Glucose- and Non-Glucose-Induced Mitochondrial Dysfunction in Diabetic Kidney Disease

ESRRA modulation by empagliflozin mitigates diabetic tubular injury via mitochondrial restoration

BACKGROUND

The protection of the diabetic kidney by Empagliflozin (EMPA) is attributed to its interaction with the sodium glucose cotransporter 2 located on proximal tubular epithelial cells (PTECs). Estrogen-related receptor α (ESRRA), known for its high expression in PTECs and association with mitochondrial biogenesis, plays a crucial role in this process. This study aimed to explore the impact of ESRRA on mitochondrial mass in diabetic tubular injury and elucidate the mechanism underlying the protective effects of EMPA.

METHODS

Mitochondrial changes in PTECs of 16-week-old diabetic mice were assessed using transmission electron microscopy (TEM) and RNA-sequences. In vivo, EMPA administration was carried out in db/db mice for 8 weeks, while in vitro experiments involved modifying ESRRA expression in HK2 cells using pcDNA-ESRRA or EMPA.

RESULTS

Evaluation through TEM revealed reduced mitochondrial mass and swollen mitochondria in PTECs, whereas no significant changes were observed under light microscopy. Analysis of RNA-sequences identified 110 downregulated genes, including Esrra, associated with mitochondrial function. Notably, ESRRA overexpression rescued the loss of mitochondrial mass induced by high glucose (HG) in HK2 cells. EMPA treatment ameliorated the ultrastructural alterations and mitigated the downregulation of ESRRA both in db/db mice and HG-treated HK2 cells.

CONCLUSION

The diminished expression of ESRRA is implicated in the decline of mitochondrial mass in PTECs during the early stages of diabetes, highlighting it as a key target of EMPA for preventing the progression of diabetic kidney injury.

Targeting pyruvate kinase M2 for the treatment of kidney disease

Pyruvate kinase M2 (PKM2), a rate limiting enzyme in glycolysis, is a cellular regulator that has received extensive attention and regards as a metabolic regulator of cellular metabolism and energy. Kidney is a highly metabolically active organ, and glycolysis is the important energy resource for kidney. The accumulated evidences indicates that the enzymatic activity of PKM2 is disturbed in kidney disease progression and treatment, especially diabetic kidney disease and acute kidney injury. Modulating PKM2 post-translational modification determines its enzymatic activity and nuclear translocation that serves as an important interventional approach to regulate PKM2. Emerging evidences show that PKM2 and its post-translational modification participate in kidney disease progression and treatment through modulating metabolism regulation, podocyte injury, fibroblast activation and proliferation, macrophage polarization, and T cell regulation. Interestingly, PKM2 activators (TEPP-46, DASA-58, mitapivat, and TP-1454) and PKM2 inhibitors (shikonin, alkannin, compound 3k and compound 3h) have exhibited potential therapeutic property in kidney disease, which indicates the pleiotropic effects of PKM2 in kidney. In the future, the deep investigation of PKM2 pleiotropic effects in kidney is urgently needed to determine the therapeutic effect of PKM2 activator/inhibitor to benefit patients. The information in this review highlights that PKM2 functions as a potential biomarker and therapeutic target for kidney diseases.

The unique association between the level of plateletcrit and the prevalence of diabetic kidney disease: a cross-sectional study

Objective

The activation of platelets in individuals with type 2 diabetes mellitus (T2DM) triggers inflammation and hemodynamic abnormalities, contributing to the development of diabetic kidney disease (DKD). Despite this, research into the relationship between plateletcrit (PCT) levels and DKD is sparse, with inconsistent conclusions drawn regarding the connection between various platelet parameters and DKD. This highlights the necessity for comprehensive, large-scale population studies. Therefore, our objective is to explore the association between PCT levels and various platelet parameters in relation to DKD.

