Volatile Short-Chain Aliphatic Aldehydes Act as Taste Modulators through the Orally Expressed Calcium-Sensing Receptor CaSR.

Aldehydes are natural volatile aroma compounds generated by the Maillard reaction of sugars and amino acids in food and affect the flavor of food. They have been reported to exert taste-modifying effects, such as increases in taste intensity at concentrations below the odor detection threshold. The present study examined the taste-enhancing effects of short-chain aliphatic aldehydes, such as isovaleraldehyde (IVAH) and 2-methylbutyraldehyde, thus attempting to identify the taste receptors involved. The results obtained revealed that IVAH enhanced the taste intensity of taste solutions even under the condition of olfactory deprivation by a noseclip. Furthermore, IVAH activated the calcium-sensing receptor CaSR in vitro. Receptor assays on aldehyde analogues showed that C3-C6 aliphatic aldehydes and methional, a C4 sulfur aldehyde, activated CaSR. These aldehydes functioned as a positive allosteric modulator for CaSR. The relationship between the activation of CaSR and taste-modifying effects was investigated by a sensory evaluation. Taste-modifying effects were found to be dependent on the activation state of CaSR. Collectively, these results suggest that short-chain aliphatic aldehydes function as taste modulators that modify sensations by activating orally expressed CaSR. We propose that volatile aroma aldehydes may also partially contribute to the taste-modifying effect via the same molecular mechanism as kokumi substances.

Effects of TUG-891, a potent GPR120 agonist, on the physical and oral lipid- coating properties, and secretion of saliva.

GPR120 agonists were recently shown to enhance the fatty orosensation in humans when added to vegetable oil or a low-fat food system, but did not evoke it by themselves. Furthermore, an emulsion prepared from vegetable oil had a stronger fatty orosensation than that prepared from mineral oil even though the physical properties of both emulsions were similar. To clarify the mechanisms underlying the enhancement of the fatty orosensation by GPR120 agonists, the present study investigated the effects of TUG-891, a potent GPR120 agonist, on physical and oral lipid-coating properties and the secretion of saliva. The addition of TUG-891 to a vegetable oil emulsion did not significantly change its physical properties, such as viscosity, particle distribution, interfacial tension, contact angle, frictional load, and ζ-electric potential, or the amount of the lipid coating remaining in the oral cavity. These results indicate that TUG-891 enhanced the fatty orosensation without changing the physical or oral lipid-coating properties of the emulsion. The addition of TUG-891 to a vegetable oil emulsion and whipped cream significantly increased the amount of saliva secreted. Therefore, TUG-891, a potent GPR120 agonist, may enhance the fatty orosensation by increasing the amount of saliva secreted.

Increases in the pungency of allyl isothiocyanate and piperine by CaSR agonists, glutathione and γ-glutamyl-valyl-glycine.

γ-Glutamyl peptides, including glutathione (γ-Glu-Cys-Gly, GSH) and γ-glutamyl-valyl-glycine (γ-Glu-Val-Gly), have been shown to increase the intensity of basic tastes, such as salty, sweet, and umami, and flavor, including mouthfulness, but had no taste themselves at the concentrations tested. Although the mechanisms of action of γ-glutamyl peptides currently remain unclear, the involvement of the calcium sensing receptor (CaSR) has been suggested. Since GSH and γ-Glu-Val-Gly increase the pungency of some spices, the present study investigated their effects on the pungency of allyl isothiocyanate (AITC) using a sensory evaluation. GSH and γ-Glu-Val-Gly both significantly increased the pungency of AITC, while anserine, a peptide without CaSR activity, did not. GSH-induced increases in pungency were suppressed by NPS-2143, a CaSR inhibitor. Further, γ-Glu-Val-Gly significantly increased the pungency of piperine. The present results suggest that GSH and γ-Glu-Val-Gly increased the pungency by activating CaSR.

Identification and Quantitation of Taste-Active Compounds in Dried Scallops by Combined Application of the Sensomics and a Quantitative NMR Approach.

