Obese subjects present an increased periodontal risk with more dental loss, associated with a greater quantity of Capnocytophaga in oral microbiota compared to normo-weighted subjects.
As reported in Table 1, the mean age of the subjects was not significantly different between obese and normo-weighted groups: 59.4 years old ± 11.65 with 50% of female (n=5) in the obese group versus 57.11 years old ± 10.49 with 44% of females (n= 4) in the normo-weighted group. As the selection criterion, mean body weight (91.4kg ± 9.38) and BMI (30.02 ± 1.48) of OS were significantly higher than NWS (67.33kg ± 6.93 and 23.11 ± 1.29, respectively, p < 0.001 for both). No significant difference between OS and NWS was observed for the stress score, dietary and hygiene habits and physical activity.
To explore the link between obesity and oral health, different clinical parameters were analyzed (Table 1). The Decay-Missing-Filled (DMF) index was similar between obese and normo-weighted subjects (14.11 ± 5.84 vs 12.89 ± 6.23, p=0.69). However, the number of missing teeth was significantly higher in obese patients (6.00 ± 3.77 vs 2.44 ± 2.50, p= 0.03). Concerning the periodontal status, OS presented a significantly higher score of periodontal support loss in relation to the patient's age corresponding to periodontitis Grade C (1.03 ± 0.35 vs 0.72 ± 0.23, p= 0.04) compared to NWS (Grade B). Periodontitis Grade C corresponds to the greatest speed of progression of the pathology. Finally, clinical attachment loss (5.39mm ± 2.05 vs 4.68 mm ± 1.29, p=0.74), plaque index (16.8% ± 14.41 vs 14.67% ± 14.56, p=0.43) and bleeding on probing (34.2% ± 22.16 vs 23% ± 17.73, p=0.19) were not significantly different between OS and NWS.
To evaluate the association between oral microbiota and obesity, we performed a taxonomic analysis of the oral microbiota in both groups (Fig. 1 and Supp. Table 1). The relative abundance of the Flavobacteriaceae family (2.47% ± 3.02 vs 0.27% ± 0.29, p= 0.04) and Capnocytophaga genus (2.47% ± 3.02 vs 0.27% ± 0.29, p= 0.04) were higher in OS compared to NWS, and the Capnocytophaga genus was the only genus to be present in the Flavobacteriaceae family (Fig. 1A and 1B). In addition, no difference was observed for the alpha diversity following the Chao 1 index (32.93 ± 10.45 vs 30.94 ± 14.16, p=0.93) and the beta diversity (p=0.27) in the oral microbiota between obese and normo-weighted groups (Fig. 1C and 1D).
To explore the interaction between clinical and microbial parameters related to obesity, we performed a multivariate analysis by Principal Component Analysis (PCA) (Fig.1E). We identified a specific cluster for each group of subjects. Pearson’s correlation analysis was then performed to estimate the relationships between all the parameters that directly influence the group distribution. The relative abundance of Neisseriaceae was positively and significantly correlated with bleeding index. Fusobacteriaceae abundance was positively and significantly correlated with microbiota diversity according to the Chao 1 index. The number of missing teeth and the relative abundance of Flavobacteriaceae were positively and significantly correlated with BMI and we observed that the closest clinical parameter associated with Flavobacteriaceae was the sex gender. Thus, we hypothesized a link between the sex gender and the oral microbiota and we analyzed the implication of the sex gender within the group of obese subjects.
Obese females have a higher number of decayed and filled teeth compared to obese males associated with a dysbiotic oral microbiota.
Besides the weight and height that were higher in obese males, overall general parameters were similar in both obese females (OF) and males (OM) except for the stress score significantly higher in females (6.40 ± 1.52 vs 2.8 ± 1.92, p=0.01) (Table 2).
In order to investigate gender-related differences in obese subjects, the oral health status was analyzed. OF had a higher DMF index than OM (18.50 ± 3.11 vs 10.6 ± 5.12, p=0.08) due to an increase in the number of decayed (2.25 ± 2.21 vs 0, p=0.04)) and filled teeth (11.75 ± 2.50 vs 3.40 ± 2.07, p=0.01). However, concerning the periodontal status, OM presented seemingly more severe cases of periodontitis measured by the clinical attachment loss (6.10mm ± 2.60 vs 4.68 mm ± 1.20, p=0.46), the score of periodontal support loss in relation to the patient's age (1.16 ± 0.40 vs 0.90 ± 0.28, p=0.24), the number of missing teeth (7.2 ± 4.86 vs 4.80 ± 2.16, p=0.59), the plaque index (21% ± 13.73 vs 12.6% ± 15.32, p=0.34) and bleeding on probing (BOP) index (49% ± 22.33 vs 19.4% ± 7.64, p=0.07) compared to OF.
