University of Groningen
Tongue coating
Seerangaiyan, Kavitha
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Publication date: 2018
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Seerangaiyan, K. (2018). Tongue coating: It’s impact on intra-oral halitosis and taste. Rijksuniversiteit Groningen.
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CHAPTER 6
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References
1. Patil S, Kaswan S, Rahman F, Doni B (2013) Prevalence of tongue lesions in the Indian population. J Clin Exp Dent. 5:e128-132
2. Tomooka K, Saito I, Furukawa S, et al (2018) Yellow tongue coating is associated with diabetes mellitus among japanese non-smoking men and women: the Toon Health Study. J Epidemiol. 28:287-291
3. Jung Y, Park K, Kim J (2009) A digital tongue imaging system for evaluation in patients with oral malodour. Oral Dis 15:565–569.
4. De Baat C, Mulder J, Van Den Broek AMWT, Feenstra L (2014) Diagnostics of halitosis complaints by a multidisciplinary team. Oral Health Dent Manag 13:348–53.
5. Delanghe G, Ghyselen J, Feenstra L, van Steenberghe D (1997) Experiences of a Belgian multidisciplinary breath odour clinic. Acta Otorhinolaryngol Belg 51:43–48.
6. Tyrrell KL, Citron DM, Warren YA, et al (2003) Anaerobic bacteria cultured from the tongue dorsum of subjects with oral malodor. Anaerobe 9:243–246. 7. Kazor CE, Mitchell PM, Lee AM, et al (2003) Diversity of bacterial
populations on the tongue dorsa of patients with halitosis and healthy patients. J Clin Microbiol 41:558–563.
8. Haraszthy VI, Zambon JJ, Sreenivasan PK, et al (2007) Identification of oral bacterial species associated with halitosis. J Am Dent Assoc 138:1113–1120. 9. Vancauwenberghe F, Dadamio J, Laleman I, Van Tornout M, Teughels W,
Coucke W, Quirynen M (2013) The role of Solobacterium moorei in oral malodour. J Breath Res 7:46006.
10. Seerangaiyan K, van Winkelhoff AJ, Harmsen HJM, Rossen JWA and Winkel EG et al (2017) The tongue microbiome in healthy subjects and patients with intra-oral halitosis. J Breath Res 11:36010. doi: 10.1088/1752-7163/aa7c24 11. Elsden SR, Hilton MG (1978) Volatile acid production from threonine, valine,
leucine and isoleucine by Clostridia. Arch Microbiol 117:165–172.
12. Ran-Ressler RR, Devapatla S, Lawrence P, Brenna JT (2008) Branched chain fatty acids are constituents of the normal healthy newborn gastrointestinal tract. Pediatr Res 64:605–9.
13. Wang DH, Yang Y, Lawrence, Brenna TJ (2017) Branched chain fatty acids content of natto. FASEB J. 31
14. Nisman B (1954) The Stickland reaction. Bacteriol Rev 18:16–42.
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SUMMARY
Kavitha Seerangaiyan
96
Summary
The oral cavity, an orifice through which food and air enter the body, is the beginning of the digestive system. The oral cavity is bounded by various structures including hard and soft palate, teeth, and tongue, which together comprise the initial step in the digestive process. Of these structures, the tongue, a mobile muscular organ, helps in chewing and swallowing and also is mainly involved in speech and taste. The dorsum of the tongue has numerous projections called papillae, which contain taste buds that are sensitive to the chemical constituents of the food. In addition, the tongue plays an essential role in maintaining oral hygiene. Tongue coating (TC) is the main cause of bad breath from the oral cavity, or so-called intra-oral halitosis (IOH) in people with a healthy periodontium, as well as in those with periodontal disease. Removal of the TC results in improved taste perception; thus, TC plays a role in both IOH and taste perception.
TC has long been used as a diagnostic tool for gastrointestinal and other organ disorders in Chinese and Ayurvedic medicine traditions. In Chapter 2, we reviewed the literature to update the pros and cons of TC in general and in the context of IOH. In ancient medicine, the color, moisture, and texture of the TC were taken into account in diagnosing disease. Earlier, western medicine also made use of TC in diagnosis. However, recent advances in medical technologies and instrumentation have replaced TC in disease diagnosis. Recently, the tongue and its coating have gained more attention. For example, a yellow coating has been observed in patients with diabetes mellitus. In conditions such as IOH, the quantity of the TC and the microbiome of the tongue play a significant role in etiology. The current view of IOH is that it is treatable rather than curable. Therefore, extensive research is needed into the likeliest cause of IOH, the microbiome of the TC.
