The key role of altered tubule cell lipid metabolism in kidney disease development

Huangqi and Danshen improve the chronic nephrotoxicity of cyclosporin A by regulating lipid metabolism

BACKGROUND

The clinical application of cyclosporine A (CsA) is limited due to nephrotoxicity. Lipid metabolism disorders play important roles in renal injury, but their role in CsA nephrotoxicity is not yet clear. Huangqi (Astragalus mongholicus Bunge) and Danshen (Salvia miltiorrhiza Bunge) (HD) play roles in ameliorating the nephrotoxicity of CsA, but their mechanisms still need to be fully clarified.

OBJECTIVE

This study innovatively aimed to analyse the coexpression of renal proteins and serum metabolites for the identification of key pathways and targets. This study provides novel insight into the mechanism by which HD ameliorates CsA-induced nephrotoxicity.

METHODS

We utilized HD to intervene in both in vivo and in vitro nephrotoxicity models induced by CsA. For the in vivo experiments, we constructed a coexpression network of renal proteins and serum metabolites, which was used to screen for key pathways. To validate these findings, we knocked down key proteins in vivo. For the in vitro studies, we employed MTT, Transwell, flow cytometry, and immunofluorescence assays to monitor the epithelial-mesenchymal transition (EMT) of HK-2 cells. Additionally, we used electron microscopy and Seahorse assays to examine the effects of HD on mitochondrial structure and function. Furthermore, we overexpressed Ppara to further confirm the mechanism by which HD improves renal function.

RESULTS

HD can improve renal pathological damage and function; regulate blood lipids, inflammation and oxidative stress indicators; and reduce apoptosis in renal tissues. Joint protein and metabolomics analyses revealed that two lipid metabolism-related pathways (the PPAR signalling pathway and linoleic acid metabolism pathway) were coenriched, involving six differential proteins (Cyp2e1, Cyp4a10, Gk, Lpl, Ppara, and Pck1) and two differentially abundant metabolites (alpha-Dimorphecolic acid and 12,13-EpOME). Western blot was used to verify differentially expressed proteins. HD improved mitochondrial damage and lipid accumulation, as demonstrated by transmission electron microscopy (TEM) analysis and Oil Red O staining. Knockdown of the key protein Ppara affected the expression of ACOX1 and exacerbated RF. In vitro verification demonstrated that HD significantly inhibited CsA-induced EMT in HK-2 cells and improved mitochondrial structure and function. Ppara overexpression promoted HD-mediated regulation of mitochondrial function, reduced apoptosis, and improved HK-2 RF.

CONCLUSION

HD can ameliorate CsA nephrotoxicity through renal protein-serum metabolism coexpression, the PPAR signalling pathway, and linoleic acid metabolism. HD-induced upregulation of Ppara to regulate lipid metabolism, improve mitochondrial function and reduce apoptosis are important mechanisms. The Ppara/ACOX1/TGF-β1 axis may play an important role in this process. These findings offer potential targets for the future development of therapeutic strategies and novel drugs.

Targeting lipid metabolic reprogramming to alleviate diabetic kidney disease: molecular insights and therapeutic strategies

Diabetic kidney disease (DKD) is one of the major complications of diabetes, and its pathological progression is closely associated with lipid metabolic reprogramming. Under diabetic conditions, renal cells undergo significant lipid metabolic abnormalities, including increased lipid uptake, impaired fatty acid oxidation, disrupted cholesterol efflux, and enhanced lipid catabolism, as adaptive responses to metabolic stress. These changes result in the accumulation of lipids such as free fatty acids, diacylglycerol, and ceramides, leading to lipotoxicity that triggers inflammation and fibrosis. Hypoxia in the DKD microenvironment suppresses fatty acid oxidation and promotes lipid synthesis through the HIF-1α pathway, while chronic inflammation exacerbates lipid metabolic disturbances via inflammatory cytokines, inflammasomes, and macrophage polarization. Targeting lipid metabolism represents a promising therapeutic strategy for alleviating DKD; however, further clinical translational studies are warranted to validate the efficacy and safety of these approaches.

