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Natural genetic variation can have a pronounced influence on human taste perception, which in turn may influence food preference and dietary choice. Genome-wide association studies represent a powerful tool to understand this influence. To help optimize the design of future genome-wide-association studies on human taste perception we have used the well-known TAS2R38-PROP association as a tool to determine the relative power and efficiency of different phenotyping and data-analysis strategies. The results show that the choice of both data collection and data processing schemes can have a very substantial impact on the power to detect genotypic variation that affects chemosensory perception. Based on these results we provide practical guidelines for the design of future GWAS studies on chemosensory phenotypes. Moreover, in addition to the TAS2R38 gene past studies have implicated a number of other genetic loci to affect taste sensitivity to PROP and the related bitter compound PTC. None of these other locations showed genome-wide significant associations in our study. To facilitate further, target-gene driven, studies on PROP taste perception we provide the genome-wide list of p-values for all SNPs genotyped in the current study.

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.

Sweet taste perception and preference play crucial roles in dietary habits and health outcomes. Understanding the genetic basis of taste thresholds and preferences can provide insights into individual differences in dietary behavior and susceptibility to metabolic disorders such as type 2 diabetes mellitus (T2DM). In Zambia, there is paucity of data concerning taste perception and preference in relation to genetics among diabetic and non-diabetic individuals. This study aimed to determine the relationship between the genotype and sweet taste thresholds, among individuals with and without T2DM in Zambia. A cross-sectional study was conducted among 89 adults at Livingstone University Teaching Hospital (42 non-diabetic and 47 diabetics). Saliva samples were used to determine the TRPV1 rs4790522, and TAS1R3 rs307355 genotype. We assessed sweet taste threshold and preference using a series of aqueous sucrose solutions. Demographic characteristics, anthropometrics, lifestyle factors, and dietary habits were collected using a structured questionnaire. Sweet taste threshold positively correlated with preferred concentration in both groups (p < 0.05). A higher proportion of PwT2D with elevated preferred sweet concentrations carried one or both homozygous risk alleles (77.8%, TT/AA). When compared to healthy controls, PwT2D had higher BMI, systolic and diastolic blood pressure, and pulse rate. They also exhibited higher taste thresholds but lower preferred concentrations, though this group was significantly older, potentially confounding results. These findings suggest taste perception and genetic variation may differ in PwT2D, highlighting the need for further research in Sub-Saharan African populations to inform personalized, cost-effective treatment strategies. However, studies with a larger sample size are required to validate our findings.

Fatty acid taste (FAT) perception is involved in the regulation of dietary fat intake, where impaired FAT is associated with increased fatty food intake. There are a number of FAT receptors identified on human taste cells that are potentially responsible for FAT perception. Manipulating dietary fat intake, and in turn FAT perception, would elucidate the receptors that are associated with long-term regulation of FAT perception. The present study aimed to assess associations between diet-mediated changes to FAT receptors and FAT perception in humans. A co-twin randomised controlled trial was conducted, where each matching twin within a pair were randomly allocated to either an 8-week low-fat (LF; <20 % energy fat) or an 8-week high-fat (HF; >35 % energy fat) diet. At baseline and week 8, fungiform papillae were biopsied in the fasted state and FAT receptor gene expressions (cluster of differentiation 36 ( CD36 ), free fatty acid receptor 2 ( FFAR2 ), FFAR4 , G protein-coupled receptor 84 ( GPR84 ) and a delayed rectifying K + channel (K + voltage-gated channel subfamily A member 2; KCNA2 )) were measured using RT-PCR; and FAT threshold (FATT) was assessed using three-alternate forced choice methodology. Linear mixed models were fitted, adjusting for correlation between co-twins. Intake was compliant with the study design, with the LF and HF groups consuming 14·8 and 39·9 % energy from fat, respectively. Expression of FFAR4 increased by 38 % in the LF group ( P = 0·023; time–diet interaction P = 0·063). Δ FFAR4 (Δ, week 8–baseline) was associated with Δfat intake (g) ( = −159·4; P < 0·001) and ΔFATT ( = −8·8; P = 0·016). In summary, FFAR4 is involved in long-term diet-mediated changes to FAT perception. Manipulating dietary fat intake, and therefore FFAR4 expression, might aid in reducing taste-mediated passive overconsumption of fatty foods.

