Effects of dietary fish oil or pectin on blood pressure and lipid metabolism in the DOCA-salt hypertensive rat

This study investigated the effects of diets containing fish oil or pectin on blood pressure and lipid metabolism in the deoxycorticosterone acetate (DOCA)-salt hypertensive rat. Three groups (8 rats/group) of unilaterally nephrectomized rats were fed for 21 d one of three purified diets: a) 8% fish oil + 2% safflower oil + 5% alpha cellulose (fish oil diet), b) 10% safflower oil + 5% pectin (pectin diet), or c) 10% safflower oil + 5% alpha cellulose (control diet). Each of the diets contained 6% NaCl and all rats received DOCA (30 mg/kg body wt, subcutaneously) twice weekly. Systolic blood pressure of rats fed fish oil was significantly lower (P less than 0.05) than that of rats fed the control diet; there was no significant difference between the pectin and control groups. Plasma renin activity and net sodium and potassium balances were similar among the three groups. Plasma total cholesterol, LDL cholesterol and HDL cholesterol were significantly lower (P less than 0.05) in the group fed the fish oil diet than in the group fed the control diet. Total, LDL and HDL cholesterol did not differ between rats fed the pectin and rats fed the control diet. Plasma triglyceride concentration did not differ among the three groups. Thus, dietary fish oil attenuated the development of DOCA-salt hypertension, unrelated to alterations of net sodium balance. Fish oil feeding also lowered total, LDL and HDL cholesterol, but did not alter the HDL/LDL ratio. In contrast, dietary pectin exerted no effect on blood pressure or lipid metabolism.     

Relative effects of dietary oleic- and linoleic-rich oils on plasma lipoprotein composition in rats

Plasma lipoprotein composition and hepatic lipid content were investigated in male Sprague-Dawley rats (104 +/- 2 g) fed diets containing 12% olive oil [OO, 70% 18:1(n-9)], 12% high oleic safflower oil [SO, 70% 18:(ln-9)] or 12% high linoleic safflower oil [SL, 73% 18:2(n-6)] for periods of up to 10 wk. Fasting plasma triglycerides were significantly higher after feeding oleic-rich diets than after feeding SL for 3, 5 and 6 wk. At 6 wk VLDL triglycerides were two- to threefold higher in rats fed OO or SO than in those fed SL, but by 10 wk both plasma and VLDL triglycerides were similar. A greater proportion of HDL2 (diameter 8.0-12.1 nm), a lower proportion of HDL1 (diameter 12.2-17.0 nm) and lower HDL apo E content occurred in rats fed OO and SO than in those fed SL at both 6 and 10 wk. LDL and HDL protein and cholesterol concentrations were not different with feeding SO or SL. After 10 wk of feeding the experimental diets, rats fed OO had significantly lower HDL protein, cholesterol and apo E concentrations and significantly higher hepatic triglyceride content compared to rats fed SO or SL, P less than 0.05. These data suggest that HDL and hepatic lipid content are determined by some property of the dietary oil other than its oleic acid content.     

Dietary palmitic and oleic acids exert similar effects on serum cholesterol and lipoprotein profiles in normocholesterolemic men and women.

To compare the effects of dietary palmitic acid (16:0) vs oleic acid (18:1) on serum lipids, lipoproteins, and plasma eicosanoids, 33 normocholesterolemic subjects (20 males, 13 females; ages 22-41 years) were challenged with a coconut oil-rich diet for 4 weeks. Subsequently they were assigned to either a palm olein-rich or olive oil-rich diet followed by a dietary crossover during two consecutive 6-week periods. Each test oil served as the sole cooking oil and contributed 23% of dietary energy or two-thirds of the total daily fat intake. Dietary myristic acid (14:0) and lauric acid (12:0) from coconut oil significantly raised all the serum lipid and lipoprotein parameters measured. Subsequent one-to-one exchange of 7% energy between 16:0 (palm olein diet) and 18:1 (olive oil diet) resulted in identical serum total cholesterol (192, 193 mg/dl), low-density lipoprotein cholesterol (LDL-C) (130, 131 mg/dl), high-density lipoprotein cholesterol (HDL-C) (41, 42 mg/dl), and triglyceride (TG) (108, 106 mg/dl) concentrations. Effects attributed to gender included higher HDL in females and higher TG in males associated with the tendency for higher LDL and LDL/HDL ratios in men. However, both sexes were equally responsive to changes in dietary fat saturation. The results indicate that in healthy, normocholesterolemic humans, dietary 16:0 can be exchanged for 18:1 within the range of these fatty acids normally present in typical diets without affecting the serum lipoprotein cholesterol concentration or distribution. In addition, replacement of 12:0 + 14:0 by 16:0 + 18:1, but especially 16:0 or some component of palm olein, appeared to have a beneficial impact on an important index of thrombogenesis, i.e., the thromboxane/prostacyclin ratio in plasma.     

