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)

Levels of the G-protein alpha-subunits alpha-Gi-2, alpha-Gi-3 and the 42 kDa, form of alpha-Gs were markedly decreased in hepatocyte membranes from streptozotocin-diabetic animals as compared with normals. In contrast, no detectable changes in alpha-Gi subunits were seen in liver plasma membranes of streptozotocin-diabetic animals, although levels of the 45 kDa form of Gs were increased. G-protein beta subunits in plasma membranes were unaffected by diabetes induction. Analysis of whole-liver RNA indicated that the induction of diabetes had little effect on transcript levels of Gi-3, caused an increase in Gs transcripts and decreased transcript number for Gi-2, albeit to a much lesser extent than was observed upon analysis of hepatocyte RNA. In both hepatocyte and liver plasma membranes, immunoblot analysis showed that levels of the catalytic unit of adenylate cyclase were increased upon induction of diabetes. Under basal conditions, alpha-Gi-2 from hepatocytes of diabetic animals was found to be both phosphorylated to a greater extent than alpha-Gi-2 isolated from hepatocytes of normal animals, and furthermore was resistant to any further phosphorylation upon challenge of hepatocytes with angiotensin, vasopressin or the phorbol ester 12-O-tetradecanoylphorbol 13-acetate. Treatment of isolated plasma membranes from normal, but not diabetic, animals with purified protein kinase C caused the phosphorylation of alpha-Gi-2. Treatment of membranes from diabetic animals with alkaline phosphatase caused the dephosphorylation of alpha-Gi-2 and rendered it susceptible to subsequent phosphorylation with protein kinase C. Low concentrations of the non-hydrolysable GTP analogue guanylyl 5'-imidodiphosphate inhibited adenylate cyclase activity in both hepatocyte and liver plasma membranes from normal, but not diabetic, animals.
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PMID:Diabetes-induced alterations in the expression, functioning and phosphorylation state of the inhibitory guanine nucleotide regulatory protein Gi-2 in hepatocytes. 170 Jul

The vasoconstrictor response is defective in diabetes mellitus (DM). Activation of protein kinase C (PKC) is also known to prevail in diabetes mellitus, and it is thought to be secondary to abnormal diacylglycerol metabolism. To ascertain whether this PKC activation in diabetes underlies the vasomotor defect by regulating biological receptors, we studied the characteristics of the receptor for endothelin (ET), "the vasoconstrictor of injury." For this purpose, diabetes was induced in rats by intravenous streptozotocin. One to 2 weeks after streptozotocin treatment (average glucose at time of experiments: 518 mg/dl), glomeruli were isolated and assessed for ET receptor and PKC activity. ET receptor characteristics were also assessed following infusion of a specific PKC inhibitor, 1-(5-isoquinolinesulfonyl)piperazine (CI). For comparison, nondiabetic controls with and without PKC inhibitor were studied. No differences in high-affinity ET-1 receptor (ER-1) characteristics were found among the diabetic and normal rats. In contrast, receptor density for the lower-affinity receptor (ER-2) was significantly depressed in DM without changes in the equilibrium dissociation constant. Infusion of CI 20 min before glomerular harvesting did not affect the glomerular PKC activity in controls (particulate: 28.0 +/- 4.0% of total activity to 22.0 +/- 3.9%, n = 3). In contrast, in diabetes mellitus rats infused with CI, PKC activity decreased (particulate: from 44.7 +/- 2.9% of total activity to 18.5 +/- 3.2%, n = 3, p less than 0.05). This CI-induced suppression of PKC in DM was accompanied by complete reversal in down-regulation of ER-2 receptors. Thus, DM is characterized by down-regulation in low-affinity ET-1 receptors. Furthermore, this receptor down-regulation can be reversed by abolishing abnormally enhanced PKC activity. These results indicate that abnormal activation of PKC may underlie the profoundly vasodilative status and defective vasoconstrictor response characterizing DM.
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PMID:Down-regulation of endothelin-1 receptors by protein kinase C in streptozotocin diabetic rats. 172 24

