[Mechanism of obesity affecting periodontal tissue regeneration and therapeutic strategies]

Obesity is an important health problem in our society today, which can lead to the chronic low-grade inflammation state, to be an inducement for many chronic diseases such as hypertension, type 2 diabetes and non-alcoholic fatty liver disease. As a common oral chronic infectious disease, periodontitis is mainly characterized by gingival inflammation, periodontal pocket formation, alveolar bone resorption and tooth mobility. The ultimate goal of periodontitis treatment is to achieve periodontal tissue regeneration in the defect area. As a major risk factor for periodontitis, obesity can alter the periodontal inflammatory microenvironment in multiple ways, affecting the effects of periodontal tissue regeneration ultimately. Therefore, this paper will review the relationship between obesity and periodontal tissue regeneration, mechanism of obesity affecting periodontal tissue regeneration and the therapeutic strategies of periodontal tissue regeneration, providing new ideas for periodontal tissue regeneration treatment in obesity.

[Effects of salivary microbiota on tryptophan-aryl hydrocarbon receptor signaling axis in mice with periodontitis]

Objective: To study the effects of salivary microbiota in patients with periodontitis on the tryptophan-aryl hydrocarbon receptor (AhR) signaling axis in mice with periodontitis and to provide theoretical basis as well as new ideas for the influences of periodontitis on systemic metabolism. Methods: Salivary microbiota of 12 healthy individuals and 14 patients with periodontitis were collected in Nanjing Stomatological Hospital, Medical School of Nanjing University from June to December of 2020. According to the random number table method, twenty-four mice were randomly divided into three groups: Sham group (control group), P group (periodontitis patients' salivary microbiota group) and H group (periodontal healthy individuals' salivary microbiota group). The maxillary second molars of all mice were treated with silk thread ligation to induce periodontitis. Phosphate buffer as well as salivary microbiota of periodontal healthy individuals and periodontitis patients were gavaged into periodontitis mice for 2 weeks. The expression of inflammatory factors in mice serum were detected by enzyme linked immunosorbent assay, and the expression of tryptophan and indole metabolites in intestinal tract and serum were detected by liquid chromatography-mass spectrometry. The expression of AhR in intestinal tract of mice was detected by immunohistochemistry and quantitative real time-PCR while gut microbiota constitution was detected by 16S rRNA gene sequencing. The remaining saliva samples of periodontitis patients and periodontal healthy individuals were applied to detect the expression of tryptophan and indole metabolites themselves. Results: The salivary microbiota of periodontitis patients could induce the expression of interleukin-1β [P group: (162.38±39.46) pg/ml, H group: (82.83±20.01) pg/ml; t=4.40, P=0.001) and tumor necrosis factor-α [P group: (361.16±123.90) pg/ml, H group: (191.66±106.87) pg/ml; t=2.54, P=0.030) in serum of periodontitis mice, and reduce the expression of AhR in colon (P group: 1.18±0.05, H group:1.83±0.47; t=3.09, P=0.015) and ileum (P group: 0.80±0.13, H group: 1.18±0.11; t=4.93, P=0.001). After gavage of salivary microbiota of periodontitis patients to the mice, tryptophan (P group: (18.1±3.8)×10⁷, H group: (26.6±6.6)×10⁷; t=2.49, P=0.037] and indole lactic acid [P group: (1.9±0.7)×10⁷, H group: (3.7±0.6)×10⁷; t=4.49, P=0.002) in serum of periodontitis mice were significantly decreased, but was relatively disorder in intestinal tract. However, the expressions of tryptophan and indole metabolites in saliva of periodontitis patients were higher than those of periodontal healthy individuals. There were significant differences in indole propionic acid [P group: (1 239.39±818.72) nmol/L, H group: (56.96±38.33) nmol/L; t=2.83, P=0.022]. What we find noteworthy was that the expressions of indolelactic acid metabolism in saliva, serum and intestinal were consistent, and salivary microbiota of periodontitis patients could reduce the relative abundance of indolelactic acid-producing bacteria in the gut, suggesting that the salivary microbiota of periodontitis patients might affect the expression of AhR through gut microbiota disorder and indolelactic acid downregulation. Conclusions: Salivary microbiota in patients with periodontitis may affect the systemic inflammatory state through down-regulating the expression of tryptophan-AhR signal axis.

