Plasma Triacylglycerol Response Research Articles

Corn Oil, Palm Oil and Butterfat Fractions Affect Postprandial Lipemia and Lipoprotein Lipase in Meal-Fed Rats

Our objective was to investigate the time course of postprandial lipemia and lipolytic activity in male Sprague-Dawley rats trained to eat meals containing butterfat fractions, palm oil or corn oil. Baseline and postprandial blood samples were obtained via a carotid cannula in rats fed the experimental diets for 4 wk. Rats fed saturated fats compared with corn oil showed a significantly greater peak increase in postprandial triacylglycerol concentrations. Corn oil ingestion resulted in significantly lower concentrations of cholesterol and triacylglycerol in plasma and significantly less triacylglycerol accumulation (millimoles per liter per 24 h) compared with ingestion of saturated fats. Postheparin plasma lipoprotein lipase activity and plasma insulin concentration were generally greater with ingestion of corn oil compared with palm oil or butterfat. Palm oil ingestion resulted in a biphasic plasma triacylglycerol response curve and greater postheparin plasma lipoprotein lipase activity compared with butterfat ingestion, suggesting differential effects of saturated fats on postprandial lipemia. Our results indicate that greater postprandial lipemia with ingestion of saturated fats compared with corn oil may be due in part to slower plasma triacylglycerol clearance.

An interesterified palm olein test meal decreases early-phase postprandial lipemia compared to palm olein: a randomized controlled trial.

Palm oil that has been interesterified to produce a higher proportion of palmitic acid (16:0) in the sn-2 position reduces postprandial lipemia in young, normolipidemic men and women, but effects in older subjects with higher fasting triacylglycerol (TAG) concentrations are unknown. We tested the hypothesis that high-fat meals rich in interesterified palm olein (IPO) decrease lipemia and alter plasma lipoprotein fraction composition compared to native palm olein (NPO) in men aged 40-70 years with fasting TAG concentrations ≥1.2 mmol/L. Postprandial changes in plasma lipids following meals containing 75 g fat (NPO and IPO) were compared using a randomized, double-blind crossover design (n = 11). Although there were no significant differences in plasma TAG concentrations between meals over the total 6-h postprandial measurement period, IPO resulted in a decreased plasma TAG response during the first 4 h of the postprandial period (iAUC 1.65 mmol/L h, 95% CI 1.01-2.29) compared to NPO (iAUC 2.33 mmol/L h, 95% CI 1.58-3.07); meal effect P = 0.024. Chylomicron fraction TAG concentrations at 4-6 h were slightly reduced following IPO compared to NPO [NPO-IPO mean difference 0.29 mmol/L (95% CI -0.01-0.59), P = 0.055]. There were no differences in IDL fraction TAG, cholesterol or apolipoprotein B48 concentrations following IPO compared with NPO. In conclusion, consuming a meal containing palm olein with a higher proportion of 16:0 in the sn-2 position decreases postprandial lipemia compared to native palm olein during the early phase of the postprandial period in men with higher than optimal fasting triacylglycerol concentrations.

Polymorphisms, de novo lipogenesis, and plasma triglyceride response following fish oil supplementation

Interindividual variability in the response of plasma triglyceride concentrations (TG) following fish oil consumption has been observed. Our objective was to examine the associations between single-nucleotide polymorphisms (SNPs) within genes encoding proteins involved in de novo lipogenesis and the relative change in plasma TG levels following a fish oil supplementation. Two hundred and eight participants were recruited in the greater Quebec City area. The participants completed a six-week fish oil supplementation (5 g fish oil/day: 1.9-2.2 g eicosapentaenoic acid and 1.1 g docosahexaenoic acid. SNPs within SREBF1, ACLY, and ACACA genes were genotyped using TAQMAN methodology. After correction for multiple comparison, only two SNPs, rs8071753 (ACLY) and rs1714987 (ACACA), were associated with the relative change in plasma TG concentrations (P = 0.004 and P = 0.005, respectively). These two SNPs explained 7.73% of the variance in plasma TG relative change following fish oil consumption. Genotype frequencies of rs8071753 according to the TG response groups (responders versus nonresponders) were different (P = 0.02). We conclude that the presence of certain SNPs within genes, such as ACLY and ACACA, encoding proteins involved in de novo lipogenesis seem to influence the plasma TG response following fish oil consumption.

