Urinary excretion of advanced glycation endproducts in patients with type 2 diabetes and various stages of proteinuria.

OBJECTIVE: The objective of the study was to detect AGE-immunoreactive proteins in urine, and to evaluate AGE excretion at various stages of diabetic nephropathy in type 2 diabetes assessed by the level of proteinuria. METHODS: AGEs were measured in 24-h urine collection of patients with normoalbuminuria (N) (n=22), microalbuminuria (Mi) (n=31), macroalbuminuria (Ma) (n=28), and overt proteinuria with elevated serum creatinine level (PC) (n=25). A competitive ELISA with polyclonal anti-AGE antibodies was used to monitor AGE excretion. RESULTS: Multiple comparison of urine AGE content among various stages of proteinuria showed significant differences (summary p<0.000). Fifty percent of samples from the group of normoalbuminuric, and only 15% of samples from the group of microalbuminuria patients were AGE negative. However, there was no significant difference in AGE excretion between the patients with persistent proteinuria and elevated serum creatinine, and those with macroalbuminuria (PC vs Ma, p=0.265). None of the samples from these two groups of patients with highest AGE content in 24-h urine was negative for AGE-immunoreactivity. In addition, the ratio between 24-h urinary AGEs and urinary albumin excretion was calculated to determine whether total 24-h urinary AGE content is an index of the toxic form of albumin released in the course of diabetic nephropathy. The ratio values were log-transformed and bivariate comparison showed significant differences between the N vs Mi (p=0.006) and Mi vs Ma (p=0.000) groups. However, there was no significant difference (p=0.407) between values in the Ma and PC groups of patients. Multiple stepwise regression analysis indicated a relationship of urinary AGE-immunoreactivity with creatinine clearance values (r=0.52, p<0.001). CONCLUSION: The study demonstrated the presence of AGE-immunoreactivity in the urine of diabetic patients with various stages of proteinuria. Study results pointed to creatinine clearance as the main predictor of AGE excretion. Therefore, the measurement of urinary AGE appears to offer limited extra information in patients with impaired renal function.

Effect of creatine on erythrocyte rheology in vitro.

To evaluate how creatine influences erythrocyte deformability, we determined its effect on erythrocyte filterability in 9 subjects with insulin dependent diabetes (IDDM) without complications, 14 diabetics with uremia and 10 non-diabetic controls. The short-term incubation (15 min at 37 degrees C) of diabetic erythrocytes with 3 mM creatine improved cell filterability (assessed according to the Reid method) from IDDM subjects without complications by 28.4% and that from diabetics with uremia by 18.9%. No rheological effect of creatine was found in erythrocytes from non-diabetic controls. However, a significant protective effect against erythrocyte filterability impairment induced by treatment of red blood cells from non-diabetic controls with hydrogen peroxide was observed with 3 mM (p < 0.04) and 5 mM (p < 0.01) creatine, respectively. Measurement of the thiobarbituric acid (TBA) reactivity was used to assess hydrogen peroxide induced formation of malondialdehyde (MDA). We found that creatine inhibits hydrogen peroxide-induced erythrocyte MDA-formation in a dose dependent manner by 20.4%, 22.3% and 41.4% for 1, 3 and 5 mM creatine, respectively. These results suggest that creatine by its ability to inhibit erythrocyte lipid peroxidation may contribute to the maintenance of normal cell deformability.

Paraoxonase and arylesterase activities in the serum of two hyperlipoproteinaemic patients after repeated extracorporal lipid precipitation.

The effect of heparin-induced extracorporal lipid precipitation (HELP) on the activities of paraoxonase (EC 3.1.8.1) and arylesterase (EC 3.1.1.2) was studied in serum of a patient with hyperlipoproteinaemia (A) and of a patient with non-insulin dependent diabetes mellitus and hyperlipoproteinaemia (B). The enzyme activities were measured spectrophotometrically (Tris-HCl buffer, pH 7.4, 37 degrees C) with paraoxon and phenylacetate as substrates of paraoxonase and arylesterase, respectively. Both patients underwent HELP applications once a week over a period of 7 weeks. Over that period no overall change was observed either in enzyme activities or in the lipid and protein content of the sera. However, each HELP session caused an immediate decrease of EDTA-insensitive arylesterase activity (on average 56% in A and 42% in B), while EDTA-sensitive arylesterase remained almost unaltered. Paraoxonase remained unchanged in A, but decreased in B (approximately 60%). Of the atherogenic lipoprotein parameters, the most pronounced decrease was found in VLDL-cholesterol and in triglycerides (on average 45% in A and 32% in B), while the anti-atherogenic HDL-cholesterol decreased < 10%. Possible implications of the effect of HELP on the enzyme activities studied remain to be explained.

Changes of autoantibodies against oxidatively modified low density lipoproteins during long-term LDL-apheresis.

