Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We identified the earliest events in autophosphorylation of the insulin receptor after insulin addition. Insulin-stimulated autophosphorylation at specific sites in the tyrosine kinase domain of the receptor's beta-subunit is correlated kinetically with activation of kinase-catalyzed phosphorylation of a model substrate (reduced and carboxyamidomethylated lysozyme; RCAM-lysozyme). To identify these sites, the deduced amino acid sequence of the 3T3-L1 adipocyte insulin receptor of the mouse was determined. Insulin-induced activation of substrate phosphorylation was shown to require autophosphorylation of three neighboring tyrosines (Tyr1148, Tyr1152, and Tyr1153) in the mouse receptor. A search for cellular substrates of the receptor kinase revealed that insulin causes accumulation of a 15,000-Mr phosphorylated (on tyrosine) cytosolic protein (pp15) in 3T3-L1 adipocytes treated with oxophenylarsine (PAO). PAO blocks turnover of the phosphoryl group of pp15, causing its accumulation, and thereby appears to interrupt signal transmission from the receptor to the glucose-transport system. Two membrane-bound protein phosphotyrosine phosphatases that are inhibited by PAO and are apparently responsible for the turnover of the pp15 phosphoryl group have been purified from 3T3-L1 adipocytes and characterized. These and other results support the hypothesis that turnover of the phosphoryl group of pp15, a product of insulin-receptor tyrosine kinase action, couples signal transmission to the glucose-transport system. [32P]pp15 was purified to homogeneity from 3T3-L1 adipocytes. Amino acid and radiochemical sequence analysis of the purified tryptic [32P]phosphopeptide revealed that pp15 is the phosphorylation product of 422(aP2) protein, a 15,000-Mr adipocyte protein whose cDNA we previously cloned and sequenced. 422(aP2) protein was found to bind fatty acids. When exposed to a free fatty acid, notably oleic acid, 422(aP2) protein becomes an excellent substrate of the isolated insulin-receptor tyrosine kinase. Compelling evidence indicates that on binding fatty acid, 422(aP2) protein undergoes a conformational change whereby Tyr19 becomes accessible to the receptor tyrosine kinase and undergoes O-phosphorylation. Adipose tissue and skeletal and heart muscle, which exhibit insulin-stimulated glucose uptake, express a specific insulin-responsive glucose transporter. A cDNA (GT2) that encodes this protein was isolated from a mouse 3T3-L1 adipocyte library and sequenced. We also isolated and characterized the corresponding mouse gene GLUT4. DNase I footprinting with nuclear extracts from 3T3-L1 cells revealed that a differentiation-specific nuclear factor binds to the GLUT4 promoter. The purified transcription factor C/EBP binds at the same position.(ABSTRACT TRUNCATED AT 400 WORDS)
Diabetes Care 1990 Jun
PMID:Insulin-receptor tyrosine kinase and glucose transport. 216 54

Neonatal rats that receive injections of streptozotocin develop insulin resistance and non-insulin-dependent diabetes mellitus (NIDDM). Insulin resistance precedes development of overt diabetes, and some insulin bioeffects are known to be impaired at the postreceptor level in several target tissues of this rat model. We studied a possible contribution of altered insulin receptor function to the impaired insulin action in these animals. Activity of the insulin-sensitive tyrosine kinase of receptors from kidney cortical basolateral membranes (BLMs) obtained from these nonobese, normoinsulinemic, insulin-resistant rats was examined at the age of 5 weeks (before overt hyperglycemia developed) and at 10 weeks (after NIDDM was fully manifested). In experimental animals, at both 5 and 10 weeks, binding of insulin labeled with iodine 125 to crude kidney BLM was higher than in their control littermates. However, no such difference was found with insulin binding to purified insulin receptors from BLM. The insulin receptor, tyrosine kinase activity (TKA), to an exogenous substrate was higher in diabetic tissue both at basal condition and after insulin stimulation at both 5 and 10 weeks of age. Autophosphorylation of the beta-subunit of the insulin receptor and the proportion of tyrosine-phosphorylated ("active") insulin receptors from BLM was also higher in diabetic rats. There was an age-related increase in the receptor TKA between 5 and 10 weeks in both diabetic and control animals. A 24-hour fast normalized insulin binding and nearly abolished the difference in TKA of the BLM receptors from 5-week-old insulin-resistant rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Abnormal insulin receptor tyrosine kinase activity in kidney basolateral membranes from non-insulin-dependent diabetic rats. 216 78

