scholarly journals Selective labelling of hepatic fatty acids in vivo. Studies on the synthesis and secretion of glycerolipids in the rat

1992 ◽  
Vol 283 (1) ◽  
pp. 145-149 ◽  
Author(s):  
A M B Moir ◽  
V A Zammit
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Cholesteryl Ester ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Streptozotocin Diabetes ◽  
In Vivo Studies ◽  
Selective Labelling ◽  
Glycerolipid Synthesis

1. We describe a method for the selective labelling of hepatic fatty acids in the rat in vivo. It relies on (i) the rapid and preferential uptake of cholesteryl ester from chylomicron and/or very-low-density-lipoprotein remnants by the liver [Holder, Zammit & Robinson (1990) Biochem. J. 272, 735-741] (without prior exchange of the ester to other lipoproteins in the plasma), and (ii) the very short half-life of the cholesteryl ester in the liver. The 14C-labelled fatty acid moiety generated by cholesteryl ester hydrolysis was shown to be utilized by the liver for glycerolipid synthesis in a very similar pattern to that demonstrated for exogenous fatty acids by isolated cultured hepatocytes in previous studies. 2. Starvation (24 h) was shown to decrease the proportion of fatty acid utilized for glycerolipid synthesis, but to result in a proportionately smaller effect on incorporation into phospholipid. This was accompanied by a decrease in the fraction of synthesized triacylglycerol that was secreted by the liver. 3. Streptozotocin-diabetes did not affect the phospholipid/triacylglycerol ratio, but resulted in a small, but significant, decline in the fraction of triacylglycerol secreted by the liver. 4. In both starved and diabetic animals fatty acid esterification to the glycerol moiety constituted a smaller proportion of the total disposal of label. 5. These findings appear to validate the present method for the selective labelling of liver fatty acids in vivo in a non-invasive manner. Other possible uses for the method are suggested.

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 Monitoring of changes in hepatic fatty acid and glycerolipid metabolism during the starved-to-fed transition in vivo. Studies on awake, unrestrained rats

1993 ◽  
Vol 289 (1) ◽  
pp. 49-55 ◽  
Author(s):  
A M B Moir ◽  
V A Zammit
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Liver Mitochondria ◽  
In Vivo Studies ◽  
Maximal Effect ◽  
Jugular Veins ◽  
Selective Labelling ◽  
Malonyl Coa ◽  
Cpt I

1. The technique of selective labelling of hepatic fatty acids in vivo [Moir and Zammit (1992) Biochem. J. 283, 145-149] has been used to monitor non-invasively the metabolism of fatty acids in the livers of awake unrestrained rats during the starved-to-refed transition. Values for the incorporation of labelled fatty acid into liver and plasma glycerolipids and into exhaled carbon dioxide after injection of labelled lipoprotein and Triton WR 1339 into rats with chronically cannulated jugular veins were obtained for successive 1 h periods from the start of refeeding of 24 h-starved rats. 2. Starvation for 24 h resulted in marked and reciprocal changes in the incorporation of label into glycerolipids and exhaled 14CO2, such that a 4-fold higher value was obtained for the oxidation/esterification ratio in livers of starved rats compared with fed animals. 3. Refeeding of starved rats did not return this ratio to the value observed for fed animals for at least 7 h; during the first 3 h of refeeding the ratio was at least as high as that for starved rats. Between 4 h and 6 h of refeeding the ratio was still approx. 70% of that in starved animals, and 2.5-fold higher than in fed rats. 4. These data support the hypothesis that the capacity of the liver to oxidize fatty acids is maintained at a high level during the initial stages of refeeding [Grantham and Zammit (1986) Biochem. J. 239, 485-488] and that control of the flux of hepatic fatty acids into the oxidative pathway is largely lost from the reaction catalysed by mitochondrial overt carnitine palmitoyltransferase (CPT I) during this phase of recovery from the starved state. 5. Refeeding also resulted in a rapid (< 1 h) increase in hepatic malonyl-CoA concentrations to values intermediate between those in livers of fed and starved animals. The sensitivity of CPT I to malonyl-CoA inhibition in isolated liver mitochondria was only partially reversed even after 5 h of refeeding. 6. Refeeding resulted in an acute 35% inhibition of the fraction of synthesized triacylglycerol that was secreted into the plasma; the maximal effect occurred 2-3 h after the start of refeeding. The inhibition of the fractional secretion rate was fully reversed after 5 h of refeeding. 7. The amount of 14C label that was incorporated into phospholipids as a fraction of total glycerolipid synthesis was doubled within 2 h of the start of refeeding.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Quantification in vivo of the effects of different types of dietary fat on the loci of control involved in hepatic triacylglycerol secretion