Application of the sensomics concept on dried scallops, a Japanese specialty produced from the adductor muscle of scallops, revealed after activity-guided fractionation with subsequent (comparative) taste dilution analyses besides nucleotides, amino acids, organic acids, and inorganic ions, the presence of taste-modulating quaternary ammonium compounds and opines in highly taste-active fractions. In order to recreate the taste of dried scallops, two independent quantitation approaches were applied and compared. The first approach used multiple targeted UHPLC-MS/MS and high-performance ion chromatography methods. Besides already established quantitation methods for basic taste compounds, a new HILIC-UHPLC-MS/MSMRM method for the quantitation of chromatographically challenging opines, using synthesized stable isotope-labeled standards, was developed. Furthermore, a qHNMR approach was applied, enabling a direct identification and quantitation of organic taste compounds in a food extract without prior fractionation using a reference 1H NMR database. Both methods yielded similar quantitative results of taste-active compounds in dried scallop extracts and subsequent taste recombination experiments based on these data were able to recreate the taste of dried scallops.

GPR120 agonists enhance the fatty orosensation when added to fat-containing system, but do not evoke it by themselves in humans.

Dietary fat, an important macronutrient, has been considered to be perceived by texture and olfaction. Recently, fatty acid transporter, CD36, and fatty acid receptor, GPR120 are considered to be involved in human gustatory fatty acids perception in humans. However, limited information is currently available to show that agonists of CD36 and GPR120 evoke fatty oral sensations regarding to dietary fat in humans. Therefore, the role of GPR120 agonists in dietary fat perception in humans was investigated herein. An emulsion prepared from vegetable oil had a stronger fatty orosensation, an orosensation similar to an oily mouth-coating sensed 5 - 10 s after tasting, than that prepared from mineral oil; however, the physical properties of both emulsions, such as viscosity, particle distribution, interfacial tension, contact angle, frictional load, and ζ-electric potential were similar. The potent GPR120 agonist, TUG-891 enhanced the fatty orosensation when added to the emulsion prepared from vegetable oil, but not to that from mineral oil. All GPR120 agonists tested enhanced the fatty orosensation when added to a low-fat food system whereas they did not evoke any fatty sensation in aqueous solution at the concentrations tested in food system, and sensory activity positively correlated with GPR120 activity. These results suggest that GPR120 agonists enhance the fatty orosensation in humans when added to vegetable oil or a low-fat food system, but do not evoke it by themselves.

Design, synthesis and evaluation of unnatural peptides as T1R2/T1R3 PAMs.

The sweet receptor T1R2/T1R3 is a member of G protein-coupled receptor family and recognizes diverse natural and synthetic sweeteners. Previously, we reported a novel class of positive allosteric modulators (PAMs) of T1R2/T1R3 comprising an unnatural tripeptide structure. We classified the structure of these PAMs into three parts: "head", "linker" and "tail". Here, we report the design, synthesis and evaluation of various tail structures to obtain highly active unnatural peptide structure of PAM. In conclusion, we discovered the novel unnatural tetrapeptide with highly potent PAM activity on T1R2/T1R3 in a cell-based assay system.

Unnatural Tripeptides as Potent Positive Allosteric Modulators of T1R2/T1R3.

T1R2/T1R3 belongs to G protein coupled receptors, which recognizes diverse natural and synthetic sweeteners. A novel class of positive allosteric modulators (PAMs) of T1R2/T1R3 was identified through high-throughput screening campaign. Comparing the structure of the potent compound with previously known PAM, we classified the structure of known PAM into three parts, defined as "head", "linker", and "tail". We then investigated the linker-tail structure. It was suggested by molecular docking models of T1R2/T1R3 that an amine that we introduced in the tail was the key for interaction with the receptor binding pocket. We thus synthesized various molecules and found unnatural tripeptide-PAMs, which potently enhance the sweetness of sucrose in sensory evaluation tests.

Superior canal dehiscence syndrome associated with scuba diving.

A 28-year-old female diver presented with dizziness and difficulty clearing her left ear whilst scuba diving. Her pure-tone audiometry and tympanometry were normal. Testing of Eustachian tube function revealed tubal stenosis. Video-oculography revealed a predominantly torsional nystagmus while the patient was in the lordotic position. Fistula signs were positive. High-resolution computed tomography (HRCT) of the temporal bone revealed a diagnosis of bilateral superior semicircular canal dehiscence (SCDS). Cervical vestibular-evoked myogenic potential (cVEMP) testing showed that the amplitude of the cVEMP measured from her left ear was larger than that from the right. In electronystagmography (ENG), nose-pinched Valsalva manoeuvres caused eye movements to be mainly directed counterclockwise with a vertical component. Tullio phenomenon was also positive for both ears. SCDS patients tend to be misdiagnosed and misunderstood; common misdiagnoses in these cases are alternobaric vertigo (AV), inner ear barotrauma, and inner-ear decompression sickness. It is difficult to diagnose vertigo attacks after scuba diving as SCDS; however, when the patient develops sound- and/or pressure-induced vertical-torsional nystagmus, HRCT should be conducted to confirm a diagnosis of SCDS.

