Hui-Kim Yap

Overexpression of Interleukin-13 Induces Minimal-Change–Like Nephropathy in Rats

IL-13 has been implicated in the pathogenesis of minimal-change nephrotic syndrome. This study aimed to investigate the role of IL-13 on the development of proteinuria and expression of podocyte-related genes that are associated with nephrotic syndrome. IL-13 was overexpressed in Wistar rats through transfection of a mammalian expression vector cloned with the rat IL-13 gene, into the quadriceps by in vivo electroporation. Serum IL-13, albumin, cholesterol, and creatinine and urine albumin were measured serially. Kidneys were harvested after day 70 for histology and electron microscopy. Glomerular gene expression of nephrin, podocin, dystroglycan, B7-1, and IL-13 receptor subunits were examined using real-time PCR with hybridization probes and expressed as an index against beta-actin. Protein expression of these molecules was determined by immunofluorescence staining. The IL-13-transfected rats (n = 41) showed significant albuminuria, hypoalbuminemia, and hypercholesterolemia when compared with control rats (n = 17). No significant histologic changes were seen in glomeruli of IL-13-transfected rats. However, electron microscopy showed up to 80% of podocyte foot process fusion. Glomerular gene expression was significantly upregulated for B7-1, IL-4Ralpha, and IL-13Ralpha2 but downregulated for nephrin, podocin, and dystroglycan. Immunofluorescence staining intensity was reduced for nephrin, podocin, and dystroglycan but increased for B7-1 and IL-4Ralpha in IL-13-transfected rats compared with controls. In conclusion, these results suggest that IL-13 overexpression in the rat could lead to podocyte injury with downregulation of nephrin, podocin, and dystroglycan and a concurrent upregulation of B7-1 in the glomeruli, inducing a minimal change-like nephropathy that is characterized by increased proteinuria, hypoalbuminemia, hypercholesterolemia, and fusion of podocyte foot processes.

Age- and Sex-Related Changes in Lymphocyte Subpopulations of Healthy Asian Subjects: From Birth to Adulthood

Flow cytometric analysis of lymphocyte subsets were evaluated in 391 healthy Asian subjects ranging in age from birth to 40 years. Lymphocyte subsets were analysed using specific monoclonal antibodies: CD20 (B cells), CD3 and CD2 (T cells), CD16 and CD56+ (NK cells), CD4/CD3+ (helper-inducer T cells), CD8/ CD3+ (suppressor/cytotoxic T cells), HLA-DR expression on CD3 and CD25 (Tac) on CD3. The total white cell count, absolute lymphocyte counts, and B cell percentages peaked in infancy and declined steadily with age. Absolute counts of each subset, which were derived from absolute lymphocyte counts, also followed this trend. Increases with age were seen in the NK, T cell (CD2, CD3), and CD8 percentages. Males tended to have higher NK and CD8 percentages than females, and, conversely, females had higher CD3 and CD4 percentages than males. Comparison of our results with studies involving Caucasian subjects indicated higher NK percentages in our Asian population and lower CD4 absolute counts in the males of our population. These results indicate the presence of age, sex, and probable racial differences in lymphocyte subset expression. Our results may serve as reference standards for the Asian population.

Risk factors for steroid dependency in children with idiopathic nephrotic syndrome

Abstract. Minimal change disease, the most common cause of idiopathic nephrotic syndrome (INS) in children, has a high relapse rate, with approximately half of patients developing steroid dependency. This study was aimed at determining the predictive risk factors for the development of steroid dependency in children diagnosed with INS. A retrospective study of 123 children with steroid-responsive INS, followed for at least 6 months between December 1974 and December 1999, was conducted. The following parameters were studied as predictors of steroid dependency: age at onset, gender, race, microscopic hematuria at onset, atopy, concomitant upper respiratory tract infections (URTI) during relapses, and days to remission with initial steroid therapy. Of the 91 children who fulfilled the inclusion criteria, 61.5% became steroid dependent. Both univariate and logistic regression analyses revealed that initial remission time of 9 or more days (P=0.02, OR=3.0, 95% CI=1.2–7.9) and concomitant URTI during relapses (P=0.01, OR=3.4, 95% CI=1.3–8.8) were significant predictors of steroid dependency. By identifying those children with predictive factors of steroid dependency, the clinician will be better able to plan the long-term management of these patients and reduce the morbidity seen with the frequent relapses and steroid treatment, in a disease that is otherwise associated with a favorable prognosis.

