ObjectiveTo describe the characteristics of cardiorespiratory fitness levels in the baseline population of the South China Cohort， and to identify the potential contributing factors. MethodsFace-to-face surveys and physical examinations were conducted to collect information on demographic characteristics， medical histories， medications， lifestyles， and physical activity conditions. After excluding individuals with missing cardiorespiratory fitness-related data and covariates including physical activity and dietary information， a total of 77 024 participants aged 25 to 85 were included. Cardiorespiratory fitness levels were evaluated using a non-exercise algorithm， and low cardiorespiratory fitness level was defined as below the lower tertile of the population distribution. Logistic regression analysis was used to examine the distribution of low cardiorespiratory fitness level， and log-binomial regression and ordered logistic regression analyses were used to analyze the associations of cardiorespiratory fitness with demographic characteristics， socioeconomic factors， lifestyle factors （including alcohol consumption and dietary diversity）， and chronic diseases conditions （including diabetes， hypertension， pulmonary diseases， and cardiovascular diseases）. ResultsCardiorespiratory fitness levels showed a sufficiently normal distribution in both male and female group. We found that the proportion of low cardiorespiratory fitness level was higher among Han ethnicity， those with an educational level below 9th grade， households with an annual income of more than 100 000 Yuan， as well as those who drank alcohol at least one time per week and who exhibited low dietary diversity （all P＜0.001）. Ethnicity， socioeconomic status， lifestyle factors， and chronic diseases were found to be statistically associated with cardiorespiratory fitness levels in the South China population （all P＜0.001）. ConclusionCardiorespiratory fitness levels varied across different population groups in South China， with ethnicity， socioeconomic status， lifestyle factors， and chronic diseases serving as key determinants. Therefore， it is recommended that the public pay attention to cardiorespiratory fitness， as strengthening population-level monitoring and interventions for cardiorespiratory fitness carries significant public health implications.

Objective:To investigate the correlation between the changes of oral bacterial flora during head and neck radiotherapy and radiation-induced oral mucositis (ROM).Methods:The oral bacterial samples of patients with nasopharyngeal carcinoma and accompanying family members were obtained before and at the end of radiotherapy and subjected to high-throughput sequencing. C57BL/6 mice were used to establish the ROM models. On the 9 th day after radiotherapy, oral bacterial samples were collected in the radiotherapy group and the negative control group. On the 3 rd, 5 th, 7 th, and 9 th days post-radiotherapy, the tongue tissues were obtained from another batch of mice in the negative control and radiotherapy groups. Inflammatory factors were detected with PCR and HE staining was performed. Results:The oral bacterial diversity of patients after radiotherapy significantly differed from that of patients before radiotherapy and their accompanying family members before and after radiotherapy in Observed species, Chao1, Simpson index (all P<0.05). There was a significant difference in Shannon index between the severe and mild ROM patients ( P=0.036). LEfSe analysis showed that patients with severe ROM had higher levels of g_ Streptococcus and f_ Streptococcus, and lower levels of f_ Familyxl, g_ Gemini and o_ Bacillus. The Simpson index and PCoA results in the oral bacterial samples significantly differed between the negative control and radiotherapy groups (all P<0.05). Conclusions:Radiotherapy can disrupt the balance of bacterial flora. The dysregulated oral bacterial flora is closely associated with the aggravation of ROM.

Objective To investigate the effect of miR-15b and miR-16 on the expression of vascular endothelial growth factor (VEGF) protein in human embryonic lung fibroblast (HLF) cells under hyperoxia.Methods The expression level of miR-15b and miR-16 was up-regulated and down-regulated in HLF cells by transfection technology, respectively.The expression of VEGF protein in HLF cells was assessed by Western blot.Furthermore, under hyperoxia exposure in vitro, the expression of miR-15b, miR-16 and VEGF protein in HLF cells was analyzed.Results Up-regulation of miR-15b and miR-16 suppressed VEGF protein expression, while down-regulated miR-15b and miR-16 promoted VEGF protein expression.In addition, hyperoxia exposure induced up-regulation of miR-15b and miR-16, but down-regulation of VEGF protein in HLF cells.Conclusions Hyperoxia exposure may up-regulate the expression level of miR-15b and miR-16, but suppress VEGF protein expression.These may contribute to the development of bronchopulmonary dysplasia.