Bitter taste markers explain variability in vegetable sweetness, bitterness, and intake

Taste Receptors: New Players in Sperm Biology

Taste receptors were first described as sensory receptors located on the tongue, where they are expressed in small clusters of specialized epithelial cells. However, more studies were published in recent years pointing to an expression of these proteins not only in the oral cavity but throughout the body and thus to a physiological role beyond the tongue. The recent observation that taste receptors and components of the coupled taste transduction cascade are also expressed during the different phases of spermatogenesis as well as in mature spermatozoa from mouse to humans and the overlap between the ligand spectrum of taste receptors with compounds in the male and female reproductive organs makes it reasonable to assume that sperm "taste" these different cues in their natural microenvironments. This assumption is assisted by the recent observations of a reproductive phenotype of different mouse lines carrying a targeted deletion of a taste receptor gene as well as the finding of a significant correlation between human male infertility and some polymorphisms in taste receptors genes. In this review, we depict recent findings on the role of taste receptors in male fertility, especially focusing on their possible involvement in mechanisms underlying spermatogenesis and post testicular sperm maturation. We also highlight the impact of genetic deletions of taste receptors, as well as their polymorphisms on male reproduction.

Modeling Associations between Chemosensation, Liking for Fats and Sweets, Dietary Behaviors and Body Mass Index in Chronic Smokers

Chronic smokers have a greater risk for altered chemosensation, unhealthy dietary patterns, and excessive adiposity. In an observational study of chronic smokers, we modeled relationships between chemosensation, fat/carbohydrate liking, smoking-associated dietary behaviors, and body mass index (BMI). Also tested in the model was liking for sweet electronic cigarette juice (e-juice). Smokers (n = 135, 37 ± 11 years) were measured for: Taste genetics (intensity of 6-n-propylthiouracil-PROP); taste (NaCl and quinine intensities) and olfactory (odor identification) function; liking for cherry e-juice; and weight/height to calculate BMI. Smokers survey-reported their food liking and use of smoking for appetite/weight control. Structural equation models tested direct and indirect relationships between chemosensation, fat/carbohydrate liking, dietary behaviors, and BMI. In good-fitting models, taste intensity was linked to BMI variation through fat/carbohydrate liking (greater PROP intensity→greater NaCl intensity→greater food liking→higher BMI). Olfactory function tended to predict sweet e-juice liking, which, in turn, partially mediated the food liking and BMI association. The path between smoking-associated dietary behaviors and BMI was direct and independent of chemosensation or liking. These findings indicate that taste associates with BMI in chronic smokers through liking of fats/carbohydrates. Future research should determine if vaping sweet e-juice could improve diet quality and adiposity for smokers.

Taste disorders are partly genetically determined: Role of the TAS2R38 gene, a pilot study

OBJECTIVES/HYPOTHESIS

Taste sensitivity varies greatly among individuals influencing eating behavior and health, consequently the disorders of this sense can affect the quality of life. The ability to perceive the bitter of thiourea compounds, such as phenylthiocarbamide (PTC), has been largely reported as a marker of the general taste sensitivity, food preferences, and health. PTC sensitivity is mediated by the TAS2R38 receptor and its genetic common variants. We study the role of the TAS2R38 receptor in taste disorders with the aim of understanding if these can be genetically determined.

STUDY DESIGN

Prospective cohort study.

METHODS

Differences in the PTC responsiveness between the patients cohort and healthy controls were assessed. All subjects received standardized tests for smell and taste function and were genotyped for the TAS2R38 gene.

RESULTS

PAV/PAV homozygous patients gave high PTC ratings, whereas PAV/AVI genotypes reported lower values, which are similar to those determined in AVI/AVI or rare genotypes. In addition, the patients cohort did not meet the Hardy-Weinberg equilibrium at the TAS2R38 locus, showing a very low frequency of subjects carrying the PAV/AVI diplotype. Independently, in healthy controls who were in equilibrium at the locus, PAV/PAV homozygous and heterozygous rated PTC bitterness higher compared to AVI/AVI or rare genotypes.

CONCLUSIONS

Our findings, by showing that an only taster haplotype (PAV) is not sufficient to evoke high responses of TAS2R38 receptor in patients with taste disorders, suggest that the genetic constitution may represent a risk factor for the development of taste disorders.

LEVEL OF EVIDENCE

2c Laryngoscope, 129:E307-E312, 2019.

Investigation of the link between PROP taste perception and vegetables consumption using FAOSTAT data

In this work we investigated, in populations located in Central Asia, the relationship between PROP taste perception and vegetables liking and consumption using FAOSTAT dataset. Collected data were analysed using distance matrices, Mantel test and Pearson correlation. Populations showing similar ability in tasting PROP bitterness are more similar as respect to vegetable consumption (r = 0.63, p-value = .05). Moreover, a significant negative correlation was found between the percentage of Non Taster (NT) in different countries and the percentage of vegetable consumption (r = -0.87, p-value = .02), while a significant positive correlation emerged between the percentage of Super Taster (ST) and the percentage of vegetable liking (r = 0.87, p-value = .02). In our work we showed that differences in bitter perception among populations contributes to differences in vegetable liking and vegetable consumption. More in detail, populations with higher percentage of ST consume more vegetables than population where the majority of individuals are NT.

