Do Gut Microbes Taste?

Patients with Taste Disorders in a Hospital's Dental Department and Strategies for Taste Disorders

Background/Objectives: A retrospective study was conducted to clarify the clinical characteristics of taste disorder cases at the Department of Oral Medicine of Hokkaido University Hospital. The subjects were 322 taste disorder patients (86 male, 236 female, average age: 66 (13.1) years, mean duration of disorder: 15.2 (20.0) months) who were treated at our department from 2007 to 2018. Methods: Associations between symptoms and classification were examined. Results: When looking at the taste symptoms, 154 cases of quantitative taste disorder were observed as taste loss, abscission, and dissociative taste disorder, and 168 cases of qualitative taste disorder were observed as spontaneous abnormal taste, dysgeusia, and maltaste. There was no relationship between sex and quantitative/qualitative taste disorders at V = 0.08. When looking at the causes of taste disorders, the majority were psychogenic, idiopathic, and oral diseases. Conclusions: Approximately 20% of taste disorders are caused by oral diseases, so it should be noted that oral diseases such as oral candidiasis and xerostomia can cause taste disorders and that many of them can be improved with oral treatment.

Sensory Dysfunction, Microbial Infections, and Host Responses in Alzheimer's Disease

Sensory functions of organs of the head and neck allow humans to interact with the environment and establish social bonds. With aging, smell, taste, vision, and hearing decline. Evidence suggests that accelerated impairment in sensory abilities can reflect a shift from healthy to pathological aging, including the development of Alzheimer's disease (AD) and other neurological disorders. While the drivers of early sensory alteration in AD are not elucidated, insults such as trauma and infections can affect sensory function. Herein, we review the involvement of the major head and neck sensory systems in AD, with emphasis on microbes exploiting sensory pathways to enter the brain (the "gateway" hypothesis) and the potential feedback loop by which sensory function may be impacted by central nervous system infection. We emphasize detection of sensory changes as first-line surveillance in senior adults to identify and remove potential insults, like microbial infections, that could precipitate brain pathology.

Taste Preferences at Different Ambient Temperatures and Associated Changes in Gut Microbiota and Body Weight in Mice

Taste, dietary choices, and gut microbiota are often analyzed as major factors of metabolic health. Populations living in cold or hot regions have different dietary habits. This study aims to investigate the potential association among ambient temperature, food taste preferences, and cecal microbiota community profiles in mice. By exposing mice to mixed diets containing sweet, sour, salty, and bitter flavors at low (4 °C) and high (37 °C) ambient temperatures, the taste preferences of mice at both ambient temperatures were in the order of saltiness > sweetness > bitterness > sourness. Exposing mice to sweet, sour, salty, and bitter diets, respectively, revealed that in a low-temperature environment, mice consuming salty (5.00 ± 1.49 g), sweet (4.99 ± 0.35 g), and sour (3.90 ± 0.61 g) diets had significantly higher weight gain compared to those consuming normal feeds (2.34 ± 0.43 g, p < 0.05). Conversely, in a high-temperature environment, no significant changes in body weight were observed among mice consuming different flavored diets (p > 0.05). In a low-temperature environment, mice fed sour and sweet diets showed a significant difference in the gut microbiota composition when compared to those fed a normal diet. A higher abundance of Lachnospiraceae, UBA1819, and Clostridiales was identified as the most significant taxa in the sour group, and a higher abundance of Ruminiclostridium was identified in the sweet group. These differences were associated with microbial pathways involved in carbohydrate metabolism, amino acid metabolism, and energy metabolism. A high-temperature environment exhibited only minor effects on the gut microbiota profile. Overall, our findings provide evidence for temperature-modulated responses to the taste, gut microbiota functions, and body weight changes in mice.