Mutational analysis of mitochondrial tRNA genes in patients with lung cancer

Mutations in mitochondrial tRNA (mt-tRNA) genes have been found to be associated with various diseases including lung cancer. To understand the possible relationship between mtRNA mutations and lung cancer, we sequenced the 22 mt-tRNA genes from 200 lung cancer blood samples, as well as 100 healthy subjects. As a result, five mutations were identified including the tRNA^Ala T5655C, tRNA^Arg T10454C, tRNA^Leu(CUN) A12330G, tRNA^Ser(UCN) T7505C and tRNA^Thr G15927A. These mutations were absent in the healthy subjects. These mutations and polymorphisms were localized at the highly conserved nucleotides of the corresponding mitochondrial tRNAs, which are critical for the tRNA steady state level and may result in failure in the tRNA metabolism. Moreover, through the application of the pathogenicity scoring system, we found that only the T10454C mutation should be classified as a “neutral polymorphism,” while the other mutations were regarded as “definitely pathogenic.” Taken together, our data indicate that tRNA genes are the hot-spots for pathogenic mutations associated with lung cancer. Our findings may provide valuable information for pathophysiology, management and genetic counseling of lung cancer.

Alterations of microbial populations and composition in the rhizosphere and bulk soil as affected by residual acetochlor

Acetochlor is a widely used herbicide in maize fields; however, the ecological risk of its residue in the soil-plant system remains unknown. We investigated the dissipation dynamics of field dose acetochlor and clarified its impact on microbial biomass and community structure both in the rhizosphere and bulk soil over 1 month after its application. Soil microbial parameters such as quantities of culturable bacteria and fungi represented by colony-forming units, soil microbial biomass carbon (SMB(C)), and phospholipid fatty acids (PLFAs) were determined across different sampling times. The results showed that the dissipation half-lives of acetochlor were, respectively, 2.8 and 3.4 days in the rhizosphere and bulk soil, and 0.02-0.07 μg/g residual acetochlor could be detected in the soil 40 days after its application. Compared to the bulk soil, microbial communities in the rhizosphere soil were inclined to be affected by the application of acetochlor: SMB(C) content and bacterial growth were most likely to be increased; however, fungal growth was prone to be inhibited. The principal component analysis of PLFAs, as well as the comparisons of fungi/bacteria and cy17:0/C16:1ω9c ratios between different treatments over sampling time, revealed that the soil microbial community composition was significantly affected by acetochlor at its early application stage (at day 15); thereafter, the effects of acetochlor were attenuated or even could not be detected. Our results suggested that residual acetochlor did not confer a long-term impairment on viable bacterial groups in the rhizosphere and bulk soil.

[Effects of extraneous inorganic nitrogen forms on the dynamics of soil amino sugars]

Substrate availability affects microbial growth, whereas extraneous nitrogen forms can significantly affect microbial metabolic processes. As for soil amino sugars, the stable residues in microbial cell wall, their synthesis, decomposition and turnover are closely related to the availability of extraneous carbon and nitrogen. Using isotope tracing technique to study soil amino sugars can further understand the substrate utilization profiles by soil microorganisms. In this study, two incubation tests were conducted, with glucose plus 15N-labelled NH4+ or NO3- as the substrates, respectively. The 15N enrichment in each kind of soil amino sugars was identified by gas chromatography/ mass spectrometry (GC/MS) to trace the dynamics of soil 15N-labelled and native amino sugars. During the incubation, the content of soil 15N-labelled amino sugars increased significantly, and the transformation rate from NH4+ to amino sugars was significantly higher than that from NO3-, suggesting the preferred utilization of NH4+ than NO3- by soil microorganisms. Significant changes in the amounts of soil unlabelled amino sugars were observed. The amount of unlabelled glucosamine increased with NH4+ addition, but decreased gradually with NO3- addition. The content of unlabelled muramic acid decreased gradually, especially with NO3- addition. Either the increase or the decrease of galactosamine did not exceed 20% to the original value. These compound-specific changes showed that the heterogeneous microbial residues played different roles on the turnover and stabilization of nitrogen in soil matrix. Fungal cell wall residues were easily accumulated in soil matrix, which benefited the stabilization of soil organic matter, while bacterial cell wall residues were easily degraded, playing an important role in the turnover of soil organic matter.