ATP-citrate lyase is an epigenetic regulator to promote obesity-related kidney injury

Molecular mechanisms underlying the effects of beta-sitosterol on TGF-β1/Nrf2/SIRT1/p53-mediated signaling in the kidney of a high-fat diet and sucrose-induced type-2 diabetic rat

Diabetic nephropathy, a severe problem of diabetes mellitus, is exacerbated by high-fat diets, prompting a need for interventions. Previous study from our laboratory has shown that β-sitosterol, a potent plant sterol has anti-inflammatory and glucose-lowering efficacy by involving insulin metabolic signalling pathway but its role on anti-oxidant signaling pathways, play a crucial role in mitigating oxidative stress and inflammation associated diabetic nephropathy, highlighting its importance as a potential therapeutic target for managing this debilitating complication of diabetes is unknown. This study was aimed to intricate the molecular mechanisms involved in the potential of β-sitosterol (BSIT) on TGF-β1/Nrf2/SIRT1/p53 signaling in high fat diet (HFD) and sucrose induced diabetic nephropathy (DN) in the rat kidney by employing various comprehensive bioinformatic analysis. We have used various comprehensive methods such as pathway predictions, Drug-Protein Interaction, Functional annotation analysis, and molecular docking techniques. Further, in vivo analysis of BSIT on biochemical profiles, gene and protein expression analysis of anti-oxidant and inflammatory signaling molecules was performed in the kidney of high fat diet (HFD) and sucrose-induced diabetic nephropathy. Computational studies provided insights into β-sitosterol's binding affinities and interaction modes with key proteins, suggesting its potential to regulate TGF-β1/Nrf2/SIRT1/p53 signaling pathways. Results of in vivo findings validated computational predictions, showcasing BSIT's multifaceted effects in mitigating diabetic nephropathy and associated complications including regulation of lipid metabolism, combating oxidative stress, and inflammation. The findings underscore BSIT's therapeutic potential by preserving cellular viability, regulating cell death, enhancing antioxidant defence, and stabilizing metabolic processes. Our study concludes that BSIT's ability to potentially regulate TGF-β1/Nrf2/SIRT1/p53 pathways, emphasizing its promising role in managing diabetic nephropathy and associated complications.

The role of lipid profile in the relationship between skipping breakfast and hyperuricemia: a moderated mediation model

BACKGROUND

The prevalence of hyperuricemia is rising among oilfield workers in China. This study aimed to explore the underlying mechanisms between skipping breakfast and serum uric acid.

METHODS

A total of 21,676 participants aged 20--60 from a large oilfield company in China were included. Association analysis, multivariate logistic, subgroup analysis, and moderated mediation analysis were performed to assess the association between skipping breakfast and hyperuricemia.

RESULTS

We found that 24.48% of oilfield employees had hyperuricemia. The odds ratio of hyperuricemia linked to skipping breakfast was 0.78 (95%CI: 0.69--0.88). The association between skipping breakfast and hyperuricemia was mediated by TC (22.32%) and LDL-C (21.57%). Age moderated this mediation, with significant effects for skipping breakfast (ß: 0.553, 95%CI: 0.042--1.063) and TC (ß: -0.339, 95%CI: -0.586- -0.093). Similar results were observed for LDL-C mediation (ß: 0.522, 95%CI: 0.009--1.035; ß: -0.585, 95%CI: -0.894- -0.276).

CONCLUSION

Skipping breakfast positively influenced hyperuricemia through TC and LDL-C. Age moderated the relationship between skipping breakfast and serum uric acid. Greater attention should be given to young employees in Chinese oilfield enterprises, with dietary interventions implemented to reduce abnormal lipids metabolism and hyperuricemia.

Obesity-Related Kidney Disease in Bariatric Surgery Candidates

BACKGROUND

Obesity has a negative impact in kidney health. However, the hallmarks of kidney dysfunction in bariatric surgery candidates are poorly characterized. To address this knowledge gap, we used a propensity score-matched analysis to compare kidney lesion biomarkers in bariatric surgery candidates and living kidney donors.

METHODS

Bariatric surgery candidates attending a single center for obesity treatment were pair-matched for sex and age to potential living kidney transplant donors (PLKD) using a 1:1 nearest-neighbor approach (N = 400, n = 200/group). A 24-h urine collection was used to analyze proteinuria and creatinine clearance.