Glutathione-specific gamma-glutamylcyclotransferase 1 (CHAC1) increases kidney disease risk by modulating ferroptosis

Genome-wide association studies (GWASs) have identified more than 1000 loci where genetic variants correlate with kidney function. However, the specific genes, cell types, and mechanisms influenced by these genetic variants remain largely uncharted. Here, we identified glutathione-specific gamma-glutamylcyclotransferase 1 (CHAC1) on chromosome 15 as affected by GWAS variants by analyzing human kidney gene expression and methylation information. Both CHAC1 RNA and protein were expressed in the loop of Henle region in mouse and human kidneys, and CHAC1 expression was higher in patients carrying disease risk variants. Using CRISPR technology, we created mice with a single functional copy of the Chac1 gene (Chac1+/-) that displayed no baseline phenotypic alterations in kidney structure or function. These mice demonstrated resilience to kidney disease in multiple models, including folic acid-induced nephropathy, adenine-induced chronic kidney disease, and uninephrectomy-streptozotocin-induced diabetic nephropathy. We further showed that CHAC1 plays a critical role in degrading the cellular antioxidant glutathione. Tubule cells isolated from Chac1+/- mice showed increased glutathione, decreased lipid peroxidation, improved cell viability, and protection against ferroptosis. Expression of ferroptosis-associated genes was also lower in mice with only one copy of Chac1. Higher CHAC1 protein also correlated with ferroptosis-related protein abundance in kidney biopsies from patients with kidney disease. This study positions CHAC1 as an important mediator of kidney disease that influences glutathione concentrations and ferroptosis, suggesting potential avenues to explore for the treatment of kidney diseases.

Protein handling in kidney tubules

The kidney proximal tubule reabsorbs and degrades filtered plasma proteins to reclaim valuable nutrients and maintain body homeostasis. Defects in this process result in proteinuria, one of the most frequently used biomarkers of kidney disease. Filtered proteins enter proximal tubules via receptor-mediated endocytosis and are processed within a highly developed apical endo-lysosomal system (ELS). Proteinuria is a strong risk factor for chronic kidney disease progression and genetic disorders of the ELS cause hereditary kidney diseases, so deepening understanding of how the proximal tubule handles proteins is crucial for translational nephrology. Moreover, the ELS is both an entry point for nephrotoxins that induce tubular damage and a target for novel therapies to prevent it. Cutting-edge research techniques, such as functional intravital imaging and computational modelling, are shedding light on spatial and integrative aspects of renal tubular protein processing in vivo, how these are altered under pathological conditions and the consequences for other tubular functions. These insights have potentially important implications for understanding the origins of systemic complications arising in proteinuric states, and might lead to the development of new ways of monitoring and treating kidney diseases.

Galloflavin mitigates acute kidney injury by suppressing LDHA-dependent macrophage glycolysis

Macrophage-mediated inflammation is closely linked to the pathogenesis of acute kidney injury (AKI) and the shift of macrophages to a pro-inflammatory phenotype being reliant on glycolytic metabolism. Galloflavin, a polyphenol derived from tea, functions as a lactate dehydrogenase A (LDHA) inhibitor, effectively obstructing glycolytic metabolic pathways. However, the specific immunometabolic regulatory functions of galloflavin in macrophages remain unclear. Here, we observed that galloflavin drives alleviation of glycolytic metabolism levels in lipopolysaccharide (LPS)-induced macrophages (RAW264.7 cells and human peripheral blood mononuclear cells-derived macrophages) through downregulation of LDHA expression, thereby inhibiting macrophage conversion to a pro-inflammatory phenotype and reducing the release of inflammatory cytokines. However, the overexpression of LDHA counteracts the effects of galloflavin in macrophages. In addition, in vivo experiments observed a protective effect of galloflavin against cecal ligation and puncture (CLP) and cisplatin-induced renal injury. The ability of galloflavin to inhibit glycolysis in renal macrophages, thereby regulating their phenotypic transition during AKI was further validated through the isolation of renal primary macrophages. This intervention ultimately ameliorated the inflammatory response and decelerated the progression of AKI. Collectively, galloflavin confers protection against AKI by suppressing glycolysis in macrophages through a LDHA-dependent mechanism, thereby positioning it as a potential therapeutic option for AKI in the future.

