Friedrich Priem

Effects of Endothelin Receptor Antagonists on the Progression of Diabetic Nephropathy

Background: Diabetic nephropathy is the leading cause of end-stage renal disease in European countries and is associated with an enhanced renal synthesis of endothelin (ET)-1. ETs are – beside its potent vasoconstrictor properties – very potent profibrotic acting paracrine hormones especially in the kidney. Methods: We analyzed in rats with streptozotocin-induced diabetes the effects of an ETA-type (ETA) receptor antagonist (LU 135252) in comparison to a combined ETA/ETB receptor antagonist (LU 224332) on the expression of interstitial and glomerular collagen type I, III and IV as well as on fibronectin and laminin by quantitative immunohistochemistry using a computer-aided image analysis system. Global glomerular matrix deposition was analyzed after PAS staining. In addition to the morphometric examination of the kidneys, we also investigated GFR, urinary albumin and total protein excretion. The diabetic rats were treated for 36 weeks. Results: Treatment with either LU 135252 or LU 224332 normalized the amount of PAS-positive material within the glomeruli. The expression of glomerular fibronectin and type IV collagen was increased 36 weeks after induction of diabetes. The overexpression of these two matrix proteins within the glomeruli of diabetic rats was completely abolished by both ET receptor antagonists, whereas protein excretion was only reduced by about 50% as compared to diabetic rats without treatment. Conclusion: The present study indicates that ETA receptor antagonists as well as combined ETA/ETB receptor antagonists reduce proteinuria and completely normalize the renal matrix protein expression in hyperglycemic rats with streptozotocin-induced diabetes. The antifibrotic effect seems to be mediated via the ETA receptor. ET receptor antagonists might be a new approach in the treatment of diabetic nephropathy.

Diagnostic sensitivity of serum cystatin for impaired glomerular filtration rate

Abstract Recently, the reciprocal of cystatin C (Cys-C), a non-glycosylated 13-kilodalton protein that is produced by all investigated nucleated cells, was found to correlate closely with glomerular filtration rate (GFR). In order to determine the diagnostic validity in children for the detection of impaired GFR, venous blood samples from 381 children (aged 1.7–18 years) with various renal pathology referred for 51Cr-EDTA clearance investigations were obtained for measurement of Cys-C as well as β2-microglobulin (β2-MG) and serum creatinine. Two hundred and sixteen children with clearance values >90 ml/min per 1.73 m2 constituted a control group, with a normal GFR. In the control group, Cys-C values were normally distributed with a mean of 0.94±0.27 mg/l and an upper reference limit (97.5th percentile) of 1.47 mg/l. In all children, there was a positive correlation between 51Cr-EDTA clearance and the reciprocal of Cys-C (r=0.64, P<0.0001), β2-MG (r=0.59, P<0.0001), creatinine (r=0.55, P<0.0001), and the height/creatinine ratio (r=0.73, P<0.0001). Receiver-operating characteristics analysis showed that there were no significant differences between these three parameters for discriminating between patients with normal and reduced GFR, although there was a tendency towards the best diagnostic sensitivity of the GFR estimate according to the Schwartz formula. We conclude that for the detection of mildly impaired GFR, a full clearance study cannot be replaced by measurement of serum Cys-C or β2-MG concentrations.

Matrix metalloproteinases 1 and 3, tissue inhibitor of metalloproteinase-1 and the complex of metalloproteinase-1/tissue inhibitor in plasma of patients with prostate cancer

We analyzed blood plasma concentrations of matrix metalloproteinase‐1 and ‐3 (MMP‐1; MMP‐3), the tissue inhibitor of metalloproteinase‐1 (TIMP‐1) and the complex MMP‐1/TIMP‐1, and looked for any correlation with prostate cancer stage. These components were measured by ELISA tests specific for these proteins in healthy male controls (n = 35), and in patients with benign prostatic hyperplasia (BPH; n = 29), with prostate cancer (PCa) without metastasis (T2,3pN0M0; n = 29) and with PCa with metastatic disease (T2,3,4pN1,2M1; n = 18). Mean values of MMP‐1 and of the complex MMP‐1/TIMP‐1 were not different among the 4 groups studied. The mean MMP‐3 and especially TIMP‐1 concentrations were significantly higher in PCa patients with metastases compared with controls, BPH and PCa patients without metastases. Ten of these 18 patients had TIMP‐1 concentrations higher than the upper reference limit. TIMP‐1 concentrations were correlated with staging but not with grading. Our results point towards plasma TIMP‐1 concentration as a potential marker of malignant progression of PCa. Int. J. Cancer 74:220‐223, 1997.

