New insights into the relationship between taste perception and oral microbiota composition

Nitrate supplementation affects taste by changing the oral metabolome and microbiome

Nitrate, an inorganic anion found in various foods is also present in saliva and has emerged as a potential prebiotic for the oral microbiome. Salivary glands concentrate nitrate from the bloodstream and release it into the oral cavity via the anion transporter sialin SLC17A5. In previous studies dietary nitrate supplementation altered oral bacteria composition, favouring genera like Rothia and Neisseria while reducing Streptococcus, Veillonella, Prevotella, and Actinomyces. The present study hypothesized that taste intensity might adapt to changes in the oral microbiome caused by nitrate supplementation. Participants underwent taste tests before, during, and after supplementation. All subjects showed greater levels of salivary nitrate during supplementation and had higher levels of Neisseria compared to before. Subjects were then grouped according to taste tests (before vs. during) as responders (ANOVA p < 0.05, n = 7), and non-responders (ANOVA p > 0.05, n = 6) and their salivary metabolome and oral microbiome further analysed. Responders had significantly less 5-amino pentanoate, formate, propionate and butyrate in saliva while non-responders showed no metabolite changes between before and during supplementation. In contrast, non-responders had increased Capnocytophaga gingivalis and altered lysosomal degradation pathways. Overall, nitrate supplementation shifted the oral microbiome composition in all subjects and when taste intensity was altered this correlated to bacteria-derived short-chain fatty acid production. This suggests taste perception is affected by the oral microbiome.

"Evaluation of the effect of nutrition and oral hygiene on Dmft index of patients applying to restorative dentistry clinic"

OBJECTIVES

The aim of this study was to investigate the effects of diet, oral hygiene, visits to the dentist, and body mass index (BMI) on the risk of dental decay.

METHODS

240 patients aged 18-50 were included in the study. Participants completed a questionnaire that included demographic information and oral hygiene habits. They were also required to submit dietary analysis forms, which asked about the foods and amounts consumed at breakfast, lunch, dinner, and during two snacks. Intraoral and radiographic examinations of the patients were performed, and the values for DMFT, plaque index, dental calculus index, and oral hygiene index (OHI-S) were recorded. Statistical analysis, including Chi-square tests, independent samples t-tests, and one-way ANOVA, was conducted on the data (p < 0.05).

RESULTS

The oral hygiene index(OHI-S) was determined to be good in 58.3% of the study participants and poor in 10%. No statistical difference was found between BMI and DMFT index (p > 0,005). When the relationship between food consumption frequencies and DMFT was evaluated, it was determined that there was no statistically significant relationship between bread, rice, milk, legumes, and DMFT values (p > 0,005), but there was a statistically significant relationship between fruit, vegetables, yoghurt, cheese, meat/chicken/fish, eggs, honey, sugar, glutens, acidic drinks, tae/coffee consumption and DMFT indices (p < 0,005 ).

CONCLUSION

The types of food consumed by patients and the frequency of consumption affect the risk of caries.

Contributions and future potential of animal models for geroscience research on sensory systems

Sensory systems mediate our social interactions, food intake, livelihoods, and other essential daily functions. Age-related decline and disease in sensory systems pose a significant challenge to healthy aging. Research on sensory decline in humans is informative but can often be difficult, subject to sampling bias, and influenced by environmental variation. Study of animal models, including mice, rats, rabbits, pigs, cats, dogs, and non-human primates, plays a complementary role in biomedical research, offering advantages such as controlled conditions and shorter lifespans for longitudinal study. Various species offer different advantages and limitations but have provided key insights in geroscience research. Here we review research on age-related decline and disease in vision, hearing, olfaction, taste, and touch. For each sense, we provide an epidemiological overview of impairment in humans, describing the physiological processes and diseases for each sense. We then discuss contributions made by research on animal models and ideas for future research. We additionally highlight the need for integrative, multimodal research across the senses as well as across disciplines. Long-term studies spanning multiple generations, including on species with longer life spans, are also highly valuable. Overall, integrative studies of appropriate animal models have high translational potential for clinical applications, the development of novel diagnostics, therapies, and medical interventions and future research will continue to close gaps in these areas. Research on animal models to improve understanding of the biology of the aging senses and improve the healthspan and additional research on sensory systems hold special promise for new breakthroughs.

Burden of oral diseases predicts development of excess weight in early adolescence: a 2-year longitudinal study

Dental caries, gingivitis, and excess weight are highly prevalent, interconnected chronic conditions. The association of oral health with the development of adiposity among children is sparsely addressed. We examined the association of oral health to the development of excess weight and central obesity in early adolescence during a 2-year follow-up period. This prospective study was conducted with 2702 children aged 9-12 years at baseline from the Finnish Health in Teens study. Their weight development was followed up for 2 years. Body mass index with age- and sex-specific cut-offs and the waist-height ratio indicated weight status and central obesity. Oral health data (caries experience and gingivitis/calculus) were collected from outpatient records of public dental services. Having both caries experience and gingivitis/calculus was considered burden of oral diseases. Of the sample, 74% were caries-free but 70% exhibited gingivitis and/or calculus, and 20% had both caries experience and gingivitis/calculus. During the follow-up period, 5.3% (n = 124) and 4.7% (n = 118) of the children became overweight/obese or centrally obese, respectively. Having both caries experience and gingivitis/calculus associated with the development of excess weight in a fully adjusted model (HR 1.75, 95% CI 1.03-2.97) but not of central obesity. Caries experience or gingivitis/calculus alone did not associate with adiposity development.

CONCLUSION

Having burden of oral diseases without excess weight at early adolescence could imply future weight gain; thus, normal-weight individuals with both caries experience and gingivitis/calculus could be targeted with preventive measures. Our findings warrant further research to explore whether oral diseases and the development of obesity merely share risk factors or if their relationship is of causal nature.

WHAT IS KNOWN

• Association of excess weight with caries experience and gingivitis is known to exist both cross-sectionally and longitudinally in children and adolescents.

WHAT IS NEW

• Burden of oral diseases, that is, having both caries experience and gingivitis/calculus, was associated with becoming overweight or obese 2 years later during early adolescence. • Normal-weight individuals with burden of oral diseases at early adolescence could be targeted with preventive measures against excess weight gain.

Impaired metal perception and regulation of associated human foliate papillae tongue transcriptome in long-COVID-19

Chemosensory impairment is an outstanding symptom of SARS-CoV-2 infections. We hypothesized that measured sensory impairments are accompanied by transcriptomic changes in the foliate papillae area of the tongue. Hospital personnel with known SARS-CoV-2 immunoglobulin G (IgG) status completed questionnaires on sensory perception (n = 158). A subcohort of n = 141 participated in forced choice taste tests, and n = 43 participants consented to donate tongue swabs of the foliate papillae area for whole transcriptome analysis. The study included four groups of participants differing in IgG levels (≥ 10 AU/mL = IgG+; < 10 AU/mL = IgG-) and self-reported sensory impairment (SSI±). IgG+ subjects not detecting metallic taste had higher IgG+ levels than IgG+ participants detecting iron gluconate (p = 0.03). Smell perception was the most impaired biological process in the transcriptome data from IgG+/SSI+ participants subjected to gene ontology enrichment. IgG+/SSI+ subjects demonstrated lower expression levels of 166 olfactory receptors (OR) and 9 taste associated receptors (TAS) of which OR1A2, OR2J2, OR1A1, OR5K1 and OR1G1, as well as TAS2R7 are linked to metallic perception. The question raised by this study is whether odorant receptors on the tongue (i) might play a role in metal sensation, and (ii) are potential targets for virus-initiated sensory impairments, which needs to be investigated in future functional studies.

