Association Between The Exposure To PM_2.5 And TMAO Level In Stage 1 Hypertensive Chinese Students

Background:Particulate matter(PM_2.5)has been constantly linked to human health effects.Exposure to PM_2.5.5 is associated with increased cardiovascular disease?CVD?risk mortality and morbidity worldwide.Hypertension and stage 1 hypertension are the prevalent cause worldwide associated with the high risks of CVD.Association between PM_2.5 and the elevated trimethylamine N-Oxide?TMAO?levels have also been proposed in recent years for the cause of CVD.Epidemiologic studies among hypertensive population support the possibility that PM_2.5 exposures increased risk of CVD.Many studies have evidenced that exposure to PM_2.5 with elevated blood pressure and TMAO levels are most susceptible for the risks of CVD.PM_2.5 consists of various air pollutants,and some studies have evaluated whether air pollutants may have differential effects on the cardiovascular system,but it still remains unclear whether specific air pollutants are directly responsible for PM_2.5.5 involved in cardiovascular adverse health effects.Increased blood pressure is a major risk factor for CVD.Air pollution control has been verified to benefit cardiovascular mortality in urban China,although reduction the total emission of PM_2.5 still require long-term efforts,especially in severely air-polluted areas.It can be an effective strategy to protect the susceptible population through finding out the key toxic air pollutants existing in PM_2.5.5 and reducing their emissions by targeting their sources.Numerous epidemiological studies have connected with particulate air pollution to adverse cardiovascular health effects,and the strongest epidemiological has been shown for the elevated risk of cardiovascular morbidity and mortality which is constantly linked with exposure to PM_2.5.PM related to traffic in particular has been evidenced to play an important role in PM-induced cardiovascular health issues both epidemiologically and experimentally.It has been suggested that air pollutants especially the PM may enter the circulation influencing systemic inflammation and hypercoagulability,alter cardiac autonomic nervous system,increase peripheral blood pressure,and causing of atherosclerosis through oxidation pathway.Epidemiological studies suggesting this biological mechanism of air pollution is adversely linked with cardiovascular outcomes are growing during recent years.Several studies have suggested the reality that the exposure to particulate matter was directly linked with exhilaration of systemic inflammation and hypercoagulability,raised peripheral blood pressure,and raised plasma homocysteine?a risk factor for CVD?.The short-term effects of PM_2.5.5 on cardiovascular diseases have been widely reported in the Europe and U.S,which is evidenced as mortality and morbidity indicators;such as hospital admissions and emergency room visits?ERVs?.Understanding the better concepts on PM exposure and their associated sources could lead a bad impact on the public health.However,it is still unknown to date that the roles of various PM exposures in the aforementioned biological mechanisms relating air pollution to adverse cardiovascular health effects.Most previous studies done in this field have evidenced a limited number of air pollutants or PM,whereas air pollution research requires measurements of a cluster of air pollutants which evidenced in better understanding of the features of a complex air pollution mixture that are most toxic to the human health.The sources of these particles develop mainly from a number of different immobile and portable mission sources as well as from natural sources.The particles that produced from burning sources are thought to be more harmful to human health than particles produced from other sources.It remains unclear that whether individuals with hypertension or stage 1 hypertension are at greater risk of CVD after PM_2.5.5 exposures when compared with those with normal blood pressures.This study is aimed to evaluate the risk factors of CVD associated with the exposure of PM_2.5.5 with elevated TMAO level in stage 1 hypertensive Chinese students.Methods:This is a retrospective,descriptive population-based study conducted among the stage 1hypertensive college students in Nanjing city.40 college students were recruited from the Nanjing Xiaozhuang University,which is located in the northern urban area of Nanjing,China.The inclusion criteria were 18 years old or more and a commitment of living on campus during the study period,who has been found with a stage 1 hypertension condition?a systolic pressure?SBP?from 120 to 139 millimeters of mercury?mm Hg?or a diastolic pressure?DBP?from 80 to 89 mm Hg?during the routine admission physical examinations.Those who are having a history of tobacco smoking,alcohol drinking,diabetes,obesity?body mass index over 30?,hypertension,and clinically diagnosed CVD are excluded.This study was approved by the Institutional Review Board at the Zhongda Hospital,Southeast University.Written informed consents were obtained from all participants at enrollment.This design composed is composed of a panel study with repeated measurements of ambient PM_2.5 air pollutant,blood pressure and plasma parameters in enrolled individuals.For each participant,6 times of blood collection were scheduled from Feb.10^th,2017 to Mar.17^th,2017.The blood sample was collected from 8:00 am to 11:00 am during each blood sampling to control for possible biological rhythm.Data on individual demographic characteristics?gender,height,weight,and BMI?were collected at enrollment.To minimize the effects of diet on the levels of TMAO and precursors,all participants were asked to refrain from overeating,barbeque or buffet during the