Regulation of lipoprotein lipase mRNA content in 3T3-L1 cells by tumour necrosis factor.
Ontology highlight
ABSTRACT:
SUBMITTER: Cornelius P
PROVIDER: S-EPMC1148772 | biostudies-other | 1988 Feb
REPOSITORIES: biostudies-other
Similar Datasets
Project description:We investigated the mechanism by which the endotoxin-induced macrophage secretory protein cachectin is able to suppress the activity of lipoprotein lipase in 3T3-L1 adipocytes. The loss in activity results from an effect on the synthesis of the enzyme, as determined by a decreased incorporation of [35S]methionine into immunoprecipitable lipoprotein lipase. The results were nearly identical whether crude conditioned medium or a highly purified preparation was utilized as a source of cachectin. [35S]Methionine incorporation into acid-precipitable protein was minimally affected by purified cachectin, suggesting that the suppression of the lipoprotein lipase was not due to a general suppression of protein synthesis. These results, taken together with our previous work, provide additional evidence that cachectin and tumour necrosis factor are functionally identical.
| S-EPMC1147456 | biostudies-other
Project description:Tumour necrosis factor (TNF) has previously been shown to decrease lipoprotein lipase (LPL) activity and mRNA levels in 3T3-L1 cells and in adipose tissue from rats and guinea pigs when injected in vivo, but not to alter LPL activity in human adipocytes incubated in vitro. The effect of recombinant human TNF on LPL activity and mRNA levels in rat epididymal adipose tissue incubated in vitro was examined. LPL activity and mRNA levels fell in adipose tissue taken from fed rats and incubated in Krebs-Henseleit bicarbonate medium with glucose. The addition of insulin and dexamethasone prevented these falls. TNF (400 ng/ml) produced a fall of approx. 50% in LPL activity after 2 h of incubation and of approx. 30% in LPL mRNA levels after 3 h. TNF did not decrease LPL activity in isolated adipocytes. These results demonstrate that rat adipose tissue incubated in vitro is responsive to TNF whereas isolated adipocytes are not.
| S-EPMC1131540 | biostudies-other
Project description:We have used murine 3T3-L1 cells, which differentiate in culture and acquire morphological and biochemical features of mature adipocytes, as a model for studying the expression of cyclic-nucleotide phosphodiesterase (PDE) 3B activity, protein and mRNA during differentiation and during long-term treatment of the cells with tumour necrosis factor alpha (TNF-alpha), a cytokine associated with insulin resistance, and a cAMP analogue, N(6),2'-O-dibutyryl cAMP (dbcAMP). PDE3B activity, protein and mRNA could be detected 4 days after the initiation of differentiation of 3T3-L1 preadipocytes. Treatment of 3T3-L1 adipocytes with 10 ng/ml TNF-alpha for 24 h produced a maximal (50%) decrease in PDE3B activity, protein and mRNA, which was well correlated with both activation of protein kinase A (PKA) and stimulation of lipolysis, presumably reflecting an increase in intracellular cAMP concentration. To investigate the effect of cAMP on PDE3B we treated 3T3-L1 adipocytes with dbcAMP. After 4 h with 0.5 mM dbcAMP, PDE3B activity was decreased by 80%, which was also correlated with a decrease in PDE3B protein and mRNA. This effect was abolished in the presence of N-[2-(bromocinnamylamino)ethyl]-5-isoquinolinesulphonamide] (H-89), a specific PKA inhibitor. We conclude that the lipolytic effect of TNF-alpha involves the down-regulation of PDE3B, which is associated with increased activation of PKA, presumably owing to increased levels of cAMP. In addition, the PKA activation induced by dbcAMP resulted in the down-regulation of PDE3B. These results, which suggest that PDE3B is a novel target for long-term regulation by TNF-alpha and cAMP, could contribute to the understanding of the mechanisms of insulin resistance.
| S-EPMC1220858 | biostudies-other
Project description:Tumour necrosis factor alpha (TNF-alpha) regulates the transport of myo-inositol in 3T3-L1 adipocytes. Treating 3T3-L1 adipocytes with TNF-alpha decreases Na+/myo-inositol co-transporter (SMIT) mRNA levels and myo-inositol accumulation in a concentration-and time-dependent manner. TNF-alpha decreases the V'max for high-affinity myo-inositol transport with little change in the K'm. Studies with actinomycin D suggest that RNA synthesis is required for the TNF-alpha-induced effect on SMIT mRNA levels. In contrast with the effect of TNF-alpha, hyperosmolarity increases SMIT mRNA levels and myo-inositol accumulation in 3T3-L1 adipocytes. Hyperosmolarity increases SMIT gene expression as evidenced by the inhibition of hyperosmotic induction of SMIT mRNA levels by actinomycin D, and of myo-inositol accumulation by actinomycin D and cycloheximide. TNF-alpha and osmotic stress have previously been shown to activate similar signal transduction pathways in mammalian cells. In 3T3-L1 adipocytes, both TNF-alpha and hyperosmolarity increase mitogen-activated protein kinase kinase pathway activity; however, with the possible exception of c-Jun N-terminal kinase, this pathway does not seem to regulate SMIT mRNA levels or myo-inositol accumulation. TNF-alpha activates nuclear factor kappaB (NF-kappaB) in 3T3-L1 adipocytes but, unlike the effect of TNF-alpha on cultured endothelial cells, NF-kappaB does not seem to contribute to the regulation by TNF-alpha of SMIT gene expression in 3T3-L1 adipocytes. Therefore other signal transduction pathways must be considered in the regulation by TNF-alpha of SMIT mRNA levels and activity. Thus TNF-alpha and hyperosmolarity have opposing effects on SMIT mRNA levels and activity in 3T3-L1 adipocytes. Because myo-inositol in the form of phosphoinositides is an important component of membranes and signal transduction pathways, the regulation of myo-inositol metabolism by TNF-alpha might represent another mechanism by which TNF-alpha regulates adipocyte function.
