FOLLOW-UP-STUDY ON URINARY TYPE-IV COLLAGEN IN PATIENTS WITH EARLY-STAGE DIABETIC NEPHROPATHY

Type IV collagen is a major component released from the glomerular and tubular basement membranes. To investigate the alteration of renal ty pe IV collagen turnover in early stage diabetic nephropathy, urinary t ype IV collagen was measured by a highly sensitive one-step sandwich e nzyme immunoassay (EIA). Urinary samples were obtained from 94 diabeti c patients without overt proteinuria. Among those patients, 61 were no rmoalbuminuric and 33 patients were in the microalbuminuric group. Lev els of urinary type IV collagen were serially examined at the start of this study and again one year later. The levels of urinary type IV co llagen in patients in the microalbuminuric group were significantly hi gher than those in the normoalbuminuric group (P < 0.01). There was a significant correlation between the concentration of urinary albumin a nd urinary type IV collagen in both groups (P < 0.05). Twenty-eight pa tients (45.3%) in the normoalbuminuric group who showed an abnormal el evation of urinary type IV collagen in comparison to the reference ran ge of normal healthy adults (normal range; less than 3.5 mu g/g . Cr). Seven (25%) out of these 28 normoalbuminuric patients with increased urinary type IV collagen progressed to the microalbuminuric group one year later. The levels of urinary type IV collagen in such patients we re significantly increased. In the 21 patients who stayed within the n ormoalbuminuric group, the urinary type IV collagen levels were signif icantly decreased one year later. It appears that the levels of urinar y type IV collagen might reflect ongoing alteration of the extracellul ar matrix (ECM) turnover and might define more specifically the early stage diabetic nephropathy than the detection of microalbuminuria. It is concluded that the serial measurement of urinary type IV collagen c an be a useful marker for detecting renal injury in diabetes. J. Clin. Lab. Anal. 12:378-382, 1998. (C) 1998 Wiley-Liss, Inc.