Renoprotective effect of the angiotensin-receptor antagonist irbesartan in patients with nephropathy due to type 2 diabetes

BACKGROUND

It is unknown whether either the angiotensin-II-receptor blocker irbesartan or the calcium-channel blocker amlodipine slows the progression of nephropathy in patients with type 2 diabetes independently of its capacity to lower the systemic blood pressure.

METHODS

We randomly assigned 1715 hypertensive patients with nephropathy due to type 2 diabetes to treatment with irbesartan (300 mg daily), amlodipine (10 mg daily), or placebo. The target blood pressure was 135/85 mm Hg or less in all groups. We compared the groups with regard to the time to the primary composite end point of a doubling of the base-line serum creatinine concentration, the development of end-stage renal disease, or death from any cause. We also compared them with regard to the time to a secondary, cardiovascular composite end point.

RESULTS

The mean duration of follow-up was 2.6 years. Treatment with irbesartan was associated with a risk of the primary composite end point that was 20 percent lower than that in the placebo group (P=0.02) and 23 percent lower than that in the amlodipine group (P=0.006). The risk of a doubling of the serum creatinine concentration was 33 percent lower in the irbesartan group than in the placebo group (P=0.003) and 37 percent lower in the irbesartan group than in the amlodipine group (P<0.001). Treatment with irbesartan was associated with a relative risk of end-stage renal disease that was 23 percent lower than that in both other groups (P=0.07 for both comparisons). These differences were not explained by differences in the blood pressures that were achieved. The serum creatinine concentration increased 24 percent more slowly in the irbesartan group than in the placebo group (P=0.008) and 21 percent more slowly than in the amlodipine group (P=0.02). There were no significant differences in the rates of death from any cause or in the cardiovascular composite end point.

CONCLUSIONS

The angiotensin-II-receptor blocker irbesartan is effective in protecting against the progression of nephropathy due to type 2 diabetes. This protection is independent of the reduction in blood pressure it causes.

Effect of the angiotensin-converting-enzyme inhibitor benazepril on the progression of chronic renal insufficiency. The Angiotensin-Converting-Enzyme Inhibition in Progressive Renal Insufficiency Study Group

BACKGROUND

Drugs that inhibit angiotensin-converting enzyme slow the progression of renal insufficiency in patients with diabetic neuropathy. Whether these drugs have a similar action in patients with other renal diseases is not known. We conducted a study to determine the effect of the angiotensin-converting-enzyme inhibitor benazepril on the progression of renal insufficiency in patients with various underlying renal diseases.

METHODS

In a three-year trial involving 583 patients with renal insufficiency caused by various disorders, 300 patients received benazepril and 283 received placebo. The underlying diseases included glomerulopathies (in 192 patients), interstitial nephritis (in 105), nephrosclerosis (in 97), polycystic kidney disease (in 64), diabetic nephropathy (in 21), and miscellaneous or unknown disorders (in 104). The severity of renal insufficiency was classified according to the base-line creatinine clearance: 227 patients had mild insufficiency (creatinine clearance, 46 TO 60 ml per minute), and 356 had moderate insufficiency (creatinine clearance, 30 to 45 ml per minute). The primary end point was a doubling of the base-line serum creatine concentration or the need for dialysis.

RESULTS

At three years. 31 patients in the benazepril group and 57 in the placebo group had reached the primary end point (P<0.001). In the benazepril group, the reduction in the risk of reaching the end point was 53 percent overall (95 percent confidence interval, 27 to 70 percent), 71 percent (95 percent confidence interval, 21 to 90 percent) among the patients with mild renal insufficiency, and 46 percent (95 percent confidence interval, 12 to 67 percent) among those with moderate renal insufficiency. The reduction in risk was greatest among the male patients; those with glomerular diseases, diabetic nephropathy, or miscellaneous or unknown causes of renal disease; and those with base-line urinary protein excretion above 1 g per 24 hours. Benazepril was not effective in patients with polycystic disease. Diastolic pressure decreased by 3.5 to 5.0 mm Hg in the benazepril group and increased by 0.2 to 1.5 mm Hg in the placebo group.

CONCLUSIONS

Benazepril provides protection against the progression of renal insufficiency in patients with various renal diseases.

The Heidelberg classification of renal cell tumours

This paper presents the conclusions of a workshop entitled 'Impact of Molecular Genetics on the Classification of Renal Cell Tumours', which was held in Heidelberg in October 1996. The focus on 'renal cell tumours' excludes any discussion of Wilms' tumour and its variants, or of tumours metastatic to the kidneys. The proposed classification subdivides renal cell tumours into benign and malignant parenchymal neoplasms and, where possible, limits each subcategory to the most commonly documented genetic abnormalities. Benign tumours are subclassified into metanephric adenoma and adenofibroma, papillary renal cell adenoma, and renal oncocytoma. Malignant tumours are subclassified into common or conventional renal cell carcinoma; papillary renal cell carcinoma; chromophobe renal cell carcinoma; collecting duct carcinoma, with medullary carcinoma of the kidney; and renal cell carcinoma, unclassified. This classification is based on current genetic knowledge, correlates with recognizable histological findings, and is applicable to routine diagnostic practice.

