scholarly journals Effects of ethynyloestradiol on the metabolism of [1-14C]-oleate by perfused livers and hepatocytes from female rats

1979 ◽  
Vol 180 (2) ◽  
pp. 265-271 ◽  
Author(s):  
Ira Weinstein ◽  
Carlos Soler-Argilaga ◽  
Harold V. Werner ◽  
Murray Heimberg
Keyword(s):  
Fatty Acid ◽  
Ketone Bodies ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Experimental Period ◽  
Female Rats ◽  
Normal Female ◽  
Unesterified Fatty Acid ◽  
Very Low Density Lipoprotein ◽  
Low Density

Normal female rats were given 15μg of ethynyloestradiol/kg body wt. for 14 days and were killed on day 15 after starvation for 12–14h. The livers were isolated and were perfused with a medium containing washed bovine erythrocytes, bovine serum albumin, glucose and [1-14C]oleic acid; 414μmol of oleate were infused/h during a 3h experimental period. The output of bile and the flow of perfusate/g of liver were decreased in livers from animals pretreated with ethynyloestradiol, whereas the liver weight was increased slightly. The rates of uptake and of utilization of [1-14C]oleate were measured when the concentration of unesterified fatty acid in the perfusate plasma was constant. The uptake of unesterified fatty acid was unaffected by pretreatment of the animal with oestrogen; however, the rate of incorporation of [1-14C]oleate into hepatic and perfusate triacylglycerol was stimulated, whereas the rate of conversion into ketone bodies was impaired by treatment of the rat with ethynyloestradiol. Pretreatment of the rat with ethynyloestradiol increased the output of very-low-density lipoprotein triacylglycerol, cholesterol, phospholipid and protein. The production of 14CO2 and the incorporation of radioactivity into phospholipid, cholesteryl ester and diacylglycerol was unaffected by treatment with the steroid. The net output of glucose by livers from oestrogen-treated rats was impaired despite the apparent increased quantities of glycogen in the liver. The overall effect of pretreatment with oestrogen on hepatic metabolism of fatty acids is the channeling of [1-14C]oleate into synthesis and increased output of triacylglycerol as a moiety of the very-low-density lipoprotein, whereas ketogenesis is decreased. The effect of ethynyloestradiol on the liver is apparently independent of the nutritional state of the animal from which the liver was obtained. It is pertinent that hepatocytes prepared from livers of fed rats that had been treated with ethynyloestradiol produced fewer ketone bodies and secreted more triacylglycerol than did hepatocytes prepared from control animals. In these respects, the effects of the steroid were similar in livers from fed or starved (12–14h) rats. Oestrogens may possibly inhibit hepatic oxidation of fatty acid, making more fatty acid available for the synthesis of triacylglycerol, or may stimulate the biosynthesis of triacylglycerol, or may be active on both metabolic pathways.

scholarly journals The preferential uptake of very-low-density lipoprotein cholesteryl ester by rat liver in vivo

1990 ◽  
Vol 272 (3) ◽  
pp. 735-741 ◽  
Author(s):  
J C Holder ◽  
V A Zammit ◽  
D S Robinson
Keyword(s):  
Fatty Acid ◽  
Cholesteryl Ester ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Apoprotein B ◽  
Preferential Uptake ◽  
Triacylglycerol Fraction

The removal from the blood and the uptake by the liver of injected very-low-density lipoprotein (VLDL) preparations that had been radiolabelled in their apoprotein and cholesteryl ester moieties was studied in lactating rats. Radiolabelled cholesteryl ester was removed from the blood and taken up by the liver more rapidly than sucrose-radiolabelled apoprotein. Near-maximum cholesteryl ester uptake by the liver occurred within 5 min of the injection of the VLDL. At this time, apoprotein B uptake by the liver was only about 25% of the maximum. Maximum uptake of the injected VLDL apoprotein B label was not achieved until at least 15 min after injection, by which time the total uptakes of cholesteryl ester and apoprotein B label were very similar. The results suggest that preferential uptake of the lipoprotein cholesteryl ester by the liver occurred before endocytosis of the entire lipoprotein complex. The fate of the injected VLDL cholesteryl ester after its uptake by the liver was also monitored. Radiolabel associated with the hepatic cholesteryl ester fraction fell steadily from its early maximum level, the rate of fall being faster and more extensive when the fatty acid, rather than the cholesterol, moiety of the ester was labelled. By 30 min after the injection of VLDL containing [3H]cholesteryl ester, over one-third of the injected label was already present as [3H]cholesterol in the liver. When VLDL containing cholesteryl [14C]oleate was injected, a substantial proportion (about 25%) of the injected radiolabelled fatty acid appeared in the hepatic triacylglycerol fraction within 60 min: very little was present in the plasma triacylglycerol fraction at this time.

