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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To further define the mechanism(s) of insulin resistance in the liver associated with diabetes and fasting, we evaluated the ability of insulin to release an activator of pyruvate dehydrogenase activity from a liver particulate fraction. Insulin reproduceably and significantly enhanced the release of mediator from the liver particulate fraction of control animals. The particulate fractions from fasted and diabetic animals were resistant to this effect of insulin. Refeeding and insulin treatment, respectively, restored responsiveness to insulin. These data support the concept that alterations at or near the plasma membrane can be responsible for or accompany the insulin resistance observed in the liver in fasting and diabetes mellitus.
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PMID:Insulin resistance in the liver in fasting and diabetes mellitus: the failure of insulin to stimulate the release of a chemical modulator of pyruvate dehydrogenase. 634 Jun 85

Cultured human fibroblasts represent an appropriate model for studying both insulin receptor interaction and hormone responsiveness. We have investigated the properties of the pyruvate dehydrogenase multi-enzyme complex (PDC) and have studied the effects of various concentrations of porcine and biosynthetic human insulin (BHI) on the activity of the enzyme. Under optimal conditions of the assay, both BHI and porcine insulin activated PDC in a dose-dependent fashion in which full activation of the enzyme was achieved with 10(-8) M insulin. The half-maximal concentration for porcine and human insulin was similar, occurring at the level of 5 X 10(-9) M for activation of the PDC of human fibroblasts. We conclude that the PDC of cultured human fibroblasts is activated by both human and porcine insulin at a comparable physiologic concentration. Human fibroblasts may therefore serve as a useful model to study insulin action in isolated human tissue.
Diabetes 1984 Jul
PMID:Activation of pyruvate dehydrogenase complex by porcine and biosynthetic human insulin in cultured human fibroblasts. 637 23

The activity of pyruvate dehydrogenase complex was measured in skeletal muscle of congenital diabetic mice (KK mice) and control mice (ddN mice), each group in a starved or unstarved state, with or without muscular contraction. The age related increment of the level of active form pyruvate dehydrogenase complex in KK mice was not found compared with that in ddN mice. In 4 weeks old KK mice, the increment of the active form by muscular contraction or the decrease by 48 hours starvation was not different from the control mice. On the other hand, in 12 week old KK mice, the changes of the enzyme activity by muscular contraction were different from the normal control. These results suggest that the activity of pyruvate dehydrogenase complex is intimately related to the onset of diabetes.
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PMID:Change of skeletal muscles pyruvate dehydrogenase complex activities in congenital diabetic mice (KK mice) by aging or contraction. 661 27

The effects of increased cardiac work and availability of pyruvate on the activation of pyruvate dehydrogenase (PDH) was studied in hearts isolated from diabetic rats. Diabetes resulted in complete inactivation of myocardial PDH. At low levels of cardiac work, PDH in hearts perfused with glucose or glucose plus insulin as substrate remained in the inactive form even after 25 min of in vitro perfusion indicating that the factors causing inactivation in the diabetic animal were not easily reversed in vitro. Raising the level of ventricular pressure development from 60 to 180 mmHg caused only a small increase in the percent of active PDH (from 0.3 to 16%). Comparable values in control hearts were 61 and 96% active PDH. Addition of high levels of perfusate pyruvate along with glucose increased the percent active PDH from 0.3 to 45 at 60 mmHg ventricular pressure. Although pyruvate increased active PDH the effect was much less than in normal hearts (85% active under comparable conditions). Increased ventricular pressure development (180 mmHg) in diabetic hearts receiving pyruvate caused a further activation of PDH to 66% but again this effect was much less than occurred in normal hearts (96% active). Inactivation of PDH in hearts from diabetic animals could not be accounted for by high mitochondrial levels of known effectors such as NADH/NAD, acetyl CoA/CoA and ATP/ADP. Increasing cardiac work resulted in decreased mitochondrial levels of NADH, acetyl CoA and ATP, but these changes had little effect on PDH activity. The date indicate that PDH in hearts of diabetic animals is resistant to activation by increased cardiac work and high tissue levels of pyruvate.
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PMID:Effects of increased cardiac work on pyruvate dehydrogenase activity in hearts from diabetic animals. 687 84