Microalgal docosahexaenoic acid decreases plasma triacylglycerol in normolipidaemic vegetarians: a randomised trial

Triacylglycerol (TG) lowering effects of n-3 long-chain PUFA (n-3 LCPUFA) have been repeatedly demonstrated, but studies investigating the individual effects of EPA or DHA on plasma TG and lipoproteins in man are rare. The effects of a new DHA-rich, almost EPA-free microalgae oil (Ulkenia sp.) on plasma lipids and several safety parameters were investigated in a double-blind, placebo-controlled, parallel design intervention study. Normolipidaemic vegetarians (eighty-seven females, twenty-seven males) consumed daily microalgae oil (0.94 g DHA/d) or olive oil (as placebo) for 8 weeks. DHA supplementation decreased plasma TG by 23 % from 1.08 (sem 0.07) to 0.83 (sem 0.04) mmol/l (P<0.001). Absolute TG decreases after DHA supplementation were inversely correlated to baseline TG concentrations (r -0.627, P<0.001). Plasma total, LDL and HDL cholesterol increased significantly in the DHA group, resulting in lower TG:HDL cholesterol and unchanged LDL:HDL and total cholesterol:HDL cholesterol ratios. The intake of DHA-rich microalgae oil did not result in any physiologically relevant changes of safety and haemostatic factors. In conclusion, DHA-rich oil from microalgae Ulkenia sp. was well tolerated and can be considered a suitable vegetarian source of n-3 LCPUFA. Although DHA supplementation improved some CHD risk factors (plasma TG, TG:HDL cholesterol ratio), LDL cholesterol increased. Therefore, the overall effects of this intervention on CHD risk deserve further investigation.     

Replacing 40% of dietary animal fat with vegetable oil is associated with lower HDL cholesterol and higher cholesterol ester transfer protein in cynomolgus monkeys fed sufficient linoleic acid

This study was designed to evaluate whether replacing approximately 40 g/100 g dietary animal fat with vegetable oil would improve plasma lipids and lipoproteins when diets contained prudent levels of total saturated acid (SFA), monounsaturated acid (MUFA) and PUFA. Using a cross-over design, male Cynomolgus monkeys (n = 10) were fed purified diets containing a mixture of fats. For the diet based on animal fat (AF-diet), approximately 85 g/100 g of the total fat was derived from pork fat, and approximately 40 g/100 g of this was replaced with olive oil for the vegetable oil-based diet (VO-diet). Thus, the fat content of the VO diet comprised 50% pork fat and 35% olive oil. The remaining 15% of the total fat (for both diets) was safflower oil. Both diets provided approximately 30% of total energy (%en) from fat, <10%en SFA and approximately 6-7%en from PUFA. Monkeys were rotated through two 7-wk feeding periods, during which time plasma lipids and lipoproteins were evaluated. Compared with the AF diet, plasma total cholesterol (TC) concentrations tended to be lower ( approximately 10%) after monkeys consumed the VO diet (3.18 +/- 0.83 vs. 3.52 +/- 0.93 mmol/L, P = 0.099), and this was due entirely to a significant 12% reduction in HDL cholesterol (1.53 +/- 0.41 vs. 1.73 +/- 0.47, mmol/L, P = 0.0009). Although plasma lipoprotein compositional analyses revealed no significant differences in either lipoprotein composition or the estimated particle diameters, the measurement of cholesterol ester transfer protein (CETP) using (3)H-cholesterol ester-labeled HDL revealed that the lower HDL cholesterol (HDL-C) when monkeys consumed the VO diet was associated with a 31% increase in transfer (P = 0.04). However, despite the changes in HDL-C, the TC/HDL-C ratio did not differ between monkeys after the two diet treatments. Regression analyses of data from these monkeys revealed a significant correlation between the dietary 16:0/18:2 ratio and plasma HDL-C. These data suggest that within the context of currently recommended prudent diets, it may be possible to manipulate HDL-C beneficially. Whether a similar effect would occur in humans warrants investigation.     

