Saturated fat-induced changes in S-f 60-400 particle composition reduces uptake of LDL by HepG2 cells

The ability of human postprandial triacylglycerol-rich lipoproteins (TRLs), isolated after meals enriched in saturated fatty acids (SFAs), n-6 PUFAs, and MUFAs, to inhibit the uptake of I-125-labeled LDL by the LDL receptor was investigated in HepG2 cells. Addition of TRLs resulted in a dose-dependent inhibition of heparin-releasable binding, cell-associated radioactivity, and degradation products of I-125-labeled LDL (P < 0.001). SFA-rich Svedberg flotation rate (S-f) 60-400 resulted in significantly greater inhibition of cell-associated radioactivity than PUFA-rich particles (P = 0.016) and total uptake of I-125-labeled LDL compared with PUFA- and MUFA-rich particles (P = 0.02). Normalization of the apolipoprotein (apo)E but not apoC-III content of the TRLs removed the effect of meal fatty acid composition, and addition of an anti-apoE antibody reversed the inhibitory effect of TRLs on the total uptake of I-125-labeled LDL. Real time RT-PCR showed that the SFA-rich Sf 60-400 increased the expression of genes involved in hepatic lipid synthesis (P < 0.05) and decreased the expression of the LDL receptor-related protein 1 compared with MUFAs (P = 0.008). In conclusion, these findings suggest an alternative or additional mechanism whereby acute fat ingestion can influence LDL clearance via competitive apoE-dependent effects of TRL on the LDL receptor.-Jackson, K. G., V. Maitin, D. S. Leake, P. Yaqoob, and C. M. Williams. Saturated fat-induced changes in Sf 60 400 particle composition reduces uptake of LDL by HepG2 cells.

Performance of palm- based fat blends with a low saturated fat content in puff pastry

Four fat blends based on palm fractions in combination with high oleic sunflower oil (HOSF) with a relatively low saturated fatty acid content (29.2±0.85%, i.e. less than 50% of that of butter) were prepared. The saturated fat was located in different triacylglycerols (TAG) structures in each blend. Principal saturated TAG were derived from palm stearin (POs, containing tripalmitoyl glycerol - PPP), palm mid fraction (PMF, containing 1,3-dipalmitoyl-2-oleoyl glycerol - POP) and interesterified PMF (inPMF, containing PPP, POP and rac-1,2-dipalmitoyl-3-oleoyl glycerol - PPO). Thus, in blend 1, composed of POs and HOSF, the saturates resided principally in PPP. In blend 2, composed of POs, PMF and HOSF, the principal saturate-containing TAG were PPP and POP. Blend 3, composed of inPMF and HOSF, was similar to blend 2 except that the disaturated TAG comprised a 2:1 mixture of PPO:POP. Finally, blend 4, a mixture of PMF and HOSF, had saturates present mainly as POP. The physical properties and the functionality of blends, as shortenings for puff pastry laminated in a warm bakery environment (20-30°C), were compared with each other, and with butter. Puff pastry prepared with blend 1 (POs:HOSF 29:71) and blend 4 (PMF:HOSF 41:59), was very hard; blend 2 (POs:PMF:HOSF 13:19:68) was most similar to butter in the compressibility of the baked product and it performed well in an independent baking trial; blend 3 (inPMF:HOSF 40:60) gave a product that required a higher force for compression than butter.

Genetic predisposition to type 2 diabetes is associated with impaired insulin secretion but does not modify insulin resistance or secretion in response to an intervention to lower dietary saturated fat

