Fatty Acid β-Oxidation in Kidney Diseases: Perspectives on Pathophysiological Mechanisms and Therapeutic Opportunities

Fluxomics combined with shotgun proteomics reveals a differential response of bovine kidney cells to extracellular palmitic and α-linolenic acid

Pyruvate carboxylase (PC) catalyzes the formation of oxaloacetate, a TCA cycle intermediate and gluconeogenic substrate. Altering saturated to unsaturated fatty acid ratio alters PC expression, suggesting a central role in mediating carbon flow through metabolic pathways. Herein, we describe changes in metabolic flux of TCA cycle intermediates and proteome in Madin-Darby bovine kidney (MDBK) cells with PC expression knocked-down (PC-KD), overexpressed (PC-OE), unaltered using a Scramble control, or cells pretreated for 21 h with vehicle control bovine serum albumin (BSA) or different ratios of palmitic acid (P) and α-linolenic acid (L) ranging from 1 mM P:0 mM L (1P:0L) to 0P:1L. All cells were collected for proteome analysis and to measure [U-13C] pyruvate flux or oxidation of [1-14C] palmitic acid and [U-14C] lactate. Compared with Scramble, 13C enrichment of all TCA cycle intermediates was greater in PC-OE, but all were reduced in PC-KD except succinate. Proteins greater in abundance in both cell lines included solute transporters, propionyl CoA carboxylase, and fatty acid binding protein 3. Relative to BSA, 1P:0L increased cell death and increased 13C flux to citrate but decreased enrichment of succinate. Abundance of citrate synthase, aconitase, glutamine aminotransferases, and succinyl CoA synthetases was greater in 1P:0L, but not different in other pretreatments. Results indicate preferential utilization of pyruvate and amino acids by 1P:0L cells whereas 0P:1L treated cells show preference for α-linolenic acid metabolism. PC regulates metabolic flux, C18:3n - 3 cis prevents lipotoxicity, and both alterations in PC and the addition of C18:3n - 3 cis promote oxidation of fatty acids.NEW & NOTEWORTHY PC overexpression increases the capacity for fatty acid oxidation, whereas PC knockdown requires extracellular amino acids to support TCA cycle intermediates. Cells incubated in palmitic acid demonstrated dependency of pyruvate and amino acids as substrates for the TCA cycle. Exposure to α-linolenic acid reduces the dependency of pyruvate as a substrate likely because carbon from α-linolenic acid can be used to supply TCA cycle intermediates whereas palmitic acid carbon is not used.

Modulation of the thiol redox proteome by sugarcane ash-derived silica nanoparticles: insights into chronic kidney disease of unknown etiology

INTRODUCTION

Chronic kidney disease of unknown etiology (CKDu) is an epidemic which is increasingly prevalent among agricultural workers and nearby communities, particularly those involved in the harvest of sugarcane. While CKDu is likely multifactorial, occupational exposure to silica nanoparticles (SiNPs), a major constituent within sugarcane ash, has gained increased attention as a potential contributor. SiNPs have high potential for generation of reactive oxygen species (ROS), and their accumulation in kidney could result in oxidative stress induced kidney damage consistent with CKDu pathology.

METHODS

In order to characterize the impact of sugarcane ash derived (SAD) SiNPs on human kidney proximal convoluted tubule (PCT) cells and identify potential mechanisms of toxicity, HK-2 cells were exposed to treatments of either pristine, manufactured, 200 nm SiNPs or SAD SiNPs and changes to cellular energy metabolism and redox state were determined. To determine how the cellular redox environment may influence PCT cell function and toxicity, the redox proteome was examined using cysteine-targeted click chemistry proteomics.

RESULTS

Pristine, 200 nm SiNPs induced minimal changes to energy metabolism and proteomic profiles in vitro while treatment with SAD SiNPs resulted in mitochondrial membrane hyperpolarization, inhibited mitochondrial respiration, increased reactive oxygen species generation, and redox proteomic trends suggesting activation of aryl hydrocarbon receptor (AHR) and other signaling pathways with known roles in mitochondrial inhibition and CKD progression.

CONCLUSION

Results suggest that PCT cell exposure to SAD SiNPs could promote glycolytic and fibrotic shifts consistent with CKDu pathology via oxidative stress-mediated disruption of redox signaling pathways.

