Lupus: The Immunological Impact of Altered DNA Methylation

Methyl donor micronutrients, CD40-ligand methylation and disease activity in systemic lupus erythematosus: A cross-sectional association study

Objective

Hypomethylation of CD40-ligand (CD40L) in T-cells is associated with increased disease activity in systemic lupus erythematosus (SLE). We therefore investigated possible associations of dietary methyl donors and products with CD40L methylation status in SLE.

Methods

Food frequency questionnaires were employed to calculate methyl donor micronutrients in 61 female SLE patients (age 45.7 ± 12.0 years, disease duration 16.2 ± 8.4 years) and compared to methylation levels of previously identified key DNA methylation sites (CpG17 and CpG22) within CD40L promotor of T-cells using quantitative DNA methylation analysis on the EpiTYPER mass spectrometry platform. Disease activity was assessed by SLE Disease Activity Index (SLEDAI). Linear regression modelling was used. P values were adjusted according to Benjamini & Hochberg.

Results

Amongst the micronutrients assessed (g per day), methionine and cysteine were associated with methylation of CpG17 (β = 5.0 (95%CI: 0.6-9.4), p = 0.04; and β = 2.4 (0.6-4.1), p = 0.02, respectively). Methionine, choline, and cysteine were additionally associated with the mean methylation of the entire CD40L (β = 9.5 (1.0-18.0), p = 0.04; β = 1.6 (0.4-3.0), p = 0.04; and β = 4.3 (0.9-7.7), p = 0.02, respectively). Associations of the SLEDAI with hypomethylation were confirmed for CpG17 (β=-32.6 (-60.6 to -4.6), p = 0.04) and CpG22 (β=-38.3 (-61.2 to -15.4), p = 0.004), but not the mean methylation of CD40L. Dietary products with the highest impact on methylation included meat, ice cream, white bread, and cooked potatoes.

Conclusions

Dietary methyl donors may influence DNA methylation levels and thereby disease activity in SLE.

Associations of site-specific CD4+-T-cell hypomethylation within CD40-ligand promotor and enhancer regions with disease activity of women with systemic lupus erythematosus

OBJECTIVE

To comprehensively assess associations of site-specific CD4⁺-T-cell hypomethylation of the CD40-Ligand gene (CD40L) with disease activity of women with systemic lupus erythematosus (SLE).

METHODS

CpG-sites within the DNA of the promotor and two enhancer regions (n = 22) of CD40L were identified and numbered consecutively. The rate of methylated DNA in isolated CD4⁺-T-cells of women with SLE were quantified for each methylation site by MALDI-TOF. Disease activity was assessed by SLE Disease Activity Index (SLEDAI). Associations of site-specific methylation rates with the SLEDAI scores were assessed by linear regression modelling. P values were adjusted according to Bonferroni-Holm as indicated.

RESULTS

60 female SLE patients participated in the study (age 45.7 ± 11.1 years, disease duration 17.0 ± 8.3 years). Significant associations to the SLEDAI were noted for CpG22 hypomethylation of the promotor (β = -40.1, p = 0.017, adjusted p = 0.027), trends were noted for CpG17 hypomethylation of the promotor (β = -30.5, p = 0.032, adjusted p = 0.6), and for CpG11 hypermethylation of the second enhancer (β = 15.0, p = 0.046, adjusted p = 0.8).

CONCLUSION

Site-specific hypomethylation of the CD40L promotor in CD4⁺-T-cells show associations with disease activity in female SLE patients.