Cystatin C in children on chronic hemodialysis

Levels of cystatin C in low- and high-flux hemodialysis in children with end-stage renal disease

BACKGROUND

Cystatin-C (CyC) is a middle molecule that is freely filtered at the glomerulus and almost completely reabsorbed by the proximal tubules. The aim of this study was to evaluate serum CyC and its reduction ratio as a biomarker for assessing the adequacy of the hemodialysis (HD) sessions in children with end-stage renal disease on maintenance HD. We also compared levels of CyC in patients on low-flux HD (LFH) and high-flux HD (HFH).

METHODS

Forty patients were included in the study and divided into two groups, with one group (16 patients) receiving HFH and the other group receiving LFH (24 patients) (high-flux and low-flux polysulfone filters, respectively). Before and after each dialysis session serum CyC and beta-2-microglobulin (B2M) levels were measured using an ELISA technique, and routine laboratory tests were performed for each patient.

RESULTS

Pre-dialytic levels of CyC were significantly lower in the patients receiving HFH than in those receiving LFH (7.33 ± 1.35 vs. 9.73 ± 0.93, respectively; p < 0.0001). In the HFH group, post-dialytic levels of serum CyC were significantly lower than pre-dialytic levels (4.49 ± 0.71 vs. 7.33 ± 1.35, respectively; p < 0.0001). The reduction ratio (RR) of CyC was significantly higher in the HFH group than in the LFH group (38.2 ± 3.91 vs. -6.49 ± 5.05, respectively; p < 0.0001). Serum CyC level significantly correlated with B2M, urea and creatinine levels in both the LFH and HFH groups, whereas its RR significantly correlated with the RRs of urea, creatinine, and B2M in the HFH group.

CONCLUSION

The results of our study emphasize the role of CyC as a good marker for assessing the adequacy of HD sessions in children on HFH and show that the CyC RR may be used as an index of middle-molecule toxin clearance following HFH sessions.

Effect of Kidney Function on Drug Kinetics and Dosing in Neonates, Infants, and Children

Neonates, infants, and children differ from adults in many aspects, not just in age, weight, and body composition. Growth, maturation and environmental factors affect drug kinetics, response and dosing in pediatric patients. Almost 80% of drugs have not been studied in children, and dosing of these drugs is derived from adult doses by adjusting for body weight/size. As developmental and maturational changes are complex processes, such simplified methods may result in subtherapeutic effects or adverse events. Kidney function is impaired during the first 2 years of life as a result of normal growth and development. Reduced kidney function during childhood has an impact not only on renal clearance but also on absorption, distribution, metabolism and nonrenal clearance of drugs. 'Omics'-based technologies, such as proteomics and metabolomics, can be leveraged to uncover novel markers for kidney function during normal development, acute kidney injury, and chronic diseases. Pharmacometric modeling and simulation can be applied to simplify the design of pediatric investigations, characterize the effects of kidney function on drug exposure and response, and fine-tune dosing in pediatric patients, especially in those with impaired kidney function. One case study of amikacin dosing in neonates with reduced kidney function is presented. Collaborative efforts between clinicians and scientists in academia, industry, and regulatory agencies are required to evaluate new renal biomarkers, collect and share prospective pharmacokinetic, genetic and clinical data, build integrated pharmacometric models for key drugs, optimize and standardize dosing strategies, develop bedside decision tools, and enhance labels of drugs utilized in neonates, infants, and children.

Solving the Measurement Problem and then Steppin' Out over the Line Riding the Rarest Italian: Crossing the Streams to Retrieve Stable Bioactivity in Majorana Bound States of Dialy zed Human Platelet Lysates

Exhaustive dialysis (ED) of lysed human platelets against dilute HCl yields stable angiogenic activity. Dialysis against a constrained external volume, with subsequent relaxation of the separation upon opening the dialysis bag, produces material able to maintain phenotypes and viability of human cells in culture better than ED material. Significant graded changes in MTT viability measurement tracked with external volume. The presence of elements smaller than the MW cutoff, capable of setting up cycling currents initiated by oriented flow of HCl across the membrane, suggests that maturation of bioactivity occurred through establishment of a novel type of geometric phase. These information-rich bound states fit recent descriptions of topological order and Majorana fermions, suggesting relevance in testing Penrose and Hameroff's theory of Orchestrated Objective Reduction, under conditions more general, and on finer scales, than those dependent on tubulin protein. The Berry curvature appears to be a good tool for building a general field theory of physiologic stress dependent on the quantum Hall effect. A new form of geometric phase, and an associated "geometric" quantum Hall effect underlying memory retrieval, dependent on the rate of path traversal and reduction from more than two initial field influences is described.

Comparison of cystatin C and Beta-2-microglobulin kinetics in children on maintenance hemodialysis

Middle-molecules (MM) are not monitored in children on hemodialysis (HD), but are accumulated and increase the risk of cardiovascular disease and mortality. Molecular properties of Cystatin C (CyC), 13 kDa, potentially make it a preferred MM marker over Beta-2-Microglobulin (B2M), 12 kDa. We compared CyC and B2M kinetics to investigate if CyC can be used as preferred MM marker. CyC (mg/L) and B2M (μg/mL) were measured in 21 low-flux HD sessions in seven children. Blood samples were taken at HD start (pre), 1 and 2 hours into HD and at end of HD (post) for all sessions and 60 minutes after the first HD (Eq). PreCyC (9.85 ± 2.15) did not differ (P > 0.05) from postCyC (10.04 ± 2.83). PostB2M (38.87 ± 7.12) was higher (P < 0.05) than preHD B2M (33.27 ± 7.41). There was no change in CyC at 1 and 2 hours into HD, while B2M progressively increased. CyC or B2M changes did not significantly correlate with spKt/V (2.09 ± 0.86), ultrafiltration (4.61 ± 1.98%) or HD duration (218 ± 20 minutes). EqCyC was not different from postCyC (11.07 ± 3.14 vs. 10.71 ± 2.85, P > 0.05), while EqB2M was lower than postB2M (36.48 ± 7.68 vs. 41.09 ± 8.99, P < 0.05). MMs as represented by B2M and CyC are elevated in children on standard HD. Intensified HD modalities would be needed for their removal. B2M is affected by the dialytic process with a rise during HD independent of ultrafiltration and decrease 1 hour after, while CyC remains unchanged. We suggest that CyC be used as preferred marker of MM removal and as a marker of adequacy of intensified HD regimens.