ACOT12, a novel factor in the pathogenesis of kidney fibrosis, modulates ACBD5

Lipid metabolism, particularly fatty acid oxidation dysfunction, is a major driver of renal fibrosis. However, the detailed regulatory mechanisms underlying this process remain unclear. Here we demonstrated that acyl-CoA thioesterase 12 (Acot12), an enzyme involved in the hydrolysis of acyl-CoA thioesters into free fatty acids and CoA, is a key regulator of lipid metabolism in fibrotic kidneys. A significantly decreased level of ACOT12 was observed in kidney samples from human patients with chronic kidney disease as well as in samples from mice with kidney injuries. Acot12 deficiency induces lipid accumulation and fibrosis in mice subjected to unilateral ureteral obstruction (UUO). Fenofibrate administration does not reduce renal fibrosis in Acot12-/- mice with UUO. Moreover, the restoration of peroxisome proliferator-activated receptor α (PPARα) in Acot12-/-Pparα-/- kidneys with UUO exacerbated lipid accumulation and renal fibrosis, whereas the restoration of Acot12 in Acot12-/- Pparα-/- kidneys with UUO significantly reduced lipid accumulation and renal fibrosis, suggesting that, mechanistically, Acot12 deficiency exacerbates renal fibrosis independently of PPARα. In Acot12-/- kidneys with UUO, a reduction in the selective autophagic degradation of peroxisomes and pexophagy with a decreased level of ACBD5 was observed. In conclusion, our study demonstrates the functional role and mechanistic details of Acot12 in the progression of renal fibrosis, provides a preclinical rationale for regulating Acot12 expression and presents a novel means of preventing renal fibrosis.

Sirtuins in kidney homeostasis and disease: where are we now?

Sirtuins, identified as (NAD+)- dependent class III histone deacetylases, engage in a spectrum of biological functions, encompassing DNA damage repair, oxidative stress, immune modulation, mitochondrial homeostasis, apoptosis and autophagy. Sirtuins play an apoptosis role in regulating cellular operations and overall organism health. Mounting data indicate that dysregulated sirtuin expression is linked to the onset of renal diseases. Effective modulation of sirtuins expression and activity has been shown to improve renal function and attenuate the advancement of kidney diseases. In this review, we present a comprehensive overview of the biological impacts of sirtuins and their molecular targets in regulating renal diseases. Additionally, we detail advancements in elucidating sirtuin roles in the pathophysiology of both chronic and acute renal disorders. We review compounds that modulate sirtuin activity through activation or inhibition, potentially improving outcomes in renal disease. In summary, strategic manipulation of sirtuin activity represents a prospective therapeutic approach for renal diseases.

Unveiling the intricacies of chronic kidney disease: From ocular manifestations to therapeutic frontiers

BACKGROUND

Shared anatomical, histological and physiological pathways between the kidney and the eye are well documented, demonstrating that ocular manifestations serve as valuable prognostic indicators in chronic kidney disease (CKD), providing insights into disease severity and progression. Through non-invasive imaging modalities such as retinal fundus photography, early retinal microvascular alterations indicative of CKD progression can be detected, enabling timely intervention and risk stratification. However, the conclusions drawn from the review primarily demonstrate a strong or independent association between glaucoma or retinopathy and CKD.

RESULTS AND CONCLUSION

Multiple shared pathophysiological events have been implicated in the pathogenesis in the alterations at eye and kidney including renin-angiotensin-aldosterone system. Patients with CKD are more likely to experience glaucoma, age-related macular degeneration, cataracts, uremic optic neuropathy and retinopathy. To establish the role of ocular manifestations in predicting CKD progression, it is crucial to address the limitations of correlation and explore the underlying causality with further research on common disease pathogenesis. Additionally, specific methods for risk stratification based on retinal changes, the effectiveness of timely interventions, and the development of predictive tools combining ocular and renal data are of utmost importance research topics to enlighten the bidirectional causality.