Differences in metabolomic and transcriptomic profiles between responders and non-responders to an n-3 polyunsaturated fatty acids (PUFAs) supplementation

Studies have demonstrated large within-population heterogeneity in plasma triacylglycerol (TG) response to n-3 PUFA supplementation. The objective of the study was to compare metabolomic and transcriptomic profiles of responders and non-responders of an n-3 PUFA supplementation. Thirty subjects completed a 2-week run-in period followed by a 6-week supplementation with n-3 PUFA (3g/d). Six subjects did not lower their plasma TG (+9%) levels (non-responders) and were matched to 6 subjects who lowered TG (-41%) concentrations (responders) after the n-3 PUFA supplementation. Pre-n-3 PUFA supplementation characteristics did not differ between the non-responders and responders except for plasma glucose concentrations. In responders, changes were observed for plasma hexose concentrations, docosahexaenoic acid, stearoyl-CoA-desaturase-18 ratio, and the extent of saturation of glycerophosphatidylcholine after n-3 PUFA supplementation; however, no change in these parameters was observed in non-responders. Transcriptomic profiles after n-3 PUFA supplementation indicate changes in glycerophospholipid metabolism in both subgroups and sphingolipid metabolism in non-responders. Six key genes in lipid metabolism: fatty acid desaturase 2, phospholipase A2 group IVA, arachidonate 15-lipoxygenase, phosphatidylethanolamine N-methyltransferase, monoglyceride lipase, and glycerol-3-phosphate acyltransferase, were expressed in opposing direction between subgroups. In sum, results highlight key differences in lipid metabolism of non-responders compared to responders after an n-3 PUFA supplementation, which may explain the inter-individual variability in plasma TG response.

Association between Polymorphisms in the Fatty Acid Desaturase Gene Cluster and the Plasma Triacylglycerol Response to an n-3 PUFA Supplementation

Eicosapentaenoic and docosahexaenoic acids have been reported to have a variety of beneficial effects on cardiovascular disease risk factors. However, a large inter-individual variability in the plasma lipid response to an omega-3 (n-3) polyunsaturated fatty acid (PUFA) supplementation is observed in different studies. Genetic variations may influence plasma lipid responsiveness. The aim of the present study was to examine the effects of a supplementation with n-3 PUFA on the plasma lipid profile in relation to the presence of single-nucleotide polymorphisms (SNPs) in the fatty acid desaturase (FADS) gene cluster. A total of 208 subjects from Quebec City area were supplemented with 3 g/day of n-3 PUFA, during six weeks. In a statistical model including the effect of the genotype, the supplementation and the genotype by supplementation interaction, SNP rs174546 was significantly associated (p = 0.02) with plasma triglyceride (TG) levels, pre- and post-supplementation. The n-3 supplementation had an independent effect on plasma TG levels and no significant genotype by supplementation interaction effects were observed. In summary, our data support the notion that the FADS gene cluster is a major determinant of plasma TG levels. SNP rs174546 may be an important SNP associated with plasma TG levels and FADS1 gene expression independently of a nutritional intervention with n-3 PUFA.

Association between polymorphisms in the FADS gene cluster and the plasma triacylglycerol response to an ω‐3 PUFA supplementation

The purpose of the present study is to increase knowledge about the effects of a supplementation with omega‐3 (ω‐3) polyunsaturated fatty acids (PUFA) on lipid profile in relation to the presence of single‐nucleotide polymorphisms (SNPs) in the FADS gene cluster. Plasma lipid levels were measured in 122 subjects prior and after a 5 g/d fish oil (including 3 g/d of ω‐3 PUFA) supplement for 6‐weeks. DNA was extracted and then genotyping of 19 SNPs (covering 100% of the FADS gene cluster area) was performed using TaqMan technology. The ω‐3 PUFA supplementation had an independent effect on plasma TG levels, as expected. Thirty‐six individuals (29.6%) were classified as non‐responders, meaning there was no reduction of plasma TG levels, and eighty‐six (70.4%) were responders. Two SNPs (rs174546 and rs174611) were significantly associated (p ≤ 0.05) with plasma triglyceride (TG) levels, before and after the supplementation. These results suggest that SNPs influencing plasma TG levels are also those influencing the plasma TG response to a TG‐lowering therapy.

