Emma L. Feeney

Exploring associations between taste perception, oral anatomy and polymorphisms in the carbonic anhydrase (gustin) gene CA6

Recent reports suggest that polymorphisms in the carbonic anhydrase gene CA6 (also known as gustin) may explain additional variation in the bitterness of 6-n-propylthiouracil beyond that explained by variation in the bitter receptor gene TAS2R38. CA6 (gustin) has been implicated in taste bud function and salivary buffer capacity. In the present study we examined associations between polymorphisms in the CA6 gene with salt and bitter taste perception, and oral anatomy. 243 subjects (146 female) aged 18-45 rated the intensity of five concentrations of 6-n-propylthiouracil and NaCl on a generalized Labeled Magnitude Scale (gLMS) in duplicate and one concentration of potassium chloride (KCl). Using salivary DNA, we examined 12 SNPs within CA6 in relation to taste intensity and number of fungiform papillae. We observed no difference in bitter taste perception from 6-n-propylthiouracil (PROP) or from potassium chloride for any of the SNPs examined. Perceived saltiness of NaCl on the other hand was significantly associated with a number of CA6 polymorphisms, and particularly rs3737665. Nonetheless, FP density did not vary between alleles of rs3737665, nor with any of the other CA6 SNPs. Also, we fail to find any evidence that CA6 effects on taste perception are due to differences in fungiform papilla number. Additional work is needed to confirm whether variations within the CA6 gene may be responsible for differences in salt taste perception.

Whole dairy matrix or single nutrients in assessment of health effects: current evidence and knowledge gaps

Foods consist of a large number of different nutrients that are contained in a complex structure. The nature of the food structure and the nutrients therein (i.e., the food matrix) will determine the nutrient digestion and absorption, thereby altering the overall nutritional properties of the food. Thus, the food matrix may exhibit a different relation with health indicators compared to single nutrients studied in isolation. The evidence for a dairy matrix effect was presented and discussed by an expert panel at a closed workshop, and the following consensus was reached: 1) Current evidence does not support a positive association between intake of dairy products and risk of cardiovascular disease (i.e., stroke and coronary heart disease) and type 2 diabetes. In contrast, fermented dairy products, such as cheese and yogurt, generally show inverse associations. 2) Intervention studies have indicated that the metabolic effects of whole dairy may be different than those of single dairy constituents when considering the effects on body weight, cardiometabolic disease risk, and bone health. 3) Different dairy products seem to be distinctly linked to health effects and disease risk markers. 4) Different dairy structures and common processing methods may enhance interactions between nutrients in the dairy matrix, which may modify the metabolic effects of dairy consumption. 5) In conclusion, the nutritional values of dairy products should not be considered equivalent to their nutrient contents but, rather, be considered on the basis of the biofunctionality of the nutrients within dairy food structures. 6) Further research on the health effects of whole dairy foods is warranted alongside the more traditional approach of studying the health effects of single nutrients. Future diet assessments and recommendations should carefully consider the evidence of the effects of whole foods alongside the evidence of the effects of individual nutrients. Current knowledge gaps and recommendations for priorities in future research on dairy were identified and presented.

Quinine Bitterness and Grapefruit Liking Associate with Allelic Variants in TAS2R31

Multiple psychophysical gene-association studies suggest a single nucleotide polymorphism (SNP) within the bitter receptor gene TAS2R19 on chromosome 12 may be functional. Previously, the Arg299Cys SNP (rs10772420) has been associated with differential bitterness of quinine and differential liking for grapefruit juice. However, quinine does not activate TAS2R19 in vitro; likewise, limonin and naringin, bitter compounds in grapefruit, do not activate TAS2R19 in vitro. Here, we examined quinine bitterness (whole-mouth swish-and-spit stimuli and regionally delivered quinine across 4 loci) and remembered liking for grapefruit juice to test whether they associate with SNPs in another nearby gene, TASR2R31. We observed SNP-phenotype associations between whole-mouth quinine bitterness and self-reported liking for grapefruit juice with SNPs in TAS2R31, and regional quinine bitterness followed a similar trend, but did not reach significance. Present data provide independent replication of prior associations reported for TAS2R19. However, we also observed strong linkage disequilibrium (LD) between TAS2R19 and TAS2R31 SNPs. When present data are considered in light of existing functional expression data, this suggests phenotypic associations reported previously for rs10772420 may potentially be due to LD between this SNP and polymorphism(s) in, or closer to, TAS2R31. If confirmed, this would reduce the number of TAS2Rs with putatively functional polymorphisms to 5.

