Solid monounsaturated diet lowers LDL unsaturation trait and oxidisability in hypercholesterolemic (Type IIb) patients

Lowering high cholesterol concentration decreases the probability of atherosclerotic-related pathology onset. MUFA and PUFA decrease total plasma and LDL cholesterol but PUFA may increase the susceptibility of LDL to undergo oxidative modifications thus becoming more atherogenetic. Olive oil, the predominant fat source in Mediterranean diet, may combine the advantages of both lowering cholesterol level and decreasing LDL susceptibility to oxidation. We studied the effects of feeding MUFA vs PUFA enriched diet on LDL composition and feature in hypercholesterolemic (IIb) patients Antioxidant values remained constant during the study while LDL fatty acids composition reflected the dietary intake: MUFA concentration increased 11% whereas PUFA decreased 10% after olive oil diet (p < 0.05). PUFA/MUFA ratio and the unsaturation index were lower at the end of MUFA-enriched diet. The challenge, in vitro, of oleate-enriched LDL with Cu²⁺ yielded to lower lag-phase (p < 0.05) in diene conjugated production; the same LDL gave lower lipid hydroperoxide contents after exposition to AAPH. We conclude that oleate-enriched LDL and with lower PUFA content were more resistant to oxidative modifications, as measured by different peroxidation indexes. This feature acquired with the diet may be an useful tool for lowering LDL oxidation and indirectly their atherogenicity.     

Monounsaturated diet lowers LDL oxidisability in type IIb and type IV dyslipidemia without affecting coenzyme Q10 and vitamin E contents.

The purpose of the present study was to evaluate the effects of MUFA vs PUFA enriched diets on the plasma and LDL lipid profile and antioxidant contents in mild hypercholesterolemic and triglyceridemic subjects. The study was divided in two consecutive diet periods. Two groups of 11 dyslipidemic patients each (type IIb and type IV) were recruited and during the first period (lasting four weeks) received a linoleic rich diet while during the following four weeks took an oleate rich diet. Both groups showed no significant changes in cholesterol and TG concentration either in plasma or in LDL. Coenzyme Q10 and vitamin E were also unaffected by the dietary treatments. LDL proneness to be oxidatively modified increased after dietary PUFA administration and markedly decreased following the virgin olive oil enriched diet. In fact, LDL from hypertrigliceridemic subjects on a oleate-enriched diet displayed a 26% (p < 0.05) longer lag-phase in conjugated dienes generation than during linoleate-enriched diet and at recruitment. In hypercholesterolemic subjects similar results were obtained: the lag-phase was 28% longer after MUFA diet that after PUFA diet. No differences were found in the maximum propagation rate and maximum concentration of conjugated dienes among dietary periods and at recruitment. Since we found that the vit. E and CoQ10 levels in plasma and in LDL particles remained unchanged during the course of the study, we may conclude that LDL proneness to undergo oxidative modifications is mainly the result of compositional change due to the enrichment from the different diets of the relative fats.     

Decreased aortic early atherosclerosis in hypercholesterolemic hamsters fed oleic acid-rich TriSun oil compared to linoleic acid-rich sunflower oil

Previous studies have demonstrated that low density lipoprotein (LDL) enriched in polyunsaturated fatty acids (PUFA) are more susceptible to oxidation (ex vivo) than those containing monounsaturated fatty acids (MUFA). To test whether this observation was associated with various parameters considered to be related with the development of early aortic atherosclerosis, hamsters were fed commercial hypercholesterolemic diets (HCD) containing either the PUFA, sunflower oil (SF) or the MUFA, TriSun oil (TS) at 10% with 0.4% cholesterol (wt/wt). LDL isolated from hamsters fed TS had significantly longer lag phase (30%, P < 0.05), a decreased propagation phase (-62%, P < 0.005), and fewer conjugated dienes formed (-37%, P < 0.007) compared to hamsters fed SF. Aortic vasomotor function, measured as degree of aortic relaxation, was significantly greater in the TS vs SF-fed hamsters whether acetylcholine or the calcium ionophore A23187 was used as the endothelium-dependent agonist. As a group, the SF-fed hamsters had significantly more early atherosclerosis than hamsters fed TS (46%, P < 0.006). When animals across the two diets were pair-matched by plasma LDL-C levels, there was an 82% greater mean difference (P < 0.002) in early atherosclerosis in the SF versus the TS-fed hamsters. While there were no significant associations with plasma lipids and lipoprotein cholesterol, early atherosclerosis was significantly correlated with lag phase (r = -0.67, p < 0.02), rate of LDL conjugated diene formation (r = 0.74, p < 0.006) and maximum dienes formed (r = 0.67, p < 0.02). Compared to TS-fed animals, aortic sections from hamsters fed the SF-containing diet revealed that the cytoplasm of numerous foam cells in the subendothelial space reacted positively with the monoclonal anti-bodies MDA-2 and NA59 antibody, epitopes found on oxidized forms of LDL. The present study suggests that compared to TS, hamsters fed the SF-diet demonstrated enhanced LDL oxidative susceptibility, reduced aortic relaxation, greater early aortic atherosclerosis and accumulation of epitopes found on oxidized forms of LDL.     

