Sirtuin and metabolic kidney disease

E1231/SR647 protects against unilateral renal ischemia-reperfusion injury by modulating SIRT1/FOXO3 interactions with Nrf2 and NFκB pathways

Ischemia is a major contributor to acute kidney injury (AKI), for which current treatment options remain limited. One NAD+-dependent deacetylase that can preserve renal cells is SIRT1. To date, no research has directly explored the effects of E1231, a SIRT1 activator, in the context of renal ischemia-reperfusion (IR) injury. Enhancing NAD+ levels is essential for sustaining SIRT1 activity. Hence, the combined use of E1231 and SR647, a NAD+ precursor, could potentially amplify protective effects by supporting prolonged SIRT1 activation. This study is the first to investigate the therapeutic potential of combining E1231 and SR647 in mitigating unilateral renal IR injury. Rats treated with E1231/SR647 effectively demonstrated reduced tubular damage, inflammation, and necrosis. These improvements correlated with a reduced kidney-to-body weight ratio and increased urine output and flow rate. Additionally, rats with IR injury demonstrated reductions in serum creatinine, BUN, UAER, and cystatin C, as well as urinary NGAL and both serum and urinary KIM-1 levels. On the other hand, elevations in urine creatinine and creatinine CL were recorded. E1231 alone provided moderate functional recovery, which was negated when co-administered with a SIRT1 inhibitor. E1231/SR647 treatment upregulated SIRT1 levels and activity, subsequently enhancing FOXO3 activation. It also boosted Nrf2 levels and activity, upregulating the antioxidant protein expression of HO-1 and NQO1. Furthermore, E1231/SR647 reduced the inflammatory response by inhibiting NFκB activity. In conclusion, E1231/SR647 is a promising therapy that may protect renal function during ischemic events through the modulation of SIRT1/FOXO3 control over Nrf2 and NFκB pathways.

Sirtuins in kidney homeostasis and disease: where are we now?

Sirtuins, identified as (NAD+)- dependent class III histone deacetylases, engage in a spectrum of biological functions, encompassing DNA damage repair, oxidative stress, immune modulation, mitochondrial homeostasis, apoptosis and autophagy. Sirtuins play an apoptosis role in regulating cellular operations and overall organism health. Mounting data indicate that dysregulated sirtuin expression is linked to the onset of renal diseases. Effective modulation of sirtuins expression and activity has been shown to improve renal function and attenuate the advancement of kidney diseases. In this review, we present a comprehensive overview of the biological impacts of sirtuins and their molecular targets in regulating renal diseases. Additionally, we detail advancements in elucidating sirtuin roles in the pathophysiology of both chronic and acute renal disorders. We review compounds that modulate sirtuin activity through activation or inhibition, potentially improving outcomes in renal disease. In summary, strategic manipulation of sirtuin activity represents a prospective therapeutic approach for renal diseases.

MiR-128-3p promotes hyperproliferation of keratinocytes and psoriasis-like inflammation by targeting SIRT1/HIF-1α

Psoriasis is a long-lasting inflammatory skin condition characterized by excessive keratinocyte growth. Recent studies have confirmed abnormal regulation of microRNAs (miRNAs/miRs) in individuals with psoriasis. This study aimed to investigate the function and specific mechanism of action of miR-128a-3p in interleukin-22 (IL-22)-stimulated HaCaT cells. The expression level of miR-128-3p and sirtuin 1 (SIRT1)/hypoxia inducible factor (HIF-1α) was detected using qRT-PCR on patients with psoriasis and IL-22-treated HaCaT cell model. Western blotting was used to detect apoptosis-associated proteins and SIRT1/HIFα pathway protein expression levels. The cell viability was determined using the CCK-8 method. Flow cytometry was performed to detect apoptosis following IL-22 stimulation or transfection. Enzyme-linked immunosorbent assay (ELISA) was used to detect cellular inflammatory factor secretion. The relationship between miR-128-3p and SIRT1 was predicted using the Starbase database and verified using a dual-luciferase reporter gene assay. In patients with psoriasis and IL-22-stimulated HaCaT cells, miR-128-3p and HIF-1α expression levels were elevated and SIRT1 expression was decreased. miR-128-3p directly targeted SIRT1. IL-22 stimulation significantly elevated cell viability, inhibited apoptosis levels and cleaved-caspase3 protein expression, and promoted an inflammatory response in HaCaT cells, which was further promoted by the miR-128-3p mimic. The miR-128-3p inhibitor reduced cell viability, promoted cell apoptosis and cleaved-caspase3 protein expression, and inhibited the inflammatory response in IL-22-induced HaCaT cells; these effects were at least partly reversed by SIRT1-siRNA. miR-128-3p expression is elevated in psoriasis and promotes psoriasis progression by inhibiting SIRT1 expression.

JiangyaTongluo decoction ameliorates tubulointerstitial fibrosis via regulating the SIRT1/PGC-1α/mitophagy axis in hypertensive nephropathy

Introduction

With the increasing prevalence of hypertension, the incidence of kidney diseases is also increasing, resulting in a serious public burden. Jiangya Tongluo decoction (JYTL), a recognized prescription in traditional Chinese medicine (TCM), is commonly used to calm an overactive liver and reduce excess yang, while also promoting blood flow to alleviate obstructions in the meridians. Previous research has indicated that JYTL may help mitigate kidney damage caused by hypertension; however, the underlying mechanisms have not been thoroughly assessed.

Methods

First, an amalgamation of UPLC-QE/MS and network pharmacology techniques was employed to pinpoint potential active components, primary targets, and crucial action mechanisms of JYTL in treating hypertensive nephropathy (HN). Then, we used spontaneous hypertensive rats (SHRs) and Wistar-Kyoto rats (WKYs) to evaluate the efficacy of JYTL on HN with valsartan as a positive reference. We also conducted DCFH-DA fluorescence staining in rat renal tissues to detect the level of ROS. Western blotting and immunohistochemistry were performed to investigate further the effect of JYTL decoction on key targets and signaling pathways.

Results

Through UPLC-QE/MS and network analysis, 189 active ingredients and 5 hub targets were identified from JYTL. GSEA in the MitoCarta3.0 database and PPI network analysis revealed that JYTL predominantly engages in the Sirt1-mitophagy signaling pathway. Tanshinone iia, quercetin, and adenosine in JYTL are the main active ingredients for treating HN. In vivo validation showed that JYTL decoction could improve kidney function, ameliorate tubulointerstitial fibrosis (TIF), and improve mitochondrial function by inhibiting ROS production and regulating mitochondrial dynamics in SHRs. JYTL treatment could also increase the expression of SIRT1, PGC-1α, Nrf1, and TFAM, and activate PINK1/Parkin-mediated mitophagy.

Conclusion

JYTL decoction may exert renal function protective and anti-fibrosis effects in HN by ameliorating mitochondrial function and regulating the SIRT1/PGC-1α-mitophagy pathway.

Dapagliflozin attenuates AKI to CKD transition in diabetes by activating SIRT3/PGC1-α signaling and alleviating aberrant metabolic reprogramming

BACKGROUND

Patients with diabetes are prone to acute kidney injury (AKI) with a high mortality rate, poor prognosis, and a higher risk of progression to chronic kidney disease than non-diabetic patients.

METHODS

Streptozotocin (STZ)-treated type 1 and db/db type 2 diabetes model were established, AKI model was induced in mice by ischemia-reperfusion injury(IRI). Mouse proximal tubular cell cells were subjected to high glucose and hypoxia-reoxygenation in vitro. Transcriptional RNA sequencing was performed for clustering analysis and target gene screening. Renal structural damage was determined by histological staining, whereas creatinine and urea nitrogen levels were used to measure renal function.

RESULTS

Deteriorated renal function and renal tissue damage were observed in AKI mice with diabetic background. RNA sequencing showed a decrease in fatty acid oxidation (FAO) pathway and an increase in abnormal glycolysis. Treatment with Dapa, Sitagliptin(a DPP-4 inhibitor)and insulin reduced blood glucose levels in mice, and improved renal function. However, Dapa had a superior therapeutic effect and alleviated aberrant FAO and glycosis. Dapa reduced cellular death in cultured cells under high glucose hypoxia-reoxygenation conditions, alleviated FAO dysfunction, and reduced abnormal glycolysis. RNA sequencing showed that SIRT3 expression was reduced in diabetic IRI, which was largely restored by Dapa intervention. 3-TYP, a SIRT3 inhibitor, reversed the renal protective effects of Dapa and mediated abnormal FAO and glycolysis in mice and tubular cells.

CONCLUSION

Our study provides experimental evidence for the use of Dapa as a means to reduce diabetic AKI by ameliorating metabolic reprogramming in renal tubular cells.

