Effects Of Dietary Fat Quality Research Articles

Lipidome changes due to improved dietary fat quality inform cardiometabolic risk reduction and precision nutrition

Current cardiometabolic disease prevention guidelines recommend increasing dietary unsaturated fat intake while reducing saturated fats. Here we use lipidomics data from a randomized controlled dietary intervention trial to construct a multilipid score (MLS), summarizing the effects of replacing saturated fat with unsaturated fat on 45 lipid metabolite concentrations. In the EPIC-Potsdam cohort, a difference in the MLS, reflecting better dietary fat quality, was associated with a significant reduction in the incidence of cardiovascular disease (−32%; 95% confidence interval (95% CI): −21% to −42%) and type 2 diabetes (−26%; 95% CI: −15% to −35%). We built a closely correlated simplified score, reduced MLS (rMLS), and observed that beneficial rMLS changes, suggesting improved dietary fat quality over 10 years, were associated with lower diabetes risk (odds ratio per standard deviation of 0.76; 95% CI: 0.59 to 0.98) in the Nurses’ Health Study. Furthermore, in the PREDIMED trial, an olive oil-rich Mediterranean diet intervention primarily reduced diabetes incidence among participants with unfavorable preintervention rMLS levels, suggestive of disturbed lipid metabolism before intervention. Our findings indicate that the effects of dietary fat quality on the lipidome can contribute to a more precise understanding and possible prediction of the health outcomes of specific dietary fat modifications.

Replacing saturated fatty acids with polyunsaturated fatty acids increases the abundance of Lachnospiraceae and is associated with reduced total cholesterol levels-a randomized controlled trial in healthy individuals.

BackgroundImproving dietary fat quality strongly affects serum cholesterol levels and hence the risk of cardiovascular diseases (CVDs). Recent studies have identified dietary fat as a potential modulator of the gut microbiota, a central regulator of host metabolism including lipid metabolism. We have previously shown a significant reduction in total cholesterol levels after replacing saturated fatty acids (SFAs) with polyunsaturated fatty acids (PUFAs). The aim of the present study was to investigate the effect of dietary fat quality on gut microbiota, short-chain fatty acids (SCFAs), and bile acids in healthy individuals. In addition, to investigate how changes in gut microbiota correlate with blood lipids, bile acids, and fatty acids.MethodsSeventeen participants completed a randomized, controlled dietary crossover study. The participants received products with SFAs (control) or PUFAs in random order for three days. Fecal samples for gut microbiota analyses and fasting blood samples (lipids, fatty acids, and bile acids) were measured before and after the three-day intervention.ResultsOf a panel of 40 bacteria, Lachnospiraceae and Bifidobacterium spp. were significantly increased after intervention with PUFAs compared with SFAs. Interestingly, changes in Lachnospiraceae, as well as Phascolarlactobacterium sp. and Eubacterium hallii, was also found to be negatively correlated with changes in total cholesterol levels after replacing the intake of SFAs with PUFAs for three days. No significant differences in SCFAs or bile acids were found after the intervention.ConclusionReplacing SFAs with PUFAs increased the abundance of the gut microbiota family of Lachnospiraceae and Bifidobacterium spp. Furthermore, the reduction in total cholesterol after improving dietary fat quality correlated with changes in the gut microbiota family Lachnospiraceae. Future studies are needed to reveal whether Lachnospiraceae may be targeted to reduce total cholesterol levels.Trial registrationThe study was registered at Clinical Trials (https://clinicaltrials.gov/, registration identification number: NCT03658681).

Eucaloric diets enriched in palm olein, cocoa butter, and soybean oil did not differentially affect liver fat concentration in healthy participants: a 16-week randomized controlled trial