ECHS1 as a Lipid Metabolism Biomarker for Pediatric Focal Segmental Glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a common cause of nephrotic syndrome and often leads to end-stage renal disease. However, the underlying pathophysiological mechanisms that contribute to disease progression require further investigation to establish appropriate therapeutic targets and biomarkers. This study aimed to clarify the molecular mechanisms underlying FSGS by focusing on differentially expressed genes (DEGs) and lipid metabolism-related genes (LMRGs). We utilized the GSE69814, GSE129973, and GSE121233 datasets, which comprise glomerular transcriptomes from patients with FSGS, minimal change disease (MCD), and unaffected kidney tissues. We identified 2,459 DEGs from the GSE69814 dataset and 982 DEGs from the GSE129973 dataset. These DEGs intersected 1,450 LMRGs, resulting in 56 differentially expressed LMRGs (DELMRGs). Enrichment analysis revealed that these DELMRGs were primarily involved in fatty acid metabolic processes; localized in microbodies, peroxisomes, and mitochondrial matrices; and exhibited oxidoreductase activity. Protein-protein interaction networks were constructed using Cytoscape, and five hub DELMRGs (enoyl-CoA hydratase, short chain 1 [ECHS1], EHHADH, IDH1, SUCLG1, and ALDH3A2) were identified using multiple algorithms. We assessed the diagnostic performance using receiver operating characteristic curves and expression levels from the GSE121233 dataset, and found that ECHS1 and ALDH3A2 showed strong diagnostic potential. Immunohistochemical verification of clinical specimens from children confirmed significant expression of ECHS1 in FSGS compared with that in normal and MCD tissues. This study highlights ECHS1 as a potential biomarker for pediatric FSGS, suggesting a potential role in early diagnosis or personalized treatment, offering insights into its pathogenesis and paving the way for targeted therapeutic strategies.

Renal tubular S100A7a impairs fatty acid oxidation and exacerbates renal fibrosis via both intracellular and extracellular pathway

A couple of S100 family proteins (S100s) have been reported to exert pro-inflammatory functions in the progression of renal fibrosis. Unlike some S100s which are expressed by both epithelial and stromal inflammatory cells, S100A7 is restricted expressed in epithelium. Persistent S100A7 expression occurs in some invasive carcinomas and is associated with poor prognostic factors. Whereas, whether it is implicated in renal tubular epithelial cell injury and kidney disease remains unexplored. In this study, we demonstrate that S100A7 is highly upregulated in tubular cells of both mouse renal fibrotic lesions and kidney biopsies from patients with chronic kidney disease (CKD). The level of renal S100A7 was associated with both the decline of renal function and the progression of renal fibrosis in CKD patients. Overexpressing S100A7a impaired fatty acid oxidation (FAO) and promoted lipid peroxidation in proximal tubular cells (PTCs). Mechanistically, S100A7a interacts with β-catenin, thereby preventing its ubiquitination and degradation by the β-TrCP-SCF complex, and in turn activated β-catenin signaling, downregulated the expression of PGC-1α. Additionally, S100A7a exacerbated lipid peroxidation via RAGE-p-ERK-NOX2 pathway. Specific deletion of S100a7a in tubular cells enhanced FAO and reduced lipid peroxidation, resulting in improved renal function and alleviation of renal fibrosis induced by unilateral ureteral obstruction and unilateral ischemia-reperfusion injury. Collectively, we delineate a previously unrecognized function of S100A7a in the progression of renal fibrosis.

Lipidomics reveals potential biomarkers and pathophysiological insights in the progression of diabetic kidney disease

Background

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease, affecting over 30 % of diabetes mellitus (DM) patients. Early detection of DKD in DM patients can enable timely preventive therapies, and potentially delay disease progression. Since the kidney relies on fatty acid oxidation for energy, dysregulated lipid metabolism has been implicated in proximal tubular cell damage and DKD pathogenesis. This study aimed to identify lipid alterations during DKD development and potential biomarkers differentiating DKD from DM.

