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  • Type II diabetes  (2)
  • catecholamines  (2)
  • glucose production  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Impaired phosphorylation and insulin-stimulated translocation to the plasma membrane of protein kinase B/Akt in adipocytes from Type II diabetic subjects (2000)
    Springer
    Diabetologia 43 (2000), S. 1107-1115 
    Details
    ISSN: 1432-0428
    Keywords: Keywords PKB/Akt ; PI3-kinase ; insulin action ; Type II diabetes ; GLUT-4.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aims/hypothesis. To examine protein kinase B/Akt distribution and phosphorylation in response to insulin in different subcellular fractions of human fat cells from healthy subjects and subjects with Type II (non-insulin-dependent) diabetes mellitus. Methods. We prepared subcellular fractions of plasma membranes (PM), low density microsomes and cytosol and examined gene and protein expression as well as serine and threonine phosphorylation in response to insulin. Results. Protein kinase B/Akt mRNA as well as total protein kinase B/Akt protein in whole-cell lysate and cytosol were similar in both groups. Insulin increased protein kinase B/Akt translocation to the the plasma membrane about twofold [(p 〈 0.03) in non-diabetic cells but this effect was impaired in diabetic cells (∼ 30 %; p 〉 0.1)]. In both groups, protein kinase B/Akt threonine phosphorylation considerably increased in low density microsomes and cytosol whereas serine phosphorylation was predominant in the plasma membrane. Phosphatidylinositol-dependent kinase 1, which partially activates and phosphorylates protein kinase B/Akt on the specific threonine site, was predominant in cytosol but it was also recovered in low density microsomes. Serine phosphorylation in response to insulin was considerably reduced (50–70 %; p 〈 0.05) in diabetic cells but threonine phosphorylation was less reduced (∼ 20 %). Wortmannin inhibited these effects of insulin supporting a role for PI3-kinase activation. Conclusion/interpretation. Insulin stimulates a differential subcellular pattern of phosphorylation of protein kinase B/Akt. Furthermore, insulin-stimulated translocation of protein kinase B/Akt to the plasma membrane, where serine phosphorylation and full activation occurs, is impaired in Type II diabetes. Threonine phosphorylation was much less reduced. This discrepancy may be related to differential activation of phosphatidylinositol 3-kinase in the different subcellular compartments and phosphatidylinositol-dependent kinase 1 having high affinity for phosphatidylinositol phosphate 3. [Diabetologia (2000) 43: 1107–1115]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001250051501
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  • 2
    Electronic Resource
    Electronic Resource
    Studies on the insulin-antagonistic effect of catecholamines in normal man (1986)
    Springer
    Diabetologia 29 (1986), S. 409-416 
    Details
    ISSN: 1432-0428
    Keywords: Adrenaline ; insulin ; glucose clamp ; glucose production ; glucose utilization ; β-adrenoceptor blockade
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The insulin-antagonistic effect of adrenaline was studied in seven healthy subjects with the euglycaemic clamp technique using two insulin infusion rates (40 and 1200 mU (m2)−1 min−1). The adrenergic receptor mediating the adrenaline effect was characterized by concomitant infusion of propranolol β 1+β 2-antagonist) or metoprolol (β 1-antagonist). Each subject was studied four times (placebo, adrenaline, adrenaline + propranolol, adrenaline + metoprolol). Glucose turnover was measured with D(3-3H)-glucose. Similar plasma insulin levels were reached in all studies with the two insulin infusion rates (mean; placebo 51 ± 3 and 7421 ± 337 mU/l respectively). Glucose production was completely inhibited by the low insulin level during placebo infusion. Adrenaline antagonized this effect so that a significant glucose production was seen at the low but not at the high insulin level. Propranolol, but not metoprolol, reversed this insulin-antagonistic effeet of adrenaline. Glucose utilization increased from 2.53 ±0.17 to 7.28 ± 0.88 mg · kg−1 · min−1 during placebo when the insulin levels were increased from 4± 0.3 to 51 ± 3 mU/l. Increasing the insulin levels 150-fold to ∼7500 mU/l only doubled the glucose utilization (14.68 ±1.14 mg·kg−1·min−1). Adrenaline induced a pronounced inhibition of glucose utilization at both insulin levels (78% and 37% inhibition respectively). Propranolol, but not metoprolol, prevented this effect of adrenaline. Thus, physiological adrenaline levels exert a pronounced insulin-antagonistic effect which is mediated by β 2-receptor stimulation. The inhibitory effect on glucose uptake is maintained even at high insulin levels when hepatic glucose production is completely abolished.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00506530
