【作者】 周莉；

【导师】 刘烈刚；

【作者基本信息】 华中科技大学 ， 营养与食品卫生学， 2020， 博士

【摘要】 血脂是一系列动态变化的生化指标,临床上常以血液中甘油三酯(triglyceride,TG)、总胆固醇(total cholesterol,TC)、高密度脂蛋白胆固醇(high-density lipoprotein cholesterol,HDL-C)和低密度脂蛋白胆固醇(low-density lipoprotein cholesterol,LDL-C)水平反映机体血脂水平。随着膳食结构和生活方式的改变,中国居民的血脂水平大幅升高。TG、TC和LDL-C水平的升高,尤其是LDL-C水平的升高,是心血管疾病的重要危险因素。因此,识别血脂水平的影响因素进而调控血脂水平,成为降低心血管疾病负担、促进人类健康的重要手段之一。众所周知,膳食因素对血脂水平的调控具有重要意义。硒是一种人体必需微量元素,主要通过膳食摄入。血浆和血清硒是硒摄入的生物标志物,流行病学研究常通过检测血浆或血清硒水平反映硒摄入量。硒在人体具有多种生理功能,包括参与调节糖代谢、脂代谢、氧化还原反应、炎症反应和生殖功能等。动物研究结果提示高硒饮食可能促进肝脏脂类合成,抑制肝脏脂类分解,进而升高肝脏TG和TC水平。然而,目前关于硒水平与血脂水平关联的流行病学研究结论不一致。此外,目前关于硒水平与血脂水平关联的流行病学研究主要探讨两者的横断面关联,鲜有研究探讨硒水平与血脂水平纵向变化的关联。而探讨硒与血脂水平纵向变化的关联,对预测血脂水平变化具有重要意义。除膳食因素外,遗传因素对血脂水平也具有重要影响。据估计,遗传因素可解释约40%至70%血脂水平变化。近年来,大量横断面研究揭示了约300个与血脂水平相关的基因位点。然而,却鲜有研究探讨基因多态性与血脂水平纵向变化的关联。硒在人体主要通过参与合成硒蛋白发挥生理功能。研究提示硒蛋白P(selenoprotein P,SELENOP)和硒蛋白S(selenoprotein S,SELENOS)可能参与调控血脂水平。此外,研究发现SELENOP、SELENOS基因多态性与心血管疾病有关。然而,目前尚无研究探讨SELENOP、SELENOS基因多态性与血脂水平纵向变化的关联,也未见文献报道硒水平和SELENOP、SELENOS基因多态性交互作用与血脂水平纵向变化的关联。因此,本研究依托于同济-鄂州队列,在较大规模中国人群中,首先探讨血浆硒水平与血脂水平的横断面关联,及血浆硒水平与血脂水平纵向变化的关联,然后探讨SELENOP、SELENOS基因多态性与血脂水平纵向变化的关联,及血浆硒水平和SELENOP、SELENOS基因多态性交互作用与血脂水平纵向变化的关联。本研究主要内容分为如下两个部分:第一部分血浆硒水平与血脂水平的关联性研究目的:探讨血浆硒水平与血脂水平的横断面关联,以及血浆硒水平与血脂水平纵向变化的关联。方法:研究对象来源于同济-鄂州队列,基线调查时间为2013至2015年,随访调查时间为2016至2018年,平均随访时间为3年。由经专业培训的研究生采用半结构化问卷收集研究对象的基本信息,采用实验室已建立的电感耦合等离子体质谱仪(inductively coupled plasma mass spectrometry,ICP-MS)方法定量检测2012名研究对象基线时血浆硒水平,并按统一的标准化方法对2012名研究对象基线时血脂水平和随访到的1961名研究对象随访时血脂水平进行检测,检测的血脂指标包括:TG、TC、HDL-C和LDL-C。分别开展横断面分析和纵向分析,横断面分析中采用多因素线性回归探讨血浆硒水平与血脂水平的关联,纵向分析中采用多因素线性回归探讨血浆硒水平与血脂水平纵向变化的关联,并采用限制性三次样条回归模型探讨血浆硒水平与血脂水平纵向变化的非线性关系。结果:研究对象血浆硒水平中位数为92.09μg/L。横断面分析中多因素线性回归结果显示,校正性别、年龄、身体质量指数(body mass index,BMI)和吸烟状况等混杂因素后,血浆硒水平与TG、TC、HDL-C和LDL-C水平呈显著正关联关系(P<0.05),血浆硒水平最高三分位和最低三分位相比,TG水平升高6.54%(95%CI:0.80%,12.27%;P<0.05),TC水平升高6.31%(95%CI:3.11%,9.52%;P<0.05),HDL-C水平升高3.97%(95%CI:0.86%,7.08%;P<0.05),LDL-C水平升高9.11%(95%CI:5.35%,12.88%;P<0.05)。纵向分析中多因素线性回归结果显示,校正性别、年龄、BMI、吸烟状况、饮酒状况、随访时间和各自的基线血脂水平等混杂因素后,血浆硒水平与TC、LDL-C水平纵向变化呈显著正关联关系(P<0.05),血浆硒水平最高三分位和最低三分位相比,TC水平纵向升高4.41%(95%CI:2.22%,6.59%;P<0.05),LDL-C水平纵向升高4.96%(95%CI:1.60%,8.32%;P<0.05)。分层分析结果表明,在所有亚组人群中血浆硒水平与TC水平纵向变化均呈显著正关联关系(P<0.05);除“女性”、“BMI≥24 kg/m~2”,“不吸烟”、“锻炼”和“无血脂异常”亚组人群外,其余亚组人群中血浆硒水平与LDL-C水平纵向变化呈显著正关联关系(P<0.05)。限制性三次样条回归模型结果表明,血浆硒水平与TC、LDL-C水平纵向变化呈非线性正关联关系(非线性检验P<0.05)。结论:本研究横断面分析结果表明,血浆硒水平与TG、TC、HDL-C和LDL-C水平呈显著正关联关系,纵向分析结果表明血浆硒水平与TC、LDL-C水平纵向变化呈显著正关联关系。第二部分血浆硒水平和硒蛋白P、硒蛋白S基因多态性交互作用与血脂水平纵向变化的关联性研究目的:探究SELENOP、SELENOS基因多态性与血脂水平纵向变化的关联,以及血浆硒水平和SELENOP、SELENOS基因多态性交互作用与血脂水平纵向变化的关联。方法:研究对象来源于同济-鄂州队列。研究对象基本信息收集,基线血浆硒水平检测,及基线、随访时血脂水平检测方法同第一部分。在第一部分纵向分析纳入的研究对象中,采用基质辅助激光解吸电离飞行时间质谱方法对其中1621名研究对象的2个候选单核苷酸多态性(single nucleotide polymorphism,SNP)位点进行基因分型,2个候选SNP位点分别为SELENOP rs7579位点和SELENOS rs4965814位点。采用拟合优度卡方检验判断纳入人群基因分布是否符合哈迪-温伯格平衡定律,采用多因素线性回归探究SELENOP、SELENOS基因多态性与血脂水平纵向变化的关联,采用似然比检验探究血浆硒水平和SELENOP、SELENOS基因多态性交互作用与血脂水平纵向变化的关联。结果:研究对象血浆硒水平中位数为91.41μg/L。SELENOP rs7579和SELENOS rs4965814在研究对象中的基因型分布均符合哈迪-温伯格平衡定律(哈迪-温伯格平衡检验P>0.05)。多因素线性回归结果表明,SELENOP rs7579和SELENOS rs4965814基因多态性与TG、TC、HDL-C和LDL-C水平纵向变化均没有显著关联(P>0.05)。