Objective: To study the effects of periodontitis on bone and tryptophan metabolism of gut microbiota in the context of estrogen deficiency. Methods: Thirty-two female C57BL6/J mice were randomly divided into four groups based on table of random numbers (n=8 in each group): Sham group, in which mice were given sham surgery; Sham_Lig group, in which mice were given sham surgery and were induced to periodontitis by ligating the bilateral maxillary second molars with 5-0 silk threads at the fourth week; Ovx group, in which mice were given bilateral ovariectomy; Ovx_Lig group, in which mice were given bilateral ovariectomy and were induced to periodontitis at the fourth week. After 8 weeks of ligation, the mice of 4 groups were euthanized for collecting the samples of femur, tibia, mandible and skull. Those samples were scanned by micro-CT to measure the bone mineral density (BMD), bone volume versus total volume ratio (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th) and trabecular spacing (Tb.Sp). The cecum contents of 4 groups of mice were collected for gut microbiota 16S rRNA gene sequencing. The tryptophan and its metabolites in intestinal tracts were detected by liquid chromatography-mass spectrometry. Pearson correlation analysis was performed to analyze the correlation between the abundance of gut microbiota and the content of tryptophan and its metabolites. Results: Femur BMD [(82.23±3.97) mg/cm3], BV/TV [(9.25±1.37)%] and Tb.Th [(70.95±5.70) μm] in Ovx_Lig group were significantly lower than Ovx group [(96.30±3.76) mg/cm3 (P=0.004); (14.45±1.55)% (P=0.022) and (87.58±8.02) μm (P<0.001), respectively]. The β-diversity analysis of gut microbiota based on Bray-Curtis distance showed that samples of Ovx_Lig group and Ovx group were obviously grouped. Linear discriminant analysis effect size (LEfSe) showed that Alistipes was the representative genus in Ovx_Lig group. The relative abundance of Alistipes in Ovx_Lig group [(0.42±0.14)%] were significantly higher than that in Ovx group [(0.17±0.05)%] (t=4.45, P<0.001). Tryptophan metabolism analysis showed that the content of kynurenic acid [(531.12±158.60) ng/g] in Ovx_Lig group were significantly higher than that in Ovx group [(400.42±57.96) ng/g] (t=2.19, P=0.046). And the content of indole-3-carbaldehyde [(383.37±144.06) ng/g] in Ovx_Lig group were significantly lower than Ovx group [(701.72±141.93) ng/g] (t=4.45, P<0.001). Correlation analysis showed that relative abundance of Alistipes was positively correlated with kynurenic acid (r=0.32, P=0.088), while negatively correlated with indole-3-carbaldehyde (r=-0.32, P=0.088). Conclusions: Periodontitis can induce bone destruction of femur in estrogen-deficient mice, the mechanism of which may be related to Alistipes in gut and the tryptophan metabolites kynurenic acid and indole-3-carbaldehyde.
目的： 研究雌激素缺乏背景下，牙周炎对骨组织和肠道色氨酸代谢的影响。 方法： 将32只雌性C57BL6/J小鼠根据随机数字表法随机分为4组（每组8只）：假手术组（Sham组）；假手术牙周炎组（Sham_Lig组）；去卵巢组（Ovx组）；去卵巢牙周炎组（Ovx_Lig组）。Sham_Lig组与Ovx_Lig组小鼠术后4周，以5-0号丝线结扎双侧上颌第二磨牙诱导牙周炎。丝线结扎8周后对4组小鼠实施安乐死，取材小鼠股骨、胫骨、下颌骨及颅骨样本行显微CT（micro-CT）扫描，并检测样本骨密度、骨体积分数（BV/TV）、骨小梁数量（Tb.N）、骨小梁厚度（Tb.Th）和骨小梁分离度（Tb.Sp）。收集4组小鼠盲肠内容物，利用16S rRNA基因测序检测肠道菌群的组成，通过液相色谱-质谱法检测肠道中的色氨酸及其代谢物的含量，并对肠道菌群相对丰度水平与色氨酸代谢物含量行相关性分析。 结果： Ovx_Lig组小鼠股骨骨密度［（82.23±3.97）mg/cm3］、BV/TV［（9.25±1.37）%］和Tb.Th［（70.95±5.70）μm］均显著低于Ovx组［分别为（96.30±3.76）mg/cm3（P=0.004）、（14.45±1.55）%（P=0.022）和（87.58±8.02）μm（P<0.001）］。肠道菌群基于Bray-Curtis距离的β多样性分析显示，Ovx_Lig组小鼠肠道菌群与Ovx组分群明显。线性判别分析效应量显示，另枝菌属为Ovx_Lig组显著差异菌属。Ovx_Lig组另枝菌属的相对丰度［（0.42±0.14）%］显著高于Ovx组［（0.17±0.05）%］（t=4.45，P<0.001）。色氨酸代谢分析显示，Ovx_Lig组小鼠肠道内犬尿酸的含量［（531.12±158.60）ng/g］显著高于Ovx组［（400.42±57.96）ng/g］（t=2.19，P=0.046），吲哚-3-甲醛的含量［（383.37±144.06）ng/g］显著低于Ovx组［（701.72±141.93）ng/g］（t=4.45，P<0.001）。相关性分析显示另枝菌属的相对丰度与犬尿酸呈正相关（r=0.32，P=0.088），与吲哚-3-甲醛呈负相关（r=-0.32，P=0.088）。 结论： 小鼠雌激素缺乏背景下，牙周炎可导致小鼠股骨骨质破坏，其机制可能与肠道另枝菌属及色氨酸代谢物犬尿酸和吲哚-3-甲醛有关。.