Genome-wide association studies have identified SNPs reproducibly associated with type 2 diabetes (T2D). We examined the effect of genetic predisposition to T2D on insulin sensitivity and secretion using detailed phenotyping in overweight individuals with no diagnosis of T2D. Furthermore, we investigated whether this genetic predisposition modifies the responses in beta-cell function and insulin sensitivity to a 24-week dietary intervention. We genotyped 25 T2D-associated SNPs in 377 white participants from the RISCK study. Participants underwent an IVGTT prior to and following a dietary intervention that aimed to lower saturated fat intake by replacement with monounsaturated fat or carbohydrate. We composed a genetic predisposition score (T2D-GPS) by summing the T2D risk-increasing alleles of the 25 SNPs and tested for association with insulin secretion and sensitivity at baseline, and with the change in response to the dietary intervention. At baseline, a higher T2D-GPS was associated with lower acute insulin secretion (AIRg 4% lower/risk allele, P = 0.006) and lower insulin secretion for a given level of insulin sensitivity, assessed by the disposition index (DI 5% lower/risk allele, P = 0.002), but not with insulin sensitivity (Si). T2D-GPS did not modify changes in insulin secretion, insulin sensitivity or the disposition index in response to the dietary interventions to lower saturated fat. Participants genetically predisposed to T2D have an impaired ability to compensate for peripheral insulin resistance with insulin secretion at baseline, but this does not modify the response to a reduction in dietary saturated fat through iso-energetic replacement with carbohydrate or monounsaturated fat.

Development of a food-exchange model to replace saturated fat with MUFAS and n-6 PUFAS in adults at moderate cardiovascular risk

The recommendation to reduce saturated fatty acid (SFA) consumption to ≤10% of total energy (%TE) is a key public health target aimed at lowering cardiovascular disease (CVD) risk. Replacement of SFA with unsaturated fats may provide greater benefit than replacement with carbohydrates, yet the optimal type of fat is unclear. The aim was to develop a flexible food-exchange model to investigate the effects of substituting SFAs with monounsaturated fatty acids (MUFAs) or n-6 (ω-6) polyunsaturated fatty acids (PUFAs) on CVD risk factors. In this parallel study, UK adults aged 21-60 y with moderate CVD risk (50% greater than the population mean) were identified using a risk assessment tool (n = 195; 56% females). Three 16-wk isoenergetic diets of specific fatty acid (FA) composition (%TE SFA:%TE MUFA:%TE n-6 PUFA) were designed using spreads, oils, dairy products, and snacks as follows: 1) SFA-rich diet (17:11:4; n = 65); 2) MUFA-rich diet (9:19:4; n = 64); and 3) n-6 PUFA-rich diet (9:13:10; n = 66). Each diet provided 36%TE total fat. Dietary targets were broadly met for all intervention groups, reaching 17.6 ± 0.4%TE SFA, 18.5 ± 0.3%TE MUFA, and 10.4 ± 0.3%TE n-6 PUFA in the respective diets, with significant overall diet effects for the changes in SFA, MUFA, and n-6 PUFA between groups (P < 0.001). There were no differences in the changes of total fat, protein, carbohydrate, and alcohol intake or anthropometric measures between groups. Plasma phospholipid FA composition showed changes from baseline in the proportions of total SFA, MUFA, and n-6 PUFA for each diet group, with significant overall diet effects for total SFA and MUFA between groups (P < 0.001). In conclusion, successful implementation of the food-exchange model broadly achieved the dietary target intakes for the exchange of SFA with MUFA or n-6 PUFA with minimal disruption to the overall diet in a free-living population. This trial was registered at clinicaltrials.gov as NCT01478958.

ApoE genotype, cardiovascular risk and responsiveness to dietary fat manipulation

Cardiovascular risk is determined by the complex interactions between genetic and environmental factors. The apoE genotype represents the most-widely-studied single nucleotide polymorphism in relation to CVD risk, with >3600 publications cited in PubMed. Although originally described as a mediator of lipoprotein metabolism, the lipoprotein-independent functions of apoE are being increasingly recognised, with limited data available on the potential impact of genotype on these metabolic processes. Furthermore, although meta-analyses suggest that apoE4 carriers may have a 40-50% increased CVD risk, the associations reported in individual studies are highly heterogeneous and it is recognised that environmental factors such as smoking status and dietary fat composition influence genotype-phenotype associations. However, information is often derived from observational studies or small intervention trials in which retrospective genotyping of the cohort results in small group sizes in the rarer E2 and E4 subgroups. Either larger well-standardised intervention trials or smaller trials with prospective recruitment according to apoE genotype are needed to fully establish the impact of diet on genotype-CVD associations and to establish the potential of dietary strategies such as reduced total fat, saturated fat, or increased antioxidant intakes to counteract the increased CVD burden in apoE4 carriers.