Interpreting the relationship between different taste function tests of different stimuli, such as chemical and electrical stimulation, is still poorly understood. This study aims to analyze visually as well as quantitatively how to interpret the relationship of results between taste function tests using different stimuli. Patients who underwent the whole mouth test and Electrogustometry (EGM) at a tertiary medical center between August 2018 and December 2018 were reviewed retrospectively with electronic medical records. Of the 110 patients, a total of 86 adults who self-reported that their taste function was normal through a questionnaire were enrolled. EGM measured the thresholds of the chorda tympani (CT) and glossopharyngeal nerve (GL) area of the tongue. The whole mouth test measured detection and recognition thresholds for sweet, salty, bitter, sour, and umami taste. Statistical analyses of Pearson’s, Spearman’s rank and polyserial correlation and multidimensional scaling (MDS) was performed. The EGM threshold for the average value of both CT regions and the recognition threshold of the whole mouth test were significantly correlated in sweet, salty, bitter, and sour taste (r = 0.244–0.398, P  < 0.05), and the detection threshold was correlated only significant in sweet (r = 0.360, P  = 0.007). In the MDS analysis results, the three-dimensional ( D ) solution was chosen over the 2- D solution because of the lower stress. Detection-, recognition threshold of whole mouth test and EGM thresholds of CT and GL area, those were standardized by Z-score, formed well-distinguished sections in the MDS analyses. The EGM threshold of the CT area was closer to the detection and recognition thresholds than the EGM threshold of the GL area. In general, the EGM threshold was closer to the recognition threshold than the detection threshold for each taste. Overall, visualization of the relationship of whole mouth test and EGM by MDS was in good agreement with quantitative analysis. EGM and whole mouth test seem to reflect different aspects of taste. However, when interpreting the EGM results, the EGM threshold of the CT area will show more similarity to the recognition threshold than the detection threshold for the whole mouth test.

Background The aim of this review is to evaluate the relationship between weight status and taste perception and preference of sweet, salt, fat, bitter, and sour through reviewing observational and interventional studies with objective methods. Methods A comprehensive literature search was performed in 6 online databases of PubMed, Scopus, Web of Science, Cochrane, Embase, and Google Scholar up to October 2021. The following keywords were used in the search strategy: (Taste OR \"Taste Perception\" OR \"Taste Threshold\" OR \"Taste preference\" OR \"Taste sensitivity\" OR \"Taste changes\") AND (weight OR \"Weight gain\" OR \"weight loss\" OR \"weight change\"). Results Most observational studies indicate that four taste sensitivities or perceptions (especially sweet and salt taste perception) are lower in subjects with overweight and obesity. The longitudinal studies reported that sweet and fat preference is increased along with weight gain in adults. It is concluded that taste perceptions are decreased in individuals with overweight and obesity, especially in men. Also, taste perception and preference change after weight loss but not significantly. Conclusion It is suggested that the results of the interventional studies are not conclusive and need further studies with the same and standard design adjusting cofounding variables including genetic, gender, age and food condition of subjects.

The artificial sweetener isomalt is widely used due to its low caloric, non-diabetogenic and non-cariogenic properties. Although the sweetening potency of isomalt has been reported to be lower than that of sucrose, no data on the sensitivity of humans for this polyol are available. Using an up-down, two-alternative forced choice staircase procedure we therefore determined taste detection thresholds for isomalt in human subjects (n = 10; five females and five males) and compared them to taste preference thresholds, determined using a two-bottle preference test of short duration, in a highly frugivorous nonhuman primate, the spider monkey (n = 4; one female, three males). We found that both species detected concentrations of isomalt as low as 20 mM. Both humans and spider monkeys are less sensitive to isomalt than to sucrose, which is consistent with the notion of the former being a low-potency sweetener. The spider monkeys clearly preferred all suprathreshold concentrations tested over water, suggesting that, similar to humans, they perceive isomalt as having a purely sweet taste that is indistinguishable from that of sucrose. As isomalt, like most sweet-tasting polyols, may elicit gastric distress when consumed in large quantities, the present findings may contribute to the choice of appropriate amounts and concentrations of this sweetener when it is employed as a sugar substitute or food additive for human consumption. Similarly, the taste preference threshold values of spider monkeys for isomalt reported here may be useful for determining how much of it should be used when it is employed as a low-caloric sweetener for frugivorous primates kept on a vegetable-based diet, or when medication needs to be administered orally.