Methods

In this cross-sectional study, hematological parameter data were collected from a cohort of 4,302 hospitalized Chinese patients. We analyzed the relationships between PCT, platelet count (PLT), mean platelet volume (MPV), platelet distribution width (PDW), platelet large cell ratio (P-LCR), and DKD, along with the urinary albumin-to-creatinine ratio (UACR), and estimated glomerular filtration rate (eGFR). Receiver operating characteristic (ROC) curve analysis was conducted to evaluate the diagnostic potential of these parameters.

Results

DKD patients exhibited significantly higher PCT levels compared to those without DKD. Multivariate regression analysis identified elevated PCT and PLT levels as potential independent risk factors for both DKD and UACR, while lower MPV levels might serve as independent protective factors for eGFR. The areas under the ROC curve for PCT in relation to DKD and UACR (≥30 mg/g) were 0.523 and 0.526, respectively. The area under the ROC curve for PLT in relation to UACR (≥30 mg/g) was 0.523.

Conclusion

PCT demonstrates a weak diagnostic value for T2DM patients at risk of developing DKD and experiencing proteinuria, and PLT shows a similarly modest diagnostic utility for detecting proteinuria. These insights contribute to a deeper understanding of the complex dynamics involved in DKD. Additionally, incorporating these markers into routine clinical assessments could enhance risk stratification, facilitating early interventions and personalized management strategies.

Protective Factors and the Pathogenesis of Complications in Diabetes

Chronic complications of diabetes are due to myriad disorders of numerous metabolic pathways that are responsible for most of the morbidity and mortality associated with the disease. Traditionally, diabetes complications are divided into those of microvascular and macrovascular origin. We suggest revising this antiquated classification into diabetes complications of vascular, parenchymal, and hybrid (both vascular and parenchymal) tissue origin, since the profile of diabetes complications ranges from those involving only vascular tissues to those involving mostly parenchymal organs. A major paradigm shift has occurred in recent years regarding the pathogenesis of diabetes complications, in which the focus has shifted from studies on risks to those on the interplay between risk and protective factors. While risk factors are clearly important for the development of chronic complications in diabetes, recent studies have established that protective factors are equally significant in modulating the development and severity of diabetes complications. These protective responses may help explain the differential severity of complications, and even the lack of pathologies, in some tissues. Nevertheless, despite the growing number of studies on this field, comprehensive reviews on protective factors and their mechanisms of action are not available. This review thus focused on the clinical, biochemical, and molecular mechanisms that support the idea of endogenous protective factors, and their roles in the initiation and progression of chronic complications in diabetes. In addition, this review also aimed to identify the main needs of this field for future studies.

Exosomes as nanostructures deliver miR-204 in alleviation of mitochondrial dysfunction in diabetic nephropathy through suppressing methyltransferase-like 7A-mediated CIDEC N6-methyladenosine methylation

OBJECTIVE

The exosomal cargo mainly comprises proteins, lipids, and microRNAs (miRNAs). Among these, miRNAs undertake multiple biological effects of exosomes (Exos). Some stem cell-derived exosomal miRNAs have shown the potential to treat diabetic nephropathy (DN). However, there is little research into the therapeutic effects of adipose-derived stem cell (ADSC)-derived exosomal miRNAs on DN. We aimed to explore the potential of miR-204-modified ADSC-derived Exos to mitigate DN.

METHODS

Exos were extracted and identified from ADSCs. Histopathological injury, oxidative stress (OS), mitochondrial function, cell viability, and apoptosis were assessed to explore the effects of ADSC-derived Exos on DN. For mechanism exploration, quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to measure miR-204, methyltransferase (METTL3, METTL14, and METTL7A), and CIDEC. Also, CIDEC m6A methylation and miR-204-METTL7A, and METTL7A-CIDEC interactions were determined.