study period.A self-administered questionnaire of daily diet was completed by all participants.Trained technicians performed standardized resting BP measurements using a mercury sphygmomanometer.Briefly,participants rested in a sitting position in a quiet room for at least15minutes before left upper arm BP was measured at least three times with a 2-min.the minimum interval between measurements.In most cases,the second and third sets of readings were average to calculate the systolic BP?SBP?,diastolic BP?DBP?.However,if the differences of the second and third measurements were over 5mmHg,the BP was considered unstable,and another one to three measurements were taken until the differences were within 5 mmHg.Serum TMAO levels were detected by HPLC-MS/MS system?Agilent 6400 series Triple Quad LCMS,USA?as described.Briefly,60?l of serum sample was added with 100?l acetonitrile containing 10?M internal standards?TMAO-d9 and choline-d9,Toronto Research Chemicals Inc,Canada?,and centrifuged at 13,000 g for 10 min to precipitate the proteins.Then the supernatant was analyzed.The linear mixed-effect model was applied to evaluate the BP-PM_2.5 association and plasma parameter-PM_2.5 associations.We fit the single-constituent model by replacing those concentrations lower than the limits of detection?LODs?with a value of half LODs.In the single-constituent model,PM_2.5 and the criteria air pollutants were incorporated as the fixed-effect terms on at a time;a random intercept for each subject was added to account for co-relations among multiple repeated measurements collected per subject.This include several covariates as fixed-effect terms,the moving average of mean temperature and relative humidity on the present day and previous 7 days to control for the confounding effects of weather conditions;and individual characteristic including age,gender,and body mass index.The researcher has demonstrated that association between biological effects and cumulative exposures over multiple days are more robustly than exposure accounting for a single day.Therefore,we fit the model using moving-average lags from 1 day to a maximum lag of 7 days to explore the lag structures in the acute effects of PM_2.5 on BP and plasma parameters.In addition to the above basic single-constituent model,we also built a“two-pollutant model”to assess whether the effects of PM_2.5 were dependent on the simultaneous exposure to other criteria air pollutants to assess the robustness in the efficient estimation of a PM_2.5.5 air pollutant.The residual of each air pollutant was obtained by a linear regression model between total PM_2.5and air pollutant where the“independent”contribution to the observed effects of PM_2.5 was measured after excluding its collinearity with other constituents.Results were expressed as estimated percent changes with 95%confidence intervals?CIs?in BP and plasma parameter associated with interquartile range?IQR?increases in the air pollutants.All models were performed using SAS 9.4 software?SAS Institute,Cary,NC,USA?.And significant level was set at p<0.05,two-tailed.Results:The association of blood pressure was analyzed with lag 0-1 day exposures and found PM_2.5,NO₂,CO is significant association with elevated blood pressure.After controlling for PM_2.5in the two-pollutant model NO₂ and CO exposure are not associated with elevated blood pressure.Also we found PM_2.5,PM₁₀,NO₂,SO₂ and CO are significant positive association with elevated blood pressure.After controlling for PM_2.5.5 in two-pollutant model PM₁₀,NO₂,SO₂ and CO exposure are not associated with elevated blood pressure anymore.We also analyzed the association between PM_2.5 and SBP by different moving average day,it shows lag 0-1,lag 0-2,lag0-3 day PM_2.5.5 exposures are associated with elevated SBP even after controlling for other gaseous pollutant.PM_2.5.5 lag 0-1 to lag 0-3 are consistently positive or significantly positive associated with elevated blood pressure.The association between PM_2.5.5 and DBP were analyzed by different moving average day,and found lag 0-1,lag 0-2 day PM_2.5.5 exposures are associated with elevated DBP even after controlling for other gaseous pollutant.For PM₁₀,NO₂,SO₂,CO and O₃ lag 0-1day shows statistical significant associated with elevated blood pressure.The effect of PM_2.5 and air pollutant on serum TMAO levels were firstly estimated in single constituent model,and found significant association of PM_2.5.5 from lag 0-4 until lag 0-7 days.Also found significant positive association of PM₁₀,NO₂,SO₂,and CO from lag 0-5 until lag 0-7 days.There were no significant association of O₃ on serum TMAO level.After adjusting the PM_2.5,there is no any positive statistical significance.So,there is no any association between elevated change in TMAO for two-pollutant model.The association between PM_2.5.5 and TMAO were analyzed by different moving average day.Therefore,the result shows lag 0-4,lag 0-5,lag 0-6,lag 0-7 days,PM_2.5 exposures are associated with elevated change in TMAO level even after controlling for other air pollutant.PM_2.5.5 lag 0-4 until lag 0-7 are still robustly associated with elevated change in TMAO level.Conclusion:Our study evidenced that the PM_2.5.5 gaseous pollutants play a crucial role in the pathological phenomena through which particulate matters affect the cardiovascular system.It also suggested that the gaseous pollutants;NO₂,SO₂,CO,and O₃ were associated with the elevated blood pressure and TMAO levels in Chinese students;suggesting the higher risks of CVD.Further large-scale studies should be performed to evaluate the association between PM_2.5,blood pressure and TMAO levels.We can conclude that the particulate matter(PM_2.5)is associated with the elevated TMAO levels in stage 1 hypertensive Chinese students.