Project description:Innate immune pattern recognition receptors play critical roles in pathogen detection and initiation of antimicrobial responses. We and others have previously demonstrated the importance of the beta-glucan receptor Dectin-1 in the recognition of pathogenic fungi by macrophages and dendritic cells, and have elucidated some of the mechanisms by which Dectin-1 signals to coordinate the antifungal response. While Dectin-1 signals alone are sufficient to trigger phagocytosis and Src-Syk-mediated induction of antimicrobial reactive oxygen species, collaboration with Toll-like receptor (TLR)2 signaling enhances NF-kB activation and regulates cytokine production. In this study we demonstrate that Dectin-1 signaling can also directly modulate gene expression via activation of nuclear transcription of activated T cells (NFAT) transcription factors. Dectin-1 ligation by zymosan particles or live Candida albicans yeast triggers NFAT activation in macrophages and dendritic cells. Dectin-1-triggered NFAT activation plays a role in the induction of Egr2 and Egr3 transcription factors, and cyclooxygenase 2 (Cox-2). Furthermore, we show that NFAT activation regulates IL-2, IL-10 and IL-12 p70 production by zymosan-stimulated dendritic cells. These data establish NFAT activation in myeloid cells as a novel mechanism of regulation of the innate antimicrobial response. Experiment Overall Design: Bone marrow-derived macrophages deficient in MyD88 were stimulated with zymosan, and total RNA was extracted 120 minutes after stimulation for comparison to macrophages grown under the same conditions, but not stimulated.
Project description:Over 40 % of microRNAs are located in introns of coding genes, and many intronic microRNAs are co-regulated with their host genes. In such cases of co-regulation, the products of host genes and their intronic microRNAs can cooperate to coordinately regulate biologically important pathways. Therefore, we screened intronic microRNAs dysregulated in liver of obese mouse models to identify previously uncharacterized coding host genes that may contribute to the pathogenesis of obesity-associated insulin resistance and type 2 diabetes mellitus. Our approach identified that expression of both Ectodysplasin A (Eda), the causal gene of X-linked hypohidrotic ectodermal dysplasia (XLHED; MIM 305100) and its intronic microRNA, miR-676, was strongly increased in liver of obese mouse models. Moreover, hepatic EDA expression is increased in obese human subjects, reduced upon weight loss, and its hepatic expression correlates with systemic insulin resistance. Eda expression in murine liver is controlled via PPARg activation, increases in circulation and promotes JNK activation and inhibitory serine phosphorylation of IRS1 in skeletal muscle. Consistently, bi-directional modulation of hepatic Eda expression in mouse models affects systemic glucose metabolism with alterations of muscle insulin signaling, revealing a novel role of EDA as an obesity-associated hepatokine, which impairs insulin sensitivity in skeletal muscle.
Project description:Metabolic zonation in the liver is broadly defined as spatiotemporal variability in the intra-hepatic distribution of nutrients. R-spondin3 (Rspo3) regulates metabolic features around hepatic central veins. Herein, we demonstrate that altered hepatic metabolic zonation due to Rspo3 contributes to maintaining systemic glucose metabolism and body composition via inter-organ communication mechanism. Hepatic Rspo3 induction in obesity improves obesity-associated features by restoring insulin sensitivity, reversing adipose tissue enlargement and reversing overstimulated adaptive thermogenesis. These remote effects partly consist of neuronal communication via the afferent vagus from the liver. In contrast, hepatic Rspo3 suppression exacerbates diabetes due to insulin resistance and develops fatty liver.
Project description:Insulin resistance is the hallmark of obese and type 2 diabetes patients. Defective insulin sensitivity in the liver results in increased glucsoe production, which is the major cause of hyperglycemia in diabetic patients. Increased lipopolysaccharide (LPS) leakage from the gut of diet-induced obesity causes insulin resisitance; moreover, activation of deacetylase Sirtuin1 restore insulin sensitivity in obesity. However, the mechanism resulting in insulin resistance by LPS remains poorly understood. Here, we show that Ep300 (P300) harboring an intrinsic acetyltransferase activity was rapidly induced in the liver of animals fed a high-fat diet, and the induction of Ep300 is through LPS-stimulated activation of ER stress. Induced Ep300 impairs insulin signaling by acetylating mediators in insulin signaling. Inhibition of P300 acetyltransferase activity improves insulin signaling. Thus, Ep300 acetyltransferase activity is a therapeutic target.