The effect of halothane anaesthesia on the activity of the mitochondrial enzyme pyruvate dehydrogenase was studied in starved lactating rats. Extracts of freeze-clamped mammary gland and liver were assayed for pyruvate dehydrogenase activity. The fraction of the enzyme in the phosphorylated inactive form was increased greatly by starvation or by streptozotocin diabetes, and halothane anaesthesia did not disturb this effect. In starved animals not exposed to halothane, injection of insulin led to a rapid increase in the active fraction of the enzyme in mammary gland but not in liver. In animals under halothane anaesthesia this effect of insulin was largely abolished. The combination of starvation and halothane anaesthesia may impair mitochondrial accumulation of calcium which may be involved in the stimulation of pyruvate dehydrogenase by insulin.
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PMID:Halothane anaesthesia can block insulin stimulation of pyruvate dehydrogenase activity in mammary glands of 24-hour starved lactating rats. 700 Jan 4

Insulin treatment of adipocytes increased the amount or activity of a low molecular weight, acid-stable material which, when isolated from intact adipocytes by heat extraction and subsequent Sephadex G25 chromatography, yielded a single active fraction that stimulated mitochondrial pyruvate dehydrogenase by activating the phosphatase and not by altering the kinase activity. Phosphatase activation was demonstrated by the ability of the active material to increase pyruvate dehydrogenase activity in the absence of ATP and by the ability of NaF, a phosphatase inhibitor, to this stimulation. Involvement of the kinase in this activation mechanism was eliminated by the fact that, in the presence of ATP, (1) NaF completely blocked the stimulation of pyruvate dehydrogenase by the active fraction, and (2) the stimulation of pyruvate dehydrogenase by dichloroacetic acid, a kinase inhibitor, was additive to the stimulation caused by the active fraction. This active fraction may contain an intracellular chemical mediator or second messenger for insulin.
Diabetes 1980 Oct
PMID:Isolation from rat adipocytes of a chemical mediator for insulin activation of pyruvate dehydrogenase. 700 67

1. Previous studies showed that the activation of pyruvate dehydrogenase within intact rat heart mitochondria of pyruvate is much diminished in mitochondria from starved or diabetic animals [see Kerbey, Randle, Cooper, Whitehouse, Pask & Denton (1976) Biochem. J. 154, 327-348]. In the present study, diminished responses to added Ca2+ and ADP were also found in these mitochondria. 2. Starvation or diabetes did not affect the mitochondrial respiratory control ratio of the ATP content. Moreover, starvation and diabetes did not alter the response of the intramitochondrial Ca2+-sensitive enzyme, 2-oxoglutarate dehydrogenase, to changes in the extramitochondrial concentration of Ca2+ and 2-oxoglutarate, thus indicating that there were no appreciable changes in the distribution of Ca2+ and H+ across the mitochondrial inner membrane. 3. Pyruvate, Ca2+ and ADP were found to have synergistic effects on pyruvate dehydrogenase activity, particularly in mitochondria from starved and diabetic rats. 4. The results suggest that the effects of diabetes and starvation on pyruvate dehydrogenase are not brought about by changes in the distribution of these effectors across the mitochondrial inner membrane or by changes in the intrinsic sensitivity of the kinase or phosphatase of the pyruvate dehydrogenase system to pyruvate, Ca2+ or ADP; rather it is probably that there is an increase in the maximum activity of kinase relative to that of the phosphatase. 6. The results also lend further support to the hypothesis that adrenaline may bring about the activation of pyruvate dehydrogenase in the rat heart by an increase in the intramitochondrial concentration of Ca2+.
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PMID:Studies on the interactions of Ca2+ and pyruvate in the regulation of rat heart pyruvate dehydrogenase activity. Effects of starvation and diabetes. 709 23

Four patients with severe lactic acidosis associated with septic shock were treated with sodium dichloroacetate (DCA) (50 mg/kg body wt), an activator of pyruvate dehydrogenase. All patients were in a group with an expected mortality rate of 90-100%, based on previous studies. In one patient, treatment with DCA was associated with a decrease in blood lactate levels from 11.2 mM before treatment to 0.8 mM 16 h later. Markedly elevated blood pyruvate and alanine levels also decreased to normal. After treatment, the arterial blood pH rose to 7.53, and vasopressor agents were no longer needed to support blood pressure. Some degree of biochemical improvement was also noted in the other cases in whom the blood lactate levels before treatment were 15, 17, and 31 mM. However, all three patients eventually died of refractory acidosis.
Diabetes Care
PMID:Treatment of severe lactic acidosis with dichloroacetate. 715 55