Intestinal Taste Receptor Expression and Its Implications for Health: An Integrative Analysis in Female Rats after Chronic Insect Supplementation

Taste receptors are found in the gastrointestinal tract, where they are susceptible to dietary modulation, a key point that is crucial for diet-related responses. Insects are sustainable and good-quality protein sources. This study analyzed the impact of insect consumption on the modulation of taste receptor expression across various segments of the rat intestine under healthy or inflammatory conditions. Female Wistar rats were supplemented with Tenebrio molitor (T) or Alphitobius diaperinus (B), alongside a control group (C), over 21 days under healthy or LPS-induced inflammation. The present study reveals, for the first time, that insect consumption modulates taste receptor gene expression, mainly in the ascending colon. This modulation was not found under inflammation. Integrative analysis revealed colonic Tas1r1 as a key discriminator for insect consumption (C = 1.04 ± 0.32, T = 1.78 ± 0.72, B = 1.99 ± 0.82, p-value <0.05 and 0.01, respectively). Additionally, correlation analysis showed the interplay between intestinal taste receptors and metabolic and inflammatory responses. These findings underscore how insect consumption modulates taste receptors, influencing intestinal function and broader physiological mechanisms.

Perceived Taste and Olfactory Dysfunctions and Subsequent Stroke Risk

Background

Taste and olfactory dysfunction are commonly associated with neurodegenerative diseases and cardiovascular risk factors, but their specific associations with stroke risk remain uncertain.

Objectives

The purpose of this paper was to explore whether perceived taste and olfactory dysfunctions were associated with stroke risk.

Methods

Included were 85,656 participants (mean age 51.0 ± 15.3 years) of the Kailuan study. Perceived olfactory and taste dysfunctions were assessed via a questionnaire at baseline (in 2014-2016). Incident stroke cases were confirmed by review of medical records. Cox proportional hazards models were used to investigate associations of perceived olfactory and taste dysfunctions with stroke risk, and mediation analysis was used to estimate the mediating effect of chronic disease statuses.

Results

We documented 2,198 incident stroke cases during a mean of 5.6 years of follow-up. Perceived taste dysfunction was associated with a doubled risk of developing total stroke (adjusted HR: 2.03; 95% CI: 1.36-3.04; P < 0.001) even with adjustment of lifestyle factors, biomarkers (ie, blood lipids, blood glucose, blood pressure, and uric acid), and other potential confounders. However, perceived olfactory dysfunction (adjusted HR: 1.22; 95% CI: 0.79-1.90; P = 0.34) was not significantly associated with a high risk of total stroke. Similar results of both perceived taste and olfactory dysfunctions were observed for ischemic stroke. Presence of chronic diseases, including hypertension, diabetes, chronic kidney disease, and overweight/obesity, mediated 4% to 5% of the association of perceived taste dysfunction with both total stroke and ischemic stroke.

Conclusions

In this large cohort study, perceived taste dysfunction was associated with a high risk of developing stroke.

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.

Effects of dietary fibre on metabolic health and obesity

Obesity and metabolic syndrome represent a growing epidemic worldwide. Body weight is regulated through complex interactions between hormonal, neural and metabolic pathways and is influenced by numerous environmental factors. Imbalances between energy intake and expenditure can occur due to several factors, including alterations in eating behaviours, abnormal satiation and satiety, and low energy expenditure. The gut microbiota profoundly affects all aspects of energy homeostasis through diverse mechanisms involving effects on mucosal and systemic immune, hormonal and neural systems. The benefits of dietary fibre on metabolism and obesity have been demonstrated through mechanistic studies and clinical trials, but many questions remain as to how different fibres are best utilized in managing obesity. In this Review, we discuss the physiochemical properties of different fibres, current findings on how fibre and the gut microbiota interact to regulate body weight homeostasis, and knowledge gaps related to using dietary fibres as a complementary strategy. Precision medicine approaches that utilize baseline microbiota and clinical characteristics to predict individual responses to fibre supplementation represent a new paradigm with great potential to enhance weight management efficacy, but many challenges remain before these approaches can be fully implemented.

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.