Effects of dietary fat quality on liver fat remain to be elucidated. Inconsistent evidence may be influenced by fatty acid saturation, chain-length, and regio-specificity within triacylglycerol (TAG) molecules. We aimed to compare eucaloric diets enriched in palm olein (POo), cocoa butter (COB), and soybean oil (SBO) on liver fat concentration in healthy participants. Secondary outcomes included visceral (VAT) and abdominal subcutaneous (aSCAT) adipose tissue, plus other obesity and cardiometabolic health outcomes. Eighty-three healthy participants (20-45 y, BMI 18.5-27.5 kg/m2) commenced and 64 completed a 16-wk randomized parallel intervention, preceded by a 2-wk run-in. Participants consumed identical eucaloric background diets differing in test fats [contributing 20% total energy intake (%E)], providing 33%E total fat with the following ratios for PUFAs/SFAs/MUFAs: POo, 4.2/13.5/15%E; SBO, 14.4/8.8/9.4%E; COB, 2.3/19.5/11%E. Liver fat and abdominal adiposity were measured at weeks 0 and 16 using 1H-magnetic resonance spectroscopy/imaging; all other outcomes were measured at 0, 4, 8, 12, and 16 wk. Fat quality did not affect liver fat concentration, VAT, aSCAT, obesity indexes, blood pressure, liver enzymes, leptin, or fasting glucose. Body fat mass decreased with SBO and COB compared with POo. SBO decreased serum total cholesterol (TC), LDL cholesterol, and TC:HDL cholesterol relative to POo [estimated marginal mean (95% CI) differences: -0.57 (-0.94, -0.20) mmol/L; -0.37 (-0.68, -0.07) mmol/L; and -0.42 (-0.73, -0.11) mmol/L, respectively]. No diet differences were observed on HDL cholesterol, TAG, apoA1, apoB, apoB:apoA1, or fecal free fatty acids (FFAs), except for lower FFA pentadecanoic acid (15:0) with COB than with SBO and POo. In healthy adults, when consumed as part of eucaloric typical Australian diets, 3 different dietary fat sources did not differentially affect liver fat concentration and amounts of adipose tissue. Effects on serum lipids were inconsistent across lipid profiles. The findings must be confirmed in metabolically impaired individuals before recommendations can be made.

The correlation between dietary fat quality indices and lipid profile with Atherogenic index of plasma in obese and non-obese volunteers: a cross-sectional descriptive-analytic case-control study

Background and aimAbnormalities in lipid metabolism are commonly observed in patients who were obese. Alongside dyslipidemia, one of the markers in predicting the risk of cardiovascular disease is the Atherogenic Index of Plasma (AIP), which is related to dietary intake. Healthy fat quality indices might affect on AIP. The purpose of this study is to find the possible relationship between dietary fat quality, and AIP and comparison of these indices among obese and non-obese volunteers.MethodsThis study was a cross-sectional descriptive-analytic case-control study with 157 normal and overweight and obese volunteers (n = 71 normal, Age: 38.90 ± 10.976 vs n = 86 overweight/obese, Age: 38.60 ± 9.394) in the age range of 18–65 years. Food intake was measured using FFQ, anthropometric indices (weight, height, body mass index and waist to hip ratio), body composition (visceral fat level, total body water, body fat mass), and lipid profile were measured.ResultsBased on the present results, comparable biochemical parameters including TC (P = 0.580), TG (P = 0.362), LDL (P = 0.687) and HDL (P = 0.151) among overweight/obese volunteers as compared to normal ones were noticed. Effects of dietary fat quality, including Atherogenicity (AI) and Thrombogenicity (TI) hypo/hypercholesterolemic ratio (h/H), the Cholesterol-Saturated Fat Index (CSI) showed significantly higher AI (P = 0.012) in the overweight/obese group as compared to the normal group. Whereas, h/H (P = 0.034) and ω-6/ω-3 ratio (P = 0.004) were significantly higher in normal-weight volunteers. There was a positive correlation between AI, TI, CSI, SFA, MUFA, PUFA and ω-6/ω-3 ratio with AIP and negative correlation between h/H with AIP in both groups. Despite the significances of these correlations no strong relation was observed by doing multiple regression among normal and overweight/obese groups (R2 = 0.210, R2 = 0.387).ConclusionsIn summary, the present work proposes a direct relationship between dietary fat quality, increased BMI, and lipid abnormalities with AIP. Nevertheless, further large-scale studies are required to sustain a clear conclusion in this wish.

Effects of dietary fat quality on metabolic endotoxaemia: a systematic review.