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of the insulin-antagonistic effect of growth hormone in man (1991)
    Springer
    Diabetologia 34 (1991), S. 500-506 
    Details
    ISSN: 1432-0428
    Keywords: Growth hormone ; insulin resistance ; glucose production ; glucose utilization ; dose response effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The insulin-antagonistic effect of growth hormone was characterized by infusing the hormone at three different infusion rates (6, 12 or 24 mU·kg−1·min−1) for one h in 11 healthy subjects. The insulin effect was measured with the euglycaemic clamp technique combined with D-(3-3H)-glucose infusion to evaluate glucose production and utilization. A control study with NaCl (154 mmol·l−1) infusion was also performed. The insulin levels during the clamps were similar in all studies (36±0.2 mU·l−1). Peak growth hormone levels were reached at 60 min (growth hormone 6mU·kg−1·h−1: 31±5; growth hormone 12 mU·kg−1·h−1: 52±4 and growth hormone 24 mU·kg−1·h−1: 102±8mU·l−1). The insulin-antagonistic effect of growth hormone started after ∼2 h, was maximal after 4–5 h (∼39% inhibition of glucose infusion rate between control and growth hormone 24 mU·kg−1·h−1) and lasted for 6–7 h after peak levels. The resistance was due to a less pronounced insulin effect both to inhibit glucose production and to stimulate glucose utilization. Growth hormone infusion of 12 mU·kg−1·h−1 induced a similar insulin-antagonistic effect as the higher infusion rate whereas 6 mU·kg−1·h−1 induced a smaller response with a duration of 1 h between 3–4 h after peak levels of growth hormone. The present study demonstrates that growth hormone levels similar to those frequently seen in Type 1 (insulin-dependent) diabetic patients during poor metabolic control or hypoglycaemia, have pronounced insulin-antagonistic effects. The effects starts after about 2–3 h, is maximal after 4–5 h and lasts for about 6–7 h. Both duration and inhibitory effect of growth hormone are related to the plasma levels, where a maximal effect is seen at about 50 mU·l−1 or higher.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00403286
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  • 4
    Electronic Resource
    Electronic Resource
    Impaired glucose transport and protein kinase B activation by insulin, but not okadaic acid, in adipocytes from subjects with Type II diabetes mellitus (1999)
    Springer
    Diabetologia 42 (1999), S. 819-825 
    Details
    ISSN: 1432-0428
    Keywords: Keywords PKB ; insulin ; okadaic acid ; Type II diabetes ; glucose transport.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aims/hypothesis. To study the effects of insulin and okadaic acid, a serine/threonine phosphatase inhibitor which does not increase PI3-kinase activity, on the rate of glucose transport and protein kinase B activation in adipocytes from healthy subjects and subjects with Type II (non-insulin-dependent) diabetes mellitus. Methods. Adipocytes were incubated with or without insulin or okadaic acid or both and glucose transport, protein kinase B activity, phosphorylation and protein expression measured. Results. Insulin and okadaic acid alone increased glucose uptake to a similar degree in adipocytes from healthy subjects and, when combined, exerted a partial additive effect. The effect of insulin was reduced by about 60 % in adipocytes from Type II diabetic patients, whereas the effect of okadaic acid was essentially unchanged and no further increase was seen when okadaic acid and insulin were combined. Okadaic acid increased protein kinase B activity to a greater extent (two to threefold) than insulin but only slightly increased the serine phosphorylation of protein kinase B. Adipocytes from Type II diabetic subjects exhibited both an impaired sensitivity as well as a reduced total serine phosphorylation and activation of protein kinase B in response to insulin but protein kinase B activity in response to okadaic acid was intact. Conclusion/interpretation. These results show that the ability of insulin to increase glucose transport and activate protein kinase B is reduced in fat cells from Type II diabetic subjects. Protein kinase B can, however, be activated by agents like okadaic acid which bypass the upstream defects in the insulin signalling pathway in Type II diabetic cells and, thus, increase glucose uptake. [Diabetologia (1999) 42: 819–825]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001250051232
