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)

The presence of an enzyme that hydrolyzes ATP to AMP and PPi was demonstrated in a 27,000 X g particulate and supernatant fraction of mouse pancreatic islets. The enzyme was stimulated by addition of Ca2+, Zn2+, and Co2+. Addition of calmodulin or trifluoperazine had no effect. In the presence of Ca2+ and Zn2+, the Michaelis constant (Km) for ATP was approximately 0.1 mM and the maximum velocity (Vmax) was close to 90 nmol X min-1 X mg protein-1. After preincubation of the islets for 30 min with 16.7 mM glucose or 5 mM glucose with 1 mM 3-isobutyl-1-methylxanthine (IBMX), a three- to fourfold increase in enzyme activity was seen. Direct addition of IBMX or cAMP to the enzyme assay also had a small stimulatory effect. Preincubation with the insulin secretagogues leucine and alpha-ketoisocaproic acid did not affect the enzyme activity. The possible function of the enzyme in pancreatic islets is discussed in relation to hypotheses given for the function of similar enzyme(s) in other tissues.
Diabetes 1986 Oct
PMID:Presence of ATP-pyrophosphohydrolase in mouse pancreatic islets. 242 87

Ca2+ pump activity of skeletal muscle microsomes containing fragments of sarcoplasmic reticulum was examined in rats 8 wk after the induction of chronic diabetes by an intravenous injection of streptozotocin (65 mg/kg). In comparison with the control values, both ATP-dependent Ca2+ uptake and Ca2+-stimulated ATPase activities were increased in the microsomal fraction from diabetic rats. These changes were seen as early as 7 days after streptozotocin injection and were apparent at various times of incubation (1-10 min) as well as at different concentrations of free Ca2+ (10(-7)-5 X 10(-5) M Ca2+). Insulin administration to diabetic animals for 2 wk reversed Ca2+ uptake and ATPase activities to control levels. The increase in microsomal ATPase activity of the diabetic preparation due to cAMP-dependent protein kinase or calmodulin was greater than in the control microsomes and the depression by a specific inhibitor of protein kinase, but not of calmodulin, was greater in diabetic muscle. The enhanced Ca2+ pump activity was associated with altered phospholipid composition and protein profile of the diabetic preparations. The rate of Ca2+ release from microsomal vesicles was unaffected by the diabetic condition. Isometric contractile force development as well as positive dF/dt and negative dF/dt of the skeletal muscle from diabetic animals were higher at different pulse strengths (0.5-100 V) and at different Ca2+ concentrations (0.25-2.5 mM). These results suggest that diabetes is associated with enhanced sarcoplasmic reticular Ca2+ pump activity, and this may account for the hyperfunction of skeletal muscle in this disease.
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PMID:Calcium pump activity of sarcoplasmic reticulum in diabetic rat skeletal muscle. 243 Apr 66

Calmodulin is a substrate for insulin-receptor kinase obtained from rat adipocytes and hepatocytes and human placenta. In this study, we demonstrate that insulin stimulates the phosphorylation of calmodulin via insulin receptors partially purified from rat skeletal muscle. Phosphorylation of calmodulin was maximal in the presence of Mg2+ and insulin and the absence of Ca2+. Free-Ca2+ concentrations greater than 0.1 microM progressively inhibited phosphorylation with almost total inhibition at 200 microM Ca2+. Insulin-stimulated phosphorylation of calmodulin was dose dependent and saturable with half-maximal effect obtained at approximately 5 x 10(-10) M insulin. There was an absolute requirement for certain basic proteins, e.g., polylysine or protamine sulfate, to obtain phosphate incorporation into calmodulin. Polylysine stimulated the phosphorylation of calmodulin independently of insulin, but this was increased up to sixfold by the addition of insulin. Phosphate incorporation into calmodulin increased with increasing concentration of the substrate up to a saturating concentration of 2.4 microM. The Km for calmodulin was approximately 0.2 microM. Up to 0.15 mol of phosphate was incorporated per mole of calmodulin with tyrosine the predominant amino acid phosphorylated. The observations that calmodulin is phosphorylated by insulin-receptor kinase from all three classic target organs for insulin confirm that calmodulin is a general substrate for this kinase and suggest that Ca2+ and calmodulin may be components of the insulin-signaling mechanism.
Diabetes 1989 Jan
PMID:Calmodulin as substrate for insulin-receptor kinase. Phosphorylation by receptors from rat skeletal muscle. 253 26

