The role of determining the levels of serum collagen type IV in diagnosing early diabetic nephropathy.

Two molecules of type IV collagen are linked via the COOH-terminal non-collagenous domain (NCI domain). In this way, type IV collagen forms the main framework of basement membrane. We have developed sandwich Enzyme-Linked Immunosorbent Assay (ELISA) for human serum type IV collage peptide monoclonals for CO5 and CO6 recognizing two different determinants on the central triplex of human collagen molecules. Using this, we explored the possibility that serum levels of type IV collagen (Col IV) are an indicator of early diabetic nephropathy (DN). Serum type IV collagen levels were determined by ELISA in 36 patients with diabetic nephropathy. Serum hemoglobin A1c (HbA1c) and in twenty-four hour urinary albumin excretion rates (UAER) were measured at the same time. A relationship was found between serum levels of this collagen IV and the presence of diabetic nephropathy. That is, serum levels of type IV collagen in diabetic nephropathy were significantly higher than those found in non-insulin-dependent diabetic (NIDDM) patients without nephropathy and in healthy subjects (HS). It is possible that an elevated serum collagen type IV level reflects increased synthetic activity in basement membrane collagen type IV. Serum type IV collagen may be a useful marker for monitoring the dynamics of basement membrane metabolism and in this way serve as a clinical indicator of the progression or the activity of diabetic nephropathy and a marker for the assessment of therapeutic effects.