Relationship between bitter-taste receptor genotype and solid medication formulation usage among young children: a retrospective analysis

Taste Preference-Related Genetic Polymorphisms Modify Alcohol Consumption Behavior of the Hungarian General and Roma Populations

Harmful alcohol consumption has been considered a major public health issue globally, with the amounts of alcohol drunk being highest in the WHO European Region including Hungary. Alcohol consumption behaviors are complex human traits influenced by environmental factors and numerous genes. Beyond alcohol metabolization and neurotransmitter gene polymorphisms, taste preference-related genetic variants may also mediate alcohol consumption behaviors. Applying the Alcohol Use Disorders Identification Test (AUDIT) we aimed to elucidate the underlying genetic determinants of alcohol consumption patterns considering taste preference gene polymorphisms (TAS1R3 rs307355, TAS2R38 rs713598, TAS2R19 rs10772420 and CA6 rs2274333) in the Hungarian general (HG) and Roma (HR) populations. Alcohol consumption assessment was available for 410 HG and 387 HR individuals with 405 HG and 364 HR DNA samples being obtained for genotyping. No significant associations were found between TAS1R3 rs307355, TAS2R19 rs10772420, and CA6 rs2274333 polymorphisms and alcohol consumption phenotypes. Significant associations were identified between TAS2R38 rs713598 and the number of standard drinks consumed in the HG sample (genotype GG negatively correlated with the number of standard drinks; coef: -0.136, p = 0.028) and the prevalence of having six or more drinks among Roma (a negative correlation was identified in the recessive model; genotype GG, coef: -0.170, p = 0.049), although, none of these findings passed the Bonferroni-corrected probability criterion (p > 0.05). Nevertheless, our findings may suggest that alcohol consumption is partially driven by genetically determined taste preferences in our study populations. Further studies are required to strengthen the findings and to understand the drivers of alcohol consumption behavior in more depth.

Clinical Associations of Bitter Taste Perception and Bitter Taste Receptor Variants and the Potential for Personalized Healthcare

Bitter taste receptors (T2Rs) consist of 25 functional receptors that can be found in various types of cells throughout the human body with responses ranging from detecting bitter taste to suppressing pathogen-induced inflammation upon activation. Numerous studies have observed clinical associations with genetic or phenotypic variants in bitter taste receptors, most notably that of the receptor isoform T2R38. With genetic variants playing a role in the response of the body to bacterial quorum-sensing molecules, bacterial metabolites, medicinal agonists and nutrients, we examine how T2R polymorphisms, expression levels and bitter taste perception can lead to varying clinical associations. From these genetic and phenotypic differences, healthcare management can potentially be individualized through appropriately administering drugs with bitter masking to increase compliance; optimizing nutritional strategies and diets; avoiding the use of T2R agonists if this pathway is already activated from bacterial infections; adjusting drug regimens based on differing prognoses; or adjusting drug regimens based on T2R expression levels in the target cell type and bodily region.

Association of single nucleotide polymorphisms with taste and food preferences of the Hungarian general and Roma populations

It is reasonable to suppose that poor diet underlies the unfavorable health status of the Roma population of Europe. Previously in the framework of a complex health survey, fruit and vegetable consumption, quantity of sugar added, salting frequency; bitter, salty, sweet and fat taste preferences were evaluated of Hungarian (HG, n = 410) and Roma (HR, n = 387) populations. In the present study the associations of taste and food preferences with TAS1R3, CD36, SCNN1B, TRPV1, TAS2R38, TAS2R19 and CA6 polymorphisms were tested in the same samples. Genotype frequencies did not differ significantly between the two populations. Although we initially observed associations between certain genetic polymorphisms and taste and food preferences in our study samples, none of the p values remained significant after the multiple test correction. However, some of our results could be considered promising (0.05<corrected p < 0.20), which showed potential ethnicity-specific effects (CA6 rs2274333 with salty taste and raw kohlrabi preference, CD36 rs1527483 with fat taste preference, TAS2R19 rs10772420 with grapefruit preference, and TAS2R38 rs713598 with quantity of sugar added). Our results may suggest that genetics may mediate food preferences, and individuals with different ethnic background may require personalized interventions to modify diet. Further investigations with greater sample sizes are essential to explore the effect of these genetic variants on taste and food preferences.

