Abstract
A prospective study was conducted in client-owned geriatric cats to evaluate the short- term effects of a test food on serum symmetric dimethylarginine (SDMA) and creatinine (Cr) concentrations. Test food contained functional lipids (fish oil), antioxidants (vitamins C and E), L-carnitine, botanicals (vegetables), highly bioavailable protein, and amino acid supplements. Cats (n = 80) were fed either test food or owner’s-choice foods (non-nutritionally controlled cohort). Cats were included based on age (≥ 9 years), indoor only, neutered, and free of chronic disease. At baseline, all cats had serum Cr concentrations within the reference interval. Renal function biomarkers and urinalysis results at baseline and after consuming test food or owner’s-choice foods for 3 and 6 months were evaluated. Cats consuming test food showed significant decreases in serum Cr and BUN concentrations across time. Overall, cats consuming owner’s-choice foods showed significant increases in serum SDMA concentrations at 3 and 6 months compared with baseline (P ≤ 0.05), whereas in cats consuming test food serum SDMA concentrations did not change. At baseline or during the 6-month feeding trial, 23 (28.8%) cats had increased serum SDMA, but normal serum Cr consistent with IRIS Stage 1 chronic kidney disease. This included 6 cats fed test food and 17 cats fed owner’s-choice foods. In the 6 cats fed test food, serum SDMA decreased in 3 cats and remained stable in 1 cat, whereas in the 17 cats fed owner’s-choice foods, serum SDMA increased in 13 cats and decreased or remained stable in 4 cats. The increase in serum SDMA concentration was significant (P = 0.02) only for cats fed owner’s-choice foods. These results suggest that nonazotemic cats with elevated serum SDMA (early renal insufficiency) when fed a food designed to promote healthy aging are more likely to demonstrate stable renal function compared with cats fed owner’s-choice foods. Cats fed owner’s-choice foods were more likely to demonstrate progressive renal insufficiency.
Highlights
Recognition of chronic kidney disease (CKD) is important for knowing when to initiate renoprotective interventions that may slow its progression, e.g., dietary modifications [1, 2]
We have previously shown in cats that serum symmetric dimethylarginine (SDMA) concentrations are inversely related to glomerular filtration rate (GFR) [3, 7], that serum SDMA concentrations can be used to detect renal dysfunction earlier in cats with chronic renal disease compared with serum Cr concentrations [3], and that serum SDMA concentrations are not affected by lean body mass [7]
The upper reference interval for serum SDMA (< 14 μg/ dL) corresponds to a reduction in GFR of approximately 24% from mean GFR, whereas the upper reference interval for serum Cr corresponds to a reduction of approximately 60% from mean GFR in cats [3]
Summary
Recognition of chronic kidney disease (CKD) is important for knowing when to initiate renoprotective interventions that may slow its progression, e.g., dietary modifications [1, 2]. Serum SDMA is useful as a renal biomarker for identifying early compromise in renal function compared with serum Cr. Symmetric dimethylarginine is produced when nitrogen molecules on arginine containing polypeptides are postranslationally modified to contain methyl groups. Symmetric dimethylarginine is produced when nitrogen molecules on arginine containing polypeptides are postranslationally modified to contain methyl groups When proteins containing these methylated amino acids are degraded, free methylarginines are released into the cytosol and enter the plasma. Because serum SDMA is filtered by the kidneys, plasma concentrations are correlated with changes in glomerular filtration rate (GFR). We have shown that serum SDMA correlates with GFR in cats [3, 7] as well as in dogs [8]. Serum SDMA concentrations are not affected by lean body mass in cats [7] or in dogs [9]
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