In this systematic review, we critically evaluated human clinical trials that assessed the effects of dietary fat quality on metabolic endotoxaemia. The studies were selected from three databases (PubMed, Scopus and Cochrane Library), and the keywords were defined according to the Medical Subject Headings indexing terminology. Two authors searched independently, according to the pre-defined selection criteria. Quality and risk assessment of bias for each selected study were also evaluated. The results of the included studies demonstrated associations between higher SFA intake and increased postprandial lipopolysaccharide (LPS) concentrations. On the other hand, after the consumption of PUFA, bloodstream LPS concentrations were lower. However, in none of the long-term studies, the consumption of dietary fats did not seem to exert effects on LPS concentration. Hence, SFA seem to act as a risk factor for transient increase in endotoxaemia, while PUFA demonstrated exerting a protective effect. Taken together, the evidence suggests that the dietary fatty acid profile may influence bloodstream endotoxin concentrations through modulation of factors such LPS clearance, alkaline phosphatase activity, bile acid metabolism, intestinal permeability and intestinal microbiota composition.

Colonic bacterial composition is sex-specific in aged CD-1 mice fed diets varying in fat quality.

Evidence suggests that sex influences the effect of diet on the gut bacterial composition, yet, no studies have been performed assessing dietary fatty acid composition (i.e., fat quality) in this context. This study examined the effect of dietary fat quality on colonic bacterial composition in an aged, genetically-diverse mouse population. CD-1 mice were fed isoenergetic diets consisting of (1) control fat (CO; “Western-style” fat blend), (2) CO supplemented with 30% fish oil, (3) CO supplemented with 30% dairy fat, or (4) CO supplemented with 30% echium oil. Fecal samples were collected at mid-life and aged (reproductively senescent) time points. Overall, the abundance of Bacteroidetes was greater in mice fed echium oil compared to mice fed the control fat. Examination of colonic bacterial relative abundance also revealed sex differences, with 73 bacterial taxa being differentially expressed in males and females. Notably, results showed a strong interactive effect among the diet, sex, and age of mice which influenced colonic bacterial relative abundance and alpha diversity. In males, supplementation of the diet with dairy fat or echium oil caused the abundance of Bacteroidetes and Bacteroides to change with age. Additionally, supplementation of the diet with fish oil induced sex-dependent changes in the alpha diversity of aged mice compared to mid-life. This work supports that sex is a critical factor in colonic bacterial composition of an aged, genetically-heterogenous population. Moreover, this study establishes that the effectiveness of dietary interventions for health maintenance and disease prevention via direct or indirect manipulation of the gut microbiota is likely dependent on an individual’s sex, age, and genetic background.

Using metabolic profiling and gene expression analyses to explore molecular effects of replacing saturated fat with polyunsaturated fat—a randomized controlled dietary intervention study

ABSTRACTBackgroundReplacing dietary saturated fatty acids (SFAs) with polyunsaturated fatty acids (PUFA) reduces the plasma low-density lipoprotein (LDL) cholesterol and subsequently the risk of cardiovascular disease. However, beyond changes in LDL cholesterol, we lack a complete understanding of the physiologic alterations that occur when improving dietary fat quality.ObjectivesThe aim of this study was to gain knowledge of metabolic alterations paralleling improvements in the fat quality of the diet.MethodsWe recently conducted an 8-wk, double-blind, randomized controlled trial replacing SFAs with PUFAs in healthy subjects with moderate hypercholesterolemia (n = 99). In the present substudy, we performed comprehensive metabolic profiling with multiple platforms (both nuclear magnetic resonance- and mass spectrometry-based technology) (n = 99), and analyzed peripheral blood mononuclear cell gene expression (n = 95) by quantitative real-time polymerase chain reaction.ResultsA large number of lipoprotein subclasses, myristoylcarnitine and palmitoylcarnitine, and kynurenine were reduced when SFAs were replaced with PUFAs. In contrast, bile acids, proprotein convertase subtilisin/kexin type 9, acetate, and acetoacetate were increased by the intervention. Some amino acids were also altered by the intervention. The mRNA levels of LXRA and LDLR were increased, in addition to several liver X receptor α target genes and genes involved in inflammation, whereas the mRNA levels of UCP2 and PPARD were decreased in peripheral blood mononuclear cells after replacing SFAs with PUFAs. Partial least squares-discriminant analysis showed that the 30 most important variables that contributed to class separation spanned all classes of biomarkers, and was in accordance with the univariate analysis.ConclusionsApplying metabolomics in randomized controlled dietary intervention trials has the potential to extend our knowledge of the biological and molecular effects of dietary fat quality. This study was registered at clinicaltrials.gov as NCT 01679496.

