Lowering of plasma cholesterol and enhanced sterol excretion with the consumption of polyunsaturated ruminant fats

Apolipoprotein O modulates cholesterol metabolism via NRF2/CYB5R3 independent of LDL receptor

Apolipoprotein O (APOO) plays a critical intracellular role in regulating lipid metabolism. Here, we investigated the roles of APOO in metabolism and atherogenesis in mice. Hepatic APOO expression was increased in response to hyperlipidemia but was inhibited after simvastatin treatment. Using a novel APOO global knockout (Apoo-/-) model, it was found that APOO depletion aggravated diet-induced obesity and elevated plasma cholesterol levels. Upon crossing with low-density lipoprotein receptor (LDLR) and apolipoprotein E (APOE) knockout hyperlipidemic mouse models, Apoo-/- Apoe-/- and Apoo-/- Ldlr-/- mice exhibited elevated plasma cholesterol levels, with more severe atherosclerotic lesions than littermate controls. This indicated the effects of APOO on cholesterol metabolism independent of LDLR and APOE. Moreover, APOO deficiency reduced cholesterol excretion through bile and feces while decreasing phospholipid unsaturation by inhibiting NRF2 and CYB5R3. Restoration of CYB5R3 expression in vivo by adeno-associated virus (AAV) injection reversed the reduced degree of phospholipid unsaturation while decreasing blood cholesterol levels. This represents the first in vivo experimental validation of the role of APOO in plasma cholesterol metabolism independent of LDLR and elucidates a previously unrecognized cholesterol metabolism pathway involving NRF2/CYB5R3. APOO may be a metabolic regulator of total-body cholesterol homeostasis and a target for atherosclerosis management. Apolipoprotein O (APOO) regulates plasma cholesterol levels and atherosclerosis through a pathway involving CYB5R3 that regulates biliary and fecal cholesterol excretion, independently of the LDL receptor. In addition, down-regulation of APOO may lead to impaired mitochondrial function, which in turn aggravates diet-induced obesity and fat accumulation.

Dietary fat quality, plasma atherogenic lipoproteins, and atherosclerotic cardiovascular disease: An overview of the rationale for dietary recommendations for fat intake

The scientific evidence supporting the current dietary recommendations for fat quality keeps accumulating; however, a paradoxical distrust has taken root among many researchers, clinicians, and in parts of the general public. One explanation for this distrust may relate to an incomplete overview of the totality of the evidence for the link between fat quality as a dietary exposure, and health outcomes such as atherosclerotic cardiovascular disease (ASCVD). Therefore, the main aim of the present narrative review was to provide a comprehensive overview of the rationale for dietary recommendations for fat intake, limiting our discussion to ASCVD as outcome. Herein, we provide a core framework - a causal model - that can help us understand the evidence that has accumulated to date, and that can help us understand new evidence that may become available in the future. The causal model for fat quality and ASCVD is comprised of three key research questions (RQs), each of which determine which scientific methods are most appropriate to use, and thereby which lines of evidence that should feed into the causal model. First, we discuss the link between low-density lipoprotein (LDL) particles and ASCVD (RQ1); we draw especially on evidence from genetic studies, randomized controlled trials (RCTs), epidemiology, and mechanistic studies. Second, we explain the link between dietary fat quality and LDL particles (RQ2); we draw especially on metabolic ward studies, controlled trials (randomized and non-randomized), and mechanistic studies. Third, we explain the link between dietary fat quality, LDL particles, and ASCVD (RQ3); we draw especially on RCTs in animals and humans, epidemiology, population-based changes, and experiments of nature. Additionally, the distrust over dietary recommendations for fat quality may partly relate to an unclear understanding of the scientific method, especially as applied in nutrition research, including the process of developing dietary guidelines. We therefore also aimed to clarify this process. We discuss how we assess causality in nutrition research, and how we progress from scientific evidence to providing dietary recommendations.

Dietary interventions (plant sterols, stanols, omega-3 fatty acids, soy protein and dietary fibers) for familial hypercholesterolaemia

BACKGROUND

A cholesterol-lowering diet and several other dietary interventions have been suggested as a management approach either independently or as an adjuvant to drug therapy in children and adults with familial hypercholesterolaemia (FH). However, a consensus has yet to be reached on the most appropriate dietary treatment. Plant sterols are commonly used in FH although patients may know them by other names like phytosterols or stanols.

OBJECTIVES

To examine whether a cholesterol-lowering diet is more effective in reducing ischaemic heart disease and lowering cholesterol than no dietary intervention in children and adults with familial hypercholesterolaemia. Further, to compare the efficacy of supplementing a cholesterol-lowering diet with either omega-3 fatty acids, soya proteins, plant sterols or plant stanols.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Inborn Errors of Metabolism Trials Register, which is compiled from electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (updated with each new issue of The Cochrane Library), quarterly searches of MEDLINE and the prospective handsearching of one journal - Journal of Inherited Metabolic Disease. Most recent search of the Group's Inborn Errors of Metabolism Trials Register: 22 August 2013. We also searched PubMed to 05 February 2012.