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  • 5
    Electronic Resource
    Electronic Resource
    Reduced insulin binding to human fat cells following beta-adrenergic stimulation — experimental evidence and studies in patients with a phaeochromocytoma (1985)
    Springer
    Diabetologia 28 (1985), S. 901-906 
    Details
    ISSN: 1432-0428
    Keywords: Insulin resistance ; insulin receptors ; catecholamines ; β-adrenergic receptors ; phaeochromocytoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of β-adrenergic stimulation on insulin binding was studied in human fat cells in vitro. Isoproterenol rapidly (∼ 5 min) reduced insulin binding through a β-adrenergic and dose-dependent mechanism. The reduced binding was enhanced by the addition of adenosine deaminase and was also elicited by the addition of dibutyryl cAMP. This effect was due to a decreased number of binding sites. The reduction was rapidly reversed by propranolol (t1/2 ∼ 10 min) and other β-adrenoreceptor blocking agents. Insulin binding was also measured in fat cells from 6 patients with a phaeochromocytoma. A significant negative correlation between tracer binding and the log value of total urinary catecholamine excretion was found (r=−0.821,p〈0.05). Mean tracer insulin binding was reduced about 30% as compared to cells from 16 carefully matched control subjects. Decreased insulin binding was again mainly attributable to a decreased number of binding sites. Thus, β-adrenergic stimulation, both in vitro and in vivo, leads to a decreased number of binding sites for insulin in human fat cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00703133
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  • 6
    Electronic Resource
    Electronic Resource
    Human adipose tissue in culture V. Studies on the metabolic effects of insulin (1976)
    Springer
    Diabetologia 12 (1976), S. 137-143 
    Details
    ISSN: 1432-0428
    Keywords: Adipose tissue ; insulin ; catecholamines ; glycolytic enzymes ; glucose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Specimens of human adipose tissue were cultured for one week with or without the addition of insulin. The basal as well as the noradrenaline-stimulated lipolysis were enhanced in the explants cultured with insulin, showing that the long-term effect of the hormone is lipolytic. However, an acute antilipolytic effect of insulin could be demonstrated in these explants in the subsequent short-term incubations. The basal rate of glucose incorporation into the lipids was enhanced in the explants cultured with insulin. When insulin was added in the short-term incubations these explants did not further respond to the hormone while this was the case with the explants cultured without insulin. Thus, it seems that prolonged exposure to insulin leads to a diminished acute effect of the hormone on glucose metabolism. However, the same explants responded to the antilipolytic effect showing that insulin was able to bind itself to the membrane. The activities of hexokinase (HK), glucose-6-phosphate dehydrogenase (G6PDH), pyruvate kinase (PK) and lactate dehydrogenase (LDH) were increased in large fat cells both in freshly excised tissue and in the cultured explants. However, the activity of phosphofructokinase (PFK) did not correlate with the cell size. The presence of insulin during the culture period enhanced the activities of G6PDH, PK, and LDH, while this was not found for HK or PFK. The data thus suggest that the metabolic capacity of human fat cells is enhanced by long-term exposure to insulin. Although enzyme induction could be shown for G6PDH, PK and LDH it seems unlikely that this is of importance for the increased rates of glucose metabolism in these explants since the rate-limiting enzymes, HK and PFK, were not increased. Most probably, then, this stimulating effect of insulin is exerted on the membrane and the rate of glucose transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428979
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