Dietary fat and insulin resistance: a connection through leptin and PPARγ activation

Insulin resistance refers to reduced insulin action in peripheral tissues and impaired suppression of endogenous glucose production, a state which is critical for maintaining normal glucose homeostasis. Insulin resistance is partly explained by genetic factors and is strongly influenced by the individual's habitual lifestyle. Investigating factors that may influence the development of insulin resistance and their mechanisms of action is of huge importance; one such factor is the dietary fat. Both quantitative and qualitative terms of dietary fat have been known to play an important role in the development of insulin resistance, though the mechanism underlying this effect is not fully understood. In this regard, the classical view has been that dietary fat quality mainly affects cell membrane fatty acid composition and consequently the membrane function. Recently, the relationship between dietary fat and insulin resistance has entered an advanced level by the discovery that different fatty acids can regulate gene expression, transcriptional activity and adipocytokines secretion. In essence, this provides new mechanisms by which fatty acids exert their cellular effects. The present review critically assesses the effect of dietary fat quality on the development of insulin resistance in relation to the adipocytokine, leptin and the activation of the transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ). It is evident that fat quality influences the development of insulin resistance and has more important role than quantity. Leptin and PPARγ prove to be potential candidates linking dietary fat with insulin resistance. However, the exact role or mechanism of action of various types of dietary fat in the development of insulin resistance is still uncertain. Further well-controlled studies in humans are needed to be able to establish better evidence-based dietary fat recommendations for diabetes prevention and its clinical management. Keywords: dietary fat, insulin resistance, diabetes, PPARγ activation, leptin.

Angiopoietin-Like Protein 4 and Postprandial Skeletal Muscle Lipid Metabolism in Overweight and Obese Prediabetics.

Angiopoietin-like protein 4 (ANGPTL4) decreases plasma triacylglycerol (TAG) clearance by inhibiting lipoprotein lipase (LPL) and may contribute to impairments in lipid metabolism under compromised metabolic conditions. To investigate the effects of a high-saturated fatty acid (SFA) mixed meal on plasma ANGPTL4 concentrations in relation to in vivo muscle LPL activity, to study the effects of dietary fat quality, and to examine skeletal muscle ANGPTL4 release. Design, Participants, Setting, and Interventions: We used a dual stable-isotope tracer technique in combination with measurements of arteriovenous concentration differences across forearm muscle to investigate muscle ANGPTL4 secretion and fatty acid handling under fasting conditions and after a high-SFA mixed meal in 73 overweight and obese humans at the Metabolic Research Unit of Maastricht University. The effect of dietary fat quality manipulation on plasma ANGPTL4 was investigated in 10 obese insulin-resistant participants. The high-SFA meal decreased circulating ANGPTL4 concentrations (fasting, 5.2 ng/mL; vs 4 hours postprandial, 4.0 ng/mL; P < .001). Furthermore, skeletal muscle ANGPTL4 secretion into the circulation was observed (AUC0-4 h, P = .048). However, no association was observed between plasma ANGPTL4 and skeletal muscle very low-density lipoprotein or dietary (chylomicron) TAG extraction (AUC0-4 h, P = .372 and P = .139, respectively). In contrast to a high-SFA or high-monounsaturated fat meal, plasma ANGPTL4 remained unchanged after a high-polyunsaturated fat meal. ANGPTL4 is secreted by human forearm muscle in postprandial conditions after a high-SFA meal. Plasma ANGPTL4 concentrations were not associated with in vivo skeletal muscle LPL activity after a high-SFA meal. Dietary fat quality affects plasma ANGPTL4, but it remains to be elucidated whether this influences short-term skeletal muscle lipid handling.

Eicosapentaenoic and docosahexaenoic acid-enriched high fat diet delays the development of fatty liver in mice.