Eicosanoid production, thrombogenic ratio, and serum and LDL peroxides in normo- and hypercholesterolaemic post-menopausal women consuming two oleic acid-rich diets with different content of minor components

The present paper compares the effects of two monounsaturated oils, extra virgin olive oil (EVOO) and high-oleic acid sunflower oil (HOSO), on serum and LDL peroxides, eicosanoid production and the thrombogenic ratio (thromboxane (TX) B2:6-keto-prostaglandin F1alpha) in fourteen non-obese post-menopausal women. The subjects, mean age 63 (SD 11) years, were assigned to two consecutive oleic acid-rich 28 d dietary periods. EVOO and HOSO represented 62 % of the total lipid intake and were used as the only culinary fat during the first and second dietary periods respectively. Serum peroxides, plasma alpha-tocopherol and TXB2 levels in stimulated platelet-rich plasma (PRP-TXB2) were significantly higher (P < 0.01, P < 0.001, and P < 0.05, respectively) after the HOSO diet than after the EVOO diet. The relationship between the serum cholesterol level (< 6.21 mmol/l or > or = 6.21 mmol/l) and the type of dietary oil on eicosanoids, peroxides and alpha-tocopherol were evaluated by two-way ANOVA. Dietary oil significantly affected (P < 0.05) the PRP-TXB2 level, whereas serum and LDL peroxides were significantly affected (P < 0.001 and P < 0.01, respectively) by the serum cholesterol level. The plasma alpha-tocopherol level was significantly affected by the serum cholesterol level and the type of dietary oil (both P < 0.001). No significant relationships were found between serum cholesterol levels, serum peroxide or LDL peroxide levels, plasma alpha-tocopherol concentrations or alpha-tocopherol intakes with eicosanoid production or the thrombogenic ratio due to dietary changes. However, in spite of their higher alpha-tocopherol levels, hypercholesterolaemic subjects showed increased peroxidation in serum and LDL in comparison with normocholesterolaemic subjects on the HOSO diet in comparison with the EVOO diet. These findings suggest that differences in the type of minor compounds, as well as in the concentration of linoleic acid, in both these monounsaturated oils may play an important role in modulating eicosanoid production and lipoprotein peroxidation when they constitute a large proportion of the diet of post-menopausal women.     

ApoE distribution among lipoproteins of rhesus monkeys is modulated by dietary fat and cholesterol

The effect of dietary saturated fat and cholesterol on plasma cholesterol and apolipoprotein E (apoE) distribution among lipoproteins was studied in rhesus monkeys. Two groups of four monkeys had been fed diets containing 31% energy as either corn oil or coconut oil for 5 yr from birth. Each group was then fed short-term their respective diet with a 0.2% cholesterol supplement, the opposite fat without cholesterol, the opposite fat +0.2% cholesterol, followed by their original fat without cholesterol for 5 to 8 wk periods. Plasma was assayed for total cholesterol, total triglyclerides, and the distribution of apoE within lipoproteins (VLDL, IDL, LDL, HDL) separated by gradient-density electrophoresis. When coconut oil was fed, plasma cholesterol and triglyceride concentrations were 134% and 157%, respectively, of the levels when corn oil was fed. Cholesterol supplementation of corn oil also elevated the plasma cholesterol (141%), whereas cholesterol supplementation of coconut oil appeared to induce a synergistic increase (198%). Both groups of monkeys responded similarly to a given diet. The distribution of apoE in lipoproteins differed according to dietary treatment, with cholesterol feeding causing a major shift from HDL to IDL, whereas coconut oil caused a modest shift from HDL to VLDL. The relative amount of apoE in LDL was unchanged by diet. We conclude that dietary saturated fat or cholesterol can modulate the apoE distribution within lipoproteins in rhesus monkeys in conjunction with the previously noted expansion of the cholesteryl ester pool in VLDL and IDL.     