Methods

lipidomics analysis was performed on serum collected from 55 patients with DM, 21 with early DKD stage and 32 with advanced DKD, and 22 healthy subjects. Associations between lipids and DKD risk were evaluated by logistic regression.

Results

Lipid profiling revealed elevated levels of certain lysophosphatidylethanolamines (LPEs), phosphatidylethanolamines (PEs), ceramides (Cers), and diacylglycerols (DAGs) in the DM-DKD transition, while most LPEs, lysophosphatidylcholines (LPCs), along with several monoacylglycerol (MAG) and triacylglycerols (TAGs), increased further from DKD-E to DKD-A. Logistic regression indicated positive associations between LPCs, LPEs, PEs, and DAGs with DKD risk, with most LPEs correlating significantly with urinary albumin-to-creatinine ratio (UACR) and inversely with estimated glomerular filtration rate (eGFR). A machine-learning-derived biomarker panel, Lipid9, consisting of LPC(18:2), LPC(20:5), LPE (16:0), LPE (18:0), LPE (18:1), LPE (24:0), PE (34:1), PE (34:2), and PE (36:2), accurately distinguished DKD (AUC: 0.78, 95 % CI 0.68-0.86) from DM. Incorporating two clinical indexes, serum creatinine and blood urea nitrogen, the Lipid9-SCB model further improved DKD detection (AUC: 0.83, 95 % CI 0.75-0.90) from DM, and was notably more sensitive for identifying DKD-E (AUC: 0.79, 95 % CI 0.67-0.91).

Conclusion

This study deciphers the lipid signature in DKD progression, and suggests the Lipid9-SCB panel as a promising tool for early DKD detection in DM patients.

Metabolomics profiling in multi-ancestral individuals with type 2 diabetes in Singapore identified metabolites associated with renal function decline

AIMS/HYPOTHESIS

This study aims to explore the association between plasma metabolites and chronic kidney disease progression in individuals with type 2 diabetes.

METHODS

We performed a comprehensive metabolomic analysis in a prospective cohort study of 5144 multi-ancestral individuals with type 2 diabetes in Singapore, using eGFR slope as the primary outcome of kidney function decline. In addition, we performed genome-wide association studies on metabolites to assess how these metabolites could be genetically influenced by metabolite quantitative trait loci and performed colocalisation analysis to identify genes affecting both metabolites and kidney function.

RESULTS

Elevated levels of 61 lipids with long unsaturated fatty acid chains such as phosphatidylethanolamines, triacylglycerols, diacylglycerols, ceramides and deoxysphingolipids were prospectively associated with more rapid kidney function decline. In addition, elevated levels of seven amino acids and three lipids in the plasma were associated with a slower decline in eGFR. We also identified 15 metabolite quantitative trait loci associated with these metabolites, within which variants near TM6SF2, APOE and CPS1 could affect both metabolite levels and kidney functions.

CONCLUSIONS/INTERPRETATION

Our study identified plasma metabolites associated with prospective renal function decline, offering insights into the underlying mechanism by which the metabolite abnormalities due to fatty acid oversupply might reflect impaired β-oxidation and associate with future chronic kidney disease progression in individuals with diabetes.

Boeravinone C ameliorates lipid accumulation and inflammation in diabetic kidney disease by activating PPARα signaling

ETHNOPHARMACOLOGICAL RELEVANCE

The roots of Oxybaphus himalaicus Edgew. is a traditional Tibetan herbal medicine with kidney reinforcing and tonifying effects, which is commonly applied to treat nephritis. Boeravinone C has been identified as one of the primary constituents of O. himalaicus. However, the potential renal protective effects of boeravinone C remains unclear.

AIM OF THE STUDY

This research aimed to investigate the protective effects of boeravinone C on diabetic kidney disease and the underlying mechanisms.