Denervated muscle is generally regarded as insulin resistant because the ability of insulin to stimulate glucose transport and glycogen synthesis is impaired. Previous studies indicate that insulin resistance in these muscles is likely due to a defect at a postreceptor site in the signaling pathway. Because glucose transport into cells has been reported to be linked to changes in diacylglycerol (DAG) and protein kinase C (PKC), we investigated the effect of denervation on the content and synthesis of DAG and the activity and distribution of PKC in the soleus muscle. The DAG content in muscles denervated for 24 h was 40% greater than in control muscles. This was associated with a two- to threefold increase in the percentage of total PKC activity that was membrane associated, with no significant change in total PKC activity, suggesting an increase in PKC activity in vivo. Studies of glucose disposition confirmed that the stimulation of glycogen synthesis by insulin and, to a lesser extent, 2-deoxyglucose uptake were impaired by denervation. However, the stimulation by insulin of glucose incorporation into DAG and other lipids was two- to threefold greater in denervated than in control muscles, and conversion of glucose to lactate and pyruvate and glucose oxidation to CO2 were unchanged. The results reveal a dichotomy in the effects of denervation on various actions of insulin, with both insulin resistance and hyperresponsiveness occurring in different pathways of glucose metabolism. They also reveal a potential mechanism for the elevation of muscle DAG after denervation. The results do not support a direct link between DAG-PKC and glucose transport.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1991 Dec
PMID:Enhanced stimulation of diacylglycerol and lipid synthesis by insulin in denervated muscle. Altered protein kinase C activity and possible link to insulin resistance. 175 11

Elevated levels of 1,2-diacylglycerol (DG) have been observed in streptozotocin-induced diabetic and insulin-treated diabetic rat hearts. The fatty acid moieties of 1,2-DG are considered to be related to its ability to activate protein kinase C. Therefore, we determined the fatty acids of 1,2-DG by gas chromatography and compared them with those of triglycerides in the myocardium. The triglyceride content returned to control levels after 4 weeks of untreated diabetes followed by 4 weeks of insulin treatment. There was a significant difference in the fatty acid composition of triglycerides between diabetic and control rats. Insulin treatment also returned the fatty acids of triglycerides in diabetes to the profile observed in control rats. On the other hand, insulin treatment of the diabetic rats did not normalize 1,2-DG content and its fatty acid composition. Fatty acid analysis of 1,2-DG showed that its profile in insulin-treated diabetic rats was different from that of either control or diabetic rats, suggesting that insulin-induced 1,2-DG differs from that seen in cases of diabetes.
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PMID:Fatty acid composition in 1,2-diacylglycerol of diabetic and insulin-treated diabetic rat hearts. 177 28

We examined the effect of verapamil treatment on cardiac protein kinase C (PKC) activity in streptozocin-induced diabetic rats. Basal cardiac PKC activity in diabetes increased in both cytosolic (by 94%, P less than 0.01) and membrane (by 41%, P less than 0.05) fractions as compared with that in controls. Subcutaneous administration of 8 mg/kg verapamil twice a day for 8 weeks induced a significant decrease in both cytosolic (by 59%, P less than 0.01) and membrane (by 50%, P less than 0.01) PKC activity in diabetes as compared with the activity in the non-treated diabetic groups. In contrast, cardiac cytosolic PKC activity in control rats was significantly (P less than 0.01) decreased by 41% as compared with that of the non-treated control group without there being any change in membrane PKC activity. Our data demonstrate that verapamil treatment may ameliorate the abnormal activation of cardiac PKC in diabetes.
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PMID:Effect of verapamil on cardiac protein kinase C activity in diabetic rats. 178 95

