Urinary proteins, N‐acetyl‐β‐D‐glucosaminidase activity and estimated glomerular filtration rate in hypertensive patients with normoalbuminuria and microalbuminuria

BACKGROUND: The aim of the study was to assess novel candidate markers measured in the urine of normoalbuminuric and microalbuminuric patients (the urinary albumin-to-creatinine ratio < 30 mg/mmol) with essential hypertension to be used for early detection and assessment of progressive deterioration in renal function. METHODS: Albumin, α-1-antitrypsin, orosomucoid, transferrin, retinol-binding protein and α-1-microglobulin concentrations and the NAG (N-acetyl-β-D-glucosaminidase) activity in the urine were evaluated in 102 hypertensive subjects with urinary albumin-to-creatinine ratio (uACR) < 30 mg/mmol. The estimated glomerular filtration rate (e-GFR) was calculated using the Modification of Diet in Renal Disease Study equation. RESULTS: The decreasing e-GFR values in normo- and microalbuminuric patients with essential hypertension were accompanied by significant increases (P < 0.05) in the NAG activity and uACR value in the urine. The e-GFR significantly (P < 0.05) correlated with the NAG activity in the urine, but no association was observed with the urinary concentrations of any of the individual proteins (P > 0.05). CONCLUSIONS: In normoalbuminuric and microalbuminuric patients with essential hypertension renal impairment measured by e-GFR is related to the increased urinary NAG activity and uACR rather than elevated concentrations of individual proteins. Urinary NAG activity and uACR value seem independently promising candidate markers for use in assessing progression of early renal impairment in patients with hypertension.