Fibroblast growth factor 23 and symmetric dimethylarginine concentrations in geriatric cats

Abstract

Background: Fibroblast growth factor 23 (FGF23) is a phosphaturic hormone that is increased in azotemic cats with chronic kidney disease (CKD) and predictive of the onset of azotemia in older cats. The introduction of symmetric dimethylarginine (SDMA) as a biomarker of glomerular filtration rate has led to the identification of cats in which SDMA is increased, but plasma creatinine concentrations remains within reference range. There is currently little understanding of the metabolic changes present in such cats.Objectives: To examine the relationship between plasma FGF23 and SDMA concentrations in non-azotemic geriatric cats.Animals: Records of a cross section of client-owned cats (n = 143) without azotemic CKD.Methods: Clinicopathological information was obtained from cats (≥ 9 years) from records of 2 first opinion practices. The relationship between plasma SDMA and FGF23 concentrations was examined using Spearman's correlation and variables compared using the Mann-Whitney U test.Results: Cats with increased SDMA concentrations had significantly higher plasma FGF23 (P < .001) and creatinine (P < .001) concentrations compared to cats with SDMA concentrations within reference range. A weak positive relationship was demonstrated between plasma FGF23 and SDMA concentrations (r = .35, P < .001) and between plasma FGF23 and creatinine (r = .23, P = .005) concentrations.Conclusions and Clinical Importance: More cats with increased SDMA concentrations had higher FGF23 concentrations than those with SDMA concentrations within the reference range, suggesting the presence of an alteration in phosphate homeostasis. Further studies are warranted to identify influencing factors and to explore the utility of FGF23 concentration to inform management of cats with early stage CKD. K E Y W O R D S azotemia, feline, phosphate, renal Abbreviations: 1,25 vitamin D3, 25-dihydroxyvitamin D; AKI, acute kidney injury; CKD, chronic kidney disease; CKD-MBD, chronic kidney disease mineral and bone disorder

Renal biomarkers in cats: A review of the current status in chronic kidney disease

“… 77 Furthermore, pFGF‐23 was increased in non‐azotemic cats with SDMA concentrations >14 μg/dL despite an absence of hyperphosphatemia. 78 These findings indicate that FGF‐23 might have diagnostic potential for early detection of CKD and early phosphate derangement in cats and that phosphate dysregulation may be ongoing in the early stage of CKD before azotemia and hyperphosphatemia occur. Plasma FGF‐23 concentrations were also significantly higher in cats with azotemic CKD than in healthy cats, and these concentrations significantly increased with the severity of CKD.…”

“…Despite similar phosphate, PTH, and sCr concentrations, baseline pFGF‐23 concentrations were significantly higher in non‐azotemic geriatric cats that developed azotemia within 12 months than in cats with stable renal function 77 . Furthermore, pFGF‐23 was increased in non‐azotemic cats with SDMA concentrations >14 μg/dL despite an absence of hyperphosphatemia 78 . These findings indicate that FGF‐23 might have diagnostic potential for early detection of CKD and early phosphate derangement in cats and that phosphate dysregulation may be ongoing in the early stage of CKD before azotemia and hyperphosphatemia occur.…”

“… 37 In contrast, pFGF‐23 concentration is not correlated with phosphate concentration in cats with normal renal function. 77 , 78 It is still unclear whether this difference is specifically related to serum phosphorus concentration. Many other factors (eg, total calcium, magnesium, PTH, and PCV) also are associated with pFGF‐23 concentrations in CKD cats.…”

“… 79 , 81 In these studies, overlap existed in pFGF‐23 concentrations between the different study groups despite significantly different pFGF‐23 concentrations between groups. 37 , 38 , 77 , 78 , 80 , 81 …”

“…79,81 In these studies, overlap existed in pFGF-23 concentrations between the different study groups despite significantly different pFGF-23 concentrations between groups. 37,38,77,78,80,81 Overall, FGF-23 is an earlier biomarker for phosphate derangement as compared to other routine biomarkers such as PTH and phosphate, and could identify CKD cats benefiting from dietary management in an earlier stage. Additional studies are needed to define the true diagnostic potential of pFGF-23 concentration as marker of early phosphate derangement or marker of CKD progression in the individual cat presented in clinical practice.…”