Novel treatment strategies for chronic kidney disease: insights from the animal kingdom

The potential protective effect of propolis on diabetic nephropathy induced by streptozotocin in adult albino rats

Diabetes mellitus is a common metabolic disorder. It is associated with serious life-threatening complications if not properly managed. The current study aimed at investigating the possible protective role of propolis on streptozotocin-induced diabetic nephropathy. A diabetic rat model was induced by a single intraperitoneal injection of 55 mg/kg streptozotocin. After 4 days, the diabetic rats received oral propolis (300 mg/kg/day) via gastric gavage for 28 days. Biochemical, histopathological and ultrastructural evaluations were performed. The results showed that: streptozotocin-induced diabetes was associated with a marked decrease in the serum high-density lipoproteins and antioxidant enzymes. However, a significant elevation in the levels of serum creatinine, blood urea nitrogen, uric acid, cholesterol, triglycerides and low-density lipoproteins was detected. Furthermore, streptozotocin treatment induced histopathological alterations of the renal cortex; in the form of distorted glomerular capillaries, widened Bowman's space and signs of epithelial tubular degeneration. Ultra-structurally, thickening and irregularity of the glomerular basement membrane and podocytes foot processes effacement were observed. The tubular epithelial cells showed swollen vacuolated mitochondria, scarce basal infoldings and loss of microvilli. Conversely, propolis partially restored the normal lipid profile, antioxidant biomarkers and renal cortical morphology. Propolis exhibited a sort of renoprotection through hypoglycemic, anti-hyperlipidemic and antioxidant effects.

Determination of the reference interval for urinary klotho to creatinine ratio of healthy dogs

For several years, alpha klotho has been considered as a candidate biomarker in chronic kidney disease (CKD), progression of CKD and CKD mineral bone disorders (CKD-MBD). The evidence on the relationship between klotho and kidney function is controversial in some areas. The aim of the study was to identify the influence of age, sex and breed on urinary alpha klotho, values in the early stages of CKD within the studied population and determine a reference interval in a group of healthy dogs. Significantly higher values were measured in older dogs over 6 years old (p = 0.026, p = 0.0007) and in the breed German Shepherd than Belgian Shepherd (p = 0.0401). On the basis of sex and in small breed dogs, no significant differences were noted. In dogs with CKD stage 2, alpha klotho values were significantly lower (p = 0.0135) than in healthy dogs. Within the studied population, a reference interval for urinary klotho to creatinine ratio (UrKl/Cr) was determined in the range of 3.94-23.55 pg/gCr. Since our findings show that alpha klotho is associated with older age, we assume that this may have influenced the results in the group of dogs with CKD stage 1 due to the presence of predominantly old dogs in this group. Future studies would be needed to consider age as a factor affecting urinary alpha klotho in dogs with CKD.

Bradykinin induces acute kidney injury after hypothermic circulatory arrest through the repression of the Nrf2-xCT pathway

Postoperative acute kidney injury (AKI) is a common complication in patients undergoing deep hypothermic circulatory arrest (HCA); however, its underlying pathogenesis is unclear. In this study, we established a rat cardiopulmonary bypass model and demonstrated that hypothermia during HCA, rather than circulatory arrest, was responsible for the occurrence of AKI. By recruiting 56 patients who underwent surgery with HCA and analyzing the blood samples, we found that post-HCA AKI was associated with an increase in bradykinin. Animal experiments confirmed this and showed that hypothermia during HCA increased bradykinin levels by increasing kallikrein expression. Mechanistically, bradykinin inhibited the Nrf2-xCT pathway through B2R and caused renal oxidative stress damage. Application of Icatibant, a B2R inhibitor, reversed changes in the Nrf2-xCT pathway and oxidative stress damage. Finally, Icatibant reversed hypothermia-induced AKI in vivo. This finding reveals the pathogenesis of AKI after HCA and helps to provide therapeutic strategy for patients with post-HCA AKI.

What Can the Gut Microbiota of Animals Teach Us about the Relationship between Nutrition and Burden of Lifestyle Diseases?

The gut microbiota performs several crucial roles in a holobiont with its host, including immune regulation, nutrient absorption, synthesis, and defense against external pathogens, significantly influencing host physiology. Disruption of the gut microbiota has been linked to various chronic conditions, including cardiovascular, kidney, liver, respiratory, and intestinal diseases. Studying how animals adapt their gut microbiota across their life course at different life stages and under the dynamics of extreme environmental conditions can provide valuable insights from the natural world into how the microbiota modulates host biology, with a view to translating these into treatments or preventative measures for human diseases. By modulating the gut microbiota, opportunities to address many complications associated with chronic diseases appear. Such a biomimetic approach holds promise for exploring new strategies in healthcare and disease management.

Identification of Immune-Related Genes as Biomarkers for Uremia

Purpose

Uremia, which is characterized by immunodeficiency, is associated with the deterioration of kidney function. Immune-related genes (IRGs) are crucial for uremia progression.

Methods

The co-expression network was constructed to identify key modular genes associated with uremia. IRGs were intersected with differentially expressed genes (DEGs) between uremia and control groups and key modular genes to obtain differentially expressed IRGs (DEIRGs). DEIRGs were subjected to functional enrichment analysis. The protein-protein interaction (PPI) network was constructed. The candidate genes were identified using the cytoHubba tool. The biomarkers were identified using various machine learning algorithms. The diagnostic value of the biomarkers was evaluated using receiver operating characteristic (ROC) analysis. The immune infiltration analysis was implemented. The biological pathways of biomarkers were identified using gene set enrichment analysis and ingenuity pathway analysis. The mRNA expression of biomarkers was validated using blood samples of patients with uremia and healthy subjects with quantitative real-time polymerase chain reaction (qRT-PCR).

Results

In total, four biomarkers (PDCD1, NGF, PDGFRB, and ZAP70) were identified by machine learning methods. ROC analysis demonstrated that the area under the curve values of individual biomarkers were > 0.9, indicating good diagnostic power. The nomogram model of biomarkers exhibited good predictive power. The proportions of six immune cells significantly varied between the uremia and control groups. ZAP70 expression was positively correlated with the proportions of resting natural killer (NK) cells, naïve B cells, and regulatory T cells. Functional enrichment analysis revealed that the biomarkers were mainly associated with translational function and neuroactive ligand-receptor interaction. ZAP70 regulated NK cell signaling. The PDCD1 and NGF expression levels determined using qRT-PCR were consistent with those determined using bioinformatics analysis.

Conclusion

PDCD1, NGF, PDGFRB, and ZAP70 were identified as biomarkers for uremia, providing a theoretical foundation for uremia diagnosis.

Klotho in Cancer: Potential Diagnostic and Prognostic Applications

Klotho proteins, αKlotho, βKlotho, and γKlotho, exert tumor-suppressive activities via the fibroblast growth factor receptors and multiple cell-signaling pathways. There is a growing interest in Klotho proteins as potential diagnostic and prognostic biomarkers for multiple diseases. However, recent advances regarding their roles and potential applications in cancer remain disperse and require an integrated analysis. The present review analyzed research articles published between 2012 and 2022 in the Cochrane and Scopus scientific databases to study the role of Klotho in cancer and their potential as tools for diagnosing specific cancer types, predicting tumor aggressiveness and prognosis. Twenty-six articles were selected, dealing with acute myeloid leukemia and with bladder, breast, colorectal, esophageal, gastric, hepatocellular, ovarian, pancreatic, prostatic, pulmonary, renal, and thyroid cancers. αKlotho was consistently associated with improved prognosis and may be useful in estimating patient survival. A single study reported the use of soluble αKlotho levels in blood serum as a tool to aid the diagnosis of esophageal cancer. γKlotho was associated with increased aggressiveness of bladder, breast, and prostate cancer, and βKlotho showed mixed results. Further clinical development of Klotho-based assays will require careful identification of specific tumor subtypes where Klotho proteins may be most valuable as diagnostic or prognostic tools.