Previously it has been shown that glucagon-like peptide (GLP)-1(7-36)amide stimulates insulin secretion from tumoral RIN m5F cells by activation of adenylate cyclase. However, its mechanism in normal islets is not established. We therefore examined the effects of GLP-1(7-36)amide in isolated, overnight cultured, normal rat islets. GLP-1(7-36)amide (greater than or equal to 10(-9) M) stimulated insulin secretion by augmenting both the efficacy and potency of glucose over a wide dose-range of glucose (3.3-16.7 mM). The first 15 min of GLP-1(7-36)amide-stimulated insulin secretion was independent on extracellular Ca2+, whereas a sustained insulin secretion was seen only in the presence of extracellular Ca2+. Concurrently with this, GLP-1(7-36)amide sustainely stimulated 45Ca(2+)-efflux from prelabelled islets only in the presence of extracellular Ca2+, whereas after removal of extracellular Ca2+, the peptide stimulated only a slight 45Ca(2+)-efflux during the first 15 min. GLP-1(7-36)amide also stimulated 86Rb(+)-efflux from prelabelled islets, but in contrast to 45Ca(2+)-efflux, the 86Rb(+)-efflux was not reduced by removal of extracellular Ca2+. GLP-1(7-36)amide had no influence on 3H-efflux from myo-[2-3H]-inositol prelabelled islets. Moreover, the inhibitor of protein kinase C (PKC), staurosporine, did not affect GLP-1(7-36)amide-stimulated insulin secretion. The results show that the first phase of GLP-1(7-36)amide-stimulated insulin secretion is independent on extracellular Ca2+, whereas the sustained phase of GLP-1(7-36)amide-stimulated insulin secretion requires extracellular Ca2+. In contrast, phosphoinositide hydrolysis and PKC are not involved in the signal transduction pathway stimulated by GLP-1(7-36)amide in normal islets.
Diabetes Res 1991 Apr
PMID:GLP-1(7-36) amide stimulates insulin secretion in rat islets: studies on the mode of action. 180 86

In nonobese diabetic (NOD) mice, T cells play a major role in mediating autoimmunity against pancreatic islet beta-cells. We and others previously reported that age-related alterations in the thymic and peripheral T cell repertoire and function occur in prediabetic NOD mice. To study the mechanism responsible for these T cell alterations, we examined whether a defect exists in the thymus of NOD mice at the level of TCR-mediated signaling after activation by Con A and anti-CD3. We found that thymocytes from NOD mice respond weakly to Con A- and anti-CD3-induced proliferation, compared with thymocytes from control BALB/c, BALB.B, (BALB.B x BALB.K)F1, C57BL/6, and nonobese non-diabetic mice. This defect correlates with the onset of insulitis, because it can be detected at 7 to 8 weeks of age, whereas younger mice displayed a normal T cell responsiveness. Thymic T cells from (NOD x BALB/c)F1 mice, which are insulitis- and diabetes-free, exhibit an intermediate stage of unresponsiveness. This T cell defect is not due to a difference in the level of CD3 and IL-2R expression by NOD and BALB/c thymocytes, and both NOD CD4+ CD8- and CD4- CD8+ mature thymic T cells respond poorly to Con A. BALB/c but not NOD thymic T cells respond to Con A in the presence of either BALB/c or NOD thymic APC, suggesting that the thymic T cell defect in NOD mice is intrinsic to NOD thymic T cells and is not due to an inability of NOD APC to provide a costimulatory signal. The defect can be partially reversed by the addition of rIL-2 to NOD thymocytes. To determine whether a defect in signal transduction mediates this NOD thymic T cell unresponsiveness, we tested whether these cells elevate their intracellular free Ca2+ ion concentration in response to Con A. An equivalent Con A-induced increase in Ca2+ ion concentration in both NOD and BALB/c thymocytes was observed, suggesting a normal coupling between the CD3 complex and phospholipase C in NOD thymocytes. In contrast to their low proliferative response to Con A or anti-CD3, NOD thymocytes respond normally (i.e., as do BALB/c thymocytes) to the combinations of PMA plus the Ca2+ ionophore ionomycin and PMA plus Con A but weakly to Con A plus ionomycin. Our data suggest that the age-related NOD thymocyte unresponsiveness to Con A and anti-CD3 results from a defect in the signaling pathway of T cell activation that occurs upstream of protein kinase C activation.
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PMID:Defective thymic T cell activation by concanavalin A and anti-CD3 in autoimmune nonobese diabetic mice. Evidence for thymic T cell anergy that correlates with the onset of insulitis. 182 15

