Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

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

We have recently identified a new member of the Ras/GTPase superfamily termed Rad which has unique sequence features and is overexpressed in the skeletal muscle of humans with type II diabetes (Reynet, C., and Kahn, C. R. (1993) Science, 262, 1441-1444). When expressed in bacteria as a glutathione S-transferase fusion protein, Rad bound [alpha-32P]GTP quickly and saturably. Binding was specific for guanine nucleotides and displayed unique magnesium dependence such that both GTP and GDP binding were optimal at relatively high Mg2+ concentrations (1-10 mM). Rad had low intrinsic GTPase activity which was greatly enhanced by a GTPase-activating protein (GAP) activity present in various tissues and cell lines. Several known GAPs had no stimulatory effect toward Rad. Conversion of Ser to Asn at position 66 in Rad (equivalent to position 12 in Ras) resulted in a total loss of GTP binding. Mutation of Pro61 (equivalent to Gly12 in Ras) or Gln109 (equivalent to Gln61 in Ras) had no effect on Rad GTPase activity, whereas creation of a double mutation at these positions resulted in exceptionally high intrinsic GTPase activity. In vitro, Rad was phosphorylated by the catalytic subunit of cAMP-dependent protein kinase (PK). Phosphopeptide mapping indicated two PKA phosphorylation sites near the COOH terminus. Rad also co-precipitated a serine/threonine kinase activity from extracts of various tissues and cell lines which catalyzed phosphorylation on Rad but was not inhibited by PKA inhibitor. Thus, Rad is a GTP-binding protein and a GTPase which has some structure/function similarities to Ras, but displays unique features. Rad may also be phosphorylated on serine/threonine residues by PKA and other kinases, as well as regulated by its own GAP which is present in many tissues and cell types.
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PMID:Characterization of Rad, a new member of Ras/GTPase superfamily, and its regulation by a unique GTPase-activating protein (GAP)-like activity. 787 54

Insulin activation of skeletal muscle glycogen synthase and glucose disposal is defective in both prediabetic and diabetic primates. Reduction in the activation of glycogen synthase by insulin could be the cause of lower glucose disposal rates, and could be the result, at least in part, of the failure of insulin to inhibit cAMP-dependent protein kinase activity (protein kinase A, PKA). To examine this proposed mechanism, PKA activity was measured in skeletal muscle (vastus lateralis) samples freeze-clamped in situ under basal fasting conditions before, and again during a euglycemic hyperinsulinemic clamp in 27 rhesus monkeys. Nine of the monkeys were normal (normal fasting glucose and insulin), eight were prediabetic (normal fasting glucose and hyperinsulinemia) and ten had spontaneous non-insulin-dependent diabetes (hyperglycemia). Insulin lowered PKA activity ratio in normal monkeys (basal vs insulin-stimulated, 14.4 +/- 3.2 vs 8.1 +/- 1.8%, p < 0.05), but raised PKA activity ratio in prediabetic monkeys (5.4 +/- 1.4 vs 10.5 +/- 2.6%, p < 0.05). PKA activity ratio was unaffected by insulin in the diabetic monkeys (6.7 +/- 1.8 vs 7.5 +/- 1.4%). Basal PKA activity ratio was higher in normal monkeys compared to prediabetic (p < 0.05) and diabetic monkeys (p < 0.05). Basal PKA activity ratio was inversely related to the insulin-stimulated change in PKA activity ratio (r = -0.72, p < 0.001). We conclude that in vivo insulin during euglycemic hyperinsulinemic clamp decreases skeletal muscle PKA activity ratio in normal monkeys but fails to decrease the activity ratio of PKA in insulin resistant (prediabetic and diabetic) monkeys. The insulin resistant state is characterized by low basal fasting skeletal muscle PKA activity ratio.
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PMID:Insulin decreases skeletal muscle cAMP-dependent protein kinase (PKA) activity in normal monkeys and increases PKA activity in insulin-resistant rhesus monkeys. 965 96

