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  • 1
    Digitale Medien
    Digitale Medien
    Expression of the gene encoding glycogen phosphorylase is elevated in diabetic rat skeletal muscle and is regulated by insulin and cyclic AMP (1996)
    Springer
    Diabetologia 39 (1996), S. 183-189 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Glycogen phosphorylase ; muscle ; gene expression ; insulin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Glycogen phosphorylase regulates the breakdown of glycogen into glucose, but as previous studies have demonstrated, the control of glycogen metabolism becomes deregulated in diabetes mellitus. Messenger RNA levels encoding several different proteins are altered in skeletal muscle biopsies of patients with insulin-dependent and non-insulin-dependent diabetes. The possible alteration of expression of the gene encoding the skeletal muscle isoform of glycogen phosphorylase during diabetes has not previously been investigated. We examined the effect of streptozotocin-induced diabetes and insulin treatment on glycogen phosphorylase mRNA in rat skeletal muscle; glycogen phosphorylase mRNA levels were elevated in diabetic rat muscle tissue, but were partially suppressed in diabetic rat muscle following insulin treatment. To distinguish between the effects of insulin and counter-regulatory hormones on glycogen phosphorylase mRNA levels, we employed differentiating rat L6 myoblasts in culture. Insulin stimulated the accumulation of glycogen phosphorylase mRNA as determined by Northern blot analysis. Moreover, insulin and dibutyryl cAMP stimulated expression of a transiently transfected chloramphenicol acetyl transferase reporter gene under the control of the muscle glycogen phosphorylase promoter in differentiating myotubes in culture, suggesting that the effects of insulin and counter-regulatory hormones on glycogen phosphorylase mRNA are at the level of transcription. These results suggest that insulin and epinephrine may participate in the induction of the glycogen phosphorylase gene during myogenesis; moreover, activation of this gene in muscle tissue may be a contributing factor in impaired glycogen storage during uncontrolled diabetes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00403961
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  • 2
    Digitale Medien
    Digitale Medien
    Molecular scanning of the insulin receptor substrate-1 (IRS-1) gene in Japanese patients with NIDDM: identification of five novel polymorphisms (1996)
    Springer
    Diabetologia 39 (1996), S. 600-608 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Insulin receptor substrate-1 (IRS-1) ; non-insulin-dependent diabetes mellitus ; genetics ; single-stranded conformation polymorphisms ; insulin resistance ; polymorphism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Since the insulin receptor substrate-1 (IRS-1) is the major substrate of the insulin receptor tyrosine kinase and has been shown to activate phosphatidylinositol (PI) 3-kinase and promote GLUT4 translocation, the IRS-1 gene is a potential candidate for development of non-insulin-dependent diabetes mellitus (NIDDM). In this study, we have identified IRS-1 gene polymorphisms, evaluated their frequencies in Japanese subjects, and analysed the contribution of these polymorphisms to the development of NIDDM. The entire coding region of the IRS-1 gene of 94 subjects (47 NIDDM and 47 control subjects) was screened by polymerase chain reaction-single stranded conformation polymorphism (PCR-SSCP) analysis. Seven SSCP polymorphisms were identified. These corresponded to two previously identified polymorphisms [Gly971→Arg (GGG→AGG) and Ala804 (GCA→GCG)] as well as five novel polymorphisms [Pro190→Arg (CCC→CGC), Met209→Thr (ATG→ACG), Ser809→Phe (TCT→TTT), Leu142 (CTT→CTC), and Gly625 (GGC→GGT)]. Although the prevalence of each of these polymorphisms was not statistically different between NIDDM and control subjects, the prevalence of the four IRS-1 polymorphisms with an amino acid substitution together was significantly higher in NIDDM than in control subjects (23.4 vs 8.5%, p〈0.05), and two substitutions (Met209→Thr and Ser809→Phe) were found only in NIDDM patients. Equilibrium glucose infusion rates during a euglycaemic clamp in NIDDM and control subjects with the IRS-1 polymorphisms decreased by 29.5 and 22.0%, respectively on the average when compared to those in comparable groups without polymorphisms, although they were not statistically significant. Thus, IRS-1 polymorphisms may contribute in part to the insulin resistance and development of NIDDM in Japanese subjects; however, they do not account for the major part of the decrease in insulin-stimulated glucose uptake which is observed in subjects with clinically apparent NIDDM.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00403308
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  • 3
    Digitale Medien
    Digitale Medien
    Characterization of insulin receptors in patients with the syndromes of insulin resistance and acanthosis nigricans (1980)
    Springer
