High‐fat Diet Causes Loss of Nitric Oxide Motor Neurons and Impairs Inhibitory Neuromuscular Communication in the Mouse Distal Colon

Abstract

High‐fat (HF) diet increases the risks of gastrointestinal (GI) motility complications, however, the mechanisms that underlie these complications are still not entirely understood. We tested the hypothesis that HF diet causes oxidative stress, loss of nitric oxide (NO) motor neurons in the myenteric plexus, disrupted inhibitory neuromuscular communication and impaired GI motility.MethodsDistal colon segments from mice fed a control (10 Kcal%) or HF diet (60 Kcal%) were used in vitro. Alexa fluor 546 and 680 conjugated maleimides were used to assess the oxidized/reduced glutathione ratio in myenteric NO neurons. NO neuronal density was assessed using nNOS immunohistochemistry. Basal NO availability was measured using NO induced fluorescence of DAF‐FM diacetate. Electrical field stimulation was applied across varying voltages (60‐120V) and train (200‐1000ms) durations to evoke inhibitory junction potentials (IJPs) in colonic circular smooth muscle cells. Amplitude and area of IJP were examined to assess fast and slow IJPs respectively.ResultsWe observed an increase (17%, p<0.01) in oxidized/reduced glutathione fluorescence ratio in nNOS neurons of HF mice. HF mice had lower (28%, p<0.01) nNOS neurons per ganglionic area than controls. Fluorescence intensity of DAF‐FM diacetate was also lower (20%, p<0.01) in HF mice. HF mice showed a significant loss (52%, p<0.05) in IJP area, when stimulated at higher train duration (800‐1000ms).ConclusionWe conclude that HF diet causes oxidative stress, leading to loss of inhibitory NO neurons, lower NO availability, and disrupted neuromuscular transmission in the mouse distal colon. Supported by NIH (DK094932).