Genome-wide association study identifies susceptibility loci for IgA nephropathy.

We carried out a genome-wide association study of IgA nephropathy, a major cause of kidney failure worldwide. We studied 1,194 cases and 902 controls of Chinese Han ancestry, with targeted follow up in Chinese and European cohorts comprising 1,950 cases and 1,920 controls. We identified three independent loci in the major histocompatibility complex, as well as a common deletion of CFHR1 and CFHR3 at chromosome 1q32 and a locus at chromosome 22q12 that each surpassed genome-wide significance (P values for association between 1.59 × 10⁻²6 and 4.84 × 10⁻9 and minor allele odds ratios of 0.63-0.80). These five loci explain 4-7% of the disease variance and up to a tenfold variation in interindividual risk. Many of the alleles that protect against IgA nephropathy impart increased risk for other autoimmune or infectious diseases, and IgA nephropathy risk allele frequencies closely parallel the variation in disease prevalence among Asian, European and African populations, suggesting complex selective pressures.

IgA nephropathy: the presence of familial disease does not confer an increased risk for progression.

BACKGROUND: Immunoglobulin A (IgA) nephropathy is the most common form of glomerulonephritis worldwide. Familial and sporadic cases are recognized, and a locus associated with the familial form of the disease was mapped to chromosome 6. Recent data suggest the familial IgA nephropathy form may have a poorer outcome than the sporadic form. METHODS: We tested the hypothesis of unequal survival rates between the 2 forms of disease by analyzing time from biopsy to end-stage renal disease in patients of Italian ancestry; 589 patients with sporadic and 96 patients with familial IgA nephropathy. RESULTS: Overall 10- and 20-year renal survival probabilities of the cohort as a whole were 71% and 50%, respectively. Macroscopic hematuria was the modality of clinical presentation in 51% of patients with familial IgA nephropathy and 39% of patients with sporadic IgA nephropathy. At univariable analysis, the sporadic form of IgA nephropathy was associated significantly with increased risk for renal death. However, patients with the sporadic form tended to be more hypertensive and diagnosed later, with signs of more advanced renal disease than those with familial disease at baseline. In the regression model, form of disease lost any independent effect. Only male sex, lower baseline glomerular filtration rate, greater proteinuria, and histopathologic score proved to be independent predictors of disease progression. Treatment with steroids or angiotensin-converting enzyme inhibitors was associated with improved outcomes. CONCLUSION: Our study does not confirm that familial IgA nephropathy has a worse prognosis than the sporadic form. The similar renal phenotype may support a common pathogenic mechanism underlying familial and sporadic IgA nephropathy.

Gabapentin in the treatment of uremic itch: an index case and a pilot evaluation.

BACKGROUND: The prevalence of renal itch in patients on dialysis is approximately 30%, but its treatment is often ineffective. We describe an index case of a hemodialysis (HD) patient suffering from painful diabetic neuropathy (PDN) treated with gabapentin; the first administration of the drug led to the complete remission of the concomitant uremic pruritus. Subsequently, we report the results of a pilot evaluation aimed at testing the effectiveness and safety of low gabapentin doses in HD patients with uremic pruritus. METHODS: Five consecutive HD patients unresponsive to antihistamines received 4-week gabapentin treatment at a starting dose of 100 mg after every thrice-weekly HD, which was subsequently adjusted based on clinical response. Puritus severity was evaluated by means of a visual analogue scale (VAS) before each HD session on days 0, 2, 4, 7, 14, 21, 28 and 35. Safety was assessed using adverse event data. RESULTS: All patients experienced a rapid subjective improvement in pruritus, with the mean VAS score decreasing from 8.4-1.6 after the first drug administration. Three patients required a dose increase to 100 mg four times a week to obtain better itch control. Two patients experienced complete itch remission. CONCLUSION: Although a double-blind placebo-controlled clinical trial should be conducted to better elucidate the efficacy and toxicity of gabapentin in patients with uremic itch, our data suggest that gabapentin could be considered an effective and safe alternative treatment for uremic pruritus.

Engineering of coordinated up- and down-regulation of two glycosyltransferases of the O-glycosylation pathway in Chinese hamster ovary (CHO) cells.

Production of O-linked oligosaccharides that interact with selectins to mediate cell-cell adhesion occurs in one segment of a branched glycan biosynthesis network. Prior efforts to direct the branched pathway towards selectin-binding oligosaccharides by amplifying enzymes in this branch of the network have had limited success, suggesting that metabolic engineering to simultaneously inhibit the competing pathway may also be required. We report here the partial cloning of the CMP-sialic, acid:Galbeta1,3GalNAcalpha2,3-sialyltransferase (ST3Gal I) gene from Chinese hamster ovary (CHO) cells and the simultaneous inhibition of expression of CHO cell ST3Gal I gene and overexpression of the human UDP-GlcNAc:Galbeta1,3GalNAc-R beta1,6-N-acetylglucosaminyltransferase (C2GnT) gene. A tetracycline-regulated system adjoined to tricistronic expression technology allowed "one-step" transient manipulation of multiple enzyme activities in the O-glycosylation pathway of a previously established CHO cell line already engineered to express alpha1,3-fucosyltransferase VI (alpha1,3-Fuc-TVI). Tetracycline-regulated co-expression of a ST3Gal I fragment, cloned in the antisense orientation, and of C2GnT cDNA resulted in inhibition of the ST3Gal I enzymatic activity and increase in C2GnT activity which varied depending on the extent of tetracycline reduction in the cell culture medium. This simultaneous regulated inhibition and activation of the two key enzyme activities in the O-glycosylation pathway of mammalian cells is an important addition to the metabolic engineering field.

Uncoupling of protein-3 induces an uncontrolled uncoupling of mitochondria after expression in muscle derived L6 cells.

The uncoupling proteins (UCPs) are thought to uncouple oxidative phosphorylation in the mitochondria and thus generate heat. One of the UCP isoforms, UCP3, is abundantly expressed in skeletal muscle, the major thermogenic tissue in humans. UCP3 has been overexpressed at high levels in yeast systems, where it leads to the uncoupling of cell respiration, suggesting that UCP3 may indeed be capable of dissipating the mitochondrial proton gradient. This effect, however, was recently shown to be a consequence of the high level of expression and incorrect folding of the protein and not to its intrinsic uncoupling activity. In the present study, we investigated the properties of UCP3 overexpressed in a relevant mammalian host system such as the rat myoblast L6 cell line. UCP3 was expressed in relatively low levels (< 1 microg x mg(-1) membrane protein) with the help of an adenovirus vector. Immunofluorescence microscopy of transduced L6 cells showed that UCP3 was expressed in more than 90% of the cells and that its staining pattern was characteristic for mitochondrial localization. The oxygen consumption of L6 cells under nonphosphorylating conditions increased concomitantly with the levels of UCP3 expression. However, uncoupling was associated with an inhibition of the maximal respiratory capacity of mitochondria and was not affected by purine nucleotides and free fatty acids. Moreover, recombinant UCP3 was resistant to Triton X-100 extraction under conditions that fully solubilize membrane bound proteins. Thus, UCP3 can be uniformly overexpressed in the mitochondria of a relevant muscle-derived cell line resulting in the expected increase of mitochondrial uncoupling. However, our data suggest that the protein is present in an incompetent conformation.