Urinary Alpha- and Pi-Glutathione S-Transferases in Adult Patients with Type 1 Diabetes

BACKGROUND/AIMS Glutathione S-transferases (GSTs) are cytosolic enzymes excreted from renal tubules following tubular damage. α-GST primarily originates from proximal tubules, while π-GST from distal tubules and collecting ducts. We investigated if GST levels are associated with renal function in patients with type 1 diabetes. METHODS We conducted a cross-sectional study including 189 Caucasian patients with type 1 diabetes and 16 nondiabetic controls. α- and π-GST were measured by ELISA and reported as GST/urinary creatinine excretion (μg/mmol). RESULTS The subjects were 53 ± 14 years old, 66 (35%) were female and the estimated glomerular filtration rate was 85 ± 29 ml/min/1.73 m(2). Normo- (<30 mg/24 h), micro- (30-299 mg/24 h) and macroalbuminuria (≥300 mg/24 h) was present in 57, 61 and 71 patients, respectively. α- and π-GST/creatinine ratios in controls versus all patients were 0.07 (0-0.3) and 0.11 (0-0.8) μg/mmol versus 0.05 (0-2.3) and 0.16 (0-4.9) μg/mmol (p ≥ 0.16; adjusted for age and gender, p ≥ 0.18). The α-GST/creatinine ratio positively correlated with female gender (p = 0.04), while the π-GST/creatinine ratio was associated with age and female gender (p ≤ 0.016). Comparing normo-, micro- and macroalbuminuric patients, α- and π-GST levels were similar (p = 0.10; adjusted p = 0.11). Neither α- nor π-GST levels were significantly associated with renal function (p ≥ 0.34). CONCLUSION α- and π-GST/creatinine ratios were similar among controls and patients with type 1 diabetes. In addition, we did not find associations with albuminuria degree or level of renal function. The significance of increased or decreased excretion of α- and π-GST among patients with diabetes needs to be clarified.