Dietary fat composition and cardiovascular disease

Cardiovascular disease (CVD), which includes coronary heart disease and stroke, remains the major killer in the EU, being responsible for 42% of total mortality. The amount and composition of dietary fat is arguably the most important dietary factor contributing to disease risk. A significant body of consistent evidence indicates that a decrease in dietary saturated fat:unsaturated (polyunsaturated + monounsaturated) ratio and an increased intake of long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) found in fish, is cardioprotective. Furthermore, although the evidence is currently less convincing, such a strategy is also likely to improve insulin sensitivity, the central metabolic defect in diabetes. Currently in the UK only 12% of men, 17% of women and 8% of children have an SFA intakes <10% of energy. The average intake of LC n-3 PUFA is <0.2 g/day, which is less than half the current conservative recommendation of a minimum of 0.45 g/day. Public health strategies to reverse these dietary fatty acid imbalances, aimed at educating and motivating the consumer and making affordable and acceptable food products with an ‘enhanced’ fatty acid profile more widely available, must remain a public health priority in the ‘fight’ against CVD.

Effects of dietary fat modification on skeletal muscle fatty acid handling in the metabolic syndrome

Objective: In the metabolic syndrome (MetS), increased fat storage in ‘nonadipose’ tissues such as skeletal muscle may be related to insulin resistance (‘lipid overflow’ hypothesis). The objective of this study was to examine the effects of dietary fat modification on the capacity of skeletal muscle to handle dietary and endogenous fatty acids (FAs). Subjects and Methods: In total, 29 men with the MetS were randomly assigned to one of four diets for 12 weeks: a high-fat saturated fat diet (HSFA, n=6), a high-fat monounsaturated fat diet (HMUFA, n=7) and two low-fat high-complex carbohydrate diets supplemented with (LFHCCn−3, n=8) or without (LFHCC, n=8) 1.24 g per day docosahexaenoic and eicosapentaenoic acid. Fasting and postprandial skeletal muscle FA handling was examined by measuring arteriovenous concentration differences across the forearm muscle. [2H2]-palmitate was infused intravenously to label endogenous triacylglycerol (TAG) and free fatty acids in the circulation and subjects received a high-fat mixed meal (2.6 MJ, 61 energy% fat) containing [U-13C]-palmitate to label chylomicron-TAG. Results: Postprandial circulating TAG concentrations were significantly lower after dietary intervention in the LFHCCn−3 group compared to the HSFA group (ΔiAUC −139±67 vs 167±70 μmol l−1 min−1, P=0.009), together with decreased concentrations of [U-13C]-labeled TAG, representing dietary FA. Fasting TAG clearance across forearm muscle was decreased on the HSFA diet, whereas no differences were observed in postprandial forearm muscle FA handling between diets. Conclusion: Chronic manipulation of dietary fat quantity and quality did not affect forearm muscle FA handling in men with the MetS. Postprandial TAG concentrations decreased on the LFHCCn−3 diet, which could be (partly) explained by lower concentration of dietary FA in the circulation.

Dietary fat modifications and blood pressure in subjects with the metabolic syndrome in the LIPGENE dietary intervention study

Hypertension is a key feature of the metabolic syndrome. Lifestyle and dietary changes may affect blood pressure (BP), but the knowledge of the effects of dietary fat modification in subjects with the metabolic syndrome is limited. The objective of the present study was to investigate the effect of an isoenergetic change in the quantity and quality of dietary fat on BP in subjects with the metabolic syndrome. In a 12-week European multi-centre, parallel, randomised controlled dietary intervention trial (LIPGENE), 486 subjects were assigned to one of the four diets distinct in fat quantity and quality: two high-fat diets rich in saturated fat or monounsaturated fat and two low-fat, high-complex carbohydrate diets with or without 1·2 g/d of very long-chain n-3 PUFA supplementation. There were no overall differences in systolic BP (SBP), diastolic BP or pulse pressure (PP) between the dietary groups after the intervention. The high-fat diet rich in saturated fat had minor unfavourable effects on SBP and PP in males.