RESULTS

Patients with obesity (PWO) had higher creatinine clearance when compared to PLKD (143.35 ± 45.50 mL/min vs 133.99 ± 39.06 mL/min, p = 0.03), which was underestimated when correction for body surface area (BSA) was used (creatinine clearance corrected for BSA of 115.25 ± 33.63 mL/min/1.73 m2 in PWO vs 135.47 ± 35.56 mL/min/1.73 m2 in PLKD). Proteinuria was also higher in PWO compared to PLKD (139.82 ± 353.258 mg/day vs 136.35 ± 62.24 mg/day, p < 0.0001). Regression analysis showed that creatinine clearance was strongly correlated with proteinuria in PWO (HR 1.522, p = 0.005), but it was less evident in PLKD (HR 0.376, p = 0.001).

CONCLUSION

Hyperfiltration and disproportionate proteinuria are frequent in patients with obesity. Since hyperfiltration can be underestimated by adjusting creatinine clearance for BSA, this should not be used when evaluating kidney function in bariatric surgery candidates.

ATP citrate lyase ablation hampers exocrine regeneration via TLR4/NF-kappaB signaling after acute pancreatitis in mice

BACKGROUND

ATP citrate lyase (Acly) is widely expressed in many tissues, has been proved to be involved in the pathogenesis of many inflammatory diseases. So far, the importance of Acly in acute pancreatitis(AP) has not been clearly determined. The purpose of this study is to clarify whether Acly can evoke inflammatory cascades in the progression of AP and hamper the subsequent regeneration process of pancreas.

METHODS

Experimental pancreatitis in mice with a specific deficiency of Acly in the pancreas and in control mice through repetitive cerulein injections in vivo. The pancreas pathological grading, cell proliferative potential and the formation of acinar-to-ductal metaplasia (ADM) were evaluated. The levels of inflammatory cytokines in plasma were qualified by enzyme-linked immuno sorbent assay (ELISA). Pancreatic malondialdehyde (MDA), superoxide dismutase (SOD) activity and reduced glutathione (GSH) contents were measured for oxidative stress. The infiltration of macrophages and neutrophils, the expression of Toll like receptor 4 (TLR4), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and the activation of nuclear factor kappaB (NF-κB) and cleaved Caspase-3, were measured using immunostaining. The mRNA transcription levels of TLR4, TNF-α, and IL-1β in pancreatic tissues were detected by quantitative real-time PCR as well. Additionally, inhibition of TLR4 signaling by TAK-242 in AP mice with a pancreas-specific deletion of Acly was conducted in vivo.

RESULTS

The results demonstrated that the elimination of pancreatic Acly not only exacerbated the severity of pancreatitis in mice during the initial inflammatory phase, as evidenced by more severe pathological damage, but also impeded the healing process of the exocrine pancreas by enhancing the formation of ADM and decreasing the ability of acinar cells to proliferate. In addition, deficiency of Acly increased the circulating TNF-α, IL-1β and IL-6, the infiltration of macrophages and neutrophils, agumented the activation of nuclear factor kappaB (NF-κB) p65, the expression of TLR4, TNF-α, IL-1β and cleaved Caspase-3, and exacerbated excessive oxidative stress in the pancreas at specific time points of AP mice. However, TLR4 inhibition significantly attenuated the structural and functional damage of the pancreas induced by AP in mice with a pancreas-specific deletion of Acly, as indicated by improvement of the above indexes.

CONCLUSIONS

The present study demonstrated that ablation of pancreatic Acly intensified inflammatory reaction and cell death, and dampened exocrine regeneration following AP, due to the positive regulation of TLR4/NF-κB signaling activation.

Sphagnum cuspidatulum extract prevents acute kidney injury induced by high-fat diet and streptozotocin via alleviation of oxidative stress and apoptosis in pre-diabetic rats

Context

Obesity and pre-diabetes are associated with renal dysfunction via elevated oxidative stress. Peat moss, or Sphagnum cuspidatulum Müll. Hal., Sphagnaceae (SC), are rich in phenolic compounds that enhance antioxidant activity.

Objective

SC might show beneficial effects in pre-diabetes-associated renal dysfunction.

Materials and methods

Male Wistar rats, after 4 weeks on a high-fat diet, received low-dose streptozotocin to induce pre-diabetes. Then, the pre-diabetic rats were randomly divided into 4 groups: untreated pre-diabetic rats (P-DM), pre-diabetic rats treated with SC 50 or 100 mg/kg/day (P-DM50 or P-DM100), and pre-diabetic rats treated with metformin 100 mg/kg/day (MET). The drugs were fed by gavage for 4 weeks.

Results

Treatment with SC100 dramatically lowered serum creatinine (S.Cr.), blood urea nitrogen (BUN), and augmented creatinine clearance in pre-diabetic rats. Additionally, SC100 significantly decreased the malondialdehyde level. Furthermore, pre-diabetic rats treated with SC100 significantly upregulated the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream mediators, with downregulated apoptotic markers.

Discussion and conclusion

Our findings provide a scientific basis for the clinical application of SC and a new strategy for the prevention of nephrotoxicity and other kidney disease in the future.