Is the beneficial effect of prior exercise on postprandial lipaemia partly due to redistribution of blood flow?

Preprandial aerobic exercise lowers postprandial lipaemia (a risk factor for coronary heart disease); however, the mechanisms responsible are still not clear. The present study investigated whether blood flow to skeletal muscle and/or the liver was increased in the postprandial period after exercise, relative to a control trial, and whether this resulted from increased cardiac output or redistribution of flow. Eight overweight inactive males, aged 49.4±10.5years (mean±S.D.), acted as their own controls in a counterbalanced design, either walking briskly for 90min at 60% V̇O2max (maximal oxygen uptake), or resting in the lab, on the evening of day 1. The following morning, a fasting blood sample was collected, participants consumed a high-fat breakfast, and further venous blood samples were drawn hourly for 6h. Immediately after blood sampling, Doppler ultrasound was used to measure cardiac output and blood flow through both the femoral artery of one leg and the hepatic portal vein, with the ultrasonographer blinded to trial order. The total postprandial triacylglycerol response was 22% lower after exercise (P=0.001). Blood flow through the femoral artery and the hepatic portal vein was increased by 19% (P<0.001) and 16% (P=0.033), respectively, during the 6-h postprandial period following exercise; however, postprandial cardiac output did not differ between trials (P=0.065). Redistribution of blood flow, to both exercised skeletal muscle and the liver, may therefore play a role in reducing the plasma triacylglycerol response to a high-fat meal on the day after an exercise bout.

Impact of Saturated, Polyunsaturated and Monounsaturated Fatty Acid‐Rich Micelles on Lipoprotein Synthesis and Secretion in Caco‐2 Cells

Meal fatty acids have been shown to modulate the size and composition of triacylglycerol (TAG)-rich lipoproteins influencing the magnitude and duration of the postprandial plasma TAG response. As a result there is considerable interest in the origin of these meal fatty-acid induced differences in particle composition. Caco-2 cells were incubated over 4 days with fatty acid mixtures resembling the composition of saturated (SFA), monounsaturated (MUFA) and polyunsaturated fatty acid (PUFA)-rich meals fed in a previous postprandial study to determine their impact on lipoprotein synthesis and secretion. The MUFA- and PUFA-rich mixtures supported greater intracellular TAG, but not cholesterol accumulation compared with the SFA-rich mixture (P < 0.001). The MUFA-rich mixture promoted significantly greater TAG and cholesterol secretion than the other mixtures and significantly more apolipoprotein B-100 secretion than the PUFA-rich mixture (P < 0.05). Electron microscopy revealed the SFA-rich mixture had led to unfavourable effects on cellular morphology, compared with the unsaturated fatty acid-rich mixtures. Our findings suggest the MUFA-rich mixture, may support the formation of a greater number of TAG-rich lipoproteins, which is consistent with indirect observations from our human study. Our electron micrographs are suggestive that some endocytotic uptake of MUFA-rich taurocholate micelles may promote greater lipoprotein synthesis and secretion in Caco-2 cells.