We then analyzed the oral microbiota in both OF and OM groups. The relative abundance of many oral bacterial families was significantly higher in OF compared to OM (Figs 2A and 2B) : Actinomycetaceae (3.38% ± 2.10 vs 0.73% ± 0.62, p=0.05), Corynebacteriaceae (0.57% ± 0.47 vs 0.02% ± 0.03, p=0.01), Paludibacteriaceae (0.11% ± 0.11 vs 0.007% ± 0.02, p=0.01), Rikinellaceae (0.08% ± 0.11 vs 0.001% ± 0.001, p=0.009), Streptococcaceae (34.12% ± 14.29 vs 10.55% ± 10.42, p=0.05), Family XI (3.44% ± 2.24 vs 0.91% ± 0.91, p=0.03), Family XIII (0.39% ± 0.43 vs 0.02% ± 0.03, p=0.01), Veillonellaceae (0.36% ± 0.16 vs 0.02% ± 0.02, p= 0.01), Cardiobacteriaceae (0.11% ± 0.14 vs 0.01% ± 0.01, p=0.01), Spirochaetaceae (0.45% ± 0.13 vs 0% ± 0, p=0.02) (Supp. Table 2). The Neisseriaceae family was the only one significantly lower in OF compared to OM (6.63% ± 5.27 vs 58.20% ± 30.47, p=0.008). Higher relative abundance in OF was similarly observed for oral bacterial genera (Figs 2A and 2C) : Actinomyces (3.38% ± 2.10 vs 0.73% ± 0.62, p=0.05), Corynebacterium (0.57% ± 0.47 vs 0.02% ± 0.03, p=0.01), F0058 (0.11% ± 0.11 vs 0.007% ± 0.01, p=0.01), Parvimonas (0.40% ± 0.33 vs 0.006% ± 0.005,p=0.01), Streptococcus (34.12% ± 14.29 vs 10.55% ± 10.42, p=0.05), Moryella (0.14% ± 0.24 vs 0% ± 0, p=0.02), Filifactor (0.99% ± 1.18 vs 0.03% ± 0.03, p=0.01), Dialister (0.33% ± 0.15 vs 0.02% ± 0.02,p=0.01), Veillonella (0.02% ± 0.02 vs 0.001% ± 0.002,p=0.009), Cardiobacterium (0.11% ± 0.14 vs 0.005% ± 0.007,p=0.01), Treponema 2 (0.45% ± 0.13 vs 0% ± 0, p=0.02) (Supp. Table 2). As for the Neisseriaceae family, the Neisseria genus was the only one significantly lower in OF compared to OM (5.75% ± 5.03 vs 58.05% ± 30.64, p=0.008). Moreover, the alpha diversity was significantly higher in OF compared to OM (39.45 ± 3.74 vs 26.41 ± 11.21, p=0.03 for the Chao 1 index) (Fig. 2D) and the beta diversity was also significantly different (p=0.01) (Fig. 2E).
To identify clinical and microbiota parameters associated with sex gender in obesity, we performed a Principal Component Analysis (PCA) and a Pearson’s correlation analysis (Fig. 2F). The PCA reported that the relative abundance of Neisseriaceae (key bacterial family in OM) was positively and significantly correlated with parameters determining the periodontal status (number of missing teeth, probing depth, loss of attachment and BOP index). The relative abundance of Streptococcaceae (a key bacterial family of OF) was positively and significantly correlated with the number of filled teeth.
More interestingly, when performing a Principal Component Analysis (PCA) separating the four groups (normo-weighted males, normo-weighted females, obese males and obese females), we observed that obese females formed clearly an independent group (Fig. 3).
Obesity is associated with an impaired oral health and a dysbiotic oral microbiota in females .
When analyzing overall general parameters in normo-weighted females versus obese females, we found no significant differences except for the selection criterion BMI (32.72 ± 1.73 vs 22.58 ± 1.36, p= 0.01) and the mean body weight (86kg ± 4.47 vs 61kg ± 2.45, p= 0.01) (Table 3). The DMF index (18.50 ± 3.11 vs 8 ± 2.16, p=0.02) as well as the number of missing (4.80 ± 2.16 vs 0.25 ± 0.5, p= 0.01) and filled (11.75 ± 2.50 vs 7.75 ± 1.70, p=0.05) teeth of OF were significantly higher compared to normo-weighted females (NWF). Although no decayed tooth was observed in the normo-weighted group, the higher value in the obese group (2.25 ± 2.21) appeared non-significant (p=0.06). Also, no significant difference was observed for the other parameters of the periodontal status.
To explore the association between obesity and the oral microbiota in females, we compared microbiota differences between normo-weighted and obese females (Supp. Table 3). The relative abundance of five oral bacterial families was significantly higher in OF compared to NWF : Actinomycetacea (3.38% ± 2.10 vs 0.49% ± 0.62, p=0.03), Corynebacteriaceae (0.57% ± 0.47 vs 0.04% ± 0.06, p=0.03), Flavobacteriaceae (3.86% ± 3.66 vs 0.22% ± 0.15, p=0.01), Leptotrichiaceae (3.25% ± 2.85 vs 0.38% ± 0.42, p=0.01), Cardiobacteriaceae (0.11% ± 0.14 vs 0.004% ± 0.003, p=0.01) (Figs. 4A and 4B). Similarly, the relative abundance of five oral bacterial genera was significantly higher in OF compared to NWF : Actinomyces (3.38% ± 2.10 vs 0.49% ± 0.62, p=0.03), Corynebacterium (0.57% ± 0.47 vs 0.04% ± 0.06, p=0.03), Capnocytophaga (3.86% ± 3.66 vs 0.22% ± 0.15, p=0.01), Leptotrichia (3.25% ± 2.85 vs 0.26 ± 0.35, p=0.01), Cardiobacterium (0.11% ± 0.14 vs 0.004% ± 0.003, p=0.01) (Figs. 4A and 4C). No difference was observed in the alpha diversity between both groups (31.69 ± 15.28 vs 39.45 ± 3.74, p=0.55 for the Chao 1 index) (Fig. 4D). By contrast, the microbiota beta diversity was significantly different with a close clustering for obese females (p= 0.02) (Fig. 4E).
To evaluate the link between obesity and all parameters (clinical and microbial) in females, we performed a Principal Component Analysis and a Pearson’s correlation (Fig. 4F). PCA identified two distinct clusters represented by obese and normo-weighted females. We observed that Actinomycetaceae abundance was positively and significantly correlated with the number of missing teeth. Streptococcaceae abundance and BMI were positively and significantly correlated with the number of filled teeth. Furthermore, Neisseriaceae abundance was negatively and significantly correlated with microbiota diversity according to the Chao 1 index.