Genetic predisposition influences plasma lipids of participants on habitual diet, but not the response to reductions in dietary intake of saturated fatty acids

Objective: SNPs identified from genome wide association studies associate with lipid risk markers of cardiovascular disease. This study investigated whether these SNPs altered the plasma lipid response to diet in the ‘RISCK’ study cohort. Methods: Participants (n = 490) from a dietary intervention to lower saturated fat by replacement with carbohydrate or monounsaturated fat, were genotyped for 39 lipid-associated SNPs. The association of each individual SNP, and of the SNPs combined (using genetic predisposition scores), with plasma lipid concentrations was assessed at baseline, and on change in response to 24 weeks on diets. Results: The associations between SNPs and lipid concentrations were directionally consistent with previous findings. The genetic predisposition scores were associated with higher baseline concentrations of plasma total(P = 0.02) and LDL (P = 0.002) cholesterol, triglycerides (P = 0.001) and apolipoprotein B (P = 0.004), and with lower baseline concentrations of HDL cholesterol (P < 0.001) and apolipoprotein A-I (P < 0.001). None of the SNPs showed significant association with the reduction of plasma lipids in response to the dietary interventions and there was no evidence of diet-gene interactions. Conclusion: Results from this exploratory study have shown that increased genetic predisposition was associated with an unfavourable plasma lipid profile at baseline, but did not influence the improvement in lipid profiles by the low-saturated-fat diets.

SATgene dietary model to implement diets of differing fat composition in prospectively genotyped groups (apoE) using commercially available foods

esponse to dietary fat manipulation is highly heterogeneous, yet generic population-based recommendations aimed at reducing the burden of CVD are given. The APOE epsilon genotype has been proposed to be an important determinant of this response. The present study reports on the dietary strategy employed in the SATgenɛ (SATurated fat and gene APOE) study, to assess the impact of altered fat content and composition on the blood lipid profile according to the APOE genotype. A flexible dietary exchange model was developed to implement three isoenergetic diets: a low-fat (LF) diet (target composition: 24 % of energy (%E) as fat, 8 %E SFA and 59 %E carbohydrate), a high-saturated fat (HSF) diet (38 %E fat, 18 %E SFA and 45 %E carbohydrate) and a HSF-DHA diet (HSF diet with 3 g DHA/d). Free-living participants (n 88; n 44 E3/E3 and n 44 E3/E4) followed the diets in a sequential design for 8 weeks, each using commercially available spreads, oils and snacks with specific fatty acid profiles. Dietary compositional targets were broadly met with significantly higher total fat (42·8 %E and 41·0 %E v. 25·1 %E, P ≤ 0·0011) and SFA (19·3 %E and 18·6 %E v. 8·33 %E, P ≤ 0·0011) intakes during the HSF and HSF-DHA diets compared with the LF diet, in addition to significantly higher DHA intake during the HSF-DHA diet (P ≤ 0·0011). Plasma phospholipid fatty acid analysis revealed a 2-fold increase in the proportion of DHA after consumption of the HSF-DHA diet for 8 weeks, which was independent of the APOE genotype. In summary, the dietary strategy was successfully implemented in a free-living population resulting in well-tolerated diets which broadly met the dietary targets set.

Obesity and body fat classification in the metabolic syndrome: impact on cardiometabolic risk metabotype