Vitamin D receptor alleviates lipid peroxidation in diabetic nephropathy by regulating ACLY/Nrf2/Keap1 pathway

The membrane lipid damage caused by reactive oxygen species(ROS) and various peroxides, namely lipid peroxidation, plays an important role in the progression of diabetic nephropathy (DN).We previously reported that vitamin D receptor(VDR) plays an active role in DN mice by modulating autophagy disorders. However, it is unclear whether the ATP-citrate lyase (ACLY)/NF-E2-related factor-2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1) pathway is associated with the reduction of lipid peroxidation by VDR in the DN model. We found that in the DN mouse model, VDR knockout significantly aggravated mitochondrial morphological damage caused by DN, increased the expression of ACLY, promoted the accumulation of ROS, lipid peroxidation products Malondialdehyde(MDA) and 4-hydroxy-2-nonenal (4-HNE),consumed the Nrf2/Keap1 system, thus increasing lipid peroxidation. However, the overexpression of VDR and intervention with the VDR agonist paricalcitol (Pari) can reduce the above damage. On the other hand, cellular experiments have shown that Pari can significantly reduce the elevated expression of ACLY and ROS induced by advanced glycation end products (AGE). However, ACLY overexpression partially eliminated the positive effects of the VDR agonist. Next, we verified the transcriptional regulation of ACLY by VDR through chromatin immunoprecipitation (ChIP)-qPCR and dual luciferase experiments. Moreover, in AGE models, knockdown of ACLY decreased lipid peroxidation and ROS production, while intervention with Nrf2 inhibitor ML385 partially weakened the protective effect of ACLY downregulation. In summary, VDR negatively regulates the expression of ACLY through transcription, thereby affecting the state of Nrf2/Keap1 system and regulating lipid peroxidation, thereby inhibiting kidney injury induced by DN.

CILP2 promotes hypertrophic scar through Snail acetylation by interaction with ACLY

BACKGROUND & AIMS

Hypertrophic scar (HS) is a skin fibroproliferative disorder occurring after burns, surgeries or traumatic injuries, and it has caused a tremendous economic and medical burden. Its molecular mechanism is associated with the abnormal proliferation and transition of fibroblasts and excessive deposition of extracellular matrix. Cartilage intermediate layer protein 2 (CILP2), highly homologous to cartilage intermediate layer protein 1 (CILP1), is mainly secreted predominantly from chondrocytes in the middle/deeper layers of articular cartilage. Recent reports indicate that CILP2 is involved in the development of fibrotic diseases. We investigated the role of CILP2 in the progression of HS.

METHODS AND RESULTS

It was found in this study that CILP2 expression was significantly higher in HS than in normal skin, especially in myofibroblasts. In a clinical cohort, we discovered that CILP2 was more abundant in the serum of patients with HS, especially in the early stage of HS. In vitro studies indicated that knockdown of CILP2 suppressed proliferation, migration, myofibroblast activation and collagen synthesis of hypertrophic scar fibroblasts (HSFs). Further, we revealed that CILP2 interacts with ATP citrate lyase (ACLY), in which CILP2 stabilizes the expression of ACLY by reducing the ubiquitination of ACLY, therefore prompting Snail acetylation and avoiding reduced expression of Snail. In vivo studies indicated that knockdown of CILP2 or ACLY inhibitor, SB-204990, significantly alleviated HS formation.

CONCLUSION

CILP2 exerts a vital role in hypertrophic scar formation and might be a detectable biomarker reflecting the progression of hypertrophic scar and a therapeutic target for hypertrophic scar.

Obesity-related glomerulopathy: recent advances in inflammatory mechanisms and related treatments

Obesity-related glomerulopathy, which is an obesity-triggered kidney damage, has become a significant threat to human health. Several studies have recently highlighted the critical role of inflammation in obesity-related glomerulopathy development. Additionally, excess adipose tissue and adipocytes in patients with obesity produce various inflammatory factors that cause systemic low-grade inflammation with consequent damage to vascular endothelial cells, exacerbating glomerular injury. Therefore, we conducted a comprehensive review of obesity-related glomerulopathy and addressed the critical role of obesity-induced chronic inflammation in obesity-related glomerulopathy pathogenesis and progression, which leads to tubular damage and proteinuria, ultimately impairing renal function. The relationship between obesity and obesity-related glomerulopathy is facilitated by a network of various inflammation-associated cells (including macrophages, lymphocytes, and mast cells) and a series of inflammatory mediators (such as tumor necrosis factor α, interleukin 6, leptin, adiponectin, resistin, chemokines, adhesion molecules, and plasminogen activator inhibitor 1) and their inflammatory pathways. Furthermore, we discuss a recently discovered relationship between micronutrients and obesity-related glomerulopathy inflammation and the important role of micronutrients in the body's anti-inflammatory response. Therefore, assessing these inflammatory molecules and pathways will provide a strong theoretical basis for developing therapeutic strategies based on anti-inflammatory effects to prevent or delay the onset of kidney injury.

