Metabolic profiles may be used to identify patients with systemic lupus erythematosus, and, more importantly, to distinguish between lupus patients with and without kidney disease.
The study, “NMR based serum metabolomics reveals a distinctive signature in patients with Lupus Nephritis,” published in the journal Scientific Reports, suggests that metabolic signatures could become a valuable clinical tool in the diagnosis and care of patients with lupus nephritis.
Current monitoring of kidney disease (nephritis) in people with lupus requires that physicians analyze tissue from a kidney biopsy. Although the approach offers valuable information in guiding patient treatment, a kidney biopsy is invasive, and ill-suited to the consecutive analyses necessary for monitoring disease progression. Markers that are more easy to assess are wanted.
Researchers at Sanjay Gandhi Postgraduate Institute of Medical Sciences in India took an approach that has been used to study metabolic changes in patients with other inflammatory and autoimmune conditions — nuclear magnetic resonance (NMR) spectroscopy.
The team recruited 22 lupus patients without kidney disease, 40 with kidney disease, and 30 healthy controls. Analyzing serum samples, they noted that lupus patients without kidney disease had lower levels of lipids (fats) and lipoproteins (molecules containing both fat and protein) than healthy people.
This picture, however, changed in patients who had acquired kidney disease, with samples showing increased levels of both fats and lipoproteins compared to controls. Kidney disease patients also had higher levels of creatinine and lower levels of acetate compared to lupus patients without the disease.
Next, the team took a closer look at the specific metabolites found to characterize lupus kidney disease, and assessed whether they were linked to disease activity. Interestingly, the researchers found that the levels of fat metabolites, including the cholesterol types LDL and VLDL, as well as acetate, were associated with SLEDAI scores — a measure of lupus activity.
Among patients with lupus but no kidney disease, metabolite levels had no connection to symptoms, indicating that the finding was specific for kidney disease.
Researchers underscored that all patients in the study were being treated with various immunosuppressive drugs, and these medications may have affected patients’ metabolism. Comparing different drug classes, however, they could not find any signs that the treatment had impacted the results.
“Our results revealed that metabolic markers, especially lipids and acetate derived from NMR spectroscopy, has high sensitivity and specificity to distinguish LN [lupus nephritis] among SLE patients and has the potential to be a useful adjunctive tool in diagnosis and clinical management of LN,” the team concluded.