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

A systematic review of epigenetic interplay in kidney diseases: Crosstalk between long noncoding RNAs and methylation, acetylation of chromatin and histone

The intricate crosstalk between long noncoding RNAs (lncRNAs) and epigenetic modifications such as chromatin/histone methylation and acetylation offer new perspectives on the pathogenesis and treatment of kidney diseases. lncRNAs, a class of transcripts longer than 200 nucleotides with no protein-coding potential, are now recognized as key regulatory molecules influencing gene expression through diverse mechanisms. They modulate the epigenetic modifications by recruiting or blocking enzymes responsible for adding or removing methyl or acetyl groups, such as DNA, N6-methyladenosine (m6A) and histone methylation and acetylation, subsequently altering chromatin structure and accessibility. In kidney diseases such as acute kidney injury (AKI), chronic kidney disease (CKD), diabetic nephropathy (DN), glomerulonephritis (GN), and renal cell carcinoma (RCC), aberrant patterns of DNA/RNA/histone methylation and acetylation have been associated with disease onset and progression, revealing a complex interplay with lncRNA dynamics. Recent studies have highlighted how lncRNAs can impact renal pathology by affecting the expression and function of key genes involved in cell cycle control, fibrosis, and inflammatory responses. This review will separately address the roles of lncRNAs and epigenetic modifications in renal diseases, with a particular emphasis on elucidating the bidirectional regulatory effects and underlying mechanisms of lncRNAs in conjunction with DNA/RNA/histone methylation and acetylation, in addition to the potential exacerbating or renoprotective effects in renal pathologies. Understanding the reciprocal relationships between lncRNAs and epigenetic modifications will not only shed light on the molecular underpinnings of renal pathologies but also present new avenues for therapeutic interventions and biomarker development, advancing precision medicine in nephrology.

Probucol-bile acid nanoparticles: a novel approach and promising solution to prevent cellular oxidative stress in sensorineural hearing loss

The use of antioxidants could thus prove an effective medication to prevent or facilitate recovery from oxidative stress-induced sensorineural hearing loss (SNHL). One promising strategy to prevent SNHL is developing probucol (PB)-based nanoparticles using encapsulation technology and administering them to the inner ear via the established intratympanic route. The preclinical, clinical and epidemiological studies support that PB is a proven antioxidant that could effectively prevent oxidative stress in different study models. Such findings suggest its applicability in preventing oxidative stress within the inner ear and its associated neural cells. However, several hurdles, such as overcoming the blood-labyrinth barrier, ensuring sustained release, minimising systemic side effects and optimising targeted delivery in the intricate inner ear structures, must be overcome to efficiently deliver PB to the inner ear. This review explores the background and pathogenesis of hearing loss, the potential of PB in treating oxidative stress and its cellular mechanisms, and the obstacles linked to inner ear drug delivery for effectively introducing PB to the inner ear.

Heterogeneous nuclear ribonucleoprotein F deficiency in mouse podocyte promotes podocytopathy mediated by methyltransferase-like 14 nuclear translocation resulting in Sirtuin 1 gene inhibition

Heterogeneous nuclear ribonucleoprotein F (HnRNP F) is a key regulator for nucleic acid metabolism; however, whether HnRNP F expression is important in maintaining podocyte integrity is unclear. Nephroseq analysis from a registry of human kidney biopsies was performed. Age- and sex-matched podocyte-specific HnRNP F knockout (HnRNP FPOD KO) mice and control (HnRNP Ffl/fl) were studied. Podocytopathy was induced in male mice (more susceptible) either by adriamycin (ADR)- or low-dose streptozotocin treatment for 2 or 8 weeks. The mouse podocyte cell line (mPODs) was used in vitro. Nephroseq data in three human cohorts were varied greatly. Both sexes of HnRNP FPOD KO mice were fertile and appeared grossly normal. However, male 20-week-old HnRNP FPOD KO than HnRNP Ffl/fl mice had increased urinary albumin/creatinine ratio, and lower expression of podocyte markers. ADR- or diabetic- HnRNP FPOD KO (vs. HnRNP Ffl/fl) mice had more severe podocytopathy. Moreover, methyltransferase-like 14 (Mettl14) gene expression was increased in podocytes from HnRNP FPOD KO mice, further enhanced in ADR- or diabetic-treated HnRNP FPOD KO mice. Consequently, this elevated Mettl14 expression led to sirtuin1 (Sirt1) inhibition, associated with podocyte loss. In mPODs, knock-down of HnRNP F promoted Mettl14 nuclear translocation, which was associated with podocyte dysmorphology and Sirt1 inhibition-mediated podocyte loss. This process was more severe in ADR- or high glucose- treated mPODs. Conclusion: HnRNP F deficiency in podocytes promotes podocytopathy through activation of Mettl14 expression and its nuclear translocation to inhibit Sirt1 expression, underscoring the protective role of HnRNP F against podocyte injury.