Renal Elimination of Troponin T and Troponin I

Cardiovascular complications represent the predominant cause of death in patients in the terminal stage of renal failure. Increased concentrations of cardiac troponin T (cTnT) may be a valuable predictor of cardiac risk (1)(2). However, cardiac troponin I (cTnI), clinical symptoms, and electrocardiogram (ECG) indications may be absent in patients with a positive cTnT. This may be attributable to instability of the cTnI molecule (3) or dissimilar glomerular filtration of cTnT and cTnI (4). Positive cTnT values are of cardiac origin because the second generation of cTnT assays will not detect cTnT isoforms expressed in the skeletal muscle of hemodialysis patients (5). We therefore measured the cardiac troponins cTnT and cTnI in the plasma and urine of selected patients differing in their kidney function. We examined 24 patients with increased plasma cTnT. Patients were grouped according to their basic disease and renal function as follows: Group A included five patients (patients 1–5) who had suffered an acute myocardial infarction and three patients (patients 6–8) with cardiac damage as a result of heart surgery, all with normal or only slightly restricted glomerular filtration rate of >80 mL/min. All eight patients were male, with a mean (SD) age of 63 (11) years. Patients had clinically typical chest pain (with the exception of patient 8), and electrocardiography (ECG) showed signs of old myocardial infarction, signs of ST-segment reduction or elevation >0.1 mV with and without chest pain, or signs any arrhythmia of unknown origin. Group B included two patients (patients 9 and 10) who had suffered an acute myocardial infarction and six patients (patients 11–16) with cardiac damage as a result of heart surgery; all had a substantially restricted glomerular filtration rate (only patient 9 had values for creatinine and creatinine clearance that were within the appropriate reference intervals). All patients in …

Decreased oxidative stress in patients with idiopathic dilated cardiomyopathy one year after immunoglobulin adsorption

OBJECTIVES In a substudy to a recently reported investigation that demonstrated the benefit of immunoglobulin adsorption (immunoadsorption) for patients with idiopathic dilated cardiomyopathy (IDC), we tested whether this benefit is associated with a reduction of oxidative stress. BACKGROUND The progression of cardiomyopathy is believed to be related to the increase of oxidative stress. Therefore, reduction of oxidative stress could be one of the effects of immunoadsorption for improvement of cardiac performance and clinical status. METHODS Plasma markers for oxidative stress-thiobarbituric acid-reactive substances (TBARS), lipid peroxides (LPO), anti-oxidized low-density lipoprotein-autoantibodies (anti-oxLDL-AB), thiol groups and vitamin E-were compared in 31 patients, of whom 16 underwent immunoadsorption and 15 received conventional treatment (controls). All patients received a daily supplement of vitamins, minerals and trace elements. RESULTS After one year, TBARS (p = 0.026), LPO (p = 0.026) and anti-oxLD

Low Birth Weight, a Risk Factor for Cardiovascular Diseases in Later Life, Is Already Associated With Elevated Fetal Glycosylated Hemoglobin at Birth

Background— It remains unclear whether the association between low birth weight and insulin resistance in adulthood has its origin in utero or whether it develops later in life depending on predisposition and exogenous factors. Methods and Results— Total glycosylated hemoglobin (TGH) was quantified at delivery in 1295 mother/child pairs serving as a surrogate of maternal and fetal glycemia. Multivariable regression analysis considering gestational age at delivery, the child’s sex, maternal body mass index, and smoking during pregnancy revealed that an increase in TGH by 1% in the child was significantly associated with a mean birth weight reduction of 135 g (P<0.0001), whereas the same increase in the mother was associated with a mean birth weight increase of 88 g (P<0.0001). The ratio of fetal/maternal TGH suggests that lighter newborns have a higher percentage of TGH than would be expected from maternal TGH. Conclusions— The study demonstrates for the first time in a large population that there is an inverse association between TGH of a newborn and its birth weight. This might be due to increased insulin resistance in newborns with lower birth weight. Our data suggest that the pathophysiological mechanisms linking prenatal growth and postnatal sensitivity to insulin are present as early as before birth.

Renal endothelin system in diabetes : Comparison of angiotensin-converting enzyme inhibition and endothelin-A antagonism

An activated renal endothelin (ET) system is implicated in the pathogenesis of renal fibrosis, as recently shown in ET-1 transgenic mice. Because progressive renal fibrosis is also a major finding in diabetic nephropathy, we analyzed the activity of the renal ET system in rats with streptozotocin-induced diabetes mellitus and the effect of blocking the ETA receptor, using the orally active ETA antagonist LU 135252. The effects of long-term treatment with LU 135252 were compared with those of an ACE inhibitor. Plasma and urinary ET-1 concentrations were measured. Progression of diabetic nephropathy was analyzed by measuring urinary albumin and protein excretion. Urinary ET-1 excretion was significantly elevated as early as 7 days after induction of diabetes and increased further. The daily urine volume was significantly correlated with urine ET-1 excretion. Treatment with LU 135252 significantly decreased the ET-1 excretion by more than 50%, whereas ACE inhibition resulted only in a mild decrease. Albumin excretion was significantly decreased after ACE inhibition, whereas ETA inhibition resulted in a nonsignificant decrease. Urinary ET and albumin excretion probably reflect independent mechanisms of renal damage in diabetes.

