Preloading magnesium attenuates cisplatin-associated nephrotoxicity: pilot randomized controlled trial (PRAGMATIC study).

BACKGROUND: Cisplatin is one of the most potent chemotherapeutic drugs used in head and neck cancer treatment; however, nephrotoxicity is the major side-effect limiting usage. Magnesium supplementation has been reported to reduce risk in non-controlled studies. We investigated whether preloading with magnesium prevents nephrotoxicity with a low-dose weekly cisplatin regimen. METHODS: We carried out a prospective pilot, single-blinded, randomized controlled trial to compare cisplatin-associated acute kidney injury (cis-AKI) and acute kidney disease (cis-AKD) between two groups: intravenous 0.9% NaCl 500 ml + KCL 20 mEq over 4 h pre-cisplatin 40 mg/m2 weekly for 7-8 weeks (control group) compared with additional 16 mEq magnesium added to the saline infusion (Mg group) in 30 head and neck cancer patients. Cis-AKI was defined as an increased serum creatinine (SCr) ≥ 0.3 mg/dl within 7 days and cis-AKD is an increased SCr ≥ 0.3 mg/dl between last SCr and baseline pre-chemotherapy SCr. RESULTS: The overall cisplatin tumor response rate and survival were comparable between groups. The baseline characteristics were comparable between groups, although SCr was lower in the controls (0.70 ± 0.17 versus 0.87 ± 0.17 mg/dl, P = 0.01). The incidence of cis-AKI was similar (4.6% versus 1.3%); however, the incidence of cis-AKD was higher for the control group (46.7% versus 6.7%, hazard ratio = 0.082, 95% confidence interval 0.008-0.79, P = 0.03). The time to develop cis-AKD was significantly shorter in the control group (P = 0.007). CONCLUSIONS: The magnesium-preloading regimen was safe and significantly showed a decreased incidence of cis-AKD. The encouraging results of our pilot study need to be confirmed in a large-scale randomized controlled trial.

Thirteen novel mutations of the replicated region of PKD1 in an Asian population.

BACKGROUND: Mutations of PKD1 are thought to account for approximately 85% of all mutations in autosomal dominant polycystic kidney disease (ADPKD). The search for PKD1 mutations has been hindered by both its large size and complicated genomic structure. To date, few mutations that affect the replicated segment of PKD1 have been described, and virtually all have been reported in Caucasian patients. METHODS: In the present study, we have used a long-range polymerase chain reaction (PCR)-based strategy previously developed by our laboratory to analyze exons in the replicated region of PKD1 in a population of 41 unrelated Thai and 6 unrelated Korean families with ADPKD. We have amplified approximately 3.5 and approximately 5 kb PKD1 gene-specific fragments (5'MR and 5'LR) containing exons 13 to 15 and 15 to 21 and performed single-stand conformation analysis (SSCA) on nested PCR products. RESULTS: Nine novel pathogenic mutations were detected, including six nonsense and three frameshift mutations. One of the deletions was shown to be a de novo mutation. Four potentially pathogenic variants, including one 3 bp insertion and three missense mutations, were also discovered. Two of the nonconservative amino acid substitutions were predicted to disrupt the three-dimensional structure of the PKD repeats. In addition, six polymorphisms, including two missense and four silent nucleotide substitutions, were identified. Approximately 25% of both the pathogenic and normal variants were found to be present in at least one of the homologous loci. CONCLUSION: To our knowledge, this is the first report of mutation analysis of the replicated region of PKD1 in a non-Caucasian population. The methods used in this study are widely applicable and can be used to characterize PKD1 in a number of ethnic groups using DNA samples prepared using standard techniques. Our data suggest that gene conversion may play a significant role in producing variability of the PKD1 sequence in this population. The identification of additional mutations will help guide the study of polycystin-1 and better help us to understand the pathophysiology of this common disease.

Polycystin-1, the gene product of PKD1, induces resistance to apoptosis and spontaneous tubulogenesis in MDCK cells.

The major form of autosomal dominant polycystic kidney disease (ADPKD) results from mutation of a gene (PKD1) of unknown function that is essential for the later stages of renal tubular differentiation. In this report, we describe a novel cell culture system for studying how PKD1 regulates this process. We show that expression of human PKD1 in MDCK cells slows their growth and protects them from programmed cell death. MDCK cells expressing PKD1 also spontaneously form branching tubules while control cells form simple cysts. Increased cell proliferation and apoptosis have been implicated in the pathogenesis of cystic diseases. Our study suggests that PKD1 may function to regulate both pathways, allowing cells to enter a differentiation pathway that results in tubule formation.

Mutation detection of PKD1 identifies a novel mutation common to three families with aneurysms and/or very-early-onset disease.

It is known that several of the most severe complications of autosomal-dominant polycystic kidney disease, such as intracranial aneurysms, cluster in families. There have been no studies reported to date, however, that have attempted to correlate severely affected pedigrees with a particular genotype. Until recently, in fact, mutation detection for most of the PKD1 gene was virtually impossible because of the presence of several highly homologous loci also located on chromosome 16. In this report we describe a cluster of 4 bp in exon 15 that are unique to PKD1. Forward and reverse PKD1-specific primers were designed in this location to amplify regions of the gene from exons 11-21 by use of long-range PCR. The two templates described were used to analyze 35 pedigrees selected for study because they included individuals with either intracranial aneurysms and/or very-early-onset disease. We identified eight novel truncating mutations, two missense mutations not found in a panel of controls, and several informative polymorphisms. Many of the polymorphisms were also present in the homologous loci, supporting the idea that they may serve as a reservoir for genetic variability in the PKD1 gene. Surprisingly, we found that three independently ascertained pedigrees had an identical 2-bp deletion in exon 15. This raises the possibility that particular genotypes may be associated with more-severe disease.