Deteriorated high-fat diet-induced diabetes caused by pancreatic β-cell-specific overexpression of Reg3β gene in mice

Reg3β: A Potential Therapeutic Target for Tissue Injury and Inflammation-Associated Disorders

Since regenerating islet-derived 3β (Reg3β) was first reported, various studies have been conducted to explore the involvement of Reg3β in a gamut of maladies, such as diabetes, pancreatitis, pancreatic ductal adenocarcinoma, and extrapancreatic maladies such as inflammatory bowel disease, acute liver failure, and myocardial infarction. Surprisingly, there is currently no systematic review of Reg3β. Therefore, we summarize the structural characteristics, transcriptional regulation, putative receptors, and signaling pathways of Reg3β. The exact functional roles in various diseases, especially gastrointestinal and liver diseases, are also discussed. Reg3β plays multiple roles in promoting proliferation, inducing differentiation, preventing apoptosis, and resisting bacteria. The present review may provide new directions for the diagnosis and treatment of gastrointestinal, liver, and pancreatic diseases.

Dimorphic autoantigenic and protective effects of Reg2 peptide in the treatment of diabetic β-cell loss

AIMS

The potential effect of regenerating (Reg) proteins in the treatment of diabetes has been indicated in the past decade, but the clinical use of Reg proteins requires more advances in translational medicine. In the present study, we produced recombinant regenerating protein 2 (rReg2), to prove its protective effect against streptozocin (STZ)-induced diabetes in BALB/c mice.

MATERIALS AND METHODS

rReg2 was administrated in STZ-induced diabetic mice. Blood glucose, body weight, serum insulin and islet β-cell loss were determined. However, Reg2 has also been reported to serve as an autoantigen that induces autoimmune attacks on islets and aggravates diabetic development in non-obese diabetic mice. To address this contradiction, complete Freund's adjuvant was injected to generate a model that was hypersensitive to Reg2. In this model, islet CD8 T-cell infiltration, serum Reg2 antibody and interleukin (IL)-4 and IL-10, and splenic CD4+/interferon (IFN)-γ+ T cells were determined.

RESULTS

Direct rReg2 pretreatment preserved islet β-cell mass against STZ and improved glycaemia, body weight and serum insulin content. The protection against cell death was further confirmed in cultured mouse islets and MIN6 cells. On the other hand, significant elevations of serum Reg2 antibody and splenic CD4+/IFN-γ+ T cells, and decreases in serum IL-4 and IL-10 were detected in rReg2-vaccinated mice, which may contribute to the accelerated diabetes. Interestingly, these mice, upon further rReg2 treatment, exhibited alleviated diabetic conditions with less islet CD8+ T-cell infiltration.

CONCLUSION

rReg2 treatment ameliorated STZ-induced diabetes in normal BALB/c mice. By contrast, rReg2 vaccination exacerbated, but further rReg2 treatment alleviated, the severity of STZ-induced diabetes. Thus, the protective effect of rReg2 is predominant over the autoantigenic β-cell destruction, supporting the potential of rReg2 in the clinical treatment of diabetes.

The Role of Intestinal C-type Regenerating Islet Derived-3 Lectins for Nonalcoholic Steatohepatitis

C-type regenerating islet derived-3 (Reg3) lectins defend against pathogens and keep commensal bacteria at a distance. Deficiency of Reg3g and Reg3b facilitates alcohol-induced bacterial translocation and alcoholic liver disease. Intestinal Reg3g is down-regulated in animal models of diet-induced obesity, but the functional consequences for nonalcoholic steatohepatitis (NASH) are unknown. The aim of this study was to investigate the role of Reg3 lectins in NASH. NASH was induced by a Western-style fast-food diet in mice deficient for Reg3g or Reg3b and in transgenic mice overexpressing Reg3g in intestinal epithelial cells (Reg3gTg). Glucose tolerance was assessed after 18 weeks and insulin resistance after 19 weeks of feeding. After 20 weeks, mice were assessed for features of the metabolic syndrome. Obesity was not different in genetically modified mice compared with their respective wild-type littermates. Glucose intolerance, liver injury, hepatic inflammation, steatosis, fibrosis, and bacterial translocation to mesenteric lymph nodes and to the liver were not different in Reg3g-deficient mice compared with wild-type littermates. Plasma endotoxin levels were higher in Reg3g-deficient mice. Reg3b deficiency protected against glucose intolerance, but liver disease, bacterial translocation, and plasma endotoxin levels were similar to wild-type littermates. Absence of either REG3G or REG3B protein in the ileum was not compensated for by up-regulation of the respective other REG3 protein. Transgenic Reg3g mice also developed liver injury, steatosis, and fibrosis similar to their wild-type littermates. Conclusion: In contrast to alcoholic liver disease, loss of intestinal Reg3 lectins is not sufficient to aggravate diet-induced obesity and NASH. This supports a multi-hit pathogenesis in NASH. Only glucose metabolism is affected by Reg3b deficiency. (Hepatology Communications 2018;2:393-406).