Interactions between Bitter Taste, Diet and Dysbiosis: Consequences for Appetite and Obesity

The type 2 family of taste receptors (T2Rs) detect and respond to bitter tastants. These receptors are expressed throughout the gastrointestinal (GI) tract, with location dependant roles. In the oral cavity, T2Rs are involved in the conscious perception of bitter tastants, while in the lower GI tract they have roles in chemoreception and regulation of GI function. Through these diverse roles, these receptors may be involved in modulating appetite and diet, with consequences for weight regulation and obesity. Interestingly, the concentration of T2Rs in the GI tract is greatest in the large intestine, the organ with the densest colonisation of bacteria. The gut microbiome has been the subject of intense research, as a plethora of roles linking microbiota to human health continue to be uncovered. Of particular interest is the microbial signature associated with obesity. Obesity is a leading health concern, and advances in our understanding of this disease are needed. Diet is a known modifiable factor in the development of obesity. However, diet only partially explains disease risk. Changes in microbial energy harvesting by the microbiota plays a role in obesity, and the composition of these energy harvesting populations may be controlled by taste receptors. This review explores T2Rs as a potential link between obesity and the human GI microbiome.

Political orientation, political environment, and health behaviors in the United States

Political orientation (Republican/Democrat and conservative/liberal) and political environment (geo-spatial political party affiliated voting patterns) are both associated with various health outcomes, including mortality. Modern disease etiology in the U.S. suggests that many of our health outcomes derive from behaviors and lifestyle choices. Thus, we examine the associations of political orientation and political environment with health behaviors. We used the Annenberg National Health Communication Survey (ANHCS) data, which is a nationally representative U.S. survey fielded continuously from 2005 through 2012. The health behaviors studied include health information search, flu vaccination, excessive alcohol consumption, tobacco consumption, exercise, and dietary patterns. Democrats/liberals had higher odds of cigarette smoking and excessive drinking compared to Republicans/conservatives. Whereas, Republicans/conservatives ate fewer servings and fewer varieties of fruit and vegetables; ate more high fat and processed foods; and engaged in less in-depth health information searches compared to Democrats/liberals. Also, conservatives had lower odds of exercise participation than liberals; whereas Republicans had lower odds of flu vaccination. Greater Republican vote share in the 2008 and 2012 presidential elections at the state and/or county levels was associated with higher odds of flu vaccination and smoking cigarettes and lower odds of avoiding fat/calories, avoiding fast/processed food, eating a variety of fruits and vegetables, and eating more servings of fruit. We use the distinct cognitive-motivational styles attributed to political orientation in discussing the findings. Health communication strategies could leverage these relationships to produce tailored and targeted messages as well as to develop and advocate for policy.

Environmental Forces that Shape Early Development: What We Know and Still Need to Know

Understanding health requires more than knowledge of the genome. Environmental factors regulate gene function through epigenetics. Collectively, environmental exposures have been called the "exposome." Caregivers are instrumental in shaping exposures in a child's initial years. Maternal dietary patterns, physical activity, degree of weight gain, and body composition while pregnant will influence not only fetal growth, but also the infant's metabolic response to nutrients and energy. Maternal over- or underweight, excess caloric intake, nutrient imbalances, glucose dysregulation, and presence of chronic inflammatory states have been shown to establish risk for many later chronic diseases. During the period from birth to age 3 y, when the infant's metabolic rate is high and synaptogenesis and myelination of the brain are occurring extremely rapidly, the infant is especially prone to damaging effects from nutrient imbalances. During this period, the infant changes from a purely milk-based diet to one including a wide variety of foods. The process, timing, quality, and ultimate dietary pattern acquired are a direct outcome of the caregiver-infant feeding relationship, with potentially lifelong consequences. More research on how meal time interactions shape food acceptance is needed to avoid eating patterns that augment existing disease risk. Traditional clinical trials in nutrition, meant to isolate single factors for study, are inadequate to study the highly interconnected realm of environment-gene interactions in early life. Novel technologies are being used to gather broad exposure data on disparate populations, employing pioneering statistical approaches and correlations applied specifically to the individual, based on their genetic make-up and unique environmental experiences.

Children Residing in Low-Income Households Like a Variety of Vegetables

Child vegetable intake falls far below the minimum recommended levels. Knowing which vegetables children may like help those responsible for providing vegetables to children to improve intake. The objective of this study was to measure vegetable liking for a wide variety of vegetables by a racially and ethnically diverse population of 9–12-year old children from low-income families. Children rated their liking of 35 vegetables using a 10-point hedonic scale. We tabulated the number of children that found each vegetable acceptable (ratings of ‘okay’ or above) and the number that found each vegetable unacceptable (ratings below ‘okay’). More than 50% of children who had tried a vegetable considered it acceptable. A large majority of the vegetables had mean ratings in the acceptable range. Corn was the most liked vegetable, closely followed by potatoes, lettuce, and carrots. Artichoke had the lowest mean liking, followed by onion and beets. We found children liked a wide variety of vegetables which offers counter evidence to the commonly held perception that children do not like vegetables.

