Project description:Obesity is tightly linked to hepatic steatosis and insulin resistance. One feature of this association is the paradox of selective insulin resistance: insulin fails to suppress hepatic gluconeogenesis but activates lipid synthesis in the liver. How lipid accumulation interferes selectively with some branches of hepatic insulin signaling is not well understood. Here we provide a resource, based on unbiased approaches and established in a simple cell culture system, to enable investigations of the phenomenon of selective insulin resistance. We analyzed the phosphoproteome of insulin-treated human hepatoma cells and identified sites in which palmitate selectively impairs insulin signaling. As an example, we show that palmitate interferes with insulin signaling to FoxO1, a key transcription factor regulating gluconeogenesis, and identify a possible mechanism. This model system, together with our comprehensive characterization of the proteome, phosphoproteome, and lipidome changes in response to palmitate treatment, provides a novel and useful resource for unraveling the mechanisms underlying selective insulin resistance.
Project description:Puberty unmasks or accelerates nephropathies, including the nephropathy of diabetes mellitus (DM). A number of cellular systems implicated in the kidney disease of DM interweave, forming an interdependent functional web. We performed focused microarray analysis to test the hypothesis that one or more genes in the transforming growth factor beta (TGF-β) signaling system would be differentially regulated in male rats depending on the age of onset of DM. Experiment Overall Design: Male rat littermates began the 6-week-protocol at 4 or 14 weeks of age with injection of streptozocin, 65 mg/kg iv, or equal volume of vehicle. 3 days later insulin palmitate or palmitate vehicle pellets were implanted once hyperglycemia was confirmed. Rats received ad lib food and water for 6 weeks and maintained blood glucose levels 350-350 mg/dl in diabetic groups. Kidneys were removed under isoflurane anesthesia. The cortex was rapidly dissected from the medulla and snap-frozen. Cortex was stored at -80 until all rats had completed the protocol. RNA was isolated from renal cortex and the transcriptome analyzed using gene chips with more than 30,000 transcripts. Age-specific effects of DM were demonstrated for 1,760 transcripts. Analysis then focused on 89 genes involved in the TGF-β signaling pathway.
Project description:DNA microarray analysis was performed to investigate the expression of genes in HGF stimulated with palmitate Type 2 diabetes (T2D) is characterized by decreased insulin sensitivity and higher concentrations of free fatty acids (FFAs) in plasma. Among FFAs, saturated fatty acids (SFAs), such as palmitate, have been proposed to promote inflammatory responses. Although many epidemiological studies have shown a link between periodontitis and T2D, little is known about the clinical significance of SFAs in periodontitis. The goal of this study is to demonstrate a potential link between the pathogenesis of periodontitis and SFAs in plasma. HGF were treated with either with 0 (1% Bovine serum albumin) or 100 µM Palmitate for 36 hours (n=2 each).
Project description:In this study we performed an RNA-seq analysis of lipopolysaccharide (LPS) and palmitate (PAL) stimulated THP-1 macrophages to study the gene regulatory mechanisms underlying classical innnate immune response and chronical inflammatory response caused by metabolic stress. This analysis was done to complement single-cell transcriptome analyses of the same cell models.
Project description:Pancreatic beta-cell dysfunction and death are central in the pathogenesis of type 2 diabetes. Saturated fatty acids cause beta-cell failure and contribute to diabetes development in genetically predisposed individuals. Here we used RNA-sequencing to map transcripts expressed in five palmitate-treated human islet preparations, observing 1,325 modified genes. Palmitate induced fatty acid metabolism and endoplasmic reticulum (ER) stress. Functional studies identified novel mediators of adaptive ER stress signaling. Palmitate modified genes regulating ubiquitin and proteasome function, autophagy and apoptosis. Inhibition of autophagic flux and lysosome function contributed to lipotoxicity. Palmitate inhibited transcription factors controlling beta-cell phenotype including PAX4 and GATA6. 59 type 2 diabetes candidate genes were expressed in human islets, and 11 were modified by palmitate. Palmitate modified expression of 17 splicing factors and shifted alternative splicing of 3,525 transcripts. Ingenuity Pathway Analysis of modified transcripts and genes confirmed that top changed functions related to cell death. DAVID analysis of transcription binding sites in palmitate-modified transcripts revealed a role for PAX4, GATA and the ER stress response regulators XBP1 and ATF6. This human islet transcriptome study identified novel mechanisms of palmitate-induced beta-cell dysfunction and death. The data point to crosstalk between metabolic stress and candidate genes at the beta-cell level. 5 human islet of Langerhans preparations examined under 2 conditions (control and palmitate treatment)
Project description:In this study we performed single-cell transcriptome analysis of THP-1 macrophages, stimulated with high levels of free fatty acids (palmitate, PAL) typical for obese adipose tissue microenvironment or lipopolysaccharide (LPS), representing a classical stimulus activating innate immune response. Analysing full transcriptomes of individual cells, we were able to distinguish 3 macrophage transcriptional states and decipher gene regulatory pathways underlying macrophage state identity in both stimulations.
