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)

Exposure of cultured rat hepatocytes to a high concentration of insulin (78 nM) for 24 h in the presence of extracellular oleate (0.75 mM) resulted in a decrease in the secretion of apoprotein B (apoB) and triacylglycerol associated with very-low-density lipoprotein (VLDL). However, continuous exposure of the cells to insulin for longer periods (72 h) stimulated the secretion of apoB and triacylglycerol. Treatment of hepatocytes with glucagon (0.1 microM) for 24 h also suppressed the secretion of VLDL apoB, cholesterol and triacylglycerol. The cells remained responsive to the inhibitory effect of glucagon for at least 3 days. In contrast with insulin, however, exposure of the cells to glucagon for a continuous period of 72 h did not lead to a reversal of the initial inhibition. Glucagon also stimulated ketogenesis, and in this regard the cells were responsive for at least 3 days in culture. These changes were accompanied by a transient increase in intracellular cyclic AMP (cAMP) concentration, which reached a peak 10 min after addition of glucagon. Between 12 h and 24 h after glucagon addition, cAMP levels had returned almost to normal, but the secretion of VLDL remained suppressed during this period.
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PMID:The role of pancreatic hormones in the regulation of lipid storage, oxidation and secretion in primary cultures of rat hepatocytes. Short- and long-term effects. 131 May 93

Apolipoprotein (apo) E is a predominant protein in developing mammalian brain and in damaged peripheral nerve. Of particular interest is the observation that astrocytes in the central nervous system cease to produce apoE after nerve damage, whereas an increase in apoE production results after peripheral nerve injury. Differences in the response to injury with regard to the production of apoE may be related to dissimilarities in the abilities of the central and peripheral nervous systems to regenerate. As there are few data concerning the regulation of apoE gene expression in extrahepatic tissues, we employed a human astrocytoma cell line (CCF-STTG1) as a model to study apoE production in astrocytes. CCF-STTG1 cells secreted apoE constitutively in serum-free media. Cholesterol added to the media as cholesterol:phospholipid liposomes (2-100 micrograms/ml) or as human plasma LDL increased the amount of apoE secreted into the media, but had little or no effect on the relative abundance of apoE mRNA. By contrast, the commercially available triglyceride-phospholipid emulsion Intralipid added at dilutions of 1:50 to 1:500 caused a total inhibition of apoE secretion by the cells, but again, little change was noted in the relative abundance of apoE mRNA. Insulin (5 micrograms/ml) caused a 45-55% reduction in the amount of apoE secreted by the astrocytoma cells. Glucagon (5 micrograms/ml), on the other hand, did not increase apoE secretion, and apoE mRNA concentrations were not affected by either hormone treatment. ApoE was secreted from the astrocytoma cells associated with particles of plasma VLDL to IDL and HDL size. After feeding the cells with 20 micrograms/ml cholesterol as cholesterol:phospholipid liposomes, an increased proportion of apoE was secreted associated with the larger VLDL to IDL size particles, with a concomitant decrease in the proportion associated with the smaller HDL-size particles. When cells were incubated with 5 micrograms/ml insulin, most of the apoE was associated with the HDL-size particles. When cholesterol:phospholipid liposomes were added in the presence of insulin virtually all of the secreted apoE was found associated with the VLDL to IDL size particles. In summary, the regulation of apoE production in CCF-STTG1 cells in many respects resembles that of other cells, including hepatocytes. However, it is clear that there remain to be identified cell specific factors which regulate apoE production in astrocytes. The CCF-STTG1 cell line promises to provide a suitable model to investigate these questions.
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PMID:Secretion of apolipoprotein E by an astrocytoma cell line. 140 94

