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Frontiers in Immunology 2022Weight loss improves obesity-associated diabetes risk. However, most individuals regain weight, which worsens the risk of developing diabetes and cardiovascular disease....
INTRODUCTION
Weight loss improves obesity-associated diabetes risk. However, most individuals regain weight, which worsens the risk of developing diabetes and cardiovascular disease. We previously reported that male mice retain obesity-associated immunological changes even after weight loss, suggesting that immune cells may remember the state of obesity. Therefore, we hypothesized that cycles of weight gain and loss, otherwise known as weight cycling, can induce innate memory in adipose macrophages.
METHODS
Bone marrow derived macrophages were primed with palmitic acid or adipose tissue conditioned media in a culture model of innate immune memory. Mice also put on low fat or high fat diets over 14-27 weeks to induce weight gain, weight loss, and weight cycling.
RESULTS
Priming cells with palmitic acid or adipose tissue conditioned media from obese mice increased maximal glycolysis and oxidative phosphorylation and increased LPS-induced TNFα and IL-6 production. Palmitic acid effects were dependent on TLR4 and impaired by methyltransferase inhibition and AMPK activation. While weight loss improved glucose tolerance in mice, adipose macrophages were primed for greater activation to subsequent stimulation by LPS as measured by cytokine production. In the model of weight cycling, adipose macrophages had elevated metabolism and secreted higher levels of basal TNFα, suggesting that weight loss can also prime macrophages for heighted activation to weight regain.
DISCUSSION
Together, these data suggest that weight loss following obesity can prime adipose macrophages for enhanced inflammation upon weight regain. This innate immune memory response may contribute to worsened glucose tolerance following weight cycling.
Topics: Male; Mice; Animals; Tumor Necrosis Factor-alpha; Weight Cycling; Trained Immunity; Palmitic Acid; Culture Media, Conditioned; Lipopolysaccharides; Insulin Resistance; Adipose Tissue; Obesity; Macrophages; Weight Gain; Diabetes Mellitus; Weight Loss; Glucose
PubMed: 36713396
DOI: 10.3389/fimmu.2022.984859 -
Prostaglandins, Leukotrienes, and... Jun 2021Adipose tissue resident macrophages play an important role in the regulation of the inflammatory response. Monounsaturated fatty acids assist in the prevention of...
Adipose tissue resident macrophages play an important role in the regulation of the inflammatory response. Monounsaturated fatty acids assist in the prevention of cardiovascular diseases via an anti-inflammatory effect. However, the mechanisms by which monounsaturated fatty acids, such as palmitoleic acid, regulate the inflammatory response has not been well investigated. In this study, we found that a high concentration of palmitic acid induced J774A.1 murine macrophages toward a pro-inflammatory state, possibly through the activation of the TLR2 or TLR4 genes, and their downstream signaling pathways. In contrast, palmitoleic acid induced a protective effect against inflammation in macrophage of non-obese rodents by inducing an alternative activation pathway via reducing TLR2 or TLR4 signaling. This study indicates that the balance of palmitic acid (saturated fatty acid) and palmitoleic acid (monounsaturated fatty acid) effects macrophage activation. The potential therapeutic impact of palmitoleic acid to ameliorate non-obese-mediated inflammation warrants further investigation.
Topics: Animals; Anti-Infective Agents; Cell Line; Fatty Acids, Monounsaturated; Gene Expression Regulation; Macrophage Activation; Macrophages; Mice; Palmitic Acid; Rats; Signal Transduction; Toll-Like Receptor 4; Tumor Necrosis Factor-alpha
PubMed: 33930845
DOI: 10.1016/j.plefa.2021.102270 -
Biomolecules May 2024Epidemiological and clinical evidence have extensively documented the role of obesity in the development of endometrial cancer. However, the effect of fatty acids on...
Epidemiological and clinical evidence have extensively documented the role of obesity in the development of endometrial cancer. However, the effect of fatty acids on cell growth in endometrial cancer has not been widely studied. Here, we reported that palmitic acid significantly inhibited cell proliferation of endometrial cancer cells and primary cultures of endometrial cancer and reduced tumor growth in a transgenic mouse model of endometrial cancer, in parallel with increased cellular stress and apoptosis and decreased cellular adhesion and invasion. Inhibition of cellular stress by N-acetyl-L-cysteine effectively reversed the effects of palmitic acid on cell proliferation, apoptosis, and invasive capacity in endometrial cancer cells. Palmitic acid increased the intracellular formation of lipid droplets in a time- and dose-dependent manner. Depletion of lipid droplets by blocking DGAT1 and DGAT2 effectively increased the ability of palmitic acid to inhibit cell proliferation and induce cleaved caspase 3 activity. Collectively, this study provides new insight into the effect of palmitic acid on cell proliferation and invasion and the formation of lipid droplets that may have potential clinical relevance in the treatment of obesity-driven endometrial cancer.
