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 VSMC is an important target for the injurious effects of hyperglycemia in vivo. PKC plays a key role in the regulation of VSMC contraction and growth. This study examines whether elevated extracellular glucose concentrations (10-30 mM [180-540 mg/dl]) activate PKC in cultured rat VSMCs in vitro. A new, rapid, and highly specific assay was used to determine in situ PKC activity in digitonin-permeabilized VSMCs. PKC activity in VSMCs responded rapidly to variations in extracellular glucose concentrations. PKC was activated significantly within 10 min of exposure to D-glucose (20 mM) versus glucose (5 mM). Moreover, with continued exposure to D-glucose (20 mM), PKC activation was sustained for up to 48 h. Reducing D-glucose concentrations to 5 mM restored PKC activity to control values within 1 h. PKC activation was also glucose-concentration dependent. A threshold of only 15 mM (270 mg/dl) was required to significantly and maximally activate PKC in VSMC. PKC was not activated in the presence of osmotic control media that contained either elevated mannitol or L-glucose concentrations. In marked contrast to the sustained PKC activation induced by D-glucose in VSMCs, the normal physiological PKC response to the pressor hormones, AII and AVP, was short-lived and returned to base line within minutes. Sustained PKC activation in the presence of elevated D-glucose concentrations in vitro could disturb the normal physiological regulation of VSMC function and growth and thereby may contribute to the apparent vasotoxicity of hyperglycemia in vivo.
Diabetes 1992 Nov
PMID:Characterization of glucose-induced in situ protein kinase C activity in cultured vascular smooth muscle cells. 139 22

Because retinal pericytes have contractile properties and are affected by diabetes, we have studied the responsiveness of pericytes to ET-1, a potent vasoconstrictor, in the presence of various concentrations of glucose. Cultured calf retinal pericytes were exposed to glucose levels of 5.5 or 25 mM for up to 8 days. Radioreceptor studies that used [125I]ET-1 showed that pericytes contained high-affinity binding sites with Kd of 3 x 10(-10) M, and these binding affinities were unaffected by glucose concentration. Receptor number appears to be elevated, but this increase was NS. Responsiveness of pericytes to ET-1 was studied with respect to stimulation of DAG and IP3 levels and PKC activities. In contrast to receptor binding, exposure to 25 mM glucose for > 6 days blunted pericyte responsiveness to ET-1. The time course of ET-1 stimulation as measured by [3H]glycerol labeling, and IP3 level showed a 98% increase in [3H]DAG at 10 min and a fourfold increase for IP3, respectively. Cells exposed to 25 mM glucose only had a 32% increase for DAG, and no increase for IP3 was observed. Dose-response studies on the stimulation of [3H]DAG increase showed the range of ET-1's effect to be between 10(-9) and 10(-7) M. At maximum, cells exposed to 5.5 mM glucose had a 70% increase versus only a 30% increase in those exposed to 25 mM glucose. Similarly, ET-1 only increased the total DAG levels in pericytes exposed to 5.5 mM glucose by 41%. PKC activity also was measured because DAG is one of its cellular activators.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1992 Dec
PMID:Induction of resistance to endothelin-1's biochemical actions by elevated glucose levels in retinal pericytes. 144 93

Diabetic retinopathy is one of the leading causes of vision loss in industrialized countries. Despite recent advances, the biochemical basis for the development of this diabetic complication is uncertain. Although retinal circulation is unique in that it is readily observable noninvasively, retinal tissue is extremely difficult to study in humans because of the problems inherent in obtaining fresh, appropriate biopsy material. Moreover, because of the difficulties in working with animal models of diabetic retinopathy, such as the dog, many investigators have turned to cell-culture models, especially those using primary cultures of retinal capillary endothelial cells and pericytes. Diabetic retinopathy involves both morphological and functional changes in the retinal capillaries. Morphological changes include basement membrane thickening and pericyte disappearance; functional changes include one important early change--increased permeability--which may be attributable to endothelial cell changes and basement membrane leakiness. Investigators have described major biochemical changes in cellular signaling pathways, including myo-inositol, inositol phosphates, and DAG metabolism, as well as decreased Na(+)-K(+)-ATPase and increased PKC activity. These defects may be related to the way endothelial cells and pericytes synthesize and interact with the extracellular matrix. Abnormalities in endothelial cell or pericyte interaction with the basement membrane may in turn lead to functional abnormalities, such as increased permeability.
Diabetes Care 1992 Dec
PMID:Current hypotheses for the biochemical basis of diabetic retinopathy. 146 44