交互作用分析结果表明,血浆硒水平和rs7579基因多态性交互作用与TC、LDL-C水平纵向变化存在显著关联(交互作用P<0.05)。交互作用表现为:按血浆硒水平三分位分层,在血浆硒水平最高三分位亚组人群中,rs7579基因多态性与TC、LDL-C水平纵向变化存在显著关联(P<0.05);其余亚组人群中,rs7579基因多态性与TC、LDL-C水平纵向变化关联不显著(P>0.05)。在血浆硒水平最低三分位、中间三分位和最高三分位亚组人群中,rs7579CT基因型携带者和CC基因型携带者相比,TC水平纵向变化分别为1.34%(95%CI:-2.26%,4.94%;P>0.05),0.43%(95%CI:-3.24%,4.09%;P>0.05)和-4.44%(95%CI:-7.77%,-1.11%;P<0.05),LDL-C水平纵向变化分别为3.19%(95%CI:-1.95%,8.34%;P>0.05),3.97%(95%CI:-2.41%,10.34%;P>0.05)和-5.31%(95%CI:-10.38%,-0.24%;P<0.05)。血浆硒水平和SELENOS rs4965814基因多态性交互作用与血脂水平纵向变化没有显著关联(交互作用P>0.05)。此外,联合作用分析结果表明,和血浆硒水平位于最低三分位且具有rs7579CC基因型携带者相比,血浆硒水平位于最高三分位且具有rs7579 CC基因型者TC、LDL-C水平纵向变化程度最大,分别升高7.18%(95%CI:3.91%,10.45%;P<0.05)和9.66%(95%CI:4.52%,14.80%;P<0.05)。结论:本研究结果表明,在全部研究对象中SELENOP rs7579和SELENOS rs4965814基因多态性与血脂水平纵向变化没有显著关联,血浆硒水平和SELENOP rs7579基因多态性交互作用与TC、LDL-C水平纵向变化存在显著关联。在高血浆硒水平亚组人群中,rs7579基因多态性与TC、LDL-C水平纵向变化存在显著关联。更多还原

【Abstract】 Blood lipids are a cluster of biochemical indicators which are changing dynamically,and blood levels of triglycerides(TG),total cholesterol(TC),high-density lipoprotein cholesterol(HDL-C),low-density lipoprotein cholesterol(LDL-C)are usually used to reflect blood lipid levels clinically.With changes of dietary pattern and lifestyle,the blood lipid levels among Chinese increased dramatically.The increase of TG,TC,and LDL-C,especially the increase of LDL-C,is a main risk factor of cardiovascular disease.Therefore,identifying factors affecting blood lipid levels and regulating blood lipid levels become an important means to reduce the burden of cardiovascular disease,as well as to promote health.As we all know,environmental factors are associated with blood lipid levels.As the modifiable environment factors,dietary factors are of great significance to the regulation of blood lipid levels.Selenium is an essential trace element ingested mainly through food.Both plasma and serum selenium levels are biomarkers of selenium intake,and epidemiological studies usually measure plasma or serum selenium levels to reflect selenium intake.Selenium is involved in various physiological functions,including oxidation-reduction reactions,inflammatory response,thyroid hormone metabolism,immune function,reproductive function,and so on.Previous studies revealed that high selenium levels might induce oxidative stress and inflammatory injury,and then might have adverse effects on cardiovascular health.However,findings from studies examining associations between selenium levels and blood lipid levels are contradictory.In addition,most studies examining associations between selenium levels and blood lipid levels are cross-sectional,and studies exploring associations between selenium levels and longitudinal changes of blood lipid levels are limited.Exploring associations between selenium levels and longitudinal changes of blood lipid levels is of great importance to predict longitudinal changes of blood lipid levels.Beyond environmental factors,genetic factors also of great significance to blood lipid levels.It is estimated