BACKGROUND: The regulation of mesangial extracellular matrix (ECM) turnover engages a number of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). High glucose concentration affects ECM degradation and the activities of MMPs and TIMPs. ECM accumulation is involved in the pathogenesis of diabetic nephropathy. METHODS: Serum MMP-9, MMP-2, TIMP-2 and TIMP-1 were measured with ELISA in patients with either chronic renal failure (CRF, n=20), type 2 diabetes mellitus (DM2, n=16) or diabetic nephropathy (DM2+CRF, n=14), and healthy controls (n=20). RESULTS: Diabetic nephropathy was related with profound decrease of serum TIMP-2 (122.2 +/- 47.2 vs. 263.0 +/- 89.2 ng/mL), TIMP-1 (242.5 +/- 96.9 vs. 347.4 +/- 87.2 ng/mL) and MMP-2 (385.4 +/- 42.6 vs. 517.2 +/- 75.4 ng/mL) (p<0.001). Both TIMP-1 and TIMP-2 were reduced in diabetic nephropathy in comparison with either diabetes alone (p<0.01 and p<0.001; respectively) or CRF alone (p<0.001 for both). An approximately 2-fold increase of MMP-9/TIMP-1 and MMP-2/TIMP-2 ratio was found in diabetic nephropathy when compared with diabetes with normal renal function (p<0.01). Further, in DM2 patients, TIMP-2 was decreased when compared with CRF alone (219.2 +/- 71.8 vs. 296.8 +/- 58.4 ng/mL). MMP-2 was lowered in both groups of DM2 and CRF patients (413.8 +/- 59.0 ng/mL and 409.7 +/- 93.1 ng/mL, vs. normal control value of 517.2 +/- 75.4 ng/mL; p<0.001). CONCLUSIONS: These data indicate that circulating TIMP-1, TIMP-2 and MMP-2 are decreased in patients with diabetic nephropathy when compared with either CRF or diabetes.