Zebrafish as an in vivo screening tool to establish PARP inhibitor efficacy.

Double strand break (DSB) repair through Homologous Recombination (HR) is essential in maintaining genomic stability of the cell. Mutations in the HR pathway confer an increased risk for breast, ovarian, pancreatic and prostate cancer. PARP inhibitors (PARPi) are compounds that specifically target tumours deficient in HR. Novel PARPi are constantly being developed, but research is still heavily focussed on in vitro data, with mouse xenografts only being used in late stages of development. There is a need for assays that can: 1) provide in vivo data, 2) early in the development process of novel PARPi, 3) provide fast results and 4) at an affordable cost. Here we propose a combination of in vivo zebrafish assays to accurately quantify PARP inhibitor efficacy. We showed that PARPi display functional effects in zebrafish, generally correlating with their PARP trapping capacities. Furthermore, we displayed how olaparib mediated radiosensitization is conserved in our zebrafish model. These assays could aid the development of novel PARPi by providing early in vivo data. In addition, using zebrafish allows for high-throughput testing of combination therapies in search of novel treatment strategies.

Phosphorus metabolism in peritoneal dialysis- and haemodialysis-treated patients.

BACKGROUND: Phosphorus control is generally considered to be better in peritoneal dialysis (PD) patients as compared with haemodialysis (HD) patients. Predialysis phosphorus concentrations are misleading as a measure of phosphorus exposure in HD, as these neglect significant dialysis-related fluctuations. METHODS: Parameters of mineral metabolism, including parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF-23), were determined in 79 HD and 61 PD patients. In PD, phosphorus levels were determined mid-morning. In HD, time-averaged phosphorus concentrations were modelled from measurements before and after the mid-week dialysis session. Weekly renal, dialytic and total phosphorus clearances as well as total mass removal were calculated from urine and dialysate collections. RESULTS: Time-averaged serum phosphorus concentrations in HD (3.5 ± 1.0 mg/dL) were significantly lower than the mid-morning concentrations in PD (5.0 ± 1.4 mg/dL, P < 0.0001). In contrast, predialysis phosphorus concentrations (4.6 ± 1.4 mg/dL) were not different from PD. PTH and FGF-23 levels were significantly higher in PD. Despite higher residual renal function, total phosphorus clearance was significantly lower in PD (P < 0.0001). Total phosphorus mass removal, conversely, was significantly higher in PD (P < 0.05). CONCLUSIONS: Our data suggest that the time-averaged phosphorus concentrations in patients treated with PD are higher as compared with patients treated with HD. Despite a better preserved renal function, total phosphorus clearance is lower in patients treated with PD. Additional studies are needed to confirm these findings in a population with a different demographic profile and dietary background and to define clinical implications.

Impact of early parenteral nutrition on metabolism and kidney injury.

A poor nutritional state and a caloric deficit associate with increased morbidity and mortality, but a recent multicenter, randomized controlled trial found that early parenteral nutrition to supplement insufficient enteral nutrition increases morbidity in the intensive care unit, including prolonging the duration of renal replacement therapy, compared with withholding parenteral nutrition for 1 week. Whether early versus late parenteral nutrition impacts the incidence and recovery of AKI is unknown. Here, we report a prespecified analysis from this trial, the Early Parenteral Nutrition Completing Enteral Nutrition in Adult Critically Ill Patients (EPaNIC) study. The timing of parenteral nutrition did not affect the incidence of AKI, but early initiation seemed to slow renal recovery in patients with stage 2 AKI. Early parenteral nutrition did not affect the time course of creatinine and creatinine clearance but did increase plasma urea, urea/creatinine ratio, and nitrogen excretion beginning on the first day of amino acid infusion. In the group that received late parenteral nutrition, infusing amino acids after the first week also increased ureagenesis. During the first 2 weeks, ureagenesis resulted in net waste of 63% of the extra nitrogen intake from early parenteral nutrition. In conclusion, early parenteral nutrition does not seem to impact AKI incidence, although it may delay recovery in patients with stage 2 AKI. Substantial catabolism of the extra amino acids, which leads to higher levels of plasma urea, might explain the prolonged duration of renal replacement therapy observed with early parenteral nutrition.

Prevalence and determinants of anemia in the immediate postkidney transplant period.

