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

Periportal and perivenous hepatocytes possess different amounts and activities of the rate-generating enzymes of carbohydrate and oxidative energy metabolism and thus different metabolic capacities. This is the basis of the model of metabolic zonation, according to which periportal cells catalyze predominantly the oxidative catabolism of fatty and amino acids as well as glucose release and glycogen formation via gluconeogenesis, and perivenous cells carry out preferentially glucose uptake for glycogen synthesis and glycolysis coupled to liponeogenesis. The input of humoral and nervous signals into the periportal and perivenous zones is different; gradients of oxygen, substrates and products, hormones and mediators and nerve densities exist which are important not only for the short-term regulation of carbohydrate metabolism but also for the long-term regulation of zonal gene expression. The specialization of periportal and perivenous hepatocytes in carbohydrate metabolism has been well characterized. In vivo evidence is provided by the complex metabolic situation termed the 'glucose paradox' and by zonal flux differences calculated on the basis of the distribution of enzymes and metabolites. In vitro evidence is given by the different flux rates determined with classical invasive techniques, e.g. in periportal-like and perivenous-like hepatocytes in cell culture, in periportal- and perivenous-enriched hepatocyte populations and in perfused livers during orthograde and retrograde flow, as well as with noninvasive techniques using miniature oxygen electrodes, e.g. in livers perfused in either direction. Differences of opinion in the interpretation of studies with invasive and noninvasive techniques by the authors are discussed. The declining gradient in oxygen concentrations, the decreasing glucagon/insulin ratio and the different innervation could be important factors in the zonal expression of the genes of carbohydrate-metabolizing enzymes. While it is clear that the hepatocytes sense the glucagon/insulin gradients via the respective hormone receptors, it is not known how they sense different oxygen tensions; the O2 sensor may be an oxygen-binding heme protein. The zonal separation of glucose release and uptake appears to be important for the liver to operate as a 'glucostat'. Thus, zonation of carbohydrate metabolism develops gradually during the first weeks of life, in part before and in part with weaning, when (in rat and mouse) the fat- and protein-rich but carbohydrate-poor nutrition via milk is replaced by carbohydrate-rich food. Similarly, zonation of carbohydrate metabolism adapts to longer lasting alterations in the need of a 'glucostat', such as starvation, diabetes, portocaval anastomoses or partial hepatectomy.
 ...
PMID:Hepatocyte heterogeneity in the metabolism of carbohydrates. 128 81

Rat (Rattus norvegicus) and spiny mouse (Acomys cahirinus) are closely related murine species that, due to their altricial (rat) and precocial (spiny mouse) modes of development, differ in the developmental timing of birth. A comparison between the developmental profiles of plasma glucagon, insulin, thyroxine, triiodothyronine, and glucocorticosteroid hormone was carried out to elucidate the question to what extent these hormonal profiles were related to the timing of birth. Although corticosterone is the major circulating glucocorticosteroid in rat, only cortisol was found in the spiny mouse. The onset of increases in glucocorticosteroid and thyroid hormone levels occurred at the same developmental time points in both species. A neonatal increase in triiodothyronine levels was observed in the spiny mouse only. In both species the immediate perinatal period was characterized by decreases in the ratio of insulin and glucagon levels and the level of glucocorticosteroids. The observed developmental patterns of hormonal levels were found to be consistent with the observed developmental pattern of enzymic maturation in the respiratory and gastrointestinal tract, which play a critical role in the adaptation to the extrauterine environment.
 ...
PMID:Hormones in perinatal rat and spiny mouse: relation to altricial and precocial timing of birth. 352 60

Besides being degraded to glucose-6-phosphate and to free glucose, glycogen is degraded by alpha-1,4-glucan lyase to 1, 5-anhydro-D-fructose. We examined the influence of 1, 5-anhydro-D-fructose on glucose-stimulated insulin secretion in vivo and in vitro in mice. When administered together with i.v. glucose (1 g/kg), 1,5-anhydro-D-fructose did not affect (at 0.2 g/kg) or inhibited (at 1 g/kg) insulin secretion without affecting glucose elimination. When incubated with isolated islets, 1, 5-anhydro-D-fructose at <16.7 mmol/l, did not affect glucose (11.1 mM)-stimulated insulin secretion but inhibited insulin secretion at 16.7 mmol/l. When given through a gastric gavage (150 mg/mouse) together with glucose (150 mg/mouse), 1,5-anhydro-D-fructose increased glucose tolerance and insulin secretion. Furthermore, 1, 5-anhydro-D-fructose potentiated the increase in plasma levels of the gut hormone, glucagon-like peptide-1 (GLP-1). We therefore conclude that when given enterally, but not parenterally, 1, 5-anhydro-D-fructose increases glucose tolerance in mice by increasing insulin secretion due to increased plasma levels of GLP-1. The sugar may therefore be explored for increasing endogenous GLP-1 secretion in the treatment of type 2 diabetes.
 ...
PMID:1,5-Anhydro-D-fructose increases glucose tolerance by increasing glucagon-like peptide-1 and insulin in mice. 1084 16