A myo-inositol-related defect in nerve Na(+)-K(+)-ATPase in experimental diabetes has been invoked in the pathogenesis of diabetic neuropathy, but the mechanism linking altered myo-inositol metabolism and Na(+)-K(+)-ATPase regulation in diabetic nerve is uncertain. Decreased Na(+)-K(+)-ATPase in diabetic rat nerve is normalized by aldose reductase inhibitors or dietary myo-inositol, which preserve normal nerve myo-inositol content in vivo. Decreased Na(+)-K(+)-ATPase in diabetic rabbit nerve is acutely reversed by exposure to protein kinase C agonists in vitro. This study explored the relationship between the myo-inositol-sensitive and protein kinase C-agonist-sensitive Na(+)-K(+)-ATPase defects in diabetic rat nerve. Ouabain-sensitive ATPase activity was measured in an enriched membrane fraction isolated from nondiabetic, streptozocin-induced diabetic, and myo-inositol-supplemented streptozocin-induced diabetic rats before and after the membranes were exposed to protein kinase C agonists in vitro. The decreased ouabain-sensitive ATPase activity in plasma membranes from untreated diabetic rats was increased after exposure to two structurally unrelated protein kinase C agonists; the normal ouabain-sensitive ATPase in plasma membranes from myo-inositol-supplemented diabetic rats was unaffected by protein kinase C agonists. The nonadditivity and implied equivalence of the Na(+)-K(+)-ATPase defect corrected by myo-inositol in vivo and by protein kinase C agonists in vitro are consistent with the postulated existence of a deficient myo-inositol-dependent phospholipid-derived protein kinase C agonist (presumably diacylglycerol) in diabetic nerve that regulates nerve Na(+)-K(+)-ATPase either directly or via a protein kinase C mechanism.
Diabetes 1991 May
PMID:Normalization of Na(+)-K(+)-ATPase activity in isolated membrane fraction from sciatic nerves of streptozocin-induced diabetic rats by dietary myo-inositol supplementation in vivo or protein kinase C agonists in vitro. 185 Jul 4

Calcium- and phospholipid-dependent protein kinase (protein kinase C; PKC) may be an important mediator in transduction of some of the cellular actions of insulin. We studied PKC activity in freshly isolated circulating mononuclear cells obtained from healthy subjects and patients with non-insulin-dependent (type II) diabetes mellitus (NIDDM). The kinase activity was measured using a specific nonapeptide substrate, Ala-Ala-Ala-Ser-Phe-Lys-Ala-Lys-Lys-amide. There was negligible calcium- and phospholipid-independent kinase activity in cytosolic and particulate fractions of cells from both control and diabetic subjects. Total (cytosolic and particulate) PKC activity of mononuclear cells from poorly controlled diabetic patients was significantly reduced compared with controls; this reduction was mainly due to a decrease in the cytosolic kinase activity. Tumor-promoting phorbol ester (TPA, 0.1 mumol/L) induced translocation of PKC activity in control cells; in contrast, this subcellular redistribution was not observed in cells from a majority of poorly controlled diabetic subjects. Increased calcium influx into the cells caused by the calcium ionophore A23187-triggered translocation of PKC activity in control cells, while it was ineffective in cells from poorly controlled diabetic patients. Cells from well-controlled diabetic patients demonstrated TPA-induced translocation of the PKC activity approaching that of control cells. The total PKC activity in cells from patients with good glycemic control was normal. Impaired activation of PKC is thus associated with the insulin resistance found in patients with poorly controlled NIDDM.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Impaired translocation of protein kinase C activity in human non-insulin-dependent diabetes mellitus. 186 31

Proposed mechanisms by which insulin exerts its effects are discussed. Evidence for a role for the tyrosine kinase activity of the insulin receptor and of a phosphorylation/dephosphorylation cascade is presented. The possible roles of phospholipid breakdown, diacylglycerol, and protein kinase C are discussed. The hypothesis that insulin elicits the hydrolysis of a glycosyl phosphatidylinositol to form a mediator of certain of its actions is considered in detail. The evidence that a G protein is involved in insulin action is analyzed.
Diabetes 1991 May
PMID:Some thoughts on the mechanism of action of insulin. 190 25


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