Exploring the role and therapeutic potential of lipid metabolism in acute kidney injury

Acute kidney injury (AKI) is a prevalent condition, yet no specific treatment is available. Extensive research has revealed the pivotal role of lipid-related alterations in AKI. Lipid metabolism plays an essential role in the sustenance of the kidneys. In addition to their energy-supplying function, lipids contribute to the formation of renal biomembranes and the establishment of the renal microenvironment. Moreover, lipids or their metabolites actively participate in signal transduction, which governs various vital biological processes, such as proliferation, differentiation, apoptosis, autophagy, and epithelial-mesenchymal transition. While previous studies have focused predominantly on abnormalities in lipid metabolism in chronic kidney disease, this review focuses on lipid metabolism anomalies in AKI. We explore the significance of lipid metabolism products as potential biomarkers for the early diagnosis and classification of AKI. Additionally, this review assesses current preclinical investigations on the modulation of lipid metabolism in the progression of AKI. Finally, on the basis of existing research, this review proposes future directions, highlights challenges, and presents novel targets and innovative ideas for the treatment of and intervention in AKI.

The role of inflammatory response and metabolic reprogramming in sepsis-associated acute kidney injury: mechanistic insights and therapeutic potential

Sepsis represents a severe condition characterized by organ dysfunction resulting from a dysregulated host response to infection. Among the organs affected, the kidneys are particularly vulnerable, with significant functional impairment that markedly elevates mortality rates. Previous researches have highlighted that both inflammatory response dysregulation and metabolic reprogramming are crucial in the onset and progression of sepsis associated acute kidney injury (SA-AKI), making these processes potential targets for innovative therapies. This study aims to elucidate the pathophysiological mechanisms of renal injury in sepsis by perspective of inflammatory response dysregulation, with particular emphasis on pyroptosis, necroptosis, autophagy, and ferroptosis. Furthermore, it will incorporate insights into metabolic reprogramming to provide a detailed analysis of the mechanisms driving SA-AKI and explore potential targeted therapeutic strategies, providing solid theoretical framework for the development of targeted therapies for SA-AKI.

Renoprotective effects of empagliflozin in high-fat diet-induced obesity-related glomerulopathy by regulation of gut-kidney axis

The increasing prevalence of obesity-related glomerulopathy (ORG) poses a significant threat to public health. Sodium-glucose cotransporter-2 (SGLT2) inhibitors effectively reduce body weight and total fat mass in individuals with obesity and halt the progression of ORG. However, the underlying mechanisms of their reno-protective effects in ORG remain unclear. We established a high-fat diet-induced ORG model using C57BL/6J mice, which were divided into three groups: normal chow diet (NCD group), high-fat diet (HFD) mice treated with placebo (ORG group), and HFD mice treated with empagliflozin (EMPA group). We conducted 16S ribosomal RNA gene sequencing of feces and analyzed metabolites from kidney, feces, liver, and serum samples. ORG mice showed increased urinary albumin creatinine ratio, cholesterol, triglyceride levels, and glomerular diameter compared with NCD mice (all P < 0.05). EMPA treatment significantly alleviated these parameters (all P < 0.05). Multitissue metabolomics analysis revealed lipid metabolic reprogramming in ORG mice, which was significantly altered by EMPA treatment. MetOrigin analysis showed a close association between EMPA-related lipid metabolic pathways and gut microbiota alterations, characterized by reduced abundances of Firmicutes and Desulfovibrio and increased abundance of Akkermansia (all P < 0.05). The metabolic homeostasis of ORG mice, especially in lipid metabolism, was disrupted and closely associated with gut microbiota alterations, contributing to the progression of ORG. EMPA treatment improved kidney function and morphology by regulating lipid metabolism through the gut-kidney axis, highlighting a novel therapeutic approach for ORG. NEW & NOTEWORTHY Our study uncovered that empagliflozin (EMPA) potentially protects renal function and morphology in obesity-related glomerulopathy (ORG) mice by regulating the gut-kidney axis. EMPA's reno-protective effects in ORG mice are associated with the lipid metabolism, especially in glycerophospholipid metabolism and the pantothenate/CoA synthesis pathways. EMPA's modulation of gut microbiota appears to be pivotal in suppressing glycerol 3-phosphate and CoA synthesis. The insights into gut microbiota-host metabolic interactions offer a novel therapeutic approach for ORG.

