Islet Endothelial Activation and Oxidative Stress Gene Expression Is Reduced by IL-1Ra Treatment in the Type 2 Diabetic GK Rat

Abstract

BackgroundInflammation followed by fibrosis is a component of islet dysfunction in both rodent and human type 2 diabetes. Because islet inflammation may originate from endothelial cells, we assessed the expression of selected genes involved in endothelial cell activation in islets from a spontaneous model of type 2 diabetes, the Goto-Kakizaki (GK) rat. We also examined islet endotheliuml/oxidative stress (OS)/inflammation-related gene expression, islet vascularization and fibrosis after treatment with the interleukin-1 (IL-1) receptor antagonist (IL-1Ra).Methodology/Principal FindingsGene expression was analyzed by quantitative RT-PCR on islets isolated from 10-week-old diabetic GK and control Wistar rats. Furthermore, GK rats were treated s.c twice daily with IL-1Ra (Kineret, Amgen, 100 mg/kg/day) or saline, from 4 weeks of age onwards (onset of diabetes). Four weeks later, islet gene analysis and pancreas immunochemistry were performed. Thirty-two genes were selected encoding molecules involved in endothelial cell activation, particularly fibrinolysis, vascular tone, OS, angiogenesis and also inflammation. All genes except those encoding angiotensinogen and epoxide hydrolase (that were decreased), and 12-lipoxygenase and vascular endothelial growth factor (that showed no change), were significantly up-regulated in GK islets. After IL-1Ra treatment of GK rats in vivo, most selected genes implied in endothelium/OS/immune cells/fibrosis were significantly down-regulated. IL-1Ra also improved islet vascularization, reduced fibrosis and ameliorated glycemia.Conclusions/SignificanceGK rat islets have increased mRNA expression of markers of early islet endothelial cell activation, possibly triggered by several metabolic factors, and also some defense mechanisms. The beneficial effect of IL-1Ra on most islet endothelial/OS/immune cells/fibrosis parameters analyzed highlights a major endothelial-related role for IL-1 in GK islet alterations. Thus, metabolically-altered islet endothelium might affect the β-cell microenvironment and contribute to progressive type 2 diabetic β-cell dysfunction in GK rats. Counteracting islet endothelial cell inflammation might be one way to ameliorate/prevent β-cell dysfunction in type 2 diabetes.

Isolation and characterization of islet stellate cells in rat

“…Thus, previous studies using classical PSCs have demonstrated that hyperglycemia, 16,31 activation of the RAS, 32 oxidative stress, 17,30 platelet-derived growth factors, 33 and inflammatory cytokines 34 all enhance PSC activation and proliferation. The environment of the diabetic islet is characterized by the presence of the hyperglycemia [35][36][37] and oxidative stress, [38][39][40] as well as macrophage infiltration and increased expression of inflammatory molecules such as IL-1, IL-6, TNF-α, MCP-1, and MIP-1α.…”

Hypercholesterolaemia, signs of islet microangiopathy and altered angiogenesis precede onset of type 2 diabetes in the Goto–Kakizaki (GK) rat

“…GK rats were bred in our own colony at the University Paris-Diderot, together with Wistar control rats from the GK strain derived after backcrossing of animals selected at the upper limit of normal distribution for glucose tolerance [19]. Characteristics of GK rats have been previously described [1,[4][5][6]10,11,[18][19][20][21]. At the indicated age, rats were weighed, bled at time of decapitation and blood, liver and pancreas collected for analysis.…”

“…Serum leptin was measured using Luminex technology (Millipore, Zug, Switzerland) [5]. Plasma paroxonase-1 (PON-1) activity and lecithin: cholesterol acyltransferase (LCAT) activity were determined, as previously described [6,22].…”

“…As a 'pre-microangiopathy-like state' appears to already characterise islets of normoglycaemic/hypercholesterolaemic GK neonates, we measured the neonatal islet expression of other endothelial activation-related genes which were mostly overexpressed in islets of diabetic GK adults [6]. showed islet upregulation of almost all endothelial activation-related genes investigated, as well as the expected panel of inflammatory cytokine/chemokine genes (ESM Fig.…”

“…We suggested that endothelial activation might underlie inflammation in type 2 diabetic islets, as it does in the eye (retinopathy), kidney (glomerulopathy) and nerves (neuropathy). To test this hypothesis, we treated GK rats with the soluble IL-1 receptor antagonist (IL-1Ra): 1 month of IL-1Ra treatment from onset of diabetes onwards reduced markers of islet endothelial cell activation/dysfunction, inflammation and fibrosis [5,6]. In vivo, IL-1Ra normalised islet capillaries with decreased evidence of microangiopathy and reduced hyperglycaemia in GK rats as observed in type 2 diabetic patients [7].…”