title: Hypomethylation of long interspersed nucleotide element-1 in peripheral mononuclear cells of juvenile systemic lupus erythematosus patients in China.
abstract: OBJECTIVE
  Methylation abnormalities in T lymphocytes have been reported to correlate with systemic lupus erythematosus (SLE). Previous studies identified hypomethylation in the promoter of several genes linked to SLE. Long interspersed nucleotide element-1 (LINE-1) constitutes 17-25% of the human genome, and LINE-1 hypomethylation has been reported in SLE. Limited information is available regarding LINE-1 methylation in juvenile SLE (JSLE).
  
  
  METHODS
  Methylation levels of LINE-1 in peripheral blood mononuclear cells (PBMCs) from 59 JSLE and 47 control samples were examined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Total homocysteine (tHcy) concentrations in plasma were measured by immunoassay.
  
  
  RESULTS
  Significant hypomethylation of LINE-1 was observed in PBMCs from JSLE patients (60.93% in cases compared with 62.88% in controls, P = 0.001). Significant LINE-1 hypomethylation was observed in active SLE compared to controls (60.66% vs. 62.88%, P = 0.001). According to other clinical parameters, a significant correlation was found between LINE-1 methylation levels and the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2000) of the cases (r = -0.285, P = 0.032). The risk of JSLE increased with decreasing levels of LINE-1 methylation, with an odds ratio of 14.5 (95% CI: 2.8-75.6, P = 0.002). Cases had significantly higher plasma concentrations of tHcy than controls (15.11 vs. 11.02 μmol/L, P = 0.028); the correlation between LINE-1 methylation levels and tHcy was significant (r = -0.4, P = 0.013). Correlations between methylation levels of LINE-1 and complement component 3 were significant (r = 0.317, P = 0.044; r = 0.387, P = 0.031, in total JSLE and active JSLE, respectively).
  
  
  CONCLUSIONS
  Hypomethylation of LINE-1 is associated with risk of JSLE, and LINE-1 methylation levels were related to disease activity and clinical manifestations. The correlation between tHcy levels and LINE-1 methylation was significant.
authors: Central Laboratory for Clinical Research, Capital Institute of Pediatrics, Beijing, China.
authors: Xiaolan
authors: X
authors: Huang
authors: Gaixiu
authors: G
authors: Su
authors: Zhen
authors: Z
authors: Wang
authors: Shaofang
authors: S
authors: Shangguan
authors: Xiaodai
authors: X
authors: Cui
authors: Jia
authors: J
authors: Zhu
authors: Min
authors: M
authors: Kang
authors: Shengnan
authors: S
authors: Li
authors: Ting
authors: T
authors: Zhang
authors: Fengqi
authors: F
authors: Wu
authors: Li
authors: L
authors: Wang
mesh_terms: D000293:Adolescent; D000367:Age Factors; D044466:Asian People; D016022:Case-Control Studies; D002648:Child; D002681:China; D019175:DNA Methylation; D005260:Female; D006710:Homocysteine / Q000097:blood; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000378:metabolism* / Q000473:pathology; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics*; D008180:Lupus Erythematosus, Systemic / Q000208:ethnology / Q000378:metabolism* / Q000473:pathology; D008297:Male; D012720:Severity of Illness Index; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D006710:Homocysteine
keywords: juvenile; long interspersed nucleotide element-1; methylation; systemic lupus erythematosus