LRG1 loss effectively restrains glomerular TGF-β signaling to attenuate diabetic kidney disease

Transforming growth factor (TGF)-β signaling is a well-established pathogenic mediator of diabetic kidney disease (DKD). However, owing to its pleiotropic actions, its systemic blockade is not therapeutically optimal. The expression of TGF-β signaling regulators can substantially influence TGF-β's effects in a cell- or context-specific manner. Among these, leucine-rich α2-glycoprotein 1 (LRG1) is significantly increased in glomerular endothelial cells (GECs) in DKD. As LRG1 is a secreted molecule that can exert autocrine and paracrine effects, we examined the effects of LRG1 loss in kidney cells in diabetic OVE26 mice by single-cell transcriptomic analysis. Gene expression analysis confirmed a predominant expression of Lrg1 in GECs, which further increased in diabetic kidneys. Loss of Lrg1 led to the reversal of angiogenic and TGF-β-induced gene expression in GECs, which were associated with DKD attenuation. Notably, Lrg1 loss also mitigated the increased TGF-β-mediated gene expression in both podocytes and mesangial cells in diabetic mice, indicating that GEC-derived LRG1 potentiates TGF-β signaling in glomerular cells in an autocrine and paracrine manner. Indeed, a significant reduction in phospho-Smad proteins was observed in the glomerular cells of OVE26 mice with LRG1 loss. These results indicate that specific antagonisms of LRG1 may be an effective approach to curb the hyperactive glomerular TGF-β signaling to attenuate DKD.

Retinal Degeneration Response to Graphene Quantum Dots: Disruption of the Blood-Retina Barrier Modulated by Surface Modification-Dependent DNA Methylation

Graphene quantum dots (GQDs) are used in diverse fields from chemistry-related materials to biomedicines, thus causing their substantial release into the environment. Appropriate visual function is crucial for facilitating the decision-making process within the nervous system. Given the direct interaction of eyes with the environment and even nanoparticles, herein, GQDs, sulfonic acid-doped GQDs (S-GQDs), and amino-functionalized GQDs (A-GQDs) were employed to understand the potential optic neurotoxicity disruption mechanism by GQDs. The negatively charged GQDs and S-GQDs disturbed the response to light stimulation and impaired the structure of the retinal nuclear layer of zebrafish larvae, causing vision disorder and retinal degeneration. Albeit with sublethal concentrations, a considerably reduced expression of the retinal vascular sprouting factor sirt1 through increased DNA methylation damaged the blood-retina barrier. Importantly, the regulatory effect on vision function was influenced by negatively charged GQDs and S-GQDs but not positively charged A-GQDs. Moreover, cluster analysis and computational simulation studies indicated that binding affinities between GQDs and the DNMT1-ligand binding might be the dominant determinant of the vision function response. The previously unknown pathway of blood-retinal barrier interference offers opportunities to investigate the biological consequences of GQD-based nanomaterials, guiding innovation in the industry toward environmental sustainability.

Sirtuin 3 in renal diseases and aging: From mechanisms to potential therapies

The longevity protein sirtuins (SIRTs) belong to a family of nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases. In mammals, SIRTs comprise seven members (SIRT1-7) which are localized to different subcellular compartments. As the most prominent mitochondrial deacetylases, SIRT3 is known to be regulated by various mechanisms and participate in virtually all aspects of mitochondrial homeostasis and metabolism, exerting significant impact on multiple organs. Notably, the kidneys possess an abundance of mitochondria that provide substantial energy for filtration and reabsorption. A growing body of evidence now supports the involvement of SIRT3 in several renal diseases, including acute kidney injury, chronic kidney disease, and diabetic nephropathy; notably, these diseases are all associated with aging. In this review, we summarize the emerging role of SIRT3 in renal diseases and aging, and highlights the intricate mechanisms by which SIRT3 exerts its effects. In addition, we highlight the potential therapeutic significance of modulating SIRT3 and provide valuable insights into the therapeutic role of SIRT3 in renal diseases to facilitate clinical application.

Ultrasmall Polyphenol-NAD+ Nanoparticle-Mediated Renal Delivery for Mitochondrial Repair and Anti-Inflammatory Treatment of AKI-to-CKD Progression

As a central metabolic molecule, nicotinamide adenine dinucleotide (NAD+) can potentially treat acute kidney injury (AKI) and chronic kidney disease (CKD); however, its bioavailability is poor due to short half-life, instability, the deficiency of targeting, and difficulties in transmembrane transport. Here a physiologically adaptive gallic acid-NAD+ nanoparticle is designed, which has ultrasmall size and pH-responsiveness, passes through the glomerular filtration membrane to reach injured renal tubules, and efficiently delivers NAD+ into the kidneys. With an effective accumulation in the kidneys, it restores renal function, immune microenvironment homeostasis, and mitochondrial homeostasis of AKI mice via the NAD+-Sirtuin-1 axis, and exerts strong antifibrotic effects on the AKI-to-CKD transition by inhibiting TGF-β signaling. It also exhibits excellent stability, biodegradable, and biocompatible properties, ensuring its long-term safety, practicality, and clinical translational feasibility. The present study shows a potential modality of mitochondrial repair and immunomodulation through nanoagents for the efficient and safe treatment of AKI and CKD.

Ability of NAD and Sirt1 to epigenetically suppress albuminuria

The time for diabetic nephropathy (DN) to progress from mild to severe is long. Thus, methods to continuously repress DN are required to exert long-lasting effects mediated through epigenetic regulation. In this study, we demonstrated the ability of nicotinamide adenine dinucleotide (NAD) and its metabolites to reduce albuminuria through Sirt1- or Nampt-dependent epigenetic regulation. We previously reported that proximal tubular Sirt1 was lowered before glomerular Sirt1. Repressed glomerular Sirt1 was found to epigenetically elevate Claudin-1. In addition, we reported that proximal tubular Nampt deficiency epigenetically augmented TIMP-1 levels in Sirt6-mediated pathways, leading to type-IV collagen deposition and diabetic fibrosis. Altogether, we propose that the Sirt1/Claudin-1 axis may be crucial in the onset of albuminuria at the early stages of DN and that the Nampt/Sirt6/TIMP-1 axis promotes diabetic fibrosis in the middle to late stages of DN. Finally, administration of NMN, an NAD precursor, epigenetically potentiates the regression of the onset of DN to maintain Sirt1 and repress Claudin-1 in podocytes, suggesting the potential use of NAD metabolites as epigenetic medications for DN.

Metabolite accumulation from oral NMN supplementation drives aging-specific kidney inflammation

The mitochondrial-rich renal tubule cells are key regulators of blood homeostasis via excretion and reabsorption of metabolic waste. With age, tubules are subject to increasing mitochondrial dysfunction and declining nicotinamide adenine dinucleotide (NAD+) levels, both hampering ATP production efficiency. We tested two mitochondrial interventions in young (6-mo) and aged (26-mo) adult male mice: elamipretide (ELAM), a tetrapeptide in clinical trials that improves mitochondrial structure and function, and nicotinamide mononucleotide (NMN), an NAD+ intermediate and commercially available oral supplement. Kidneys were analyzed from young and aged mice after eight weeks of treatment with ELAM (3 mg/kg/day), NMN (300 mg/kg/day), or from aged mice treated with the two interventions combined (ELAM+NMN). We hypothesized that combining pharmacologic treatments to ameliorate mitochondrial dysfunction and boost NAD+ levels, would more effectively reduce kidney aging than either intervention alone. Unexpectedly, in aged kidneys, NMN increased expression of genetic markers of inflammation (IL-1-beta; and Ccl2) and tubule injury (Kim-1). Metabolomics of endpoint sera showed that NMN-treated aged mice had higher circulating levels of uremic toxins than either aged controls or young NMN-treated mice. ELAM+NMN-treated aged mice accumulated uremic toxins like NMN-only aged mice, but reduced IL-1-beta; and Ccl2 kidney mRNA. This suggests that pre-existing mitochondrial dysfunction in aged kidney underlies susceptibility to inflammatory signaling with NMN supplementation in aged, but not young, mice. These findings demonstrate age and tissue dependent effects on downstream metabolic accumulation from NMN and highlight the need for targeted analysis of aged kidneys to assess the safety of anti-aging supplements in older populations.

Research progress on Sirtuins (SIRTs) family modulators

Sirtuins (SIRTs) represent a class of nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylases that exert a crucial role in cellular signal transduction and various biological processes. The mammalian sirtuins family encompasses SIRT1 to SIRT7, exhibiting therapeutic potential in counteracting cellular aging, modulating metabolism, responding to oxidative stress, inhibiting tumors, and improving cellular microenvironment. These enzymes are intricately linked to the occurrence and treatment of diverse pathological conditions, including cancer, autoimmune diseases, and cardiovascular disorders. Given the significance of histone modification in gene expression and chromatin structure, maintaining the equilibrium of the sirtuins family is imperative for disease prevention and health restoration. Mounting evidence suggests that modulators of SIRTs play a crucial role in treating various diseases and maintaining physiological balance. This review delves into the molecular structure and regulatory functions of the sirtuins family, reviews the classification and historical evolution of SIRTs modulators, offers a systematic overview of existing SIRTs modulation strategies, and elucidates the regulatory mechanisms of SIRTs modulators (agonists and inhibitors) and their clinical applications. The article concludes by summarizing the challenges encountered in SIRTs modulator research and offering insights into future research directions.

The therapeutic effects of marine sulfated polysaccharides on diabetic nephropathy

Marine sulfated polysaccharide (MSP) is a natural high molecular polysaccharide containing sulfate groups, which widely exists in various marine organisms. The sources determine structural variabilities of MSPs which have high security and wide biological activities, such as anticoagulation, antitumor, antivirus, immune regulation, regulation of glucose and lipid metabolism, antioxidant, etc. Due to the structural similarities between MSP and endogenous heparan sulfate, a majority of studies have shown that MSP can be used to treat diabetic nephropathy (DN) in vivo and in vitro. In this paper, we reviewed the anti-DN activities, the dominant mechanisms and structure-activity relationship of MSPs in order to provide the overall scene of MSPs as a modality of treating DN.