Dietary fat saturation and gender/hormonal status modulate plasma lipids and lipoprotein composition(1)

Male, female and ovariectomized (to mimic menopause) guinea pigs were fed a saturated (SFA) or a polyunsaturated (PUFA) fat diet for 4 weeks to determine the effects of dietary fat saturation on lipoprotein levels and composition and to assess whether gender and hormonal status modulate the cholesterolemic response. Both diets contained 15g/100 g fat and 0.04 g/100 g cholesterol and were identical in composition except for the type of fat. The SFA diet contained 50% saturated fat (25% lauric + myristic fatty acids), 25% PUFA and 25% monounsaturated fatty acids while the PUFA diet had 50% PUFA (linoleic acid), 25% monounsaturated and 25% SFA fatty acids. Plasma LDL cholesterol (LDL-C) was an average 21% lower in guinea pigs fed PUFA compared to those fed SFA (P < 0.05). In addition, ovariectomized guinea pigs, both in the SFA and PUFA groups, had 20–33% higher LDL-C than either males or females (P < 0.01). VLDL cholesterol was 70% higher in the PUFA-fed animals (P < 0.0001). A gender effect was observed in plasma HDL cholesterol (HDL-C) with females and ovariectomized guinea pigs having 30–42% higher HDL-C than males (P < 0.01). LDL susceptibility to oxidation was not affected by dietary fat saturation or gender. In contrast, VLDL and LDL composition were significantly influenced by diet and gender. VLDL particles were larger in size in guinea pigs fed the SFA diets (P < 0.01) while LDL particles were larger in female guinea pigs (P < 0.001). Hepatic lipids were influenced by the interaction between diet and group. Hepatic cholesterol (P < 0.01) and TAG concentrations (P < 0.0001) were highest in female guinea pigs fed the PUFA diet. Since the liver is the major site of lipoprotein synthesis and catabolism, these results suggest that not only diet but also gender may play a major role in determining the composition and size of lipoproteins.     

Supplementation of postmenopausal women with fish oil does not increase overall oxidation of LDL ex vivo compared to dietary oils rich in oleate and linoleate

Although replacement of dietary saturated fat with monounsaturated and polyunsaturated fatty acids (MUFA and PUFA) has been advocated for the reduction of cardiovascular disease risk, diets high in PUFA could increase low density lipoprotein (LDL) susceptibility to oxidation, potentially contributing to the pathology of atherosclerosis. To investigate this possibility, 15 postmenopausal women in a blinded crossover trial consumed 15 g of sunflower oil (SU) providing 12.3 g/day of oleate, safflower oil (SA) providing 10.5 g/day of linoleate, and fish oil (FO) providing 2.0 g/day of eicosapentaenoate (EPA) and 1.4 g/day of docosahexaenoate (DHA). During CuSO(4)-mediated oxidation, LDL was depleted of alpha-tocopherol more rapidly after FO supplementation than after supplementation with SU (P = 0.0001) and SA (P = 0.05). In LDL phospholipid and cholesteryl ester fractions, loss of n-3 PUFA was greater and loss of n-6 PUFA less after FO supplementation than after SU and SA supplementation (P < 0.05 for all), but loss of total PUFA did not differ. The lag phase for phosphatidylcholine hydroperoxide (PCOOH) formation was shorter after FO supplementation than after supplementation with SU (P = 0.0001) and SA (P = 0.006), whereas the lag phase for cholesteryl linoleate hydroperoxide (CE18:2OOH) formation was shorter after FO supplementation than after SU (P = 0.03) but not SA. In contrast, maximal rates of PCOOH and CE18:2OOH formation were lower after FO supplementation than after SA (P = 0.02 and 0.0001, respectively) and maximal concentrations of PCOOH and CE18:2OOH were lower after FO supplementation than after SA (P = 0.03 and 0.0006, respectively). Taken together, our results suggest that FO supplementation does not increase the overall oxidation of LDL ex vivo, especially when compared with SA supplementation. Consequently, health benefits related to increased fish consumption may not be offset by increased LDL oxidative susceptibility.-- Higdon, J. V., S. H. Du, Y. S. Lee, T. Wu, and R. C. Wander. Supplementation of postmenopausal women with fish oil does not increase overall oxidation of LDL ex vivo compared to dietary oils rich in oleate and linoleate. J. Lipid Res. 2001. 42: 407--418.     

