Are lupus animal models useful for understanding and developing new therapies for human SLE?

Systemic lupus erythematosus is a systemic autoimmune disease driven by a complex combination of genetic, environmental, and other immunoregulatory factors. The development of targeted therapies is complicated by heterogeneous clinical manifestations, varying organ involvement, and toxicity. Despite advances in understanding the mechanisms contributing to SLE, only one biologic drug, belimumab, is FDA-approved. The identification and development of potential therapies have largely been driven by studies in lupus animal models. Therefore, direct comparison of both the therapeutic and immunological findings in human and murine SLE studies is critical and can reveal important insights into indeed how useful and relevant are murine studies in SLE drug development. Studies involving belimumab, mycophenolate mofetil, abatacept, rituximab, and anti-interferon strategies generally demonstrated analogous findings in the attenuation of SLE manifestations and modulation of select immune cell populations in human and murine SLE. While further basic and translational studies are needed to identify SLE patient subsets likely to respond to particular therapeutic modalities and in dissecting complex mechanisms, we believe that despite some inherent weaknesses SLE mouse models will continue to be integral in developing targeted SLE therapies.

Metabolic disturbances associated with systemic lupus erythematosus.

The metabolic disturbances that underlie systemic lupus erythematosus are currently unknown. A metabolomic study was executed, comparing the sera of 20 SLE patients against that of healthy controls, using LC/MS and GC/MS platforms. Validation of key differences was performed using an independent cohort of 38 SLE patients and orthogonal assays. SLE sera showed evidence of profoundly dampened glycolysis, Krebs cycle, fatty acid ß oxidation and amino acid metabolism, alluding to reduced energy biogenesis from all sources. Whereas long-chain fatty acids, including the n3 and n6 essential fatty acids, were significantly reduced, medium chain fatty acids and serum free fatty acids were elevated. The SLE metabolome exhibited profound lipid peroxidation, reflective of oxidative damage. Deficiencies were noted in the cellular anti-oxidant, glutathione, and all methyl group donors, including cysteine, methionine, and choline, as well as phosphocholines. The best discriminators of SLE included elevated lipid peroxidation products, MDA, gamma-glutamyl peptides, GGT, leukotriene B4 and 5-HETE. Importantly, similar elevations were not observed in another chronic inflammatory autoimmune disease, rheumatoid arthritis. To sum, comprehensive profiling of the SLE metabolome reveals evidence of heightened oxidative stress, inflammation, reduced energy generation, altered lipid profiles and a pro-thrombotic state. Resetting the SLE metabolome, either by targeting selected molecules or by supplementing the diet with essential fatty acids, vitamins and methyl group donors offers novel opportunities for disease modulation in this disabling systemic autoimmune ailment.

Disease-specific definitions of vitamin D deficiency need to be established in autoimmune and non-autoimmune chronic diseases: a retrospective comparison of three chronic diseases.

INTRODUCTION: We compared the odds of vitamin D deficiency in three chronic diseases: systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and type 2 diabetes (T2DM), adjusting for medications, demographics, and laboratory parameters, common to all three diseases. We also designed multivariate models to determine whether different factors are associated with vitamin D deficiency in different racial/ethnic groups. METHODS: We identified all patients with non-overlapping diagnoses of SLE, RA, and T2DM, with 25-hydroxyvitamin D (25OHD) levels measured between 2000 and 2009. Vitamin D deficiency was defined as 25OHD levels <20 ng/ml, based on previously established definitions. Race/ethnicity was analyzed as African-American non-Hispanic (African-American), Hispanic non-African-American (Hispanic), and Other based on self report. RESULTS: We included 3,914 patients in the final analysis: 123 SLE, 100 RA, and 3,691 T2DM. Among African-Americans the frequency of vitamin D deficiency was 59% in SLE, 47% in RA, and 67% in T2DM. Among Hispanics the frequency of vitamin D deficiency was 67% in SLE, 50% in RA, and 59% in T2DM. Compared with the SLE group, the adjusted odds ratio of vitamin D deficiency was 1.1, 95% CI (0.62, 2.1) in the RA group, and 2.0, 95% CI (1.3, 3.1) in the T2DM group. In the multivariate analysis, older age, higher serum calcium and bisphosphonate therapy were associated with a lower odds of vitamin D deficiency in all three racial/ethnic groups: 1,330 African-American, 1,257 Hispanic, and 1,100 Other. T2DM, serum creatinine, and vitamin D supplementation were associated with vitamin D deficiency in some, but not all, racial/ethnic groups. CONCLUSIONS: Vitamin D deficiency is highly prevalent in our patients with SLE, RA, and T2DM. While the odds of vitamin D deficiency are similar in RA and SLE patients in a multivariate analysis, T2DM patients have much higher odds of being vitamin D deficient. Different demographic and laboratory factors may be associated with vitamin D deficiency within different racial/ethnic groups. Therefore, disease-specific and race/ethnicity-specific definitions of vitamin D deficiency need to be established in future studies in order to define goals of vitamin D replacement in patients with autoimmune and non-autoimmune chronic diseases.