Virtue of courage as modulator in interactions among oral health beliefs, oral hygiene habits and dietary preferences

The impact of virtue of courage as mediating and moderating variable in interactions of oral health beliefs with oral hygiene habits and dietary preferences is of interest. A total of 100 patients with a complain of periodontal ailments and dental caries were enrolled from dental institute. 40 items belonging to character strengths of psychological virtue of courage in values in action Inventory of Strength (VIA-IS) Questionnaire and 15 Oral Health Belief Questionnaire items were recorded. Oral hygiene habits and dietary preferences congruent with oral health were also recorded. A significant positive correlation was observed in the following variables: barriers/gender (correlation coefficient =.212, P =.034) There was positive correlation between perseverance and nutritional preferences (correlation coefficient = .239, P =.017); courage and nutritional preferences (correlation coefficient = .241, P = .016). Virtue of courage and its character strengths have significant positive impact over dietary preferences congruent with oral health. Inculcation of character strengths belonging to courage as virtue may have the potential to modulate compliance to oral health beliefs and consequently oral health.

Association between self-reported oral habits and oral health related quality of life of adolescents in Ibadan, Nigeria

Oral habits such as nail biting, thumb/digit sucking and teeth grinding could be harmful, and may lead to teeth misalignment, anterior open bite, protruded or flared upper anterior teeth especially if they persist into adolescence. Such orofacial dysfunction may result to impairment of the Oral Health Related Quality of Life (OHRQoL) of an individual. The extent to which oral habits affect the major domains of the self-reported outcomes remains understudied especially during adolescence, a unique period of growth, where there is increased aesthetic desire, increased self-awareness, and unique social and psychological needs. The aim of this study, therefore, was to determine the prevalence of oral habits and its association with oral health related quality of life of adolescents. This cross-sectional study was conducted among 700 adolescents aged 10 to 19 years (with mean age 14.6 (±1.3) years) attending 14 secondary schools in Ibadan, Nigeria. Data were collected using a self-administered questionnaire, which assessed sociodemographic characteristics of the students, oral habits and OHRQoL with Oral Health Impact Profile 5 (OHIP-5). Data were analyzed with SPSS and p value was at <5%. Mann Whitney U statistics was used to test for associations between OHIP-5 scores and presence or absence of oral habits. Logistic regression was used for multivariate analysis. A total of 363 (51.9%; 95%CI = 48.1%-55.6%) bite their nails, 216 (30.9%; 95%CI = 27.5%-34.4%) breathe with their mouth, 122 (17.4%; 95%CI = 14.7%-20.4%) suck their lips, 89 (12.7%; 95%CI = 10.3%-15.4%) grind their teeth together and 32 (4.6%; 95%CI = 3.1%-6.7%) sucked their thumbs. A total of 403 (81.1%) adolescents who engaged in at least an oral habit reported an impairment of their OHRQoL. Painful aching in the mouth was the most frequently affected OHRQoL item reported by the adolescents who engaged in oral habits. Those who sucked their thumbs (OR = 2.3, 95%CI = 1.1-4.7, p = 0.028) and those who sucked their lips were more likely to have poorer OHRQoL (OR = 1.6, 95%CI = 1.1-2.5, p = 0.024). Oral habits were prevalent among the adolescents and affected their OHRQoL. Those who sucked their thumbs and lips were more likely to report poorer OHRQoL than those who did not.

Characterization of dysgeusia and xerostomia in patients with multiple myeloma treated with the T-cell redirecting GPRC5D bispecific antibody talquetamab

PURPOSE

In recent years, various immunotherapies have improved the survival of patients with multiple myeloma (MM). However, there remains an unmet need for novel agents. Talquetamab is the first-in-class GPRC5D-targeting T-cell redirecting bispecific antibody, which has substantial activity in advanced MM. Rapidly after the start of talquetamab treatment, patients reported taste changes (dysgeusia; 60% of patients), and a feeling of dry mouth (xerostomia; 30-57% of patients), which may be related to expression of the target antigen in healthy tissues, such as taste buds. Here, we aimed at better characterizing these oral toxicities.

METHODS

We measured salivary flow and the ability to taste (objectively and patient-reported), assessed the feeling of dry mouth, and evaluated quality of life before and 8 weeks after the start of talquetamab therapy in eight heavily pretreated MM patients.

RESULTS

Talquetamab treatment led to the rapid and significant decrease in objectively measured taste scores (total score 8.8 ± 2.0 vs 4.9 ± 2.5). All patients reported moderate to severe taste changes. Moreover, patients experienced severe xerostomia after the initiation of talquetamab treatment, in the absence of changes in unstimulated and stimulated salivary flow. Because of these oral toxicities a significant impairment in global health status/(oral health related) quality of life was reported.

CONCLUSION

Studying taste changes in patients treated with talquetamab following up on the described leads provides a new and unique opportunity to further unravel the pathophysiology of taste changes after cancer treatment.

The bacterial species profiles of the lingual and salivary microbiota differ with basic tastes sensitivity in human

Taste perception is crucial and impairments, which can be linked to pathologies, can lead to eating disorders. It is triggered by taste compounds stimulating receptors located on the tongue. However, the tongue is covered by a film containing saliva and microorganisms suspected to modulate the taste receptor environment. The present study aimed to elucidate the links between taste sensitivity (sweetness, sourness, bitterness, saltiness, umami) and the salivary as well as the tongue microbiota using shotgun metagenomics. 109 bacterial species were correlated with at least one taste. Interestingly, when a species was correlated with at least two tastes, the correlations were unidirectional, indicating a putative global implication. Some Streptococcus, SR1 and Rickenellaceae species correlated with five tastes. When comparing both ecosystems, saliva appears to be a better taste predictor than tongue. This work shows the implication of the oral microbiota in taste and exhibits specificities depending on the ecosystem considered.

Oral Microbiota: The Influences and Interactions of Saliva, IgA, and Dietary Factors in Health and Disease

Recent advances in metagenomic analyses have made it easier to analyze microbiota. The microbiota, a symbiotic community of microorganisms including bacteria, archaea, fungi, and viruses within a specific environment in tissues such as the digestive tract and skin, has a complex relationship with the host. Recent studies have revealed that microbiota composition and balance particularly affect the health of the host and the onset of disease. Influences such as diet, food preferences, and sanitation play crucial roles in microbiota composition. The oral cavity is where the digestive tract directly communicates with the outside. Stable temperature and humidity provide optimal growth environments for many bacteria. However, the oral cavity is a unique environment that is susceptible to pH changes, salinity, food nutrients, and external pathogens. Recent studies have emphasized the importance of the oral microbiota, as changes in bacterial composition and balance could contribute to the development of systemic diseases. This review focuses on saliva, IgA, and fermented foods because they play critical roles in maintaining the oral bacterial environment by regulating its composition and balance. More attention should be paid to the oral microbiota and its regulatory factors in oral and systemic health.