Endogenous activation of peroxisome proliferator-activated receptor-α in proximal tubule cells in counteracting phosphate toxicity

Increased dietary phosphate consumption intensifies renal phosphate burden. Several mechanisms for phosphate-induced renal tubulointerstitial fibrosis have been reported. Considering the dual nature of phosphate as both a potential renal toxin and an essential nutrient for the body, kidneys may possess inherent protective mechanisms against phosphate overload, rather than succumbing solely to injury. However, there is limited understanding of such mechanisms. To identify these mechanisms, we conducted single-cell RNA sequencing (scRNA-seq) analysis of the kidneys of control and dietary phosphate-loaded (Phos) mice at a time point when the Phos group had not yet developed tubulointerstitial fibrosis. scRNA-seq analysis identified the highest number of differentially expressed genes in the clusters belonging to proximal tubular epithelial cells (PTECs). Based on these differentially expressed genes, in silico analyses suggested that the Phos group activated peroxisome proliferator-activated receptor-α (PPAR-α) and fatty acid β-oxidation (FAO) in the PTECs. This activation was further substantiated through various experiments, including the use of an FAO activity visualization probe. Compared with wild-type mice, Ppara knockout mice exhibited exacerbated tubulointerstitial fibrosis in response to phosphate overload. Experiments conducted with cultured PTECs demonstrated that activation of the PPAR-α/FAO pathway leads to improved cellular viability under high-phosphate conditions. The Phos group mice showed a decreased serum concentration of free fatty acids, which are endogenous PPAR-α agonists. Instead, experiments using cultured PTECs revealed that phosphate directly activates the PPAR-α/FAO pathway. These findings indicate that noncanonical metabolic reprogramming via endogenous activation of the PPAR-α/FAO pathway in PTECs is essential to counteract phosphate toxicity.NEW & NOTEWORTHY This study revealed the activation of peroxisome proliferator-activated receptor-α and fatty acid β-oxidation in proximal tubular epithelial cells as an endogenous mechanism to protect the kidney from phosphate toxicity. These findings highlight noncanonical metabolic reprogramming as a potential target for suppressing phosphate toxicity in the kidneys.

CPT1A Protects Podocytes From Lipotoxicity and Apoptosis In Vitro and Alleviates Diabetic Nephropathy In Vivo

Defective fatty acid oxidation (FAO) has been implicated in diabetic kidney disease (DKD), yet little is known about the role of carnitine palmitoyltransferase-1A (CPT1A), a pivotal rate-limiting enzyme of FAO, in the progression of DKD. Here, we investigate whether CPT1A is a reliable therapeutic target for DKD. We first confirmed the downregulation expression of CPT1A in glomeruli from patients with diabetes. We further evaluated the function of CPT1A in diabetic models. Overexpression of CPT1A exhibited protective effects in diabetic conditions, improving albuminuria and glomerular sclerosis as well as mitigating glomerular lipid deposits and podocyte injury in streptozotocin-induced diabetic mice. Mechanistically, CPT1A not only fostered lipid consumption via fatty acid metabolism pathways, thereby reducing lipotoxicity, but also anchored Bcl2 to the mitochondrial membrane, thence preventing cytochrome C release and inhibiting the mitochondrial apoptotic process. Furthermore, a novel transcription factor of CPT1A, FOXA1, was identified. We elucidate the crucial role of CPT1A in mitigating podocyte injury and the progression of DKD, indicating that targeting CPT1A may be a promising avenue for DKD treatment.

ARTICLE HIGHLIGHTS

Exposome and Metabolome Analysis of Sugarcane Workers Reveals Predictors of Kidney Injury

Introduction

Sugarcane workers are exposed to potentially hazardous agrochemicals, including pesticides, heavy metals, and silica. Such occupational exposures present health risks and have been implicated in a high rate of kidney disease seen in these workers.

Methods

To investigate potential biomarkers and mechanisms that could explain chronic kidney disease (CKD) among this worker population, paired urine samples were collected from sugarcane cutters at the beginning and end of a harvest season in Guatemala. Workers were then separated into 2 groups, namely those with or without kidney function decline (KFD) across the harvest season. Urine samples from these 2 groups underwent elemental analysis and untargeted metabolomics.