Pork fat and chicken fat similarly affect plasma lipoprotein metabolism in cynomolgus monkeys fed diets with adequate levels of linoleic acid

The effects on plasma lipoprotein metabolism of replacing pork fat (PF) with chicken fat (CF) (formulated as part of currently recommended prudent diets) was evaluated in 10 male cynomolgus monkeys. Monkeys were rotated through three dietary periods, (each of 10-wk duration), during which total cholesterol (TC), triacylglycerol (TG) and HDL-cholesterol (HDL-C) were measured (7, 8 and 9 wk) and in vivo lipoprotein metabolism evaluated (after 9 wk). Initially, all monkeys were fed a high-fat, high-cholesterol reference diet [38% of energy (en) from fat, 18%en saturated fatty acids (SFA), 10%en monounsaturated fatty acids (MUFA), 10%en polyunsaturated fatty acids (PUFA), 0.045 mg cholesterol/kJ diet]. Subsequently, monkeys were rotated through two test diets (30%en fat, SFA/MUFA/PUFA 1:1:1, 0.004-0.005 mg cholesterol/kJ diet), in which 80% of the fat was either PF or CF, with the remaining 20% derived from high-linoleic safflower oil. There was no significant difference between the two test diets for TG, TC, nonHDL-C, HDL-C or the ratio of TC/HDL-C. Lipoprotein composition, LDL apolipoprotein B pool size, fractional catabolic rate and transport rate were also not significantly different when monkeys consumed the two test diets. These data suggest that when incorporated into diets following current guidelines and containing adequate PUFA ( approximately 7-9%en), PF and CF similarly affect plasma lipids.     

Dietary fat type and cholesterol quantity interact to affect cholesterol metabolism in guinea pigs.

Interactions of dietary fat saturation with dietary cholesterol on cholesterol homeostasis in guinea pigs were studied by feeding 15% (wt/wt) fat diets containing lard, olive oil or corn oil, with 0.00, 0.08, 0.17 or 0.33% added cholesterol. Plasma total and LDL cholesterol concentrations significantly increased with increasing dietary cholesterol, with pronounced increments occurring at the pharmacologic (0.33%) level. An interaction between fat type and dietary cholesterol was seen for HDL cholesterol concentrations. Saturated fat and the pharmacologic level of dietary cholesterol increased plasma HDL concentrations, whereas polyunsaturated fat minimized the dietary cholesterol-mediated increase. Interactions were also observed for hepatic cholesterol: dietary cholesterol increased both free and esterified hepatic cholesterol concentrations in all groups fed all the dietary fats, and fat type influenced the extent of hepatic cholesterol accumulation. Lard-fed animals accumulated the least hepatic cholesterol over the range of dietary cholesterol intakes. Dietary cholesterol suppressed hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity, with maximal suppression at all levels of cholesterol intake. Dietary cholesterol had a greater effect on plasma and hepatic cholesterol concentrations and hepatic HMG-CoA reductase activity than did fat type. The data indicated limited interactions of fat type and cholesterol quantity in altering mechanisms regulating plasma cholesterol homeostasis.     

The effect of dietary fat saturation on plasma and hepatic lipoproteins in the rat

Semipurified diets containing 10% kilocalories from either safflower oil (SO), corn oil (CO), olive oil (OO) or palm oil (PO) were fed to weanling male rats for 2 weeks. The effects of dietary fat saturation on plasma lipids and lipoproteins were: 1) Nonfasted plasma cholesterol concentration was higher in rats fed OO (mean +/- SEM = 81.0 +/- 2.9 mg/dl) vs. CO (67.5 +/- 2.9); 2) plasma chylomicron cholesterol concentration was higher in rats fed OO vs. SO and CO, with PO values in between; and 3) the cholesterol concentration of plasma very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL) did not differ among groups. The effects of dietary fat saturation on hepatic lipoproteins (determined by liver perfusion techniques) were: 1) hepatic higher density lipoprotein (d = 1.006-1.21 g/ml) cholesterol production was greater in rats fed SO and CO vs. PO [19.1 +/- 1.2, 17.2 +/- 0.8 and 13.7 +/- 1.6 micrograms/(g liver X 1.5 hour), respectively]; 2) there was no difference in hepatic VLDL cholesterol production among groups; and 3) the ratio of cholesterol to protein of hepatic VLDL and the higher density lipoprotein fraction was higher in rats fed diets rich in polyunsaturated fatty acids versus saturated fatty acids. Dietary fat saturation had no effect on carcass and liver cholesterol concentrations. Since differences in hepatic lipoprotein production were not reflected in plasma lipoprotein patterns, these results suggest that extrahepatic lipoprotein metabolism differs in rats fed diets containing fatty acids of varying saturation.     