Salivary microbial profiles associate with responsiveness to warning oral sensations and dietary intakes

Oral microbiota-host interactions are gaining recognition as potential factors contributing to interindividual variations in taste perception. However, whether such possible links imply specific bacterial co-occurrence networks remains unknown. To address this issue, we used 16 s rRNA gene sequencing to profile the salivary microbiota of 100 healthy individuals (52 % women; 18-30 y/o), who provided hedonic and psychophysical responses to 5 liquid and 5 solid commercially-available foods, each chosen to elicit a target sensation (sweet, sour, bitter, salty, pungent). The same cohort also completed several psychometric measures and a 4-day food diary. Unsupervised data-driven clustering of genus-level Aitchison distances supported the existence of two salivary microbial profiles (CL-1, CL-2). While CL-1 (n = 57; 49.1 % women) exhibited higher α-diversity metrics and was enriched in microbial genera assigned to the class Clostridia (e.g., Lachnospiraceae_[G-3]), CL-2 (n = 43; 55.8 % women) harbored greater amounts of taxa with potential cariogenic effects (e.g., genus Lactobacillus) and significantly lower abundances of inferred MetaCyc pathways related to the metabolic fate of acetate. Intriguingly, CL-2 showed enhanced responsiveness to warning oral sensations (bitter, sour, astringent) and a higher propensity to crave sweet foods or engage in prosocial behaviors. Further, the same cluster reported habitually consuming more simple carbohydrates and fewer beneficial nutrients (vegetable proteins, monounsaturated fatty acids). In summary, while the mediating role of participants' baseline diet on findings can not be definitively excluded, this work provides evidence suggesting that microbe-microbe and microbe-taste interactions may exert an influence on dietary habits and motivates further research to uncover a potential "core" taste-related salivary microbiota.

Influence of Bariatric Surgery on Oral Microbiota: A Systematic Review

The study aims to systematically review the available literature to evaluate the changes in oral microbiota in patients after bariatric surgery (BS) and correlates these alterations in microorganisms with common oral manifestations. Relevant Electronic databases were systematically searched for indexed English literature. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed for framework designing, application, and reporting of the current systematic review. The focused PICO question was: "Is there any change in oral microbiota (O) of patients (P) who underwent BS (I) when compared with non-BS groups (C)?' Seven articles were selected for qualitative synthesis. On application of the National Institutes of Health (NIH) quality assessment tool, six studies were found to be of fair quality and one was of good quality. All the seven included studies evaluated the effect of BS on oral microbiota in humans. The outcomes of this review suggest that considerable changes take place in oral microbiota after BS which can be correlated with common oral manifestations. These changes are mainly due to the indirect effect of BS and may vary with the individuals. Due to variations in the included studies, it is difficult to proclaim any persistent pattern of oral microbiota found after BS.

The role of the oral microbiome in obesity and metabolic disease: potential systemic implications and effects on taste perception

Obesity and its metabolic sequelae still comprise a challenge when it comes to understanding mechanisms, which drive these pandemic diseases. The human microbiome as a potential key player has attracted the attention of broader research for the past decade. Most of it focused on the gut microbiome while the oral microbiome has received less attention. As the second largest niche, the oral microbiome is associated with a multitude of mechanisms, which are potentially involved in the complex etiology of obesity and associated metabolic diseases. These mechanisms include local effects of oral bacteria on taste perception and subsequent food preference as well as systemic effects on adipose tissue function, the gut microbiome and systemic inflammation. This review summarizes a growing body of research, pointing towards a more prominent role of the oral microbiome in obesity and associated metabolic diseases than expected. Ultimately, our knowledge on the oral microbiome may support the development of new patient oriented therapeutic approaches inevitable to relieve the health burden of metabolic diseases and to reach long-term benefits in patients´ lives.

Alteration of taste perception, food neophobia and oral microbiota composition in children with food allergy

Currently, the mechanisms underlying sensory perception and sensory performance in children with food allergies are far from being understood. As well, only recently, single research afforded the oral host-commensal milieu, addressing oral microbial communities in children with peanut allergies. To bridge the current gaps in knowledge both in the sensory and microbial fields, a psychophysiological case-control study was performed in allergic children (n = 29) and a healthy sex-age-matched control group (n = 30). Taste perception, food neophobia, and liking were compared in allergic and non-allergic children. The same subjects were characterized for their oral microbiota composition by addressing saliva to assess whether specific profiles were associated with the loss of oral tolerance in children with food allergies. Our study evidenced an impaired ability to correctly identify taste qualities in the allergic group compared to controls. These results were also consistent with anatomical data related to the fungiform papillae on the tongue, which are lower in number in the allergic group. Furthermore, distinct oral microbial profiles were associated with allergic disease, with significant down-representations of the phylum Firmicutes and of the genera Veillonella spp., Streptococcus spp., Prevotella spp., and Neisseria spp. For the first time, this study emphasizes the link between sensory perception and food allergy, which is a novel and whole-organism view of this pathology. Our data indicated that an impaired taste perception, as regards both functionality and physiologically, was associated with food allergy, which marginally influences the food neophobia attitude. It is also accompanied by compositional shifts in oral microbiota, which is, in turn, another actor of this complex interplay and is deeply interconnected with mucosal immunity. This multidisciplinary research will likely open exciting new approaches to therapeutic interventions.

Physiology of the tongue with emphasis on taste transduction

The tongue is a complex multifunctional organ that interacts and senses both interoceptively and exteroceptively. Although it is easily visible to almost all of us, it is relatively understudied and what is in the literature is often contradictory or is not comprehensively reported. The tongue is both a motor and a sensory organ: motor in that it is required for speech and mastication, and sensory in that it receives information to be relayed to the central nervous system pertaining to the safety and quality of the contents of the oral cavity. Additionally, the tongue and its taste apparatus form part of an innate immune surveillance system. For example, loss or alteration in taste perception can be an early indication of infection as became evident during the present global SARS-CoV-2 pandemic. Here, we particularly emphasize the latest updates in the mechanisms of taste perception, taste bud formation and adult taste bud renewal, and the presence and effects of hormones on taste perception, review the understudied lingual immune system with specific reference to SARS-CoV-2, discuss nascent work on tongue microbiome, as well as address the effect of systemic disease on tongue structure and function, especially in relation to taste.

Unlocking Modifiable Risk Factors for Alzheimer's Disease: Does the Oral Microbiome Hold Some of the Keys?

Advancing age is recognized as the primary risk factor for Alzheimer's disease (AD); however approximately one third of dementia cases are attributable to modifiable risk factors such as hypertension, diabetes, smoking, and obesity. Recent research also implicates oral health and the oral microbiome in AD risk and pathophysiology. The oral microbiome contributes to the cerebrovascular and neurodegenerative pathology of AD via the inflammatory, vascular, neurotoxic, and oxidative stress pathways of known modifiable risk factors. This review proposes a conceptual framework that integrates the emerging evidence regarding the oral microbiome with established modifiable risk factors. There are numerous mechanisms by which the oral microbiome may interact with AD pathophysiology. Microbiota have immunomodulatory functions, including the activation of systemic pro-inflammatory cytokines. This inflammation can affect the integrity of the blood-brain barrier, which in turn modulates translocation of bacteria and their metabolites to brain parenchyma. Amyloid-β is an antimicrobial peptide, a feature which may in part explain its accumulation. There are microbial interactions with cardiovascular health, glucose tolerance, physical activity, and sleep, suggesting that these modifiable lifestyle risk factors of dementia may have microbial contributors. There is mounting evidence to suggest the relevance of oral health practices and the microbiome to AD. The conceptual framework presented here additionally demonstrates the potential for the oral microbiome to comprise a mechanistic intermediary between some lifestyle risk factors and AD pathophysiology. Future clinical studies may identify specific oral microbial targets and the optimum oral health practices to reduce dementia risk.