At the time of renal transplantation, erythropoiesis-stimulating agents and iron supplementation are routinely discontinued in the prospect of recovery of renal function. This recovery, however, is often delayed and suboptimal. In addition, blood loss because of frequent diagnostic phlebotomies may be substantial. Renal transplant recipients may thus be considered at high risk of anemia in the immediate post-transplant period. We performed a single-center observational study, including 391 recipients of a single kidney. Hemoglobin levels and parameters of iron metabolism were monitored during the immediate post-transplant period, i.e., the first 3 months after transplantation. Hemoglobin levels decreased by 3.8 ± 1.5 g/dl to reach a nadir of 9.1 ± 1.2 g/dl at day 7. Transient severe anemia was observed in 91.3% of the patients. Donor age, gender, renal diagnosis of polycystic disease, pretransplant hemoglobin and ferritin level, estimated glomerular filtration rate at month 3, and duration of initial hospitalization were observed to be independently associated with the hemoglobin level at month 3. Transient severe anemia is an almost universal observation in incident renal transplant recipients. Poor graft function, high donor age, and low iron stores are independently associated with low hemoglobin levels at month 3.

Fibroblast growth factor-23 in early chronic kidney disease: additional support in favor of a phosphate-centric paradigm for the pathogenesis of secondary hyperparathyroidism.

BACKGROUND AND OBJECTIVES: The discovery of fibroblast growth factor-23 (FGF-23) and the elucidation of its function as a phosphaturic and 1,25(OH)2VitD counter-regulatory hormone provides a new conceptual framework for the understanding of the pathogenesis of secondary hyperparathyroidism. This study aims to elucidate the complex associations between FGF-23, parathyroid hormone (PTH), 1,25(OH)2D, and phosphate in patients with early-stage chronic kidney disease (CKD) and to provide clinical evidence in favor of the new phosphate-centric paradigm for the pathogenesis of secondary hyperparathyroidism. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Serum biointact PTH and FGF-23, 25(OH)D, 1,25(OH)2D, calcium, phosphate, 24-hour urine excretion of phosphate and calcium, and urinary fractional excretion of phosphate were determined in a cross-sectional study including 125 patients with CKD stages 1 to 3. RESULTS: Serum phosphate levels showed an inverse association with estimated GFR (eGFR), but were within the normal range in all but one patient. FGF-23 and PTH were inversely associated with eGFR, even in the subgroup of patients with CKD stages 1 and 2. High FGF-23 levels were significantly more prevalent than high PTH levels. The urinary fractional excretion of phosphate was highest in patients with both a high serum FGF-23 and PTH level. Increased FGF-23 and phosphate and decreased 25(OH)D were independently associated with decreased 1,25(OH)2D. CONCLUSIONS: Our data are in favor of the new paradigm for the pathogenesis of secondary hyperparathyroidism according to which a reduced phosphate excretion capacity is the principal abnormality that initiates secondary hyperparathyroidism.

Immunogenicity of a standard trivalent influenza vaccine in patients on long-term hemodialysis: an open-label trial.

BACKGROUND: Disturbances in acquired immunity are considered to be responsible, at least in part, for the high infection rate and inadequate response to vaccinations observed in hemodialysis (HD) patients. The present prospective trial aimed to: (1) evaluate the immunogenicity of a standard influenza vaccine in HD patients, and (2) identify determinants of the immune response. STUDY DESIGN: Prospective interventional open-label study. SETTING & PARTICIPANTS: 201 long-term HD patients and 41 healthy volunteers. INTERVENTION: Vaccination with a standard trivalent inactivated influenza vaccine. OUTCOMES: The primary outcome was seroprotection rate, defined as percentage of participants with an antibody titer of 40 or greater 1 month after vaccination. MEASUREMENTS: All antibody titers were determined in duplicate by using the hemagglutination inhibition assay. Regression analyses were performed to investigate the association between demographics, uremic retention solutes (including p-cresol), inflammation, nutrition, iron status, trace elements, and immune response in HD patients. RESULTS: More than 80% of HD patients showed seroprotection after vaccination. The immune response of HD patients was similar to that of healthy volunteers. Booster vaccination did not improve the immune response. High serum ferritin level was the only parameter independently associated with a better vaccination-induced antibody response in HD patients. LIMITATIONS: A high seroprotection rate at baseline undermined the power to identify clinical determinants of the immune response. CONCLUSIONS: Influenza vaccination is as efficacious in HD patients as in healthy volunteers. With the exception of serum ferritin, none of the investigated parameters of nutrition, inflammation, and dialysis adequacy had a significant impact on the immune response. Our data support annual vaccination of HD patients and question the clinical relevance of disturbances in acquired immunity in contemporary HD patients.

