Serum SDMA levels linked to inflammation in cats

Abstract

BACKGROUND: Serum symmetric dimethylarginine (SDMA) concentrations are higher in some hyperthyroid cats with normal renal function, presumably due to increased protein catabolism. OBJECTIVES: To investigate if SDMA is higher in cats with inflammation (defined as elevated serum amyloid A [SAA]). ANIMALS: Twenty-eight cats: 12 with elevated SAA concentrations (> 3.9 μg/mL) and 16 with normal SAA. METHODS: Retrospective case control study. Cats presenting to a referral institution between 2016 and 2022 with a documented SAA were identified. Individuals with renal and extrarenal factors known to affect SDMA were excluded. SDMA was measured from stored serum samples. Comparisons were made using the Mann-Whitney U test, and correlations assessed using Spearman's correlation coefficient. Data are presented as median [minimum-maximum]. RESULTS: SDMA was not significantly different between cats with elevated SAA and normal SAA (11 [5-17] μg/dL vs. 13 [9-21] μg/dL, respectively; p = 0.28). There was no correlation between SDMA and SAA (r = -0.105; p = 0.594) or serum TT4 concentrations (r = -0.023; p = 0.906). No difference in age or USG was present between elevated SAA and normal SAA groups (p = 0.908 and p = 0.165, respectively). Serum urea and creatinine concentrations were both significantly lower in cats with elevated SAA compared to those with normal SAA (6.3 [3.6-8.8] mmol/L vs. 8.4 [6.2-10.5] mmol/L; p = 0.008, and 96 [62-129] μmol/L vs. 118 [90-147] μmol/L; p = 0.008, respectively). CONCLUSIONS AND CLINICAL IMPORTANCE: SDMA might be a more representative biomarker of GFR during inflammatory states, provided other confounding factors that affect SDMA are eliminated.