Taste receptor polymorphisms and male infertility

STUDY QUESTION

Are polymorphisms of taste receptor genes associated with male infertility?

SUMMARY ANSWER

This study has showed the associations between three single nucleotide polymorphisms (SNPs) in taste receptors genes (TASR) and male infertility.

WHAT IS KNOWN ALREADY

Recent studies showed the expression of taste receptors in the testis and in spermatozoa, suggesting their possible role in infertility. The vast genetic variability in taste genes results in a large degree of diversity in various human phenotypes.

STUDY DESIGN, SIZE, DURATION

In this study, we genotyped 19 SNPs in 12 taste related genes in a total of 494 Caucasian male patients undergoing semen evaluation at the Centre of Couple Sterility of the Siena University Hospital. Consecutive patients were enrolled during infertility investigations from October 2014 to February 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Median age of the patients was 36 years (18-58) and 141 were smokers. Genotyping was performed using the allele-specific PCR. The statistical analysis was carried out using generalized linear model (GLM) to explore the association between age, smoking, the genetic polymorphisms and sperm parameters.

MAIN RESULTS AND THE ROLE OF CHANCE

We observed that the homozygous carriers of the (G) allele of the TAS2R14-rs3741843 polymorphism showed a decreased sperm progressive motility compared to heterozygotes and (A) homozygotes (P = 0.003). Moreover, the homozygous carriers of the (T) allele of the TAS2R3-rs11763979 SNP showed fewer normal acrosome compared with the heterozygous and the homozygous carriers of the (G) allele (P = 0.002). Multiple comparisons correction was applied and the Bonferroni-corrected critical P-value was = 0.003.

LIMITATIONS, REASONS FOR CAUTION

The analysis is restricted to SNPs within genes and to men of Caucasian ancestry.

WIDER IMPLICATIONS OF THE FINDINGS

In silico analyses strongly point towards a functional effect of the two SNPs: TAS2R14-rs3741843 regulates TAS2R43 expression, a gene that is involved in cilia motility and therefore could influences sperm mobility; the (T) allele of TAS2R3-rs11763979 increases the expression of the WEE2 antisense RNA one gene (WEE2-AS1). According to Genotype-Tissue Expression (GTEx) project the WEE2 gene is expressed in the testes where presumably it has the role of down regulating meiotic cell division. It is plausible to hypothesize that the WEE2-AS1 increased expression may down regulate WEE2 which in turn can alter the natural timing of sperm maturation increasing the number of abnormal sperm cells.

STUDY FUNDING/COMPETING INTEREST(S)

None.

TAS2R38 Predisposition to Bitter Taste Associated with Differential Changes in Vegetable Intake in Response to a Community-Based Dietary Intervention

Although vegetable consumption associates with decreased risk for a variety of diseases, few Americans meet dietary recommendations for vegetable intake. TAS2R38 encodes a taste receptor that confers bitter taste sensing from chemicals found in some vegetables. Common polymorphisms in TAS2R38 lead to coding substitutions that alter receptor function and result in the loss of bitter taste perception. Our study examined whether bitter taste perception TAS2R38 diplotypes associated with vegetable consumption in participants enrolled in either an enhanced or a minimal nutrition counseling intervention. DNA was isolated from the peripheral blood cells of study participants (N = 497) and analyzed for polymorphisms. Vegetable consumption was determined using the Block Fruit and Vegetable screener. We tested for differences in the frequency of vegetable consumption between intervention and genotype groups over time using mixed effects models. Baseline vegetable consumption frequency did not associate with bitter taste diplotypes (P = 0.937), however after six months of the intervention, we observed an interaction between bitter taste diplotypes and time (P = 0.046). Participants in the enhanced intervention increased their vegetable consumption frequency (P = 0.020) and within this intervention group, the bitter non-tasters and intermediate-bitter tasters had the largest increase in vegetable consumption. In contrast, in the minimal intervention group, the bitter tasting participants reported a decrease in vegetable consumption. Bitter-non tasters and intermediate-bitter tasters increased vegetable consumption in either intervention more than those who perceive bitterness. Future precision medicine applications could consider genetic variation in bitter taste perception genes when designing dietary interventions.