Insulin action in skeletal muscle is markedly depressed at late pregnancy. The purpose of this study was to investigate whether insulin resistance of skeletal muscle during pregnancy is associated to intrinsic alterations in the biological activities of insulin receptor. To that end, insulin receptors from mixed, red and white skeletal muscle from control and 19-20 days pregnant rats were partially purified and insulin binding and tyrosine kinase activities were evaluated. Muscle insulin receptors from diabetic rats were also studied provided that changes in receptor number and tyrosine kinase activities had been clearly substantiated. Total high affinity insulin binding sites expressed either per gram of tissue or per milligram of protein were similar in muscles from control and pregnant rats, in contrast to diabetic rats in which an increased high affinity receptor number was observed. No differences in affinity were detected for high affinity binding sites in any of the groups investigated. The integrity of the partially purified insulin receptors from control and pregnant groups was identical as determined by affinity cross-linking of [125I-TyrB26]insulin to the receptor and by beta-subunit phosphorylation. Autophosphorylation of the beta-subunit and the pattern of phosphopeptides obtained after digestion of phosphorylated beta-subunit with trypsin, elastase, and staphylococcal V8 protease were indistinguishable in control and pregnant groups. Tyrosine receptor kinase was also similar in receptor preparations from control and pregnant muscle. This is in contrast to diabetes in which a defective tyrosine kinase was confirmed. In order to detect possible differences due to the fiber type, further sets of experiments were performed in receptor preparations from red and white muscle. In keeping with previous data, tyrosine kinase activity of the insulin receptor was 2.5-fold greater in red muscle than white muscle; however, under these conditions, receptor kinase activity was unmodified in preparations from pregnant rats in red and white muscle fibers. Recent evidence has revealed the existence of an insulin binding inhibitor in muscle extracts. We detected the presence of such an inhibitor in the flow-through fraction after WGA chromatography. This inhibitory activity was found to be greater in muscle extracts obtained from pregnant rats as compared to fractions from control rats. We conclude that insulin resistance of skeletal muscle at late pregnancy is not explained by intrinsic modifications of insulin receptor binding or kinase activities.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Insulin resistance of skeletal muscle during pregnancy is not a consequence of intrinsic modifications of insulin receptor binding or kinase activities. 217 19

In vivo insulin resistance is a characteristic of the liver and peripheral tissues in 10-wk-old female rats with non-insulin-dependent diabetes induced by streptozotocin given on day 5 after birth. Oral administration of vanadate (0.2 mg/ml) for 20 days in the diabetic rats lowered their plasma glucose levels to normal values without affecting their basal plasma insulin levels. In the basal state as well as after submaximal or maximal hyperinsulinemia (euglycemic clamp studies), peripheral glucose utilization and hepatic glucose production in vivo were normalized in the diabetic rats after the vanadate treatment. In wheat germ agglutinin purified receptors, 125I-labeled porcine insulin binding, basal and insulin-stimulated insulin receptor kinase activities for both the autophosphorylation of the beta-subunit and the phosphorylation of the artificial substrate poly (Glu-Tyr) 4:1, were found identical in diabetic and control rats, treated or not with vanadate. Liver phosphoenolpyruvate carboxykinase activity was significantly enhanced in untreated diabetic rats (P less than 0.01) as compared with control rats and returned to normal values after the 20-day vanadate treatment. Thus, in that model of non-insulin-dependent diabetes, 1) oral vanadate exerts a corrective insulin-like effect on impaired insulin action both at the level of liver and peripheral tissues, 2) impaired insulin action with no alteration of the insulin receptor tyrosine kinase is observed in the liver of untreated rats, and 3) corrective effect of vanadate on liver glucose metabolism is probably distal to the insulin receptor kinase activity.
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PMID:Impaired insulin action but normal insulin receptor activity in diabetic rat liver: effect of vanadate. 218 Mar 15

