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There are 47 results for Insulin (displaying 31 to 40).

Cardiac LXRα protects against pathological cardiac hypertrophy and dysfunction by enhancing glucose uptake and utilization

Pathological cardiac hypertrophy is characterized by a shift in metabolic substrate utilization from fatty acids to glucose, but the molecular events underlying the metabolic remodeling remain poorly understood. Here, we investigated the role of liver X receptors ( LXR s), which are key regulators of glucose and lipid metabolism, in cardiac hypertrophic pathogenesis. Using a transgenic approach in mice, we show that overexpression of LXR α acts to protect the heart against hypertrophy, fibrosis, and dysfunction. Gene expression profiling studies revealed that genes regulating metabolic pathways were differentially expressed in hearts with elevated LXR α. Functionally, LXR α overexpression in isolated cardiomyocytes and murine hearts markedly enhanced the capacity for myocardial glucose uptake following hypertrophic stress. Conversely, this adaptive response was diminished in LXR α‐deficient mice. Transcriptional changes induced by LXR α overexpression promoted energy‐independent utilization of glucose via the hexosamine biosynthesis pathway, resulting in O‐Glc NA c modification of GATA 4 and Mef2c and the induction of cytoprotective natriuretic peptide expression. Our results identify LXR α as a key cardiac transcriptional regulator that helps orchestrate an adaptive metabolic response to chronic cardiac stress, and suggest that modulating LXR α may provide a unique opportunity for intervening in myocyte metabolism.

… , ; Domenighetti et al , ). With cardiac insulin resistance and metabolic dysregulation known to precede the development of heart failure (Witteles & Fowler, ; Brouwers et al , ), strategies sensitizing the heart to glucose uptake may thus have clinically relevant implications in the long‐term prognosis of heart failure. Since glucose uptake rates were enhanced by LXRα activation, we hypothesized that this would also lead to downstream changes in energy‐dependent pathways, causing increased …

Megan V Cannon et al. EMBO molecular medicine September 2015

A lysosome‐to‐nucleus signalling mechanism senses and regulates the lysosome via mTOR and TFEB

The lysosome plays a key role in cellular homeostasis by controlling both cellular clearance and energy production to respond to environmental cues. However, the mechanisms mediating lysosomal adaptation are largely unknown. Here, we show that the Transcription Factor EB (TFEB), a master regulator of lysosomal biogenesis, colocalizes with master growth regulator mTOR complex 1 (mTORC1) on the lysosomal membrane. When nutrients are present, phosphorylation of TFEB by mTORC1 inhibits TFEB activity. Conversely, pharmacological inhibition of mTORC1, as well as starvation and lysosomal disruption, activates TFEB by promoting its nuclear translocation. In addition, the transcriptional response of lysosomal and autophagic genes to either lysosomal dysfunction or pharmacological inhibition of mTORC1 is suppressed in TFEB−/− cells. Interestingly, the Rag GTPase complex, which senses lysosomal amino acids and activates mTORC1, is both necessary and sufficient to regulate starvation‐ and stress‐induced nuclear translocation of TFEB. These data indicate that the lysosome senses its content and regulates its own biogenesis by a lysosome‐to‐nucleus signalling mechanism that involves TFEB and mTOR.

… 100 U/ml of Collagenase (Wako) and 0.05 mg/ml of Trypsin inhibitor (Sigma). Liver was dissociated in a petri dish, cell pellet was washed in HBSS and plated at density of 5 × 105 cells/35 mm dish and cultured in William's medium E supplemented with 10% FBS, 2 mM glutamine, 0.1 μM Insulin, 1 μM Dexamethasone and pen/strep. The next day, cells were treated as described in the text. Sin1−/− and control MEFs were generated as previously described ( ) and maintained in DMEM supplemented with 10% FBS …

Carmine Settembre et al. The EMBO Journal March 2012

Suppression of the HSF1‐mediated proteotoxic stress response by the metabolic stress sensor AMPK

Numerous extrinsic and intrinsic insults trigger the HSF 1‐mediated proteotoxic stress response ( PSR ), an ancient transcriptional program that is essential to proteostasis and survival under such conditions. In contrast to its well‐recognized mobilization by proteotoxic stress, little is known about how this powerful adaptive mechanism reacts to other stresses. Surprisingly, we discovered that metabolic stress suppresses the PSR . This suppression is largely mediated through the central metabolic sensor AMPK , which physically interacts with and phosphorylates HSF 1 at Ser121. Through AMPK activation, metabolic stress represses HSF 1, rendering cells vulnerable to proteotoxic stress. Conversely, proteotoxic stress inactivates AMPK and thereby interferes with the metabolic stress response. Importantly, metformin, a metabolic stressor and popular anti‐diabetic drug, inactivates HSF 1 and provokes proteotoxic stress within tumor cells, thereby impeding tumor growth. Thus, these findings uncover a novel interplay between the metabolic stress sensor AMPK and the proteotoxic stress sensor HSF 1 that profoundly impacts stress resistance, proteostasis, and malignant growth.

