97 research outputs found

    Sensitivity to chemical stimuli plays a fundamental role in the food preferences. Examples in the evolutionary scale: 1. Role of the walking leg chemoreceptors in the red swamp crayfish Procambarus Clarkii 2. PROP bitter taste sensitivity and its nutritional implications in Humans

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    In this thesis, we studied two examples of the sensitivity to chemical stimuli and its role in the food preferences in two models of the evolutionary scale. The red swamp crayfish Procambarus clarkii (Girard, 1852) (Crustacea: Decapoda) is an invasive species of freshwater habitats that has spread worldwide. In crayfish, like in other decapod crustaceans, reception of chemical cues occurs by way of peripheral chemoreceptors grouped within sensory hairs and typically located on the cuticle of cephalothoracic appendages. Antennules and pereopods (walking legs), in particular, have been reported to be olfactory organs involved in a number of behavioral responses, such as, sex recognition and localization of food sources in the environment. By way of extracellular nerve recordings coupled with behavioral bioassays, we investigated the sensitivity spectra of the walking leg chemoreceptors in the crayfish P. clarkii in response to different compounds of feeding significance and related to its omnivorous habits. Our results confirmed a marked sensitivity of the legs to trehalose, cellobiose, sucrose, maltose, glycine and leucine. Some sensitivity to glucose, fructose, asparagine (all food indicators) and taurocholic acid was also found, the sugar-sensitive chemoreceptor units resulting as broadly tuned to the carbohydrates. Responses were highly phasic to trehalose (hemolymph sugar in the body fluid of many invertebrates), phasic to glycine and leucine and phasic-tonic to the other compounds. This suggests that chemoreceptor phasicity is an additional property for better discrimination of the protein components in the diet from other stimuli. The behavioral bioassays excluded, at least under confined experimental conditions, any involvement of antennules in the detection of food-related compounds, thus emphasizing the role of the crayfish legs as the main short-distance, broad-spectrum sensors for feeding. Such information may be valuable for the identification of key chemicals aimed at the future development of strategies for crayfish population control programs. Taste sensitivity varies greatly in humans, influencing eating behavior and therefore may play a role in body composition. PROP bitter taste sensitivity is the most studied example of the individual variability of taste sensitivity. Some studies show that PROP bitter taste sensitivity may be correlated with sensitivity to other oral stimuli, food preferences and BMI, while other studies did not confirm this association. It is known that PROP phenotype is associated with variant in bitter taste receptors TAS2R38 and with density of fungiform papillae on tongue surface. Although most of PROP phenotypic variations are explained by the allelic diversity of the bitter receptor TAS2R38, they cannot explain the PROP taster status-related differences above all that in the perception to different oral stimuli. The aim of this study was identify and characterize other factors that may contribute to differences in the genetic predisposition to taste PROP and identify confounding variables which may explain the controversial data in the literature about the relationship between PROP taste sensitivity and BMI. 1) We investigated the possible relationship between PROP bitter taste responsiveness and salivary proteins by using HPLC-ESI-MS on saliva sample before and after PROP taste stimulation. 2) We evaluated the role of proteins and free amino acids in modulating bitter taste responsiveness. Subjects rated PROP bitterness after supplementation of two salivary proteins (Ps-1 and II-2), and the free form of constituent amino acids of the two proteins sequences (L-Arg and L-Lys) whose interaction with PROP was demonstrated by 1H-NMR spectroscopy. 3) We investigate the role of polymorphism rs2274333 (A/G) in the gene that codify for the salivary trofic factor gustin protein, in PROP sensitivity and fungiform papilla density and morphology and in vitro we investigate the effect of this gustin gene polymorphism on 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. 4) We investigated whether the endocannabinoid system, which modulates hunger/satiety and energy balance, plays a role in modulating eating behaviour influenced by a sensitivity to PROP which could explain the controversial data in literature. In particular we determined the plasma profile of the endocannabinoids 2-arachidonoylglycerol (2-AG), anandamide (AEA) and congeners in normal-weight PROP super-tasters and non-tasters, also we assessed the cognitive eating behavior disorder by the Three-Factor Eating Questionnaire. The results showed that: 1) Basal levels of II-2 and Ps-1 proteins, belonging to the basic proline-rich protein (bPRPs) family, were significantly higher in PROP super-taster than in non-taster unstimulated saliva, and PROP stimulation elicited a rapid increase in the levels of these same proteins only in PROP super-taster saliva. 2) Supplementation of Ps-1 protein in individuals lacking it in saliva enhanced their PROP bitter responsiveness. 1H-NMR results showed that the interaction between PROP and L-Arg is stonger than that involving L-Lys, and taste experiments confirmed that oral supplementation with L-Arg increase more PROP bitterness intensity than L-Lys. 3) Gustin and TAS2R38 genotypes were associated with PROP threshold, while bitterness intensity was mostly determined by TAS2R38 genotypes. Fungiform papillae densities were associated with both genotypes (with a stronger effect for gustin), but papilla morphology was a function of gustin alone. In vitro experiment, the treatment of isolated cells with saliva from individuals with AA form, and direct application of the active iso-form of gustin protein, increased cell proliferation and metabolic activity. 4) The disinhibition score of non-taster was higher than those of super-tasters. In addition, we found that the concentration of endocannabinoid AEA (anandamide) and 2-AG (2-arachidonoylglycerol) was lower in the plasma of non taster compared with super-tasters subjects. In conclusion, among the factors contributing to individual differences of PROP sensitivity, in addition to the TAS2R38 variants with its different affinity for the stimulus, we found: 1-2) the specific salivary proteins of bPRP family (Ps-1) and L-Arg that could be involved in twist and turn of the PROP molecule, thus facilitating its binding with the receptor. 3) A gustin gene polymorphism that, by modulating the protein activity, controls the growth and maintenance of taste buds and 4) the higher disinhibition behaviour in non-tasters may be compensated in part, in normal-weight subjects, by the decrease of peripheral endocannabinoids to downregulate the hunger-energy intake circuitry