Pharmacological inhibition of SMYD2 protects against cisplatin-induced renal fibrosis and inflammation

SET and MYND domain protein 2 (SMYD2) can methylate histone H3 at lysine36 (H3K36) and some non-histone substrates to play a role in tumorigenesis. However, It is unclear how SMYD2 contributes to chronic kidney disease (CKD). Here, AZ505 or LLY507, which could inhibit SMYD2, were used in cisplatin-induced CKD to investigate the effects and possible mechanisms by which they might act. We found that high expression of SMYD2 in cisplatin-induced CKD. However, AZ505 or LLY507 can significantly inhibit its expression, improve renal function injury and fibrosis induced by cisplatin, inhibit the transition of epithelial cells to a fibrogenic phenotype and fibrosis-related proteins, inhibit the expression of Inflammatory Cytokines (such as IL-6 and TNF-α), And inhibit the phosphorylation of pro-fibrosis molecule Smad3 and signal transduction and transcription activator-3 (STAT3) and up-regulated the expression of renal protective factor Smad7. In cultured tubular epithelial cells, AZ505 also can inhibit the expression of EMT, fibrosis-related proteins, and inflammatory cytokines in cisplatin-induced tubular epithelial cells. Based on these findings, SMYD2 may be a critical regulator of cisplatin-induced CKD and targeted pharmacological inhibition of SMYD2 may prevent cisplatin-induced CKD through Smad3 or STAT3-related signaling pathways.

Microvesicle-Mediated Tissue Regeneration Mitigates the Effects of Cellular Ageing

Extracellular vesicles (EVs), comprising microvesicles (MVs) and exosomes (Exos), are membranous vesicles secreted by cells which mediate the repair of cellular and tissue damage via paracrine mechanisms. The action of EVs under normative and morbid conditions in the context of ageing remains largely unexplored. We demonstrate that MVs, but not Exos, from Pathfinder cells (PCs), a putative stem cell regulatory cell type, enhance the repair of human dermal fibroblast (HDF) and mesenchymal stem cell (MSC) co-cultures, following both mechanical and genotoxic stress. Critically, this effect was found to be both cellular age and stress specific. Notably, MV treatment was unable to repair mechanical injury in older co-cultures but remained therapeutic following genotoxic stress. These observations were further confirmed in human dermal fibroblast (HDF) and vascular smooth muscle cell (VSMC) co-cultures of increasing cellular age. In a model of comorbidity comprising co-cultures of HDFs and highly senescent abdominal aortic aneurysm (AAA) VSMCs, MV administration appeared to be senotherapeutic, following both mechanical and genotoxic stress. Our data provide insights into EVs and the specific roles they play during tissue repair and ageing. These data will potentiate the development of novel cell-free therapeutic interventions capable of attenuating age-associated morbidities and avoiding undesired effects.

Formerly bile-farmed bears as a model of accelerated ageing

Bear bile-farming is common in East and Southeast Asia and this farming practice often results in irreversible health outcomes for the animals. We studied long-term effects of chronic bacterial and sterile hepatobiliary inflammation in 42 Asiatic black bears (Ursus thibetanus) rescued from Vietnamese bile farms. The bears were examined under anesthesia at least twice as part of essential medical interventions. All bears were diagnosed with chronic low-grade sterile or bacterial hepatobiliary inflammation along with pathologies from other systems. Our main finding was that the chronic low-grade inflammatory environment associated with bile extraction in conjunction with the suboptimal living conditions on the farms promoted and accelerated the development of age-related pathologies such as chronic kidney disease, obese sarcopenia, cardiovascular remodeling, and degenerative joint disease. Through a biomimetic approach, we identified similarities with inflammation related to premature aging in humans and found significant deviations from the healthy ursid phenotype. The pathological parallels with inflammageing and immuno-senescence induced conditions in humans suggest that bile-farmed bears may serve as animal models to investigate pathophysiology and deleterious effects of lifestyle-related diseases.

Regulation of PKC/TLR-4/NF-kB signaling by sulbutiamine improves diabetic nephropathy in rats

One of the serious complications of diabetes mellitus is diabetic nephropathy (DN) which may finally lead to renal failure. The current study aimed to explore the effect of sulbutiamine, a synthetic derivative of vitamin B1, in streptozotocin (STZ)-induced DN and related pathways. Experimental DN was successfully induced 8 weeks after a single low dose of STZ (45 mg/kg, I.P.). Four groups of rats were used in this study and divided randomly into: control group, diabetic group, sulbutiamine control (control + sulbutiamine) group, and sulbutiamine-treated (60 mg/kg) (diabetic + sulbutiamine) group. The fasting blood glucose level (BGL) and the levels of kidney injury molecule-1 (Kim-1), urea, creatinine in serum, and the renal content of malondialdehyde (MDA), protein kinase C (PKC), toll-like receptor-4 (TLR-4) and nuclear factor kappa B (NF-κB) were determined. Additionally, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and transforming growth factor-β1 (TGF-β1) contents were evaluated immunohistochemically. Sulbutiamine treatment decreased fasting BGL and improved the kidney function tests compared to diabetic rats. Moreover, TLR-4, NF-κB, MDA and PKC contents were substantially reduced following sulbutiamine treatment compared to the diabetic group. Sulbutiamine managed to obstruct the production of the pro-inflammatory TNF-α and IL-1β and suppressed TGF-β1 level, in addition to attenuating the histopathological changes associated with DN. This study revealed, for the first time, the ability of sulbutiamine to ameliorate STZ-induced diabetic nephropathy in rats. This nephroprotective outcome of sulbutiamine against DN may be attributed to glycemic control in addition to its anti-oxidative, anti-inflammatory and anti-fibrotic effects.

Accelerated Vascular Aging in Chronic Kidney Disease: The Potential for Novel Therapies

The pathophysiology of vascular disease is linked to accelerated biological aging and a combination of genetic, lifestyle, biological, and environmental risk factors. Within the scenario of uncontrolled artery wall aging processes, CKD (chronic kidney disease) stands out as a valid model for detailed structural, functional, and molecular studies of this process. The cardiorenal syndrome relates to the detrimental bidirectional interplay between the kidney and the cardiovascular system. In addition to established risk factors, this group of patients is subjected to a plethora of other emerging vascular risk factors, such as inflammation, oxidative stress, mitochondrial dysfunction, vitamin K deficiency, cellular senescence, somatic mutations, epigenetic modifications, and increased apoptosis. A better understanding of the molecular mechanisms through which the uremic milieu triggers and maintains early vascular aging processes, has provided important new clues on inflammatory pathways and emerging risk factors alike, and to the altered behavior of cells in the arterial wall. Advances in the understanding of the biology of uremic early vascular aging opens avenues to novel pharmacological and nutritional therapeutic interventions. Such strategies hold promise to improve future prevention and treatment of early vascular aging not only in CKD but also in the elderly general population.