MATERIALS AND METHODS

Streptozotocin (100 mg/kg) was intraperitoneally injected to induce DKD in mice. High glucose (50 mM)-induced HK-2 cells were utilized to investigate the mechanisms of boeravinone C against tubular injuries in vitro. Anti-DKD activity was assessed by measuring reactive oxygen species (ROS) levels, analyzing apoptosis through flow cytometry, and evaluating inflammation, apoptosis, and FAO-related proteins via Western blotting. Additionally, serum biochemical assays, as well as histopathological and immunohistochemical analyses of kidney tissues, were performed to explore the pharmacological effects of boeravinone C.

RESULTS

In vivo, boeravinone C administered significantly reduced the creatinine (CRE), blood urea nitrogen (BUN), triglycerides (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) levels in serum of DKD mice. In vitro, boeravinone C significantly restored the apoptosis induced by HG in HK-2 cells, which is further validated by an upregulation of the apoptosis-inhibiting protein Bcl-2, along with a decreased expression of the apoptosis-promoting proteins Bax and caspase-3. Mechanistically, boeravinone C reversed HG-induced downregulation of peroxisome proliferator-activated receptor α (PPARα) expression. As a transcription factor, elevated expression of PPARα led to upregulation of CPT1A and ACOX1, which then enhanced fatty acid oxidation (FAO) to reduce lipid accumulation in HK-2 cells. Furthermore, boeravinone C-mediated high expression of PPARα sequestered p65 subunit of NF-κB in the cytoplasm, leading to reduced expression of proinflammatory cytokines such as iNOS, TNF-α and IL-6. To verify that the therapeutic effects of boeravinone C in diabetic kidney disease (DKD) are mediated via PPARα activation, we developed a PPARα knockdown HK-2 cell line. Our findings revealed that PPARα downregulation modified biological effects of boeravinone C, especially regarding fatty acid metabolism and the inflammatory response, with significant repercussions on apoptosis.

CONCLUSION

This study demonstrates that the major component boeravinone C from O. himalaicus promotes the fatty acid oxidation and suppresses inflammatory response by upregulating PPARα expression, thereby reducing apoptosis in HG-induced renal tubule cells. Consequently, boeravinone C restores tubular function in DKD mice. Collectively, this study provides a pharmacological basis for utilizing of O. himalaicus in treating DKD.

Precision medicine in diabetes care

PURPOSE OF REVIEW

This review highlights emerging evidence supporting the premise of precision diabetes care including but not limited to monogenic diabetes and discuss potential opportunities, challenges, and limitations for clinical adoption.

RECENT FINDINGS

Driven by a single gene mutation, monogenic diabetes remains the best use-case for precision diabetes care. However, the increasing prevalence of diabetes among adolescents and young adults in an obesogenic environment makes triaging potential patients for genetic screening clinically challenging. High-dimensional molecular biomarkers (i.e., multiomics) can improve the risk prediction for incident type 2 diabetes (T2D), over and above a well established prediction model based on clinical variables alone. Machine learning approaches using clinical variable-based clustering methods have generated novel and reproducible T2D subgroups with distinct phenotypic and omics characteristics that are associated with differential long-term outcomes. This stratification-strategy may inform clinical decisions. However, on-going discussion and research will be needed to understand the clinical utility of sub-phenotyping T2D for precision care.

SUMMARY

Precision diabetes care has extended from uncommon monogenic diabetes to T2D which will need more complex approaches like multiomics and machine-learning methods. The successful clinical translation will require cumulative evidence and close collaboration among the stake holders.

Exploring the nephrotoxicity and molecular mechanisms of Di-2-ethylhexyl phthalate: A comprehensive review

Di-2-ethylhexyl phthalate (DEHP), a widely applied plasticizer in various products, can be absorbed into the human body through several channels and accumulate in the lungs, liver, testes, and kidneys, potentially impairing the function of these organs. Recently, the nephrotoxicity of DEHP has received heightened attention. Numerous epidemiologic findings have demonstrated that DEHP exposure may contribute to renal damage, leading to structural and functional abnormalities and exacerbating the progression of kidney disease. Recent research has discovered the mechanisms behind DEHP-induced nephrotoxicity may involve a variety of pathways, including apoptosis, autophagy, ferroptosis, oxidative stress, inflammation, DNA damage, and lipid metabolism disorders. This review discusses the impact of DEHP on kidney function and delves into the molecular mechanisms of nephrotoxicity mediated by DEHP in recent years. In addition, the review examines evidence for the antioxidant and anti-inflammatory capacities of lycopene, green tea polyphenols, and quercetin in ameliorating DEHP-induced renal injury is reviewed, providing a basis for further research.