Project description:High-fat diet or exposure to saturated fatty acids affects skeletal muscle growth and function. The aim of the present study was to investigate the effect of palmitate on the transcriptomic profile of mouse C2C12 myoblasts. Global gene expression was evaluated using whole mouse genome oligonucleotide microarrays, and the results were validated through real-time PCR. A total of 4047genes were identified as differentially expressed, including 3492 down-regulated and 555 up-regulated genes during 48-h-exposure to palmitate (0.1 mmol/l). Functional classification showed the involvement of PA-regulated genes in several processes which regulate cell growth. In conclusion, palmitate modifies the expression of genes associated with: i) myoblast responsiveness to hormones and growth factors, ii) cytokine and growth factor expression, and iii) regulation of cell-cell cell-matrix communication. Such alterations can affect myoblast growth and differentiation, however further studies in this field are required. To whom the correspondence should be addressed: Dr K. Grzelkowska-Kowalczyk; e-mail: firstname.lastname@example.org, tel/fax: (48 22) 847 24 52 After scanning of hybridized microarrays, quantitation of slide images was performed using Feature Extraction Software (Agilent) using default parameters and the raw data were exported to GeneSpring GX 12 (Agilent, Santa Clara, CA) and log2 transformed. For identification of genes significantly altered in cell compared with the control normal gene set. Total detected entities were filtered by flags (detected, non detected) and error (coefficient of variation: CV < 50.0 percent) to remove very low signal entities and to select reproducible signal values of entities among the replicated experiments, respectively. In statistical analysis, separated for experiment with myoblasts treated with palmitate acid was used t-test unpaired (p < 0.05) with multiple testing correction: Benjamini-Hochberg <0.05, all significant changes over fold change 1.6 were selected.
Project description:Obesity-induced insulin resistance of the liver is characterised by increased gluconeogenesis, which contributes to elevated blood glucose levels in individuals with type 2 diabetes. Research into how fatty acids induce insulin resistance has commonly focused on the induction of insulin resistance. We hypothesise that by shifting focus to the reversal of an insulin resistant phenotype, novel insights can be made into the mechanisms by which insulin resistance can be overcome. Using global gene and lipid expression profiling, we aimed to identify biological pathways altered in parallel with restoration of palmitate-induced deregulation of glucose production using metformin and sodium salicylate. FAO hepatoma cells were treated with palmitate (0.075mM, 48h) with or without metformin (0.25mM) and sodium salicylate (2mM) in the final 24h of palmitate treatment, and effects on glucose production were determined. Microarray followed by gene set enrichment analysis was performed to investigate pathway regulation. A lipidomic analysis (HPLC-MS/MS) and measurement of secreted bile acids and cholesterol were performed. Reversal of palmitate-induced impairment of glucose production by metformin and sodium salicylate was characterised by down-regulated expression of metabolic pathways regulating acetyl-CoA to cholesterol and bile acid biosynthesis. Total levels of intracellular and secreted cholesterol and bile acids were not different between impaired and restored glucose production. Total intracellular levels of diacylgycerol, triacylglycerol and cholesterol esters increased with palmitate (impaired glucose production), however, these were not further altered with metformin and sodium salicylate (restored glucose production). Six individual lipid species containing 18:0 and 18:1 side-chains were reduced by metformin and sodium salicylate. Widespread lipid metabolism changes induced by the reversal of palmitate-induced deregulation of glucose production with metformin and sodium salicylate were identified. While cholesterol and bile acid levels remained unchanged, the flux through these pathways may in part explain these findings. The identification of lipid species containing 18:0 and 18:1 side chains being regulated alongside changes to glucose production may indicate potential mediators of glucose production and insulin resistance. Three-condition experiment, Vehicle, Palmitate (PA) and Palmitate (PA) + Metformin (Met) + Sodium Sailcylate (NaS) with biological replicates: 8 Vehicle, 20 PA and 20 PA+Met+NaS , independently grown and harvested. One replicate per array.
Project description:A global transcriptomic study enables investigating human skeletal muscle gene targets of palmitate versus oleate and the capacity of oleate to alter palmitate-effects. Overall design: LHCN-M2 myotubes were treated with 0.5 mM palmitate, 0.5 mM oleate or 0.25 mM palmitate plus 0.25 mM oleate (mixture) or not (controls) for 16 h. Changes in gene expression were analyzed by DNA microarray. The experimental design was a loop with 4 biological replicates.