… benefits, epidemiological studies have revealed reduced tumor incidence in T2D patients taking metformin (Evans et al , ; Garrett et al , ; Sadeghi et al , ). Preclinical investigations show that metformin impaired de novo oncogenesis in mice and impeded tumor growth in xenograft models (Anisimov et al , ; Memmott et al , ; Iliopoulos et al , ; Tomic et al , ). Despite this exciting promise, the proposed underlying mechanisms are diverse, ranging from reduced insulin levels, to suppressed mTORC1 …

Siyuan Dai et al. The EMBO Journal February 2015

Autolysosomal β‐catenin degradation regulates Wnt‐autophagy‐p62 crosstalk

The Wnt/β‐catenin signalling and autophagy pathways each play important roles during development, adult tissue homeostasis and tumorigenesis. Here we identify the Wnt/β‐catenin signalling pathway as a negative regulator of both basal and stress‐induced autophagy. Manipulation of β‐catenin expression levels in vitro and in vivo revealed that β‐catenin suppresses autophagosome formation and directly represses p62/SQSTM1 (encoding the autophagy adaptor p62) via TCF4. Furthermore, we show that during nutrient deprivation β‐catenin is selectively degraded via the formation of a β‐catenin–LC3 complex, attenuating β‐catenin/TCF‐driven transcription and proliferation to favour adaptation during metabolic stress. Formation of the β‐catenin–LC3 complex is mediated by a W/YXXI/L motif and LC3‐interacting region (LIR) in β‐catenin, which is required for interaction with LC3 and non‐proteasomal degradation of β‐catenin. Thus, Wnt/β‐catenin represses autophagy and p62 expression, while β‐catenin is itself targeted for autophagic clearance in autolysosomes upon autophagy induction. These findings reveal a regulatory feedback mechanism that place β‐catenin at a key cellular integration point coordinating proliferation with autophagy, with implications for targeting these pathways for cancer therapy.

… to hyperactivation of Nrf2, resulting in a positive‐feedback loop that drives further expression of p62 ( ; ), which can contribute to the development of hepatocellular carcinoma ( ). In future investigations it will be important to fully understand the roles of p62 in colorectal tumorigenesis and the mechanisms controlling its regulation during the adenoma‐carcinoma sequence. Since p62 deregulation is observed in Parkinson's disease, insulin resistance and Paget's disease of bone ( ), our finding …

Katy J Petherick et al. The EMBO Journal July 2013

Endocytosis and intracellular trafficking contribute to necrotic neurodegeneration in C. elegans

Unlike apoptosis, necrotic cell death is characterized by marked loss of plasma membrane integrity. Leakage of cytoplasmic material to the extracellular space contributes to cell demise, and is the cause of acute inflammatory responses, which typically accompany necrosis. The mechanisms underlying plasma membrane damage during necrotic cell death are not well understood. We report that endocytosis is critically required for the execution of necrosis. Depletion of the key endocytic machinery components dynamin, synaptotagmin and endophilin suppresses necrotic neurodegeneration induced by diverse genetic and environmental insults in C. elegans . We used genetically encoded fluorescent markers to monitor the formation and fate of specific types of endosomes during cell death in vivo . Strikingly, we find that the number of early and recycling endosomes increases sharply and transiently upon initiation of necrosis. Endosomes subsequently coalesce around the nucleus and disintegrate during the final stage of necrosis. Interfering with kinesin‐mediated endosome trafficking impedes cell death. Endocytosis synergizes with autophagy and lysosomal proteolytic mechanisms to facilitate necrotic neurodegeneration. These findings demonstrate a prominent role for endocytosis in cellular destruction during neurodegeneration, which is likely conserved in metazoans.

