Twenty‐Four–Hour Urine α1‐Microglobulin as a Marker of Hypertension‐Induced Renal Impairment and Its Response on Different Blood Pressure–Lowering Drugs

The purpose of this study was to assess the role of urine α1-microglobulin as a marker of hypertension-induced renal damage compared with estimated glomerular filtration rate, (eGFR), urine albumin, and urine albumin-to-creatinine ratio (ACR). Its response on different blood pressure (BP)–lowering drugs was also studied. Sixty never-treated hypertensive patients (65.0% men, 46.9 years, BP 141.4/94.0 mm Hg) were randomized to an irbesartan (an angiotensin receptor blocker [ARB]) or a diltiazem (a nondihydropyridine calcium channel blocker [CCB])-based regimen. Patients with diabetes or established cardiovascular, renal, or liver disease were excluded. Blood samples and 24-hour urine were analyzed at baseline and 6 months after pharmaceutical BP normalization. Serum creatinine was measured and eGFR was calculated. Urine albumin, creatinine, and α1-microglobulin were measured and ACR was calculated. Minor changes (P=not significant [NS]) in eGFR were noted during follow-up in both groups (from 111.0 mL/min/1.73 m2 to 108.4 mL/min/1.73 m2 in the ARB group and from 111.3 mL/min/1.73 m2 to 114.0 mL/min/1.73 m2 in the CCB group). Twenty-four–hour urine indices were all significantly improved (P<.01) in the ARB group (albumin from 19.4 mg/L to 8.2 mg/L, ACR from 21.5 mg/g to 10.0 mg/g, α1-microglobulin from 5.06 mg/L to 3.64 mg/L) but not (P=NS) in the CCB group (albumin from 15.6 mg/L to 13.9 mg/L, ACR from 17.6 mg/g to 17.1 mg/g, α1-microglobulin from 4.94 mg/L to 4.79 mg/L). These differences between groups remained significant (P<.05) after adjusting for office heart rate and BP. α1-Microglobulin was significantly correlated (P<.05) with albumin and ACR both at baseline (r=0.283 and 0.299, respectively) and at the end of follow-up (r=0.432 and 0.465, respectively) but not (P=NS) with eGFR. It was also significantly related (P<.05) to cardiovascular risk scores (Framingham and HeartScore) both at baseline (r=0.264 and 0.436, respectively) and at the end of follow-up (r=0.308 and 0.472, respectively). Urine α1-microglobulin emerges as a potentially usable marker of hypertension-induced renal impairment. Its excretion rate and its response to treatment appears similar to that of albumin. Irbesartan but not diltiazem seems to be associated with reduced excretion of α1-microglobulin in urine.