On-chip construction of a fully structured scaffold-free vascularized renal tubule

Renal tubule chips have emerged as a promising platform for drug nephrotoxicity testing. However, the reported renal tubule chips hardly replicate the unique structure of renal tubules with thick proximal and distal tubules and a thin loop of Henle. In this study, we developed a fully structured scaffold-free vascularized renal tubule on a microfluidic chip. On the chip, the renal epithelial cell-laden hollow calcium-polymerized alginate tube with thick segments at both ends and a thin middle segment was U-shaped embedded in collagen hydrogel, parallel to the endothelial cell-laden hollow calcium-polymerized alginate tube with uniform tube diameter. After the alginate tubes were on-chip degraded, the renal epithelial cells and endothelial cells automatically attached to the collagen hydrogel and proliferated to form the renal tubule with proximal tubule, loop of Henle and distal tubule as well as peritubular blood vessel. We evaluated the viability of cells on the hollow alginate tubes, characterized the distribution and morphology of cells before and after the degradation of the alginate tube, and confirmed the proliferation of cells and the metabolic function of cells in terms of ATP synthesis, fibronectin secretion and VEGFR2 expression on the chip. The enhanced metabolic functions of renal epithelial cells and endothelial cells were preliminarily demonstrated. This study provides new insights into designing a more biomimetic renal tubule on a microfluidic chip.

Chronic Kidney Disease and the Exposome of Ageing

The gap between improvements in lifespan and age-related health is widening. Globally, the demographic of ageing is increasing and there has emerged a 'diseasome of ageing', typified by a range of non-communicable diseases which share a common underlying component of a dysregulated ageing process. Within this, chronic kidney disease is an emerging global epidemic.The extensive inter-individual variation displayed in how people age and how their diseasome manifests and progresses, has required a renewed focus on their life course exposures and the interplay between the environment and the (epi)genome. Termed the exposome, life course abiotic and biotic factors have a significant impact on renal health.We explore how the exposome of renal ageing can predispose and affect CKD progression. We discuss how the kidney can be used as a model to understand the impact of the exposome in health and chronic kidney disease and how this might be manipulated to improve health span.Notably, we discuss the manipulation of the foodome to mitigate acceleration of ageing processes by phosphate and to explore use of emerging senotherapies. A range of senotherapies, for removing senescent cells, diminishing inflammatory burden and either directly targeting Nrf2, or manipulating it indirectly via modification of the microbiome are discussed.

Transcription factor NRF2 as potential therapeutic target for preventing muscle wasting in aging chronic kidney disease patients

Increased muscle protein catabolism leading to muscle wasting is a prominent feature of the syndrome of protein-energy wasting (PEW) in patients with chronic kidney disease (CKD). PEW and muscle wasting are induced by factors such as inflammation, oxidative stress and metabolic acidosis that activate the ubiquitin-proteasome system, the main regulatory mechanism of skeletal muscle degradation. Whether deficiency of nuclear factor erythroid 2-related factor 2 (NRF2), which regulates expression of antioxidant proteins protecting against oxidative damage triggered by inflammation, may exacerbate PEW has yet to be examined in aging patients with CKD. This review focuses on the hypothesis that NRF2 is involved in the maintenance of muscle mass and explores whether sustained activation of NRF2 by non-pharmacological interventions using nutraceutical activators to improve redox homeostasis could be a plausible strategy to prevent skeletal muscle disorders, including muscle wasting, sarcopenia and frailty associated with PEW in aging CKD patients.

Transcriptional profile changes after treatment of ischemia reperfusion injury-induced kidney fibrosis with 18β-glycyrrhetinic acid

Introduction

Chronic kidney disease (CKD) is characterized by renal fibrosis without effective therapy. 18β-Glycyrrhetinic acid (GA) is reported to have detoxification and anti-inflammatory functions and promotes tissue repair. However, the role of GA in CKD remains unclear. In this study, we investigated whether GA has a potential therapeutic effect in kidney fibrosis.

Methods

A renal fibrosis mouse model was established by ischemia/reperfusion (I/R) injury via clamping unilateral left renal pedicle for 45 min; then, the mice were treated with vehicle or GA. Kidney tissues and blood samples were extracted 14 days after reperfusion and renal function, histopathological staining, quantitative PCR, and western blotting were performed. RNA-seq was performed to explore the changes in the transcriptional profile after GA treatment.

Results

Renal function, pathological and molecular analysis displayed that fibrosis was successfully induced in the I/R model. In the GA treatment group, the severity of fibrosis gradually reduced with the best effect seen at a concentration of 25 mg kg ⁻¹. A total of 970 differentially expressed genes were identified. Pathway enrichment showed that reduced activation and migration of inflammatory cells and decreased chemokine interaction in significant pathways. Protein–protein interaction networks were constructed and 15 hub genes were selected by degree rank, including chemokines, such as C3, Ccl6, Ccr2, Ptafr, Timp1, and Pf4.

Conclusions

GA may alleviate renal fibrosis by inhibiting the inflammatory response. GA is a promising therapy that may perhaps be used in treating renal fibrosis and CKD.

Symmetric Dimethylarginine is a Promising Biomarker for the Early Detection of Age-Related Kidney Dysfunction in Zoo Felids

Chronic renal failure is one of the leading causes of death in African lions, cheetahs, and tigers. Conventional methods to measure renal dysfunction include measuring serum creatinine and blood urea nitrogen (BUN). Symmetric dimethylarginine (SDMA) measurement is a reliable predictor of renal dysfunction in the domestic cat because SDMA serum levels increase early when the kidneys are damaged. Serum SDMA levels were assessed and correlated with creatinine as well as BUN from healthy captive Bengal tigers and lions at the Everland Zoo in Korea. Serum SDMA concentrations were increasingly associated with increased age in lions. However, SDMA concentrations were higher in some young Bengal tigers than in older ones, which may allow for earlier renal dysfunction detection in these young cats than would be BUN and creatinine alone. In Bengal tigers, the correlation between the SDMA and BUN was slightly higher than that between SDMA and creatinine. In lions, SDMA correlated better with creatinine than with BUN concentration. These results show that serum SDMA concentration can be used as a biomarker for age-associated renal dysfunction. SDMA measurement may be an essential preventive management method in zoos.

Ginsenoside Re attenuates memory impairments in aged Klotho deficient mice via interactive modulations of angiotensin II AT1 receptor, Nrf2 and GPx-1 gene

Ginseng is known to possess anti-aging potential. Klotho mutant mice exhibit phenotypes that resemble the phenotype of the human aging process. Similar to Klotho deficient mice, patients with chronic kidney disease (CKD) suffer vascular damage and cognitive impairment, which might upregulate the angiotensin II AT1 receptor. Since AT1 receptor expression was more pronounced than endothelin ET-1 expression in the hippocampus of aged Klotho deficient (±) mice, we focused on the AT1 receptor in this study. Ginsenoside Re (GRe), but not ginsenoside Rb1 (GRb1), significantly attenuated the increase in AT1 receptor expression in aged Klotho deficient mice. Both GRe and the AT1 receptor antagonist losartan failed to attenuate the decrease in phosphorylation of JAK2/STAT3 in aged Klotho deficient (±) mice but significantly activated nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated signaling. Both GRe and losartan attenuated the increased NADPH oxidase (NOX) activity and reactive oxygen species (ROS) in aged Klotho deficient mice. Furthermore, of all the antioxidant enzymes, GRe significantly increased glutathione peroxidase (GPx) activity. GRe significantly attenuated the reduced phosphorylation of ERK and CREB in GPx-1 knockout mice; however, genetic overexpression of GPx-1 did not significantly affect them in aged mice. Klotho-, Nrf2-, and GPx-1-immunoreactivities were co-localized in the same cells of the hippocampus in aged Klotho wild-type mice. Both the GPx inhibitor mercaptosuccinate and Nrf2 inhibitor brusatol counteracted the effects of GRe on all neurobehavioral impairments in aged Klotho deficient (±) mice. Our results suggest that GRe attenuates all alterations, such as AT1 receptor expression, NOX-, ROS-, and GPx-levels, and cognitive dysfunction in aged Klotho deficient (±) mice via upregulation of Nrf2/GPx-1/ERK/CREB signaling.