Diabetic microangiopathy has been implicated as a fundamental feature of the pathological complications of diabetes including retinopathy, neuropathy, and diabetic foot ulceration. However, previous studies devoted to examining the deleterious effects of elevated glucose on the endothelium have been performed largely in primary cultured cells of macrovessel origin. Difficulty in the harvesting and maintenance of microvascular endothelial cells in culture have hindered the study of this relevant population. Therefore, the objective of this study was to characterize the effect of elevated glucose on the proliferation and involved signaling pathways of an immortalized human dermal microvascular endothelial cell line (HMEC-1) that possess similar characteristics to their in vivo counterparts. Human dermal microvascular endothelial cells (HMEC-1) were grown in the presence of normal (5 mM) or high D-glucose (20 mM) for 14 days. The proliferative response of HMEC-1 was compared under these conditions as well as the cAMP and PKC pathways by in vitro assays. Elevated glucose significantly inhibited (P < 0.05) HMEC-1 proliferation after 7, 10, and 14 days. This effect was not mimicked by 20 mM mannitol. The antiproliferative effect was more pronounced with longer exposure (1-14 days) to elevated glucose and was irreversible 4 days after a 10-day exposure. The antiproliferative effect was partially reversed in the presence of a PKA inhibitor, Rp-cAMP (10-50 microM), and/or a PKC inhibitor, Calphostin C (10 nM). HMEC-1 exposed to elevated glucose (20 mM) for 14 days caused an increase in cyclic AMP accumulation, PKA, and PKC activity but was not associated with the activation of downstream events such as CRE and AP-1 binding activity. These data support the hypothesis that HMEC-1 is a suitable model to study the deleterious effects of elevated glucose on microvascular endothelial cells. Continued studies with HMEC-1 may prove advantageous in delineation of the molecular pathophysiology associated with diabetic microangiopathy.
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PMID:Antiproliferative effect of elevated glucose in human microvascular endothelial cells. 982 95

Experiments using confocal laser microscopy on the rat osteosarcoma cell line (ROS 17/2.8) indicate that mechanical stimulation elicits pronounced [Ca2+](i)transients in the MS (mechanically stimulated) cell, which then propagate to the NB (neighbouring) cells. Experiments with Ca(2+)-free solutions or gadolinium suggest that Ca(2+)-influx through stretch-sensitive channels is required. When intracellular stores are depleted with thapsigargin, mechanical stimulation was able to evoke a Ca(2+)transient of reduced amplitude that disappeared entirely after subsequent blocking of Ca(2+)-influx. Heptanol inhibited intercellular propagation of the Ca(2+)transient, demonstrating the involvement of gap junctions in the propagation of the Ca(2+)transient in ROS cells. PKC activation has only a small inhibitory effect, while inhibition of PKC or tyrosine kinase was ineffective. PKA activation reduced the amplitude of the [Ca2+](i)-rise in NB cells, and decreased the percentage of responsive cells. Cells grown in 50mM glucose for 72h presented only a very limited decrease of the Ca(2+)-rise during mechanical stimulation in the MS and NB cells compared to control conditions. PKC downregulation in high glucose did not modulate this effect. The results of our experiments indicate that PKC or sustained high glucose concentrations do not affect gap junctional communication in ROS cells, while activation of PKA has an inhibitory effect. This might indicate that osteoblastic dysfunction in diabetes could be directly related to the high glucose concentrations and not to inhibition of the intercellular communication.
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PMID:Intra- and intercellular Ca(2+)-transient propagation in normal and high glucose solutions in ROS cells during mechanical stimulation. 1116 51

