Usefulness of a highly sensitive urinary and serum IL-6 assay in patients with diabetic nephropathy

Background/Aim: Interteukin-6 (IL-6) promotes the growth of renal mesangial cells. IL-6 may play a major role in such mesangial proliferation, but the re has been little research on IL-6 in relation to diabetic nephropathy bec ause of the difficulty in measuring urinary and serum IL-6 levels. Using a newly developed, highly sensitive IL-6 assay, we studied the relationship b etween serum and urinary IL-6 and diabetic nephropathy. Methods: We investi gated 72 patients with type 2 diabetes. Urinary and serum IL-6 concentratio ns were measured using a chemiluminescent enzyme immunoassay with a detecti on limit of 0.11 pg/ml. Results: There was a significant increase of the se rum IL-6 level as diabetic nephropathy progressed, with the level being 1.4 +/- 0.3 pg/ml in patients with normal albuminuria, rising to 2.4 +/- 0.6 p g/ml in patients with microalbuminuria and then to 4.4 +/- 0.8 pg/ml in tho se having proteinuria. The serum IL-6 level was also significantly correlat ed with fibrinogen and aortic pulse wave velocity. The urinary IL-6 level w as also significantly increased in diabetic patients as nephropathy progres sed. Both serum and urinary IL-6 levels were high in the group with nephrop athy, but there was no correlation between the two. Conclusion: The urinary IL-6 level seems to be a good indicator of diabetic nephropathy, and ather osclerotic changes were related to the serum IL-6 level. The serum IL-6 may , therefore, be useful in the evaluation of atherosclerosis including nephr opathy.