Ageing - Oxidative stress, PTMs and disease

Post-translational modifications (PTMs) have been proposed as a link between the oxidative stress-inflammation-ageing trinity, thereby affecting several hallmarks of ageing. Phosphorylation, acetylation, and ubiquitination cover >90% of all the reported PTMs. Several of the main PTMs are involved in normal "healthy" ageing and in different age-related diseases, for instance neurodegenerative, metabolic, cardiovascular, and bone diseases, as well as cancer and chronic kidney disease. Ultimately, data from human rare progeroid syndromes, but also from long-living animal species, imply that PTMs are critical regulators of the ageing process. Mechanistically, PTMs target epigenetic and non-epigenetic pathways during ageing. In particular, epigenetic histone modification has critical implications for the ageing process and can modulate lifespan. Therefore, PTM-based therapeutics appear to be attractive pharmaceutical candidates to reduce the burden of ageing-related diseases. Several phosphorylation and acetylation inhibitors have already been FDA-approved for the treatment of other diseases and offer a unique potential to investigate both beneficial effects and possible side-effects. As an example, the most well-studied senolytic compounds dasatinib and quercetin, which have already been tested in Phase 1 pilot studies, also act as kinase inhibitors, targeting cellular senescence and increasing lifespan. Future studies need to carefully determine the best PTM-based candidates for the treatment of the "diseasome of ageing".

Targeting inflammation, autophagy, and apoptosis by troxerutin attenuates methotrexate-induced renal injury in rats

BACKGROUND

Troxerutin, a bioflavonoid with marked immune-modulatory and antioxidant features, has been proven to ameliorate experimental cardiotoxicity, hepatotoxicity, and neurodegeneration. However, its impact on methotrexate (MTX)-induced nephrotoxicity has not been investigated. In the current work, we aimed to investigate the potential of troxerutin to combat MTX-triggered renal injury, exploring immune cell infiltration, inflammation, autophagy, and apoptosis, with emphasis on the HMGB1/RAGE/NF-κB, AMPK/mTOR, and Nrf2/HO-1 pathways.

METHODOLOGY

Troxerutin (150 mg/kg/day) was administered by oral gavage and the renal tissues were examined with the aid of biochemical assays, ELISA, histology, and immunohistochemistry.

KEY FINDINGS

Troxerutin mitigated MTX-induced renal dysfunction by significantly lowering creatinine, BUN, and KIM-1 alongside immune-cell infiltration and histopathologic aberrations. These favorable effects were mediated by inhibition of HMGB1/RAGE/NF-κB cascade via downregulating the protein expression of HMGB1, RAGE, and nuclear NF-κBp65 alongside its downstream signals, including COX-2 and TNF-α. Moreover, troxerutin activated the autophagy flux as evidenced by upregulating renal Beclin 1, lowering p62 SQSTM1 accumulation, and activation of AMPK/mTOR pathway, seen by increasing p-AMPK/total AMPK and lowering p-mTOR/total mTOR signals. In tandem, troxerutin combated renal apoptotic changes as proven with lowering caspase-3 activity, Bax expression, and Bax/Bcl-2 ratio and upregulating the proliferation signal PCNA. Additionally, the oxidative insult was attenuated by troxerutin, as evidenced by lowering NOX-1 and lipid peroxides, replenishing GSH, GPx, and SOD antioxidants, and activating Nrf2/HO-1 pathway.

CONCLUSION

Troxerutin attenuated MTX-triggered renal injury via inhibition of inflammation and apoptosis alongside activation of autophagy. Thus, it may serve as an adjunct modality for the management of MTX-linked nephrotoxicity.

Phosphate Restriction Promotes Longevity via Activation of Autophagy and the Multivesicular Body Pathway

Nutrient limitation results in an activation of autophagy in organisms ranging from yeast, nematodes and flies to mammals. Several evolutionary conserved nutrient-sensing kinases are critical for efficient adaptation of yeast cells to glucose, nitrogen or phosphate depletion, subsequent cell-cycle exit and the regulation of autophagy. Here, we demonstrate that phosphate restriction results in a prominent extension of yeast lifespan that requires the coordinated activity of autophagy and the multivesicular body pathway, enabling efficient turnover of cytoplasmic and plasma membrane cargo. While the multivesicular body pathway was essential during the early days of aging, autophagy contributed to long-term survival at later days. The cyclin-dependent kinase Pho85 was critical for phosphate restriction-induced autophagy and full lifespan extension. In contrast, when cell-cycle exit was triggered by exhaustion of glucose instead of phosphate, Pho85 and its cyclin, Pho80, functioned as negative regulators of autophagy and lifespan. The storage of phosphate in form of polyphosphate was completely dispensable to in sustaining viability under phosphate restriction. Collectively, our results identify the multifunctional, nutrient-sensing kinase Pho85 as critical modulator of longevity that differentially coordinates the autophagic response to distinct kinds of starvation.

Correlation and Diagnostic Value of Serum RBP4 and sRAGE and the Condition of Patients with Chronic Kidney Disease

Chronic kidney disease (CKD) is a progressive damage of renal structure and function caused by various reasons. Its course is long and irreversible. CKD can be divided into 5 stages according to the glomerular filtration rate (GFR). Early detection and early intervention of CKD can reduce the complications of patients and improve the survival rate. Retinol-binding protein 4 (RBP4) is a small molecule transporter. Receptor for advanced glycation end products (RAGE) is a multi-ligand transmembrane signal transduction receptor discovered in recent years. Soluble RAGE (sRAGE) is a new splicing heterogeneity of RAGE. Our results show that serum RBP4 is increased while sRAGE is decreased in CKD patients, both of which are closely related to the severity of CKD. The combined use of serum RBP4 and sRAGE has a high diagnostic value for CKD and can provide a reliable diagnostic basis for the clinic.

Renal Contributions to Age-Related Changes in Mineral Metabolism

Aging results in a general decline in function in most systems. This is particularly true with respect to the skeleton and renal systems, impacting mineral homeostasis. Calcium and phosphate regulation requires tight coordination among the intestine, bone, parathyroid gland, and kidney. The role of the intestine is to absorb calcium and phosphate from the diet. The bone stores or releases calcium and phosphate depending on the body's needs. In response to low plasma ionized calcium concentration, the parathyroid gland produces parathyroid hormone, which modulates bone turnover. The kidney reabsorbs or excretes the minerals and serves as the final regulator of plasma concentration. Many hormones are involved in this process in addition to parathyroid hormone, including fibroblast growth factor 23 produced by the bone and calcitriol synthesized by the kidney. Sclerostin, calcitonin, osteoprotegerin, and receptor activator of nuclear factor‐κB ligand also contribute to tissue‐specific regulation. Changes in the function of organs due to aging or disease can perturb this balance. During aging, the intestine cannot absorb calcium efficiently due to decreased expression of key proteins. In the bone, the balance between bone formation and bone resorption tends toward the latter in older individuals. The kidney may not filter blood as efficiently in the later decades of life, and the expression of certain proteins necessary for mineral homeostasis declines with age. These changes often lead to dysregulation of organismal mineral homeostasis. This review will focus on how mineral homeostasis is impacted by aging with a particular emphasis on the kidney's role in this process. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Diminishment of Nrf2 Antioxidative Defense Aggravates Nephrotoxicity of Melamine and Oxalate Coexposure

Chronic kidney disease (CKD) usually causes devastating healthy impacts on patients. However, the causes affecting the decline of kidney function are not fully revealed, especially the involvement of environmental pollutants. We have revealed that exposure to melamine, a ubiquitous chemical in daily life, is linked to adverse kidney outcomes. Hyperoxaluria that results from exposure to excessive oxalate, a potentially nephrotoxic terminal metabolite, is reportedly associated with CKD. Thus, we explored whether interaction of these two potential nephrotoxicants could enhance kidney injury. We established a renal proximal tubular HK-2 cell model and a Sprague-Dawley rat model of coexposure to melamine with sodium oxalate or hydroxy-L-proline to investigate the interacting adverse effects on kidneys. Melamine and oxalate coexposure enhanced the levels of reactive oxygen species, lipid peroxidation and oxidative DNA damage in the HK-2 cells and kidney tissues. The degrees of tubular cell apoptosis, tubular atrophy, and interstitial fibrosis were elevated under the coexposed condition, which may result from the diminishment of Nrf2 antioxidative capacity. To conclude, melamine and oxalate coexposure aggravates renal tubular injury via impairment of antioxidants. Accumulative harmful effects of exposure to multiple environmental nephrotoxicants should be carefully investigated in the etiology of CKD progression.