Activation of the G-protein-coupled receptor for glucose-dependent insulinotropic polypeptide facilitates insulin-release from pancreatic beta-cells. In the present study, we examined whether glucose-dependent insulinotropic polypeptide also acts as a growth factor for the beta-cell line INS-1. Here, we show that glucose-dependent insulinotropic polypeptide induced cellular proliferation synergistically with glucose between 2.5 mM and 15 mM by pleiotropic activation of signaling pathways. Glucose-dependent insulinotropic polypeptide stimulated the signaling modules of PKA/cAMP regulatory element binder, MAPK, and PI3K/protein kinase B in a glucose- and dose-dependent manner. Janus kinase 2 and signal transducer and activators of transcription 5/6 pathways were not stimulated by glucose-dependent insulinotropic polypeptide. Activation of PI3K by glucose-dependent insulinotropic polypeptide and glucose was associated with insulin receptor substrate isoforms insulin receptor substrate-2 and growth factor bound-2 associated binder-1 and PI3K isoforms p85alpha, p110alpha, p110beta, and p110gamma. Downstream of PI3K, glucose-dependent insulinotropic polypeptide-stimulated protein kinase Balpha and protein kinase Bbeta isoforms and phosphorylated glycogen synthase kinase-3, forkhead transcription factor FKHR, and p70S6K. These data indicate that glucose-dependent insulinotropic polypeptide functions synergistically with glucose as a pleiotropic growth factor for insulin-producing beta-cells, which may play a role for metabolic adaptations of insulin-producing cells during type II diabetes.
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PMID:Glucose-dependent insulinotropic polypeptide is a growth factor for beta (INS-1) cells by pleiotropic signaling. 1151 6

We previously demonstrated the presence of an enhancer that is located between nucleotides - 2264 and - 2495 in the 5' flanking region of the rat sodium/iodide symporter (NIS) gene (Ohno et al., 1999). When attached to NIS or heterologous promoters, this 232 bp fragment, which we call NUE, is able to stimulate transcription in a thyroid-specific and cAMP-dependent manner. A paired-domain transcription factor Pax8 binds to this enhancer and can stimulate the transcription in non-thyroid cells that do not normally support the NUE activities. Cotransfection of PKA, a downstream effector of cAMP, further potentiates the Pax8-mediated transactivation. However, this transcriptional machinery containing pax8 seems to require contributions from the neighboring cis-acting element that is similar to CRE/AP-1 consensus sequences. Modification of this putative CRE/AP-1 site not only represses the NUE transcriptional activities by 90% in FRTL-5 cells, but also nullifies the synergistic effect of PKA on pax8-mediated transactivation in HeLa cells. In this report, we have further characterized the putative CRE/AP-1 site within the NIS upstream enhancer using gel mobility shift assay. An oligonucleotide probe with NIS CRE/AP-1 sequence produced complex binding patterns in both FRTL-5 and HeLa cell, reflecting the presence of diverse classes of binding factors. When compared with CRE or AP-1 elements in other genes, the mobility shift pattern of NIS CRE/AP-1 was similar to those of collagenase TRE, c-Jun TRE, and somatostatin CRE, but the relative intensities of the binding complexes were quite different. This observation raises a possibility that the NIS CRE/AP-site is regulated by a novel mechanism.
Exp Clin Endocrinol Diabetes 2001
PMID:Characterization of the upstream enhancer of the rat sodium/iodide symporter gene. 1157 34

A full biphasic insulin response is the most sensitive index for well-coupled beta-cell signal transduction. While first-phase insulin response is extremely sensitive to potentiating and inhibiting modulations, full expression of second-phase response requires near maximally activated beta-cell fuel metabolism. In the isolated rat pancreas, accelerated calcium entry or activation of protein kinase (PK)-A or PKC result in no insulin response in the absence of fuel metabolism. At submaximal levels of beta-cell fuel secretagogue, arginine (which promotes calcium entry) or glucagon (which activates PKA) produces a small first-phase insulin response but minimal or no second-phase response; carbachol (which activates PKC and promotes calcium entry) generates biphasic insulin response in the presence of minimal fuel (3.3 mmol/l glucose). Glucagon produces full biphasic response in the presence of 10.0 mmol/l glucose, whereas arginine requires near-maximal stimulatory glucose (16.7 mmol) to produce full biphasic insulin response. Thus, PKA and PKC signal pathways potentiate primary signals generated by fuel secretagogues to induce full biphasic insulin response, while calcium recruitment alone is insufficient to potentiate primary signals generated at low levels of fuel secretagogue. We suggest that three families of PKs (calmodulin-dependent PK [CaMK], PKA, and PKC) function as distal amplifiers for stimulus-secretion coupling signals originating from fuel metabolism, as well as from incretins acting through membrane receptors, adenylate cyclase, and phospholipase C. Several isoenzymes of PKA and PKC are present in pancreatic beta-cells, but the specific function of most is still undefined. Each PK isoenzyme is activated and subsequently phosphorylates its specific effector protein by binding to a highly specific anchoring protein. Some diabetes-related beta-cell derangements may be linked to abnormal function of one or more PK isoenzymes. Identification and characterization of the specific function of the individual PK isoenzymes may provide the tool to improve the insulin response of the diabetic patient.
Diabetes 2002 Feb
PMID:Beta-cell protein kinases and the dynamics of the insulin response to glucose. 1181 61