Impact of prematurity on neurodevelopment

The consequences of prematurity on brain functional development are numerous and diverse, and impact all brain functions at different levels. Prematurity occurs between 22 and 36 weeks of gestation. This period is marked by extreme dynamics in the physiologic maturation, structural, and functional processes. These different processes appear sequentially or simultaneously. They are dependent on genetic and/or environmental factors. Disturbance of these processes or of the fine-tuning between them, when caring for premature children, is likely to induce disturbances in the structural and functional development of the immature neural networks. These will appear as impairments in learning skills progress and are likely to have a lasting impact on the development of children born prematurely. The level of severity depends on the initial alteration, whether structural or functional. In this chapter, after having briefly reviewed the neurodevelopmental, structural, and functional processes, we describe, in a nonexhaustive manner, the impact of prematurity on the different brain, motor, sensory, and cognitive functions.

Genetic Background of Taste Perception, Taste Preferences, and Its Nutritional Implications: A Systematic Review

Background: The rise in nutrition-related morbidity and mortality requires public health intervention programs targeting nutritional behavior. In addition to socio-economical, socio-cultural, psychological determinants, taste is one of the main factors that influence food choices. Differences in taste perception and sensitivity may be explained by genetic variations, therefore the knowledge of the extent to which genetic factors influence the development of individual taste preferences and eating patterns is important for public policy actions addressing nutritional behaviors. Our aim was to review genetic polymorphisms accounting for variability in taste and food preferences to contribute to an improved understanding of development of taste and food preferences.

Methods: The electronic databases PubMed, Scopus, and Web of Science were searched using MeSH in PubMed and free text terms for articles published between January 1, 2000 and April 13, 2018. The search strategy was conducted following the PRISMA statement. The quality of the included studies was assessed by the validated Q-Genie tool.

Results: Following the PRISMA flowchart, finally 103 articles were included in the review. Among the reviewed studies, 43 were rated to have good quality, 47 were rated to have moderate quality, and 13 were rated to have low quality. The majority of the studies assessed the association of genetic variants with the bitter taste modality, followed by articles analyzing the impact of polymorphisms on sweet and fat preferences. The number of studies investigating the association between umami, salty, and sour taste qualities and genetic polymorphisms was limited.

Conclusions: Our findings suggest that a significant association exists between TAS2R38 variants (rs713598, rs1726866, rs10246939) and bitter and sweet taste preference. Other confirmed results are related to rs1761667 (CD36) and fat taste responsiveness. Otherwise further research is essential to confirm results of studies related to genetic variants and individual taste sensitivity. This knowledge may enhance our understanding of the development of individual taste and related food preferences and food choices that will aid the development of tailored public health strategy to reduce nutrition-related disease and morbidity.

Register-based study showed that the age when children were prescribed antibiotic tablets and capsules instead of liquids increased from 2004 to 2016

AIM

We investigated the age when the prescriptions of oral antibiotic formulations for children from birth to 12 years of age changed from being mostly liquid to mostly solid and the associations between solid formulations and child, prescriber and medication characteristics.

METHODS

This register-based study comprised data from the Norwegian Prescription Database on oral antibiotics dispensed between 2004 and 2016 when both solid and liquid dosage forms were available in appropriate doses.

RESULTS

Just over 1.2 million prescriptions were studied, and the age when children were prescribed oral solid antibiotics gradually increased. The mean age of conversion from liquids to solid formulations was 6.9 years and ranged from 5.7 years in 2004/2005 to 7.9 years in 2015/2016. Patient factors associated with solid dosage forms were the children's increasing age and male gender. Practitioner factors were the prescribers' increasing age, male gender, being a general practitioner and issuing fewer than 23 paediatric antibiotic prescriptions per year. Medication factors were bad-tasting liquids and the size and shape of solid dosage forms.

CONCLUSION

The age when children were prescribed antibiotic tablets and capsules increased from 2004 to 2016. The medicine characteristics were quite consistent, so this was probably caused by a shift in formulation preferences.

Diagnosis and treatment of ADHD in children vs adults: What nurses should know

Attention-deficit/hyperactivity disorder (ADHD) commonly occurs in childhood and may persist into adulthood. Important differences exist between pediatric and adult ADHD with regard to symptoms, comorbidities, diagnosis, and management. Both patient populations benefit from a treatment plan tailored to individual patient needs, and the availability of new stimulant formulations contributes to treatment personalization. To guide nurses' clinical practice in improving ADHD treatment outcomes, this review examines the differences between pediatric and adult ADHD and new treatment options.