The Idiosyncratic Physiological Traits of the Naked Mole-Rat; a Resilient Animal Model of Aging, Longevity, and Healthspan

The subterranean-dwelling naked mole-rat (Heterocephalus glaber) is an extremophilic rodent, able to thrive in the harsh underground conditions of sub-Saharan Northeast Africa. This pelage-free mammal exhibits numerous unusual ecophysiological features including pronounced tolerance of thermolability, hypoxia, hypercapnia and noxious substances. As a mammal, the naked mole-rat provides a proof-of-concept that age-related changes in physiology are avoidable. At ages far beyond their expected lifespans given both their body size and/or the timing of early developmental milestones, naked mole-rats fail to exhibit meaningful changes in physiological health or demographic mortality. Lack of physiological deterioration with age is also evident in lean and fat mass, bone quality, and reproductive capacity. Rather, regardless of age, under basal conditions naked mole-rats appear to "idle on low" with their "shields up" as is manifested by low body temperature, metabolic rate, cardiac output and kidney concentrating ability, enabling better protection of organs and cellular function. When needed, they can nevertheless ramp up these functions, increasing cardiac output and metabolism 2-5 fold. Here we review many unusual aspects of their physiology and examine how these attributes facilitate both tolerance of the diverse suite of hostile conditions encountered in their natural milieu as well as contribute to their extraordinary longevity and resistance to common, age-related chronic diseases.

Klotho and calciprotein particles as therapeutic targets against accelerated ageing

The klotho gene, named after a Greek goddess who spins the thread of life, was identified as a putative 'ageing-suppressor' gene. Klotho-deficient mice exhibit complex ageing-like phenotypes including hypogonadism, arteriosclerosis (vascular calcification), cardiac hypertrophy, osteopenia, sarcopenia, frailty, and premature death. Klotho protein functions as the obligate co-receptor for fibroblast growth factor-23 (FGF23), a bone-derived hormone that promotes urinary phosphate excretion in response to phosphate intake. Thus, Klotho-deficient mice suffer not only from accelerated ageing but also from phosphate retention due to impaired phosphate excretion. Importantly, restoration of the phosphate balance by placing Klotho-deficient mice on low phosphate diet rescued them from premature ageing, leading us to the notion that phosphate accelerates ageing. Because the extracellular fluid is super-saturated in terms of phosphate and calcium ions, an increase in the phosphate concentration can trigger precipitation of calcium-phosphate. In the blood, calcium-phosphate precipitated upon increase in the blood phosphate concentration is adsorbed by serum protein fetuin-A to form colloidal nanoparticles called calciprotein particles (CPPs). In the urine, CPPs appear in the renal tubular fluid when FGF23 increases phosphate load excreted per nephron. CPPs can induce cell damage, ectopic calcification, and inflammatory responses. CPPs in the blood can induce arteriosclerosis and non-infectious chronic inflammation, whereas CPPs in the urine can induce renal tubular damage and interstitial inflammation/fibrosis. Thus, we propose that CPPs behave like a pathogen that accelerates ageing and should be regarded as a novel therapeutic target against age-related disorders including chronic kidney disease.

Manipulating the exposome to enable better ageing

The sum total of life course exposures creates an exposome that has a significant impact on age-related health. Understanding the interplay between exposome factors and the (epi) genome, offers pertinent insights into the ageing process and its relationship with the accumulation of allostatic load. We propose to exploit this to develop a biomimetic approach that will provide insight into how evolution through natural selection in other species has solved many age related human health issues. In particular, we will emphasise the need to reconnect a more mechanistic approach to medical science with a broader natural sciences approach, using biomimetics to mitigate the global burden of age related ill health. In particular, we will discuss how such an approach indicates leverage of the activities of the Nrf 2 gene to enhance health span via reintroduction of the classical 'Food as Medicine' concept, including modulation of the microbiome and the creation of more salutogenic and biophilic environments. Additionally, we will discuss how this approach integrates with novel and developing senotherapies.

Extrarenal expression of α-klotho, the kidney related longevity gene, in Heterocephalus glaber, the long living Naked Mole Rat

The Naked Mole Rat (NMR), Heterocephalus glaber, provides an interesting model for studying biomarkers of longevity due to its long lifespan of more than 30 years, almost ten times longer than that of mice and rats. α-Klotho (klotho) is an aging-suppressor gene, and overexpression of klotho is associated with extended lifespan in mice. Klotho is predominantly expressed in the kidney. The expression profile of klotho in the NMR has not previously been reported. The present investigation studied the expression of klotho in the kidney of NMR with that of Rattus Norvegicus (RN) and demonstrated that klotho was expressed in the kidney of NMR at the same level as found in RN. Besides, a significant expression of Kl mRNA was found in the liver of NMR, in contrast to RN, where no hepatic expression was detected. The Klotho expression was further confirmed at the protein level. Thus, the results of the present comparative study indicate a differential tissue expression of klotho between different species. Besides its important function in the kidney, Klotho might also be of significance in the liver of NMR. It is suggested that the hepatic extrarenal expression of klotho may function as a further longevity-related factor in supplement to the Klotho in the kidney.

Loss of αklotho causes reduced motor ability and short lifespan in zebrafish

The klotho gene encodes a transmembrane protein αKlotho that interacts with a fibroblast growth factor (FGF) receptor in renal tubular epithelial cells and functions as a co-receptor for FGF23, which is an osteocytes-derived hormone. This bone-to-kidney signal promotes urinary phosphate excretion. Interestingly, αKlotho knockout mice show an accelerated aging and a shortened life span. Similarly, C. elegans lacking the αklotho homologue showed a short life span. However, the physiological basis of aging-related function of αklotho remain unclear. The αklotho-deficient vertebrate animals other than mice have been awaited as an alternative model of premature aging. We here employed zebrafish in our study and revealed that αklotho mutant zebrafish appeared to be normal at 3 months postfertilization (mpf) but eventually underwent premature death by 9 mpf, while normal zebrafish is known to survive for 42 months. We also assessed the motor ability of zebrafish in a forced swimming assay and found that αklotho mutant zebrafish displayed reduced swimming performance before their survival declined. A recent study also reported a similar finding that αklotho-deficient zebrafish exhibited a short life span and reduced spontaneous movements. Taken together, these results suggest that αKlotho mutant zebrafish show premature aging and are useful to investigate aging in vertebrates.