To describe quantitatively the in vivo distribution and elimination of insulin, high-performance liquid chromatography (HPLC) separation was applied to the pharmacokinetic study of human insulin labeled with 125I at tyrosine A14 (A14-125I-insulin) as a tracer. Intact A14-125I-insulin levels were determined by HPLC and trichloroacetic acid (TCA) precipitation in plasma and various tissues after its intravenous bolus injection into mice. TCA precipitation consistently overestimated the intactness of A14-125I-insulin compared with HPLC, possibly due to the presence of both a TCA-precipitable intermediate degradation product of labeled insulin found in HPLC elution profiles and reported high-molecular-weight forms of labeled insulin in plasma. Thus, TCA precipitation gave a considerably lower total plasma clearance (Cltot) value than HPLC. The half-life of A14-125I-insulin was prolonged by a simultaneous injection of 8 U/kg unlabeled insulin, and labeled insulin behaved similarly to [14C]inulin (an extracellular fluid marker). The concentration time profiles of HPLC-separated labeled insulin in plasma were analyzed by a noncompartmental moment method, and both Cltot and steady-state apparent volume distribution (VDss) of A14-125I-insulin were considerably decreased by unlabeled insulin coadministration. In particular, VDss of labeled insulin decreased by 79%, similar to that of inulin (181 ml/kg), suggesting that the nonspecific binding of labeled insulin to tissues was so small that VDss of labeled insulin was reduced to the extracellular fluid volume (approximately 20% of the body weight) when its receptor binding was blocked effectively by unlabeled insulin.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1990 May
PMID:Application of HPLC in disposition study of A14-125I-labeled insulin in mice. 218 7

The effect on skeletal muscle proteolysis of acute (20-hour) glucocorticoid treatment (dexamethasone 1.5 mg/kg, subcutaneously [SC]) was tested using the eviscerated rat preparation. According to this method, the peripheral tissues (primarily the skeletal muscles) are isolated by functional hepatectomy-nephrectomy. Total proteolysis is estimated from the rate of rise of plasma tyrosine concentration in the presence of cycloheximide to block protein synthesis. Myofibrillar proteolysis is measured from the rate of release into the plasma of the nonreutilized, nonmetabolized amino acid 3-methylhistidine (3MH), in the absence of cycloheximide. In normal rats, dexamethasone increased total proteolysis by 20% and myofibrillar proteolysis by 75% (both P less than .025 v saline controls). In diabetic-adrenalectomized rats prepared 2 weeks earlier (65 mg/kg streptozocin [STZ] followed by adrenalectomy), dexamethasone caused much greater increments in rates of total proteolysis (94%) and myofibrillar proteolysis (240%) (both P less than .001 v saline controls). Because diabetic animals are extremely sensitive to glucocorticoid-induced proteolysis, we also examined whether the acute proteolytic effect of diabetes itself might be mediated by adrenal cortical hormones. Previously adrenalectomized rats studied 20 hours after STZ showed a 40% augmentation of total proteolysis (P less than .01), an effect similar to that produced by acute diabetes in rats with intact adrenals. We conclude that glucocortical hormones cause a catabolic effect on total and myofibrillar skeletal muscle protein which is exaggerated when the counteracting action of insulin is reduced, but that the excess proteolysis of acute insulin deficiency is independent of the endogenous glucocorticoids secretion.
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PMID:Influence of glucocorticoids on skeletal muscle proteolysis in normal and diabetic-adrenalectomized eviscerated rats. 219 Nov 92

Vanadate ions, low-molecular-weight phosphate analogues, mimic most of the rapid actions of insulin in various cell types. When administered orally to diabetic hyperglycemic rats, vanadate reaches the circulation, mimics insulin stimulation of glucose uptake and metabolism, and leads to normoglycemic and partial anabolic states. In addition, vanadate restores tissue responsiveness to insulin and hepatic glycogen levels and activates new synthesis of key enzymes for carbohydrate metabolism. This suggests that correcting hyperglycemia is sufficient to correct the typical metabolic alterations found in streptozocin-induced diabetic rats. Several weeks of oral administration of vanadate to diabetic rats has not produced detectable liver or kidney toxicity. The mechanism by which vanadate mimics the actions of insulin is still obscure. Unlike insulin, vanadate does not seem to stimulate the autophosphorylation and endogenous tyrosine phosphorylation of insulin-receptor kinase or other intracellular proteins either directly or by virtue of its known inhibitory effect on protein phosphotyrosine phosphatase. Results from many studies support a model in which vanadate activates glucose metabolism by either utilizing an alternative (insulin-independent) cascade or bypassing the early events of the insulin-dependent cascade. Either of these possibilities is of clinical importance, because early insulin events may become defective, as a result of severe hyperinsulinemia, and may contribute to insulin resistance. Alternative pathways by which vanadate may stimulate glucose metabolism, e.g., by increasing intracellular Ca2+ levels and/or regulating intracellular and intravesicular pH, are discussed. From a clinical perspective, studies should be continued in evaluating the level of vanadate toxicity after prolonged treatment and searching for agents that potentiate its insulin mimetic actions in vitro and in vivo.
Diabetes 1990 Jan
PMID:Insulin-mimetic effects of vanadate. Possible implications for future treatment of diabetes. 221 51

