Transcription profiling of mouse LXRalpha null, LXRbeta null mutants reveals liver X receptor beta is the dominant LXR subtype in skeletal muscle
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
SUBMITTER: Guido Hooiveld
PROVIDER: E-MTAB-61 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Liver X receptors (LXRs) are important regulators of cholesterol, lipid and glucose metabolism and have been extensively studied in liver, macrophages and adipose tissue. However, their role in skeletal muscle is not yet fully elucidated and the functional role of each of the LXRM-NM-1 and LXRM-NM-2 subtypes in skeletal muscle is at present unknown. To study the importance of each of the receptor subtypes, myotube cultures derived from wild type (WT), LXRM-NM-1 and LXRM-NM-2 knockout (KO) mice were established. The present study shows that treatment with the unselective LXR agonist T0901317 increased mRNA levels of LXR target genes such as sterol regulatory element-binding transcription factor 1 (SREBF1), fatty acid synthase (FASN), stearoyl-CoA desaturase 1 (SCD1) and ATP-binding cassette transporter A1 (ABCA1) in myotubes established from WT and LXRM-NM-1 KO mice. However, only minor changes in expression level were observed for these genes after treatment with T0901317 in myotubes from LXRM-NM-2 KO mice. Gene expression analysis using Affymetrix NuGO Genechip arrays showed that few other genes than the classical, well known LXR target genes were regulated by LXR in skeletal muscle. Furthermore, functional studies using radiolabeled substrates showed that treatment with T0901317 increased lipogenesis and apoA1 dependent cholesterol efflux, in myotubes from WT and LXRM-NM-1 KO mice, but not LXRM-NM-2 KO mice. The data suggest that the lipogenic effects of LXRs, as well as the LXR-stimulated cholesterol efflux, are mainly mediated by LXRM-NM-2 in skeletal muscle. To study the importance of each of the receptor subtypes, myotube cultures derived from wild type (WT), LXRa and LXRb knockout (KO) mice were established. Sixteen samples were examined. Half the samples were treated with the unselective LXR agonist T0901317.
2010-03-30 | E-GEOD-13192 | biostudies-arrayexpress
Project description:Liver X receptors (LXRs) are important regulators of cholesterol, lipid and glucose metabolism and have been extensively studied in liver, macrophages and adipose tissue. However, their role in skeletal muscle is not yet fully elucidated and the functional role of each of the LXRα and LXRβ subtypes in skeletal muscle is at present unknown. To study the importance of each of the receptor subtypes, myotube cultures derived from wild type (WT), LXRα and LXRβ knockout (KO) mice were established. The present study shows that treatment with the unselective LXR agonist T0901317 increased mRNA levels of LXR target genes such as sterol regulatory element-binding transcription factor 1 (SREBF1), fatty acid synthase (FASN), stearoyl-CoA desaturase 1 (SCD1) and ATP-binding cassette transporter A1 (ABCA1) in myotubes established from WT and LXRα KO mice. However, only minor changes in expression level were observed for these genes after treatment with T0901317 in myotubes from LXRβ KO mice. Gene expression analysis using Affymetrix NuGO Genechip arrays showed that few other genes than the classical, well known LXR target genes were regulated by LXR in skeletal muscle. Furthermore, functional studies using radiolabeled substrates showed that treatment with T0901317 increased lipogenesis and apoA1 dependent cholesterol efflux, in myotubes from WT and LXRα KO mice, but not LXRβ KO mice. The data suggest that the lipogenic effects of LXRs, as well as the LXR-stimulated cholesterol efflux, are mainly mediated by LXRβ in skeletal muscle.
