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1.
Ana Maria P. Lottenberg Helena C. F. Oliveira Edna R. Nakandakare Eder C. R. Quintão 《Lipids》1992,27(5):326-330
The mechanism by which ω3 fatty acids lower plasma triacylglycerol levels was investigated. Rats were fed fish oil, olive
oil (10% fat by weight) or a nonpurified diet 4% fat by weight) for 15 days. Lipoprotein lipase was inhibited by intra-arterial
administration of Triton WR 1339 to estimate hepatic triacylglycerol output. Rats fed the olive oil diet showed a higher rate
of triacylglycerol formation than rats fed the ω3 fatty acid diet or the low-fat diet. All three groups showed identical rates
of removal from plasma of intraarterially administered artificial chylomicrons that had simultaneously been labeled with cholesteryl
[1-14C]oleate and [9,10(n)-3H]triolein. Liver radioactivity and total fat content were lowest in rats fed the fish oil diet, indicating that ω3 fatty
acids were preferentially metabolized in liver. Chylomicrons obtained from donor rats fed either fish oil containg [14C]cholesterol or olive oil containing [3H]cholesterol were removed at similar rates when infused together intraarterially into recipient animals. A slower formation
of plasma very low density lipoprotein triacylglycerols in rats fed fish oil is probably due to a faster rate of oxidation
of the fatty acid chains in the liver resulting in decreased plasma triacylglycerol concentrations. 相似文献
2.
Cholesterol fed guinea pigs develop a hemolytic anemia accompanied by high cholesterol concentrations in the liver, plasma,
and red cells. We have studied the bile acid metabolism of guinea pigs fed a diet with or without cholesterol in a search
for the factor(s) which prevent adequate control of their body cholesterol pool and, therefore, its pathological consequences.
The results show that in the cholesterol fed guinea pig the synthesis (and excretion) of bile acids was at least three times
greater than in controls. This is the result of a doubling of the fractional turnover rate and a smaller increase in the pool
size. The major increase of the bile acid pool was in the liver. The main bile acid in gall bladder bile and small intestines
was chenodeoxycholic acid, with smaller amounts of 7-ketolithocholic and ursodeoxycholic acids. In the caecum, large intestines,
and feces, the major bile acid was lithocholic acid. 相似文献
3.
The hydrolysis by lipoprotein lipase of a very low density lipoprotein/chylomicron fraction, obtained from the intestinal
lymph of sheep, has been studied in vitro. Rapid hydrolysis of triacylglycerols, with an accumulation of free fatty acids,
was observed. After an initial lag period, phosphatidylcholine also was hydrolyzed. No specificity for particular fatty acids
in the triacylglycerols (or phosphatidylcholines) was observed. 相似文献
4.
Rabbits fed semipurified diets containing casein have elevated plasma cholesterol levels compared to those fed soy protein.
As part of continuing studies on the mechanism of casein-induced hypercholesterolemia, two groups of six rabbits were fed
these diets for 14 to 16 weeks. Animals fed the casein diet were found to have significantly higher plasma concentrations
of protein, cholesterol, triacylglycerol, phospholipid and apolipoprotein B (apo B) associated with low density lipoprotein
(LDL) than those fed the soy protein diet. Kinetic studies showed that the fractional catabolic rate of LDL-apo B was significantly
lower in animals fed casein than in those fed soy protein regardless of whether the tracer LDL was obtained from donors fed
casein or soy protein. The production rate of LDL-apo B was higher in casein-fed animals but this was not statistically significant.
These results show that the efficiency of removal of LDL is significantly reduced in animals fed casein compared to those
fed soy protein, and that the source of LDL did not affect the efficiency of its subsequent removal. The acumulation of LDL
in casein-fed animals is consistent with down-regulation of the LDL receptor. 相似文献
5.