… consequence of endocytosis and trafficking downregulation, originating from non‐specific metabolic alterations in the corresponding mutants. However, we consider this scenario unlikely because several genetic lesions affecting energy metabolism either directly or indirectly (insulin/IGF‐1 pathway and mitochondrial mutants) do not suppress necrosis ( ). In‐vivo monitoring of necrotic cell death revealed that the number of both early and recycling endosomes increases upon initiation of neurodegeneration …

Kostoula Troulinaki et al. The EMBO Journal February 2012

In vivo generation of a mature and functional artificial skeletal muscle

Extensive loss of skeletal muscle tissue results in mutilations and severe loss of function. In vitro ‐generated artificial muscles undergo necrosis when transplanted in vivo before host angiogenesis may provide oxygen for fibre survival. Here, we report a novel strategy based upon the use of mouse or human mesoangioblasts encapsulated inside PEG ‐fibrinogen hydrogel. Once engineered to express placental‐derived growth factor, mesoangioblasts attract host vessels and nerves, contributing to in vivo survival and maturation of newly formed myofibres. When the graft was implanted underneath the skin on the surface of the tibialis anterior , mature and aligned myofibres formed within several weeks as a complete and functional extra muscle. Moreover, replacing the ablated tibialis anterior with PEG ‐fibrinogen‐embedded mesoangioblasts also resulted in an artificial muscle very similar to a normal tibialis anterior . This strategy opens the possibility for patient‐specific muscle creation for a large number of pathological conditions involving muscle tissue wasting.

… ), 1.5 mM Fe 2+ [iron(II) chloride tetrahydrate, Sigma; or Fer‐In‐Sol, Mead Johnson], 0.12 mM Fe 3+ [iron(III) nitrate nonahydrate, Sigma; or Ferlixit, Aventis] and 1% insulin/transferrin/selenium (Gibco). PEG‐fibrinogen precursor solution was prepared and photopolymerized as described elsewhere (Corona et al , ). We prepared PEG hydrogels containing Mabs by mixing a PBS cell suspension and PEGylated fibrinogen precursor solution containing 0.1% of Igracuret ™ 2959 photoinitiator (Ciba Specialty …

Claudia Fuoco et al. EMBO molecular medicine April 2015

Navigator‐3, a modulator of cell migration, may act as a suppressor of breast cancer progression

Dissemination of primary tumor cells depends on migratory and invasive attributes. Here, we identify Navigator‐3 ( NAV 3 ), a gene frequently mutated or deleted in human tumors, as a regulator of epithelial migration and invasion. Following induction by growth factors, NAV 3 localizes to the plus ends of microtubules and enhances their polarized growth. Accordingly, NAV 3 depletion trimmed microtubule growth, prolonged growth factor signaling, prevented apoptosis and enhanced random cell migration. Mathematical modeling suggested that NAV 3‐depleted cells acquire an advantage in terms of the way they explore their environment. In animal models, silencing NAV 3 increased metastasis, whereas ectopic expression of the wild‐type form, unlike expression of two, relatively unstable oncogenic mutants from human tumors, inhibited metastasis. Congruently, analyses of > 2,500 breast and lung cancer patients associated low NAV 3 with shorter survival. We propose that NAV 3 inhibits breast cancer progression by regulating microtubule dynamics, biasing directionally persistent rather than random migration, and inhibiting locomotion of initiated cells.

… supplemented with 2% horse serum, insulin, cholera toxin and hydrocortisone. Eight‐chambered plates (BD Biosciences) were coated with 35 μl growth factor‐reduced Matrigel (BD Bioscience) per well. The cells were mixed 1:1 with assay medium containing Matrigel (4%) and EGF (20 ng/ml), and 400 μl was added to each chamber. Thereafter, acini were fixed in methanol–acetone, and the slides were blocked in goat serum (10%) containing buffer and processed for microscopy using a spinning disk confocal …

Hadas Cohen‐Dvashi et al. EMBO molecular medicine March 2015

Autophagy proteins control goblet cell function by potentiating reactive oxygen species production

Delivery of granule contents to epithelial surfaces by secretory cells is a critical physiologic process. In the intestine, goblet cells secrete mucus that is required for homeostasis. Autophagy proteins are required for secretion in some cases, though the mechanism and cell biological basis for this requirement remain unknown. We found that in colonic goblet cells, proteins involved in initiation and elongation of autophagosomes were required for efficient mucus secretion. The autophagy protein LC3 localized to intracellular multi‐vesicular vacuoles that were consistent with a fusion of autophagosomes and endosomes. Using cultured intestinal epithelial cells, we found that NADPH oxidases localized to and enhanced the formation of these LC3‐positive vacuoles. Both autophagy proteins and endosome formation were required for maximal production of reactive oxygen species (ROS) derived from NADPH oxidases. Importantly, generation of ROS was critical to control mucin granule accumulation in colonic goblet cells. Thus, autophagy proteins can control secretory function through ROS, which is in part generated by LC3‐positive vacuole‐associated NADPH oxidases. These findings provide a novel mechanism by which autophagy proteins can control secretion.

