糖尿病是一种以高血糖为特征的代谢性疾病。已有研究表明，口腔疾病与2型糖尿病之间具有紧密的联系，龋病、牙髓根尖周病、牙周病等在糖尿病患者中发病率增加，疾病的严重程度亦增加。我们前期研究发现2型糖尿病患者的口腔菌群与正常人群有差异，且有些种类细菌的差异与空腹血糖、糖化血红蛋白水平相关，提示这些菌群可能与口腔疾病以及系统性疾病的发生发展有关。但糖尿病患者的口腔菌群构成在种水平上有何差异，其龋病高发是何机制等仍需进一步明确。在此基础上，本课题拟采用横断面研究和纵向研究策略，应用高通量宏基因组测序和基因表达谱测序技术，深入研究2型糖尿病患者与正常人群口腔唾液和龈上菌斑在细菌种水平上的差异，揭示血糖水平与口腔菌群构成的相关性，明确龈上菌斑中致龋相关基因的表达差异导致其龋病高发。这些研究有望揭示2型糖尿病患者龋病高发且其进展程度更严重的可能机制，拓展对糖尿病与口腔菌群之间关系的认识，具有重要的理论意义。

Diabetes is a metabolic disease characterized by hyperglycemia. Studies have shown that there is a close relationship between oral diseases and type 2 diabetes. The incidence of dental caries, periapical periodontitis and periodontal disease is increasing in diabetic patients. The severity of these diseases is also much higher in diabetic patients. Our previous study found that oral bacteria in patients with type 2 diabetes and normal people are different, and the difference of some species of bacteria has a positive correlation with fasting blood glucose and glycosylated hemoglobin levels, suggesting that these bacteria may be associated with the occurrence and development of oral diseases and systemic.disease. However, what is the difference in the oral flora of the diabetic patients at the level of the species, and the mechanism of the high incidence of dental caries still need to be further clarified..On this basis, this study intends to use a cross-sectional study and longitudinal study strategy, by application of high-throughput metagenomic sequencing and gene expression profile sequencing technology, differences in the level of bacterial species on saliva and supragingival plaque is studied between patients with type 2 diabetes and normal people. The relationship between blood glucose level and oral flora composition will be revealed, and the different expression profile of cariogenic related genes in supragingival plaque might lead to high caries incidence in diabetic patients. These studies are expected to reveal the possible mechanism of the high incidence of dental caries and the more serious progression of the caries in type 2 diabetes mellitus. It is of great theoretical significance to expand the understanding of the relationship between diabetes and oral micro flora.