Metabolic potency of des-(B26-B30)-insulin-B25-amide, [TyrB25]des- (B26-B30)-insulin-B25-amide and [HisB25]des-(B26-B30)-insulin-B25-amide was studied in anaesthetized rats. Compared to insulin, full potency for des-(B26-B30)-insulin-B25-amide and an enhanced potency for both substituted analogues has been described previously on rat adipocytes in vitro. Hypoglycaemic effects following i.v. injection of all of these analogues were almost identical to those of native insulin with a half-maximal effective dose of approximately 3 nmol.kg-1. Stimulation of glucose metabolism during euglycaemic hyperinsulin-/analogueaemic clamp studies was indistinguishable from that of the native hormone with a maximal stimulation of approximately 19 mg.kg-1.min-1 and half-maximal effective hormone concentrations of approximately 1 pmol.ml-1. Analogue action on individual peripheral tissues estimated by the uptake of 2-deoxyglucose as well as stimulation of lipogenesis in epididymal fat was not different to that of insulin. These data demonstrate that C-terminal amidation of des-(B26-B30)-insulin results in a shortened molecule with full in vivo metabolic potency. When substituting phenylalanine in position B25 by tyrosine or histidine, the insulin-identical potency is preserved.
Diabetes Res Clin Pract 1990 Jul
PMID:In vivo metabolic activity of des-(B26-B30)-insulin-B25-amide and related analogues in the rat. 222 26

We identified a possible endogenous substrate (pp185) of the insulin-receptor kinase in human adipocytes by treating intact cells with insulin and immunoblotting the cellular extracts with polyclonal antiphosphotyrosine antibody. This 185,000-Mr protein was phosphorylated on tyrosine residues in response to insulin in both rat and human adipocytes. The time course of pp185 phosphorylation at 37 degrees C was rapid and corresponded closely to insulin-receptor autophosphorylation but preceded insulin-stimulated glucose transport. Unlike many growth factor receptors, including the insulin receptor, pp185 was not adsorbed to wheat-germ agglutinin. We found that pp185 phosphorylation occurred at 12 degrees C and that the phosphoprotein was associated with both cytoplasmic and membrane fractions at this temperature. Furthermore, pp185 phosphorylation was induced to the same extent as insulin by vanadate and hydrogen peroxide, compounds previously shown to mimic the biologic effects of insulin. In addition, dose-response analysis of insulin-stimulated glucose transport, receptor autophosphorylation, and pp185 phosphorylation resulted in ED50 values of 0.3, 12, and 12 ng/ml, respectively. These results demonstrate the magnitude of "spare" autophosphorylation and pp185 phosphorylation with respect to glucose transport stimulation in human adipocytes. To determine whether the insulin resistance characteristic of non-insulin-dependent diabetes mellitus (NIDDM) and obesity is associated with a defect in receptor autophosphorylation and/or endogenous substrate phosphorylation, we estimated the extent of beta-subunit and pp185 phosphorylation in adipocytes from NIDDM, obese, and healthy subjects. Although the efficiency of coupling between receptor activation and pp185 phosphorylation was normal in obesity and NIDDM, the capacity for insulin-receptor autophosphorylation was approximately 50% lower in NIDDM subjects compared with nondiabetic obese or lean subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1990 Feb
PMID:Insulin-receptor autophosphorylation and endogenous substrate phosphorylation in human adipocytes from control, obese, and NIDDM subjects. 222 34

We examined insulin binding, insulin-stimulated autophosphorylation, and phosphorylation of poly(Glu.Na,Tyr)4:1 by liver and skeletal muscle insulin receptor from lean, obese, and obese streptozocin-induced diabetic Zucker rats. Induction of diabetes with streptozocin (30 mg/kg) lowered the lasting insulin level from 11.4 to 3.8 ng/ml, which was not significantly greater than the lean control level. Autophosphorylation and tyrosine kinase activity of liver insulin receptors were increased 70-100% in the obese control group (relative to lean rats), but diabetes reversed this hyperresponsiveness to insulin. In muscle, obesity was associated with a 40-50% decrease in autophosphorylation and tyrosine kinase activity, which was also reversed in the diabetic state. Autophosphorylation and tyrosine kinase activity were significantly correlated in liver and muscle and were also correlated with fasting insulin levels. These data suggest that insulin-receptor tyrosine kinase activity is regulated differently in liver and muscle and that the abnormalities in kinase activity associated with the obese Zucker rat are at least partly secondary to hyperinsulinemia.
Diabetes 1990 May
PMID:Effect of streptozocin-induced diabetes on insulin-receptor tyrosine kinase activity in obese Zucker rats. 233 19


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