Effect of fish oil and coconut oil diet on the LDL receptor activity of rat liver plasma membranes

The influence of 4 weeks treatment with fish oil and coconut oil enriched diets on the chemical composition of rat liver plasma membranes and LDL and on the binding of LDL to liver membranes was investigated. Rats fed fish oil diet showed a total, LDL and HDL plasma cholesterol concentration lower than the values observed in rats fed coconut oil and to a lesser extent lower than those of rats fed standard laboratory diet. LDL of rats on fish oil diet had a relative percentage of cholesterol and phospholipid lower, while that of triacylglycerol was greater. Furthermore, fish oil feeding was associated with a greater concentration of n - 3 fatty acids and a lower arachidonic and linoleic acid content in LDL. Liver plasma membranes isolated from fish oil rats showed a higher percentage of n - 3 fatty acids, while only a trace amount of these fatty acids was found in control and coconut oil fed animals. In binding experiments performed with LDL and liver membranes from fish oil fed rats and control rats, binding affinity (Kd = 3.47 +/- 0.93 and 4.56 +/- 1.27, respectively) was significantly higher (P less than 0.05) as compared to that found using membranes and lipoprotein from coconut oil fed rats (Kd = 6.82 +/- 2.69). In cross-binding experiments performed with fish oil LDL and coconut oil liver plasma membranes or coconut oil LDL and fish oil liver plasma membranes, the LDL binding affinity was comparable and similar to that found in fish oil fed animals. No difference was found in the Bmax among all the groups of binding experiments. Our data seem to indicate that during fish oil diet the higher binding affinity of LDL to liver plasma membranes might be partly responsible of the hypocholesterolemic action of marine oil rich diet as compared to saturated diet. Furthermore, the modifications of binding affinity induced by changes of LDL and membrane source, suggest that lipoprotein and liver plasma membrane composition may be an important variable in binding studies.     

Effects of dietary factors on oxidation of low-density lipoprotein particles

Oxidized low-density lipoproteins (ox-LDLs) appear to play a significant role in atherogenesis. In fact, circulating ox-LDL concentrations have been recognized as a risk factor for cardiovascular disease (CVD). A higher intake of some nutrients and specific food compounds such as monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs) and flavonoids have also been associated with a lower risk of CVD. These dietary factors could be associated to a lower risk of CVD through a reduction of the atherogenicity of LDL particles through limited oxidation. Therefore, the purpose of this article is to review human clinical studies that evaluated effects of dietary antioxidant vitamins, fatty acids (MUFA, PUFA) and specific flavonoid-rich foods on LDL particle oxidation and describe potential mechanisms by which dietary factors may prevent oxidation of LDL particles. Antioxidant vitamin supplements such as alpha-tocopherol and ascorbic acid as well as beta-carotene and fish-oil supplements have not been clearly demonstrated to prevent oxidation of LDL particles. Moreover, inconsistent documented effects of flavonoid-rich food such as olive oil, tea, red wine and soy on LDL particle oxidizability may be explained by difference in variety and quantity of flavonoid compounds used among studies. However, a healthy food pattern such as the Mediterranean diet, which includes a combination of antioxidant compounds and flavonoid-rich foods, appears effective to decrease LDL particle oxidizability, which may give some insight of the cardiovascular benefits associated with the Mediterranean diet.     