Project description:The chronic inflammatory state that accompanies obesity is a major contributor to insulin resistance and other metabolic dysfunction features. Despite recent advances in our understanding of the cellular and secreted factors that promote the inflammatory milieu of obesity, we have much less insight into the transcriptional pathways that drive these processes. While most attention has focused on the canonical inflammatory transcription factor NF-KB, other potentially important factors exist, including members of the interferon regultory factor (IRF) family. Here we show that IRF3 expression is upregulated in the adipocytes of obese mice and humans. TLR3/TLR4 activation induces insulin resistance in adipocytes, which can be prevented by IRF3 knockdown. Furthermore, Irf3KO mice display improved insulin sensitivity, associated with reduced intra-adipose and systemic inflammation in the high-fat fed state, enhanced browning of subcutaneous fat, and increased adipose expression of Glut4. Taken together, our data indicates that IRF3 is a major transcriptional regulator of adipose inflammation to maintain systemic glucose and energy homeostasis. Transcriptional profiling of murine 3T3-L1 adipocytes with altered expression of IRF3. Overexpression or knockdown of IRF3 was achieved by lentivirus transduction for 6 days. 3T3-L1 adipocytes with IRF3 knockdown were further treated in the absence or presence of LPS for 6 days. Samples consist of triplicate replica with appropriate control.
Project description:Cytokines of the IL-1 family are important modulators of obesity-induced inflammation and the development of systemic insulin resistance. Here, we report that IL-37, a newly-described antiinflammatory member of the IL-1 family, affects obesity-induced inflammation and insulin resistance. IL-37 transgenic mice (IL-37tg) did not develop an obese phenotype in response to a high-fat diet (HFD). Unlike WT mice, IL-37tg mice exhibited reduced numbers of adipose tissue macrophages and preserved glucose tolerance and insulin sensitivity after 16 weeks of HFD. A short-term HFD intervention revealed that the IL-37-mediated improvement in glucose tolerance is independent of bodyweight. IL-37tg mice manifested a beneficial metabolic profile with higher circulating levels of the anti-inflammatory adipokine adiponectin. In vitro treatment of differentiating adipocytes with recombinant IL-37 reduced adipogenesis. The beneficial effects of recombinant IL-37 involved activation of AMPK signaling. In humans, steady-state IL-37 adipose tissue mRNA levels were positively correlated with insulin sensitivity, lower adipose tissue levels of leptin and a lower inflammatory status of the adipose tissue. These findings reveal IL-37 as an important anti-inflammatory modulator during obesity-induced inflammation and insulin resistance in both mice and humans and suggest that IL-37 is a potential target for the treatment of obesity-induced insulin resistance and type 2 diabetes. Gene arrays were performed on epidydimal white adipose tissue samples from wild type and human IL37-overexpressing transgenic mice fed a high fat diet for 16 weeks.
Project description:Tissue inflammation is a key factor underlying insulin resistance in established obesity. Several models of immuno-compromised mice are protected from obesity-induced insulin resistance. However, it is unanswered whether inflammation triggers systemic insulin resistance or vice versa in obesity. The purpose of this study was to assess these questions. 8-week-old C57BL/6J male mice was treated with 60% HFD for 0 day (NCD), 3 days, and 7 days. Eipididymal fat was fractionated. Each groups have three replicates.
Project description:Tissue inflammation is a key factor underlying insulin resistance in established obesity. Several models of immuno-compromised mice are protected from obesity-induced insulin resistance. However, it is unanswered whether inflammation triggers systemic insulin resistance or vice versa in obesity. The purpose of this study was to assess these questions.
Project description:The contribution of altered posttranscriptional gene silencing (PTGS) to the development of insulin resistance and type 2 diabetes mellitus so far remains elusive. We have described that expression of microRNAs (miR)-143 and -145 is dysregulated in genetic and dietary mouse models of obesity. Induced transgenic overexpression of miR-143, but not miR-145, causes insulin resistance and impaired insulin-stimulated AKT activation. We used microarrays to analyze the underlying molecular mechanisms of miR-143-mediated development of insulin resistance. miR-143DOX mice (n=3) and wildtype littermate controls (n=3) were treated with doxycycline via the drinking water to induce miR-143 overexpression in the transgenic animals. Primary hepatocytes were isolated for RNA extraction and hybridization on Affymetrix microarrays.
Project description:Mice overexpressing reverse tetracycline-transactivator (rtTA) exhibited all four sequelae of metabolic syndrome (visceral obesity insulin resistance, dyslipidemia, and hypertension), a pro-inflammatory state and marked hepatic steatosis. Gene expression profiling of the adipose tissue, muscle and liver revealed changes in gene expression of key factors involved in lipid metabolism, insulin resistance, and inflammation.