Long-Term Outcome of Steroid-Resistant Nephrotic Syndrome in Children

We investigated the value of genetic, histopathologic, and early treatment response information in prognosing long-term renal outcome in children with primary steroid-resistant nephrotic syndrome. From the PodoNet Registry, we obtained longitudinal clinical information for 1354 patients (disease onset at >3 months and <20 years of age): 612 had documented responsiveness to intensified immunosuppression (IIS), 1155 had kidney biopsy results, and 212 had an established genetic diagnosis. We assessed risk factors for ESRD using multivariate Cox regression models. Complete and partial remission of proteinuria within 12 months of disease onset occurred in 24.5% and 16.5% of children, respectively, with the highest remission rates achieved with calcineurin inhibitor-based protocols. Ten-year ESRD-free survival rates were 43%, 94%, and 72% in children with IIS resistance, complete remission, and partial remission, respectively; 27% in children with a genetic diagnosis; and 79% and 52% in children with histopathologic findings of minimal change glomerulopathy and FSGS, respectively. Five-year ESRD-free survival rate was 21% for diffuse mesangial sclerosis. IIS responsiveness, presence of a genetic diagnosis, and FSGS or diffuse mesangial sclerosis on initial biopsy as well as age, serum albumin concentration, and CKD stage at onset affected ESRD risk. Our findings suggest that responsiveness to initial IIS and detection of a hereditary podocytopathy are prognostic indicators of favorable and poor long-term outcome, respectively, in children with steroid-resistant nephrotic syndrome. Children with multidrug-resistant sporadic disease show better renal survival than those with genetic disease. Furthermore, histopathologic findings may retain prognostic relevance when a genetic diagnosis is established.

Genetic screening in adolescents with steroid-resistant nephrotic syndrome

Genetic screening paradigms for congenital and infantile nephrotic syndrome are well established; however, screening in adolescents has received only minor attention. To help rectify this, we analyzed an unselected adolescent cohort of the international PodoNet registry to develop a rational screening approach based on 227 patients with nonsyndromic steroid-resistant nephrotic syndrome aged 10-20 years. Of these, 21% had a positive family history. Autosomal dominant cases were screened for WT1, TRPC6, ACTN4, and INF2 mutations. All other patients had the NPHS2 gene screened, and WT1 was tested in sporadic cases. In addition, 40 sporadic cases had the entire coding region of INF2 tested. Of the autosomal recessive and the sporadic cases, 13 and 6%, respectively, were found to have podocin-associated nephrotic syndrome, and 56% of them were compound heterozygous for the nonneutral p.R229Q polymorphism. Four percent of the sporadic and 10% of the autosomal dominant cases had a mutation in WT1. Pathogenic INF2 mutations were found in 20% of the dominant but none of the sporadic cases. In a large cohort of adolescents including both familial and sporadic disease, NPHS2 mutations explained about 7% and WT1 4% of cases, whereas INF2 proved relevant only in autosomal dominant familial disease. Thus, screening of the entire coding sequence of NPHS2 and exons 8-9 of WT1 appears to be the most rational and cost-effective screening approach in sporadic juvenile steroid-resistant nephrotic syndrome.

Renal dopaminergic mechanisms in renal parenchymal diseases and hypertension

The present report addresses the status of the renal dopaminergic system activity in patients afflicted with different renal disorders and in the remnant kidney of uninephrectomized (UNX) rats, based on the urinary excretion of L-DOPA, dopamine and amine metabolites. In renal transplant recipients with good recovery of graft function (group 1, n=11), the daily urinary excretion of DOPAC, but not that of HVA, was found to increase progressively throughout the first 12 days post-transplantation from 698+/-57 nmol in the first day to 3498+/-414 nmol on day 9, and then remained constant until day 12. This resulted in a 6-fold increase in the urinary DOPAC/dopamine ratios. In renal transplant recipients with acute tubular necrosis (group 2, n=8), the urinary levels of dopamine, DOPAC and HVA were approximately 30% of those in group 1. In a group of 28 patients with chronic renal parenchymal disorders, the daily urinary excretion of L-DOPA, free dopamine and dopamine metabolites (DOPAC and HVA) correlated positively with the degree of deterioration of renal function (P<0.01). However, the U(Dopamine/(L)-DOPA) and U(DOPAC/Dopamine) ratios in patients with chronic renal insufficiency were found to be similar to those observed in patients with normal renal function. In 14 IgA nephropathy (IgA-N) patients with near normal renal function, the changes in 24 h mean blood pressure when going from 20 to 350 mmol/day sodium intake correlated negatively with the daily urinary excretion of dopamine (r(2)=0.597, P<0.01). The urinary excretion of L-DOPA and dopamine in IgA-N patients with salt-sensitive (SS) blood pressure was lower than in salt-resistant (SR) patients (P<0.05), irrespective of their daily sodium intake. However, the rise in urinary dopamine output during salt loading (from 20 to 350 mmol/day) was greater (P<0.05) in IgA-N SS patients (21.2+/-2.5% increase) than in SR patients (6.3+/-1.4% increase). Fifteen days after the surgery, uninephrectomy (UNX) in the rat was accompanied by an enhanced (P<0.05) urinary excretion of dopamine (36+/-3 vs 26+/-2), DOPAC (124+/-11 vs 69+/-6) and HVA (611+/-42 vs 354+/-7) (nmol/g kidney/kg body weight). This was accompanied by an increase in V(max) values for renal aromatic L-amino acid decarboxylase in the remnant kidney of UNX rats (P<0.05). Sch 23390, a D1 dopamine receptor antagonist, produced a marked reduction in the urinary excretion of sodium in UNX rats, whereas in sham-operated rats the decrease in urinary sodium did not attain a significant difference. It is concluded that the study of the renal dopaminergic system in patients afflicted with renal parenchymal disorders should address parameters other than free urinary dopamine, namely the urinary excretion of L-DOPA and dopamine metabolites (DOPAC and HVA). It is also suggested that in SS hypertension of chronic renal parenchymal diseases, renal dopamine produced in the residual tubular units may be enhanced during a sodium challenge, thus behaving appropriately as a compensatory natriuretic hormone.