Obesity is a key factor in the development of the metabolic syndrome (MetS), which is associated with increased cardiometabolic risk. We investigated whether obesity classification by body mass index (BMI) and body fat percentage (BF%) influences cardiometabolic profile and dietary responsiveness in 486 MetS subjects (LIPGENE dietary intervention study). Anthropometric measures, markers of inflammation and glucose metabolism, lipid profiles, adhesion molecules and haemostatic factors were determined at baseline and after 12 weeks of 4 dietary interventions (high saturated fat (SFA), high monounsaturated fat (MUFA) and 2 low fat high complex carbohydrate (LFHCC) diets, 1 supplemented with long chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs)). 39% and 87% of subjects classified as normal and overweight by BMI were obese according to their BF%. Individuals classified as obese by BMI (± 30 kg/m2) and BF% (± 25% (men) and ± 35% (women)) (OO, n = 284) had larger waist and hip measurements, higher BMI and were heavier (P < 0.001) than those classified as non-obese by BMI but obese by BF% (NOO, n = 92). OO individuals displayed a more pro-inflammatory (higher C reactive protein (CRP) and leptin), pro-thrombotic (higher plasminogen activator inhibitor-1 (PAI-1)), pro-atherogenic (higher leptin/adiponectin ratio) and more insulin resistant (higher HOMA-IR) metabolic profile relative to the NOO group (P < 0.001). Interestingly, tumour necrosis factor alpha (TNF-α) concentrations were lower post-intervention in NOO individuals compared to OO subjects (P < 0.001). In conclusion, assessing BF% and BMI as part of a metabotype may help identify individuals at greater cardiometabolic risk than BMI alone.

Dietary fat manipulation has a greater impact on postprandial lipid metabolism than the apolipoprotein E (epsilon) genotype: insights from the SATgenε study

Scope: Our aim was to determine the effects of chronic dietary fat manipulation on postprandial lipaemia according to apolipoprotein (APO)E genotype. Methods and results:Men (mean age 53 (SD 9) years), prospectively recruited for the APOE genotype (n = 12 E3/E3, n = 11 E3/E4), were assigned to a low fat (LF), high fat, high-saturated fat (HSF), and HSF diet with 3.45 g/day docosahexaenoic acid (HSF-DHA), each for an 8-week period in the same order. At the end of each dietary period, a postprandial assessment was performed using a test meal with a macronutrient profile representative of that dietary intervention. A variable postprandial plasma triacylglycerol (TAG) response according to APOE genotype was evident, with a greater sensitivity to the TAG-lowering effects of DHA in APOE4 carriers (p ≤ 0.005). There was a lack of an independent genotype effect on any of the lipid measures. In the groups combined, dietary fat manipulation had a significant impact on lipids in plasma and Svedberg flotation rate (Sf) 60–400 TAG-rich lipoprotein fraction, with lower responses following the HSF-DHA than HSF intervention (p < 0.05). Conclusion: Although a modest impact of APOE genotype was observed on the plasma TAG profile, dietary fat manipulation emerged as a greater modulator of the postprandial lipid response in normolipidaemic men.

Greater impact of dietary fat manipulation than apolipoprotein E genotype on ex-vivo cytokine production – insights from the SATgenε study

Apolipoprotein E (APOE) genotype is believed to play an important role in cardiovascular risk. APOE4 carriers have been associated with higher blood lipid levels and a more pro-inflammatory state compared with APOE3/E3 individuals. Although dietary fat composition has been considered to modulate the inflammatory state in humans, very little is known about how APOE genotype can impact on this response. In a follow-up to the main SATgene study, we aimed to explore the effects of APOE genotype, as well as, dietary fat manipulation on ex vivo cytokine production. Blood samples were collected from a subset of SATgene participants (n = 52/88), prospectively recruited according to APOE genotype (n = 26 E3/E3 and n = 26 E3/E4) after low-fat (LF), high saturated fat (HSF) and HSF with 3.45 g docosahexaenoic acid (DHA) dietary periods (each diet eight weeks in duration assigned in the same order) for the measurement of ex vivo cytokine production using whole blood culture (WBC). Concentrations of IL-1beta, IL-6, IL-8, IL-10 and TNF-alpha were measured in WBC supernatant samples after stimulation for 24 h with either 0.05 or 1 lg/ml of bacterial lipopolysaccharide (LPS). Cytokine levels were not influenced by genotype, whereas, dietary fat manipulation had a significant impact on TNF-a and IL-10 production; TNF-a concentration was higher after consumption of the HSF diet compared with baseline and the LF diet (P < 0.05), whereas, IL-10 concentration was higher after the LF diet compared with baseline (P < 0.05). In conclusion, our study has revealed the amount and type of dietary fat can significantly modulate the production of TNF-a and IL-10 by ex vivo LPS-stimulated WBC samples obtained from normolipidaemic subjects.