Bitter and sweet tasting molecules: It's complicated

"Bitter" and "sweet" are frequently framed in opposition, both functionally and metaphorically, in regard to affective responses, emotion, and nutrition. This oppositional relationship is complicated by the fact that some molecules are simultaneously bitter and sweet. In some cases, a small chemical modification, or a chirality switch, flips the taste from sweet to bitter. Molecules humans describe as bitter are recognized by a 25-member subfamily of class A G-protein coupled receptors (GPCRs) known as TAS2Rs. Molecules humans describe as sweet are recognized by a TAS1R2/TAS1R3 heterodimer of class C GPCRs. Here we characterize the chemical space of bitter and sweet molecules: the majority of bitter compounds show higher hydrophobicity compared to sweet compounds, while sweet molecules have a wider range of sizes. Importantly, recent evidence indicates that TAS1Rs and TAS2Rs are not limited to the oral cavity; moreover, some bitterants are pharmacologically promiscuous, with the hERG potassium channel, cytochrome P450 enzymes, and carbonic anhydrases as common off-targets. Further focus on polypharmacology may unravel new physiological roles for tastant molecules.

6-n-propylthiouracil taste disruption and TAS2R38 nontasting form in Parkinson's disease

BACKGROUND

The few studies that evaluated taste function in Parkinson's disease (PD) showed inconsistent results. The inherited ability to taste the bitter compound of 6-n-propylthiouracil has been considered to be a paradigm of general taste perception. 6-n-propylthiouracil taste perception is mediated by the TAS2R38 receptor, and reduced 6-n-propylthiouracil sensitivity has been associated with several diseases not typically related to taste function.

OBJECTIVES

We evaluated the 6-n-propylthiouracil taste perception and the TAS2R38 gene as genetic risk factors for the development of idiopathic PD in PD patients and healthy controls (HC).

METHODS

The 6-n-propylthiouracil taste perception was assessed by testing the responsiveness, and the ability to recognize, 6-n-propylthiouracil and sodium chloride. The participants were classified for 6-n-propylthiouracil taster status and genotyped for the TAS2R38 gene.

RESULTS

A significant increase in the frequency of participants classified as 6-n-propylthiouracil nontasters and a reduced ability to recognize bitter taste quality of 6-n-propylthiouracil were found in PD patients when compared with healthy controls. The results also showed that only 5% of PD patients had the homozygous genotype for the dominant tasting variant of TAS2R38, whereas most of them carried the recessive nontaster form and a high number had a rare variant.

CONCLUSIONS

Our results show that 6-n-propylthiouracil taster status and TAS2R38 locus are associated with PD. The 6-n-propylthiouracil test may therefore represent a novel, simple way to identify increased vulnerability to PD. Moreover, the presence of the nontasting form of TAS2R38 in PD may further substantiate that disease-associated taste disruption may represent a risk factor associated with the disease. © 2018 International Parkinson and Movement Disorder Society.

Consumer Acceptance Comparison Between Seasoned and Unseasoned Vegetables

Abstract

Recent findings show that approximately 87% of the U.S. population fail to meet the vegetable intake recommendations, with unpleasant taste of vegetables being listed as the primary reason for this shortfall. In this study, spice and herb seasoning was used to enhance palatability of vegetables, in order to increase consumer acceptance. In total, 749 panelists were screened and recruited as specific vegetable likers of the vegetable being tested or general vegetable likers. Four sessions were designed to evaluate the effect of seasoning within each type of vegetable, including broccoli, cauliflower, carrot, and green bean. Each panelist was only allowed to participate in one test session to evaluate only one vegetable type, so as to mitigate potential learning effect. Overall, the results showed that seasoned vegetables were significantly preferred over unseasoned vegetables (P < 0.001), indicating the sensory properties were significantly improved with seasoning. When general vegetable likers and specific vegetable likers were compared in terms of their preference between seasoned and unseasoned vegetables, the pattern varied across different vegetables; however, general trend of seasoned vegetable being preferred remained. The findings from this study demonstrate the effect of seasoning in enhancing consumer liking of vegetables, which may lead to increased consumption to be assessed in future studies.

Practical Application

To improve the sensory properties of vegetables, masking the bitter taste of vegetables using spice and herb seasoning are gaining increasing attention. Our findings suggest that the overall liking of vegetables could be improved by incorporating spice and herb seasonings that are specifically formulated for each vegetable. Ultimately, developing and commercializing spice and herb seasonings may aid to increase vegetable consumption, as well as expanding the vegetable seasoning market.

Is food refusal in autistic children related to TAS2R38 genotype?

Several studies suggest that atypical eating behaviors, in particular food selectivity, are more frequent in children with autism spectrum disorder (ASD). A link between bitter taste perception, namely PROP/PTC sensitivity and food preferences is known in healthy children. The aim of this study is to investigate whether genetic variants of the TAS2R38 taste receptor responsible for different bitter sensitivity could affect foods preferences and consequently food refusal in ASD children. We recruited 43 children with ASD and 41 with normotypic development (TD) with or without food selectivity, aged between 2 and 11 years. Children were characterized for bitter sensitivity by means of PROP strips and FACS analysis and genotyped for TAS2R38 polymorphisms. Food selectivity was assessed by a validated food preference questionnaire filled by parents. A statistically significant correlation between PROP sensitivity and food refusal was observed. Furthermore, a prevalence of the PAV-sensitive haplotype compared to the AVI-insensitive one was seen in ASD children with food selectivity. In agreement with the initial hypothesis the results show that food refusal in ASD children is mediated by bitter taste sensitivity thus suggesting that the bitter sensitivity test may be used as a device to orientate tailored food proposals for the practical management of food selectivity in ASD. Autism Res 2018, 11: 531-538. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

