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

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.

Kaolinite ingestion facilitates restoration of body energy reserves during refeeding after prolonged fasting.

Clay consumption is a spontaneous behavior currently observed in animals and humans, particularly during undernutrition. Often regarded as intestinal care products, ingested clays also enhance food efficiency, notably by increasing intestinal lipid uptake. Clay complementation could then optimize the reconstitution of energy reserves in animals with low lipid stocks consecutive to intensive fasting. The aim of this study was therefore to observe the effects of voluntarily kaolinite complementation during the refeeding of fasted rats to determine whether body mass, food uptake, lipid and mineral contents as intestinal morphology and protein profile were modified. This study examined two types of refeeding experiments after prolonged fasting. Firstly, rats with ad libitum access to food were compared to rats with ad libitum access to food and kaolinite pellets. Animals were randomly put into the different groups when the third phase of fasting (phase III) reached by each individual was detected. In a second set of experiments, rats starting phase III were refed with free access to food and kaolinite pellets. When animals had regained their body mass prior to fasting, they were euthanized for chemical, morphological, and proteomic analyses. Although kaolinite ingestion did not change the time needed for regaining prefasting body mass, daily food ingestion was seen to decrease by 6.8% compared with normally refed rats, without affecting lipid composition. Along the intestinal lining, enterocytes of complemented animals contained abundant lipid droplets and a structural modification of the brushborder was observed. Moreover, the expression of two apolipoproteins involved in lipid transport and satiety (ApoA-I and ApoA-IV) increased in complemented rats. These results suggest that kaolinite complementation favors intestinal nutrient absorption during refeeding despite reduced food uptake. Within the intestinal lumen, clay particles could increase the passive absorption capacity and/or nutrient availability that induce mucosal morphological changes. Therefore, clay ingestion appears to be beneficial for individuals undergoing extreme nutritional conditions such as refeeding and limited food supplies.

Interactions between ingested kaolinite and the intestinal mucosa in rat: proteomic and cellular evidences.

Although some of the effects of clay ingestion by humans and animals, such as gastrointestinal wellness and the increase in food efficiency are well known, the underlying mechanisms are not yet fully understood. Therefore, the interactions between the intestinal mucosa and kaolinite particles and their effects on mucosal morphology were observed using light microscopy (LM), transmission electron microscopy (TEM), conventional (CSEM) and environmental (ESEM) scanning electron microscopy combined with an EDX micro-analysis system. Kaolinite consumption, given with free access to rats, varied considerably from one animal to the other but was regular through time for each individual. Some kaolinite particles appeared chemically dissociated in the lumen and within the mucus barrier. Aluminium (Al) originating from ingested clay and present in the mucus layer could directly cross the intestinal mucosa. A significant increase in the thickness of the villi with large vacuoles at the base of the mucosal cells and a decrease in the length of enterocyte microvilli characterized complemented animals. The proteomic analyses of the intestinal mucosa of complemented rats also revealed several modifications in the expression level of cytoskeleton proteins. In summary, kaolinite particles ingested as food complement interact with the intestinal mucosa and modify nutrient absorption. However, these data, together with the potential neurotoxicity of Al, need further investigation.

Clay ingestion enhances intestinal triacylglycerol hydrolysis and non-esterified fatty acid absorption.

Consumption by animals and humans of earthy materials such as clay is often related to gut pathologies. Our aim was to determine the impact of kaolinite ingestion on glucose and NEFA transport through the intestinal mucosa. The expression of hexose transporters (Na/glucose co-transporter 1 (SGLT1), GLUT2, GLUT5) and of proteins involved in NEFA absorption (fatty acid transporter/cluster of differentiation 36 (FAT/CD36), fatty acid transport protein 4 (FATP4) and liver fatty acid binding protein (L-FABP)) was measured (1) in rats whose jejunum was perfused with a solution of kaolinite, and (2) in rats who ate spontaneously kaolinite pellets during 7 and 28 d. Also, we determined TAG and glucose absorption in the kaolinite-perfused group, and pancreatic lipase activity, gastric emptying and intestinal transit in rats orally administered with kaolinite. Glucose absorption was not affected by kaolinite perfusion or ingestion. However, kaolinite induced a significant increase in intestinal TAG hydrolysis and NEFA absorption. The cytoplasmic expression of L-FABP and FATP4 also increased due to kaolinite ingestion. NEFA may enter the enterocytes via endocytosis mainly since expression of NEFA transporters in the brush-border membrane was not affected by kaolinite. After uptake, rapid binding of NEFA by L-FABP and FATP4 could act as an intracellular NEFA buffer to prevent NEFA efflux. Increased TAG hydrolysis and NEFA absorption may be due to the adsorption properties of clay and also because kaolinite ingestion caused a slowing down of gastric emptying and intestinal transit.