Fatty acid desaturase regulation in adipose tissue by dietary composition is independent of weight loss and is correlated with the plasma triacylglycerol response

Fatty acid desaturase regulation in adipose tissue by dietary composition is independent of weight loss and is correlated with the plasma triacylglycerol response

Fatty acid desaturase regulation in adipose tissue by dietary composition is independent of weight loss and is correlated with the plasma triacylglycerol response

Background:Atherogenic dyslipidemia associated with elevated plasma triacylglycerol concentrations and reduced HDL is improved by both caloric restriction and reduced carbohydrate consumption.Objective:We aimed to identify the molecular pathways responsive to both caloric restriction and dietary composition within adipose tissue by monitoring transcriptional expression.Design:Subcutaneous adipose tissue biopsy specimens were obtained from 131 moderately overweight men [body mass index (in kg/m2): 29.2 ± 2.0] after 1 wk of a basal diet [54%, 16%, and 30% carbohydrate, protein, and fat, respectively; 7% saturated fat), after 3 wk with 1 of 4 randomized diets [basal diet; moderate-carbohydrate (39%) diet; low-carbohydrate (26%) and low-saturated-fat (9%) diet; low-carbohydrate (26%) and high-saturated-fat (15%) diet], after 5 wk of acute weight loss with a randomized diet (−1103.0 ± 216.5 kcal/d, which resulted in a loss of 10.0 ± 3.3 lb, or 4.5 ± 1.5 kg), and after 4 wk of being stabilized at a reduced weight. Transcriptional response was identified by using expression array analysis and was confirmed by using real-time polymerase chain reaction analysis.Results:Of the 1473 transcripts significantly decreased in expression in response to acute weight loss, 30 were responsive to isocaloric alterations in dietary composition, including stearoyl-coenzyme A desaturase (SCD), fatty acid desaturases 1 and 2 (FADS1 and FADS2), and diacylglycerol transferase 2 (DGAT2). Response was confirmed by real-time polymerase chain reaction analysis for these genes (P < 0.003). SCD expression in response to isocaloric dietary change was most strongly correlated with carbohydrate intake (P = 0.019) and, with the low-carbohydrate diet, SCD expression was inversely correlated with saturated fat intake (P = 0.05). Triacylglycerol responses to changes in dietary composition were independently correlated with SCD (P = 0.003) and DGAT2 (P = 0.05) responses.Conclusions:SCD expression in adipose tissue is independently regulated by weight loss and by carbohydrate and saturated fat intakes. Moreover, SCD and DGAT2 expression may be involved in dietary regulation of systemic triacylglycerol metabolism.

Postprandial lipemia after short-term variation in dietary fat and carbohydrate

Replacement of dietary fat with carbohydrate may not reduce the overall risk of coronary heart disease (CHD), because this elevates plasma triacylglycerol (TAG) concentrations. The lipoproteinemic effects of a high-carbohydrate diet are likely to be more marked shortly after the initiation of such a diet than after longer periods of intervention during which adaptive processes may counteract the initial effects. Therefore, we studied the postprandial responses to a standard meal after 3-day dietary intervention periods. An additional objective was to establish a model for future study of the mechanisms involved. Nine normolipidemic men consumed the meal (1.2 g fat, 1.1 g carbohydrate, and 0.2 g protein per 1 kg body mass) after 3 days on a high-carbohydrate diet (68% ± 3% energy from carbohydrate, mean ± SD) and also after 3 days on an isoenergetic high-fat diet (66% ± 5% energy). Venous blood samples were obtained from fasted subjects and for 6 hours after the meal. In the fasted state, TAG was higher after the high-carbohydrate diet (1.18 ± 0.18 v 0.62 ± 0.09 mmol/L, mean ± SEM, P = .02) and high-density lipoprotein (HDL) cholesterol was lower (1.01 ± 0.08 v 1.10 ± 0.09 mmol/L, P = .002). The area under the plasma TAG concentration versus time curve was 42% ± 7% higher after the high-carbohydrate diet (P = .003). After the high-carbohydrate diet, the postprandial insulin response did not differ between trials, but glucose and 3-hydroxybutyrate responses were lower (P = .009 and P = .02, respectively) and the lactate response was higher (P = .001). Plasma nonesterified fatty acids (NEFAs) were lower after the high-carbohydrate diet in the fasted state and for 4 hours postprandially, but were higher thereafter (interaction of time × trial, P = .001). These results indicate that compared with a high-fat diet, the plasma TAG response to a standard high-fat meal is markedly higher after a few days on a high-carbohydrate diet, with major differences in the associated metabolic milieu. The magnitude of these changes and the rapidity with which they developed suggest that this model may be attractive for future studies of the underlying mechanisms.

