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Type 1 diabetes results from autoimmune destruction of pancreatic β-cells. β-cell neoformation has been shown to increase in response to islet neogenesis-associated protein (INGAP) in hamsters. Using immunohistochemistry and morphometry, INGAP effects in diabetes-prone BioBreeding (BBdp) rats were investigated. At 23 d, rats were fed a hydrolyzed casein (HC) diet or a cereal-based NTP-2000 diet. Rats were administered saline intraperitoneally (n=7) or 250 gg of INGAP-peptide (n=7) twice daily for two weeks and killed at 45 d. In HC-fed rats, the number of small and total islets was greater in INGAP-treated rats compared with controls (59 ± 17 vs. 37 ± 8 islets/cm², mean ± SD, p=0.01 and 143 ± 19 vs. 114 ± 24 islets/cm², p<0.03). In rats given INGAP, insulin+extra-islet clusters, markers of islet neoformation, were more frequent in those fed HC compared with NTP (82 ± 20 vs. 46 ± 8 clusters/cm², p<0.01). HC-fed rats given INGAP had a higher percentage of BrdU+/insulin+ clusters compared with controls, indicating enhanced proliferation (26.0 ± 7.6 vs. 13.1 ± 2.7%, p<0.001). INGAP-treated rats fed either an HC or NTP diet had a higher percentage of insulin+ cells in small ducts compared with saline controls. These findings demonstrate the presence of INGAP-stimulated β-cell neoformation, some aspects of which were further enhanced in BBdp rats fed a protective HC diet. [ABSTRACT FROM AUTHOR]

Cellular prion protein (PrPC) is expressed in several tissues including neurons and pancreatic islets. To investigate whether PrPC expression was altered during the development of diabetes, we examined the pancreas in diabetes-prone BioBreeding (BBdp) rats as well as nonobese diabetic mice using light, fluorescent and confocal microscopy. PrPC was abundantly expressed in the four major endocrine cells within islets in BBdp rats and NOD mice. Surprisingly, cytosolic PrPC inclusions were observed in a subpopulation of beta-cells in rats only. Inclusions were present in the islets of several rat strains including Wistar Furth, Sprague Dawley and Komeda. PrPC expression in the cytosol was weak, with strong staining of the cell membrane and pronounced aggregation in a subset of rat beta-cells, particularly in older BBdp animals. The frequency of beta-cells with inclusions increased with age in BBdp but not in controls. Moreover, in Sprague Dawley rats chronically infused with glucose, cytosolic PrPC expression was suppressed whereas the number of beta-cells with inclusions increased. There was no co-localization of gamma-tubulin (microtubule complex), ubiquitin and proteasomes (protein degradation) and HSP70 (protein folding) with the PrPC inclusions consistent with proper folding of the PrPC protein. Thus, PrPC could play a role in glucoregulation and/or diabetes pathogenesis. [ABSTRACT FROM AUTHOR]

Diabetes incidence is reduced in diabetes-prone BioBreeding (BBdp) rats fed a hydrolyzed casein (HC) diet compared with a standard cereal-based rodent diet such as NTP-2000 (NTP). To further characterize the basis of this protective effect, islet neogenesis, apoptosis and cell proliferation were analyzed using immunohistochemistry, morphometry, Laser Capture Microdissection, and RT-PCR in BBdp rats weaned onto an NTP or HC diet at 23 d and sacrificed at 25, 30, and 45 d. Islet area fraction was greater in medium and large islets of HC-fed rats at 30 d and in large islets only at 45 d. There were more small islets in HC-fed rats both at 30 and 45 d and β-cell mass was significantly greater at 45 d. Cell cycle analysis revealed an increased ratio of S+G2/G0+G1 in HC-fed animals between 25 and 45 d. PDX-1+ clusters (<4 cells) were increased in HC-fed rats, whereas extra-islet insulin+ clusters (EIC) and insulin+ cells in ducts, representative of islet neogenesis, were increased at 45 d. Ngn3 mRNA was higher in EIC of HC-fed rats at 24 d. Glucagon-like peptide-1 receptor protein and mRNA were increased in islets of HC-fed rats. In summary, the protective HC diet increased β-cell mass in diabetes-prone rats through upregulation of islet neogenesis and β-cell proliferation. [ABSTRACT FROM AUTHOR]

Type 1 diabetes (T1D) is a T cell mediated autoimmune disease dependent on gene-environment interaction. A wheat storage globulin with 80% amino acid homology to Glb1 (referred to as Glb1), was identified as the first candidate diabetes-related wheat protein in diabetes-prone rats. Glb1 antibodies were also found in pooled diabetic serum (MacFarlane et al., JBC, 2003). In this study, we evaluated the response of peripheral blood T cells to recombinant Glb1 protein in T1D patients and healthy controls. T cell response was measured using a CFSE proliferation assay and reported as cell division index (CDI). Th1 and Th2 cytokines were analyzed using cytometric bead arrays. Glb1 antibodies were evaluated by ELISA. T1D patients showed a higher mean CDI in response to Glb1. More than 1/3 of patients were responders (CDI > control mean + 3 SD). Cytokine analysis of the culture supernatant from Glb1-stimulated PBMC of patients showed a Th1 response, with IFN-γ most abundant. Approximately 25% of patients displayed Glb1 antibody levels higher than the control group mean + 2 SD. This study demonstrates high T cell reactivity with a Th1 response and antibodies to Glb1 in a subset of T1D patients. Further study is required to determine whether Glb1 plays a direct role in the pathogenesis of T1D or whether immune reactivity against this protein is a biomarker of a related process. [ABSTRACT FROM AUTHOR]