The Effects of Cranberry Polyphenol Extract (CPE) Supplementation on Astringency and Flavor Perception as a Function of PROP Taster Status and Other Individual Factors.

This study investigated whether PROP (6-n-propylthiouracil) taster status and other individual factors (gender, ethnicity, BMI, and age) are markers of variation in perceptions of astringency and other flavor attributes. Participants (n = 125) evaluated cranberry juice cocktail samples (CJC) supplemented with cranberry-derived polyphenol extract (CPE, added at 0, 0.3, 0.5 and 0.75 g/L), as well as control samples, unsweetened cranberry juice (CJ) and an aqueous solution of 0.75 g/L CPE. Subjects evaluated samples for key sensory attributes and overall liking using a 15 cm line scale. The data were analyzed using ANCOVA and machine learning tools (regression trees and random forest modeling) to examine if the latter approach would extract more meaningful insights about the roles of personal factors in sensory perceptions of cranberry-derived stimuli. ANCOVA revealed robust stimulus effects, but no effect of PROP taster status on astringency perception was observed. Several effects of PROP×gender, ethnicity, and other factors were observed on other sensory attributes and liking. ANCOVA and machine learning tools yielded similar findings, but regression trees provided a more visualized framework. These data show that PROP taster status has a limited role in astringency perception in complex samples and that other personal factors deserve greater focus in future research on astringency perception.

Daily Exposure to a Cranberry Polyphenol Oral Rinse Alters the Oral Microbiome but Not Taste Perception in PROP Taster Status Classified Individuals.

Diet and salivary proteins influence the composition of the oral microbiome, and recent data suggest that TAS2R38 bitter taste genetics may also play a role. We investigated the effects of daily exposure to a cranberry polyphenol oral rinse on taste perception, salivary proteins, and oral microbiota. 6-n-Propylthiouracil (PROP) super-tasters (ST, n = 10) and non-tasters (NT, n = 10) rinsed with 30 mL of 0.75 g/L cranberry polyphenol extract (CPE) in spring water, twice daily for 11 days while consuming their habitual diets. The 16S rRNA gene sequencing showed that the NT oral microbiome composition was different than that of STs at baseline (p = 0.012) but not after the intervention (p = 0.525). Principal coordinates analysis using unweighted UniFrac distance showed that CPE modified microbiome composition in NTs (p = 0.023) but not in STs (p = 0.096). The intervention also altered specific salivary protein levels (α-amylase, MUC-5B, and selected S-type Cystatins) with no changes in sensory perception. Correlation networks between oral microbiota, salivary proteins, and sensory ratings showed that the ST microbiome had a more complex relationship with salivary proteins, particularly proline-rich proteins, than that in NTs. These findings show that CPE modulated the oral microbiome of NTs to be similar to that of STs, which could have implications for oral health.

Time Course of Salivary Protein Responses to Cranberry-Derived Polyphenol Exposure as a Function of PROP Taster Status.

Astringency is a complex oral sensation, commonly experienced when dietary polyphenols interact with salivary proteins. Most astringent stimuli alter protein levels, which then require time to be replenished. Although it is standard practice in astringency research to provide breaks in between stimuli, there is limited consensus over the amount of time needed to restore the oral environment to baseline levels. Here we examined salivary protein levels after exposure to 20 mL of a model stimulus (cranberry polyphenol extract, 0.75 g/L CPE) or unsweetened cranberry juice (CJ), over a 10 min period. Whole saliva from healthy subjects (n = 60) was collected at baseline and after 5 and 10 min following either stimulus. Five families of proteins: basic proline-rich proteins (bPRPs); acidic proline-rich proteins (aPRPs); histatins; statherin; and S-type cystatins, were analyzed in whole saliva via HPLC-low resolution-ESI-IT-MS, using the area of the extracted ion current (XIC) peaks. Amylase was quantified via immunoblotting. In comparison to baseline (resting), both stimuli led to a rise in levels of aPRPs (p < 0.000) at 5 min which remained elevated at 10 min after stimulation. Additionally, an interaction of PROP taster status and time was observed, wherein super-tasters had higher levels of amylase in comparison to non-tasters after stimulation with CJ at both timepoints (p = 0.014-0.000). Further, male super-tasters had higher levels of bPRPs at 5 min after stimulation with both CJ and CPE (p = 0.015-0.007) in comparison to baseline. These data provide novel findings of interindividual differences in the salivary proteome that may influence the development of astringency and that help inform the design of sensory experiments of astringency.