The tongue biofilm metatranscriptome identifies metabolic pathways associated with the presence or absence of halitosis

Intra-oral halitosis usually results from the production of volatile sulfur compounds, such as methyl mercaptan and hydrogen sulfide, by the tongue microbiota. There are currently no reports on the microbial gene-expression profiles of the tongue microbiota in halitosis. In this study, we performed RNAseq of tongue coating samples from individuals with and without halitosis. The activity of Streptococcus (including S. parasanguinis), Veillonella (including V. dispar) and Rothia (including R. mucilaginosa) was associated with halitosis-free individuals while Prevotella (including P. shahi), Fusobacterium (including F. nucleatum) and Leptotrichia were associated with halitosis. Interestingly, the metatranscriptome of patients that only had halitosis levels of methyl mercaptan was similar to that of halitosis-free individuals. Finally, gene expression profiles showed a significant over-expression of genes involved in L-cysteine and L-homocysteine synthesis, as well as nitrate reduction genes, in halitosis-free individuals and an over-expression of genes responsible for cysteine degradation into hydrogen sulfide in halitosis patients.

Influence of the Gut Microbiome on Feed Intake of Farm Animals

With the advancement of microbiome research, the requirement to consider the intestinal microbiome as the “last organ” of an animal emerged. Through the production of metabolites and/or the stimulation of the host’s hormone and neurotransmitter synthesis, the gut microbiota can potentially affect the host’s eating behavior both long and short-term. Based on current evidence, the major mediators appear to be short-chain fatty acids (SCFA), peptide hormones such as peptide YY (PYY) and glucagon-like peptide-1 (GLP-1), as well as the amino acid tryptophan with the associated neurotransmitter serotonin, dopamine and γ-Aminobutyrate (GABA). The influence appears to extend into central neuronal networks and the expression of taste receptors. An interconnection of metabolic processes with mechanisms of taste sensation suggests that the gut microbiota may even influence the sensations of their host. This review provides a summary of the current status of microbiome research in farm animals with respect to general appetite regulation and microbiota-related observations made on the influence on feed intake. This is briefly contrasted with the existing findings from research with rodent models in order to identify future research needs. Increasing our understanding of appetite regulation could improve the management of feed intake, feed frustration and anorexia related to unhealthy conditions in farm animals.

Individual Sweet Taste Perception Influences Salivary Characteristics After Orosensory Stimulation With Sucrose and Noncaloric Sweeteners

Emerging evidence points to a major role of salivary flow and viscoelastic properties in taste perception and mouthfeel. It has been proposed that sweet-tasting compounds influence salivary characteristics. However, whether perceived differences in the sensory properties of structurally diverse sweet-tasting compounds contribute to salivary flow and saliva viscoelasticity as part of mouthfeel and overall sweet taste perception remains to be clarified. In this study, we hypothesized that the sensory diversity of sweeteners would differentially change salivary characteristics in response to oral sweet taste stimulation. Therefore, we investigated salivary flow and saliva viscoelasticity from 21 healthy test subjects after orosensory stimulation with sucrose, rebaudioside M (RebM), sucralose, and neohesperidin dihydrochalcone (NHDC) in a crossover design and considered the basal level of selected influencing factors, including the basal oral microbiome. All test compounds enhanced the salivary flow rate by up to 1.51 ± 0.12 g/min for RebM compared to 1.10 ± 0.09 g/min for water within the 1st min after stimulation. The increase in flow rate was moderately correlated with the individually perceived sweet taste (r = 0.3, p < 0.01) but did not differ between the test compounds. The complex viscosity of saliva was not affected by the test compounds, but the analysis of covariance showed that it was associated (p < 0.05) with mucin 5B (Muc5B) concentration. The oral microbiome was of typical composition and diversity but was strongly individual-dependent (permutational analysis of variance (PERMANOVA): R 2 = 0.76, p < 0.001) and was not associated with changes in salivary characteristics. In conclusion, this study indicates an impact of individual sweet taste impressions on the flow rate without measurable changes in the complex viscosity of saliva, which may contribute to the overall taste perception and mouthfeel of sweet-tasting compounds.

The capacity and organization of gustatory working memory

Remembering a particular taste is crucial in food intake and associative learning. We investigated whether taste can be dynamically encoded, maintained, and retrieved on short time scales consistent with working memory (WM). We use novel single and multi-item taste recognition tasks to show that a single taste can be reliably recognized despite repeated oro-sensory interference suggesting active and resilient maintenance (Experiment 1, N = 21). When multiple tastes were presented (Experiment 2, N = 20), the resolution with which these were maintained depended on their serial position, and recognition was reliable for up to three tastes suggesting a limited capacity of gustatory WM. Lastly, stimulus similarity impaired recognition with increasing set size, which seemed to mask the awareness of capacity limitations. Together, the results advocate a hybrid model of gustatory WM with a limited number of slots where items are stored with varying precision.

Daily Exposure to a Cranberry Polyphenol Oral Rinse Alters the Oral Microbiome but Not Taste Perception in PROP Taster Status Classified Individuals

Diet and salivary proteins influence the composition of the oral microbiome, and recent data suggest that TAS2R38 bitter taste genetics may also play a role. We investigated the effects of daily exposure to a cranberry polyphenol oral rinse on taste perception, salivary proteins, and oral microbiota. 6-n-Propylthiouracil (PROP) super-tasters (ST, n = 10) and non-tasters (NT, n = 10) rinsed with 30 mL of 0.75 g/L cranberry polyphenol extract (CPE) in spring water, twice daily for 11 days while consuming their habitual diets. The 16S rRNA gene sequencing showed that the NT oral microbiome composition was different than that of STs at baseline (p = 0.012) but not after the intervention (p = 0.525). Principal coordinates analysis using unweighted UniFrac distance showed that CPE modified microbiome composition in NTs (p = 0.023) but not in STs (p = 0.096). The intervention also altered specific salivary protein levels (α-amylase, MUC-5B, and selected S-type Cystatins) with no changes in sensory perception. Correlation networks between oral microbiota, salivary proteins, and sensory ratings showed that the ST microbiome had a more complex relationship with salivary proteins, particularly proline-rich proteins, than that in NTs. These findings show that CPE modulated the oral microbiome of NTs to be similar to that of STs, which could have implications for oral health.

Oral Microbiota-Host Interaction Mediated by Taste Receptors

Taste receptors, originally identified in taste buds, function as the periphery receptors for taste stimuli and play an important role in food choice. Cohort studies have revealed that single nucleotide polymorphisms of taste receptors such as T1R1, T1R2, T2R38 are associated with susceptibility to oral diseases like dental caries. Recent studies have demonstrated the wide expression of taste receptors in various tissues, including intestinal epithelia, respiratory tract, and gingiva, with an emerging role of participating in the interaction between mucosa surface and microorganisms via monitoring a wide range of metabolites. On the one hand, individuals with different oral microbiomes exhibited varied taste sensitivity, suggesting a potential impact of the oral microbiota composition on taste receptor function. On the other hand, animal studies and in vitro studies have uncovered that a variety of oral cells expressing taste receptors such as gingival solitary chemosensory cells, gingival epithelial cells (GECs), and gingival fibroblasts can detect bacterial signals through bitter taste receptors to trigger host innate immune responses, thus regulating oral microbial homeostasis. This review focuses on how taste receptors, particularly bitter and sweet taste receptors, mediate the oral microbiota-host interaction as well as impact the occurrence and development of oral diseases. Further studies delineating the role of taste receptors in mediating oral microbiota-host interaction will advance our knowledge in oral ecological homeostasis establishment, providing a novel paradigm and treatment target for the better management of dental infectious diseases.

