Butter differs from olive oil and sunflower oil in its effects on postprandial lipemia and triacylglycerol-rich lipoproteins after single mixed meals in healthy young men

Accumulation of postprandial triacylglycerol-rich lipoproteins is generated by assimilation of ingested dietary fat and has been increasingly related to atherogenic risk. Nevertheless, the influence of different kinds of dietary fatty acids on postprandial lipid metabolism is not well established, except for (n-3) polyunsaturated long-chain fatty acids. Our goal was to evaluate the effects of test meals containing a common edible fat source of saturated (butter), monounsaturated (olive oil) or (n-6) polyunsaturated (sunflower oil) fatty acids on postprandial lipid and triacylglycerol-rich lipoprotein responses. After a 12-h fast, 10 healthy young men ingested mixed meals containing 0 g (control) or 40 g fat, provided as butter, olive oil or sunflower oil in a random order. Fasting and postmeal blood samples were collected for 7 h. The no-fat test meal did not elicit any change over baseline except for plasma phospholipids, insulin and nonesterified fatty acids. Conversely, the three fat-containing meals elicited bell-shaped postprandial changes (P < 0.05) in serum triacylglycerols, free and esterified cholesterol, and nonesterified fatty acids. The butter meal induced a lower postprandial rise of triacylglycerols in serum and chylomicrons (incremental AUC, mmol.h/L: 0.72) than the two unsaturated oils (olive oil: 1.6, sunflower oil: 1.8), which did not differ. Circulating chylomicrons were smaller after the butter meal than after the two vegetable oil meals. The in vitro susceptibility of circulating chylomicrons to hydrolysis by postheparin plasma was higher after sunflower oil than after butter or olive oil. We conclude that butter results in lower postprandial lipemia and chylomicron accumulation in the circulation of young men than olive or sunflower oils after consumption of a single mixed meal.     

Differential effects of saturated and monounsaturated fats on postprandial lipemia and glucagon-like peptide 1 responses in patients with type 2 diabetes

BACKGROUND: Postprandial lipemia is important in the development of coronary artery disease because of elevated postprandial triacylglycerol-rich plasma lipoproteins and suppressed HDL-cholesterol concentrations. We showed in healthy subjects a possible association between postprandial lipid metabolism and the responses of the duodenal incretin hormones glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide after meals rich in saturated and monounsaturated fatty acids (oleic acid), respectively. OBJECTIVE: The objective was to compare the postprandial responses (8 h) of glucose, insulin, fatty acids, triacylglycerol, gastric inhibitory polypeptide, and GLP-1 to saturated- and monounsaturated-rich test meals. DESIGN: Twelve overweight patients with type 2 diabetes ingested 3 meals randomly: an energy-free soup with 50 g carbohydrate (control meal), the control meal plus 100 g butter, and the control meal plus 80 g olive oil. Triacylglycerol responses were measured in total plasma and in a chylomicron-rich and a chylomicron-poor fraction. RESULTS: No significant differences in the glucose, insulin, or fatty acid responses to the 2 fat-rich meals were seen. The plasma triacylglycerol and chylomicron triacylglycerol responses were highest after the butter meal. HDL-cholesterol concentrations decreased significantly after the butter meal but did not change significantly after the olive oil meal. GLP-1 responses were highest after the olive oil meal. CONCLUSIONS: Olive oil induced lower triacylglycerol concentrations and higher HDL-cholesterol concentrations than did butter, without eliciting significant changes in glucose, insulin, or fatty acids. Furthermore, olive oil induced higher concentrations of GLP-1, which may indicate a relation between fatty acid composition, incretin responses, and triacylglycerol metabolism postprandially in patients with type 2 diabetes.     

Differential effects of saturated and monounsaturated fatty acids on postprandial lipemia and incretin responses in healthy subjects.