Reduced urinary excretion of dopamine and metabolites in chronic renal parenchymal disease

BACKGROUND

Chronic renal parenchymal diseases are accompanied by a progressive loss of tubular units endowed with the ability to synthesise dopamine from L-3,4-dihydroxyphenylalanine (L-DOPA), and preliminary evidence has suggested that the urinary excretion of free dopamine may be reduced in these disorders. However, it is well recognized now that under in vitro conditions, dopamine newly synthesised in tubular epithelial cells undergoes extensive deamination to 3,4-dihydroxyphenylacetic acid (DOPAC) by monoamine oxidase (MAO); a small amount of the amine is converted to homovanillic acid by both MAO and catechol-O-methyltransferase (COMT) and a minor amount is methylated to 3-methoxytyramine.

AIMS

The present study aimed at examining the relationship between renal function and daily urinary levels of L-DOPA, free dopamine and its main metabolites, DOPAC and homovanillic acid (HVA) in patients (n = 28) with chronic renal parenchymal disease, in conditions of controlled sodium, potassium and phosphate intake. The levels of 5-hydroxyindolacetic acid (5-HIAA) were also evaluated in the same cohort of patients.

RESULTS

The patients were divided in two groups according to creatinine clearance (group 1, 39 +/- 6 ml/min/1.73 m2, n = 14; group 2, 139 +/- 6 ml/min/1.73 m2, n = 14). In patients of group 1, the urinary levels of L-DOPA, dopamine and DOPAC (in nmol/24 h) were significantly lower (60% reduction) than in patients in group 2 (L-DOPA, 134 +/- 36 vs. 308 +/- 51; dopamine, 759 +/- 175 vs. 1,936 +/- 117; DOPAC 2,595 +/- 340 vs. 7,938 +/- 833). Also, the urinary excretion of HVA in patients group 1 was significantly lower (40% reduction) than in patients of group 2 (17,434 +/- 2,455 vs. 27,179 +/- 2,271 nmol/24 h). By contrast, no significant difference was observed in daily urinary excretion of 5-HIAA between the two groups of patients (group 1,27,280 +/- 3,721 nmol/day; group 2, 28,851 +/- 2,854 nmol/day). A positive linear relationship was found in these 28 patients between the creatinine clearance and the daily urinary excretion of L-DOPA (r = 0.64, p < 0.001), free dopamine (r = 0.83; p < 0.0001), DOPAC (r = 0.86; p < 0.0001) and HVA (r = 0.65; p < 0.002), but not with that of 5-HIAA (r = 0.14; ns). The Udopamine:L-DOPA and UDOPAC/dopamine ratios were found to be similar in both groups of patients whereas the UHVA/DOPAC ratios in patients of group 1 were found greater than in group 2 (p < 0.05).

CONCLUSION

Patients suffering from chronic parenchymal disease with a compromised renal function present with a reduced activity of their renal dopaminergic system which correlates well with the degree of deterioration of renal function. The reduced urinary dopamine output in renal insufficiency is not attributable to enhanced metabolism of renal dopamine. We suggest that the urinary levels of DOPAC may represent a useful parameter for the assessment of renal dopamine synthesis.

Renal dopaminergic system in nephrotic syndrome and after remission

BACKGROUND

Although intrarenal dopamine is known to behave as an endogenous natriuretic hormone the role of the renal dopaminergic system in the sodium handling of nephrotic oedema remains unknown.

STUDY DESIGN

We monitored the daily urinary excretion of free dopamine, L-DOPA-its precursor, and its metabolites, DOPAC and HVA, during sodium retention accompanying the nephrotic state and natriuresis leading to oedema mobilization in eight patients (mean age 8.0+/-2.4 years) with drug-induced remission of minimal-change nephrotic syndrome (MCNS).

