Histone deacetylase 3 inhibition improves glycaemia and insulin secretion in obese diabetic rats.

Failure of pancreatic ß cells to compensate for insulin resistance is a prerequisite for the development of type 2 diabetes. Sustained elevated circulating levels of free fatty acids and glucose contribute to ß-cell failure. Selective inhibition of histone deacetylase (HDAC)-3 protects pancreatic ß cells against inflammatory and metabolic insults in vitro. In the present study, we tested the ability of a selective HDAC3 inhibitor, BRD3308, to reduce hyperglycaemia and increase insulin secretion in a rat model of type 2 diabetes. At diabetes onset, an ambulatory hyperglycaemic clamp was performed. HDAC3 inhibition improved hyperglycaemia over the study period without affecting weight gain. At the end of the hyperglycaemic clamp, circulating insulin levels were significantly higher in BRD3308-treated rats. Pancreatic insulin staining and contents were also significantly higher. These findings highlight HDAC3 as a key therapeutic target for ß-cell protection in type 2 diabetes.

Small-molecule inhibition of inflammatory ß-cell death.

With the worldwide increase in diabetes prevalence there is a pressing unmet need for novel antidiabetic therapies. Insufficient insulin production due to impaired ß-cell function and apoptotic reduction of ß-cell mass is a common denominator in the pathogenesis of diabetes. Current treatments are directed at improving insulin sensitivity, and stimulating insulin secretion or replacing the hormone, but do not target progressive apoptotic ß-cell loss. Here we review the current development of small-molecule inhibitors designed to rescue ß-cells from apoptosis. Several distinct classes of small molecules have been identified that protect ß-cells from inflammatory, oxidative and/or metabolically induced apoptosis. Although none of these have yet reached the clinic, ß-cell protective small molecules alone or in combination with current therapies provide exciting opportunities for the development of novel treatments for diabetes.

Histone deacetylases 1 and 3 but not 2 mediate cytokine-induced beta cell apoptosis in INS-1 cells and dispersed primary islets from rats and are differentially regulated in the islets of type 1 diabetic children.

AIMS/HYPOTHESIS: Histone deacetylases (HDACs) are promising pharmacological targets in cancer and autoimmune diseases. All 11 classical HDACs (HDAC1-11) are found in the pancreatic beta cell, and HDAC inhibitors (HDACi) protect beta cells from inflammatory insults. We investigated which HDACs mediate inflammatory beta cell damage and how the islet content of these HDACs is regulated in recent-onset type 1 diabetes. METHODS: The rat beta cell line INS-1 and dispersed primary islets from rats, either wild type or HDAC1-3 deficient, were exposed to cytokines and HDACi. Molecular mechanisms were investigated using real-time PCR, chromatin immunoprecipitation and ELISA assays. Pancreases from healthy children and children with type 1 diabetes were assessed using immunohistochemistry and immunofluorescence. RESULTS: Screening of 19 compounds with different HDAC selectivity revealed that inhibitors of HDAC1, -2 and -3 rescued INS-1 cells from inflammatory damage. Small hairpin RNAs against HDAC1 and -3, but not HDAC2, reduced pro-inflammatory cytokine-induced beta cell apoptosis in INS-1 and primary rat islets. The protective properties of specific HDAC knock-down correlated with attenuated cytokine-induced iNos expression but not with altered expression of the pro-inflammatory mediators Il1α, Il1ß, Tnfα or Cxcl2. HDAC3 knock-down reduced nuclear factor κB binding to the iNos promoter and HDAC1 knock-down restored insulin secretion. In pancreatic sections from children with type 1 diabetes of recent onset, HDAC1 was upregulated in beta cells whereas HDAC2 and -3 were downregulated in comparison with five paediatric controls. CONCLUSIONS/INTERPRETATION: These data demonstrate non-redundant functions of islet class I HDACs and suggest that targeting HDAC1 and HDAC3 would provide optimal protection of beta cell mass and function in clinical islet transplantation and recent-onset type 1 diabetic patients.

Lysine deacetylases are produced in pancreatic beta cells and are differentially regulated by proinflammatory cytokines.

AIMS/HYPOTHESIS: Cytokine-induced beta cell toxicity is abrogated by non-selective inhibitors of lysine deacetylases (KDACs). The KDAC family consists of 11 members, namely histone deacetylases HDAC1 to HDAC11, but it is not known which KDAC members play a role in cytokine-mediated beta cell death. The aim of the present study was to examine the KDAC gene expression profile of the beta cell and to investigate whether KDAC expression is regulated by cytokines. In addition, the protective effect of the non-selective KDAC inhibitor ITF2357 and interdependent regulation of four selected KDACs were investigated. METHODS: The beta cell line INS-1 and intact rat and human islets were exposed to cytokines with or without ITF2357. Expression of mRNA was assessed by real-time PCR and selected targets validated at the protein level by immunoblotting. Effects on cytokine-induced toxicity were investigated by in vitro assays. RESULTS: Hdac1 to Hdac11 were expressed and differentially regulated by cytokines in INS-1 cells and rat islets. HDAC1, -2, -6 and -11 were found to be expressed and regulated by cytokines in human islets. ITF2357 protected against cytokine-induced beta cell apoptosis and counteracted cytokine-induced attenuation of basal insulin secretion. In addition, cytokine-induced regulation of Hdac2 and Hdac6, but not Hdac1 and Hdac11, was reduced by KDAC inhibition. CONCLUSIONS/INTERPRETATION: All classical KDAC genes are expressed by beta cells and differentially regulated by cytokines. Based on the relative expression levels and degree of regulation by cytokines, we propose that HDAC1, -2, -6 and -11 are of particular importance for beta cell function. These observations may help in the design of specific KDAC inhibitors to prevent beta cell destruction in situ and in islet grafts.

The flow structure in the separation zone of a DAF pilot plant and the relation with bubble concentration.

Fluid dynamics is believed to be of crucial importance for the removal mechanism in Dissolved Air Flotation. The paper is a presentation of experimental studies on velocity and air-content profiles in a DAF pilot plant. The correlation between air content and flow patterns is discussed. Two flow structures are detected. A stratified flow structure is defined by a horizontal transport of the water in a upper, less-dense layer, and a lower, downwards-vertical transport in the lower, dense layer. Between the layers a return flow is found. The short-circuiting flow is defined as an immediate downward deviation towards the outlet arrangement at the bottom of the tank, probably causing decreasing effluent quality. Density gradients, caused by differences in air content in the tank, are believed to generate a stratification of the water body, thus causing the water to be transported in layers. Measurements of air-content profiles correlate to the measured flow structures, also indicating a separation of the water body in two layers with a distinct boundary.