BACKGROUND: Elevations of postprandial triacylglycerol-rich plasma lipoproteins and suppressions of HDL-cholesterol concentrations are considered potentially atherogenic. Long-term studies have shown beneficial effects of monounsaturated fatty acids (eg, oleic acid) on fasting lipid and lipoprotein concentrations in humans. A direct stimulatory effect of oleic acid on the secretion of glucagon-like peptide 1 (GLP-1) was shown in animal studies. OBJECTIVE: We compared the postprandial responses of glucose, insulin, fatty acids, triacylglycerol, gastric inhibitory polypeptide (GIP), and GLP-1 to test meals rich in saturated and monounsaturated fatty acids. DESIGN: Ten young, lean, healthy persons ingested 3 meals: an energy-free soup consumed with 50 g carbohydrate (control meal), the control meal plus 100 g butter, and the control meal plus 80 g olive oil. Triacylglycerol and retinyl palmitate responses were measured in total plasma, in a chylomicron-rich fraction, and in a chylomicron-poor fraction. RESULTS: No significant differences in glucose, insulin, or fatty acid responses to the 2 fat-rich meals were seen. Plasma triacylglycerol responses were highest after the butter meal, with chylomicron triacylglycerol rising 2.5-5-fold. Retinyl palmitate responses were higher and more prolonged after the butter meal than after the control and olive oil meals, whereas both postprandial HDL-cholesterol concentrations and GLP-1 and GIP responses were higher after the olive oil meal than after the butter meal. CONCLUSIONS: Olive oil induced lower triacylglycerol concentrations and higher HDL-cholesterol concentrations than butter, without eliciting differences in concentrations of glucose, insulin, or fatty acids. Furthermore, olive oil induced higher concentrations of GLP-1 and GIP than did butter, which may point to a relation between fatty acid composition, incretin responses, and triacylglycerol metabolism in the postprandial phase.     

Dietary fat and carbohydrate quality have independent effects on postprandial glucose and lipid responses

Purpose

The magnitude of postprandial lipemia is influenced not only by the amount but also the type of fat and carbohydrate consumed. The aim of this study was to evaluate differences in postprandial glucose and lipid responses after a mixed meal containing low- or high-glycemic-index (GI) carbohydrate and three different types of fat varying in the degree of saturation in healthy subjects.

Methods

A randomized, controlled, single-blinded crossover study was conducted in 20 healthy Chinese men. Subjects consumed in random order six experimental isocaloric meals that differed in carbohydrate and fat quality, and contained 40 g of either saturated fat (SFA, butter), monounsaturated fat (MUFA, olive oil) or polyunsaturated fat (PUFA, grapeseed oil), and 50 g of either low-GI (basmati rice) or high-GI (jasmine rice) carbohydrate. Glucose, insulin, c-peptide, triglycerides (TG) and non-esterified fatty acids (NEFA) were measured over 4 h.

Results

For all substrates evaluated, there were no significant interactions between fat and carbohydrate. The incremental area under the curve (iAUC) for TG was significantly lower after the SFA and PUFA meals compared with the MUFA meal, irrespective of GI. No significant difference was found for NEFA iAUC in all treatments. Glucose, insulin and c-peptide iAUCs were significantly lower after ingestion of low-GI than high-GI meals, independent of the type of fat.

Conclusions

A carbohydrate-rich meal (of either low or high GI) that contains butter or grapeseed oil results in lower postprandial TG concentrations relative to olive oil in healthy Chinese males. Glucose, insulin and c-peptide responses, however, are directly dependent on the GI of the meal and not on the degree of saturation of dietary fat.The trial was registered at clinicaltrials.gov as NCT02585427.

     

Acute effects of meal fatty acid composition on insulin sensitivity in healthy post-menopausal women

Postprandial plasma insulin concentrations after a single high-fat meal may be modified by the presence of specific fatty acids although the effects of sequential meal ingestion are unknown. The aim of the present study was to examine the effects of altering the fatty acid composition in a single mixed fat-carbohydrate meal on glucose metabolism and insulin sensitivity of a second meal eaten 5 h later. Insulin sensitivity was assessed using a minimal model approach. Ten healthy post-menopausal women underwent four two-meal studies in random order. A high-fat breakfast (40 g fat) where the fatty acid composition was predominantly saturated fatty acids (SFA), n-6 polyunsaturated fatty acids (PUFA), long-chain n-3 PUFA or monounsaturated fatty acids (MUFA) was followed 5 h later by a low-fat, high-carbohydrate lunch (5.7 g fat), which was identical in all four studies. The plasma insulin response was significantly higher following the SFA meal than the other meals after both breakfast and lunch (P<0.006) although there was no effect of breakfast fatty acid composition on plasma glucose concentrations. Postprandial insulin sensitivity (SI(Oral)) was assessed for 180 min after each meal. SI(Oral) was significantly lower after lunch than after breakfast for all four test meals (P=0.019) following the same rank order (SFA < n-6 PUFA < n-3 PUFA < MUFA) for each meal. The present study demonstrates that a single meal rich in SFA reduces postprandial insulin sensitivity with 'carry-over' effects for the next meal.     