Taste, Nutrition, and Health.

The sensation of flavour reflects the complex integration of aroma, taste, texture, and chemesthetic (oral and nasal irritation cues) from a food or food component. Flavour is a major determinant of food palatability-the extent to which a food is accepted or rejected-and can profoundly influence diet selection, nutrition, and health. Despite recent progress, there are still gaps in knowledge on how taste and flavour cues are detected at the periphery, conveyed by the brainstem to higher cortical levels and then interpreted as a conscious sensation. Taste signals are also projected to central feeding centers where they can regulate hunger and fullness. Individual differences in sensory perceptions are also well known and can arise from genetic variation, environmental causes, or a variety of metabolic diseases, such as obesity, metabolic syndrome, and cancer. Genetic taste/smell variation could predispose individuals to these same diseases. Recent findings have also opened new avenues of inquiry, suggesting that fatty acids and carbohydrates may provide nutrient-specific signals informing the gut and brain of the nature of the ingested nutrients. This special issue on "Taste, Nutrition, and Health" presents original research communications and comprehensive reviews on topics of broad interest to researchers and educators in sensory science, nutrition, physiology, public health, and health care.

Effects of CD36 Genotype on Oral Perception of Oleic Acid Supplemented Safflower Oil Emulsions in Two Ethnic Groups: A Preliminary Study.

Previous studies demonstrate humans can detect fatty acids via specialized sensors on the tongue, such as the CD36 receptor. Genetic variation at the common single nucleotide polymorphism rs1761667 of CD36 has been shown to differentially impact the perception of fatty acids, but comparative data among different ethnic groups are lacking. In a small cohort of Caucasian and East Asian young adults, we investigated if: (1) participants could detect oleic acid (C18:1) added to safflower oil emulsions at a constant ratio of 3% (w/v); (2) supplementation of oleic acid to safflower oil emulsions enhanced perception of fattiness and creaminess; and (3) variation at rs1761667 influenced oleic acid detection and fat taste perception. In a 3-alternate forced choice test, 62% of participants detected 2.9 ± 0.7 mM oleic acid (or 0.08% w/v) in a 2.8% safflower oil emulsion. Supplementation of oleic acid did not enhance fattiness and creaminess perception for the cohort as a whole, though East Asians carrying the GG genotype perceived more overall fattiness and creaminess than their AA genotype counterparts (P < 0.001). No differences were observed for the Caucasians. These preliminary findings indicate that free oleic acid can be detected in an oil-in-water emulsion at concentrations found in commercial oils, but it does not increase fattiness or creaminess perception. Additionally, variation at rs1761667 may have ethnic-specific effects on fat taste perception.

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.

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.

Consumption of a high-fat soup preload leads to differences in short-term energy and fat intake between PROP non-taster and super-taster women.