BackgroundLow hepatic content of n-3 PUFA has been associated with NAFLD in humans. Whether this is associated with reduced dietary intake or increased turnover of these FA is not clear. We have here investigated the effects of dietary fat quality on hepatic lipid storage and transcriptomics over time.AimTo investigate the effects of quality of fat in a high fat diet (HFD) over time on hepatic lipid storage and liver transcriptomics.Methods and ResultsMale C57BL/6J mice were fed control, HFD-eicosapentaenoic acid (EPA)/ docosahexaenoic acid (DHA) or HFD-corn oil diet for 8 or 12 weeks. Body weight, body composition, plasma and hepatic triglyceride contents were measured. Hepatic transcriptomes were analysed by microarray followed by gene-set enrichment analyses. At 8 weeks, the HFD-corn oil mice had higher body weight and adipose depot mass than the HFD-EPA/DHA but there were no differences at 12 weeks. Hepatic triglyceride content was lower in HFD-EPA/DHA fed compared with the HFD-corn oil fed mice at both time-points. Enrichment analyses of the hepatic transcriptomes showed that lipid/fatty acid biosynthesis; transport and homeostasis were lower in the HFD-EPA/DHA fed compared with the HFD-corn oil fed mice. Genes encoding proteins associated to cytoplasmic lipid droplets were expressed at higher levels in livers from the HFD-corn oil compared to HFD-EPA/DHA mice.ConclusionsDietary EPA and DHA counteracted development of HFD-induced fatty liver. The liver transcriptome data implicate that the quality of dietary fat could modulate Ppar-related gene expression that in turn affects hepatic lipid storage and maintenance of metabolic health.Electronic supplementary materialThe online version of this article (doi:10.1186/s12944-015-0072-8) contains supplementary material, which is available to authorized users.

Time-dependent effects of safflower oil to improve glycemia, inflammation and blood lipids in obese, post-menopausal women with type 2 diabetes: A randomized, double-masked, crossover study

Metabolic effects of dietary fat quality in people with type 2 diabetes are not well-understood. The study objective was to evaluate effects of conjugated linoleic acid (CLA) and safflower (SAF) oils on glycemia, blood lipids, and inflammation. The hypothesis we tested is that dietary oils improve glycemia, lipids, and inflammatory markers in a time-dependent way that follows accumulation of linoleic acid and CLA isomers in serum of subjects supplemented with dietary oils. Fifty-five post-menopausal, obese women with type 2 diabetes enrolled, and 35 completed this randomized, double-masked crossover study. Treatments were 8g daily of CLA and SAF for 16 weeks each. We used a multiple testing procedure with pre-determined steps analysis to determine the earliest time that a significant effect was detected. CLA did not alter measured metabolic parameters. SAF decreased HbA1c (-0.64±0.18%, p=0.0007) and C-reactive protein (-13.6±8.2mg/L, p=0.0472), increased QUICKI (0.0077±0.0035, p=0.0146) with a minimum time to effect observed 16 weeks after treatment. SAF increased HDL cholesterol (0.12±0.05mmol/L, p=0.0228) with the minimum time to detect an effect of SAF at 12 weeks. The minimum time to detect an increase of c9t11-CLA, t10c12-CLA, and linoleic acid in serum of women supplemented CLA or SAF, respectively, was four weeks. We conclude that 8g of SAF daily improved glycemia, inflammation, and blood lipids, indicating that small changes in dietary fat quality may augment diabetes treatments to improve risk factors for diabetes-related complications.

Efeito do uso de óleo de vísceras de aves oxidado na ração de frangos de corte sobre o desempenho, a composição da carcaça e a estabilidade oxidativa da carne da sobrecoxa

