Contributory role of sex differences in the variations of gustatory function

The sweet taste signalling pathways in the oral cavity and the gastrointestinal tract affect human appetite and food intake: a review

Sweet taste is associated with food reward and energy source in the form of carbohydrate. Excessive sweet consumption is blamed for the prevalence of obesity. However, evidence for the potential of sweet taste to influence food intake and bodyweight regulation in humans remains unclear. The purpose of this review was to examine the physiological responses relevant to sweet taste mechanisms and the impact on appetite control. The literature was examined for studies that assessed the effects of non-nutritive sweeteners and natural sugars on hormonal secretions and neural activations via oral and gastrointestinal pathways. The findings indicated that a network of sweet taste signalling pathways in the oral cavity and the gut seem to mediate hormonal responses and some metabolism differences in neural circus that orchestrating the hunger-satiety cycle. Individual variations of sweet taste perception which is modulated by hormonal and genetic factors have been associated with dietary nutrient and sugar consumption.

Effects of sex on ethanol conditioned place preference, activity and variability in C57BL/6J and DBA/2J mice

Previous studies of ethanol drinking in rodents have shown greater intake in females than in males, but the reasons behind this difference are unknown. To address one possible interpretation of the drinking difference, these studies tested the hypothesis that female and male mice differ in sensitivity to the rewarding effects of ethanol using the conditioned place preference (CPP) procedure. To increase the generalizability of the results, sex differences were examined in two inbred mouse strains known to differ in their sensitivity to ethanol reward: C57BL/6J (B6) and DBA/2J (D2). Mice were conditioned in an unbiased CPP procedure using either 1 or 2 g/kg ethanol. To detect possible differences in learning rate, they were tested once at the midpoint of conditioning and again after conditioning ended. As expected, CPP was stronger with 2 g/kg than with 1 g/kg, and D2 mice generally showed stronger CPP than B6 mice. However, there were no sex differences in the rate of CPP acquisition or in CPP magnitude, suggesting no sex difference in ethanol reward sensitivity as indexed by CPP. Nevertheless, there were sex differences in locomotor activity. B6 females were generally more active than B6 males during CPP acquisition whereas D2 females were slightly less active than D2 males during both CPP acquisition and preference testing. Unexpectedly, female mice showed more variability than males in the behavioral measures recorded in these studies, encouraging greater attention to variability in the design, analysis and interpretation of future studies of sex differences in mice.

A bittersweet symphony: Evidence for taste-sound correspondences without effects on taste quality-specific perception

Music has been associated with taste and shown to influence the dining experience. We asked whether sound that is associated with taste affects taste perception of food. In two studies (study 1: N = 20, 13 women; study 2: N = 20, 17 women), participants evaluated the taste of cinder toffee while listening to either of two soundscapes associated with sweet and bitter taste, respectively, or no sound. In study 1, participants rated the taste on a visual-analog scale (VAS) anchored with "bitter" and "sweet", aiming to replicate a previous study (Crisinel et al., ). In contrast, four separate scales were used in study 2 to report the extent of bitter, sweet, sour, and salty taste to test whether taste qualities were influenced by sound differentially. Additionally, taste intensity and pleasantness were rated in both studies. Taste intensity was increased in the presence of a sound, while pleasantness was not affected. In study 1, sound shifted bitter-sweet ratings in the direction of the congruent sound, i.e. samples tasted sweeter with "sweet" sound and more bitter with "bitter" sound, replicating Crisinel et al.'s () results. However, this effect was abolished when a "no-sound" control was included in the statistical model. Taste ratings in study 2 showed no effect of sound on any specific taste quality, suggesting that the influence of sound on taste in study 1 reflects an artifact of the scale rather than an actual shift in perception. Together, the data provide evidence for taste-sound correspondences without effects on taste-quality specific perception.

Effects of an odor or taste stimulus applied to an artificial teat on the suckling behavior of newborn dairy calves

Background

In their first days of life, dairy calves in artificial rearing systems often have difficulty using an artificial teat for feeding.

Methods

We examined the age at which calves are able to stand up voluntarily and suckle as well as their suckling behavior when presented with a plain dry teat versus a dry teat modified with a presumably attractive odor or taste substance. Single-housed newborn dairy calves (n = 51) were presented for ten consecutive days with a two-minute two-choice test, in which suckling time was recorded for 1) a plain (control) teat versus a glucose-coated teat (taste test) and 2) a plain teat versus a teat with a "Freshly Cut Grass" odor (odor test).

Results

On average, the calves were able to stand up voluntarily and suckle from the second or third day of age on. The "Freshly Cut Grass" odor had no significant effect on their suckling behavior. In contrast, the calves showed a significant preference for suckling the glucose-coated teat and displayed a significantly longer total suckling time in the taste test compared to the odor test. There were no significant differences between sexes regarding suckling behavior.

Conclusion

The results of the present study show that glucose had a significant effect on the calves’ teat preference and significantly increased total suckling time with a dry artificial teat. As such, glucose may increase suckling motivation in non-efficient drinkers or ill calves with low motivation to suckle.

