PPARgamma activation in adipocytes is sufficient for systemic insulin sensitization.
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ABSTRACT:
SUBMITTER: Sugii S
PROVIDER: S-EPMC2794650 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Obesity and insulin resistance, the cardinal features of metabolic syndrome, are closely associated with a state of low-grade inflammation. In adipose tissue chronic overnutrition leads to macrophage infiltration, resulting in local inflammation that potentiates insulin resistance. For instance, transgenic expression of Mcp1 (also known as chemokine ligand 2, Ccl2) in adipose tissue increases macrophage infiltration, inflammation and insulin resistance. Conversely, disruption of Mcp1 or its receptor Ccr2 impairs migration of macrophages into adipose tissue, thereby lowering adipose tissue inflammation and improving insulin sensitivity. These findings together suggest a correlation between macrophage content in adipose tissue and insulin resistance. However, resident macrophages in tissues display tremendous heterogeneity in their activities and functions, primarily reflecting their local metabolic and immune microenvironment. While Mcp1 directs recruitment of pro-inflammatory classically activated macrophages to sites of tissue damage, resident macrophages, such as those present in the adipose tissue of lean mice, display the alternatively activated phenotype. Despite their higher capacity to repair tissue, the precise role of alternatively activated macrophages in obesity-induced insulin resistance remains unknown. Using mice with macrophage-specific deletion of the peroxisome proliferator activated receptor-gamma (PPARgamma), we show here that PPARgamma is required for maturation of alternatively activated macrophages. Disruption of PPARgamma in myeloid cells impairs alternative macrophage activation, and predisposes these animals to development of diet-induced obesity, insulin resistance, and glucose intolerance. Furthermore, gene expression profiling revealed that downregulation of oxidative phosphorylation gene expression in skeletal muscle and liver leads to decreased insulin sensitivity in these tissues. Together, our findings suggest that resident alternatively activated macrophages have a beneficial role in regulating nutrient homeostasis and suggest that macrophage polarization towards the alternative state might be a useful strategy for treating type 2 diabetes.
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Project description:Emerging evidence indicates that epigenetic mechanisms like DNA methylation directly contribute to metabolic regulation. For example, we previously demonstrated that de novo DNA methyltransferase Dnmt3a plays a causal role in the development of adipocyte insulin resistance. Recent studies suggest that DNA demethylation plays an important role in the developmental process of adipocytes. However, little is known about whether DNA demethylase ten-eleven translocation (TET) proteins regulate the metabolic functions of adipocytes.MethodsThe expression of Tet genes was assessed in the fractionated adipocytes of chow- and high fat diet-fed C57/Bl6 mice using qPCR and western blotting. The effect of Tet2 gain- or loss-of-function in fully mature 3T3-L1 adipocytes in the presence/absence of Rosiglitazone (Rosi) and TNF-α on insulin sensitivity was using the insulin-stimulated glucose uptake and insulin signaling assays. Gene expression and DNA methylation analyses of PPARγ target genes was performed in the same setting. In addition, PPARγ reporter assays, co-immunoprecipitation assays, PPARγ ChIP-PCR analyses were performed.ResultsWe found that adipose expression of TET2, alone among its family members, was significantly reduced in diet-induced insulin resistance. TET2 gain-of-function was sufficient to promote insulin sensitivity while loss-of-function was necessary to facilitate insulin sensitization in response to the PPARγ agonist Rosiglitazone (Rosi) in cultured adipocytes. Consistent with this, TET2 was required for Rosi-dependent gene activation of certain PPARγ targets accompanied by changes in DNA demethylation at the promoter regions. Furthermore, TET2 was necessary to sustain PPARγ binding to target loci upon activation with Rosi via physical interaction with PPARγ.ConclusionsOur data demonstrate that TET2 works as an epigenetic regulator of Rosi-mediated insulin sensitization and transcriptional regulation in adipocytes.
