A Retrospective Analysis of Longitudinal Changes in Bone Mineral Density in Women with Systemic Lupus Erythematosus

The Relationship Between Systemic Lupus Erythematosus and Osteoporosis Based on Different Ethnic Groups: a Two-Sample Mendelian Randomization Analysis

The previous observational studies could not overcome the effects of confounding variables and reverse causality. We aimed to determine whether there is a causal relationship between systemic lupus erythematosus and osteoporosis in East Asian and European populations, respectively, by two-sample Mendelian Randomization analysis. We obtained and downloaded data from publicly available genome-wide association study databases and analyses for East Asian and European populations, including systemic lupus erythematosus (SLE), osteoporosis (OP), multisite bone mineral density (BMD), and OP with fracture. After screening for instrumental single-nucleotide polymorphisms (SNPs) significantly correlated to SLE, the inverse-variance weighted (IVW) method was used for calculating the ratio and 95% confidence interval, besides utilizing MR-Egger, weighted median, and weighted mode to assess the robustness of the primary outcome. Moreover, multiple analyses, including MR-PRESSO, MR-Egger intercept, Cochran's Q test, as well as "leave-one-out" sensitivity, were used for evaluating horizontal pleiotropy, heterogeneity, and stability. Finally, we exchanged exposure and outcome and performed a reverse MR analysis. IVW (OR = 1.05, 95% CI = 1.01-1.09, P = 0.009) indicated a significant positive correlation between genetically predicted SLE and OP in East Asians. Furthermore, neither heterogeneity nor horizontal pleiotropy was observed. In Europe, there was no significant genetically predicted causal relation between SLE and OP. Bi-directional MR analysis showed no reverse causality between SLE and OP. In the East Asian population, genetically predicted SLE may have had a positive causal relationship with OP. In Europe, there is insufficient evidence for a potential causal relation between SLE and OP or BMD and fracture, and the correlations currently observed may be attributed to a variety of confounder variables.

Low disease activity state associated with fewer incident vertebral fractures in Mestizo women with systemic lupus erythematosus

BACKGROUND

Low disease activity state (LDAS) has been linked to a significant reduction in flares and damage accrual in patients with systemic lupus erythematosus (SLE); however, the effect of LDAS on the risk of vertebral fractures (VFs) in subjects with SLE is unknown, considering that low bone mineral density (BMD) and VF are frequent in SLE.

OBJECTIVE

to evaluate whether achieving LDAS ≥50% of the observation time prevents new VF and BMD changes in Mestizo women.

METHODS

We carried out a longitudinal, observational, and retrospective study. Mestizo women with SLE were included for a median of an 8-year follow-up. LDAS was described as Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score ≤4, prednisone ≤7.5 mg/day, and stable immunosuppressive therapies. BMD measurements and lateral thoracic and lumbar radiographs for a semiquantitative analysis for VF were assessed at baseline and during the follow-up. Uni- and multivariable interval-censored survival regression models were carried out.

RESULTS

We included 110 patients: 35 (31.8%) had new VF. A total of 56 patients (50.1%) achieved LDAS ≥50% of the time during the follow-up and achieved a significantly lesser risk of incident VF (HR = 0.16; 95% CI, 0.06-0.49). After adjusting by age, BMI, menopause, prevalent VF, baseline BMD, cumulative glucocorticoid use, and anti-osteoporotic therapy, LDAS-50 was significantly related to a decrease in the risk of a new VF (HR = 0.39; 95% CI, 0.16-0.98). There was no association between LDAS and BMD measurement changes. When only patients on LDAS but not in remission (n = 43) were evaluated for the risk of incident VF, both uni- and multivariate analyses were significant (HR = 0.12; 95 CI, 0.04-47; p = 0.001, and HR = 0.26; 95% CI, 0.7-0.88; p = 0.03).

CONCLUSIONS

LDAS ≥50% of the time was significantly associated with a diminished risk of new VF in Mestizo women with SLE, even in patients not in remission. However, LDAS did not help modify BMD changes over time.

Mycophenolic Acid Exposure Optimization Based on Vitamin D Status in Children with Systemic Lupus Erythematosus: A Single-Center Retrospective Study

Introduction

Systemic lupus erythematosus (SLE) can affect bone metabolism and homeostasis of serum electrolytes that are associated with abnormal levels of vitamin D. Mycophenolate mofetil (MMF) is a commonly used immunosuppressant with the active metabolite mycophenolic acid (MPA). The area under the plasma concentration–time curve (AUC) of MPA is often monitored during the treatment to assess the exposure levels. This study aims to explore the association between exposure levels of MPA and 25-hydroxyvitamin D [25(OH)D] levels in children with SLE.

Methods

Repeated measured data of children with SLE who were treated with MMF and under therapeutic drug monitoring (TDM) were retrospectively collected from the electronic medical records. MPA exposure levels were reflected by the area under the concentration–time curve over 24 h (AUC_0–24h). Univariate and multivariate linear regression models were employed to analyze factors associated with 25(OH)D levels. Hierarchical linear models were developed to analyze the intra- and inter-individual effects of AUC_0–24h on the variance of 25(OH)D levels.

Results

Data from 184 children with SLE (142 female and 42 male) with 518 follow-ups were collected. The median age was 14 years (range 3–18 years) at TDM. Children with normal 25(OH)D levels had significantly higher AUC_0–24h than children with low 25(OH)D levels (98.71 vs. 84.05 mg·h/L, P = 0.004). Intra- and inter-individual effects of AUC_0–24h on 25(OH)D levels were similar (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\gamma }_{10}$$\end{document}γ10 = 0.034 vs. \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\gamma }_{01}$$\end{document}γ01 = 0.037) but only the intra-individual effect was significant (P = 0.001) in hierarchical models. Other associated factors include age, sex, season at measurement, glucocorticoid daily dose, and external vitamin D₃ supplements.

Conclusion

25(OH)D levels are associated with MPA exposure levels, and may serve as a potential indicator to optimize the exposure level of MPA during treatment. AUC_0–24h of 98.71 mg·h/L or AUC_0–12h of 49.36 mg·h/L could be the targeted exposure level for children with SLE.