SELECTION CRITERIA

Randomised controlled trials, both published and unpublished, where a cholesterol-lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trial eligibility and risk of bias and one extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

In the 2014 update of the review, 15 trials have been included, with a total of 453 participants across seven comparison groups. The included trials had either a low or unclear risk of bias for most of the parameters used for risk assessment. Only short-term outcomes could be assessed due to the short duration of follow up in the included trials. None of the primary outcomes, (incidence of ischaemic heart disease, number of deaths and age at death) were evaluated in any of the included trials. No significant differences were noted for the majority of secondary outcomes for any of the planned comparisons. However, a significant difference was found for the following comparisons and outcomes: for the comparison between plant sterols and cholesterol-lowering diet (in favour of plant sterols), total cholesterol levels, mean difference 0.30 mmol/l (95% confidence interval 0.12 to 0.48); decreased serum LDL cholesterol, mean difference -0.60 mmol/l (95% CI -0.89 to -0.31). Fasting serum HDL cholesterol levels were elevated, mean difference -0.04 mmol/l (95% CI -0.11 to 0.03) and serum triglyceride concentration was reduced, mean difference -0.03 mmol/l (95% CI -0.15 to -0.09), although these changes were not statistically significant. Similarly, guar gum when given as an add on therapy to bezafibrate reduced total cholesterol and LDL levels as compared to bezafibrate alone.

AUTHORS' CONCLUSIONS

No conclusions can be made about the effectiveness of a cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, for the primary outcomes: evidence and incidence of ischaemic heart disease, number of deaths and age at death,due to the lack of data on these. Large, parallel, randomised controlled trials are needed to investigate the effectiveness of a cholesterol-lowering diet and the addition of omega-3 fatty acids, plant sterols or stanols, soya protein, dietary fibers to a cholesterol-lowering diet.

Dietary treatment for familial hypercholesterolaemia

BACKGROUND

A cholesterol-lowering diet and several other dietary interventions have been suggested as a management approach either independently or as an adjuvant to drug therapy in children and adults with familial hypercholesterolemia. However, a consensus has yet to be reached on the most appropriate dietary treatment.

OBJECTIVES

To examine whether a cholesterol-lowering diet is more effective in reducing ischaemic heart disease and lowering cholesterol than no dietary intervention in children and adults with familial hypercholesterolaemia. Further, to compare the efficacy of supplementing a cholesterol-lowering diet with either omega-3 fatty acids, soya proteins, plant sterols or plant stanols.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Inborn Errors of Metabolism Trials Register.Most recent search of the Group's Inborn Errors of Metabolism Trials Register: 09 October 2009.We also searched PubMed till 01 June 2008.

SELECTION CRITERIA

Randomised controlled trials, both published and unpublished, where a cholesterol-lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trial eligibility and methodological quality and one extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

In the present update, four new trials have been added making eleven trials with a total of 331 participants eligible for inclusion. Only short-term outcomes could be assessed due to the short duration of follow up in the included studies. None of the primary outcomes, (incidence of ischaemic heart disease, number of deaths and age at death) were evaluated in any of the included studies. No significant difference was noted for the majority of secondary outcomes for any of the planned comparisons. However, a significant difference was found only for the following comparison and outcome: total cholesterol levels for the comparison between plant sterols and cholesterol-lowering diet, mean difference 0.70 (95% confidence interval 0.19 to 1.21).

AUTHORS' CONCLUSIONS

No conclusions can be made about the effectiveness of a cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, due to the lack of adequate data. Large, parallel, randomised controlled trials are needed to investigate the effectiveness of a cholesterol-lowering diet and the addition of omega-3 fatty acids, plant sterols or stanols, soya protein to a cholesterol-lowering diet.

Cholesterol-lowering potential in human subjects of fat from pigs fed rapeseed oil

The possibility of achieving blood-lipid-lowering characteristics of pig fat by increasing the content of unsaturated fat in pig feed was evaluated. Three pig feeding regimens were applied: basal feed (no added fat or vitamin E), basal feed + rapeseed oil (60 g/kg feed), and basal feed + rapeseed oil (60 g/kg) + vitamin E (200 mg/kg). Meat and meat products from the three pig groups were incorporated into diets providing 86 g pig fat/10 MJ. The diets were served to twelve healthy human male subjects for 3 weeks each in a randomised crossover design. The diets prepared from pigs fed rapeseed oil had a lower content of saturated fatty acids (approximately 9 v. 11 % of energy) and a higher content of polyunsaturated fatty acids (approximately 6 v. 4 % of energy) than the diet prepared from pigs fed the basal feed. Diets based on fat from pigs fed the rapeseed oil resulted in significantly lower (approximately 4 %, P = 0·019) total serum cholesterol concentration compared with the diet from pigs fed the basal feed. No differences were observed in LDL-, HDL- or VLDL-cholesterol, or in triacylglycerol or VLDL-triacylglycerol concentrations. Addition of vitamin E to the pig feed resulted in only a minor increase in vitamin E content in the human subjects' diet and the vitamin E content was low in all three pig diets. Plasma vitamin E concentration in the human subjects at the end of the period with diets from pigs fed rapeseed oil without vitamin E was significantly lower (P = 0·04) than in the other two diet periods. In conclusion, an increased content of rapeseed oil in pig feed changes the fatty acid composition of the pig fat in a way that has a potential to reduce blood cholesterol concentrations in human subjects. However, intake of pig fat with a higher content of unsaturated fatty acids needs to be matched by a higher dietary intake of vitamin E.