Endothelial function and insulin sensitivity during acute non-esterified fatty acid elevation: effects of fat composition and gender

Background and Aims: We have reported that adverse effects on flow-mediated dilation of an acute elevation of non-esterified fatty acids rich in saturated fat (SFA) are reversed following addition of long-chain (LC) n-3 polyunsaturated fatty acids (PUFA), and hypothesised that these effects may be mediated through alterations in insulin signalling pathways. In a subgroup, we explored the effects of raised NEFA enriched with SFA, with or without LC n-3 PUFA, on whole body insulin sensitivity (SI) and responsiveness of the endothelium to insulin infusion. Methods and Results: Thirty adults (mean age 27.8 y, BMI 23.2 kg/m2) consumed oral fat loads on separate occasions with continuous heparin infusion to elevate NEFA between 60-390 min. For the final 150 min, a hyperinsulinaemic-euglycaemic clamp was performed, whilst FMD and circulating markers of endothelial function were measured at baseline, pre-clamp (240 min) and post-clamp (390 min). NEFA elevation during the SFA-rich drinks was associated with impaired FMD (P=0.027) whilst SFA+LC n-3 PUFA improved FMD at 240 min (P=0.003). In males, insulin infusion attenuated the increase in FMD with SFA+LC n-3 PUFA (P=0.049), with SI 10% greater with SFA+LC n-3 PUFA than SFA (P=0.041). Conclusion: This study provides evidence that NEFA composition during acute elevation influences both FMD and SI, with some indication of a difference by gender. However our findings are not consistent with the hypothesis that the effects of fatty acids on endothelial function and SI operate through a common pathway. Trial registered at clinicaltrials.gov, NCT01351324.

Intake of total and subgroups of fat minimally affect the associations between selected single nucleotide polymorphisms in the PPARγ pathway and changes in anthropometry among European adults from cohorts of the DiOGenes study

BACKGROUND: Although the peroxisome proliferator-activated receptor γ (PPARγ) pathway is central in adipogenesis, it remains unknown whether it influences change in body weight (BW) and whether dietary fat has a modifying effect on the association. OBJECTIVES: We examined whether 27 single nucleotide polymorphisms (SNPs) within 4 genes in the PPARγ pathway are associated with the OR of being a BW gainer or with annual changes in anthropometry and whether intake of total fat, monounsaturated fat, polyunsaturated fat, or saturated fat has a modifying effect on these associations. METHODS: A case-noncase study included 11,048 men and women from cohorts in the European Diet, Obesity and Genes study; 5552 were cases, defined as individuals with the greatest BW gain during follow-up, and 6548 were randomly selected, including 5496 noncases. We selected 4 genes [CCAAT/enhancer binding protein β (CEBPB), phosphoenolpyruvate carboxykinase 2, PPARγ gene (PPARG), and sterol regulatory element binding transcription factor 1] according to evidence about biologic plausibility for interactions with dietary fat in weight regulation. Diet was assessed at baseline, and anthropometry was followed for 7 y. RESULTS: The ORs for being a BW gainer for the 27 genetic variants ranged from 0.87 (95% CI: 0.79, 1.03) to 1.12 (95% CI: 0.96, 1.22) per additional minor allele. Uncorrected, CEBPB rs4253449 had a significant interaction with the intake of total fat and subgroups of fat. The OR for being a BW gainer for each additional rs4253449 minor allele per 100 kcal higher total fat intake was 1.07 (95% CI: 1.02, 1.12; P = 0.008), and similar associations were found for subgroups of fat. CONCLUSIONS: Among European men and women, the influence of dietary fat on associations between SNPs in the PPARγ pathway and anthropometry is likely to be absent or marginal. The observed interaction between rs4253449 and dietary fat needs confirmation.