LAY SUMMARY

A variation of the gene TAS2R38, associated with bitter taste sensitivity, can cause a different perception of some foods. In particular, some children are hypersensitive to bitterness and show a more restricted repertoire of accepted foods. We evaluate bitter sensitivity in ASD children with or without food selectivity, through a simple bitter taste test with edible strips. The results show that food refusal in ASD children can be mediated by bitter taste sensitivity thus suggesting that the bitter sensitivity test may be used as a device to orientate tailored food proposals for the practical management of food selectivity in ASD.

Carbohydrate Taste Sensitivity Is Associated with Starch Intake and Waist Circumference in Adults

Background: Recent studies have proposed that humans may perceive complex carbohydrates and that sensitivity to simple carbohydrates is independent of sensitivity to complex carbohydrates. Variation in oral complex carbohydrate sensitivity may influence food consumption.Objective: This study aimed to investigate the associations between oral complex carbohydrate sensitivity, anthropometry, and dietary intake in adults.Methods: We assessed oral sensitivity to complex carbohydrates (maltodextrin and oligofructose) by measuring detection thresholds (DTs) and suprathreshold intensity perceptions (STs) for 34 participants, including 16 men (mean ± SEM age : 26.2 ± 0.4 y; range: 24-30 y) and 18 women (age: 29.4 ± 2.1 y; range: 24-55 y). We also measured height, weight, and waist circumference (WC) and participants completed a 4-d food diary and a food-frequency questionnaire.Results: Measurements of oral sensitivity to complex carbohydrates were significantly correlated with WC and dietary energy and starch intakes (DT: r = -0.38, P < 0.05; ST: r = 0.36-0.48, P < 0.05). When participants were grouped into tertiles, there were significant differences in WC and total energy or starch intakes for those who were more sensitive or experienced high intensity compared with those who were less sensitive or experienced low intensity. Being more sensitive or experiencing high intensity was associated with greater energy (7968-8954 kJ/d) and starch (29.1-29.8% of energy) intakes and a greater WC (88.2-91.4 cm) than was being less sensitive or experiencing low intensity (6693-7747 kJ/d, 20.9-22.2% of energy, and 75.5-80.5 cm, respectively).Conclusion: Complex carbohydrate sensing is associated with WC and consumption of complex carbohydrates and energy in adults. This trial was registered at anzctr.org.au as ACTRN12616001356459.

Factors Influencing the Phenotypic Characterization of the Oral Marker, PROP

In the last several decades, the genetic ability to taste the bitter compound, 6-n-propyltiouracil (PROP) has attracted considerable attention as a model for understanding individual differences in taste perception, and as an oral marker for food preferences and eating behavior that ultimately impacts nutritional status and health. However, some studies do not support this role. This review describes common factors that can influence the characterization of this phenotype including: (1) changes in taste sensitivity with increasing age; (2) gender differences in taste perception; and (3) effects of smoking and obesity. We suggest that attention to these factors during PROP screening could strengthen the associations between this phenotype and a variety of health outcomes ranging from variation in body composition to oral health and cancer risk.

The role of smell, taste, flavour and texture cues in the identification of vegetables

It has been shown that the identification of many foods including vegetables based on flavour cues is often difficult. The effect of providing texture cues in addition to flavour cues on the identification of foods and the effect of providing taste cues only on the identification of foods have not been studied. The aim of this study was to assess the role of smell, taste, flavour and texture cues in the identification of ten vegetables commonly consumed in The Netherlands (broccoli, cauliflower, French bean, leek, bell pepper, carrot, cucumber, iceberg lettuce, onion and tomato). Subjects (n = 194) were randomly assigned to one of four test conditions which differed in the sensory cues available for vegetable identification: taste, smell (orthonasal), flavour (taste and smell) and flavour-texture (taste, smell and texture). Blindfolded subjects were asked to identify the vegetable from a list of 24 vegetables. Identification was the highest in the flavour-texture condition (87.5%). Identification was significantly lower in the flavour condition (62.8%). Identification was the lowest when only taste cues (38.3%) or only smell cues (39.4%) were provided. For four raw vegetables (carrot, cucumber, onion and tomato) providing texture cues in addition to flavour cues did not significantly change identification suggesting that flavour cues were sufficient to identify these vegetables. Identification frequency increased for all vegetables when perceived intensity of the smell, taste or flavour cue increased. We conclude that providing flavour cues (taste and smell) increases identification compared to only taste or only smell cues, combined flavour and texture cues are needed for the identification of many vegetables commonly consumed in The Netherlands.

Could Vaping be a New Weapon in the Battle of the Bulge?