The mammalian insulin gene is exclusively expressed in the beta cells of the endocrine pancreas. Two decades of intensive physiological and biochemical studies have led to the identification of regulatory sequence motifs along the insulin promoter and to the isolation of transcription factors which interact to activate gene transcription. The majority of the islet-restricted (BETA2, PDX-1, RIP3b1-Act/C1) and ubiquitous (E2A, HEB) insulin-binding proteins have been characterized. Transcriptional regulation results not only from specific combinations of these activators through DNA-protein and protein-protein interactions, but also from their relative nuclear concentrations, generating a cooperativity and transcriptional synergism unique to the insulin gene. Their DNA binding activity and their transactivating potency can be modified in response to nutrients (glucose, NEFA) or hormonal stimuli (insulin, leptin, glucagon like peptide-1, growth hormone, prolactin) through kinase-dependent signalling pathways (PI3-K, p38MAPK, PKA, CaMK) modulating their affinities for DNA and/or for each other. From the overview of the research presented, it is clear that much more study is required to fully comprehend the mechanisms involved in the regulated-expression of the insulin gene in the beta cell to prevent its impairment in diabetes.
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PMID:Regulation of insulin gene transcription. 1191 36

The purpose of the current study was to determine whether nuclear factor-kappaB (NF-kappaB) activation is a component of the depolarization/Ca(2+)-dependent signaling in beta-cells. MIN6 cells were transfected with a plasmid containing five tandem repeats of NF-kappaB binding sites linked to a luciferase reporter. The results of these experiments showed that KCl induced depolarization-activated NF-kappaB-dependent transcription (3.8-fold at 45 mmol/l, P < 0.01) in a concentration-dependent manner. Tumor necrosis factor-alpha (TNF-alpha), a known inducer of NF-kappaB signaling, activated this construct by 3.4-fold (P < 0.01). The response of NF-kappaB to depolarization was inhibited by the Ca(2+)-channel blocker verapamil and by the mitogen-activated protein kinase kinase (MEK) inhibitor PD98059 (70 and 62%, respectively). TNF-alpha, glucose, and KCl treatment resulted in inhibitory kappaBalpha degradation by Western blot analysis. TNF-alpha treatment and depolarization activation of NF-kappaB differed significantly in that TNF-alpha activation was not blocked by PD98059. Transfection with PKA, MEK, and MEK kinase induced NF-kappaB-dependent transcription by 20-, 90-, and 300-fold, respectively, suggesting that these pathways contribute to the activation in the depolarization response. These findings demonstrate that depolarization/Ca(2+) influx, as well as TNF-alpha treatment, can activate NF-kappaB-dependent transcription in pancreatic beta-cells, but by different signaling pathways. The current studies show that Ca(2+) signals in pancreatic beta-cells can activate transcription factors involved in the regulation of cell cycle and apoptosis. These findings now add NF-kappaB to the list of depolarization-induced transcription factors in pancreatic beta-cells.
Diabetes 2002 Dec
PMID:Activation of nuclear factor-kappaB by depolarization and Ca(2+) influx in MIN6 insulinoma cells. 1247 94


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