that genetic factors can account for nearly 40-70%of the total variance in blood lipid levels.At present,over 300 genetic loci are identified to be associated with blood lipid levels.However,very few studies have explored genetic loci associated with longitudinal changes in blood lipid levels.In human beings,the physiology functions of selenium are achieved mainly through selenoproteins.Findings from studies suggested that selenoporotein P(SELENOP)and selenoprotein S(SELENOS)might take part in the regulation of blood lipid levels.In addition,several single nucleotide polymorphisms(SNPs)located in SELENOP or SELENOS genes have been associated with cardiovascular diseases.However,no study has examined the associations of SELENOP and SELENOS genes polymorphisms with longitudinal changes in blood lipid levels,as well as the interactions between plasma selenium levels and SELENOP and SELENOS genes polymorphisms in relation to longitudinal changes in blood lipid levels.Hence,based on Tongji-Ezhou cohort,we designed a group of studies among a large-scale of Chinese population to investigate several issues.Firstly,to evaluate cross-sectional associations between plasma selenium levels and blood lipid levels,as well as associations between plasma selenium levels and longitudinal changes in blood lipid levels.Secondly,to examine associations of SELENOP and SELENOS genes polymorphisms with longitudinal changes in blood lipid levels,as well as the interactions between plasma selenium levels and SELENOP and SELENOS genes polymorphisms in relation to longitudinal changes in blood lipid levels.The main content of our study covers the following two parts:Part 1 Associations between plasma selenium levels and blood lipid levelsObjective:To examine cross-sectional associations between plasma selenium levels and blood lipid levels,and associations between plasma selenium levels and longitudinal changes in blood lipid levels.Methods:All participants came from Tongji-Ezhou cohort study.The baseline survey of Tongji-Ezhou cohort study was conducted between 2013 and 2015,and the follow-up survey was conducted between 2016 and 2018,with an average follow-up period of 3 years.Baseline plasma selenium levels were quantified by inductively coupled plasma mass spectrometry(ICP-MS)among 2012 participants.Baseline blood lipid levels were measured according to standard methods among 2012 participants,and blood lipid levels at follow-up were measured among 1961 participants who have participated the follow-up survey.Blood lipid indicators that we have measured include TG,TC,HDL-C,and LDL-C.Cross-sectional and longitudinal analyses were conducted respectively.In cross-sectional analyses,multivariable linear regression model was used to evaluate associations of plasma selenium levels with blood lipid levels.In longitudinal analyses,multivariable linear regression model was used to evaluate associations of plasma selenium levels with longitudinal changes in blood lipid levels,and restricted cubic spline model was used to explore