To elucidate the role of calmodulin in insulin action, we examined the effect of the calmodulin antagonists, W-7 and W-5, on glucose transport in isolated rat adipocytes. W-7 inhibited insulin-stimulated 2-deoxyglucose uptake by 18% at 100 microM, but it did not affect basal uptake levels. W-5, a less potent analogue of W-7, however, had no significant effect at the same concentration, indicating that the effect was specific to calmodulin. Similar results were observed in a 3-O-methylglucose uptake study. Kinetic analysis of 2-deoxyglucose uptake revealed that W-7 affected the insulin-induced increase in Vmax but not Km. These results suggest that calmodulin modifies insulin action in the glucose transport system.
Diabetes Res Clin Pract 1989 Feb 15
PMID:W-7 specifically inhibits insulin-induced increase in glucose transport. 264 41

Treatment of pancreatic acini from diabetic rats with insulin resulted in a dose-dependent increase in the phosphorylation of ribosomal protein S6 when analyzed by two-dimensional gel electrophoresis. To study the presence of the protein kinase mediating this phosphorylation, soluble extracts of intact acini that had been previously treated with insulin were prepared and assayed for protein kinase activity with rat pancreatic ribosomes as a substrate. Activation of S6 kinase activity, observed in a time-dependent manner, was maximal after 20-30 min and, in a dose-dependent manner, was half-maximal at 1 nM and maximal at 10 nM insulin concentration. Based on cofactor requirements, substrate specificity, and a slow activation of the enzyme, the S6 kinase was distinct from cAMP-dependent, Ca2+-calmodulin-dependent, and Ca2+-phospholipid-dependent protein kinases and protease-activated kinase II. The S6 kinase activated by insulin was highly specific for the ribosomal protein S6 when compared with various substrates, including casein, glycogen synthase, phosphorylase b, phosvitin, histone HIII-S, and histone HVIII-S. Protein S6 phosphorylation in intact acini and activation of the S6 kinase by insulin showed similar dose-response curves, consistent with the S6 kinase being responsible for the protein S6 phosphorylation in intact acini. The comparison of the dose-response curves for S6 phosphorylation and protein synthesis in acini suggests that there is a close correlation between these two insulin actions.
Diabetes 1989 May
PMID:Insulin and ribosomal protein S6 kinase in rat pancreatic acini. 265 25

Calmodulin is implicated as the primary transducer of the calcium signal in pancreatic beta cells, where it is present at very high concentrations. We have produced three lines of transgenic mice carrying a calmodulin minigene regulated by the rat insulin II promoter. Immunohistochemistry and hybridization analyses indicated a 5-fold increase in the content of calmodulin and its mRNA in beta cells. Transgenic mice developed severe diabetes within hours of birth. The diabetes was progressive and characterized by elevated blood glucose and glucagon that coincided with reduced serum and pancreatic insulin. The disease appears to have both secretory and cell destruction components. beta Cell pathology was evident in the diabetic neonate but not in the fetus, suggesting that the early onset of diabetes exacerbated possible toxic effects of excess calmodulin. These animals provide a new diabetes model to evaluate how abnormal calcium homeostasis alters the carefully programmed secretory activity and development of the beta cell.
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PMID:Calmodulin-induced early-onset diabetes in transgenic mice. 267 40

The In-R1-G9 cell line is one of the clones derived from the In-111-R1 hamster insulinoma cell line and produces glucagon. The secretory responses of In-R1-G9 cells were further examined to characterize the nature of the cells. Vincristine had no effect on glucagon secretion and colchicine enhanced glucagon secretion slightly after a short incubation. Two calmodulin inhibitors, trifluoperazine and chlorpromazine, did not affect glucagon secretion. Monensin at 10(-8) M suppressed glucagon secretion by 50%. Secretion of glucagon was calcium-dependent. The addition of A23187 to the incubation medium resulted in a 180% increase over control for 1 h and calcium deprivation from the medium suppressed glucagon secretion markedly. Theophylline, a phosphodiesterase inhibitor, caused a 230% increase in glucagon secretion. An experiment using cycloheximide suggested that newly synthesized glucagon appears in the medium at 30 min. This cell line should be useful for various experiments in many fields of research.
Diabetes Res Clin Pract 1988 Feb 19
PMID:Characterization of secretory responses of a glucagon-producing In-R1-G9 cell line. 283 60