Reducing the Bitter Taste of Pharmaceuticals Using Cell-Based Identification of Bitter-Masking Compounds

The palatability of a pharmaceutical preparation is a significant obstacle in developing a patient-friendly dosage form. Bitter taste is an important factor for patients in (i) selecting a certain drug from generic products available in the market and (ii) adhering to a therapeutic regimen. The various methods developed for identification of bitter tasting and bitter-taste modulating compounds present a number of limitations, ranging from limited sensitivity to lack of close correlations with sensory data. In this study, we demonstrate a fluorescence-based assay, analyzing the bitter receptor TAS2R-linked intracellular pH (pH_i) of human gastric parietal (HGT-1) cells as a suitable tool for the identification of bitter tasting and bitter-taste modulating pharmaceutical compounds and preparations, which resembles bitter taste perception. Among the fluorometric protocols established to analyze pH_i changes, one of the most commonly employed assays is based on the use of the pH-sensitive dye SNARF-1 AM. This methodology presents some limitations; over time, the assay shows a relatively low signal amplitude and sensitivity. Here, the SNARF-1 AM methodology was optimized. The identified bicarbonate extrusion mechanisms were partially inhibited, and measurements were carried out in a medium with lower intrinsic fluorescence, with no need for controlling external CO₂ levels. We applied the assay for the screening of flavonoids as potential bitter-masking compounds for guaifenesin, a bitter-tasting antitussive drug. Our findings revealed that eriodictyol, hesperitin and phyllodulcin were the most potent suitable candidates for bitter-masking activity, verified in a human sensory trial.

The tongue map and the spatial modulation of taste perception

There is undoubtedly a spatial component to our experience of gustatory stimulus qualities such as sweet, bitter, salty, sour, and umami, however its importance is currently unknown. Taste thresholds have been shown to differ at different locations within the oral cavity where gustatory receptors are found. However, the relationship between the stimulation of particular taste receptors and the subjective spatially-localized experience of taste qualities is uncertain. Although the existence of the so-called ‘tongue map’ has long been discredited, the psychophysical evidence clearly demonstrates significant (albeit small) differences in taste sensitivity across the tongue, soft palate, and pharynx (all sites where taste buds have been documented). Biases in the perceived localization of gustatory stimuli have also been reported, often resulting from tactile capture (i.e., a form of crossmodal, or multisensory, interaction). At the same time, varying responses to supratheshold tastants along the tongue's anterior-posterior axis have putatively been linked to the ingestion-ejection response. This narrative review highlights what is currently known concerning the spatial aspects of gustatory perception, considers how such findings might be explained, given the suggested balanced distribution of taste receptors for each basic taste quality where taste papillae are present, and suggests why knowing about such differences may be important.

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The existence of the tongue map has long been discredited.

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Taste receptors in the oral cavity respond to all tastes regardless of their location.

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Human psychophysical data highlights a significant spatial modulation of taste perception in the oral cavity.

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Highly-controlled studies of taste psychophysics rarely capture the full multisensory experience associated with eating and drinking.

The Influence of Common Noncommunicable Diseases on Chemosensory Perception and Clinical Implications in Children and Adolescents

An increased incidence of noninfectious chronic diseases, such as obesity, diabetes, and allergies, has been noted in the last century, especially in the last 2 to 3 generations. Evidence suggested that the interrelation among these chronic conditions in pediatric age (e.g., children and adolescents aged 4-16 y) is complex and still unknown, reinforcing the interest of pediatricians in these diseases. Of interest is the need to better understand the link between these pathologies and sensory perception, since the chemical senses of taste and smell, together with chemesthesis, are reported to have a role in food choices and may provide a novel target for intervention in the treatment of these pathologies. This review aims to explore the current evidence on the link between these chronic conditions and chemosensory perception (i.e., taste and smell). In addition, the putative role that chemosensory perception may have on food choices and eating behavior of children and adolescents affected by these diseases are highlighted. Furthermore, the review addresses the unexplored issues that need to be investigated in this area. The literature data search suggested that no clear relation between taste and smell perception and the aforementioned diseases in young population yet exists. However, some possible trends have been highlighted in the adult population, in whom the duration of disease might have affected the relation. There is a need for further, high-quality, hypothesis-led research, with robust measures of taste and smell functions as the primary outcomes, to strengthen or deny this evidence.

Dynamic sensations of fresh and roasted salmon (Salmo salar) during chewing

The sensory perception of food is a dynamic procedure, which is closely related to the released flavor stimuli. Thus, we evaluated the dynamic sensations of fresh and roasted salmon during the chewing process and investigated the tastants released in saliva. For fresh salmon, the fishy, umami, salty, and sweet attributes were perceived successively. Meanwhile, the smoky and fried flavors were the most dominant attributes of roasted salmon at the beginning, then various attributes were perceived. During the chewing process, free amino acids and 5'-nucleotides released in saliva were quantified. Compared to the sensory data, the results demonstrated that glutamic acid and inosine 5'-monophosphate released in saliva might induce the umami perception. The sweet-tasting amino acids alanine and glycine may contribute to sweetness. Therefore, we suggested that the time dimension of tastants dissolved in saliva would affect the dynamic sensation of food, even for complex food materials.

Taste of Fat and Obesity: Different Hypotheses and Our Point of View

Obesity results from a temporary or prolonged positive energy balance due to an alteration in the homeostatic feedback of energy balance. Food, with its discriminative and hedonic qualities, is a key element of reward-based energy intake. An alteration in the brain reward system for highly palatable energy-rich foods, comprised of fat and carbohydrates, could be one of the main factors involved in the development of obesity by increasing the attractiveness and consumption of fat-rich foods. This would induce, in turn, a decrease in the taste of fat. A better understanding of the altered reward system in obesity may open the door to a new era for the diagnosis, management and treatment of this disease.

Huoxue Jiangtang Decoction Alleviates Type 2 Diabetes Mellitus by Regulating the Oral Microbiota and Food Preferences

PURPOSE

As a formula of traditional Chinese medicine (TCM), Huoxue Jiangtang Decoction (HJD) has positive effects on diabetes mellitus (DM) through improving of the metabolism of glycolipid and the function of β-cell. Hence, this research aims to explore the potential therapeutic effects of HJD on diabetes and reveal its underlying mechanisms.

METHODS

Diabetic rat models induced by high-fat diet (HFD) and streptozotocin (STZ) were included in this study. Following successful modeling, diabetic rats were treated with HJD, and then its therapeutic effects in eight weeks were evaluated. In addition to biochemical indicators, two-bottle preference tests were carried out to examine the rats' preferences for fat and sugar, and 16S rRNA gene sequencing was performed to disclose the differences of oral microbiota among groups. Finally, Pearson correlation coefficient was used to explore the correlation between oral microbiota and the preferences for fat and sugar.

RESULTS

It was found that HJD significantly improved the levels of fasting blood glucose (FBG), glucose tolerance, and dyslipidemia. Additionally, HJD contributed to decreasing preferences for fat and sugar in diabetic rats, which plays an important role in food intake. Furthermore, HJD regulated the abundance, distribution, and structure of oral microbiota in diabetic rats, serving as one of the underlying mechanisms of its antidiabetic effects.