Taste Exam: A Brief and Validated Test

The emerging importance of taste in medicine and biomedical research, and new knowledge about its genetic underpinnings, has motivated us to supplement classic taste-testing methods in two ways. First, we explain how to do a brief assessment of the mouth, including the tongue, to ensure that taste papillae are present and to note evidence of relevant disease. Second, we draw on genetics to validate taste test data by comparing reports of perceived bitterness intensity and inborn receptor genotypes. Discordance between objective measures of genotype and subjective reports of taste experience can identify data collection errors, distracted subjects or those who have not understood or followed instructions. Our expectation is that fast and valid taste tests may persuade researchers and clinicians to assess taste regularly, making taste testing as common as testing for hearing and vision. Finally, because many tissues of the body express taste receptors, taste responses may provide a proxy for tissue sensitivity elsewhere in the body and, thereby, serve as a rapid, point-of-care test to guide diagnosis and a research tool to evaluate taste receptor protein function.

Toward Improving Medication Adherence: The Suppression of Bitter Taste in Edible Taste Films

Bitter taste is aversive to humans, and many oral medications exhibit a bitter taste. Bitter taste can be suppressed by the use of inhibitors or by masking agents such as sucralose. Another approach is to encapsulate bitter tasting compounds in order to delay their release. This delayed release can permit the prior release of bitter masking agents. Suppression of bitter taste was accomplished by encapsulating a bitter taste stimulus in erodible stearic acid microspheres, and embedding these 5 µmeter diameter microspheres in pullulan films that contain sucralose and peppermint oil as masking agents, along with an encapsulated masking agent (sucralose). Psychophysical tests demonstrated that films which encapsulated both quinine and sucralose produced a significant and continuous sweet percept when compared to films without sucralose microspheres. Films with both quinine and sucralose microspheres also produced positive hedonic scores that did not differ from control films that contained only sucralose microspheres or only empty (blank) microspheres. The encapsulation of bitter taste stimuli in lipid microspheres, and embedding these microspheres in rapidly dissolving edible taste films that contain masking agents in both the film base and in microspheres, is a promising approach for diminishing the bitter taste of drugs and related compounds.

Variation in the Ability to Taste Bitter Thiourea Compounds: Implications for Food Acceptance, Dietary Intake, and Obesity Risk in Children

The ability to taste bitter thiourea compounds, such as phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP), is inherited. Polymorphisms in the bitter-taste receptor TAS2R38 explain the majority of phenotypic variation in the PROP phenotype. It has been hypothesized that the PROP phenotype is a marker for perception of a variety of chemosensory experiences. In this review, we discuss studies that have investigated the relationship between bitter-taste response and dietary behaviors and chronic health in children. Investigators have hypothesized that children who are PROP tasters have lower liking and consumption of bitter foods, such as cruciferous vegetables. Additionally, several studies suggest that children who are unable to taste PROP (i.e., nontasters) like and consume more dietary fat and are prone to obesity. The relationship between the PROP phenotype and obesity is influenced by multiple confounders, including sex, food access, ethnicity, and socioeconomic status. Future studies that adjust for these variables are needed.

The sweetness and bitterness of childhood: Insights from basic research on taste preferences

In this article, we review findings from basic, experimental research on children that suggest that the liking of sweet and the dislike of bitter tastes reflect children's basic biology. Children are born preferring sweet tastes, which attract them to mother's milk and even act as an analgesic. They prefer higher levels of sweet than do adults, with preferences declining to adult levels during middle to late adolescence, which coincides with the cessation of physical growth. The level of sweetness most preferred by children has remained heightened relative to adults for nearly a decade, despite reductions in sugar, both consumed and in the food environment. In spite of these reductions, however, children's intake of sugar remains higher than that recommended by health organizations worldwide. In contrast to sweet taste, children dislike and reject bitter taste, which protects them from ingesting poisons. Although variation in bitter taste receptor genes such as TAS2R38 accounts for people's marked differences in perceptions of the same bitter-tasting compounds, basic research revealed that these genotype-phenotype relationships are modified with age, with children of the same genotype being more bitter sensitive than adults and the changeover occurring during mid-adolescence. This heightened bitter sensitivity is also evident in the taste of the foods (green vegetables) or medicines (liquid formulations of drugs) they dislike and reject. While bitter taste can be masked or blocked to varying degrees by sugars and salts, their efficacy in modulating bitterness is not only based on the type of bitter ligand but on the person's age. Children's heightened preference for sweet and dislike of bitter, though often detrimental in the modern food environment, reflects their basic biology. Increasing knowledge of individual variation in taste due to both age and genetics will shed light on potential strategies to promote healthier eating since chronic diseases derive in large part from poor food choice dictated by taste preferences, and will contribute to a new era of drug formulations designed especially for the taste palate of children.

