The protein podocin shows promise as a potential biomarker for kidney problems in horses, according to researchers.
Scientists in Poland, writing in the open-access journal PLOS ONE, noted that no sensitive method for diagnosing early kidney dysfunction in horses has been identified so far.
Current diagnosis of kidney disease in horses is based mainly on the presence of elevated serum creatinine. However, this increase is observed when more than 50% of the organ is dysfunctional.
Natalia Siwińska and her colleagues noted that many studies in humans and small animals had shown that the membrane protein podocin can be useful to diagnose various kidney diseases, mainly affecting the glomeruli — the network of small blood vessels responsible for blood filtration.
The study team set out to analyse podocin levels in urine samples from 71 horses, divided into three groups.
The first group comprised 30 healthy horses while the second was made up of 11 horses with confirmed kidney dysfunction.
The third group comprised 30 horses considered at risk for kidney problems, but without signs of kidney disease. They were considered at-risk because they required medications potentially toxic to the kidneys or had serious gastrointestinal problems which can cause changes in blood dynamics that may result in a lack of blood to the kidneys.
The researchers found evidence of podocin in three of the healthy horses and in all of the horses diagnosed with kidney dysfunction.
Half of the animals at risk for acute kidney injury had podocin in their urine. “It is interesting that positive results were obtained in so many horses from this group,” they said.
This may mean that drug toxicity or issues around blood flow to the kidneys arising from gastrointestinal disorders may have led to a detachment of podocytes from the glomerular basement membrane or contributed to glomerular damage.
The researchers, from the Wrocław University of Environmental and Life Sciences and the University of Wrocław, used two methods to detect podocin — an ELISA test and an LC-MS-MRM test. They delivered largely corresponding results, although the latter seemed to be the more sensitive test for detecting podocin.
However, the ELISA test was found to be more effective at excluding kidney disease than confirming it.
The study team concluded that podocin may be a potential biomarker of injury to the glomeruli and clinical kidney disease in horses.
Additionally, it shows promise in the assessment of subclinical cases involving drug-induced kidney injury or hypoperfusion-induced issues, which can arise through changes to the blood dynamics from the likes of colic.
They say more research is needed to assess the clinical use of both test methods.
“Also, the study showed the possibility of more frequent occurrence of glomerular injury in kidney pathologies in horses than it was previously thought and also the potential effect of NSAIDs, aminoglycosides, and hypoperfusion on glomerular damage.”
The study team comprised Siwińska, Urszula Pasławska, Remigiusz Bąchor, Barbara Szczepankiewicz, Agnieszka Żak, Paulina Grocholska and Zbigniew Szewczuk.
Siwińska N, Pasławska U, Bąchor R, Szczepankiewicz B, Żak A, Grocholska P, et al. (2020) Evaluation of podocin in urine in horses using qualitative and quantitative methods. PLoS ONE 15(10): e0240586. https://doi.org/10.1371/journal.pone.0240586