    Effect of the rs2821557 Polymorphism of the Human Kv1.3 Gene on Olfactory Function and BMI in Different Age Groups

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    The sense of smell plays an important role in influencing the eating habits of individuals and consequently, their body weight, and its impairment has been associated with modified eating behaviors and malnutrition problems. The inter-individual variability of olfactory function depends on several factors, including genetic and physiological ones. In this study, we evaluated the role of the Kv1.3 channel genotype and age, as well as their mutual relationships, on the olfactory function and BMI of individuals divided into young, adult and elderly groups. We assessed olfactory performance in 112 healthy individuals (young n = 39, adult n = 36, elderly n = 37) based on their TDI olfactory score obtained through the Sniffin' Sticks test and their BMI. Participants were genotyped for the rs2821557 polymorphism of the human gene encoding Kv1.3 channels, the minor C allele of which was associated with a decreased sense of smell and higher BMIs compared to the major T allele. The results show that TT homozygous subjects obtained higher TDI olfactory scores and showed lower BMIs than CC homozygous subjects, in all age groups considered. Furthermore, the positive effect of the T allele on olfactory function and BMI decreased with increasing age. The contribution of the genetic factor is less evident with advancing age, while the importance of the age factor is compensated for by genetics. These results show that genetic and physiological factors such as age act to balance each other

    The Implications of Taste and Olfaction in Nutrition and Health

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    Taste and olfaction are sensory modalities that act synergistically to orchestrate the behaviors essential for survival, such as interactions with the environment, nutrient-rich food identification, and the avoidance of noxious substances [...]

    Emotional responses to taste and smell stimuli: Self-reports, physiological measures, and a potential role for individual and genetic factors

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    Taste and olfaction elicit conscious feelings by direct connection with the neural circuits of emotions that affects physiological responses in the body (e.g., heart rate and skin conductance). While sensory attributes are strong determinants of food liking, other factors such as emotional reactions to foods may be better predictors of consumer choices even for products that are equally-liked. Thus, important insights can be gained for understanding the full spectrum of emotional reactions to foods that inform the activities of product developers and marketers, eating psychologist and nutritionists, and policy makers. Today, self-reported questionnaires and physiological measures are the most common tools applied to study variations in emotional perception. The present review discusses these methodological approaches, underlining their different strengths and weaknesses. We also discuss a small, emerging literature suggesting that individual differences and genetic variations in taste and smell perception, like the genetic ability to perceive the bitter compound PROP, may also play a role in emotional reactions to aromas and foods

