Exploring the potential of symmetric dimethylarginine (SDMA) as a renal function biomarker in lions (Panthera leo)

Symmetric dimethylarginine (SDMA) is increasingly utilized as a biomarker of renal dysfunction in Felidae, but its clinical utility in lions has not been explored. This prospective study aimed to establish a preliminary method-specific reference interval (RI) for serum SDMA in healthy lions and assess the influence of age and sex; compare SDMA concentrations between lions with chronic kidney disease (CKD) and healthy controls and evaluate its relationship with traditional renal biomarkers; and investigate interspecies variation in SDMA concentrations among healthy Felidae. Thirty-seven lions (Panthera leo) housed in accredited Western European zoological institutions were included over a three-year period, with 32 classified as healthy and five diagnosed with CKD. SDMA was measured using the gold-standard liquid chromatography–tandem mass spectrometry (LC-MS/MS) method. The preliminary RI for healthy lions was 10.2–18.2 µg/dL, highlighting discrepancy with the Species360-derived range. Sex had no significant effect on SDMA concentrations, while juvenile lions had lower values than adults. Lions with CKD had significantly elevated SDMA compared to healthy senior controls. SDMA showed a strong positive correlation with serum creatinine and a good negative correlation with urine specific gravity (USG), but no significant correlation with urea. Cross-species comparisons demonstrated that healthy lions had significantly higher SDMA concentrations than domestic cats (n = 87) and tigers (n = 16), whereas levels were comparable to leopards (n = 5), snow leopards (n = 7), cheetahs (n = 7), and lynxes (n = 8). These results highlight the need for method-, age-, and species-specific RIs, as relying on multi-institutional databases or data from other Felidae may misrepresent renal status. SDMA shows promise for inclusion in clinical assessment panels, offering a potentially valuable tool for evaluating renal function in lions. These findings lay the groundwork for future studies to confirm SDMA's diagnostic accuracy, assess its role in CKD staging, and track early renal dysfunction over time.