A healthy human body harbors approximately 3.8 × 1013 bacteria and other microorganisms that contribute more than 200 g of the total weight of an average 70-kg human body. The human oral cavity harbors the second most abundant microbiota next to the gastrointestinal tract. The first bacterium identified from the human healthy oral cavity was Streptococcus mutans. Since that discovery, numerous microorganisms have been identified and extensively characterized. Traditional and non-traditional molecular approaches have been widely used to establish a human oral database from various parts of the oral cavity. According to the human oral microbiome database, 70% of microorganisms are cultivable, and the remaining 30% are non-cultivable. A new era of bacterial identification began in 1987, when Carl Woese described the bacterial phylogenetic relationship based on 16S rDNA sequences. This work identified nine hypervariable regions, among them V1, V2, V3, and V4, which are highly useful for studying microbial diversity. At present, sequencing studies rely on the V1-V2 or V3-V4 hypervariable region. The study of
97
the tongue microbiota began in 1966 when Gordon and Gibbsons identified the tongue bacteria; however, the tongue bacteria were not well characterized. Because the bacteria were shown in in vitro studies to produce volatile sulfur compounds related to bad breath, studies have focused on the microbial composition of IOH. Nevertheless, the microbial composition of IOH is not clear. In chapter 3, we evaluated the microbial composition of the TC of IOH and healthy control samples using 16S amplicon sequencing of hypervariable region V3-V4. We identified 7 phyla, 27 genera, and 825 species. Our study revealed that the bacterial composition of IOH samples was highly similar to that of the healthy control samples. We identified few bacteria that were significantly higher in representation in the IOH group. This finding shows the adaptability of the bacteria to IOH ecosystem. As a result of our findings, we hypothesized that the microbial-derived bacterial metabolism of the TC might play a role in IOH etiology.
In Chapter 4, we aimed to characterize the metabolic profile (metabolomics)
of the IOH group by comparing their samples with those of healthy controls using liquid chromatography/mass spectrometry. The results clearly showed differences in the metabolic profile of IOH; indeed, we identified 39 metabolites that were significantly different in IOH. This study is the first to show the mechanism of TC formation based on our metabolites (i.e., branched-chain fatty acid). Also, we identified the mechanism of the sulfur gas metabolic pathway.
Among 39 metabolites, the branched-chain fatty acids (BCFAs) were highly enriched. Next were the metabolites 3-fumaryl pyruvate and acetyl phosphate. Of note, BCFAs showed different key possibilities: BCFAs ferment foods and release bad odors, so our finding is promising because BCFA could ferment food particles of the TC and cause bad breath. BCFAs also are known for the formation of the white coating on newborn babies, and it is plausible that the BCFAs might help in the formation and increase of the TC in IOH. Also of note, BCFA is a product of bacteria, and bacteria like Clostridiales produce BCFA. The other major finding in this chapter is that the metabolites 3-fumaryl pyruvate and acetyl phosphate show a clear association with the hydrogen sulfide (H2S)-producing metabolic pathway and anaerobic fermentation. The above findings together add novel information about TC formation and the production of volatile sulfur compounds (such as H2S), which causes bad breath or IOH. However, tongue hygiene has a major impact in several aspects. For example, the tongue contains the taste buds, and the TC blocks the direct contact of the food in reaching the taste buds. In Chapter 5, we studied the effect of TC removal in relation to salt taste and found that the intensity of salt taste increased after coating removal. Mechanical TC removal stimulated the taste buds and increased salt taste perception, which has a potential link to general health. Therefore, removal of the coating (tongue cleaning) must be a part of oral hygienic procedures.
96
Summary
The oral cavity, an orifice through which food and air enter the body, is the beginning of the digestive system. The oral cavity is bounded by various structures including hard and soft palate, teeth, and tongue, which together comprise the initial step in the digestive process. Of these structures, the tongue, a mobile muscular organ, helps in chewing and swallowing and also is mainly involved in speech and taste. The dorsum of the tongue has numerous projections called papillae, which contain taste buds that are sensitive to the chemical constituents of the food. In addition, the tongue plays an essential role in maintaining oral hygiene. Tongue coating (TC) is the main cause of bad breath from the oral cavity, or so-called intra-oral halitosis (IOH) in people with a healthy periodontium, as well as in those with periodontal disease. Removal of the TC results in improved taste perception; thus, TC plays a role in both IOH and taste perception.