Critical roles of SMYD2 lysine methyltransferase in mediating renal fibroblast activation and kidney fibrosis

SET and MYND domain protein 2 (SMYD2) is a lysine methyltransferase that mediates histone H3 lysine 36 trimethylation (H3K36me3) and acts as a regulator of tumorgenesis and cystic growth. However, its role in renal fibrosis remains unknown. In this study, we found that SMYD2 was highly expressed in the murine kidney of renal fibrosis induced by unilateral ureteral obstruction, and primarily located in interstitial fibroblasts and renal tubular epithelial cells. Pharmacological inhibition of SMYD2 with AZ505, a highly selective inhibitor of SMYD2, protected against renal fibrosis and inhibited activation/proliferation of renal interstitial fibroblasts and conversion of epithelial cells to a profibrotic phenotype in this model. In cultured renal interstitial fibroblasts, treatment with AZ505 or silencing of SMYD2 by specific siRNA also inhibited serum- or TGF-β1-induced activation and proliferation of renal interstitial fibroblasts. Mechanistic studies showed that SMYD2 inhibition reduced phosphorylation of several profibrotic signaling molecules, including Smad3, extracellular signal-regulated kinase 1/2, AKT, signal transducer and activator of transcription-3 and nuclear factor-κB in both injured kidney and cultured renal fibroblasts. AZ505 was also effective in suppressing renal expression of Snail and Twist, two transcriptional factors that mediate renal partial epithelial-mesenchymal transition and fibrosis. Conversely, AZ505 treatment prevented downregulation of Smad7, a renoprotective factor in vivo and in vitro. These results indicate that SMYD2 plays a critical role in mediating conversion of epithelial cells to a profibrotic phenotype, renal fibroblast activation and renal fibrogenesis, and suggest that SMYD2 may be a potential target for the treatment of chronic fibrosis in kidney disease.

Bioinspired materials and technology for advanced cryopreservation

Cryopreservation can help to meet the demand for biosamples of high medical value. However, it remains difficult to effectively cryopreserve some sensitive cells, tissues, and reproductive organs. A coordinated effort from the perspective of the whole frozen biological system is necessary to advance cryopreservation technology. Animals that survive in cold temperatures, such as hibernators and cold-tolerant insects, offer excellent natural models. Their anti-cold strategies, such as programmed suppression of metabolism and the synthesis of cryoprotectants (CPAs), warrant systematic study. Furthermore, the discovery and synthesis of metabolism-regulating and cryoprotective biomaterials, combined with biotechnological breakthroughs, can also promote the development of cryopreservation. Further advances in the quality and duration of biosample storage inspired by nature will promote the application of cryopreserved biosamples in clinical therapy.

Socioeconomic position links circulatory microbiota differences with biological age

Imbalanced nutrition is associated with accelerated ageing, possibly mediated by microbiota. An analysis of the circulatory microbiota obtained from the leukocytes of participants in the MRC Twenty-07 general population cohort was performed. We now report that in this cohort, the most biologically aged exhibit a significantly higher abundance of circulatory pathogenic bacteria, including Neisseria, Rothia and Porphyromonas, while those less biologically aged possess more circulatory salutogenic (defined as being supportive of human health and wellbeing) bacteria, including Lactobacillus, Lachnospiraceae UCG-004 and Kocuria. The presence of these salutogenic bactreria is consistent with a capacity to metabolise and produce Nrf2 agonists. We also demonstrate that associated one carbon metabolism, notably betaine levels, did not vary with chronological age, but displayed a difference with socioeconomic position (SEP). Those at lower SEP possessed significantly lower betaine levels indicative of a poorer diet and poorer health span and consistent with reduced global DNA methylation levels in this group. Our data suggest a clear route to improving age related health and resilience based on dietary modulation of the microbiota.

A biomimetic natural sciences approach to understanding the mechanisms of ageing in burden of lifestyle diseases

The worldwide landscape of an ageing population and age-related disease brings with it huge socio-economic and public healthcare concerns across nations. Correspondingly, monumental human and financial resources have been invested in biomedical research, with a mission to decode the mechanisms of ageing and how these contribute to age-related disease. Multiple hallmarks of ageing have been identified that are common across taxa, highlighting their fundamental importance. These include dysregulated mitochondrial metabolism and telomeres biology, epigenetic modifications, cell-matrix interactions, proteostasis, dysregulated nutrient sensing, stem cell exhaustion, inflammageing and immuno-senescence. While our understanding of the molecular basis of ageing is improving, it remains a complex and multifactorial process that remains to be fully understood. A key aspect of the shortfall in our understanding of the ageing process lies in translating data from standard animal models to humans. Consequently, we suggest that a 'biomimetic' and comparative approach, integrating knowledge from species in the wild, as opposed to inbred genetically homogenous laboratory animals, can provide powerful insights into human ageing processes. Here we discuss some particularities and comparative patterns among several species from the animal kingdom, endowed with longevity or short lifespans and unique metabolic profiles that could be potentially exploited to the understanding of ageing and age-related diseases. Based upon lessons from nature, we also highlight several avenues for renewed focus in the pathophysiology of ageing and age-related disease (i.e. diet-microbiome-health axis, oxidative protein damage, adaptive homoeostasis and planetary health). We propose that a biomimetic alliance with collaborative research from different disciplines can improve our understanding of ageing and age-related diseases with long-term sustainable utility.

Biomimetics provides lessons from nature for contemporary ways to improve human health

Homo sapiens is currently living in serious disharmony with the rest of the natural world. For our species to survive, and for our well-being, we must gather knowledge from multiple perspectives and actively engage in studies of planetary health. The enormous diversity of species, one of the most striking aspects of life on our planet, provides a source of solutions that have been developed through evolution by natural selection by animals living in extreme environments. The food system is central to finding solutions; our current global eating patterns have a negative impact on human health, driven climate change and loss of biodiversity. We propose that the use of solutions derived from nature, an approach termed biomimetics, could mitigate the effects of a changing climate on planetary health as well as human health. For example, activation of the transcription factor Nrf2 may play a role in protecting animals living in extreme environments, or animals exposed to heat stress, pollution and pesticides. In order to meet these challenges, we call for the creation of novel interdisciplinary planetary health research teams.

Understanding the role of the cytoprotective transcription factor nuclear factor erythroid 2-related factor 2-lessons from evolution, the animal kingdom and rare progeroid syndromes

The cytoprotective transcriptor factor nuclear factor erythroid 2– related factor 2 (NRF2) is part of a complex regulatory network that responds to environmental cues. To better understand its role in a cluster of inflammatory and pro-oxidative burden of lifestyle diseases that accumulate with age, lessons can be learned from evolution, the animal kingdom and progeroid syndromes. When levels of oxygen increased in the atmosphere, mammals required ways to protect themselves from the metabolic toxicity that arose from the production of reactive oxygen species. The evolutionary origin of the NRF2–Kelch-like ECH-associated protein 1 (KEAP1) signalling pathway from primitive origins has been a prerequisite for a successful life on earth, with checkpoints in antioxidant gene expression, inflammation, detoxification and protein homoeostasis. Examples from the animal kingdom suggest that superior antioxidant defense mechanisms with enhanced NRF2 expression have been developed during evolution to protect animals during extreme environmental conditions, such as deep sea diving, hibernation and habitual hypoxia. The NRF2–KEAP1 signalling pathway is repressed in progeroid (accelerated ageing) syndromes and a cluster of burden of lifestyle disorders that accumulate with age. Compelling links exist between tissue hypoxia, senescence and a repressed NRF2 system. Effects of interventions that activate NRF2, including nutrients, and more potent (semi)synthetic NRF2 agonists on clinical outcomes are of major interest. Given the broad-ranging actions of NRF2, we need to better understand the mechanisms of activation, biological function and regulation of NRF2 and its inhibitor, KEAP1, in different clinical conditions to ensure that modulation of this thiol-based system will not result in major adverse effects. Lessons from evolution, the animal kingdom and conditions of accelerated ageing clarify a major role of a controlled NRF2–KEAP1 system in healthy ageing and well-being.