CONCLUSION

Taken with other formulas, HJD functions to improve the metabolism of glycolipid and the function of β-cell by inhibiting preferences for fat and sugar, as well as regulating the oral microbiota of diabetic rats. Furthermore, a potential correlation between the oral micro-environment and preferences for fat and sugar in STZ-induced diabetic rats is likely to exist.

Associations of the oral microbiota and Candida with taste, smell, appetite and undernutrition in older adults

Poor taste and smell function are widely thought to contribute to the development of poor appetite and undernutrition in older adults. It has been hypothesized that the oral microbiota play a role as well, but evidence is scarce. In a cross-sectional cohort of 356 older adults, we performed taste and smell tests, collected anthropometric measurements and tongue swabs for analysis of microbial composition (16S rRNA sequencing) and Candida albicans abundance (qPCR). Older age, edentation, poor smell and poor appetite were associated with lower alpha diversity and explained a significant amount of beta diversity. Moreover, a lower Streptococcus salivarius abundance was associated with poor smell identification score, whereas high C. albicans abundance seemed to be associated with poor smell discrimination score. In our population, neither the tongue microbiota, nor C. albicans were associated with poor taste or directly with undernutrition. Our findings do suggest a host-microbe interaction with regard to smell perception and appetite.

Comparing Taste Detection Thresholds across Individuals Following Vegan, Vegetarian, or Omnivore Diets

Taste perception plays an undisputed role in food choice, preference, and intake. Recent literature suggests that individual diet and taste sensitivity may have a reciprocal relationship, with evidence highlighting that specific diets can alter taste sensitivities. Commensurate with an increase in the prevalence of plant-based diets is the importance of investigating if following a vegetarian or vegan diet is associated with altered taste sensitivities. In this study, the taste detection thresholds for six compounds (i.e., sweet-sucrose, salty-sodium chloride, sour-citric acid, umami-monosodium glutamate, MSG, bitter-caffeine, and metallic-iron II sulphate heptahydrate) were measured for a total of 80 healthy, New Zealand European females aged 18-45 years old, who were categorised as 22 vegans, 23 vegetarians, and 35 omnivores. Each participant's detection thresholds to these compounds were measured across two sessions, using an ascending Method of Limits with two-alternative-forced-choice presentations. The threshold data were analysed using both multivariate (i.e., principal component analysis) and univariate (i.e., ANCOVA) techniques to assess differences across the three types of diet. Multivariate analysis suggested that the omnivore group had distinct taste sensitivity patterns across the six compounds compared to the vegetarian or vegan group, which were characterised by relatively heightened sensitivity to metallic and lowered sensitivity to sweetness. Furthermore, the vegetarian group was shown to have a significantly lower detection threshold to bitterness (i.e., caffeine) relative to the other two groups (p < 0.001). While future study is required to investigate the cause-effect relationship between individual diet and taste sensitivities, the present study provides a systematic evaluation of taste sensitivities of individuals following distinct diets. This information may be valuable to future gustatory research as well as to food manufacturers.

Bitter and sweet taste perception: relationships to self-reported oral hygiene habits and oral health status in a survey of Australian adults

Background

Oral health, an essential part of general health and well-being, is influenced by multiple factors, including oral hygiene habits and dietary factors. Dietary preferences are influenced by variation in taste perceptions and threshold tasting. Polymorphisms in specific genes for sweet and bitter taste receptors and bitter taste perception have been associated with dental caries. However, taste is complex with multiple receptors, each with multiple potential polymorphisms contributing to taste perception as well as social, cultural, and environmental influences. Additionally, these association studies have been conducted in restricted cohorts (e.g., children only). Furthermore, outcomes have been limited to dental caries and studies between taste perception and oral hygiene habits have not been completed.

Methods

A cross-sectional online survey was conducted to investigate the relationships between bitter and sweet taste perception (liking and intensity of index food items), self-reported oral hygiene habits and oral health (n = 518).

Results

Higher mean intensity scores for bitter (16–21%) and sweet (< 5%-60%) were seen with higher frequencies of oral hygiene habits (brushing, use of mouthwash, chewing gum and tongue cleaning). Lower mean bitter liking scores (18–21%) were seen with higher frequencies of oral hygiene habits (brushing, mouthwash use, floss use and chewing gum). Sweet liking scores varied by reported frequency of mouthwash use and flossing only, with mixed patterns of variance. Mean bitter and sweet intensity perception scores varied with the number of dental caries ((13–20% higher in those with 3 or more caries, compared to none).

Conclusions

While there were numerous relationships identified between liking and perception of sweet and bitter and oral health outcomes, the magnitude and direction of associations varied by outcome. The direction of the associations cannot be inferred due to the cross-sectional nature of the study. The demonstrated relationships justify further future investigations, which could help better understand if taste liking and perception is impacted by oral hygiene and health, or vice versa. This could be important in understanding the causation and progression of oral health diseases or the development of novel therapeutics for oral health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01910-8.

The oral microbiome: Role of key organisms and complex networks in oral health and disease

States of oral health and disease reflect the compositional and functional capacities of, as well as the interspecies interactions within, the oral microbiota. The oral cavity exists as a highly dynamic microbial environment that harbors many distinct substrata and microenvironments that house diverse microbial communities. Specific to the oral cavity, the nonshedding dental surfaces facilitate the development of highly complex polymicrobial biofilm communities, characterized not only by the distinct microbes comprising them, but cumulatively by their activities. Adding to this complexity, the oral cavity faces near-constant environmental challenges, including those from host diet, salivary flow, masticatory forces, and introduction of exogenous microbes. The composition of the oral microbiome is shaped throughout life by factors including host genetics, maternal transmission, as well as environmental factors, such as dietary habits, oral hygiene practice, medications, and systemic factors. This dynamic ecosystem presents opportunities for oral microbial dysbiosis and the development of dental and periodontal diseases. The application of both in vitro and culture-independent approaches has broadened the mechanistic understandings of complex polymicrobial communities within the oral cavity, as well as the environmental, local, and systemic underpinnings that influence the dynamics of the oral microbiome. Here, we review the present knowledge and current understanding of microbial communities within the oral cavity and the influences and challenges upon this system that encourage homeostasis or provoke microbiome perturbation, and thus contribute to states of oral health or disease.

How does the early life environment influence the oral microbiome and determine oral health outcomes in childhood?

The first 1000 days of life, from conception to 2 years, are a critical window for the influence of environmental exposures on the assembly of the oral microbiome, which is the precursor to dental caries (decay), one of the most prevalent microbially induced disorders worldwide. While it is known that the human microbiome is susceptible to environmental exposures, there is limited understanding of the impact of prenatal and early childhood exposures on the oral microbiome trajectory and oral health. A barrier has been the lack of technology to directly measure the foetal "exposome", which includes nutritional and toxic exposures crossing the placenta. Another barrier has been the lack of statistical methods to account for the high dimensional data generated by-omic assays. Through identifying which early life exposures influence the oral microbiome and modify oral health, these findings can be translated into interventions to reduce dental decay prevalence.

Do Gut Microbes Taste?