Association of a human G-protein beta3 subunit variant with hypertension

Hypertension is a common disorder of multifactorial origin that constitutes a major risk factor for cardiovascular events such as stroke and myocardial infarction. Previous studies demonstrated an enhanced signal transduction via pertussis toxin-sensitive G proteins in lymphoblasts and fibroblasts from selected patients with essential hypertension. We have detected a novel polymorphism (C825T) in exon 10 of the gene encoding the beta3 subunit of heterotrimeric G proteins (GNB3). The T allele is associated with the occurrence of a splice variant, GNB3-s (encoding G beta3-s), in which the nucleotides 498-620 of exon 9 are deleted. This in-frame deletion causes the loss of 41 amino acids and one WD repeat domain of the G beta subunit. By western-blot analysis, G beta3-s appears to be predominantly expressed in cells from individuals carrying the T allele. Significant enhancement of stimulated GTPgammaS binding to Sf9 insect cells expressing G beta3-s together with G alpha(i)2 and G gamma5 indicates that this splice variant is biologically active. Genotype analysis of 427 normotensive and 426 hypertensive subjects suggests a significant association of the T allele with essential hypertension.

End-stage renal failure in type 2 diabetes: A medical catastrophe of worldwide dimensions

The incidence of patients with end-stage renal failure and diabetes mellitus type 2 as a comorbid condition has increased progressively in the past decades, first in the United States and Japan, but subsequently in all countries with a western lifestyle. Although there are explanations for this increase, the major factor is presumably diminishing mortality from hypertension and cardiovascular causes, so that patients survive long enough to develop nephropathy and end-stage renal failure. This review summarizes the striking differences between countries against the background of a similar tendency of an increasing incidence in all countries. Survival on renal replacement therapy continues to be substantially worse for patients with type 2 diabetes. A major reason for this observation is that patients enter renal replacement programs with cardiovascular morbidity acquired in the preterminal phase of renal failure. It is argued that the challenge for the future will be better patient management in earlier phases of diabetic nephropathy to attenuate or prevent progression, as well as cardiovascular complications.

Morphology of coronary atherosclerotic lesions in patients with end-stage renal failure

BACKGROUND

An excessive rate of cardiac death is a well-known feature of renal failure. Coronary heart disease is frequent and the possibility has been raised that the natural history of the coronary plaque is different in uraemic patients. We assessed the morphology of coronary arteries in patients with end-stage renal failure and compared them with coronary arteries of matched non-uraemic control patients.

METHODS

Fifty-four cases were identified at autopsy who met the inclusion criteria: cases, end-stage renal disease (n=27); controls, non-renal patients with coronary artery disease (n=27). At autopsy all three coronary arteries were prepared at corresponding sites for investigations: (i) qualitative analysis (after Stary), (ii) quantitative measurements of intima and media thickness (by planimetry), (iii) immunohistochemical analysis of the coronary plaques and (iv) X-ray diffraction of selected calcified plaques.

RESULTS

Qualitative analysis of the coronary arteries showed significantly more calcified plaques of coronary arteries in patients with end-stage renal failure. Plaques of non-uraemic patients were mostly fibroatheromatous. Media thickness of coronary arteries was significantly higher in uraemic patients (187+/-53 microm vs 135+/-29 microm in controls) and intima thickness tended to be higher (158+/-38 microm vs 142+/-31 microm) but this difference was not statistically significant. Plaque area (4.09+/-1. 50 mm(2) vs 4.39+/-0.88 mm(2)) was comparable in both groups. Lumen area, however, was significantly lower in end-stage renal patients. Immunohistochemical analysis of the cellular infiltrate in coronary arteries showed no major differences in these advanced plaques of uraemic and non-uraemic subjects.

CONCLUSION

Coronary plaques in patients with end-stage renal failure are characterized by increased media thickness and marked calcification. In contrast to the previous opinion the most marked difference compared to non-uraemic controls does not concern the size, but the composition of the plaque. Deposition of calcium within the plaques may contribute to the high complication rate in uraemic patients.

Association of chronic kidney graft failure with recipient blood pressure. Collaborative Transplant Study

Immunological rejection is the most important cause of kidney transplant failure. Recently, nonimmunological causes of long-term allograft failure have become more widely appreciated. In primary chronic renal disease, blood pressure is of overriding importance for long-term renal function. The role of blood pressure in determining long-term transplant outcome has not yet been established. We studied the influence of blood pressure post-transplantation on long-term kidney graft outcome in 29,751 patients. Outpatient blood pressure measurements were recorded and reported to the Collaborative Transplant Study. Graft and patient survival rates were analyzed over seven years in relation to blood pressure. Increased levels of systolic and diastolic blood pressure post-transplantation were associated with a graded increase of subsequent graft failure (P < 0.0001). Chronic graft failure was significantly associated with blood pressure even when patient death was censored (P < 0.0001). Cox regression analysis established increased blood pressure as an independent risk factor for graft failure. We conclude that post-transplant blood pressure is a highly significant predictor of long-term kidney graft outcome. Whether aggressive lowering of blood pressure improves long-term transplant outcome will have to be studied prospectively.

