Efficiency of delivery observed treatment in hemodialysis patients: the example of the native vitamin D therapy

Osteoporosis in Patients with Chronic Kidney Diseases: A Systemic Review

Chronic kidney disease (CKD) is associated with the development of mineral bone disorder (MBD), osteoporosis, and fragility fractures. Among CKD patients, adynamic bone disease or low bone turnover is the most common type of renal osteodystrophy. The consequences of CKD-MBD include increased fracture risk, greater morbidity, and mortality. Thus, the goal is to prevent the occurrences of fractures by means of alleviating CKD-induced MBD and treating subsequent osteoporosis. Changes in mineral and humoral metabolism as well as bone structure develop early in the course of CKD. CKD-MBD includes abnormalities of calcium, phosphorus, PTH, and/or vitamin D; abnormalities in bone turnover, mineralization, volume, linear growth, or strength; and/or vascular or other soft tissue calcification. In patients with CKD-MBD, using either DXA or FRAX to screen fracture risk should be considered. Biomarkers such as bALP and iPTH may assist to assess bone turnover. Before initiating an antiresorptive or anabolic agent to treat osteoporosis in CKD patients, lifestyle modifications, such as exercise, calcium, and vitamin D supplementation, smoking cessation, and avoidance of excessive alcohol intake are important. Managing hyperphosphatemia and SHPT are also crucial. Understanding the complex pathogenesis of CKD-MBD is crucial in improving one's short- and long-term outcomes. Treatment strategies for CKD-associated osteoporosis should be patient-centered to determine the type of renal osteodystrophy. This review focuses on the mechanism, evaluation and management of patients with CKD-MBD. However, further studies are needed to explore more details regarding the underlying pathophysiology and to assess the safety and efficacy of agents for treating CKD-MBD.

Vitamin D in Chronic Kidney Disease and Dialysis Patients

Vitamin D deficiency (<20 ng/mL) and insufficiency (20–29 ng/mL) are common among patients with chronic kidney disease (CKD) or undergoing dialysis. In addition to nutritional and sunlight exposure deficits, factors that affect vitamin D deficiency include race, sex, age, obesity and impaired vitamin D synthesis and metabolism. Serum 1,25(OH)₂D levels also decrease progressively because of 25(OH)D deficiency, together with impaired availability of 25(OH)D by renal proximal tubular cells, high fibroblast growth factor (FGF)-23 and decreased functional renal tissue. As in the general population, this condition is associated with increased morbidity and poor outcomes. Together with the progressive decline of serum calcitriol, vitamin D deficiency leads to secondary hyperparathyroidism (SHPT) and its complications, tertiary hyperparathyroidism and hypercalcemia, which require surgical parathyroidectomy or calcimimetics. Kidney Disease Outcomes Quality Initiative (KDOQI) and Kidney Disease Improving Global Outcomes (KDIGO) experts have recognized that vitamin D insufficiency and deficiency should be avoided in CKD and dialysis patients by using supplementation to prevent SHPT. Many vitamin D supplementation regimens using either ergocalciferol or cholecalciferol daily, weekly or monthly have been reported. The benefit of native vitamin D supplementation remains debatable because observational studies suggest that vitamin D receptor activator (VDRA) use is associated with better outcomes and it is more efficient for decreasing the serum parathormone (PTH) levels. Vitamin D has pleiotropic effects on the immune, cardiovascular and neurological systems and on antineoplastic activity. Extra-renal organs possess the enzymatic capacity to convert 25(OH)D to 1,25(OH)₂D. Despite many unanswered questions, much data support vitamin D use in renal patients. This article emphasizes the role of native vitamin D replacement during all-phases of CKD together with VDRA when SHPT persists.

Impact of the type of dialysis membranes on the circulating concentration of markers of vitamin D metabolism

INTRODUCTION

Kidney Disease Improving Global Outcomes (KDIGO) guidelines recommend vitamin D supplementation in hemodialyzed patients to monitor 25(OH)-vitamin D 25(OH)D levels. However, patient-to-patient inconsistency can be observed in response to the treatment. In this study, we aimed to evaluate the impact of the dialysis membrane on 25(OH)D, albumin (Alb) and vitamin D-binding protein (VDBP), the major players of vitamin D transport and storage.

MATERIAL AND METHODS

Alb (Cobas), VDBP (R&amp;D) and 25(OH)D (liquid chromatography-tandem mass spectrometry) were measured in 75 patients before and after a 4-hour dialysis session. Ten dialysis membranes were used: FX10, FX80, FX800, BK-2.1F, BG-2.1U, Rexeed 15 A, Rexeed 21 A, TS 1.8 SL and TS 2.1 SL manque la ELISIO 21H. Accordingly, 13 patients were dialyzed with membranes possessing high adsorption and high cut-off properties (BK), 17 with membranes possessing high adsorption but usual cut-off properties (BG) and all the remaining 45 patients with polysufone (PS) membranes with usual adsorptive and cut-off properties. Among these 45 patients treated with PS, we compared those treated by classical dialysis (HD) (n = 14) and hemodiafiltration (HDF) (n = 31). Results were corrected for total extracellular volume to take into consideration the hemoconcentration after dialysis.

RESULTS

The 3 analytes showed a decreased concentration after the dialysis session. The decrease of ALB, VDBP and 25(OH)D was similar with the adsorptive (BG) and PS membranes. However, patients treated with adsorptive and high cut-off membrane (BK) presented a significantly higher decrease values of Alb (-9.6%[-15.1; -7.5]), of VDBP (-20.6%[-36.6; -17.2] and 25(OH)D (-17%[-27.3; -12.3]) compared to other membranes (BG and PS).When we limited our study to PS membranes, we did not observe any significant difference between the HD or HDF modalities in the decrease for any of the studied parameters.

CONCLUSIONS

A significant loss of Alb, VDBP and 25(OH)D occurs after a dialysis session. This loss is significantly more important when patients are dialyzed with high adsorption and high cut-off dialysis membranes.