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Project description:Objective Olanzapine and Aripiprazole are widely used second-generation antipsychotic drugs. Olanzapine, more than Aripiprazole, leads to considerable metabolic side effects including obesity and diabetes. While the underlying mechanisms are not fully understood, these side effects are likely associated with mild inflammation in the metabolic organs. An in vitro model that accurately recapitulates the metabolic impact of olanzapine and aripiprazole should be useful to elucidate the underlying mechanisms. Methods We established co-cultures of matured adipocytes derived from the human SGBS cell line and the THP-1 human monocytic cell-derived or primary macrophages to explore the effects of both drugs on the response to insulin. Results Olanzapine, but not aripiprazole induced insulin resistance in SGBS adipocytes only when co-cultured with THP-1 or primary macrophages, polarized either into M0, M1 or M2. Noteworthy, M2 macrophages induced olanzapine-dependent insulin resistance in the absence of induction of pro-inflammatory cytokines. Insulin resistance by olanzapine was stronger than induced by high concentration of pro-inflammatory cytokines even in combinations, suggesting the contribution of factors other than the classical inflammatory cytokines to promote insulin resistance in adipocytes by olanzapine. Conclusion Macrophage/adipocyte co-cultures recapitulate the features of olanzapine-induced insulin resistance and implicate the existence of yet unknown factors in mediating this effect. Highlights • Olanzapine has no direct effect on insulin signalling in adipocytes.• Olanzapine compromises insulin signalling in adipocytes by affecting macrophage secretome.• Naïve, M1 and M2 macrophages are affected by Olanzapine.• The metabolic effects of Olanzapine are recapitulated in co-cultures of SGBS and THP-1 cell lines.• Unkown secreteable factors are presumed to be involved in debilitating insulin signaling by Olanzapine.
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Project description:Insulin resistance is a major risk factor for metabolic diseases such as Type 2 diabetes. Although the underlying mechanisms of insulin resistance remain elusive, oxidative stress is a unifying driver by which numerous extrinsic signals and cellular stresses trigger insulin resistance. Consequently, we sought to understand the cellular response to oxidative stress and its role in insulin resistance. Using cultured 3T3-L1 adipocytes, we established a model of physiologically-derived oxidative stress by inhibiting the cycling of glutathione and thioredoxin, which induced insulin resistance as measured by impaired insulin-stimulated 2-deoxyglucose uptake. Using time-resolved transcriptomics, we found?>?2000 genes differentially-expressed over 24?hours, with specific metabolic and signalling pathways enriched at different times. We explored this coordination using a knowledge-based hierarchical-clustering approach to generate a temporal transcriptional cascade and identify key transcription factors responding to oxidative stress. This response shared many similarities with changes observed in distinct insulin resistance models. However, an anti-oxidant reversed insulin resistance phenotypically but not transcriptionally, implying that the transcriptional response to oxidative stress is insufficient for insulin resistance. This suggests that the primary site by which oxidative stress impairs insulin action occurs post-transcriptionally, warranting a multi-level 'trans-omic' approach when studying time-resolved responses to cellular perturbations.
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Project description:Cellular and tissue defects associated with insulin resistance are coincident with transcriptional abnormalities and are improved after insulin sensitization with thiazolidinedione (TZD) PPAR? ligands. We transcriptionally profiled 364 biopsies gathered from 72 human subjects harvested before and after hyperinsulinemic-euglycemic clamp, at baseline and after three-month TZD treatment. Subjects range from insulin-sensitive to insulin-resistant. Insulin resistant subjects responded to TZD treatment with varied improvements in insulin sensitivity, thus they were ranked by their degree of TZD response to define responder and non-responder subgroups. Skeletal muscle biopsies were obtained from vastus lateralis before and after hyperinsulinemic-euglycemic clamp, at baseline and after three-month TZD treatment. Adipose tissue biopsies were obtained from abdominal subcutaneous before clamp, at baseline and after three-month TZD treatment. *** CEL files not provided for 40 Samples. ***
2010-05-17 | E-GEOD-13070 | biostudies-arrayexpress
Project description:The effects of LXR stimulation by GW3965 treatment on global mRNA and miRNA expression in primary human in vitro differentiated adipocytes was investigated using microarray profiling. Preadipocytes were isolated from human adipose tissue obtained from healthy subjects and differentiated in vitro. Around day 11 of differentiation cells were treated with the Liver X Receptor agonist GW3865 for 24 h and lysed. Total RNA as prepared and hybridised biotinylated complementary RNA to Gene 1.0 ST Arrays using standardized protocols (Affymetrix Inc., Santa Clara, CA). The GeneChip Operating Software Version 1.4 was used for analysis. Arrays were normalized using PLIER and all samples were subjected to an all-probeset scaling-to-target signal of 100. Preadipocytes were isolated from human adipose tissue obtained from healthy subjects and differentiated in vitro. Around day 11 of differentiation cells were treated with the Liver X Receptor agonist GW3865 for 12 h and lysed. Total RNA was prepared and and labelled using the FlashTag biotin HSR labeling kit (Genisphere Inc., Hatfield, PA) according to the supplier's protocol. The labelled samples were placed in a hybridization cocktail mix containing 4% formamide and hybridised overnight to Affymetrix miRNA Arrays (Affymetrix Inc.) following the indicated Genisphere protocol. The arrays were washed, stained and scanned in an Affymetrix GCS 3000 scanner. Signal intensities and present calls were generated by using the microRNA QC tool by Affymetrix using default settings i.e. Background Adjustment: BC-CG adjust, Normalization: Quantile: Summarization: Median Polish.