Cardiovascular disease risk factors in 2 distinct ethnic groups: Indian and Pakistani compared with American premenopausal women

BACKGROUND: Although people from the Indian subcontinent have high rates of cardiovascular disease (CVD), studies of such in Indian and Pakistani women living in the United States are lacking. OBJECTIVE: This study accounted for variability in serum lipid (total cholesterol and triacylglycerol) and lipoprotein [LDL cholesterol, lipoprotein(a), and HDL cholesterol] concentrations in Indian and Pakistani compared with American premenopausal women in the United States. Body composition, regional fat distribution, dietary intake, and energy expenditure were compared between groups. DESIGN: The 2 groups were 47 Indian and Pakistani and 47 American women. Health was assessed via medical history, physical activity, body composition (via anthropometry and dual-energy X-ray absorptiometry), dietary intake (via 7-d food records), and serum lipids. RESULTS: Serum total cholesterol, triacylglycerol, LDL cholesterol, lipoprotein(a), the ratio of total to HDL cholesterol, and the ratio of LDL to HDL cholesterol were greater (P <0.03), whereas HDL-cholesterol values were lower (P = 0.011) in Indians and Pakistanis than in Americans. Multiple regression analysis indicated that approximately 18% of the variance in total cholesterol (P = 0.0010) and LDL cholesterol (P = 0.0009) was accounted for by ethnicity, energy expenditure, and the ratio of the sum of central to the sum of peripheral skinfold thicknesses. Ethnicity, sum of central skinfold thicknesses, ratio of polyunsaturated to saturated fat, and monounsaturated fat intake accounted for approximately 43% of the variance in triacylglycerol concentration (P < 0.0001). Monounsaturated fat, percentage body fat, and alcohol intake accounted for approximately 26% of variance in HDL cholesterol. Ethnicity contributed approximately 22% of the 25% overall variance in lipoprotein(a). CONCLUSIONS: Results suggest that these Indian and Pakistani women are at higher CVD risk than their American counterparts, but that increasing their physical activity is likely to decrease overall and regional adiposity, thereby improving their serum lipid profiles.     

Effects of minor constituents (non-glyceride compounds) of virgin olive oil on plasma lipid concentrations in male Wistar rats.

We aimed to assess the effects of minor constituents (MC) from virgin olive oil upon the plasma lipid profile of experimental animals. Therefore, 32 Wistar rats were fed for 6 weeks with one of four different diets with a similar fatty acid composition but different MC: high-oleic sunflower oil (HOSO), virgin olive oil (VOO), 400%-MC enriched olive oil (EOO) and MC poor (impoverished) olive oil (IOO). At the end of the week 6 of dietary treatment, blood samples were obtained for analysis of lipid composition. A statistically significant influence was observed upon both total HDL (1.593+/-0.4, 1.204+/-0.212, 0.991+/-0.244 and 0.827+/-0.279 mmol/L for EOO, HOSO, VOO and IOO, respectively, Kruskal-Wallis test, P<0.05) and HDL(2)cholesterol levels (1.16+/-0.26, 0.576+/-0.191, 0.585+/-0.216 and 0.583+/-0.207 mmol/L for EOO, HOSO, VOO and IOO, respectively, Kruskal-Wallis test, P<0.05). No statistically significant effect was observed upon LDL-cholesterol or triglycerides. Thus, MC supplementation has beneficial effects on HDL concentrations in Wistar rats.     

Differential effects of the trans-18:1 isomer profile of partially hydrogenated vegetable oils on cholesterol and lipoprotein metabolism in male F1B hamsters

