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Cell Metabolism May 2021Tubulointerstitial abnormalities are predictive of the progression of diabetic kidney disease (DKD), and their targeting may be an effective means for prevention....
Tubulointerstitial abnormalities are predictive of the progression of diabetic kidney disease (DKD), and their targeting may be an effective means for prevention. Proximal tubular (PT) expression of kidney injury molecule (KIM)-1, as well as blood and urinary levels, are increased early in human diabetes and can predict the rate of disease progression. Here, we report that KIM-1 mediates PT uptake of palmitic acid (PA)-bound albumin, leading to enhanced tubule injury with DNA damage, PT cell-cycle arrest, interstitial inflammation and fibrosis, and secondary glomerulosclerosis. Such injury can be ameliorated by genetic ablation of the KIM-1 mucin domain in a high-fat-fed streptozotocin mouse model of DKD. We also identified TW-37 as a small molecule inhibitor of KIM-1-mediated PA-albumin uptake and showed in vivo in a kidney injury model in mice that it ameliorates renal inflammation and fibrosis. Together, our findings support KIM-1 as a new therapeutic target for DKD.
Topics: Animals; Benzamides; Cell Cycle Checkpoints; DNA Damage; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Endocytosis; Fatty Acids; Fibrosis; Hepatitis A Virus Cellular Receptor 1; Humans; Kidney Tubules, Proximal; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Palmitic Acid; RNA Interference; RNA, Small Interfering; Serum Albumin, Bovine; Sulfones
PubMed: 33951465
DOI: 10.1016/j.cmet.2021.04.004 -
Physiological Reviews Apr 2015Protein S-acylation, the only fully reversible posttranslational lipid modification of proteins, is emerging as a ubiquitous mechanism to control the properties and... (Review)
Review
Protein S-acylation, the only fully reversible posttranslational lipid modification of proteins, is emerging as a ubiquitous mechanism to control the properties and function of a diverse array of proteins and consequently physiological processes. S-acylation results from the enzymatic addition of long-chain lipids, most typically palmitate, onto intracellular cysteine residues of soluble and transmembrane proteins via a labile thioester linkage. Addition of lipid results in increases in protein hydrophobicity that can impact on protein structure, assembly, maturation, trafficking, and function. The recent explosion in global S-acylation (palmitoyl) proteomic profiling as a result of improved biochemical tools to assay S-acylation, in conjunction with the recent identification of enzymes that control protein S-acylation and de-acylation, has opened a new vista into the physiological function of S-acylation. This review introduces key features of S-acylation and tools to interrogate this process, and highlights the eclectic array of proteins regulated including membrane receptors, ion channels and transporters, enzymes and kinases, signaling adapters and chaperones, cell adhesion, and structural proteins. We highlight recent findings correlating disruption of S-acylation to pathophysiology and disease and discuss some of the major challenges and opportunities in this rapidly expanding field.
Topics: Acylation; Animals; Humans; Palmitic Acid; Protein Conformation; Protein Processing, Post-Translational; Proteins; Proteomics; Signal Transduction; Structure-Activity Relationship
PubMed: 25834228
DOI: 10.1152/physrev.00032.2014 -
Inflammation Research : Official... Nov 2019Palmitic acid is a saturated fatty acid whose blood concentration is elevated in obese patients. This causes inflammatory responses, where toll-like receptors (TLR),... (Review)
Review
Palmitic acid is a saturated fatty acid whose blood concentration is elevated in obese patients. This causes inflammatory responses, where toll-like receptors (TLR), TLR2 and TLR4, play an important role. Nevertheless, palmitic acid is not only a TLR agonist. In the cell, this fatty acid is converted into phospholipids, diacylglycerol and ceramides. They trigger the activation of various signaling pathways that are common for LPS-mediated TLR4 activation. In particular, metabolic products of palmitic acid affect the activation of various PKCs, ER stress and cause an increase in ROS generation. Thanks to this, palmitic acid also strengthens the TLR4-induced signaling. In this review, we discuss the mechanisms of inflammatory response induced by palmitic acid. In particular, we focus on describing its effect on ER stress and IRE1α, and the mechanisms of NF-κB activation. We also present the mechanisms of inflammasome NLRP3 activation and the effect of palmitic acid on enhanced inflammatory response by increasing the expression of FABP4/aP2. Finally, we focus on the consequences of inflammatory responses, in particular, the effect of TNF-α, IL-1β and IL-6 on insulin resistance. Due to the high importance of macrophages and the production of proinflammatory cytokines by them, this work mainly focuses on these cells.