Exercise alleviates renal interstitial fibrosis by ameliorating the Sirt1-mediated TGF-β1/Smad3 pathway in T2DM mice

Background

Renal interstitial fibrosis is the pathophysiological basis of type 2 diabetes mellitus (T2DM). Exercise appears to improve kidney interstitial fibrosis in T2DM, in which silent information regulator factor 2-related enzyme 1 (Sirt1) is a critical regulator. However, the role of Sirt1 in mediating exercise on renal tissue as well as its mechanism remains unknown.

Methods

T2DM mouse models were created using a high-fat diet mixed with streptozotocin, followed by 8 weeks of treadmill exercise and niacinamide (Sirt1 inhibitor) intervention. Kits for detecting biochemical indices of renal function were used. The pathological appearance and severity of renal tissue were examined using hematoxylin and eosin, Masson and immunohistochemical staining. The mRNA and protein expression of relevant signaling pathway factors were determined to use real-time reverse transcriptase-polymerase chain reaction and western blotting.

Results

T2DM can promote renal interstitial fibrosis, increase kidney index, serum creatinine, blood urea nitrogen and 24 h urinary total protein and cause pathological changes in renal tissue and affect renal function. After 8 weeks of exercise intervention, the biochemical indicators in the kidney of T2DM mice were decreased, Sirt1 expression was increased, the expression of TGF-β1, Smad3, collagen type I (COL1) and collagen type III (COL3) were decreased, and the renal interstitial fibrosis, renal tissue structural lesions and renal function were improved. However, after the nicotinamide intervention, renal interstitial fibrosis of T2DM mice was aggravated, and the improvement effect of exercise on renal interstitial fibrosis of T2DM mice was abolished.

Conclusion

The upregulation of Sirt1 expression by exercise can inhibit the transforming growth factor β1/Smad3 pathway, thereby inhibiting the expression and deposition of COL1 and COL3 in renal interstitium, thereby improving renal interstitial fibrosis in T2DM.

The anti-inflammatory activity of probiotic Dadiah to activate Sirtuin-1 in inhibiting diabetic nephropathy progression

Purpose

The activation of SIRT-1 in the kidney has become a new therapeutic target to increase resistance to many causal factors in DN development. Furthermore, antioxidative stress and anti-inflammation are essential to preventing renal fibrosis in DN. Therefore, finding "probiotic products" to treat and prevent DN is necessary. This study aimed to analyze the anti-inflammatory of probiotic dadiah to activate SIRT-1 in inhibiting DN progression.

Methods

This study is an experimental group designed with a post-test-only control group to observe the effect of dadiah, LAB, and bacteriocin on alloxan-induced nephropathy diabetic rats through two control groups and five intervention groups for eight weeks. The expression of antibodies SIRT-1 and TNF-α was examined using Immunohistochemistry and histopathology of kidney tissue. All data were analyzed using ANOVA test.

Results

The treatment of dadiah, lactic acid bacteria, and bacteriocin showed a higher expression of Sirtuin-1 than the positive control. They also, reduce TNF-α expression varies significantly between treatments. The highest average of interstitial fibrosis in the C + groups was substantially different from all groups, but all treatments showed decreased kidney fibrosis. Although all treatments showed a decrease in interstitial kidney fibrosis found in the control group, the treatment using dadiah showed the highest result.

Conclusions

Dadiah has the potential to the prevention of fibrosis on kidney tissue of alloxan-induced nephropathy diabetic rats. The findings could be to develop novel treatments for DN that aim to reduce the cascade of oxidative stress and inflammatory signals in kidney tissue.

Functioning and mechanisms of PTMs in renal diseases

Post-translational modifications (PTMs) are crucial epigenetic mechanisms that regulate various cellular biological processes. The use of mass spectrometry (MS)-proteomics has led to the discovery of numerous novel types of protein PTMs, such as acetylation, crotonylation, 2-hydroxyisobutyrylation, β-hydroxybutyrylation, protein propionylation and butyrylation, succinylation, malonylation, lactylation, and histone methylation. In this review, we specifically highlight the molecular mechanisms and roles of various histone and some non-histone PTMs in renal diseases, including diabetic kidney disease. PTMs exhibit diverse effects on renal diseases, which can be either protective or detrimental, depending on the specific type of protein PTMs and their respective targets. Different PTMs activate various signaling pathways in diverse renal pathological conditions, which could provide novel insights for studying epigenetic mechanisms and developing potential therapeutic strategies for renal diseases.

Crocin improves the renal autophagy in rat experimental membranous nephropathy via regulating the SIRT1/Nrf2/HO-1 signaling pathway

Membranous nephropathy (MN) is a glomerular disease. Crocin is isolated from saffron and gardenia. Its antioxidant, anti-inflammatory, anti-hyperlipidemic, anti-atherosclerotic, anti-tumor, free-radical scavenging and neuroprotective activities have been well established. We investigated the biological functions of crocin and its related mechanisms in MN. We established an experimental passive Heymann nephritis (PHN) rat model induced by anti-Fx1A antiserum. The rats were divided into sham, sham + crocin, PHN, PHN + crocin, and PHN + enalapril groups. Blood samples and kidneys of rats were collected for estimation of biochemical parameters in serum and oxidative stress indicators in kidney tissues. Histopathological changes of renal tissues were evaluated by hematoxylin and eosin, periodic acid-Schiff (PAS) and Masson staining. The podocyte number was estimated by immunohistochemistry staining of Wilms tumor type 1 (WT1). The deposition of rat anti-rabbit IgG antibodies, complement C3 and C5b-9 was detected by immunofluorescence staining. Western blotting was performed to measure the levels of Sirtuin 1 (Sirt1), nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1) and apoptosis-related proteins. The total cholesterol, triglycerides, creatinine, blood urea nitrogen, urine volume and urine albumin of PMN rats were significantly reduced by crocin. Additionally, crocin attenuated the renal histopathological changes. Moreover, the oxidative stress damage and podocyte loss and immune injury were relieved by crocin in PHN rats. Mechanistically, crocin administration activated the Sirt1/Nrf2/HO-1 pathways. The results provide a scientific basis that crocin could alleviate MN by inhibiting immune injury and podocyte damage through activating the Sirt1/Nrf2/HO-1 pathways.

The impact of metabolic stressors on mitochondrial homeostasis in a renal epithelial cell model of methylmalonic aciduria

Methylmalonic aciduria (MMA-uria) is caused by deficiency of the mitochondrial enzyme methylmalonyl-CoA mutase (MUT). MUT deficiency hampers energy generation from specific amino acids, odd-chain fatty acids and cholesterol. Chronic kidney disease (CKD) is a well-known long-term complication. We exposed human renal epithelial cells from healthy controls and MMA-uria patients to different culture conditions (normal treatment (NT), high protein (HP) and isoleucine/valine (I/V)) to test the effect of metabolic stressors on renal mitochondrial energy metabolism. Creatinine levels were increased and antioxidant stress defense was severely comprised in MMA-uria cells. Alterations in mitochondrial homeostasis were observed. Changes in tricarboxylic acid cycle metabolites and impaired energy generation from fatty acid oxidation were detected. Methylcitrate as potentially toxic, disease-specific metabolite was increased by HP and I/V load. Mitophagy was disabled in MMA-uria cells, while autophagy was highly active particularly under HP and I/V conditions. Mitochondrial dynamics were shifted towards fission. Sirtuin1, a stress-resistance protein, was down-regulated by HP and I/V exposure in MMA-uria cells. Taken together, both interventions aggravated metabolic fingerprints observed in MMA-uria cells at baseline. The results point to protein toxicity in MMA-uria and lead to a better understanding, how the accumulating, potentially toxic organic acids might trigger CKD.

Tobacco exposure in adults and children with proteinuric glomerulopathies: a NEPTUNE cohort study

BACKGROUND

Tobacco exposure has been recognized as a risk factor for cardiovascular disease (CVD) and progression of kidney disease. Patients with proteinuric glomerulopathies are at increased risk for cardiovascular morbidity and mortality. Multiple studies have linked tobacco exposure to CVD and chronic kidney disease, but the relationships between smoking and proteinuric glomerulopathies in adults and children have not been previously explored.

METHODS

Data from the Nephrotic Syndrome Study Network (NEPTUNE), a multi-center prospective observational study of participants with proteinuric glomerulopathies, was analyzed. 371 adults and 192 children enrolled in NEPTUNE were included in the analysis. Self-reported tobacco exposure was classified as non-smoker, active smoker, former smoker, or exclusive passive smoker. Baseline serum cotinine levels were measured in a sub-cohort of 178 participants.

RESULTS

The prevalence of active smokers, former smokers and exclusive passive smoking among adults at baseline was 14.6%, 29.1% and 4.9%, respectively. Passive smoke exposure was 16.7% among children. Active smoking (reference non-smoking) was significantly associated with greater total cholesterol among adults (β 17.91 95% CI 0.06, 35.76, p = 0.049) while passive smoking (reference non-smoking) was significantly associated with greater proteinuria over time among children (β 1.23 95% CI 0.13, 2.33, p = 0.03). Higher cotinine levels were associated with higher baseline eGFR (r = 0.17, p = 0.03).

