Project description:Cutibacterium acnes (C. acnes) is a ubiquitous skin commensal bacterium that is generally well tolerated by the immune system. Different strain-types of C. acnes have been reported to be enriched on patients with acne. To understand if these strain-types contribute to skin inflammation, we generated a library of over 200 C. acnes isolates from skin swabs of healthy and acne subjects and assessed their strain-level identity and inflammatory potential. Phylotype II K-type strains were more frequent on healthy and acne non-lesional skin compared to lesional. Phylotype IA-1 C-type strains were dominant on acne lesional skin but absent from healthy. Measurement of host cytokine responses from C. acnes supernatant revealed neither strain-type nor skin-type association predicted inflammatory potential. However, differential proinflammatory responses were induced from identical strain-types, but these differences were not attributable to protease, short chain fatty acid or porphyrin production. Instead, whole genome sequencing revealed the presence of a linear plasmid in high inflammatory strain-types. Intradermal injection of C. acnes in mouse skin revealed a plasmid-associated inflammatory response in dermal fibroblasts, revealed by single-cell RNA sequencing. We conclude that C. acnes strain-type is not sufficient to predict inflammation but other virulence factors including a plasmid may contribute to disease.
Project description:The pathogenesis of acne has been linked to multiple factors such as increased sebum production, inflammation, follicular hyperkeratinization, and the action of Propionibacterium acnes within the follicle. 13-cis Retinoic Acid (13-cis RA, isotretinoin) is the most potent agent in acne treatment. Surprisingly, its mechanism of action in acne is still unknown. Gene expression profiling of skin from 8 patients treated with isotretinoin was performed to gain insights into its mechanism of action. Skin biopsies were obtained from the patients at baseline and at 8 weeks isotretinoin treatment. Gene array expression profiling was conducted using Affymetrix HG-U133A 2.0 arrays in order to examine changes in gene expression as a result of treatment. After treatment, 784 genes were significantly changed: 197 up-regulated and 587 down-regulated. The majority of genes that were up-regulated at 8 weeks encode structural proteins of the extracellular matrix such as collagens, fibulin and fibronectin. The preponderance of genes that were down-regulated at 8 weeks are involved in the metabolism of steroids, cholesterol and fatty acids. Experiment Overall Design: Total 16 chips: 8 baseline/before isotretinoin and 8 after 8 weeks isotretinoin treatment.
Project description:The beneficial effects of dietary long-chain (LC) n-3 polyunsaturated fatty acids (PUFA) in the prevention and/or treatment of some metabolic disorders result largely from their capacity to regulate the transcription level of many genes involved in metabolic and physiological homeostasis, especially in the liver. In this respect, they are known to bind and activate the Peroxisome Proliferator-Activated Receptor alpha (PPARalpha). The precursor of LC-PUFA, a-linoleic acid (ALA, C18:3 n-3) share some beneficial metabolic effects with its LC derivatives, however its role in gene regulation is poorly documented. Here, we analysed the hepatic transcriptome of mice fed for 5 weeks diets rich in either saturated FA from palm oil (PALM group) or ALA from linseed oil (LIN group). This modification of dietary fatty acid composition in a context of a high fat diet had a subtle but significant effect on the hepatic transcriptome. We identified mainly a group of genes that were upregulated in the LIN vs the PALM group and that include several well-known PPARalpha target genes involved in lipid and xenobiotic metabolism. Liver gene expression was measured in male C57BL/6J mice fed during 5 weeks a high fat diet (51% energy from fat) containing palm oil, rich in saturated fatty acids (n=10) or linseed oil, rich in 18:3 n-3 (n=8)
Project description:Nutrient limitation in the microenvironment of poorly perfused tumors constrains the metabolism of cancer cells. Identifying these microenvironmental constraints can provide new insight into the nutritional biochemistry of tumors and reveal metabolic liabilities of cancer cells. We have found that limitation of arginine in pancreatic cancers inhibits fatty acid synthesis by suppressing the lipogenic transcription factor SREBP1. SREBP1-driven fatty acid synthesis produces saturated and monounsaturated fatty acids. Producing these fatty acids enables cells to maintain a balance of differently saturated fatty acids needed for lipid homeostasis, even upon exposure to environments enriched in one specific class of fatty acids. Given the constraints on lipid synthesis in the microenvironment, we asked if pancreatic cancers are sensitive to exposure to fats with imbalanced levels of saturated and unsaturated fats. We found microenvironmental constraints on lipid synthesis sensitize pancreatic cancer cells and tumors to exposure to fat sources that are enriched in polyunsaturated fatty acids. Thus, amino acid restriction in the tumor microenvironment constrains lipid metabolism in pancreatic cancer, which renders pancreatic tumors incapable of maintaining lipid homeostasis upon exposure to polyunsaturated-enriched fats.
