Elena Atzori

Sensitivity to 6-n-propylthiouracil is associated with gustin (carbonic anhydrase VI) gene polymorphism, salivary zinc, and body mass index in humans

BACKGROUND The individual ability to taste 6-n-propylthiouracil (PROP) may be correlated with body mass index (BMI) and differences in the salivary proteins involved in taste function, such as the zinc-dependent enzyme gustin, which is a trophic factor of taste buds. OBJECTIVE We investigated the possible association of PROP taste responsiveness with gustin gene polymorphism rs2274333 (A/G), salivary ionic zinc concentrations, and BMI. DESIGN We measured cognitive eating behaviors and BMI in 75 volunteers (28 men and 47 women; mean plusmn SEM age: 25 plusmn 3 y). The intensity of taste perception evoked by PROP and sodium chloride solutions was estimated to evaluate PROP taster status. Salivary ionic zinc concentrations were measured, and molecular analyses of the gustin gene polymorphism were performed in individuals classified by PROP status by using polymerase chain reaction techniques. RESULTS We classified subjects as PROP supertasters (n = 27), medium tasters (n = 28), or nontasters (n = 20). Salivary ionic zinc concentrations and BMI were greater in nontasters than in supertasters (P = 0.003 and P = 0.042, respectively). Molecular analyses of gustin DNA showed that allele A and genotype AA were significantly more frequent in supertasters, whereas allele G and genotype GG were significantly more frequent in nontasters (P lt 0.001). CONCLUSIONS These data showed that responsiveness to PROP is inversely related to BMI and salivary ionic zinc concentrations. The gustin gene dimorphism rs2274333 observed in supertaster and nontaster subjects may influence the protein conformation and, thereby, affect zinc ion binding. Our data showed a direct association between PROP sensitivity and a polymorphism in the gustin gene that is hypothesized to affect its function. This trial was registered at clinicaltrials.gov as UNICADBSITB-1.

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.

First step towards the biomolecular characterization of Pompia, an endemic Citrus-like fruit from Sardinia (Italy)

Abstract This study is the first molecular and biochemical analysis conducted on Pompia, a plant of unknown origin that is endemic to Sardinia; this plant is thought to belong to the Citrus genus. Here, genes coding for the enzymes superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7), and polyphenol oxidase (PPO, EC 1.14.18.1) were identified. We detected the aforementioned enzymes in fresh leaf tissue and assessed the catalytic activity of each to support the molecular and biochemical data. This was the first molecular study to define the primary structure of proteins with antioxidant activity in Pompia. The study also contributed to the enrichment of gene databases and created the basis for molecular phylogenetic studies, which is important because this plant currently has no taxonomic or phylogenetic classification.

A Rapid Screening Method for the Identification of a Single-Nucleotide Polymorphism in the Carbonic Anhydrase VI Gene in Studies of Sensitivity to the Bitter Taste of 6-n-Propylthiouracil

The ability to perceive the bitter taste of 6-n-propylthiouracil (PROP) is a variable phenotype that has been associated with body mass index (in kg/m(2)) and linked to food choice and satiety. PROP-sensitive and -nonsensitive individuals are defined as tasters and nontasters, respectively. Sensitivity to PROP is a heritable trait based on the TAS2R38 gene on chromosome 7q34. In a recent study we demonstrated an association between PROP sensitivity and the single-nucleotide polymorphism (SNP) rs2274333 (+292A/G) within a coding sequence of the gustin/carbonic anhydrase VI gene. The purpose of this study was to develop a rapid and inexpensive screening method for identification of the rs2274333 SNP in individuals with varying sensitivity to PROP. Our results show that the methodology employed allows distinguishing A/G alleles perfectly, with a simple DNA digestion of a polymerase chain reaction fragment covering the SNP site of interest. So, the polymerase chain reaction followed by restriction fragment length polymorphism assay described in this article can be used as an alternative to sequencing in bitter taster status research, and could be employed as a survey tool in nutrigenomic studies.

Development of a molecular method for the rapid screening and identification of the three functionally relevant polymorphisms in the human TAS2R38 receptor gene in studies of sensitivity to the bitter taste of PROP.

The objective of this work was to develop a rapid screening method to identify the three single nucleotide polymorphisms (SNPs) in the TAS2R38 gene, with the aim of providing a significant contribution to studies designed to assess sensitivity to the bitter taste of 6-n-propylthiouracil (PROP). Specifically, the objective of this study was to characterize the TAS2R38 gene haplotypes in a group of 60 subjects with variable sensitivity to PROP and preliminarily genotyped for the rs2274333 allele (A/G) of carbonic anhydrase isoform VI gene (CA6). The molecular characterization of the TAS2R38 gene was conducted using the PCR-restriction fragment length polymorphism technique after creating artificial restriction sites upstream or downstream of the SNPs, as none of the three polymorphisms contributes to the formation of a restriction site for a specific endonuclease. The results indicate that the method described in this paper could be a valid and simple experimental strategy to identify genetic differences related to taste sensitivity to bitter taste, and could be applied as a nutrigenetics test in studies aimed at understanding people’s eating behaviors.