CONCLUSION

Tobacco exposure is associated with greater risk for CVD and worse kidney disease outcomes in adults and children with proteinuric glomerulopathies. Preventive strategies to reduce tobacco exposure may help protect against future cardiovascular and kidney morbidity and mortality in patients with proteinuric glomerulopathies.

Bibliometric Analysis and Visualization of Research Progress in the Diabetic Nephropathy Field from 2001 to 2021

Methods

The PubMed database was searched to identify all studies related to DN that were published from 2001 to 2021, with these studies being separated into four time-based groups. The characteristics of these studies were analyzed and extracted using BICOMB. Biclustering analyses for each of these groups were then performed using gCLUTO, with these results then being analyzed and GraphPad Prism 5 being used to construct strategy diagrams. The social network analyses (SNAs) for each group of studies were conducted using NetDraw and UCINET.

Results

In total, 18,889 DN-associated studies published from 2001 to 2021 and included in the PubMed database were incorporated into the present bibliometric analysis. Biclustering analysis and strategy diagrams revealed that active areas of research interest in the DN field include studies of the drug-based treatment, diagnosis, etiology, pathology, physiopathology, and epidemiology of DN. The specific research topics associated with these individual areas, however, have evolved over time in a dynamic manner. Strategy diagrams and SNA results revealed podocyte metabolism as an emerging research hotspot in the DN research field from 2010 to 2015, while DN-related microRNAs, signal transduction, and mesangial cell metabolism have emerged as more recent research hotspots in the interval from 2016 to 2021.

Conclusion

Through analyses of PubMed-indexed studies pertaining to DN published since 2001, the results of this bibliometric analysis offer a knowledge framework and insight into active and historical research hotspots in the DN research space, enabling investigators to readily understand the dynamic evolution of this field over the past two decades. Importantly, these analyses also enable the prediction of future DN-related research hotspots, thereby potentially guiding more focused and impactful research efforts.

Roles of NAD+ in Acute and Chronic Kidney Diseases

Nicotinamide adenine dinucleotide (oxidized form, NAD⁺) is a critical coenzyme, with functions ranging from redox reactions and energy metabolism in mitochondrial respiration and oxidative phosphorylation to being a central player in multiple cellular signaling pathways, organ resilience, health, and longevity. Many of its cellular functions are executed via serving as a co-substrate for sirtuins (SIRTs), poly (ADP-ribose) polymerases (PARPs), and CD38. Kidney damage and diseases are common in the general population, especially in elderly persons and diabetic patients. While NAD⁺ is reduced in acute kidney injury (AKI) and chronic kidney disease (CKD), mounting evidence indicates that NAD⁺ augmentation is beneficial to AKI, although conflicting results exist for cases of CKD. Here, we review recent progress in the field of NAD⁺, mainly focusing on compromised NAD⁺ levels in AKI and its effect on essential cellular pathways, such as mitochondrial dysfunction, compromised autophagy, and low expression of the aging biomarker αKlotho (Klotho) in the kidney. We also review the compromised NAD⁺ levels in renal fibrosis and senescence cells in the case of CKD. As there is an urgent need for more effective treatments for patients with injured kidneys, further studies on NAD⁺ in relation to AKI/CKD may shed light on novel therapeutics.

The IRE1α pathway in glomerular diseases: The unfolded protein response and beyond

Endoplasmic reticulum (ER) function is vital for protein homeostasis ("proteostasis"). Protein misfolding in the ER of podocytes (glomerular visceral epithelial cells) is an important contributor to the pathogenesis of human glomerular diseases. ER protein misfolding causes ER stress and activates a compensatory signaling network called the unfolded protein response (UPR). Disruption of the UPR, in particular deletion of the UPR transducer, inositol-requiring enzyme 1α (IRE1α) in mouse podocytes leads to podocyte injury and albuminuria in aging, and exacerbates injury in glomerulonephritis. The UPR may interact in a coordinated manner with autophagy to relieve protein misfolding and its consequences. Recent studies have identified novel downstream targets of IRE1α, which provide new mechanistic insights into proteostatic pathways. Novel pathways of IRE1α signaling involve reticulophagy, mitochondria, metabolism, vesicular trafficking, microRNAs, and others. Mechanism-based therapies for glomerulopathies are limited, and development of non-invasive ER stress biomarkers, as well as targeting ER stress with pharmacological compounds may represent a therapeutic opportunity for preventing or attenuating progression of chronic kidney disease.

Histone modification in podocyte injury of diabetic nephropathy

Diabetic nephropathy (DN), an important complication of diabetic microvascular disease, is one of the leading causes of end-stage renal disease (ESRD), which brings heavy burdens to the whole society. Podocytes are terminally differentiated glomerular cells, which act as a pivotal component of glomerular filtration barrier. When podocytes are injured, glomerular filtration barrier is damaged, and proteinuria would occur. Dysfunction of podocytes contributes to DN. And degrees of podocyte injury influence prognosis of DN. Growing evidences have shown that epigenetics does a lot in the evolvement of podocyte injury. Epigenetics includes DNA methylation, histone modification, and non-coding RNA. Among them, histone modification plays an indelible role. Histone modification includes histone methylation, histone acetylation, and other modifications such as histone phosphorylation, histone ubiquitination, histone ADP-ribosylation, histone crotonylation, and histone β-hydroxybutyrylation. It can affect chromatin structure and regulate gene transcription to exert its function. This review is to summarize documents about pathogenesis of podocyte injury, most importantly, histone modification of podocyte injury in DN recently to provide new ideas for further molecular research, diagnosis, and treatment.

Resveratrol Reestablishes Mitochondrial Quality Control in Myocardial Ischemia/Reperfusion Injury through Sirt1/Sirt3-Mfn2-Parkin-PGC-1α Pathway

Resveratrol is a natural polyphenol found in various plants. It has been widely studied on cardiovascular disorders. It is known that resveratrol can activate Sirtuin proteins and participate in cellular energy metabolism through a Sirtuin-dependent pathway. Here, we hypothesized that resveratrol may protect against myocardial ischemia/reperfusion injury (MIRI) through the target of Sirt1/Sirt3 on mitochondrial dynamics, cardiac autophagy, bioenergetics and oxidative damage in hypoxia/reoxygenation (H/R)-induced neonatal rat cardiomyocytes. We observed that resveratrol could activate the Sirt1/Sirt3-FoxO pathway on myocardial mitochondria in H/R cardiomyocytes. Subsequently, we found that resveratrol repaired the fission–fusion balance, autophagic flux and mitochondrial biosynthesis compared by H/R group. These changes were followed by increased functional mitochondrial number, mitochondrial bioenergetics and a better mitochondrial antioxidant enzyme system. Meanwhile, these effects were antagonized by co-treatment with Selisistat (Ex527), a Sirtuin inhibitor. Together, our findings uncover the potential contribution of resveratrol in reestablishing a mitochondrial quality control network with Parkin, Mfn2 and PGC-1α as the key nodes.

Immunometabolic rewiring of tubular epithelial cells in kidney disease

Kidney tubular epithelial cells (TECs) have a crucial role in the damage and repair response to acute and chronic injury. To adequately respond to constant changes in the environment, TECs have considerable bioenergetic needs, which are supported by metabolic pathways. Although little is known about TEC metabolism, a number of ground-breaking studies have shown that defective glucose metabolism or fatty acid oxidation in the kidney has a key role in the response to kidney injury. Imbalanced use of these metabolic pathways can predispose TECs to apoptosis and dedifferentiation, and contribute to lipotoxicity and kidney injury. The accumulation of lipids and aberrant metabolic adaptations of TECs during kidney disease can also be driven by receptors of the innate immune system. Similar to their actions in innate immune cells, pattern recognition receptors regulate the metabolic rewiring of TECs, causing cellular dysfunction and lipid accumulation. TECs should therefore be considered a specialized cell type - like cells of the innate immune system - that is subject to regulation by immunometabolism. Targeting energy metabolism in TECs could represent a strategy for metabolically reprogramming the kidney and promoting kidney repair.

SIRT1 rs7896005 polymorphism affects major vascular outcomes, not all-cause mortality, in Caucasians with type 2 diabetes: A 13-year observational study

AIMS

SIRT1 exerts effects on ageing and lifespan, as well cardiovascular (CV) disease risk. SIRT1 gene is very polymorph with a few tagging single nucleotide polymorphisms (SNPs) so far identified. Some SNPs, including rs7896005, were associated with type 2 diabetes (T2DM). We aimed to ascertain whether this SNP may be associated with CV disease at baseline as well with these same outcomes and all-cause mortality over a 13-year follow-up.

MATERIALS AND METHODS

Genotypes of SIRT1 gene were determined using TaqMan SNP assay.