Identification and regulation of 1,25-dihydroxyvitamin D3 receptor activity and biosynthesis of 1,25-dihydroxyvitamin D3. Studies in cultured bovine aortic endothelial cells and human dermal capillaries

Because 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) has been shown to play roles in both proliferation and differentiation of novel target cells, the potential expression of 1,25(OH)2D3 receptor (VDR) activity was investigated in cultured bovine aortic endothelial cells (BAEC). Receptor binding assays performed on nuclear extracts of BAEC revealed a single class of specific, high-affinity VDR that displayed a 4.5-fold increase in maximal ligand binding (Nmax) in rapidly proliferating BAEC compared with confluent, density-arrested cells. When confluent BAEC were incubated with activators of protein kinase C (PKC), Nmax increased 2.5-fold within 6-24 h and this upregulation was prevented by sphingosine, an inhibitor of PKC, as well as by actinomycin D or cycloheximide. Immunohistochemical visualization using a specific MAb disclosed nuclear localized VDR in venular and capillary endothelial cells of human skin biopsies, documenting the expression of VDR, in vivo, and validating the BAEC model. Finally, additional experiments indicated that BAEC formed the 1,25(OH)2D3 hormonal metabolite from 25(OH)D3 substrate, in vitro, and growth curves of BAEC maintained in the presence of 10(-8) M 1,25(OH)2D3 showed a 36% decrease in saturation density. These data provide evidence for the presence of a vitamin D microendocrine system in endothelial cells, consisting of the VDR and a 1 alpha-hydroxylase enzyme capable of producing 1,25(OH)2D3. That both components of this system are coordinately regulated, and that BAEC respond to the 1,25(OH)2D3 hormone by modulating growth kinetics, suggests the existence of a vitamin D autocrine loop in endothelium that may play a role in the development and/or functions of this pathophysiologically significant cell population.

Insulin resistance and hyperinsulinemia are already present in patients with incipient renal disease

In uremic patients resistance to the action of insulin has been documented, but it is not known at what stage of renal disease it appears. We therefore examined 29 patients with IgA glomerulonephritis (IgAGN) and 21 patients with adult polycystic kidney disease (ADPKD) in different stages of renal failure, and in addition, healthy age-matched subjects. Insulin sensitivity and other variables of glucose metabolism were assessed using a frequent sampling intravenous glucose tolerance test (minimal-model technique). Glomerular filtration rate (GFR) was assessed in renal patients using the inulin-clearance technique. Mean insulin sensitivity index (SI), that is, insulin sensitivity, was significantly lower (P < 0.001) in all patients combined than in matched healthy subjects (N = 16; 14 males, mean age 42 +/- 3 years; mean SI 8.6 +/- 0.8 min-1 uU/ml). The mean SI was not significantly different in patients with renal disease of immune (IgAGN) or non-immune (ADPKD) origin, and it was not correlated with GFR (r = 0.01, P < 0.52), intact PTH (r = -0.23, P < 0.11) or calcitriol concentration (r = -0.03, P < 0.82). Consequently, the mean SI was similar in renal patients with GFR within the normal range (N = 19; 17 males, mean age 41 +/- 2 years; mean GFR 119 +/- 5 ml/min/1.73 m2; 5.1 +/- 0.7 min-1 uU/ml), in patients with mild to moderate renal failure (N = 16; 15 males, 46 +/- 3 years; 67 +/- 4 ml/min/1.73 m2; 5.1 +/- 0.7 min-1 microU/ml) and in patients with advanced renal failure (N = 15; 13 males, 46 +/- 3 years; 25 +/- 2 ml/min/1.73 m2; 4.7 +/- 0.6 min-1 uU/ml). Mean fasted plasma insulin concentration, the area under the curve for plasma insulin concentration (AUC) and total insulin delivery (TID) during the glucose tolerance test were significantly higher in patients than in healthy subjects, reflecting hyperinsulinemia in renal patients. Further, fasted plasma insulin concentration (r = -0.32, P < 0.009), AUC (r = -0.62, P < 0.0001) and TID (r = -0.34, P < 0.004) in patients were significantly correlated with insulin sensitivity (SI). The present data document that insulin resistance and concomitant hyperinsulinemia are present early in the course of renal disease, that is, even in patients with GFR within the normal range, irrespective of the type of renal disease. This observation may have potential implications with respect to the high cardiovascular morbidity and mortality in patients with renal disease.

