High-fat diet-induced obesity alters nitric oxide-mediated neuromuscular transmission and smooth muscle excitability in the mouse distal colon.
We tested the hypothesis that colonic enteric neurotransmission and smooth muscle cell (SMC) function are altered in mice fed a high-fat diet (HFD). We used wild-type (WT) mice and mice lacking the β1-subunit of the BK channel (BKβ1 (-/-)). WT mice fed a HFD had increased myenteric plexus oxidative stress, a 28% decrease in nitrergic neurons, and a 20% decrease in basal nitric oxide (NO) levels. Circular muscle inhibitory junction potentials (IJPs) were reduced in HFD WT mice. The NO synthase inhibitor nitro-l-arginine (NLA) was less effective at inhibiting relaxations in HFD compared with control diet (CD) WT mice (11 vs. 37%, P < 0.05). SMCs from HFD WT mice had depolarized membrane potentials (-47 ± 2 mV) and continuous action potential firing compared with CD WT mice (-53 ± 2 mV, P < 0.05), which showed rhythmic firing. SMCs from HFD or CD fed BKβ1 (-/-) mice fired action potentials continuously. NLA depolarized membrane potential and caused continuous firing only in SMCs from CD WT mice. Sodium nitroprusside (NO donor) hyperpolarized membrane potential and changed continuous to rhythmic action potential firing in SMCs from HFD WT and BKβ1 (-/-) mice. Migrating motor complexes were disrupted in colons from BKβ1 (-/-) mice and HFD WT mice. BK channel α-subunit protein and β1-subunit mRNA expression were similar in CD and HFD WT mice. We conclude that HFD-induced obesity disrupts inhibitory neuromuscular transmission, SMC excitability, and colonic motility by promoting oxidative stress, loss of nitrergic neurons, and SMC BK channel dysfunction.
The Neuroscience Program, Michigan State University, East Lansing, Michigan;
Yogesh
Y
Bhattarai
Department of Physiology, Michigan State University, East Lansing, Michigan; and.
David
D
Fried
The Neuroscience Program, Michigan State University, East Lansing, Michigan; Department of Physiology, Michigan State University, East Lansing, Michigan; and.
Brian
0000-0003-1145-3227
B
Gulbransen
Department of Pediatrics and Human Development, Michigan State University, East Lansing, Michigan.
Mark
M
Kadrofske
Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan;
Roxanne
R
Fernandes
The Neuroscience Program, Michigan State University, East Lansing, Michigan; Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan;
Hui
H
Xu
The Neuroscience Program, Michigan State University, East Lansing, Michigan; Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan; galliga1@msu.edu.
James
J
Galligan
D000200:Action Potentials; D000818:Animals; D003106:Colon / Q000294:innervation*; D059305:Diet, High-Fat; D004195:Disease Models, Animal; D005769:Gastrointestinal Motility; D005838:Genotype; D007700:Kinetics; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits / Q000172:deficiency / Q000235:genetics; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009130:Muscle, Smooth / Q000294:innervation*; D009197:Myenteric Plexus / Q000378:metabolism* / Q000503:physiopathology; D016065:Myoelectric Complex, Migrating; D009433:Neural Inhibition; D009469:Neuromuscular Junction / Q000378:metabolism* / Q000503:physiopathology; D026602:Nitrergic Neurons / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D009765:Obesity / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D018384:Oxidative Stress; D010641:Phenotype; D009435:Synaptic Transmission
D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D009569:Nitric Oxide
enteric nervous system; gastrointestinal motility; large conductance calcium-activated K+ channel; obesity