Effects of controlled ingestion of kaolinite (5%) on food intake, gut morphology and in vitro motility in rats

Abstract

Geophagia is found in various animal species and in humans. We have previously shown that spontaneously ingested kaolinite interacts with the intestinal mucosa modifies nutrient absorption and slows down gastric emptying and intestinal transit in rats in vivo. However, the precise mechanisms involved are not elucidated. The aim of this work was to investigate the effects of controlled kaolinite ingestion on food intake, gut morphology and in vitro motility in rats. Male Wistar rats were fed with 5% kaolinite in standard food pellets during 7, 14 and 28 days. Body mass and food consumption were measured daily. Intestinal morphological and proteomic analyses were conducted. The length of mucosal lacteals was evaluated. Plasmatic levels of leptin and adiponectin were determined. Finally, organ bath studies were conducted to evaluate smooth muscle contractility. Food consumption was significantly increased during the first two weeks of kaolinite ingestion without any mass gain compared to controls. Kaolinite induced weak variations in proteins that are involved in various biological processes. Compared to control animals, the length of intestinal lacteals was significantly reduced in kaolinite group whatever the duration of the experiment. Leptin and adiponectin plasmatic levels were significantly increased after 14 days of kaolinite consumption. Changes in spontaneous motility and responses to electrical nerve stimulation of the jejunum and proximal colon were observed at day 14. Altogether, the present data give evidence for a modulation by kaolinite-controlled ingestion on satiety and anorexigenic signals as well as on intestinal and colonic motility.

Controlled ingestion of kaolinite (5%) modulates enteric nitrergic innervation in rats

“…Our data indicate that kaolinite may modulate activities of enteric nerves at 14 days of imposed ingestion. These data emphasized our previous results which indicated that spontaneous mechanical activities were depressed in both jejunum and proximal colon and that the tone increase was enhanced in the presence of acetylcholine in jejunum at 14 days of kaolinite ingestion in rats [19]. Furthermore, we showed that the decrease of the relaxation induced by L-NNA was significantly reduced in the jejunum, whereas the contraction was enhanced in the proximal colon at 14 days of kaolinite ingestion.…”

“…As we have previously shown that kaolinite induces an increase in food intake and in plasmatic levels of leptin at 14 days of ingestion , leptin may be involved in the changes in mechanical activities and enteric nerves activities. Indeed, leptin has been shown to activate guinea pig colonic submucosal and myenteric plexus and to modulate enteric neurotransmission in rat colon and particularly nitrergic neurotransmission (unpublished data).…”

“…Gut motility and events leading to transit disorders such as diarrhea and constipation are largely mediated by the enteric nervous system [21,22]. We previously showed that kaolinite induced changes in spontaneous mechanical activity and mechanical responses to electrical nerve stimulation [19]. Thus, we suggested that kaolinite might induce a mechanical adaptation to changes in viscosity of intraluminal content through excitatory enteric neurons.…”

“…Kaolinite has previously been shown to interact with the GI tract when imposed or spontaneously ingested . In these conditions, kaolinite lead to changes in the expression of mucosal proteins involved in various biological processes, gut morphology as well as in nutrient and water absorption.…”

“…Furthermore, kaolinite has been shown to induce an increase in food intake during the first and second week of ingestion . This hyperphagia may be the cause of the increase in plasmatic levels of leptin.…”