Downregulation of the kidney glucagon receptor, essential for renal function and systemic homeostasis, contributes to chronic kidney disease

The glucagon receptor (GCGR) in the kidney is expressed in nephron tubules. In humans and animal models with chronic kidney disease, renal GCGR expression is reduced. However, the role of kidney GCGR in normal renal function and in disease development has not been addressed. Here, we examined its role by analyzing mice with constitutive or conditional kidney-specific loss of the Gcgr. Adult renal Gcgr knockout mice exhibit metabolic dysregulation and a functional impairment of the kidneys. These mice exhibit hyperaminoacidemia associated with reduced kidney glucose output, oxidative stress, enhanced inflammasome activity, and excess lipid accumulation in the kidney. Upon a lipid challenge, they display maladaptive responses with acute hypertriglyceridemia and chronic proinflammatory and profibrotic activation. In aged mice, kidney Gcgr ablation elicits widespread renal deposition of collagen and fibronectin, indicative of fibrosis. Taken together, our findings demonstrate an essential role of the renal GCGR in normal kidney metabolic and homeostatic functions. Importantly, mice deficient for kidney Gcgr recapitulate some of the key pathophysiological features of chronic kidney disease.

Effect of alpha-lipoic acid and caffeine-loaded chitosan nanoparticles on obesity and its complications in liver and kidney in rats

The present work investigated the effect of α-lipoic acid (ALA) and caffeine-loaded chitosan nanoparticles (CAF-CS NPs) on obesity and its hepatic and renal complications in rats. Rats were divided into control, rat model of obesity induced by high fat diet (HFD), and obese rats treated with ALA and/or CAF-CS NPs. At the end of the experiment, the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) and the levels of urea, creatinine, interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) were determined in the sera of animals. In addition, malondialdehyde (MDA), nitric oxide (NO), and reduced glutathione (GSH) were measured in hepatic and renal tissues. Renal Na+, K+-ATPase was assessed. The histopathological changes were examined in the hepatic and renal tissues. Obese rats showed a significant increase in AST, ALT, ALP, urea, and creatinine. This was associated with a significant increase in IL-1β, TNF-α, MDA, and NO. A significant decrease in hepatic and renal GSH and renal Na+, K+-ATPase activity was recorded in obese rats. Obese rats also showed histopathological alterations in hepatic and renal tissues. Treatment with ALA and/or CAF-CS NPs reduced the weight of obese rats and ameliorated almost all the hepatic and renal biochemical and histopathological changes induced in obese rats. In conclusion, the present findings indicate that ALA and/or CAF-CS NPs offered an effective therapy against obesity induced by HFD and its hepatic and renal complications. The therapeutic effect of ALA and CAF-CS NPs could be mediated through their antioxidant and anti-inflammatory properties.

Modeling SILAC Data to Assess Protein Turnover in a Cellular Model of Diabetic Nephropathy

Protein turnover rate is finely regulated through intracellular mechanisms and signals that are still incompletely understood but that are essential for the correct function of cellular processes. Indeed, a dysfunctional proteostasis often impacts the cell's ability to remove unfolded, misfolded, degraded, non-functional, or damaged proteins. Thus, altered cellular mechanisms controlling protein turnover impinge on the pathophysiology of many diseases, making the study of protein synthesis and degradation rates an important step for a more comprehensive understanding of these pathologies. In this manuscript, we describe the application of a dynamic-SILAC approach to study the turnover rate and the abundance of proteins in a cellular model of diabetic nephropathy. We estimated protein half-lives and relative abundance for thousands of proteins, several of which are characterized by either an altered turnover rate or altered abundance between diabetic nephropathic subjects and diabetic controls. Many of these proteins were previously shown to be related to diabetic complications and represent therefore, possible biomarkers or therapeutic targets. Beside the aspects strictly related to the pathological condition, our data also represent a consistent compendium of protein half-lives in human fibroblasts and a rich source of important information related to basic cell biology.

