Increased lipoproteins and fibrinogen in chronic renal allograft dysfunction

Chronic rejection - also called chronic renal allograft dysfunction (CRAD) - is the main cause of long-term loss of the transplanted kidney, but its pathogenesis is not well known. The aim of this study was to know if lipoproteins, fibrinogen, plasminogen activator inhibitor-1 (PAI-1) and platelet aggregation show more abnormalities in renal transplant patients with CRAD than in those with stable renal function. Sixty patients with renal allograft have been studied; 20 patients with CRAD and 40 controls matched for age, gender and time after transplantation. In a univariate analysis patients with CRAD had higher total serum triglycerides (214+/-153 vs. 133+/-39 mg/dl; p = 0.04) and very-low-density lipoprotein (VLDL) triglycerides (128+/-116 vs. 59+/-29 mg/dl; p = 0.04). Apolipoprotein B levels were also increased in patients with CRAD although this difference was only borderline significant (131+/-58 vs. 98+/-16 mg/dl; p = 0.05). Similarly, there was a trend toward increased total, VLDL, and low-density lipoprotein (LDL) cholesterol and reduced high-density lipoprotein (HDL) cholesterol in CRAD patients, but these differences did not reach statistical significance. Apolipoprotein A-1 and lipoprotein(a) levels were similar in both groups. Neither platelet aggregation nor PAI-1 levels differed between both groups. In contrast, fibrinogen was increased in patients with CRAD (373+/-81 vs. 322+/-62 mg/dl; p = 0.01). In a multivariate analysis triglycerides and fibrinogen were positively correlated to CRAD. These findings add further support to the hypothesis that lipid abnormalities may be involved in the pathophysiology of CRAD. In addition, this is the first report showing that fibrinogen levels are increased in patients with CRAD. Further studies are needed to evaluate a potential role of fibrinogen in the development of CRAD.

Randomised double-blind comparison of placebo and active treatment for older patients with isolated systolic hypertension. The Systolic Hypertension in Europe (Syst-Eur) Trial Investigators

BACKGROUND

Isolated systolic hypertension occurs in about 15% of people aged 60 years or older. In 1989, the European Working Party on High Blood Pressure in the Elderly investigated whether active treatment could reduce cardiovascular complications of isolated systolic hypertension. Fatal and non-fatal stroke combined was the primary endpoint.

METHODS

All patients (> 60 years) were initially started on masked placebo. At three run-in visits 1 month apart, their average sitting systolic blood pressure was 160-219 mm Hg with a diastolic blood pressure lower than 95 mm Hg. After stratification for centre, sex, and previous cardiovascular complications, 4695 patients were randomly assigned to nitrendipine 10-40 mg daily, with the possible addition of enalapril 5-20 mg daily and hydrochlorothiazide 12.5-25.0 mg daily, or matching placebos. Patients withdrawing from double-blind treatment were still followed up. We compared occurrence of major endpoints by intention to treat.

FINDINGS

At a median of 2 years' follow-up, sitting systolic and diastolic blood pressures had fallen by 13 mm Hg and 2 mm Hg in the placebo group (n = 2297) and by 23 mm Hg and 7 mm Hg in the active treatment group (n = 2398). The between-group differences were systolic 10.1 mm Hg (95% CI 8.8-11.4) and diastolic, 4.5 mm Hg (3.9-5.1). Active treatment reduced the total rate of stroke from 13.7 to 7.9 endpoints per 1000 patient-years (42% reduction; p = 0.003). Non-fatal stroke decreased by 44% (p = 0.007). In the active treatment group, all fatal and non-fatal cardiac endpoints, including sudden death, declined by 26% (p = 0.03). Non-fatal cardiac endpoints decreased by 33% (p = 0.03) and all fatal and non-fatal cardiovascular endpoints by 31% (p < 0.001). Cardiovascular mortality was slightly lower on active treatment (-27%, p = 0.07), but all-cause mortality was not influenced (-14%; p = 0.22).

