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1Traditional Medicine Research  2019, Vol. 4 Issue (6): 326-337    DOI: 10.12032/TMR20190530122
Special Issue on Endocrine and Metabolism     
Study on the relationship between the structure of bacterial flora on the tongue and types of tongue coating in patients with type 2 diabetes mellitus
Yu-Hong Ding1,#, Xing-Yu Zheng2,3,*,#(), Wei-Wei Chen3, Xin-Fu Lin2,4, Xiao Yang5, Jie-Wei Luo2,3,*(), Fang-Meng Huang2,3, Yong-Xi Wu3, Shi-Chao Wei3
1Community Healthcare Services Center of Gudong Street, Fuzhou, China
2Provincial Clinical Medical College, Fujian Medical University, Fuzhou, China
3Department of Traditional Chinese Medicine, Fujian Provincial Hospital, Fuzhou, China
4Department of Paediatrics, Fujian Provincial Hospital, Fuzhou, China
5Teaching and Research Office of Medical Cosmetology, Department of Management, Fujian Health College, Fuzhou, China
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The incidence of type 2 diabetes mellitus (T2DM) is related to the imbalance of oral microflora in the human body. The characteristic tongue coating flora structure, containing Prevotella, Fusobacterium, Streptococcus, Neisseria, etc., can influence the formation of yellow thick coating. However, the role of yellow thick coating in the incidence of T2DM needs further investigation.


Diabetes is called “Xiaoke” in traditional Chinese medicine. According to the record of Jin Kui Yao Lue (an ancient book of Chinese medicine published in the Han dynasty of China), the typical clinical symptoms of “Xiaoke” is thirsty for drinking water and dry mouth, suggesting that as early as Han dynasty, Chinese medicine associated the onset of diabetes with the mouth and tongue symptoms. Currently, it is believed that a two-way interaction exists between diabetes and periodontitis, a disease resulted from the imbalance oral microbial community. In 2015, “National Individual Microbiome Detection Project” was launched with the aim of finding biomarkers or risk factors for diseases in oral, skin, and intestinal microbial communities.


Objective: To analyze the characteristics of bacterial flora on the tongue and types of tongue coating between healthy individuals and patients with type 2 diabetes mellitus (T2DM) via detecting 16S rDNA of oral tongue coating microbial group. Methods: A total of 42 patients with T2DM were recruited, including 6 with thin white coating, 9 with mirror-like coating, 27 with yellow thick coating (YTC), and 28 healthy individuals. The V4 region of 16S rDNA from the tongue coating microbiota was sequenced using the Linux ubuntu sequencing platform, and the structure of bacterial flora in the tongue was analyzed. Treeplot construction, principal coordinates analysis, redundancy analysis, and linear discriminant analysis were conducted using R software to analyze the differences of bacterial flora in the tongue coating in each group. Results: A total of 8131 different operational taxonomic units (OTUs) were obtained via sequencing, of which 719 OTU samples showed significant differences (P < 0.05). Comparing OTUs with the 16S rDNA database of known species and annotation of parallel species revealed 16 species with differences at the phylum level, 31 at the class level, 54 at the order level, 88 at the family level, and 161 at the genus level. The dominant bacteria found in patients with T2DM included Lactobacillus, Streptophyta, Chloroplast, Cyanobacteria-Chloroplast, and Bifidobacteriaceae, etc. Dominant bacteria in the control group belonged to Pasteurellales, Pasteurellaceae, Leptotrichiaceae, Lachnoanaerobaculum, and Ignavibacteria among other bacterial families. All samples were clustered into three groups, each group characterized by dominant bacteria. The order of dominant bacteria in group 1 were Prevotella > Neisseria > Veillonella > Streptococcus > Fusobacterium > Leptotrichia and so on. The order of dominant bacteria of group 2 were Neisseria > Prevotella > Fusobacterium > Streptococcus > porphyromonas and so on. The dominant bacteria of group 3 were Prevotella > Fusobacterium > Streptococcus > Neisseria > Leptotrichia > Rothia > Veillonella > porphyromonas > f_Pasteurellaceae > Capnocytophaga > Actinomyces > Alloprevotella and so on. Single factor risk estimation: with group 1 used as the reference (OR = 1), the risk of carrying group 2 and group 3 microflora with T2DM increased (OR values were 4.77 and 7.78, respectively). The proportion of group 1 microflora in the control group (25.9%) was higher than that in the T2DM group (5.4%) (χ2 = 3.873, P = 0.049). Compared with group 1 and group 2, group 3 had a significantly dominant microflora structure in YTC group (χ2 = 7.120, P = 0.008). RDA analysis indicated that Neisseria, Fusobacterium, and Prevotella were associated with HbA1c values > 10 mmol/L, whereas Rothia, Streptococcus, and Veillonella were more correlated with HbA1c ≤ 10 mmol/L. Conclusion: The incidence of T2DM is related to the imbalance of oral microflora in the human body. The tongue coating flora structure may influence the formation of different tongue coating types in this metabolic condition. Additionally, flora structures of Prevotella, Neisseria, and Fusobacterium were associated with elevated HbA1c.

