Study Of The Causal Relationship Between Female Reproductive Factors And Systemic Lupus Erythematosus Based On Mendelian Randomization Method

ObjectiveTo investigate whether female estradiol levels,age at menarche(AAM)and age at first live birth(AFB)are risk factors for Systemic lupus erythematosus(SLE),we conduct a two-sample Mendelian randomization(MR)study.After that,the correlation between real risk factors and clinical features of SLE was further analyzed,and the role of the above reproductive factors in the pathogenesis of SLE was preliminarily discussed.Methods1.Statistical data related to estradiol levels,AAM,AFB,and SLE were obtained from genome-wide association analysis(GWAS)databases.After the screening of single nucleotide polymorphisms(SNPs),the inverse variance weighted(IVW),weighted median(WM)and MR-Egger regression were used for two-sample Mendelian randomization(MR)analysis to assess the genetic causal relationship between the above factors and SLE.The risk factors for the onset of SLE were identified.2.The medical records of female newly diagnosed SLE patients admitted to the Affiliated Hospital of Yangzhou University from March 1,2015 to March 1,2023 were selected and collected,including the clinical data of the two groups,including:(1)General situation;(2)Clinical symptoms:presence or absence of arthralgia,fever,rash,mucosal ulcers(oral or nasal),hair loss,edema,and neurological symptoms(delirium,psychosis,or epilepsy);(3)Biochemical indicators:White blood cell(WBC)count,Hemoglobin(HB)count,Platele(PLT)count,Neutrophil lymphocyte ratio(NLR),C-reactive protein(CRP),Erythrocyte sedimentation rate(ESR),Albumin(ALB),Globulin(GLO)and 24h urinary protein quantization;(4)Immunological indicators:CD3+T cells,CD4+T cells,CD8+T cells,CD19+B cells,Natural killer cell(NK)cell proportion,Immune globulin(Ig)G,IgM,IgA,complement 3,complement 4,anti-dsDNA antibody,anti-SM antibody,anti-nRNP/Sm antibody,anti-SSA antibody,anti-Ro-52 antibody,anti-SSB antibody,anti-Scl-70 antibody,anti-phospholipid antibody(Antiphospholipid antibodies were considered positive if any of the anticardiolipin antibodies were IgG,IgM,or anti-β 2-glycoprotein);(5)Involvement of organs and systems(Whether blood system,skin mucous membrane,nervous system,serous membrane,joint or kidney involved);(6)Systemic Lupus Erythematosus Disease Activity Index-2000(SLEDAI-2000)score;(7)Systemic Lupus Intemnational Collaborating Clinic/American College of Rheumatology Rheumatology Damage Index(SDI)score.The collected data were grouped according to the previously identified risk factors.t test,Mann-Whitney U test,Chi-square test or Fisher exact test were used to compare the differences among patients in different groups,and Spearman rank sum test was used to analyze the correlation between risk factors and different clinical features of SLE.Results1.A two-sample MR study is conducted,in that 6 SNPs related to the occurrence of SLE caused by AAM were identified as instrumental variables to evaluate the causal relationship between AAM and SLE.We found there is a negative genetic causal relationship between AAM and SLE(IVW:beta=-0.395,SE=0.165,P=0.016;WM:beta=-0.416,SE=0.192,P=0.030;MR-Eegger:beta=0.116,SE=0.948,P=0.909),no level pleipotency or outlier was found by MR-PRESSO’s global detection(P=0.230),and the results were also proved reliable by heterogeneity test and sensitivity analysis,suggesting that AAM was a risk factor for SLE.AFB(MR-Eegger:beta=-2.815,SE=1.469,P=0.065;WM:beta=0.334,SE=0.378,P=0.377;IVW:beta=0.188,SE=0.282,P=0.505)and estradiol levels(MR-Eegger:beta=0.139,SE=0.294,P=0.651;WM:beta=0.063,SE=0.108,P=0.559;IVW:beta=0.126,SE=0.097,P=0.192),no significant genetic causal relationship was found with SLE.2.A total of 128 primarily diagnosed SLE patients were included,with an average AAM of 12.84 ± 1.75 years old,and were divided into AAM premature group(AAM≤12 years old)and AAM normal group(AAM>12 years old and AAM≤16 years old)according to the AAM of the patients.Compared with AAM normal group,AAM premature group had higher proportion of mucosal ulcer,proportion of CD19+B cells,positive rate of anti-dsDNA,proportion of blood system involvement,proportion of skin mucous membrane involvement,SLEDAI-2000 score and proportion of SDI≥1;and lower WBC count,PLT count,ALB level and NK cell proportion(P>0.05).HB,NLR,CRP,ESR,CD3+T cell proportion,CD4+T cell proportion,CD8+T cell proportion,IgG,IgM,IgA,complement C3,complement C4,anti-SM antibody,anti-nRNP/Sm antibody,anti-SSA antibody,anti-Ro-52 antibody,anti-S SB antibody,anti-SCL-70 antibody,anti-phospholipid antibody,nervous system involvement,serous membrane involvement,joint involvement and kidney involvement had no significant differences(P>0.05).3.Correlation analysis showed that AAM was positively correlated with white cell count(r=0.215,P=0.015),platelet count(r=0.209,P=0.018)and natural killer cell proportion(r=0.314,P<0.001).And having mucosal ulcer(r=-0.205,P=0.020),CD19+B lymphocyte ratio(r=-0.259,P=0.003),anti-DSDNA antibody(r=-0.313,P<0.001),systemic lupus erythematosus activity index-2000 score(r=-0.377,P<0.001),SDI score ≥ 1(r=-0.237,P=0.007),blood system involvement(r=-0.209,P=0.018)and cutaneous mucosal system involvement(r=-0.219,P=0.013)were negatively correlated.ConclusionAAM may increase the risk of SLE.And also AAM is associated with changes in lymphocyte proportion,the appearance of anti-dsdna antibody,disease activity,skin,mucosa and blood system involvement in SLE patients,suggesting that AAM may be closely related to the pathogenesis and disease progression of SLE.