INTERPRETATION

Among elderly patients with isolated systolic hypertension, antihypertensive drug treatment starting with nitrendipine reduces the rate of cardiovascular complications. Treatment of 1000 patients for 5 years with this type of regimen may prevent 29 strokes or 53 major cardiovascular endpoints.

Elevation of von Willebrand factor levels in patients with IgA nephropathy: effect of ACE inhibition

The von Willebrand factor (vWF) has been used as a marker of endothelial dysfunction in several diseases. We measured plasma vWF in patients with immunoglobulin A nephropathy (IgAN). In a group of 10 IgAN patients with normal renal function, normal blood pressure, and no proteinuria, vWF plasma levels were significantly higher than in a group of 21 healthy volunteers (134% +/- 38% v 80% +/- 22%; P < 0.01). In another group of 16 IgAN patients with normal renal function and proteinuria ranging between 0.3 and 3.8 g/d, vWF levels were also significantly higher than in the control group (148% +/- 63% v 80% +/- 22%; P < 0.001). Afterward, we studied the effects of enalapril administered for 4 weeks on vWF levels and proteinuria in a group of 11 IgAN patients with normal renal function and proteinuria > or = 1 g/d. After 2 weeks on enalapril treatment, both vWF levels and proteinuria had significantly decreased (vWF: 158% +/- 122% to 117% +/- 72%, P < 0.05; proteinuria: 1.6 +/- 0.7 g/d to 0.9 +/- 0.4 g/ d, P < 0.05). After enalapril withdrawal, both vWF and proteinuria significantly increased. A significant correlation between the variations in vWF levels and proteinuria was observed (r = 0.6; P < 0.05). No correlations between blood pressure and changes in vWF or proteinuria were found. We conclude that endothelial dysfunction is observed in patients with IgAN. This abnormality is already present in some patients with normal blood pressure, normal renal function, and absence of proteinuria. Angiotensin-converting enzyme inhibition induced a significant decrease in both vWF levels and proteinuria.

L-arginine reverses the antinatriuretic effect of cyclosporin in renal transplant patients

BACKGROUND

Cyclosporin has been shown to facilitate renal vasoconstriction and to have an antinatriuretic effect. The existence of an interference of cyclosporin with the vasodilating properties of endothelium mediated by nitric oxide production could mediate these effects. On the other hand, the infusion of the nitric oxide precursor L-arginine has been shown to induce renal vasodilatation and to facilitate natriuresis in normal volunteers. We have investigated the renal effects of the administration of an infusion of L-arginine in renal transplant patients chronically treated with cyclosporin. To facilitate the analysis of the data the effects of the administration of a similar dose of cyclosporin on renal function during the infusion of a vehicle were also investigated during the administration of a vehicle of L-arginine.

DESIGN

Ten male renal transplant patients, chronically treated with cyclosporin and with a stable renal function were studied during 2 consecutive days after the administration of the usual morning dose of cyclosporin. The first day they received an intravenous infusion of vehicle and the second the infusion of graded doses of L-arginine (50, 100, 150 mg/kg/h) during 3 consecutive h.

RESULTS

The first day, after cyclosporin administration a significant fall (P < 0.01) was observed in natriuresis and kaliuresis in the absence of changes in renal plasma flow and glomerular filtration rate. After the administration of L-arginine significant (P < 0.01) increases of renal plasma flow, glomerular filtration rate, and natriuresis were seen. The increase in blood levels of cyclosporin after its administration did not differ between days 1 and 2.

CONCLUSION

These results indicate that L-arginine facilitates renal vasodilatation and natriuresis in renal transplant patients. Furthermore, the observed increase in sodium excretion could indicate that L-arginine counteracts the antinatriuretic effect of cyclosporin.

Membranous glomerulonephritis associated with hepatitis C virus infection in renal transplant patients

BACKGROUND

Hepatitis C virus (HCV) infection has been described in association with various types of glomerular diseases, usually type I membranoproliferative glomerulonephritis and rarely membranous glomerulonephritis (MGN). In this article, we describe the first series of MGN exhibited in renal transplant patients and associated with HCV infection.