RESULTS

Out of 905 T2DM, 9.1% had the AA genotype, 43.2% the AG, and 47.7% the GG. Hardy-Weinberg Equilibrium was met (minor allele frequency 0.306; p = 0.8899). At baseline, there was no difference across genotypes for sex, age, diabetes duration, CV risk factors, treatments, and microangiopathy. Major CV outcomes, myocardial infarction (MI), any coronary heart disease (CHD), and peripheral artery disease (PAD) were more frequent in GG than in AA/AG (p from 0.013 to 0.027), with no association with cerebrovascular events. By fully adjusted regression, GG remained independently related to major CV outcomes, MI, CHD, and PAD. Over follow-up, we recorded 258 major CV events (28.5%; AA/AG 25.2%, GG 32.2%; p = 0.014) with an adjusted hazard ratio (HR) of GG versus AA/AG of 1.296 (95% CI 1.007-1.668, p = 0.044); 169 coronary events (18.7%; AA/AG 15.4%, GG 22.2%; p = 0.006) with HR 1.522 (1.113-2.080, p = 0.008); 79 (8.7%) hospitalisation for heart failure (AA/AG 7.0%, GG 10.6%; p = 0.045) and HR 1.457 (0.919-2.309, p = 0.109); 36 PAD (4.0%; AA/AG 2.3%, GG 5.8%; p = 0.007) with HR 2.225 (1.057-4.684, p = 0.035). No association was found with cerebrovascular events, end stage renal disease, and all-cause mortality.

CONCLUSIONS

The rs7896005 SNP of SIRT1 might play a role in cardiovascular disease, mainly CHD risk in T2DM. Results call for larger association studies as well as studies to ascertain mechanisms by which this variant confers increased risk.

Recent Advances in Epigenetics of Age-Related Kidney Diseases

Renal aging has attracted increasing attention in today’s aging society, as elderly people with advanced age are more susceptible to various kidney disorders such as acute kidney injury (AKI) and chronic kidney disease (CKD). There is no clear-cut universal mechanism for identifying age-related kidney diseases, and therefore, they pose a considerable medical and public health challenge. Epigenetics refers to the study of heritable modifications in the regulation of gene expression that do not require changes in the underlying genomic DNA sequence. A variety of epigenetic modifiers such as histone deacetylases (HDAC) inhibitors and DNA methyltransferase (DNMT) inhibitors have been proposed as potential biomarkers and therapeutic targets in numerous fields including cardiovascular diseases, immune system disease, nervous system diseases, and neoplasms. Accumulating evidence in recent years indicates that epigenetic modifications have been implicated in renal aging. However, no previous systematic review has been performed to systematically generalize the relationship between epigenetics and age-related kidney diseases. In this review, we aim to summarize the recent advances in epigenetic mechanisms of age-related kidney diseases as well as discuss the application of epigenetic modifiers as potential biomarkers and therapeutic targets in the field of age-related kidney diseases. In summary, the main types of epigenetic processes including DNA methylation, histone modifications, non-coding RNA (ncRNA) modulation have all been implicated in the progression of age-related kidney diseases, and therapeutic targeting of these processes will yield novel therapeutic strategies for the prevention and/or treatment of age-related kidney diseases.

The significance of NAD + metabolites and nicotinamide N-methyltransferase in chronic kidney disease

Dysregulation of nicotinamide adenine dinucleotide (NAD +) metabolism contributes to the initiation and progression of age-associated diseases, including chronic kidney disease (CKD). Nicotinamide N-methyltransferase (NNMT), a nicotinamide (NAM) metabolizing enzyme, regulates both NAD + and methionine metabolism. Although NNMT is expressed abundantly in the kidney, its role in CKD and renal fibrosis remains unclear. We generated NNMT-deficient mice and a unilateral ureter obstruction (UUO) model and conducted two clinical studies on human CKD to investigate the role of NNMT in CKD and fibrosis. In UUO, renal NNMT expression and the degraded metabolites of NAM increased, while NAD + and NAD + precursors decreased. NNMT deficiency ameliorated renal fibrosis; mechanistically, it (1) increased the DNA methylation of connective tissue growth factor (CTGF), and (2) improved renal inflammation by increasing renal NAD + and Sirt1 and decreasing NF-κB acetylation. In humans, along with CKD progression, a trend toward a decrease in serum NAD + precursors was observed, while the final NAD + metabolites were accumulated, and the level of eGFR was an independent variable for serum NAM. In addition, NNMT was highly expressed in fibrotic areas of human kidney tissues. In conclusion, increased renal NNMT expression induces NAD + and methionine metabolism perturbation and contributes to renal fibrosis.

NAD+ Anabolism Disturbance Causes Glomerular Mesangial Cell Injury in Diabetic Nephropathy

The homeostasis of NAD⁺ anabolism is indispensable for maintaining the NAD⁺ pool. In mammals, the mainly synthetic pathway of NAD⁺ is the salvage synthesis, a reaction catalyzed by nicotinamide mononucleotide adenylyltransferase (NAMPT) and nicotinamide mononucleotide adenylyltransferase (NMNATs) successively, converting nicotinamide (NAM) to nicotinamide mononucleotide (NMN) and NMN to NAD⁺, respectively. However, the relationship between NAD⁺ anabolism disturbance and diabetic nephropathy (DN) remains elusive. Here our study found that the disruption of NAD⁺ anabolism homeostasis caused an elevation in both oxidative stress and fibronectin expression, along with a decrease in Sirt1 and an increase in both NF-κB P65 expression and acetylation, culminating in extracellular matrix deposition and globular fibrosis in DN. More importantly, through constitutively overexpressing NMNAT1 or NAMPT in human mesangial cells, we revealed NAD⁺ levels altered inversely with NMN levels in the context of DN and, further, their changes affect Sirt1/NF-κB P65, thus playing a crucial role in the pathogenesis of DN. Accordingly, FK866, a NAMPT inhibitor, and quercetin, a Sirt1 agonist, have favorable effects on the maintenance of NAD⁺ homeostasis and renal function in db/db mice. Collectively, our findings suggest that NMN accumulation may provide a causal link between NAD⁺ anabolism disturbance and diabetic nephropathy (DN) as well as a promising therapeutic target for DN treatment.

The effects of two different dietary regimens during exercise on outcome of experimental acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is a syndrome characterized by rapid loss of excretory function of kidney. Both exercise and some diets have been shown to increase silent information regulator (SIRT1) expression leading to reduction of kidney injury. In this study, the effect of two different diets during exercise on kidney function, oxidative stress, inflammation and also SIRT1 in AKI was investigated.

MATERIALS AND METHODS

A number of rats were randomly divided into four groups; control without exercise, control with exercise, exercise + calorie restriction (CR), and exercise + time restriction (TR). Each group was divided into two subgroups of without AKI and with AKI (six rats in each group). Endurance exercise and diets were implemented before AKI. Serum urea and creatinine, urinary albumin, kidney malondialdehyde (MDA), total antioxidant capacity (TAC), transforming growth factor (TGF-β1), and SIRT1 levels, glomerular filtration rate (GFR) and relative kidney weight were measured before and 24 h after AKI induction.

RESULTS

After induction of kidney injury, serum urea and creatinine, urinary albumin, kidney MDA and TGF-β1 levels increased in rats with both previous exercise and no previous exercise, while GFR, and kidney TAC and SIRT1 levels significantly decreased. These changes after AKI were less in the group with previous exercise than in the group that had no exercise (p <0.001). The TR diet during exercise caused a less increase in serum urea (p <0.01) and creatinine (p <0.01), and urinary albumin (p <0.001) levels after the injury compared to the just exercise group. Also, both CR and TR diets during exercise caused less change in MDA (p <0.001) and TAC (p <0.05, p <0.001, respectively) levels compared to just exercise group.

CONCLUSIONS

The results showed that exercise alone had no effect on preventing function impairment of kidney, oxidative stress, inflammation and also SIRT1 alteration following AKI, although these indexes were less among those with exercise than those without exercise. However, when the CR and TR diets were implemented during exercise, strong renoprotective effects appeared, and the protective effect of TR diet was greater.

Potential of Polyphenols to Restore SIRT1 and NAD+ Metabolism in Renal Disease

SIRT1 is an NAD⁺-dependent class III histone deacetylase that is abundantly expressed in the kidney, where it modulates gene expression, apoptosis, energy homeostasis, autophagy, acute stress responses, and mitochondrial biogenesis. Alterations in SIRT1 activity and NAD⁺ metabolism are frequently observed in acute and chronic kidney diseases of diverse origins, including obesity and diabetes. Nevertheless, in vitro and in vivo studies and clinical trials with humans show that the SIRT1-activating compounds derived from natural sources, such as polyphenols found in fruits, vegetables, and plants, including resveratrol, quercetin, and isoflavones, can prevent disease and be part of treatments for a wide variety of diseases. Here, we summarize the roles of SIRT1 and NAD⁺ metabolism in renal pathophysiology and provide an overview of polyphenols that have the potential to restore SIRT1 and NAD⁺ metabolism in renal diseases.