Trans-fatty acid consumption from partially hydrogenated vegetable oil (PHVO) has been positively associated with multiple cardiovascular disease risk factors and events. This study was designed to examine the effects of trans-fatty acid isomer profile of PHVO on plasma lipids and lipoproteins and hepatic expression of key genes involved in cholesterol and fatty acid metabolism. Thirty-three male F(1)B strain Syrian Golden Hamsters were allocated to 1 of 3 hypercholesterolemic diets containing (5% by weight): 1) tristearin [control fat (CON)]; 2) partially hydrogenated high-oleic acid sunflower oil (PH-SUN); or 3) partially hydrogenated high-linoleic acid safflower oil (PH-SAF). PH-SUN contained more trans-4 to trans-10 18:1 compared with PH-SAF, which contained more trans-11 to trans-16 18:1. The addition of both PHVO to the diet increased plasma total cholesterol concentrations relative to CON, but only PH-SUN increased the plasma ratio of non-HDL:HDL cholesterol compared with CON. PH-SUN increased VLDL (total, large, and medium) and IDL particle concentrations while decreasing total, medium, and small HDL particle concentrations relative to CON. Both PHVO diets increased the hepatic cholesterol ester concentration, whereas the hepatic TG concentration was lower in PH-SUN compared with PH-SAF and CON. Levels of hepatic LDL receptor, HMG-CoA reductase, and sterol response element binding protein 1 mRNA were specifically reduced in the PH-SUN group compared to the CON group. Expression of SREBP1c was upregulated in both PHVO groups compared to CON, whereas only the PH-SAF group had higher levels of the lipogenic enzymes acetyl-CoA carboxylase, fatty acid synthase, and stearoyl-CoA desaturase-1 compared to CON. These results indicate that differences in the trans-fatty acid profile of PHVO can differentially affect lipid and lipoprotein metabolism.     

Effect of animal and vegetable fats and proteins on distribution of cholesterol in plasma and organs of young growing pigs

Young, growing pigs were fed for 8 wk diets containing either soy protein isolate or ground beef as the main protein source and soybean oil or beef tallow as the main fat source to examine effects of types of dietary protein and fat on cholesterol distribution between blood plasma, plasma lipoproteins and body organs. Type of dietary protein did not influence concentrations of a) cholesterol in plasma, b) low-density-lipoprotein (LDL) cholesterol, c) high-density-lipoprotein (HDL) cholesterol or d) cholesterol in several organs of pigs. Pigs fed tallow had greater concentrations of plasma cholesterol and LDL and HDL cholesterol than did pigs fed soybean oil. Ratios of HDL to LDL were not altered by dietary fat. Cholesterol concentrations were greater in heart, skeletal muscle and viscera of pigs fed soybean oil than in those fed tallow. Plasma cholesterol varied reciprocally with cholesterol in several tissues. Thus, dietary beef and soy protein isolate had similar effects on cholesterol concentrations in plasma, LDL, HDL and organs, whether pigs consumed soybean oil or beef tallow as a major fat source. Soybean oil, however, exerted a hypocholesterolemic effect, irrespective of major source of dietary protein.     

Effects of medium-chain fatty acids and oleic acid on blood lipids, lipoproteins, glucose, insulin, and lipid transfer protein activities

BACKGROUND: Dietary medium-chain fatty acids (MCFAs) are of nutritional interest because they are more easily absorbed from dietary medium-chain triacylglycerols (MCTs) than are long-chain fatty acids from, for example, vegetable oils. It has generally been claimed that MCFAs do not increase plasma cholesterol, although this claim is poorly documented. OBJECTIVE: We compared the effects of a diet rich in either MCFAs or oleic acid on fasting blood lipids, lipoproteins, glucose, insulin, and lipid transfer protein activities in healthy men. DESIGN: In a study with a double-blind, randomized, crossover design, 17 healthy young men replaced part of their habitual dietary fat intake with 70 g MCTs (66% 8:0 and 34% 10:0) or high-oleic sunflower oil (89.4% 18:1). Each intervention period lasted 21 d, and the 2 periods were separated by a washout period of 2 wk. Blood samples were taken before and after the intervention periods. RESULTS: Compared with the intake of high-oleic sunflower oil, MCT intake resulted in 11% higher plasma total cholesterol (P = 0.0005), 12% higher LDL cholesterol (P = 0.0001), 32% higher VLDL cholesterol (P = 0.080), a 12% higher ratio of LDL to HDL cholesterol (P = 0.002), 22% higher plasma total triacylglycerol (P = 0.0361), and higher plasma glucose (P = 0.033). Plasma HDL-cholesterol and insulin concentrations and activities of cholesterol ester transfer protein and phospholipid transfer protein did not differ significantly between the diets. CONCLUSIONS: Compared with fat high in oleic acid, MCT fat unfavorably affected lipid profiles in healthy young men by increasing plasma LDL cholesterol and triacylglycerol. No changes in the activities of phospholipid transfer protein and cholesterol ester transfer protein were evident.     