METHODS

From January 1980 to December 1994, 2045 kidney transplantations were performed in our renal transplant units. A retrospective analysis demonstrated an overall 20% prevalence of HCV virus-positive patients; 409 transplanted patients were HCV positive (ELISA and RIBA).

RESULTS

Fifteen patients developed an allograft MGN (3.66%) 24 months after renal transplantation. MGN appeared in the form of significant proteinuria (>1.5 g/24 h) with stable renal function. In all cases, graft biopsy demonstrated a thickening of the capillary wall, subepithelial electron-dense deposits, and IgG and C3 diffuse granular deposits along the basal membrane. Ten cases were considered de novo, two cases were considered recurrent MGN, and three cases were considered undetermined because the primary renal disease was chronic glomerulonephritis. All patients showed negative antinuclear antibodies and cryoglobulins, normal complement, and negative rheumatoid factors. During follow-up (an average of 2 years), 12 patients developed a progressive worsening of renal function, with increased serum creatinine and persistent proteinuria; 8 of the 12 patients returned to dialysis. Of the remaining three cases, two patients showed partial remission of nephrotic syndrome after high doses of steroids, and one patient persisted with stable renal function and proteinuria (<2 g/24 h.).

CONCLUSIONS

In summary, HCV is preferentially associated with MGN in renal transplant patients, rather than with membranoproliferative glomerulonephritis as in the normal adult population. MGN associated with HCV infection has a similar clinical picture and outcome to posttransplant idiopathic de novo MGN, with persistent massive proteinuria and progressive deterioration of renal function.

Determining the trough-to-peak ratio in parallel-group trials. Systolic Hypertension in Europe (SYST-EUR) Trial Investigators

We explored how in parallel-group trials interindividual variability, correction for placebo effects, and smoothing of blood pressure profiles can be handled in measuring the trough-to-peak ratio in 244 individuals with isolated systolic hypertension (> or = 60 years) enrolled in the placebo-controlled Systolic Hypertension in europe Trial. Net treatment effects were computed by subtracting the mean changes from baseline during placebo (n = 133) from those during active treatment (n = 111). At entry, systolic/diastolic pressures averaged 176/86 mm Hg in the clinic and 149/80 mm Hg on 24-hour ambulatory monitoring. With corrections applied for baseline and placebo, nitrendipine (10 to 40 mg/d), with the possible addition of enalapril (5 to 20 mg/d) and/or hydrochlorothiazide (12.5 to 25 mg/d), reduced (P < .001) these blood pressure values by 16.6/7.3 and 9.8/4.7 mm Hg, respectively. The net trough-to-peak ratios were first determined from blood pressure profiles (12 hours) with 1-hour precision, synchronized by the morning and evening doses of the double-blind medication. According to the usual approach, disregarding interindividual variability, the systolic/diastolic net trough-to-peak ratios were 0.46/0.40 in the morning and 0.77/0.99 in the evening. In individual subjects, the baseline-adjusted trough-to-peak ratios were nonnormally distributed. We therefore used a nonparametric technique to calculate the net trough-to-peak ratios from the results in individual subjects. In the morning, these ratios averaged 0.25 systolic (95% confidence interval, 0.09 to 0.41) and 0.15 diastolic (95% confidence interval, 0.00 to 0.31) and in the evening, 0.19 and 0.36 (95% confidence intervals, 0.00 to 0.38 and 0.14 to 0.56), respectively. When the blood pressure profiles were smoothed by substituting the 1-hour averages by moving or fixed 2-hour averages or by Fourier modeling, the trough-to-peak ratios remained unchanged after the morning dose (0.20/0.13, 0.20/0.14, and 0.16/0.21, respectively) but tended to increase in the evening (0.32/0.38, 0.28/0.40, and 0.48/0.49). In conclusion, the parallel-group analysis proposed makes it possible for one to correct the trough-to-peak ratio for baseline as well as placebo, to account for interindividual variability, and to calculate a confidence interval for the net trough-to-peak ratio. Accounting for interindividual variability reduces the trough-to-peak ratio. Smoothing affects the individualized net trough-to-peak ratios in an unpredictable way and should therefore be avoided.