Exercise in Diabetic Nephropathy: Protective Effects and Molecular Mechanism

Diabetic nephropathy (DN) is a serious complication of diabetes, and its progression is influenced by factors like oxidative stress, inflammation, cell death, and fibrosis. Compared to drug treatment, exercise offers a cost-effective and low-risk approach to slowing down DN progression. Through multiple ways and mechanisms, exercise helps to control blood sugar and blood pressure and reduce serum creatinine and albuminuria, thereby alleviating kidney damage. This review explores the beneficial effects of exercise on DN improvement and highlights its potential mechanisms for ameliorating DN. In-depth understanding of the role and mechanism of exercise in improving DN would pave the way for formulating safe and effective exercise programs for the treatment and prevention of DN.

Acetyl-CoA synthetase 2 promotes diabetic renal tubular injury in mice by rewiring fatty acid metabolism through SIRT1/ChREBP pathway

Diabetic nephropathy (DN) is characterized by chronic low-grade renal inflammatory responses, which greatly contribute to disease progression. Abnormal glucose metabolism disrupts renal lipid metabolism, leading to lipid accumulation, nephrotoxicity, and subsequent aseptic renal interstitial inflammation. In this study, we investigated the mechanisms underlying the renal inflammation in diabetes, driven by glucose-lipid metabolic rearrangement with a focus on the role of acetyl-CoA synthetase 2 (ACSS2) in lipid accumulation and renal tubular injury. Diabetic models were established in mice by the injection of streptozotocin and in human renal tubular epithelial HK-2 cells cultured under a high glucose (HG, 30 mmol/L) condition. We showed that the expression levels of ACSS2 were significantly increased in renal tubular epithelial cells (RTECs) from the diabetic mice and human diabetic kidney biopsy samples, and ACSS2 was co-localized with the pro-inflammatory cytokine IL-1β in RTECs. Diabetic ACSS2-deficient mice exhibited reduced renal tubular injury and inflammatory responses. Similarly, ACSS2 knockdown or inhibition of ACSS2 by ACSS2i (10 µmol/L) in HK-2 cells significantly ameliorated HG-induced inflammation, mitochondrial stress, and fatty acid synthesis. Molecular docking revealed that ACSS2 interacted with Sirtuin 1 (SIRT1). In HG-treated HK-2 cells, we demonstrated that ACSS2 suppressed SIRT1 expression and activated fatty acid synthesis by modulating SIRT1-carbohydrate responsive element binding protein (ChREBP) activity, leading to mitochondrial oxidative stress and inflammation. We conclude that ACSS2 promotes mitochondrial oxidative stress and renal tubular inflammation in DN by regulating the SIRT1-ChREBP pathway. This highlights the potential therapeutic value of pharmacological inhibition of ACSS2 for alleviating renal inflammation and dysregulation of fatty acid metabolic homeostasis in DN. Metabolic inflammation in the renal region, driven by lipid metabolism disorder, is a key factor in renal injury in diabetic nephropathy (DN). Acetyl-CoA synthetase 2 (ACSS2) is abundantly expressed in renal tubular epithelial cells (RTECs) and highly upregulated in diabetic kidneys. Deleting ACSS2 reduces renal fatty acid accumulation and markers of renal tubular injury in diabetic mice. We demonstrate that ACSS2 deletion inhibits ChREBP-mediated fatty acid lipogenesis, mitochondrial oxidative stress, and inflammatory response in RTECs, which play a major role in the progression of diabetic renal tubular injury in the kidney. These findings support the potential use of ACSS2 inhibitors in treating patients with DN.

Sirtuin 6 protects against podocyte injury by blocking the renin-angiotensin system by inhibiting the Wnt1/β-catenin pathway

