MicroRNA-21 mediates high phosphate-induced endothelial cell apoptosis

The true cost of phosphate control in chronic kidney disease

The loss of kidney function entails the development of a positive phosphate balance. The burden of addressing elevated phosphate levels is high. Both parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) are increased to promote phosphaturia, thereby preventing the rise in serum phosphate. However, if the phosphate load is excessive, the corresponding phosphaturia is maximal, kidney function deteriorates and hyperphosphataemia becomes clinically evident in advanced stages of chronic kidney disease (CKD). In addition to its role in CKD progression, hyperphosphataemia has been linked to a multitude of adverse outcomes, including overt inflammation, vascular calcifications, endothelial dysfunction, cardiovascular disease, renal osteodystrophy and secondary hyperparathyroidism. Collectively, these factors contribute to the markedly elevated mortality rates observed among individuals with CKD. Furthermore, hyperphosphataemia has been identified as a significant contributor to the development of inflammatory processes, oxidative stress and fibrosis, which underlie the aetiology of numerous comorbidities. Additionally, elevated levels of PTH and FGF23 have been demonstrated to independently induce organ and tissue injury, which is associated with poor outcomes in CKD. This article provides a concise overview of the current understanding of phosphate handling by the kidney in the context of CKD. It outlines the detrimental effects of phosphate on various organs and the mechanisms through which it contributes to CKD progression. Additionally, we discuss the tools available for clinicians to identify patients at risk of an excessive phosphate load.

Sciadonic acid attenuates high-fat diet-induced bone metabolism disorders in mice

High-fat diet (HFD) has been associated with certain negative bone-related outcomes, such as bone metabolism disruption and bone loss. Sciadonic acid (SC), one of the main nutritional and functional components of Torreya grandis seed oil, is a unique Δ5-unsaturated-polymethylene-interrupted fatty acid (Δ5-UPIFA) that has been claimed to counteract such disorders owing to some of its physiological effects. However, the role of SC in ameliorating bone metabolism disorders due to HFD remains unclear. In the present investigation, we observed that SC modulates the OPG/RANKL/RANK signaling pathway by modifying the lipid metabolic state and decreasing inflammation in mice. In turn, it could balance bone resorption and formation as well as calcium and phosphorus levels, enhance bone strength and bone mineral density (BMD), and improve its microstructure. In addition, SC could inhibit fat vacuoles in bone, reverse the phenomenon of reduced numbers and poor continuity of bone trabeculae, and promote orderly arrangement of collagen fibers and cartilage repair. This study provides some theoretical basis for SC as a dietary intervention agent to enhance bone nutrition.

Association between serum phosphate and in-hospital mortality of patients with AECOPD: A retrospective analysis on eICU database

Acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is an important adverse event in the development of chronic obstructive pulmonary disease (COPD). Hyperphosphatemia is associated with higher mortality in patients with multiple diseases. In this study, we aimed to determine the relationship between serum phosphate and the risk of in-hospital mortality in patients with AECOPD. Methods: In the present study, patients with AECOPD were enrolled in the electronic Intensive Care Unit Collaborative Research Database (eICU-CRD), and divided into three groups according to the tertiles of serum phosphate level. The primary outcome measure was all-cause in-hospital mortality. The association between serum phosphate level and in-hospital mortality was investigated using multivariate logistic regression analysis. Moreover, subgroup analysis was performed to explore whether the relationship was consistent among different subgroups. Results: A total of 1199 AECOPD patients were included in this study. Non-survivors had higher serum phosphate levels than survivors. All patients were classified into lowest tertile, median tertile, and highest tertile, respectively. Multivariate logistic regression analysis indicated that serum phosphate was positively associated with in-hospital mortality after adjusting for confounders. Moreover, there was a significant trend across tertiles when serum phosphate level was diverted as a categorical variable. In addition, subgroup analysis demonstrated that serum phosphate was consistently associated with a higher risk of in-hospital mortality in different subgroups. Conclusion: Higher serum phosphate was positively associated with the increased in-hospital mortality in patients with AECOPD. Hyperphosphatemia may be an underlying high-risk factor for in-hospital mortality owing to AECOPD.

Phosphate in the Context of Cognitive Impairment and Other Neurological Disorders Occurrence in Chronic Kidney Disease

The nervous system and the kidneys are linked under physiological states to maintain normal body homeostasis. In chronic kidney disease (CKD), damaged kidneys can impair the central nervous system, including cerebrovascular disease and cognitive impairment (CI). Recently, kidney disease has been proposed as a new modifiable risk factor for dementia. It is reported that uremic toxins may have direct neurotoxic (astrocyte activation and neuronal death) and/or indirect action through vascular effects (cerebral endothelial dysfunction, calcification, and inflammation). This review summarizes the evidence from research investigating the pathophysiological effects of phosphate toxicity in the nervous system, raising the question of whether the control of hyperphosphatemia in CKD would lower patients’ risk of developing cognitive impairment and dementia.