IMPLICATIONS

Obesity is set to overtake tobacco smoking in many countries as the primary cause of several high-cost diseases. Tobacco smoking mitigates weight gain through nicotine's effect on the brain and metabolism. Smoking, however, is associated with many illnesses and premature death and appropriately has been discouraged leading to declining prevalence rates. This article explores the emerging perception that vaping electronic cigarettes with nicotine and flavors could deliver similar appetite and weight control effects as smoking. The potential to reduce risks associated with excess weight deserves exploration. An initial research agenda is suggested.

Genetic variation in bitter taste receptor gene TAS2R38, PROP taster status and their association with body mass index and food preferences in Indian population

Polymorphisms in bitter taste receptor gene TAS2R38 alter the ability to sense the intensity of bitterness of phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP). Genetic variation in sensitivity towards PTC and PROP may affect food preferences and susceptibility to certain diseases. This is the first study aimed at investigating frequency and distribution of TAS2R38 haplotypes in an Indian cohort. Additionally, we studied the association of TAS2R38 and PROP taster status with BMI and food preference. Three hundred and ninety three healthy adults who were 19-55years of age were selected as a convenience sample from 4 geographical regions of India. Single nucleotide polymorphisms (SNPs) of TAS2R38 (rs713598, s1726866 and rs10246939) were analyzed using polymerase chain reaction-restriction fragment length polymorphism. The prevalence of PAV/PAV diplotype was 9.9% and that of AVI/AVI diplotype was 43.76% among this Indian population. PROP status was determined on the basis of its threshold concentration of detecting bitterness, as evaluated by one-solution test. The PROP status revealed 25.95% supertasters, 32.06% medium tasters and 41.98% non-tasters (NT). BMI neither significantly (p>0.05) correlated with TAS2R38 genotypes nor with PROP taster status. Food preferences did not significantly (p>0.05) correlate with TAS2R38 diplotypes or PROP phenotypes.

Taste Perception of Sweet, Sour, Salty, Bitter, and Umami and Changes Due to l-Arginine Supplementation, as a Function of Genetic Ability to Taste 6-n-Propylthiouracil

Behavioral reaction to different taste qualities affects nutritional status and health. 6-n-Propylthiouracil (PROP) tasting has been reported to be a marker of variation in taste perception, food preferences, and eating behavior, but results have been inconsistent. We showed that l-Arg can enhance the bitterness intensity of PROP, whilst others have demonstrated a suppression of the bitterness of quinine. Here, we analyze the taste perception of sweet, sour, salty, bitter, and umami and the modifications caused by l-Arg supplementation, as a function of PROP-taster status. Taste perception was assessed by testing the ability to recognize, and the responsiveness to, representative solutions of the five primary taste qualities, also when supplemented with l-Arg, in subjects classified as PROP-tasting. Super-tasters, who showed high papilla density, gave higher ratings to sucrose, citric acid, caffeine, and monosodium l-glutamate than non-tasters. l-Arg supplementation mainly modified sucrose perception, enhanced the umami taste, increased NaCl saltiness and caffeine bitterness only in tasters, and decreased citric acid sourness. Our findings confirm the role of PROP phenotype in the taste perception of sweet, sour, and bitter and show its role in umami. The results suggest that l-Arg could be used as a strategic tool to specifically modify taste responses related to eating behaviors.

Structural equation modeling of associations among taste-related risk factors, taste functioning, and adiposity

OBJECTIVE

Variation in taste perception and exposure to risk factors of taste alterations have been independently linked with elevated adiposity. Using a laboratory database, taste-adiposity associations were modeled and examined for whether taste functioning mediates the association between taste-related risk factors and adiposity.

METHODS

Healthy women (n = 407, 35.5 ± 16.9 y) self-reported histories of risk factors of altered taste functioning (tonsillectomy, multiple ear infections, head trauma) and were assessed for taste functioning (tongue-tip and whole-mouth intensities of quinine and salt) and density of taste papillae. Twenty-four percent had elevated waist circumferences; thirty-nine percent had overweight or obesity. Using structural equation modeling, direct and indirect associations between taste-related risk factors, taste functioning, and adiposity were tested.

RESULTS

In models with good fit, elevated central adiposity was explained directly by history of risk factors (tonsillectomy, multiple ear infections) and directly by lower taste functioning (lower tongue-tip taste function, lower papillae density). Risk factors of taste alterations were significantly associated with lower taste functioning, with taste mediating the association between head trauma and reduced adiposity.

CONCLUSIONS

This large laboratory-based study supports associations between taste-related risk factors, taste functioning, and adiposity. These findings need to be confirmed with other population-based studies, including the National Health and Nutrition Examination Survey 2013-2014 taste data.