Bone histology in incipient and advanced renal failure

Quantitative bone histology (micromorphometry of undecalcified sections, analysis under polarized light; fluorescence microscopy with tetracycline double labelling) as well as serum and urinary chemistry (creatinine clearance, parathyroid hormone, ionized Ca, bone phosphatase, pH), were studied in 50 patients with incipient to advanced (glomerular filtration rate, 80 to 6 ml/min x 1.73 m2 renal insufficiency. In incipient renal failure, indirect evidence of parathyroid hormone excess was found in the skeleton (empty osteoclastic lacunae, woven osteoid). Osteoclastic surface resorption was abnormally high when GFR fell below 50ml/min x 1.73 m2. With the tetracycline double-labelling technique, a mineralization defect was demonstrable in many but not all patients.

Serum cystatin C concentration as a marker of renal dysfunction in the elderly

Serum cystatin C is a novel marker of renal function claimed to be superior to plasma creatinine. We assessed both parameters in young normotensive subjects (n = 12; 6 men; mean age, 25 +/- 2 years) and elderly normotensive and hypertensive subjects (n = 41; 19 men; mean age, 67 +/- 6 years). Glomerular filtration rate (GFR) was measured in all individuals using the inulin clearance (C(in)) technique. Compared with young subjects, mean GFR was modestly but significantly (P: < 0.001) less in elderly subjects (young, 119 +/- 11 mL/min/1.73 m(2) versus elderly, 104 +/- 12 mL/min/1.73 m(2)). Mean plasma creatinine concentration was identical in both groups (young, 0.93 +/- 0.11 mg/dL versus elderly, 0.93 +/- 0.10 mg/dL; P: < 0.90). Mean serum cystatin C concentration was significantly (P: < 0.001) greater in elderly subjects (0.84 +/- 0.10 mg/L) compared with young subjects (0.69 +/- 0.08 mg/L). In all but one elderly subject, plasma creatinine concentration was within the 95% confidence interval of plasma creatinine concentration in young subjects. Eleven of 41 elderly subjects (27%) had GFRs less than the lower 95% confidence interval, respectively, and 12 of 41 elderly subjects (29%) had a serum cystatin C concentration greater than the upper 95% confidence interval in young subjects. The correlation between serum cystatin C concentration and C(in) (r = -0.65; P: < 0.001) was considerably better than between plasma creatinine concentration and C(in) (r = -0.30; P: < 0.02). Serum cystatin C concentration is a better marker of renal dysfunction (ie, reduced GFR) than plasma creatinine concentration, at least in elderly subjects with plasma creatinine concentrations within the normal range.

Myocyte/capillary mismatch in the heart of uremic patients

Experiments indicate that capillary density is reduced in the hypertrophied left ventricle of rats with subtotal nephrectomy compared to control rats with similar BP and left ventricular hypertrophy, suggesting that in uremia, hypertrophying cardiomyocytes outgrow their capillary supply. No information on myocardial capillary supply in humans is currently available. The hearts of nine dialyzed patients, nine patients with essential hypertension, and 10 normotensive control subjects at postmortem were obtained. Subjects with stenosing coronary lesions and left ventricular pump failure were excluded. Special sampling procedures were used to exclude stereologic artefacts. Capillaries were specifically stained with ulex lectin and analyzed by stereologic techniques. Length density of myocardial capillaries (Lv; mm/mm3) was significantly (P < 0.001) lower in dialyzed patients (1483 +/- 238) than in patients with essential hypertension (1872 +/- 243) or in normotensive control patients (2898 +/- 456). In parallel, myocyte diameter and volume density of myocardial interstitial tissue were significantly (P < 0.001) increased in uremic patients compared to patients with essential hypertension and control patients, respectively. Diminished left ventricular capillary supply in renal failure must increase critical oxygen diffusion distance in the myocardium, thus exposing cardiomyocytes to the risk of hypoxia. It is unknown whether such reduced ischemia tolerance can be reversed by increasing oxygen supply (e.g., by reversing anemia).

In situ production of TNF-alpha, IL-1 beta and IL-2R in ANCA-positive glomerulonephritis

