The dynamics of urinary N-acetyl-ß-D-glucosaminidase (NAG), a marker of renal tubular dysfunction, in patients with lupus nephritis undergoing oral prednisone therapy.

INTRODUCTION AND AIMS: N-Acetyl-ß-D-glucosaminidase (NAG), a marker of renal tubular dysfunction, is increased in patients with lupus nephritis. In addition to the toxic effects of proteinuria, patients with lupus nephritis may exhibit other factors that contribute to tubular dysfunction, such as pathogenic antitubular basement membrane antibodies. The aim of our study was to assess urinary NAG, proteinuria, and glomerular filtration rate (GFR) before treatment and after 7 and 30 days of oral prednisone therapy in patients with lupus nephritis. METHODS: Ten patients with lupus nephritis, all females, mean age: 29.4 ± 10.17 years, were enrolled into the study. All the patients received oral prednisone 1 mg/kg. Twenty healthy subjects served as controls. We measured urinary NAG before treatment and after 7 and 30 days of oral prednisone therapy. Proteinuria, GFR, blood pressure, and side effects of therapy were also followed up. Urinary NAG was measured using the colorimetrical method and expressed as units per gram of creatinine (U/gCr). Statistical analysis (Wilcoxon signed ranks test and Wilcoxon rank sum test) was performed using SPSS 17. RESULTS: In the 10 patients with lupus nephritis, urinary NAG before treatment was 16.9 ± 13.39 U/gCr (P = 0.005 compared with controls). NAG in controls was 1.73 ± 0.51 U/gCr. Proteinuria before treatment was 3.84 ± 1.93 g/24 h. The GFR before treatment was 50.48 ± 11.98 mL/min/1.73 m². After 7 days of prednisone, urinary NAG was 23.55 ± 25.25 U/gCr (P = 0.878 compared with baseline, and P = 0.02 compared with controls). Proteinuria was 2.94 ± 1.3 g/24 h (P = 0.005 compared with baseline), and the GFR was 58.11 ± 13.64 mL/min/1.73 m² (P = 0.005 compared with baseline). After 30 days of prednisone, urinary NAG was 11.77 ± 12.18 U/gCr (P = 0.203 compared with baseline, P = 0.022 compared with the value after 7 days of prednisone, and P = 0.01 compared with controls). Proteinuria was 1.73 ± 0.68 g/24 h (P = 0.005 compared with baseline, and P = 0.005 compared with the value after 7 days of prednisone), and the GFR was 67.49 ± 16.42 mL/min/1.73 m² (P = 0.005 compared with baseline and P = 0.009 compared with the value after 7 days of prednisone). Blood pressure measurements did not show any significant changes. No major side effects of steroid therapy were noticed. CONCLUSIONS: Urinary NAG showed a significant reduction between 7 and 30 days of therapy. The reduction in urinary NAG set in later than the decline in proteinuria and the improvement in GFR. Further studies incorporating a longer follow-up are needed to observe whether the reduction in NAG persists upon continuation of prednisone therapy.

Pioglitazone delays proximal tubule dysfunction and improves cerebral vessel endothelial dysfunction in normoalbuminuric people with type 2 diabetes mellitus.