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Project description:Metabolically healthy skeletal muscle is characterized by the ability to switch easily between glucose and fat oxidation, whereas loss of this ability seems to be related to insulin resistance. The aim of this study was to investigate whether different fatty acids (FAs) and the LXR ligand T0901317 affected metabolic switching in human skeletal muscle cells (myotubes). Pretreatment of myotubes with eicosapentaenoic acid (EPA) increased suppressibility, the ability of glucose to suppress FA oxidation, and metabolic flexibility, the ability to increase FA oxidation when changing from “fed” to “fasted” state. Adaptability, the capacity to increase FA oxidation with increasing FA availability, was increased after pretreatment with EPA, linoleic acid (LA) and palmitic acid (PA). T0901317 counteracted the effect of EPA on suppressibility and adaptability, but did not affect these parameters alone. EPA itself accumulated less, however, EPA, LA, OA and T0901317 increased the number of lipid droplets (LDs) in myotubes, whereas LD size and mitochondria amount were independent of pretreatment. Microarray analysis showed that EPA regulated more genes than the other FAs. Some pathways involved in carbohydrate metabolism were induced only by EPA. The present study suggests a possible favorable effect of EPA on skeletal muscle metabolic switching and glucose utilization. Keywords: Analysis of target gene regulation by using microarrays. Primary human myotubes, derived from 3 healthy, female donors, were preincubated with different fatty acids (oleic acid [OA], palmitic acid [PA], eicosapentaenoic acid [EPA] or linoleic acid [LA], each at 100 µM) or bovine serum albumin [BSA] (40 µM) for 24 h.
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Project description:Metabolically healthy skeletal muscle is characterized by the ability to switch easily between glucose and fat oxidation, whereas loss of this ability seems to be related to insulin resistance. The aim of this study was to investigate whether different fatty acids (FAs) and the LXR ligand T0901317 affected metabolic switching in human skeletal muscle cells (myotubes). Pretreatment of myotubes with eicosapentaenoic acid (EPA) increased suppressibility, the ability of glucose to suppress FA oxidation, and metabolic flexibility, the ability to increase FA oxidation when changing from “fed” to “fasted” state. Adaptability, the capacity to increase FA oxidation with increasing FA availability, was increased after pretreatment with EPA, linoleic acid (LA) and palmitic acid (PA). T0901317 counteracted the effect of EPA on suppressibility and adaptability, but did not affect these parameters alone. EPA itself accumulated less, however, EPA, LA, OA and T0901317 increased the number of lipid droplets (LDs) in myotubes, whereas LD size and mitochondria amount were independent of pretreatment. Microarray analysis showed that EPA regulated more genes than the other FAs. Some pathways involved in carbohydrate metabolism were induced only by EPA. The present study suggests a possible favorable effect of EPA on skeletal muscle metabolic switching and glucose utilization. Keywords: Analysis of target gene regulation by using microarrays.
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Project description:Skeletal muscle mediates the beneficial effects of exercise, thereby improving insulin sensitivity and reducing the risk for type 2 diabetes. Current skeletal-muscle-models in vitro are incapable of fully recapitulating its physiological functions especially regarding exercise. Supplementation of IGF1, a growth factor secreted by myofibers in vivo, might help to overcome these limitations. Primary human CD56-positive myoblasts were differentiated into myotubes in the presence/absence of IGF1 in serum-free medium for 10 days. Daily collected samples were analyzed by proteomics, qRT-PCR and myotube contractibility via electrical-pulse-stimulation (EPS). Mitochondrial respiration and glucose uptake were measured. IGF1-supported differentiation formed thicker multinucleated myotubes showing physiological contraction upon EPS following day 6 while myotubes without IGF1 were almost incapable of contraction. IGF1-treatment upregulated particularly muscle-specific proteins that contribute to myofibril and sarcomere assembly, striated muscle contraction, and ATP production. Elevated PPARGC1A, MYH7 and reduced MYH1/2 suggest a switch towards a more oxidative phenotype in line with elevated mitochondrial respiration. IGF1-treatment also upregulated expression of GLUT4 and increased insulin-dependent glucose uptake. To conclude, utilizing IGF1, we engineered human myotubes that recapitulate the physiological traits of skeletal muscle in vivo vastly superior to established protocols. This novel model enables investigation of exercise on a molecular level, drug screening and interorgan-crosstalk by transfer to organ-on-chip.
