Effect of visfatin on KATP channel upregulation in colonic smooth muscle cells in diabetic colon dysmotility.

Yurong Tang,Lin Lin,Lin Zhang,Yan Wang,Xiaoxue Shen,Ting Yu

doi:10.18632/aging.203871

Abstract

The mechanisms of diabetes-related gastrointestinal dysmotility remains unclear. This study aimed to investigate the effect and mechanisms of proinflammatory adipokine visfatin (VF) in the contractile dysfunction of diabetic rat colonic smooth muscle. Twenty Sprague-Dawley rats were randomly divided into control and type 2 diabetes mellitus groups. VF levels in the serum and colonic muscle tissues were tested, the time of the bead ejection and contractility of colonic smooth muscle strips were measured, and the expression of ATP-sensitive potassium (KATP) channels in the colonic muscle tissues was analyzed. In vitro, we tested VF’s effects on intracellular reactive oxygen species (ROS) levels, NF-κB’s nuclear transcription, KATP channel expression, intracellular Ca2+ concentrations, and myosin light chain (MLC) phosphorylation in colonic smooth muscle cells (CSMCs). The effects of NAC (ROS inhibitor) and BAY 11-7082 (NF-κB inhibitor) on KATP expression were also tested. Diabetic rats showed elevated VF levels in serum and colonic muscle tissues, a delayed distal colon ejection response time, weakened contractility of colonic smooth muscle strips, and increased KATP channel expression in colonic muscle tissues. VF significantly inhibited the contractility of colonic smooth muscle strips from normal rats. In cultured CSMCs, VF caused ROS overload, increased NF-κB nuclear transcription activity and increased expression of Kir6.1, eventually reducing intracellular Ca2+ levels and MLC phosphorylation. NAC and BAY 11-7082 inhibited the VF–induced Kir6.1 upregulation. In conclusion, VF may cause contractile dysfunction of CSMCs by upregulating the expression of the Kir6.1 subunit of KATP channels via the ROS/NF-κB pathway and interfering with Ca2+ signaling.

Highlights

Diabetes mellitus (DM) and its common complications, such as gastrointestinal (GI) symptoms, have become major worldwide public health problems, with type 2 diabetes (T2DM) making up about 90% of cases [1]
The contractile status of colonic smooth muscle cells (CSMCs) is primarily determined by the level of intracellular free Ca2+ ([Ca2+]i), which influxes through voltage-operated Ca2+ channels (VOCCs). [Ca2+]i can be affected by many factors, such as K+ channel activation leading to hyperpolarization and smooth muscle relaxation by inactivating the VOCCs and inhibiting Ca2+ entry
We found that in T2DM rats, the distal colon ejection response time was delayed significantly, the contractility of colonic smooth muscle strips was reactive oxygen species (ROS) in CSMCs treated with vehicle (PBS solution) or VF (200 ng/mL), with or without NAC (1 mmol/L) for 24 h

Summary

Introduction

Diabetes mellitus (DM) and its common complications, such as gastrointestinal (GI) symptoms, have become major worldwide public health problems, with type 2 diabetes (T2DM) making up about 90% of cases [1]. Colonic smooth muscle contraction disorders are one of the causes of constipation in patients with T2DM, other factors including autonomic neuropathy, reduced number of interstitial cells of Cajal networks, loss of enteric neurons, and neuroendocrine www.aging‐us.com imbalances are involved [3]. [Ca2+]i can be affected by many factors, such as K+ channel activation leading to hyperpolarization and smooth muscle relaxation by inactivating the VOCCs and inhibiting Ca2+ entry. The increased expression and activity of KATP channels contribute to decreased smooth muscle motility [4]. Previous studies suggested that KATP channels (Kir6.1/SUR2B) expression in the vascular smooth muscle of T2DM rats was increased [5], we speculated that colonic smooth muscle contraction disorders might involve changes in KATP expression in T2DM rats

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