    Gene Methylation Affects Salivary Levels of the Taste Buds' Trophic Factor, Gustin Protein

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    The salivary protein, Gustin/carbonic anhydrase VI, has been described as a trophic factor responsible for the growth of taste buds. We found, in a genetically homogeneous population, that the polymorphism rs2274333 (A/G) of the Gustin gene is crucial for the full functionality of the protein and is associated with taste sensitivity. However, other studies have failed to find this evidence. Here, we verified if Gustin gene methylation can affect the salivary levels of the protein, also concerning the polymorphism rs2274333 and PROP bitter responsiveness. The Gustin gene methylation profiling and the quantification of the Gustin salivary levels were determined in sixty-six volunteers genotyped for the polymorphism rs2274333 (A/G) (Ser90Gly in the protein sequence). The fungiform papillae density was also determined. The results confirm our earlier observations by showing that AA genotypes had a greater density of fungiform taste papillae, whereas the GG genotypes showed a lower density. We also found variations in the protein levels in the three genotype groups and an inverse relationship between Gustin gene methylation and the salivary levels of the protein, mostly evident in AA and ST volunteers, i.e., in volunteers who would be carriers of the functional isoform of the protein. These findings could justify the conflicting data in the literature

    A supervised learning regression method for the analysis of oral sensitivity of healthy individuals and patients with chemosensory loss

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    The gustatory, olfactory, and trigeminal systems are anatomically separated. However, they interact cognitively to give rise to oral perception, which can significantly affect health and quality of life. We built a Supervised Learning (SL) regression model that, exploiting participants' features, was capable of automatically analyzing with high precision the self-ratings of oral sensitivity of healthy participants and patients with chemosensory loss, determining the contribution of its components: gustatory, olfactory, and trigeminal. CatBoost regressor provided predicted values of the self-rated oral sensitivity close to experimental values. Patients showed lower predicted values of oral sensitivity, lower scores for measured taste, spiciness, astringency, and smell sensitivity, higher BMI, and lower levels of well-being. CatBoost regressor defined the impact of the single components of oral perception in the two groups. The trigeminal component was the most significant, though astringency and spiciness provided similar contributions in controls, while astringency was most important in patients. Taste was more important in controls while smell was the least important in both groups. Identifying the significance of the oral perception components and the differences between the two groups provide important information to allow for more targeted examinations supporting both patients and healthcare professionals in clinical practice

    Responsiveness to 6-n-Propylthiouracil (PROP) Is Associated with Salivary Levels of Two Specific Basic Proline-Rich Proteins in Humans

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    Thiourea tasting can be predictive of individual differences in bitter taste responses, general food preferences and eating behavior, and could be correlated with saliva chemical composition. We investigated the possible relationship between PROP bitter taste responsiveness and the salivary proteome in subjects genotyped for TAS2R38 and gustin gene polymorphisms. Taste perception intensity evoked by PROP and NaCl solutions was measured in sixty-three volunteers (21 males, 42 females, age 25±3 y) to establish their PROP taster status, and 24 PROP super-tasters and 21 nontasters were selected to participate in the study. TAS2R38 and gustin gene molecular analysis were performed using PCR techniques. Qualitative and quantitative determination of salivary proteins was performed by HPLC-ESI-MS before and after PROP taste stimulation. PROP super-tastings was strongly associated with the ‘taster’ variant (PAV haplotype) of TAS2R38 and the A allele of rs2274333 polymorphism in the gustin gene and nontasting was associated with the minor alleles at both loci. ANOVA revealed that basal levels of II-2 and Ps-1 proteins, belonging to the basic proline-rich protein (bPRPs) family, were significantly higher in PROP super-taster than in nontaster un-stimulated saliva, and that PROP stimulation elicited a rapid increase in the levels of these same proteins only in PROP super-taster saliva. These data show for the first time that responsiveness to PROP is associated with salivary levels of II-2 peptide and Ps-1 protein, which are products of the PRB1 gene. These findings suggest that PRB1, in addition to TAS2R38 and gustin, could contribute to individual differences in thiourea sensitivity, and the expression of the PROP phenotype as a complex genetic trait

