Searching for IgA nephropathy candidate genes: genetic studies combined with high throughput innovative investigations

Idiopathic IgA Nephropathy (IgAN) is the most common biopsy-proven glomerulonephritis worldwide. All races with the exception of Blacks and Indians are involved. Families with two or more relatives affected by IgAN may be observed in 15-20% of pedigrees of IgAN patients. Genome wide linkage study has been considered the most promising approach to identify IgAN susceptibility genes. Therefore, some European investigators constituted the European IgAN Consortium which was initially funded by the European Union. Data from linkage analysis studies, family association studies and case-control association studies are reported. To date, the Consortium has identified two loci (located on chromosomes 4q26-31 and 17q12-22), in addition to the previous study which described the first IgAN locus on chromosome 6q22-23. The functional mapping of genes involved in the disease proceeds from the identification of susceptibility loci identified by linkage analysis (step 1) to the isolation of candidate genes within gene disease-susceptibility loci, after obtaining information by microarray analysis carried out on peripheral leukocytes and renal tissue samples (step 2). Then, the process will proceed from the design of RNA interferenceagents against selected genes (step 3) to the application of systematically tested effect of RNA agents on functional cellular assay (step 4). The above combined high-throughput technologies will give information on the pathogenic mechanisms of IgAN. In addition, these data may indicate potential targets for screening, prevention and early diagnosis of the disease and more appropriate and effective treatment.

PDGF-B gene single-nucleotide polymorphisms are not predictive for disease onset or progression of IgA nephropathy

BACKGROUND

Few genetic factors have been identified that determine susceptibility to and progression of IgA-nephropathy (IgAN). Given that IgAN is usually characterized by mesangioproliferative glomerulonephritis and that PDGF-B is of central pathophysiological relevance in this process, we analyzed four single-nucleotide polymorphisms (SNPs) of the PDGF-B gene to evaluate a possible association of these SNPs with disease onset and progression, histological grading and responses to ACE inhibitor (ACEi) therapy.

METHODS

The total study population consisted of 195 IgAN patients (127 from southern Italy and 68 from northern Germany) and 200 healthy controls (100 from each region). All four SNPs were in Hardy-Weinberg equilibrium and genotype distributions did not differ between patients and controls in either region.

RESULTS

SNP distribution in Italian patients reaching end-stage renal disease (n=45) also was not significantly different from patients maintaining a serum creatinine below 1.2 mg/dl (n=60) during 5.6 +/- 5.5 years of follow-up. Furthermore, we failed to detect significant effects of any SNP on the slope of 1/serum creatinine, proteinuria level or the antiproteinuric response to ACEi. Additionally, particular PDGF-B genotypes did not correlate with histological grading using the Lee classification.

CONCLUSION

We conclude that none of the four PDGF-B SNPs is related to the onset of IgAN in two different populations and that none of them has a major influence on the course of IgAN.

Antimicrobial agents and catheter-related interventions to prevent peritonitis in peritoneal dialysis: Using evidence in the context of clinical practice

BACKGROUND

Peritonitis still represents a common and major complication of peritoneal dialysis. The broader adoption of several strategies, including antimicrobial and catheter related interventions, has been advocated to prevent or reduce the risk of peritonitis in peritoneal dialysis.

METHODS

In this article we start with the presentation of a clinical case where concern exists about the strategies for preventing peritoneal dialysis peritonitis. We then look at the available evidence in the form of systematic reviews of randomized trials and individual randomized trials of interventions to prevent peritonitis in peritoneal dialysis. A summary of the evidence is provided and then put in context with the clinical case scenario.

RESULTS

Nineteen eligible trials (1949 patients) of antimicrobial agents and 37 (2822 patients) of catheter related interventions to prevent peritonitis in peritoneal dialysis were identified. Nasal mupirocin compared with placebo significantly reduced the exit-site and tunnel infection rate (1 trial, 2716 patient months, RR 0.58, 95% CI 0.40 to 0.85) but not peritonitis rate (1 trial, 2716 patient months, RR 0.84, 95% CI 0.44 to 1.60). As for antimicrobial strategies, perioperative intravenous antibiotics compared with no treatment significantly reduced the risk of early peritonitis (4 trials, 335 patients, RR 0.35, 95% CI 0.15 to 0.80) but not exit site and tunnel infection (3 trials, 114 patients, RR 0.32, 95% CI 0.02 to 4.81). As for catheter related strategies, Y-set and twin-bag systems were superior to conventional spike systems (7 trials, 485 patients, RR 0.64, 95% CI 0.53 to 0.77) and no other catheter-related intervention was demonstrated to prevent peritonitis in PD.

CONCLUSIONS

Evidence exists to support the use of perioperative intravenous antibiotic prophylaxis at the time of catheter placement, the twin-bag and Y-set system, as well as prophylaxis with mupirocin in Staphylococcus aureus nasal carriers. Despite lack of evidence, several other agents are used and recommended in major international guidelines, which is reasonable but requires further investigation.