Linolenic acid, a polyunsaturated fatty acid, has an insulin synergizing stimulatory effect on adipocyte lipogenesis. Since phorbol esters are also known to exert a similar effect through the activation of protein kinase C, and since they have fatty acid moieties, we investigated whether linolenic acid exerted its stimulatory effect through protein kinase C activation and whether calcium was involved in this mechanism. Our experiments show that H7, an inhibitor of protein kinase C; verapamil, a calcium blocker; and calmodulin inhibitors inhibited basal, insulin- and linolenic acid-stimulated lipogenesis. They also negated the insulin synergizing effect of linolenic acid. We conclude that linolenic acid, and possibly other unsaturated fatty acids, exert their stimulatory effect through stimulation of protein kinase C, calcium entry and calmodulin activation. These three processes are also important in maintaining basal lipogenesis.
Diabetes Res 1988 Jul
PMID:The effect of polyunsaturated fatty acids on rat adipocyte lipogenesis: the role of protein kinase C, calcium and calmodulin. 290 78

The direct effect of insulin on the high-affinity Ca2+-Mg2+-ATPase was studied in kidney proximal tubular basolateral membranes (BLM) obtained from control and streptozocin-induced non-insulin-dependent diabetes mellitus (NIDDM) rats. Plasma glucose of the diabetic animals was only mildly elevated (217 +/- 9 vs. 138 +/- 3 mg/dl). Both high- and low-affinity calcium-dependent Ca2+-Mg2+-ATPase activities were identified in the BLM. Enzyme activity in BLM from diabetic rats was higher at all Ca2+ concentrations tested due to a higher maximum velocity of the enzyme from NIDDM rats. The high-affinity Ca2+-Mg2+-ATPase activity was inhibited by trifluoroperazine (TFP) in both membranes. No difference in calmodulin content was found in the membranes from the diabetic and control rats. Insulin (16-200 microU/ml) significantly increased the high-affinity Ca2+-Mg2+-ATPase activity (17-40%) in membranes from control animals but had no effect on the enzyme activity in the membranes from the NIDDM rats. The basal activity of the enzyme at 0.1 microM free Ca2+ was higher in the BLM from the NIDDM animals compared to controls (17.8 +/- 0.5 vs. 14.7 +/- 0.8 nM Pi X mg-1 X min-1; P less than .02). There was no effect of insulin on the Ca2+-independent ATPase activity of BLM preparations. These findings demonstrate a defect in the ability of insulin to regulate the high-affinity Ca2+-Mg2+-ATPase activity in BLM from diabetic rats. Such a defect in enzyme activity may play a role in the mechanism of impaired insulin action observed in these NIDDM rats.
Diabetes 1986 Aug
PMID:Ca2+-Mg2+-ATPase activity in kidney basolateral membrane in non-insulin-dependent diabetic rats. Effect of insulin. 294 33

At clinically achievable concentrations (10(-9) to 5 X 10(-6) M), tolbutamide and tolazamide are in vitro inhibitors of Ca2+-transporting ATPase activity in sarcolemma-enriched rabbit myocardial membranes (sulfonylurea IC50, 10(-7) M). Thyroid hormone stimulation of this calcium pump-associated enzyme in vitro has been previously reported; in our study, this hormonal action was shown to be inhibited by tolbutamide and tolazamide. In contrast to these two sulfonylureas, glyburide (up to 5 X 10(-6) M) had no effect on basal or thyroid hormone-stimulable Ca2+-ATPase activity in vitro. Studies of binding of radiolabeled purified calmodulin to heart membranes showed that tolbutamide and tolazamide inhibited this interaction, whereas glyburide had no effect on calmodulin binding. Addition of purified calmodulin (5-40 ng/micrograms membrane protein) to myocardial membranes incubated with 10(-7) M tolbutamide or tolazamide restored Ca2+-ATPase activity and thyroid hormone responsiveness of the enzyme. Inhibition by tolbutamide and tolazamide of myocardial sarcolemmal Ca2+-ATPase is a mechanism by which these two sulfonylureas may at least transiently raise resting sarcoplasmic Ca2+ concentration. This effect of sulfonylureas on Ca2+-ATPase is not expressed in the presence of the benzamide side chain of glyburide. The inhibitory action of certain sulfonylureas on Ca2+-ATPase is mediated by interference of the agents with the binding of calmodulin to cardiac membranes.
Diabetes 1986 Sep
PMID:Differential activities of tolbutamide, tolazamide, and glyburide in vitro on rabbit myocardial membrane Ca2+-transporting ATPase activity. 294 19


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