    The gustin (CA6) gene polymorphism, rs2274333 (A/G), is associated with fungiform papilla density, whereas PROP bitterness is mostly due to TAS2R38 in an ethnically-mixed population

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    PROP responsiveness is associated with TAS2R38 haplotypes and fungiform papilla density. Recently, we showed that a polymorphism in the gene coding for the salivary trophic factor, gustin (CA6), affects PROP sensitivity by acting on cell growth and fungiform papillae maintenance, in a genetically homogeneous cohort. Since population homogeneity can lead to over estimation of gene effects, the primary aim of the present work was to confirm gustin’s role in PROP bitterness intensity and fungiform papillae density in a genetically diverse population. Eighty subjects were genotyped for both genes by PCR techniques. PROP responsiveness was assessed by filter paper method and fungiform papilla density was determined in each subject. As expected, PROP bitterness ratings were lower in individuals with the AVI/AVI diplotype of TAS2R38 than in individuals with PAV/PAV and PAV/AVI diplotype. However, no differences in PROP bitterness among genotypes of the gustin gene, and no differences in the density of fungiform papillae related to TAS2R38 diplotype were found. In contrast, the density of fungiform papillae decreased as the number of minor (G) alleles at the gustin locus increased. In addition, the distribution of TAS2R38 genotypes within each gustin genotype group showed that the occurrence of recessive alleles at both loci was infrequent in the present sample compared to other populations. These findings confirm that papillae density is associated with gustin gene polymorphism, rs2274333 (A/G), in an ancestrally heterogeneous population, and suggest that variations in the frequency of allele combinations for these two genes could provide a salient explanation for discrepant findings for gustin gene effects across population

    Olfactory Function in Patients with Inflammatory Bowel Disease (IBD) Is Associated with Their Body Mass Index and Polymorphism in the Odor Binding Protein (OBPIIa) Gene

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    Smell strongly contributes to food choice and intake, influencing energy balance and body weight; its reduction or loss has been related to malnutrition problems. Some patients with inflammatory bowel disease (IBD), mainly Crohn’s disease (CD) and ulcerative colitis (UC), are underweight, while others are overweight. Some studies suggest that changes in eating habits could be linked to specific disorders of the olfactory functions. We assessed the olfactory performance in 199 subjects (healthy control (HC) n = 99, IBD n = 100), based on the olfactory Threshold, Discrimination and Identification score (TDI score), measured with the “Sniffin’ Sticks” test. Subjects were genotyped for the rs2590498 polymorphism of the OBPIIa gene. IBD patients showed both a slightly, but significantly, lower olfactory function and a higher BMI compared to HC subjects. Threshold (in both population) and Discrimination (in IBD patients) olfactory score were affected by the OBPIIa genotype. BMI was influenced by both health status and OBPIIa genotype. A lower olfactory function may delay the satiety sensation and thus increase meal duration and body weight in IBD patients. However, the AA genotype of the OBPIIa seems to “protect” IBD patients from more severe olfactory dysfunction

    Participants with Normal Weight or with Obesity Show Different Relationships of 6-n-Propylthiouracil (PROP) Taster Status with BMI and Plasma Endocannabinoids

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    Reduced taste sensitivity to 6-n-propylthiouracil (PROP), a genetic trait regarded as a general index for oral chemosensory perception, has been associated with a calorie-rich food preference and lower circulating endocannabinoid levels in participants with normal weight (NW), which suggests an adaptive mechanism to maintain a lean phenotype. In this study, we assessed whether participants with obesity (OB) show different patterns of plasma endocannabinoids and lipid metabolism biomarkers from those of NW, with further categorization based on their PROP sensitivity. NW and OB were classified by their PROP taster status as non-tasters (NT), medium-tasters (MT) and supertasters (ST). The blood samples were analysed for plasma endocannabinoids, nonesterified fatty acids (NEFA) and retinol, which have been associated to metabolic syndrome. In OB, we found a higher BMI and lower circulating endocannabinoids in ST vs. OB NT. However, OB ST showed lower circulating NEFA and retinol levels, which suggested a more favourable lipid metabolism and body fat distribution than those of OB NT. We confirmed lower plasma endocannabinoid levels in NW NT than in NW ST. These data suggest that PROP taste sensitivity determines metabolic changes and ultimately body mass composition differently in OB and NW
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