Genetic factors influence the atherogenic response of lipoproteins to dietary fat and cholesterol in nonhuman primates.

Comparative studies of diet responsiveness have carried out in five different old world primate species, including African green, stumptail, rhesus, patas, and cynomolgus monkeys. The dietary variables examined were level of cholesterol (0.03 and 0.8 mg cholesterol/kcal) and type of fat (enriched in saturated vs. n-6 polyunsaturated fatty acids). In all cases, hypercholesterolemia resulted from the high cholesterol diet, making it possible to identify low, moderate, and high responding species. Polyunsaturated vs. saturated fat effects to lower plasma cholesterol did not appear to be remarkably species specific, except for the more pronounced response in African green monkeys. For low-density lipoprotein (LDL) cholesterol concentrations, African green monkeys were the lowest responding species and cynomolgus monkeys were the highest. LDL particle enlargement was least in African green monkeys and highest in rhesus and cynomolgus monkeys. High-density lipoprotein (HDL) cholesterol levels were similar among species on the low cholesterol diet, but decreased when the high cholesterol diet was fed in all species except African green monkeys, where HDL increased with added dietary cholesterol. Coronary artery atherosclerosis developed only when the high cholesterol diet was fed, occurred more rapidly, and became more extensive in cynomolgus compared to African green monkeys. Polyunsaturated fat limited the amount of atherosclerosis that developed in both species. Genetic factors regulating the response to dietary cholesterol in degree of hyperlipoproteinemia, cholesterol distribution among lipoproteins, LDL particle size, and HDL cholesterol concentration were characteristically unique among different primate species. The effects of lipoproteins were well correlated with the extent of coronary artery atherosclerosis.     

Palmitic and stearic acids similarly affect plasma lipoprotein metabolism in cynomolgus monkeys fed diets with adequate levels of linoleic acid

This study was designed to evaluate whether the exchange of specific saturated fatty acids [SFA; palmitic acid (16:0) for stearic acid (18:0)] would differentially affect plasma lipids and lipoproteins, when diets contained the currently recommended levels of total SFA, monounsaturated fatty acids and polyunsaturated fatty acids (PUFA). Ten male cynomolgus monkeys were fed one of two purified diets (using a cross-over design) enriched either in 16:0 (palmitic acid diet) or 18:0 (stearic acid diet). Both diets provided 30% of energy as fat (SFA/monounsaturated fatty acid/PUFA: 1/1/1). The palmitic acid and stearic acid diets were based on palm oil or cocoa butter (59% and 50% of the total fat, respectively). By adding different amounts of sunflower, safflower and olive oils, an effective exchange of 16:0 for 18:0 of approximately 5% of energy was achieved with all other fatty acids being held constant. Monkeys were rotated through two 10-wk feeding periods, during which time plasma lipids and in vivo lipoprotein metabolism (following the simultaneous injection of (131)I-LDL and (125)I- HDL were evaluated). Plasma triacyglycerol (0.40 +/- 0.03 vs. 0.37 +/- 0.03 mmol/L), plasma total cholesterol (3.59 +/- 0.18 vs. 3.39 +/- 0.23 mmol/L), HDL cholesterol (1.60 +/- 0.16 vs 1.53 +/- 0.16 mmol/L) and non-HDL cholesterol (2.02 +/- 0.26 vs. 1.86 +/- 0.23 mmol/L) concentrations did not differ when monkeys consumed the palmitic acid and stearic acid diets, respectively. Plasma lipoprotein compositional analyses revealed a higher cholesteryl ester content in the VLDL fraction isolated after consumption of the stearic acid diet (P < 0.10), as well as a larger VLDL particle diameter (16.3 +/- 1.7 nm vs. 13.8 +/- 3.6 nm; P < 0.05). Kinetic analyses revealed no significant differences in LDL or HDL transport parameters. These data suggest that when incorporated into diets following current guidelines, containing adequate PUFA, an exchange of 16:0 for 18:0, representing approximately 11 g/(d.10.46 mJ) [ approximately 11 g/(d.2500 kcal)] does not affect the plasma lipid profile and has minor effects on lipoprotein composition. Whether a similar effect would occur in humans under comparable dietary conditions remains to be established.     

Effects of quantity and unsaturation of dietary fat on serum components in normal and diabetic Macaca nigra.

