Although leptin and endocannabinoids are not expressed in
taste buds, the presence of their cognate receptors on the surface of
TRC
[36]
suggests that these mediators also exert regulatory func-
tions in gustatory papillae. Leptin is an anorexigenic hormone
primarily produced in adipocytes. It regulates food intake, energy
expenditure and, thereby, body mass by acting on hypothalamic
receptors and, toa lesserextent, on few peripheral organs including
gustatory papillae. To date, there are no published data concerning
leptin or endocannabinoids associated with fat taste. However, it
has been reported that circulating leptin act as a negative modu-
lator for sweet taste
[36]
which is, like fat taste, a gustatory mo-
dality involved in the detection of energy-dense foods. Since
plasma leptin levels are positively correlated to fat mass, it is likely
that this endocrine pro
fi
le contribute to the degradation of sweet
taste sensitivity observed in obese subject
[37]
(
Fig. 1-5
). By
contrast, the endocannabinoid anandamide (AEA) is an orexigenic
mediator which enhances the sweet taste sensitivity by binding to
CB1 receptor which is found in TRC
[38]
. By analogy, a regulation of
fat taste by leptin and endocannabinoids might also exist. Consis-
tent with this assumption, preliminary data from our laboratory
strongly suggest that the preference for oily solution is changed in
ob/ob mice in which leptin is lacking.
In brief, further studies are required to fully understand the
speci
fi
c roles played by each of the modulators (hormones and
others) in the physiology of taste buds and the regulation of taste
sensitivity. Already,
“
fatty
”
and sweet taste sensitivities appear to
be tightly controlled parameters. The balance between positive and
negative modulators is likely to be determinant for the homeostatic
regulation of the taste sensitivity and an adequate adaptation of
eating behavior (e.g. choice of food) to the real-time requirements
of the body. Therefore, it can be thought that a dysregulation of this
homeostatic system might induce dietarychanges byimpacting the
body weight