Does antihypertensive therapy protect the kidney in essential hypertension?

AIM

To review the beneficial effect on renal function of antihypertensive treatment in patients with essential hypertension.

EPIDEMIOLOGY

Several prospective, randomized trials have demonstrated that blood pressure control reduces the incidence of stroke and coronary heart disease mortality but end-stage renal disease secondary to essential hypertension has increased by 16-26% during the last decade. This apparent discordance can be explained by the reduction in brain and heart mortality, so that a greater proportion of renal damage is produced, or by a failure of antihypertensive drugs to protect the kidney as efficiently as other organs. MECHANISMS OF RENAL DAMAGE IN ESSENTIAL HYPERTENSION: Two mechanisms have been proposed. One hypothesis is that renal ischemia affects different kidney zones by producing periglomerular fibrosis, intimal amplification with hyaline deposits and reduction of the vessel lumen. The second hypothesis proposes that the elevation of intraglomerular pressure observed with secondary glomerular sclerosis is regulated by afferent-efferent arteriolar vasoconstriction or vasodilation. PARAMETERS FOR MEASURING RENAL FUNCTION: Creatinine clearance is the most appropriate method to measure glomerular filtration rate in routine clinical practice. Serum creatinine is not elevated until renal function is reduced below 50 ml/ min. The Cockcroft formula has been proposed in order to calculate creatinine clearance from plasma creatinine levels. Microalbuminuria and proteinuria are two other parameters that can be used to measure renal damage. ANTIHYPERTENSIVE TREATMENT: Antihypertensive therapy with concomitant control of blood pressure reduces protein excretion and the hypertension-induced deterioration in renal function. Angiotensin converting enzyme (ACE) inhibitors and calcium antagonists have shown good renal protection, and a combination of these two types of drugs may improve results and reduce side effects.

CONCLUSIONS

In the past decade, end-stage renal disease secondary to essential hypertension is increased despite a clear reduction in stroke and coronary heart disease mortality resulting from blood pressure control. Measurements of creatinine clearance, serum creatinine in advanced renal failure, microalbuminuria and proteinuria are adequate indicators of renal damage. Blood pressure control with any class of drugs reduces the progression of renal failure and proteinuria, but ACE inhibitors and calcium antagonists seem to provide better renal protection; ACE inhibitors have a greater antiproteinuric effect. The combination of these two types of drugs might further reduce renal damage and side effects.

Aging abolishes the renal response to L-arginine infusion in essential hypertension

A defect in the endothelium-dependent vasorelaxation could contribute to the development of arterial hypertension through the facilitation of renal vasoconstriction and sodium retention. In this study, we tested the hypothesis that aging impairs kidney function in essential hypertension through a derangement of nitric oxide-dependent renal mechanisms. To this end, we compared the renal response to an intravenous infusion of the precursor of nitric oxide synthesis, L-arginine, in young and aged essential hypertensives. In young hypertensives, L-arginine induced a significant increase in renal plasma flow, glomerular filtration rate, natriuresis and kaliuresis, without changes in filtration fraction. These effects were not observed in aged hypertensives. Neither PRA nor PA were affected by L-arginine infusion in any group. These results indicate that aging produces a derangement of endothelial function in essential hypertension.

Can the kidney prevent cardiovascular diseases?

The kidneys play an important role in the development of cardiovascular risk factors. It is well known that heavy proteinuria can induce hyperlipidemia, the uric acid is elevated in some renal deficiencies and that hypertension develops in most end stage renal diseases. In prehypertensive states, specially in subjects with a family history of hypertension, some hemodynamic changes take place, characterized by an increase in renal vasoconstriction with a reduction in renal plasma flow and an elevation of sodium reabsorption. The mechanisms for these alterations are not well understood, but an increase in intracytosolic calcium in vascular smooth muscle cells, a reduction in vasodilatory substances such as nitric oxide and an increased sympathetic nervous activity have been proposed. In normotensive subjects with two hypertensive parents a reduction in sodium diet, an increase in protein intake or in arginine diet could prevent established essential hypertension from developing. In borderline hypertension an early therapy with low doses of calcium antagonists, ACE inhibition or diuretics could be indicated.

