Soluble Klotho, a Potential Biomarker of Chronic Kidney Disease-Mineral Bone Disorders Involved in Healthy Ageing: Lights and Shadows.

Shortly after the discovery of Klotho, interest grew in its potential role in chronic kidney disease (CKD). There are three isoforms of the Klotho protein: αKlotho, ßKlotho and γKlotho. This review will focus on αKlotho due to its relevance as a biomarker in CKD. αKlotho is synthesized mainly in the kidneys, but it can be released into the bloodstream and urine as soluble Klotho (sKlotho), which undertakes systemic actions, independently or in combination with FGF23. It is usually accepted that sKlotho levels are reduced early in CKD and that lower levels of sKlotho might be associated with the main chronic kidney disease-mineral bone disorders (CKD-MBDs): cardiovascular and bone disease. However, as results are inconsistent, the applicability of sKlotho as a CKD-MBD biomarker is still a matter of controversy. Much of the inconsistency can be explained due to low sample numbers, the low quality of clinical studies, the lack of standardized assays to assess sKlotho and a lack of consensus on sample processing, especially in urine. In recent decades, because of our longer life expectancies, the prevalence of accelerated-ageing diseases, such as CKD, has increased. Exercise, social interaction and caloric restriction are considered key factors for healthy ageing. While exercise and social interaction seem to be related to higher serum sKlotho levels, it is not clear whether serum sKlotho might be influenced by caloric restriction. This review focuses on the possible role of sKlotho as a biomarker in CKD-MBD, highlighting the difference between solid knowledge and areas requiring further research, including the role of sKlotho in healthy ageing.

RANKL, but Not R-Spondins, Is Involved in Vascular Smooth Muscle Cell Calcification through LGR4 Interaction.

Vascular calcification has a global health impact that is closely linked to bone loss. The Receptor Activator of Nuclear Factor Kappa B (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system, fundamental for bone metabolism, also plays an important role in vascular calcification. The Leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4), a novel receptor for RANKL, regulates bone remodeling, and it appears to be involved in vascular calcification. Besides RANKL, LGR4 interacts with R-spondins (RSPOs), which are known for their roles in bone but are less understood in vascular calcification. Studies were conducted in rats with chronic renal failure fed normal or high phosphorus diets for 18 weeks, with and without control of circulating parathormone (PTH) levels, resulting in different degrees of aortic calcification. Additionally, vascular smooth muscle cells (VSMCs) were cultured under non-calcifying (1 mM phosphate) and calcifying (3 mM phosphate) media with different concentrations of PTH. To explore the role of RANKL in VSMC calcification, increasing concentrations of soluble RANKL were added to non-calcifying and calcifying media. The effects mediated by RANKL binding to its receptor LGR4 were investigated by silencing the LGR4 receptor in VSMCs. Furthermore, the gene expression of the RANK/RANKL/OPG system and the ligands of LGR4 was assessed in human epigastric arteries obtained from kidney transplant recipients with calcification scores (Kauppila Index). Increased aortic calcium in rats coincided with elevated systolic blood pressure, upregulated Lgr4 and Rankl gene expression, downregulated Opg gene expression, and higher serum RANKL/OPG ratio without changes in Rspos gene expression. Elevated phosphate in vitro increased calcium content and expression of Rankl and Lgr4 while reducing Opg. Elevated PTH in the presence of high phosphate exacerbated the increase in calcium content. No changes in Rspos were observed under the conditions employed. The addition of soluble RANKL to VSMCs induced genotypic differentiation and calcification, partly prevented by LGR4 silencing. In the epigastric arteries of individuals presenting vascular calcification, the gene expression of RANKL was higher. While RSPOs show minimal impact on VSMC calcification, RANKL, interacting with LGR4, drives osteogenic differentiation in VSMCs, unveiling a novel mechanism beyond RANKL-RANK binding.

Clinical features and disease progression of elderly patients at the ICU setting.

OBJECTIVE: To describe and characterize a cohort of octogenarian patients admitted to the ICU of the University Central Hospital of Asturias (HUCA). DESIGN: Retrospective, observational and descriptive study of 14 months' duration. SETTING: Cardiac and Medical intensive care units (ICU) of the HUCA (Oviedo). PARTICIPANTS: Patients over 80 years old who were admitted to the ICU for more than 24 h. INTERVENTIONS: None. MAIN VARIABLES OF INTEREST: Age, sex, comorbidity, functional dependence, treatment, complications, evolution, mortality. RESULTS: The most frequent reasons for admission were cardiac surgery and pneumonia. The average admission stay was significantly longer in patients under 85 years of age (p = 0,037). 84,3% of the latter benefited from invasive mechanical ventilation compared to 46,2% of older patients (p = <0,001). Patients over 85 years of age presented greater fragility. Admission for cardiac surgery was associated with a lower risk of mortality (HR = 0,18; 95% CI (0,062-0,527; p = 0,002). CONCLUSIONS: The results have shown an association between the reason for admission to the ICU and the risk of mortality in octogenarian patients. Cardiac surgery was associated with a better prognosis compared to medical pathology, where pneumonia was associated with a higher risk of mortality. Furthermore, a significant positive association was observed between age and frailty.