TongueSim: Development of an Automated Method for Rapid Assessment of Fungiform Papillae Density for Taste Research

Taste buds are found on the tongue in 3 types of structures: the fungiform papillae, the foliate papillae, and the circumvallate papillae. Of these, the fungiform papillae (FP) are present in the greatest numbers on the tongue, and are thought to be correlated to the overall number of taste buds. For this reason, FP density on the tongue is often used to infer taste function, although this has been controversial. Historically, videomicroscopy techniques were used to assess FP. More recently, advances in digital still photography and in software have allowed the development of rapid methods for obtaining high quality images in situ. However, these can be subject to inter-researcher variation in FP identification, and are somewhat limited in the parameters that can be measured. Here, we describe the development of a novel, automated method to count the FP, using the TongueSim suite of software. Advantages include the reduction in time required for image analysis, elimination of researcher bias, and the added potential to measure characteristics such as the degree of roundness of each papilla. We envisage that such software has a wide variety of novel research applications.

An overview of the contribution of dairy and cheese intakes to nutrient intakes in the Irish diet: results from the National Adult Nutrition Survey

Dairy products are important contributors to nutrient intakes. However, dairy intakes are reportedly declining in developed populations, potentially due to concerns regarding Na and SFA in dairy foods, particularly cheese. This could impact other nutrient intakes. The present study used data from the National Adult Nutrition Survey (NANS) to (1) examine dairy intakes, with a specific focus on cheese, and (2) to examine the contribution of cheese to population nutrient intakes. The NANS captured detailed dietary intake data from a nationally representative sample (n 1500) between 2008 and 2010 using 4-d semi-weighed food diaries; 99·9% of the population reported dairy intake. Mean daily population dairy intake was 290·0 (SD 202·1) g. Dairy products provided 8·7% of the population intake of reported dietary Na, 19·8% SFA, 39% Ca, 34·5% vitamin B12 and 10·5% Mg. Cheese alone provided 3·9% Na intake, 9·1% Ca, 12·6% retinol, 8·3% SFA, 3·7% protein, 3·4% vitamin B12 and 3·2% riboflavin. High dairy consumers had greater Ca and Mg intakes per 10 MJ, greater total energy intake, greater percentage of energy from carbohydrate and SFA and lower Na intakes compared with low dairy consumers. Similar trends were observed for high consumers of cheese for most nutrients except Na. These results demonstrate that dairy and cheese are important contributors to nutrient intakes of public health interest, such as Ca and B12. Our analysis also demonstrated that food-based dietary guidelines recommending lower-fat versions of dairy products are warranted.

Perceived sucrose intensity is related to 6-n-propylthiouracil sensitivity and to markers of sugar intake

Taste perception of 6-n-propylthiouracil (PROP) can vary in individuals depending partly on polymorphisms of the bitter-taste receptor gene TAS2R38. Super-taster (ST) individuals are highly sensitive to the bitter taste of PROP, while non-tasters are much less sensitive and medium tasters lie between the two. Previous studies have shown that ST are highly sensitive not only to PROP, but also to the tastes of quinine and sucrose and can perceive differences in foods with altered fat content, possibly as a result of an increased number of trigeminal nerve fibres on the tongue.The main aim of the present study was to examine some of the wide-ranging reasons for food choice within a group of children (n 199) and their parents (n 52) and to look at the role of PROP taster status in sucrose perception and sugar intake. Children aged 8–12 years and their parents were recruited from schools across Dublin. To determine taster status, PROPimpregnated paper discs were rated on the general labelled magnitude scale (gLMS) as previously described. Subjects were then given a series of drinks of varying sucrose concentration, which they also rated on the gLMS. Average daily sugar intakes were obtained through a 3 d diet history, which was then analysed using WISP g (Tinuviel Software, Llanfechell, Anglesey, UK). Values for non-milk extrinsic sugars (NMES) were taken as a marker for sugar intake.