Cyclosporine nephrotoxicity and rejection crisis: diagnosis by urinary enzyme excretion

The urinary enzymes alanine aminopeptidase (AAP; EC 3.4.11.2) and N-acetyl-B-D-glucosaminidase (NAG; EC 3.2.1.30) were measured daily in 35 renal transplant recipients during the early postoperative period. Each peak value of fractional excretion was corrected for its baseline value (CFE). CFE values above normal for both NAG and AAP were more frequently found in episodes of acute rejection than in cyclosporine acute nephrotoxicity episodes (76 vs. 0%; p < 0.001). Consequently, a rise in CFE levels for both NAG and AAP is strongly suggestive of acute rejection crisis.

Lipoprotein(a) and vascular access survival in patients on chronic hemodialysis

Lipoprotein(a) [Lp(a)] is an independent risk factor for atherosclerotic and cardiovascular complications in the general population and in hemodialysis patients. Increased Lp(a) levels have been also described as a possible predictor of vascular access occlusion in patients on chronic hemodialysis. We have studied prospectively the relationship between vascular access survival and Lp(a) levels in 40 hemodialysis patients. The Lp(a) plasma concentrations were measured by enzyme-linked immunosorbent assay in all patients in April 1993. Throughout the following year, evolution and survival of their vascular accesses were analyzed. Failure of vascular access was established when there were complications requiring surgical repair or transluminal angioplasty. Fourteen patients showed failure of vascular access, and the cumulative survival of vascular accesses after 1 year of follow-up was 63.8%. The Lp(a) levels were higher in patients with failure of vascular access than in the others (35.2 +/- 31 vs. 22.4 +/- 25 md/dl), but this difference did not reach statistical significance (p = 0.064). The vascular access survival in patients with Lp(a) levels > 75th percentile (52.5 mg/dl) was significantly lower than in the remaining patients (40 vs. 72%; p = 0.045). This difference increased when we analyzed the patients with Lp(a) levels > 90th percentile (76 md/dl; 25 vs. 68%; p = 0.002). Our results suggest that patients with the highest levels of Lp(a) are at risk of developing complications in their vascular accesses, and they also have lower vascular access survival.

Assessing renal effects and renal protection

ASSESSMENT OF RENAL FUNCTION: There are a number of methods of evaluating renal function, including measurements of glomerular filtration, renal plasma flow, tubular function, micro- and macroalbuminuria and urinary sediment. Of these, microalbuminuria, glomerular filtration and renal plasma flow are the most appropriate. RENAL EFFECTS OF CALCIUM ANTAGONISTS: Calcium antagonists have important effects on renal function, including a reduction in renal vasoconstriction, increased renal blood flow and, in some circumstances, reduced protein excretion. In particular, these agents can reverse the mild renal vasoconstriction that is seen in the offspring of hypertensive patients. The renal effects of calcium antagonists have been studied in animal models, where radioimaging techniques have shown a biphasic haemodynamic response. RENAL PROTECTION WITH CALCIUM ANTAGONISTS: Two important beneficial effects of calcium antagonists are prevention of acute renal failure and protection against cyclosporin nephrotoxicity. Calcium antagonists have thus been used therapeutically in renal transplant patients and in patients with acute renal failure secondary to the effects of nephrotoxic agents.