1995 ◽  
Vol 308 (2) ◽  
pp. 537-542 ◽  
Author(s):  
A M B Moir ◽  
B S Park ◽  
V A Zammit
Keyword(s):  
Fatty Acids ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Branch Points ◽  
Pharmacological Agents ◽  
Acid Diet ◽  
Fractional Rate ◽  
Selective Labelling ◽  
Hepatic Triacylglycerol

Polyunsaturated fatty acids (PUFA) have been suggested to exert their hypotriglyceridaemic effect through several possible mechanisms that would be expected to decrease the rate of hepatic very-low-density-lipoprotein-triacylglycerol secretion. We have quantified the role played in vivo by changes in the pattern of partitioning of (i) acyl-CoA between oxidation and esterification, (ii) diacylglycerol between synthesis of triacylglycerol and of the major phospholipids, and (iii) triacylglycerol between secretion and storage within the liver, in response to two dietary levels of n-6 and n-3 PUFA. In order to achieve this we used the technique of selective labelling of hepatic fatty acids in vivo. Compared with a predominantly saturated fatty acid diet, both n-6 and n-3 PUFA intake resulted in a decrease in the proportion of acyl moieties that were secreted by the liver, through an increased diversion of acyl-CoA towards oxidation and a lower fractional rate of secretion of newly synthesized triacylglycerol. In addition, a diet rich in n-3 fatty acids resulted not only in a greater magnitude of these effects but also in a doubling of the partitioning of diacylglycerol towards phospholipid labelling. It is shown that the overall 50% reduction achieved by fish oil feeding in the proportion of acyl groups that were secreted by the liver was distributed over all three branch points. The contribution of each of these adaptations was quantified. The application of such an approach, i.e. the localization and in vivo quantification of the importance of loci of control, in studies on dietary and pharmacological agents that affect lipaemia, is discussed.

scholarly journals Secretion and storage of newly synthesized hepatic triacylglycerol fatty acids in vivo in different nutritional states and in diabetes

1988 ◽  
Vol 255 (3) ◽  
pp. 929-935 ◽  
Author(s):  
J M Duerden ◽  
G F Gibbons
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Diurnal Variation ◽  
Low Density Lipoprotein ◽  
Specific Radioactivity ◽  
Lipid Synthesis ◽  
Density Lipoprotein ◽  
Dark Phase ◽  
Light Phase

Hepatic lipid synthesis was measured in rats in vivo with 3H2O, and the appearance of label in triacylglycerol and its constituent fatty acid and glycerol moieties was determined. In rats treated with Triton WR1339, the amount of newly synthesized fatty acid secreted as very-low-density lipoprotein (VLDL) triacylglycerol was greater during the dark phase of the diurnal cycle than during the light phase (11.3 versus 4.8 mumol of 3H2O/3 h per g of liver respectively). However, the total mass of VLDL triacylglycerol secreted remained constant, as did the amount of label in the secreted triacylglycerol glycerol. Newly synthesized fatty acids comprised only a small proportion of the total VLDL triacylglycerol fatty acids (TGFA) at both times (dark phase, 7.7%; light phase, 2.4%). Starvation for 24 h resulted in a small increase in the secretion of VLDL triacylglycerol. However, the contribution from newly synthesized fatty acids was decreased. Similar effects were observed in streptozotocin-diabetic animals. During the light and dark phases of the cycle, similar quantities of newly synthesized TGFA entered the hepatic cytosol, and these amounts were much smaller than those secreted as VLDL triacylglycerol. The mass of cytosolic triacylglycerol showed a diurnal variation, with a greater concentration during the light phase than in the dark. In diabetes, the mass of triacylglycerol was increased in the cytosol, as was the incorporation of labelled acylglycerol glycerol. Diabetes also abolished the diurnal variation in the quantity of cytosolic triacylglycerol. In each group of animals the specific radioactivity of the microsomal triacylglycerol was similar to that of the respective newly secreted plasma VLDL. The specific radioactivity of the cytosolic triacylglycerol was only 15.8% (dark phase) or 16.8% (light phase) that of the microsomal triacylglycerol. This increased to 35.5% in the starved animals and 40.2% in the diabetic animals.