Results

Urine profiles demonstrated increases in silicon, certain pesticides, and phosphorus levels in all workers, whereas heavy metals remained low. The KFD group had a reduction in estimated glomerular filtration rate (eGFR) across the harvest season; however, kidney injury marker 1 did not significantly change. Cross-harvest metabolomic analysis found trends of fatty acid accumulation, perturbed amino acid metabolism, presence of pesticides, and other known signs of impaired kidney function.

Conclusion

Silica and certain pesticides were significantly elevated in the urine of sugarcane workers with or without KFD. Future work should determine whether long-term occupational exposure to silica and pesticides across multiple seasons contributes to CKD in these workers. Overall, these results confirmed that multiple exposures are occurring in sugarcane workers and may provide insight into early warning signs of kidney injury and may help explain the increased incidence of CKD among agricultural workers.

Comprehensive Analysis of Fatty Acid Metabolism in Diabetic Nephropathy from the Perspective of Immune Landscapes, Diagnosis and Precise Therapy

Objective

Diabetic nephropathy (DN) represents the principal cause of end-stage renal diseases worldwide, lacking effective therapies. Fatty acid (FA) serves as the primary energy source in the kidney and its dysregulation is frequently observed in DN. Nevertheless, the roles of FA metabolism in the occurrence and progression of DN have not been fully elucidated.

Methods

Three DN datasets (GSE96804/GSE30528/GSE104948) were obtained and combined. Differentially expressed FA metabolism-related genes were identified and subjected to DN classification using "ConsensusClusterPlus". DN subtypes-associated modules were discovered by "WGCNA", and module genes underwent functional enrichment analysis. The immune landscapes and potential drugs were analyzed using "CIBERSORT" and "CMAP", respectively. Candidate diagnostic biomarkers of DN were screened using machine learning algorithms. A prediction model was constructed, and the performance was assessed using receiver operating characteristic (ROC) curves, calibration curves, and decision curve analysis (DCA). The online tool "Nephroseq v5" was conducted to reveal the clinical significance of the candidate diagnostic biomarkers in patients with DN. A DN mouse model was established to verify the biomarkers' expression.

Results

According to 39 dysregulated FA metabolism-related genes, DN samples were divided into two molecular subtypes. Patients in Cluster B exhibited worse outcomes with a different immune landscape compared with those in Cluster A. Ten potential small-molecular drugs were predicted to treat DN in Cluster B. The diagnostic model based on PRKAR2B/ANXA1 was created with ideal predictive values in early and advanced stages of DN. The correlation analysis revealed significant association between PRKAR2B/ANXA1 and clinical characteristics. The DN mouse model validated the expression patterns of PRKAR2B/ANXA1.

Conclusion

Our study provides new insights into the role of FA metabolism in the classification, immunological pathogenesis, early diagnosis, and precise therapy of DN.

Advances in metabolic reprogramming of renal tubular epithelial cells in sepsis-associated acute kidney injury

Sepsis-associated acute kidney injury presents as a critical condition characterized by prolonged hospital stays, elevated mortality rates, and an increased likelihood of transition to chronic kidney disease. Sepsis-associated acute kidney injury suppresses fatty acid oxidation and oxidative phosphorylation in the mitochondria of renal tubular epithelial cells, thus favoring a metabolic shift towards glycolysis for energy production. This shift acts as a protective mechanism for the kidneys. However, an extended reliance on glycolysis may contribute to tubular atrophy, fibrosis, and subsequent chronic kidney disease progression. Metabolic reprogramming interventions have emerged as prospective strategies to counteract sepsis-associated acute kidney injury by restoring normal metabolic function, offering potential therapeutic and preventive modalities. This review delves into the metabolic alterations of tubular epithelial cells associated with sepsis-associated acute kidney injury, stressing the importance of metabolic reprogramming for the immune response and the urgency of metabolic normalization. We present various intervention targets that could facilitate the recovery of oxidative phosphorylation-centric metabolism. These novel insights and strategies aim to transform the clinical prevention and treatment landscape of sepsis-associated acute kidney injury, with a focus on metabolic mechanisms. This investigation could provide valuable insights for clinicians aiming to enhance patient outcomes in the context of sepsis-associated acute kidney injury.