Topics: Female; Palmitic Acid; Endometrial Neoplasms; Humans; Lipid Droplets; Animals; Cell Proliferation; Mice; Apoptosis; Cell Line, Tumor; Diacylglycerol O-Acyltransferase; Mice, Transgenic
PubMed: 38786008
DOI: 10.3390/biom14050601 -
Journal of Translational Medicine Jan 2024Non-alcoholic fatty liver disease (NAFLD) is a liver disorder characterized by the ac-cumulation of fat in hepatocytes without alcohol consumption. Mitochondrial...
BACKGROUND
Non-alcoholic fatty liver disease (NAFLD) is a liver disorder characterized by the ac-cumulation of fat in hepatocytes without alcohol consumption. Mitochondrial dysfunction and endoplasmic reticulum (ER) stress play significant roles in NAFLD pathogenesis. The unfolded protein response in mitochondria (UPRmt) is an adaptive mechanism that aims to restore mitochondrial protein homeostasis and mitigate cellular stress. This study aimed to investigate the effects of ( +)-Lipoic acid (ALA) on UPRmt, inflammation, and oxidative stress in an in vitro model of NAFLD using HepG2 cells treated with palmitic acid and oleic acid to induce steatosis.
RESULTS
Treatment with palmitic and oleic acids increased UPRmt-related proteins HSP90 and HSP60 (heat shock protein), and decreased CLPP (caseinolytic protease P), indicating ER stress activation. ALA treatment at 1 μM and 5 μM restored UPRmt-related protein levels. PA:OA (palmitic acid:oleic acid)-induced ER stress markers IRE1α (Inositol requiring enzyme-1), CHOP (C/EBP Homologous Protein), BIP (Binding Immunoglobulin Protein), and BAX (Bcl-2-associated X protein) were significantly reduced by ALA treatment. ALA also enhanced ER-mediated protein glycosylation and reduced oxidative stress, as evidenced by decreased GPX1 (Glutathione peroxidase 1), GSTP1 (glutathione S-transferase pi 1), and GSR (glutathione-disulfide reductase) expression and increased GSH (Glutathione) levels, and improved cellular senescence as shown by the markers β-galactosidase, γH2Ax and Klotho-beta.
CONCLUSIONS
In conclusion, ALA ameliorated ER stress, oxidative stress, and inflammation in HepG2 cells treated with palmitic and oleic acids, potentially offering therapeutic benefits for NAFLD providing a possible biochemical mechanism underlying ALA beneficial effects.
Topics: Humans; Non-alcoholic Fatty Liver Disease; Thioctic Acid; Endoribonucleases; Oleic Acid; Protein Serine-Threonine Kinases; Unfolded Protein Response; Oxidative Stress; Endoplasmic Reticulum Stress; Hepatocytes; Cellular Senescence; Inflammation; Palmitic Acids; Liver; Palmitic Acid
PubMed: 38245790
DOI: 10.1186/s12967-024-04880-x -
Cells May 2024Research on retinoid-based cancer prevention, spurred by the effects of vitamin A deficiency on gastric cancer and subsequent clinical studies on digestive tract cancer,... (Comparative Study)
Comparative Study Review
Research on retinoid-based cancer prevention, spurred by the effects of vitamin A deficiency on gastric cancer and subsequent clinical studies on digestive tract cancer, unveils novel avenues for chemoprevention. Acyclic retinoids like 4,5-didehydrogeranylgeranoic acid (4,5-didehydroGGA) have emerged as potent agents against hepatocellular carcinoma (HCC), distinct from natural retinoids such as all- retinoic acid (ATRA). Mechanistic studies reveal GGA's unique induction of pyroptosis, a rapid cell death pathway, in HCC cells. GGA triggers mitochondrial superoxide hyperproduction and ER stress responses through Toll-like receptor 4 (TLR4) signaling and modulates autophagy, ultimately activating pyroptotic cell death in HCC cells. Unlike ATRA-induced apoptosis, GGA and palmitic acid (PA) induce pyroptosis, underscoring their distinct mechanisms. While all three fatty acids evoke mitochondrial dysfunction and ER stress responses, GGA and PA inhibit autophagy, leading to incomplete autophagic responses and pyroptosis, whereas ATRA promotes autophagic flux. In vivo experiments demonstrate GGA's potential as an anti-oncometabolite, inducing cell death selectively in tumor cells and thus suppressing liver cancer development. This review provides a comprehensive overview of the molecular mechanisms underlying GGA's anti-HCC effects and underscores its promising role in cancer prevention, highlighting its importance in HCC prevention.