Absorption of the n-3 eicosapentaenoic and docosahexaenoic acids as ethyl esters and triglycerides by humans.

Five normolipemic subjects received three test meals containing 28 g n-3 (omega-3) fatty acids provided as 1) triglycerides, 2) ethyl esters, and 3) ethyl esters + 12 g olive oil. The control meal contained olive oil. When equivalent amounts of fat were given, the increase in chylomicron and plasma triglycerides was similar; n-3 fatty acid contents were also similar after n-3 fatty acid intake as ethyl esters or triglycerides. Ethyl esters alone were well absorbed and produced similar n-3 fatty acid responses in plasma triglycerides and chylomicrons. At 24 h after the n-3 fatty acid-containing meals, the fatty acid plasma concentration of these acids was similar. This study showed that n-3 fatty acids in fish oil given as ethyl esters or triglycerides were equally well absorbed. Eicosapentaenoic and docosahexaenoic acids were also equally absorbed.     

The influence of dietary fibre source and gender on the postprandial glucose and lipid response in healthy subjects

Background

Consumption of soluble dietary fibre is correlated with decreased postprandial glucose and insulin responses and hence has beneficial effects on the metabolic syndrome.

Aim of the study

To investigate the effects on postprandial glucose, insulin and triglyceride concentrations of meals enriched with soluble dietary fibres from oats, rye bran, sugar beet fibre or a mixture of these three fibres.

Methods

Thirteen healthy human volunteers (6 men and 7 women, aged 20–28 years) were included in the study. The subjects came to the study centre once a week after an overnight fast to ingest test meals and a control meal in random order. The meals contained either oat powder (62 g, of which 2.7 soluble fibre), rye bran (31 g, of which 1.7 g soluble fibre), sugar beet fibre (19 g, of which 5 g soluble fibre), a mixture of these three fibres (74 g, of which 1.7 g soluble fibre from each source, giving 5 g soluble fibre) or no added fibre (control) and were all adjusted to contain the same total amount of available carbohydrates. Blood samples were drawn before and every 30 min up to 180 min after the meals.

Results

Meals with rye bran gave a lower postprandial glucose peak when compared with the control meal, and this effect was more pronounced in women compared to men. Oat powder, containing a low amount of total fibre and a high amount of carbohydrates in liquid matrix, gave a higher incremental glucose peak concentration compared to rye bran and sugar beet fibre and higher insulin incremental area under curve compared to control. The oat powder also influenced the effects of the mixed meal, diminishing the glucose-lowering effects. Postprandial triglyceride levels tended to be higher after all fibre-rich meals, but only significant for oat powder and the mixed meal when compared with the control meal.

Conclusions

Postprandial glucose, insulin and triglyceride concentrations are influenced by dietary fibre-rich meals, depending on fibre source, dose of soluble and total fibre and possibly gender.     

Exchanging saturated fatty acids for (n-6) polyunsaturated fatty acids in a mixed meal may decrease postprandial lipemia and markers of inflammation and endothelial activity in overweight men

