Magnetic bead-based proteomic technology to study paricalcitol effect in kidney transplant recipients

Systematic Review of the Treatment of Persistent Hyperparathyroidism Following Kidney Transplantation

Chronic kidney disease-mineral and bone disorder is one of the complications associated with chronic kidney disease. About 10-50% of patients following kidney transplantation have persistent hyperparathyroidism. Hypercalcaemic hyperparathyroidism has a negative impact on the kidney transplant outcome; therefore, it requires treatment. The data regarding the treatment of persistent hyperparathyroidism provided in scientific publications are divergent and contradictory. Therefore, the aim of our systematic review was to evaluate the efficacy of persistent hyperparathyroidism treatment in patients following kidney transplantation. The Cochrane, PubMed, and Scopus databases were browsed independently by two authors. The search strategy included controlled vocabulary and keywords. The effectiveness of calcitriol, paricalcitol, cinacalcet, and parathyroidectomy was compared and analysed. The mean calcium and parathormone (PTH) concentrations per patient in the group of paricalcitol increased by 1.27% and decreased by 35.14% (n = 248); in the group of cinacalcet decreased by 12.09% and 32.16% (n = 368); and in the group of parathyroidectomy decreased by 19.06% and 86.49% (n = 15) at the end of the study compared to the baseline (n = 244, n = 342 and n = 15), respectively. Paricalcitol, cinacalcet, and parathyroidectomy decreased the intact PTH level. Cinacalcet and parathyroidectomy lowered calcium levels in renal transplant patients with hypercalcaemia. Conversely, paricalcitol increased the serum calcium concentration. Cinacalcet seems to be a good candidate in the treatment of post-transplant hyperparathyroidism.

Exploring the potential effect of paricalcitol on markers of inflammation in de novo renal transplant recipients

Following a successful renal transplantation circulating markers of inflammation may remain elevated, and systemic inflammation is associated with worse clinical outcome in renal transplant recipients (RTRs). Vitamin D-receptor (VDR) activation is postulated to modulate inflammation and endothelial function. We aimed to explore if a synthetic vitamin D, paricalcitol, could influence systemic inflammation and immune activation in RTRs. Newly transplanted RTRs were included in an open-label randomized controlled trial on the effect of paricalcitol on top of standard care over the first post-transplant year. Fourteen pre-defined circulating biomarkers reflecting leukocyte activation, endothelial activation, fibrosis and general inflammatory burden were analyzed in 74 RTRs at 8 weeks (baseline) and 1 year post-engraftment. Mean changes in plasma biomarker concentrations were compared by t-test. The expression of genes coding for the same biomarkers were investigated in 1-year surveillance graft biopsies (n = 60). In patients treated with paricalcitol circulating osteoprotegerin levels increased by 0.19 ng/ml, compared with a 0.05 ng/ml increase in controls (p = 0.030). In graft tissue, a 21% higher median gene expression level of TNFRSF11B coding for osteoprotegerin was found in paricalcitol-treated patients compared with controls (p = 0.026). Paricalcitol treatment did not significantly affect the blood- or tissue levels of any other investigated inflammatory marker. In RTRs, paricalcitol treatment might increase both circulating and tissue levels of osteoprotegerin, a modulator of calcification, but potential anti-inflammatory treatment effects in RTRs are likely very modest. [NCT01694160 (2012/107D)]; [www.clinicaltrials.gov].

Interventions for preventing bone disease in kidney transplant recipients

BACKGROUND

People who have chronic kidney disease (CKD) have important changes to bone structure, strength, and metabolism. Children experience bone deformity, pain, and delayed or impaired growth. Adults experience limb and vertebral fractures, avascular necrosis, and pain. The fracture risk after kidney transplantation is four times that of the general population and is related to Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) occurring with end-stage kidney failure, steroid-induced bone loss, and persistent hyperparathyroidism after transplantation. Fractures may reduce quality of life and lead to being unable to work or contribute to community roles and responsibilities. Earlier versions of this review have found low certainty evidence for effects of treatment. This is an update of a review first published in 2005 and updated in 2007.