Evgeniy A. Podrez Vladimir A. Kosykh Yuri V. Lakeev Evgeniy I. Kosenkov Elvira T. Mambetisaeva Vadim S. Repin Vladimir N. Sminov Tatu A. Miettinen 《Lipids》1993,28(8):709-713
Two groups of rabbits, either hyperresponsive or hyporesponsive to dietary cholesterol, wereselected after ten weeks of cholesterol
feeding (0.2 g cholesterol/kg body weight per day). Bile acids and very low density lipoprotein (VLDL) production were determined
in primary hepatocyte cultures from control, hyper- and hyporesponsive rabbits. Free cholesterol and cholesteryl ester contents
in hepatocytes of the hyperresponsive rabbits was significantly increased. In contrast, lipid composition in hepatocytes of
the hyporesponders was similar to that of control cells. Cholic acid was the predominant bile acid in the culture medium of
hepatocytes together with small amounts of chenodeoxycholic and deoxycholic acids. The rate of cholic acid production by hepatocytes
in the hyporesponsive group was two times higher than that in the hyperresponsive group. Bile acid production by control hepatocytes
was slightly higher than in the hyperresponsive group. In contrast, secretion of VLDL cholesteryl ester was significantly
increased by hepatocytes of the hyperresponsive rabbits. Similar differences, in bile acid production were found between hypo-
and hyperresponsive rabbits selected after five days of cholesterol feeding and subsequent maintenance on a low cholesterol
diet for a period of one month. The results suggest that the increased rate of bile acid production could contribute to the
apparent resistance of hyporesponders to the atherogenic diet. 相似文献
6.
The concentration and composition of the very low density lipoprotein (VLDL) lipids and the behavior of the VLDL in a density
gradient in the zonal ultracentrifuge were examined in plasma obtained from normal fed male and female rats before and after
intravenous injection of Triton WR-1339. Concentration of lipids in plasma VLDL of female rats was about half that of male
animals. Following injection with Triton WR-1339, the concentration of VLDL lipids was higher in female rats (triacylglycerol)
or similar (phospholipid, cholesterol, and cholesteryl esters) in both sexes. Female rats secreted much more VLDL triacylglycerol
into the plasma compartment than did the male animals under the same experimental conditions. No differences were observed
in lipid composition of the VLDL or in the position of the VLDL in the zonal rotor after ultracentrifugation in a density
gradient of the lipoprotein from plasma of normal male and female rats before treatment with the detergent. However, after
treatment with Triton, a higher proportion of the VLDL particles isolated from plasma of female rats displayed a more rapid
rate-zonal flotation in the ultracentrifuge than did the VLDL produced by the male. The VLDL secreted by female rats contained
fewer moles of phospholipid and free sterol per mol triacylglycerol than did the VLDL secreted by male animals under identical
experimental conditions. The molar ratio of free cholesterol: cholesteryl ester in the VLDL secreted after treatment with
Triton increased in both male and female rats. Simultaneously, the content of arachidonic acid in phospholipid of VLDL increased
with a concomitant decrease in cholesteryl ester. These changes in fatty acid composition suggest that the inhibitory effect
of Triton on lecithin-cholesterol acyl transferase activity affects the exchange of lipids between VLDL and high density lipoprotein.
It can be concluded from the data reported here that sex influences the concentration of plasma lipids in vivo and the output
and properties of the VLDL.
Presented in part at the 59th annual meeting of the Federation of American Societies for Experimental Biology, Atlantic City,
NJ, April 1975 (1).
Recipient of a Career Development Award from the U.S. Public Health Service, No. 1-K4-HL-70329. 相似文献
7.
