Pancreatic amyloid formation by islet amyloid polypeptide (IAPP) is a hallmark pathological feature of type 2 diabetes. IAPP is stored in the secretory granules of pancreatic beta-cells and co-secreted with insulin to maintain glucose homeostasis. IAPP is innocuous under homeostatic conditions but imbalances in production or processing of IAPP may result in homodimer formation leading to the rapid production of cytotoxic oligomers and amyloid fibrils. The consequence is beta-cell dysfunction and the accumulation of proteinaceous plaques in and around pancreatic islets. Beta-site APP-cleaving enzyme 2, BACE2, is an aspartyl protease commonly associated with BACE1, a related homolog responsible for amyloid processing in the brain and strongly implicated in Alzheimer’s disease. Herein, we identify two distinct sites of the mature human IAPP sequence that are susceptible to BACE2-mediated proteolytic activity. The result of proteolysis is modulation of human IAPP fibrillation and human IAPP protein degradation. These results suggest a potential therapeutic role for BACE2 in type 2 diabetes-associated hyperamylinaemia.

Elucidating the role of secreted frizzled-related protein 5 (SFRP5) in metabolism and obesity has been complicated by contradictory findings when knockout mice were used to determine metabolic phenotypes. By overexpressing SFRP5 in obese, prediabetic mice we consistently observed elevated hyperglycemia and glucose intolerance, supporting SFRP5 as a negative regulator of glucose metabolism. Accordingly, Sfrp5 mRNA expression analysis of both epididymal and subcutaneous adipose depots of mice indicated a correlation with obesity. Thus, we generated a monoclonal antibody (mAb) against SFRP5 to ascertain the effect of SFRP5 inhibition in vivo. Congruent with SFRP5 overexpression worsening blood glucose levels and glucose intolerance, anti-SFRP5 mAb therapy improved these phenotypes in vivo. The results from both the overexpression and mAb inhibition studies suggest a role for SFRP5 in glucose metabolism and pancreatic ␤-cell function and thus establish the use of an anti-SFRP5 mAb as a potential approach to treat type 2 diabetes. secreted frizzled-related protein 5; diabetes; obesity; pancreatic ␤-cell; Wnt GENOME-WIDE ASSOCIATION STUDIES (GWAS) have identified multiple genomic loci associated with susceptibility to type 2 diabetes (T2D). One such locus reported by several groups to be highly associated with T2D risk, transcription factor 7-like 2 (TCF7L2), is located in the noncoding region of a gene in the Wnt-signaling pathway (10,12,35,36,38,39,46). Although expressed in many tissues, the variant in TCF7L2 associates with impaired pancreatic ␤-cell insulin secretion and ␤-cell survival (8,9,17,18,20,21,33,37,40,41,47). The commonality of the TCF7L2 variants among the population and across ethnicities, combined with the reported associated risk, places TCF7L2 as the strongest identified genetic risk factor for T2D (12,44). Findings such as this fuel the incentive to better understand how modulation of the Wnt signaling pathway drives T2D pathogenesis and determine whether a Wnt pathway-associated protein could be a suitable therapeutic target for treating this disease.Secreted frizzled-related proteins (SFRPs) comprise a family of secreted proteins that contain an NH 2 terminus cysteine-rich domain (CRD) homologous to that found in the Wnt-binding seven-transmembrane receptor, Frizzled (24, 31). Via their CRD, SFRPs bind to Wnt proteins, thereby blocking their interactions with Frizzled and inhibiting canonical Wnt signaling (7). Of the family members, Sfrp5 mRNA expression in mice has been shown to be sensitive to metabolic queues and changes with fat mass expansion (16,25,27). The role of SFRP5 in metabolism, however, remains unclear due to contradictory phenotypes observed with different lines of Sfrp5-deficient mice. In the first published study, Sfrp5-deficient mice were reported to exhibit severe glucose intolerance and hepatic steatosis upon consumption of a high-fat/high-sugar diet; both phenotypes were reversed upon adenovirus-mediated SFRP5 overexpression (27). The authors proposed that, in the context ...

These results suggest that the IGF2BP2 gene may play a role in susceptibility to schizophrenia, supporting the hypothesis that the co-occurrence of type 2 diabetes mellitus and schizophrenia may be explained by shared genetic risk variants. However, this finding remains preliminary since this association has yet to be replicated.

The SLC30A8 gene variation does not appear to contribute a genetic basis for the co-occurrence of schizophrenia and T2DM.