scholarly journals Leptin Augments the Acute Suppressive Effects of Insulin on Hepatic Very Low-Density Lipoprotein Production in Rats

Endocrinology ◽  
2009 ◽  
Vol 150 (5) ◽  
pp. 2169-2174 ◽  
Author(s):  
Wan Huang ◽  
Anantha Metlakunta ◽  
Nikolas Dedousis ◽  
Heidi K. Ortmeyer ◽  
Maja Stefanovic-Racic ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Lipid Metabolism ◽  
Fatty Acid Oxidation ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Saline Control ◽  
Acid Oxidation ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Vldl Metabolism

It is well established that leptin increases the sensitivity of carbohydrate metabolism to the effects of insulin. Leptin and insulin also have potent effects on lipid metabolism. However, the effects of leptin on the regulation of liver lipid metabolism by insulin have not been investigated. The current study addressed the effects of leptin on insulin-regulated hepatic very low-density lipoprotein (VLDL) metabolism in vivo in rats. A 90-min hyperinsulinemic/euglycemic clamp (4 mU/kg · min−1) reduced plasma VLDL triglyceride (TG) by about 50% (P < 0.001 vs. saline control). Importantly, a leptin infusion (0.2 μg/kg · min−1) in combination with insulin reduced plasma VLDL-TG by about 80% (P < 0.001 vs. insulin alone). These effects did not require altered skeletal muscle lipoprotein lipase activity but did include differential effects of insulin and leptin on liver apolipoprotein (apo) B and TG metabolism. Thus, insulin decreased liver and plasma apoB100/B48 levels (∼50%, P < 0.01), increased liver TGs (∼20%, P < 0.05), and had no effect on fatty acid oxidation. Conversely, leptin decreased liver TGs (∼50%, P < 0.01) and increased fatty acid oxidation (∼50%, P < 0.01) but had no effects on liver or plasma apoB levels. Importantly, the TG-depleting and prooxidative effects of leptin were maintained in the presence of insulin. We conclude that leptin additively increases the suppressive effects of insulin on hepatic and systemic VLDL metabolism by stimulating depletion of liver TGs and increasing oxidative metabolism. The net effect of the combined actions of insulin and leptin is to decrease the production and TG content of VLDL particles.

scholarly journals Acute effects of ethanol on the perfused rat liver. Studies on lipid and carbohydrate metabolism, substrate cycling and perfusate amino acids

1979 ◽  
Vol 184 (1) ◽  
pp. 97-106 ◽  
Author(s):  
David L. Topping ◽  
Dallas G. Clark ◽  
Gerald B. Storer ◽  
Rodney P. Trimble ◽  
Richard J. Illman
Keyword(s):  
Amino Acids ◽  
Carbohydrate Metabolism ◽  
Ketone Bodies ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Fold Increase ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Ethanol Infusion ◽  
Glucose Output

1. Livers from fed rats were perfused in situ with whole rat blood containing glucose labelled uniformly with 14C and specifically with 3H at positions 2, 3 or 6. 2. When ethanol was infused at a concentration of 24μmol/ml of blood the rate of utilization was 2.8μmol/min per g of liver. 3. Ethanol infusion raised perfusate glucose concentrations and caused a 2.5-fold increase in hepatic glucose output. 4. Final blood lactate concentrations were decreased in ethanol-infused livers, but the mean uptake of lactate from erythrocyte glycolysis was unaffected. 5. Production of ketone bodies (3‐hydroxybutyrate+3‐oxobutyrate) and the ratio [3‐hydroxybutyrate]/[3‐oxobutyrate] were raised by ethanol. 6. Formation of 3H2O from specifically 3H-labelled glucoses increased in the order [6-3H]<[3-3H]<[2-3H]. Production of 3H2O from [2-3H]glucose was significantly greater than that from [3-3H]glucose in both control and ethanol-infused livers. Ethanol significantly decreased 3H2O formation from all [3H]glucoses. 7. Liver glycogen content was unaffected by ethanol infusion. 8. Production of very-low-density lipoprotein triacylglycerols was inhibited by ethanol and there was a small increase in liver triacylglycerols. Very-low-density-lipoprotein secretion was negatively correlated with the ratio [3‐hydroxybutyrate]/[3‐oxobutyrate]. Perfusate fatty acid concentrations and molar composition were unaffected by perfusion with ethanol. 9. Ethanol decreased the incorporation of [U-14C]glucose into fatty acids and cholesterol. 10. The concentration of total plasma amino acids was unchanged by ethanol, but the concentrations of alanine and glycine were decreased and ([glutamate]+[glutamine]) was raised. 11. It is proposed that the observed effects of ethanol on carbohydrate metabolism are due to an increased conversion of lactate into glucose, possibly by inhibition of pyruvate dehydrogenase. The increase in gluconeogenesis is accompanied by diminished substrate cycling at glucose–glucose 6-phosphate and at fructose 6-phosphate–fructose 1,6-bisphosphate.

