Leptin is known to selectively suppress neural and behavioral responses to sweet-tasting compounds. However, the molecular basis for the effect of leptin on sweet taste is not known. Here, we report that leptin suppresses sweet taste via leptin receptors (Ob-Rb) and KATP channels expressed selectively in sweet-sensitive taste cells. Ob-Rb was more often expressed in taste cells that expressed T1R3 (a sweet receptor component) than in those that expressed glutamate-aspartate transporter (a marker for Type I taste cells) or GAD67 (a marker for Type III taste cells). Systemically administered leptin suppressed taste cell responses to sweet but not to bitter or sour compounds. This effect was blocked by a leptin antagonist and was absent in leptin receptor–deficient db/db mice and mice with diet-induced obesity. Blocking the KATP channel subunit sulfonylurea receptor 1, which was frequently coexpressed with Ob-Rb in T1R3-expressing taste cells, eliminated the effect of leptin on sweet taste. In contrast, activating the KATP channel with diazoxide mimicked the sweet-suppressing effect of leptin. These results indicate that leptin acts via Ob-Rb and KATP channels that are present in T1R3-expressing taste cells to selectively suppress their responses to sweet compounds.

Natural rubber with filler nanomatrix structure was prepared by forming chemical linkages between natural rubber particles and filler nanoparticles. The filler nanomatrix structure was formed by graft copolymerization of vinyltriethoxysilane (VTES) onto natural rubber particles in the latex stage followed by casting of the latex to prepare an as-cast film. The silica nanoparticles were produced during the graft copolymerization through hydrolysis and condensation, i.e., sol-gel reaction; hence, they linked to the natural rubber particles. The nanomatrix structure was observed by transmission electron microscopy, in which the natural rubber particles of about 1 μm in diameter were well dispersed in the filler nanomatrix. Tensile properties were significantly improved by forming filler nanomatrix structure. The loss modulus and loss tangent of the natural rubber with the filler nanomatrix structure were almost independent of deformation frequency in the rubbery plateau region, which was explained to be due to the energetic elasticity and entropic elasticity characteristic of the nanomatrix structure.

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