scholarly journals Effects of an oral and intravenous fat load on adipose tissue and forearm lipid metabolism

1999 ◽  
Vol 276 (2) ◽  
pp. E241-E248 ◽  
Author(s):  
Kevin Evans ◽  
Mo L. Clark ◽  
Keith N. Frayn
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acids ◽  
Adipose Tissue ◽  
Fatty Acid ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Hormone Sensitive Lipase ◽  
Nonesterified Fatty Acid ◽  
Subcutaneous Adipose

We have studied the fate of lipoprotein lipase (LPL)-derived fatty acids by measuring arteriovenous differences across subcutaneous adipose tissue and skeletal muscle in vivo. Six subjects were fasted overnight and were then given 40 g of triacylglycerol either orally or as an intravenous infusion over 4 h. Intracellular lipolysis (hormone-sensitive lipase action; HSL) was suppressed after both oral and intravenous fat loads ( P < 0.001). Insulin, a major regulator of HSL activity, showed little change after either oral or intravenous fat load, suggesting that suppression of HSL action occurred independently of insulin. The rate of action of LPL (measured as triacylglycerol extraction) increased with both oral and intravenous fat loads in adipose tissue ( P = 0.002) and skeletal muscle ( P = 0.001). There was increased escape of LPL-derived fatty acids into the circulation from adipose tissue, shown by lack of reesterification of fatty acids. There was no release into the circulation of LPL-derived fatty acids from skeletal muscle. These results suggest that insulin is not essential for HSL suppression or increased triacylglycerol clearance but is important in reesterification of fatty acids in adipose tissue but not uptake by skeletal muscle, thus affecting fatty acid partitioning between adipose tissue and the circulation, postprandial nonesterified fatty acid concentrations, and hepatic very low density lipoprotein secretion.

scholarly journals Effect of atorvastatin and rosuvasta tin on the fatty acid spectrum of lymphocyte membranes in patients with unstable angina

2020 ◽  
pp. 92-95
Author(s):  
T.V. Bogdan ◽  
Keyword(s):  
Cardiovascular Disease ◽  
Fatty Acids ◽  
Fatty Acid ◽  
Unstable Angina ◽  
Unsaturated Fatty Acids ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Membrane Phospholipids ◽  
Stabilization Of Membranes ◽  
Dynamic Structures

Numerous studies have demonstrated the superiority of rosuvastatin over other statins in the treatment of cardiovascular disease. It has been proven that rosuvastatin is more effectively lowers low-density lipoprotein cholesterol in patients with cardiovascular disease than other members of this drug group. Despite the known mechanisms of action of statins on blood lipids, their effective use in patients with cardiovascular disease, as well as side effects, the influence of these drugs on the fatty acid spectrum of lymphocyte (LC) membrane phospholipids in patients with ischemic heart disease remains unexplored. The results of the studies cited in the article indicate that, in patients with unstable angina who received the therapy that included rosuvastatin, unlike patients receiving the basic treatment with atorvastatin, the relative phosphate lipid contents of palmitic, stearic, and stearin arachidonic polyunsaturated fatty acids and the amount of unsaturated fatty acids are normalized, which testifies to the stabilization of membranes as dynamic structures.

Guggulsterone, a farnesoid X receptor antagonist lowers plasma trimethylamine-N-oxide levels: An evidence from in vitro and in vivo studies

2018 ◽  
Vol 38 (3) ◽  
pp. 356-370 ◽  
Author(s):  
A Gautam ◽  
YN Paudel ◽  
SAZ Abidin ◽  
U Bhandari
Keyword(s):  
Hepatic Injury ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Farnesoid X Receptor ◽  
Lipoprotein Cholesterol ◽  
In Vivo Studies ◽  
Low Density Lipoprotein Cholesterol ◽  
Pro Inflammatory Cytokines