The metabolic pathway regulation in kidney injury and repair

Kidney injury and repair are accompanied by significant disruptions in metabolic pathways, leading to renal cell dysfunction and further contributing to the progression of renal pathology. This review outlines the complex involvement of various energy production pathways in glucose, lipid, amino acid, and ketone body metabolism within the kidney. We provide a comprehensive summary of the aberrant regulation of these metabolic pathways in kidney injury and repair. After acute kidney injury (AKI), there is notable mitochondrial damage and oxygen/nutrient deprivation, leading to reduced activity in glycolysis and mitochondrial bioenergetics. Additionally, disruptions occur in the pentose phosphate pathway (PPP), amino acid metabolism, and the supply of ketone bodies. The subsequent kidney repair phase is characterized by a metabolic shift toward glycolysis, along with decreased fatty acid β-oxidation and continued disturbances in amino acid metabolism. Furthermore, the impact of metabolism dysfunction on renal cell injury, regeneration, and the development of renal fibrosis is analyzed. Finally, we discuss the potential therapeutic strategies by targeting renal metabolic regulation to ameliorate kidney injury and fibrosis and promote kidney repair.

Untargeted and spatial-resolved metabolomics characterize serum and tissue-specific metabolic reprogramming in acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is one of the most common clinical emergencies characterized by rapid progression, difficulty in early diagnosis, and high mortality. Currently, there are no effective AKI early diagnostic methods and treatments. Therefore, identifying new mechanisms of AKI have become urgent for development new targets for early diagnosis and treatment of AKI in the current clinical setting.

METHODS

In this study, systematic analysis and comparison of serum metabolic profiles of clinical AKI patients, chronic kidney disease (CKD) patients, and healthy subjects were performed using untargeted metabolomics. Moreover, the first spatial metabolomic analysis of kidney tissues in an AKI mouse model using MALDI-TOF MS technology was conducted. Differentially expressed metabolites were identified using a comprehensive, publicly available database. The metabolic data obtained were evaluated using principal component analysis, (orthogonal) partial least squares discriminant analysis, and metabolic pathway analysis to explore the unique serum metabolic profile of the patients, as well as to characterize the spatial distribution of differential metabolites in the kidneys of AKI mice.

RESULTS

Significant changes in the metabolite levels of amino acids, carnitine, and lipids were observed in the AKI and CKD groups versus the healthy population, suggesting that kidney injury may lead to abnormalities in various metabolic pathways, such as amino acids, fatty acids, and lipids. The significant difference between the AKI and CKD groups were found for the first time in these indexes including amino acid, carnitine, fatty acid, and lipid levels. Additionally, spatial metabolomics results revealed that amino acid, carnitine, organic acid, and fatty acid metabolites were more likely significantly altered in the renal cortex, while lipid metabolites were both differentially distributed in the cortex and medulla of the AKI group.

CONCLUSION

Abnormalities in the serum metabolism of amino acids, carnitine, and lipids in patients with kidney diseases, such as AKI and CKD, are closely associated with the physiological dysfunction of kidney injury. Metabolic differences between patients with AKI and CKD were compared for the first time, showing that fatty acid oxidative inhibition was more severe in patients with AKI. Furthermore, spatial metabolomics has revealed metabolic reprogramming with tissue heterogeneity in AKI mice model. Our study provides valuable information in the molecular pathological features of AKI in the kidney tissues.

Potential Benefits of Antioxidant Phytochemicals in Type 2 Diabetes

The clinical relationship between diabetes and inflammation is well established. Evidence clearly indicates that disrupting oxidant-antioxidant equilibrium and elevated lipid peroxidation could be a potential mechanism for chronic kidney disease associated with type 2 diabetes mellitus (T2DM). Under diabetic conditions, hyperglycemia, especially inflammation, and increased reactive oxygen species generation are bidirectionally associated. Inflammation, oxidative stress, and tissue damage are believed to play a role in the development of diabetes. Although the exact mechanism underlying oxidative stress and its impact on diabetes progression remains uncertain, the hyperglycemia-inflammation-oxidative stress interaction clearly plays a significant role in the onset and progression of vascular disease, kidney disease, hepatic injury, and pancreas damage and, therefore, holds promise as a therapeutic target. Evidence strongly indicates that the use of multiple antidiabetic medications fails to achieve the normal range for glycated hemoglobin targets, signifying treatment-resistant diabetes. Antioxidants with polyphenols are considered useful as adjuvant therapy for their potential anti-inflammatory effect and antioxidant activity. We aimed to analyze the current major points reported in preclinical, in vivo, and clinical studies of antioxidants in the prevention or treatment of inflammation in T2DM. Then, we will share our speculative vision for future diabetes clinical trials.