Quantitative analysis of inner-ear barotrauma using a Eustachian tube function analyzer.

OBJECTIVES: We investigated the relationship between Eustachian tube function and incidence of inner-ear barotrauma (IEBt) in recreational divers. METHODS: Sixteen patients who experienced a scuba diving injury affecting the inner ear and 20 healthy volunteers who had not experienced a diving injury participated. Healthy volunteers and divers with IEBt received impedance tests regularly to assess Eustachian tube function. Test results from these groups were compared. RESULTS: There were no significant differences between test results of IEBt divers and healthy volunteers. However, seven IEBt divers were judged to have irregular compliance curves on impedance testing. Seven of the 16 IEBt divers experienced vertigo. In nearly all of the IEBt divers with vertigo, hearing loss type was manifested as high-tone deafness, and IEBt symptoms appeared during diving. These symptoms were more serious especially when the diving depth was deeper. CONCLUSIONS: To prevent IEBt in scuba divers, we recommend a thorough Eustachian tube function evaluation. Any dysfunction should be treated before engaging in scuba diving. We need to assess more divers who have experienced IEBt and thoroughly examine how their injury happened.

A case of patulous Eustachian tube associated with dizziness induced by nasal respiration.

OBJECTIVE: To determine the relationship between Eustachian tube function and inner ear function in patulous Eustachian tube (pET). METHODS: We encountered a patient with pET accompanied by dizziness that was induced by nasal respiration. Eye movements were recorded using video-oculography, and Eustachian tube function was assessed using a Eustachian tube function analyzer. Horizontal and vertical components of pupil position were assessed to test fixation, positional, and positioning nystagmus. Impedance testing with a Eustachian tube function analyzer was performed to confirm tympanometry results. We recorded these outcomes until the patient's symptoms improved. RESULTS: When pET improved, the patient's symptoms were alleviated. CONCLUSION: The present pET patient had mild vestibular symptoms. Therefore, pET patients with dizziness might be misdiagnosed with, for example, superior semicircular canal dehiscence, psychogenic vertigo, or Ménière's disease. For patients with few clinical symptoms or laboratory findings, clinicians need to consider dizziness-induced pET as a possible diagnosis.

Altered eustachian tube function in SCUBA divers with alternobaric vertigo.

OBJECTIVES: The number of people participating in sport self-contained underwater breathing apparatus (SCUBA) diving has increased tremendously, bringing with it a rise in diving accidents. Alternobaric vertigo (AV) is a common problem in SCUBA divers. We investigated the relationship between Eustachian tube function and incidence of AV in sport SCUBA divers. We also followed the progress of these divers after Eustachian tube function improved. METHOD: Forty-four patients who experienced a SCUBA diving accident affecting the middle ear (11 men and 33 women; mean ± SD: 37.5 ± 11.5 yr) and 20 healthy volunteer divers who did not experience an accident (6 men and 14 women; mean ± SD: 33.5 ± 13.9 yr) were compared. We divided the divers with an accident into two groups (those with AV vs. those without) and then compared the two groups. All patients regularly underwent Eustachian tube function tests (sonotubometry and impedance test). RESULTS: In sonotubometry and impedance testing, the mean duration (p < 0.001), amplitude (p < 0.002), and maximum air content (p < 0.05) of divers who experienced a diving accident were significantly different from those of healthy volunteers. However, these parameters in divers with AV did not differ significantly from those in divers without AV. In 7 of 15 divers, vestibular symptoms disappeared immediately after ascent. In the remaining eight divers, however, vertigo/dizziness persisted and even was observed at their first clinic visit. CONCLUSION: To prevent AV or barotraumas in SCUBA divers, we recommend a thorough Eustachian tube function evaluation. Any dysfunction should be treated before engaging in SCUBA diving.

[A study of the Eustachian tube function in patients with a scuba diving accident].