LDL particle subclasses in hypercholesterolemia. Molecular determinants of reduced lipid hydroperoxide stability

Hypercholesterolemia is characterized by elevated plasma levels of LDL in which the cholesteryl ester (CE)-rich LDL subclasses of light and intermediate density (LDL1+2 and LDL3, respectively) typically predominate. The molecular mechanisms implicated in oxidation of LDL particle subclasses in hypercholesterolemia are indeterminate. Lipid hydroperoxides (LOOH), primary oxidation products in LDL, are implicated in atherogenesis. LOOH formation was evaluated in light (LDL1+2), intermediate (LDL3), and dense (LDL4+5) LDL subclasses from hypercholesterolemic (HC) subjects (n = 7) during copper-mediated oxidative stress, and compared with that in corresponding subclasses from normolipidemic subjects (n = 7). HC LDL subclasses were distinguished by lower polyunsaturated phospholipid-alpha-tocopherol ratios (P < 0.02), lower contents of phosphatidyl choline (PC)16:0-18:0/18:2 and PC16:0-18:0/20:4+22:6 (P < 0.002), and higher surface phospholipid-free cholesterol ratios (P < 0.04). The LDL3, LDL4, and LDL5 subclasses in HC subjects displayed low-core polyunsaturated CE-alpha-tocopherol ratios (P < 0.05), despite similar PUFA CE content. These physicochemical differences did not modify the oxidative susceptibility of HC LDL but underlie the marked instability of cholesterol linoleate hydroperoxides in HC LDL1+2, LDL3, and LDL4 subclasses.Elevated concentrations of large, CE-rich, light, and intermediate LDL subclasses (LDL1+2, LDL3) in hypercholesterolemia may therefore act as an abundant proatherogenic source of highly unstable LOOH in the arterial wall.     

Acute ingestion of different dietary fatty acid species modulates postprandial lipid responses in New Zealand white rabbits

Although several investigations have linked the degree of fatty acid saturation to plasma lipid responses in the postprandial state, further evaluation is necessary. In this study, we compared the effect of saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids on postprandial lipid metabolism using complementary in vivo and in vitro approaches. Fat (10 g) cholesterol (0.5 g) test meals that provided either lard (SFA), olive oil (MUFA), or sunflower oil (PUFA) were ingested by chow-fed New Zealand white rabbits (n = 8). In addition, hepatic uptake of triglyceride-cholesterol-rich lipoproteins (TCRL) isolated from rabbits chronically ingesting SFA, MUFA, or PUFA diets was measured using freshly isolated chow-fed rabbit hepatocytes. Whatever dietary fatty acids ingested, postprandial triglyceridemia and occurrence of radiolabelled dietary lipids in plasma were not markedly different. Conversely, SFA induced higher postprandial cholesterolemia and phospholipemia than MUFA (P < 0.05) whereas PUFA prevented postprandial cholesterol increase. TCRL disappearance from cultured liver cell media was delayed with SFA-rich TCRL and faster with PUFA whereas MUFA-rich TCRL showed an intermediate figure. From these data, we conclude that SFA, MUFA, and PUFA elicited different postprandial plasma and lipoprotein lipid responses. The fatty acid composition of TCRL had a major impact on their subsequent metabolism, especially uptake by cultured hepatocytes. The SFA-induced hypercholesterolemia could be related to an altered hepatic uptake whereas a faster clearance and hepatic uptake could explain the cholesterol-lowering effect of PUFA in rabbits. MUFA, like PUFA, accelerate uptake by hepatocytes but favor cholesterol ester enrichment of TCRL.     

Tissue fatty acid composition of pigs fed different fat sources

Dietary fat influences the physico-chemical properties of meat, and fatty acid (FA) composition may have implications on human health. The objectives of the experiment were to study tissue FA partitioning and the effect of dietary fat source on tissue FA composition. Seventy crossbred gilts (61.8 ± 5.2 kg BW average) were fed one of seven treatments: a diet containing a very low level of fat (no fat (NF)) and six fat-supplemented diets (10%: tallow (T), high-oleic sunflower oil (HOSF), sunflower oil (SFO), linseed oil (LO), fat blend (FB: 55% tallow, 35% SFO, 10% LO) and fish oil blend (FO: 40% fish oil, 60% LO). Differential tissue FA depositions were observed, with flare fat being the most saturated, followed by intermuscular, and subcutaneous being the least saturated. Monounsaturated fatty acid (MUFA) deposition showed an opposite tissue pattern. Subcutaneous fat showed the highest MUFAs, intermuscular fat showed intermediate values and flare fat showed the lowest MUFAs. Intramuscular polyunsaturated fatty acid (PUFA) content was less susceptible to dietary treatment modifications compared with other depots. Significant tissue FA modifications were observed due to dietary treatments, mainly in diets rich in PUFA. The saturated fatty acids (SFA) were high in NF-fed and low in HOSF-fed animals, MUFA were high in HOSF-fed and low in SFO-, LO- and FO-fed animals, while PUFA were high in SFO- and LO-fed and low in HOSF-, T- and NF-fed animals. Pigs fed LO and FB showed detectable levels of EPA, which depended on the linolenic content of the diet. The only effective way to increase tissue DHA contents was to add DHA in the diet through FO feeding. Araquidonic acid was high in SFO diets and low in LO and FB diets, and also high in intramuscular fat compared with other tissues. EPA and DHA were also high in intramuscular fat compared with other fat depots. The deposition of oleic and linoleic acids depended on the composition of dietary fat, as their deposition varied between diets, even at similar levels of intake of each FA. The NF diet resulted in the greatest proportion of SFAs (palmitic and stearic) of all treatments tested. SFAs were less susceptible to modification than MUFA in response to the different PUFA levels supplemented in the diet. T resulted in less fat deposition in some of the fat depots and more in others, suggesting that T could partition fat differently among fat depots.     