The current study investigated the role of guggulsterone (GS), a farnesoid X receptor antagonist, in the choline metabolism and its trimethylamine (TMA)/flavin monooxygenases/trimethylamine- N-oxide (TMAO) inhibiting potential in a series of in vitro and in vivo studies as determined by high-performance liquid chromatography (HPLC), mass spectroscopy (MS), and liquid chromatography (LC)-MS techniques. Atherosclerosis (AS) was successfully induced in a group of experimental animals fed with 2% choline diet for 6 weeks. Serum lipid profiles such as total cholesterol, triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and very low-density lipoprotein cholesterol were measured. Pro-inflammatory cytokines levels, markers for a hepatic injury, and oxidative stress markers were assessed. Interestingly, GS reduced the level of TMA/TMAO in both in vitro and in vivo studies as demonstrated by the peaks obtained from HPLC, MS, and LC–MS. Furthermore, GS exhibited cardioprotective and antihyperlipidemic effects as evidenced by the attenuation of levels of several serum lipid profiles and different atherogenic risk predictor indexes. GS also prevented hepatic injury by successfully restoring the levels of hepatic injury biomarkers to normal. Similarly, GS inhibited the production of pro-inflammatory cytokines levels, as well as GS, enhanced antioxidant capacity, and reduced lipid peroxidation. Histopathological study of aortic sections demonstrated that GS maintained the normal architecture in AS-induced rats. On the basis of results obtained from current investigation, we suggest that GS might have a great therapeutic potential for the treatment of AS.

scholarly journals Heterogeneity of very-low-density lipoprotein remnants bound and taken up by liver of starved rat in vivo

1983 ◽  
Vol 212 (1) ◽  
pp. 173-182
Author(s):  
M M Ittmann ◽  
C Cooper
Keyword(s):  
Cholesteryl Ester ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Water Soluble ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Density Range ◽  
Mean Diameter ◽  
Vldl Remnant

Very-low-density lipoprotein (VLDL), labelled in vivo with [9,10-3H]oleate, was taken up rapidly by liver after injection in vivo. Initially, radioactive lipoprotein remnants in the VLDL density range were present in liver as a bound extracellular pool that could be released by perfusion with polyphosphate or heparin. The bound remnant showed a decrease in mean diameter and an increased proportion of cholesteryl ester as a function of time after injection. When VLDL of different mean diameters was injected, it was found that: (1) total uptake by liver was independent of diameter; (2) small VLDL was not taken up more rapidly than large VLDL; and (3) Large VLDL lost no more triacylglycerol before binding than did small VLDL and larger species of mean diameter greater than 40 nm were bound. It is concluded that there is no unique VLDL remnant taken up by liver in vivo. When livers were perfused after binding radioactive VLDL in vivo, the lipoprotein was metabolized, with the production of water-soluble products, and this metabolism was inhibited by chloroquine.

Nascent and remnant lipoprotein turnover in rats: experimental design and simulation

1983 ◽  
Vol 245 (3) ◽  
pp. R386-R395
Author(s):  
N. Baker ◽  
H. J. Rostami ◽  
J. Elovson
Keyword(s):  
Fatty Acids ◽  
Molecular Weight ◽  
Simulation Analysis ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Kinetic Behavior ◽  
Turnover Rates ◽  
Apoprotein B ◽  
Hydrolysis Of

We have attempted to predict the kinetic behavior of the complex very low-density lipoprotein (VLDL; d less than 1.006) fraction in blood plasma of rats in the steady state. Specifically we proposed a simple model with two different kinds of nascent VLDL particles derived from the liver, one containing apoprotein B (PI/II) [apoB(PI/II)], the high-molecular-weight apoB, and the other, apoprotein B (PIII) [apoB(PIII)], the low-molecular-weight apoB. Two other particles, the corresponding remnants derived from the nascent VLDL particles were also included. Then a number of feasible in vivo tracer experiments were considered in which VLDL labeled in the apoB and/or triglyceride (TG) moieties would be injected into recipient rats and the kinetic behavior of the various compartments predicted by simulation analysis. In addition the kinetic behavior of products such as free fatty acids formed during hydrolysis of labeled TG fatty acids and liver TG derived from labeled circulating remnants was considered. Both the relative sizes of nascent and remnant particles and the extent of average hydrolysis of nascent VLDL-TG (before formation of a remnant particle) were considered in our analysis. On the basis of these predictions we have suggested a number of experimental approaches that should be helpful in defining the relative pool sizes and the turnover rates of each kind of particle in vivo.

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