AIM: The renal and cerebral protective effects of pioglitazone were assessed in normoalbuminuric patients with type 2 diabetes mellitus (DM). METHODS: A total of 68 normoalbuminuric type 2 DM patients were enrolled in a one-year open-label randomized controlled trial: 34 patients (pioglitazone-metformin) vs. 34 patients (glimepiride-metformin). All patients were assessed concerning urinary albumin: creatinine ratio (UACR), urinary alpha1-microglobulin, urinary beta2-microglobulin, plasma asymmetric dymethyl-arginine (ADMA), GFR, hsC-reactive protein, fibrinogen, HbA1c; pulsatility index, resistance index in the internal carotid artery and middle cerebral artery, intima-media thickness in the common carotid artery; cerebrovascular reactivity was evaluated through the breath-holding test. RESULTS: At 1 year there were differences between groups regarding ADMA, urinary beta2-microglobulin, urinary alpha1-microglobulin, parameters of inflammation, serum creatinine, GFR, UACR, the cerebral haemodynamic indices. Significant correlations were found between alpha 1-microglobulin-UACR (R(2)=0.143; P=0.001) and GFR (R(2)=0.081; P=0.01); beta2-microglobulin-UACR (R(2)=0.241; P=0.0001) and GFR (R(2)=0.064; P=0.036); ADMA-GFR (R(2)=0.338; P=0.0001), parameters of inflammation, HbA1c, duration of DM, cerebral indices. There were no correlations between ADMA-UACR, urinary alpha1-microglobulin and beta2-microglobulin. CONCLUSION: Proximal tubule (PT) dysfunction precedes albuminuria and is dissociated from endothelial dysfunction in patients with type 2 DM. Pioglitazone delays PT dysfunction and improves cerebral vessels endothelial dysfunction in normoalbuminuric patients with type 2 DM.

Nephro- and neuroprotective effects of rosiglitazone versus glimepiride in normoalbuminuric patients with type 2 diabetes mellitus: a randomized controlled trial.

BACKGROUND: Thiazolidinediones represent a novel class of drugs that exert pleiotropic effects at various levels and lower blood glucose through reduction of insulin resistance in patients with type 2 diabetes mellitus. MAIN PURPOSE: The nephro- and neuroprotective effects of rosiglitazone vs. glimepiride were evaluated in normoalbuminuric patients with type 2 diabetes mellitus. The relevance of several biomarkers in the diagnosis of incipient diabetic nephropathy and cerebral microangiopathy was also assessed. METHODS: A total of 34 normoalbuminuric patients with type 2 diabetes mellitus were enrolled in a 1-year open-label randomized controlled trial. Group A comprised 17 patients (7 men, 10 women, mean age 63 +/- 8.07 years) treated with rosiglitazone plus metformin; Group B comprised 17 patients (7 men, 10 women, mean age 63.2 +/- 7.19 years) treated with glimepiride plus metformin. All patients were assessed at initiation, at 6 months and by the end of the study concerning serum and urinary beta2-microglobulin, urinary a1-microglobulin, serum cystatin C, serum creatinine, glomerular filtration rate, C-reactive protein, fibrinogen, glycated hemoglobin, cholesterol, triglycerides, hemoglobin, and the urinary albumin/creatinine ratio (UACR). Cerebral hemodynamic parameters were also measured: pulsatility index and resistance index in the internal carotid artery and middle cerebral artery, and intima-media thickness in the common carotid artery. RESULTS: At 1 year there were differences between groups A and B regarding serum cystatin C (P < 0.04), urinary beta2-microglobulin (P < 0.004), urinary a1-microglobulin (P < 0.0001), C-reactive protein (P < 0.0001), fibrinogen (P < 0.0001), serum creatinine (P < 0.0024), glomerular filtration rate (P < 0.0010), UACR (P < 0.0001), and the cerebral hemodynamic indices. The increase in a1- and beta2-microglobulin preceded the occurrence of microalbuminuria. UACR correlated with urinary a1- microglobulin (r = 0.4854), urinary beta2-microglobulin (r = 0.4867), and serum cystatin C (r = 0.3702). The cerebrovascular parameters improved in group A vs. group B and correlated with urinary beta2- and a1-microglobulin, C-reactive protein, fibrinogen, glomerular filtration rate, and duration of diabetes. CONCLUSION: Rosiglitazone demonstrated its nephro- and neuroprotective effects in normoalbuminuric patients with type 2 diabetes mellitus by the end of the follow-up period and these effects were beyond glycemic control. Urinary beta2- and a1-microglobulin are significant biomarkers for incipient diabetic nephropathy and diabetic cerebral microangiopathy. These biomarkers showed that proximal tubule dysfunction may develop before the stage of microalbuminuria.