Effects of LDL enriched with different dietary fatty acids on cholesteryl ester accumulation and turnover in THP-1 macrophages

LDL enriched with either saturated, monounsaturated, n-6 polyunsaturated, or n-3 polyunsaturated fatty acids were used to study the effects of dietary fatty acids on macrophage cholesteryl ester (CE) accumulation, physical state, hydrolysis, and cholesterol efflux. Incubation of THP-1 macrophages with acetylated LDL (AcLDL) from each of the four diet groups resulted in both CE and triglyceride (TG) accumulation, in addition to alterations of cellular CE, TG, and phospholipid fatty acyl compositions reflective of the individual LDLs. Incubation with monounsaturated LDL resulted in significantly higher total and CE accumulation when compared with the other groups. After TG depletion, intracellular anisotropic lipid droplets were visible in all four groups, with 71% of the cells incubated with monounsaturated AcLDL containing anisotropic lipid droplets, compared with 30% of cells incubated with n-3 AcLDL. These physical state differences translated into higher rates of both CE hydrolysis and cholesterol efflux in the n-3 group. These data suggest that monounsaturated fatty acids may enhance atherosclerosis by increasing both cholesterol delivery to macrophage foam cells and the percentage of anisotropic lipid droplets, while n-3 PUFAs decrease atherosclerosis by creating more fluid cellular CE droplets that accelerate the rate of CE hydrolysis and the efflux of cholesterol from the cell.

Lipid-lowering effects of a modified butter-fat: a controlled intervention trial in healthy men

OBJECTIVE

To investigate the lipid-lowering potential of a butter-fat modified through manipulations in bovine feeding to increase the unsaturated:saturated fatty acid ratio.

DESIGN

Double-blind, randomised, cross-over intervention trial.

SETTING

University of Auckland Human Nutrition Unit, New Zealand.

SUBJECTS

Twenty healthy, male subjects.

INTERVENTION

A residential trial in which all foods and beverages were provided during two intervention periods, comprising 3 weeks of high unsaturated 'modified' vs. 3 weeks of saturated 'control' butter feeding separated by a 4 week washout. Diets were of typical composition of 39 percentage energy (en%) fat (20 en% butter-fat), 48 en% CHO, 13 en% protein.

RESULTS

There was a significant decrease in both total (P<0.05, -7.9%) and LDL-cholesterol (P<0.01, -9.5%) during modified butter feeding. There was no significant effect of treatment on a range of other risk factors including HDL-cholesterol, triglyceride, apolipoprotein A or B, nonesterified fatty acids (NEFA), haemostatic clotting factor VII and fibrinogen or glucose (P>0.05). Subjects were maintained in energy balance and there was no significant change in body weight during intervention. Butter-fat composition alone differed between treatments.

CONCLUSIONS

A significant improvement in cardiovascular risk can be achieved by moderate changes in dietary fatty acid profile, achieved through a common and well accepted food source, butter-fat.

Dietary treatment for familial hypercholesterolaemia

BACKGROUND

Familial hypercholesterolaemia is an inherited disorder characterised by a raised blood cholesterol, the presence of xanthomatosis and premature ischaemic heart disease. The aim of treatment is the reduction of blood LDL cholesterol concentrations in order to reduce the risk of ischaemic heart disease. Current treatment is based on a cholesterol lowering diet alone or in combination with drug therapy. Many of the drugs found to be effective in treating adults with this disease are not licensed for use in children, therefore diet is the main treatment of children with familial hypercholesterolaemia. In addition to the cholesterol-lowering diet, several other dietary interventions have been suggested and consensus has yet to be reached on the most appropriate dietary treatment for children and adults with familial hypercholesterolaemia.

OBJECTIVES

To examine the evidence that in children and adults with familial hypercholesterolaemia, a cholesterol lowering diet is more effective at lowering cholesterol and reducing incidence of ischaemic heart disease than no intervention or than other dietary interventions.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Trials Register, a specialist trials register which comprises references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings. Additional studies were identified from handsearching the Journal of Inherited Metabolic Disease (from inception, 1978 to 2000) and from the reference lists of identified studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs), both published and unpublished, where a cholesterol lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention. Trials which include patients with familial hypercholesterolaemia alongside patients with non-familial hypercholesterolaemia were only included if the group of familial patients was well defined and the results for these patients were available.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the trial eligibility and methodological quality and one reviewer extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

Only short term outcomes could be assessed in this review due to the length of the five eligible studies. Compliance to treatment, quality of life, mortality and evidence of ischaemic or atheromatous disease were not assessed in the studies identified. No differences were found between the cholesterol-lowering diet and all other diets for all of the short term outcomes assessed.

REVIEWER'S CONCLUSIONS

No conclusions can be made about the effectiveness of the cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, due to the lack of adequate data. A large, parallel, randomised controlled trial is needed to investigate the effectiveness of the cholesterol-lowering diet and other dietary interventions for FH. It is also possible that data from trials including subjects with both familial and non-familial hypercholesterolaemia could alter the results of future updates of this review and until further evidence is available current dietary treatment of FH should continue to be observed and monitored with care.

