The fatty acid translocase gene CD36 and lingual lipase influence oral sensitivity to fat in obese subjects

Abstract

Obesity is caused by ingesting more energy than is expended over a long period of time. Dietary fat is the most energy-dense macronutrient, and its overconsumption has been linked to obesity ( 1-4 ). Obese people prefer foods with higher fat content ( 5 ), crave high-fat foods more frequently ( 6, 7 ), and consume more fat than lean individuals ( 8 ).Traditionally, perception of fat in the oral cavity is thought to rely almost entirely on textural and aromatic cues activating the somatosensory and olfactory systems. However, there is now increasing evidence to support an important role of the gustatory system in fat perception ( 9-20 ) as well as in intestinal lipid metabolism ( 10, 21 ). Oral and gastrointestinal fat sensory sensitivity appear to be associated ( 16 ) and there is similarity in the chemosensory reception events and their signaling transduction pathways in the tongue and gastrointestinal tract ( 21 ). An important requirement for the involvement of a gustatory component in dietary lipid detection is the hydrolysis of triacylglycerols (TGs) to release free FAs, the signaling stimulus, as was demonstrated through the use of the lipase inhibitor orlistat ( 22 ). In rodents, lingual lipase is essential for the gustatory perception of dietary fats ( 22 ) and the addition of orlistat to fat emulsions diminishes the rat's preference for TG, but not FA ( 22 ). Although it is not known whether lingual lipase is important for oral fat perception in humans, data from a recent study suggests that lingual lipase lipolytic activity can produce FA within the concentration range required to activate oral sensors ( 18 ).Several putative fat taste receptor classes have been identifi ed in rodents ( 12,23,24 ), including the glycoprotein CD36 ( 25 ). The presence of CD36, a scavenger receptor that mediates uptake and traffi cking of lipids in diverse cell types ( 26 ), has been documented in the gustatory papillae of rodents ( 25, 27 ), pigs, and humans ( 28 ). In rodents, the interaction between CD36 and FA results in signaling events that depend on an intact neuronal gustatory pathway ( 15,29 ). CD36 gene knockout impedes fat detection in mice without affecting sweet or bitter perception Abstract The precise orosensory inputs engaged for dietary lipids detection in humans are unknown. We evaluated whether a common single nucleotide polymorphism (rs1761667) in the CD36 gene that reduces CD36 expression and the addition of orlistat, a lipase inhibitor, to reduce FA release from triacylglycerols (TGs), the main component of dietary fats, would attenuate fat orosensory sensitivity in humans. Twenty-one obese subjects with different rs1761667 genotypes (6 AA, 7 AG, and 8 GG) were studied on two occasions in which oleic acid and triolein orosensory detection thresholds were measured using emulsions prepared with and without orlistat. Subjects homozygous for the G-allele had 8-fold lower oral detection thresholds for oleic acid and triolein than subjects homozygous for the A allele, which associates with lower CD36 expr...

Measuring Oral Fatty Acid Thresholds, Fat Perception, Fatty Food Liking, and Papillae Density in Humans

“…Two sensory-based methods have been commonly described in the literature; one being the ascending forced choice triangle procedure and the alternate, the staircase method 35 . The ascending forced choice triangle methodology is an established method for taste threshold determination and can be considered useful for several reasons, including the fact that, unlike the staircase method, the ascending method begins with the lowest concentration of C18:1 (0.02 mM) and increases until the participant is able to detect the presence of fatty acid in solution 9 .…”

“…Using the remaining base solution, prepare the control vehicle. In a 2 L glass beaker, add 5% of the remaining volume in liquid paraffin (e.g., 35 ml liquid paraffin in a final volume of 750 ml) together with the remaining base solution and homogenize for 30 sec per 100 ml of liquid. 13.…”

Heritable differences in chemosensory ability among humans

“…Gene knockout studies in mice [88,89] suggest that inactivating mutations in humans are likely to have an effect on human oral fat perception [90]. Recently, variants of the putative lipid receptor CD36 have been associated with differences in oral fat perception [91,92]. In addition, some heritable variation for the textural quality 'astringency' has been identified [93].…”

STIM1, CD36 lingual et perception gustative lipidique

“…Notre étude contribue à renforcer l'hypothèse de l'existence d'une sixième modalité gustative dédiée à la détection des lipides alimentaires chez la souris. Des études récentes ont démontré qu'un polymorphisme du gène codant pour CD36, aboutissant à une baisse de l'expression de celui-ci, est responsable d'une augmentation du seuil de détection oral des lipides alimentaires chez l'homme [13]. …”