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Molecules (Basel, Switzerland) Sep 2023Non-alcoholic fatty liver disease (NAFLD) is the primary chronic liver disease worldwide, mainly manifested by hepatic steatosis. Hepatic lipids may be derived from...
Non-alcoholic fatty liver disease (NAFLD) is the primary chronic liver disease worldwide, mainly manifested by hepatic steatosis. Hepatic lipids may be derived from dietary intake, plasma free fatty acid (FFA) uptake, or hepatic de novo lipogenesis (DNL). Currently, cellular and animal models of hepatocellular steatosis are widely used to study the pathogenesis of NAFLD and to investigate therapeutic agents. However, whether there are differences between the in vivo and in vitro models of the mechanisms that cause lipid accumulation has not been reported. We used OA/PA-induced NCTC 1469 cells and high-fat-diet-fed C57BL/6J mice to simulate a hepatocyte steatosis model of NAFLD and to detect indicators related to FFA uptake and DNL. In addition, when serological indicators were analysed in the mouse model, it was found that serum FASN levels decreased. The results revealed that, in the cellular model, indicators related to DNL were decreased, FASN enzyme activity was unchanged, and indicators related to FFA uptake were increased, including the high expression of CD36; while, in the animal model, indicators related to both FFA uptake and de novo synthesis were increased, including the high expression of CD36 and the increased protein levels of FASN with enhanced enzyme activity. In addition, after an analysis of the serological indicators in the mouse model, it was found that the serum levels of FASN were reduced. In conclusion, the OA/PA-induced cellular model can be used to study the mechanism of FFA uptake, whereas the high-fat-diet-induced mouse model can be used to study the mechanism of FFA uptake and DNL. Combined treatment with CD36 and FASN may be more effective against NAFLD. FASN in the serum can be used as one of the indicators for the clinical diagnosis of NAFLD.
Topics: Mice; Animals; Mice, Inbred C57BL; Oleic Acid; Palmitic Acid; Non-alcoholic Fatty Liver Disease; Diet, High-Fat; Hepatocytes; Disease Models, Animal; CD36 Antigens; Fatty Acids, Nonesterified
PubMed: 37764494
DOI: 10.3390/molecules28186714 -
The FEBS Journal Dec 2021Protein cysteine palmitoylation, or S-palmitoylation, has been known for about 40 years, and thousands of proteins in humans are known to be modified. Because of the... (Review)
Review
Protein cysteine palmitoylation, or S-palmitoylation, has been known for about 40 years, and thousands of proteins in humans are known to be modified. Because of the large number of proteins modified, the importance and physiological functions of S-palmitoylation are enormous. However, most of the known physiological functions of S-palmitoylation can be broadly classified into two categories, neurological or immunological. This review provides a summary on the function of S-palmitoylation from the immunological perspective. Several important immune signaling pathways are discussed, including STING, NOD1/2, JAK-STAT in cytokine signaling, T-cell receptor signaling, chemotactic GPCR signaling, apoptosis, phagocytosis, and endothelial and epithelial integrity. This review is not meant to be comprehensive, but rather focuses on specific examples to highlight the versatility of palmitoylation in regulating immune signaling, as well as the potential and challenges of targeting palmitoylation to treat immune diseases.
Topics: Animals; Cysteine; Cytokines; Humans; Inflammation; Palmitic Acid; Signal Transduction
PubMed: 33506611
DOI: 10.1111/febs.15728 -
Journal of Lipid Research Oct 2022The main fatty acids at the sn-1 position of phospholipids (PLs) are saturated or monounsaturated fatty acids such as palmitic acid (C16:0), stearic acid (C18:0), and...