Sirtuins (Sirts) are a family of nicotinamide adenine dinucleotide-dependent protein deacetylases that share diverse cellular functions. Increasing evidence shows that Sirts play a critical role in podocyte injury, which is a major determinant of proteinuria-associated renal disease. Membranous nephropathy (MN) is a typical glomerular disease in which podocyte damage mediates proteinuria development. In this study we investigated the molecular mechanisms underlying the regulatory roles of Sirt in podocyte injury in MN patients, rats with cationic bovine serum albumin (CBSA)-induced MN and zymosan activation serum (ZAS)-stimulated podocytes. Compared with healthy controls, MN patients showed significant reduction in intrarenal Sirt1 and Sirt6 protein expression. In CBSA-induced MN rats, significant reduction in intrarenal Sirt1, Sirt3 and Sirt6 protein expression was observed. However, only significant decrease in Sirt6 protein expression was found in ZAS-stimulated podocytes. MN patients showed significantly upregulated protein expression of Wnt1 and β-catenin and renin-angiotensin system (RAS) components in glomeruli. CBSA-induced MN rats exhibited significantly upregulated protein expression of intrarenal Wnt1 and β-catenin and their downstream gene products as well as RAS components. Similar results were observed in ZAS-stimulated podocytes. In ZAS-stimulated podocytes, treatment with a specific Sirt6 activator UBCS039 preserved the protein expression of podocin, nephrin and podocalyxin, accompanied by significant inhibition of the protein expression of β-catenin and its downstream gene products, including Snail1 and Twist; treatment with a β-catenin inhibitor ICG-001 significantly preserved the expression of podocyte-specific proteins and inhibited the upregulation of downstream β-catenin gene products accompanied by significant suppression of the protein expression of RAS components. Thus, we demonstrate that Sirt6 ameliorates podocyte injury by blocking RAS signalling via the Wnt1/β-catenin pathway. Sirt6 is a specific therapeutic target for the treatment of podocyte damage-associated renal disease.

5-HT3 antagonist, tropisetron, ameliorates age-related renal injury induced by D-galactose in male mice: Up-regulation of sirtuin 1

Objectives

The kidney ages faster than other organs due to changes in energy metabolism, mitochondrial dysfunction, and oxidative stress. This study looked into the anti-aging effect of tropisetron.

Materials and Methods

D-galactose was administrated subcutaneously in a mouse model for eight weeks in order to induce renal aging. Three separate intraperitoneal doses of tropisetron (1, 3, and 5 mg/kg body weight) were given at the same time. We assessed markers of mitochondrial dysfunction, oxidative stress, and inflammation. Via Real-Time PCR, the expressions of genes linked to aging (SIRT1) and apoptosis (Bax and Bcl-2) were ascertained. In addition, an assessment of histopathological changes, blood urea nitrogen, and creatinine concentrations was done.

Results

In kidney tissue, tropisetron reduces mitochondrial dysfunction and oxidative stress, which are caused by D-galactose-induced overproduction of inflammatory mediators. Additionally, tropisetron demonstrated antiapoptotic activity in renal tissue and augmented the decrease in SIRT1 gene expression associated with D-galactose administration. Besides, tropisetron significantly improved the histological alterations in the renal tissues of aged mice and effectively decreased the elevated levels of creatinine and also blood urea nitrogen.

Conclusion

The results provided additional insight into the effect of tropisetron on renal aging and the underlying mechanisms, particularly through its ability to modulate SIRT1 signaling.

Therapeutic application of traditional Chinese medicine in kidney disease: Sirtuins as potential targets

Sirtuins are a family of NAD+ III-dependent histone deacetylases that consists of seven family members, Sirt1-Sirt7, which regulate various signalling pathways and are involved in many critical biological processes of kidney diseases. Traditional Chinese medicine (TCM), as an essential part of the global healthcare system, has multi-component and multi-pathway therapeutic characteristics and plays a role in preventing and controlling various diseases. Through ongoing collaboration with modern medicine, TCM has recently achieved many remarkable advancements in theoretical investigation, mechanistic research, and clinical applications related to kidney diseases. Therefore, a comprehensive and systematic summary of TCM that focuses on sirtuins as the intervention target for kidney diseases is necessary. This review introduces the relationship between abnormal sirtuins levels and common kidney diseases, such as diabetic kidney disease and acute kidney injury. Based on the standard biological processes, such as inflammation, oxidative stress, autophagy, mitochondrial homeostasis, and fibrosis, which are underlying kidney diseases, comprehensively describes the roles and regulatory effects of TCM targeting the sirtuins family in various kidney diseases.

JAK/STAT signaling in diabetic kidney disease

Diabetic kidney disease (DKD) is the most important microvascular complication of diabetes and the leading cause of end-stage renal disease (ESRD) worldwide. The Janus kinase/signal transducer and activator of the transcription (JAK/STAT) signaling pathway, which is out of balance in the context of DKD, acts through a range of metabolism-related cytokines and hormones. JAK/STAT is the primary signaling node in the progression of DKD. The latest research on JAK/STAT signaling helps determine the role of this pathway in the factors associated with DKD progression. These factors include the renin-angiotensin system (RAS), fibrosis, immunity, inflammation, aging, autophagy, and EMT. This review epitomizes the progress in understanding the complicated explanation of the etiologies of DKD and the role of the JAK/STAT pathway in the progression of DKD and discusses whether it can be a potential target for treating DKD. It further summarizes the JAK/STAT inhibitors, natural products, and other drugs that are promising for treating DKD and discusses how these inhibitors can alleviate DKD to explore possible potential drugs that will contribute to formulating effective treatment strategies for DKD in the near future.