Fucoxanthin Attenuates Oxidative Damage by Activating the Sirt1/Nrf2/HO-1 Signaling Pathway to Protect the Kidney from Ischemia-Reperfusion Injury

Oxidative stress is a key component of renal ischemia/reperfusion (I/R) injury. Fucoxanthin (Fx), a marine carotenoid with enhanced antioxidant capacity, acts as a ROS inhibitor in diseases such as ischemic stroke and acute lung injury. We hypothesized that fucoxanthin could attenuate renal I/R-induced oxidative damage. C57BL/6 mice ( $n=30$ ) were randomly assigned to sham, IR, $\text{IR}+\text{DMSO}$ , and $\text{IR}+\text{Fx}$ (25, 50, and 100 mg/kg) groups. The renal I/R injury was induced by clamping the left kidney nephron tip in mice. Fucoxanthin was injected intraperitoneally 24 hours before surgery. Compared with the IR group, pretreatment with fucoxanthin significantly improved renal dysfunction and tissue structural damage and inhibited ROS levels and apoptosis. Consistent results were observed in HK-2 cells. Besides, we found that renal I/R resulted in decreased expression of Sirt1, Nrf2, and HO-1, while fucoxanthin upregulated the expression of Sirt1, Nrf2, and HO-1. The protective effects of fucoxanthin were significantly reversed by EX527 (a selective inhibitor of Sirt1) or si-Sirt1. In conclusion, our study investigated the protective effect of fucoxanthin against renal I/R injury, and the underlying mechanism may be related to the activation of the Sirt1/Nrf2/HO-1 signaling pathway by fucoxanthin to attenuate oxidative stress-induced apoptosis.

TangShenWeiNing Formula Prevents Diabetic Nephropathy by Protecting Podocytes Through the SIRT1/HIF-1α Pathway

BACKGROUND

Diabetic nephropathy (DN) represents a major complication of diabetes, and podocyte injury has a critical function in DN development. TangShenWeiNing formula (TSWN) has been demonstrated to efficiently decrease proteinuria and protect podocytes in DN. This work aimed to explore the mechanism by which TSWN alleviates DN and protects podocytes.

METHODS

The major bioactive components of TSWN were detected by mass spectrometry (MS) and pharmacological databases. Eight-week-old male C57BLKS/J db/m and db/db mice were provided pure water, valsartan, low dose TSWN, middle dose TSWN and high dose TSWN by gavage for 12 weeks, respectively.

RESULTS

MS and network pharmacology analyses suggested that TSWN might prevent DN through the sirtuin (SIRT)1/hypoxia-inducible factor (HIF)-1α pathway. Diabetic mice showed elevated urinary albumin in comparison with non-diabetic mice, and TSWN decreased urinary albumin in diabetic mice. Histological injury increased in the kidney in diabetic mice, which could be improved by TSWN. Fibrosis and collagen I expression were induced in the diabetic mouse kidney in comparison with the non-diabetic mouse kidney; TSWN alleviated these effects. Apoptosis and cleaved caspase-3 were induced in the diabetic mouse kidney in comparison with the non-diabetic mouse kidney, and TSWN blunted these effects. Podocytes were damaged in the diabetic mouse kidney, which was improved by TSWN. Podocin and nephrin amounts were decreased in the diabetic mouse kidney in comparison with the non-diabetic mouse kidney, and podocalyxin was increased in urine of diabetic animals in comparison with non-diabetic counterparts. After TSWN treatment, podocin and nephrin were raised in the diabetic mouse kidney, and urinary podocalyxin was depressed in diabetic animals. Diabetic mice had lower SIRT1 and higher HIF-1α amounts in kidney specimens in comparison with non-diabetic mice, and TSWN promoted SIRT1 and inhibited HIF-1α in the diabetic mouse kidney. Moreover, co-staining of SIRT1 and podocin revealed that SIRT1 decreased in podocytes from diabetic mice in comparison with those from non-diabetic mice, and TSWN elevated SIRT1 in podocytes.

CONCLUSIONS

This study indicated that TSWN alleviates DN by improving podocyte injury through the SIRT1/HIF-1α pathway in diabetic mouse kidneys.

SIRT1-SIRT7 in Diabetic Kidney Disease: Biological Functions and Molecular Mechanisms

Diabetic kidney disease (DKD) is a severe microvascular complication in patients with diabetes and is one of the main causes of renal failure. The current clinical treatment methods for DKD are not completely effective, and further exploration of the molecular mechanisms underlying the pathology of DKD is necessary to improve and promote the treatment strategy. Sirtuins are class III histone deacetylases, which play an important role in many biological functions, including DNA repair, apoptosis, cell cycle, oxidative stress, mitochondrial function, energy metabolism, lifespan, and aging. In the last decade, research on sirtuins and DKD has gained increasing attention, and it is important to summarize the relationship between DKD and sirtuins to increase the awareness of DKD and improve the cure rates. We have found that miRNAs, lncRNAs, compounds, or drugs that up-regulate the activity and expression of sirtuins play protective roles in renal function. Therefore, in this review, we summarize the biological functions, molecular targets, mechanisms, and signaling pathways of SIRT1-SIRT7 in DKD models. Existing research has shown that sirtuins have the potential as effective targets for the clinical treatment of DKD. This review aims to lay a solid foundation for clinical research and provide a theoretical basis to slow the development of DKD in patients.

A comprehensive insight into autophagy and its potential signaling pathways as a therapeutic target in podocyte injury

As part of the glomerular filtration membrane, podocyte is terminally differentiated, structurally unique, and highly specialized in maintaining kidney function. Proteinuria caused by podocyte injury (foot process effacement) is the clinical symptom of various kidney diseases (CKD), including nephrotic syndrome. Podocyte autophagy has become a powerful therapeutic strategy target in ameliorating podocyte injury. Autophagy is known to be associated significantly with sirtuin-1, proteinuria, and podocyte injury. Various key findings in podocyte autophagy were reported in the past ten years, such as the role of endoplasmic reticulum (ER) stress in podocyte autophagy impairment, podocyte autophagy-related gene, essential roles of the signaling pathways: Mammalian Target of Rapamycin (mTOR)/ Phosphoinositide 3-kinase (PI3k)/ serine/threonine kinase 1 (Akt) in podocyte autophagy. These significant factors caused podocyte injury associated with autophagy impairment. Sirtuin-1 was reported to have a vital key role in mTOR signaling, 5'AMP-activated protein kinase (AMPK) regulation, autophagy activation, and various critical pathways associated with podocyte's function and health; it has potential value to podocyte injury pathogenesis investigation. From these findings, podocyte autophagy has become an attractive therapeutic strategy to ameliorate podocyte injury, and this review will provide an in-depth review on therapeutic targets he podocyte autophagy.

Bicalutamide Exhibits Potential to Damage Kidney via Destroying Complex I and Affecting Mitochondrial Dynamics

Bicalutamide (Bic) is an androgen deprivation therapy (ADT) for treating prostate cancer, while ADT is potentially associated with acute kidney injury. Previously, we recognized Bic induced renal mitochondria dysfunction in vitro and in vivo via the ROS -HIF1α pathway. Whether OXPHOS complex, as well as mitochondrial dynamics, can be influenced by Bic via modulation of peroxisome proliferator-activated receptor coactivator 1α (PGC1α), NADPH oxidase 4 (Nox4), mitofusins 1/2 (MFN 1/2), optic atrophy 1 (OPA1), and sirtuins (SIRTs) has not been documented. Renal mesangial cell line was treated with Bic (30~60 μM) for the indicated time. SIRTs, complex I, mitochondrial dynamics- and oxidative stress-related proteins were analyzed. Bic dose-dependently reduced mitochondrial potential, but dose- and time-dependently suppressed translocase of the outer mitochondrial membrane member 20 (Tomm 20), complex I activity. Nox4 and glutathione lead to decreased NAD⁺/NADH ratio, with upregulated superoxide dismutase 2. SIRT1 was initially stimulated and then suppressed, while SIRT3 was time- and dose-dependently downregulated. PGC1α, MFN2, and OPA1 were all upregulated, with MFN1 and pro-fission dynamin-related protein I downregulated. Bic exhibits potential to damage mitochondria via destroying complex I, complex I activity, and mitochondrial dynamics. Long-term treatment with Bic should be carefully followed up.

Role of Polyphenol in Regulating Oxidative Stress, Inflammation, Fibrosis, and Apoptosis in Diabetic Nephropathy

Diabetic nephropathy (DN) is known as one of the driving sources of end-stage renal disease (ESRD). DN prevalence continues to increase in every corner of the world andthat has been a major concern to healthcare professionals as DN is the key driver of diabetes mellitus (DM) morbidity and mortality. Hyperglycaemia is closely connected with the production of reactive oxygen species (ROS) that cause oxidative stress response as well as numerous cellular and molecular modifications. Oxidative stress is a significant causative factor to renal damage, as it can activate other immunological pathways, such as inflammatory, fibrosis, and apoptosis pathways. These pathways can lead to cellular impairment and death as well as cellular senescence. Natural substances containing bioactive compounds, such as polyphenols, have been reported to exert valuable effects on various pathological conditions, including DM. The role of polyphenols in alleviating DN conditions has been documented in many studies. In this review, the potential of polyphenols in ameliorating the progression of DN via modulation of oxidative stress, inflammation, fibrosis, and apoptosis, as well as cellular senescence, has been addressed. This information may be used as the strategies for the management of DN and development as nutraceutical products to overcome DN development.