… of the pathways required for goblet cell secretion (autophagy, endocytosis, ROS generation by NADPH oxidases) converge. We therefore propose that these organelles may act as a scaffold in other secretory cell types such as β‐islet cells. Interestingly, separate studies in these cells have shown that autophagy proteins ( ; ) as well as the NADPH oxidase (Nox2) regulate insulin secretion ( ; ); however, these two pathways have not yet been functionally linked in this cell type. It is interesting that our …

Khushbu K Patel et al. The EMBO Journal December 2013

STAMP2 increases oxidative stress and is critical for prostate cancer

The six transmembrane protein of prostate 2 ( STAMP 2) is an androgen‐regulated gene whose mRNA expression is increased in prostate cancer ( PC a). Here, we show that STAMP 2 protein expression is increased in human PC a compared with benign prostate that is also correlated with tumor grade and treatment response. We also show that STAMP 2 significantly increased reactive oxygen species ( ROS ) in PC a cells through its iron reductase activity which also depleted NADPH levels. Knockdown of STAMP 2 expression in PC a cells inhibited proliferation, colony formation, and anchorage‐independent growth, and significantly increased apoptosis. Furthermore, STAMP 2 effects were, at least in part, mediated by activating transcription factor 4 ( ATF 4), whose expression is regulated by ROS . Consistent with in vitro findings, silencing STAMP 2 significantly inhibited PC a xenograft growth in mice. Finally, therapeutic silencing of STAMP 2 by systemically administered nanoliposomal si RNA profoundly inhibited tumor growth in two established preclinical PC a models in mice. These data suggest that STAMP 2 is required for PC a progression and thus may serve as a novel therapeutic target.

… (Korkmaz et al , ). Although these observations suggested that STAMP2 may have a role in PCa biology, it is not clear as to how STAMP2 modulates cell growth in PCa cells and whether it can serve as a therapeutic target. Interestingly, STAMP2 has also been linked to inflammation and insulin action in adipocytes and macrophages and thus has been implicated in metabolic disease and atherosclerosis (Wellen et al , ; ten Freyhaus et al , ). Here, we show that STAMP2 is a critical survival factor …

Yang Jin et al. EMBO molecular medicine March 2015

Spontaneous development of hepatocellular carcinoma with cancer stem cell properties in PR‐SET7‐deficient livers

PR ‐ SET 7‐mediated histone 4 lysine 20 methylation has been implicated in mitotic condensation, DNA damage response and replication licensing. Here, we show that PR ‐ SET 7 function in the liver is pivotal for maintaining genome integrity. Hepatocyte‐specific deletion of PR ‐ SET 7 in mouse embryos resulted in G2 phase arrest followed by massive cell death and defect in liver organogenesis. Inactivation at postnatal stages caused cell duplication‐dependent hepatocyte necrosis, accompanied by inflammation, fibrosis and compensatory growth induction of neighboring hepatocytes and resident ductal progenitor cells. Prolonged necrotic regenerative cycles coupled with oncogenic STAT 3 activation led to the spontaneous development of hepatic tumors composed of cells with cancer stem cell characteristics. These include a capacity to self‐renew in culture or in xenografts and the ability to differentiate to phenotypically distinct hepatic cells. Hepatocellular carcinoma in PR ‐ SET 7‐deficient mice displays a cancer stem cell gene signature specified by the co‐expression of ductal progenitor markers and oncofetal genes.

… for the analyses of the RNAseq data are described in the . Primary hepatocytes were isolated from P240 PR‐SET7 ΔHepA mice using collagenase perfusion protocol (Tatarakis et al , ). The cells were seeded to tissue culture plates coated with 50 μg/ml rat collagen (type 1) and cultured in a medium containing DMEM/F12, 10% fetal bovine serum (FBS), 5 μg/ml insulin, 5 μg/ml transferin, 5 ng/ml selenious acid, 10 −7 M dexamethasone and 20 ng/ml EGF. The cells could survive at least four passages …

Kostas C Nikolaou et al. The EMBO Journal February 2015
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