Zu Jun Zhang Henry G. Wilcox Lawrence Castellani Thomas V. Fungwe Marshall B. Elam Murray Heimberg 《Lipids》1993,28(5):419-425
The effects of increasing concentrations of eicosapentaenoic acid (20∶5n?3; EPA) and oleic acid (18∶1n?9; OA) on esterification to triacylglycerols (TG) and phospholipids (PL), and the relationship to formation and secretion of the very low density lipoproteins (VLDL) were compared in the isolated perfused rat liver. Mixtures of EPA and OA were also studied to determine whether substrate levels of one fatty acid might influence the metabolism of the other. The basal perfusion medium, which contained 30% (vol/vol) washed bovine erythrocytes, 6% (wt/vol) bovine serum albumin (BSA), and 100 mg glucose/dL in Krebs-Henseleit bicarbonate buffer (pH 7.4) was recycled through the liver for 2 h. EPA or OA, as a complex with 6% BSA, was infused at rates of 70, 105, 140 and 210 μmol/h. In other experiments, mixtures of EPA and oleic acid (70 μmol total), with molar percentages of 100, 75, 50, 25 and 0% of each fatty acid were infused per hour. BSA (6%) in the buffer was infused alone and served as the control. At an infusion rate of 70 μmol EPA per hour, hepatic VLDL lipid output was not different from that when fatty acid was not infused (approximately half that when 70 μmol OA/h was infused). However, when larger amounts of EPA and OA were infused individually, rates of VLDL secretion were stimulated to a similar extent with either fatty acid. The apparent inhibitory influence of EPA on TG synthesis and VLDL lipid output when 70 μmol EPA were infused per hour could also be overcome by the presence of as little as 25 mol% OA in a mixture. Furthermore, the presence of EPA in the infused fatty acid mixture stimulated the incorporation of OA into TG, enhancing VLDL secretion. When EPA or OA was infused at rates exceeding 70 μmol/h, a constant amount of endogenously-derived fatty acids was incorporated into VLDL-TG, similar in amount to that when exogenous fatty acid was not supplied. However, when EPA was infused at a rate of 70 μmol/h, incorporation of endogenous fatty acid was depressed. AT this low rate of EPA infusion, esterification of EPA and endogenous fatty acid was inhibited. Conceivably, this may reflect the existence of independently-regulated pools of fatty acid (exogenous and endogenous), in that only exogenously available fatty acid preferentially enrich the secreted TG. Enrichment of PL by the infused fatty acid at the higher rates of fatty acid infusion showed similar, but much less pronounced, differences between VLDL and liver, compared to that for TG, providing additional evidence for a distinct metabolic pool of PL used for VLDL fabrication. It now appears that when EPA is available to the liver in high enough concentrations, or when OA (or other fatty acids?) is present in substrate amounts along with EPA, competing reactions and/or specific inhibitory influences of EPA on enzymatic reactions are overcome, and EPA can be utilized in a manner similar to OA for esterification to TG with subsequent enhanced VLDL formation and secretion. 相似文献
8.
Angeliki I. Karakatsani Theodoros A. Liapikos Anastasios N. Troganis Demokritos C. Tsoukatos 《Lipids》1998,33(12):1159-1162
An increased amount of phospholipids remained attached on delipidated apolipoprotein B originated from oxidized low density lipoprotein (LDL). 31P nuclear magnetic resonance analysis of such apolipoprotein showed an organic phosphorus peak at −0.55 ppm, which suggests the formation of adducts (most probably Schiff bases) of oxidized phospholipids with apolipoprotein B. The above reaction occurs in parallel with the hydrolysis of oxidized phospholipids, catalyzed by the LDL-attached platelet-activating factor acetylhydrolase, and may contribute to the proatherogenic effect of oxidatively modified low density lipoprotein. 相似文献
9.
Marshall B. Elam Matthew A. von Wronski Lauren Cagen Fayanne Thorngate Poonam Kumar Murray Heimberg Henry G. Wilcox 《Lipids》1999,34(8):809-816
We previously demonstrated increased apolipoprotein B (apoB) mRNA editing, elevated levels of mRNA for the catalytic component
of the apoB mRNA editing complex, apobec-1, and increased secretion of the product of the edited mRNA, apoB48, in very low
density lipoproteins (VLDL) in primary cultures of Sprague-Dawley rat hepatocytes following insulin treatment. In order to
determine the effect of in vivo hyperinsulinemia on these processes, we determined apoB mRNA editing, apobec-1 expression, hepatic expression of mRNA for
apoB and other VLDL apoproteins, and the quantity and composition of plasma VLDL in the hyperinsulinemic fatty Zucker rat.