Deuterium uptake and plasma cholesterol precursor levels correspond as methods for measurement of endogenous cholesterol synthesis in hypercholesterolemic women

To assess the validity of two techniques used to measure human cholesterol synthesis, the rate of uptake of deuterium (D) into plasma free cholesterol (FC), and plasma cholesterol precursor (squalene, lanosterol, desmosterol and lathosterol) levels were compared in 14 women [65-71 yr with low density lipoprotein-cholesterol (LDL-C) > or = 3.36 mmol x L(-1)]. Subjects consumed each of six diets for 5-wk periods according to a randomized crossover design. The experimental diets included a baseline diet (39% energy as fat, 164 mg chol x 4.2 MJ(-1)) and five reduced-fat diets (30% of energy as fat), where two-thirds of the fat was either soybean oil; squeeze, tub or stick margarines; or butter. Fractional and absolute synthesis rates (FSR and ASR) of FC were determined using the deuterium incorporation (DI) method, while cholesterol precursor levels were measured using gas-liquid chromatography. Data were pooled across diets for each variable and correlation coefficients were calculated to determine if associations were present. There was good agreement among levels of the various cholesterol precursors. In addition, FSR in pools/d (p x d(-1)) and ASR in grams/d (g x d(-1)) were strongly associated with lathosterol (r= 0.72 and 0.71, P= 0.0001), desmosterol (r= 0.75 and 0.75, P = 0.0001), lanosterol (r = 0.67 and 0.67), and squalene (r = 0.69 and 0.68) when levels of the precursors were expressed as micromol x mmol(-1) C. Significant but lower correlations were observed between the D uptake and plasma cholesterol precursor levels when the latter were expressed in absolute amounts (micromol x L(-1)). The wide range of fatty acid profiles of the experimental diets did not influence the degree of association between methods. In conclusion, the DI method and levels of some cholesterol precursors correspond as methods for shortterm measurement of cholesterol synthesis.

Dietary stearic acid reduces cholesterol absorption and increases endogenous cholesterol excretion in hamsters fed cereal-based diets

The observation that dietary stearic acid does not raise plasma cholesterol concentration is well documented, although the regulating mechanisms are not completely understood. Therefore, we examined the effect of dietary stearic acid on cholesterol absorption and sterol balance using male Syrian hamsters fed modified NIH-07 cereal-based diets selectively enriched in palmitic acid (16:0), stearic acid (18:0), trans fatty acid (18:1t), cis oleic acid (18:1c) or linoleic acid (18:2). All diets contained 17 g/100 g total fat and 0.05 g/100 g cholesterol; the five fat blends were enriched 30% with the fatty acid of interest above a constant fatty acid background. Cholesterol absorption efficiency was 50-55% in all treatment groups except for the 18:0 group, in which cholesterol absorption was significantly reduced to 21%. Plasma total cholesterol concentration was significantly lower in the 18:0 group compared to the 16:0 group. Fecal neutral steroid excretion was significantly greater in hamsters fed the high 18:0 diet compared to the other treatment groups. After accounting for unabsorbed dietary cholesterol, endogenous cholesterol excretion was about 100% higher in the 18:0 group. Consequently, the calculated rate of whole body cholesterol synthesis was significantly increased by dietary 18:0. Bile acid excretion accounted for only 12-20% of total sterol output by the hamsters in this study. Thus, the data suggest that reduced plasma cholesterol concentration in hamsters fed high 18:0 diets may be influenced by reduced cholesterol absorption and increased excretion of endogenous cholesterol.

Use of hierarchical models for meta-analysis: experience in the metabolic ward studies of diet and blood cholesterol

Overviews that combine single effect estimates from published studies generally use a summary statistic approach where the effect of interest is first estimated within each study and then averaged across studies in an appropriately weighted manner. Combining multiple regression coefficients from publications is more problematic, particularly when there are differences in study design and inconsistent reporting of effect sizes and standard errors. This paper describes the use of a hierarchical model in such circumstances. Its use is illustrated in a meta-analysis of the metabolic ward studies that have investigated the effect of changes in intake of various dietary lipids on blood cholesterol. These studies all reported average blood cholesterol for groups of individuals who were studied on one or more diets. Thirty-one studies had randomized cross-over designs, 12 had matched parallel group designs, 12 had non-randomized Latin square designs and 16 had other uncontrolled designs. The hierarchical model allowed the different types of comparison (within-group between-diet, between matched group) that were made in the various studies to each contribute to the overall estimates in an appropriately weighted manner by distinguishing between-study variation, within-study between-matched-group variation and within-group between-diet variation. The hierarchical models do not require consistent specification of effect sizes and standard errors and hence have particular utility in combining results from published studies where the relationships between a dependent variable and two or more predictors have been investigated using heterogeneous methods of analysis.