An olive oil-rich diet results in higher concentrations of LDL cholesterol and a higher number of LDL subfraction particles than rapeseed oil and sunflower oil diets

We investigated the effect of olive oil, rapeseed oil, and sunflower oil on blood lipids and lipoproteins including number and lipid composition of lipoprotein subclasses. Eighteen young, healthy men participated in a double-blinded randomized cross-over study (3-week intervention period) with 50 g of oil per 10 MJ incorporated into a constant diet. Plasma cholesterol, triacylglycerol, apolipoprotein B, and very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL), and low density lipoprotein (LDL) cholesterol concentrations were 10;-20% higher after consumption of the olive oil diet compared with the rapeseed oil and sunflower oil diets [analysis of variance (ANOVA), P < 0.05]. The size of IDL, VLDL, and LDL subfractions did not differ between the diets, whereas a significantly higher number (apolipoprotein B concentration) and lipid content of the larger and medium-sized LDL subfractions were observed after the olive oil diet compared with the rapeseed oil and sunflower oil diets (ANOVA, P < 0.05). Total HDL cholesterol concentration did not differ significantly, but HDL(2a) cholesterol was higher after olive oil and rapeseed oil compared with sunflower oil (ANOVA, P < 0.05).In conclusion, rapeseed oil and sunflower oil had more favorable effects on blood lipids and plasma apolipoproteins as well as on the number and lipid content of LDL subfractions compared with olive oil. Some of the differences may be attributed to differences in the squalene and phytosterol contents of the oils.     

Pectin and psyllium decrease the susceptibility of LDL to oxidation in guinea pigs

These studies were undertaken to determine whether pectin (PE) and psyllium (PSY) intake affect the circulating levels of alpha-tocopherol and the susceptibility of low density lipoprotein (LDL) to oxidation. For that purpose, male Hartley guinea pigs were fed 19 g/100 g of a fat mix with a 2:1:1 ratio of saturated:polyunsaturated:monounsaturated fatty acids and 35 g/100 g total carbohydrate with 80% of the carbohydrate energy contributed by sucrose. Diets were identical in composition except for the fiber source: cellulose (control diet), PE, or PSY. Guinea pigs fed PE or PSY had 36% and 67% lower plasma cholesterol concentrations, respectively, compared with controls (P < 0.001). This plasma cholesterol lowering was associated with both very low density lipoproteins and LDL cholesterol fractions. Intake of PE or PSY resulted in 54% lower plasma triacylglycerol (TAG) concentrations compared with the control group (P < 0.001). LDL from PE and PSY fed guinea pigs contained fewer molecules of cholesteryl ester, and alpha-tocopherol concentrations in this particle were 49% and 66% higher, respectively, compared with controls. In addition, LDL from guinea pigs fed soluble fiber exhibited less susceptibility to oxidation than those from the control group, as determined by thiobarbituric acid-reactive substances formation. Hepatic free and esterified cholesterol were 32% lower and hepatic TAG was 25% lower in guinea pigs fed PE and PSY compared with controls. The data from these studies confirm that PE and PSY reverse the hyperlipidemia associated with high fat-sucrose diets and demonstrate a potential antioxidant effect of soluble fiber on circulating LDL.     