Synthetic peptides that differ in their lipid-peptide interactions were combined with dipalmitoylphosphatidylcholine (DPPC) and tested in an adult rat lavaged lung model in vitro for efficacy as totally synthetic lung surfactants. The putative amphipathic alpha-helical region of the major lung surfactant apoprotein (SP-A81-102), an analogue with increased amphipathic alpha-helical potential ([Lys88,97,Glu99,Trp102]-SP-A81-102]), and the hydrophobic peptide gramicidin D were all ineffective. Three water-soluble lipid-binding peptides that contain amphipathic alpha-helical regions were also tested. Of these, only a 24-residue amphipathic alpha-helical peptide (18As) based on the lipid-binding sequences of the plasma apolipoproteins was effective. Melittin and glucagon were ineffective. Mixtures of 18As and DPPC also restored gas exchange in an in vivo lavaged guinea pig lung model to 90-95% of its prelavage value and maintained it for at least 3 h. Mixtures of DPPC and 18As are also surface active (gamma min less than 4 mN/m in the pulsating bubble). These data demonstrate the efficacy of a combination of a single lipid and a small, water-soluble, nonhemolytic, synthetic peptide containing an amphipathic alpha-helical structure and a sequence unrelated to any of the reported lung surfactant apoprotein sequences.
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PMID:Mixtures of synthetic peptides and dipalmitoylphosphatidylcholine as lung surfactants. 155 Feb 52

The sexually dimorphic GH secretory pattern is thought to be the major factor regulating constitutive expression of hepatic P450IIC11 (P-450h) and P450IIC12 (P-450i). In this study we investigated whether factors other than the diabetes-induced decrease in GH secretion contribute to alterations in P-450 isozyme expression in streptozotocin (STZ)-diabetic rats. In male rats, hepatic P-450h apoprotein and mRNA decreased to 13% and 24% of control male levels, respectively, within 14 days of STZ injection. STZ-diabetes had little effect on expression of P-450i in females. Treatment of diabetic male rats with GH did not reverse the suppression of P-450h. STZ treatment also suppressed P-450h expression in GH-treated hypophysectomized (Hx) male rats, but incompletely. Thus, GH can partially reverse diabetic suppression of P-450h. However, in Hx male rats without GH supplementation, STZ treatment suppressed P-450h apoprotein and mRNA expression to 16% and 6% of nondiabetic Hx male levels, respectively, demonstrating the existence of GH-independent regulation of P-450h expression. In Hx female rats, P-450h apoprotein levels were 40% of those in intact control males and were not significantly decreased by STZ. Concomitantly, STZ produced a greater decrease in serum insulin levels and a greater increase in serum glucagon in Hx male rats than in Hx females. The results provide evidence for the existence of STZ-sensitive GH-independent expression of P-450h and further document the gender differences in STZ sensitivity.
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PMID:Growth hormone-dependent and -independent regulation of cytochrome P-450 isozyme expression in streptozotocin-diabetic rats. 170 65

The relationship between plasma insulin (IRI) and lipid concentration, or triglyceride (TG) kinetics was studied in streptozotocin-induced diabetic rats (DM) to examine how insulin deficiency is associated with the mechanism of hypertriglyceridemia (HTG) in diabetes. Plasma glucose and ketones were significantly elevated and IRI reduced in DM. Plasma glucagon concentration in DM was similar to controls. The plasma concentration of TG, total cholesterol phospholipid and apoprotein B was 3-4-fold higher in DM compared to control rats. The HTG in DM was mainly attributable to an increase in the concentration of TG-rich lipoprotein (TRL). Multiple linear regression analysis showed a positive relationship between the concentration of non-esterified fatty acid and plasma lipids, but the decrease in IRI best correlated with increased concentrations of lipids and apoprotein B in plasma and TRL. Neither glucose nor glucagon correlated significantly with lipids or apoprotein B concentration in plasma or TRL. The rate of entry of TG into blood was similar between DM and controls, and in DM this significantly correlated with IRI. Clearance of radiolabeled TRL-TG in DM was significantly decreased and correlated with IRI. Conversely, the removal of radiolabeled Intralipid-TG was similar for DM and controls. The data suggest that insulin critically regulates TRL-TG metabolism in DM and that a catabolic defect of TRL-TG due to insulin deficiency is a main reason for the HTG.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Correlation of insulin deficiency and hypertriglyceridemia in diabetic rats. 188 46