Slc25a21 in cisplatin-induced acute kidney injury: a new target for renal tubular epithelial protection by regulating mitochondrial metabolic homeostasis

Acute kidney injury (AKI) is a significant global health issue, which is often caused by cisplatin therapy and characterized by mitochondrial dysfunction. Restoring mitochondrial homeostasis in tubular cells could exert therapeutic effects. Here, we investigated Slc25a21, a mitochondrial carrier, as a potential target for AKI intervention. Renal Slc25a21 expression is negatively associated with kidney function in both AKI patients and cisplatin-induced murine models. Sustaining renal expression of Slc25a21 slowed down AKI progression by reducing cellular apoptosis, necroptosis, and the inflammatory response, likely through its regulation of 2-oxoadipate conversion. Slc25a21 is highly expressed in proximal tubular epithelial cells, and its down-regulation contributes to compromised mitochondrial biogenesis and integrity, as well as impaired oxidative phosphorylation. Mechanistically, reduced Slc25a21 in AKI disrupts mitochondrial 2-oxoadipate transport, affecting related metabolites influx and the tricarboxylic acid cycle. These findings demonstrate a previously unappreciated metabolic function of Slc25a21 in tubular cells, and suggest that targeting mitochondrial metabolic homeostasis by sustaining Slc25a21 expression could be a potential novel therapeutic strategy for AKI.

From Adipose to Ailing Kidneys: The Role of Lipid Metabolism in Obesity-Related Chronic Kidney Disease

Obesity has emerged as a significant public health crisis, closely linked to the pathogenesis and progression of chronic kidney disease (CKD). This review explores the intricate relationship between obesity-induced lipid metabolism disorders and renal health. We discuss how excessive free fatty acids (FFAs) lead to lipid accumulation in renal tissues, resulting in cellular lipotoxicity, oxidative stress, and inflammation, ultimately contributing to renal injury. Key molecular mechanisms, including the roles of transcriptional regulators like PPARs and SREBP-1, are examined for their implications in lipid metabolism dysregulation. The review also highlights the impact of glomerular and tubular lipid overload on kidney pathology, emphasizing the roles of podocytes and tubular cells in maintaining kidney function. Various therapeutic strategies targeting lipid metabolism, including pharmacological agents such as statins and SGLT2 inhibitors, as well as lifestyle modifications, are discussed for their potential to mitigate CKD progression in obese individuals. Future research directions are suggested to better understand the mechanisms linking lipid metabolism to kidney disease and to develop personalized therapeutic approaches. Ultimately, addressing obesity-related lipid metabolism disorders may enhance kidney health and improve outcomes for individuals suffering from CKD.

Renal Angptl4 is a key fibrogenic molecule in progressive diabetic kidney disease

Angiopoietin-like 4 (ANGPTL4), a key protein involved in lipoprotein metabolism, has diverse effects. There is an association between Angptl4 and diabetic kidney disease; however, this association has not been well investigated. We show that both podocyte- and tubule-specific ANGPTL4 are crucial fibrogenic molecules in diabetes. Diabetes accelerates the fibrogenic phenotype in control mice but not in ANGPTL4 mutant mice. The protective effect observed in ANGPTL4 mutant mice is correlated with a reduction in stimulator of interferon genes pathway activation, expression of pro-inflammatory cytokines, reduced epithelial-to-mesenchymal transition and endothelial-to-mesenchymal transition, lessened mitochondrial damage, and increased fatty acid oxidation. Mechanistically, we demonstrate that podocyte- or tubule-secreted Angptl4 interacts with Integrin β1 and influences the association between dipeptidyl-4 with Integrin β1. We demonstrate the utility of a targeted pharmacologic therapy that specifically inhibits Angptl4 gene expression in the kidneys and protects diabetic kidneys from proteinuria and fibrosis. Together, these data demonstrate that podocyte- and tubule-derived Angptl4 is fibrogenic in diabetic kidneys.