Topics: Animals; Fatty Acid-Binding Proteins; Humans; Macrophages; Obesity; PPAR gamma; Palmitic Acid; Toll-Like Receptors
PubMed: 31363792
DOI: 10.1007/s00011-019-01273-5 -
Genomics, Proteomics & Bioinformatics Oct 2021Oleic acid (OA), a monounsaturated fatty acid (MUFA), has previously been shown to reverse saturated fatty acid palmitic acid (PA)-induced hepatic insulin resistance...
Oleic acid (OA), a monounsaturated fatty acid (MUFA), has previously been shown to reverse saturated fatty acid palmitic acid (PA)-induced hepatic insulin resistance (IR). However, its underlying molecular mechanism is unclear. In addition, previous studies have shown that eicosapentaenoic acid (EPA), a ω-3 polyunsaturated fatty acid (PUFA), reverses PA-induced muscle IR, but whether EPA plays the same role in hepatic IR and its possible mechanism involved need to be further clarified. Here, we confirmed that EPA reversed PA-induced IR in HepG2 cells and compared the proteomic changes in HepG2 cells after treatment with different free fatty acids (FFAs). A total of 234 proteins were determined to be differentially expressed after PA+OA treatment. Their functions were mainly related to responses to stress and endogenous stimuli, lipid metabolic process, and protein binding. For PA+EPA treatment, the PA-induced expression changes of 1326 proteins could be reversed by EPA, 415 of which were mitochondrial proteins, with most of the functional proteins involved in oxidative phosphorylation (OXPHOS) and tricarboxylic acid (TCA) cycle. Mechanistic studies revealed that the protein encoded by JUN and reactive oxygen species (ROS) play a role in OA- and EPA-reversed PA-induced IR, respectively. EPA and OA alleviated PA-induced abnormal adenosine triphosphate (ATP) production, ROS generation, and calcium (Ca) content. Importantly, HO-activated production of ROS increased the protein expression of JUN, further resulting in IR in HepG2 cells. Taken together, we demonstrate that ROS/JUN is a common response pathway employed by HepG2 cells toward FFA-regulated IR.
Topics: Eicosapentaenoic Acid; Hep G2 Cells; Humans; Hydrogen Peroxide; Insulin Resistance; Oleic Acid; Palmitic Acid; Proteomics; Reactive Oxygen Species
PubMed: 33631425
DOI: 10.1016/j.gpb.2019.06.005 -
Redox Biology Aug 2022Blood-testis barrier (BTB) damage promotes spermatogenesis dysfunction, which is a critical cause of male infertility. Dyslipidemia has been correlated with male...
Blood-testis barrier (BTB) damage promotes spermatogenesis dysfunction, which is a critical cause of male infertility. Dyslipidemia has been correlated with male infertility, but the major hazardous lipid and the underlying mechanism remains unclear. In this study, we firstly discovered an elevation of palmitic acid (PA) and a decrease of inhibin B in patients with severe dyszoospermia, which leaded us to explore the effects of PA on Sertoli cells. We observed a damage of BTB by PA. PA penetration to endoplasmic reticulum (ER) and its damage to ER structures were exhibited by microimaging and dynamic observation, and consequent ER stress was proved to mediate PA-induced Sertoli cell barrier disruption. Remarkably, we demonstrated a critical role of aberrant protein palmitoylation in PA-induced Sertoli cell barrier dysfunction. An ER protein, Calnexin, was screened out and was demonstrated to participate in this process, and suppression of its palmitoylation showed an ameliorating effect. We also found that ω-3 poly-unsaturated fatty acids down-regulated Calnexin palmitoylation, and alleviated BTB dysfunction. Our results indicate that dysregulated palmitoylation induced by PA plays a pivotal role in BTB disruption and subsequent spermatogenesis dysfunction, suggesting that protein palmitoylation might be therapeutically targetable in male infertility.
Topics: Blood-Testis Barrier; Calnexin; Humans; Infertility, Male; Lipoylation; Male; Palmitic Acid; Spermatogenesis
PubMed: 35803125
DOI: 10.1016/j.redox.2022.102380 -
Free Radical Research Jul 2019Insulin resistance (IR) is known to precede onset of type 2 diabetes and increased oxidative stress appears to be a deleterious factor leading to IR. In this study, we...
