Functional effects of cold stimulation on taste perception in humans

Exploration of the mechanism of temperature influence on bitter taste of theacrine by activating human bitter taste receptor hTAS2R14

Theacrine, a purine alkaloid derived from Camellia assamica var. kucha, has a distinct bitter taste. Our previous study found the lower recognition threshold of theacrine at 25 °C than 45 °C. This study aims to investigate the bitterness characterizations of theacrine at aforementioned temperatures and its taste perception mechanism. Sensory analysis exhibited higher bitterness intensity for theacrine at 25 °C than 45 °C. Subsequently, flow cytometry was performed to verify the above characterization at the cellular level. It revealed that theacrine could activated the bitter receptor hTAS2R14 and the calcium signal at 25 °C was higher than 45 °C. Ultimately, the interaction mechanism was studied by molecular dynamics simulations, indicating that the conformation of theacrine-hTAS2R14 had a higher binding capacity and better stability at 25 °C. Overall, temperature affected the binding of theacrine to the bitter receptor hTAS2R14, resulting in the stronger bitterness intensity of theacrine at 25 °C than 45 °C.

Taste Preferences at Different Ambient Temperatures and Associated Changes in Gut Microbiota and Body Weight in Mice

Taste, dietary choices, and gut microbiota are often analyzed as major factors of metabolic health. Populations living in cold or hot regions have different dietary habits. This study aims to investigate the potential association among ambient temperature, food taste preferences, and cecal microbiota community profiles in mice. By exposing mice to mixed diets containing sweet, sour, salty, and bitter flavors at low (4 °C) and high (37 °C) ambient temperatures, the taste preferences of mice at both ambient temperatures were in the order of saltiness > sweetness > bitterness > sourness. Exposing mice to sweet, sour, salty, and bitter diets, respectively, revealed that in a low-temperature environment, mice consuming salty (5.00 ± 1.49 g), sweet (4.99 ± 0.35 g), and sour (3.90 ± 0.61 g) diets had significantly higher weight gain compared to those consuming normal feeds (2.34 ± 0.43 g, p < 0.05). Conversely, in a high-temperature environment, no significant changes in body weight were observed among mice consuming different flavored diets (p > 0.05). In a low-temperature environment, mice fed sour and sweet diets showed a significant difference in the gut microbiota composition when compared to those fed a normal diet. A higher abundance of Lachnospiraceae, UBA1819, and Clostridiales was identified as the most significant taxa in the sour group, and a higher abundance of Ruminiclostridium was identified in the sweet group. These differences were associated with microbial pathways involved in carbohydrate metabolism, amino acid metabolism, and energy metabolism. A high-temperature environment exhibited only minor effects on the gut microbiota profile. Overall, our findings provide evidence for temperature-modulated responses to the taste, gut microbiota functions, and body weight changes in mice.

Effects of Oral Cryotherapy on Anticipatory, and Acute Nausea and Vomiting in Patients With Breast Cancer Undergoing Adjuvant Chemotherapy: A Randomized Controlled Clinical Trial

PURPOSE

To determine the effects of oral cryotherapy (OC) on the anticipatory, and acute nausea and vomiting of patients with breast cancer who are receiving adjuvant chemotherapy.

PATIENTS AND METHODS

Seventy eligible patients with breast cancer were assigned to 2 groups by stratified randomization. This parallel grouped, randomized, clinical trial used the ice application protocol. OC application for an intervention group (IG, n = 35) was performed in 3 stages: i) instructions on by the investigator at the hospital; ii) the implementation accompanied by the investigator at the hospital; iii) the individual application of at home by patients. The IG had been doing the application for 12 weeks. The patients in the control group (CG, n = 35) received standard care. Additionally, Rhodes Index of Nausea Vomiting, and Retching, and EORTC QLQ-C30 Life Quality Index were conducted on the first (T1 = cycle 1 day 0), second (T2 = cycle 2 day 21), third (T3 = cycle 3 day 42), and fourth (T4 = cycle 4 day 63) cycles of adjuvant chemotherapy.

RESULTS

The anticipatory nausea scores in the T2 and T4, IG were significantly lower than the CG (P < .05). In the T3, all symptom sub-dimensions except symptom occurrence (t = -0,48; P = .63) of the IG were significantly lower than those of the CG (P < .05). In the T1, T2, T3, and T4, acute nausea, acute vomiting, acute retching, and anticipatory retching scores, were significantly lower than the CG (P < .05).

CONCLUSION

OC alone was effective and safe for the treatment of nausea and vomiting. The results of this study showed the clinical applicability of OC in the management of nausea and vomiting.

Effects of visual and aromatic stimulations on the perception of five fundamental tastes

Taste perception is affected by various environmental factors. In the present study, we investigated the effects of visual and aromatic stimulations on stress responses and taste perception. Fourteen young healthy participants were assessed for stress levels and taste intensities under 5 different conditions: normal (no stimuli), watching an action scene, watching a forest scene, sniffing a rosemary aroma, and sniffing a lavender aroma. Compared to participants under the action scene condition, participants under the forest scene or under the rosemary aroma condition showed significantly lower stress levels. Furthermore, the forest scene condition significantly increased the saltiness intensity, whereas the rosemary aroma condition significantly increased the bitterness intensity. A positive or negative correlation was observed between the stress level and taste intensity of sourness and saltiness, respectively. These findings indicate that visual image and aroma have the potential to change taste perception as well as modulate stress conditions.

Does the indoor thermal environment influence the dominant sensation in a functional beverage attribute?