Key wordsType 2 diabetes mellitus      Oral flora      16S rDNA sequence      Yellow thick coating     
Published: 05 November 2019
Fund:  The study was financially supported by Fujian Province Traditional Chinese Medicine Research Project (2017FJZYJC105) and Financial Scheme for Young Talents Training Program of Fujian Health Industry (Grant #2015-ZQN-ZD-7).
Corresponding Authors: Jie-Wei Luo, Xing-Yu Zheng   
About author: # They contributed equally to this work.
Cite this article:

Yu-Hong Ding, Xing-Yu Zheng, Wei-Wei Chen, Xin-Fu Lin, Xiao Yang, Jie-Wei Luo, Fang-Meng Huang, Yong-Xi Wu, Shi-Chao Wei. Study on the relationship between the structure of bacterial flora on the tongue and types of tongue coating in patients with type 2 diabetes mellitus. 1Traditional Medicine Research, 2019, 4(6): 326-337. doi: 10.12032/TMR20190530122


Figure 1 Classification of tongue coating

A: White thin coating; B: Yellow thick coating; C: Mirror-like coating.

Figure 2 Principal coordinates analysis of inter-sample species diversity at the genus level

T2DM: Type 2 diabetes mellitus patients; Orange area: Group 1 sample; Red area: Group 2 sample; and Yellow area: Group 3 sample. The closer the two samples is, the more similar the species composition between the two samples is.

Figure 3 LDA value histogram of type 2 diabetes mellitus group and the control group

T2DM: Type 2 diabetes mellitus group; LDA, Linear discriminant analysis.

Figure 4 Evolutionary bifurcation diagram of LDA effect size

The red nodes in the branches depict dominant bacteria in the control group, the green nodes depict dominant bacteria in the T2DM group, and the yellow nodes depict non-dominant bacteria in two groups. T2DM: Type 2 diabetes mellitus group; LDA, Linear discriminant analysis.

Figure 5 Treeplot at the level

The red line is the threshold value, all 70 samples are clustered together in three categories, and the last three types of bacteria include 64 samples.

Figure 6 Distribution chart of bacterial groups in type 2 diabetes mellitus and control groups

T2DM: Type 2 diabetes mellitus group.

Group T2DM Control OR OR (95% confidence interval)
Group 1 2 (5.4%) 7 (25.9%) a 1
Group 2 15 (40.5%) 11 (40.7%) 4.77 0.83-27.78
Group 3 20 (54.1%) 9 (33.3%) 7.78 1.34-45.45
χ2 = 5.916, P = 0.044
Table 1 Comparison with risk estimates of the structure and distribution of microflora of the type 2 diabetes mellitus group and the control group
Group Control (27) WTC (5) in T2DM MLC (6) in T2DM Non-YTC (38) in T2DM YTC (26) in T2DM
Group 1 7 (25.9%) 1 (20.0%) 0 (0%) 8 (21.1%) 1 (3.8%)
Group 2 11 (40.7%) 3 (60.0%) 4 (66.7%) 18 (47.4%) 8 (30.8%)
Group 3 9 (33.3%) 1 (20.0%) 2 (33.3%) 12 (31.6%) 17 (65.4%)a
Table 2 Comparison of the microflora structure of non-YTC group and YTC group
Figure 7 Box plots of the association between the microflora structure of each group and HbA1c
Figure 8 RDA analysis diagram

HbA1c1 is the group with HbA1c value less than or equal to 10 mmol/L; HbA1c2 is group with HbA1c value more than 10 mmol/L. Neisseria, Fusobacterium and Prevotella and HbA1c2 are highly correlated, while Rothia, Streptococcus, and Veillonella are highly correlated with HbA1c1 group. RDA, Redundancy analysis.

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