Higher body mass index and lower intake of dairy products predict poor glycaemic control among Type 2 Diabetes patients in Malaysia

This cross-sectional study was designed to determine factors contributing to glyceamic control in order to provide better understanding of diabetes management among Type 2 Diabetes patients. A pre-tested structured questionnaire was used to obtain information on socio-demographic and medical history. As a proxy measure for glycaemic control, glycosylated haemoglobin (HbA1c) was obtained as secondary data from the medical reports. Perceived self-care barrier on diabetes management, diet knowledge and skills, and diet quality were assessed using pretested instruments. With a response rate of 80.3%, 155 subjects were recruited for the study. Mean HbA1c level of the subjects was 9.02 ± 2.25% with more than 70% not able to achieve acceptable level in accordance to WHO recommendation. Diet quality of the subjects was unsatisfactory especially for vegetables, fruits, fish and legumes as well as from the milk and dairy products group. Higher body mass index (BMI), poorer medication compliance, lower diet knowledge and skill scores and lower intake of milk and dairy products contributed significantly on poor glycaemic control. In conclusion, while perceived self-care barriers and diet quality failed to predict HbA1c, good knowledge and skill ability, together with appropriate BMI and adequate intake of dairy products should be emphasized to optimize glycaemic control among type 2 diabetes patients.

Sensory perception of and salivary protein response to astringency as a function of the 6-n-propylthioural (PROP) bitter-taste phenotype

Individual differences in astringency perception are poorly understood. Astringency from tannins stimulates the release of specific classes of salivary proteins. These proteins form complexes with tannins, altering their perceived astringency and reducing their bioavailability. We studied the bitter compound, 6-n-propylthioural (PROP), as a phenotypic marker for variation in astringency perception and salivary protein responses. Seventy-nine subjects classified by PROP taster status rated cranberry juice cocktail (CJC; with added sugar) supplemented with 0, 1.5 or 2.0g/L tannic acid (TA). Saliva for protein analyses was collected at rest, or after stimulation with TA or cranberry juice (CJ; without added sugar). CJC with 1.5g/L tannic acid was found to be less astringent, and was liked more by PROP non-taster males than PROP taster males, consistent with the expectation that non-tasters are less sensitive to astringency. Levels of acidic Proline Rich Proteins (aPRPs) and basic Proline Rich Proteins (bPRPs) decreased after TA, while levels of aPRPs, bPRPs and Cystatins unexpectedly rose after CJ. Increases in bPRPs and Cystatins were only observed in PROP tasters. The PROP phenotype plays a gender-specific, but somewhat limited role in the perceived astringency of tannic-acid supplemented, cranberry juice cocktail. The PROP phenotype (regardless of gender) may also be involved in the release of salivary proteins previously implicated in oral health.

First objective evaluation of taste sensitivity to 6-n-propylthiouracil (PROP), a paradigm gustatory stimulus in humans

Practical and reliable methods for the objective measure of taste function are critically important for studying eating behavior and taste function impairment. Here, we present direct measures of human gustatory response to a prototypical bitter compound, 6-n-propyltiouracil (PROP), obtained by electrophysiological recordings from the tongue of subjects who were classified for taster status and genotyped for the specific receptor gene (TAS2R38), and in which taste papilla density was determined. PROP stimulation evoked negative slow potentials that represent the summated depolarization of taste cells. Depolarization amplitude and rate were correlated with papilla density and perceived bitterness, and associated with taster status and TAS2R38. Our study provides a robust and generalizable research tool for the quantitative measure of peripheral taste function, which can greatly help to resolve controversial outcomes on the PROP phenotype role in taste perception and food preferences, and be potentially useful for evaluating nutritional status and health.

Sensory determinants of stated liking for vegetable names and actual liking for canned vegetables: A cross-country study among European adolescents

Sensory properties are reported as one of the main factors hindering an appropriate vegetable intake by the young. In the present work the sensory determinants of likings for vegetables were explored in adolescents of four European countries (Denmark, n = 88; France, n = 206; Italy, n = 110 and United Kingdom, n = 93). A questionnaire was designed to study cross country differences in stated liking for and familiarity with a list of vegetables popular among European markets (between-vegetable approach). A within-vegetable comparison approach with actual tasting was used to analyze differences and similarities in liking for canned pea and sweet corn samples across the countries. A close positive relationship between stated liking and familiarity was found. Irrespective of the country, one group of highly liked vegetables (carrots, tomatoes, green salad) was identified, characterized by innately liked tastes (sweet, umami), delicate flavour and bright appealing colour. A second group of highly disliked vegetables consists of cauliflowers and broccoli, characterized by disliked sensations such as bitter taste and objectionable flavour. Internal Preference Maps from actual liking scores indicate that the generally disliked tastes (bitter, sour), are clearly correlated with a negative hedonic response for both peas and sweet corn. The hedonic valence of a generally well accepted taste such as salty and texture descriptors depends on the type of vegetable. Internal preference maps from actual liking data indicate that flavour and appearance descriptors of the distinct sensory properties of each type of vegetable positively affect liking, while the intensity of unusual flavours is related to sample disliking.

Genetic and environmental influences on food preferences in adolescence

BACKGROUND

Food preferences vary substantially among adults and children. Twin studies have established that genes and aspects of the shared family environment both play important roles in shaping children's food preferences. The transition from childhood to adulthood is characterized by large gains in independence, but the relative influences of genes and the environment on food preferences in late adolescence are unknown.