Calcium metabolism in the early posttransplantation period.

BACKGROUND AND OBJECTIVES: Information on the time course of serum calcium levels after renal transplantation is scanty, especially in the early posttransplantation period. Both the abrupt cessation of calcium-containing phosphorus binders and vitamin D (analogs) at the time of surgery and the recovery of renal function may be hypothesized to affect serum calcium levels in this period. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: In this prospective observational study, biointact parathyroid hormone, calcidiol, calcitriol, calcium, and phosphorus levels were monitored in 201 renal transplant recipients at the time of transplantation and 3 mo thereafter. In addition, the serum calcium nadir and peak in each individual patient within this time frame were identified and the urinary fractional calcium excretion was determined at month 3. RESULTS: Serum calcium levels followed a biphasic pattern with a significant decline during the first postoperative week, followed by a significant increase. High pretransplantation parathyroid hormone levels protect against hypocalcemia within the first postoperative week but put patients at risk for hypercalcemia later. These complications, occurring in 41 and 14% of the patients, respectively, most probably reflect inappropriate calcium release from the skeleton, rather than inappropriate renal calcium handling. CONCLUSIONS: Our data indicate that both hypo- and hypercalcemia are prevalent in the early posttransplantation period. Pretransplantation parathyroid function is an important predictor of posttransplantation calcium levels.

Recovery of hyperphosphatoninism and renal phosphorus wasting one year after successful renal transplantation.

BACKGROUND AND OBJECTIVES: In the first months after successful kidney transplantation, hypophosphatemia and renal phosphorus wasting are common and related to inappropriately high parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF-23) levels. Little is known about the long-term natural history of renal phosphorus homeostasis in renal transplant recipients. DESIGN, SETTING, PARTICIPANTS: We prospectively followed parameters of mineral metabolism (including full-length PTH and FGF-23) in 50 renal transplant recipients at the time of transplantation (Tx), at month 3 (M3) and at month 12 (M12). Transplant recipients were (1:1) matched for estimated GFR with chronic kidney disease (CKD) patients. RESULTS: FGF-23 levels (Tx: 2816 [641 to 10665] versus M3: 73 [43 to 111] versus M12: 56 [34 to 78] ng/L, median [interquartile range]) and fractional phosphorus excretion (FE(phos); M3: 45 +/- 19% versus M12: 37 +/- 13%) significantly declined over time after renal transplantation. Levels 1 yr after transplantation were similar to those in CKD patients (FGF-23: 47 [34 to 77] ng/L; FE(phos) 35 +/- 16%). Calcium (9.1 +/- 0.5 versus 8.9 +/- 0.3 mg/dl) and PTH (27.2 [17.0 to 46.0] versus 17.5 [11.7 to 24.4] ng/L) levels were significantly higher, whereas phosphorus (3.0 +/- 0.6 versus 3.3 +/- 0.6 mg/dl) levels were significantly lower 1 yr after renal transplantation as compared with CKD patients. CONCLUSIONS: Data indicate that hyperphosphatoninism and renal phosphorus wasting regress by 1 yr after successful renal transplantation.

Calcium requirements after parathyroidectomy in patients with refractory secondary hyperparathyroidism.

BACKGROUND/AIMS: Calcium supplements are often required following successful parathyroidectomy (PTX) in order to prevent overt hypocalcemia. The current study aims to quantify these calcium needs and to identify predictors of a high calcium need present at the time of surgery. METHODS: Charts of 42 patients with chronic kidney disease stage 5D, who underwent a successful subtotal PTX, were reviewed in detail. Biochemical indices of mineral metabolism available within a time frame of 4 weeks before and 6 weeks after the surgery were registered. Details concerning active vitamin D (1-alpha-calcidiol and calcitriol) and calcium supplementation were recorded as well. RESULTS: Serum calcium, phosphorus and PTH levels declined whereas total alkaline phosphatase levels increased significantly in the early post-PTX period. Transient hypocalcemia was observed in 83% of the patients. The median daily postoperative elemental calcium requirements amounted to 3.2 g during week 1, and declined to 2.4 g during week 6. A high preoperative PTH level and a low serum calcium level were identified as independent predictors of a high postoperative calcium need. CONCLUSION: Substantial amounts of elemental calcium are required following successful subtotal PTX in order to avoid frank hypocalcemia, especially in patients with a high PTH level and a low calcium level before surgery.