Diet fat saturation and feeding state modulate rates of cholesterol synthesis in normolipidemic men

To determine whether diets differing in fats affect cholesterol synthesis in normal individuals, nine men were randomly assigned to three groups that received three diets in a crossover design for 2 wk. Diets were either monounsaturated (MONO), polyunsaturated (POLY), or saturated (SAT). Subjects then drank a dose of deuterium oxide, and unesterified cholesterol fractional synthesis rates (FSR) were calculated during consecutive fed and unfed periods. Absolute synthesis was calculated as the product of FSR and pool size, the latter obtained from a decay curve following a [4-(14)C]cholesterol injection. Serum cholesterol concentrations varied with each diet consumed (P = 0.001); the SAT diet produced the highest and the POLY diet the lowest. Triglyceride concentrations were highest when subjects consumed the SAT diet and lowest with the POLY diet (P = 0.03); values obtained with the MONO diet did not differ significantly from those seen otherwise. HDL cholesterol concentrations were lowest when the SAT diet was consumed, highest when subjects were fed the MONO diet (P = 0.05), and midway but not significantly different with the POLY diet. Cholesterol FSR were greater when subjects consumed (P = 0.001) rather than not, and FSR during 12-h periods were greater (P = 0.045) when subjects ate the POLY diet rather than the SAT diet. Absolute synthesis was also greater (P = 0.04) when subjects were fed, but did not differ with fat type (P = 0.789). Results suggest that cholesterol synthesis is greater when men are fed than when they are not fed, and reduced synthesis is not responsible for the effect of different fats on cholesterol concentrations.

Relations between nutrient intake and serum lipid and apolipoprotein levels

OBJECTIVE

To study the relation between diet and serum lipid and apolipoprotein levels in a large, homogeneous group of Spanish children.

DESIGN

Survey.

SETTING

Eleven schools chosen at random in Madrid City and the surrounding area.

SUBJECTS AND METHODS

Subjects comprised 1682 children, 2 to 12 years of age. Dietary data were obtained with a 24-hour record performed by the child's main caregiver. For statistical analysis the sample was divided into tertiles on the basis of calorie-adjusted consumption of dietary components.

RESULTS

Children in the highest tertile of total fat consumption, compared with children in the lowest tertile, had significantly higher mean serum levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), apolipoprotein A-I (Apo A) and apolipoprotein B-100 (Apo B). When compared with children in the lowest tertile, children in the highest tertile of saturated fat consumption had significantly higher mean levels of TC, LDL-C, and Apo B, and lower mean levels of HDL-C and Apo A. Children in the highest tertile of monounsaturated fat consumption, compared with children in the lowest tertile, had significantly higher mean levels of HDL-C and Apo A, and lower mean levels of TC, LDL-C, and Apo B.

CONCLUSIONS

Our findings suggest that diet composition strongly influences lipid profile in children and point out the importance of monounsaturated fatty acids as modulators of serum lipid and apolipoprotein levels.

Relationships of dietary fat consumption to serum total and low-density lipoprotein cholesterol in hispanic preschool children

BACKGROUND

Studies of the relationship between dietary fat intake and serum lipids in young children have yielded inconclusive results. We studied this relationship in 108 Hispanic children ages 4-5 years.

METHODS

Four 24-hr recalls approximately 3 months apart and two Willett semiquantitative food frequency questionnaires approximately 6 months apart were obtained by interviewing the children's mothers. Diet measures were averaged for the multiple administrations of each of these instruments.

RESULTS

Based on the 24-hr recalls, children in the highest tertile of total fat consumption (36.2% of total calories) compared with the lowest tertile (30.2% of total calories) had mean total serum cholesterol of 4.32 mmol/liter (167 mg/dl) vs 3.91 mmol/liter (151 mg/d) (test for linear trend across tertiles, P less than 0.05) and mean low-density lipoprotein cholesterol of 2.74 mmol/liter (106 mg/dl) vs 2.29 mmol/liter (89 mg/dl) (test for linear trend, P less than 0.01). Children in the highest tertile of saturated fat consumption (14.6% of total calories) compared with the lowest tertile (11.2% of total calories) had mean total serum cholesterol of 4.39 mmol/liter (170 mg/dl) vs 3.97 mmol/liter (154 mg/dl) (test for linear trend, P less than 0.05) and mean low-density lipoprotein cholesterol of 2.80 mmol/liter (108 mg/dl) vs 2.35 mmol/liter (91 mg/dl) (test for linear trend, P less than 0.01). These relationships remained significant when calorie-adjusted nutrient intakes were examined and after adjustment in multiple linear regression models for age, sex, and body mass index, with the exception of the association of calorie-adjusted total fat with total serum cholesterol level (P = 0.07). Similar results were obtained using the Willett questionnaires.

CONCLUSIONS

These findings indicate that dietary fat, particularly saturated fat consumption, is an important correlate of blood lipid levels in preschool children. These are also the first reported data indicating that the Willett questionnaire, as a method for measuring the atherogenic components of diet, has criterion-related validity in young children.

A review of five major community-based cardiovascular disease prevention programs. Part I: Rationale, design, and theoretical framework

Major community-based cardiovascular disease prevention programs have been conducted in North Karelia, Finland; the state of Minnesota; Pawtucket, Rhode Island; and in three communities and more recently in five cities near Stanford, California. These primary prevention programs aim to reduce cardiovascular disease incidence by reducing risk factors in whole communities. These risk factors are smoking, high blood cholesterol, diet high in cholesterol and saturated fat, hypertension, sedentary lifestyle, and obesity. This strategy may be contrasted with secondary prevention programs directed at patients who already have symptomatic cardiovascular disease and "high risk" primary prevention programs directed at individuals found through screening to have one or more risk factors. The design of the five major programs is similar in that intervention communities are matched for purposes of evaluation with nearby comparison communities. Underlying these programs are theories of community health education, social learning, communication, social marketing, and community activation, as well as more traditional biomedical and public health disciplines. This is Part I of a two-part article.

