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  • 1
    Electronic Resource
    Electronic Resource
    Insulin-induced translocation of GLUT 4 in skeletal muscle of insulin-resistant Zucker rats (1994)
    Springer
    Diabetologia 37 (1994), S. 3-9 
    Details
    ISSN: 1432-0428
    Keywords: Zucker rats ; skeletal muscle ; insulin resistance ; glucose transporter (GLUT 1 and GLUT 4) ; GLUT 4 translocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The genetically obese Zucker rat (fa/fa) is an animal model with severe insulin resistance of the skeletal muscle. We investigated whether a defect of insulin-dependent glucose transporter (GLUT 4) translocation might contribute to the pathogenesis of the insulin-resistant state. fa/fa rats, lean controls (Fa/Fa) as well as normal Wistar rats were injected intraperitoneally with insulin and were killed after 2 or 20 min, respectively. Subcellular fractions were prepared from-hind-limb skeletal muscle and were characterized by determination of marker-enzyme activities and immunoblotting applying antibodies against α1 Na+/K+ AT Pase. The relative amounts of GLUT 1 and GLUT 4 were determined in the fractions by immunoblotting with the respective antibodies. Insulin induced an approximately two-fold increase of GLUT 4 in a plasma membrane and transverse tubule enriched fraction and a decrease in the low density enriched membrane fraction in all three groups of rats. There was a high individual variation in GLUT 4 translocation efficiency within the groups. However, no statistically significant difference was noted between the groups. No effect of insulin was detectable on the distribution of GLUT 1 or α1 Na+K+ ATPase. The data suggest that skeletal muscle insulin resistance of obese Zucker rats is not associated with a lack of GLUT 4 translocation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428770
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  • 2
    Electronic Resource
    Electronic Resource
    Modulation of insulin receptor signalling: significance of altered receptor isoform patterns and mechanism of hyperglycaemia-induced receptor modulation (1994)
    Springer
    Diabetologia 37 (1994), S. S149 
    Details
    ISSN: 1432-0428
    Keywords: Insulin receptor ; skeletal muscle ; proteinkinase C ; non-insulin-dependent diabetes mellitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Insulin resistance of the skeletal muscle plays a key role in the development of the metabolic endocrine syndrome and its further progression to non-insulin dependent diabetes (NIDDM). Available data suggest that insulin resistance is caused by an impaired signal from the insulin receptor to the glucose transport system and to glycogen synthase. The impaired response of the insulin receptor tyrosine kinase which is found in NIDDM appears to contribute to the pathogenesis of the signalling defect. The reduced kinase activation is not caused by mutations within the insulin receptor gene. We investigated two potential mechanisms that might be relevant for the abnormal function of the insulin receptor in NIDDM, i.e. changes in the expression of the receptor isoforms and the effect of hyperglycaemia on insulin receptor tyrosine kinase activity. The insulin receptor is expressed in two different isoforms (HIRA and HIR-B). We found that HIR-B expression in the skeletal muscle is increased in NIDDM. However, the characterisation of the functional properties of HIR-A and HIR-B revealed no difference in their tyrosine kinase activity in vivo. The increased expression of HIR-B might represent a compensatory event. In contrast, hyperglycaemia might directly inhibit insulin-receptor function. We have found that in rat-1 fibroblasts which overexpressing human insulin receptor an inhibition of the tyrosine kinase activity of the receptor may be induced by high glucose levels. This appears to be mediated through activation of certain protein kinase C isoforms which form stable complexes with the insulin receptor and modulate the tyrosine kinase activity of the insulin receptor through serine phosphorylation of the receptor beta subunit. This mechanism might also be relevant in human skeletal muscle and contribute to the pathogenesis of insulin resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00400838
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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