The main fatty acids at the sn-1 position of phospholipids (PLs) are saturated or monounsaturated fatty acids such as palmitic acid (C16:0), stearic acid (C18:0), and oleic acid (C18:1) and are constantly replaced, like unsaturated fatty acids at the sn-2 position. However, little is known about the molecular mechanism underlying the replacement of fatty acids at the sn-1 position, i.e., the sn-1 remodeling. Previously, we established a method to evaluate the incorporation of fatty acids into the sn-1 position of lysophospholipids (lyso-PLs). Here, we used this method to identify the enzymes capable of incorporating fatty acids into the sn-1 position of lyso-PLs (sn-1 lysophospholipid acyltransferase [LPLAT]). Screenings using siRNA knockdown and recombinant proteins for 14 LPLATs identified LPLAT7/lysophosphatidylglycerol acyltransferase 1 (LPGAT1) as a candidate. In vitro, we found LPLAT7 mainly incorporated several fatty acids into the sn-1 position of lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE), with weak activities toward other lyso-PLs. Interestingly, however, only C18:0-containing phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were specifically reduced in the LPLAT7-mutant cells and tissues from knockout mice, with a concomitant increase in the level of C16:0- and C18:1-containing PC and PE. Consistent with this, the incorporation of deuterium-labeled C18:0 into PLs dramatically decreased in the mutant cells, while deuterium-labeled C16:0 and C18:1 showed the opposite dynamic. Identifying LPLAT7 as an sn-1 LPLAT facilitates understanding the biological significance of sn-1 fatty acid remodeling of PLs. We also propose to use the new nomenclature, LPLAT7, for LPGAT1 since the newly assigned enzymatic activities are quite different from the LPGAT1s previously reported.
Topics: Mice; Animals; 1-Acylglycerophosphocholine O-Acyltransferase; Phosphatidylethanolamines; Lysophosphatidylcholines; RNA, Small Interfering; Deuterium; Lysophospholipids; Fatty Acids; Phosphatidylcholines; Stearic Acids; Palmitic Acid; Fatty Acids, Unsaturated; Recombinant Proteins; Oleic Acids; Fatty Acids, Monounsaturated
PubMed: 36049524
DOI: 10.1016/j.jlr.2022.100271 -
International Journal of Molecular... Mar 2023Sarcopenia associated with aging and obesity is characterized by the atrophy of fast-twitch muscle fibers and an increase in intramuscular fat deposits. However, the...
Sarcopenia associated with aging and obesity is characterized by the atrophy of fast-twitch muscle fibers and an increase in intramuscular fat deposits. However, the mechanism of fast-twitch fiber-specific atrophy remains unclear. In this study, we aimed to assess the effect of palmitic acid (PA), the most common fatty acid component of human fat, on muscle fiber type, focusing on the expression of fiber-type-specific myosin heavy chain (MHC). Myotubes differentiated from C2C12 myoblasts were treated with PA. The PA treatment inhibited myotube formation and hypertrophy while reducing the gene expression of MHC IIb and IIx, specific isoforms of fast-twitch fibers. Consistent with this, a significant suppression of MHC IIb protein expression in PA-treated cells was observed. A reporter assay using plasmids containing the MHC IIb gene promoter revealed that the PA-induced reduction in MHC IIb gene expression was caused by the suppression of MyoD transcriptional activity through its phosphorylation. Treatment with a specific protein kinase C (PKC) inhibitor recovered the reduction in MHC IIb gene expression levels in PA-treated cells, suggesting the involvement of the PA-induced activation of PKC. Thus, PA selectively suppresses the mRNA and protein expression of fast-twitch MHC by modulating MyoD activity. This finding provides a potential pathogenic mechanism for age-related sarcopenia.
Topics: Humans; Muscle Fibers, Skeletal; Muscle, Skeletal; Myosin Heavy Chains; Palmitic Acid; Phosphorylation; Sarcopenia; Animals; Mice; MyoD Protein
PubMed: 36982919
DOI: 10.3390/ijms24065847 -
Arteriosclerosis, Thrombosis, and... Jul 2023Obesity and diabetes are associated with elevated free fatty acids like palmitic acid (PA), which promote chronic inflammation and impaired inflammation resolution...