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis

Very few patients with familial hypomagnesemia, hypercalciuria and nephrocalcinosis have been described. Information about clinical course, familial studies or evolution after renal transplantation is very scant. We have studied eight patients with this syndrome who belong to five different families. The mean age at diagnosis was 15 +/- 7 years (5 to 25 years). The primary clinical data were polyuria-polydipsia (8 cases), ocular abnormalities (5), recurrent urinary tract infections (5) and recurrent renal colics with stone passage (2). Bilateral nephrocalcinosis was observed in all cases. Every patient showed hypomagnesemia (1.1 +/- 0.2 mg/dl) with inappropriately high urinary magnesium (Mg) excretions (70 +/- 17 mg/day), Mg clearances (4.4 +/- 1.2 ml/m) and Mg fractional excretions (16.2 +/- 7.1%). Hypercalciuria was present in every case except in those with advanced renal insufficiency. Serum parathormone levels were abnormally high. Serum calcium (Ca), phosphorus and potassium, and urinary excretions of uric acid and oxalate were normal. Neither chronic oral Mg administration nor thiazide diuretics normalized serum Mg levels or urinary Ca excretions, respectively. Follow-up was 6 +/- 4.5 years. Renal function worsened in every case with six patients starting on chronic dialysis after 4.3 +/- 3.8 years. The progression rate of renal insufficiency correlated with the severity of nephrocalcinosis. Five patients have received a kidney graft, and their serum Mg and urinary Ca have always been within normal values after transplantation. Twenty-six members of four of the affected families were studied: none of them showed hypomagnesemia, renal insufficiency or nephrocalcinosis. However, eleven cases (42%) had hypercalciuria and four of them presented with recurrent renal stones. Two family members had medullary sponge kidneys. In conclusion, progression to renal insufficiency is common in this syndrome; oral Mg and thiazide diuretics are ineffective to correct abnormalities. After kidney graft, tubular handling of Mg and Ca was normal. A striking incidence (42%) of hypercalciuria was found in the familial study.

Effects of body-weight loss and captopril treatment on proteinuria associated with obesity

We have identified 17 obese patients (body mass index, BMI, 37.9 +/- 4.1) with proteinuria > 1 g/day (1.3-6.4 g/24 h, mean 3.1 +/- 1.7). Their age was 34-70 years (48.3 +/- 10); 11 were females and 6 males. Six patients had only one functioning kidney and a sleep apnea syndrome had been diagnosed in 5. Renal biopsies, obtained in 5 cases, showed focal glomerulosclerosis in 2 cases, minimal changes in 2 and mesangial proliferation in 1. Nine patients (group 1) were treated with hypocaloric diets; body weight significantly decreased (BMI 37.1 +/- 3, 34 +/- 3.5 and 32.6 +/- 3.2 at 0, 6 and 12 months, respectively) as well as proteinuria (2.9 +/- 1.7, 1.2 +/- 1 and 0.4 +/- 0.6 g/24 h). There was a significant correlation between body weight loss and decrease in proteinuria (r = 0.69, p < 0.05). Eight patients (group 2) were treated with captopril, without dietary changes. BMI remained stable but proteinuria showed a dramatic decrease, similar to that in group 1 (3.4 +/- 1.7, 1.2 +/- 0.9 and 0.7 +/- 1 g/24 h, respectively). Renal function remained stable in both groups. In summary, both body weight loss and captopril treatment can induce a sharp decrease in obesity-related proteinuria.

Relationship between blood pressure and renal function

RENAL DAMAGE CAUSED BY HYPERTENSION: Renal vasoconstriction seems to be a key factor in the origin of arterial hypertension and accounts for the decrease in renal blood flow commonly observed in patients with hypertension. An inverse correlation has been found between renal blood flow and clinic blood pressure levels in established hypertension. Other features of renal damage attributable to high blood pressure have also been correlated with clinic blood pressure levels. Microalbuminuria is a good example of an alteration in renal function that depends in part on blood pressure levels.

EFFECTS OF ANTIHYPERTENSIVE AGENTS

Antihypertensive agents can prevent or ameliorate renal vascular damage secondary to arterial hypertension, including renal failure. Ambulatory blood pressure monitoring is an excellent method of studying blood pressure levels in relation to end-organ damage and the blood pressure response to antihypertensive agents. Preliminary studies using this technique indicate that changes in renal function are closely correlated with the average daily blood pressure in arterial hypertension.

CONCLUSIONS

Further studies are needed on the mechanisms of renal deterioration and on how to preserve renal function in arterial hypertension.