Identification of potential target genes of breast cancer in response to Chidamide treatment

Chidamide, a new chemically structured HDACi-like drug, has been shown to inhibit breast cancer, but its specific mechanism has not been fully elucidated. In this paper, we selected ER-positive breast cancer MCF-7 cells and used RNA-seq technique to analyze the gene expression differences of Chidamide-treated breast cancer cells to identify the drug targets of Chidamide's anti-breast cancer effect and to lay the foundation for the development of new drugs for breast cancer treatment. The results showed that the MCF-7 CHID group expressed 320 up-regulated genes and 222 down-regulated genes compared to the control group; Gene Ontology functional enrichment analysis showed that most genes were enriched to biological processes. Subsequently, 10 hub genes for Chidamide treatment of breast cancer were identified based on high scores using CytoHubba, a plug-in for Cytoscape: TP53, JUN, CAD, ACLY, IL-6, peroxisome proliferator-activated receptor gamma, THBS1, CXCL8, IMPDH2, and YARS. Finally, a combination of the Gene Expression Profiling Interactive Analysis database and Kaplan Meier mapper to compare the expression and survival analysis of these 10 hub genes, TP53, ACLY, PPARG, and JUN were found to be potential candidate genes significantly associated with Chidamide for breast cancer treatment. Among them, TP53 may be a potential target gene for Chidamide to overcome multi-drug resistance in breast cancer. Therefore, we identified four genes central to the treatment of breast cancer with Chidamide by bioinformatics analysis, and clarified that TP53 may be a potential target gene for Chidamide to overcome multi-drug resistance in breast cancer. This study lays a solid experimental and theoretical foundation for the treatment of breast cancer at the molecular level with Chidamide and for the combination of Chidamide.

The role of lipid profile in the relationship between particulate matters and hyperuricemia: A prospective population study

CONTEXT

Recent studies in specific population subgroups (e.g., pregnant women) have suggested PM exposure increases the risk of hyperuricemia. However, no studies have examined this in the general population. Furthermore, the underlying mechanism through which PM impacts hyperuricemia risk is poorly understood.

OBJECTIVE

To assess the association between long-term exposure to PM and risk of hyperuricemia and whether this association is mediated by lipid profile.

METHODS

We included 5939 participants in Southwest China from the China Multi-Ethnic Cohort (baseline 2018-2019, follow-up 2020-2021). Long-term PM pollutants (PM₁, PM_2.5, PM₁₀) exposure for each individual was represented by the three-year average PM levels before the baseline survey. Hyperuricemia at follow-up was defined as the serum uric acid above 7.0 mg/dL in men and 6.0 mg/dL in women. Serum lipids were measured at baseline including total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG). The association of PM with hyperuricemia was accessed through logistic regression. The potential mediation effects of serum lipids were evaluated through causal mediation analyses.

RESULTS

A total of 837 participants were newly diagnosed with hyperuricemia. The odds ratios of hyperuricemia associated with an interquartile range (IQR) increase in PM₁, PM_2.5, and PM₁₀ (IQR: 21.10, 25.78, 30.43 μg m^-3) were 1.72 (95% CI: 1.23, 2.39), 2.68 (95% CI: 1.59, 4.49), and 1.81 (95% CI: 1.20, 2.72), respectively. The association between PM_2.5, PM₁, and PM₁₀ on hyperuricemia was mediated by HDL-C (10%) and LDL-C (3%).

CONCLUSION

Higher particulate matter exposure was associated with higher hyperuricemia incidence. The decline in HDL-C and rise in LDL-C partially mediated this association. These findings were conducive to scientific research about the underlying mechanism of PM on hyperuricemia.

ACLY and CKD: A Mendelian Randomization Analysis

Introduction

Adenosine triphosphate-citrate lyase (ACLY) inhibition is a therapeutic strategy under investigation for atherosclerotic cardiovascular disease, nonalcoholic steatohepatitis, and metabolic syndrome. Mouse models suggest that ACLY inhibition could reduce inflammation and kidney fibrosis. Genetic analysis of ACLY in chronic kidney disease (CKD) has not been performed.

Methods

We constructed a genetic instrument by selecting variants associated with ACLY expression in the expression quantitative trait loci genetics consortium (eQTLGen) from blood samples from 31,684 participants. In a 2-sample Mendelian randomization analysis, we evaluated the effect of genetically predicted ACLY expression on the risk of CKD, estimated glomerular filtration rate (eGFR), and albumin-to-creatinine ratio (ACR) using the CKD Genetics (CKDGen) consortium, UK Biobank, and the Finnish Genetics (FinnGen) consortium totaling 66,396 CKD cases and 958,517 controls.

Results

ACLY is constitutively expressed in all cell types including in whole blood. The genetic instrument included 13 variants and explained 1.5% of the variation in whole blood ACLY gene expression. A 34% reduction in ACLY expression score was associated with a 0.04 mmol/l reduced low-density lipoprotein (LDL) cholesterol (P = 3.4 × 10^-4) and a 9% reduced risk of CKD (stages 3, 4, 5, dialysis, or eGFR < 60 ml/min per 1.73 m²) (odds ratio [OR] = 0.91, 95% CI: 0.85-0.98, P = 0.008), but no association was observed with either eGFR or ACR.