Endoplasmic reticulum stress induces renal fibrosis in high‑fat diet mice via the TGF‑β/SMAD pathway

The aim of the present study was to investigate the role and mechanism of endoplasmic reticulum stress (ERS) in kidney injury caused by high‑fat diet (HFD). An obese mouse model was established via HFD feeding and intervention was performed by intraperitoneal injection of the ERS inhibitor salubrinal (Sal). Changes in the body and kidney weight and serum biochemical indices of the mice were determined. Hematoxylin and eosin and Masson staining were used to observe the pathological changes of renal tissues. Reverse transcription‑quantitative PCR and western blotting were used to observe the expression of ERS‑related proteins and TGF‑β/SMAD pathway‑related proteins. Immunohistochemistry was employed to explore the distribution of these proteins. Compared with those in the control group, the weight gain, lipid metabolism disorders and deterioration of renal function in the model group were greater. Malondialdehyde was elevated and superoxide dismutase was decreased in renal tissues. The mRNA and protein levels of TGF‑β1, SMAD2/3, α‑smooth muscle actin, collagen I, glucose‑regulated protein 78 and C/EBP‑homologous protein were markedly elevated, whereas SMAD7 was markedly decreased. Sal markedly inhibited the aforementioned effects. This investigation revealed a link between ERS and renal injury caused by HFD. ERS in HFD‑fed mice triggers renal fibrosis through the TGF‑β/SMAD pathway.

Dysfunctional mitochondria in age-related neurodegeneration: Utility of melatonin as an antioxidant treatment

Mitochondria functionally degrade as neurons age. Degenerative changes cause inefficient oxidative phosphorylation (OXPHOS) and elevated electron leakage from the electron transport chain (ETC) promoting increased intramitochondrial generation of damaging reactive oxygen and reactive nitrogen species (ROS and RNS). The associated progressive accumulation of molecular damage causes an increasingly rapid decline in mitochondrial physiology contributing to aging. Melatonin, a multifunctional free radical scavenger and indirect antioxidant, is synthesized in the mitochondrial matrix of neurons. Melatonin reduces electron leakage from the ETC and elevates ATP production; it also detoxifies ROS/RNS and via the SIRT3/FOXO pathway it upregulates activities of superoxide dismutase 2 and glutathione peroxidase. Melatonin also influences glucose processing by neurons. In neurogenerative diseases, neurons often adopt Warburg-type metabolism which excludes pyruvate from the mitochondria causing reduced intramitochondrial acetyl coenzyme A production. Acetyl coenzyme A supports the citric acid cycle and OXPHOS. Additionally, acetyl coenzyme A is a required co-substrate for arylalkylamine-N-acetyl transferase, which rate limits melatonin synthesis; therefore, melatonin production is diminished in cells that experience Warburg-type metabolism making mitochondria more vulnerable to oxidative stress. Moreover, endogenously produced melatonin diminishes during aging, further increasing oxidative damage to mitochondrial components. More normal mitochondrial physiology is preserved in aging neurons with melatonin supplementation.

Spatial Metabolomics and Lipidomics in Kidney Disease

Kidney disease is a global health issue that affects over 850 million people, and early detection is key to preventing severe disease and complications. Kidney diseases are associated with complex and dysregulation of lipid metabolism. Spatial metabolomics through mass spectrometry imaging (MSI) enables spatial mapping of the lipids in tissue and includes a variety of techniques that can be used to image lipids. In the kidney, MSI studies often seek to resolve individual functional tissue units such as glomeruli and proximal tubules. Several different MSI techniques, such as matrix-assisted laser desorption/ionization (MALDI) and desorption electrospray ionization (DESI), have been used to characterize lipids and small molecules in chronic kidney disease, acute kidney injury, genetic kidney disease, and cancer. In this review we provide several examples of how spatial metabolomics data can provide critical information concerning the localization of changes in various disease states. Additionally, when combined with pathology, transcriptomics, or proteomics, the metabolomic changes can illuminate underlying mechanisms and provide new clinical insights into disease mechanisms.

