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.

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.

NLRP3 Contributes to Sarcopenia Associated to Dependency Recapitulating Inflammatory-Associated Muscle Degeneration.

Sarcopenia, a complex and debilitating condition characterized by progressive deterioration of skeletal muscle, is the primary cause of age-associated disability and significantly impacts healthspan in elderly patients. Despite its prevalence among the aging population, the underlying molecular mechanisms are still under investigation. The NLRP3 inflammasome is crucial in the innate immune response and has a significant impact on diseases related to inflammation and aging. Here, we investigated the expression of the NLRP3 inflammasome pathway and pro-inflammatory cytokines in skeletal muscle and peripheral blood of dependent and independent patients who underwent hip surgery. Patients were categorized into independent and dependent individuals based on their Barthel Index. The expression of NLRP3 inflammasome components was significantly upregulated in sarcopenic muscle from dependent patients, accompanied by higher levels of Caspase-1, IL-1ß and IL-6. Among older dependent individuals with sarcopenia, there was a significant increase in the MYH3/MYH2 ratio, indicating a transcriptional shift in expression from mature to developmental myosin isoforms. Creatine kinase levels and senescence markers were also higher in dependent patients, altogether resembling dystrophic diseases and indicating muscle degeneration. In summary, we present evidence for the involvement of the NLRP3/ASC/NEK7/Caspase-1 inflammasome pathway with activation of pro-inflammatory SASP in the outcome of sarcopenia in the elderly.

Asociación de la gamma glutamil transferasa con la presencia y progresión de calcificaciones aórticas abdominales y con cambios en densidad mineral ósea / Association of gamma glutamyl transferase in the presence and progression of abdominal aortic calcifications and changes to bone mineral density

Introducción y objetivo: la calcificación aórtica abdominal (CAA) es predictora de eventos cardiovasculares. El objetivo de este trabajo fue valorar la asociación de la gamma glutamil transferasa (GGT) con presencia y progresión de CAA y los cambios en densidad mineral ósea (DMO) en columna lumbar y cuello femoral. Material y métodos: se seleccionaron 326 hombres y mujeres mayores de 50 años que realizaron un cuestionario, dos radiografías laterales dorso-lumbares y DMO, repitiendo a los 4 años las mismas pruebas y un estudio analítico. Resultados: la presencia y progresión de CAA (nuevas o mayor severidad) fue inferior en el cuartil 1 (Q1) de GGT respecto a los otros cuartiles (40 % vs. 58 %, p = 0,021; 24 % vs. 44 %, p = 0,022). Comparado con Q1, el análisis de regresión logística ajustado por confusores mostró que los Q2 y Q4 se asociaron con aumentos en la presencia de CAA [odds ratio (OR) = 2,53, intervalo de confianza del 95 % (IC 96 %) = (1,22-5,25) y OR = 3,04, IC 95 % = (1,36-6,77)] y Q2, Q3 y Q4 se asociaron con aumentos en progresión de CAA [OR = 2,24, IC 95 % = (1,07-4,67); OR = 2,35, IC 95 % = (1,09-5,07) y OR = 3,47, IC 95 % = (1,56-7,70)]. El análisis multivariante por sexos mostró que tanto en hombres como mujeres el Q4 de GGT se asoció con progresión de CAA [OR = 3,27, IC 95 % = (1,14-9,36) y OR = 3,26, IC 95 % = (1,03-10,29) respectivamente] y en mujeres con mayores pérdidas de DMO a nivel lumbar. No hubo efecto con respecto a la prevalencia de CAA. Conclusiones: valores elevados de GGT podrían ser un indicador de presencia y progresión de CAA en población mayor de 50 años. De forma separada por sexo, los mayores niveles de GGT se asociaron con progresión de CAA, siendo un marcador pronóstico de daño cardiovascular.(AU)

Introduction and objective: abdominal aortic calcification (AAC) is a predictor of cardiovascular events. This study aimedto assess the association of gamma glutamyl transferase (GGT) in the presence and progression of AAC, as well as changesto bone mineral density (BMD) in the lumbar spine and femoral neck.Materials and methods: a total of 326 men and women over 50 years of age were selected for this study. They completeda questionnaire, underwent two lateral dorso-lumbar spine X-rays, and BMD measurements. The same tests and 1 analyticalassessment were repeated after 4 years.Results: the presence and progression of AAC (new occurrences or increased severity) were lower in GGT quartile 1 (Q1)compared with the other quartiles (40 % vs 58 %; p = 0.021; 24 % vs 44 %; p = 0.022). Compared with Q1, the confound -ers-adjusted logistic regression analysis showed that Q2 and Q4 were associated with more presence of AAC [odds ratio(OR), 2.53; 95 % confidence interval (95 % CI), 1.22-5.25 and OR, 3.04; 95 % CI, 1.36-6.77]. Additionally, Q2, Q3, and Q4were associated with more AAC progression [OR, 2.24; 95 % CI, 1.07-4.67; OR, 2.35; 95 % CI, 1.09-5.07; and OR, 3.47;95 % CI, 1.56-7.70]. The gender-stratified multivariate analysis revealed that in both men and women, the Q4 of GGT wasassociated with AAC progression [OR, 3.27; 95 % CI, 1.14-9.36, and OR, 3.26; 95 % CI, 1.03-10.29, respectively], and inwomen alone, with greater lumbar BMD losses. There were no effects regarding the prevalence of AAC.Conclusions: elevated GGT levels could serve as an indicator of the presence and progression of AAC in individuals olderthan 50 years. When analyzed separately by gender, higher GGT levels were associated with AAC progression, which actedas a prognostic marker for cardiovascular disease.(AU)