2012-09-29 | E-GEOD-41223 | biostudies-arrayexpress
Project description:The recent insight that brown adipocytes and muscle cells share a common origin and in this respect are distinct from white adipocytes has spurred questions concerning the origin and molecular characteristics of the UCP1-expressing cells observed in classic white adipose tissue depots under certain physiological or pharmacological conditions. Examining precursors from the purest white adipose tissue depot (epididymal), we report here that chronic treatment with the peroxisome proliferator-activated receptor gamma agonist rosiglitazone promotes not only the expression of PGC-1alpha and mitochondriogenesis in these cells but also a norepinephrine-augmentable UCP1 gene expression in a significant subset of the cells, providing these cells with a genuine thermogenic capacity. However, although functional thermogenic genes are expressed, the cells are devoid of transcripts for the novel transcription factors now associated with classic brown adipocytes (Zic1, Lhx8, Meox2, and characteristically PRDM16) or for myocyte-associated genes (myogenin and myomirs (muscle-specific microRNAs)) and retain white fat characteristics such as Hoxc9 expression. Co-culture experiments verify that the UCP1-expressing cells are not proliferating classic brown adipocytes (adipomyocytes), and these cells therefore constitute a subset of adipocytes ("brite" adipocytes) with a developmental origin and molecular characteristics distinguishing them as a separate class of cells.
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Project description:Sarcopoterium spinosum (S. spinosum) is a medicinal plant, traditionally used as an antidiabetic remedy. Previous studies demonstrated its beneficial properties in the treatment of insulin resistance. The aim of this study was to further clarify the effect of S. spinosum extract (SSE) on insulin signaling. Phosphoproteomic analysis, performed in 3T3-L1 adipocytes treated with SSE, revealed the activation of insulin receptor pathways. SSE increased Glut4-facilitated glucose uptake in adipocytes, with an additive effect between SSE and insulin. While the maximal effect of insulin on glucose uptake was found at days 15-16 of differentiation, SSE-induced glucose uptake was found at an earlier stage of differentiation. Inhibition of PI3K and Akt blocked SSE-dependent glucose uptake. Western blot analysis, performed on 3T3-L1 adipocytes and L6 myotubes, showed that in contrast to insulin action, Akt was only marginally phosphorylated by SSE. Furthermore, GSK3β and PRAS40 phosphorylation as well as glucose uptake were increased by the extract. SSE also induced the phosphorylation of ERK similar to insulin. In conclusion, SSE activates insulin signaling, although the upstream event mediating its effects should be further clarified. Identifying the active molecules in SSE may lead to the development of new agents for the treatment of insulin resistance.
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Project description:Cellular and tissue defects associated with insulin resistance are coincident with transcriptional abnormalities and are improved after insulin sensitization with thiazolidinedione (TZD) PPARγ ligands. We transcriptionally profiled 364 biopsies gathered from 72 human subjects harvested before and after hyperinsulinemic-euglycemic clamp, at baseline and after three-month TZD treatment. Subjects range from insulin-sensitive to insulin-resistant. Insulin resistant subjects responded to TZD treatment with varied improvements in insulin sensitivity, thus they were ranked by their degree of TZD response to define responder and non-responder subgroups.
2010-05-17 | GSE13070 | GEO
Project description:Dysfunctional adipose tissue represents a hallmark of type 2 diabetes and systemic insulin resistance, characterized by fibrotic deposition of collagens and increased immune cell infiltration within the depots. Here we generate an inducible model of loss of function of the protein phosphatase and tensin homologue (PTEN), a phosphatase critically involved in turning off the insulin signal transduction cascade, to assess the role of enhanced insulin signalling specifically in mature adipocytes. These mice gain more weight on chow diet and short-term as well as long-term high-fat diet exposure. Despite the increase in weight, they retain enhanced insulin sensitivity, show improvements in oral glucose tolerance tests, display reduced adipose tissue inflammation and maintain elevated adiponectin levels. These improvements also lead to reduced hepatic steatosis and enhanced hepatic insulin sensitivity. Prolonging insulin action selectively in the mature adipocyte is therefore sufficient to maintain normal systemic metabolic homeostasis.
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