Insulin resistance (IR) is known to precede onset of type 2 diabetes and increased oxidative stress appears to be a deleterious factor leading to IR. In this study, we evaluated ability of pterostilbene (PTS), a methoxylated analogue of resveratrol and a known antioxidant, to reverse palmitic acid (PA)-mediated IR in HepG2 cells. PTS prevented reactive oxygen species (ROS) formation and subsequent oxidative lipid damage by reducing the expression of NADPH oxidase 3 (NOX3) in PA treated HepG2 cells. Hepatic glucose production was used as a measure of IR and PTS reversed PA-mediated increase in hepatic glucose production by reducing expression of genes coding for gluconeogenic enzymes namely glucose-6-phosphatase (G6Pase), phosphoenolpyruvate carboxykinase (PEPCK), and pyruvate carboxylase (PC); and their transcription factors cAMP response element binding protein (CREB) and fork head class Box O (FOXO1) along with its coactivator peroxisome proliferator-activated receptor gamma co-activator-1 α (PGC1α). PTS reversed PA-mediated activation of c-Jun N-terminal kinase (JNK), which in turn altered insulin signalling pathway by phosphorylating IRS-1 at Ser 307, leading to inhibition of phosphorylation of Akt and GSK-3β. PTS also reduced PA-mediated lipid accumulation by reducing expression of transcription factors SREBP1c and PPARα. SREBP1c activates genes involved in fatty acid and triglyceride synthesis while PPARα activates CPT1, a rate limiting enzyme for controlling entry and oxidation of fatty acids into mitochondria. PTS, however, did not influence PA uptake confirmed by using BODIPY-labelled fluorescent C16 fatty acid analogue. Thus, our data provides a possible mechanistic explanation for reversal of PA-mediated IR in HepG2 cells.
Topics: Hep G2 Cells; Humans; Insulin Resistance; Oxidative Stress; Palmitic Acid; Stilbenes; Triglycerides
PubMed: 31223033
DOI: 10.1080/10715762.2019.1635252 -
Proceedings of the National Academy of... Mar 2003Excess lipid accumulation in non-adipose tissues is associated with insulin resistance, pancreatic beta-cell apoptosis and heart failure. Here, we demonstrate in...
Excess lipid accumulation in non-adipose tissues is associated with insulin resistance, pancreatic beta-cell apoptosis and heart failure. Here, we demonstrate in cultured cells that the relative toxicity of two common dietary long chain fatty acids is related to channeling of these lipids to distinct cellular metabolic fates. Oleic acid supplementation leads to triglyceride accumulation and is well tolerated, whereas excess palmitic acid is poorly incorporated into triglyceride and causes apoptosis. Unsaturated fatty acids rescue palmitate-induced apoptosis by channeling palmitate into triglyceride pools and away from pathways leading to apoptosis. Moreover, in the setting of impaired triglyceride synthesis, oleate induces lipotoxicity. Our findings support a model of cellular lipid metabolism in which unsaturated fatty acids serve a protective function against lipotoxicity though promotion of triglyceride accumulation.
Topics: Animals; Apoptosis; CHO Cells; Cell Line; Cricetinae; Drug Resistance; Fatty Acid Desaturases; Fatty Acids; Lipid Metabolism; Mice; Models, Biological; Oleic Acid; Palmitic Acid; Triglycerides
PubMed: 12629214
DOI: 10.1073/pnas.0630588100 -
Autophagy Jan 2022Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease globally. NAFLD is a consequence of fat accumulation in the liver leading to...
Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease globally. NAFLD is a consequence of fat accumulation in the liver leading to lipotoxicity. Increasing evidence has demonstrated the critical role of autophagy in NAFLD. This study uncovers the unexpected role of immune surveillance protein DDX58/Rig-1 (DExD/H box helicase 58) in activating macroautophagy/autophagy and protecting from lipotoxicity associated with NAFLD. Here we show for the first time that DDX58 protein is significantly reduced in nonalcoholic steatohepatitis (NASH) mouse model, an aggressive form of NAFLD characterized by inflammation and fibrosis of the liver. In addition to decreased expression of DDX58, we found that DDX58 activity can be attenuated by treatments with palmitic acid (PA), a saturated fatty acid. To investigate whether PA inhibition of DDX58 is harmful to the cell, we characterized DDX58 function in hepatocytes when exposed to high doses of PA in the presence and/or absence of DDX58. We show that siRNA knockdown of DDX58 promotes apoptosis. Importantly, we show that stable overexpression of DDX58 is protective against toxic levels of PA and stimulates autophagy. This study begins to demonstrate the regulation of the autophagy receptor protein SQSTM1/p62 through DDX58. DDX58 expression directly influences mRNA and protein levels. This work proposes a model in which activating DDX58 increases an autophagic response and this aids in clearing toxic lipid inclusion bodies, which leads to inflammation and apoptosis. Activating a DDX58-induced autophagy response may be a strategy for treating NAFLD.5'pppdsRNA: 5' triphosphate double-stranded RNA; CDAHFD: choline-deficient, L-amino acid defined high-fat diet; CEBPB: CCAAT/enhancer binding protein (C/EBP), beta; CQ: chloroquine; DDX58/retinoic acid inducible gene 1/Rig-1: DExD/H box helicase 58; h: hours; IFIH1/MDA5: interferon induced with helicase C domain 1; IFNB/IFN-β: interferon beta 1, fibroblast; KO: knockout; MAVS: mitochondrial antiviral signaling protein; NAFLD: nonalcoholic fatty liver disease; NASH: nonalcoholic steatohepatitis; NFKB/NF-κB: nuclear factor of kappa light polypeptide gene enhancer in B cells; PA: palmitic acid; poly:IC: polyinosinic:polycytidylic acid; PRR: pattern recognition receptors; PSR: picrosirus red; RAP: rapamycin; RLR: RIG-I-like receptor; SQSTM1/p62: sequestosome 1; STING1: stimulator of interferon response cGAMP interactor 1; TBK1: TANK-binding kinase 1.