Total apoB mRNA content of the livers of the fatty rats and lean littermates did not differ, however, edited apoB message
coding for hepatic apo B48, and abundance of mRNA for the catalytic subunit of the apoB mRNA editing complex, apobec-1, was
increased by 1.7-and 3.3-fold, respectively, in fatty rats. ApoCIII mRNA abundance was increased in livers of fatty rats as
well, but the abundance of hepatic apoE mRNA in the fatty animal was not different from that of the lean rat. Hepatic apoAI
mRNA abundance was also increased in the fatty rats. Associated with increased apoB mRNA editing, was the 1.7-fold increase
in the fraction of apoB in plasma as apoB48 in fatty rats. VLDL-triglyceride and-apoB in plasma were 15-and 3-fold higher,
respectively, in fatty Zucker rats compared to lean littermates, indicating both enrichment of VLDL with triglycerides and
increased accumulation of VLDL particles. Increased hepatic expression of mRNA for apoCIII and apoAI was associated with increased
content of apoC (and relative depletion of apoE) in VLDL of fatty rats, and plasma apoAI was increased in fatty Zucker rats,
primarily in the HDL fraction. The current study provides further evidence that chronic exposure to high levels of insulin
influences both the quantity of and lipid/apoprotein composition of VLDL in plasma. The increased apoC and decreased apoE
(as well as increased triglyceride) content of VLDL in the fatty Zucker rat observed in the current study may affect VLDL
clearance and therefore may be a factor in the observed accumulation of VLDL in the plasma of the fatty hyperinsulinemic Zucker
rats. 相似文献
10.
Injections of [24-14C] chenodeoxycholate and3H-cholate were made by heart puncture into 300 g male rats that bore T-cannulas in their bile ducts. The animals had been
raised on diet A, containing glucose, cholesterol and cholate, or diet B, containing sucrose and cholesterol; each of the
diets contained 5% safflower oil or 5% beef tallow as variables. From analysis of bile samples collected from the T at intervals
over a 5 day period, it was observed that the safflower oil group fed diet B had a 17% shorter cholate half-life, a 29% larger
cholate pool size and 52% higher rate of cholate synthesis than those fed beef tallow in the same diet. The safflower group
fed diet A also had a larger cholate pool size, but synthesis and half-life were obscured by cholate feeding. Chenodeoxycholate
turnover data were not obtainable because the decay curves were bimodal for all treatments and hence did not conform to a
simple pool model. It is concluded that dietary safflower oil causes more rapid formation of cholate than does dietary beef
tallow in the cholesterol-fed rat.
Journal Paper No. 4952 AES, Purdue University. 相似文献
11.
The composition of circulating very low density lipoprotein (VLDL) was compared with the composition and secretion of nascent
VLDL from perfused livers of squirrel monkeys that were fed unsaturated or saturated fat diets to elicit different degrees
of plasma hypercholesterolemia. All squirrel monkeys studied had cholesteryl ester-rich plasma VLDL, although greater enrichment
occurred in hypercholesterolemic animals fed saturated fat. Livers from hypercholesterolemic animals were capable of secreting
VLDL particles enriched in cholesteryl ester, suggesting hepatic origin for a portion of this circulating lipid moiety. Total
VLDL lipid, but not protein output by perfused livers of hypercholesterolemic monkeys, was greater than that by livers from
hypocholesterolemic animals. These results indicate that saturated fat-induced hypercholesterolemia is associated with changes
in the composition of hepatic VLDL in the squirrel monkey. 相似文献
12.
Roberta Masella Claudio Giovannini Rosaria Varì Roberta Di Benedetto Ettore Coni Roberto Volpe Nadia Fraone Antonello Bucci 《Lipids》2001,36(11):1195-1202
The aim of this study was to assess the effects of the dietary intake of extra virgin olive oil on the oxidative susceptibility of low density lipoproteins (LDL) isolated from the plasma of hyperlipidemic patients. Ten patients with combined hyperlipidemia (mean plasma cholesterol 281 mg/dL, triglycerides 283 mg/dL) consumed a low-fat, low-cholesterol diet, with olive oil (20 g/d) as the only added fat, with no drug or vitamin supplementation for 6 wk. Then they were asked to replace the olive oil they usually consumed with extra virgin olive oil for 4 wk. LDL were isolated at the beginning, and after the 4 wk of dietary treatment. LDL susceptibility to CuSO4-mediated oxidation was evaluated by measuring the extent of lipid peroxidation. We also determined fatty acid composition and vitamin E in plasma and LDL and plasma phenolic content. Extra virgin olive oil intake did not affect fatty acid composition of LDL but significantly reduced the copper-induced formation of LDL hydroperoxides and lipoperoxidation end products as well as the depletion of LDL linoleic and arachidonic acid. A significant increase in the lag phase of conjugated diene formation was observed after dietary treatment. These differences are statistically correlated with the increase in plasma phenolic content observed at the end of the treatment with extra virgin olive oil; they are not correlated with LDL fatty acid composition or vitamin E content, which both remained unmodified after the added fat change. This report suggests that the daily intake of extra virgin olive oil in hyperlipidemic patients could reduce the susceptibility of LDL to oxidation, not only because of its high monounsaturated fatty acid content but probably also because of the antioxidative activity of its phenolic compounds. 相似文献
13.
