Kumiko Sugimoto

Leptin and sweet taste.

Leptin, the product of the obese (ob) gene, is a hormone primarily produced in adipose cells, and also at smaller amounts in some other peripheral organs. It regulates food intake, energy expenditure, and body weight. Leptin is thought to promote weight loss, at least in rodents, by suppressing appetite and stimulating metabolism. Mutant mice that lack either leptin or functional leptin receptors, such as ob/ob and db/db mice, are hyperphagic, massively obese, and diabetic. Central hypothalamic targets are mainly responsible for the effects of leptin on food intake and weight loss. However, there are also direct effects on peripheral tissues. Recently, the taste organ was found to be one of the peripheral targets for leptin. The hormone specifically inhibits sweet taste responses in lean mice and not in db/db mice. Thus leptin appears to act as a modulator of sweet taste, provided a functional leptin receptor is expressed by the taste cells. This chapter reviews the genetics and molecular biology of leptin and its receptors, the receptor mechanisms for sweet taste, the modulating action of leptin on taste receptor cells, and the consequences for the regulation of food intake.

Characteristic changes of saliva and taste in burning mouth syndrome patients.

BACKGROUND Burning mouth syndrome (BMS) is characterized by chronic pain with a burning sensation of the tongue and oral mucosa and reported to be often accompanied by subjective xerostomia and dysgeusia. Since the etiology of BMS has not been elucidated, to understand the characteristics of BMS, we measured some components of saliva and taste sensitivity and compared the measured values between BMS and healthy subjects. METHODS Unstimulated saliva was collected from 15 female BMS patients and 30 healthy women. The flow rate, viscosity (spinnability) and concentration of secretory IgA (SIgA) of saliva and serum antioxidant capacity were measured. The recognition thresholds for sweet, salty, sour, bitter, and umami tastes were measured by whole-mouth method. The statistical analyses were performed using Students t-test, and P < 0.05 was considered to be significant. RESULTS In BMS group, the flow rate of saliva was significantly lower and the spinnability was significantly higher compared with healthy group. The secreted amount of SIgA per min and serum antioxidant capacity was significantly lower in the patients. The threshold for sourness in patients was significantly higher, while those for other tastes did not differ from healthy group. CONCLUSIONS BMS patients showed lower salivary flow and higher salivary spinnability. These results together with decreased SIgA amount, suggest that BMS may be relevant to the deterioration of salivary condition, which could in turn affect taste function. Furthermore, the lower antioxidant capacity in patients serum suggests that it can serve as a diagnostic tool for BMS.

The adaptation of the frog tongue to bitter solutions: Enhancing effect on gustatory neural response to salt stimuli

Abstract 1. 1. The initial phasic component of frog gustatory neural responses to various 0.1 M salt solutions was greatly augmented in amplitude after the tongue was adapted for 10 sec to 1 mM quinine-HC1 (Q-HCl), quinine-H2SO4 (Q-H2SO4) and picric acid. 2. 2. Out of 103 examined gustatory units responding to both 0.5 M NaCl and 1 mM Q-HCl or to 0.5 M NaCl alone, 67% exhibited an enhancement of response to the NaCl after the Q-HCl adaptation but the remaining 33% showed a suppression or no alteration of NaCl response after the Q-HCl. 3. 3. Intracellular taste cell responses to salt stimuli after 1 mM Q-HCl adaptation showed an initial phasic depolarization which was not observed under control Ringer adaptation. This de polarization might be concerned with the enhancement of initial phasic neural responses to salts following the Q-HCl adaptation.

Effectiveness of an oral health educational program on community-dwelling older people with xerostomia.

The purpose of the present study was to evaluate the changes in oral health and function through an oral health educational program for the independent older people with xerostomia.

Objective assessment of internal stress in children during dental treatment by analysis of autonomic nervous activity

AIMS The aim of this study was to assess the internal stress of children during dental treatment based on autonomic nerve activity and facial muscle activity. METHODS We recorded the electrocardiogram of children during the treatment of composite resin restoration and analysed autonomic nerve activity by means of power spectral analysis of heart rate variability. Simultaneously, electromyography (EMG) activity of the corrugator muscle was recorded in children during dental treatment, and the relationship between sympathetic nerve activity and corrugator EMG activity was analysed. RESULTS In all subjects, the mean sympathetic nerve activity was significantly higher during oral examination and after treatment compared with pre-treatment. Depending on the sympathetic nerve responses to the other treatment procedures, the subjects could be classified into two groups: the stress group and the nonstress group. Sympathetic nerve activity was significantly higher during infiltration anaesthesia and cavity preparation compared with pre-treatment activity in the stress group, whereas it was consistently lower than the pre-treatment levels during most treatment procedures in the nonstress group. The mean amplitudes of the averaged corrugator muscle EMG during dental treatment did not differ between the stress and nonstress groups. CONCLUSION The present results suggest that the measurement of autonomic nervous activity, especially sympathetic nervous activity, is quite useful in assessing the internal stress of children, even when no expressed sign of unease are present during dental treatment.