Dietary fat affects serum lipids independently of dietary cholesterol. Normal and diabetic monkeys (Macaca nigra) were fed cereal-based, specially formulated diets with either a low fat (LF = 2.5%) or a higher fat (13.2%) content; the latter had varying concentrations of safflower and coconut oil to attain greater polyunsaturation (SFO) or saturation (CCO) in the diets. Dietary cholesterol was less than 0.01%. Serum triglyceride concentrations were greatest when monkeys consumed the LF (higher carbohydrate) diet and lowest when they consumed the SFO diet. Concentrations were greater in diabetic than in normal monkeys fed the LF and SFO diets, but both groups had similar concentrations when fed the CCO diet. Cholesterol levels in diabetic monkeys were only slightly higher than in normals regardless of diet; in both groups, levels were lowest when the LF diet was fed and highest when the CCO diet was fed. The quantity of fat had a greater effect on serum cholesterol than did the degree of polyunsaturation. In both groups, triglyceride concentrations correlated significantly with VLDL protein, and cholesterol levels correlated with LDL protein. Thus the responses of Macaca nigra to dietary fat manipulation depend upon both the diet fat content and composition as well as the normal or diabetic metabolic state of each monkey.     

Comparison of dietary casein or soy protein effects on plasma lipids and hormone concentrations in the gerbil (Meriones unguiculatus)

The effects of dietary animal protein (casein) or soy protein (soy isolate) on plasma lipids and hormones were investigated in the gerbil. Diets, fed to male gerbils (initial weight, 60 g) for 4 wk, contained either 18% casein or soy isolate as the protein source. The dietary fat sources were lard (16%) and safflower oil (1%). The cholesterol content of the diet was 0.1%. Plasma total cholesterol concentrations were lower in gerbils fed the soy protein diet (159 mg/dl) than in the gerbils fed the casein diet (190 mg/dl). Absolute HDL-cholesterol concentrations were unaffected by the protein source, but LDL-cholesterol concentrations were lower in the soy-fed gerbils. Thus, the ratio of LDL to HDL cholesterol was lower in the soy-fed gerbils (0.42) compared with the casein-fed gerbils (0.70). Plasma insulin levels were higher in the soy-fed gerbils as were plasma thyroxine and thyroid-stimulating hormone levels. The results indicate that the gerbils can be used to study dietary effects on cholesterol parameters. These data also suggest that changes in plasma thyroxine levels may in part account for the hypocholesterolemic effect of soy protein.     

Serum lipid concentrations and mean life span are modulated by dietary polyunsaturated fatty acids in the senescence-accelerated mouse

The senescence-accelerated mouse (SAMP8) is an animal model used in studies of aging. This study was undertaken to investigate the effects of dietary PUFA on longevity (Experiment 1) and serum lipid concentrations (Experiment 2) in SAMP8 mice. Male mice were fed either an (n-3) PUFA-rich (9 g/100 g perilla oil) or an (n-6) PUFA-rich (9 g/100 g safflower oil) diet beginning at 6 wk of age. Experiment 1: The groups did not differ in body weight gain, but those fed perilla oil had significantly lower scores of senescence relative to those fed safflower oil (P<0.05). The mean life span of mice fed perilla oil was 357+/-21 d and of those fed safflower oil, 426+/-24 d (P<0.05). Pathological studies revealed that the incidence of tumors was significantly lower in the perilla oil group than in the safflower oil group (P<0.05). Approximately half the mice fed perilla oil had died after 10 mo, and the direct causes closely connected with death could not be specified. Experiment 2: The serum total cholesterol, HDL cholesterol, triglyceride and phospholipid concentrations were significantly lower in the perilla oil group than in the safflower oil group (P<0.01). A marked decrease of serum HDL cholesterol and apolipoprotein A-II (ApoA-II)concentrations in advanced age were observed in the mice fed perilla oil (P<0.01). Ten-month-old mice fed perilla oil had a significantly greater ratio of apolipoprotein A-I (ApoA-I) to ApoA-II than those fed safflower oil. Separation of HDL subfractions revealed that the smaller HDL species were much more abundant than the larger HDL species in both dietary oil groups. These findings suggest that dietary (n-3) and (n-6) PUFA differ in their effects on serum lipid metabolism which may modulate the mean life span of SAMP8 mice fed each dietary oil.