RESULTS

During natriuresis the urinary levels of dopamine did not increase in parallel with sodium excretion in any of the eight patients studied. Moreover, after remission of the nephrotic syndrome the urinary levels of dopamine were significantly lower than during the nephrotic state (1565.3+/-361.7 vs 2416.1+/-558.4, P= 0.02). In contrast, the urinary excretion of L-DOPA increased markedly during natriuresis resulting from remission of proteinuria (from 87.0+/-40.5 up to 296.9+/-86.3 nmol/24 h; P< 0.01).

CONCLUSION

We conclude that the natriuretic response resulting from drug-induced remission of proteinuria in MCNS is accompanied by a decrease in the renal uptake/decarboxylation of L-DOPA to dopamine.

Genetic and environmental factors regulating blood pressure in childhood: prospective study from 0 to 3 years

OBJECTIVES

Blood pressure (BP) regulation depends on the interaction between multiple environmental and genetic factors. Of these, BP sensitivity to dietary sodium intake has been one that has been investigated in adults but not in children. The aim of the present study was to investigate, prospectively, the BP profile in relation to different genetic and hormonal factors, in the first 3 years of life.

POPULATION AND METHODS

Thirty-nine children born at term following normal pregnancies, with uncomplicated neonatal periods, were randomly selected to take part in the study. BP, weight and length were evaluated every 3 months from birth to 3 years. At the age of 12 months, haptoglobin phenotypes and plasma active renin concentration were determined as well as random urine evaluation of aldosterone, cAMP, dopamine and digoxin-like immunoreactive substances (DLIS). Family history of cardio-vascular diseases was also recorded.

RESULTS

Systolic BP (SBP) demonstrated a gradual increase until the age of 6 months with little variation up to 36 months. Tracking of SBP values was also observed from the first year as infants with high values (above the 75 percentile) maintained this tendency up to, at least, the age of 36 months. The comparison between SBP and diastolic BP (DBP) according haptoglobin phenotypes demonstrated that SBP was systematically higher in allele 1, with apparently an increasing tendency with age, although the differences did not have statistical significance. The comparative study between haptoglobin phenotypes, with correction for the covariates fractional excretion of sodium and potassium, showed that allele 1 carriers had significantly lower plasma renin and urine aldosterone and cAMP concentrations than allele 2, but dopamine excretion was found to be higher in allele 1 than in allele 2. There were no differences among variables relating to family history of cardiovascular disease.

CONCLUSIONS

There was an early tracking process of BP values from the first 6 months of life which persists through, at least, to the age of 36 months. Differences in sodium handling between haptoglobin 1 and 2 phenotypes were already present in early childhood, although no significant repercussion in BP values could be demonstrated in the 3-year duration of this study.

[How our pediatric services work]

The results of a questionnaire sent by the College of Pediatrics of the Portuguese Doctors Association (Ordem dos Médicos) to the pediatric departments all over the country are presented. From the answers of fifty-one services, physical conditions, equipment, human resources, assistancial and scientific activities developed are characterized.

Abnormalities of erythrocyte sodium transport in reflux nephropathy

Hypertension is a complication of reflux nephropathy commonly occurring during adolescence and young adult life. We studied cellular sodium transport in an adolescent cohort with this condition as abnormal sodium transport is a feature of human hypertension. Thirty males and 52 females with reflux nephropathy, (median age 20.3 years) had erythrocyte ouabain sensitive sodium-potassium ATPase (Na/K ATPase) pump site number (Bmax) and red cell sodium concentration (RBC Na+) measured in 1988. Six years later, 55 of those had red cell sodium-lithium counter transport (LCT) measured. On both occasions, their renal function and blood pressure (BP) were determined. Bmax in the study group (median 10.3 nmol/l) was significantly less than that of controls (median 11.45 nmol/l). Nine patients who were diagnosed as having hypertension during the 6 year study period appeared to have a lower Bmax compared with that of normotensives in the group. RBC Na+ and LCT of the study group were not significantly different from that of controls. The Na/K ATPase activity is diminished, and sodium-lithium counter transport is unchanged in reflux nephropathy. Further study is needed to ascertain the link between these observations and the onset of high BP.

Prediction of blood pressure from plasma renin activity in reflux nephropathy

As there is a 10% risk of hypertension developing in children with reflux nephropathy and the renin-angiotensin system has been implicated in its aetiology, a long term prospective study has been undertaken to explore the relationship between plasma renin activity (PRA) and blood pressure in such patients. In 1978, of 100 normotensive children with reflux nephropathy 8% were shown to have PRA above normal. Five years later of 85 subjects suitable for analysis 13% had increased PRA and it was shown that PRA and blood pressure SD scores significantly increased. The present study refers to the 10 year follow up in which 95 of the original group were traced but eight of these were unavailable for study and 28 others were excluded from analysis because of extraneous factors that might influence blood pressure or PRA. Results therefore on 59 have been analysed. PRA was above normal in 13/59 (20%) subjects, and PRA and blood pressure SD scores had further increased. The data continue to support the role of the renin-angiotensin system in the observed rise of blood pressure in reflux nephropathy, but individual PRA measurements do not appear so far to predict reliably the onset of hypertension in affected patients.