An apolipoprotein-E (apo-E) cDNA probe, cloned by immunoscreening of a lambda GT11 rat liver cDNA library, was used to further characterize the expression of the apo-E gene in rat liver during development, in relation to plasma insulin and glucagon levels. The apo-E mRNA level was low in fetus liver, then abruptly increased at birth and rose further during the suckling period. It returned to the level at birth in 10-week-old adults. These variations were paralleled with dramatic changes in plasma glucagon, which rose at birth and remained high during suckling. At the same time, the insulin/glucagon molar ratio fell. Administration of N6,O2-dibutyryl cAMP to 5-day-old rats resulted in a significant induction of liver apo-E mRNA. Moreover, liver apo-E mRNA rose in 10-h-fasted suckling rats as compared to controls, while plasma glucagon increased and the insulin/glucagon ratio decreased. Conversely, glucose feeding of suckling rats did not induce any increase in liver apo-E mRNA, the insulin/glucagon ratio was 10-fold higher than in fasted animals. Our results are consistent with liver apo-E gene expression being under the control of plasma glucagon and of the glucagon/insulin balance.
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PMID:Apolipoprotein-E-gene expression in rat liver during development in relation to insulin and glucagon. 265 21

Recently numerous reports show deleterious effects of alcohol abuse on pregnant women giving their children a high risk of stillbirth and/or several developmental abnormalities and mental retardation, i.e. the Fetal alcohol syndrome (FAS). In the present study, the effects of maternal alcohol consumption on lipid metabolism in the litter liver were investigated in rats. These rats showed not only quite less lipid deposition in spite of large amount of alcohol consumption up to adulthood, but also showed increased FFA oxidation in the livers. In addition, increased level of very low density lipoprotein and hypoglucagonemia were found. 40 micrograms/kg of glucagon which is known as an inhibitory factor of apoprotein production in the liver, was injected for 2 weeks into the rat tail vein and resulted in apparent fatty liver and hypolipoproteinemia. Norepinephrine injection (1 mg/kg) caused plasma glucagon to be depressed in the rat as compared with adult alcohol rats. Plasma cyclic AMP response to glucagon was also depressed in these rats. From these results, it is suggested that the deranged glucagon secretion from the pancreas and lowered glucagon-induced cyclic AMP response would relate to the abnormal lipoprotein metabolism in the rat.
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PMID:[Experimental studies on lipoprotein metabolism in rats reared with liquid alcohol diet from the fetal life]. 298 81

When hepatocytes were cultured for 24 h in the presence of forskolin (10(-4) mol l-1) or isobutylmethylxanthine (IBMX, 10(-3) mol l-1), the intracellular cAMP concentration peaked (320-380 pmol mg-1 protein) after 10-20 min of culture. This increase was accompanied by a decrease in the secretion of triacylglycerol, cholesterol and apoprotein B associated with VLDL. After 4 h cAMP levels had returned almost to basal values but the inhibition of VLDL secretion persisted. There was a small intracellular accumulation of triacylglycerol but not of apoprotein B. Addition of forskolin and IBMX together led to a further increase in intracellular cAMP and a further suppression of VLDL output. Similar effects on the secretion of VLDL were also observed after addition of Bt2cAMP. Exposure of cell cultures to glucagon (10(-7) mol l-1) for only 10 min raised cellular cAMP levels to > 200 pmol mg-1 protein, and suppressed VLDL secretion during the next 24 h to < 40% of control. All of the substances tested inhibited de novo synthesis of fatty acids but had little or no effect on cholesterol synthesis and did not inhibit oleate esterification to triacylglycerol. The cAMP-dependent protein kinase antagonist Rp-cAMPS prevented suppression of VLDL triacylglycerol secretion induced by glucagon (10(-7) mol l-1) and abolished glucagon-induced ketogenesis. Rp-cAMPS also inhibited Bt2cAMP (7.5 x 10(-6) mol l-1)-induced suppression of VLDL secretion and enhancement of ketogenesis. It is concluded that rat hepatic VLDL metabolism can be regulated by cAMP and cAMP-dependent protein kinases, and that the initial transient rise in cellular cAMP levels induced by glucagon is sufficient to maintain a long-term inhibitory effect on assembly and secretion of VLDL.
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PMID:Regulation of VLDL secretion in primary culture of rat hepatocytes: involvement of cAMP and cAMP-dependent protein kinases. 820 83

