Increased Oral Detection, but Decreased Intestinal Signaling for Fats in Mice Lacking Gut Microbiota

Germ-free (GF) mice lacking intestinal microbiota are significantly leaner than normal (NORM) control mice despite consuming more calories. The contribution of microbiota on the recognition and intake of fats is not known. Thus, we investigated the preference for, and acceptance of, fat emulsions in GF and NORM mice, and associated changes in lingual and intestinal fatty acid receptors, intestinal peptide content, and plasma levels of gut peptides. GF and NORM C57Bl/6J mice were given 48-h two-bottle access to water and increasing concentrations of intralipid emulsions. Gene expression of the lingual fatty acid translocase CD36 and protein expression of intestinal satiety peptides and fatty-acid receptors from isolated intestinal epithelial cells were determined. Differences in intestinal enteroendocrine cells along the length of the GI tract were quantified. Circulating plasma satiety peptides reflecting adiposity and biochemical parameters of fat metabolism were also examined. GF mice had an increased preference and intake of intralipid relative to NORM mice. This was associated with increased lingual CD36 (P<0.05) and decreased intestinal expression of fatty acid receptors GPR40 (P<0.0001), GPR41 (P<0.0001), GPR43 (P<0.05), and GPR120 (P<0.0001) and satiety peptides CCK (P<0.0001), PYY (P<0.001), and GLP-1 (P<0.001). GF mice had fewer enteroendocrine cells in the ileum (P<0.05), and more in the colon (P<0.05), relative to NORM controls. Finally, GF mice had lower levels of circulating leptin and ghrelin (P<0.001), and altered plasma lipid metabolic markers indicative of energy deficits. Increased preference and caloric intake from fats in GF mice are associated with increased oral receptors for fats coupled with broad and marked decreases in expression of intestinal satiety peptides and fatty-acid receptors

Détection oro-sensorielle des lipides alimentaires : Impacts sur le comportement alimentaire et la santé

Colloque du 9 novembre 2010 : Les lipides: enjeux sensoriels et nutritionelsNational audienceFor the first time in its history, much of the world's population no longer has to "run after calories." An abundance of food has obvious consequences: it promotes our specific appetites. Lipids account for about 40% of the calories ingested in Western countries, whereas nutritional recommendations are in the range of 30-35%. This excessive lipid intake, associated with a qualitative imbalance (excess of saturated fatty acids and cholesterol, too high ω6/ω3 ratio) strongly favours the development of obesity and associated diseases (atherosclerosis, non insulin-dependent diabetes, hypertension, cancer). This attraction to fatty foods is not specific to humans. Rats and mice spontaneously prefer lipid-rich foods if provided with a free choice. Until recently, it was thought that oral lipid detection involved only textural and olfactory cues. This restrictive view has been challenged by recent observations suggesting that sense of taste is also involved in spontaneous fat preference underlying that the “fatty” taste might constitute a sixth gustatory modality. This mini-review highlights recent findings in this new field of investigations in both rodents and humans.Pour la première fois de son histoire, une large partie de la population mondiale « ne court plus après les calories ». Cette opulence alimentaire donne libre cours à nos appétits spécifiques. C’est ainsi que, dans le régime occidental, les lipides alimentaires représentent près de 40% des apports caloriques journaliers alors que les recommandations nutritionnelles se situent à 30-35%. Cet apport excessif, associé à un déséquilibre qualitatif (excès d’acides gras saturés et de cholestérol, rapport des acides gras polyinsaturés ω6/ω3 trop élevé) participe à l'augmentation de la prévalence de l’obésité et des pathologies associées (atteintes vasculaires, diabète de type II, hypertension, cancers). Cette attirance pour les corps gras n’est pas spécifique à l’Homme. Les rongeurs (rats, souris) présentent également une préférence spontanée pour les boissons et les aliments enrichis en lipides. Jusqu’à une période récente, on pensait que seules la texture et l’odeur des lipides étaient responsables de leur détection oro-sensorielle. Cette vision restrictive a été récemment battue en brèche par une série de travaux montrant que le choix de consommer préférentiellement des lipides comporte également une dimension gustative. Cette mini-revue se propose de faire le point des connaissances dans ce nouveau domaine d’investigation à la fois chez les rongeurs et chez l’Homme

CD36 mRNA in the Gastrointestinal Tract Is Differentially Regulated by Dietary Fat Intake in Obesity-Prone and Obesity-Resistant Rats

BACKGROUND: The gastrointestinal tract (GI) is important for detection and transport of consumed nutrients and has been implicated in susceptibility to diet-induced obesity in various rat strains. AIMS: The current studies investigated the regulation of CD36, a receptor which facilitates uptake of long-chain fatty acids, in the GI tract of obesity-prone Osborne–Mendel and obesity-resistant S5B rats fed a high-fat diet. METHODS: Osborne–Mendel and S5B rats consumed a high-fat diet (HFD, 55 % kcal from fat) or a low-fat diet (10 % kcal from fat) for either 3 or 14 days. CD36 messenger RNA (mRNA) levels were measured from circumvallate papillae of the tongue and from duodenal enterocytes. RESULTS: In Osborne–Mendel rats, consumption of HFD for 3 and 14 days led to an increase in CD36 mRNA on circumvallate papillae and in duodenal enterocytes. CD36 mRNA levels were positively correlated with body weight gain and kilocalories consumed at 3 days. In S5B rats, consumption of HFD for 3 days did not alter CD36 mRNA levels on circumvallate papillae or in the duodenum. Duodenal CD36 levels were elevated in S5B rats following 14 days of HFD consumption. CD36 mRNA levels in the duodenum were positively correlated with body weight gain and kilocalories consumed at 14 days. CONCLUSIONS: These data support the differential sensing of nutrients by two regions of the GI tract of obesity-prone and obesity-resistant rats consuming HFD and suggest a role for CD36 in the strain-specific susceptibility to obesity