Reduction of serum lipoproteins in man by the oral administration of a prostaglandin analogue (enprostil)

Retrospective analysis of ulcer healing trials utilizing enprostil, a synthetic dehydroprostaglandin E2 analogue, has demonstrated a 10% or greater reduction in total serum cholesterol in 64%, 64% and 67%, respectively, of hypercholesterolemic subjects receiving the drug in doses of 70 micrograms, 35 micrograms, and 7 micrograms bid, respectively. Only 16% of subjects receiving placebo exhibited a similar reduction (P less than 0.05). The median percent changes for hypercholesterolemic patients receiving enprostil 70 micrograms, 35 micrograms, or 7 micrograms bid, and placebo were -17%, -13%, -11%, respectively, while the median percent change for those on placebo was 0% (P less than 0.05). Eight normocholesterolemic subjects participated in a double-blind crossover study comparing enprostil 70 micrograms/d with its placebo. Nine days of enprostil administration was associated with reductions in total serum cholesterol (-16%) and apolipoprotein B (-16%) and with significant reductions from baseline for LDL-cholesterol (-22%), the LDL/HDL-cholesterol ratio (-13%), and the ratio of serum apolipoprotein B to apolipoprotein A-1 (-12%). Relative to placebo, mean HDL-cholesterol, total triglycerides, and apolipoprotein A-1 concentrations remained unchanged. Daily oral administration of microgram quantities of enprostil is associated with reductions in total cholesterol, LDL-cholesterol, and apolipoprotein B suggesting therapeutic potential of this synthetic prostaglandin for the treatment of hyperlipidemia.

Regulation of indices of cholesterol synthesis in human mononuclear leukocytes by dietary cholesterol and fat saturation

The responses of 2 indices of cholesterol synthesis, 3-hydroxy-3-methylglutaryl-CoA reductase activity and incorporation of [14C]acetate into sterols, in mononuclear leukocytes freshly isolated from peripheral blood to variation in the ratio of saturated to unsaturated fat (S:U) and the amount of cholesterol absorbed from the diet were examined in 24 free-living men. Increasing S:U was associated with increasing plasma cholesterol level (r = 0.27, P = 0.03) and increasing reductase activity in leukocytes (r = 0.60, p less than 0.001). This finding is consistent with the hypothesis that saturated fat decreases the flux of cholesterol from plasma into cells thereby releasing reductase from product feedback inhibition. Reductase activity, after controlling for the effect of S:U, was negatively correlated with absorbed cholesterol from sources other than eggs (r = 0.42, P = 0.02). Surprisingly, change in reductase activity was positively correlated with change in absorbed cholesterol upon eating eggs (r = 0.49, P = 0.008). Sterol labeling was negatively correlated with absorbed cholesterol from all sources including eggs (r = -0.64, P less than 0.001) and was uncorrelated with S:U. Reductase activity and sterol labeling responded in parallel to cholesterol in foods other than eggs but not to egg feeding nor to S:U, thus it is unclear which test best reflects endogenous sterol synthesis in these cells.

Relationship between changes in plasma lipoprotein concentrations and fecal steroid excretion in man during consumption of four experimental diets

Limited information is available on the mechanism by which changes in nutrient intake influence plasma lipids. We compared the effects on plasma lipoprotein levels of 3 dietary modifications involving changes in total fat intake (27-40% of calories), cholesterol intake (100-250 mg/1000 kcal), the dietary polyunsaturated to saturated fatty acid ratio (0.3-1.0) and intake of vegetable-derived fiber and protein. On these 3 diets, plasma low density lipoprotein was reduced by 26-34%. Fecal bile acid excretion was similar on all diets (363-379 mg/day). There was no alteration in fecal bile acid output associated with an increase in polyunsaturated or total fat intake. Sterol balance became significantly more negative during consumption of only 1 of the 3 cholesterol-lowering diets. The observed reduction in plasma cholesterol levels was not associated with an increase in fecal bile acid output suggesting that diet-induced changes in circulating cholesterol are not maintained by an increase in sterol turnover but may reflect alterations in hepatic cholesterol and lipoprotein synthesis.

Hypo-atherogenic effect of dietary corn oil exceeds hypo-cholesterolemic effect in swine

Three groups of young swine were fed semi-purified diets enriched in fat and cholesterol for 90 days. In one group 40% of calories were from butter; in another 40% were from corn oil; in a third group 20% were from corn oil. Mean serum cholesterol values were respectively 530, 458 and 400 mg/dl. Amounts of atherosclerosis in the abdominal aortas expressed as mean number of nuclear profiles per cross-section were respectively 1611, 734 and 585; expressed as mean lesion area per cross section 46.7, 21.4 and 19.4 mm2 X 10(2). All differences between the butter group and either of the two corn oil groups were statistically significant. We found that intimal response to the butter containing diet was significantly greater than to the corn oil containing diet for equivalent hypercholesterolemic response. We present detailed statistical validation of the disproportionately larger intimal response to butter containing diet. Furthermore, we suggest that estimates of comparative atherogenic risk of food fats based on response of serum cholesterol may mask important atherogenic differences.