Topics: Humans; Carcinoma, Hepatocellular; Diterpenes; Palmitic Acid; Pyroptosis; Liver Neoplasms; Tretinoin; Animals; Autophagy; Cell Line, Tumor; Endoplasmic Reticulum Stress
PubMed: 38786033
DOI: 10.3390/cells13100809 -
Nature Communications Jan 2022Epidemiological studies have established a positive association between obesity and the incidence of postmenopausal breast cancer. Moreover, it is known that obesity...
Epidemiological studies have established a positive association between obesity and the incidence of postmenopausal breast cancer. Moreover, it is known that obesity promotes stem cell-like properties of breast cancer cells. However, the cancer cell-autonomous mechanisms underlying this correlation are not well defined. Here we demonstrate that obesity-associated tumor formation is driven by cellular adaptation rather than expansion of pre-existing clones within the cancer cell population. While there is no correlation with specific mutations, cellular adaptation to obesity is governed by palmitic acid (PA) and leads to enhanced tumor formation capacity of breast cancer cells. This process is governed epigenetically through increased chromatin occupancy of the transcription factor CCAAT/enhancer-binding protein beta (C/EBPB). Obesity-induced epigenetic activation of C/EBPB regulates cancer stem-like properties by modulating the expression of key downstream regulators including CLDN1 and LCN2. Collectively, our findings demonstrate that obesity drives cellular adaptation to PA drives tumor initiation in the obese setting through activation of a C/EBPB dependent transcriptional network.
Topics: Adult; Aged; Animals; Breast Neoplasms; CCAAT-Enhancer-Binding Protein-beta; Cell Line, Tumor; Epigenomics; Female; Gene Expression Regulation, Neoplastic; Hormones; Humans; Mice; Mice, Inbred C57BL; Middle Aged; Obesity; Palmitic Acid
PubMed: 35013251
DOI: 10.1038/s41467-021-27734-2 -
Cell Death & Disease Jul 2022Palmitic acid (PA) is significantly increased in the hypothalamus of mice, when fed chronically with a high-fat diet (HFD). PA impairs insulin signaling in hypothalamic...
Palmitic acid (PA) is significantly increased in the hypothalamus of mice, when fed chronically with a high-fat diet (HFD). PA impairs insulin signaling in hypothalamic neurons, by a mechanism dependent on autophagy, a process of lysosomal-mediated degradation of cytoplasmic material. In addition, previous work shows a crosstalk between autophagy and the primary cilium (hereafter cilium), an antenna-like structure on the cell surface that acts as a signaling platform for the cell. Ciliopathies, human diseases characterized by cilia dysfunction, manifest, type 2 diabetes, among other features, suggesting a role of the cilium in insulin signaling. Cilium depletion in hypothalamic pro-opiomelanocortin (POMC) neurons triggers obesity and insulin resistance in mice, the same phenotype as mice deficient in autophagy in POMC neurons. Here we investigated the effect of chronic consumption of HFD on cilia; and our results indicate that chronic feeding with HFD reduces the percentage of cilia in hypothalamic POMC neurons. This effect may be due to an increased amount of PA, as treatment with this saturated fatty acid in vitro reduces the percentage of ciliated cells and cilia length in hypothalamic neurons. Importantly, the same effect of cilia depletion was obtained following chemical and genetic inhibition of autophagy, indicating autophagy is required for ciliogenesis. We further demonstrate a role for the cilium in insulin sensitivity, as cilium loss in hypothalamic neuronal cells disrupts insulin signaling and insulin-dependent glucose uptake, an effect that correlates with the ciliary localization of the insulin receptor (IR). Consistently, increased percentage of ciliated hypothalamic neuronal cells promotes insulin signaling, even when cells are exposed to PA. Altogether, our results indicate that, in hypothalamic neurons, impairment of autophagy, either by PA exposure, chemical or genetic manipulation, cause cilia loss that impairs insulin sensitivity.
Topics: Animals; Autophagy; Cilia; Diabetes Mellitus, Type 2; Humans; Hypothalamus; Insulin; Insulin Resistance; Mice; Neurons; Palmitic Acid; Pro-Opiomelanocortin
PubMed: 35902579
DOI: 10.1038/s41419-022-05109-9 -
Cellular and Molecular Life Sciences :... Jul 2019Emerging evidence shows that palmitic acid (PA), a common fatty acid in the human diet, serves as a signaling molecule regulating the progression and development of many... (Review)
Review
Emerging evidence shows that palmitic acid (PA), a common fatty acid in the human diet, serves as a signaling molecule regulating the progression and development of many diseases at the molecular level. In this review, we focus on its regulatory roles in the development of five pathological conditions, namely, metabolic syndrome, cardiovascular diseases, cancer, neurodegenerative diseases, and inflammation. We summarize the clinical and epidemiological studies; and also the mechanistic studies which have identified the molecular targets for PA in these pathological conditions. Activation or inactivation of these molecular targets by PA controls disease development. Therefore, identifying the specific targets and signaling pathways that are regulated by PA can give us a better understanding of how these diseases develop for the design of effective targeted therapeutics.
