Serum metabolite signature predicts the acute onset of diabetes in spontaneously diabetic congenic BB rats

The clinical presentation of type 1 diabetes is preceded by a prodrome of beta cell autoimmunity. We probed the short period of subtle metabolic abnormalities, which precede the acute onset of diabetes in the spontaneously diabetic BB rat, by analyzing the serum metabolite profile detected with combined gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS). We found that the metabolite pattern prior to diabetes included 17 metabolites, which differed between individual diabetes prone (DP) BB rats and their age and sex matched diabetes resistant (DR) littermates. As the metabolite signature at the 40 days of age baseline failed to distinguish DP from DR, there was a brief 10-day period after which the diabetes prediction pattern was observed, that includes fatty acids (e.g. oleamide), phospholipids (e.g. phosphocholines) and amino acids (e.g. isoleucine). It is concluded that distinct changes in the serum metabolite pattern predict type 1 diabetes and precede the appearance of insulitis in spontaneously diabetic BB DP rats. This observation should prove useful to dissect mechanisms of type 1 diabetes

Genetic Dissection Reveals Diabetes Loci Proximal to the Gimap5 Lymphopenia Gene.

Congenic DRF.(f/f) rats are protected from type 1 diabetes (T1D) by 34 Mb of F344 DNA introgressed proximal to the Gimap5 lymphopenia gene. To dissect the genetic factor(s) that confer protection from T1D in the DRF.(f/f) rat line, DRF.(f/f) rats were crossed to inbred BBDR or DR.(lyp/lyp) rats to generate congenic sublines that were genotyped, monitored for T1D and positional candidate genes sequenced. All (100%) DR.(lyp/lyp) rats developed T1D by 83 days of age. Reduction of the DRF.(f/f) F344 DNA fragment by 26 Mb (42.52 Mb-68.51 Mb) retained complete T1D protection. Further dissection revealed that a 2 Mb interval of F344 DNA (67.41-70.17 Mb) (Region 1) resulted in 47% protection and significantly delayed onset (p<0.001 compared to DR.(lyp/lyp)). Retaining <1 Mb of F344 DNA at the distal end (76.49-76.83 Mb) (Region 2) resulted in 28% protection and also delayed onset (p<0.001 compared to DR.(lyp/lyp)). Comparative analysis of diabetes frequency in the DRF.(f/f) congenic sublines further refined the RNO4 Region 1 interval to approximately 670 Kb and Region 2 to the 340 Kb proximal to Gimap5. All congenic DRF.(f/f) sublines were prone to low-grade pancreatic mononuclear cell infiltration around ducts and vessels but less than 20% of islets in non-diabetic rats showed islet infiltration. Coding sequence analysis revealed TCR Vbeta 8E, 12 and 13 as candidate genes in Region 1 and Znf467 and Atp6v0e2 as candidate genes in Region 2. Our results show that spontaneous T1D is controlled by at least two genetic loci 7 Mb apart on rat chromosome 4. Key words: Type 1 diabetes, BB rat, T cell receptor, autoimmune