Humoral and cellular immune mechanisms are thought to be involved in various forms of vasculitis and glomerulonephritis. Recent clinical and experimental results point to a role of cytokines in ANCA-positive vasculitides. We analyzed tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and interleukin-2 receptors (IL-2R) in renal biopsies and in plasma from 22 patients with Wegener's granulomatosis and microscopic polyangiitis. Kidney biopsies were examined by immunocytochemistry, polymerase chain reaction and in situ hybridization. Immunoreactive TNF-alpha, IL-1 beta and/or IL-2R positive infiltrating cells were observed in 21 of 22 biopsies. TNF-alpha, IL-1 beta and IL-2R staining was evident in the interstitium and at periglomerular and perivascular sites. The number of positive cells was markedly increased in biopsies with active lesions. Positive cells were also present in cellular and fibrocellular crescents, surrounding tuft necrosis and in the walls of arteries and arterioles with acute vasculitic lesion. Some tubular epithelial cells stained for TNF-alpha and IL-1 beta. TNF-alpha, IL-1 beta and IL-2R positive infiltrating cells correlated with the presence of histologically active renal lesions. The evaluation of TNF-alpha and IL-1 beta expression at the mRNA level assessed by the polymerase chain reaction demonstrated specific transcripts for TNF-alpha and IL-1 beta in all six cases analyzed. In situ hybridization studies showed an increased expression of mRNA for TNF-alpha and IL-1 beta in infiltrating mononuclear cells, in epithelial cells of Bowman's capsule and in some tubules, predominantly of patients with active renal lesions. The results at the mRNA level correlated with the immunocytochemical findings. Compared to healthy individuals higher TNF-alpha plasma levels were observed in patients with vasculitis (34.4 +/- 16.6 pg/ml (SEM) vs. 1.9 +/- 0.7 pg/ml in controls; P < 0.01). All patients presented a marked increase in sIL-2R plasma levels (3512 +/- 485 U/ml vs. 397 +/- 21 U/ml in healthy controls; P < 0.001). IL-1 beta was not detected in most plasma samples. Elevated TNF-alpha and sIL-2R plasma levels were related to active renal lesions. Our study clearly demonstrates that in ANCA-positive vasculitis TNF-alpha and IL-1 beta are produced in situ by activated infiltrating mononuclear cells and resident renal cells. Intrarenal localization of cytokine producing cells and the correlation between cytokine production and histological signs of activity suggest that TNF-alpha and IL-1 beta are important locally acting mediators in the vasculitic/glomerulonephritic process.

Effect of 1,25 (OH)2 vitamin D3 on glomerulosclerosis in subtotally nephrectomized rats

In the past, there has been considerable concern that treatment with active vitamin D might accelerate progression independent of hypercalcemia and hypercalcuria. Nevertheless, 1,25(OH)2D3 has known antiproliferative properties and has also been shown to inhibit renal growth. Since glomerular growth is a permissive factor for the development of glomerulosclerosis, we reasoned that 1,25(OH)2D3 might even attenuate progression. To test this working hypothesis we performed two experiments of 8 and 16 weeks duration, respectively, to compare subtotally nephrectomized (SNX) rats treated with ethanol and SNX treated with 1,25(OH)2D3. Control animals were sham operated and pair-fed with SNX animals. 1,25(OH)2D3 (3 ng/100 g body wt/day) was administered by osmotic minipump. 1,25(OH)2D3 had no significant effect on systolic blood pressure and only a transient effect on weight gain. SNX reduced the number of glomeruli (left kidney) from an average of 3.3 x 10(4) to 1.2 x 10(4) per kidney. Mean glomerular volume was 3.87 +/- 0.71 x 10(6) microns 3 in sham operated animals and significantly (P < 0.05) higher (10.1 +/- 1.75 x 10(6) microns 3) in untreated animals 16 weeks after SNX. Glomerular volume was significantly (P < 0.05) less in 1,25(OH)2D3 treated SNX [10.1 +/- 1.75 in ethanol vs. 7.04 +/- 1.78 in 1,25(OH)2D3 treated SNX]. In parallel, there was significantly (P < 0.01) less glomerulosclerosis [glomerulosclerosis index 1.16 +/- 0.14 in the ethanol treated SNX vs. 0.80 +/- 0.16 in SNX treated with 1,25(OH)2D3] in the eight week experiment. Albuminuria was significantly (P < 0.01) lower in 1,25(OH)2D3 treated than in ethanol treated SNX (mean 0.785 mg/24 hr, range 0.43 to 1.80, vs. 3.75 mg/24 hr, 1.29 to 14.2). The morphological data were directionally analogous in a second 16 week experiment. Only slight changes of the vascular sclerosis index and tubulointerstitial index were seen in SNX and were not affected by 1,25(OH)2D3 further. To prove that the effect of 1,25(OH)2D3 was independent of PTH, parathyreoidectomized SNX rats without or with 1,25(OH)2D3 treatment were examined seven days post-SNX. PCNA staining showed suppression of cell proliferation. Furthermore, in situ hybridization for transforming growth factor-B (TGF-beta) showed less vascular and tubular expression in 1,25(OH)2D3 treated rats. We conclude that 1,25(OH)2D3 has antiproliferative actions during the compensatory growth of nephrons in response to subtotal nephrectomy. These effects are independent of PTH. The data document that 1,25(OH)2D3 reduces renal cell proliferation and glomerular growth as well as glomerulosclerosis and albuminuria as indicators of progressive glomerular damage.