TC has long been used as a diagnostic tool for gastrointestinal and other organ disorders in Chinese and Ayurvedic medicine traditions. In Chapter 2, we reviewed the literature to update the pros and cons of TC in general and in the context of IOH. In ancient medicine, the color, moisture, and texture of the TC were taken into account in diagnosing disease. Earlier, western medicine also made use of TC in diagnosis. However, recent advances in medical technologies and instrumentation have replaced TC in disease diagnosis. Recently, the tongue and its coating have gained more attention. For example, a yellow coating has been observed in patients with diabetes mellitus. In conditions such as IOH, the quantity of the TC and the microbiome of the tongue play a significant role in etiology. The current view of IOH is that it is treatable rather than curable. Therefore, extensive research is needed into the likeliest cause of IOH, the microbiome of the TC.
A healthy human body harbors approximately 3.8 × 1013 bacteria and other microorganisms that contribute more than 200 g of the total weight of an average 70-kg human body. The human oral cavity harbors the second most abundant microbiota next to the gastrointestinal tract. The first bacterium identified from the human healthy oral cavity was Streptococcus mutans. Since that discovery, numerous microorganisms have been identified and extensively characterized. Traditional and non-traditional molecular approaches have been widely used to establish a human oral database from various parts of the oral cavity. According to the human oral microbiome database, 70% of microorganisms are cultivable, and the remaining 30% are non-cultivable. A new era of bacterial identification began in 1987, when Carl Woese described the bacterial phylogenetic relationship based on 16S rDNA sequences. This work identified nine hypervariable regions, among them V1, V2, V3, and V4, which are highly useful for studying microbial diversity. At present, sequencing studies rely on the V1-V2 or V3-V4 hypervariable region. The study of
97
the tongue microbiota began in 1966 when Gordon and Gibbsons identified the tongue bacteria; however, the tongue bacteria were not well characterized. Because the bacteria were shown in in vitro studies to produce volatile sulfur compounds related to bad breath, studies have focused on the microbial composition of IOH. Nevertheless, the microbial composition of IOH is not clear. In chapter 3, we evaluated the microbial composition of the TC of IOH and healthy control samples using 16S amplicon sequencing of hypervariable region V3-V4. We identified 7 phyla, 27 genera, and 825 species. Our study revealed that the bacterial composition of IOH samples was highly similar to that of the healthy control samples. We identified few bacteria that were significantly higher in representation in the IOH group. This finding shows the adaptability of the bacteria to IOH ecosystem. As a result of our findings, we hypothesized that the microbial-derived bacterial metabolism of the TC might play a role in IOH etiology.
In Chapter 4, we aimed to characterize the metabolic profile (metabolomics)
of the IOH group by comparing their samples with those of healthy controls using liquid chromatography/mass spectrometry. The results clearly showed differences in the metabolic profile of IOH; indeed, we identified 39 metabolites that were significantly different in IOH. This study is the first to show the mechanism of TC formation based on our metabolites (i.e., branched-chain fatty acid). Also, we identified the mechanism of the sulfur gas metabolic pathway.
Among 39 metabolites, the branched-chain fatty acids (BCFAs) were highly enriched. Next were the metabolites 3-fumaryl pyruvate and acetyl phosphate. Of note, BCFAs showed different key possibilities: BCFAs ferment foods and release bad odors, so our finding is promising because BCFA could ferment food particles of the TC and cause bad breath. BCFAs also are known for the formation of the white coating on newborn babies, and it is plausible that the BCFAs might help in the formation and increase of the TC in IOH. Also of note, BCFA is a product of bacteria, and bacteria like Clostridiales produce BCFA. The other major finding in this chapter is that the metabolites 3-fumaryl pyruvate and acetyl phosphate show a clear association with the hydrogen sulfide (H2S)-producing metabolic pathway and anaerobic fermentation. The above findings together add novel information about TC formation and the production of volatile sulfur compounds (such as H2S), which causes bad breath or IOH. However, tongue hygiene has a major impact in several aspects. For example, the tongue contains the taste buds, and the TC blocks the direct contact of the food in reaching the taste buds. In Chapter 5, we studied the effect of TC removal in relation to salt taste and found that the intensity of salt taste increased after coating removal. Mechanical TC removal stimulated the taste buds and increased salt taste perception, which has a potential link to general health. Therefore, removal of the coating (tongue cleaning) must be a part of oral hygienic procedures.