Influences of Microbial Symbionts on Chemoreception of Their Insect Hosts

Chemical communication is widespread among insects and exploited to adjust their behavior, such as food and habitat seeking and preferences, recruitment, defense, and mate attraction. Recently, many studies have revealed that microbial symbionts could regulate host chemical communication by affecting the synthesis and perception of insect semiochemicals. In this paper, we review recent studies of the influence of microbial symbionts on insect chemoreception. Microbial symbionts may influence insect sensitivity to semiochemicals by regulating the synthesis of odorant-binding proteins or chemosensory proteins and olfactory or gustatory receptors and regulating host neurotransmission, thereby adjusting insect behavior. The manipulation of insect chemosensory behavior by microbial symbionts is conducive to their proliferation and dispersal and provides the impetus for insects to change their feeding habits and aggregation and dispersal behavior, which contributes to population differentiation in insects. Future research is necessary to reveal the material and information exchange between both partners to improve our comprehension of the evolution of chemoreception in insects. Manipulating insect chemoreception physiology by inoculating them with microbes could be utilized as a potential approach to managing insect populations.

[Mechanisms and Management of COVID-19-Associated Taste Disorders]

The taste buds in the human tongue contain specialized cells that generate taste signals when they are stimulated. These signals are then transmitted to the central nervous system, allowing the human body to distinguish nutritious substances from toxic or harmful ones. This process is critical to the survival of humans and other mammals. A number of studies have shown that dysgeusia, or taste disorder, is a common complication of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which can severely affect patients' nutritional intake and quality of life. Based on the physiological process of taste perception, the direct causes of dysgeusia include dysfunction of taste receptors and damage to the taste nervous system, while indirect causes include genetic factors, aging-related changes, bacterial and viral infections, and cancer treatments such as radiotherapy and chemotherapy. The pathogenic factors of dysgeusia are complicated, further research is needed to fully understand the underlying mechanisms, and some of the reported findings and conclusions still need further validation. All these form a great challenge for clinical diagnosis of the cause and targeted treatment of dysgeusia. Herein, we reviewed published research on the physiological process of taste perception, the potential mechanisms of taste disorders related to SARS-CoV-2 infection, and strategies for prevention and treatment, providing theoretical support for establishing and improving the comprehensive management of COVID-19 complicated by taste disorders.

Phylogenetically under-dispersed gut microbiomes are not correlated with host genomic heterozygosity in a genetically diverse reptile community

While key elements of fitness in vertebrate animals are impacted by their microbiomes, the host genetic characteristics that factor into microbiome composition are not fully understood. Here, we correlate host genomic heterozygosity and gut microbiome phylogenetic diversity across a community of reptiles in southwestern New Mexico to test hypotheses about the behaviour of host genes that drive microbiome assembly. We find that microbiome communities are phylogenetically under-dispersed relative to random expectations, and that host heterozygosity is not correlated with microbiome diversity. Our analyses reinforce results from functional genomic work that identify conserved host immune and nonimmune genes as key players in microbiome assembly, rather than gene families that rely on heterozygosity for their function.

Impact of facemasks on the mouth as an emerging dental concern: A survey among residents of Karachi

Background

The illness known as "mask-mouth syndrome," which is brought on by constantly covering one's mouth and nose with a mask, was particularly prevalent among healthcare personnel. The covid-19 pandemic, however, had far-reaching effects on people's daily lives all around the world, to the point where mask use became practically mandatory. With Covid-19 posing a new threat to dental health, this study aims to assess the public's awareness of the issue and investigate how wearing a facemask affects oral hygiene.

Methods

Cross-sectional research was conducted at Karachi's Jinnah Medical & Dental College. From February to May of 2022, it was carried out in the Dental Opd. A survey of 400 people was conducted, representing a cross-section of society in terms of age, gender, occupation, and other criteria. The poll had 11 closed-ended questions. The data was analyzed using SPSS 24. Descriptive analysis was used to examine the responses.

Results

Men made up 44.5% (n = 174) of responses and women 56.5% (n = 226). Mean participant age was 27.31, ranging from 18 to 50. 99% (n = 396) of respondents wear masks. 48% (n = 192) of participants were uncomfortable using facemasks. Disposable face masks were voted the best option by 60.5% of respondents (n = 242). Negative effects or conditions brought on by mask use, such as halitosis (47.3%, n = 189) and dehydration (64.3%, n = 257).

Conclusion

Mask-mouth syndrome can occur as a result of using a face mask for prolonged periods of time. Mask benefits outweigh the danger of mask mouth syndrome.

