Renal Osteodystrophy-Time for Common Nomenclature

Pathophysiology of chronic kidney disease-mineral bone disorder (CKD-MBD): from adaptive to maladaptive mineral homeostasis

Chronic kidney disease-mineral bone disorder (CKD-MBD) is a multifaceted condition commonly seen in people with reduced kidney function. It involves a range of interconnected issues in mineral metabolism, bone health and cardiovascular calcification, which are linked to a lower quality of life and shorter life expectancy. Although various epidemiological studies show that the laboratory changes defining CKD-MBD become more common as the glomerular filtration rate declines, the pathophysiology of CKD-MBD is still largely unexplained. We herein review the current understanding of CKD-MBD, provide a conceptual framework to understand this syndrome, and review the genetic and environmental factors that may influence the clinical manifestation of CKD-MBD. However, a deeper understanding of the pathophysiology of CKD-MBD is needed to understand the phenotype variability and the relative contribution to organ damage of factors involved in CKD-MBD to develop more effective interventions to improve outcomes in patients with CKD.

Application of artificial intelligence to chronic kidney disease mineral bone disorder

The global derangement of mineral metabolism that accompanies chronic kidney disease (CKD-MBD) is a major driver of the accelerated mortality for individuals with kidney disease. Advances in the delivery of dialysis, in the composition of phosphate binders, and in the therapies directed towards secondary hyperparathyroidism have failed to improve the cardiovascular event profile in this population. Many obstacles have prevented progress in this field including the incomplete understanding of pathophysiology, the lack of clinical targets for early stages of chronic kidney disease, and the remarkably wide diversity in clinical manifestations. We describe in this review a novel approach to CKD-MBD combining mathematical modelling of biologic processes with machine learning artificial intelligence techniques as a tool for the generation of new hypotheses and for the development of innovative therapeutic approaches to this syndrome. Clinicians need alternative targets of therapy, tools for risk profile assessment, and new therapies to address complications early in the course of disease and to personalize therapy to each individual. The complexity of CKD-MBD suggests that incorporating artificial intelligence techniques into the diagnostic, therapeutic, and research armamentarium could accelerate the achievement of these goals.

Osteocytic Sclerostin Expression as an Indicator of Altered Bone Turnover

Renal osteodystrophy (ROD) is a complex and serious complication of chronic kidney disease (CKD), a major global health problem caused by loss of renal function. Currently, the gold standard to accurately diagnose ROD is based on quantitative histomorphometric analysis of trabecular bone. Although this analysis encompasses the evaluation of osteoblast and osteoclast number/activity, tfigurehe interest in osteocytes remains almost nihil. Nevertheless, this cell type is evidenced to perform a key role in bone turnover, particularly through its production of various bone proteins, such as sclerostin. In this study, we aim to investigate, in the context of ROD, to which extent an association exists between bone turnover and the abundance of osteocytes and osteocytic sclerostin expression in both the trabecular and cortical bone compartments. Additionally, the effect of parathyroid hormone (PTH) on bone sclerostin expression was examined in parathyroidectomized rats. Our results indicate that PTH exerts a direct inhibitory function on sclerostin, which in turn negatively affects bone turnover and mineralization. Moreover, this study emphasizes the functional differences between cortical and trabecular bone, as the number of (sclerostin-positive) osteocytes is dependent on the respective bone compartment. Finally, we evaluated the potential of sclerostin as a marker for CKD and found that the diagnostic performance of circulating sclerostin is limited and that changes in skeletal sclerostin expression occur more rapidly and more pronounced. The inclusion of osteocytic sclerostin expression and cortical bone analysis could be relevant when performing bone histomorphometric analysis for diagnostic purposes and to unravel pathological mechanisms of bone disease.

Renal osteodystrophy: A historical review of its origins and conceptual evolution

Long considered an inert supporting framework, bone studies went neglected until the 17th century when they began as descriptive microscopic studies of structure which over time progressed into that of chemistry and physiology. It was in the mid-19th century that studies evolved into an inquisitive discipline which matured into the experimental investigation of bone in health and disease in the 20th century, and ultimately that of molecular studies now deciphering the genetic language of bone biology. These fundamental studies were catalyzed by increasing clinical interest in bone disease. The first bone disease to be identified was rickets in 1645. Its subsequent connection to albuminuric patients reported in 1883 later became renal osteodystrophy in 1942, launching studies that elucidated the functions of vitamin D and parathyroid hormone and their role in the altered calcium and phosphate metabolism of the disease. Studies in osteoporosis and renal osteodystrophy have driven most recent progress benefitting from technological advances in imaging and the precision of evaluating bone turnover, mineralization, and volume. This review exposes the progress of bone biology from a passive support structure to a dynamically regulated organ with vital homeostatic functions whose understanding has undergone more revisions and paradigm shifts than that of any other organ.