Project description:Necroptosis is a caspase-independent form of regulated cell death that is characterized by membrane permeabilization and rupture. This membrane rupture is responsible for the inflammatory properties of necroptosis and is critical for disease states involving this process. In efforts to understand how lipids might contribute to necroptosis, we previously showed that saturated very long chain fatty acids (VLCFAs) are functionally involved in this process, potentially through protein fatty acylation. Here we define the scope of protein acylation by saturated VLCFAs during necroptosis using a clickable lipid analog and IonStar quantitative proteomics.As a result, a total of 1672 proteins were quantified with high precision and no missing data across samples in the same condition. 1267 were detected with higher abundances in control cells and 405 were detected with higher abundance in necroptotic conditions.
Project description:When macrophages are activated by sensing bacterial lipopolysaccharides (LPS), they greatly increase their motility, mRNA synthesis and protein production. Most of the ATP needed for these responses is derived from the uptake and catabolism of glucose, a relatively inefficient ATP source. Although the stimulated cells also increase their uptake of free fatty acids, they store a large fraction as triglycerides (TAG). We report here that both Toll-like receptor 4 (TLR4) and TLR2 agonists stimulate prolonged TAG retention by primary murine and human macrophages. Agonist-induced TAG storage lasted at least 72-96 hrs in vitro and was associated with increases in fatty acid (FA) uptake, FA esterification, and FA incorporation into TAG; FA oxidation decreased. The results of expression and inhibitor studies support a prominent role for increases in long chain acyl CoA synthase 1 (ACSL1) and diacylglycerol acyltransferase-2 (DGAT2) during the sustained response to TLR2/4 activation; decreases in adipose triglyceride lipase (ATGL, Pnpla2) and monoacylglycerol lipase (MgII) may also contribute. Stimulated murine macrophages that retained TAG carried out phagocytosis more effectively and were protected from saturated fatty acid-induced cell death (lipotoxicity). TLR agonist-induced TAG retention in macrophages is thus an active, sustained process that may have important adaptive functions. It may also contribute to the persistence of lipid-laden macrophages in infected tissues, host susceptibility to some microbial pathogens, and the pathogenesis of atherosclerosis. RNA from macrophage loaded with Fatty Acids, stimulated with bacterial lipopolysaccharides (LPS), or both compared to untreated controls (FA, LPS, FA+LPS, untreated). Replicates from 4 independent experiments.
Project description:Prolonged exposure to a high-fat diet (HFD) exacerbates intestinal disease pathology, yet the early events preceding the development of gut inflammation remain poorly understood. Here we show that within 48 hours, HFD impairs intestinal group 3 innate lymphoid cells (ILC3) and their capacity to produce interleukin-22 (IL-22), critical for maintaining gut homeostasis. This loss of function was associated with rapid dysbiosis, increased gut permeability, and reduced production of antimicrobial peptides, mucus, and tight junction proteins. While saturated fatty acids metabolized through oxidation impaired ILC3 function, unsaturated fatty acids sustained IL-22 secretion by ILC3 through the formation of lipid droplets using DGAT enzymes. Upon inflammation, saturated fatty acids significantly impaired IL-22 production by ILC3 and increased the susceptibility of the gut to injury. Our findings reveal the differential acute impact of saturated and unsaturated fatty acids on gut homeostasis through distinct metabolic pathways in ILC3.