Objective Systemic lupus erythematosus (SLE) features high frequency of cardiovascular disease (CVD) and fluctuating complement levels. The clinical trial Atherosclerosis Prevention in Pediatric Lupus Erythematosus (APPLE) aimed to evaluate whether atorvastatin treatment reduced the progression of atherosclerosis in 221 patients with childhood-onset SLE (cSLE), using carotid intima media thickness (CIMT) as surrogates. We leveraged APPLE biorepository and trial data to investigate the relationship between complement and CVD in cSLE.
Methods Gene copy numbers (GCNs) for total C4, C4A and C4B were measured by TaqMan-based real-time PCR and Southern blotting, and analysed with laboratory and clinical parameters through Student’s t-test and χ2 analyses. Effects of total C4, C4A and C4B GCNs on the response to placebo or atorvastatin treatment and progression of CIMT were examined by regression analyses.
Results At baseline, C4 protein levels strongly correlated with GCNs of total C4 (p=1.8×10−6). Each copy of C4 gene increased mean serum C4 by 3.28 mg/dL. Compared with those without hypertension (N=142), individuals with hypertension demonstrated significantly elevated serum levels for C4 and C3 at baseline and serially (C4: P=5.0×10−25; C3: P=5.84×10−20). Individuals with ≥2 C4B genes had 2.5 times the odds of having hypertension (p=0.016) and higher diastolic blood pressure (p=0.015) compared with those with C4B deficiency. At the study end, subjects with ≥2 C4B and atorvastatin treatment had significantly slower increase in CIMT compared with those treated with placebo (p=0.018).
Conclusions cSLE with hypertension had elevated serum levels of C4 and C3 and higher GCN of C4B; cSLE with ≥2 C4B genes would benefit from statins therapy to prevent atherosclerosis.
- gene copy number variation
- complement C4 and C3
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Contributors SA, LES, EM and CYY conceived project. ST, SA, NS, DL, HB and LES examined and approved study protocol, provided APPLE repository genomic DNA and plasma samples, repository data and inputs on rheumatic disease studies. CYY, BZ, GRY, EHK and YLW designed and performed molecular genetics and immunology experiments. EM, SA, HNN and CYY conducted clinical, genetic and immunologic data analyses. EM, SA, HNN and CYY drafted the first version of the manuscript. All authors read and approved the final draft of the manuscript.
Funding This work was supported in parts by NIH/NIAMS grants 1R01 AR073311 and 1R21 AR070509 (CYY), and a Childhood Arthritis and Rheumatology Research Alliance (CARRA)-Arthritis Foundation Fellows Small Grant (EM). The APPLE clinical trial was supported by the NIH (National Institute of Arthritis and Musculoskeletal and Skin Diseases contract N01-AR-2-2265), the Edna and Fred L Mandel Jr Center for Hypertension and Atherosclerosis, and Pfizer, which provided atorvastatin and matching placebo. Dr Singer’s work was supported by the NIH (Clinical and Translational Science Award program grant UL1-RR-024989).
Competing interests The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Patient consent for publication Not required.
Ethics approval information This study was approved by Institutional Review Board at the Nationwide Children’s Hospital, the Data and Specimen Repository Review Committees of the APPLE clinical trial, and the CARRA Publication Committee in the USA.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Aggregate research data is presented in this manuscript. APPLE clinical trial data can be requested from the APPLE Data Committee.
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