Conclusion

Mendelian randomization analyses revealed that genetically reduced ACLY expression was associated with reduced risk of CKD but had no effect on either eGFR or ACR. Further evaluation of ACLY in kidney disease is warranted.

Obesity-related glomerulopathy: Current approaches and future perspectives

Obesity-related glomerulopathy (ORG) is a silent comorbidity which is increasing in incidence as the obesity epidemic escalates. ORG is associated with serious health consequences including chronic kidney disease, end-stage renal disease (ESRD), and increased mortality. Although the pathogenic mechanisms involved in the development of ORG are not fully understood, glomerular hemodynamic changes, renin-angiotensin-aldosterone system (RAAS) overactivation, insulin-resistance, inflammation and ectopic lipid accumulation seem to play a major role. Despite albuminuria being commonly used for the non-invasive evaluation of ORG, promising biomarkers of early kidney injury that are emerging, as well as new approaches with proteomics and metabolomics, might permit an earlier diagnosis of this disease. In addition, the assessment of ectopic kidney fat by renal imaging could be a useful tool to detect and evaluate the progression of ORG. Weight loss interventions appear to be effective in ORG, although large-scale trials are needed. RAAS blockade has a renoprotective effect in patients with ORG, but even so, a significant proportion of patients with ORG will eventually progress to ESRD despite therapeutic efforts. It is noteworthy that certain antidiabetic agents such as sodium-glucose cotransporter 2 inhibitors (SGLT2i) or glucagon-like peptide-1 receptor agonists (GLP-1 RAs) could be useful in the treatment of ORG through different pleiotropic effects. In this article, we review current approaches and future perspectives in the care and treatment of ORG.

ATP-citrate lyase inhibitor improves ectopic lipid accumulation in the kidney in a db/db mouse model

AIM

We evaluated a novel treatment for obesity-related renal, an ATP-citrate lyase (ACL) inhibitor, to attenuate ectopic lipid accumulation (ELA) in the kidney and the ensuing inflammation.

MATERIALS AND METHODS

An ACL inhibitor was administered intragastrically to 12-week-old db/db mice for 30 days. The appearance of ELA was observed by staining kidney sections with Oil Red O, and the differences in tissue lipid metabolites were assessed by mass spectrometry. The anti-obesity and renoprotection effects of ACL inhibitors were observed by histological examination and multiple biochemical assays.

RESULTS

Using the AutoDock Vina application, we determined that among the four known ACL inhibitors (SB-204990, ETC-1002, NDI-091143, and BMS-303141), BMS-303141 had the highest affinity for ACL and reduced ACL expression in the kidneys of db/db mice. We reported that BMS-303141 administration could decrease the levels of serum lipid and renal lipogenic enzymes acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), HMG-CoA reductase (HMGCR), and diminish renal ELA in db/db mice. In addition, we found that reducing ELA improved renal injuries, inflammation, and tubulointerstitial fibrosis.

CONCLUSION

ACL inhibitor BMS-303141 protects against obesity-related renal injuries.

Involvement of Tricarboxylic Acid Cycle Metabolites in Kidney Diseases

Mitochondria are complex organelles that orchestrate several functions in the cell. The primary function recognized is energy production; however, other functions involve the communication with the rest of the cell through reactive oxygen species (ROS), calcium influx, mitochondrial DNA (mtDNA), adenosine triphosphate (ATP) levels, cytochrome c release, and also through tricarboxylic acid (TCA) metabolites. Kidney function highly depends on mitochondria; hence mitochondrial dysfunction is associated with kidney diseases. In addition to oxidative phosphorylation impairment, other mitochondrial abnormalities have been described in kidney diseases, such as induction of mitophagy, intrinsic pathway of apoptosis, and releasing molecules to communicate to the rest of the cell. The TCA cycle is a metabolic pathway whose primary function is to generate electrons to feed the electron transport system (ETS) to drives energy production. However, TCA cycle metabolites can also release from mitochondria or produced in the cytosol to exert different functions and modify cell behavior. Here we review the involvement of some of the functions of TCA metabolites in kidney diseases.

Mitochondria: A critical hub for hepatic stellate cells activation during chronic liver diseases

BACKGROUND

Upon liver injury, quiescent hepatic stellate cells (qHSCs), reside in the perisinusoidal space, phenotypically transdifferentiate into myofibroblast-like cells (MFBs). The qHSCs in the normal liver are less fibrogenic, migratory, and also have less proliferative potential. However, activated HSCs (aHSCs) are more fibrogenic and have a high migratory and proliferative MFBs phenotype. HSCs activation is a highly energetic process that needs abundant intracellular energy in the form of adenosine triphosphate (ATP) for the synthesis of extracellular matrix (ECM) in the injured liver to substantiate the injury.

