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  • 1
    ISSN: 1432-0428
    Keywords: Anti-insulin receptor antibodies ; insulin-like effects ; insulin resistance ; skeletal muscle ; insulin receptor ; insulin binding ; insulin action ; glucose transport ; glycolysis ; glycogen synthesis ; obese mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0428
    Keywords: Insulin receptors ; acanthosis nigricans ; insulin resistance ; insulin receptor autoantibodies ; Type A patients ; Type B patients ; negative cooperativity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0428
    Keywords: Keywords Insulin receptor substrate-1 (IRS-1) ; non-insulin-dependent diabetes mellitus ; genetics ; single-stranded conformation polymorphisms ; insulin resistance ; polymorphism.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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]
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0428
    Keywords: Hyperinsulinaemic glucose clamp ; skeletal muscle ; liver ; insulin receptors ; tyrosine kinase ; insulin resistance ; β-subunit C-terminus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0428
    Keywords: Insulin receptor substrate-1 (IRS-1) ; non-insulin-dependent diabetes mellitus ; genetics ; single-stranded conformation polymorphisms ; insulin resistance ; polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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