Intravenous administration of the fatty acid oxidation inhibitor 2-tetradecylglycidic acid had no effect on the proportion of pyruvate dehydrogenase complex in the active form in heart, diaphragm or gastrocnemius muscles or in liver, kidney or adipose tissue of fed normal rats. The compound reversed the effect of 48h starvation (which decreased the proportion of active complex) in heart muscle, partially reversed the effect of starvation in kidney, but had no effect in the other tissues listed. The compound failed to reverse the effect of alloxan-diabetes (which decreased the proportion of active complex) in any of these tissues. In perfused hearts of fed normal rats, 2-tetradecylglycidate reversed effects of palmitate (which decreased the proportion of active complex), but it had no effect in the absence of palmitate. In perfused hearts of 48h-starved rats the compound increased the proportion of active complex to that found in fed normal rats in the presence or absence of insulin. In perfused hearts of diabetic rats the compound normalized the proportion of active complex in the presence of insulin, but not in its absence. Palmitate reversed the effects of 2-tetradecylglycidate in perfused hearts of starved or diabetic rats. Evidence is given that 2-tetradecylglycidate only reverses effects of starvation and alloxan-diabetes on the proportion of active complex in heart muscle under conditions in which it inhibits fatty acid oxidation. It is concluded that effects of starvation and alloxan-diabetes on the proportion of active complex in heart muscle are dependent on fatty acid oxidation. Insulin had no effect on the proportion of active complex in hearts or diaphragms of fed or starved rats in vitro. In perfused hearts of alloxan-diabetic rats, insulin induced a modest increase in the proportion of active complex in the presence of albumin, but not in its absence.
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PMID:Effect of the fatty acid oxidation inhibitor 2-tetradecylglycidic acid on pyruvate dehydrogenase complex activity in starved and alloxan-diabetic rats. 715 98

1. Inactive pyruvate dehydrogenase phosphate complexes were partially purified from hearts of fed, starved or alloxan-diabetic rats by using conditions that prevent phosphorylation or dephosphorylation. 2. Unoccupied sites of phosphorylation were assayed by incorporation of 32P from [gamma-32P]ATP into the complexes. Total sites of phosphorylation were assayed by the same method after complete reactivation, and thus dephosphorylation, of complexes by incubation with pyruvate dehydrogenase phosphate phosphatase. Occupancy is assumed from the difference (total sites--unoccupied sites). Percentage incorporation into individual sites was measured by high-voltage electrophoresis after tryptic digestion. 3. Values (means +/- S.E.M., in nmol of phosphate/unit of inactive complex) for total sites, occupied sites and percentage occupancies, with numbers of observations in parentheses were: fed, 2.1 +/- 0.04, 1.15 +/- 0.04, 54.8 +/- 1.6% (39); starved, 2.05 +/- 0.03, 1.85 +/- 0.03, 90.2 +/- 1.4% (28); alloxan-diabetic, 1.99 +/- 0.03, 1.72 +/- 0.03, 86.4 +/- 1.4% (68%). 4. Values (means +/- S.E.M. for percentage occupancy) for individual sites of phosphorylation in pyruvate dehydrogenase phosphate given in the order sites 1, 2 and 3 were : fed, 100 +/- 2.7, 27.8 +/- 1.6, 33.9 +/- .9; starved, 100 +/- 1.4, 76.2 +/- 2.0, 92.4 +/- 1.5; alloxan-diabetic, 100 +/- 1.2, 64.0 +/- 1.7, 94.6 +/- 1.4. 5. It is concluded that starvation or alloxan-diabetes leads to a 2--3-fold increase in the occupancy of phosphorylation sites 2 and 3 in pyruvate dehydrogenase phosphate in rat heart in vivo.
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PMID:Occupancy of sites of phosphorylation in inactive rat heart pyruvate dehydrogenase phosphate in vivo. 730 68


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