    Diabetologia 18 (1980), S. 209-216 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Insulin receptors ; acanthosis nigricans ; insulin resistance ; insulin receptor autoantibodies ; Type A patients ; Type B patients ; negative cooperativity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary This report analyzes the in vitro characteristics of 125I-insulin binding to the monocytes of nine patients with the syndromes of acanthosis nigricans and insulin resistance. The 3 Type A patients (without demonstrable autoantibodies to the insulin receptor) had decreased binding of insulin due to a decreased concentration of receptors. In these patients the residual receptors demonstrated normal dissociation kinetics, negative cooperativity, and were blocked by anti-receptor antibodies in a manner similar to normal cells. In contrast, monocytes from the 6 Type B patients (with circulating anti-receptor autoantibodies) had decreased binding of insulin due to a decrease in receptor affinity. Insulin binding to monocytes of Type B patients demonstrated accelerated rates of dissociation with no evidence of cooperative interactions among insulin receptors. When coupled with previous data, the present studies further suggest that different mechanisms account for the defects in insulin binding and insulin resistance observed in these patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00251918
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  • 4
    Digitale Medien
    Digitale Medien
    Activation of liver and muscle insulin receptor tyrosine kinase activity during in vivo insulin administration in rats (1990)
    Springer
    Diabetologia 33 (1990), S. 77-83 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Hyperinsulinaemic glucose clamp ; skeletal muscle ; liver ; insulin receptors ; tyrosine kinase ; insulin resistance ; β-subunit C-terminus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We have studied autophosphorylation and tyrosine kinase activity of the insulin receptor purified from liver and muscle of fasted rats before and after infusion of insulin (100 mU/h) during a 2.5 h glucose clamp. Recovery of insulin receptors and insulin binding to the solubilised receptors was unaffected by the glucose clamp. Autophosphorylation of the insulin receptor β subunit was increased in liver receptors prepared from rats at the end of the glucose clamp compared to rats in the basal state both in the absence of insulin in vitro (109% increase, p〈0.001) and after in vitro stimulation with 10−7 mol/l insulin (clamped vs fasted; 96% increase, p〈0.001). Insulin (10−7 mol/l) stimulated autophosphorylation was also increased in muscle receptor preparations from clamped rats compared with rats in the basal state (58% increase, p〈0.05). In both liver and muscle receptors, the clamp increased the amount of [32P]-phosphate incorporated into the β subunit without changing the sensitivity of the insulin stimulation. HPLC analysis of the tryptic phosphopeptides derived from the β subunit after insulin stimulated autophosphorylation of liver receptors revealed an increase of 32P in all phosphorylation sites without any change in the overall pattern. Tyrosine kinase activity of liver and muscle insulin receptors from clamped rats was also increased approximately twofold (p〈0.05) when analysed using a synthetic substrate (poly Glu4 Tyr1). Our results support the notion that the insulin receptor exists in an active and inactive form, and that elevated plasma insulin concentrations increases the proportion of active receptors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00401044
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  • 5
    Digitale Medien
    Digitale Medien
    Molecular scanning of the insulin receptor substrate-1 (IRS-1) gene in Japanese patients with NIDDM: identification of five novel polymorphisms (1996)
    Springer
    Diabetologia 39 (1996), S. 600-608 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Keywords Insulin receptor substrate-1 (IRS-1) ; non-insulin-dependent diabetes mellitus ; genetics ; single-stranded conformation polymorphisms ; insulin resistance ; polymorphism.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Since the insulin receptor substrate-1 (IRS-1) is the major substrate of the insulin receptor tyrosine kinase and has been shown to activate phosphatidylinositol (PI) 3-kinase and promote GLUT4 translocation, the IRS-1 gene is a potential candidate for development of non-insulin-dependent diabetes mellitus (NIDDM). In this study, we have identified IRS-1 gene polymorphisms, evaluated their frequencies in Japanese subjects, and analysed the contribution of these polymorphisms to the development of NIDDM. The entire coding region of the IRS-1 gene of 94 subjects (47 NIDDM and 47 control subjects) was screened by polymerase chain reaction-single stranded conformation polymorphism (PCR-SSCP) analysis. Seven SSCP polymorphisms were identified. These corresponded to two previously identified polymorphisms [Gly971→Arg (GGG→AGG) and Ala804 (GCA→GCG)] as well as five novel polymorphisms [Pro190→Arg (CCC→CGC), Met209→Thr (ATG→ACG), Ser809→Phe (TCT→TTT), Leu142 (CTT→CTC), and Gly625 (GGC→GGT)]. Although the prevalence of each of these polymorphisms was not statistically different between NIDDM and control subjects, the prevalence of the four IRS-1 polymorphisms with an amino acid substitution together was significantly higher in NIDDM than in control subjects (23.4 vs 8.5 %, p 〈 0.05), and two substitutions (Met209→Thr and Ser809→Phe) were found only in NIDDM patients. Equilibrium glucose infusion rates during a euglycaemic clamp in NIDDM and control subjects with the IRS-1 polymorphisms decreased by 29.5 and 22.0 %, respectively on the average when compared to those in comparable groups without polymorphisms, although they were not statistically significant. Thus, IRS-1 polymorphisms may contribute in part to the insulin resistance and development of NIDDM in Japanese subjects; however, they do not account for the major part of the decrease in insulin-stimulated glucose uptake which is observed in subjects with clinically apparent NIDDM. [Diabetologia (1996) 39: 600–608]
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00403308
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  • 6
    Digitale Medien
    Digitale Medien
    Anti-insulin receptor antibodies inhibit insulin binding and stimulate glucose metabolism in skeletal muscle (1978)
    Springer
    Diabetologia 14 (1978), S. 311-317 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Anti-insulin receptor antibodies ; insulin-like effects ; insulin resistance ; skeletal muscle ; insulin receptor ; insulin binding ; insulin action ; glucose transport ; glycolysis ; glycogen synthesis ; obese mice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Autoantibodies against the insulin receptor are found in the serum of some patients with severe insulin resistance. The effects of one of these sera on insulin binding and on glucose transport and metabolism were investigated in the isolated mouse soleus muscle. Preincubation of muscles with the patient's serum resulted in an inhibition of subsequent125I-insulin binding (half-maximal effect at 1∶500 dilution) and in a two to three-fold stimulation of glucose transport and metabolism (half-maximal effect at 1∶2000 dilution). The insulin-like effects were blocked by anti-human IgG, but not by antiinsulin antibodies. The magnitude of the serum effects on 2-deoxyglucose uptake and glycolysis was similar to that of insulin, but the effect on glycogen synthesis was smaller than that of insulin. It is suggested that the patient's serum and insulin promote glucose transport and glycolysis through a common pathway, but act differently on glycogen synthesis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01223022
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  • 7
    Digitale Medien
    Digitale Medien
    Effect of phospholipase treatment on insulin receptor signal transduction (1992)
    Springer
    Diabetologia 35 (1992), S. 109-115 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Membrane lipids ; insulin receptors ; insulin action ; tyrosine phosphorylation ; pp 185
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary To study the role of membrane lipids in signal transduction by the insulin receptor, we have studied the effect of phospholipase C (Clostridium perfringens) and a phosphatidylinositol-specific phospholipase (Staphylococcus aureus) on insulin binding, a function of the α-subunit, and tyrosine kinase activity, a function of the β-subunit in IM-9 lymphocytes and NIH 3T3 fibroblasts transfected with the human insulin receptor. Treatment of the cells with phospholipase C at concentrations up to 3.4 U/ml did not affect specific insulin binding, but reduced insulin-stimulated receptor phosphorylation by 50%. This effect of phospholipase C was observed within 10 min of treatment and occurred with no change in the basal level of phosphorylation. Pre-treatment of cells with insulin for 5 min prior to enzyme addition prevented any change in kinase activity. Insulin-stimulated phosphorylation of pp 185, the presumed endogenous substrate for the insulin receptor kinase, was also reduced following phospholipase C treatment, with an almost complete loss of insulin stimulation after exposure of cells to enzyme at concentrations as low as 0.6 U/ml. In contrast to these effects of phospholipase C on intact cells, receptor autophosphorylation was not affected in insulin receptors purified on wheat germ agglutinin-agarose from phospholipase C treated cells. Likewise, the phospholipase C effect was reduced by the addition of phosphatidylcholine, but not by the addition of the protease inhibitors, aprotinin and phenylmethylsulfonyl fluoride, to the incubation indicating its dependence on phospholipid hydrolysis. Treatment of cells with the phosphatidylinositol-specific phospholipase C did not affect any of the parameters studied. These data suggest that the phospholipid environment in the plasma membrane is an important modulator of transmembrane signalling within the insulin receptor heterotetramer and at the level of substrate phosphorylation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00402541
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