The Physiological and Pathological Role of Acyl-CoA Oxidation

Fatty acid metabolism, including β-oxidation (βOX), plays an important role in human physiology and pathology. βOX is an essential process in the energy metabolism of most human cells. Moreover, βOX is also the source of acetyl-CoA, the substrate for (a) ketone bodies synthesis, (b) cholesterol synthesis, (c) phase II detoxication, (d) protein acetylation, and (d) the synthesis of many other compounds, including N-acetylglutamate-an important regulator of urea synthesis. This review describes the current knowledge on the importance of the mitochondrial and peroxisomal βOX in various organs, including the liver, heart, kidney, lung, gastrointestinal tract, peripheral white blood cells, and other cells. In addition, the diseases associated with a disturbance of fatty acid oxidation (FAO) in the liver, heart, kidney, lung, alimentary tract, and other organs or cells are presented. Special attention was paid to abnormalities of FAO in cancer cells and the diseases caused by mutations in gene-encoding enzymes involved in FAO. Finally, issues related to α- and ω- fatty acid oxidation are discussed.

Metabolomics Point out the Effects of Carfilzomib on Aromatic Amino Acid Biosynthesis and Degradation

(1) Carfilzomib (Cfz) is an antineoplastic agent indicated for the treatment of multiple myeloma. However, its beneficial action is attenuated by the occurrence of cardiotoxicity and nephrotoxicity as the most common adverse effects. Presently, there is well-established knowledge on the pathomechanisms related to these side effects; however, the research on the metabolic alterations provoked by the drug is limited. (2) An in vivo simulation of Cfz-induced toxicity was developed in (i) Cfz-treated and (ii) control mice. An RP-HRMS-based protocol and an advanced statistical treatment were used to investigate the impact of Cfz on the non-polar metabolome. (3) The differential analysis classified the Cfz-treated and control mice and resulted in a significant number of identified biomarkers with AUC > 0.9. The drug impaired the biosynthesis and degradation of aromatic amino acids (AAA) and led to alterations of uremic toxins in the renal and urine levels. Furthermore, the renal degradation of tryptophan was affected, inducing its degradation via the kynurenine pathway. (4) The renal levels of metabolites showed impaired excretion and degradation of AAAs. Cfz was, finally, correlated with the biosynthesis of renal dopamine, explaining the biochemical causes of water and ion retention and the increase in systolic pressure.

Immunometabolism changes in fibrosis: from mechanisms to therapeutic strategies

Immune cells are essential for initiating and developing the fibrotic process by releasing cytokines and growth factors that activate fibroblasts and promote extracellular matrix deposition. Immunometabolism describes how metabolic alterations affect the function of immune cells and how inflammation and immune responses regulate systemic metabolism. The disturbed immune cell function and their interactions with other cells in the tissue microenvironment lead to the origin and advancement of fibrosis. Understanding the dysregulated metabolic alterations and interactions between fibroblasts and the immune cells is critical for providing new therapeutic targets for fibrosis. This review provides an overview of recent advances in the pathophysiology of fibrosis from the immunometabolism aspect, highlighting the altered metabolic pathways in critical immune cell populations and the impact of inflammation on fibroblast metabolism during the development of fibrosis. We also discuss how this knowledge could be leveraged to develop novel therapeutic strategies for treating fibrotic diseases.

Regulation of Autophagy via Carbohydrate and Lipid Metabolism in Cancer

Metabolic changes are an important component of tumor cell progression. Tumor cells adapt to environmental stresses via changes to carbohydrate and lipid metabolism. Autophagy, a physiological process in mammalian cells that digests damaged organelles and misfolded proteins via lysosomal degradation, is closely associated with metabolism in mammalian cells, acting as a meter of cellular ATP levels. In this review, we discuss the changes in glycolytic and lipid biosynthetic pathways in mammalian cells and their impact on carcinogenesis via the autophagy pathway. In addition, we discuss the impact of these metabolic pathways on autophagy in lung cancer.