THE INTESTINAL MICROBIOME IN PATIENTS UNDERGOING BARIATRIC SURGERY: A SYSTEMATIC REVIEW

BACKGROUND

Dysbiosis of the gut microbiota is frequently found in cases of obesity and related metabolic diseases, such as type 2 diabetes mellitus. The composition of the microbiota in diabetics is similar to that of obese people, thereby causing increased energy uptake efficiency in the large intestine of obese people, maintenance of a systemic inflammatory state, and increased insulin resistance. Bariatric surgery seems to entail an improvement in gut dysbiosis, leading to an increased diversity of the gut microbiota.

AIMS

This study aimed to present a literature review on obesity-associated gut dysbiosis and its status post-bariatric surgery.

METHODS

A systematic review of primary studies was conducted in PubMed, SciELO, BIREME, LILACS, Embase, ScienceDirect, and Scopus databases using DeCS (Health Science Descriptors) with the terms "obesity," "intestinal dysbiosis," "bariatric surgery," and "microbiota."

RESULTS

We analyzed 28 articles that had clinical studies or literature reviews as their main characteristics, of which 82% (n=23) corresponded to retrospective studies. The sample size of the studies ranged from 9 to 257 participants and/or fecal samples. The epidemiological profile showed a higher prevalence of obesity in females, ranging from 24.4 to 35.1%, with a mean age of around 25-40 years. There was a variation regarding the type of bariatric surgery, migrating between the Roux-en-Y bypass, adjustable gastric banding, and vertical gastrectomy. Of the 28 studies, 6 of them evaluated the gut microbiota of obese patients undergoing bariatric surgery and their relationship with type 2 diabetes mellitus/glucose metabolism/insulin resistance.

CONCLUSIONS

The intestinal microbiota is an important influencer in the regulation of the digestive tract, and obese individuals with comorbidities (diabetes mellitus, hypercholesterolemia, and metabolic syndrome) present important alterations, with an unbalance normal state, generating dysbiosis and the proliferation of bacterial species that favor the appearance of new diseases. Patients who undergo bariatric surgery present an improvement in the intestinal microbiota imbalance as well as reversibility of their comorbidities, increasing their life expectancy.

Total Sesquiterpenoids of Loquat Leaves Alleviated High-Fat Diet-Induced Obesity by Targeting Fecal Metabolic Profiling and Gut Microbiota Composition

In the present study, we demonstrated that whether the gut microbiota and related metabolites contribute to the therapeutic effect of total sesquiterpenoids (TSs) from loquat leaves on obesity. A 4-week high fat diet was used to induce obesity which was then treated with TSs for another 4 weeks. TSs remarkedly reduced the weight of body and white adipose and the levels of total cholesterol (TC) and triglyceride (TG) in serum. We also found that TSs restored the diversity and richness of gut microbiota. In addition, TSs administration affected the relative abundance of seven key genera. Meanwhile, TSs were determined to affect the metabolism of the host through detecting the metabolites in feces. By applying KEGG and the correlation analysis with gut microbiota, 10 differential metabolites were identified to be the key. The results in this work proved that TSs inhibited obesity by remodeling gut microbiota and related metabolites.

Relationship Between the Gut Microbiota and Alzheimer’s Disease: A Systematic Review

Background: In recent years, scientific research on the gut microbiota and their relationship with some diseases, including neurological ones, has notably increased. As a result of these investigations, the so-called gut-brain axis arises. Despite its influence on the evolution and development of cognitive impairment, the gut-brain axis is little defined and demonstrated. Objective: To provide the best scientific evidence available on the relationship between the gut microbiota and Alzheimer’s disease. Method: Systematic and narrative review of the information generated in the last 5 years in national and international databases, in English and Spanish. Results: Eight observational studies were selected, carried out in humans and, therefore, suitable for inclusion in this review. Conclusion: The results of these studies support the hypothesis that there is a relationship between the gut microbiota and cognitive disorders through the gut-brain axis. However, today, there is a substantial lack of human studies, especially clinical trials, which makes it difficult to formulate clinical recommendations on this topic.

