The deacylase sirtuin 5 reduces malonylation in nonmitochondrial metabolic pathways in diabetic kidney disease

The Role of Mitochondrial Sirtuins (SIRT3, SIRT4 and SIRT5) in Renal Cell Metabolism: Implication for Kidney Diseases

Kidney diseases, including chronic kidney disease (CKD), diabetic nephropathy, and acute kidney injury (AKI), represent a significant global health burden. The kidneys are metabolically very active organs demanding a large amount of ATP. They are composed of highly specialized cell types in the glomerulus and subsequent tubular compartments which fine-tune metabolism to meet their numerous and diverse functions. Defective renal cell metabolism, including altered fatty acid oxidation or glycolysis, has been linked to both AKI and CKD. Mitochondria play a vital role in renal metabolism, and emerging research has identified mitochondrial sirtuins (SIRT3, SIRT4 and SIRT5) as key regulators of renal cell metabolic adaptation, especially SIRT3. Sirtuins belong to an evolutionarily conserved family of mainly NAD+-dependent deacetylases, deacylases, and ADP-ribosyl transferases. Their dependence on NAD+, used as a co-substrate, directly links their enzymatic activity to the metabolic status of the cell. In the kidney, SIRT3 has been described to play crucial roles in the regulation of mitochondrial function, and the antioxidative and antifibrotic response. SIRT3 has been found to be constantly downregulated in renal diseases. Genetic or pharmacologic upregulation of SIRT3 has also been associated with beneficial renal outcomes. Importantly, experimental pieces of evidence suggest that SIRT3 may act as an important energy sensor in renal cells by regulating the activity of key enzymes involved in metabolic adaptation. Activation of SIRT3 may thus represent an interesting strategy to ameliorate renal cell energetics. In this review, we discuss the roles of SIRT3 in lipid and glucose metabolism and in mediating a metabolic switch in a physiological and pathological context. Moreover, we highlight the emerging significance of other mitochondrial sirtuins, SIRT4 and SIRT5, in renal metabolism. Understanding the role of mitochondrial sirtuins in kidney diseases may also open new avenues for innovative and efficient therapeutic interventions and ultimately improve the management of renal injuries.

Mitochondrial metabolic reprogramming in diabetic kidney disease

Diabetic kidney disease, known as a glomerular disease, arises from a metabolic disorder impairing renal cell function. Mitochondria, crucial organelles, play a key role in substance metabolism via oxidative phosphorylation to generate ATP. Cells undergo metabolic reprogramming as a compensatory mechanism to fulfill energy needs for survival and growth, attracting scholarly attention in recent years. Studies indicate that mitochondrial metabolic reprogramming significantly influences the pathophysiological progression of DKD. Alterations in kidney metabolism lead to abnormal expression of signaling molecules and activation of pathways, inducing oxidative stress-related cellular damage, inflammatory responses, apoptosis, and autophagy irregularities, culminating in renal fibrosis and insufficiency. This review delves into the impact of mitochondrial metabolic reprogramming on DKD pathogenesis, emphasizing the regulation of metabolic regulators and downstream signaling pathways. Therapeutic interventions targeting renal metabolic reprogramming can potentially delay DKD progression. The findings underscore the importance of focusing on metabolic reprogramming to develop safer and more effective therapeutic approaches.

Sirtuins in kidney diseases: potential mechanism and therapeutic targets

Sirtuins, which are NAD+-dependent class III histone deacetylases, are involved in various biological processes, including DNA damage repair, immune inflammation, oxidative stress, mitochondrial homeostasis, autophagy, and apoptosis. Sirtuins are essential regulators of cellular function and organismal health. Increasing evidence suggests that the development of age-related diseases, including kidney diseases, is associated with aberrant expression of sirtuins, and that regulation of sirtuins expression and activity can effectively improve kidney function and delay the progression of kidney disease. In this review, we summarise current studies highlighting the role of sirtuins in renal diseases. First, we discuss sirtuin family members and their main mechanisms of action. We then outline the possible roles of sirtuins in various cell types in kidney diseases. Finally, we summarise the compounds that activate or inhibit sirtuin activity and that consequently ameliorate renal diseases. In conclusion, targeted modulation of sirtuins is a potential therapeutic strategy for kidney diseases. Video Abstract.

[Role of Histone Modifications in Acute Kidney Injury Progressing to Chronic Kidney Disease]

Acute kidney injury (AKI), a clinical syndrome caused by various factors, is characterized by a rapid decline in kidney function in a short period of time. AKI affects the short-term prognosis of patients and may also induce chronic kidney disease (CKD). However, the current treatment options for AKI mainly focus on symptom management. Specific therapeutic measures available for the prevention of transition from AKI to CKD are very limited in number. Histones are basic proteins that intricately bind the DNA in chromosomes. After translation, histones undergo various modifications on their amino-terminal tails, such as methylation, acetylation, phosphorylation, ubiquitination, and lactylation, collectively forming the "histone code", which affects the expression of genes mainly by regulating the elastic structure of chromatin or recruiting specific proteins. Extensive research conducted in recent years on histone post-translational modifications (PTMs) has also sparked continuous interest in their association with the AKI-to-CKD transition. Therefore, this paper highlights the significant role of PTMs in the process of AKI developing and progressing to CKD, with a view to finding new approaches to preventing the progression of AKI to CKD.