The role of Sirtuin 1 and its activators in age-related lung disease

Aging is a major driving factor in lung diseases. Age-related lung disease is associated with downregulated expression of SIRT1, an NAD⁺-dependent deacetylase that regulates inflammation and stress resistance. SIRT1 acts by inducing the deacetylation of various substrates and regulates several mechanisms that relate to lung aging, such as genomic instability, lung stem cell exhaustion, mitochondrial dysfunction, telomere shortening, and immune senescence. Chinese herbal medicines have many biological activities, exerting anti-inflammatory, anti-oxidation, anti-tumor, and immune regulatory effects. Recent studies have confirmed that many Chinese herbs have the effect of activating SIRT1. Therefore, we reviewed the mechanism of SIRT1 in age-related lung disease and explored the potential roles of Chinese herbs as SIRT1 activators in the treatment of age-related lung disease.

Loss of Sirt1 promotes exosome secretion from podocytes by inhibiting lysosomal acidification in diabetic nephropathy

Podocyte injury is a characteristic feature of diabetic nephropathy (DN). The secretion of exosomes in podocytes increases significantly in DN; however, the precise mechanisms remain poorly understood. Here, we demonstrated that Sirtuin1 (Sirt1) was significantly downregulated in podocytes in DN, which correlated negatively with increased exosome secretion. Similar results were observed in vitro. We found that lysosomal acidification in podocytes following high glucose administration was markedly inhibited, resulting in the decreased lysosomal degradation of multivesicular bodies. Mechanistically, we indicated that loss of Sirt1 contributed to the inhibited lysosomal acidification by decreasing the expression of the A subunit of the lysosomal vacuolar-type H⁺ ATPase proton pump (ATP6V1A) in podocytes. Overexpression of Sirt1 significantly improved lysosomal acidification with increased expression of ATP6V1A and inhibited exosome secretion. These findings suggest that dysfunctional Sirt1-mediated lysosomal acidification is the exact mechanism of increased secretion of exosomes in podocytes in DN, providing insights into potential therapeutic strategies for preventing DN progression.

Synergistic Beneficial Effects of Resveratrol and Diet on High-Fat Diet-Induced Obesity

Introduction: Despite decades of research, obesity and its related medical complications remain a major health concern globally. Therefore, novel therapeutic strategies are needed to combat obesity and its numerous debilitating complications. Resveratrol (RES) has a potential therapeutic effect in obesity and diabetes by improving oxidative metabolism and insulin signaling. Background and Objectives: The aim of this study was to investigate the effect of RES treatment on weight loss and glucose and fatty acid metabolism. Methods: Obesity was induced in 24 mice by exposure to a high-fat diet (HFD) for 8 weeks. Mice were randomly assigned to one group of either: group 1: control, non-treated low-fat diet (LFD) for 12 weeks (n = 8), group 2: non-treated high-fat diet (HFD) for 12 weeks (n = 8), group 3: RES-treated HFD (HFD + RES) (n = 8), or group 4: RES-treated and switched to LFD (HFD-LFD + RES) (n = 8). HFD + RES mice were first fed an HFD for 8 weeks followed by 4 weeks of RES. The HFD-LFD + RES group was first fed an HFD for 8 weeks and then treated with RES and switched to an LFD for 4 weeks. Results: After 12 weeks, group 2 mice had significantly higher body weights compared to group 1 (23.71 ± 1.95 vs. 47.83 ± 2.27; p < 0.05). Group 4 had a significant decrease in body weight and improvement in glucose tolerance compared to mice in group 2 (71.3 ± 1.17 vs. 46.1 ± 1.82 and 40.9 ± 1.75, respectively; p < 0.05). Skeletal muscles expression of SIRT1, SIRT3, and PGC1α were induced in group 3 and 4 mice compared to group 2 (p < 0.01), with no changes in AMP-activated protein kinase expression levels. Furthermore, combination of RES and diet ameliorated skeletal muscle intermediate lipid accumulation and significantly improved insulin sensitivity and secretion. Conclusions: The results of this study suggest a synergistic beneficial effect of LFD and RES to lower body weight and enhance glucose and fatty acid metabolism.