Lipoprotein subfraction oxidation in acute exercise and ageing

Exercise and ageing can independently increase free radical production that may enhance the susceptibility of LDL to oxidation and create a more atherogenic LDL particle. This investigation was designed to examine exercise and ageing on the susceptibility of LDL subfractions to oxidation. Eleven aged (55?± 4 years) and twelve young (21?± 2 years) participants completed a progressive exercise test to exhaustion and within one week performed a 1?h bout of moderate intensity (65% VO_2max) exercise. Blood was assayed for metabolites associated with lipid composition (total cholesterol, free cholesterol, triglycerides) and lipoprotein susceptibility to oxidation. Exercise increased small density (sdLDL) oxidation, independently of age (p?<?0.05). However, sdLDL oxidation further increased 24?h post exercise in the aged group (p?<?0.05). With regards to the changes in lipid components within LDL, free and total cholesterol and triglycerides in large buoyant (lbLDL) were all elevated 24?h post exercise in aged compared with young (p?<?0.05 for all comparisons). There was a decrease in triglycerides in medium density (mdLDL) 24?h post exercise in the aged group (p?<?0.05). The lipid composition of sdLDL, VLDL, HDL₂, HDL₃ and serum lipid hydroperoxides remained unchanged as a function of exercise and ageing (p?>?0.05). Although regular exercise training is known to be protective against cardiovascular disease (CVD) onset, our data demonstrates that acute exercise can increase sdLDL oxidative susceptibility, and this is independent of age and regardless of a change in LDL lipid composition. However, age seems to be a determining factor with regards the susceptibility of sdLDL to oxidation 24?h following exercise.     

A fibre cocktail of fenugreek, guar gum and wheat bran reduces oxidative modification of LDL induced by an atherogenic diet in rats

Background LDL (low-density lipoprotein) oxidation is a key trigger factor for the development of atherosclerosis. Relatively few studies exist on the impact of dietary fibre on LDL oxidation. This study was undertaken to evaluate the influence of a novel fibre mix of fenugreek seed powder, guar gum and wheat bran (Fibernat) on LDL oxidation induced by an atherogenic diet. Method Male Wistar albino rats were administered one of the following diets: (1) a control diet that was fibre-free (Group I); (2) an atherogenic diet containing 1.5% cholesterol and 0.1% cholic acid (Group II) or (3) an atherogenic diet supplemented with Fibernat (Group III). Peroxidative changes in low-density lipoprotein (LDL) and the oxidative susceptibility of LDL and the LDL + VLDL (very low-density lipoprotein) fraction were determined. As a corollary to the oxidative modification theory, the titer of autoantibodies to oxidised LDL (oxLDL) was determined at various time points of the study. In addition, plasma homocysteine (tHcy) and lipoprotein (Lp (a)), apolipoprotein (apoB), cholesterol, triglyceride, phospholipid and α-tocopherol content of LDL were determined. Results A decrease in malonaldehyde (MDA) content (p < 0.05) and relative electrophoretic mobility (REM) of LDL was observed in the group III rats as compared to the group II rats. An increase in lag time to oxidation (p < 0.01) and decrease in maximum oxidation (p < 0.01) and oxidation rate (p < 0.01) were observed in the LDL + VLDL fraction of group III rats. In group II rats, formation of autoantibodies to oxLDL occurred at an earlier time point and at levels greater than in the group III rats. Fibernat, had a sparing effect on LDL α-tocopherol, which was about 51% higher in the group III rats than in the group II rats; apo B content of LDL was reduced by 37.6% in group III rats. LDL of group III rats displayed a decrease in free and ester cholesterol (p < 0.01) as compared to that of group II. A decrease in plasma homocysteine (p < 0.01) and an increase in GSH (p < 0.05) were also observed in group III rats when compared with that of group II. Conclusion Fibernat administration appears to combat oxidative stress resulting in a trend to lower oxidative modification of LDL. In addition, the cholesterol and apo B content of LDL were reduced significantly with a sparing effect on LDL α-tocopherol. This novel fibre preparation could be an effective diet therapy and therefore needs further investigation.     

Effects of isoflavones containing soy protein isolate compared with fish protein on serum lipids and susceptibility of low density lipoprotein and liver lipids to in vitro oxidation in hamsters