BACKGROUND
Obesity and diabetes are associated with elevated free fatty acids like palmitic acid (PA), which promote chronic inflammation and impaired inflammation resolution associated with cardiometabolic disorders. Long noncoding RNAs (lncRNAs) are implicated in inflammatory processes; however, their roles in PA-regulated inflammation and resolution are unclear.
METHODS
We performed RNA-sequencing analysis to identify PA-regulated coding genes and novel lncRNAs in CD14 monocytes from healthy volunteers. We investigated the regulation and function of an uncharacterized PA-induced lncRNA (PA-egulated nti-nflammatory ncRNA). We examined its role in inflammation resolution by employing knockdown and overexpression strategies in human and mouse macrophages. We also used RNA pulldown coupled with mass spectrometry to identify interacting nuclear proteins and their mechanistic involvement in functions in human macrophages.
RESULTS
Treatment of human CD14 monocytes with PA-induced several lncRNAs and genes associated with inflammatory phenotype. PA strongly induced lncRNA expressed near . was also induced by cytokines and infectious agents in human monocytes/macrophages and was regulated by NF-κB (nuclear factor-kappa B). Time course studies showed was induced during inflammation resolution phase in PA-treated macrophages. knockdown with antisense oligonucleotides upregulated key inflammatory genes and vice versa with overexpression. We found that interacts with ELAVL1 (ELAV-like RNA-binding protein 1) protein via adenylate/uridylate-rich elements (AU-rich elements; AREs). ELAVL1 knockdown inhibited the anti-inflammatory functions of . Moreover, knockdown increased cytosolic localization of ELAVL1 and increased the stability of ARE-containing inflammatory genes. Mouse orthologous was downregulated in macrophages from mice with diabetes and atherosclerosis. overexpression attenuated proinflammatory genes in mouse macrophages.
CONCLUSIONS
Upregulation of under acute inflammatory conditions contributes to proresolution mechanisms via -ELAVL1 interactions. Conversely, downregulation in cardiometabolic diseases enhances ELAVL1 function and impairs inflammation resolution to further augment inflammation. Thus, inflammation-resolving lncRNAs like represent novel targets to combat inflammatory cardiometabolic diseases.
Topics: Humans; Mice; Animals; Monocytes; RNA, Long Noncoding; Palmitic Acid; Macrophages; Inflammation; NF-kappa B; Atherosclerosis; RNA-Binding Proteins; ELAV-Like Protein 1
PubMed: 37128912
DOI: 10.1161/ATVBAHA.122.318536 -
Scientific Reports Oct 2023To investigate the effects and potential mechanisms of human umbilical cord mesenchymal stem cells, exosomes, and their conditioned media on lipid storage in oleic acid...
To investigate the effects and potential mechanisms of human umbilical cord mesenchymal stem cells, exosomes, and their conditioned media on lipid storage in oleic acid (OA) and palmitic acid (PA) treated hepatocytes and high-fat methionine- choline deficient diet (HFMRCD) induced non-alcoholic steatohepatitis (NASH) mice. AML12 cells were stimulated with OA and PA to establish the lipid storage cell model. HucMSCs, exosomes, and culture medium were then co-cultured. At the same time, C57BL/6 mice were fed an HFMRCD for 6 or 8 weeks to establish a NASH mouse model. The effect of HucMSCs, exosomes, and culture medium on lipid droplet repair of hepatocytes or NASH mice was then assessed. The weight of hepatocytes or liver tissue, Oil Red O, hematoxylin-eosin staining, Masson staining, Western blot, and qPCR were used to detect the related IL-6, TNF-α, TGF-β1 andEI24/AMPK/mTOR pathway expression in hepatocytes and liver tissue. Compared with the model group, the effect of HucMSCs-Ex on inhibiting the accumulation of lipid droplets was more obvious at the cell level. In vivo study showed that HucMSCs-Ex reduces activity scores in NASH mice and improves liver tissue morphology by reducing vacuolar degeneration, fat deposition, and collagen deposition of liver tissue. Western blot and qPCR results showed that inflammatory factors and AMPK/mTOR or EI24-related autophagy pathways were altered before and after treatment. HucMSCs, HucMSC-Ex, and CM can promote autophagy in hepatocytes or NASH mice through the AMPK/mTOR or EI24-related autophagy pathway and alleviate injury associated with lipid deposition, collagen deposition or inflammation, reversing the progression of NASH.