Foi conduzido um experimento utilizando-se 200 pintos de corte da linhagem Ross de 10 a 40 dias de idade alimentados com ração à base de milho e farelo de soja e suplementada com 4% de óleo de vísceras de aves fresco ou oxidado, com o objetivo de avaliar os efeitos da qualidade do óleo utilizado nas rações sobre o desempenho de frangos de corte e a estabilidade oxidativa da carne de sobrecoxa congelada. Óleo de vísceras recém produzido com absorbâncias específicas de 5,80 a 232 nm e 0,690 a 532 nm, indicando a presença de quantidades mínimas de compostos de oxidação, foi congelado (-18ºC) até o momento da produção das rações. O óleo oxidado foi produzido a partir deste mesmo lote, que foi aquecido em uma fritadeira elétrica com temperatura em torno de 110 a 120ºC até atingir absorbâncias específicas de 11,33 (232 nm) e 2,31 (532 nm), caracterizando o acúmulo de compostos de ranço. Aos 41 dias de idade, 136 animais foram abatidos para avaliação das características de rendimento da carcaça e das partes e as sobrecoxas desossadas e sem pele foram embaladas e mantidas sob congelamento (-20ºC). O acompanhamento do processo de oxidação lipídica da carne congelada foi avaliado mensalmente pela determinação dos compostos secundários da oxidação (TBARS). O uso do óleo de vísceras oxidado não afetou o desempenho das aves, nem as características principais da carcaça. A partir do sexto mês de armazenamento, a estabilidade oxidativa da carne de sobrecoxa congelada foi comprometida pelo consumo de rações contendo o óleo oxidado, evidenciado pelo maior valor de TBARS.

Effect of dietary fat quality on C 18:1 fatty acids and conjugated linoleic acid production: An in vitro rumen fermentation study

Samples of three diets, previously tested with lactating dairy cows, were incubated in vitro with rumen fluid with the aim of monitoring the concentration of cis and trans C 18:1 fatty acids and of the isomers of conjugated linoleic acid with fermentation time. The three diets had a common forage basis (lucerne hay and maize silage), but different fat sources in the concentrate (basically made up of maize meal and soybean meal). The control diet (diet C) had no fat added and the other two diets were supplemented either with a calcium salt of olive oil (diet O) or with extruded full fat soybean (diet S). The fatty acid pattern in the fermentation vessels was affected by the kind of dietary fat in the samples, both in terms of concentration and of fermentation times (12, 24, 36, 48 h). Oleic acid (OA), elaidic acid and conjugated linoleic acid (CLA) isomers were particularly looked at. OA was not completely saturated to stearic acid, but isomerized to other acids of the C 18:1 family as well. Vaccenic acid was increased with all the three diets, especially with diet O after 36 h. CLA resulted increased with diet S only (P<0.05), with significant differences between isomers. The saponification of olive oil appeared to be a partial protection against rumen biohydrogenation. The possibility of affecting the concentration of intermediate acids of the biohydrogenation pathways by dietary means was confirmed.

Effects of Different Dietary Fat Types on Postprandial Appetite and Energy Expenditure

Observational studies suggest that monounsaturated (MUFA) and trans fatty acids (TRANS) are more fattening than polyunsaturated fatty acids (PUFA). Therefore, the aim of this study was to investigate the acute effect of intake of PUFA, MUFA, or TRANS on appetite and energy expenditure (EE). Three test meals were randomly given in a cross-over design to 19 overweight (BMI: 26.8 +/- 0.4 kg/m2), young (25.2 +/- 0.7 years) men. The fat-rich breakfasts (0.8 g fat/kg body weight, 60% energy from fat) varied only in the source of C:18-fat. EE was measured continuously in a respiration chamber, and appetite sensations were rated by visual analog scales before and every 30 minutes, for 5 hours, after the meal. After 5 hours, an ad libitum meal was served, and energy intake was registered. Sensory evaluations of all meals were given using visual analog scales. Data were analyzed by two-way ANOVA. There were no differences in basal or postprandial values of appetite ratings and EE, in subsequent ad libitum energy intake, or in the sensory evaluation of the test meals among the 3 test days. Giving acutely large amounts of MUFA, PUFA, or TRANS did not impose any differences in appetite and EE in overweight humans. However, studies with extended protocols and other subject groups are warranted to investigate the long-term effect of dietary fat quality on the regulation of energy balance and body weight.

Diet, Nutrition and Diabetes Mellitus

Nutritional management of diabetes mellitus, and the importance of diet in the development of insulin resistance, have for many years been important areas of research and education at the Unit for Clinical Nutrition Research at the Department of Public Health and Caring Sciences (formerly Department of Geriatrics) at Uppsala University. The research has more recently focussed on effects of dietary fat quality in the development of insulin resistance and in treatment of diabetes, on interaction between dietary fat and physical activity in relation to insulin sensitivity and on the importance of carbohydrate rich foods with low glycaemic index in the diabetic diet. Much work has also been directed towards development of educational material about nutrition recommendations and dietary treatment in diabetes mellitus. The ultimate goals for all our efforts are to visualize, and promote, the possibilities and fundamental importance of lifestyle changes. This includes an improved diet and increased physical activity, in the prevention and treatment of diabetes mellitus.