Acute glomerulonephritis—changing patterns in Singapore children

This study compared the pattern of acute glomerulonephritis (AGN), a disease known to be influenced by socioeconomic and environmental factors, in children 12 years and under, for the years 1971 and 1985. All children admitted to the four major paediatric departments with haematuria and at least two of the following (oedema, hypertension or oliguria) had an initial diagnosis of AGN. A sample population from one unit from 1980 to 1984 showed that over 70% of these children had evidence of a post-streptococcal aetiology. In 1971, 411 children were admitted with AGN, as compared with only 58 in 1985. The age-sex-race standardized rates for 1971 and 1985 were 0.632 and 0.023/1,000 children 12 years and under, respectively (P<0.001). The mean age of presentation was lower in 1971. Over this period, Singapore saw a threefold rise in the gross national product, accompanied by rapid urbanization. On analysis of the housing pattern, only 31% of the children lived in high-rise apartments in 1971, in contrast with 86% in 1985 (P<0.001). The majority of non-apartment dwellers had homes in runal districts. From an epidemiological perspective, factors which could have led to the highly significant decline in prevalence of AGN in Singapore children included improvement in the socioeconomic status and health care system, and urbanization of the country.

Hematuria and Proteinuria

Hematuria or proteinuria may be just a normal transient finding in children, usually accompanying a non-specific viral infection, or it can be an indicator of a kidney or urinary tract disorder. In this chapter, the various causes and significance of discolored urine, hematuria and proteinuria in children are discussed. A pragmatic clinical approach to evaluate a child with isolated hematuria or isolated proteinuria is suggested to reduce unnecessary extensive workup in benign cases and yet not miss the cases with significant glomerular or urinary tract disease. Early detection and treatment of significant disorders would hopefully delay or prevent the onset of renal insufficiency in children.

ACE Gene Polymorphism and Disease Progression of IgA Nephropathy in Asians in Singapore

The deletion polymorphism of the angiotensin-converting enzyme (ACE) gene has been considered as a risk factor for IgA nephropathy and for its progression to end-stage renal failure. However, results from various studies are conflicting. We had genotyped the ACE gene in 100 patients with IgA nephropathy, 32 of whom were in end-stage renal failure and in 90 normal adult subjects. All DD cases were subjected to confirmation with a second PCR, performed with the insert-specific forward primer. Similar genotype frequencies were obtained for the 90 normal control subjects (II: 47%, ID: 44%, DD: 9%); for the 68 patients not in end-stage renal failure (ESRF) (II: 47%, ID: 46%, DD: 7%) and for the 32 patients with ESRF (II: 53%, ID: 38%, DD: 9%). The genotype frequencies in all 3 series are in Hardy-Weinberg equilibrium. These results suggest that ACE gene polymorphism is not a risk factor for IgA nephropathy and is not a predictor for its progression. Definitive proof of association between ACE gene polymorphism and progression in IgA nephropathy will require a prospective study, controlled for important risk factors, with adequate patient numbers and facility for confirming DD genotypes.

Eighteen years experience in pediatric acute dialysis: analysis of predictors of outcome

Abstract This study reviewed the 18-year experience of acute dialysis in the pediatric intensive care unit, in order to identify factors that could predict outcome, and to determine whether newer modalities of acute dialysis have influenced this outcome. Sixty-six children (ages 1 day to 19 years) received acute dialysis from May 1980 to April 1998. Factors predicting outcome were analyzed using univariate and Cox regression analysis. Modality of dialysis in the first 15 years was exclusively peritoneal dialysis, with a mortality of 63.9%. However, in the last 3 years, with increasing patient numbers, continuous hemodiafiltration (CHDF) was the modality of choice (56.7%), with a mortality of 73.3%. Univariate analysis showed that age <1 year, coma, acute tubular necrosis, disseminated intravascular coagulopathy, assisted ventilation, and hypotension were associated significantly with poor outcome (P<0.05). Cox regression analysis revealed that mortality was significantly higher in patients on mechanical ventilation (RR 5.96, 95% CI 1.82–19.50), or with age <1 year (RR 2.00, 95% CI 1.08–3.73). In conclusion, despite the increasing use of CHDF over the last 3 years, there was no significant improvement in mortality, probably related to the fact that more critically ill patients were dialyzed.

