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)

Highly purified insulin receptor was shown to be a substrate for cAMP kinase. Approximately 1 phosphate was incorporated per molecule of receptor, and the cAMP kinase's affinity for the receptor was at least as high as its affinity for histone. The sites phosphorylated by cAMP kinase seemed distinct from those phosphorylated by the protein kinase C. Phosphorylation by cAMP kinase had no effect on the ability of several monoclonal antibodies to recognize the receptor or on the insulin-binding activity of the receptor. However, cAMP phosphorylation partially inhibited the tyrosine kinase activity of the receptor (approximately 25%). These results suggest that catecholamine-induced resistance to insulin may be partly due to a direct phosphorylation of the receptor by cAMP kinase and a subsequent inhibition of the ability of the receptor kinase to be activated by insulin.
Diabetes 1987 Jan
PMID:Phosphorylation of purified insulin receptor by cAMP kinase. 353 74

In perfused lean rat hearts, the activator of protein kinase C phorbol myristate acetate (PMA), when present alone, stimulates glucose transport but inhibits the insulin stimulation of this transport. PMA also inactivates glycogen synthase in hepatocytes. In contrast, none of these effects are observed in hearts and hepatocytes of obese animals, indicating an impaired protein kinase C activation in these tissues, which are insulin resistant. Direct measurements of protein kinase C activity in lean rat hearts revealed that PMA provokes a translocation of the enzyme from a soluble to a particulate fraction. In obese rat hearts, the basal distribution of protein kinase C is altered (more activity is found in the soluble and less in the particulate fraction), and the translocation induced by PMA is impaired. Pretreatment of lean rats with PMA in vivo, aimed at downregulating protein kinase C, induces the same defects (i.e., insulin resistance and unresponsiveness to PMA) as those observed in hearts of untreated obese animals. The results indicate that part of the insulin resistance might be the consequence of altered modulation of insulin action by protein kinase C.
Diabetes 1987 Mar
PMID:Identification of a major defect in insulin-resistant tissues of genetically obese (fa/fa) rats. Impaired protein kinase C. 380 38

Nitric oxide (NO)-dependent cyclic guanosine monophosphate (cGMP) generation was examined in glomeruli isolated from 1-2-wk and 2-mo streptozotocin diabetic (D) and control (C) rats. After 1-2 wk of diabetes, ex vivo basal cGMP generation and cGMP responses to carbamylcholine (CCh) were significantly suppressed in glomeruli from D compared with those from C, whereas cGMP responses to the calcium ionophore A23187 and nitroprusside (NP) did not differ in glomeruli from D vs. those from C. After 2 mo, glomeruli from D did not respond to CCh, and responses to A23187 and NP were suppressed compared with those from C. Differences in basal, CCh, and A23187-responsive cGMP between D and C were abolished by the NO synthetase inhibitor NG-monomethyl-L-arginine. Soluble glomerular guanylate cyclase prepared from either D or C responded indistinguishably to NP, suggesting a role for NO quenching in the suppression of cGMP in intact glomeruli from D. Compared with those from C, glomeruli isolated from D demonstrated increased generation of thromboxane A2 (TXA2) and activation of protein kinase C (PKC). Both the TXA2/endoperoxide receptor antagonist Bay U3405 and inhibitors of PKC activity restored a cGMP response to CCh in glomeruli from D. Conversely, in glomeruli from C, the TXA2/endoperoxide analogue U46619 activated PKC and suppressed the cGMP response to CCh. Both of those actions were blocked by inhibitors of PKC. The results indicate a progressive impairment of NO-dependent cGMP generation in glomeruli from D which may be mediated in part by TXA2 and activation of PKC. This impairment may participate in glomerular injury in diabetes.
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PMID:Impaired nitric oxide-dependent cyclic guanosine monophosphate generation in glomeruli from diabetic rats. Evidence for protein kinase C-mediated suppression of the cholinergic response. 750 12