Topics: Animals; Autophagy; Cardiovascular Diseases; Humans; Inflammation; Metabolic Syndrome; Neoplasms; Neurodegenerative Diseases; Palmitic Acid; Signal Transduction
PubMed: 30968170
DOI: 10.1007/s00018-019-03092-7 -
Biochimica Et Biophysica Acta.... Jun 2023Cholangiocarcinoma (CCA), a cancer of the biliary tract, is a significant health problem in Thailand. Reprogramming of cellular metabolism and upregulation of lipogenic...
Cholangiocarcinoma (CCA), a cancer of the biliary tract, is a significant health problem in Thailand. Reprogramming of cellular metabolism and upregulation of lipogenic enzymes have been revealed in CCA, but the mechanism is unclear. The current study highlighted the importance of acetyl-CoA carboxylase 1 (ACC1), a rate-limiting enzyme in de novo lipogenesis, on CCA migration. ACC1 expression in human CCA tissues was determined by immunohistochemistry. The results demonstrated that increased ACC1 was related to the shorter survival of CCA patients. Herein, ACC1-deficient cell lines (ACC1-KD) were generated by the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (cas9) system and were used for the comparative study. The ACC1 levels in ACC1-KD were 80-90 % lower than in parental cells. Suppression of ACC1 significantly reduced intracellular malonyl-CoA and neutral lipid contents. Two-fold growth retardation and 60-80 % reduced CCA cell migration and invasion were observed in ACC1-KD cells. The reduced 20-40 % of intracellular ATP levels, AMPK activation, lowered NF-κB p65 nuclear translocation, and snail expression were emphasized. Migration of ACC1-KD cells was restored by supplementation with palmitic acid and malonyl-CoA. Altogether, the importance of rate-limiting enzyme in de novo fatty acid synthesis, ACC1, and AMPK-NF-κB-snail axis on CCA progression was suggested herein. These might be the novel targets for CCA drug design. (ACC1, AMPK, Cholangiocarcinoma, De novo lipogenesis, NF-κB, Palmitic acid).
Topics: Humans; Acetyl-CoA Carboxylase; AMP-Activated Protein Kinases; Cholangiocarcinoma; NF-kappa B; Palmitic Acid; Snail Family Transcription Factors
PubMed: 36972768
DOI: 10.1016/j.bbadis.2023.166694 -
Molecular Neurobiology Aug 2023Chronic intake of a high-fat diet increases saturated fatty acids in the brain causing the progression of neurodegenerative diseases. Palmitic acid is a free fatty acid...
Chronic intake of a high-fat diet increases saturated fatty acids in the brain causing the progression of neurodegenerative diseases. Palmitic acid is a free fatty acid abundant in the diet that at high concentrations may penetrate the blood-brain barrier and stimulate the production of pro-inflammatory cytokines, leading to inflammation in astrocytes. The use of the synthetic neurosteroid tibolone in protection against fatty acid toxicity is emerging, but its transcriptional effects on palmitic acid-induced lipotoxicity remain unclear. Herein, we performed a transcriptome profiling of normal human astrocytes to investigate the molecular mechanisms by which palmitic acid causes cellular damage to astrocytes, and whether tibolone could reverse its detrimental effects. Astrocytes undergo a profound transcriptional change at 2 mM palmitic acid, affecting the expression of 739 genes, 366 upregulated and 373 downregulated. However, tibolone at 10 nM does not entirely reverse palmitic acid effects. Additionally, the protein-protein interaction reveals two novel gene clustering modules. The first module involves astrocyte defense responses by upregulation of pathways associated with antiviral innate immunity, and the second is linked to lipid metabolism. Our data suggest that activation of viral response signaling pathways might be so far, the initial molecular mechanism of astrocytes in response to a lipotoxic insult by palmitic acid, triggered particularly upon increased expression levels of IFIT2, IRF1, and XAF1. Therefore, this novel approach using a global gene expression analysis may shed light on the pleiotropic effects of palmitic acid on astrocytes, and provide a basis for future studies addressed to elucidate these responses in neurodegenerative conditions, which is highly valuable for the design of therapeutic strategies.
Topics: Humans; Palmitic Acid; Antiviral Agents; Astrocytes; Interferon Type I; Fatty Acids; Cholesterol
PubMed: 37184765
DOI: 10.1007/s12035-023-03366-z