Internal stress in children and parental attitude to dental treatment with passive restraint

Abstract Purpose The purpose of this study was to examine the internal stress in uncooperative children treated under passive restraint and the changes of it in later treatments under cooperative condition with no need of restraint. We also conducted questionnaire among parents to survey their opinion towards the treatment with restraining device. Methods The subjects for electrocardiogram (ECG) recording were the child patients who were referred to the university clinic by the primary care dentists. We recorded ECG of the patients during dental treatment and assessed the autonomic nervous activity as a physiological response to stress. The recordings from uncooperative children were continued at every visit until they became cooperative and no longer restrained. A questionnaire survey was conducted among parents who have experienced the use of the restraining device to their children. Results Though the sympathetic nerve activity, which elevates with internal stress, and the heart rate were relatively high under restraint in uncooperative children, both diminished in the later session when children became cooperative enough to remove restraint. The questionnaire survey demonstrated that most parents whose children underwent treatment with restraining device showed positive attitudes toward the use of it. Conclusions The results of this study suggest that the experience of dental treatment with passive restraint would not necessarily be a traumatic event for children in a short term and parents would accept the necessity through the experience of the treatment in case urgent treatments are required.

Glutamate transduction mechanism in mouse taste cells

In order to clarify the role of group III metabotropic glutamate receptor (including mGluR4) in transduction for umami taste, we investigated the effects of monosodium glutamate (MSG) and 2-amino-4-phosphonobutyrate (L-AP4), a mGluR4 agonist, on taste cells by use of electrophysiological and biochemical methods, and Ca2+ imaging in C57BL mice. The responses of the chorda tympani (CT) nerve to MSG were suppressed by gurmarin, a sweet response inhibitor, indicating that the MSG response may be partly mediated by sweet receptors, while the CT responses to L-AP4 and the glossopharyngeal (GL) nerve responses to MSG were little suppressed by gurmarin suggesting that these responses may be mediated by only umami receptors. Biochemical study demonstrated that MSG stimulation significantly elevated both adenosine 3′, 5′-cyclic monophosphate (cAMP) and inositol 1,4,5-triphosphate (IP3) levels in the fungiform papillae. The increase in cAMP might occur through sweet receptors, which is consistent with CT nerve responses. The increase in IP3 levels may relate to intracellular events mediated by group III mGluRs, because MSG and L-AP4 induced increment of intracellular Ca2+ concentration in some taste cells. Whole-cell patchclamp recording from isolated taste cells showed that L-AP4 induced not only outward currents with a conductance decreases but also inward currents with conductance increases at about resting potentials. These inward currents reversed at +10-+30 mV suggesting that cation conductance was activated by L-AP4. These results strongly support the idea that phospholipase C activation mediated by group III mGluRs is involved in transduction mechanism for umami taste, and also suggest the possibility that stimulation of the mGluRs may cause activation of cation conductance as well as [Ca2+]i elevation.

Quinine-HCl-induced modification of receptor potentials for taste stimuli in frog taste cells.

Abstract After frog taste cells were adapted to 1 mM quinine-HCl (Q-HCl) for 10 sec, modification of receptor potentials in the taste cells induced by salt, acid, sugar and bitter stimuli was studied with microelectrodes. The phasic component of receptor potentials induced by 0.1 M NaCl, KCl, NH4Cl and MgCl2 was enhanced following adaptation to Q-HCl. The rate of rise of receptor potentials in response to the salts was increased after Q-HCl adaptation. The amplitude and the rate of rise of receptor potentials induced by 1 mM acetic acid were larger after Q-HCl adaptation than after water adaptation. The amplitude of phasic component and rate of rise of receptor potentials for 0.5 M sucrose after Q-HCl were the same as those after water. The amplitudes of tonic receptor potentials for 1 mM Q-H2SO4, brucine and picric acid after Q-HCl adaptation were the same as those after 1 mM NaCl adaptation. Correlation coefficient between taste cell responses induced by 1 mM Q-HCl and 1 mM Q-H2SO4 was very high, but those between 1 mM Q-HCl and 1 mM brucine responses and between 1 mM Q-HCl and 1 mM picric acid responses were low. This indicates that Q-HCl and Q-H2SO4 bind to the same receptor site, but brucine and picric acid bind to different receptor sites to which Q-HCl does not bind.

Electrophysiological Properties and Chemically-induced Responses of Mammalian Taste Bud Cells

To elucidate the transduction mechanisms for sweet and umami tastes, it is necessary to use mammals for experiments, since they are more responsive to these tastes than amphibians, which have been used for numbers of patch-clamp studies. In the present study, therefore, we used isolated mouse taste bud cells and recorded voltage-gated and chemically-induced responses, using patch-clamp techniques.

Emotional relationships between child patients and their mothers during dental treatments

Background/purpose The behavioral control of child patients is an important issue in pediatric dentistry. The emotional states of the mothers of patients may influence the attitudes of their children. The aim of this study was to investigate the emotional states estimated from physiological responses of child patients and the subjective anxieties of their mothers during dental treatments and discuss the emotional relationships between children and their mothers. Materials and methods To assess physiological responses associated with emotional changes induced by dental treatments in child patients aged 3–6 years, activity in the autonomic nervous were analyzed from variations in inter-beat intervals in electrocardiogram. Anxiety levels of accompanying mothers were examined using the State Trait Anxiety Inventory, which was filled out during the treatment of their child. Results Regarding the stress of child patients from the aspect of autonomic nervous activities during dental treatments, comparison between the cooperative and uncooperative patient groups showed that the uncooperative group demonstrated significantly higher sympathetic nervous activity and significantly lower parasympathetic nervous activity relative to the cooperative group, and their accompanying mothers showed significantly higher state anxiety scores relative to the mothers of cooperative children. Moreover, positive correlation between state anxiety scores of mothers and sympathetic nervous activities of their children was observed. Conclusion These results indicated that uncooperative child patients undergo more stress and their mothers feel more anxiety from dental treatments, resulting in an emotional relationship between children and their mothers, which requires dental professionals to make special considerations to calm the anxiety of the mother, as well as the stress of the child patient.