Givaudan-Roure Lecture - Association for Chemoreception Sciences

29 Poster [ ] Taste: Fats
THE GUSTATORY SENSATION FROM FREE FATTY ACID
Kawai T. 1, Nishiduka T. 1, Kajii Y. 2, Shingai T. 2, Kuwasako T. 3, Hirano
K. 3, Yamashita S. 3, Kawada T. 1, Fushiki T. 1 1Graduate School of
Agriculture, Kyoto University, Kyoto, Kyoto, Japan; 2Graduate School
of Medical and Dental Sciences, Niigata University, Niigata, Niigata,
Japan; 3Graduate School of Medicine, Osaka University, Suita, Osaka,
Japan
Fat in food often increases the palatability of food, even though it
does not give us obvious taste by itself. Some researches have reported
that taste cells recognize free fatty acid, a hydrolysate from common
dietary fat, though the free fatty acid has not be defined as one of
tastants. Its perceptual mechanism is still unclear. We demonstrated
immunohistochemically that CD36, one of fatty acid transport proteins,
was localized on the apical part of the taste cells isolated from rat
vallate papillae. This localization supports the hypothesis that CD36
plays a role in the oral recognition of dietary fat. In this study, we used
CD36-null mice for behavioral studies and nerve recordings and
compared with the wild type mice that had the same background. The
wild type mice preferred oleic acid solution to mineral oil solution in
short-time two-bottle preference tests, but the CD36-null mice did not
show the preference for either solution. Neural recording revealed that
small but significant response to oleic acid was observed on the lingual
branch of glossopharyngeal nerve in the wild type mice, but not in the
CD36-null mice. These results suggest that gustatory signal of fat was
conveyed via the lingual branch of glossopharyngeal nerve and that the
CD36 molecule, which exists on the tongue innervated by the lingual
branch of glossopharyngeal nerve, plays an important role in enjoying a
taste of fatty acid.
30 Poster [ ] Taste: Fats
PROP TASTER STATUS AND PERCEPTION OF FATS AND
FREE FATTY ACIDS
Armstrong C.L. 1, Mattes R. 1 1Department of Foods and Nutrition,
Purdue University, West Lafayette, IN
PROP tasters, especially supertasters, are reportedly better able to
perceive the level of fat in foods than PROP non-tasters. This study
tested perception of fat in both foods and free fatty acids in water.
PROP taster status was determined by the 5-solution method. To date,
7 non-tasters, 12 tasters and 7 supertasters have been tested. Subjects
were randomly presented 5 ml samples of milk, (0.00, 3.25, 10.00,
18.00, 36.00% fat/wt), 5 ml of vanilla pudding (4.1, 8.2, 16.3, 24.4,
29.7% fat/wt) and 5 gm of brownies (8.0, 16.0, 24.0, 31.8, 35.6%
fat/wt) and rated the level of fat in duplicate using the gLMS. Milk and
vanilla pudding were served at 7° C and brownies at 22° C. To mask
texture, oleic and linoleic acids (0.40, 0.71, 1.267, 2.25, 4.00% wt/wt)
were suspended in a solidified unflavored gelatin starch-thickened
water mixture and 5 gm samples were served at 22° C. Stearic acid (0.5,
1.0, 2.0, 4.0, 8.0% wt/wt) was suspended in starch-thickened water and
5 ml samples were served at 71° C. Samples were randomly presented
in duplicate and the level of fat rated using the gLMS. Subjects
correctly ranked the fat levels (p < 0.0001) in all foods and free fatty
acids solutions, but no differences were observed between PROP taster
groups. These data demonstrate a taste component for free fatty acids,
but no differences in fat perception based on PROP taster status. This
research was funded in part by the Rose Marie Pangborn Scholarship to
CLA and NIH Grant #DK045294.
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31 Poster [ ] Taste: Fats
FAT TASTE - ARE FREE FATTY ACIDS OR CONJUGATED
DIENES THE EFECTIVE STIMULUS?
Chalé A. 1, Burgess J.R. 2, Mattes R.D. 1 1Foods and Nutrition, Purdue
University, W Lafayette, IN; 2Foods & Nutrition, Purdue University, W
Lafayette, IN
"Fattiness" is hypothesized to be a basic taste quality, most
efficiently elicited by long-chain poly- and monounsaturated fatty acids.
Free fatty acids (FFA) have been prepared in solutions containing an
emulsifier or thickening agent to mask textural cues or in foods.
Whether the effective stimulus was the FFA or oxidation product has
not been established. This work examined the effects of addition of
EDTA and sonification (to reduce oxidation) on oxidation product
concentration. Linoleic acid was prepared at a concentration of
10mg/dl and mixed in a solution of 5% Acacia and de-mineralized
water. The concentration of EDTA was 0.01%. Samples were sonified
for 40 minutes. This preparation increased linoleic acid recovery 100X
over a simple oil-water mixture. These results suggest extensive
degradation of FFAs in previously used fat taste samples resulting in
conjugated dienes that may be effective taste stimuli. This is being
explored through psychophysical studies.
32 Poster [ ] Vomeronasal Organ
REGULATOR OF G-PROTEIN SIGNALING PROTEINS IN
THE VOMERONASAL ORGAN OF GARTER SNAKES
Wang D. 1, Liu W. 2, Chen P. 1, Halpern M. 3 1Biochemistry, Downstate
Medical Center, Brooklyn, NY; 2Anatomy and Cell Biology, Downstate
Medical Center, Brooklyn, NY; 3Anatomy & Cell Biology, Downstate
Medical Center, Brooklyn, NY
The response to prey chemoattractants in garter snakes is mediated
by the vomeronasal (VN) system.The chemosignal transduction
pathway in the VN epithelium involves the binding of agonist to its Gprotein
coupled receptors leading to activation of Gi/o-proteins which
in turn activate PLC, converting PIP2 to IP3 and DAG, and resulting in
a transient cytosolic Ca2+ increase and changes in membrane potential.
However, the desensitization mechanism so far remains unknown. We
found that the chemoattractant-induced signal is modulated by two
membrane-bound proteins, p42/44, which modulate the exchange of
GTP for GDP on the Ga subunit. During recent years, regulators of Gprotein
signaling (RGS proteins) have been identified. These proteins
enhance the activity of GTPase intrinsic to G alpha subunits and have
been shown, in a wide number of biological systems, to play an
important role in modulating agonist-induced signals. Using
commercially available RGS antibodies, we detected the expression of
several isotypes of RGS proteins in the VN sensory epithelium of garter
snakes. In addition, by screening a snake VN cDNA library, we
obtained several clones which show high homology to RGS2, RGS3
and RGS4. These RGSs may play a role in desensitization of
chemoattractant-induced signal transduction.
Supported by NIDCD Grant #DC03735