CD36 involvement in orosensory detection of dietary lipids, spontaneous fat preference, and digestive secretions

TLDR

Rats and mice spontaneously attract lipids, implying an orosensory system may detect dietary lipids, and the fatty acid transporter CD36—highly expressed in lingual papillae and binding long‑chain fatty acids—is a plausible candidate. The study aimed to determine whether CD36 mediates lipid detection by comparing wild‑type and CD36‑null mice. Experiments were conducted in rats and mice, involving behavioral assays and molecular analyses of CD36 expression. CD36 is expressed only in lingual papillae, localizes to the apical side of circumvallate taste bud cells, and its deletion abolishes preference for LCFA‑enriched solutions and solid diet, while LCFA deposition on the tongue triggers rapid increases in pancreatic and biliary secretions, demonstrating CD36’s role in oral LCFA detection and suggesting a link to feeding regulation.

Abstract

Rats and mice exhibit a spontaneous attraction for lipids. Such a behavior raises the possibility that an orosensory system is responsible for the detection of dietary lipids. The fatty acid transporter CD36 appears to be a plausible candidate for this function since it has a high affinity for long-chain fatty acids (LCFAs) and is found in lingual papillae in the rat. To explore this hypothesis further, experiments were conducted in rats and in wild-type and CD36-null mice. In mice, RT-PCR experiments with primers specific for candidate lipid-binding proteins revealed that only CD36 expression was restricted to lingual papillae although absent from the palatal papillae. Immunostaining studies showed a distribution of CD36 along the apical side of circumvallate taste bud cells. CD36 gene inactivation fully abolished the preference for LCFA-enriched solutions and solid diet observed in wild-type mice. Furthermore, in rats and wild-type mice with an esophageal ligation, deposition of unsaturated LCFAs onto the tongue led to a rapid and sustained rise in flux and protein content of pancreatobiliary secretions. These findings demonstrate that CD36 is involved in oral LCFA detection and raise the possibility that an alteration in the lingual fat perception may be linked to feeding dysregulation.