RESULTS

Initially, OS-induced mitochondrial dysfunction was observed in DN rats. ADSC-derived Exos inhibited histopathological injury, cell apoptosis, OS, and mitochondrial dysfunction in DN rats. The similar therapeutic effects of ADSC-derived Exos were detected in the in vitro model. Intriguingly, miR-204 was released by ADSC-derived Exos and its upregulation enhanced the anti-DN effects of Exos. Mechanically, miR-204 reduced METTL7A expression to CIDEC m6A methylation, thus suppressing OS and mitochondrial dysfunction.

CONCLUSIONS

ADSC-derived exosomal miR-204 rescued OS-induced mitochondrial dysfunction by inhibiting METTL7A-mediated CIDEC m6A methylation. This study first revealed the significant role of ADSC-derived exosomal miR-204 in DN, paving the way for the development of novel therapeutic strategies to improve the clinical outcomes of DN patients.

[Linagliptin improves diabetic kidney disease in rats by promoting mitochondrial biogenesis through the AMPK/PGC-1α/TFAM pathway]

OBJECTIVE

To investigate whether linagliptin improves diabetic kidney disease (DKD) by promoting mitochondrial biosynthesis via activating adenosine monophosphate activated protein kinase/peroxisome proliferator-activated receptor gamma coactivator 1α/mitochondrial transcription factor A (AMPK/PGC-1α/TFAM) pathway.

METHODS

With 6 male SD rats feeding normal chow as the control group, 16 SD rat models of DKD induced by intraperitoneal injection of 45 mg/kg STZ and high-fat and high-glucose feeding for 4 weeks were randomized into DKD model group and linagliptin treatment group. The rats in the latter two groups were subjected to daily intragastric administration of vehicle or 5 mg/kg linagliptin (dissolved in 5 g/L sodium carboxymethylcellulose, final concentration of 2 mg/mL) for 12 weeks with further high-fat and high-glucose feeding. After the treatments, the rats were sacrificed and blood samples from the abdominal aorta and kidney tissues were collected for testing blood glucose, liver function and lipid metabolism; HE, PAS, Masson, Sirius red staining and electron microscopy were used to observe renal tissue damage. Renal expressions of transforming growth factor β1 (TGF-β1), fibronectin (FN) and collagen I (Col I) were detected by immunohistochemistry, and the changes in membrane potential (ΔψM) and ATP enzyme content were analyzed to assess mitochondrial damage; The expressions of AMPK/PGC-1α/TFAM pathway proteins were detected using Western blotting.

RESULTS

Compared with DKD model rats, the rats receiving linagliptin treatment showed significantly decreased blood glucose level (P < 0.01) and improved proteinuria (P < 0.05) with obviously alleviated renal ultrastructural damage and fibrosis, increased ATPase content and ΔψM (P < 0.0001), and enhanced renal expressions of P-AMPK/AMPK, PGC-1α and TFAM (P < 0.05).

CONCLUSIONS

Linagliptin improves proteinuria and renal fibrosis in rat models of DKD possibly by activating the AMPK/PGC-1α/TFAM pathway to promote mitochondrial biosynthesis.

Resveratrol prevents Drp1-mediated mitochondrial fission in the diabetic kidney through the PDE4D/PKA pathway

To explore the role of PDE4D in diabetic nephropathy (DN) and investigate whether resveratrol protects against DN via inhibiting PDE4D. Diabetic db/db mouse and glomerular mesangial cell line (GMCs) were used to investigate the role of PDE4D and the protective effect of resveratrol on renal fibrosis under high glucose (HG) environment. Resveratrol alleviated the progress of DN via inhibiting mitochondrial fragmentation and restoring the expression of PDE4D, PKA, phosphorylated Drp1-Ser637 and Drp1 in kidney of db/db mice. In HG-exposed GMCs, resveratrol treatment decreased the expression of PDE4D, increased PKA level, and inhibited Drp1-mediated mitochondrial fission. In contrast, PDE4D over-expression blunted the inhibitory effects of resveratrol on Drp1 expression and mitochondrial fission. Moreover, PKA inhibitor H89 blunted the effects of resveratrol on phosphorylated Drp1-Ser637 expression and mitochondrial fission in HG-treated GMCs. Inhibition of mitochondrial fission with Drp1 inhibitor Mdivi-1 alleviated mitochondrial dysfunction in GMCs under HG. These findings indicate PDE4D plays an important role in the process of DN. Resveratrol attenuates the development of DN by preventing mitochondrial fission through inhibiting PDE4D, which regulates the expression of phosphorylated Drp1-Ser637 directly.