| S-EPMC1219874 | biostudies-other
Project description:In obesity, high levels of tumor necrosis factor ? (TNF?) stimulate lipolysis in adipocytes, leading to hyperlipidemia and insulin resistance. Thiazolidinediones (TZDs), the insulin-sensitizing drugs, antagonize TNF?-induced lipolysis in adipocytes, thereby increasing insulin sensitivity in diabetes patients. The cellular target of TZDs is peroxisome proliferator-activated receptor ? (PPAR?), a nuclear receptor that controls many adipocyte functions. As a transcription factor, PPAR? is closely modulated by coregulators, which include coactivators and corepressors. Previous studies have revealed that in macrophages, the insulin-sensitizing effect of PPAR? may involve suppression of proinflammatory gene expression by recruiting the corepressor complex that contains corepressors and histone deacetylases (HDACs). Therefore, we investigated whether the corepressor complex is involved in TZD-mediated suppression of TNF?-induced lipolysis in 3T3-L1 adipocytes. Trichostatin A (TSA), a pan HDAC inhibitor (HDACI) that inhibits class I and II HDACs, was used to examine the involvement of HDACs in the actions of TZDs. TSA alone increased basal lipolysis and attenuated TZD-mediated suppression of TNF?-induced lipolysis. Increased basal lipolysis may in part result from class I HDAC inhibition because selective class I HDACI treatment had similar results. However, attenuation of TZD-mediated TNF? antagonism may be specific to TSA and related hydroxamate-based HDACI rather than to HDAC inhibition. Consistently, corepressor depletion did not affect TZD-mediated suppression. Interestingly, TSA treatment greatly reduced PPAR? levels in differentiated adipocytes. Finally, extracellular signal-related kinase 1/2 (ERK1/2) mediated TNF?-induced lipolysis, and TZDs suppressed TNF?-induced ERK phosphorylation. We determined that TSA increased basal ERK phosphorylation, and attenuated TZD-mediated suppression of TNF?-induced ERK phosphorylation, consistent with TSA's effects on lipolysis. These studies suggest that TSA, through down-regulating PPAR?, attenuates TZD-mediated suppression of TNF?-induced ERK phosphorylation and lipolysis in adipocytes.
| S-EPMC3739734 | biostudies-literature
Project description:In 3T3-L1 adipocytes, glutamine synthetase (GS; EC 6.3.1.2) is subject to regulation by dexamethasone, insulin and dibutyryl cyclic AMP (Bt2cAMP). Dexamethasone increases GS-mRNA content and GS-gene transcription, whereas insulin and Bt2cAMP prevent these increases. The effects of these modulators on the control of GS-mRNA stability were investigated. We report here that GS mRNA has a half-life of about 110 min. Bt2cAMP increases GS-mRNA degradation by greater than 2-fold (half-life 50 min), whereas insulin or dexamethasone have little effect on GS-mRNA stability. Down-regulation of GS-gene expression by Bt2cAMP will involve a co-ordinate response at the level of gene transcription and mRNA stability. However, the molecular mechanisms by which insulin and dexamethasone regulate GS-gene expression in cultured adipocytes remains to be elucidated.
| S-EPMC1131270 | biostudies-other
Project description:The effect of recombinant human tumour necrosis factor-alpha (TNF-alpha) on synthesis, activity and secretion of lipoprotein lipase (LPL) was examined using a human osteosarcoma cell line, osteosarcoma Takase (OST). Treatment of OST cells with TNF-alpha decreased LPL synthesis, resulting in a decrease in expression of activity and secretion of LPL. When OST cells were incubated with glycerol tri[1-14C]palmitate, TNF-alpha decreased dose- and time-dependently the production of 14CO2 and the amounts of radioactivity incorporated into cellular triacylglycerol and phospholipid. The similar reduction of synthesis and activity of LPL as suppression of CO2 production and cellular lipid synthesis indicated that the suppression of 14CO2 production and 14C-labelled lipid synthesis was secondary. TNF-alpha also suppressed expression of proliferating cell nuclear antigen, indicating that it had an anti-proliferative activity on OST cells. The findings suggest that one cause of the anti-proliferative activity of TNF-alpha is the suppression of the LPL-mediated supply of non-esterified fatty acids as an energy source for growth.
