Exploring uric acid as a biomarker in lipedema and lymphedema: A metabolomics study with prospective validation

AIMS: Lipedema is a condition often mistaken for other causes of limb swelling including lymphedema and obesity. Lipedema may have a unique metabolic profile. Interrogation of the metabolome is a strategy that could reveal unique biomarkers to distinguish lipedema from lymphedema and obesity. METHODS: Unbiased metabolomics was utilized to examine 38 BMI-matched overweight patients compared with patients with lipedema, lymphedema, and lipolymphedema. Machine learning identified biomarkers to distinguish diseases, and further examined in a validation cohort of 198 patients with each disorders. Adjustments were made for baseline clinical and demographic variables. RESULTS: Plasma metabolomics firstly revealed uric acid as a biomarker that performs well to distinguish between phenotypically similar diseases in patients with elevated BMI. In a validation cohort of 64 patients with lipedema, uric acid (5.05 mg/dL) was compared with 64 patients with lymphedema (5.4 mg/dl), and 70 overweight patients without these conditions (4.6 mg/dL, p < 0.05). Uric acid-to-cystatin c ratio distinguished between all three groups (Lipedema: 5.2; Lymphedema: 6.3; overweight: 4.0, p < 0.01); however, significance was lost after adjustment for renal function. CONCLUSION: Metabolomic analysis revealed uric acid may differentiate between lipedema, lymphedema, lipolymphedema and obese individuals without those conditions. In a validation cohort, while uric acid was higher in lipedema and lymphedema, uric acid adjusted by cystatin c clearance revealed uric acid to be a less useful marker to distinguish lipedema from lymphedema in the context of renal insufficiency.