Gut microbiota has emerged as a major metabolically active organ with critical functions in both health and disease. The trillions of microorganisms hosted by the gastrointestinal tract are involved in numerous physiological and metabolic processes including modulation of appetite and regulation of energy in the host spanning from periphery to the brain. Indeed, bacteria and their metabolic byproducts are working in concert with the host chemosensory signaling pathways to affect both short- and long-term ingestive behavior. Sensing of nutrients and taste by specialized G protein-coupled receptor cells is important in transmitting food-related signals, optimizing nutrition as well as in prevention and treatment of several diseases, notably obesity, diabetes and associated metabolic disorders. Further, bacteria metabolites interact with specialized receptors cells expressed by gut epithelium leading to taste and appetite response changes to nutrients. This review describes recent advances on the role of gut bacteria in taste perception and functions. It further discusses how intestinal dysbiosis characteristic of several pathological conditions may alter and modulate taste preference and food consumption via changes in taste receptor expression.

Perceived Intensity and Palatability of Fatty Culinary Preparations is Associated with Individual Fatty Acid Detection Threshold and the Fatty Acid Profile of Oils Used as Ingredients

The term oleogustus was recently proposed to describe a sixth basic taste that could guide preference for fatty foods and dishes to an extent. However, experimental data on food preference based on fatty acid (FA) content is scarce. Our aim was to examine the role of FA profile of oils and preparations as well as FA sensory thresholds on the palatability of salty and sweet culinary preparations representative of traditional Spanish Mediterranean cooking. In this study, we used three oils with similar texture and odor profile but different in their FA composition (saturated, monounsaturated, and polyunsaturated) and compared subjects in regard to their FA detection threshold and perceived pleasantness and intensity. Our results indicate that whereas saturated FAs cannot be detected at physiological concentrations, individuals can be categorized as tasters and nontasters, according to their sensory threshold to linoleic acid, which is negatively associated with perceived intensity (r = -0.393, P < 0.001) but positively with palatability (r = 0.246, P = 0.018). These differences may be due to a possible response to a fat taste. This sixth taste, or oleogustus. would allow establishing differences in taste intensity/palatability considering the FA profile of the culinary preparations. Given that tasters can detect linoleic and oleic acid at lower concentrations than nontasters, a greater amount of unsaturated FAs in culinary preparations could provoke an unpleasant experience. This finding could be relevant in the context of the culinary sector and to further our understanding of food preference and eating behavior.

Upper-airway dysbiosis related to frequent sweets consumption increases the risk of asthma in children with chronic rhinosinusitis

BACKGROUND

Innate immunity response to local dysbiosis seems to be one of the most important immunologic backgrounds of chronic rhinosinusitis (CRS) and concomitant asthma. We aimed to assess clinical determinants of upper-airway dysbiosis and its effect on nasal inflammatory profile and asthma risk in young children with CRS.

METHODS

We recruited one hundred and thirty-three children, aged 4-8 years with doctor-diagnosed CRS with or without asthma. The following procedures were performed in all participants: face-to-face standardized Sinus and Nasal Quality of Life questionnaire, skin prick test, taste perception testing, nasopharynx swab, and sampling of the nasal mucosa. Upper-airway dysbiosis was defined separately by asthma-specific microbiome composition and reduced biodiversity. Multivariate methods were used to define the risk factors for asthma and upper-airway dysbiosis and their specific inflammatory profile of nasal mucosa.

RESULTS

The asthma-specific upper-airway microbiome composition reflected by the decreased ratio of Patescibacteria/Actinobacteria independently of atopy increased the risk of asthma (OR:8.32; 95%CI: 2.93-23.6). This asthma-specific microbiome composition was associated with ≥ 7/week sweet consumption (OR:2.64; 95%C:1.11-6.28), reduced biodiversity (OR:3.83; 95%CI:1.65-8.87), the presence of Staphylococcus strains in the nasopharynx (OR:4.25; 95%CI:1.12-16.1), and lower expression of beta-defensin 2, IL-5, and IL-13 in the nasal mucosa. The reduced biodiversity was associated with frequent antibiotic use and with a higher nasal expression of IL-17 and T1R3 (sweet taste receptor). In asthmatic children, reduced sweet taste perception was observed.

CONCLUSIONS

Specific upper-airway dysbiosis related to frequent sweet consumption, frequent antibiotic courses, and altered nasal immune function increases the risk of asthma in young children with CRS.

Salivary microbiome composition changes after bariatric surgery

Recent studies show that the salivary microbiome in subjects with obesity differ from those without obesity, but the mechanism of interaction between the salivary microbiome composition and body weight is unclear. Herein we investigate this relation by analyzing saliva samples from 35 adult patients with obesity undergoing bariatric surgery. Our aim was to describe salivary microbiome changes during body weight loss on an individual-specific level, and to elucidate the effect of bariatric surgery on the salivary microbiome which has not been studied before. Analysis of samples collected before and 1 day after surgery, as well as 3 and 12 months after surgery, showed that the salivary microbiome changed in all study participants, but these changes were heterogeneous. In the majority of participants proportions of Gemella species, Granulicatella elegans, Porphyromonas pasteri, Prevotella nanceiensis and Streptococcus oralis decreased, while Veillonella species, Megasphaera micronuciformis and Prevotella saliva increased. Nevertheless, we found participants deviating from this general trend which suggests that a variety of individual-specific factors influence the salivary microbiome composition more effectively than the body weight dynamics alone. The observed microbiome alternations could be related to dietary changes. Therefore, further studies should focus on association with altered taste preferences and potential oral health consequences.

Comparison of manual and machine learning image processing approaches to determine fungiform papillae on the tongue

Human taste perception is associated with the papillae on the tongue as they contain a large proportion of chemoreceptors for basic tastes and other chemosensation. Especially the density of fungiform papillae (FP) is considered as an index for responsiveness to oral chemosensory stimuli. The standard procedure for FP counting involves visual identification and manual counting of specific parts of the tongue by trained operators. This is a tedious task and automated image analysis methods are desirable. In this paper a machine learning image processing method based on a convolutional neural network is presented. This automated method was compared with three standard manual FP counting procedures using tongue pictures from 132 subjects. Automated FP counts, within the selected areas and the whole tongue, significantly correlated with the manual counting methods (all ρs ≥ 0.76). When comparing the images for gender and PROP status, the density of FP predicted from automated analysis was in good agreement with data from the manual counting methods, especially in the case of gender. Moreover, the present results reinforce the idea that caution should be applied in considering the relationship between FP density and PROP responsiveness since this relationship can be an oversimplification of the complexity of phenomena arising at the central and peripherical levels. Indeed, no significant correlations were found between FP and PROP bitterness ratings using the automated method for selected areas or the whole tongue. Besides providing estimates of the number of FP, the machine learning approach used a tongue coordinate system that normalizes the size and shape of an individual tongue and generated a heat map of the FP position and normalized area they cover. The present study demonstrated that the machine learning approach could provide similar estimates of FP on the tongue as compared to manual counting methods and provide estimates of more difficult-to-measure parameters, such as the papillae's areas and shape.

Factors affecting flavor perception in space: Does the spacecraft environment influence food intake by astronauts?

The intention to send a crewed mission to Mars involves a huge amount of planning to ensure a safe and successful mission. Providing adequate amounts of food for the crew is a major task, but 20 years of feeding astronauts on the International Space Station (ISS) have resulted in a good knowledge base. A crucial observation from the ISS is that astronauts typically consume only 80% of their daily calorie requirements when in space. This is despite daily exercise regimes that keep energy usage at very similar levels to those found on Earth. This calorie deficit seems to have little effect on astronauts who spend up to 12 months on the ISS, but given that a mission to Mars would take 30 to 36 months to complete, there is concern that a calorie deficit over this period may lead to adverse effects in crew members. The key question is why astronauts undereat when they have a supply of food designed to fully deliver their nutritional needs. This review focuses on evidence from astronauts that foods taste different in space, compared to on Earth. The underlying hypothesis is that conditions in space may change the perceived flavor of the food, and this flavor change may, in turn, lead to underconsumption by astronauts. The key areas investigated in this review for their potential impact on food intake are the effects of food shelf life, physiological changes, noise, air and water quality on the perception of food flavor, as well as the link between food flavor and food intake.

