Serum and fecal zonulin as a biomarker of increased intestinal epithelial permeability in patients with renal insufficiency

BACKGROUND: Determination of zonulin level in body fluids is one of the widely used clinical methods for diagnosing the leaky gut syndrome. Meanwhile, a decrease in the glomerular filtration rate can potentially affect the content of zonulin in patients with impaired renal function.

AIM: to evaluate the content of serum and fecal zonulin in subjects at different stages of chronic kidney disease.

MATERIALS AND METHODS: The cross-sectional study included 3 groups of patients: 1) 155 patients with end-stage renal disease receiving hemodialysis treatment; 2) 30 patients with chronic kidney disease C3a-5 (glomerular filtration rate <60 ml/min/1.73 m²); 3) 20 relatively healthy individuals with glomerular filtration rate >60 ml/min/1.73 m². The groups were comparable in gender, age, body mass index, smoking status and etiological structure of chronic kidney disease. The concentration of zonulin in blood serum and feces was assessed by using commercially available ELISA kit.

RESULTS: There were no significant differences in serum zonulin between groups. There was a significant direct correlation of serum zonulin with age, creatinine, C-reactive protein and inverse with glomerular filtration rate in patients at predialysis stages of chronic kidney disease. At the same time, in hemodialysis patients serum zonulin did not depend on any of the defined clinical and demographic indicators.It was also found that the concentration of fecal zonulin significantly increased concurrently with an advance of renal insufficiency and reached maximum values in patients with end-stage renal disease. Meanwhile, the correlation analysis did not reveal association between fecal zonulin and kidney function parameters in individuals with mild and moderate chronic kidney disease. Only the hemodialysis group observed a significant direct correlation of fecal zonulin with C-reactive protein.

CONCLUSION: Evaluation of fecal, but not serum zonulin level is preferable to use as a biomarker of increased intestinal epithelial permeability in patients with impaired renal function, since its concentration in the blood is likely to be significantly affected by reduced glomerular filtration rate.