Topics: Mice; Humans; Animals; Non-alcoholic Fatty Liver Disease; Culture Media, Conditioned; Exosomes; AMP-Activated Protein Kinases; Mice, Inbred C57BL; Liver; TOR Serine-Threonine Kinases; Palmitic Acid; Choline; Oleic Acid; Collagen; Mesenchymal Stem Cells
PubMed: 37891247
DOI: 10.1038/s41598-023-45828-3 -
Biomolecules Aug 2022Palmitoylethanolamide (PEA), the naturally occurring amide of ethanolamine and palmitic acid, is an endogenous lipid compound endowed with a plethora of pharmacological... (Review)
Review
Palmitoylethanolamide (PEA), the naturally occurring amide of ethanolamine and palmitic acid, is an endogenous lipid compound endowed with a plethora of pharmacological functions, including analgesic, neuroprotective, immune-modulating, and anti-inflammatory effects. Although the properties of PEA were first characterized nearly 65 years ago, the identity of the receptor mediating these actions has long remained elusive, causing a period of research stasis. In the last two decades, a renewal of interest in PEA occurred, and a series of interesting studies have demonstrated the pharmacological properties of PEA and clarified its mechanisms of action. Recent findings showed the ability of formulations containing PEA in promoting oligodendrocyte differentiation, which represents the first step for the proper formation of myelin. This evidence opens new and promising research opportunities. White matter defects have been detected in a vast and heterogeneous group of diseases, including age-related neurodegenerative disorders. Here, we summarize the history and pharmacology of PEA and discuss its therapeutic potential in restoring white matter defects.
Topics: Amides; Analgesics; Anti-Inflammatory Agents; Ethanolamines; Palmitic Acid; Palmitic Acids; White Matter
PubMed: 36139030
DOI: 10.3390/biom12091191 -
Nutrition & Diabetes Apr 2022Our previous results have shown that obesity-induced excessive palmitic acid (PA) can promote the expression of KLF7, which plays a vital role in regulation of...
OBJECTIVE
Our previous results have shown that obesity-induced excessive palmitic acid (PA) can promote the expression of KLF7, which plays a vital role in regulation of inflammation, glucose metabolism. But the exact mechanism of PA up-regulating the expression of KLF7 is not clear yet. This study is intend to explore whether PA promoting KLF7 expression through GPRs/NF-κB signaling pathway, causing inflammation and glucose metabolism disorders.
METHODS
Cells were blocked GPRs/NF-κB under PA stimulation in vitro to demonstrate the molecular mechanism of PA up-regulates KLF7 expression. The regulatory effect of p65 on KLF7 was detected by luciferase reporter gene assay. Blocking GPRs/NF-κB in diet-induced obesity mice to detect the expression of KLF7, inflammatory cytokines and glucose metabolism related factors, clarifying the effects of GPRs/NF-κB on KLF7 in vivo.
RESULTS
In 3T3-L1 adipocytes and HepG2 cells, PA could up-regulate the expression of KLF7 by promoting the GPR40/120-NF-κB signaling pathway, leading to inflammation and reduced glucose consumption (p < 0.05 for both). Luciferase reporter gene assay and ChIP assay showed that p65 could transcriptionally up-regulates the expression of KLF7. In high-fat diet (HFD) mice, after intraperitoneal injection of GPR40 or GPR120 blocker, the levels of p-p65 and KLF7 in epididymal white adipose tissue and liver were significantly decreased (p < 0.05 for both). Pharmacological inhibition of p-p65 significantly attenuated KLF7 expression and improved glucose tolerant and insulin sensitive (p < 0.05 for both).