Taste blindness to the bitterness of PROP (6-n-propylthiouracil) has been used as a genetic marker for food selection and adiposity. We have shown that PROP non-taster (NT) women have higher BMIs and habitually consume more fat and energy than either medium-taster (MT) or super-taster (ST) women. These data imply that differences in dietary selection underlie the body weight differences among PROP taster groups. However, no studies investigated energy compensation in women classified by PROP status. We investigated if NTs would compensate less accurately for the calories and fat in a high-fat soup preload in a subsequent test meal compared to MTs and STs. Energy intake from a buffet meal was measured in 75 healthy non-diet-restrained, lean women 30 min after the ingestion of a high-fat soup preload (0.8 kcal/g; 55% calories from fat), calculated to represent 10% of resting energy expenditure for each subject, or the same volume of water. Subjects (n = 20-28/taster group) ate a standard breakfast followed 3 hr later by an ad-libitum buffet lunch, on two occasions. There were no differences in energy intake or macronutrient selection across taster groups after water. After soup, NTs consumed more energy than STs. Fat intake (as %-energy) was higher in NTs (46.4% ± 2.4) compared to either MTs (36.1 ± 1.9%) or STs (38.1% ± 2.3; p < 0.05). NTs overate by 11% ± 5 after the soup compared to MTs and STs who underrate by 16% ± 6 and 26% ± 10, respectively (p < 0.01). These data suggest that small discrepancies in short-term energy compensation and selection of fat after a mixed-nutrient, high-fat preload may play a role in positive energy balance and increased adiposity in women with the PROP non-taster phenotype.

Relationships of PROP Taste Phenotype, Taste Receptor Genotype, and Oral Nicotine Replacement Use.

INTRODUCTION: Recommended dosage of oral nicotine replacement therapy (NRT) product is often not achieved in smoking cessation attempts. n-6-propylthiouracil (PROP) bitter taste phenotype may be a potential risk factor for non-adherence to oral NRT products due to their bitter taste. There is limited literature on this phenotype in the context of smoking and none in relation to oral NRT pharmacotherapy. METHODS: The association of PROP taste phenotype with NRT usage and sensory response to products was examined. In a cross-over experimental design, 120 participants received a 1 week supply of nicotine inhalers and 1 week of nicotine lozenges with random assignment to order. Mixed effects linear model analyses were conducted. RESULTS: PROP taste phenotype and taste receptor genotype were not associated with NRT usage or sensory response to NRT, after adjusting for other factors. However, PROP non-tasters used a higher number of lozenges per day (continuous exposure) than nicotine cartridges (intermittent exposure). Unexpectedly, half of baseline PROP non-tasters shifted to taster phenotype 2 weeks after smoking cessation or reduction. Menthol cigarette smokers identified higher NRT strength of sensation scores than nonmenthol smokers. Taste receptor genotype was related to PROP taste phenotype (Kendall τ = .591, p = .0001). CONCLUSIONS: A nonsignificant relationship of PROP phenotype and NRT usage may be associated with NRT under-dosing and limited variance in the outcome variable. PROP non-tasters' greater use of lozenges is consistent with nicotine exposure being less aversive to non-tasters. Further research of this and other factors impacting NRT usage are warranted to effectively inform smoking cessation pharmacotherapy.

Energy intake and diet selection during buffet consumption in women classified by the 6-n-propylthiouracil bitter taste phenotype.

BACKGROUND: Exposure to a variety of energy-dense foods promotes increased energy intake and adiposity. Taste blindness to the bitterness of 6-n-propylthiouracil (PROP) has been associated with increased adiposity in women and might be linked to an increased energy intake and greater selection of dietary fat. OBJECTIVE: We investigated whether PROP nontaster (NT) women would consume more fat and energy in a buffet setting than medium taster (MT) or supertaster (ST) women. DESIGN: Seventy-five non-diet-restrained, lean, young women [mean ± SEM BMI (in kg/m²): 21.5 ± 0.6; age: 26.1 ± 1.3 y) ate lunch and dinner in the laboratory for 3 consecutive days under the following 2 conditions: ad libitum control meals (CONTs) or high-variety buffet meals (BUFFs). A standard breakfast was consumed each day of the study (4 - d washout between conditions). RESULTS: NTs and MTs consumed more energy and fat (as the percentage of energy) from BUFFs than did STs (P < 0.01), which contributed to higher daily energy intakes in these 2 groups of women during BUFFs (2149 ± 49 kcal/d for NTs and 2209 ± 48 kcal/d for MTs compared with 1933 ± 50 kcal/d for STs; P < 0.01). Together, NTs and MTs consumed an extra 246 kcal/d during BUFFs than during CONTs. In addition, compared with STs, NTs and MTs consumed more added fats and sweets (servings/d; P < 0.003) and more energy from snacks (P < 0.01) across all study days. CONCLUSIONS: NT and MT women consume more daily energy than do ST women when eating in a buffet setting, which is a common type of dietary exposure. This increase in energy intake over time could contribute to a positive energy balance and increased adiposity previously reported in these women.