Effect of Dextranase and Dextranase-and-Nisin-Containing Mouthwashes on Oral Microbial Community of Healthy Adults—A Pilot Study

This study analyzed the alteration of oral microbial composition in healthy subjects after using dextranase-containing mouthwash (DMW; Mouthwash formulation I) and dextranase-and-nisin-containing mouthwash (DNMW; Mouthwash formulation II). Eighteen participants were recruited and were randomly allocated to two groups: G1 (DMW user; n = 8) and G2 (DNMW user; n = 10). The subjects were instructed to use the provided mouthwash regularly twice a day for 30 days. The bleeding on probing (BOP), plaque index (PI), probing depth (PBD), and gingival index (GI) were analyzed, and saliva samples were collected before (day 0) and after (day 30) the use of mouthwashes. The saliva metagenomic DNA was extracted and sequenced (next-generation sequencing, Miseq paired-end Illumina 2 × 250 bp platform). The oral microbial community in the pre-and post-treated samples were annotated using QIIME 2™. The results showed the PI and PBD values were significantly reduced in G2 samples. The BOP and GI values of both groups were not significantly altered. The post-treated samples of both groups yielded a reduced amount of microbial DNA. The computed phylogenetic diversity, species richness, and evenness were reduced significantly in the post-treated samples of G2 compared to the post-treated G1 samples. The mouthwash formulations also supported some pathogens’ growth, which indicated that formulations required further improvement. The study needs further experiments to conclude the results. The study suggested that the improved DNMW could be an adjuvant product to improve oral hygiene.

Microbiome First Approaches to Rescue Public Health and Reduce Human Suffering

The is a sequential article to an initial review suggesting that Microbiome First medical approaches to human health and wellness could both aid the fight against noncommunicable diseases and conditions (NCDs) and help to usher in sustainable healthcare. This current review article specifically focuses on public health programs and initiatives and what has been termed by medical journals as a catastrophic record of recent failures. Included in the review is a discussion of the four priority behavioral modifications (food choices, cessation of two drugs of abuse, and exercise) advocated by the World Health Organization as the way to stop the ongoing NCD epidemic. The lack of public health focus on the majority of cells and genes in the human superorganism, the microbiome, is highlighted as is the "regulatory gap" failure to protect humans, particularly the young, from a series of mass population toxic exposures (e.g., asbestos, trichloroethylene, dioxin, polychlorinated biphenyls, triclosan, bisphenol A and other plasticizers, polyfluorinated compounds, herbicides, food emulsifiers, high fructose corn syrup, certain nanoparticles, endocrine disruptors, and obesogens). The combination of early life toxicity for the microbiome and connected human physiological systems (e.g., immune, neurological), plus a lack of attention to the importance of microbial rebiosis has facilitated rather than suppressed, the NCD epidemic. This review article concludes with a call to place the microbiome first and foremost in public health initiatives as a way to both rescue public health effectiveness and reduce the human suffering connected to comorbid NCDs.

Enhancing Human Superorganism Ecosystem Resilience by Holistically ‘Managing Our Microbes’

Microbes in the 21st century are understood as symbionts ‘completing’ the human ‘superorganism’ (Homo sapiens plus microbial partners-in-health). This paper addresses a significant paradox: despite the vast majority of our genes being microbial, the lack of routine safety testing for the microbiome has led to unintended collateral side effects from pharmaceuticals that can damage the microbiome and inhibit innate ‘colonization resistance’ against pathobionts. Examples are discussed in which a Microbiome First Medicine approach provides opportunities to ‘manage our microbes’ holistically, repair dysbiotic superorganisms, and restore health and resilience in the gut and throughout the body: namely, managing nosocomial infections for Clostridioides difficile and Staphylococcus aureus and managing the gut and neural systems (gut–brain axis) in autism spectrum disorder. We then introduce a risk analysis tool: the evidence map. This ‘mapping’ tool was recently applied by us to evaluate evidence for benefits, risks, and uncertainties pertaining to the breastmilk ecosystem. Here, we discuss the potential role of the evidence map as a risk analysis methodology to guide scientific and societal efforts to: (1) enhance ecosystem resilience, (2) ‘manage our microbes’, and (3) minimize the adverse effects of both acute and chronic diseases.