CONCLUSIONS
Our results indicate that obesity-induced elevated palmitic acid promotes inflammation and glucose metabolism disorders through GPRs/NF-κB/KLF7 signaling pathway.
Topics: Animals; Glucose; Glucose Metabolism Disorders; Inflammation; Kruppel-Like Transcription Factors; Mice; NF-kappa B; Obesity; Palmitic Acid
PubMed: 35443706
DOI: 10.1038/s41387-022-00202-6 -
Nature Communications Feb 2024Patients with Type 2 Diabetes Mellitus are increasingly susceptible to atherosclerotic plaque vulnerability, leading to severe cardiovascular events. In this study, we...
Patients with Type 2 Diabetes Mellitus are increasingly susceptible to atherosclerotic plaque vulnerability, leading to severe cardiovascular events. In this study, we demonstrate that elevated serum levels of palmitic acid, a type of saturated fatty acid, are significantly linked to this enhanced vulnerability in patients with Type 2 Diabetes Mellitus. Through a combination of human cohort studies and animal models, our research identifies a key mechanistic pathway: palmitic acid induces macrophage Delta-like ligand 4 signaling, which in turn triggers senescence in vascular smooth muscle cells. This process is critical for plaque instability due to reduced collagen synthesis and deposition. Importantly, our findings reveal that macrophage-specific knockout of Delta-like ligand 4 in atherosclerotic mice leads to reduced plaque burden and improved stability, highlighting the potential of targeting this pathway. These insights offer a promising direction for developing therapeutic strategies to mitigate cardiovascular risks in patients with Type 2 Diabetes Mellitus.
Topics: Animals; Humans; Mice; Apolipoproteins E; Diabetes Mellitus, Type 2; Disease Models, Animal; Macrophages; Mice, Knockout; Myocytes, Smooth Muscle; Palmitic Acid; Plaque, Atherosclerotic
PubMed: 38346959
DOI: 10.1038/s41467-024-45582-8 -
The Journal of Biological Chemistry Nov 2023A high-fat diet (HFD) plays a critical role in hepatocyte insulin resistance. Numerous models and factors have been proposed to elucidate the mechanism of palmitic acid...
A high-fat diet (HFD) plays a critical role in hepatocyte insulin resistance. Numerous models and factors have been proposed to elucidate the mechanism of palmitic acid (PA)-induced insulin resistance. However, proteomic studies of insulin resistance by HFD stimulation are usually performed under insulin conditions, leading to an unclear understanding of how a HFD alone affects hepatocytes. Here, we mapped the phosphorylation rewiring events in PA-stimulated HepG2 cells and found PA decreased the phosphorylation level of the eukaryotic translation initiation factor 4E-binding protein 2 (4EBP2) at S65/T70. Further experiments identified 4EBP2 as a key node of insulin resistance in either HFD mice or PA-treated cells. Reduced 4EBP2 levels increased glucose uptake and insulin sensitivity, whereas the 4EBP2_S65A/T70A mutation exacerbated PA-induced insulin resistance. Additionally, the nascent proteome revealed many glycolysis-related proteins translationally regulated by 4EBP2 such as hexokinase-2, pyruvate kinase PKM, TBC1 domain family member 4, and glucose-6-phosphate 1-dehydrogenase. In summary, we report the critical role of 4EBP2 in regulating HFD-stimulated insulin resistance in hepatocytes.
Topics: Animals; Male; Mice; Carrier Proteins; Cell Line; Diet, High-Fat; Hepatocytes; Insulin; Insulin Resistance; Mice, Inbred C57BL; Palmitic Acid; Protein Biosynthesis; Proteomics
PubMed: 37797700
DOI: 10.1016/j.jbc.2023.105315