Post-infectious Proliferative Glomerulonephritis with Monoclonal Immunoglobulin G Deposits Associated with Complement Factor H Mutation

A 55-year-old man developed rapidly progressive glomerulonephritis and nephrotic syndrome. A kidney biopsy specimen showed diffuse proliferative and crescentic glomerulonephritis with monoclonal IgG1κ, humps, and nephritis-associated plasmin receptor, indicating infection-associated proliferative glomerulonephritis with monoclonal immunoglobulin G deposits (PGNMID). Despite dialysis-dependent renal failure, symptomatic therapy resulted in spontaneous recovery of the renal function, mimicking post-infectious glomerulonephritis (PIGN). A heterozygous complement factor H mutation was detected by comprehensive genetic testing of alternative pathway regulatory genes, which might lead to persistent infection-triggered alternative pathway activation and account for severe glomerulonephritis. Post-infectious PGNMID and PIGN might share common clinical presentations and pathogenesis related to the complement pathway.

Effects of Cardiovascular Events on End-Stage Renal Disease and Mortality in Patients With Chronic Kidney Disease Before Dialysis

Cardiovascular events (CVEs) are major complications in patients with chronic kidney disease (CKD). However, few studies have investigated the effects of CVEs on end-stage renal disease (ESRD) and mortality of pre-dialysis patients. We followed 377 CKD patients who were at stage ≥G3 at first clinic visit in the Shuuwa General Hospital between April 2005 and July 2014. After taking baseline patient data, we evaluated renal survival rates and all-cause and CVE-related mortality in patients with CVEs [(+)CVEs] and without CVEs [(-)CVEs]. A total of 99 CVEs occurred in 93 study patients (57.0% cardiac events, 43.0% cerebrovascular events, and 6.5% peripheral artery disease events). During the study period, 127 patients reached ESRD over a median of 4.51 years' follow-up. Kaplan-Meier analysis found longer renal survival rates in the (-)CVEs group compared with the (+)CVEs group. Forty patients died during the study period over a median of 5.43 years' follow-up. Survival rates for all-cause and CVE-related mortality of (-)CVEs patients were higher than in (+)CVEs patients. After adjustment for sex, age, current smoking, blood pressure, diabetes, estimated glomerular filtration rate, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, left ventricular hypertrophy, body mass index, albumin, hemoglobin, calcium, phosphate, C-reactive protein, and spot urine protein, the occurrence of CVEs was still a significant risk factor for ESRD (HR 1.516, P = 0.017) and all-cause mortality (HR 7.871, P < 0.001). Our findings suggest that the occurrence of CVEs is a potent risk factor for ESRD and mortality in CKD patients before dialysis.

Early response to erythropoiesis-stimulating agents in non-dialysis chronic kidney disease patients

BACKGROUND

Renal anemia complicated with chronic kidney disease is usually treated with erythropoiesis-stimulating agents (ESAs). However, few studies have compared the early response of hemoglobin (Hb) to different kinds of ESAs.

METHODS

The effects of three types of ESAs-epoetin alfa or beta (EPO), darbepoetin alfa (DPO), and epoetin beta pegol (EPObp)-on renal anemia were followed in 416 pre-dialysis chronic kidney disease (CKD) patients. After the initial 12-week administration of ESAs, ΔHb/ESA dose/kg was calculated as an index of efficacy of each ESA. Furthermore, independent variables associated with ΔHb/ESA dose/kg (dependent variable) were determined using multiple linear regression analysis. The ten independent variables selected for analysis were: presence of diabetic nephropathy, estimated glomerular filtration rate (eGFR), Hb, albumin, iron (Fe), transferrin saturation (TSAT), ferritin, phosphate (P), intact parathyroid hormone (iPTH), and C-reactive protein.

RESULTS

The efficacy of DPO and EPObp were similar and higher than EPO. TSAT was most strongly correlated with ΔHb/EPO dose/kg in all three types of ESAs. Other significant independent factors were Hb, albumin, P, iPTH, and diabetic nephropathy in the EPO group, eGFR in the DPO group, and Fe in the EPObp group. The adjusted coefficient of determination (R (2)) ranged from 0.415 to 0.520 in the three ESA groups.

CONCLUSIONS

The study results suggest that TSAT is the best predictor of the initial 12-week responsiveness to ESA, irrespective of the type. Variables not investigated in this study also affect responsiveness to ESA in Japanese pre-dialysis CKD patients.

Gene replacement analysis of the Streptomyces virginiae barA gene encoding the butyrolactone autoregulator receptor reveals that BarA acts as a repressor in virginiamycin biosynthesis

Virginiae butanolides (VBs), which are among the butyrolactone autoregulators of Streptomyces species, act as a primary signal in Streptomyces virginiae to trigger virginiamycin biosynthesis and possess a specific binding protein, BarA. To clarify the in vivo function of BarA in the VB-mediated signal pathway that leads to virginiamycin biosynthesis, two barA mutant strains (strains NH1 and NH2) were created by homologous recombination. In strain NH1, an internal 99-bp EcoT14I fragment of barA was deleted, resulting in an in-frame deletion of 33 amino acid residues, including the second helix of the probable helix-turn-helix DNA-binding motif. With the same growth rate as wild-type S. virginiae on both solid and liquid media, strain NH1 showed no apparent changes in its morphological behavior, indicating that the VB-BarA pathway does not participate in morphological control in S. virginiae. In contrast, virginiamycin production started 6 h earlier in strain NH1 than in the wild-type strain, demonstrating for the first time that BarA is actively engaged in the control of virginiamycin production and implying that BarA acts as a repressor in virginiamycin biosynthesis. In strain NH2, an internal EcoNI-SmaI fragment of barA was replaced with a divergently oriented neomycin resistance gene cassette, resulting in the C-terminally truncated BarA retaining the intact helix-turn-helix motif. In strain NH2 and in a plasmid-integrated strain containing both intact and mutated barA genes, virginiamycin production was abolished irrespective of the presence of VB, suggesting that the mutated BarA retaining the intact DNA-binding motif was dominant over the wild-type BarA. These results further support the hypothesis that BarA works as a repressor in virginiamycin production and suggests that the helix-turn-helix motif is essential to its function. In strain NH1, VB production was also abolished, thus indicating that BarA is a pleiotropic regulatory protein controlling not only virginiamycin production but also autoregulator biosynthesis.