Multifaced role of protein deacetylase sirtuins in neurodegenerative disease

Sirtuins, a class III histone/protein deacetylase, is a central regulator of metabolic function and cellular stress response. This plays a pivotal role in the pathogenesis and progression of diseases such as cancer, neurodegeneration, metabolic syndromes, and cardiovascular disease. Sirtuins regulate biological and cellular processes, for instance, mitochondrial biogenesis, lipid and fatty acid oxidation, oxidative stress, gene transcriptional activity, apoptosis, inflammatory response, DNA repair mechanism, and autophagic cell degradation, which are known components for the progression of the neurodegenerative diseases (NDDs). Emerging evidence suggests that sirtuins are the useful molecular targets against NDDs like, Alzheimer's Disease (AD), Parkinson's Disease (PD), Huntington's Disease (HD), and Amyotrophic Lateral Sclerosis (ALS). However, the exact mechanism of neuroprotection mediated through sirtuins remains unsettled. The manipulation of sirtuins activity with its modulators, calorie restriction (CR), and micro RNAs (miR) is a novel therapeutic approach for the treatment of NDDs. Herein, we reviewed the current putative therapeutic role of sirtuins in regulating synaptic plasticity and cognitive functions, which are mediated through the different molecular phenomenon to prevent neurodegeneration. We also explained the implications of sirtuin modulators, and miR based therapies for the treatment of life-threatening NDDs.

Improving SIRT1 by trehalose supplementation reduces oxidative stress, inflammation, and histopathological scores in the kidney of aged rats

The aging process leads to progressive loss of kidney function. Sirtuin1 (SIRT1) exerts renoprotective effects by conferring resistance to cellular stresses. Trehalose potentially displayed various beneficial effects to promote health span. In this study, we investigated the effects of trehalose on renal SIRT1 and kidney function in senescent rats. Trehalose (2% w/v) was administrated in drinking water for 1 month to male aged rats (24 months). Then, the level of SIRT1 mRNA and protein, malondialdehyde, total antioxidant capacity, tumor necrosis factor α as well as parameters related to the function and histology of the kidneys were evaluated. Trehalose supplementation increased the level of SIRT1, whereas alleviated the level of oxidative stress, inflammation, and histopathology scores in senescent tissues. However, trehalose administration did not alter kidney function indices in old rats. Collectively, these findings suggested that trehalose was an effective intervention to ameliorate some aspects of age-associated injury in the old kidneys. PRACTICAL APPLICATIONS: Aging is associated with impairment in renal structure and function. Trehalose is a natural disaccharide, which is widely distributed in many organisms. The consumption of trehalose as a dietary supplement is increasing worldwide. This study showed that trehalose administration to aged rats had renoprotective effects through reducing oxidative stress and inflammation, which was mediated by SIRT1. Our results provide useful information for individuals using this sugar as a supplement.

The effects of compound centella formula on OxInflammation and silent information regulator 1 in a high-fat diet/streptozotocin-induced diabetic kidney disease rat model

The Chinese decoction compound centella formula (CCF) is clinically effective against diabetic kidney disease (DKD), but the exact mechanism remains unclear. The present study aimed to investigate the effects of CCF on OxInflammation and silent information regulator 1 (SIRT1) levels in rats with streptozotocin (STZ)-induced diabetes. Sprague-Dawley rats were divided into CCF, losartan, diabetic control (DC) and normal control (NC) groups (n=7). Except for the NC, all subgroups of rats were fed a high-fat diet for 112 days and received a single intraperitoneal injection of 35 mg/kg STZ on day 29. All rats were sacrificed on day 112. High-performance liquid chromatography was performed to analyse asiaticoside, astragaloside and triptolide levels in CCF (0.3400, 0.0640 and 0.0001 mg/ml, respectively). Fasting blood glucose, urine protein-to-creatinine ratio, serum creatinine and blood urea nitrogen were quantified. Periodic acid Schiff staining, H&E staining and transmission electron microscopy were used to examine kidney pathological changes. The mRNA and protein expression levels of SIRT1 in renal tissues were analysed by reverse transcription-quantitative PCR, western blotting and immunohistochemistry. Oxidative stress was evaluated by measuring the levels of superoxide dismutase (SOD), malondialdehyde (MDA) and nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) in renal tissues. TNF-α and NF-κB p65 subunit in renal tissues were assessed for inflammation. Compared with the rats in the NC group, the rats in the DC group exhibited renal injury with proteinuria, decreased expression levels of SIRT1 and SOD (P<0.01) and increased levels of MDA, NOX4, TNF-α and NF-κB p65 (P<0.01). CCF treatment reduced proteinuria (P<0.01), alleviated renal damage, decreased MDA, NOX4, TNF-α and NF-κB p65 levels (P<0.01), increased SOD levels (P<0.05) and increased SIRT1 mRNA and protein expression levels (P<0.01). The present study indicates that CCF effectively protects the kidney from diabetes by inhibiting OxInflammation and upregulating SIRT1.

Atorvastatin (ATV)-Loaded Lipid Bilayer-Coated Mesoporous Silica Nanoparticles Enhance the Therapeutic Efficacy of Acute Kidney Injury

Background: Acute kidney injury (AKI) increases the risk of chronic kidney disease. Atorvastatin (ATV)-loaded lipid bilayer-coated mesoporous silica nanoparticles (L-AMSNs) were synthesized, and their physicochemical parameters were characterized. L-AMSNs exhibited excellent stability; it did not increase in size over time, indicating that the lipid membrane coating prohibited mesoporous silica nanoparticles (MSNs) coalescence. Results: The rate of drug release differed significantly between AMSNs and L-AMSNs at all tested time points. A remarkable improvement in hydrogen peroxide (H₂O₂)-treated human umbilical vein endothelial cell (HUVEC) viability was observed after treatment with L-AMSNs; the malondialdehyde (MDA) level was significantly reduced compared to control cells. The extent of apoptosis was only 15% that of control H₂O₂-treated cells. L-AMSNs induced a remarkable decrease in the levels of pro-inflammatory cytokines (tumor necrosis factor [TNF]-α and interleukin [IL]-6), showing the therapeutic potential of nanocarrier-based ATV. L-AMSNs significantly increased the superoxide dismutase level and decreased the MDA level, indicating superior anti-inflammatory activity under conditions of oxidative stress. The L-AMSN showed a remarkable improvement in the outer stripe of outer medulla (OSOM) region and maintained the tubular structure of the kidney tissue. Besides, kidney injury score of L-AMSN is significantly lower compared to that of LPS-AKI and ATV indicating the excellent therapeutic efficacy of nanoparticulate system based L-AMSN. Conclusions: Nanoparticles system-based L-AMSNs maintained the tubular structure of kidney tissue, indicating excellent therapeutic efficacy. After clinical translation, L-AMSNs could serve as a promising treatment for AKI.

Defective lysosomal storage in Fabry disease modifies mitochondrial structure, metabolism and turnover in renal epithelial cells

Fabry disease (FD) is an X-linked lysosomal storage disorder. Deficiency of the lysosomal enzyme alpha-galactosidase (GLA) leads to accumulation of potentially toxic globotriaosylceramide (Gb3) on a multisystem level. Cardiac and cerebrovascular abnormalities as well as progressive renal failure are severe, life-threatening long-term complications. The complete pathophysiology of chronic kidney disease (CKD) in FD and the role of tubular involvement for its progression are unclear. We established human renal tubular epithelial cell lines from the urine of male FD patients and male controls. The renal tubular system is rich in mitochondria and involved in transport processes at high-energy costs. Our studies revealed fragmented mitochondria with disrupted cristae structure in FD patient cells. Oxidative stress levels were elevated and oxidative phosphorylation was upregulated in FD pointing at enhanced energetic needs. Mitochondrial homeostasis and energy metabolism revealed major changes as evidenced by differences in mitochondrial number, energy production and fuel consumption. The changes were accompanied by activation of the autophagy machinery in FD. Sirtuin1, an important sensor of (renal) metabolic stress and modifier of different defense pathways, was highly expressed in FD. Our data show that lysosomal FD impairs mitochondrial function and results in severe disturbance of mitochondrial energy metabolism in renal cells. This insight on a tissue-specific level points to new therapeutic targets which might enhance treatment efficacy.

LncRNA TUG1/miR-29c-3p/SIRT1 axis regulates endoplasmic reticulum stress-mediated renal epithelial cells injury in diabetic nephropathy model in vitro

Long non-coding RNAs (lncRNAs) are important regulators in diabetic nephropathy. In this study, we investigated the potential role of lncRNA TUG1 in regulating endoplasmic reticulum stress (ERS)-mediated apoptosis in high glucose induced renal tubular epithelial cells. Human renal tubular epithelial cell line HK-2 was challenged with high glucose following transfection with lncRNA TUG1, miR-29c-3p mimics or inhibitor expression plasmid, either alone or in combination, for different experimental purposes. Potential binding effects between TUG1 and miR-29c-3p, as well as between miR-29c-3p and SIRT1 were verified. High glucose induced apoptosis and ERS in HK-2 cells, and significantly decreased TUG1 expression. Overexpressed TUG1 could prevent high glucose-induced apoptosis and alleviated ERS via negatively regulating miR-29c-3p. In contrast, miR-29c-3p increased HK-2 cells apoptosis and ERS upon high glucose-challenge. SIRT1 was a direct target gene of miR-29c-3p in HK-2 cells, which participated in the effects of miR-29c-3p on HK-2 cells. Mechanistically, TUG1 suppressed the expression of miR-29c-3p, thus counteracting its function in downregulating the level of SIRT1. TUG1 regulates miR-29c-3p/SIRT1 and subsequent ERS to relieve high glucose induced renal epithelial cells injury, and suggests a potential role for TUG1 as a promising diagnostic marker of diabetic nephropathy.