DATA SOURCES

The articles were collected through PubMed and EMBASE using search terms "mitochondria and hepatic stellate cells", "mitochondria and HSCs", "mitochondria and hepatic fibrosis", "mitochondria and liver diseases", and "mitochondria and chronic liver disease", and relevant publications published before September 31, 2020 were included in this review.

RESULTS

Mitochondria homeostasis is affected during HSCs activation. Mitochondria in aHSCs are highly energetic and are in a high metabolically active state exhibiting increased activity such as glycolysis and respiration. aHSCs have high glycolytic enzymes expression and glycolytic activity induced by Hedgehog (Hh) signaling from injured hepatocytes. Increased glycolysis and aerobic glycolysis (Warburg effect) end-products in aHSCs consequently activate the ECM-related gene expressions. Increased Hh signaling from injured hepatocytes downregulates peroxisome proliferator-activated receptor-γ expression and decreases lipogenesis in aHSCs. Glutaminolysis and tricarboxylic acid cycle liberate ATPs that fuel HSCs to proliferate and produce ECM during their activation.

CONCLUSIONS

Available studies suggest that mitochondria functions can increase in parallel with HSCs activation. Therefore, mitochondrial modulators should be tested in an elaborate manner to control or prevent the HSCs activation during liver injury to subsequently regress hepatic fibrosis.

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.

Curcumin analogue C66 attenuates obesity-induced renal injury by inhibiting chronic inflammation

Obesity has been recognized as a major risk factor for the development of chronic kidney disease, which is accompanied by increased renal inflammation, fibrosis, and apoptosis. C66 is a curcumin derivative that exerts anti-inflammatory effects by inhibiting the JNK pathway and prevents diabetic nephropathy. The present study investigates the possible protective effect of C66 on high-fat diet (HFD)-induced obesity-related glomerulopathy. Mice were fed with HFD for 8 weeks while some were treated with C66 every 2 days for 11 weeks. The HFD-fed mice developed renal dysfunction, as well as elevated triglyceride and cholesterol. Kidneys of the HFD-fed mice showed marked glomerular injuries, apoptosis, and inflammation with markedly increased cytokine production. Interestingly, treating HFD-fed mice with C66 remarkably reversed these pathological changes via inhibiting inflammation and NF-κB/JNK activation. In cultured mesangial cells, Palmitic Acid was able to activate the pro-fibrotic mechanisms, apoptosis, inflammatory response, and NF-κB and JNK signaling pathways, all of which could be attenuated by C66 treatment. In all, we demonstrated that curcumin analogue C66 attenuates obesity-induced renal injury by inhibiting chronic inflammation and apoptosis via targeting NF-κB and JNK. Our data suggest that C66 can be potentially used to prevent obesity-associated renal diseases warranting future investigations.

THBS1/CD47 Modulates the Interaction of γ-Catenin With E-Cadherin and Participates in Epithelial-Mesenchymal Transformation in Lipid Nephrotoxicity

Hyperlipidemia, an important risk factor for cardiovascular and end-stage renal diseases, often aggravates renal injury and compromises kidney function. Here, histological analysis of human kidney samples revealed that high lipid levels induced the development of renal fibrosis. To elucidate the mechanism underlying lipid nephrotoxicity, we used two types of mouse models (Apoe^−/− and C57BL/6 mice fed a 45 and 60% high-fat diet, respectively). Histological analysis of kidney tissues revealed high-lipid-induced renal fibrosis and inflammation; this was confirmed by examining fibrotic and inflammatory marker expression using Western blotting and real-time polymerase chain reaction. Oxidized low-density lipoprotein (OX-LDL) significantly induced the fibrotic response in HK-2 tubular epithelial cells. RNA-sequencing and Gene Ontology analysis of differentially expressed mRNAs in OX-LDL-treated HK-2 tubular epithelial cells and real-time PCR validation in Apoe^−/− mice showed that the expression of thrombospondin-1 (THBS1) in the high-fat group was significantly higher than that of the other top known genes, along with significant overexpression of its receptor CD47. THBS1 knockdown cells verified its relation to OX-LDL-induced fibrosis and inflammation. Liquid chromatography tandem mass spectrometry and STRING functional protein association network analyses predicted that THBS1/CD47 modulated the interaction between γ-catenin and E-cadherin and was involved in epithelial–mesenchymal transition, which was supported by immunoprecipitation and immunohistochemistry. CD47 downregulation following transfection with small-hairpin RNA in OX-LDL-treated tubular epithelial cells and treatment with anti-CD47 antibody restored the expression of E-cadherin and attenuated renal injury, fibrosis, and inflammatory response in OX-LDL-treated cells and in type 2 diabetes mellitus. These findings indicate that CD47 may serve as a potential therapeutic target in long-term lipid-induced kidney injury.

