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 expression (P = 0.03). Thresholds for heterozygous subjects were intermediate. The addition of orlistat increased detection thresholds for triolein (log threshold = -0.3 ± 0.2 vs. 0.3 ± 0.1; P < 0.001) but not oleic acid (log threshold = -1.0 ± 0.2 vs. -0.8 ± 0.2; P > 0.2). In conclusion, this is the first experimental evidence for a role of CD36 in fat gustatory perception in humans. The data also support involvement of lingual lipase and are consistent with the concept that FA and not TG is the sensed stimulus.
Highlights
The precise orosensory inputs engaged for dietary lipids detection in humans are unknown
Subjects homozygous for the rs1761667 G-allele had lower detection thresholds for oleic acid and triolein than subjects homozygous for the A allele, which associates with lower cluster of differentiation 36 (CD36) expression (Fig. 1)
This issue is important in obesity because obese subjects prefer foods with higher fat content [5] and crave more high-fat foods [6, 7] as compared with lean subjects [8]
Summary
The precise orosensory inputs engaged for dietary lipids detection in humans are unknown. 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]. 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] 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]
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