Chronic cyclooxygenase-2 inhibition does not alter blood pressure and kidney function in renovascular hypertensive rats.

Background It has been shown that the macula densa participates in the regulation of increased renin expression in two-kidney one-clip (2K1C) renovascular hypertension. Prostaglandins might be one of the mediators of macula densa function, because the cyclooxygenase-2 (COX-2), one of the rate-limiting enzymes of the prostaglandin pathway, is upregulated in 2K1C renovascular hypertensive rats. We tested the effect of chronic COX-2 inhibition on blood pressure, urinary aldosterone excretion and kidney morphology, as well as kidney function. Methods Four groups were established: two groups of 2K1C renovascular hypertensive rats treated with the specific COX-2 inhibitor Celecoxib (cele) (15 mg/kg per day) or placebo immediately after operation, and two sham-operated control groups fed with Celecoxib or placebo. Results Long-term COX-2 inhibition in 2K1C renovascular hypertensive rats did not alter blood pressure at any point of time. Urinary aldosterone excretion was elevated by clipping the renal artery (2K1C, 8.1 ± 1.9, versus controls, 3.6 ± 0.5 ng/24 h; P = 0.05) but was not influenced by treatment with Celecoxib. Also, Celecoxib treatment did not alter glomerular filtration rate (GFR), serum sodium, serum creatinine, serum urea or proteinuria in 2K1C renovascular hypertensive rats. Interstitial fibrosis of the left clipped kidney was markedly reduced (2K1C, 6.19 ± 0.83% versus 2K1C + cele 3.00 ± 0.68% of total area; P = 0.012), whereas the interstitial fibrosis of the non-clipped kidney or the glomerulosclerosis of both kidneys were not affected by Celecoxib treatment. Conclusions Celecoxib reduces the interstitial fibrosis of the clipped kidney. Blood pressure, urinary aldosterone excretion or whole kidney function were not affected in renal hypertensive rats.

Fetal and Maternal Peroxisome Proliferator‐activated Receptor γ2 Pro12Ala Does Not Influence Birth Weight

The association between the peroxisome proliferator‐activated receptor (PPAR)γ2 Pro12Ala polymorphism and insulin resistance is reported to depend on low birth weight. Low birth weight itself has been linked to type 2 diabetes and cardiovascular diseases in adulthood. We assessed whether the PPARγ2 Pro12Ala polymorphism determines body size at birth and whether metabolic differences between the genotypes are already detectable in the newborn. This study was conducted at the obstetrics department of the Charité, Berlin, Germany. One thousand nine hundred thirty white woman/child pairs were consecutively included and genotyped. The newborns weight, length, and head circumference were measured. Total glycated hemoglobin in blood served as a surrogate of fetal insulin resistance and glucose use. We found that neither the fetal nor the maternal Pro12Ala genotype determined body size or total glycated hemoglobin at birth. The results suggest that the PPARγ2 Pro12Ala polymorphism is not relevant for intrauterine growth. Previously reported effects of PPARγ2 Pro12Ala on insulin resistance seem to arise later in life.

Evaluation of pediatric nephropathies by a computerized Urine Protein Expert System (UPES)

Abstract A computerized Urine Protein Expert System (UPES) measuring creatinine, total protein, albumin, IgG, α1-microglobulin, α2-macroglobulin, and N-acetyl-β-D-glucosaminidase, together with urine dipstick testing for granulocyte esterase and hemoglobin pseudoperoxidase, and measurement of serum creatinine had been found to be useful in adults for differentiating between renal disorders. The objective of this study was to investigate UPES for identifying the different types of proteinuria and their underlying prerenal, glomerular, tubular, and postrenal causes in 146 children characterized by routine and invasive nephrological investigations. UPES proved to be a useful tool in pediatric renal patients after refinements were implemented in the program. Comparing UPES with the pediatric nephrologist’s interpretation of all available clinical and laboratory data, UPES diagnosed glomerulopathies in 46 (75%) of 61 patients. In a further 23% it suggested glomerular involvement by indicating either a disturbed glomerular permeability or increased excretion of albumin. Tubular proteinuria was correctly described by UPES in 23 (100%) patients with different tubulopathies. UPES revealed normal kidney function in all healthy children and all children with remission of renal disorders. Therefore, UPES can be regarded as a useful tool in the automated differentiation of renal diseases in children.