Dietary Cocoa Butter or Refined Olive Oil Does Not Alter Postprandial hsCRP and IL-6 Concentrations in Healthy Women

Contrary to other long chain saturated fatty acids (SFA), fats high in stearic acid do not raise plasma cholesterol concentrations, however, a slight elevation in inflammatory markers, plasma fibrinogen and interleukin-6 (IL-6), has been observed in the fasting state. The effect of stearic acid on inflammation in the postprandial state has not yet been reported. We conducted a single blind crossover, randomized, postprandial study to compare the effects of a fat load of cocoa butter high in stearic acid and olive oil in ten healthy women. The test meals contained 1 g of fat per kg body weight (mean 62 g). Blood samples were collected at 0 (fasting), 4 and 6 h. Both diets resulted in a significant increase in serum triacylglycerol (TAG) concentration over time (P = 0.003) and a decrease in serum IL-6 concentration after 4 h followed by an increase to post absorptive values after 6 h (P < 0.001); whereas serum high sensitivity C-reactive protein (hsCRP) concentration was not affected. There was no difference between diets in effects on serum TAG, hsCRP and IL-6 concentrations and no association between postprandial lipemia and inflammatory markers. High intake of dietary fats increase postprandial serum TAG, however, may not affect inflammatory markers postprandially. Thus, fat rich in stearic acid does not seem to increase postprandial inflammation.     

Influence of Interesterification of a Stearic Acid-Rich Spreadable Fat on Acute Metabolic Risk Factors

Chemical and enzymatic interesterification are used to create spreadable fats. However, a comparison between the two processes in terms of their acute metabolic effects has not yet been investigated. A randomised crossover study in obese (plasma TAG > 1.69 mmol/L, and BMI > 30 (BMI = kg/m²) or waist circumference > 102 cm, n = 11, age = 59.3 ± 1.8 years) and non-obese (plasma triacylglycerol (TAG) < 1.69 mmol/L, and BMI < 30  or waist circumference < 102 cm, n = 10, age = 55.8 ± 2.2 years) men was undertaken to compare the effects of chemical versus enzymatic interesterification on postprandial risk factors for type 2 diabetes (T2D) and cardiovascular disease (CVD). TAG, cholesterol, glucose, insulin and free fatty acid concentrations were measured for 6 h following consumption of 1 g fat/kg body mass of non-interesterified (NIE), chemically interesterified (CIE), enzymatically interesterified (EIE) stearic acid-rich fat spread or no fat, each with 50 g available carbohydrate from white bread. Interesterification did not affect postprandial glucose, insulin, free fatty acids or cholesterol (P > 0.05). Following ingestion of NIE, increases in serum oleic acid were observed, whereas both oleic and stearic acids were increased with CIE and EIE (P < 0.05). While postprandial TAG concentrations in non-obese subjects were not affected by fat treatment (P > 0.05), obese subjects had an 85% increase in TAGs with CIE versus NIE (P < 0.05). The differences in TAG response between non-obese and obese subjects suggest that interesterification may affect healthy individuals differently compared to those already at risk for T2D and/or CVD.     

Conjugated Linoleic Acid Reduces Hepatic Steatosis and Restores Liver Triacylglycerol Secretion and the Fatty Acid Profile During Protein Repletion in Rats

Protein depletion is associated with hepatic steatosis and decreased circulating triacylglycerol (TAG). Since conjugated linoleic acid (CLA) increases lean body mass, protects against muscle catabolism, and modulates lipid metabolism, the aim of this work was to investigate the effects of CLA with two different amounts of dietary fat on the regulation of plasma and hepatic TAG concentration, and its possible connections with changes in fatty acid (FA) profile in plasma, liver and adipose tissue and hepatic oxidative status during protein repletion. Rats were fed a low protein diet (14 days) and then a protein repletion diet (30 days), supplemented or not with CLA, containing 7% (w/w) or 20% (w/w) of fat. Hepatic TAG secretion and removal by muscle and adipose tissue lipoprotein lipase, FA profile and liver oxidative status were evaluated. Protein depletion affected hepatic TAG secretion and peripheral removal, decreasing plasma and increasing liver TAG concentration, whereas protein repletion with CLA improved these abnormalities independently of the amount of dietary fat by increasing hepatic TAG secretion. This prevention in the absence of CLA was not observed. CLA was incorporated in plasma and tissues (adipose > liver > plasma, and c9,t11-CLA > t10,c12-CLA), accompanied by alterations in FA composition, mainly in adipose tissue. The hepatic oxidative stress was overcome by protein repletion. CLA had a beneficial impact on TAG metabolism in protein repleted animals, preventing hepatic steatosis through higher hepatic TAG secretion.     