| S-EPMC1217422 | biostudies-other
Project description:BACKGROUND: Adipogenesis is a complex process, in which immature pre-adipocytes change morphology, micro-anatomy and physiology to become mature adipocytes. These store and accumulate fat and release diverse hormones. Massive changes in protein content and protein composition of the transforming cell take place within a short time-frame.In a previous study we analyzed changes in the abundance of free and polysomal, i.e. ribosome bound, RNAs in the first hours of adipogenesis in the murine cell line 3T3-L1. Here we analyze changes of mRNA levels and their potential contribution to the changing protein pool by determination of mRNA levels and ribosome binding to mRNAs in 3T3-L1 cells stimulated for adipogenesis. We grouped mRNA species into categories with respect to up- or down-regulated transcription and translation and analyzed the groups regarding specific functionalities based on Gene Ontology (GO). RESULTS: A shift towards up-regulation of gene expression in early adipogenesis was detected. Genes up-regulated at the transcriptional (TC:up) and translational (TL:up) level (TC:up/TL:up) are very likely involved in control and logistics of translation. Many of them are known to contain a TOP motif. In the TC:up/TL:unchanged group we detected most of the metal binding proteins and metal transporters. In the TC:unchanged/TL:up group several factors of the olfactory receptor family were identified, while in TC:unchanged/TL:down methylation and repair genes are represented. In the TC:down/TL:up group we detected many signaling factors. The TC:down/TL:unchanged group mainly consists of regulatory factors. CONCLUSIONS: Within the first hours of adipogenesis, changes in transcriptional and translational regulation take place. Notably, genes with a specific biological or molecular function tend to cluster in groups according to their transcriptional and translational regulation.
| S-EPMC4039748 | biostudies-literature
Project description:The beneficial effect of n-3 fatty acids can be related to anti-inflammatory properties. The aim of the study was to analyzed the effect of eicosapentaenoic acid (EPA) on 3T3-L1 cells (murine embryonic fibroblasts‒preadipocytes) activated with inflammatory factors (IF). Cells were incubated with 50 µmol of EPA for 48 h, and then activated with lipopolysaccharide (LPS) or tumor necrosis factor-α (TNF-α). The level of cycloxygenase-2 (Prostaglandin-Endoperoxide Synthase 2, PTGS2, COX-2), cytosolic prostaglandin synthase E2 (cPGES), fatty acid binding protein 4 (FABP4), toll-like receptor 4 (TLR4), glucose receptor type 4 (GLUT-4), and cannabinoid receptor 2 (CB2) was determined using Western blot analysis. The phospholipase A2 (Pla2g4a), and prostaglandin-Endoperoxide Synthase 2 (Ptgs2) gene expression was analyzed by real-time qPCR. After EPA and IF activation, a significant decrease in the COX-2, cPGES, and TRL4 protein levels was observed. Incubation of cells with EPA and IF resulted in a decrease in Ptgs2 and an increase in the Pla2g4a gene. A significant increase in the CB2 protein was observed in adipocytes co-treated with EPA and IF. The results indicated an anti-inflammatory properties of EPA. Interestingly, the activation of the GLUT4 receptor by EPA suggests an unique role of this FA in the regulation of the adipocyte metabolism and prevention of insulin resistance.
| S-EPMC8472223 | biostudies-literature
Project description:Lipoprotein lipase (LPL) plays a major role in the lipid homeostasis mainly by mediating the intravascular lipolysis of triglyceride rich lipoproteins. Impaired LPL activity leads to the accumulation of chylomicrons and very low-density lipoproteins (VLDL) in plasma, resulting in hypertriglyceridemia. While low-density lipoprotein cholesterol (LDL-C) is recognized as a primary risk factor for atherosclerosis, hypertriglyceridemia has been shown to be an independent risk factor for cardiovascular disease (CVD) and a residual risk factor in atherosclerosis development. In this review, we focus on the lipolysis machinery and discuss the potential role of triglycerides, remnant particles, and lipolysis mediators in the onset and progression of atherosclerotic cardiovascular disease (ASCVD). This review details a number of important factors involved in the maturation and transportation of LPL to the capillaries, where the triglycerides are hydrolyzed, generating remnant lipoproteins. Moreover, LPL and other factors involved in intravascular lipolysis are also reported to impact the clearance of remnant lipoproteins from plasma and promote lipoprotein retention in capillaries. Apolipoproteins (Apo) and angiopoietin-like proteins (ANGPTLs) play a crucial role in regulating LPL activity and recent insights into LPL regulation may elucidate new pharmacological means to address the challenge of hypertriglyceridemia in atherosclerosis development.
| S-EPMC8301479 | biostudies-literature