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

Using several novel in vitro culture systems, we have examined the tissue-specific regulation of the proglucagon-derived peptides, at the levels of proglucagon gene expression and pGdp synthesis and secretion. Our studies indicate that proglucagon gene expression in intenstine, hypothalamus and pancreas is under the regulatory control of protein kinase A- but not a protein kinase C-dependent pathway. PKA and PKC stimulate secretion of the intestinal pGdp's, whereas only PKA stimulates secretion of the hypothalamic peptides. Pancreatic glucagon secretion in response to PKA is subject to further modulation by prevailing glucose concentrations. This diversity in intracellular regulation of the pGdp's may account for some of the tissue-specific differences in synthesis and secretion of the pGdp's that we have observed in diabetes and during development.
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PMID:Proglucagon-derived peptides in the neuroendocrine system. 192 80

A possible relationship between protein kinase C activation and impaired receptor-mediated endothelium-dependent relaxation in diabetes mellitus was examined in isolated aorta from normal rabbit exposed to elevated glucose. Aorta treated for 10 min with 4-phorbol 12-myristate 13-acetate (PMA), a protein kinase C activator, showed decreased relaxations to the endothelium-dependent vasodilator, acetylcholine, similar to normal aorta exposed to elevated glucose (22 and 44 mM) for 6 h. Relaxations to the receptor-independent endothelium-dependent vasodilator, A23187, and those caused by the direct smooth muscle vasodilator, sodium nitroprusside, were unaffected by treatment with PMA or exposure to elevated glucose. Indomethacin increased relaxations to acetylcholine of aorta treated with PMA indicating a role for vasoconstrictor prostanoids. PMA caused a significant increase in basal and acetylcholine-stimulated release of vasoconstrictor prostanoids including thromboxane A2 from aortic segments with, but not without endothelium. Protein kinase C inhibitors, H-7 or sphingosine, restored the abnormal acetylcholine-induced relaxations as well as suppressed the abnormal release of prostanoids in aorta exposed to elevated glucose. These findings suggest that the dysfunction of receptor-mediated endothelium-dependent relaxation associated with exposure to elevated glucose is due to increased production of vasoconstrictor prostanoids by the endothelium as a consequence of protein kinase C activation.
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PMID:Elevated glucose impairs endothelium-dependent relaxation by activating protein kinase C. 202 34

We have found a defect in the ouabain-sensitive Na+, K+-ATPase (Na+ pump, EC 3.6.1.37) of erythrocytes from streptozocin diabetic rats. This defect was accompanied by an increase in cell volume and osmotic fragility and a decrease in the cytosolic K+/Na+ ratio. There was also a doubling in the time needed for diabetic erythrocytes to pass through 4.7-micron channels in a polycarbonate filter. Our data are consistent with a primary defect in the erythrocyte Na+ pump and secondary changes in cell volume, osmotic fragility, K+/Na+ ratio, and cell filterability. All were reversed or prevented in vivo by insulin or the aldose reductase inhibitor Sorbinil. Protein kinase C agonists (phorbol ester and diacylglycerol) and agonist precursor (myoinositol) reversed the Na+ pump lesion, suggesting that protein kinase C-dependent phosphorylation of the 100-kDa subunit regulates Na+ pump activity and that insulin can influence erythrocyte protein kinase C activity. Ouabain inhibition of the erythrocyte Na+ pump also produced increases in cell size and reductions in rates of filtration. Theoretical treatment of the volume changes also predicts reduction in filterability as a consequence of cell swelling. We suggest that enlarged erythrocytes could play a role in the evolution of the microvascular changes of diabetes mellitus.
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PMID:Reversible sodium pump defect and swelling in the diabetic rat erythrocyte: effects on filterability and implications for microangiopathy. 254 40