Co-interventions with Clostridium butyricum and soluble dietary fiber targeting the gut microbiota improve MAFLD via the Acly/Nrf2/NF-κB signaling pathway

Purpose: The pathogenesis of metabolic associated fatty liver disease (MAFLD) is complex. Lipid metabolic disorder, chronic inflammation, and oxidative stress are the core events for MAFLD. Dietary intervention is an important treatment strategy for preventing the onset and progression of MAFLD. Clostridium butyricum (CB) and soluble dietary fiber (SDF) are often considered beneficial for health. We explored how two microbiota-targeted interventions (SDF and CB) influence the hepatic immune system, oxidative stress, and lipid metabolism in MAFLD mice. Methods: To explore the role of SDF and CB in MAFLD, we generated MAFLD mouse models by feeding C57BL/6 mice with a high-fat diet (HFD). After 8 weeks of intervention, we measured immune cell function, lipid metabolism, and oxidative stress levels in the livers of mice. Results: Single intervention with SDF or CB was not effective in improving MAFLD; however, co-interventions with SDF and CB increased microbiota diversity and decreased inflammation, oxidative stress, and lipid synthesis. Moreover, we determined that co-intervention with SDF and CB mediated fatty acid oxidation by activating the Acly/Nrf2/NF-κB signaling pathway. Most importantly, co-intervention exerted anti-inflammatory effects by inhibiting the differentiation of macrophages into pro-inflammatory M1 macrophages. Conclusion: This study show that co-intervention with SDF and CB can improve MAFLD, and co-intervention with  SDF and CB are suggested to be potential gut microbiota modulators and therapeutic substances for MAFLD.

A new perspective on the function of Tissue Non-Specific Alkaline Phosphatase: from bone mineralization to intra-cellular lipid accumulation

Tissue-nonspecific alkaline phosphatase (TNAP) is one of four isozymes, which include germ cell, placental and intestinal alkaline phosphatases. The TNAP isozyme has 3 isoforms (liver, bone and kidney) which differ by tissue expression and glycosylation pattern. Despite a long history of investigation, the exact function of TNAP in many tissues is largely unknown. Only the bone isoform has been well characterised during mineralization where the enzyme hydrolyses pyrophosphate to inorganic phosphate, which combines with calcium to form hydroxyapatite crystals deposited as new bone. The inorganic phosphate also increases gene expression of proteins that support tissue mineralization. Recent studies have shown that TNAP is expressed in preadipocytes from several species, and that inhibition of TNAP activity causes attenuation of intracellular lipid accumulation in these and other lipid-storing cells. The mechanism by which TNAP stimulates lipid accumulation is not known; however, proteins that are important for controlling phosphate levels in bone are also expressed in adipocytes. This review examines the evidence that inorganic phosphate generated by TNAP promotes transcription that enhances the expression of the regulators of lipid storage and consequently, that TNAP has a major function of lipid metabolism.

Phosphate and Cellular Senescence

Cellular senescence is one type of permeant arrest of cell growth and one of increasingly recognized contributor to aging and age-associated disease. High phosphate and low Klotho individually and synergistically lead to age-related degeneration in multiple organs. Substantial evidence supports the causality of high phosphate in cellular senescence, and potential contribution to human aging, cancer, cardiovascular, kidney, neurodegenerative, and musculoskeletal diseases. Phosphate can induce cellular senescence both by direct phosphotoxicity, and indirectly through downregulation of Klotho and upregulation of plasminogen activator inhibitor-1. Restriction of dietary phosphate intake and blockage of intestinal absorption of phosphate help suppress cellular senescence. Supplementation of Klotho protein, cellular senescence inhibitor, and removal of senescent cells with senolytic agents are potential novel strategies to attenuate phosphate-induced cellular senescence, retard aging, and ameliorate age-associated, and phosphate-induced disorders.

Role of crosstalk between endothelial cells and smooth muscle cells in vascular calcification in chronic kidney disease

Chronic kidney disease (CKD) is a severe health problem worldwide, and vascular calcification (VC) contributes substantially to the cardiovascular morbidity and high mortality of CKD. CKD is often accompanied by a variety of pathophysiological states, such as inflammation, oxidative stress, hyperglycaemia, hyperparathyroidism and haemodynamic derangement, that can cause injuries to smooth muscle cells (SMCs) and endothelial cells (ECs) to promote VC. Similar to SMCs, whose role has been widely explored in VC, ECs may contribute to VC via osteochondral transdifferentiation, apoptosis, etc. In addition, given their location in the innermost layer of the blood vessel lumen and preferential reception of various pro‐calcification stimuli, ECs can pass messages to vascular wall cells and communicate with them. Crosstalk between ECs and SMCs via cytokines through a paracrine mechanism, extracellular vesicles, miRNAs and myoendothelial gap junctions also plays a role in VC. In this review, we emphasize the role of intercellular crosstalk between ECs and SMCs in VC associated with CKD.