The gustin (CA6) gene polymorphism, rs2274333 (A/G), as a mechanistic link between PROP tasting and fungiform taste papilla density and maintenance.

Taste sensitivity to PROP varies greatly among individuals and is associated with polymorphisms in the bitter receptor gene TAS2R38, and with differences in fungiform papilla density on the anterior tongue surface. Recently we showed that the PROP non-taster phenotype is strongly associated with the G variant of polymorphism rs2274333 (A/G) of the gene that controls the salivary trophic factor, gustin. The aims of this study were 1) to investigate the role of gustin gene polymorphism rs2274333 (A/G), in PROP sensitivity and fungiform papilla density and morphology, and 2) to investigate the effect of this gustin gene polymorphism on cell proliferation and metabolic activity. Sixty-four subjects were genotyped for both genes by PCR techniques, their PROP sensitivity was assessed by scaling and threshold methods, and their fungiform papilla density, diameter and morphology were determined. In vitro experiments examined cell proliferation and metabolic activity, following treatment with saliva of individuals with and without the gustin gene mutation, and with isolated protein, in the two iso-forms. Gustin and TAS2R38 genotypes were associated with PROP threshold (p=0.0001 and p=0.0042), but bitterness intensity was mostly determined by TAS2R38 genotypes (p<0.000001). Fungiform papillae densities were associated with both genotypes (p<0.014) (with a stronger effect for gustin; p=0.0006), but papilla morphology was a function of gustin alone (p<0.0012). Treatment of isolated cells with saliva from individuals with the AA form of gustin or direct application of the active iso-form of gustin protein increased cell proliferation and metabolic activity (p<0.0135). These novel findings suggest that the rs2274333 polymorphism of the gustin gene affects PROP sensitivity by acting on fungiform papilla development and maintenance, and could provide the first mechanistic explanation for why PROP super-tasters are more responsive to a broad range of oral stimuli.

Marked increase in PROP taste responsiveness following oral supplementation with selected salivary proteins or their related free amino acids.

The genetic predisposition to taste 6-n-propylthiouracil (PROP) varies among individuals and is associated with salivary levels of Ps-1 and II-2 peptides, belonging to the basic proline-rich protein family (bPRP). We evaluated the role of these proteins and free amino acids that selectively interact with the PROP molecule, in modulating bitter taste responsiveness. Subjects were classified by their PROP taster status based on ratings of perceived taste intensity for PROP and NaCl solutions. Quantitative and qualitative determinations of Ps-1 and II-2 proteins in unstimulated saliva were performed by HPLC-ESI-MS analysis. Subjects rated PROP bitterness after supplementation with Ps-1 and II-2, and two amino acids (L-Arg and L-Lys) whose interaction with PROP was demonstrated by (1)H-NMR spectroscopy. ANOVA showed that salivary levels of II-2 and Ps-1 proteins were higher in unstimulated saliva of PROP super-tasters and medium tasters than in non-tasters. Supplementation of Ps-1 protein in individuals lacking it in saliva enhanced their PROP bitter taste responsiveness, and this effect was specific to the non-taster group.(1)H-NMR results showed that the interaction between PROP and L-Arg is stronger than that involving L-Lys, and taste experiments confirmed that oral supplementation with these two amino acids increased PROP bitterness intensity, more for L-Arg than for L-Lys. These data suggest that Ps-1 protein facilitates PROP bitter taste perception and identifies a role for free L-Arg and L-Lys in PROP tasting.

Greater energy intake from a buffet meal in lean, young women is associated with the 6-n-propylthiouracil (PROP) non-taster phenotype.