Children's perceptions about medicines: individual differences and taste

BACKGROUND

Bitter taste receptors are genetically diverse, so children likely vary in sensitivity to the "bad" taste of some pediatric formulations. Based on prior results that variation in a bitter taste receptor gene, TAS2R38, was related to solid (pill) formulation usage, we investigated whether this variation related to liquid formulation usage and young children's reports of past experiences with medicines and whether maternal reports of these past experiences were concordant with those of their children.

METHODS

We conducted retrospective interviews of 172 children 3 to 10 years old and their mothers (N = 130) separately in a clinical research setting about issues related to medication usage. Children were genotyped for the TASR38 variant A49P (alanine to proline at position 49). Children's responses were compared with their TAS2R38 genotype and with maternal reports.

RESULTS

Children (>4 years) reported rejecting medication primarily because of taste complaints, and those with at least one sensitive TAS2R38 allele (AP or PP genotype) were more likely to report rejecting liquid medications than were those without a taster allele (AA genotype; χ(2) = 5.72, df = 1, p = 0.02). Children's and mothers' reports of the children's past problems with medication were in concordance (p = 0.03).

CONCLUSIONS

Individual differences in taste responses to medications highlight the need to consider children's genetic variation and their own perceptions when developing formulations acceptable to the pediatric palate. Pediatric trials could systematically collect valid information directly from children and from their caregivers regarding palatability (rejection) issues, providing data to develop well-accepted pediatric formulations that effectively treat illnesses for all children.

TRIAL REGISTRATION

Clinicaltrials.gov protocol registration system (NCT01407939). Registered 19 July 2011.

Dose-Dependent Effects of L-Arginine on PROP Bitterness Intensity and Latency and Characteristics of the Chemical Interaction between PROP and L-Arginine

Genetic variation in the ability to taste the bitterness of 6-n-propylthiouracil (PROP) is a complex trait that has been used to predict food preferences and eating habits. PROP tasting is primarily controlled by polymorphisms in the TAS2R38 gene. However, a variety of factors are known to modify the phenotype. Principle among them is the salivary protein Ps-1 belonging to the basic proline-rich protein family (bPRP). Recently, we showed that oral supplementation with Ps-1 as well as its related free amino acids (L-Arg and L-Lys) enhances PROP bitterness perception, especially for PROP non-tasters who have low salivary levels of Ps-1. Here, we show that salivary L-Arg levels are higher in PROP super-tasters compared to medium tasters and non-tasters, and that oral supplementation with free L-Arg enhances PROP bitterness intensity as well as reduces bitterness latency in a dose-dependent manner, particularly in individuals with low salivary levels of both free L-Arg and Ps-1 protein. Supplementation with L-Arg also enhanced the bitterness of caffeine. We also used 1H-NMR spectroscopy and quantum-mechanical calculations carried out by Density Functional Theory (DFT) to characterize the chemical interaction between free L-Arg and the PROP molecule. Results showed that the -NH2 terminal group of the L-ArgH+ side chain interacts with the carbonyl or thiocarbonyl groups of PROP by forming two hydrogen bonds with the resulting charged adduct. The formation of this PROP•ArgH+ hydrogen-bonded adduct could enhance bitterness intensity by increasing the solubility of PROP in saliva and its availability to receptor sites. Our data suggest that L-Arg could act as a 'carrier' of various bitter molecules in saliva.

Playing hide and seek with poorly tasting paediatric medicines: do not forget the excipients

The development of paediatric medicines can be challenging since this is a diverse patient population with specific needs. For example, the toxicity of excipients may differ in children compared to adults and children have different taste preferences. Acceptable palatability of oral paediatric medicinal products is of great importance to facilitate patient adherence. This has been recognised by regulatory authorities and so is becoming a key aspect of paediatric pharmaceutical development studies. Many active pharmaceutical ingredients (APIs) have aversive taste characteristics and so it is necessary to utilise taste masking techniques to improve the palatability of paediatric oral formulations. The aim of this review is to provide an overview of different approaches to taste masking APIs in paediatric oral dosage forms, with a focus on the tolerability of excipients used. In addition, where possible, the provision of examples of some marketed products is made.

Pharmacogenetics of taste: turning bitter pills sweet?

Poor palatability of oral drug formulations used for young children negatively influences medication intake, resulting in suboptimal treatment. Some children are more sensitive to bitter tastes than others. Bitter tasting status is currently assessed by phenotyping with 6-n-propylthiouracil (PROP) as a bitter probe. Recent studies showed that interindividual differences in PROP sensitivity can be largely explained by three SNPs in TAS2R38, encoding a bitter taste receptor. Gustin, involved in the development of taste buds, and the sweet receptor genotype potentially explain remaining parts of PROP sensitivity variability. Other TAS2 receptor bitter receptor genes may also play a role in bitter aversions. Dependent on their genotype, children may have different medication formulation preferences. Taste genetics could improve drug acceptance by enabling better-informed choices on adapting oral formulations to children’s taste preferences. This paper presents an overview of recent findings concerning bitter taste genetics and discusses these in the context of pediatric drug formulation.