the dose-response relationships between plasma selenium levels and longitudinal changes in blood lipid levels.Results:The median of plasma selenium levels was 92.09μg/L.In cross-sectional analyses,after adjustment for sex,age,body mass index(BMI),smoking status,and so on,results of multivariable linear regression analyses indicated that plasma selenium levels were positively associated with TG,TC,HDL-C and LDL-C(P<0.05),when comparing the highest to the lowest tertiles of plasma selenium levels,TG increased by6.54%(95%CI:0.80%,12.27%;P<0.05),TC increased by 6.31%(95%CI:3.11%,9.52%;P<0.05),HDL-C increased by 3.97%(95%CI:0.86%,7.08%;P<0.05),and LDL-C increased by 9.11%(95%CI:5.35%,12.88%;P<0.05).In longitudinal analyses,after adjustment for sex,age,BMI,smoking status,alcohol drinking status,duration of follow-up,respective baseline blood lipid levels,and so on,results of multivariable linear regression analyses indicated that plasma selenium levels were positively associated with longitudinal changes in TC,LDL-C levels(P<0.05),when comparing the highest to the lowest tertiles of plasma selenium levels,TC increased by 4.41%(95%CI:2.22%,6.59%;P<0.05),LDL-C increased by4.96%(95%CI:1.60%,8.32%;P<0.05).Findings from stratified analyses revealed that the positive association between plasma selenium and longitudinal change in TC was consistent among all subgroups,while the positive association between plasma selenium and longitudinal change in LDL-C was consistent among most subgroups except for women,subjects with BMI≥24 kg/m~2,subjects without smoking habit,and subjects with physical activity.Findings from the restricted cubic spline regression analyses demonstrated nonlinear positive relationships between plasma selenium levels and longitudinal changes in TC,LDL-C levels(non-linearity test:P<0.05).Conclusions:Findings from cross-sectional analyses indicated significantly positive associations between plasma selenium levels and TG,TC,HDL-C,and LDL-C levels,and findings from longitudinal analyses indicated significantly positive associations between plasma selenium levels and longitudinal changes in TC,LDL-C levels.Part 2 Interactions between plasma selenium levels and selenoprotein P,selenoprotein S genes polymorphisms in relation to longitudinal changes in blood lipid levelsObjective:To examine the associations of SELENOP and SELENOS genes polymorphisms with longitudinal changes in blood lipid levels,as well as the interactions between plasma selenium levels and SELENOP and SELENOS genes polymorphisms in relation to longitudinal changes in blood lipid levels.Methods:All participants came from Tongji-Ezhou cohort study.The collection of basic information,the quantitative determination of plasma selenium levels,and the measurement of lipid levels at baseline and follow-up have been described in part one.Among subjects included in the longitudinal analyses of part one,1621 subjects have been genotyped on 2 candidate SNPs by using a matrix-assisted laser desorption ionization time-of-flight MS system,these 