High-fat diet promotes renal injury by inducing oxidative stress and mitochondrial dysfunction

Obesity has been recognized as a major risk factor for chronic kidney disease, but the underlying mechanism remains elusive. Here, we investigated the mechanism whereby long-term high-fat diet (HFD) feeding induces renal injury in mice. The C57BL/6 mice fed HFD for 16 weeks developed obesity, diabetes, and kidney dysfunction manifested by albuminuria and blood accumulation of BUN and creatinine. The HFD-fed kidney showed marked glomerular and tubular injuries, including prominent defects in the glomerular filtration barrier and increased tubular cell apoptosis. Mechanistically, HFD feeding markedly increased triglyceride and cholesterol contents in the kidney and activated lipogenic pathways for cholesterol and triglyceride synthesis. HFD feeding also increased oxidative stress and induced mitochondrial fission in tubular cells, thereby activating the pro-apoptotic pathway. In HK-2 and mesangial cell cultures, high glucose, fatty acid, and TNF-α combination was able to activate the lipogenic pathways, increase oxidative stress, promote mitochondrial fission, and activate the pro-apoptotic pathway, all of which could be attenuated by an inhibitor that depleted reactive oxygen species. Taken together, these observations suggest that long-term HFD feeding causes kidney injury at least in part as a result of tissue lipid accumulation, increased oxidative stress, and mitochondrial dysfunction, which promote excess programmed cell death.

The Drosophila Citrate Lyase Is Required for Cell Division during Spermatogenesis

The Drosophila melanogasterDmATPCL gene encodes for the human ATP Citrate Lyase (ACL) ortholog, a metabolic enzyme that from citrate generates glucose-derived Acetyl-CoA, which fuels central biochemical reactions such as the synthesis of fatty acids, cholesterol and acetylcholine, and the acetylation of proteins and histones. We had previously reported that, although loss of Drosophila ATPCL reduced levels of Acetyl-CoA, unlike its human counterpart, it does not affect global histone acetylation and gene expression, suggesting that its role in histone acetylation is either partially redundant in Drosophila or compensated by alternative pathways. Here, we describe that depletion of DmATPCL affects spindle organization, cytokinesis, and fusome assembly during male meiosis, revealing an unanticipated role for DmATPCL during spermatogenesis. We also show that DmATPCL mutant meiotic phenotype is in part caused by a reduction of fatty acids, but not of triglycerides or cholesterol, indicating that DmATPCL-derived Acetyl-CoA is predominantly devoted to the biosynthesis of fatty acids during spermatogenesis. Collectively, our results unveil for the first time an involvement for DmATPCL in the regulation of meiotic cell division, which is likely conserved in human cells.

High-fat diet promotes experimental colitis by inducing oxidative stress in the colon

Diets high in animal fats are associated with increased risks of inflammatory bowel disease, but the mechanism remains unclear. In this study, we investigated the effect of high-fat diet (HFD) on the development of experimental colitis in mice. Relative to mice fed low-fat diet (LFD), HFD feeding for 4 wk increased the levels of triglyceride, cholesterol, and free fatty acids in the plasma as well as within the colonic mucosa. In an experimental colitis model induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS), mice on 4-wk HFD exhibited more severe colonic inflammation and developed more severe colitis compared with the LFD counterparts. HFD feeding resulted in higher production of mucosal pro-inflammatory cytokines, greater activation of the myosin light chain kinase (MLCK) tight junction regulatory pathway, and greater increases in mucosal barrier permeability in mice following TNBS induction. HFD feeding also induced gp91, an NADPH oxidase subunit, and promoted reactive oxygen species (ROS) production in both colonic epithelial cells and lamina propria cells. In HCT116 cell culture, palmitic acid or palmitic acid and TNF-α combination markedly increased ROS production and induced the MLCK pathway, and these effects were markedly diminished in the presence of a ROS scavenger. Taken together, these data suggest that HFD promotes colitis by aggravating mucosal oxidative stress, which rapidly drives mucosal inflammation and increases intestinal mucosal barrier permeability.NEW & NOTEWORTHY This study demonstrates high-fat diet feeding promotes colitis in a 2,4,6-trinitrobenzenesulfonic acid-induced experimental colitis model in mice. The underlying mechanism is that high-fat diet induces oxidative stress in the colonic mucosa, which increases colonic epithelial barrier permeability and drives colonic mucosal inflammation. These observations provide molecular evidence that diets high in saturated fats are detrimental to patients with inflammatory bowel diseases.