Troglitazone (CS045), a compound belonging to the thiazolidine diones, is being tested as a new oral antidiabetic agent. Evidence exists from animal studies and clinical trials with non-insulin-dependent diabetes mellitus patients that Troglitazone might reduce insulin resistance. The molecular mechanism of this effect is not understood. In this study, we investigated whether Troglitazone might interfere with the mechanism of glucose-induced insulin resistance. Several studies indicate that hyperglycemia reduces the kinase activity of the insulin receptor in different cell types. This effect is paralleled by translocation of several protein kinase C (PKC) isoforms, and it can be prevented by PKC inhibitors, which suggests that glucose-induced receptor desensitization is mediated by activation of PKC. We studied the effect of hyperglycemia on the insulin receptor kinase activity and its modulation by Troglitazone in rat-1 fibroblasts that stably overexpress the human insulin receptor. Before stimulation with insulin (10(-7) M), cells were acutely exposed to hyperglycemic conditions in the absence or presence of Troglitazone (0.01-2 micrograms/ml). The insulin receptor was solubilized from a plasma membrane fraction or whole cell lysates, and proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotted against antiphosphotyrosine and anti-insulin receptor beta-subunit (CT 104) antibodies. Acute hyperglycemia (25 mM glucose) induced a significant inhibition of the insulin receptor kinase (IRK) activity within 30 min (inhibition to 30 +/- 12.5% of maximal insulin-stimulated beta-subunit phosphorylation, n = 9, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1994 Mar
PMID:Troglitazone prevents glucose-induced insulin resistance of insulin receptor in rat-1 fibroblasts. 750 75

Murine macrophages express high levels of nitric oxide synthase and produce large amounts of nitric oxide (NO) when stimulated with certain cytokines in the presence of a trace amount of lipopolysaccharide (LPS). The stimulatory cytokines include interleukin-1 (IL-1), interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and migration inhibitory factor. Activated macrophages are highly effective killers of intra- and extra-cellular pathogens. However, as excessive NO can lead to immunopathology (diabetes, graft-v.-host disease, EAE, liver cirrhosis, rheumatoid arthritis), NO production is necessarily under tight regulation. A number of cytokines, including IL-4, IL-10 and transforming growth factor-beta, can down regulate the induction of NO synthase in macrophages. In addition, macrophages exposed to LPS alone and then stimulated with a mix of IFN-gamma and LPS express significantly lower levels of NO synthase than cells stimulated without pre-exposure to LPS. Furthermore, NO can reduce the activity of NO synthase by feedback inhibition, and also inhibit the production of IFN-gamma by Th1 cells (thus turning off its own synthesis from upstream). The regulatory pathways involve tyrosine kinase and protein kinase C.
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PMID:The role of nitric oxide in parasitic diseases. 751 Jan

The rat insulinoma beta-cell line RINm5F, which shares some homology with pancreatic islets, was used to study nitric oxide synthase induction. Nitric oxide is involved during beta-cell destruction and possibly in propagation of insulin-dependent diabetes mellitus. The cytokine interleukin-1 (IL-1) turned out to be the ultimate inducer, whereas tumour necrosis factor-alpha (TNF) and unexpectedly the phorbol ester TPA (12-O-tetradecanoylphorbol-13-acetate; 10 nM) synergistically promoted nitrite accumulation. Besides employing TPA directly, the synergistic effect of TNF could be traced back to protein kinase C activation since protein kinase C inhibitors (IC50 value for staurosporine: 4 nM) potently suppressed nitrite production in the case of IL-1/TNF administration. Further experiments using anti-TNF antibodies aimed to an autocrine loop following IL-1 addition to RINm5F cells, possibly involved in nitrite generation. Moreover, the nitric oxide synthase inductive IL-1 signal was antagonized by lipophilic cAMP analogues. Our results for nitrite accumulation in RINm5F cells point to activating protein kinase C and inhibitory protein kinase A signalling pathways.
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PMID:Modulation of inducible nitric oxide synthase in RINm5F cells. 751 91

Insulin might play a role in the hypertension occurring in insulin-resistant diabetes. In addition, insulin has recently been shown to potentiate norepinephrine (NE) induced vascular tone. We used ring segments of the rabbit facial artery mounted in a myograph to test the hypothesis that potentiation of NE-induced tone by insulin may be related to activation of protein kinase C (PKC) and tyrosine kinase (TK). NE-induced contractions in the presence of insulin (1 mU/mL) were 200% (NE 0.1 and 0.3 microM), 252% (NE 1 microM), and 129% (NE 3 microM) of control. Insulin (1 mU/mL) had no effect on NE (10 and 100 microM) induced contractions. The potentiation by insulin of NE-induced tone was not altered by endothelium removal and could be mimicked by phorbol-12-myristate-13-acetate (PMA, 0.1 microM). Histamine-induced contractions were not altered by insulin (1 mU/mL). Insulin potentiation of NE-induced tone was suppressed by pretreatment of the rabbit facial artery with the PKC inhibitor calphostin C (0.1 microM) or the TK inhibitor genistein (10 microM). 45Ca2+ influx due to NE (3 microM) did not change in the presence of insulin (1 mU/mL) or PMA (0.1 microM) despite a higher contractile response, so that wall force per unit of 45Ca2+ influx was increased by insulin (1 mU/mL) and PMA (0.1 microM). Calphostin C (0.1 microM) and genistein (10 microM) both prevented the increase in wall force per unit of 45Ca2+ influx due to insulin (1 mU/mL). Our study shows that insulin potentiates NE-induced tone through a TK- and PKC-dependent mechanism.
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PMID:Insulin potentiates norepinephrine-induced vascular tone by activation of protein kinase C and tyrosine kinase. 753 May 92