Postprandial lipemia, low-grade systemic inflammation, and endothelial activity are related to metabolic disorders. It is well known that dietary fatty acid composition modulates postprandial lipemia, but information on the other metabolic risk markers is limited. We therefore studied the acute effects of a meal rich in SFA compared with those of a meal rich in (n-6) PUFA on postprandial responses in overweight men who are at an increased risk to develop the metabolic syndrome and its comorbidities. In a crossover design, the effects of 50 g butter (rich in SFA) on lipemia and markers for inflammation and endothelial activity were compared with those of 50 g sunflower oil [rich in (n-6) PUFA] during an 8-h postprandial mixed meal tolerance test in 13 overweight men. Postprandial changes in serum TG were comparable between the meals (P = 0.38), except for a reduction in the incremental area under the curve (P = 0.046) in the late postprandial phase after (n-6) PUFA (125 ± 96 mmol?min?L(-1)) compared with SFA (148 ± 98 mmol?min?L(-1)). Compared with the SFA meal, the (n-6) PUFA meal decreased plasma IL-6 (P = 0.003), TNFα (P = 0.005), soluble TNF receptors I and II (sTNFr; P = 0.024 and P < 0.001, respectively), and soluble vascular cell adhesion molecule-1 (sVCAM-1; P = 0.030) concentrations. These results indicate that exchanging SFA from butterfat for (n-6) PUFA in a mixed meal may decrease postprandial lipemia and concentrations of IL-6, TNFα, sTNFr-I and -II, and sVCAM-1 in overweight men.     

The amount and types of fatty acids acutely affect insulin,glycemic and gastrointestinal peptide responses but not satiety in metabolic syndrome subjects

Purpose

Limited clinical evidence is available on the effects of amount and types of dietary fats on postprandial insulinemic and gastrointestinal peptide responses in metabolic syndrome subjects. We hypothesized that meals enriched with designated: (1) amount of fats (50 vs 20 g), (2) fats with differing fatty acid composition (saturated, SFA; monounsaturated, MUFA or n-6 polyunsaturated fatty acids, PUFA) would affect insulinemic and gastrointestinal peptide releases in metabolic syndrome subjects.

Methods

Using a randomized, crossover and double-blinded design, 15 men and 15 women with metabolic syndrome consumed high-fat meals enriched with SFA, MUFA or n-6 PUFA, or a low-fat/high-sucrose (SUCR) meal. C-peptide, insulin, glucose, gastrointestinal peptides and satiety were measured up to 6 h.

Results

As expected, SUCR meal induced higher C-peptide (45 %), insulin (45 %) and glucose (49 %) responses compared with high-fat meals regardless of types of fatty acids (P < 0.001). Interestingly, incremental area under the curve (AUC_0-120min) for glucagon-like peptide-1 was higher after SUCR meal compared with MUFA (27 %) and n-6 PUFA meals (23 %) (P = 0.01). AUC_0-120min for glucose-dependent insulinotropic polypeptide was higher after SFA meal compared with MUFA (23 %) and n-6 PUFA meals (20 %) (P = 0.004). Significant meal x time interaction (P = 0.007) was observed for ghrelin, but not cholecystokinin and satiety.

Conclusions

The amount of fat regardless of the types of fatty acids affects insulin and glycemic responses. Both the amount and types of fatty acids acutely affect the gastrointestinal peptide release in metabolic syndrome subjects, but not satiety.

     

Effect of meal fat quality on oxidation resistance of postprandial VLDL and LDL particles and plasma triacylglycerol level

This study was performed to examine the postprandial effects of meals containing dietary fats, with their natural fatty acid composition and tocopherol content, on the plasma triacylglycerols (TG) and tocopherols and on the resistance of VLDL and LDL to oxidation. On six separate days eighteen healthy male subjects were given low-fat meals (LF) or the LF meals enriched with sunflower oil (SO), rapeseed oil (RO), olive oil (OO), palm oil (PO), or butter (B) in a crossover design. The fat-rich meals all resulted in similar postprandial TG responses while the LF test meal did not increase plasma TG level. The postprandial plasma fatty acid profile changed to resemble the fatty acid composition of the ingested test fat. The alpha-tocopherol:gamma-tocopherol ratios in postprandial plasma and VLDL samples were greater than in the test fats. We found that the resistance of VLDL particles to oxidation in the postprandial state as assessed from lag time was increased after the PO-rich meal as compared with the SO-rich meal (p = 0.018), and the propagation rate was greater after the SO- and RO-rich meals compared with the others (p < 0.001). The resistance of LDL particles to oxidation was unaffected by the meals. In postprandial VLDL samples, the content of alpha-tocopherol was greater after the OO- and SO-rich meals compared with the meal rich in PO (P = 0.034 and 0.042 respectively). The gamma-tocopherol content of VLDL was highest after RO-meal as compared with all other test meals (P = 0.0019), and higher after SO as compared with B (P = 0.0148). Large individual differences were noted. In conclusion, meals enriched with different fats lead to the formation of VLDL particles with varying resistance to oxidation.     