Regulation of Cholesterol and Lipoprotein Metabolism in Guinea Pigs Mediated by Dietary Fat Quality and Quantity

The effects of dietary fat quality and quantity on regulation of cholesterol and lipoprotein metabolism were measured in guinea pigs. The animals were fed 7.5 or 15% (wt/wt) fat diets containing either polyunsaturated corn oil (CO), monounsaturated olive oil (OL) or saturated lard as the fat source. Dietary fat quality had a number of significant effects: animals fed the CO-based diet had lower plasma LDL levels and LDL particles of higher density with decreased ratios of core-to-surface components. Apoprotein B/E receptor-mediated binding of LDL to hepatic membranes was twofold higher for animals fed the CO-based diet. Animals fed the OL-based diet had lower hepatic 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity and increased levels of hepatic cholesterol. Hepatic cholesteryl ester levels were lowest for animals fed the lard-based diet. Increasing dietary fat quantity resulted in increased plasma LDL levels and hepatic cholesterol, HMG-CoA reductase activity and receptor affinity for LDL. No changes were observed in LDL binding. These data demonstrate that, independent of dietary fat quantity, CO-based diets lower plasma LDL levels, modify LDL composition and increase hepatic apoprotein B/E receptor number.

Characterization of high-density lipoprotein binding to guinea pig hepatic membranes: Effects of dietary fat quality and cholesterol feeding

The effects of dietary fat quality and cholesterol intake on expression of guinea pig hepatic membrane high-density lipoprotein (HDL) binding sites were studied. Animals were fed semisynthetic diets containing 7.5% (wt/wt) of either corn oil (CO), olive oil (OL), or lard. The cholesterol diet was prepared by incorporating 0.25% recrystallized cholesterol into standard guinea pig chow. Plasma cholesterol levels of guinea pigs on the CO diet were significantly lower ( P < .02) than animals on the OL or lard diets. HDL cholesterol levels did not differ between the polyunsaturated, monounsaturated, and saturated dietary fat groups. Guinea pigs on the high cholesterol diet had increased total and HDL cholesterol levels compared with animals on the chow diet ( P < .01). Initial studies demonstrated that HDL binding to hepatic membranes was temperature-dependent. A threefold increase in binding was observed when assays were performed at 37°C, as compared with 4°C, for all membrane preparations. Dietary fat quality and dietary cholesterol intake significantly altered HDL binding to hepatic membranes with increased HDL binding to membranes of animals fed polyunsaturated fat and the high cholesterol diet. At 37°C, HDL binding to hepatic membranes of CO-fed animals was 26% and 46% higher than for membranes of OL- and lard-fed guinea pigs, respectively. A high cholesterol intake increased HDL binding by 24% at both 4°C and 37°C. Scatchard analysis demonstrated that while membrane affinity for HDL (K d) was not affected by diet, changes did occur in the total number of HDL binding sites. B max values were significantly higher ( P < .05) for membranes from cholesterol- and CO-fed guinea pigs. These data demonstrate that in the guinea pig, HDL binding to hepatic membranes is regulated by both dietary fat quality and dietary cholesterol.

Influence of dietary fatty acid composition on cholesterol synthesis and esterification in hamsters

To investigate the effects of dietary fat quality on synthesis and esterification of cholesterol, Syrian hamsters were fed diets containing corn, olive, coconut or menhaden oils (10% w/w) with added cholesterol (0.1% w/w). After 3 weeks, animals were sacrificed 90 min following IP injection of 3H2O. Synthesis of free cholesterol and movement of free cholesterol into ester pools were measured from 3H-uptake rate in liver and duodenum. Plasma total cholesterol and triglycerides levels were highest in coconut oil-fed animals, whereas hepatic total cholesterol and ester levels were elevated in olive oil-fed animals, as compared with all other groups. No diet-related differences were seen in duodenal cholesterol or total fatty acid content. In duodenum, uptake of 3H per g tissue into cholesterol was greater compared with liver; however, within each tissue, 3H-uptake into cholesterol was similar across groups. Notably, 3H-uptake into cholesterol ester in liver was highest in menhaden oil-fed animals. These data suggest that menhaden fish oil consumption results in enhanced movement of newly synthesized cholesterol into ester as compared with other fat types.