The fate of an oral dose of [4-14C] cholesterol given to rats grown on diets with 20% safflower oil or 20% hydrogenated coconut oil was determined by analysis
of digestive tract, feces and tissues. The pattern of isotope distribution did not support the view that rats fed a saturated
fat absorb less cholesterol than those fed an unsaturated fat. Fasted animals growth on the diet with 5% of these two fats
and beef fallow showed no clear difference in the amount of digitonin-peecipitable sterol in their intestines. A shorter transit
time for intestinal contents was observed with the saturated fat groups. It is concluded that neither absorption of cholesterol
from the gut nor secretion of β-hydroxy sterol into the gut accounts for the hypocholesterolemic effect of polyunsaturated
fat.
Journal Paper No. 4951 AES, Purdue University. 相似文献
14.
Sandra H. Gianturco Christopher J. Packard James Shepherd Louis C. Smith Alberico L. Catapano Harley D. Sybers Antonio M. Gotto Jr. 《Lipids》1980,15(6):456-463
Our previous studies showed that hypertriglyceridemic very low density lipoproteins (HTG VLDL) are functionally abnormal.
HTG VLDL, but not normal VLDL, suppress HMG-CoA reductase in cultured normal human fibroblasts. To determine if the suppression
by HTG VLDL resulted from a subpopulation of smaller suppressive particles, more homogeneous subclasses of VLDL-VLDL1 (Sf 100–400), VLDL2 (Sf 60–100), and VLDL3 (Sf 20–60) were obtained from the d<1.006 (g°ml−1) fraction of normal and hypertriglyceridemic plasma by flotation through a discontinuous salt gradient and tested for suppression
in normal human fibroblasts. VLDL1 and VLDL2 from each of the 12 normolipemic subjects tested failed to suppress HMG-CoA reductase activity in normal fibroblasts. Eleven
out of 12 preparations of normal VLDL3 suppressed HMG-CoA reductase, but only one-third as effectively as LDL. By contrast, the VLDL1, VLDL2 and VLDL3 from 15 out of 17 hypertriglyceridemic patients (hyperlipoproteinemia Types IIb, III, IV and V) were highly effective in
suppression, with half-maximal suppression at 0.1–2.0 μg VLDL protein/ml. The VLDL abnormality is apparently associated with
hypertriglyceridemia and not hypercholesterolemia, since VLDL from a homozygous familial hypercholesterolemia patient with
a Type IIa pattern did not suppress whereas each of the VLDL subclasses from a Type IIb patient suppressed. Suppression by
HTG VLDL in normal cells is apparently a consequence of interaction of the protein portion of the VLDL with the specific LDL
cell surface receptor since HTG VLDL1 treated with 0.1 M 1,2-cyclohexanedione to block arginyl residues failed to suppress the enzyme. Moreover, hypertriglyceridemic
Sf 60–400 VLDL failed to suppress HMG-CoA reductase activity in LDL receptor-negative fibroblasts. There were no consistent
major compositional differences between comparable normal and hypertriglyceridemic VLDL subclasses which could account for
differences in suppression. All VLDL subclasses from Type III subjects were enriched in cholesteryl esters and depleted in
triglyceride, relative to the corresponding normal VLDL subclasses. However, Type IV and Type V VLDL subclasses were normal
in this repect. We conclude from these studies that small particle diameter is not required for suppression, since HTG VLDL1 and VLDL2 which contained few, if any, small particles were effective in suppression.
