1 diabetes. Different self-antigens are suggested to play a role in the development of diabetes. Antibodies against the 60-kDa heat shock protein 60, which have a high homology to bacterial heat shock protein 65, have been found in the circulation at the onset of diabetes in humans and in pre-diabetic NOD-mice. One of the immunodominant epitopes in autoimmune diabetes is p277, a specific peptide of human heat shock protein 60 corresponding to positions 437-460. In this study we investigated whether neonatal oral administration of DiaPep277 (a synthetic peptide analogue of p277) affected the development of diabetes in the BioBreeding-Diabetes Prone (BB-DP) rat, and whether this could potentiate the effect of a protective hydrolysed casein-diet., Methods: BB-DP rats were orally inoculated once per day with placebo or DiaPep277 at days 4, 5, 6 and 7 of life. At the age of 21 days rats were weaned on to a conventional, cereal-based diet or on to the hydrolysed casein-diet., Results: The development of diabetes in animals receiving DiaPep277 in combination with the hydrolysed casein-diet was delayed by 17 days, and a relative reduction of the incidence by 64% was seen. Non-diabetic animals did not show any sign of insulitis., Conclusions/interpretation: Short-term neonatal feeding with p277 in early life, combined with diet adaptation, appears to provide a procedure to significantly reduce the development of Type 1 diabetes in later life.