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Poster communications

Effects of kaolinite ingestion on regulation by leptin of intrinsic nitrergic neurons activity in jejunum and proximal colon in rats

Abstract : Objective Geophagy is the deliberate ingestion of soil by humans and animals and in particular of clay minerals such as kaolinite. In humans, geophagy has been observed in many parts of the world and is especially widespread in sub-Saharan Africa. Kaolinite ingestion has been previously shown to modulate gastric emptying and intestinal transit, and to interact with the intestinal mucosa in rats (Habold et al., Voinot et al.). As the inhibitory neurotransmitter nitric oxide is largely implied in gastrointestinal functions, the first aim of this work was to evaluate the impact of an imposed ingestion of kaolinite (5%) on enteric nitrergic innervation. Furthermore, kaolinite ingestion induced hyperphagia correlated to increase of plasmatic level of leptin. As leptin was shown to affect neurotransmission in the enteric nervous system, the second aim of this study was to determine whether the responses of enteric neurons in the presence of leptin were altered after kaolinite ingestion. Methods Male Wistar rats were fed with5% kaolinite in standard food pellets during 14 and 28 days. Ex vivo organ bath technique associated with pharmacological tools was conducted to evaluate smooth muscle contractility. Results The decrease in the nerve stimulation-induced relaxation due to L-NNA, a nitric oxide synthase inhibitor, was significantly reduced in the jejunum whereas the contraction was enhanced in the proximal colon at 14 days of kaolinite ingestion. Leptin inhibitory effects on relaxation in control animals were abolished in rats at 14 days of kaolinite ingestion. In the presence of L-NNA, leptin showed no effect on the relaxation in rats at 14 days of kaolinite ingestion compared to controls. Conclusion These data give evidence that kaolinite displays a reduction in the activation of intrinsic nitrergic neurons. This effect may explain the lack of leptin action in kaolinite rats. We hypothesized that kaolinite within the intestinal lumen stimulates intrinsic primary afferent neurons that project on these intrinsic nitrergic neurons. Changes in enteric nerves activities after kaolinite ingestion may also be due to non-beneficial effects such as iron deficiency and/or aluminum toxicity which are known to affect nitrergic neurotransmission.
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Fabielle Angel, Florian Voinot, Caroline Fischer, Camille Schmidt, Charles-Henri Malbert. Effects of kaolinite ingestion on regulation by leptin of intrinsic nitrergic neurons activity in jejunum and proximal colon in rats. Joint International Neurogastroenterology and Motility Meeting, Sep 2012, Bologne, Italy. Wiley-Blackwell, Neurogastroenterology and Motility, 24, pp.133, 2012, NGM 2012. ⟨hal-02749423⟩



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