Plasma lipid and lipoprotein responsiveness to dietary fat and cholesterol in premenopausal African American and white women

Premenopausal African American women have a 2-3 times greater incidence of coronary heart disease (CHD) than do white women. The plasma lipid responsiveness to dietary fat, which may be associated with CHD, has not been adequately studied in premenopausal African American or white women. The objective of our study was to compare the effect of diet on fasting plasma lipids and lipoproteins and postprandial lipemia in premenopausal African American and white women. Thirteen African American and 9 white healthy premenopausal women were fed a low-fat, high-fiber diet and a high-fat, low-fiber diet for 4 wk each in a randomized crossover design. Fasting plasma lipid and lipoprotein concentrations and the 24-h plasma triacylglycerol response to a standard fatty test meal were measured at the end of each dietary period. Plasma total and LDL-cholesterol concentrations were higher after the high-fat, low-fiber diet in both white and African American women (P < 0.0001). The 24-h area under the plasma triacylglycerol curve after the test meal was lower after the low-fat diet than after the high-fat diet (P < 0.04). African American and white women had lower fasting plasma total and LDL-cholesterol concentrations and less postprandial lipemia after the low-fat than the high-fat diet. Diets low in total and saturated fat and cholesterol and high in fiber may reduce the risk of CHD by lowering fasting plasma total and LDL-cholesterol concentrations and by reducing the lipemic response to fatty meals.

Intestinal absorption of β-carotene ingested with a meal rich in sunflower oil or beef tallow: postprandial appearance in triacylglycerol-rich lipoproteins in women

Evidence indicates that different types of fat have different effects on the postprandial plasma triacylglycerol response. Therefore, the type of fat may influence the appearance of beta-carotene in postprandial triacylglycerol-rich lipoproteins, which is used as an indicator of intestinal beta-carotene absorption. We compared in female subjects the appearance of beta-carotene in plasma triacylglycerol-rich lipoproteins after beta-carotene was ingested with a meal containing sunflower oil or beef tallow. Women (n = 11) each ingested 2 different vitamin A-free, fat-rich meals that were supplemented with beta-carotene (47 micromol) and contained equivalent amounts (60 g) of sunflower oil or beef tallow. Blood samples were collected hourly from 0 to 10 h; additional samples were collected at selected intervals until 528 h. In a subgroup of the women (n = 7), plasma chylomicrons and 3 subfractions of VLDLs were separated by cumulative rate ultracentrifugation. The appearance of beta-carotene in chylomicrons and in each VLDL subfraction was lower after ingestion with the meal containing sunflower oil than after ingestion with the meal containing beef tallow (P < 0.03). In chylomicrons, the area under the concentration-versus-time curve (AUC) for beta-carotene was 38.1 +/- 13.6% lower (P < 0.03); in contrast, the AUC for triacylglycerol was higher (P < 0.05) after the sunflower-oil-rich meal than after the beef-tallow-rich meal. Ingestion of beta-carotene with a meal rich in sunflower oil as compared with a meal rich in beef tallow results in lower appearance of beta-carotene and greater appearance of triacylglycerol in triacylglycerol-rich lipoproteins.

The effect of acute carbohydrate load on the monophasic or biphasic nature of the postprandial lipaemic response to acute fat ingestion in human subjects

Previous studies in this laboratory have elicited a monophasic response in postprandial plasma triacylglycerol (TAG) level with fat intakes of 0.5 g fat/kg body weight accompanied by about 17 g carbohydrate as lactose. Recent studies involving the same level of fat with a higher level of carbohydrate, 136 g of which 60 g was sucrose, appeared to elicit a biphasic response. The present study compared these two test meals and showed a significant meal x time interaction for plasma total TAG (P = 0.0228) reflecting a monophasic response with the lower-carbohydrate test meal. The higher-carbohydrate meal induced significantly higher insulin and glucose-dependent insulinotropic polypeptide responses (P = 0.0009 and P = 0.0041 respectively). A significant meal x time interaction was seen for plasma non-esterified fatty acids (P = 0.0437). The biphasic plasma TAG response seen with the high-carbohydrate meal largely reflected the TAG-rich lipoprotein (TRL) or chylomicron fraction, which would tend to suggest a biphasic pattern of absorption. This was borne out by TRL-TAG fatty acid compositions. Both peak in the biphasic response showed active incorporation of the main dietary fatty acids, 18:1n-9, 18:2n-6 and 18:3n-3 into TRL-TAG. These results indicate that under the specific test-meal conditions used in the present study, a biphasic pattern of fat absorption was seen.

