Supernatants of intestinal luminal contents from mice fed high‐fat diet impair intestinal motility by injuring enteric neurons and smooth muscle cells

Abstract

Background: Damage to enteric neurons and impaired gastrointestinal muscle contractions cause motility disorders in 70% of diabetic patients. It is thought that enteric neuropathy and dysmotility occur before overt diabetes, but triggers of these abnormalities are not fully known. We tested the hypothesis that intestinal contents of mice with and without high-fat diet-(HFD-) induced diabetic conditions contain molecules that impair gastrointestinal movements by damaging neurons and disrupting muscle contractions. Methods: Small and large intestinal segments were collected from healthy, standard chow diet (SCD) fed mice. Filtrates of ileocecal contents (ileocecal supernatants; ICS) from HFD or SCD mice were perfused through them. Cultured intact intestinal muscularis externa preparations were used to determine whether ICS and their fractions obtained by solid-phase extraction (SPE) and SPE subfractions collected by high-performance liquid chromatography (HPLC) disrupt muscle contractions by injuring neurons and smooth muscle cells. Key Results: ICS from HFD mice reduced intestinal motility, but those from SCD mice had no effect. ICS, aqueous SPE fractions and two out of twenty HPLC subfractions of aqueous SPE fractions from HFD mice blocked muscle contractions, caused a loss of nitrergic myenteric neurons through inflammation, and reduced smooth muscle excitability. Lipopolysaccharide and palmitate caused a loss of nitrergic myenteric neurons but did not affect muscle contractions. Conclusions & Inferences: Unknown molecules in intestinal contents of HFD mice trigger enteric neuropathy and dysmotility. Further studies are required to identify the toxic molecules and their mechanisms of action.

The role of the gastrointestinal barrier in obesity‐associated systemic inflammation

“…Interestingly, neuronal pyroptosis was found to preferentially increase in nNOS+ neurons in subjects with obesity compared with “normal” weight subjects, while no difference in the proportion of cholinergic neurons expressing CC1 was found, suggesting that nitrergic neurons may be more vulnerable to obesity‐associated enteric neuronal pyroptosis than cholinergic neurons 117 . These findings have been mirrored in animal studies, with changes in the ENS observed in mice fed either a western or high fat diet 102,103,118–121 …”

“…Both the gram‐positive cell wall component LPS and gram‐negative lipoteichoic acid have been shown to directly stimulate neuroinflammation and oxidative stress within myenteric nitrergic neurons, resulting in nitrergic neuron loss 102 . Similarly, exposure to ileocecal supernatants distilled from high fat diet fed mice has been found to instigate nitrergic neuronal loss through inflammation and smooth muscle excitability 103 …”

“…102 Similarly, exposure to ileocecal supernatants distilled from high fat diet fed mice has been found to instigate nitrergic neuronal loss through inflammation and smooth muscle excitability. 103…”

“…117 These findings have been mirrored in animal studies, with changes in the ENS observed in mice fed either a western or high fat diet. 102,103,[118][119][120][121] In a study examining the effects of 6-month high fat diet exposure, C57bl/6 mice had significantly fewer myenteric neuronal cell bodies in the ileum and colon compared with normal diet controls, while the numbers of both ileal and colonic submucous nerve cell bodies were unchanged. These changes were found alongside a significantly increased body weight and body fat percentage in the high fat diet fed cohort.…”