Ingestion of a single serving of saury alters postprandial levels of plasma n-3 polyunsaturated fatty acids and long-chain monounsaturated fatty acids in healthy human adults

ABSTRACT: BACKGROUND: Saury oil contains considerable amounts of n-3 polyunsaturated fatty acids (PUFA) and monounsaturated fatty acids (MUFA) with long aliphatic tails (>18C atoms). Ingestion of saury oil reduces the risk of developing metabolic syndrome concomitant with increases in n-3 PUFA and long-chain MUFA in plasma and organs of mice. We therefore evaluated changes in postprandial plasma fatty acid levels and plasma parameters in healthy human subjects after ingestion of a single meal of saury. FINDINGS: Five healthy human adults ingested 150 g of grilled saury. Blood was collected before the meal and at 2, 6, and 24 hr after the meal, and plasma was prepared. Plasma levels of eicosapentaenoic acid, docosahexaenoic acid, and long-chain MUFA (C20:1 and C22:1 isomers combined) increased significantly throughout the postprandial period compared with the pre-meal baseline. Postprandial plasma insulin concentration increased notably, and plasma levels of glucose and free fatty acids decreased significantly and subsequently returned to the pre-meal levels. CONCLUSIONS: Our study suggests that a single saury meal may alter the postprandial plasma levels of n-3 PUFA and long-chain MUFA in healthy human subjects.     

Chronic dietary fat intake modifies the postprandial response of hemostatic markers to a single fatty test meal

BACKGROUND: Hemostasis is the result of a complex equilibrium between coagulation and fibrinolysis, and the influence of different dietary models on this equilibrium is not entirely known. OBJECTIVE: The objective was to compare the effects of the chronic intake of different dietary models on postprandial hemostasis. DESIGN: In a randomized crossover design, 20 healthy men consumed for 28 d each diets rich in monounsaturated fatty acids (MUFAs), saturated fatty acids (SFAs), and carbohydrates plus n-3 fatty acids (CHO/N3). Fasting and postprandial hemostatic factors (factor VII coagulant activity, plasminogen activator inhibitor-1, tissue-type plasminogen activator, d-dimer, and thromboxane B(2)) were measured; meal tests for the postprandial measures were based on butter, virgin olive oil, and walnuts for the SFA, MUFA, and CHO/N3 diets, respectively. RESULTS: There were no differences in the fasting variables after the dietary periods. After the 3 fatty meals were consumed, we observed an increase in thromboxane B(2) and d-dimer and a reduction in tissue plasminogen activator, irrespective of the dietary model. The MUFA or CHO/N3 meals lowered postprandial concentrations of factor VII coagulant activity, although the reduction was greater after the MUFA-enriched meal. The concentration of plasminogen activator inhibitor-1 was greater after the SFA meal than after the other 2 meals. CONCLUSIONS: The administration of a fatty meal induces a postprandial procoagulant tendency, irrespective of the type of fat consumed. However, the use of a dietary model rich in SFA creates a more procoagulant environment than does a model that includes MUFA or CHO/N3 as the source of fatty acids.     

(n-3) fatty acid supplementation in moderately hypertriglyceridemic adults changes postprandial lipid and apolipoprotein B responses to a standardized test meal.