Good outcomes with mycophenolate-cyclosporine-based induction protocol in children with severe proliferative lupus nephritis

The outcomes of children with severe proliferative lupus nephritis (LN) were examined using a new mycophenolate and cyclosporine-based (MMF—CSA) induction protocol. Sixteen children with LN (WHO class III and IV), 31.3% of whom required dialysis at induction, were retrospectively studied. Median MMF dose was 942 mg/m 2/day. Thirteen patients (81%) with persistent proteinuria received CSA. Clinical and laboratory parameters were compared at pre-induction, 6 and 12 months. Treatment outcome was defined by Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), renal function, haematuria, proteinuria and serological markers (complements C3, C4 and anti-dsDNA). Comparing these parameters at induction, 6 months and 12 months, respectively, SLEDAI (25.4 ± 8.7 versus 3.2 ± 2.9 versus 2.9 ± 2.8), serum C3 (47 ± 21 versus 107 ± 27 versus 111 ± 38 mg/dl), C4 (12 ± 14 versus 23 ± 14 versus 22 ± 11 mg/dl) and urine protein (6.97 ± 7.09 versus 0.98 ± 1.56 versus 0.21 ± 0.13 g/ day/1. 73 m2) improved significantly (p < 0.05). Anti-dsDNA titres decreased in 73% by 6 and 12 months (p < 0.05). Complete renal remission was achieved in 7/16 (43.8%) at 6 months and 12/16 (75%) at 12 months, the rest achieving partial remission with no treatment failures. In conclusion, a combination MMF—CSA protocol is an effective therapeutic alternative for induction of children with severe proliferative LN, resulting in significant clinical and serological improvement with minimal adverse effects.

Myotoxicity of lipid-lowering agents in a teenager with MELAS mutation.

The use of lipid-lowering statins has been associated with raised serum muscle enzymes and, occasionally, with rhabdomyolysis, especially in patients with pre-existing metabolic myopathies. The A3243G mutation is one of the most common mutations associated with mitochondrial disorders. A teenager harboring the A3243G mutation had the unusual association of hereditary glomerulopathy and recurrent episodes of raised creatine kinase levels with the use of lipid-lowering agents. Muscle biopsy showed both normal respiratory chain enzyme activities and normal coenzyme Q(10) levels, although decreased muscle coenzyme Q(10) concentration had been postulated to have a pathogenic role in statin-related myopathies. The close temporal relationship of statin administration and raised creatine kinase levels in this patient suggests caution in the use of statins in children and teenagers with mitochondrial myopathies.

Renin-Angiotensin System Gene Polymorphisms: Its Impact on IgAN and Its Progression to End-Stage Renal Failure among Chinese in Singapore

Background: Gene polymorphisms in angiotensin-converting enzyme (ACE), angiotensinogen (AGT) and angiotensin II type 1 receptor (ATR) had been associated with IgA nephropathy (IgAN) and its progression. Several studies on Caucasian and Japanese had reported contradicting results. We determined these polymorphisms in 118 Chinese patients with IgAN and 94 healthy Chinese to assess their clinical impact. Methods: Genotyping was performed with DNA from peripheral leukocytes, PCR amplification of the polymorphic sequence, restriction enzymes digestion, separation and identification of DNA fragments. Clinical data at renal biopsy and final status on renal function were determined from patients’ records. Results: Among controls, genotype distributions were in Hardy-Weinberg equilibrium. Comparing all IgAN patients with controls, AGT and ATR genotype distributions were similar whereas there was significant increase in the ACE DD genotype (p < 0.05). Comparing patients with end-stage renal failure (IgAN-ESRF) and without (IgAN-nonESRF), there was no difference in any of the three gene polymorphisms. But in contrast, there were significant differences in higher male prevalence (p < 0.05), increased serum creatinine at presentation (p < 0.05), more sclerosis (p < 0.01) and higher tubulointerstitial lesion score (p < 0.001) in the IgAN-ESRF group. Conclusion: Among the ACE, AGT and ATR gene polymorphisms, only the DD genotype may predispose the individual to IgAN in our Chinese population. In contrast to clinical and histological risk factors, these genetic variations showed no impact on disease progression to ESRF. It is unlikely that genotyping more patients will prove these genes useful. Nevertheless, preclinically determined genetic markers are very useful as risk factors for disease occurrence and as prognostic indices for disease progression. Therefore, continuing efforts should be made to look at other genes to find those with significance.