OBJECTIVES

This review update evaluates the benefits and harms of interventions for preventing bone disease following kidney transplantation.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 16 May 2019 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

RCTs and quasi-RCTs evaluating treatments for bone disease among kidney transplant recipients of any age were eligible.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial risks of bias and extracted data. Statistical analyses were performed using random effects meta-analysis. The risk estimates were expressed as a risk ratio (RR) for dichotomous variables and mean difference (MD) for continuous outcomes together with the corresponding 95% confidence interval (CI). The primary efficacy outcome was bone fracture. The primary safety outcome was acute graft rejection. Secondary outcomes included death (all cause and cardiovascular), myocardial infarction, stroke, musculoskeletal disorders (e.g. skeletal deformity, bone pain), graft loss, nausea, hyper- or hypocalcaemia, kidney function, serum parathyroid hormone (PTH), and bone mineral density (BMD).

MAIN RESULTS

In this 2019 update, 65 studies (involving 3598 participants) were eligible; 45 studies contributed data to our meta-analyses (2698 participants). Treatments included bisphosphonates, vitamin D compounds, teriparatide, denosumab, cinacalcet, parathyroidectomy, and calcitonin. Median duration of follow-up was 12 months. Forty-three studies evaluated bone density or bone-related biomarkers, with more recent studies evaluating proteinuria and hyperparathyroidism. Bisphosphonate therapy was usually commenced in the perioperative transplantation period (within 3 weeks) and regardless of BMD. Risks of bias were generally high or unclear leading to lower certainty in the results. A single study reported outcomes among 60 children and adolescents. Studies were not designed to measure treatment effects on fracture, death or cardiovascular outcomes, or graft loss.Compared to placebo, bisphosphonate therapy administered over 12 months in transplant recipients may prevent fracture (RR 0.62, 95% CI 0.38 to 1.01; low certainty evidence) although the 95% CI included the possibility that bisphosphonate therapy might make little or no difference. Fracture events were principally vertebral fractures identified during routine radiographic surveillance. It was uncertain whether any other drug class decreased fracture (low or very low certainty evidence). It was uncertain whether interventions for bone disease in kidney transplantation reduce all-cause or cardiovascular death, myocardial infarction or stroke, or graft loss in very low certainty evidence. Bisphosphonate therapy may decrease acute graft rejection (RR 0.70, 95% CI 0.55 to 0.89; low certainty evidence), while it is uncertain whether any other treatment impacts graft rejection (very low certainty evidence). Bisphosphonate therapy may reduce bone pain (RR 0.20, 95% CI 0.04 to 0.93; very low certainty evidence), while it was very uncertain whether bisphosphonates prevent spinal deformity or avascular bone necrosis (very low certainty evidence). Bisphosphonates may increase to risk of hypocalcaemia (RR 5.59, 95% CI 1.00 to 31.06; low certainty evidence). It was uncertain whether vitamin D compounds had any effect on skeletal, cardiovascular, death, or transplant function outcomes (very low certainty or absence of evidence). Evidence for the benefits and harms of all other treatments was of very low certainty. Evidence for children and young adolescents was sparse.

AUTHORS' CONCLUSIONS

Bisphosphonate therapy may reduce fracture and bone pain after kidney transplantation, however low certainty in the evidence indicates it is possible that treatment may make little or no difference. It is uncertain whether bisphosphonate therapy or other bone treatments prevent other skeletal complications after kidney transplantation, including spinal deformity or avascular bone necrosis. The effects of bone treatment for children and adolescents after kidney transplantation are very uncertain.