An NCEP II Diet Reduces Postprandial Triacylglycerol in Normocholesterolemic Adults

We compared the fasting and postprandial response to a National Cholesterol Education Program (NCEP) II diet with that of a diet high in total (40% of energy) and saturated fat. In free-living conditions, 17 healthy normolipidemic, normoglycemic men and women consumed a high-fat diet, a maintenance diet and the NCEP II diet, for 1 mo each. At the completion of each dietary period, an oral fat load (70 g/m2 body surface area) was administered and plasma triacylglycerol (TAG) determined every 2 h for 8 h. Compared with the high-fat phase, the NCEP II diet was associated with significantly lower energy intake (12.1 ± 1.1 vs. 7 ± 0.7 MJ/d) and final body weight (78 ± 3.8 vs. 76.3 ± 3.5 kg) (P < 0.01). Plasma high density lipoprotein cholesterol, apolipoprotein (apo) A-I and ApoB concentrations were also significantly lower when subjects consumed the NCEP II diet rather than the high-fat diet (P ≤ 0.004). There were no significant differences in subjects fasting TAG, glucose or insulin concentration between the high fat and NCEP II diet periods. However, the postprandial plasma TAG response to the fat load was lower after completing the NCEP II than after the high-fat diet period (P = 0.045). Under free-living conditions, a NCEP II diet was associated with weight loss and a decrease in postprandial but not fasting TAG. Because dietary alteration may not affect fasting TAG levels, thorough assessment of a dietary intervention should include measurements of postprandial TAG.

Effect of chitin and chitosan on nutrient digestibility and plasma lipid concentrations in broiler chickens

Broiler chickens were fed on a control diet based on maize and maize starch or diets containing chitin, or 94, 82 or 76% deacetylated chitin (chitosans) with different viscosities (360, 590 and 620 m Pa.s respectively) at an inclusion level of 30 g/kg. Animals had free access to feed and water for the whole experimental period. On days 10 and 18 of the experiment chickens given the control and chitin-containing diets weighed more, had consumed more feed and had lower feed conversion ratios (g feed/g weight gain) than chitosan-fed birds. Feeding of chitosan-containing diets generally reduced total plasma cholesterol and high-density-lipoprotein (HDL)-cholesterol concentrations and gave an increased HDL:total cholesterol ratio in comparison with chickens given the control and chitin-containing diets. However, no significant reductions in plasma triacylglycerol concentrations resulting from feeding of the chitosan-containing diets were observed. The reduction in total cholesterol concentration and increased HDL:total cholesterol ratio were probably caused by enhanced reverse cholesterol transport in response to intestinal losses of dietary fats. The suggestion that dietary fat absorption was impeded by the chitosans was strengthened by the observation that ileal fat digestibility was reduced by 26% in comparison with control and chitin-fed animals. In a plasma triacylglycerol response study on day 21, feeding of 94 and 76%-chitosan-containing diets generally reduced postprandial triacylglycerol concentrations compared with chickens given the chitin-containing diet. Duodenal digestibilities of nutrients amongst chickens given the chitin-containing diet were generally lower than those of control and chitosan-fed birds indicating decreased intestinal transit time. The reduced caecal short-chain fatty acid concentrations of chickens given chitosan diets compared with the control diet illustrates the antimicrobial nature of chitosan. The fact that the three chitosan-containing diets affected the registered variables similarly indicated that the level of inclusion of chitosans in the diet exceeded the level at which the effect of the different viscosities could be significant.