Increased blood flow and vascular permeability of early diabetes have been associated with increased nitric oxide formation in diabetic rats, but the specific nitric oxide synthase responsible is unknown. We examined the modulation of the induction and activity of the inducible NOS isoform by high glucose concentration in a murine macrophage cell line, RAW 264.7, and murine glomerular mesangial cells. Culturing both cell types in high glucose concentration led to significant increases in nitrite production and the mRNA encoding iNOS upon stimulation with LPS plus interferon-gamma, as compared with normal glucose concentration. High glucose also modestly enhanced LPS/IFN-gamma-induced stimulation of the iNOS promoter in transient transfection experiments in mesangial cells. Protein kinase C activation led to enhanced mRNA expression of iNOS, and inhibitors of protein kinase C blocked nitrite accumulation in mesangial cells. These findings suggest that high glucose in combination with stimulation by LPS plus IFN-gamma enhances iNOS expression, and protein kinase C activation may be playing a role in this enhancement.
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PMID:Enhanced expression of inducible nitric oxide synthase in murine macrophages and glomerular mesangial cells by elevated glucose levels: possible mediation via protein kinase C. 753 75

To determine whether diabetes alters vascular effects mediated by activation of protein kinase C, the contractions induced by phorbol esters were examined in aortic rings from rats with 8- to 12-weeks streptozotocin-induced diabetes and compared with those from age-matched control rats. In diabetic rat aorta, phorbol 12,13-dibutyrate (PDB) (> or = 30 nM) and 12-O-tetradecanoylphorbol 13-acetate (TPA) (300 nM) elicited a delayed, sharply developing rise in tension following an initial gradually developing contraction. In control rat aorta, these agents produced only an initial slowly developing contraction. Both the initial and the delayed contractile responses observed in diabetic aorta were completely abolished by pretreatment with 20 nM staurosporine, and the delayed phase of contraction was not seen in Ca(2+)-free medium or in the presence of 1 microM nifedipine. The concentration-response curves for the contractions induced by PDB revealed that PDB at concentrations > or = 30 nM produced significantly greater responses in diabetic aorta than in control aorta. In control aorta, exposure to Ca(2+)-free medium and pretreatment with 1 microM nifedipine shifted the concentration-response curves for PDB to the right without changing the maximal response. Under these conditions, there were no differences in the curves for PDB in control and diabetic aortas. These results suggest that the appearance of the delayed phase of contraction, possibly due to a delayed opening of Ca2+ channels, during activation of protein kinase C may be responsible for the enhanced contractile responses to phorbol esters in diabetic rat aorta.
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PMID:Phorbol esters elicit Ca(2+)-dependent delayed contractions in diabetic rat aorta. 755 82

Renal injury in diabetes mellitus is a major cause of morbidity and mortality in diabetic patients. There is a clear correlation between the degree of glomerular as well as tubulointerstitial lesions and the development of reduced glomerular filtration rate. The important role of hyperglycemia in the genesis of diabetic renal disease has been strengthened by the application of tissue culture techniques. Recent in vitro studies, first in tubular epithelial cells and subsequently in the three glomerular cell types, have provided supportive evidence that high ambient glucose per se stimulates the synthesis of extracellular matrix components. Increased matrix synthesis and decreased degradation are thought to contribute to matrix accumulation in diabetic nephropathy. These processes are not mutually exclusive and they may be operating simultaneously but at different rates, with increased synthesis predominating early and decreased breakdown later in the course of the disease. Likely mediators of the effects of high glucose involve activation of the polyol pathway, altered myo-inositol metabolism, increased protein kinase C activity, and/or nonenzymatic glycation of various matrix proteins. A role for various growth factors, especially transforming growth factor-beta, also seems likely. However, the details of the cell-signaling mechanisms and the putative molecular mediators of the effect of hyperglycemia remain to be firmly established.
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PMID:Mediators of hyperglycemia and the pathogenesis of matrix accumulation in diabetic renal disease. 756 78


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