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Eicosanoids participate in the regulation of cardiac glucose transport by contribution to a rearrangement of actin cytoskeletal elements.

ABSTRACT: Intact actin microfilaments are required for insulin-regulated glucose transporter isoform 4 (GLUT4) translocation to the plasma membrane. Lipoxygenase (LO) metabolites have recently been shown to contribute to the regulation of actin cytoskeleton rearrangement. In the present investigation, ventricular cardiomyocytes were used to study the effects of two structurally different LO inhibitors (esculetin and nordihydroguaiaretic acid) on insulin signalling events, glucose uptake, GLUT4 translocation and the actin network organization. Insulin stimulation increased glucose uptake 3-fold in control cells, whereas LO inhibition completely blocked this effect. This was paralleled by a slight reduction in the insulin-induced tyrosine phosphorylation of insulin receptor substrate (IRS)-1 and IRS-2. However, inhibition of 12-LO did not affect the association of phosphatidylinositol 3-kinase with IRS-1 and the phosphorylation of Akt/protein kinase B in response to insulin. Addition of 12(S)-hydroxyeicosatetraenoic acid almost completely restored the insulin action in cells exposed to nordihydroguaiaretic acid. Insulin stimulation increased cell surface GLUT4 2-fold in control cells, whereas LO inhibition abrogated the insulin-stimulated GLUT4 translocation. LO inhibition induced a prominent disassembly of actin fibres compared with control cells. In conclusion, we show here that 12(S)-hydroxyeicosatetraenoic acid plays a role in the organization of the actin network in cardiomyocytes. LO inhibition blocks GLUT4 translocation without affecting downstream insulin signalling. These data suggest that LO metabolites participate in the regulation of glucose transport by contributing to a rearrangement of actin cytoskeletal elements.

SUBMITTER: Dransfeld O

PROVIDER: S-EPMC1222120 | biostudies-other | 2001 Oct

REPOSITORIES: biostudies-other

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Project description:The interior of a eukaryotic cell is a highly complex composite material which consists of water, structural scaffoldings, organelles, and various biomolecular solutes. All these components serve as obstacles that impede the motion of vesicles. Hence, it is hypothesized that any alteration of the cytoskeletal network may directly impact or even disrupt the vesicle transport. A disruption of the vesicle-mediated cell transport is thought to contribute to several severe diseases and disorders, such as diabetes, Parkinson's and Alzheimer's disease, emphasizing the clinical relevance. To address the outlined objective, a multiscale finite element model of the diffusive vesicle transport is proposed on the basis of the concept of homogenization, owed to the complexity of the cytoskeletal network. In order to study the microscopic effects of specific nanoscopic actin filament network alterations onto the vesicle transport, a parametrized three-dimensional geometrical model of the actin filament network was generated on the basis of experimentally observed filament densities and network geometries in an adenocarcinomic human alveolar basal epithelial cell. Numerical analyzes of the obtained effective diffusion properties within two-dimensional sampling domains of the whole cell model revealed that the computed homogenized diffusion coefficients can be predicted statistically accurate by a simple two-parameter power law as soon as the inaccessible area fraction, due to the obstacle geometries and the finite size of the vesicles, is known. This relationship, in turn, leads to a massive reduction in computation time and allows to study the impact of a variety of different cytoskeletal alterations onto the vesicle transport. Hence, the numerical simulations predicted a 35% increase in transport time due to a uniformly distributed four-fold increase of the total filament amount. On the other hand, a hypothetically reduced expression of filament cross-linking proteins led to sparser filament networks and, thus, a speed up of the vesicle transport.

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Eicosanoids participate in the regulation of cardiac glucose transport by contribution to a rearrangement of actin cytoskeletal elements.

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