Phosphate as a Pathogen of Arteriosclerosis and Aging

During the evolution of skeletons, terrestrial vertebrates acquired strong bones made of calcium-phosphate. By keeping the extracellular fluid in a supersaturated condition regarding calcium and phosphate ions, they created the bone when and where they wanted simply by providing a cue for precipitation. To secure this strategy, they acquired a novel endocrine system to strictly control the extracellular phosphate concentration. In response to phosphate intake, fibroblast growth factor-23 (FGF23) is secreted from the bone and acts on the kidney through binding to its receptor Klotho to increase urinary phosphate excretion, thereby maintaining phosphate homeostasis. The FGF23-Klotho endocrine system, when disrupted in mice, results in hyperphosphatemia and vascular calcification. Besides, mice lacking Klotho or FGF23 suffer from complex aging-like phenotypes, which are alleviated by placing them on a low- phosphate diet, indicating that phosphate is primarily responsible for the accelerated aging. Phosphate acquires the ability to induce cell damage and inflammation when precipitated with calcium. In the blood, calcium-phosphate crystals are adsorbed by serum protein fetuin-A and prevented from growing into large precipitates. Consequently, nanoparticles that comprised calcium-phosphate crystals and fetuin-A, termed calciprotein particles (CPPs), are generated and dispersed as colloids. CPPs increase in the blood with an increase in serum phosphate and age. Circulating CPP levels correlate positively with vascular stiffness and chronic non-infectious inflammation, raising the possibility that CPPs may be an endogenous pro-aging factor. Terrestrial vertebrates with the bone made of calcium- phosphate may be destined to age due to calcium-phosphate in the blood.

Body Protein Sparing in Hibernators: A Source for Biomedical Innovation

Proteins are not only the major structural components of living cells but also ensure essential physiological functions within the organism. Any change in protein abundance and/or structure is at risk for the proper body functioning and/or survival of organisms. Death following starvation is attributed to a loss of about half of total body proteins, and body protein loss induced by muscle disuse is responsible for major metabolic disorders in immobilized patients, and sedentary or elderly people. Basic knowledge of the molecular and cellular mechanisms that control proteostasis is continuously growing. Yet, finding and developing efficient treatments to limit body/muscle protein loss in humans remain a medical challenge, physical exercise and nutritional programs managing to only partially compensate for it. This is notably a major challenge for the treatment of obesity, where therapies should promote fat loss while preserving body proteins. In this context, hibernating species preserve their lean body mass, including muscles, despite total physical inactivity and low energy consumption during torpor, a state of drastic reduction in metabolic rate associated with a more or less pronounced hypothermia. The present review introduces metabolic, physiological, and behavioral adaptations, e.g., energetics, body temperature, and nutrition, of the torpor or hibernation phenotype from small to large mammals. Hibernating strategies could be linked to allometry aspects, the need for periodic rewarming from torpor, and/or the ability of animals to fast for more or less time, thus determining the capacity of individuals to save proteins. Both fat- and food-storing hibernators rely mostly on their body fat reserves during the torpid state, while minimizing body protein utilization. A number of them may also replenish lost proteins during arousals by consuming food. The review takes stock of the physiological, molecular, and cellular mechanisms that promote body protein and muscle sparing during the inactive state of hibernation. Finally, the review outlines how the detailed understanding of these mechanisms at play in various hibernators is expected to provide innovative solutions to fight human muscle atrophy, to better help the management of obese patients, or to improve the ex vivo preservation of organs.

Nuclear factor erythroid 2-related factor 2 as a treatment target of kidney diseases

PURPOSE OF REVIEW

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor which regulates a wider range of downstream pathways than previously thought. This review focuses on the novel findings about the internal regulatory mechanisms of Nrf2, the expanding understanding of its role in maintaining cellular homeostasis and the attempts to broaden the clinical application of its activators.

RECENT FINDINGS

Nrf2 is in charge of the maintenance of cellular homeostasis under stress and there exist the internal regulatory mechanisms for Nrf2 which have recently been elucidated. New downstream pathways of Nrf2 have been discovered, including the defense against ferroptosis, the latest concept of cell death. Several Nrf2 activators are at various stages of clinical development and are being tested in clinical trials for chronic kidney disease (CKD) including diabetic kidney disease, Alport syndrome, autosomal dominant polycystic kidney disease and focal segmental glomerulosclerosis.

SUMMARY

Nrf2 has been gathering attention as an emerging treatment target of chronic diseases which have oxidative stress and inflammation as their pathogenesis including CKD. Basic and clinical studies are under way to establish its role as a target for treatment of those diseases.

Research progress on the interaction between circadian clock and early vascular aging

Considerable researches implicate that the circadian clock regulates the responsive rhythms of organs and sets the orderly aging process of cells indirectly. It influences an array of diverse biological process including intestinal flora, peripheral inflammatory responses, and redox homeostasis. People with sleep disoders and other kinds of circadian disruptions are prone to have vascular aging earlier. Meanwhile, those people are always faced with chronic vascular inflammation. It has not been elucidated that the specific mechanism of the interaction between the circadian system and early vascular aging. To explore the biphasic relationship between vascular aging and the circadian system, we summarize what is linking circadian clock with early vascular aging through four major prospect: inflammatory process, oxidative stress response, intestinal flora, and cellular senescence. Meanwhile, we discuss the hypothesis that the deterioration of circadian rhythms may exacerbate the process of early vascular aging, leading to the cardiovascular diseases. It will help us to provide new ideas for understanding the process of vascular aging and exploring the possible ways to design personalized chronotherapies.

The oxygen cascade in patients treated with hemodialysis and native high-altitude dwellers: lessons from extreme physiology to benefit patients with end-stage renal disease

Patients treated with hemodialysis (HD) repeatedly undergo intradialytic low arterial oxygen saturation and low central venous oxygen saturation, reflecting an imbalance between upper body systemic oxygen supply and demand, which are associated with increased mortality. Abnormalities along the entire oxygen cascade, with impaired diffusive and convective oxygen transport, contribute to the reduced tissue oxygen supply. HD treatment impairs pulmonary gas exchange and reduces ventilatory drive, whereas ultrafiltration can reduce tissue perfusion due to a decline in cardiac output. In addition to these factors, capillary rarefaction and reduced mitochondrial efficacy can further affect the balance between cellular oxygen supply and demand. Whereas it has been convincingly demonstrated that a reduced perfusion of heart and brain during HD contributes to organ damage, the significance of systemic hypoxia remains uncertain, although it may contribute to oxidative stress, systemic inflammation, and accelerated senescence. These abnormalities along the oxygen cascade of patients treated with HD appear to be diametrically opposite to the situation in Tibetan highlanders and Sherpa, whose physiology adapted to the inescapable hypobaric hypoxia of their living environment over many generations. Their adaptation includes pulmonary, vascular, and metabolic alterations with enhanced capillary density, nitric oxide production, and mitochondrial efficacy without oxidative stress. Improving the tissue oxygen supply in patients treated with HD depends primarily on preventing hemodynamic instability by increasing dialysis time/frequency or prescribing cool dialysis. Whether dietary or pharmacological interventions, such as the administration of L-arginine, fermented food, nitrate, nuclear factor erythroid 2-related factor 2 agonists, or prolyl hydroxylase 2 inhibitors, improve clinical outcome in patients treated with HD warrants future research.