2 candidate SNPs are SELENOP rs7579 and SELENOS rs4965814.The distribution of gene genotype was analyzed for deviation from Hardy-Weinberg equilibrium by using chi-square goodness of fit test.Multivariable linear regression model was used to examine the associations of SELENOP and SELENOS genes polymorphisms with longitudinal changes in blood lipid levels,likelihood ratio test was used to investigate the interactions between plasma selenium levels and SELENOP and SELENOS genes polymorphisms in relation to longitudinal changes in blood lipid levels.Results:The median of plasma selenium levels was 91.41μg/L.Both SNPs were in accord with Hardy-Weinberg equilibrium among the participants(P-HWE>0.05).Results of multivariable linear regression analyses indicated that the associations of SELENOP rs7579 and SELENOS rs4965814 with longitudinal changes in blood lipid levels were nonsignificant(P>0.05).The interactions between plasma selenium levels and rs7579 in relation to longitudinal changes in TC,HDL-C levels were significant(P for interaction<0.05).When stratifying by tertiles of plasma selenium levels,rs7579was significantly associated with longitudinal changes in TC,HDL-C levels among participants with the highest tertile of plasma selenium levels(P<0.05);In other subgroups,the associations between rs7579 and longitudinal changes in TC,HDL-C levels were non-significant(P>0.05).When comparing rs7579 CT carriers to CC carriers,the longitudinal changes in TC levels in participants with the lowest,middle,and the highest tertiles of plasma selenium levels were 1.34(95%CI:-2.26%,4.94%;P>0.05),0.43%(95%CI:-3.24%,4.09%;P>0.05),and-4.44%(95%CI:-7.77%,-1.11%;P<0.05),respectively;the longitudinal changes in LDL-C levels in participants with the lowest,the second,and the highest tertiles of plasma selenium levels were 3.19%(95%CI:-1.95%,8.34%;P>0.05),3.97%(95%CI:-2.41%,10.34%;P>0.05),and-5.31%(95%CI:-10.38%,-0.24%;P<0.05),respectively.The interactions between plasma selenium levels and SELENOS rs4965814 in relation to longitudinal changes in blood lipid levels were non-significant(P for interaction>0.05).Moreover,findings from the joint-effect analyses revealed that participants with the highest tertile of plasma selenium levels and rs7579 CC genotype had the greatest longitudinal changes in TC,LDL-C levels when comparing with participants with the lowest tertile of plasma selenium levels and rs7579 CC genotype,and the longitudinal changes in TC,LDL-C levels were 7.18%(95%CI:3.91%,10.45%;P<0.05)and 9.66%(95%CI:4.52%,14.80%;P<0.05),respectively.Conclusions:Our findings suggested that in overall participants,the associations of SELENOP rs7579 and SELENOS rs4965814 with longitudinal changes in blood lipid levels were nonsignificant,and the interactions between plasma selenium levels and rs7579 in relation to longitudinal changes in TC,LDL-C levels were significant.In participants with high plasma selenium levels,the associations between rs7579 and longitudinal changes in TC,HDL-C levels were significant.更多还原