OBJECTIVE

The aim of this study was to quantify the contribution of genetic and environmental influences on food preferences in older adolescents.

DESIGN

Participants were 2865 twins aged 18-19 y from the TEDS (Twins Early Development Study), a large population-based cohort of British twins born during 1994-1996. Food preferences were measured by using a self-report questionnaire of 62 individual foods. Food items were categorized into 6 food groups (fruit, vegetables, meat or fish, dairy, starch foods, and snacks) by using factor analysis. Maximum likelihood structural equation modeling established genetic and environmental contributions to variations in preferences for each food group.

RESULTS

Genetic factors influenced a significant and substantial proportion of the variation in preference scores of all 6 food groups: vegetables (0.54; 95% CI: 0.47, 0.59), fruit (0.49; 95% CI: 0.43, 0.55), starchy foods (0.32; 95% CI: 0.24, 0.39), meat or fish (0.44; 95% CI: 0.38, 0.51), dairy (0.44; 95% CI: 0.37, 0.50), and snacks (0.43; 95% CI: 0.36, 0.49). Aspects of the environment that are not shared by 2 twins in a family explained all of the remaining variance in food preferences.

CONCLUSIONS

Food preferences had a moderate genetic basis in late adolescence, in keeping with findings in children. However, by this older age, the influence of the shared family environment had disappeared, and only aspects of the environment unique to each individual twin influenced food preferences. This finding suggests that shared environmental experiences that influence food preferences in childhood may not have effects that persist into adulthood.

Characterizing and improving the sensory and hedonic responses to polyphenol-rich aronia berry juice

Interest in nutrient-rich berry juices is growing, but their high polyphenol levels render them sensorily unappealing. Fifty adults, who were assessed for sensory phenotype and dietary behaviors, provided sensory and palatability ratings of juices from 'Viking' aronia berries for each of seven harvest weeks. By peak harvest, juice preference increased two-fold, averaging neither like/dislike. This hedonic shift was associated with: increases in juice sugars paralleling increases in perceived sweetness (maximum = weak); reductions in percent acidity paralleling reductions in sourness (minimum = moderate), astringency (minimum = to just above weak) and bitterness (minimum = just below weak). About 25% of adults liked the aronia juice, including adults who also liked an aqueous citric acid solution (average rating = moderately sour) or those who reported adventurous eating behaviors. Bitter taste phenotype, measured by propylthiouracil or quinine bitterness, failed to explain significant variation in juice sensation or preference. We also collected sensory and preference ratings from juice collected at peak harvest blended with sugar and/or sweet olfactory flavoring (10 ppm ethyl butyrate). Increasing juice sweetness by adding 5% sucrose decreased sourness and improved preference from weak dislike to weak like. Adding sweet olfactory flavoring decreased juice sourness without changing preference. Adding sweet flavoring and 3% sucrose resulted in reduction of sourness and improvements in preference ratings comparable to 5% added sucrose. Neither added sugar nor flavoring blocked juice astringency. In summary, these findings suggest that aronia juice, even from berries picked at peak harvest, appealed to only a few adults (sour likers or adventurous eaters). Although enhanced sweetness, with added sugar and sweet olfactory flavoring, improved aronia juice preference, broader sensory approaches are required to blunt astringency for greater consumer appeal.

Copy Number Variation in TAS2R Bitter Taste Receptor Genes: Structure, Origin, and Population Genetics

Bitter taste receptor genes (TAS2Rs) harbor extensive diversity, which is broadly distributed across human populations and strongly associated with taste response phenotypes. The majority of TAS2R variation is composed of single-nucleotide polymorphisms. However, 2 closely positioned loci at 12p13, TAS2R43 and -45, harbor high-frequency deletion (Δ) alleles in which genomic segments are absent, resulting in copy number variation (CNV). To resolve their chromosomal structure and organization, we generated maps using long-range contig alignments and local sequencing across the TAS2R43-45 region. These revealed that the deletion alleles (43Δ and 45Δ) are 37.8 and 32.2kb in length, respectively and span the complete coding region of each gene (~1kb) along with extensive up- and downstream flanking sequence, producing separate CNVs at the 2 loci. Comparisons with a chimpanzee genome, which contained intact homologs of TAS2R43, -45, and nearby TAS2Rs, indicated that the deletions evolved recently, through unequal recombination in a cluster of closely related loci. Population genetic analyses in 946 subjects from 52 worldwide populations revealed that copy number ranged from 0 to 2 at both TAS2R43 and TAS2R45, with 43Δ and 45Δ occurring at high global frequencies (0.33 and 0.18). Estimated recombination rates between the loci were low (ρ = 2.7×10(-4); r = 6.6×10(-9)) and linkage disequilibrium was high (D' = 1.0), consistent with their adjacent genomic positioning and recent origin. Geographic variation pointed to an African origin for the deletions. However, no signatures of natural selection were found in population structure or integrated haplotype scores spanning the region, suggesting that patterns of diversity at TAS2R43 and -45 are primarily due to genetic drift.