1,25(OH)2 vitamin D3 inhibits parathyroid cell proliferation in experimental uremia

Parathyroid cell proliferation and parathyroid hyperplasia are features of renal secondary hyperparathyroidism. Since parathyroids have recently been recognized as an important target for 1,25(OH)2D3, the effects of administration of variable doses of 1,25(OH)2D3 on ex vivo radiothymidine incorporation in the parathyroid glands, on parathyroid cell mitoses, on parathyroid weight, morphometric indices and on parathyroid protein/DNA ratio were examined in rats with uremia (subtotal nephrectomy; NX) or with calcium deficiency. 3H-thymidine incorporation (3 hr; 37 degrees C; PBS with 10 mmol glucose) was elevated in NX animals, that is, 204 +/- 51 dpm/micrograms DNA versus 96 +/- 28 in controls. In vivo pretreatment with 1,25(OH)2D3, either by intermittent i.p. injection or by osmotic minipump, dose-dependently decreased 3H-thymidine incorporation and parathyroid cell mitoses without affecting morphometric indices of parathyroid cells. Prophylactic administration (i.p.) of 1,25(OH)2D3, starting on the day of nephrectomy, prevented parathyroid hyperplasia (NX + 1,25(OH)2D3 0.84 micrograms tissue/g body wt vs. 1.25 micrograms in untreated NX and 0.54 in ad libitum fed controls), but 10 days of treatment beginning on the 21st day of uremia did not reverse existing hyperplasia (NX + 1,25(OH)2D3 1.5 micrograms/g body wt vs. 1.37 micrograms in untreated NX and 0.56 micrograms in ad libitum fed controls). The inhibitory effect was specific for 1,25(OH)2D3 and not imitated by Dexamethason. However, the effect was not specific for parathyroid hyperplasia of uremia, since similar inhibition of 3H-thymidine incorporation by 1,25(OH)2D3 was also observed in rats on low calcium diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal function in the elderly: impact of hypertension and cardiac function

In senescence renal function is thought to decline markedly even in the absence of renal disease. It has also been proposed that the changes in renal function with age are not uniform and that confounding factors such as hypertension or atherosclerosis may play a role. We performed a comprehensive study to compare several aspects of renal function in four groups: (i) young healthy normotensive subjects (N = 24; 13 males; mean age 26 +/- 3 years); (ii) elderly healthy normotensive subjects (elderly NT; N = 29; 13 males; 68 +/- 7 years); (iii) elderly treated and untreated hypertensive patients (elderly HT; N = 25; 13 males; 70 +/- 6 years); and (iv) elderly patients with compensated mild to moderate heart failure (elderly HF; N = 14; 6 males; 69 +/- 6 years). Compared to young subjects mean GFR (C(In)) and ERPF (C(PAH)) were significantly lower in the elderly, despite similar mean plasma creatinine levels (young, 121 +/- 11, 650 +/- 85 ml/min/1.73 m2; elderly NT, 103 +/- 11, 486 +/- 102; elderly HT, 103 +/- 13, 427 +/- 55; elderly HF, 92 +/- 14, 377 +/- 103). Nevertheless, GFR was within the normal range in the majority of elderly NT and HT, but not in elderly HF. ERPF was significantly lower in elderly HT as compared with elderly NT, and still lower in elderly HF. Mean renovascular resistance and filtration fraction were significantly higher in the elderly, particularly in elderly HT and HF as compared with the young. Mean fractional excretion of Na+ was similar in all groups studied, but the lithium clearance was significantly lower in the elderly, suggesting a greater proximal and less distal sodium reabsorption in senescence. In the elderly, mean PTH concentration and urinary excretion of pyridoline cross-links were significantly higher and mean 25-(OH)D3, calcitriol and phosphate concentrations significantly lower; the correlation between PTH and GFR was significant (r = -0.432, P < 0.001). The results document that the decrease in renal hemodynamics with senescence is less marked than suggested by some studies using less stringent methodology and inclusion criteria. Comorbid conditions confound renal function in the elderly. Age-associated changes in renal hemodynamics are accompanied by significant alterations of renal hormones and of renal sodium handling.

Similar risks of nephropathy in patients with type I or type II diabetes mellitus

It is commonly assumed that in patients the risks of developing nephropathy and uraemia are high in type I and low in type II diabetes mellitus. Since type II occurs mostly in elderly individuals with limited life expectancy and high cardiovascular mortality, the true risk may have been underestimated, as many patients do not survive to experience renal complications. To assess renal risk further, we evaluated all patients with type II and type I diabetes mellitus without severe secondary disease who were followed in the outpatient clinic between 1970 and 1985. The cumulative risk of proteinuria after 20 years of diabetes mellitus was 27% in type II and 28% in type I, the findings after 25 years were 57% and 46% respectively. The cumulative risk of renal failure, i.e. serum creatinine greater than 1.4 mg/dl, after 3 years of persisting proteinuria was 41% in both type II and type I, and after 5 years of proteinuria were 63% and 59% respectively. We conclude that the renal risk is similar in patients with type II and type I diabetes mellitus.