Electronic supplementary material

The online version of this article (10.1186/s40781-018-0164-x) contains supplementary material, which is available to authorized users.

Taste of phytocompounds: A better predictor for ethnopharmacological activities of medicinal plants than the phytochemical class?

ETHNOPHARMACOLOGICAL RELEVANCE

Understanding the patterns that shape traditional medical knowledge is essential for accelerating ethnopharmacological progress. According to Ayurveda, medicinal plants that belong to different taxa, but which have similar taste, may display similar (ethno)pharmacological activities (EPAs) (Bhishagratna, 1998; Sharma and Dash, 2006).

AIM OF THE STUDY

To understand the patterns that govern the distribution of herbal EPAs in Ayurveda and to evaluate the potential concordance between chemical class or taste of the constituent phytocompounds and EPAs.

MATERIAL AND METHODS

A mixed database (PhytoMolecularTasteDB) was constructed for Ayurvedic medicinal plants by integrating modern data (medicinal plant composition, phytochemical taste) with traditional data (ethnopharmacological activities of plant). PhytoMolecularTasteDB contains 431 Ayurvedic medicinal plants, 94 EPAs, 223 chemical classes of phytocompounds and 438 herbal tastants. Potential global or individual associations between chemical classes/taste of the phytoconstituents and EPAs were statistically analyzed.

RESULTS

There was no global statistical correlation between the various chemical classes of phytocompounds and EPAs, although there were several individual correlations. The results suggest the existence of a global statistical correlation (besides several individual correlations) between the plant "molecular taste" (various taste-based classes of phytocompounds) and EPAs.

CONCLUSIONS

These results suggest that phytochemical taste may be more relevant than chemical class for EPAs prediction.

Prolonged Exposure to Monosodium Glutamate in Healthy Young Adults Decreases Perceived Umami Taste and Diminishes Appetite for Savory Foods

Background

Research suggests that increased consumption of sweet, salt, or fat is associated with diminished perceived taste intensity and shifted preferences for the respective stimulus. It is unknown whether a similar effect occurs with the consumption of umami.

Objective

The aim of the study was to investigate the influence of habitual exposure to umami stimuli on umami taste perception, hedonics, and satiety.

Methods

Fifty-eight healthy men (n = 16) and women (n = 42) participated in a parallel-group, randomized controlled study. The normal-weight [mean ± SD body mass index (kg/m2): 21.8 ± 2.2] group of young adults (mean ± SD age: 22.7 ± 6.2 y) consumed vegetable broth daily for 4 wk. The broth for the treatment group (n = 28) was supplemented with 3.8 g monosodium glutamate (MSG), whereas the control group (n = 30) consumed a sodium-matched broth without MSG. Perceived umami taste intensity and discrimination in MSG solutions; liking, wanting, and preference of a variety of umami-rich foods; satiation and satiety from an ad libitum meal; and anthropometric measures were evaluated at baseline and at week 4. General linear models assessed the effect of treatment on change from baseline for all outcomes and tested for effect modification of sex.

Results

Relative to controls, increased consumption of MSG for 4 wk diminished umami taste in women (8.4 units on generalized Labeled Magnitude Scale; 95% CI: -13.8, -3.1 units; P = 0.013). The desire for and intake of savory foods decreased after MSG treatment in both sexes with an ad libitum meal (desire: -7.7 units; 95% CI: -13.7, -1.7 units; P = 0.04; intake: -36 g; 95% CI: -91, 19 g; P = 0.04).

Conclusion

Our results highlight that a month-long diet high in umami stimuli attenuates perceived umami taste and appetite for savory foods in a young, healthy population. Our findings contribute to the understanding of food choice, a factor in the development and maintenance of obesity, as well as the etiology of protein-related health conditions such as osteoporosis and kidney disease. This study is registered at www.clinicaltrials.gov as NCT03010930.

Carbohydrate mouth rinse does not affect performance during a 60-min running race in women

This study examined the effect of carbohydrate mouth rinsing on endurance running performance in women. Fifteen female recreational endurance runners, who used no oral contraceptives, ran two races of 1-h duration on an indoor track (216-m length) at 18:00 h after an 8-h fast with a 7-days interval between races, corresponding to the 3^rd-10th day of each premenopausal runner's menstrual cycle, or any day for the postmenopausal runners. In a double-blind random order, participants rinsed their mouth with 25 ml of either a 6.4% carbohydrate (RCHO) or a placebo solution (RP). No fluid was ingested during exercise. Serum 17β-Εstradiol (P = 0.59) and Progesterone (P = 0.35) did not differ between treatments. There was no difference in 1-hour running performance (RCHO: 10,621.88 ± 205.98 m vs. RP: 10,454.00 ± 206.64 m; t = 1.784, P = 0.096). Furthermore, the mean percentage effect (±99%CI) of RCHO relative to RP, 1.67% (-1.1% to 4.4%), and Cohen's effect size (d = 0.21) support a trivial outcome of RCHO for total distance covered. In conclusion, carbohydrate mouth rinsing did not improve 60-min track running performance in female recreational runners competing in a low ovarian hormone condition, after an 8-h fast and when no fluid was ingested during exercise.

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.