Hepatocytes derived from diabetic rats were cultured in serum-free Waymouth's medium containing various supplements, after an initial 4 h period during which the cells were allowed to attach to the culture dish in the presence of foetal-bovine serum (10%). After removal of serum, these cells secreted much less very-low-density lipoprotein (VLDL) apoprotein B (apoB) and triacylglycerol than those derived from normal rats when cultured for 24 h in the basal medium. Inclusion of oleate (0.75 mM) in the medium initially increased the output of apoB and triacylglycerol, but the rates remained lower than those observed in normal hepatocytes and declined to zero after 72 h. This time-dependent decline in VLDL output was prevented by addition of dexamethasone to the oleate-containing medium. Levels of apoB and triacylglycerol output characteristic of normal hepatocytes could only be completely restored, however, by further addition of a mixture of lipogenic substrates (lactate plus pyruvate) to the medium. Restoration of normal levels of VLDL secretion in diabetic hepatocytes in vitro by this means was accompanied by a normal inhibitory response of apoB and triacylglycerol output to short-term (24 h) treatment with insulin or glucagon. Exposure of the cells to insulin for 72 h enhanced the secretion of VLDL, whereas treatment with glucagon for the same period potentiated the original inhibitory effect. The defective secretion of VLDL apoB observed when diabetic hepatocytes were cultured in the basal medium for 24 h could also be rectified by inclusion of a mixture of oleate (0.75 mM), lactate (10 mM), pyruvate (1 mM), dexamethasone (1 microM) and insulin (78 nM) in the medium during the 4 h attachment period in the presence of serum. Under these conditions, the increase in the secretory response of triacylglycerol was not so pronounced.
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PMID:Restoration in vitro of normal rates of very-low-density lipoprotein triacylglycerol and apoprotein B secretion in hepatocyte cultures from diabetic rats. 836 68

We studied the influence of glucagon on hepatic LDL receptors and plasma lipoproteins in rats. A dose-dependent (maximum, threefold) increase in LDL-receptor binding was evident already at a dose of 2 x 4 micrograms, and detectable 3 h after injection; concomitantly, cholesterol and apolipoprotein (apo) B and apoE within LDL and large HDL decreased in plasma. LDL receptor mRNA levels were however unaltered or reduced. Hepatic microsomal cholesterol was increased and the enzymatic activities of 3-hydroxy-3-methylglutaryl coenzyme A reductase and cholesterol 7 alpha-hydroxylase in hepatic microsomes were reduced. Insulin alone increased receptor binding and receptor mRNA levels twofold, but plasma cholesterol was unchanged and plasma apoE and apoB increased. Administration of insulin to glucagon-treated animals reduced the LDL-receptor binding to control levels and apoB appeared in LDL particles. Estrogen treatment increased LDL-receptor binding and mRNA levels five- and eightfold, respectively. Combined treatment with glucagon and estrogen reduced the stimulation of LDL-receptor mRNA levels by 80% although LDL-receptor binding was unchanged. Immunoblot analysis showed that glucagon increased the number of hepatic LDL receptors. We conclude that glucagon induces the number of hepatic LDL receptors by a mechanism not related to increased mRNA levels, suggesting the presence of a posttranscriptional regulatory mechanism present in the liver in vivo.
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PMID:Stimulation of rat hepatic low density lipoprotein receptors by glucagon. Evidence of a novel regulatory mechanism in vivo. 851 87


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