The effects of (n-3) fatty acids on the postprandial state were investigated by monitoring the alimentary responses to identical test meals fed to adults [n = 11; fasting triacylglycerol (TG) 2.55 +/- 0.24 mmol/L; mean +/- SEM] after a self-selected diet baseline period (BLP) and then after a 6-wk (n-3) fatty acid period (FOP) [ approximately 5.2 g (n-3) fatty acids] and a 6-wk control oil period (COP) administered in random order. Samples were drawn immediately prior to the test meal (time 0) and then hourly from 2 to 6 h postmeal. Postprandial plasma triacylglycerol (TG) and TG-rich lipoprotein (TRL) TG apo B48, and B100 absolute concentrations were significantly lower after FOP than after COP or BLP, while plasma cholesterol was unchanged. Normalizing the results as increments over time 0 eliminated the diet effect on all but plasma TG. Time remained a significant effect for plasma TG, TRL TG, and TRL TC. Finally, only absolute TRL B48 and absolute and incremental plasma TG concentrations displayed significant time-diet interactions. These results suggest that postprandial TRL apo B reductions are likely caused by (n-3) fatty acid suppression of both hepatic and intestinal apoB secretion/synthesis. Altered TRL metabolism, i.e. changes in postprandial TG, cholesterol, apo B48, and increase in LDL particle size, may represent an additional mechanism for the reduced heart disease risk associated with fish [(n-3) fatty acid] consumption.     

Postprandial lipoprotein, glucose and insulin responses after two consecutive meals containing rapeseed oil, sunflower oil or palm oil with or without glucose at the first meal

There is increasing evidence that the degree of postprandial lipaemia may be of importance in the development of atherosclerosis and IHD. Postprandial lipid, lipoprotein, glucose, insulin and non-esterified fatty acid (NEFA) concentrations were investigated in eleven healthy young males after randomized ingestion of meals containing rapeseed oil, sunflower oil or palm oil with or without a glucose drink. On six occasions each subject consumed consecutive meals (separated by 1.75 h) containing 70 g (15 g and 55 g respectively) of each oil. On one occasion with each oil 50 g glucose was taken with the first meal. One fasting and fifteen postprandial blood samples were taken over 9 h. There were no statistically significant differences in lipoprotein and apolipoprotein responses after rapeseed, sunflower and palm oils, whereas insulin responses were lower after sunflower oil than after rapeseed oil (ANOVA, P = 0.04). The NEFA and triacylglycerol concentrations at 1.5 h were reduced when 50 g glucose was taken with the first meal (ANOVA, P < 0.0001 and P < 0.05 respectively), regardless of meal fatty acid composition. In conclusion, the consumption of glucose with a mixed meal containing either rapeseed, sunflower or palm oil influenced the immediate triacylglycerol and NEFA responses compared with the same meal without glucose, whereas no significant effect on postprandial lipaemia after a subsequent meal was observed. The fatty acid composition of the meal did not significantly affect the lipid and lipoprotein responses, whereas an effect on insulin responses was observed.     

Effects of olive oil and its fractions on oxidative stress and the liver's fatty acid composition in 2,4-Dichlorophenoxyacetic acid-treated rats

Background

Dietary long-chain polyunsaturated fatty acids (LC-PUFA) are of crucial importance for the development of neural tissues. The aim of this study was to evaluate the impact of a dietary supplementation in n-3 fatty acids in female rats during gestation and lactation on fatty acid pattern in brain glial cells phosphatidylethanolamine (PE) and phosphatidylserine (PS) in the neonates.

Methods

Sprague-Dawley rats were fed during the whole gestation and lactation period with a diet containing either docosahexaenoic acid (DHA, 0.55%) and eicosapentaenoic acid (EPA, 0.75% of total fatty acids) or α-linolenic acid (ALA, 2.90%). At two weeks of age, gastric content and brain glial cell PE and PS of rat neonates were analyzed for their fatty acid and dimethylacetal (DMA) profile. Data were analyzed by bivariate and multivariate statistics.

Results

In the neonates from the group fed with n-3 LC-PUFA, the DHA level in gastric content (+65%, P < 0.0001) and brain glial cell PE (+18%, P = 0.0001) and PS (+15%, P = 0.0009) were significantly increased compared to the ALA group. The filtered correlation analysis (P < 0.05) underlined that levels of dihomo-γ-linolenic acid (DGLA), DHA and n-3 docosapentaenoic acid (DPA) were negatively correlated with arachidonic acid (ARA) and n-6 DPA in PE of brain glial cells. No significant correlation between n-3 and n-6 LC-PUFA were found in the PS dataset. DMA level in PE was negatively correlated with n-6 DPA. DMA were found to occur in brain glial cell PS fraction; in this class DMA level was correlated negatively with DHA and positively with ARA.

