Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It has been found that leucocytes possess receptor sites for glucagon and glucagon was shown to increase during bacterial infection. To verify the interconnection between glucagon, leucocytes and bacterial infection we studied the effect of glucagon on superoxide generation and second messenger transduction in PMNs. We found that glucagon could not stimulate chemiluminescence by itself but it could enhance FMLP- but not PMA-induced chemiluminescence in a concentration (50-800 pg/ml) dependent manner. However, after incubation of PMNs with 10 microM of ST-638 (a tyrosine kinase inhibitor) the enhancement effect converted into inhibitory effect. We also found that glucagon treatment of PMNs increased both IP3 and cyclic AMP levels as second messengers. ST-638 greatly attenuated the IP3 increment in the glucagon-treated FMLP-stimulated PMNs. From these results we can conclude that glucagon could enhance superoxide generation from FMLP-stimulated PMNs by elevating IP3. Inhibition of IP3 increment by tyrosine kinase blockade uncover the inhibitory effect of the increasing cyclic AMP on superoxide production.
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PMID:Glucagon modulates superoxide generation in human polymorphonuclear leucocytes. 823 32

Glucagon elicited a profound increase in the intracellular cAMP concentration of COS-7 cells which had been transiently transfected with a cDNA encoding the rat glucagon receptor and under conditions where cAMP phosphodiesterase activity was fully inhibited. This was achieved in a dose-dependent fashion with an EC50 of 1.8+/-0.4 nM glucagon. In contrast with previous observations made using hepatocytes [Heyworth, Whetton, Kinsella and Houslay (1984) FEBS Lett. 170, 38-42], treatment of transfected COS-7 cells with PMA did not inhibit the ability of glucagon to increase intracellular cAMP levels. PMA-mediated inhibition was not conferred by treatment with okadaic acid, nor by co-transfecting cells with cDNAs encoding various protein kinase C isoforms (PKC-alpha, PKC-betaII and PKC-epsilon) or with the PMA-activated G-protein-receptor kinases GRK2 and GRK3. In contrast, PMA induced the marked inhibition of glucagon-stimulated cAMP production in COS-7 cells that had been co-transfected with a cDNA encoding protein kinase D (PKD). Such inhibition was not due to an action on the catalytic unit of adenylate cyclase, as forskolin-stimulated cAMP production was unchanged by PMA treatment of COS cells that had been co-transfected with both the glucagon receptor and PKD. PKD transcripts were detected in RNA isolated from hepatocytes but not from COS-7 cells. Transcripts for GRK2 were present in hepatocytes but not in COS cells, whereas transcripts for GRK3 were not found in either cell type. It is suggested that PKD may play a role in the regulation of glucagon-stimulated adenylate cyclase.
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PMID:Co-transfection with protein kinase D confers phorbol-ester-mediated inhibition on glucagon-stimulated cAMP accumulation in COS cells transfected to overexpress glucagon receptors. 929 Nov 30

The glycine cleavage enzyme system (GCS) is found in mitochondria. In liver it is activated by glucagon and other hormones but it is not known how the hormonal signal is transmitted to the mitochondria. We found that the cell-permeant protein phosphatase inhibitor okadaic acid stimulated flux through GCS and could induce a significant increase in the sensitivity of GCS and of glycogenolysis to glucagon. Half-maximal stimulation of GCS by glucagon occurred at 3.2+/-0.6 nM, whereas it was fully activated at 0.3 nM in the presence of 1 microM okadaic acid. The protein kinase A agonist adenosine-3',5'-cyclic monophosphorothioate, Sp isomer (10 microM) stimulated the GCS flux by approx. 100%. This stimulation was inhibited by the protein kinase A antagonist 8-bromoadenosine-3', 5'-cyclic monophosphorothioate, Rp isomer (Rp-8-Br-cAMPS). Although Rp-8-Br-cAMPS significantly inhibited glucagon-stimulated glycogenolysis it had no effect on the glucagon-stimulated GCS flux. These results indicate that a cytoplasmic phosphorylated protein is involved in transmitting glucagon's effect to the mitochondria. However, protein kinase A does not have a necessary role in transmitting glucagon's signal. We also examined the role of protein kinase C because angiotensin II also stimulated flux through GCS. However, the phorbol ester PMA had no effect on either GCS or on glycogenolysis.
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PMID:Cell signalling and the hormonal stimulation of the hepatic glycine cleavage enzyme system by glucagon. 948 Aug 87