The effect of dietary saturated fat versus polyunsaturated fat on serum cholesterol and phospholipid concentrations in rabbits with partial ileal bypass

Rabbits were fed semipurified diets containing either corn oil or coconut fat. Dietary coconut fat significantly elevated serum total cholesterol and phospholipid concentrations. Rabbits with partial ileal bypass (PIB) had significantly lower serum cholesterol and phospholipid values, irrespective of whether the diet contained corn oil or coconut fat. The effect on serum lipids of the type of fat was similar in control and PIB animals. Since PIB rabbits are known to excrete extremely high amounts of steroids with the feces, we suggest that our data point to a lack of interaction of the type of dietary fat with the fecal excretion of steroids.

Effect of dietary fat supplement on lipid metabolism of Holstein Heifers

Twenty Holstein heifers were fed four rations containing 0, 10, 20, and 30% whole sunflower seed as a source of dietary fat. All rations consisted of alfalfa hay, sunflower hulls, and grain mixtures and were isonitrogenous at 12% crude protein and isocaloric at 2.6 Mcal metabolizable energy per kilogram dry matter. Average body weight gains were not different among treatment groups. Heifers fed sunflower seed (fat) diets consumed less total dry matter, significantly improving growth efficiency (gain/feed). Concentration of total lipid and urea nitrogen in blood serum were increased whereas glucose was depressed with higher amounts of dietary fat. High fat diets (20 and 30%) elevated total lipid, triglyceride, and nonesterified fatty acids in the blood. Total and free cholesterol in blood also were increased, but high density lipoprotein-cholesterol remained unchanged with increasing concentration of dietary fat. Dietary fat was correlated positively with lipid components of blood serum and negatively with glucose.

Modes of action of lipid-lowering diets in man: studies of apolipoprotein B kinetics in relation to fat consumption and dietary fatty acid composition

The mechanisms by which dietary fat influences fasting plasma lipid concentrations have been investigated in hyperlipidaemic subjects. The synthetic and fractional catabolic (FCR) rates of the apoprotein B (apo B) of very-low density (VLDL) and low-density (LDL) lipoproteins were measured using radioiodinated autologous lipoproteins. Reductions of LDL concentration in eight subjects during low-fat (25% of energy) diets were largely explained by diminished synthesis (-20%, P less than 0.02), and possibly also by an increased FCR (+15%, P = 0.05) of LDL, compared with observations made during a high-fat (45% of energy) diet of similar fatty acid composition. VLDL apo B synthesis and FCR were not significantly altered. When a diet rich in polyunsaturated fatty acids was exchanged for one high in saturated fatty acids (fat providing 45% of energy on both occasions) in four subjects, the synthetic rates of both VLDL apo B (-31%, P less than 0.02) and LDL apo B (-23%, P less than 0.10) were reduced while their FCRs were unchanged.

The comparative reductions of the plasma lipids and lipoproteins by dietary polyunsaturated fats: salmon oil versus vegetable oils

The lower plasma lipid levels and lower incidence of atherosclerotic diseases in Greenland Eskimos suggested that the unusual fatty acids present in their diet of seal and fish may be anti-atherogenic. These fatty acids are eicosapentaenoic (C20:5) and docosahexaenoic (C22:6) acids and are of the omega-3 fatty acid family. We have compared a salmon oil diet containing high levels of these unique fatty acids to a control diet high in saturated fat and to a vegetable oil diet high in linoleic acid (C18:2). All diets contained 40% of the total calories as fat and 500 mg of cholesterol; they differed only in fatty acid composition. In 4 wk the salmon oil diet reduced plasma cholesterol levels from 188 to 162 mg/dl (p less than 0.001) and triglyceride levels from 77 to 48 mg/dl (p less than 0.005). LDL and VLDL cholesterol levels changed from 128 to 108 and 13 to 8 mg/dl (p less than 0.005), respectively. HDL cholesterol levels did not change. The vegetable oil diet caused similar decreases in cholesterol levels but did not lower triglyceride levels. The omega-3 fatty acids comprised up to 30% of the total fatty acids in each plasma lipid class after the salmon diet. Fish oils contain fatty acids which may be metabolically unique and potentially useful in the control of both hypercholesterolemia and hypertriglyceridemia.