Diabetic nephropathy in type II diabetes

The incidence of end-stage renal failure in patients with type II diabetes has dramatically increased in recent years, both in the United States and, with some delay, in some European countries. These epidemiologic observations have thoroughly dispelled the mistaken belief that renal prognosis was benign in type II diabetes. Recent interest has focused on the early stages of nephropathy in type II diabetes. With respect to renal hemodynamics, renal morphology, and progression of established diabetic nephropathy, there are no substantial differences between types I and type II diabetes. There is good evidence that preventive measures are effective, ie, glycemic control, blood pressure control, protein restriction, and discontinuation of smoking. The high prevalence of the disease (which in principle is preventable) calls for intense efforts to (1) educate the medical community, (2) substantially improve patient education and medical care, and (3) intensify research in this field.

Safety of ultrasound-guided percutaneous renal biopsy-retrospective analysis of 1090 consecutive cases

BACKGROUND

Ultrasound-guided renal biopsy with an automated spring-loaded biopsy device has become the standard method for kidney biopsy. Information on the success rate and safety of the routine use of this procedure from large series is not available. Such information is of interest for cost benefit considerations and for medicolegal purposes. We performed an audit of this procedure.

SUBJECTS AND METHODS

From January 1993 to June 1997, 1090 percutaneous renal biopsies were performed in the renal units of Heidelberg (n = 557) and Karlsruhe (n = 533) using a spring-loaded biopsy device (Biopty; Radiplast AB, Uppsala, Sweden). After intensive local disinfection, biopsies were performed under local anaesthesia and direct visualization by ultrasound (Sonolayer SSH-140 A, Toshiba Inc., Japan). A puncturing adaptor was used (model UAGV 009 A, Toshiba, Japan). Of the 1090 biopsies 114 (10.4%) were performed on renal allografts and 976 (89.6%) on orthotopic kidneys. Biopsies were performed only if patients were strictly normotensive (<140/90 mmHg) and had normal coagulation parameters (PT, PTT, factor VIII, thrombocyte count, and bleeding time). All patients had been advised not to take aspirin or non-steroidal antiinflammatory agents for at least 5 days prior biopsy. We analysed (1) yield of diagnostically useful material, and (2) frequency of postbiopsy complications (e.g. macrohaematuria, haematoma, infections, and AV fistula).

RESULTS

Except for one case requiring interventional radiology because of persisting blood loss and three cases requiring blood transfusions, no serious complications were seen in the 1090 consecutive renal biopsies, e.g. death, loss of kidney, life-threatening haemorrhage, or persisting haemodynamically relevant AV fistulae. The frequency of minor haematoma with an extension >2 x 2 cm, but no significant decrease of haemoglobin, was 2.2% (25/1090). Self-limited mild macrohaematuria occurred in 0.8% (9/1090). The incidence of small, haemodynamically irrelevant AV fistulae detected by Doppler ultrasound was 9% (48/533). Sufficient tissue for reliable histopathological diagnosis was obtained in almost all cases (1077/1090 = 98.8%). The median number of glomeruli per biopsy sample was 9 (range 1-37).

CONCLUSION

If contraindications, especially high blood pressure and abnormal haemostasis, are respected, ultrasound-guided percutaneous renal biopsy with an automated biopsy device is safe. Skilled operators obtain satisfactory amounts of kidney tissue in almost all cases.

Diffuse intermyocardiocytic fibrosis in uraemic patients

At post-mortem we examined heart tissue of (i) 31 patients with uraemia not on dialysis, (ii) 42 patients on haemodialysis for less than 6 months, (iii) 60 patients on haemodialysis for more than 6 months, (iv) 16 patients after renal transplantation, and (v) 11 patients on CAPD. Patients with stenosing coronary lesions were excluded. Diffuse non-coronary intermyocardiocytic fibrosis, assessed by a score system in trichrome-stained sections, was found in 91% of chronically uraemic patients, but not in non-hypertensive, non-diabetic controls. The lesion was present even in non-dialysed uraemic patients; in dialysed patients its severity was related to the duration of dialysis; it was demonstrable even years after renal transplantation. On electron-microscopy, collagen fibres were seen, while beta 2-M amyloid was consistently absent. Logistic regression analysis showed that uraemia was a determinant of intermyocardiocytic fibrosis independent of hypertension, diabetes mellitus, anaemia, heart weight, and presence or absence of dialysis procedure.

Smoking as a risk factor for end-stage renal failure in men with primary renal disease

BACKGROUND

It is not known whether smoking increases the risk of end-stage renal failure (ESRF) in patients with primary renal disease.