Ameliorative effect of white tea from 50-year-old tree of Camellia sinensis L. (Theaceae) on kidney damage in diabetic mice via SIRT1/AMPK pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic kidney damage (DKD) is one of the most common complications of diabetes, which is known as a chronic inflammatory kidney disease caused by persistent hyperglycemia. White tea was originally used as a folk medicine to treat measles in ancient China. What arouses our interest is that there is a traditional method to treat diabetes with white tea taken from over 30-year-old tree of Camellia sinensis L. However, there are few reports on the renal protection of white tea.

AIM OF THE STUDY

This present study was designed to study the potential protective effects of white tea (WT) and old tree white tea (OTWT) on high-fat-diet (HFD) combined with streptozotocin (STZ)-induced type 2 diabetic mice to explore the possible mechanism of WT/OTWT against DKD.

MATERIALS AND METHODS

C57BL/6 mice were randomly divided into four groups: NC, T2D, WT (400 mg/kg·b.w, p.o.), OTWT (400 mg/kg·b.w, p.o.). Diabetes was established in all groups except NC group, by six weeks of HFD feeding combined with STZ (50 mg/kg, i.p.) for 3 times, treatments were administered for six weeks and then all the animals were decapitated; kidney tissues and blood samples were collected for the further analysis, including: levels of insulin, lipid metabolism (TG, TC, HDL, LDL, FFA), antioxidative enzymes (catalase (CAT), super oxide dismutase (SOD), glutathione peroxidase (GPx)), blood urea nitrogen (BUN) and creatine, inflammatory cytokines (TNF-α, IL-1β, COX-2, iNOS, MCP-1), advanced glycation end products (AGE), receptor of AGE (RAGE), Nrf2, AMPK, SIRT1, and PGC-1α. H&E, PAS and Masson staining were performed to examine the histopathological alterations of the kidneys.

RESULTS

Our data showed that WT and OTWT reversed the abnormal serum lipids (TG, TC, HDL, LDL, FFA) in T2D mice, upregulated antioxidative enzymes levels (CAT, SOD, GPx) and inhibit the excessive production of proinflammatory mediators (including MCP-1, TNF-α, IL1β, COX-2 and iNOS) by varying degrees, and OTWT was more effective. In histopathology, OTWT could significantly alleviate the accumulation of renal AGE in T2D mice, thereby improving the structural changes of the kidneys, such as glomerular hypertrophy, glomerular basement membrane thickening and kidney FIbrosis.

CONCLUSIONS

Both WT and OTWT could alleviate the diabetic changes in T2D mice via hypoglycemic, hypolipidemic, anti-oxidative and anti-inflammatory effects, while OTWT was more evident. OTWT could prominently alleviate the accumulation of AGE in the kidneys of T2D mice, thereby ameliorating the renal oxidative stress and inflammatory damage, which was associated with the activation of SIRT1/AMPK pathway.

Targeting Premature Renal Aging: from Molecular Mechanisms of Cellular Senescence to Senolytic Trials

The biological process of renal aging is characterized by progressive structural and functional deterioration of the kidney leading to end-stage renal disease, requiring renal replacement therapy. Since the discovery of pivotal mechanisms of senescence such as cell cycle arrest, apoptosis inhibition, and the development of a senescence-associated secretory phenotype (SASP), efforts in the understanding of how senescent cells participate in renal physiological and pathological aging have grown exponentially. This has been encouraged by both preclinical studies in animal models with senescent cell clearance or genetic depletion as well as due to evidence coming from the clinical oncologic experience. This review considers the molecular mechanism and pathways that trigger premature renal aging from mitochondrial dysfunction, epigenetic modifications to autophagy, DNA damage repair (DDR), and the involvement of extracellular vesicles. We also discuss the different pharmaceutical approaches to selectively target senescent cells (namely, senolytics) or the development of systemic SASP (called senomorphics) in basic models of CKD and clinical trials. Finally, an overview will be provided on the potential opportunities for their use in renal transplantation during ex vivo machine perfusion to improve the quality of the graft.

Unraveling the epigenetic landscape of glomerular cells in kidney disease

Chronic kidney disease (CKD) is a major public health concern and its prevalence and incidence are rising quickly. It is a non-communicable disease primarily caused by diabetes and/or hypertension and is associated with high morbidity and mortality. Despite decades of research efforts, the pathogenesis of CKD remains a puzzle with missing pieces. Understanding the cellular and molecular mechanisms that govern the loss of kidney function is crucial. Abrupt regulation of gene expression in kidney cells is apparent in CKD and shown to be responsible for disease onset and progression. Gene expression regulation extends beyond DNA sequence and involves epigenetic mechanisms including changes in DNA methylation and post-translational modifications of histones, driven by the activity of specific enzymes. Recent advances demonstrate the essential participation of epigenetics in kidney (patho)physiology, as its actions regulate both the integrity of cells but also triggers deleterious signaling pathways. Here, we review the known epigenetic processes regulating the complex filtration unit of the kidney, the glomeruli. The review will elaborate on novel insights into how epigenetics contributes to cell injury in the CKD setting majorly focusing on kidney glomerular cells: the glomerular endothelial cells, the mesangial cells, and the specialized and terminally differentiated podocyte cells.

Aging-Related Functional and Structural Changes in Renal Tissues: Lesson from a Camel Model

Renal aging is a progressive, physiological, and anatomical change that naturally occurs in all animal species. To date, no information is available concerning the aging-related structural and functional changes in camel kidneys. A total of 25 healthy male camels (14 aged 4–6 years and 11 aged 18–22 years) were included in this study. After the camels were slaughtered, samples were collected from all the camels’ kidneys and prepared for histopathological, immunohistochemical, and gene expression evaluations. The most striking observation was the significant decline in the immunohistochemical abundance of podocin and the significant upregulation of smoothening in the aging camels’ kidneys. However, the nonsignificant changes have reported for nephrin, calbindin, autophagy 5 (ATG5), aquaporin 1, and toll-like receptor 9. Furthermore, the mRNA expressions of sirtuin 1, superoxide dismutase 1, superoxide dismutase 2, peroxisome proliferator-activated receptor alpha, B-cell lymphoma 2 (Bcl-2), and erythropoietin were significantly decreased in the aging camels’ kidneys. While the significant upregulation of Bcl-2-associated X protein and the nonsignificant increase in ATG5 expression levels were reported in the aging camels’ kidneys. The present findings provide better understanding of the complex events and initiating factors of aging, allowing for the development of a future therapeutic strategy to preserve adequate renal function throughout life.

Nicotinamide Supplementation Attenuates Renal Interstitial Fibrosis via Boosting the Activity of Sirtuins

Background

Progressive tubulointerstitial fibrosis (TIF) is the final common pathway leading to ESRD. There is an urgent need to develop effective approaches slowing the progression of TIF. Previous studies showed that systemic supplementation of nicotinamide (NAM) increases renal NAD⁺ and reverses ischemic-reperfusion induced acute renal injury. However, the role and mechanism of NAM in TIF has been unclear.

Methods

In vivo, we injected NAM (0.25 mg/g) 3 days before unilateral ureter obstruction (UUO) till day 7 post-operation. In vitro, mouse primary proximal tubular epithelial cells (PTCs), rat renal NRK-49F cells, and human renal proximal tubular epithelial cell (HK-2) were pretreated with the indicated concentration of NAM 1 h before incubation with transform growth factor-β1 (TGF-β1) or aristolochic acid (AA) for 24 or 48 h. To evaluate the role of sirtuins (SIRTs), PTCs were pretreated with EX527 or resveratrol 30 min before incubation with NAM and TGF-β1.

Results

In the present study, we demonstrated that NAM supplementation prevented UUO-induced TIF, and AA-induced renal injury. NAM also decreased the expression of pro-fibrotic proteins and pro-inflammatory cytokines (IL-6 and TNF-α) and attenuated interstitial inflammation. In vitro experiment showed that, NAM inhibited AA-induced G2/M arrest of HK-2 cells by downregulating the expression of cyclin G1, a target gene of p53. In addition, NAM inhibited TGF-β1-induced fibroblast proliferation and activation shown as downregulated expression of collagen I, fibronectin, PCNA, cyclin D1, IL-6, and TNF-α. NAM decreased the acetylation of Smad3 and p53. EX527, an inhibitor of SIRT1, reversed the effect of NAM on TGF-β1-induced matrix protein production. However, resveratrol, a SIRT1 activator, did not further boost the protective effect of NAM on reducing matrix protein production.

Conclusions

Taken together, these data indicate that NAM supplementation could inhibit TIF at least partially by boosting the activity of sirtuins.

SIRT1: Mechanism and Protective Effect in Diabetic Nephropathy

Diabetic nephropathy (DN) is referred to as the microvascular complication of the kidneys induced by insufficient production of insulin or an ineffective cellular response to insulin, and is the main cause of end-stage renal disease. Currently, available therapies provide only symptomatic relief and fail to improve the outcome of diabetic nephropathy. Studies on diabetic animals had shown overexpression of SIRT1 in both podocytes and renal tubular cells attenuated proteinuria and kidney injury in the animal model of DN. Sirt1 exerts renoprotective effects in DKD in part through the deacetylation of transcription factors involved in the disease pathogenesis, such as NF-кB, Smad3, FOXO and p53. The purpose of this review is to highlight the protective mechanism of SIRT1 involved in the pathogenesis of diabetic nephropathy.