Evaluation of Renal Osteodystrophy and Serum Bone-Related Biomarkers in a Peritoneal Dialysis Population

The spectrum of renal osteodystrophy (ROD) in peritoneal dialysis (PD) patients remains to be clarified. Ideal intact parathormone (iPTH) levels range is still not defined. The role of sclerostin, dickkopf-related protein 1, osteoprotegerin, and receptor activator for nuclear factor κB ligand for the diagnosis of ROD needs to be elucidated. In this cross-sectional study, tetracycline double-labeled bone biopsy was performed in 49 patients with histomorphometric analysis according Kidney Disease Improving Global Outcomes (KDIGO) guidelines. All patients were treated with biocompatible PD solutions, with calcium concentration of 1.25 mmol/L. Adynamic bone was the most frequent diagnosed pattern (42.9%) followed by hyperparathyroid-related bone disease (28.6%). Twenty-two percent of patients had normal bone. In patients with iPTH within the KDIGO recommended range for dialysis patients, adynamic bone was found in 59% of cases. Median (range) iPTH in patients with adynamic bone was 312 (60-631) pg/mL. Median (range) levels of sclerostin varied from 1511.64 (458.84-6387.70) pg/mL in patients with hyperparathyroid bone disease to 2433.1 (1049.59-11354.52) pg/mL in patients with adynamic bone. Sclerostin/iPTH ratio was the best marker of low turnover disease but iPTH performed best in the diagnosis of high turnover disease. Calcium mass transfer was positive in patients with low bone volume. Adynamic bone is the most frequent ROD pattern in contemporary PD. Our results suggest the need to review the iPTH target range for this population. The sclerostin/iPTH ratio showed improved performance compared to iPTH for the diagnosis of low turnover bone. © 2022 American Society for Bone and Mineral Research (ASBMR).

Bisphosphonate utilization across the spectrum of eGFR

Bisphosphonates are the most common treatment for osteoporosis but there are concerns regarding its use in CKD. We evaluated the frequency of BSP by eGFR categories among patients with osteoporosis from two healthcare systems. Our results show that 56% of patients were treated, with reduced odds in those with lower eGFR.

INTRODUCTION

Osteoporosis is common in patients with chronic kidney disease (CKD). Bisphosphonates (BSP) are the most common treatment but there are concerns regarding its efficacy and toxicity in CKD. We evaluated the frequency of BSP use by level of estimated glomerular filtration rate (eGFR) in patients with osteoporosis.

METHODS

We assessed BSP use in patients with incident osteoporosis from the SCREAM-Cohort, Stockholm-Sweden, and Geisinger Healthcare, PA, USA. Osteoporosis was defined as the first encountered ICD diagnosis, and BSP use was defined as the dispensation or prescription of any BSP from 6 months prior to 3 years after the diagnosis. Multinomial logistic regression was used to account for the competing risk of death.

RESULTS

A total of 15,719 women and 3011 men in SCREAM and 17,325 women and 3568 men in Geisinger with incident osteoporosis were included. Overall, 56% of individuals used BSP in both studies, with a higher proportion in women. After adjustments, the odds of BSP was lower across lower eGFR in SCREAM, ranging from 0.90 (0.81-0.99) for eGFR 75-89 mL/min/1.73m² to 0.56 (0.46-0.68) for eGFR 30-44 mL/min/1.73m² in women and from 0.72 (0.54-0.97) for eGFR of 60-74 to 0.42 (0.25-0.70) for eGFR 30-44 mL/min/1.73m² in men. In Geisinger, odds were lower for eGFR < 30 mL/min/1.73m² in both sexes and the frequency of BSP use dropped over time.

CONCLUSION

In the two healthcare systems, approximately half of the people diagnosed with osteoporosis received BSP. Practices of prescription in relation to eGFR varied, but those with lower eGFR were less likely to receive BSP.

Chronic kidney disease-related osteoporosis is associated with incident frailty among patients with diabetic kidney disease: a propensity score-matched cohort study

Chronic kidney disease (CKD)-related osteoporosis is a major complication in patients with CKD, conferring a higher risk of adverse outcomes. We found that among those with diabetic kidney disease, this complication increased the risk of incident frailty, an important mediator of adverse outcomes.

INTRODUCTION

Renal osteodystrophy and chronic kidney disease (CKD)-related osteoporosis increases complications for patients with diabetic kidney disease (DKD). Since musculoskeletal degeneration is central to frailty development, we investigated the relationship between baseline osteoporosis and the subsequent frailty risk in patients with DKD.

METHODS

From the Longitudinal Cohort of Diabetes Patients in Taiwan (n = 840,000), we identified 12,027 patients having DKD with osteoporosis and 24,054 propensity score-matched controls having DKD but without osteoporosis. The primary endpoint was incident frailty on the basis of a modified FRAIL scale. Patients were prospectively followed-up until the development of endpoints or the end of this study. The Kaplan-Meier technique and Cox proportional hazard regression were used to analyze the association between osteoporosis at baseline and incident frailty in these patients.

RESULTS

The mean age of the DKD patients was 67.2 years, with 55.4% female and a 12.6% prevalence of osteoporosis at baseline. After 3.5 ± 2.2 years of follow up, the incidence rate of frailty in patients having DKD with osteoporosis was higher than that in DKD patients without (6.6 vs. 5.7 per 1000 patient-year, p = 0.04). A Cox proportional hazard regression showed that after accounting for age, gender, obesity, comorbidities, and medications, patients having DKD with osteoporosis had a significantly higher risk of developing frailty (hazard ratio, 1.19; 95% confidence interval, 1.02-1.38) than those without osteoporosis.

CONCLUSIONS

CKD-related osteoporosis is associated with a higher risk of incident frailty in patients with DKD.