METHODS

We performed a retrospective multicenter case-control study including 582 patients from nine centers in Germany, Italy and Austria. The diseases investigated were IgA glomerulonephritis (IgA-GN) as a model of inflammatory renal disease and autosomal dominant polycystic kidney disease (ADPKD) as a model of non-inflammatory renal disease. Cases were patients who had progressed to ESRF and controls were patients who were not in ESRF, that is, whose serum-creatinine failed to progress to >3 mg/dl during the observation period and who did not require renal replacement therapy. Matching for renal disease (IgA-GN, ADPKD), gender, age at renal death and region of residence resulted in 102 individually matched pairs (IgA-GN N = 54, ADPKD N = 48). Multiple conditional logistic regression was used to estimate adjusted odds ratios for independent tobacco effects.

RESULTS

In men (matched pairs: IgA-GN N = 44, ADPKD N = 28), a significant dose-dependent increase of the risk to progress to ESRF was found (non-adjusted). The baseline risk was defined as <5 pack-years (PY): (i) 5 to 15 PY, odds ratio 3.5 (95% CI 1.3 to 9.6), P = 0.017; (ii) >15 PY = 5.8 (2.0 to 17), P = 0.001. Systolic blood pressure, ACE inhibitor treatment and age at diagnosis emerged as potential confounders. After adjustment, the risk for ESRF in men with >5 PY was highly increased for patients without ACE inhibitor treatment [10.1 (2.3 to 45), P = 0.002] but not with ACE inhibitor treatment [1.4 (0.3 to 7.1), P = 0.65].

CONCLUSION

Smoking increases the risk of ESRF in men with inflammatory and non-inflammatory renal disease.

A role of parathyroid hormone for the activation of cardiac fibroblasts in uremia

Intermyocardiocytic fibrosis, i.e., nonreparative interstitial fibrosis with collagen fiber deposition, is commonly found in uremic patients and animals. The volume density of interstitial tissue in the left papillary muscle of uremic animals was found to be increased (from 1.9 +/- 0.7 to 4.2 +/- 1.1%; P < 0.001). The nuclei of interstitial cells, but not of endothelial cells, were enlarged, pointing to an activating signal that specifically acts on interstitial cells. Because of the known action of parathyroid hormone (PTH) on the heart, a potential role of PTH in the genesis of fibrosis was explored by comparing subtotally nephrectomized (NX) parathyroidectomized (PTX) rats receiving by osmotic minipump either saline or rat 1,34 PTH (100 ng/kg per hour dissolved in NaCl). Animals were on a standard 0.95% Ca diet. After PTX, they were switched to a high-calcium (3%) diet. At the end of the 14-day experiments, NX-PTX-PTH animals and NX-PTX-solvent animals were comparable with respect to mean body weight (335 versus 338 g), serum creatinine (1.2 versus 1.2 mg/dL), and serum-Ca (2.66 versus 2.63 mmol/L). The volume densities of cardiac interstitium were 4.71 +/- 0.87 versus 1.49 +/- 0.49, and those of capillaries were 8.07 +/- 1.54 versus 7.94 +/- 2.62, respectively (P < 0.001 by analysis of variance). Thus, PTX abolished and PTH restored intermyocardiocytic changes of experimental uremia. These observations argue for a permissive role of PTH for fibroblast activation and the genesis of the cardiac fibrosis of uremia.

Renal disease and hypertension in non-insulin-dependent diabetes mellitus

Recent epidemiologic data demonstrate a dramatic increase in the incidence of end-stage renal disease (ESRD) in patients with non-insulin-dependent diabetes mellitus (NIDDM), thus dispelling the mistaken belief that renal prognosis is benign in NIDDM. Currently, the leading cause of ESRD in the United States, Japan, and in most industrialized Europe is NIDDM, accounting for nearly 90% of all cases of diabetes. In addition to profound economic costs, patients with NIDDM and diabetic nephropathy have a dramatically increased morbidity and premature mortality. NIDDM-related nephropathy varies widely among racial and ethnic groups, genders and lifestyles; and gender may interact with race to affect the disease progression. While the course of insulin-dependent diabetes mellitus (IDDM) progresses through well-defined stages, the natural history of NIDDM is less well characterized. NIDDM patients with coronary heart disease have a higher urinary albumin excretion rate at the time of diagnosis and follow-up. This greater risk may also be associated with hypertension and hyperlipidemia, and genes involved in blood pressure are obvious candidate genes for diabetic nephropathy. Hyperglycemia appears to be an important factor in the development of proteinuria in NIDDM, but its role and the influence of diet are not yet clear. Tobacco smoking can also be deleterious to the diabetic patient, and is also associated with disease progression. Maintaining euglycemia, stopping smoking and controlling blood pressure may prevent or slow the progression of NIDDM-related nephropathy and reduce extrarenal injury. Treatment recommendations include early screening for hyperlipidemia, appropriate exercise and a healthy diet. Cornerstones of management should also include: (1) educating the medical community and more widely disseminating data supporting the value of early treatment of microalbuminuria; (2) developing a comprehensive, multidisciplinary team approach that involves physicians, nurses, diabetes educators and behavioral therapists; and (3) intensifying research in this field.