The bad taste of medicines: overview of basic research on bitter taste

BACKGROUND

Many active pharmaceutical ingredients taste bitter and thus are aversive to children as well as many adults. Encapsulation of the medicine in pill or tablet form, an effective method for adults to avoid the unpleasant taste, is problematic for children. Many children cannot or will not swallow solid dose forms.

OBJECTIVE

This review highlights basic principles of gustatory function, with a special focus on the science of bitter taste, derived from studies of animal models and human psychophysics. We focus on the set of genes that encode the proteins that function as bitter receptors as well as the cascade of events that leads to multidimensional aspects of taste function, highlighting the role that animal models played in these discoveries. We also summarize psychophysical approaches to studying bitter taste in adult and pediatric populations, highlighting evidence of the similarities and differences in bitter taste perception and acceptance between adults and children and drawing on useful strategies from animal models.

RESULTS

Medicine often tastes bitter, and because children are more bitter-sensitive than are adults, this creates problems with compliance. Bitter arises from stimulating receptors in taste receptor cells, with signals processed in the taste bud and relayed to the brain. However, there are many gaps in our understanding of how best to measure bitterness and how to ameliorate it, including whether it is more efficiently addressed at the level of receptor and sensory signaling, at the level of central processing, or by masking techniques. All methods of measuring responsiveness to bitter ligands-in animal models through human psychophysics or with "electronic tongues"-have limitations.

CONCLUSIONS

Better-tasting medications may enhance pediatric adherence to drug therapy. Sugars, acids, salt, and other substances reduce perceived bitterness of several pharmaceuticals, and although pleasant flavorings may help children consume some medicines, they often are not effective in suppressing bitter tastes. Further development of psychophysical tools for children will help us better understand their sensory worlds. Multiple testing strategies will help us refine methods to assess acceptance and compliance by various pediatric populations. Research involving animal models, in which the gustatory system can be more invasively manipulated, can elucidate mechanisms, ultimately providing potential targets. These approaches, combined with new technologies and guided by findings from clinical studies, will potentially lead to effective ways to enhance drug acceptance and compliance in pediatric populations.

PROP test: prediction of caries risk by genetic taste perception among the visually impaired children

The study sample consisted of 100 children with visual impairment aged 6-14 years. 6-n-propylthiouracil (PROP) sensitivity test was carried out. The Caries experience was recorded, estimation of Streptococcus mutans done and their taste likes and dislikes assessed through a food preference questionnaire. The Caries experience and S. mutans levels were highest in the non-tasters, comparatively low in medium tasters and the least in the supertasters. Dietary preferences indicated tasters were sweet dislikers and non-tasters, sweet likers. PROP test can be a useful tool in determining genetic taste sensitivity levels amongst the visually impaired children and thus used as a screening tool in those children who are at a high risk of developing dental caries.

Heritable differences in chemosensory ability among humans

The combined senses of taste, smell and the common chemical sense merge to form what we call ‘flavor.’ People show marked differences in their ability to detect many flavors, and in this paper, we review the role of genetics underlying these differences in perception. Most of the genes identified to date encode receptors responsible for detecting tastes or odorants. We list these genes and describe their characteristics, beginning with the best-studied case, that of differences in phenylthiocarbamide (PTC) detection, encoded by variants of the bitter taste receptor gene TAS2R38. We then outline examples of genes involved in differences in sweet and umami taste, and discuss what is known about other taste qualities, including sour and salty, fat (termed pinguis), calcium, and the ‘burn’ of peppers. Although the repertoire of receptors involved in taste perception is relatively small, with 25 bitter and only a few sweet and umami receptors, the number of odorant receptors is much larger, with about 400 functional receptors and another 600 potential odorant receptors predicted to be non-functional. Despite this, to date, there are only a few cases of odorant receptor variants that encode differences in the perception of odors: receptors for androstenone (musky), isovaleric acid (cheesy), cis-3-hexen-1-ol (grassy), and the urinary metabolites of asparagus. A genome-wide study also implicates genes other than olfactory receptors for some individual differences in perception. Although there are only a small number of examples reported to date, there may be many more genetic variants in odor and taste genes yet to be discovered.