Presented as part of the symposium “Low Density and Very Low Density Lipoproteins” at the American Oil Chemists' Society meeting
on May 2, 1979, in San Francisco. 相似文献
15.
Philippe Boucher Michel de Lorgeril Patricia Salen Pierre Crozier Jacques Delaye Jean-Jacques Vallon André Geyssant Robert Dante 《Lipids》1998,33(12):1177-1186
We investigated the possibility that dietary cholesterol downregulates the expression of low density lipoprotein (LDL) receptor and 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase genes of circulating mononuclear cells in vivo in healthy humans. We also studied the variations of the LDL receptor-related protein (LRP) gene in the same conditions. Dieters (n=5) were submitted to a 4-d fat restriction (mean cholesterol intake: 6±4 mg/d), followed by a 7-d cholesterol (a mean of 791±150 mg/d) supplementation. Controls (n=3) did not change their diet. During fat restriction, serum total and LDL cholesterol decreased significantly (P<0.05), and LDL receptor and HMG-CoA reductase mRNA copy numbers in mononuclear cells increased by 57 and 147%, respectively (P<0.05). After reintroducing cholesterol, serum cholesterol was stable whereas LDL receptor and HMG-CoA reductase mRNA decreased by 46 and 72% (P<0.05) and LRP mRNA increased by 59% (P<0.005). The changes in LDL receptor and HMG-CoA reductase mRNA abundance were correlated (r=+0.79, P=0.02) during cholesterol reintroduction as were LDL receptor and LRP mRNA levels, but negatively (r=−0.70, P=0.05). Also, 70% of the variability in LRP mRNA (P<0.005) was explained by dietary cholesterol. Thus, the basic mechanisms regulating cellular cholesterol content, the coordinate feedback repression of genes governing the synthesis and uptake of cholesterol, are operating in vivo in humans. However, serum cholesterol did not increase in response to dietary cholesterol, suggesting that these mechanisms may not play as predominant a role as previously believed in the short-term control of serum cholesterol in vivo in humans. A new finding is that LRP gene is also sensitive to dietary cholesterol, suggesting that it may participate in the control of serum cholesterol. Further in vivo studies in humans are warranted to explore the molecular mechanisms of the physiological response to dietary cholesterol in humans. 相似文献
16.
This study was conducted to develop a quantitative FTIR spectroscopy method to measure LDL lipid oxidation products and determine
the effect of oxidation on LDL lipid and protein. In vitro LDL oxidation at 37°C for 1 h produced a range of conjugated diene (CD) (0.14–0.26 mM/mg protein) and carbonyl contents (0.9–3.8
μg/g protein) that were used to produce calibration sets. Spectra were collected from the calibration set and partial least
squares regression was used to develop calibration models from spectral regions 4000-650, 3750-3000, 1720-1500, and 1180-935
cm−1 to predict CD and carbonyl contents. The optimal models were selected based on their standard error of prediction (SEP),
and the selected models were performance-tested with an additional set of LDL spectra. The best models for CD prediction were
derived from spectral regions 4000-650 and 1180-935 cm−1 with the lowest SEP of 0.013 and 0.013 mM/mg protein, respectively. The peaks at 1745 (cholesterol and TAG ester C=O stretch),
1710 (carbonyl C-O stretch), and 1621 cm−1 (peptide C=O stretch) positively correlated with LDL oxidation. FTIR and chemometrics revealed protein conformation changes
during LDL oxidation and provided a simple technique that has potential for rapidly observing structural changes in human
LDL during oxidation and for measuring primary and secondary oxidation products. 相似文献
17.
The ability to evaluate various mechanical test parameters of polymers using an instrumented impact tester is reviewed. The nature of the short chain branching (SCB) in a series of linear low density polyethylenes (LLDPE) was characterized and related to several impact test parameters for these materials. The impact strength, ductility, and impact fatigue life were observed to increase with increasing branch length. This was attributed, in fact, to an increase in the number of interlamellar tie molecules as the SCB length increased. With an increase in the SCB length the SCB distribution became broader; the number of chains rich in short chain branches increased. This component acts somewhat like the rubber particles in a rubber-toughened blend which gives rise to the concept of a “one copolymer blend”. 相似文献
18.