Conclusion

The present study confirms that early supplementation of maternal diet with n-3 fatty acids supplied as LC-PUFA is more efficient in increasing n-3 in brain glial cell PE and PS in the neonate than ALA. Negative correlation between n-6 DPA, a conventional marker of DHA deficiency, and DMA in PE suggests n-6 DPA that potentially be considered as a marker of tissue ethanolamine plasmalogen status. The combination of multivariate and bivariate statistics allowed to underline that the accretion pattern of n-3 LC-PUFA in PE and PS differ.     

Long-term aerobic exercise and omega-3 supplementation modulate osteoporosis through inflammatory mechanisms in post-menopausal women: a randomized, repeated measures study

Background

Walnuts significantly decrease total and low-density lipoprotein cholesterol in normo- and hypercholesterolemic individuals. No study to date has evaluated the effects of walnuts on cholesterol efflux, the initial step in reverse cholesterol transport, in macrophage-derived foam cells (MDFC). The present study was conducted to investigate the mechanisms by which walnut oil affects cholesterol efflux.

Methods

The extract of English walnuts (walnut oil) was dissolved in DMSO and applied to cultured THP-1 MDFC cells (0.5 mg/mL). THP-1 MDFC also were treated with human sera (10%, v:v) taken from subjects in a walnut feeding study. Cholesterol efflux was examined by liquid scintillation counting. Changes in gene expression were quantified by real time PCR.

Results

Walnut oil treatment significantly increased cholesterol efflux through decreasing the expression of the lipogenic enzyme stearoyl CoA desaturase 1 (SCD1) in MDFC. Alpha-linolenic acid (ALA), the major n-3 polyunsaturated fatty acids found in walnuts, recaptured SCD1 reduction in MDFC, a mechanism mediated through activation of nuclear receptor farnesoid-X-receptor (FXR). Postprandial serum treatment also increased cholesterol efflux in MDFC. When categorized by baseline C-reactive protein (CRP; cut point of 2 mg/L), subjects in the lower CRP sub-group benefited more from dietary intervention, including a more increase in cholesterol efflux, a greater reduction in SCD1, and a blunted postprandial lipemia.

Conclusion

In conclusion, walnut oil contains bioactive molecules that significantly improve cholesterol efflux in MDFC. However, the beneficial effects of walnut intake may be reduced by the presence of a pro-inflammatory state.

Trial Registration

ClinicalTrials.gov: NCT00938340     

Greater enrichment of triacylglycerol-rich lipoproteins with apolipoproteins E and C-III after meals rich in saturated fatty acids than after meals rich in unsaturated fatty acids

BACKGROUND: Although there is considerable interest in the postprandial events involved in the absorption of dietary fats and the subsequent metabolism of diet-derived triacylglycerol-rich lipoproteins, little is known about the effects of meal fatty acids on the composition of these particles. OBJECTIVE: We examined the effect of meal fatty acids on the lipid and apolipoprotein contents of triacylglycerol-rich lipoproteins. DESIGN: Ten normolipidemic men received in random order a mixed meal containing 50 g of a mixture of palm oil and cocoa butter [rich in saturated fatty acids (SFAs)], safflower oil [n-6 polyunsaturated fatty acids (PUFAs)], or olive oil [monounsaturated fatty acids (MUFAs)] on 3 occasions. Fasting and postprandial apolipoproteins B-48, B-100, E, C-II, and C-III and lipids (triacylglycerol and cholesterol) were measured in plasma fractions with Svedberg flotation rates (S(f)) >400, S(f) 60-400, and S(f) 20-60. RESULTS: Calculation of the composition of the triacylglycerol-rich lipoproteins (expressed per mole of apolipoprotein B) showed notable differences in the lipid and apolipoprotein contents of the SFA-enriched particles in the S(f) > 400 and S(f) 60-400 fractions. After the SFA meal, triacylglycerol-rich lipoproteins in these fractions showed significantly greater amounts of triacylglycerol and of apolipoproteins C-II (S(f) 60-400 fraction only), C-III, and E than were found after the MUFA meal (P < 0.02) and more cholesterol, apolipoprotein C-III (S(f) > 400 fraction only), and apolipoprotein E than after the PUFA meal (P < 0.02). CONCLUSIONS: Differences in the composition of S(f) > 400 and S(f) 60-400 triacylglycerol-rich lipoproteins formed after saturated compared with unsaturated fatty acid-rich meals may explain differences in the metabolic handling of dietary fats.     