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.

Kidney lipid dysmetabolism and lipid droplet accumulation in chronic kidney disease

Chronic kidney disease (CKD) is a global health problem with rising incidence and prevalence. Among several pathogenetic mechanisms responsible for disease progression, lipid accumulation in the kidney parenchyma might drive inflammation and fibrosis, as has been described in fatty liver diseases. Lipids and their metabolites have several important structural and functional roles, as they are constituents of cell and organelle membranes, serve as signalling molecules and are used for energy production. However, although lipids can be stored in lipid droplets to maintain lipid homeostasis, lipid accumulation can become pathogenic. Understanding the mechanisms linking kidney parenchymal lipid accumulation to CKD of metabolic or non-metabolic origin is challenging, owing to the tremendous variety of lipid species and their functional diversity across different parenchymal cells. Nonetheless, multiple research reports have begun to emphasize the effect of dysregulated kidney lipid metabolism in CKD progression. For example, altered cholesterol and fatty acid metabolism contribute to glomerular and tubular cell injury. Newly developed lipid-targeting agents are being tested in clinical trials in CKD, raising expectations for further therapeutic development in this field.

Role of succinate in airway epithelial cell regulation following traumatic lung injury

Lung contusion and gastric aspiration (LC and GA) are major risk factors for developing acute respiratory distress following trauma. Hypoxia from lung injury is mainly regulated by hypoxia-inducible factor 1α (HIF-1α). Published data from our group indicate that HIF-1α regulation in airway epithelial cells (AEC) drives the acute inflammatory response following LC and GA. Metabolomic profiling and metabolic flux of Type II AEC following LC revealed marked increases in glycolytic and TCA intermediates in vivo and in vitro that were HIF-1α dependent. GLUT-1/4 expression was also increased in HIF-1α+/+ mice, suggesting that increased glucose entry may contribute to increased intermediates. Importantly, lactate incubation in vitro on Type II cells did not significantly increase the inflammatory byproduct IL-1β. Contrastingly, succinate had a direct proinflammatory effect on human small AEC by IL-1β generation in vitro. This effect was reversed by dimethylmalonate, suggesting an important role for succinate dehydrogenase in mediating HIF-1α effects. We confirmed the presence of the only known receptor for succinate binding, SUCNR1, on Type II AEC. These results support the hypothesis that succinate drives HIF-1α-mediated airway inflammation following LC. This is the first report to our knowledge of direct proinflammatory activation of succinate in nonimmune cells such as Type II AEC in direct lung injury models.

Roles of protein post-translational modifications in glucose and lipid metabolism: mechanisms and perspectives

The metabolism of glucose and lipids is essential for energy production in the body, and dysregulation of the metabolic pathways of these molecules is implicated in various acute and chronic diseases, such as type 2 diabetes, Alzheimer's disease, atherosclerosis (AS), obesity, tumor, and sepsis. Post-translational modifications (PTMs) of proteins, which involve the addition or removal of covalent functional groups, play a crucial role in regulating protein structure, localization function, and activity. Common PTMs include phosphorylation, acetylation, ubiquitination, methylation, and glycosylation. Emerging evidence indicates that PTMs are significant in modulating glucose and lipid metabolism by modifying key enzymes or proteins. In this review, we summarize the current understanding of the role and regulatory mechanisms of PTMs in glucose and lipid metabolism, with a focus on their involvement in disease progression associated with aberrant metabolism. Furthermore, we discuss the future prospects of PTMs, highlighting their potential for gaining deeper insights into glucose and lipid metabolism and related diseases.

Emerging Roles of SIRT5 in Metabolism, Cancer, and SARS-CoV-2 Infection

Sirtuin 5 (SIRT5) is a predominantly mitochondrial enzyme catalyzing the removal of glutaryl, succinyl, malonyl, and acetyl groups from lysine residues through a NAD+-dependent deacylase mechanism. SIRT5 is an important regulator of cellular homeostasis and modulates the activity of proteins involved in different metabolic pathways such as glycolysis, tricarboxylic acid (TCA) cycle, fatty acid oxidation, electron transport chain, generation of ketone bodies, nitrogenous waste management, and reactive oxygen species (ROS) detoxification. SIRT5 controls a wide range of aspects of myocardial energy metabolism and plays critical roles in heart physiology and stress responses. Moreover, SIRT5 has a protective function in the context of neurodegenerative diseases, while it acts as a context-dependent tumor promoter or suppressor. In addition, current research has demonstrated that SIRT5 is implicated in the SARS-CoV-2 infection, although opposing conclusions have been drawn in different studies. Here, we review the current knowledge on SIRT5 molecular actions under both healthy and diseased settings, as well as its functional effects on metabolic targets. Finally, we revise the potential of SIRT5 as a therapeutic target and provide an overview of the currently reported SIRT5 modulators, which include both activators and inhibitors.