scholarly journals Regulation of hepatic very-low-density lipoprotein secretion in rats fed on a diet high in unsaturated fat

1987 ◽  
Vol 243 (2) ◽  
pp. 487-492 ◽  
Author(s):  
G F Gibbons ◽  
C R Pullinger
Keyword(s):  
Fatty Acid ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Chow Diet ◽  
Dark Phase ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Unsaturated Fat ◽  
Wide Range ◽  
Cholesterol Secretion

Rats were fed ad libitum on either a standard, high-carbohydrate, chow diet or a similar diet supplemented with 15% unsaturated fat (corn oil). Hepatocytes were prepared either during the dark phase (D6-hepatocytes) or during the light phase (L2-hepatocytes) of the diurnal cycle. In hepatocytes from rats fed on the unsaturated-fat-containing diet, secretion of very-low-density lipoprotein (VLDL) triacylglycerol was inhibited to a greater extent in the D6- than in the L2-hepatocytes. Plasma non-esterified fatty acid concentrations were elevated to the same extent at both D6 and L2 in the unsaturated-fat-fed animals. The secretion of VLDL esterified and non-esterified cholesterol was relatively insensitive to changes in the unsaturated-fat content of the diet. This resulted in proportionate increases in the content of these lipid constituents compared with that of triacylglycerol in the nascent VLDL. There was also an increase in the ratio of esterified to non-esterified cholesterol in the nascent VLDL produced by hepatocytes of the unsaturated-fat-fed animals. In the D6-hepatocytes from the unsaturated-fat-fed animals, the decrease in the secretion of VLDL triacylglycerol could not be reversed by addition of exogenous oleate (0.7 mM) to the incubation medium. In contrast, addition of a mixture of lactate (10 mM) and pyruvate (1 mM) stimulated both fatty acid synthesis de novo and the rate of VLDL triacylglycerol secretion. Secretion of esterified and non-esterified cholesterol also increased under these conditions. Insulin suppressed the secretion of VLDL triacylglycerol and cholesteryl ester under a wide range of conditions in all types of hepatocyte preparations. Non-esterified cholesterol secretion was unaffected. In hepatocytes prepared from the fat-fed animals, these effects of insulin were more pronounced at D6 than at L2. Glucagon also inhibited VLDL lipid secretion in all types of hepatocyte preparations. The decrease in cholesterol secretion was due equally to decreases in the rates of secretion of both esterified and non-esterified cholesterol.

scholarly journals Extracellular fatty acids are not utilized directly for the synthesis of very-low-density lipoprotein in primary cultures of rat hepatocytes

1992 ◽  
Vol 287 (3) ◽  
pp. 749-753 ◽  
Author(s):  
G F Gibbons ◽  
S M Bartlett ◽  
C E Sparks ◽  
J D Sparks
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Acid Concentration ◽  
Low Density Lipoprotein ◽  
Primary Cultures ◽  
Density Lipoprotein ◽  
Fatty Acid Concentration ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Extracellular Fatty Acid

In hepatocytes cultured in the presence of oleate (initial concn. 0.75 mM), the secretion of very-low-density lipoprotein (VLDL) triacylglycerol and, to a lesser extent, apoprotein B (apoB) increased with time, whereas there was a large decline in the extracellular concentration of fatty acid. There was thus no synchronous relationship between the extracellular fatty acid concentration and the secretion of VLDL. Rather, the appearance of VLDL in the medium was dependent on the intracellular triacylglycerol concentration. At a given concentration of extracellular fatty acid, cells depleted of triacylglycerol secreted less VLDL triacylglycerol and apoB than did control cells. A similar pattern was observed for triacylglycerol newly synthesized from extracellular [3H]oleate. By contrast, the synthesis and output of ketone bodies were directly dependent on the fatty acid concentration of the medium. These results suggest that, at least for oleic acid, extracellular fatty acids are not utilized directly for VLDL assembly, but first enter a temporary intracellular storage pool of triacylglycerol, which is the immediate precursor of secreted triacylglycerol. The size of this pool then determines the rate of secretion of VLDL triacylglycerol apoB. Ketogenesis, on the other hand, relies mainly on the direct utilization of extracellular fatty acids.

scholarly journals Contribution of very low-density lipoprotein triglyceride fatty acids to postabsorptive free fatty acid flux in obese humans

Metabolism ◽  
2014 ◽  
Vol 63 (1) ◽  
pp. 137-140 ◽  
Author(s):  
Nikki C. Bush ◽  
Jessica M. Triay ◽  
Nicola W. Gathaiya ◽  
Kazanna C. Hames ◽  
Michael D. Jensen
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Free Fatty Acid ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Very Low Density Lipoprotein ◽  
Low Density
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