M. Kruger C. M. Smuts A. J. S. Benadé J. E. Fincham C. J. Lombard E. A. Albertse K. J. van der Merwe 《Lipids》1992,27(10):733-739
The effects of the degree of unsaturation and of the amount of dietary fat on low density lipoprotein (LDL) concentration
and composition were determined in vervet monkeys. Diets with fat contents of 41, 31 and 18% energy, each with a low and a
high polyunsaturated to saturated fatty acid ratio (P/S; 0.27–0.38 and 1.13–1.47) were fed to six female vervet monkeys for
two months. Another six females were given a low fat, high P/S diet for the same period of time, to serve as a reference.
The cholesterol contents of the diets were low (21–33 mg per day) and relatively constant. LDL cholesterol concentrations
decreased significantly (P≤0.01) when the dietary fat content decreased from 31 to 18% of energy. The dietary P/S ratio only affected LDL cholesterol
concentrations during moderate (31% of energy) fat intake, where LDL cholesterol increased (P≤0.01) with a decrease in dietary P/S. Substantial individual variations were observed in LDL cholesterol concentration responses
to dietary fat changes. The changes in LDL cholesterol concentrations were the result of changes in the concentration of LDL
particles, as the molecular composition did not differ significantly between dietary periods. The high density lipoprotein
choelsterol and the plasma triacylglycerol concentrations were not influenced by the dietary fat changes. During the high
P/S diets, the percentage of 18∶2 (linoleic acid) increased (P≤0.01) and that of 18∶1 (oleic acid) decreased (P≤0.01) in LDL esterified cholesterol, as compared to the low P/S diets. In adipose tissue triacylglycerol the percentage of
18∶2 was three times higher (P≤0.01) during the high P/S diets than during the low P/S diets. A decrease in the amount of dietary fat (from 31 to 18% of
energy) was associated with an increase in the percentage of 18∶1 in LDL esterified cholesterol. 相似文献
19.
Male guinea pigs fed a vitamin C-deficient diet for 3 weeks had lower concentrations of cholesteryl esters in their adrenals
than did control animals fed the recommended intake of the vitamin. Not all esters were affected to the same degree, and the
fatty acid profiles of the esters from control and deficient guinea pigs differed; there was proportionately more palmitic
and linoleic acids and less docosatetraenoic acid [22∶4 (n−6)] in the deficient guinea pig adrenal esters. [Fatty acids are
designated as X∶Y (n−Z), where X and Y are the numbers of carbon atoms and olefinic bonds in the acid and Z is the number
of carbon atoms after the terminal olefinic bond.] A 100-fold excess of vitamin C in the diet also resulted in lower concentrations
of adrenal cholesteryl esters than did the control diet, but they were not as low as in the deficient animals. Fatty acid
profiles were similar for esters from control and excessively supplemented guinea pigs. Vitamin C deficiency apparently imposes
a long term stress which results in a depletion of adrenal cholesteryl esters, possibly specific esters, to meet the requirements
for glucocorticoid synthesis. 相似文献
20.
The effect of a saturated fat diet on the apoprotein composition and radioiodination properties of plasma very low density
lipoprotein (VLDL) was studied in rats. After feeding the diet for 10 days, the proportion of125I attached to VLDL lipid decreased from 50% (control animals) to 8%, the remainder (92%) being bound to the apoportein components.
The decreased lipid labelling was associated with proportional changes in the fatty acid composition of serum and VLDL lipids,
the most notable change being a reduction in linoleic acid (30–8%) content which occurred in all the major lipid classes of
both serum and VLDL. Analysis of VLDL after radioiodination showed that most of the radioactivity incorporated into the lipid
moiety was associated with phospholipid. The proportion of125I bound to phospholipid decreased after feeding rats a saturated diet. The proportion of soluble (small molecular weight peptides
and arginine rich peptide) to insoluble (B apoprotein) did not alter during the saturated fatty acid dietary regime and no
differences in the distribution of soluble proteins were observed. It is concluded that feeding a saturated fat diet to rats
for 10 days significantly improved125I labelling of the apoprotein moiety while apparently not inducing changes in apoprotein composition. 相似文献