The effects of dietary soy protein isolate (SPI), ethanol-extracted SPI (E-SPI) low in isoflavones, and fish protein (FP) on the concentration of blood lipids and the susceptibility of low density lipoprotein (LDL) to copper-induced oxidation were compared in male golden Syrian hamsters fed a moderate hypercholesterolemic semi-purified diet for 10 weeks. SPI, E-SPI, and FP were incorporated into the isonitrogenous experimental diets as protein sources. The SPI group exhibited significantly lower serum total cholesterol concentration compared with the E-SPI group (P < 0.05) and the FP group (P < 0.01). Both the SPI and E-SPI groups showed lower LDL cholesterol (P < 0.001 and P < 0.05, respectively) and less LDL apolipoprotein B (P < 0.01) compared with the FP group. The distribution pattern of serum lipoprotein cholesterol fractions of the SPI and E-SPI groups were similar to each other, but different from that of the FP group. The lysine/arginine ratio of the three diets was significantly correlated with serum total cholesterol concentration (r = 0.462, P = 0.023). The resistance of LDL to copper-induced oxidation was greater in the SPI group than in the E-SPI and FP groups as assessed by the lower concentrations of thiobarbituric acid-reactive substances (TBARS) and the longer lag time required for the formation of conjugated dienes (P < 0.01). Livers of hamsters fed the FP diet had a higher amount of TBARS than those of hamsters fed SPI (P < 0.01) and E-SPI (P < 0.05) diets. The SPI diet showed sparing effects on alpha-tocopherol contents in both serum and liver. It seems likely that soy isoflavones protect the circulating and membrane lipids by sparing alpha-tocopherol and endogenous antioxidants.     

Superiority of dietary safflower oil over olive oil in lowering serum cholesterol and increasing hepatic mRnas for the LDL receptor and cholesterol 7alpha-hydroxylase in exogenously hypercholesterolemic (exHC) rats

The exogenously hypercholesterolemic (ExHC) rat is a strain segregated from SD rats with a high response to dietary cholesterol. To understand the underlying mechanism(s) for this hypercholesterolemia, the interactive effects of dietary fatty acid and the susceptibility of rats to dietary cholesterol on the serum cholesterol concentration and hepatic mRNA abundance of the low-density lipoprotein (LDL) receptor, cholesterol 7alpha-hydroxylase (7alpha-hydroxylase) and 3-hydroxyl-3methylglutaryl (HMG) CoA reductase were examined. Both strains were fed on a diet supplemented with 10% each of olive, safflower or coconut oil with or without the addition of 1% cholesterol for one week. The ExHC rats fed on olive, safflower and coconut oil in combination with cholesterol respectively resulted in a 3.5-, 2.0- and 2.1-fold higher serum cholesterol concentration than that in the animals fed on the corresponding dietary fats without any supplementation of cholesterol (p < 0.01 by dietary cholesterol or type of fat). The dietary cholesterol dependent-elevation of serum cholesterol in the SD rats was less than 1.5-fold (p<0.01) and there was no dietary fat effect. The ExHC rats fed on the safflower oil-containing diet supplemented with cholesterol resulted in a higher mRNA abundance of the LDL receptor and 7alpha-hydroxylase than in the corresponding fat-fed rats without cholesterol (p<0.05). There was no dietary cholesterol-dependent change of mRNA abundance in either strain fed on olive or coconut oil, except for a decreased abundance of HMG CoA reductase mRNA in the olive oil-fed ExHC rats and coconut oil-fed Sprague-Dawley (SD) rats (p<0.05). These results indicate that the hepatic mRNA abundance of the LDL receptor and of 7alpha-hydroxylase depended on the dietary combination of cholesterol and a fatty acid and suggest that a linoleic acid-rich diet may alleviate exogenous hypercholesterolemia by activating the process involved in the hepatic uptake and biliary excretion of serum cholesterol.     

Effect of long term feeding of rice bran oil upon lipids and lipoproteins in rats

The effects of feeding two levels of rice bran oil (RBO) on the growth, lipid parameters, and fatty acid composition of the plasma and liver of rats (Wistar strain) were compared with those produced on animals which had been fed the same levels of peanut oil (PNO). The control animals were fed synthetic diets containing 5 and 20% peanut oil (PNO) and the experimental groups were fed similar diets, containing the same level of rice bran oil (RBO). There was no significant difference with respect to the organ weights between the control and the experimental groups. In general, groups fed 20% oil gained more weight than groups fed 5% oil. The animals which received rice bran oil in their diet had, in general, comparatively lower levels of cholesterol, triglycerides and phospholipids. On the other hand, animals receiving 20% rice bran oil in their diet, showed an increase of 20% in high density lipoproteins (HDL-C), within 18 weeks (p<0.05), when compared to the animals fed with peanut oil. Similarly, low density lipoprotein cholesterol (LDL-C) and very low density lipoprotein cholesterol (VLDL-C) were lower in RBO-fed groups, than in the PNO-fed groups. There was, however, no significant differences in the cholesterol/phospholipid (C/P) ratio of the two groups. Analysis of plasma and of liver fatty acids indicated, in a general way, the type of fat consumed. There were no significant difference in the P/S ratio, nor any in the oleic/linoleic, oleic/stearic, palmitoleic/palmitic, oleic/palmitic, and oleic/palmitoleic ratios. Furthermore, levels of saturated (SAFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids were identical in both the groups. Thus, our results suggest that feeding a high level of rice bran oil (RBO) has no deleterious effect on the growth and blood lipid profile of rats.Abbreviations PNO peanut oil - RBO rice bran oil - HDL-C high density lipoprotein cholesterol - LDL-C low density lipoprotein cholesterol - VLDL-C very low density lipoprotein cholesterol - SAFA saturated fatty acids - MUFA mono-unsaturated fatty acids     