Advances in the pharmacological study of Chinese herbal medicine to alleviate diabetic nephropathy by improving mitochondrial oxidative stress

Diabetic nephropathy (DN) is one of the serious complications of diabetes mellitus, primarily arising from type 2 diabetes (T2DM), and can progress to chronic kidney disease (CKD) and end stage renal disease (ESRD). The pathogenesis of DN involves various factors such as hemodynamic changes, oxidative stress, inflammatory response, and lipid metabolism disorders. Increasing attention is being given to DN caused by oxidative stress in the mitochondrial pathway, prompting researchers to explore drugs that can regulate these target pathways. Chinese herbal medicine, known for its accessibility, rich historical usage, and remarkable efficacy, has shown promise in ameliorating renal injury caused by DN by modulating oxidative stress in the mitochondrial pathway. This review aims to provide a reference for the prevention and treatment of DN. Firstly, we outline the mechanisms by which mitochondrial dysfunction impairs DN, focusing on outlining the damage to mitochondria by oxidative stress. Subsequently, we describe the process by which formulas, herbs and monomeric compounds protect the kidney by ameliorating oxidative stress in the mitochondrial pathway. Finally, the rich variety of Chinese herbal medicine, combined with modern extraction techniques, has great potential, and as we gradually understand the pathogenesis of DN and research techniques are constantly updated, there will be more and more promising therapeutic targets and herbal drug candidates. This paper aims to provide a reference for the prevention and treatment of DN.

Diabetic Nephropathy: Significance of Determining Oxidative Stress and Opportunities for Antioxidant Therapies

Diabetes mellitus (DM) belongs to the category of socially significant diseases with epidemic rates of increases in prevalence. Diabetic nephropathy (DN) is a specific kind of kidney damage that occurs in 40% of patients with DM and is considered a serious complication of DM. Most modern methods for treatments aimed at slowing down the progression of DN have side effects and do not produce unambiguous positive results in the long term. This fact has encouraged researchers to search for additional or alternative treatment methods. Hyperglycemia has a negative effect on renal structures due to a number of factors, including the activation of the polyol and hexosamine glucose metabolism pathways, the activation of the renin-angiotensin-aldosterone and sympathetic nervous systems, the accumulation of advanced glycation end products and increases in the insulin resistance and endothelial dysfunction of tissues. The above mechanisms cause the development of oxidative stress (OS) reactions and mitochondrial dysfunction, which in turn contribute to the development and progression of DN. Modern antioxidant therapies for DN involve various phytochemicals (food antioxidants, resveratrol, curcumin, alpha-lipoic acid preparations, etc.), which are widely used not only for the treatment of diabetes but also other systemic diseases. It has also been suggested that therapeutic approaches that target the source of reactive oxygen species in DN may have certain advantages in terms of nephroprotection from OS. This review describes the significance of studies on OS biomarkers in the pathogenesis of DN and analyzes various approaches to reducing the intensity of OS in the prevention and treatment of DN.