CYP3A4 is a crosslink between vitamin D and calcineurin inhibitors in solid organ transplant recipients: implications for bone health

The use of calcineurin inhibitors (CNIs) and vitamin D deficiency may contribute to the pathogenesis of post-transplant bone disease. CNIs and 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) are substrates of the drug-metabolizing enzyme CYP3A4. This review summarizes the indications for the use of activated vitamin D analogs in post-transplant care and the current knowledge on the impact of CNIs on bone. We searched for clinical evidence of the interaction between CNIs and 1,25(OH)₂D₃. We also provide an overview of the literature on the interplay between vitamin D metabolism and CYP3A4 in experimental and clinical settings and discuss its possible implications for solid organ transplant recipients. In conclusion, there is a body of evidence on the interplay between vitamin D and the drug-metabolizing enzyme CYP3A4, which may have therapeutic implications.

Evaluation of protease inhibitors containing tubes for MS-based plasma peptide profiling studies

BACKGROUND

Peptide profiling of biological fluids is a promising tool for biomarker discovery. Blood is an ideal entity for proteomic studies but it is subjected to a proteolytic activity that sets up just at the moment of phlebotomy. Intending to prevent this proteolytic activity, tubes containing protease inhibitors (PI) have been developed. In this study, we evaluated the effect on plasma peptide profile of using tubes containing PI and the evolution of this effect over time.

METHODS

Blood samples from ten subjects were drawn into conventional tubes containing ethylenediaminetetraacetic acid (EDTA) and tubes containing PI. Samples were processed at time "zero" and after 1, 2, 4, and 8 hr. Plasma peptide profiles were analyzed by magnetic bead based technology coupled to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry readout.

RESULTS

When comparing plasma peptide profile of blood samples collected into tubes containing PI with samples collected into conventional EDTA tubes, differences in the area of 13 peaks were detected at time "zero"; after 8 hr these differences tended to disappear. Moreover, bradykinin and C3- and C4-derived peptides were produced promptly after blood extraction when samples were collected into conventional EDTA tubes, and the use of PI prevented their generation.

CONCLUSION

Considering that time taken to process blood samples affects their peptide profile and a decrease in PI's effect occurs over time, it may be concluded that the use of tubes containing PI for blood collection may be advantageous in the context of research, but may have some limitations regarding clinical practice.

Urinary peptide profiling to differentiate between minimal change disease and focal segmental glomerulosclerosis

BACKGROUND

Minimal change disease (MCD) and primary focal segmental glomerulosclerosis (FSGS) are the main causes of primary idiopathic nephrotic syndrome in children and adults, with diagnosis being essential for the appropriate choice of therapy and requiring renal biopsy. However, the presence of only normal glomeruli on renal biopsy of FSGS patients may lead to the misclassification of these patients as having MCD. The aim of this study was to (i) compare the peptide profile of MCD and FSGS patients with that of a group of healthy subjects, (ii) generate and validate a class prediction model to classify MCD and FSGS patients and (ii) identify candidate biomarkers of these glomerular entities by analysis of the urinary peptidome.

METHODS

The urinary peptide profile was analyzed by magnetic bead-based technology combined with MALDI-TOF mass spectrometry in 44 patients diagnosed of MCD (n = 22) and FSGS (n = 22). The resulting spectra were compiled and analyzed using ClinProTools software.

RESULTS

A class prediction model was developed to differentiate MCD and FSGS patients. The validation of this model correctly classified 81.8% (9/11) of MCD patients and 72.7% (8/11) of FSGS patients. Moreover, the signal with m/z 1913.60, identified as a fragment of uromodulin, and the signal with m/z 2392.54, identified as a fragment of alpha-1-antitrypsin, showed higher and lower peak areas, respectively, in FSGS patients compared with MCD patients.

CONCLUSIONS

The simple, non-invasive technique described in the present study may be a useful tool to help clinicians by confirming diagnoses achieved by renal biopsy, thereby reducing misdiagnoses and avoiding the implementation of inappropriate therapies.