Project description:Cells harbor two systems for the synthesis of fatty acids, one in the cytoplasm (FASN or fatty acid synthase) and one in the mitochondria (mtFAS). In contrast to FASN, mtFAS is poorly characterized, with the major product(s), metabolic roles, and cellular function(s) essentially unknown. Here we show that hypomorphic mtFAS mutants display a profound loss of electron transport chain (ETC) complexes and exhibit compensatory reductive carboxylation. This effect on ETC complexes is independent of the synthesis of lipoic acid, the best characterized function of mtFAS, as mutants lacking lipoic acid synthesis have an intact ETC. Finally, mtFAS impairment blocks the differentiation of skeletal myoblasts in vitro. These data suggest that ETC activity in mammals is profoundly controlled by mtFAS function, thereby connecting anabolic fatty acid synthesis with the oxidation of carbon fuels.
Project description:Persisters represent a small bacterial population that is dormant and that survives under antibiotic treatment without experiencing genetic adaptation. Persisters are also considered one of the major reasons for recalcitrant chronic bacterial infections. Although several mechanisms of persister formation have been proposed, it is not clear how cells enter the dormant state in the presence of antibiotics or how persister cell formation can be effectively controlled. A fatty acid compound, cis-2-decenoic acid, was reported to decrease persister formation as well as revert the dormant cells to a metabolically active state. We reasoned that some fatty acid compounds may be effective in controlling bacterial persistence because they are known to benefit host immune systems. This study investigated persister cell formation by pathogens that were exposed to nine fatty acid compounds during antibiotic treatment. We found that three medium chain unsaturated fatty acid ethyl esters (ethyl trans-2-decenoate, ethyl trans-2-octenoate, and ethyl cis-4-decenoate) decreased the level of Escherichia coli persister formation up to 110-fold when cells were exposed to ciprofloxacin or ampicillin antibiotics. RNA sequencing analysis and gene deletion persister studies elucidated that these fatty acids inhibit bacterial persistence by regulating antitoxin HipB. A similar persister cell reduction was observed for pathogenic E. coli EDL933, Pseudomonas aeruginosa PAO1, and Serratia marcescens ICU2-4 strains. This study demonstrates that fatty acid ethyl esters can be used to disrupt bacterial dormancy to combat persistent infectious diseases.
Project description:Cells harbor two systems for fatty acid synthesis, one in the cytoplasm (catalyzed by fatty acid synthase, FASN) and one in the mitochondria (mtFAS). In contrast to FASN, mtFAS is poorly characterized, especially in higher eukaryotes, with the major product(s), metabolic roles, and cellular function(s) being essentially unknown. Here we show that hypomorphic mtFAS mutant mouse skeletal myoblast cell lines display a severe loss of electron transport chain (ETC) complexes and exhibit compensatory metabolic activities including reductive carboxylation. This effect on ETC complexes appears to be independent of protein lipoylation, the best characterized function of mtFAS, as mutants lacking lipoylation have an intact ETC. Finally, mtFAS impairment blocks the differentiation of skeletal myoblasts in vitro. Together, these data suggest that ETC activity in mammals is profoundly controlled by mtFAS function, thereby connecting anabolic fatty acid synthesis with the oxidation of carbon fuels.
Project description:Adipocytes are the primary sites for fatty acid storage, but the synthesis rate of fatty acids is very low. The physiological significance of this phenomenon remains unclear. Here, we show that surplus fatty acid synthesis in adipocytes induces necroptosis and lipodystrophy. Transcriptional activation of FASN elevates fatty acid synthesis, but decreases NADPH level and increases ROS production, which ultimately leads to adipocyte necroptosis. We identify MED20, a subunit of the Mediator complex, as a negative regulator of FASN transcription. Adipocyte-specific male Med20 knockout mice progressively develop lipodystrophy, which is reversed by scavenging ROS. Further, in a murine model of HIV-associated lipodystrophy and a human patient with acquired lipodystrophy, ROS neutralization significantly improves metabolic disorders, indicating a causal role of ROS in disease onset. Our study well explains the low fatty acid synthesis rate in adipocytes, and sheds light on the management of acquired lipodystrophy.
Project description:Angiopoietin-like protein 4 (ANGPTL4, also referred to as Fiaf) has been proposed as a circulating mediator between the gut microbiota and fat storage in adipose tissue. Very little is known about the mechanisms of regulation of ANGPTL4 in the colon. Here we show that transcription and subsequent secretion of ANGPTL4 in human T84 and HT-29 colonocytes is highly induced by physiological concentrations of products of bacterial fermentation, the short-chain fatty acids. Short-chain fatty acids induce ANGPTL4 by activating the nuclear receptor PPARγ, as shown by microarray, transactivation assays, coactivator peptide recruitment assay, and use of PPARγ antagonist. At concentrations required for PPARγ activation and ANGPTL4 induction in colonocytes, SCFA do not stimulate PPARγ in mouse 3T3-L1 and human SGBS adipocytes, suggesting that SCFA act as selective PPARγ modulators (SPPARM), which is supported by coactivator peptide recruitment assay and structural modelling. It can be concluded that 1) SCFA potently stimulate ANGPTL4 synthesis in human colonocytes, and 2) SCFA transactivate and bind to PPARγ by serving as selective PPAR modulators. Our data point to activation of PPARγ as a novel mechanism of gene regulation by SCFA in the colon.
Project description:Unsaturated fatty acids (UFAs) in beef are essential for human health. Long-chain fatty acyl-CoA synthase 1 (ACSL1) is a crucial gene for UFAs synthesis in bovine adipocytes. To assess the protein expression profile during UFAs synthesis, we performed a proteomic analysis of bovine adipocytes by RNA interference and non-interference with ACSL1 using label-free techniques.
Project description:Metabolic remodeling is one of the earliest events that occur during the early differentiation of embryonic stem cells (ESCs), but how these metabolic changes are regulated and participate in the cell differentiation is still largely undissected. Here, we define the fatty acid metabolism as a key player in definitive endoderm (DE) differentiation from human ESCs. During DE differentiation, lipogenesis is decreased while fatty acid β oxidation is enhanced. This dynamic is due to the phosphorylation of lipogenic enzyme acetyl-CoA carboxylase (ACC), which is mediated by AMP-activated protein kinase (AMPK) and inhibits the de novo fatty acid synthesis. More importantly, inhibition of fatty acid synthesis by either its inhibitors or AMPK agonist, significantly promotes the human endoderm differentiation, while blockade of the fatty acid oxidation by genetic manipulation or chemical antagonists impairs the differentiation. The de novo fatty acid synthesis inhibition and fatty acid β oxidation maintaining contribute to the accumulation of cellular acetyl-CoA, which is the essential substrate for protein acetylation. Further study reveals that SMAD3 acetylation and the subsequent subcellular localization exhibit significant change upon interfering fatty acid metabolism. Mechanistically, the accumulation of cellular acetyl-CoA guarantees the acetylation of key transcription factor SMAD3, which further causes the nuclear localization and activation of SMAD signaling pathway to promote DE differentiation. Thus, our current study reveals a fatty acid synthesis/oxidation shift during early differentiation and presents an instructive role of fatty acid metabolism in regulating human early endoderm differentiation.
Project description:transcriptome analysis of enterohemorrhagic E. coli treated with either one of two different concentrations of short chain fatty acid mixes or the corresponding sodium chloride osmolarity control four conditions: 30mM SCFA mix; 30mM NaCl control; 172mM SCFA mix: 172 mM NaCl control. Biological replicates: 4 per group