The oxidation of low-density lipoproteins (LDL) is considered a key event in the initiation of atherosclerosis. The aim of this study was to follow-up the biological marker of in vivo LDL oxidation (oxidatively modified LDL autoantibody titres) during long-term LDL-apheresis treatment. A patient suffering from severe combined hyperlipidaemia underwent LDL-apheresis biweekly and was followed for two years. The significant reduction of baseline total cholesterol (58%), total triglycerides (80%), LDL-cholesterol (48%), apoprotein B (50%) and apolipoprotein (a) (61%) may be considered as a good response to the treatment. The titre of autoantibodies (IgG) against oxidatively modified LDL (malondialdehyde-derived LDL) was followed throughout the study and showed dynamic changes. The measured values were multiple compared as mean+/-SD over each semester of apheresis application: I semester 70.0+/-8.3 U/ml, n = 12; II semester 58.0+/-13.8 U/ml, n = 12; III semester 37.6+/-6.0 U/ml, n=12; IV semester 34.3+/-7.0 U/ml, n = 12; ANOVA: I vs. II semester p<0.083, II vs. III semester p<0.00053, III vs. IV semester p<0.248. In parallel to the changes in this biochemical parameter, regression of numerous xanthomas was clinically observed. In spite of this, the presence of oxidised-LDL (oxLDL) antibodies was enhanced in comparison to antibody titre detected in a group of age-matched normolipaemic healthy controls (n = 15; 19.4+/-8.6; p<0.01). Classical lipoprotein parameters were correlated with the titre of autoantibodies against oxLDL and showed low correlation coefficients: total cholesterol vs. oxLDLab, r = 0.36; triglycerides vs. oxLDLab, r = 0.43; LDL cholesterol vs. oxLDLab, r = 0.14; HDL cholesterol vs. oxLDLab, r = -0.33; apo B vs. oxLDLab, r = 0.25; apo (a) vs. oxLDLab, r = -0.05. Our study showed an additional benefit of LDL-apheresis therapy. The production of autoantibodies against oxLDL was reduced during the treatment, indicating a lower level of the atherogenic antigen.

Pharmacokinetics and safety of glimepiride at clinically effective doses in diabetic patients with renal impairment.

The pharmacokinetics, efficacy and safety of glimepiride were investigated in a single- and a multiple-dose open study in patients with non-insulin-dependent diabetes mellitus and renal impairment and an initial creatinine clearance above 10 ml/ min. Patients were divided into three groups with creatinine clearance above 50 ml/min, 20-50 ml/min and under 20 ml/min. Fifteen fasting patients received a single dose of 3 mg glimepiride and serial blood and urine samples were taken over 24 h for pharmacokinetic and efficacy analyses. A further 16 patients received glimepiride over a 3-month period, an initial dose of 1 mg glimepiride being adjusted within the range 1 to 8 mg to achieve good glucose control. Pharmacokinetic evaluation was done on day 1 and after 3 months. Mean relative total clearance and mean volume of distribution of both single (41.6 ml/ min and 8.47 litres, respectively, when creatinine clearance was above 50 ml/min) and multiple doses of glimepiride increased in proportion to the degree of renal impairment (to 91.1 ml/min and 14.98 litres, respectively, when creatinine clearance was below 20 ml/min, single dose), whereas the terminal halflife and mean time remained unchanged. Lower relative total clearance and renal clearance of both glimepiride metabolites correlated significantly with lower creatinine clearance values. Of the 16 patients 12 required between 1 and 4 mg glimepiride to stabilize their fasting blood glucose. Glimepiride was well-tolerated and there were no drug-related adverse events. In conclusion glimepiride is safe, effective and has clearly-definable pharmacokinetics in diabetic patients with renal impairment. The increased plasma elimination of glimepiride with decreasing kidney function is explainable on the basis of altered protein binding with an increase in unbound drug.

Renal vascular resistance in diabetic nephropathy: duplex Doppler US evaluation.

PURPOSE: To evaluate duplex Doppler sonography to assess renal vascular resistance (RVR) in diabetic patients. MATERIALS AND METHODS: Resistive indexes (RIs) and pulsatility indexes (PIs) were measured in intrarenal arteries of 144 patients with diabetes mellitus and 61 control subjects. RIs and PIs were compared for control subjects and patients with diabetic nephropathy and correlated with laboratory and clinical findings. RESULTS: In control subjects, the mean RI was 0.595 +/- 0.033 (standard deviation) and mean PI was 1.001 +/- 0.105. Elevated RIs and PIs accompanied progression of nephropathy. Statistically significant (P < .001) correlations were observed between both RI and PI and serum creatinine level, creatinine clearance rate, systolic and diastolic blood pressure measurements, and patient age. CONCLUSION: Doppler indexes reflect increased RVR in diabetic nephropathy and correlate with laboratory and clinical parameters, but RI and PI measurements offer no advantages over these parameters to predict disease progress or in patient care.

Improvement of insulin binding to erythrocyte insulin receptors in uraemia by haemodialysis.

Insulin binding to erythrocytes obtained from uraemic patients was determined using a radioreceptor assay. The binding was reduced by 50 per cent in 20 non-diabetic uraemic patients in comparison with 20 controls (4.7 +/- 1.79 vs 9.37 +/- 1.30 (mean +/- SD) p less than 0.01). During the course of haemodialysis insulin binding steadily increased in a time dependent manner in proportion to the efficiency of haemodialysis as assessed by relative decrease in plasma urea, uric acid or creatinine. Incubation of healthy donors' erythrocytes with uraemic plasma resulted in a dose dependent inhibition of insulin binding with a maximum of 40 per cent. These data indicate the presence of dialysable inhibitors of insulin binding in uraemic plasma.