The transcriptome of early compensatory kidney growth reveals cell and time specific responses

Following kidney removal, the remaining kidney enlarges and increases its function. The mechanism and signals driving this compensatory kidney hypertrophy and the enlargement of its constituent kidney cells remains elusive. RNA-seq studies in mice undergoing hypertrophy 24, 48, and 72 h following nephrectomy were undertaken to understand the early transcriptional changes. This revealed substantial enhancement of cholesterol biosynthesis pathways, increases in mitochondrial gene expression and cell cycle perturbations. Single nuclei RNA-seq delineated cell specific changes at 24 h post nephrectomy and showed that sterol binding protein 2 (SREBP2) activity increases in medullary thick ascending limb cells in keeping with promotion of cholesterol synthesis. Cultured renal tubular cells were examined for insulin-like growth factor-1 (IGF-1) stimulated hypertrophy and SREBP2 was found to be required for increase in cell size. This work describes the early cell specific growth pathways mediating cellular and kidney hypertrophy with an intriguing role for cholesterol synthesis.

Transcriptome Analysis of the Effect of Nickel on Lipid Metabolism in Mouse Kidney

Although the human body needs nickel as a trace element, too much nickel exposure can be hazardous. The effects of nickel on cells include inducing oxidative stress, interfering with DNA damage repair, and altering epigenetic modifications. Glucose metabolism and lipid metabolism are closely related to oxidative stress; however, their role in nickel-induced damage needs further study. In Institute of Cancer Research (ICR) mice, our findings indicated that nickel stress increased the levels of blood lipid indicators (triglycerides, high-density lipoprotein, and cholesterol) by about 50%, blood glucose by more than two-fold, and glycated serum protein by nearly 20%. At the same time, nickel stress increased oxidative stress (malondialdehyde) and inflammation (Interleukin 6) by about 30% in the kidney. Based on next-generation sequencing technology, we detected and analyzed differentially expressed genes in the kidney caused by nickel stress. Bioinformatics analysis and experimental verification showed that nickel inhibited the expression of genes related to lipid metabolism and the AMPK and PPAR signaling pathways. The finding that nickel induces kidney injury and inhibits key genes involved in lipid metabolism and the AMPK and PPAR signaling pathways provides a theoretical basis for a deeper understanding of the mechanism of nickel-induced kidney injury.

SKLB023 protects against inflammation and apoptosis in sepsis-associated acute kidney injury via the inhibition of toll-like receptor 4 signaling

Sepsis-associated acute kidney injury (SA-AKI) is one of common critical illnesses with high morbidity and mortality. At present, effective therapeutic drugs for SA-AKI are remain lacking. SKLB023 is a synthetic small-molecule compound which exerts potent anti-inflammatory effects in our previous studies. Here, this study aimed to characterize the protective effect of SKLB023 on SA-AKI and explore its underlying mechanism. The SA-AKI experimental models have been established by cecum ligation/puncture (CLP) and lipopolysaccharide (LPS) injection in male C57BL/6J mice. SKLB023 was administered by gavage (50 or 25 mg/kg in CLP model and 50 mg/kg in LPS model) daily 3 days in advance and 30 min earlier on the day of modeling. Our results confirmed SKLB023 treatment could improve the survival of SA-AKI mice and ameliorate renal pathological injury, inflammation, and apoptosis in the two types of septic AKI mice. Mechanically, SKLB023 deceased the expression of TLR4 in LPS-triggered renal tubular epithelial cells, and inhibited the activation of downstream pathways including NF-κB and MAPK pathways. Our study suggested that SKLB023 is expected to be a potential drug for the prevention and treatment of septic AKI.