Pituitary adenylate cyclase-activating polypeptide (PACAP) is localized to pancreatic ganglia governing the parasympathetic nerves, which contribute to prandial insulin secretion. We hypothesized that this contribution involves PACAP and show here that the PACAP receptor antagonist PACAP-(6---27) (1.5 nmol/kg iv) reduces the 15-min insulin response to gastric glucose (150 mg/mouse) by 18% in anesthetized mice (P = 0.041). The reduced insulinemia was not due to inhibited release of the incretin factor glucagon-like peptide 1 (GLP-1) because PACAP-(6---27) enhanced the GLP-1 response to gastric glucose. Furthermore, the GLP-1 antagonist exendin-3-(9---39) (30 nmol/kg) exerted additive inhibitory effect on the insulin response when combined with PACAP-(6---27). The PACAP antagonism was specific because intravenous PACAP-(6---27) inhibited the insulin response to intravenous PACAP-27 plus glucose without affecting the insulin response to intravenous glucose alone (1 g/kg) or glucose together with other insulin secretagogues of potential incretin relevance of intestinal (GLP-1, gastric inhibitory polypeptide, cholecystokinin) and neural (vasoactive intestinal peptide, gastrin-releasing peptide, cholinergic agonism) origin. We conclude that PACAP contributes to the insulin response to gastric glucose in mice and suggest that PACAP is involved in the regulation of prandial insulin secretion.
 ...
PMID:PACAP contributes to insulin secretion after gastric glucose gavage in mice. 1093 28

Secretin is a gastrointestinal peptide belonging to the vasoactive intestinal peptide (VIP)/glucagon/pituitary adenylate cyclase-activating polypeptide (PACAP) family recently suggested to have therapeutic effects in autism. A direct effect on brain would require secretin to cross the blood-brain barrier (BBB), an ability other members of the VIP/PACAP family have. Herein, we examined whether a secretin analog (SA) radioactively labeled with (131)I (I-SA) could cross the BBB of 4-week-old mice. We found I-SA was rapidly cleared from serum with fragments not precipitating with acid appearing in brain and serum. Levels of radioactivity were corrected to reflect only intact I-SA as estimated by acid precipitation. After i.v. injection, I-SA was taken up by brain at a modest rate of 0.9 to 1.5 microl/g-mm. Capillary depletion, brain perfusion, and high-performance liquid chromatography were used to confirm the passage of intact I-SA across the BBB. I-SA entered every brain region, with the highest uptake into the hypothalamus and cerebrospinal fluid (CSF). Unlabeled SA (10 microg/mouse) did not inhibit uptake by brain but did inhibit clearance from blood and uptake by the CSF, colon, kidney, and liver. The decreased clearance of I-SA from blood increased the percentage of the i.v. injected dose taken up per brain (%Inj/g) from about 0.118 to 0.295%Inj/g. In conclusion, SA crosses the vascular barrier by a nonsaturable process and the choroid plexus by a saturable process in amounts that for other members of its family produce central nervous system (CNS) effects. This passage provides a pathway through which peripherally administered SA could affect the CNS.
 ...
PMID:Differential transport of a secretin analog across the blood-brain and blood-cerebrospinal fluid barriers of the mouse. 1218 64

The embryonic pancreas is thought to develop from pluripotent endodermal cells that give rise to endocrine and exocrine cells. A key guidance mechanism for pancreatic development has previously been found to be epithelial-mesenchymal interaction. Interactions within the epithelium, however, have not been well studied. Glucagon is the earliest peptide hormone present at appreciable levels in the developing pancreatic epithelium (embryonic day [E]-9.5 in mouse). Insulin accumulation begins slightly later (E11 in mouse), followed by a rapid accumulation during the "second wave" of insulin differentiation ( approximately E15). Here we found that blocking early expression and function of glucagon, but not GLP-1, an alternate gene product of preproglucagon mRNA, prevented insulin-positive differentiation in early embryonic (E11) pancreas. These results suggest a novel concept and a key role for glucagon in the paracrine induction of differentiation of other pancreatic components in the early embryonic pancreas.
 ...
PMID:Glucagon is required for early insulin-positive differentiation in the developing mouse pancreas. 1240 14

To study the effect of phosphodiesterase (PDE) 3 inhibition on plasma insulin and glucose levels, the selective PDE 3 inhibitor milrinone (0.25, 1.0, and 2.5 mg/kg) was given orally to anesthetized CL57Bl/6J mice 10 min before a gastric glucose gavage (150 mg/mouse). It was found that milrinone augmented the glucose-mediated increase in plasma insulin at 1.0 and 2.5 mg/kg without, however, any improvement in glucose elimination. In contrast, when given 10 min before intravenous glucose (1 g/kg), milrinone (1 mg/kg) did not affect the insulin response to glucose. The increase in glucagon-like peptide-1 (GLP-1) levels after gastric glucose was not altered by milrinone. However, the PDE3 inhibitor augmented the insulin response to intravenous GLP-1 (2.8 nmol/kg). We therefore conclude that PDE3 inhibition by milrinone augments insulin secretion in vivo in mice after oral but not after intravenous glucose, which may be explained by enhanced response to the cAMP-dependent insulinotropic action of endogenously released GLP-1.
 ...
PMID:Milrinone efficiently potentiates insulin secretion induced by orally but not intravenously administered glucose in C57BL6J mice. 1536 11