Topics: Animals; Autophagy; Cell Death; Inflammation; Mice; Non-alcoholic Fatty Liver Disease; Palmitic Acid; Sequestosome-1 Protein
PubMed: 33966599
DOI: 10.1080/15548627.2021.1920818 -
Biochemical Pharmacology Sep 2023Post-translational modifications are an important mechanism in the regulation of protein expression, function, and degradation. Well-known post-translational... (Review)
Review
Post-translational modifications are an important mechanism in the regulation of protein expression, function, and degradation. Well-known post-translational modifications are phosphorylation, glycosylation, and ubiquitination. However, lipid modifications, including myristoylation, prenylation, and palmitoylation, are poorly studied. Since the early 2000s, researchers have become more interested in lipid modifications, especially palmitoylation. The number of articles in PubMed increased from about 350 between 2000 and 2005 to more than 600 annually during the past ten years. S-palmitoylation, where the 16-carbon saturated (C16:0) palmitic acid is added to free cysteine residues of proteins, is a reversible protein modification that can affect the expression, membrane localization, and function of the modified proteins. Various diseases like Huntington's and Alzheimer's disease have been linked to changes in protein palmitoylation. In humans, the addition of palmitic acid is mediated by 23 palmitoyl acyltransferases, also called DHHC proteins. The modification can be reversed by a few thioesterases or hydrolases. Numerous soluble and membrane-attached proteins are known to be palmitoylated, but among the approximately 400 solute carriers that are classified in 66 families, only 15 found in 8 families have so far been documented to be palmitoylated. Among the best-characterized transporters are the glucose transporters GLUT1 (SLC2A1) and GLUT4 (SLC2A4), the three monoamine transporters norepinephrine transporter (NET; SLC6A2), dopamine transporter (DAT; SLC6A3), and serotonin transporter (SERT; SLC6A4), and the sodium-calcium exchanger NCX1 (SLC8A1). While there is evidence from recent proteomics experiments that numerous solute carriers are palmitoylated, no details beyond the 15 transporters covered in this review are available.
Topics: Humans; Palmitic Acid; Lipoylation; Protein Processing, Post-Translational; Phosphorylation; Membrane Proteins; Serotonin Plasma Membrane Transport Proteins
PubMed: 37481134
DOI: 10.1016/j.bcp.2023.115695 -
American Journal of Physiology. Cell... May 2022Treatment of mouse preimplantation embryos with elevated palmitic acid (PA) reduces blastocyst development, whereas cotreatment with PA and oleic acid (OA) together...
Treatment of mouse preimplantation embryos with elevated palmitic acid (PA) reduces blastocyst development, whereas cotreatment with PA and oleic acid (OA) together rescues blastocyst development to control frequencies. To understand the mechanistic effects of PA and OA treatment on early mouse embryos, we investigated the effects of PA and OA, alone and in combination, on autophagy during preimplantation development in vitro. We hypothesized that PA would alter autophagic processes and that OA cotreatment would restore control levels of autophagy. Two-cell stage mouse embryos were placed into culture medium supplemented with 100 μM PA, 250 μM OA, 100 μM PA and 250 μM OA, or potassium simplex optimization media with amino acid (KSOMaa) medium alone (control) for 18-48 h. The results demonstrated that OA cotreatment slowed developmental progression after 30 h of cotreatment but restored control blastocyst frequencies by 48 h. PA treatment elevated light chain 3 (LC3)-II puncta and p62 levels per cell whereas OA cotreatment returned to control levels of autophagy by 48 h. Autophagic mechanisms are altered by nonesterified fatty acid (NEFA) treatments during mouse preimplantation development in vitro, where PA elevates autophagosome formation and reduces autophagosome degradation levels, whereas cotreatment with OA reversed these PA effects. Autophagosome-lysosome colocalization only differed between PA and OA alone treatment groups. These findings advance our understanding of the effects of free fatty acid exposure on preimplantation development, and they uncover principles that may underlie the associations between elevated fatty acid levels and overall declines in reproductive fertility.
Topics: Animals; Autophagy; Blastocyst; Culture Media; Fatty Acids, Nonesterified; Mice; Oleic Acid; Palmitic Acid
PubMed: 35319901
DOI: 10.1152/ajpcell.00414.2021