The Interplay between Hyperresistinemia, Elevated ROS, and Hyperglycemia in Diabetic Rats and Their Roles in Diabetes‐Associated Neutrophil Dysfunction

Abstract

Resistin originally was found as an adipocyte‐derived polypeptide leading to insulin resistanis. Emerging evidence suggests that it plays important roles in various inflammatory diseases. The levels of hyperresistinemia has been associated with immunosuppression and serves as biomarker for the severity of the diseases. Neutrophils play a key role in host defenses against invading microorganisms by releasing large quantities of Reactive Oxygen Species (ROS) via respiratory burst, which are essential for killing bacteria. Diabetic patients have an increased risk of infections mainly as a result of impaired neutrophil functions. Our recent study found that reduced Nrf2 (NF‐E2‐related factor 2), a master transcription factor regulating antioxidant defenses, contributes to elevated ROS levels and increased microvessel permeability in diabetic rats. Diabetes‐associated microvessel dysfunction is highly associated with inflammation. However, the inter‐relationship between the plasma resistin levels, elevated ROS, and their effect on neutrophil function under Diabetic conditions remains unclear and even contradictory. This study aims to examine the interplay between the plasma resistin levels, increased oxidant stress caused by downregulation of Nrf2‐dependent antioxidant defenses, and the neutrophils function in Diabetic rats. Plasma resistin concentrations were determined with a sandwich enzyme immunoassay kit from Wide‐type (WT) Rat, Nrf2 Knock out (Nrf2−/−) out rats and streptozotocin (STZ)‐induced Nrf2−/− diabetic rat. Diabetic rat had experienced elevated blood glucose and A1C level at 404 ± 10 mg/dl and 10.20% ± 0.14% for 14–21 days before the experiments. Neutrophils were isolated from normal and diabetic rats and neutrophil released ROS upon formyl‐Met‐Leu‐OH (fMLP) stimulation was quantified by measuring chemiluminescence (CL). The resistin concentration in WT rats was 6.16 ± 0.97 ng/ml. Nrf2−/− rats significantly increases the resistin level to 15.88 ± 0.45 ng/ml. The resistin levels in diabetic Nrf2−/− rats was markedly increased to 31.67 ± 2.62 ng/ml. Meanwhile, we found neutrophil killing power was significantly reduced in diabetic rats. The peak CL of diabetic neutrophils upon fMLP stimulation was reduced from 826 ± 202 RLU (normal neutrophils) to 259 ± 51 RLU. The CL area under curve, a measure of total ROS production, in normal and diabetic neutrophils was 77614 ± 5509 and 43327 ± 3561 RLU, respectively. When the normal neutrophils were incubated with high glucose solution, a reduced fMLP‐stimulated CL response was also observed, but that couldn't match the reduction of the ROS production in Diabetic rats. These results indicate that increased plasma ROS levels may play a role in increased resistin levels. Further, both increased ROS, hyperresistinemia and hyperglycemia may synergistically contribute to neutrophil dysfunction in diabetes.Support or Funding InformationSupported by HL130363 and DK097391This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.