In spontaneously fasting birds such as penguins, below a body mass threshold corresponding to the phase II-phase III transition, a metabolic and hormonal shift occurs and feeding behaviour is stimulated ('refeeding signal'). The major aim of this study was to determine whether a decrease in non-esterified fatty acid (NEFA) release from adipose tissue could be a component of this signal. Lipolytic fluxes and primary triacylglycerol:fatty acid (TAG:FA) cycling were determined in vivo in breeding, fasting king penguins (Aptenodytes patagonicus) using continuous infusions of 2-[3H]glycerol and 1-[14C]palmitate under field conditions. In phase II (after approximately 8 days of fasting, large fat stores, body protein spared, N=8), the rate of appearance (R(a)) of glycerol and of NEFA were 5.7+/-0.8 and 10.5+/-0.4 micromol kg(-1) min(-1), respectively, and the percentage of primary TAG:FA cycling was 41+/-7%. In phase III (after approximately 25 days of fasting, fat stores reduced by fourfold, increased body protein catabolism, N=9), R(a) glycerol kg(-1) body mass remained unchanged, whereas R(a) glycerol kg(-1) fat mass and R(a) NEFA kg(-1) body mass were increased by 2.8-fold and 1.5-fold, respectively. Increased R(a) glycerol kg(-1) fat mass was possibly the result of a 3.5-fold increase in circulating glucagon, the increased R(a) NEFA kg(-1) body mass being attributable to decreased primary TAG:FA cycling. Thus, triggering of the refeeding signal that redirects the behavior of fasting, incubating penguins from incubation towards the search for food after entrance into phase III cannot be ascribed to a reduction in lipolytic fluxes and NEFA availability.
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PMID:Glycerol and NEFA kinetics in long-term fasting king penguins: phase II versus phase III. 1215 80

The cooperative effect of glucagon-like peptide 1 (GLP-1) and acetylcholine (ACh) was evaluated in a beta cell line model (BRIN BD11). GLP-1 (20 nM) and ACh (100 microM) increased insulin secretion by 24-47%, whereas in combination there was a further 89% enhancement of insulin release. Overnight culture with 100 ng/mL pertussis toxin (PTX) or 10nM PMA significantly reduced the combined insulinotropic action (P<0.05 and P<0.001, respectively) and the sole stimulatory effects of GLP-1 (PTX treatment; P<0.01) or ACh (PMA treatment; P<0.05). Under control conditions, ACh (50nM-1mM) concentration-dependently inhibited by up to 40% (P<0.001) the 10-fold (P<0.001) elevation of cyclic 3',5'-adenosine monophosphate (cAMP) induced by 20 nM GLP-1. The paradoxical inhibitory action of ACh was abolished by PTX pre-treatment, suggesting involvement of G(i) and/or G(o) G protein alpha subunit. Effects of selective muscarinic receptor antagonists on the concentration-dependent insulinotropic actions of ACh (50 nM-1 mM) on 20 nM GLP-1 induced insulin secretion revealed inhibition by rho-FHHSiD (M3 antagonist, P<0.05), stimulation with pirenzepine (M1 antagonist, P<0.001) and no significant effects of either methoctramine (M2 antagonist) or MT-3 (M4 antagonist). Antagonism of M2, M3 and M4 muscarinic receptor effects with methoctramine (3-100 nM), rho-FHHSiD (3-30 nM) or MT-3 (10-300 nM) did not significantly affect the inhibitory action of ACh on GLP-1 stimulated cAMP production. In contrast, M1 receptor antagonism with pirenzepine (3-30 0nM) resulted in a concentration-dependent decrease in the inhibitory action of ACh on GLP-1 stimulated cAMP production (P<0.001). These data indicate an important functional cooperation between the cholinergic neurotransmitter ACh and the incretin hormone GLP-1 on insulin secretion mediated through the M3 muscarinic receptor subtype. However, the insulinotropic action of ACh was associated with a paradoxical inhibitory effect on GLP-1 stimulated cAMP production, achieved through a novel PTX- and pirenzepine-sensitive M1 muscarinic receptor activated pathway. An imbalance between these pathways may contribute to dysfunctional insulin secretion.
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PMID:Cooperative enhancement of insulinotropic action of GLP-1 by acetylcholine uncovers paradoxical inhibitory effect of beta cell muscarinic receptor activation on adenylate cyclase activity. 1250 4

