Basic Study
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Nov 7, 2017; 23(41): 7359-7368
Published online Nov 7, 2017. doi: 10.3748/wjg.v23.i41.7359
Region-dependent effects of diabetes and insulin-replacement on neuronal nitric oxide synthase- and heme oxygenase-immunoreactive submucous neurons
Nikolett Bódi, Zita Szalai, Lalitha Chandrakumar, Mária Bagyánszki
Nikolett Bódi, Zita Szalai, Lalitha Chandrakumar, Mária Bagyánszki, Department of Physiology, Anatomy and Neuroscience, Faculty of Science and Informatics, University of Szeged, H-6726 Szeged, Hungary
Author contributions: Bódi N designed the research and performed the majority of experiments; Szalai Z and Chandrakumar L participated in experiments; Bódi N and Bagyánszki M coordinated the research and analyzed the data; Bódi N, Szalai Z and Bagyánszki M wrote the paper.
Supported by the Hungarian Scientific Research Fund, OTKA grant, No.PD 108309 (Nikolett Bódi); by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences (Mária Bagyánszki); and by the Stipendium Hungaricum Scholarship, No. 2015-SH-500041, Tempus Public Foundation (Lalitha Chandrakumar).
Institutional review board statement: The study was reviewed and approved by the University of Szeged Faculty of Science and Informatics Dept. of Physiology, Anatomy and Neuroscience.
Conflict-of-interest statement: No conflict of interest.
Data sharing statement: Technical appendix, statistical code, and dataset available from the corresponding author, Mária Bagyánszki at bmarcsi@bio.u-szeged.hu
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Mária Bagyánszki, PhD, Associate Professor, Department of Physiology, Anatomy and Neuroscience, Faculty of Science and Informatics, University of Szeged, Közép fasor 52, H-6726 Szeged, Hungary. bmarcsi@bio.u-szeged.hu
Telephone: +36-62-544123 Fax: +36-62-544291
Received: June 15, 2017
Peer-review started: June 16, 2017
First decision: July 13, 2017
Revised: July 26, 2017
Accepted: August 25, 2017
Article in press: August 25, 2017
Published online: November 7, 2017
Abstract
AIM

To investigate the intestinal segment-specific effects of diabetes and insulin replacement on the density of different subpopulations of submucous neurons.

METHODS

Ten weeks after the onset of type 1 diabetes samples were taken from the duodenum, ileum and colon of streptozotocin-induce diabetic, insulin-treated diabetic and sex- and age-matched control rats. Whole-mount preparations of submucous plexus were prepared from the different gut segments for quantitative fluorescent immunohistochemistry. The following double-immunostainings were performed: neuronal nitric oxide synthase (nNOS) and HuC/D, heme oxygenase (HO) 1 and peripherin, as well as HO2 and peripherin. The density of nNOS-, HO1- and HO2-immunoreactive (IR) neurons was determined as a percentage of the total number of submucous neurons.

RESULTS

The total number of submucous neurons and the proportion of nNOS-, HO1- and HO2-IR subpopulations were not affected in the duodenal ganglia of control, diabetic and insulin-treated rats. While the total neuronal number did not change in either the ileum or the colon, the density of nitrergic neurons exhibited a 2- and 3-fold increase in the diabetic ileum and colon, respectively, which was further enhanced after insulin replacement. The presence of HO1- and HO2-IR submucous neurons was robust in the colon of controls (38.4%-50.8%), whereas it was significantly lower in the small intestinal segments (0.0%-4.2%, P < 0.0001). Under pathophysiological conditions the only alteration detected was an increase in the ileum and a decrease in the colon of the proportion of HO-IR neurons in insulin-treated diabetic animals.

CONCLUSION

Diabetes and immediate insulin replacement induce the most pronounced region-specific alterations of nNOS-, HO1- and HO2-IR submucous neuronal density in the distal parts of the gut.

Keywords: Nitrergic neurons, Heme oxygenase 1, Heme oxygenase 2, Submucous neurons, Gut region-specificity, Diabetes, Insulin

Core tip: Our present findings demonstrate for the first time the segment–specific alterations of the proportion of nitrergic, heme oxygenase (HO)1-immunoreactive (IR) and HO2-IR neurons in the submucous plexus of control, diabetic and insulin-treated diabetic rats. Our results suggest that duodenal nitrergic neurons are not affected, but ileal and colonic ones are induced to change their neurochemical character in diabetes and insulin replacement. The colonic ganglia are abundant in HO-IR neurons in both controls and diabetics, whereas insulin treatment decreases their proportion. In contrast to the colon, the low amount of HO-IR ileal neurons was increased by insulin-treatment.