Background: Childhood obesity is a growing public health challenge, with altered taste perception potentially influencing food choices and contributing to weight gain. Objective: To determine detection thresholds for linoleic acid (fat taste) and sucrose (sweet taste) in children aged 6–12 years, and to explore associations with obesity, dietary intake, and food preferences. Methods: In this cross-sectional study, 100 Tunisian children (mean age: 8.05 ± 1.44 years; 54% girls; 45 obese, 55 non-obese) were recruited from an educational support center in Nabeul. Taste sensitivity was evaluated using the 3-alternative forced choice (3-AFC) method with ascending concentrations of linoleic acid (0.018–12.0 mM) for fat taste and sucrose (0.00125–0.32 mol/L) for sweet taste. Participants were categorized as tasters or non-tasters based on detection thresholds. Anthropometric measurements, 24 h dietary recalls, food frequency questionnaires, and food preference assessments were also conducted. Results: Low taste sensitivity was common (93% for sweet, 49% for fat). Girls were more often fat tasters than boys (68.6% vs. 31.4%, p = 0.003). Children with obesity had higher fat taste thresholds (median 3.00 mM, range 0.37–12.0) than non-obese peers (median 1.50 mM, range 0.018–6.0; p = 0.012), indicating reduced fat taste sensitivity. Linear regression showed a significant positive association between fat taste threshold and BMI (p = 0.001), meaning higher detection thresholds corresponded to higher BMI. Sweet taste thresholds did not differ significantly between children with and without obesity (p = 0.731). Sweet non-tasters consumed more sucrose (85.9 ± 64.9 g/d vs. 70.3 ± 62.3 g/d; p = 0.033) and reported more frequent table sugar use (p = 0.047). Fat non-tasters consumed more magnesium (425 ± 414 mg/d vs. 287 ± 60.8 mg/d; p = 0.026) and fiber (22.9 ± 7.51 g/d vs. 20.3 ± 5.32 g/d; p = 0.048) and reported higher intake frequencies of cheese (p = 0.039), sour cream (p = 0.004), and fast food (p = 0.012). Food preferences reflected similar patterns, with non-tasters generally rating high-fat or high-sugar foods more favorably. While most children demonstrated high detection thresholds, girls showed significantly higher fat taste sensitivity compared to boys (p = 0.03). Children with obesity exhibited significantly higher fat taste detection thresholds compared to non-obese children (p = 0.012), with thresholds ranging from 0.37 to 12.0 mM versus 0.018 to 6.0 mM, respectively. No significant difference was observed for sweet taste perception between weight groups (p = 0.731). Conclusions: Nearly half of the children exhibited reduced fat taste sensitivity, which was moderately associated with obesity and positively linked to BMI.

Declines in sensory functioning with aging are evident for many of the senses. In the present study, thresholds were determined for somatosensory (warming and cooling temperature, pain, touch, and two-point discrimination) and taste stimuli in 178 healthy individuals aged 20-89 yrs. Somatosensory stimuli were applied to the upper lip (glabrous skin) and the chin (hairy skin). The sample was divided into two groups, based on a bimodal split “< 45 yrs” and “≥ 65 yrs”. In all instances, there were elevations in thresholds for the older individuals. Further, males were less sensitive than females for cool at the chin site, for touch, and for sour taste. We conclude that there are elevations in sensory thresholds with age for multimodal somatosensory and gustatory senses.

The loss of taste and smell is a common symptom of COVID-19, affecting individuals' quality of life and nutritional status. Detecting sweet thresholds during infection and recovery periods can assist in implementing dietary modifications and nutritional strategies for these patients. To investigate the changes and differences in sweet detection thresholds of confirmed COVID-19 patients on Day 1, Day 10, and Day 14 of the infection and recovery periods. The demographic factors such as gender, smoking status, BMI, and age group were abstracted on Excel sheet from the medical health records for confirmed COVID-19 patients, who were admitted to King Fahad General Hospital in Jeddah, Saudi Arabia, a COVID-19 care facility, from September 2021 to July 2022. Sweet detection thresholds were determined using a pair-wise comparison procedure and sugar solutions with varying concentrations, arranged in ascending order and presented to participants until the lowest detected concentration was noted after three consecutive positive detections, with the median just noticeable difference (JND) value calculated as the population average threshold. Sensory tests were conducted on COVID-19 patients during their infection and recovery periods to evaluate their taste sensation thresholds. The demographic factors of gender, smoking status, BMI, and age group were considered in the analysis. A total of 37 patients who met the inclusion criteria of the study were enrolled as participants. Significant variances in sweet detection thresholds were observed among the COVID-19 patients, with consistent decreases over the three testing days, indicating increasing sucrose sensitivity. Infected men showed significant returns to sweet detection thresholds on Day 14 compared to women, while infected smokers exhibited greater recoveries than non-smokers. Overweight patients had consistently elevated thresholds and recovery rates that were comparable to those of normal-weight patients by Day 14, while younger patients had lower thresholds than their older counterparts. On Day 14, the thresholds had significantly recovered to a level comparable to that of healthy individuals (approximately 0.23%). These findings suggest that sweet detection thresholds can be used as a marker for assessing the progression and recovery of COVID-19 patients. These findings highlight the importance of recognizing and managing alterations in sweet detection thresholds promptly in COVID-19 patients, as this could positively impact dietary management, nutritional recommendations, and interventions during infection and recovery periods.