Genetic variants of TAS2R38 bitter taste receptor associate with distinct gut microbiota traits in Parkinson's disease: A pilot study

The non-tasting form of the bitter taste receptor, TAS2R38, has been shown as a genetic risk factor associated with the development of Parkinson's disease (PD). Specific taste receptors that are expressed in the lower gastrointestinal tract may respond to alteration in gut microbiota composition, detecting bacterial molecules, and regulate immune responses. Given the importance of brain-gut-microbiota axis and gene-environment interactions in PD, we investigate the associations between the genetic variants of TAS2R38 and gut microbiota composition in 39 PD patients. The results confirm that the majority of PD patients have reduced sensitivity to 6-n-propylthiouracil (PROP) and are carriers of at least one non-functional TAS2R38 AVI haplotype. Moreover, we found this correlation to be associated with a reduction in bacteria alpha-diversity with a predominant reduction of Clostridium genus. We hypothesised that the high frequency of the non-taster form of TAS2R38 associated with a diminuition of Clostridium bacteria in PD might determine a reduction in the activation of protective signalling-molecules useful in preserving gut homeostasis. This pilot study, by identifying a decrease in specific bacteria associated with a reduced sensitivity to PROP, adds essential information that opens new avenues of research into the association of PD microbiota composition and sensory modification.

Differences in Sweet Taste Perception and Its Association with the Streptococcus mutans Cariogenic Profile in Preschool Children with Caries

The aim of the study was to verify the hypothesis about differences in sweet taste perception in the group of preschool children with and without caries, and to determine its relationship with cariogenic microbiota and the frequency of sweets consumption in children. The study group included of 63 children aged 2–6 years: 32 with caries and 31 without caries. The study consisted of collecting questionnaire data and assessment of dental status using the decayed, missing, filled in primary teeth index (dmft) and the International Caries Detection and Assessment System (ICDAS II). The evaluation of sweet taste perception was carried out using a specific method that simultaneously assessed the level of taste preferences and the sensitivity threshold for a given taste. The microbiological analysis consisted of the assessment of the quantitative and qualitative compositions of the oral microbiota of the examined children. The sweet taste perception of children with caries was characterized by a lower susceptibility to sucrose (the preferred sucrose solution concentration was >4 g/L) compared to children without caries (in the range ≤ 4 g/L, p = 0.0015, chi-square test). A similar relationship was also observed for frequent snacking between meals (p = 0.0038, chi-square test). The analysis of studied variables showed the existence of a strong positive correlation between the perception of sweet taste and the occurrence and intensity of the cariogenic process (p = 0.007 for dmft; and p = 0.012 for ICDAS II), as well as the frequency of consuming sweets (p ≤ 0.001 for frequent and repeated consumption of sweets during the day, Spearman test) in children with caries. Additionally, children with an elevated sucrose taste threshold were more than 10-times more likely to develop S. mutans presence (OR = 10.21; 95% CI 3.11–33.44). The results of this study suggest the future use of taste preferences in children as a diagnostic tool for the early detection of increased susceptibility to caries through microbial dysbiosis towards specific species of microorganisms.

Our extended genotype-An argument for the study of domesticated microbes

We interpret the domesticated organisms-plants, animals, and the domesticated microbes used for food fermentation-as an extended genotype of humans due to their close relationship with our species. We propose to analyse the role of microbes in traditionally fermented food with the approaches used in the human microbiome project, and we expect to find associations with ethnic groups, explaining part of human (culinary) culture.

Impact of a Multistrain Probiotic Formulation with High Bifidobacterial Content on the Fecal Bacterial Community and Short-Chain Fatty Acid Levels of Healthy Adults

The consumption of probiotic products is continually increasing, supported by growing scientific evidence of their efficacy. Considering that probiotics may primarily affect health (either positively or negatively) through gut microbiota modulation, the first aspect that should be evaluated is their impact on the intestinal microbial ecosystem. In this study, we longitudinally analyzed the bacterial taxonomic composition and organic acid levels in four fecal samples collected over the course of four weeks from 19 healthy adults who ingested one capsule a day for two weeks of a formulation containing at least 70 billion colony-forming units, consisting of 25% lactobacilli and 75% Bifidobacterium animalis subsp. lactis. We found that 16S rRNA gene profiling showed that probiotic intake only induced an increase in a single operational taxonomic unit ascribed to B. animalis, plausibly corresponding to the ingested bifidobacterial strain. Furthermore, liquid chromatography/mass spectrometry revealed a significant increase in the lactate and acetate/butyrate ratio and a trend toward a decrease in succinate following probiotic administration. The presented results indicate that the investigated probiotic formulation did not alter the intestinal bacterial ecosystem of healthy adults and suggest its potential ability to promote colonization resistance in the gut through a transient increase in fecal bifidobacteria, lactic acid, and the acetate/butyrate ratio.

Taste sensitivity and lifestyle are associated with food preferences and BMI in children

Oral food perception together with lifestyle may affect food preferences and choices, influencing weight gain and obesity development. The present study was designed to evaluate the association of biological (taste sensitivity) and lifestyle variables with children food preferences, assessing whether all these variables contribute to explain BMI percentile. After anthropometric evaluation, 387 children were classified for bitter and sweet taste sensitivities. Socioeconomic/lifestyle aspects and hedonics for 36 foods were collected. Watching TV during meals associate with lower preference for several vegetables, as well as being sweet taste low sensitive, in the case of girls. Moreover, regression analysis showed that bitter taste sensitivity is one of the variables contributing to explain high BMI percentiles. These results present evidences that both biological and socioeconomic and the attention that is given to food (eating in the presence or absence of distractors) are aspects that should be considered in children nutrition to prevent obesity.

Oral Microbiota Profile Associates with Sugar Intake and Taste Preference Genes

Oral microbiota ecology is influenced by environmental and host conditions, but few studies have evaluated associations between untargeted measures of the entire oral microbiome and potentially relevant environmental and host factors. This study aimed to identify salivary microbiota cluster groups using hierarchical cluster analyses (Wards method) based on 16S rRNA gene amplicon sequencing, and identify lifestyle and host factors which were associated with these groups. Group members (n = 175) were distinctly separated by microbiota profiles and differed in reported sucrose intake and allelic variation in the taste-preference-associated genes TAS1R1 (rs731024) and GNAT3 (rs2074673). Groups with higher sucrose intake were either characterized by a wide panel of species or phylotypes with fewer aciduric species, or by a narrower profile that included documented aciduric- and caries-associated species. The inferred functional profiles of the latter type were dominated by metabolic pathways associated with the carbohydrate metabolism with enrichment of glycosidase functions. In conclusion, this study supported in vivo associations between sugar intake and oral microbiota ecology, but it also found evidence for a variable microbiota response to sugar, highlighting the importance of modifying host factors and microbes beyond the commonly targeted acidogenic and acid-tolerant species. The results should be confirmed under controlled settings with comprehensive phenotypic and genotypic data.