The mechanism by which the gastrointestinal hormones peptide YY and glucagon inhibit gastric acid secretion is largely unknown. PYY-Tag transgenic mice develop endocrine tumors in the colon that are composed mainly of peptide YY/enteroglucagon-producing L type cells. Therefore we studied the functional activity of such tumors and the gastric functions of PYY-Tag mice. Fasting and fed PYY-Tag transgenic mice and CD1 controls were assayed for circulating levels of peptide YY, glucagon, insulin, and gastrin. The gastric pH was determined and gastric samples were examined for (a) histologic appearance; (b) K(+)-stimulated p-nitrophenylphosphatase activity and [(14)C]aminopyrine accumulation of apical and tubulovesicle membranes; (c) adherent mucus determination by Alcian blue recovery; and (d) DNA/RNA/protein epithelial content and in vivo incorporation of [(3)H]thymidine into DNA. Transgenic mice showed high serum levels of peptide YY and glucagon, increased gastric pH, and a high incidence of gastric ulcers after fasting. p-Nitrophenylphosphatase activity, [(14)C] aminopyrine accumulation, and proton pump redistribution from cytoplasmic tubulovesicles to apical membranes were significantly lower in the gastric mucosa of transgenic mice compared with the controls. In addition, the adherent mucus was thinner, and [(3)H]thymidine incorporation into the DNA was decreased. The abnormal and unregulated levels of circulating peptide YY and glucagon led to gastric acid inhibition and an impairment of gastric barrier function as a result of a striking reduction in epithelial proliferation.
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PMID:PYY-Tag transgenic mice displaying abnormal (H+-K+)ATPase activity and gastric mucosal barrier impairment. 1253 85

Glucagon-like peptide-1 (GLP-1) stimulates glucose-dependent insulin secretion and inhibits food intake, gastric emptying, and glucagon secretion, actions that promote reduction of fasting and postprandial glycemia in subjects with type 2 diabetes. The rapid degradation of native GLP-1 has engendered interest in more stable longer-acting GLP-1 receptor agonists such as exendin-4 (Ex-4); however, the potential consequences of sustained GLP-1 receptor activation leading to receptor desensitization has not been extensively studied. We have now examined a range of GLP-1 receptor-dependent responses following treatment with Ex-4 using INS-1 cells in vitro and both wild-type control and MT-Ex-4 transgenic mice in vivo. Although both GLP-1 and Ex-4 acutely desensitized GLP-1 receptor-dependent cAMP accumulation in INS-1 cells, Ex-4 produced more sustained receptor desensitization, relative to GLP-1, in both acute (5-120 min) and chronic (24-72 h) experiments. PMA (4-phorbol 12-myristate 13-acetate) but not glucagon, glucose-dependent insulinotropic polypeptide (GIP), or epinephrine produced heterologous desensitization in vitro. MT-Ex-4 transgenic mice exhibited a reduced glycemic response to oral but not intraperitoneal glucose challenge following acute Ex-4 administration. In contrast, no differences in glycemic excursion or plasma insulin were observed after 1 week of twice-daily Ex-4 administration to wild-type versus MT-Ex-4 mice. Similarly, the levels of insulin, pdx-1, and GLP-1 receptor mRNA transcripts were comparable in wild-type and MT-Ex-4 transgenic mice after 1 week of Ex-4 administration. However, repeated Ex-4 administration significantly reduced food intake in MT-Ex-4 but not in wild-type mice. These findings illustrate that although Ex-4 is more potent than native GLP-1 in producing GLP-1 receptor desensitization in vitro, chronic exposure to Ex-4 in normal or transgenic mice is not associated with significant downregulation of GLP-1 receptor-dependent responses coupled to glucose homeostasis in vivo.
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PMID:Chronic exposure to GLP-1R agonists promotes homologous GLP-1 receptor desensitization in vitro but does not attenuate GLP-1R-dependent glucose homeostasis in vivo. 1556 12