The scuba diving population has increased very much recently, bringing with it a rise in barotrauma. Ninety-seven patients with scuba diving-related accidents (34 males and 63 females; mean +/- SD: 36.6 +/- 10.3 years) and 39 healthy volunteers (9 males and 30 females; mean +/- SD: 41.1 +/- 16.9 years) without a history of Eustachian tube dysfunction participated in this study. All patients underwent audiometric measurements, including hearing testing, tympanometry, and Eustachian tube function testing (sonotubometry and impedance test). The tympanometry results of the majority of the patients were normal (Jerger A type), however, 83 of 97 patients (85.6%) were diagnosed as having Eustachian tube dysfunction: all patients had tubal stenosis. Compared with healthy volunteers, the Eustachian tube function in scuba diving patients was significantly lower. According to whether the affected parts were one ear or both ears, we classified these patients into 2 types, that is, the unilateral group and the bilateral group. The symptoms in the unilateral group were more serious than those in the bilateral group. In the unilateral group, the Eustachian tube functions of the affected ear did not always show lower than those of the healthy ear, so we thought that excessive positive pressure at the mesotympanum caused by the Valsalva maneuver might have affected not only the affected ear but also the healthy ear and have resulted in healthy ears being severely impaired by excessive positive pressure. To prevent scuba divers from pressure injury, we think that divers should have their Eustachian tube dysfunction accurately evaluated and any problems should be treated well.

High molecular weight lectin isolated from the mucus of the giant African snail Achatina fulica.

To understand better the host defense mechanisms of mollusks against pathogens, we examined the anti-microbial activity of mucus from the giant African snail Achatina fulica. Hemagglutination activity of the mucus secreted by the integument of snails inoculated with Escherichia coli was observed to increase and to cause hemagglutination of rabbit red blood cells. Purification of the snail mucus lectin by sequential column chromatography revealed that the relative molecular mass of the lectin was 350 kDa. The hemagglutination activity of the lectin was Ca(2+)-dependent and was inhibited by galactose. Growth arrest tests showed that the lectin did not inhibit bacterial growth, but did induce agglutination of gram-positive and gram-negative bacteria. Tissue distribution analyses using a polyclonal antibody revealed that the lectin was expressed in the tissues of the mantle collar. The lectin isolated from the mucus of the snail appeared to contribute to its innate immunity.

Silybin from Silybum Marianum Seeds Inhibits Confluent-Induced Keratinocytes Differentiation as Effectively as Retinoic Acid without Inducing Inflammatory Cytokine.

Retinoic acid (RA) has been effective for improving wrinkles. However, it has also been reported that RA induces skin irritation. In this study, we explored new botanical compounds that show RA-like activity, but do not induce inflammation in vitro. Keratinocytes were maintained in a confluent condition and induced differentiation. Under this condition keratinocytes were treated with many botanical extracts and their morphological change were observed and compared with RA-treated. We found that silybin, which is a major flavonolignan from Silybum Marianum seeds, induced RA-like morphological change and prevented differentiation. We showed that silybin, like RA, reduced the expression of keratinocyte terminal differentiation markers and stimulated the expression of basement membrane component proteins. In contrast, silybin, unlike RA, did not stimulate the secretion of IL-1alpha, which is a skin irritation mediator. These results suggest that silybin has RA-like activity on keratinocytes and has the potential to improve winkle without inducing skin irritation.

Achacin induces cell death in HeLa cells through two different mechanisms.

Achacin, which belongs to the L-amino acid oxidase group, oxidizes free amino acids and produces hydrogen peroxide in cell culture systems. Morphological changes in cells incubated with achacin were similar to those of cells incubated with H(2)O(2). In both cases, the end result was cell death. To examine the mechanism of achacin-associated cytotoxicity, the H(2)O(2) scavenger catalase was added to culture media. Features typical of apoptosis, including morphological changes, DNA fragmentation, and PARP cleavage, were observed when cells were incubated with achacin in the presence of catalase. Moreover, apoptosis was inhibited by Z-VAD-fmk, a broad-spectrum caspase inhibitor. Herein, we present evidence that two pathways are involved in achacin-induced cell death. One is direct generation of H(2)O(2) through the L-amino acid oxidase activity of achacin. The other is the caspase-mediated apoptotic pathway that is induced by depletion of L-amino acids by achacin.

Antimicrobial action of achacin is mediated by L-amino acid oxidase activity.

Achacin is an antibacterial glycoprotein purified from the mucus of the giant snail, Achatina fulica Férussac, as a humoral defense factor. We showed that achacin has L-amino acid oxidase activity and can generate cytotoxic H(2)O(2); however, the concentration of H(2)O(2) was not sufficient to kill bacteria. The antibacterial activity of achacin was inhibited by various H(2)O(2) scavengers. Immunochemical analysis revealed that achacin was preferentially bound to growth-phase bacteria, accounting for the important role in growth-phase-dependent antibacterial activity of achacin. Achacin may act as an important defense molecule against invading bacteria.