Taste blindness to 6-n-propylthiouracil (PROP) is a common phenotype that has been associated with increased adiposity in women, and might be linked to increased selection of dietary fats. Since exposure to a variety of high-fat/energy-dense foods is known to promote excess energy intake, we investigated if PROP non-taster women would consume more fat and/or energy in a buffet setting than super-taster women. Subjects were non-diet restrained, lean, young women; 14 were non-tasters and 18 were super-tasters. Subjects ate lunch in the laboratory on four separate days. On one day they consumed an ad libitum, fixed-item lunch (control). On the other three days they consumed different buffet lunches (pizza/tacos/sub sandwiches with salad bar and choice of beverage and dessert). Energy intake from the control lunch did not differ between groups. When intake was averaged across the buffet lunches, non-taster women consumed 357+64 kcal more energy than during the control lunch (88% more), whereas super-taster women consumed 198+71 kcal more energy than during the control lunch (38% more). Neither fat intake nor selection of high-fat foods differed between groups. These data suggest that non-taster women consume more energy from a buffet meal than super-taster women, but not more fat. Increased responsiveness to a variety of energy-dense foods could be one mechanism contributing to increased energy intake and greater adiposity in non-taster women.

Overeating styles and adiposity among multiethnic youth.

Reasons for inconsistent associations between overeating styles and adiposity among youth may include differences in effects by age, gender, or ethnicity; failure to control for social desirability of response; or adiposity measurement limitations. This study examined the relationship between overeating styles and multiple measures of adiposity, after controlling for social desirability and testing for moderation by ethnicity, age, and gender. Data from 304 9-10 year old children and 264 17-18 year old adolescents equally representing African American, Hispanic, and White ethnic groups were extracted from a larger cross-sectional study. Measures included the Dutch Eating Behavior Questionnaire (restrained, external, and emotional overeating subscales), the "Lie Scale" from the Revised Children's Manifest Anxiety Scale, and measured weight, height, waist circumference, and triceps skinfold. BMI z-score and a global adiposity index were calculated. Mixed model linear regression showed restraint was positively and external eating was negatively related to measures of adiposity. African American youth had a stronger inverse association between emotional eating and adiposity than White or Hispanic youth. Relationships were not influenced by social desirability nor moderated by age or gender. Overeating styles are related to adiposity in nearly all youth but the nature of these associations are moderated by ethnicity.

Serum retinol-binding protein 4 (RBP4) and retinol in a cohort of borderline obese women with and without gestational diabetes.

OBJECTIVES: To evaluate whether serum RBP4 correlates with gestational diabetes mellitus (GDM) in a cohort of borderline obese (BMI>30) pregnant women. DESIGN AND METHODS: Serum RBP4 and retinol were measured in pregnant women with (n=12) and without (n=10) GDM. RESULTS: RBP4, retinol and RBP4:retinol molar ratio were not different between the groups and were not associated with markers of insulin resistance. CONCLUSIONS: GDM is not associated with RBP4 or retinol among borderline obese pregnant women.

Genetic variation in bitter taste and plasma markers of anti-oxidant status in college women.

Genetic taste sensitivity to the bitterness of 6-n-propylthiouracil (PROP) is a potential marker for food selection. Compared with non-tasters, PROP tasters, especially super-tasters, are less accepting of cruciferous and other green vegetables, bitter citrus, added fats and chili pepper. If super-tasters avoid these foods, it may be hypothesized that they would have lower plasma antioxidant concentrations. Ninety-three healthy, non-smoking college women who did not use vitamins/supplements were classified by PROP-taster status using the paper disk method. Each participant provided a fasting blood sample that was assayed for vitamin C, beta-carotene, alpha-tocopherol, lycopene, uric acid and total peroxyl-trapping antioxidant capacity. Plasma alpha-tocopherol was lower in super-tasters than in non-tasters (P<0.05), but no other indices differed among the groups. These findings suggest that PROP status does not associate with overall antioxidant status, but may be related to alpha-tocopherol intake derived principally from vegetable oils and green vegetables.