Effects of dietary cholesterol and fatty acids on plasma lipoproteins

The effects of dietary cholesterol and fatty acids on low density and high density lipoproteins (LDL and HDL) were studied in 20 young men. After 2-3 wk of evaluations on ad lib. diets, basal diets, which consisted of 15% protein, 45% carbohydrates, 40% fat, and 300 mg/day of cholesterol, were given for 4-5 wk (Basal). The ratio of dietary polyunsaturated to saturated fatty acids (P/S) for different groups of subjects were 0.25, 0.4, 0.8, or 2.5. 750 and 1,500 mg/d of cholesterol were added to the basal diets as 3 and 6 eggs, respectively. Total cholesterol and LDL cholesterol were lower in all subjects on the basal diets than on the ad lib. diets. Addition of 750 mg cholesterol to the diet with P/S = 0.25-0.4 raised LDL cholesterol by 16 +/- 14 mg/dl to 115% of basal diet values (n = 11, P less than 0.01); 1,500 mg increased LDL cholesterol by 25 +/- 19 mg/dl to 125% (n = 9, P less than 0.01). On the diet with P/S = 0.8, 750 mg produced insignificant increases in LDL cholesterol, but 1,500 mg produced increases of 17 +/- 22 mg/dl to 115% of basal (n = 6, P less than 0.02). On the P/S = 2.5 diet, neither 750 nor 1,500 mg produced significant changes. Thus, both the cholesterol contents and P/S ratios of diets were important in determining LDL levels. The lipid and apoprotein compositions, flotation rates, molecular weights, and binding by cellular receptors of LDL were virtually unchanged by the addition of cholesterol to the diets high in saturated fat. These diets, therefore, caused an increase in the number of LDL particles of virtually unchanged physical and biological properties. On the diet with low P/S ratio, HDL2 rose, whereas this effect was absent on diets with high P/S ratios. The response of LDL to dietary manipulations is consonant with epidemiologic data relating diets high in cholesterol and saturated fat to atherogenesis. The response of HDL2, however, is opposite to that of its putative role as a negative risk factor. Further work is needed to clarify this interesting paradox.

Is increased cholesterol excretion the link between low serum cholesterol and colon cancer?

The data from several different patient groups consuming high-fat, high-cholesterol diets suggest that decreased serum cholesterol may be linked with increased cholesterol excretion. Since cholesterol or its degradation products have been implicated in the pathogenesis of colon cancer, an inverse relationship between serum and biliary cholesterol levels could explain the statistical relationship between low serum cholesterol and colon cancer observed in recent prospective studies.

Low density and high density lipoprotein kinetics and sterol balance in vegetarians

Vegetarians have lower than average plasma lipid levels. Possible mechanisms were studied by measuring the kinetics of LDL-B protein and HDL-AI protein in 7 young male vegetarians and 6 omnivorous control subjects; sterol balances were also determined in a further study with the 6 additional control subjects whose intake of cholesterol was low. Plasma total cholesterol, LDL cholesterol and LDL-B protein were significantly lower in the vegetarians and plasma AI protein concentrations also tended to be lower. The flux or production of LDL was significantly lower, 9.1 +/- 2.3 mg/kg/d (mean +/- SD) compared to 11.8 +/- 0.6 mg/kg/d in the controls and appeared to explain the low levels of LDL. The fractional removal rate of HDL-AI protein was significantly greater in the vegetarians (0.043 +/- 0.011 versus 0.027 +/- 0.011 for the fractions of pool 1 cleared per hour) and appeared to account for the low plasma AI levels. In the second study, bile acid excretion was significantly lower in the vegetarians and estimated cholesterol synthesis was in the low normal range. Low rates of LDL-B protein formation have been reported in other subjects with low LDL cholesterol concentrations and in the vegetarians presumably reflect the composite of several dietary factors.

Swine in atherosclerosis research--Development of an experimental animal model and study of the effect of dietary fats on cholesterol metabolism

The effect of saturated (beef tallow) and polyunsaturated (corn oil) fat diets on plasma cholesterol, bile flow and composition, and excretion of fecal steroids, was studied in 5 female and 6 male miniature swine. The animals were fitted with a modified Baldwin T-tube in the common bile duct for bile sampling and a catheter in the duodenum for reinfusion. Plasma cholesterol levels were increased by beef tallow and decreased by corn oil. Both fats caused an increase in the secretion of bile, biliary lipids and bile acid pool size. The increases were significant when the source of fat was corn oil. The fecal neutral steroid excretion measured in the male swine was increased by both fats. However, only the polyunsaturated fat diet caused a significant increase in the fecal acidic steroid excretion.

Treatment of hypercholesterolaemia with oral lecithin

An open clinical trial was performed to evaluate the plasma cholesterol-lowering potential of oral lecithin in large doses (20--30 g/day), with or without supplementary clofibrate. Three healthy subjects and seven patients with hypercholesterolaemia were studied over periods ranging from eight weeks to 11 months. In one-third of healthy subjects and in 3/7 patients, lecithin therapy led to a significant fall in plasma cholesterol concentration (10--18% fall). Combination of lecithin and clofibrate in two of the patients led to still lower plasma cholesterol levels (21 and 22% fall). Most of the change in plasma cholesterol concentration, when it occurred, was due to a reduction in beta lipoproteins. Evidence is presented that oral lecithin may reduce plasma cholesterol levels by acting as a source of linoleic acid.

National views: Australia

The Austrialian scene in this area would seem to show the same features, and haze, as are found in many other countries. There is general recognition of atherosclerotic problems, of the common risk factors and of the need for prevention. Learned and informed bodies such as The Australian Academy of Science and The National Heart Foundation of Australia have made recommendations along familiar lines, involving especially dietary changes, as preventive measures. The basis for these recommendations has been a general review of the subject and doses not include anything uniquely Australian. The admission of uncertainty about causes and prevention, awareness of controversy, confusion, ignorance and a natural reluctance to change habits no doubt contribute to popular disregard for the recommendations at the present time.