LIGHT/TNFSF14 is increased in patients with type 2 diabetes mellitus and promotes islet cell dysfunction and endothelial cell inflammation in vitro

Published version. Source at http://dx.doi.org/10.1007/s00125-016-4036-y Aims/hypothesis: Activation of inflammatory pathways is involved in the pathogenesis of type 2 diabetes mellitus. On the basis of its role in vascular inflammation and in metabolic disorders, we hypothesised that the TNF superfamily (TNFSF) member 14 (LIGHT/TNFSF14) could be involved in the pathogenesis of type 2 diabetes mellitus. Methods: Plasma levels of LIGHT were measured in two cohorts of type 2 diabetes mellitus patients (191 Italian and 40 Norwegian). Human pancreatic islet cells and arterial endothelial cells were used to explore regulation and relevant effects of LIGHT in vitro. Results: Our major findings were: (1) in both diabetic cohorts, plasma levels of LIGHT were significantly raised compared with sex- and age-matched healthy controls (n = 32); (2) enhanced release from activated platelets seems to be an important contributor to the raised LIGHT levels in type 2 diabetes mellitus; (3) in human pancreatic islet cells, inflammatory cytokines increased the release of LIGHT and upregulated mRNA and protein levels of the LIGHT receptors lymphotoxin β receptor (LTβR) and TNF receptor superfamily member 14 (HVEM/TNFRSF14); (4) in these cells, LIGHT attenuated the insulin release in response to high glucose at least partly via pro-apoptotic effects; and (5) in human arterial endothelial cells, glucose boosted inflammatory response to LIGHT, accompanied by an upregulation of mRNA levels of HVEM (also known as TNFRSF14) and LTβR (also known as LTBR). Conclusions/interpretation: Our findings show that patients with type 2 diabetes mellitus are characterised by increased plasma LIGHT levels. Our in vitro findings suggest that LIGHT may contribute to the progression of type 2 diabetes mellitus by attenuating insulin secretion in pancreatic islet cells and by contributing to vascular inflammation

Pankreas øytransplantasjon som behandling for diabetes mellitus

ABSTRACT. Background. Results in pancreatic islet transplantation have improved during the last decade, but long term results remain disappointing. This is partly due to loss of islets in pre-transplant culture and immediate post-transplant period. Aim. Exendin is currently being used as drug therapy of type 2 diabetes mellitus. We wanted to investigate the in vitro effect of exendin on insulin secretion, pro- and anti-inflammatory cytokines in isolated pancreatic islets from rats. Materials and methods. Freshly isolated rat islets were obtained. One half of the cells was stimulated with exendin-4 (10nmol), the other served as controls. The incubation lasted for 48-72 hours. Subsequently the islets were stimulated with two different concentrations of glucose, respectively 1,67 mM and 20 mM, followed by measure of insulin secretion with EIA. Real time quantitative reverse transcription-polymerase chain reaction was used to assess the gene expression of IL-6, IL-10 and TNF-á. Cell free supernatant was harvested to quantify the protein secretion of IL-10 and TNF-á. Results. The insulin secretion was significantly better for the islets stimulated with exendin-4 for 48-72 hours as compared to controls (p=0,01, n=5). The gene expression of both pro- and anti-inflammatory cytokines were higher in the control group compared with the exendin group, but the protein secretion of IL-10 and TNF-á was higher in the exendin group. Conclusion. These findings suggest that exendin improve the insulin secretion, and may also reduce the inflammation in the islets. Islet culture with exendin before transplantation may therefore improve the outcome, but further investigations are needed

The effects of exendin-4 treatment on graft failure: An animal study using a novel revascularized minimal human islet transplant model

Islet transplantation has become a viable clinical treatment, but is still compromised by long-term graft failure. Exendin-4, a glucagon-like peptide 1 receptor agonist, has in clinical studies been shown to improve insulin secretion in islet transplanted patients. However, little is known about the effect of exendin-4 on other metabolic parameters. We therefore aimed to determine what influence exendin-4 would have on revascularized minimal human islet grafts in a state of graft failure in terms of glucose metabolism, body weight, lipid levels and graft survival. Introducing the bilateral, subcapsular islet transplantation model, we first transplanted diabetic mice with a murine graft under the left kidney capsule sufficient to restore normoglycemia. After a convalescent period, we performed a second transplantation under the right kidney capsule with a minimal human islet graft and allowed for a second recovery. We then performed a left-sided nephrectomy, and immediately started treatment with exendin-4 with a low (20μg/kg/day) or high (200μg/kg/day) dose, or saline subcutaneously twice daily for 15 days. Blood was sampled, blood glucose and body weight monitored. The transplanted human islet grafts were collected at study end point and analyzed. We found that exendin-4 exerts its effect on failing human islet grafts in a bell-shaped dose-response curve. Both doses of exendin-4 equally and significantly reduced blood glucose. Glucagon-like peptide 1 (GLP-1), C-peptide and pro-insulin were conversely increased. In the course of the treatment, body weight and cholesterol levels were not affected. However, immunohistochemistry revealed an increase in beta cell nuclei count and reduced TUNEL staining only in the group treated with a low dose of exendin-4 compared to the high dose and control. Collectively, these results suggest that exendin-4 has a potential rescue effect on failing, revascularized human islets in terms of lowering blood glucose, maintaining beta cell numbers, and improving metabolic parameters during hyperglycemic stress