Role of Impaired Glycolysis in Perturbations of Amino Acid Metabolism in Diabetes Mellitus

The most frequent alterations in plasma amino acid concentrations in type 1 and type 2 diabetes are decreased L-serine and increased branched-chain amino acid (BCAA; valine, leucine, and isoleucine) levels. The likely cause of L-serine deficiency is decreased synthesis of 3-phosphoglycerate, the main endogenous precursor of L-serine, due to impaired glycolysis. The BCAA levels increase due to decreased supply of pyruvate and oxaloacetate from glycolysis, enhanced supply of NADH + H⁺ from beta-oxidation, and subsequent decrease in the flux through the citric acid cycle in muscles. These alterations decrease the supply of α-ketoglutarate for BCAA transamination and the activity of branched-chain keto acid dehydrogenase, the rate-limiting enzyme in BCAA catabolism. L-serine deficiency contributes to decreased synthesis of phospholipids and increased synthesis of deoxysphinganines, which play a role in diabetic neuropathy, impaired homocysteine disposal, and glycine deficiency. Enhanced BCAA levels contribute to increased levels of aromatic amino acids (phenylalanine, tyrosine, and tryptophan), insulin resistance, and accumulation of various metabolites, whose influence on diabetes progression is not clear. It is concluded that amino acid concentrations should be monitored in patients with diabetes, and systematic investigation is needed to examine the effects of L-serine and glycine supplementation on diabetes progression when these amino acids are decreased.

SUPPRESION OF MITOCHONDRIAL RESPIRATION IS A FEATURE OF CELLULAR GLUCOSE TOXICITY

Glucose toxicity is central to the myriad complications of diabetes and is now believed to encompass neurodegenerative diseases and cancer as well as microvascular and macrovascular disease. Due to the widespread benefits of SGLT2 inhibitors, which affect glucose uptake in the kidney proximal tubular cell, a focus on cell metabolism in response to glucose has important implications for overall health. We previously found that a -Warburg-type effect underlies diabetic kidney disease and involves metabolic reprogramming. This is now supported by quantitative measurements of superoxide measurement in the diabetic kidney and systems biology analysis of urine metabolites in patients. Further exploration of mechanisms underlying mediators of mitochondrial suppression will be critical in understanding the chronology of glucose-induced toxicity and developing new therapeutics to arrest the systemic glucose toxicity of diabetes.

The Role of NLRP3 Inflammasome in IgA Nephropathy

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerular disease worldwide today. The NLRP3 inflammasome is a polyprotein complex and an important participant in inflammation. Accumulating studies have shown that the NLRP3 inflammasome participates in a variety of kidney diseases, including IgAN. This review focuses on the role of the NLRP3 inflammasome in IgAN and summarizes multiple involved pathways, which may provide novel treatments for IgAN treatment.

Kidney and lipids: novel potential therapeutic targets for dyslipidemia in kidney disease?

INTRODUCTION

Altered lipid distribution and metabolism may lead to the development and/or progression of chronic kidney disease (CKD). Dyslipidemia is a major risk factor for CKD and increases the risk of cardiovascular events and mortality. Therefore, lipid-lowering treatments may decrease cardiovascular risk and prevent death.

AREAS COVERED

Key players involved in regulating lipid accumulation in the kidney; contribution of lipids to CKD progression, lipotoxicity, and mitochondrial dysfunction in kidney disease; recent therapeutic approaches for dyslipidemia.

EXPERT OPINION

The precise mechanisms for regulating lipid metabolism, particularly in kidney disease, are poorly understood. Guidelines for lipid-lowering therapy for CKD are controversial. Several hypolipemic therapies are available, but compared to others, statin therapy is the most common. No clinical trial has evaluated the efficacy of proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) in preventing cardiovascular events or improving kidney function among patients with CKD or kidney transplant recipients. Attractive alternatives, such as PCSK9-small interfering RNA (siRNA) molecules or evinacumab are available. Additionally, several promising agents, such as cyclodextrins and the FXR/TGR5 dual agonist, INT-767, can improve renal lipid metabolism disorders and delay CKD progression. Drugs targeting mitochondrial dysfunction could be an option for the treatment of dyslipidemia and lipotoxicity, particularly in renal diseases.