Different thermal environments can affect human productivity with repercussions on cognitive ability and physiological changes. However, the direct effect of room temperature on the sensations of food in the mouth during consumption is not yet well established. This study aimed to investigate the effect of indoor temperature on dominant sensations during intake of a beverage containing non-nutritive sweeteners. The temporal dominance of sensations (TDS) technique was used to evaluate seven functional beverages with different non-nutritive sweeteners. Sixty consumers participated in the test, attending 3 days of laboratory analysis with strictly controlled indoor temperatures (20, 24, and 26 °C). The indoor temperature affected the TDS curves of four functional beverages, with emphasis on the colder environment, which accentuated the sensation of bitter taste in the samples sweetened with stevia and neohesperidin. In the warmer environment, a TDS peak of fruit flavor was observed for the sucrose-sweetened sample, while the neotame-sweetened sample presented lower dominance rate for sweetness. The sensory performance of the samples sweetened with non-nutritive sweeteners, determined by the dominance rate of attributes, can change over time in different indoor temperatures. PRACTICAL APPLICATION: Cold and warm environments can affect the consumer's decision to buy beverages, but the effect of the indoor temperature on the taste sensation of beverages has not been elucidated. The objective of this research was to evaluate whether the indoor temperature can affect the dominance of sensations during the consumption of a low-calorie beverage. The results showed that the cold environment prolonged the sensation of bitter taste in the beverages sweetened with natural sweeteners, which can help the nonalcoholic beverage industry to choose another type of sweetener, considering a new product sensory influence facto: room temperature.

History of Cranial Nerve-Implanted Stimulators in Otolaryngology

This article aims to clearly understand the historical development of cranial nerve-implanted stimulators in otolaryngology. The authors also discuss cranial nerve history; initial theory of the functional concept of animal spirit; electrical nerve impulse theory; first electrical otolaryngology cranial nerve stimulation devices; and the development of implanted stimulators.

The orotrigeminal system

The trigeminal sensory nerve fiber branches supply afferent information from the skin and mucous membranes of the face and head and the oral cavity regarding information on temperature, touch, and pain. Under normal conditions, the trigeminal nerve serves to provide important information from nerve fibers and tissues using specialized receptors sensitive for irritant and painful stimuli. The current scientific consensus indicates that nerve endings responsible for chemical and thermal sensitivity of the skin and mucous membranes are the same nerves responsible for nociception. This "chemesthetic sense" allows many vertebrates to detect chemical agonists that induce sensations such as touch, burning, stinging, tingling, or changes in temperature. Research has been under way for many years to determine how exposure of the oral and/or nasal cavity to compounds that elicit pungent or irritant sensations can produce these sensations. In addition, these chemicals can alter other sensory information such as taste and smell to affect the flavor of foods and beverages. We now know that these 'chemesthetic molecules' are agonists of molecular receptors, which exist on primary afferent nerve fibers that innervate the orofacial area. However, under pathophysiologic conditions, over- or underexpression or activity of these receptors may lead to painful orotrigeminal syndromes. Some of these individual receptors are discussed in detail, including transient receptor potential channels and acid sensing ion channels, among others.

Awareness of dysgeusia and gustatory tests in patients undergoing chemotherapy for breast cancer

PURPOSE

We analyzed the prevalence of gustatory test abnormalities in breast cancer (BC) patients undergoing chemotherapy.

METHODS

We enrolled 43 BC patients undergoing chemotherapy and 38 BC patients who had never undergone chemotherapy (control group). Two gustatory tests were conducted: an instillation method examining the threshold for four basic taste stimuli and an electrogustometry method measuring the threshold for perception with electric stimulation at the front two-thirds of the tongue (cranial nerve VII) and at the back third of the tongue (cranial nerve IX). The results of the two gustatory tests and clinicopathological factors were compared between the chemotherapy and control groups and between patients with and without awareness of dysgeusia in the chemotherapy group.

RESULTS

In the chemotherapy group, 19 (44%) patients were aware of dysgeusia and 8 (19%) had hypogeusia using the instillation method. Although more patients had parageusia in the chemotherapy than control group, no significant differences in the results of the two gustatory tests were observed. Patients with dysgeusia awareness had a higher threshold at cranial nerve IX using the electrogustometry method than those without dysgeusia awareness; no significant differences in hypogeusia were observed using the instillation method. In fact, 74% (14/19) of patients with dysgeusia awareness could identify the four tastes accurately using the instillation method. Similar results were observed for the instillation and electrogustometry methods at cranial nerve VII.

CONCLUSIONS

While approximately half of the chemotherapy patients were aware of dysgeusia, 81% (35/43) of them could accurately identify the four basic tastes using the instillation method.

Extraoral Taste Receptor Discovery: New Light on Ayurvedic Pharmacology

More and more research studies are revealing unexpectedly important roles of taste for health and pathogenesis of various diseases. Only recently it has been shown that taste receptors have many extraoral locations (e.g., stomach, intestines, liver, pancreas, respiratory system, heart, brain, kidney, urinary bladder, pancreas, adipose tissue, testis, and ovary), being part of a large diffuse chemosensory system. The functional implications of these taste receptors widely dispersed in various organs or tissues shed a new light on several concepts used in ayurvedic pharmacology (dravyaguna vijnana), such as taste (rasa), postdigestive effect (vipaka), qualities (guna), and energetic nature (virya). This review summarizes the significance of extraoral taste receptors and transient receptor potential (TRP) channels for ayurvedic pharmacology, as well as the biological activities of various types of phytochemical tastants from an ayurvedic perspective. The relative importance of taste (rasa), postdigestive effect (vipaka), and energetic nature (virya) as ethnopharmacological descriptors within Ayurveda boundaries will also be discussed.