Treatment with Tacrolimus and Sirolimus Reveals No Additional Adverse Effects on Human Islets In Vitro Compared to Each Drug Alone but They Are Reduced by Adding Glucocorticoids

Tacrolimus and sirolimus are important immunosuppressive drugs used in human islet transplantation; however, they are linked to detrimental effects on islets and reduction of long-term graft function. Few studies investigate the direct effects of these drugs combined in parallel with single drug exposure. Human islets were treated with or without tacrolimus (30 mu g/L), sirolimus (30 mu g/L), or a combination thereof for 24 hrs. Islet function as well as apoptosis was assessed by glucose-stimulated insulin secretion (GSIS) and Cell Death ELISA. Proinflammatory cytokines were analysed by qRT-PCR and Bio-Plex. Islets exposed to the combination of sirolimus and tacrolimus were treated with or without methylprednisolone (1000 mu g/L) and the expression of the proinflammatory cytokines was investigated. We found the following: (i) No additive reduction in function and viability in islets existed when tacrolimus and sirolimus were combined compared to the single drug. (ii) Increased expression of proinflammatory cytokines mRNA and protein levels in islets took place. (iii) Methylprednisolone significantly decreased the proinflammatory response in islets induced by the drug combination. Although human islets are prone to direct toxic effect of tacrolimus and sirolimus, we found no additive effects of the drug combination. Short-term exposure of glucocorticoids could effectively reduce the proinflammatory response in human islets induced by the combination of tacrolimus and sirolimus

NLRP3 inflammasome mediates oxidative stress-induced pancreatic islet dysfunction

Inflammasomes are multiprotein inflammatory platforms that induce caspase-1 activation and subsequently interleukin (IL)-1beta and IL-18 processing. The NLRP3 inflammasome is activated by different forms of oxidative stress, and, based on the central role of IL-1beta in the destruction of pancreatic islets, it could be related to the development of diabetes. We therefore investigated responses in wild-type C57Bl/6 (WT) mice, NLRP3(-/-) mice, and mice deficient in apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) after exposing islets to short-term hypoxia or alloxan-induced islet damage. NLRP3-deficient islets compared with WT islets had preserved function ex vivo and were protected against hypoxia-induced cell death. Furthermore, NLRP3 and ASC-deficient mice were protected against oxidative stress-induced diabetes caused by repetitive low-dose alloxan administration, and this was associated with reduced beta-cell death and reduced macrophage infiltration. This suggests that the beneficial effect of NLRP3 inflammasome deficiency on oxidative stress-mediated beta-cell damage could involve reduced macrophage infiltration and activation. To support the role of macrophage activation in alloxan-induced diabetes, we injected WT mice with liposomal clodronate, which causes macrophage depletion before induction of a diabetic phenotype by alloxan treatment, resulting in improved glucose homeostasis in WT mice. We show here that the NLRP3 inflammasome acts as a mediator of hypoxia and oxidative stress in insulin-producing cells, suggesting that inhibition of the NLRP3 inflammasome could have beneficial effects on beta-cell preservation

Thioredoxin interacting protein is a potential regulator of glucose and energy homeostasis in endogenous Cushing's syndrome.

Recent studies have described bone as an endocrine organ regulating glucose metabolism, with insulin signaling regulating osteocalcin secretion and osteocalcin regulating β cell function. We have previously demonstrated increased bone expression of TXNIP in patients with endogenous Cushing's syndrome (CS), and we hypothesized that TXNIP could contribute to the dysregulated glucose metabolism in CS. We studied 33 CS patients and 29 matched controls, with bone biopsies from nine patients, before and after surgical treatment. In vitro, the effect of silencing TXNIP (siTXNIP) in osteoblasts, including its effect on human islet cells, was examined. Our major findings were: (i) The high mRNA levels of TXNIP in bone from CS patients were significantly associated with high levels of glucose and insulin, increased insulin resistance, and decreased insulin sensitivity in these patients. (ii) Silencing TXNIP in osteoblasts enhanced their OC response to insulin and glucose and down-regulated interleukin (IL)-8 levels in these cells. (iii) Conditional media from siTXNIP-treated osteoblasts promoted insulin content and anti-inflammatory responses in human islet cells. We recently demonstrated that the thioredoxin/TXNIP axis may mediate some detrimental effects of glucocorticoid excess on bone tissue in CS. Here we show that alterations in this axis also may affect glucose metabolism in these patients

TXNIP expression in nine paired bone biopsies pre and 3 months post surgery.

<p>(A) microarray analysis. B) mRNA expression normalized to β-actin and expressed as relative mRNA levels. (C) protein levels in three paired bone biopsies pre and 3 months post surgery and Ponceau S total protein staining by western blot and (D) protein levels in all the nine paired bone biopsies related to Ponceau S total protein staining.</p