Dark chocolate consumption increases HDL cholesterol concentration and chocolate fatty acids may inhibit lipid peroxidation in healthy humans

Cocoa powder is rich in polyphenols and, thus, may contribute to the reduction of lipid peroxidation. Our aim was to study the effects of long-term ingestion of chocolate, with differing amounts of polyphenols, on serum lipids and lipid peroxidation ex vivo and in vivo. We conducted a 3 week clinical supplementation trial of 45 nonsmoking, healthy volunteers. Participants consumed 75 g daily of either white chocolate (white chocolate, WC group), dark chocolate (dark chocolate, DC group), or dark chocolate enriched with cocoa polyphenols (high-polyphenol chocolate, HPC group). In the DC and HPC groups, an increase in serum HDL cholesterol was observed (11.4% and 13.7%, respectively), whereas in the WC group there was a small decrease (-2.9%, p < 0.001). The concentration of serum LDL diene conjugates, a marker of lipid peroxidation in vivo, decreased 11.9% in all three study groups. No changes were seen in the total antioxidant capacity of plasma, in the oxidation susceptibility of serum lipids or VLDL + LDL, or in the concentration of plasma F2-isoprostanes or hydroxy fatty acids. Cocoa polyphenols may increase the concentration of HDL cholesterol, whereas chocolate fatty acids may modify the fatty acid composition of LDL and make it more resistant to oxidative damage.     

Effects of Coffee Consumption on Oxidative Susceptibility of Low-Density Lipoproteins and Serum Lipid Levels in Humans

Since little is known about how coffee intake affects low-density lipoprotein (LDL) oxidative susceptibility and serum lipid levels, we conducted an in vivo study in 11 healthy male students of Wakayama Medical University aged between 20 and 31 years fed an average Japanese diet. On days 1-7 of the study, the subjects drank mineral water. On day 7, the subjects began drinking coffee, 24 g total per day, for one week. This was followed by a one week "washout period" during which mineral water was consumed. Fasting peripheral venous blood samples were taken at the end of each one-week period. LDL oxidation lag time was approximately 8% greater (p < 0.01) after the coffee drinking period than the other periods. Serum levels of total cholesterol and LDL-cholesterol (LDL-C) and malondialdehyde (MDA) as thiobarbituric acid reactive substances (TBARS) were significantly decreased after the coffee drinking period. Finally, regular coffee ingestion may favorably affect cardiovascular risk status by modestly reducing LDL oxidation susceptibility and decreasing LDL-cholesterol and MDA levels.     

Cholesteryl ester enrichment of plasma low-density lipoproteins in hamsters fed cereal-based diets containing cholesterol

Male Syrian hamsters were fed 0.02, 0.03, or 0.05% cholesterol to test the hypothesis that moderate cholesterol intake increases the cholesteryl ester content of the plasma low-density lipoproteins (LDL). Dietary cholesterol levels of 0.02%-0.05% were chosen to reflect typical human intakes of cholesterol. Hamsters were fed ad libitum a cereal-based diet (modified NIH-07 open formula) for 15 weeks. Increasing dietary cholesterol from 0.02% to 0.05% resulted in significantly increased plasma LDL and high-density lipoprotein cholesterol concentration, increased liver cholesterol concentration, and increased total aorta cholesterol content. The cholesteryl ester content of plasma LDL was determined as the molar ratio of cholesteryl ester to apolipoprotein B and to surface lipid (i.e., phospholipid + free cholesterol). Increasing dietary cholesterol from 0.02% to 0.05% resulted in significantly increased cholesteryl ester content of LDL particles. Furthermore, cholesteryl ester content of LDL was directly associated with increased total aorta cholesterol, whereas a linear relationship between plasma LDL cholesterol concentration and aorta cholesterol was not observed. Thus, the data suggest that LDL cholesteryl ester content may be an important atherogenic feature of plasma LDL.