Novel Biomarkers of Bone Metabolism.

Bone represents a metabolically active tissue subject to continuous remodeling orchestrated by the dynamic interplay between osteoblasts and osteoclasts. These cellular processes are modulated by a complex interplay of biochemical and mechanical factors, which are instrumental in assessing bone remodeling. This comprehensive evaluation aids in detecting disorders arising from imbalances between bone formation and reabsorption. Osteoporosis, characterized by a reduction in bone mass and strength leading to heightened bone fragility and susceptibility to fractures, is one of the more prevalent chronic diseases. Some epidemiological studies, especially in patients with chronic kidney disease (CKD), have identified an association between osteoporosis and vascular calcification. Notably, low bone mineral density has been linked to an increased incidence of aortic calcification, with shared molecules, mechanisms, and pathways between the two processes. Certain molecules emerging from these shared pathways can serve as biomarkers for bone and mineral metabolism. Detecting and evaluating these alterations early is crucial, requiring the identification of biomarkers that are reliable for early intervention. While traditional biomarkers for bone remodeling and vascular calcification exist, they suffer from limitations such as low specificity, low sensitivity, and conflicting results across studies. In response, efforts are underway to explore new, more specific biomarkers that can detect alterations at earlier stages. The aim of this review is to comprehensively examine some of the emerging biomarkers in mineral metabolism and their correlation with bone mineral density, fracture risk, and vascular calcification as well as their potential use in clinical practice.

Social determinants of health influencing the choice of dialysis modality in advanced chronic kidney disease: Need of an interdisciplinary approach.

INTRODUCTION: The influence of socioeconomic and cultural barriers in the choice of renal replacement therapy (RRT) techniques in advanced chronic kidney disease (ACKD) has been scarcely explored, which can generate problems of inequity, frequently unnoticed in health care. The aim of this study is to identify the "non-medical" barriers that influence the choice of RRT in an advanced chronic kidney disease (ACKD) consultation in Spain. MATERIAL AND METHODS: Retrospective analysis including the total number of patients seen in the ACKD consultation in a tertiary hospital from 2009 to 2020. Inclusion in the ACKD consultation began with an eligibility test and a decision-making process, conducted by a specifically trained nurse. The variables considered for the study were: age, sex, etiology of CKD, level of dependence for basic activities of daily living (Barthel Scale) and instrumental activities of daily living (Lawton and Brody Scale), Spanish versus foreign nationality, socioeconomic level and language barrier. The socioeconomic level was extrapolated according to home and health district by primary care center to which the patients belonged. RESULTS: A total of 673 persons were seen in the ACKD consultation during the study period, of whom 400 (59.4%) opted for hemodialysis (HD), 156 (23.1%) for peritoneal dialysis (PD), 4 (0.5%) for early living donor renal transplantation (LDRT) and 113 (16.7%) chose conservative care (CC). The choice of PD as the chosen RRT technique (vs. HD) was associated with people with a high socioeconomic level (38.7% vs. 22.5%) (p = 0.002), Spanish nationality (91% vs. 77.7%) (p < 0.001), to a lower language barrier (0.6% vs 10.5%) (p < 0.001), and to a higher score on the Barthel scale (97.4 vs 92.9) and on the Lawton and Brody scale (7 vs 6.1) (p < 0.001). Neither age nor sex showed significant differences in the choice of both techniques. Patients who opted for CC were significantly older (81.1 vs 67.7 years; p < 0.001), more dependent (p < 0.001), with a higher proportion of women (49.6% vs 35.2%; p = 0.006) and a higher proportion of Spaniards (94.7% vs 81%, p = 0.001) in relation to the choice of other techniques (PD and HD). Socioeconomic level did not influence the choice of CC. CONCLUSION: Despite a regulated decision-making process, there are factors such as socioeconomic status, migration, language barrier and dependency of the population that influence the type of RRT chosen. To address these aspects that may cause inequity, an intersectoral and multilevel intervention is required with interdisciplinary teams that include, among others, social workers, to provide a more holistic and person-centered assessment.