Whole body and hepatic cholesterol synthesis rates in the guinea-pig: effect of dietary fat quality

The effects of polyunsaturated, monounsaturated and saturated dietary fat on total and hepatic cholesterol synthesis were studied in the guinea-pig. Male Hartley guinea-pigs were fed semi-synthetic diets containing 7.5% (w/w) of either corn oil (CO), olive oil (OL) or lard for a period of 5 weeks and rates of endogenous cholesterol synthesis were determined from the incorporation of [ 3H]water into digitonin-precipitable sterols (DPS) and by measurement of sterol balance. In addition, total and expressed 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activities were determined in hepatic microsomes. Rates of whole body cholesterol synthesis determined by incorporation of [ 3H]water into DPS were significantly lower for guinea-pigs on the CO diet with values of 18.7 ± 1.8 μmol/h ( n = 4) vs. 26.7 ± 4.8 and 24.6 ± 1.8 μmol/h for animals on the OL ( n = 4) and lard ( n = 3) diets ( P < 0.001), respectively. Hepatic cholesterol synthesis rates were significantly decreased in animals on the OL diet, whether determined from incorporation of [ 3H]water into DPS or by analysis of HMG-CoA reductase activity. Hepatic total and free cholesterol levels were not different for animals on the three dietary fats; however, cholesteryl ester levels were 35% lower in guinea-pigs fed the lard diet ( P < 0.02). Sterol balance measurements indicated that whole body cholesterol synthesis rates were not affected by dietary fat quality (51.9 ± 12.2, 42.8 ± 7.6 and 51.2 ± 20.2 mg/kg per day for animals on the CO, OL and lard diets, respectively). This is in striking contrast to the observed reduction in cholesterol synthesis rates for animals on the polyunsaturated CO diet as determined by incorporation of [ 3H]water into DPS. One possible explanation for the discrepancy between the sterol balance and [ 3H]water incorporation data is a polyunsaturated fat-mediated effect on energy utilization, which affects the equilibration of NADPH with the body water pool such that the [ 3H]NADPH has a lower specific activity than body [ 3H]water.

Dietary fat-mediated changes in hepatic apoprotein [formula omitted] receptor in the guinea pig: Effect of polyunsaturated, monounsaturated, and saturated fat

These studies investigated the effects of dietary fat quality on guinea pig plasma total and low-density lipoprotein (LDL) cholesterol and triglyceride levels; LDL composition, density, and binding affinity to hepatic apolipoprotein (apo) B E receptors; and hepatic apo B E receptor levels. Animals were fed semi-synthetic diets containing 7.5% (weight per weight) fat—either corn oil (CO), olive oil (OL), or lard. Plasma cholesterol levels were significantly lower on the CO diet compared with the OL and lard diets. The isolated LDL had mean peak densities that ranged from 1.071 for LDL from lard-fed animals to 1.075 for LDL from CO- and OL-fed animals. The cholesterol ester to protein ratio of the LDL particle decreased in CO-fed guinea pigs. Binding studies showed that these compositional changes of the LDL had no effect on the binding affinity of the particles to a standardized hepatic membrane preparation. Membrane phospholipid fatty acid compositions were significantly different among the three dietary fat groups. When hepatic membranes were incubated with 125I-labeled LDL, the receptor-mediated binding of LDL to membranes from CO-fed animals increased 1.5-fold compared with binding to membranes from OL- and lard-fed guinea pigs. Scatchard plots indicated an increase of 50% in receptor number in membranes of animals fed the CO diet, whereas the affinity of the hepatic apo B E receptor for LDL (K d) was virtually identical for all membranes. It is concluded from these data that the increase in specific binding observed in hepatic membranes from CO-fed guinea pigs is caused by an increased number of LDL receptors and not an increased affinity for the LDL particle.