Healthy cheese - Can cheese really be healthy? A review of the current evidence

T maintenance of cholesterol homeostasis is vital for the human body therefore it is a largely controlled process at several levels (transcriptional, translational, enzyme modulation etc.). If this molecule is not absorbed with the diet, specific receptor senses the lack of the metabolite and activate specific genes and mechanisms to synthetize it. One of the not so well known but important factor in the cholesterol regulation is via thyroid. 3,3’,5-Triiodothyronine (T3) is a thyroid hormone involved in LDL-r gene expression regulation. A 20% of this hormone is secreted by thyroid but the major amount is produced from thyroxine (T4) by 5 -deiodination in peripheral tissues. This reaction is catalyzed by the selenoprotein deiodinase in (Dio1). This protein activates thyroid hormone by converting the prohormone T4 by outer ring deiodination (ORD) to bioactive T3. It also degrades both hormones by inner ring deiodination (IRD). On the other hand, a few reports indicated that 1 ppm selenium supplementation to rats decreased the total cholesterol and LDL levels, increased Dio1 expression (and T3 levels) and decreased the ApoB and HMGCoA reductase mRNAs expression. Edible mushrooms are a good source of selenium as well as hypocholesterolaemic compounds such as i.e. sterols, fibers, inhibitors of the 3-hydroxy-3-methyl-glutaryl-Co A reductase (HMGCR) and of the S-adenosylhomocysteine hydrolase (SAHH) such as eritadenine. Thus, several mushroom extracts were prepared and administrated to normo-and hypercholesterolaemic mice in order to investigate their potential influence on the Dio1 gene expression in liver, duodenum, ileum and cecum. Results indicated that hypercholesterolemia induced a marked reduction, particularly in liver, of the Dio1 mRNA expression. Moreover, the Dio1 gene expression was also modulated by the mushrooms extracts but not by the hypocholesterolaemic control drugs. Some of the extracts down-regulated its expression while others promoted its up-regulation. The effect was tissue dependent.

Are 6- n -propylthiouracil (PROP) taster status and fungiform papillae (FP) density related to alcohol intake in a group of Irish adults?

Phenylthiocarbamide and its chemically-related compound, 6-n-propylthiouracil (PROP), provide an extremely bitter taste to some individuals (super tasters; ST), a slightly bitter taste to some (medium tasters; MT) or no taste at all to others (non-tasters; NT). Studies suggest FP densities vary between taster groups, with ST having greater numbers of FP than NT on the anterior of their tongue. ST are therefore more likely to experience greater bitter oral sensations from bitter-tasting foods and drinks, e.g. alcohol, compared with NT. Studies have also linked alcohol intake to PROP taster status. The present study aims to examine whether PROP taster status is related to alcohol intake in a group of Irish adults. The data were collected as part of a larger on-going project examining PROP taster status and its effect on fruit and vegetable intake. In the study ninetyfour adults (seventy-one females and twenty-three males) were recruited from the Dublin area. Alcohol intakes were assessed through diet histories and analysed using WISP g (Tinuviel Software, Llanfechell, Anglesey, UK). PROP taster status was established using PROPimpregnated paper discs and general labelled magnitude scales (gLMS) as previously described. Statistical analysis was carried out using SPSS (SPSS Inc., Chicago, IL, USA; ANOVA (post hoc) and correlation). No significant differences were found for mean daily alcohol intake in adults when assessed using the PROP ratings from the gLMS, or when PROP ratings on the gLMS were converted to PROP-taster groups according to cut-off points previously described (P = 0.091 and R 0.155 respectively). No significant differences were observed for alcohol intake and FP density across the three groups (R 0.0012).

The effect of 6-n-propylthiouracil taster status on fruit and vegetable intake and hedonic ratings in a group of Irish children

6-n-Propylthiouracil (PROP) is a bitter-tasting compound found in some fruit and vegetables. The ability to taste this compound is determined genetically, controlled in part by alleles of bitter receptor gene TAS2R38. Individuals vary in their ability to taste this compound and may be categorised into non-tasters (NT) medium tasters (MT) and super tasters (ST) through their rating of a PROPimpregnated disc as described previously. Previous studies have shown that vegetable acceptance in young children is lower in PROPtaster groups. The aim of the present study was to examine hedonic ratings for twelve common fruits and vegetables, and overall intake in group of twenty-four Irish children aged between 10 and 11 years in relation to their PROP-taster status. Children were asked to rate twelve common fruits and vegetables on a five-point scale. Overall fruit and vegetable intake was assessed through an average 3-day diet history – deemed the most appropriate method of assessment, due the scale of the study and the time allocated.