Influence of a stearic acid-rich structured triacylglycerol on postprandial lipemia, factor VII concentrations, and fibrinolytic activity in healthy subjects

BACKGROUND: An elevated postprandial lipid concentration is believed to be atherogenic and to increase the risk of thrombosis. OBJECTIVE: The objective was to test whether the consumption of a stearic acid-rich structured triacylglycerol has adverse effects on postprandial fibrinolytic activity and lipemia, factor VII coagulant (FVII:c) activity, and activated FVII (FVIIa) concentrations. DESIGN: A randomized crossover design was used to compare the effects on middle-aged healthy men (n = 17) and women (n = 18) of meals enriched with cocoa butter, high-oleate sunflower oil (oleate), or a structured triacylglycerol containing stearic acid. RESULTS: The mean increases from fasting in plasma triacylglycerol 3 h after the oleate, cocoa butter, and structured triacylglycerol meals were 1.36 (95% CI: 1.17, 1.56), 1.39 (1.17,1.63), and 0.65 (0.50, 0.82) mmol/L, respectively. Tissue plasminogen activator activity increased and plasminogen activator type 1 activity decreased after all 3 meals. Plasma FVII:c increased after the oleate and cocoa butter meals but not after the structured triacylglycerol meal. The values 6 h after the oleate and cocoa butter meals were 11.3% (7.0%, 15.6%) and 9.9% (4.7%, 15.2%), respectively, and were significantly different (P < 0.0001 and P = 0.001, respectively) from the value after the triacylglycerol meal [2.1% (-1.1%, 5.3%)]. Plasma FVIIa increased after all 3 meals, more so after the oleate and cocoa butter meals than after the structured triacylglycerol meal. CONCLUSION: The consumption of stearic acid in the form of a structured triacylglycerol leads to less of an increase in plasma triacylglycerol and in FVII:c than does a meal enriched in cocoa butter or oleate.     

Effects of alpha-linolenic acid vs. docosahexaenoic acid supply on the distribution of fatty acids among the rat cardiac subcellular membranes after a short- or long-term dietary exposure

Background

Previous work showed that the functional cardiac effect of dietary alpha-linolenic acid (ALA) in rats requires a long feeding period (6 months), although a docosahexaenoic (DHA) acid-supply affects cardiac adrenergic response after 2 months. However, the total cardiac membrane n-3 polyunsaturated fatty acid (PUFA) composition remained unchanged after 2 months. This delay could be due to a specific reorganization of the different subcellular membrane PUFA profiles. This study was designed to investigate the evolution between 2 and 6 months of diet duration of the fatty acid profile in sarcolemmal (SL), mitochondrial (MI), nuclear (NU) and sarcoplasmic reticulum (SR) membrane fractions.

Methods

Male Wistar rats were randomly assigned to 3 dietary groups (n = 10/diet/period), either n-3 PUFA-free diet (CTL), or ALA or DHA-rich diets. After 2 or 6 months, the subcellular cardiac membrane fractions were separated by differential centrifugations and sucrose gradients. Each membrane profile was analysed by gas chromatography (GC) after lipid extraction.

Results

As expected the n-3 PUFA-rich diets incorporated n-3 PUFA instead of n-6 PUFA in all the subcellular fractions, which also exhibited individual specificities. The diet duration increased SFA and decreased PUFA in SL, whereas NU remained constant. The SR and MI enriched in n-3 PUFA exhibited a decreased DHA level with ageing in the DHA and CTL groups. Conversely, the n-3 PUFA level remained unchanged in the ALA group, due to a significant increase in docosapentaenoic acid (DPA). N-3 PUFA rich diets lead to a better PUFA profile in all the fractions and significantly prevent the profile modifications induced by ageing.

Conclusion

With the ALA diet the n-3 PUFA content, particularly in SR and SL kept increasing between 2 and 6 months, which may partly account for the delay to achieve the modification of adrenergic response.