Cellular Senescence in Kidney Fibrosis: Pathologic Significance and Therapeutic Strategies

Age-related disorders such as chronic kidney disease (CKD) are increasingly prevalent globally and pose unprecedented challenges. In many aspects, CKD can be viewed as a state of accelerated and premature aging. Aging kidney and CKD share many common characteristic features with increased cellular senescence, a conserved program characterized by an irreversible cell cycle arrest with altered transcriptome and secretome. While developmental senescence and acute senescence may positively contribute to the fine-tuning of embryogenesis and injury repair, chronic senescence, when unresolved promptly, plays a crucial role in kidney fibrogenesis and CKD progression. Senescent cells elicit their fibrogenic actions primarily by secreting an assortment of inflammatory and profibrotic factors known as the senescence-associated secretory phenotype (SASP). Increasing evidence indicates that senescent cells could be a promising new target for therapeutic intervention known as senotherapy, which includes depleting senescent cells, modulating SASP and restoration of senescence inhibitors. In this review, we discuss current understanding of the role and mechanism of cellular senescence in kidney fibrosis. We also highlight potential options of targeting senescent cells for the treatment of CKD.

Regional distribution and severity of arterial calcification in patients with chronic kidney disease stages 1-5: a cross-sectional study of the Copenhagen chronic kidney disease cohort

BACKGROUND

Patients with chronic kidney disease (CKD) and arterial calcification are considered at increased risk of adverse cardiovascular outcomes. However, the optimal site for measurement of arterial calcification has not been determined. The primary aim of this study was to examine the pattern of arterial calcification in different stages of CKD.

METHODS

This was an observational, cross-sectional study that included 580 individuals with CKD stages 1-5 (no dialysis) from the Copenhagen CKD Cohort. Calcification of the carotid, coronary and iliac arteries, thoracic and abdominal aorta was assessed using non-contrast multidetector computed tomography scans and quantified according to the Agatston method. Based on the distribution of Agatston scores in the selected arterial region, the subjects were divided into calcium score categories of 0 (no calcification), 1-100, 101-400 and > 400.

RESULTS

Participants with CKD stages 3-5 had the highest prevalence of calcification and the highest frequency of calcium scores > 400 in all arterial sites. Calcification in at least one arterial site was present in > 90% of patients with CKD stage 3. In all five CKD stages prevalence of calcification was greatest in both the thoracic and abdominal aorta, and in the iliac arteries. These arterial sites also showed the highest calcium scores. High calcium scores (> 400) in all five arterial regions were independently associated with prevalent cardiovascular disease. In multivariable analyses, after adjusting for cardiovascular risk factors, declining creatinine clearance was associated with increasing calcification of the coronary arteries (p = 0.012) and the thoracic aorta (p = 0.037) only.

CONCLUSIONS

Arterial calcification is highly prevalent throughout all five CKD stages and is most prominent in both the thoracic and abdominal aorta, and in the iliac arteries. Follow-up studies are needed to explore the potential of extracardiac calcification sites in prediction of cardiovascular events in the CKD population.

Vitamin D Metabolism and Its Role in Mineral and Bone Disorders in Chronic Kidney Disease in Humans, Dogs and Cats

Some differences regarding Vitamin D metabolism are described in dogs and cats in comparison with humans, which may be explained by an evolutionary drive among these species. Similarly, vitamin D is one of the most important regulators of mineral metabolism in dogs and cats, as well as in humans. Mineral metabolism is intrinsically related to bone metabolism, thus disturbances in vitamin D have been implicated in the development of chronic kidney disease mineral and bone disorders (CKD-MBD) in people, in addition to dogs and cats. Vitamin D deficiency may be associated with Renal Secondary Hyperparathyroidism (RSHPT), which is the most common mineral disorder in later stages of CKD in dogs and cats. Herein, we review the peculiarities of vitamin D metabolism in these species in comparison with humans, and the role of vitamin D disturbances in the development of CKD-MBD among dogs, cats, and people. Comparative studies may offer some evidence to help further research about vitamin D metabolism and bone disorders in CKD.

Food as medicine: targeting the uraemic phenotype in chronic kidney disease

The observation that unhealthy diets (those that are low in whole grains, fruits and vegetables, and high in sugar, salt, saturated fat and ultra-processed foods) are a major risk factor for poor health outcomes has boosted interest in the concept of 'food as medicine'. This concept is especially relevant to metabolic diseases, such as chronic kidney disease (CKD), in which dietary approaches are already used to ameliorate metabolic and nutritional complications. Increased awareness that toxic uraemic metabolites originate not only from intermediary metabolism but also from gut microbial metabolism, which is directly influenced by diet, has fuelled interest in the potential of 'food as medicine' approaches in CKD beyond the current strategies of protein, sodium and phosphate restriction. Bioactive nutrients can alter the composition and metabolism of the microbiota, act as modulators of transcription factors involved in inflammation and oxidative stress, mitigate mitochondrial dysfunction, act as senolytics and impact the epigenome by altering one-carbon metabolism. As gut dysbiosis, inflammation, oxidative stress, mitochondrial dysfunction, premature ageing and epigenetic changes are common features of CKD, these findings suggest that tailored, healthy diets that include bioactive nutrients as part of the foodome could potentially be used to prevent and treat CKD and its complications.

Proteomics in Non-model Organisms: A New Analytical Frontier

For the last century we have relied on model organisms to help understand fundamental biological processes. Now, with advancements in genome sequencing, assembly, and annotation, non-model organisms may be studied with the same advanced bioanalytical toolkit as model organisms. Proteomics is one such technique, which classically relies on predicted protein sequences to catalog and measure complex proteomes across tissues and biofluids. Applying proteomics to non-model organisms can advance and accelerate biomimicry studies, biomedical advancements, veterinary medicine, agricultural research, behavioral ecology, and food safety. In this postmodel organism era, we can study almost any species, meaning that many non-model organisms are, in fact, important emerging model organisms. Herein we specifically focus on eukaryotic organisms and discuss the steps to generate sequence databases, analyze proteomic data with or without a database, and interpret results as well as future research opportunities. Proteomics is more accessible than ever before and will continue to rapidly advance in the coming years, enabling critical research and discoveries in non-model organisms that were hitherto impossible.

Klotho, Aging, and the Failing Kidney

Klotho has been recognized as a gene involved in the aging process in mammals for over 30 years, where it regulates phosphate homeostasis and the activity of members of the fibroblast growth factor (FGF) family. The α-Klotho protein is the receptor for Fibroblast Growth Factor-23 (FGF23), regulating phosphate homeostasis and vitamin D metabolism. Phosphate toxicity is a hallmark of mammalian aging and correlates with diminution of Klotho levels with increasing age. As such, modulation of Klotho activity is an attractive target for therapeutic intervention in the diseasome of aging; in particular for chronic kidney disease (CKD), where Klotho has been implicated directly in the pathophysiology. A range of senotherapeutic strategies have been developed to directly or indirectly influence Klotho expression, with varying degrees of success. These include administration of exogenous Klotho, synthetic and natural Klotho agonists and indirect approaches, via modulation of the foodome and the gut microbiota. All these approaches have significant potential to mitigate loss of physiological function and resilience accompanying old age and to improve outcomes within the diseasome of aging.

Comparative Oncology: New Insights into an Ancient Disease

Cancer has deep evolutionary roots and is an important source of selective pressure in organismal evolution. Yet, we find a great deal of variation in cancer vulnerabilities across the tree of life. Comparative oncology offers insights into why some species vary in their susceptibility to cancer and the mechanisms responsible for the diversity of cancer defenses. Here we provide an overview for why cancer persists across the tree of life. We then summarize current data on cancer in mammals, reptiles, and birds in comparison with commonly reported human cancers. We report on both novel and shared mechanisms of cancer protection in animals. Cross-discipline collaborations, including zoological and aquarium institutions, wildlife and evolutionary biologists, veterinarians, medical doctors, cancer biologists, and oncologists, will be essential for progress in the field of comparative oncology. Improving medical treatment of humans and animals with cancer is the ultimate promise of comparative oncology.