Retinal capillary pericyte is a cell type selectively lost in early diabetic retinopathy. The physiological function of pericytes is not yet clearly identified, although it probably has contractile properties. We determined the specific binding of endothelin 1, a 21-amino acid peptide with potent vasoconstrictive action, and the stimulation of diacylglycerol/protein kinase C (DAG/PKC) pathway in cultured retinal capillary pericytes by endothelin. A single specific binding site for 125I-labeled endothelin was identified, with an apparent Kd of 1.3 nM and a maximal binding capacity of approximately 1-2 x 10(5) sites/cell. Endothelin (100 nM) increased total cellular DAG content by 15% at 5 min and 24% at 10 min. When pericytes were labeled isotopically with [3H]glycerol, endothelin stimulated [3H]DAG formation by 100% at 10 min and 88% at 30 min. After 10 min of endothelin treatment, PKC activities were increased by 60 and 100% in the membranous and cytosolic pools, respectively. We conclude that bovine retinal capillary pericytes possess numerous high-affinity specific binding sites for endothelin that mediate the action of endothelin by the stimulation of the DAG/PKC pathway in pericytes. These findings suggest that endothelin is a regulator of the contractile properties of pericytes, which may be adversely affected in diabetic retinopathy.
Diabetes 1989 Dec
PMID:Characterization of endothelin receptors and effects of endothelin on diacylglycerol and protein kinase C in retinal capillary pericytes. 839 Feb 75

Protein kinase C (PKC) has been generally accepted to play a key role in stimulus-response coupling in various secretory cells, including pancreatic islets and pancreatic acini. The enzyme exists as a large family of multiple subspecies with highly related structures (alpha-, beta I-, beta II-, gamma-, delta-, epsilon-, and zeta-PKC). With an immunocytochemical procedure with subspecies-specific antibodies, beta II-PKC-like immunoreactivity was identified to localize in the beta-cells of the rat pancreatic islets. Neither beta I- nor gamma-PKC-like immunoreactivity was found in both islets and acini. Biochemical analysis confirmed that the rat whole pancreatic tissues contain a significant amount of alpha-PKC and a minute amount of beta II-PKC but neither beta I- nor gamma-PKC. On the other hand, beta II-PKC-like immunoreactivity was not detected in rat insulinoma cells, in which insulin secretion was induced in response to 12-O-tetradecanoylphorbol-13-acetate and carbachol but not in response to glucose. These findings suggest that beta II-PKC is the major, if not the sole, subspecies of PKC in beta-cells of rat pancreatic islets and a possible candidate for involvement in glucose-induced insulin secretion.
Diabetes 1989 Aug
PMID:Localization of beta II subspecies of protein kinase C in beta-cells. 266 99

Six weeks after induction of diabetes, the rate of ouabain-sensitive 86Rb+ accumulation, a parameter which reflects Na+ + K+-ATPase pumping activity, was significantly reduced in endoneurial preparations of sciatic nerve from untreated diabetic rats compared with that in control rats (Trial, 1, 0.19 +/- 0.09 versus 0.48 +/- 0.13 pmol/min per mg wet weight of tissue, p less than 0.001; Trial 2, 0.27 +/- 0.16 versus 0.47 +/- 0.18, p less than 0.01). This decrease in ouabain-sensitive 86Rb+ uptake was not observed in nerves from diabetic rats maintained on sorbinil (an aldose reductase inhibitor) or myo-inositol diets. Protein kinase C activity was demonstrated in the soluble fraction of a sciatic nerve homogenate by assaying for lipid-activated, Ca+-dependent phosphorylation of calf thymus histone. No significant difference in the time course of kinase C activity was observed between cytosol fractions of nerve homogenates from control and diabetic rats (control, 6.22 +/- 0.97 pmol 32P incorporated/mg cytosol protein in 50 min; diabetic, 5.32 +/- 0.71). Three low molecular weight neural proteins (each with Mr less than 29,000) were identified as substrates for protein kinase C.
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PMID:Reduced Na+ + K+-ATPase activity in peripheral nerve of streptozotocin-diabetic rats: a role for protein kinase C? 284 Mar 14


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