The short-term regulation of multidrug resistance-associated protein 3 (Mrp3/MRP3) by cAMP and PKC was investigated in sandwich-cultured rat and human hepatocytes and isolated perfused rat livers. The modulator glucagon (500 nM) and the phorbol ester PMA (0.1 muM) were utilized to increase intracellular cAMP and PKC levels, respectively. In glucagon-treated rat hepatocytes, efflux of the Mrp3 substrate 5-(6)-carboxy-2',7'-dichlorofluorescein (CDF) increased approximately 1.5-fold, even in hepatocytes treated with the organic anion transporter (Oatp) inhibitor sulfobromophthalein (BSP). Confocal microscopy revealed more concentrated Mrp3 fluorescence in the basolateral membrane (less diffuse staining pattern) with glucagon treatment. PMA had no effect on Mrp3 activity or localization in sandwich-cultured rat hepatocytes. Glucagon and PMA treatment in isolated perfused rat livers resulted in a threefold increase (14 +/- 4.6 mul.min(-1).g liver(-1)) and a fourfold decrease (1.3 +/- 0.3 mul.min(-1).g liver(-1)) in CDF basolateral clearance compared with control livers (4.7 +/- 2.3 mul.min(-1).g liver(-1)), whereas CDF biliary clearance was not statistically different. In sandwich-cultured human hepatocytes, glucagon treatment resulted in a 1.3-fold increase in CDF efflux and a concomitant increase in MRP3 fluorescence in the basolateral membrane. In summary, cAMP and PKC appear to be involved in the short-term regulation of Mrp3/MRP3, as demonstrated by alterations in activity and localization in rat and human hepatocytes.
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PMID:Short-term regulation of multidrug resistance-associated protein 3 in rat and human hepatocytes. 1565 Jan 33

Recent data reported that inulin-type fructans extracted from chicory roots regulate appetite and lipid/glucose metabolism, namely, by promoting glucagon-like peptide-1 (GLP-1) production in the colon. The Agave genus growing in different regions of Mexico also contains important amounts of original fructans, with interesting nutritional and technological properties, but only few data report their physiological effect when added in the diet. Therefore, we decided to evaluate in parallel the effect of supplementation with 10 % agave or chicory fructans on glucose and lipid metabolism in mice. Male C57Bl/6J mice were fed a standard (STD) diet or diet supplemented with Raftilose P95 (RAF), fructans from Agave tequilana Gto. (TEQ) or fructans from Dasylirion spp. (DAS) for 5 weeks. The body weight gain and food intake in mice fed fructans-containing diets were significantly lower than the ones of mice fed the STD diet, TEQ leading to the lowest value. Serum glucose and cholesterol were similarly lower in all fructans-fed groups than in the STD group and correlated to body weight gain. Only RAF led to a significant decrease in serum TAG. As previously shown for RAF, the supplementation with agave fructans (TEQ and DAS) induced a higher concentration of GLP-1 and its precursor, proglucagon mRNA, in the different colonic segments, thus suggesting that fermentable fructans from different botanical origin and chemical structure are able to promote the production of satietogenic/incretin peptides in the lower part of the gut, with promising effects on glucose metabolism, body weight and fat mass development.
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PMID:Physiological effects of dietary fructans extracted from Agave tequilana Gto. and Dasylirion spp. 1771 12

Obesity is a global epidemic; increased consumption of energy-dense food and reduced physical activity levels are likely to be the main drivers. Previous cross-sectional research has shown that sedentary males, unlike their active counterparts, are unable to compensate for previous energy intake (EI). Using a longitudinal design a 6-week exercise intervention was found to improve short-term appetite control, leading to a more 'sensitive' eating behaviour in response to previous EI, both acutely at a test meal and for the next 24 h. Although the mechanisms whereby acute and chronic exercise improves short-term appetite remain unknown, post-ingestive satiety peptides are likely to be involved. Acute exercise was found to increase postprandial levels of polypeptide YY, glucagon-like peptide-1 and pancreatic polypeptide but to have no impact on ghrelin, suggesting that exercise can trigger physiological changes in satiety hormone secretion that could help in appetite control and weight maintenance. In the context of an increased availability of highly-palatable food, dietary restraint may be increasingly important. Although restraint has been associated with abnormal eating behaviour, in the laboratory no counter-regulation was found in restrained eaters when presented with a buffet meal 60 min after a high-energy preload or when a pasta-meal was presented 3 h after preloading. Although restraint was not found to impact on polypeptide YY or TAG, lower postprandial glucose and insulin plasma levels were observed in restrained eaters, together with increased feelings of fullness. In conclusion, short-term appetite control seems to be favourably modified by exercise, while the impact of restraint on appetite seems to be more complex.
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PMID:Effects of exercise and restrained eating behaviour on appetite control. 1823 29


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