The distribution and density of gastric endocrine cells in Balb/c mice bearing CT-26 carcinoma cells were studied immunohistochemically employing specific antisera against serotonin, somatostatin, glucagon, gastrin, cholecystokinin (CCK)-8 and human pancreatic polypeptide (hPP). The animals were divided into two groups, a non-implanted sham group and a CT-26 carcinoma cell-implanted group. Samples were collected from two regions of the stomach (fundus and pylorus) at 28 days after implantation of the medium or the CT-26 cells (1x10(5) cells/mouse). Five of the 6 types of immunoreactive (IR) cells were identified, with only the hPP IR cells not being detected. The regional distribution of the gastric endocrine cells in the CT-26 implanted group was similar to that of the non-implanted sham group. However, the endocrine cells were significantly decreased in the CT-26-implanted group as compared to those of the non-implanted sham group. Serotonin- and somatostatin-IR cells in the fundus and pylorus , and gastrin- and CCK-8-IR cells in the pylorus of the CT-26 implanted groups were significantly decreased compared to those of the sham group. In addition, glucagon-IR cells were restricted only to the fundus of the sham animals. hPP-IR cells were not detected in either the T-26 implanted- or the non-implanted group. Since endocrine cells are the anatomical units responsible for the production of gut hormones, a change in their density may reflect a change in their capacity to produce such hormones. Implantation of the tumor cell mass induced severe quantitative changes in gastric endocrine cell density, an abnormality which may contribute to the development of gastrointestinal symptoms, such as anorexia and indigestion, frequently encountered in cancer patients.
 ...
PMID:Changes in gastric endocrine cells in Balb/c mice bearing CT-26 carcinoma cells: an immunohistochemical study. 1721 38

Exogenous administration of islet amyloid polypeptide (IAPP) has been shown to inhibit both insulin and glucagon secretion. This study examined alpha-cell function in mice with beta-cell specific overexpression of human IAPP (hIAPP) after an oral protein gavage (75 mg whey protein/mouse). Baseline glucagon levels were higher in transgenic mice (41 +/- 4.0 pg/mL, n = 6) than in wildtype animals (19 +/- 5.1 pg/mL, n = 5, P = .015). In contrast, the glucagon response to protein was impaired in transgenic animals (21 +/- 2.7 pg/mL in transgenic mice versus 38 +/- 5.7 pg/mL in wildtype mice at 15 minutes; P = .027). Baseline insulin levels did not differ between the groups, while the insulin response, as the glucagon response, was impaired after protein challenge (P = .018). Glucose levels were not different between the groups and did not change significantly after protein gavage. Acetaminophen was given through gavage to the animals (2 mg/mouse) to estimate gastric emptying. The plasma acetaminophen profile was similar in the two groups of mice. We conclude that disturbances in glucagon secretion exist in mice with beta-cell specific overexpression of human IAPP, which are not secondary to changes in gastric emptying. The reduced glucagon response to protein challenge may reflect a direct inhibitory influence of hIAPP on glucagon secretion.
 ...
PMID:Disturbed alpha-cell function in mice with beta-cell specific overexpression of human islet amyloid polypeptide. 1861 1

TRPM4 is a Ca(2+)-activated non-selective cation (CAN) channel that functions in cell depolarization, which is important for Ca(2+) influx and insulin secretion in pancreatic beta-cells. We investigated TRPM4 expression and function in the beta-cell lines HIT-T15 (hamster), RINm5F (rat), beta-TC3 (mouse), MIN-6 (mouse) and the alpha-cell line INR1G9 (hamster). By RT-PCR, we identified TRPM4 transcripts in alpha- and beta-cells. Patch-clamp recordings with increasing Ca(2+) concentrations resulted in a dose-dependent activation of TRPM4 with the greatest depolarizing currents recorded from hamster-derived cells. Further, Ca(2+) imaging experiments revealed that inhibition of TRPM4 by a dominant-negative effect significantly decreased the magnitude of the Ca(2+) signals generated by agonist stimulation compared to control cells. The decrease in the [Ca(2+)](i) resulted in reduced insulin secretion. Our data suggest that depolarizing currents generated by TRPM4 are an important component in the control of intracellular Ca(2+) signals necessary for insulin secretion and perhaps glucagon from alpha-cells.
 ...
PMID:TRPM4 impacts on Ca2+ signals during agonist-induced insulin secretion in pancreatic beta-cells. 1906 36


1 2 Next >>