2024-10-17 | PXD043200 | Pride
Project description:Activation of liver X receptors (LXRs) with synthetic agonists promotes reverse cholesterol transport and protects against atherosclerosis in mouse models. Most synthetic LXR agonists also cause marked hypertriglyceridemia by inducing the expression of SREBP1c and downstream genes that drive fatty acid biosynthesis. Recent studies demonstrated that desmosterol, an intermediate in the cholesterol biosynthetic pathway that suppresses SREBP processing by binding to SCAP, also binds and activates LXRs and is the dominant LXR ligand in macrophage foam cells. Here, we explore the potential of increasing endogenous desmosterol production or mimicking its activity as a means of inducing LXR activity while simultaneously suppressing SREBP1c induced hypertriglyceridemia. Unexpectedly, while desmosterol strongly activated LXR target genes and suppressed SREBP pathways in mouse and human macrophages, it had almost no activity in mouse or human hepatocytes in vitro. We further demonstrate that sterol-based selective modulators of LXRs have biochemical and transcriptional properties predicted of desmosterol mimetics and selectively regulate LXR function in macrophages in vitro and in vivo. These studies thereby reveal cell-specific discrimination of endogenous and synthetic regulators of LXRs and SREBPs, providing a molecular basis for dissociation of LXR functions in macrophages from those in liver that lead to hypertriglyceridemia.
2018-02-12 | GSE90815 | GEO
Project description:The objective of the study was to figure out the impact of LXR signaling on human macrophages. Primary human macrophages in an early differentiating and a mature differentiation state were treated with the LXR agonist T091317 for 4 and 24 h and transcriptome-wide expression analysis were performed. As LXRa is highly induced during macrophage differentiation and 68% of all LXRs targets change their expression during this process, we suggest that LXRs have essential functions in macrophage development. More than 238 genes are regulated in early as well as mature macrophages by activation of LXRs; most of them are up-regulated. LXRs administrate differentiation state specific as well as common macrophages functions related primarily to lipid homeostasis, immune response and cell fate. Interestingly, almost only genes related to lipid and cholesterol metabolism are overrepresented among early induced genes, whereas genes related to immune functions respond later, implying the existence of indirect mechanisms of control. Furthermore, in early differentiating macrophages cell proliferation and cell death associated genes are induced after 24 h of LXR activation, whereas in mature macrophages, showing high LXRa expression, the same functional cluster respond far earlier (4 h) after LXR ligand treatment. In conclusion, our data suggest that LXRs are modulators of macrophage differentiation, operating principally as positive transcriptional regulators of genes involved in lipid and cholesterol metabolism and by this indirectly influencing the immunophenotype of macrophages. CD14 positive cells of healthy donors were isolated by magnetic separation and differentiated in the presence of human serum to macrophages. At an early differentiating state (16 h after isolation) and at in mature differentiating state (day 11 after isolation) the cells were treated with the synthetical LXR agonist T091317 respective its solvent DMSO for 4 and 24 h. RNA was isolated and a whole genome microarray was performed.
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Project description:The objective of the study was to figure out the impact of LXR signaling on human macrophages. Primary human macrophages in an early differentiating and a mature differentiation state were treated with the LXR agonist T091317 for 4 and 24 h and transcriptome-wide expression analysis were performed. As LXRa is highly induced during macrophage differentiation and 68% of all LXRs targets change their expression during this process, we suggest that LXRs have essential functions in macrophage development. More than 238 genes are regulated in early as well as mature macrophages by activation of LXRs; most of them are up-regulated. LXRs administrate differentiation state specific as well as common macrophages functions related primarily to lipid homeostasis, immune response and cell fate. Interestingly, almost only genes related to lipid and cholesterol metabolism are overrepresented among early induced genes, whereas genes related to immune functions respond later, implying the existence of indirect mechanisms of control. Furthermore, in early differentiating macrophages cell proliferation and cell death associated genes are induced after 24 h of LXR activation, whereas in mature macrophages, showing high LXRa expression, the same functional cluster respond far earlier (4 h) after LXR ligand treatment. In conclusion, our data suggest that LXRs are modulators of macrophage differentiation, operating principally as positive transcriptional regulators of genes involved in lipid and cholesterol metabolism and by this indirectly influencing the immunophenotype of macrophages.
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2016-03-07 | GSE59031 | GEO