Lipid metabolism and tissue composition in Atlantic salmon (Salmo salar L.)—Effects of capelin oil, palm oil, and oleic acid-enriched sunflower oil as dietary lipid sources

Triplicate groups of Atlantic salmon (Salmo salar L.) were fed four diets containing different oils as the sole lipid source, i.e., capelin oil, oleic acid-enriched sunflower oil, a 1∶1 (w/w) mixture of capelin oil and oleic acid-enriched sunflower oil, and palm oil (PO). The β-oxidation capacity, protein utilization, digestibility of dietary fatty acids and fatty acid composition of lipoproteins, plasma, liver, belly flap, red and white muscle were measured. Further, the lipid class and protein levels in the lipoproteins were analyzed. The different dietary fatty acid compositions did not significantly affect protein utilization or β-oxidation capacity in red muscle. The levels of total cholesterol, triacylglycerols, and protein in very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL), and plasma were not significantly affected by the dietary fatty acids. VLDL, LDL, and HDL fatty acid compositions were decreasingly affected by dietary fatty acid composition. Dietary fatty acid composition significantly affected both the relative fatty acid composition and the amount of fatty acids (mg fatty acid per g tissue, wet weight) in belly flap, liver, red and white muscle. Apparent digestibility of the fatty acids measured by adding yttrium oxide as inert marker, was significantly lower in fish fed the PO diet compared to the other three diets.     

Plasma lipids are affected similarly by dietary lauric or palmitic acid in gerbils and monkeys

To compare the relative impact of dietary lauric acid (12∶0) and palmitic acid (16∶0) on plasma lipids, two fat-sensitive species, Mongolian gerbils and cebus monkeys, were fed cholesterol-free, purified diets enriched with either 12∶0-rich or 16∶0-rich fats, while all other fatty acids were held constant by selective blending of up to five natural fats or oils. The two gerbil diets (40 en% from fat) allowed for an 8 en% exchange between 12∶0 and 16∶0, and the monkey diets (31 en% from fat) allowed for 6 en% exchange beteen these two fatty acids. Eight gerbils received the diets for eight weeks, and 12 cebus monkeys were fed each diet in a cross-over design for up to 22 wk. Both diets resulted in similar plasma cholesterol, triglyceride, and high density lipoprotein cholesterol concentrations within each species. Additionally, separation of cebus lipoproteins by discontinuous density-gradient ultracentrifugation failed to show any dietary differences in concentration or composition of the three major lipoprotein classes (d<1.019, 1.019–1.055, and 1.055–1.168 g/mL). Thus, in two species sensitive to manipulations in dietary fat while consuming cholesterol-free diets, 16∶0 was not hypercholesterolemic relative to 12∶0. Based on a paper presented at the PORIM International Palm Oil Congress (PIPOC) held in Kuala Lumpur, Malaysia, September 1993.     

Response of plasma lipids to dietary cholesterol and wine polyphenols in rats fed polyunsaturated fat diets

This experiment was designed to evaluate the effects of dietary red wine phenolic compounds (WP) and cholesterol on lipid oxidation and transport in rats. For 5 wk, weanling rats were fed polyunsaturated fat diets (n−6/n−3=6.4) supplemented or not supplemented with either 3 g/kg diet of cholesterol, 5 g/kg diet of WP, or both. The concentrations of triacylglycerols (TAG, P<0.01) and cholesterol (P<0.0002) were reduced in fasting plasma of rats fed cholesterol despite the cholesterol enrichment of very low density lipoprotein + low density lipoprotein (VLDL+LDL). The response was due to the much lower plasma concentration of high density lipoprotein (HDL) (−35%, P<0.0001). In contrast, TAG and cholesteryl ester (CE) accumulated in liver (+120 and +450%, respectively, P<0.0001). However, the cholesterol content of liver microsomes was not affected. Dietary cholesterol altered the distribution of fatty acids mainly by reducing the ratio of arachidonic acid to linoleic acid (P<0.0001) in plasma VLDL+LDL (−35%) and HDL (−42%) and in liver TAG (−42%), CE (−78%), and phospholipids (−28%). Dietary WP had little or no effect on these variables. On the other hand, dietary cholesterol lowered the α-tocopherol concentration in VLDL+LDL (−40%, P<0.003) and in microsomes (−60%, P<0.0001). In contrast, dietary WP increased the concentration in microsomes (+21%, P<0.0001), but had no effect on the concentration in VLDL+LDL. Cholesterol feeding decreased (P<0.006) whereas WP feeding increased (P<0.0001) the resistance of VLDL+LDL to copper-induced oxidation. The production of conjugated dienes after 25 h of oxidation ranged between 650 (WP without cholesterol) and 2,560 (cholesterol without WP) μmol/g VLDL+LDL protein. These findings show that dietary WP were absorbed at sufficient levels to contribute to the protection of polyunsaturated fatty acids in plasma and membranes. They could also reduce the consumption of α-tocopherol and endogenous antioxidants. The responses suggest that, in humans, these substances may be beneficial by reducing the deleterious effects of a dietary overload of cholesterol.     

Palm Olein and Olive Oil Cause a Higher Increase in Postprandial Lipemia Compared with Lard but Had No Effect on Plasma Glucose,Insulin and Adipocytokines

Postprandial lipemia impairs insulin sensitivity and triggers the pro-inflammatory state which may lead to the progression of cardiovascular diseases. A randomized, crossover single-blind study (n = 10 healthy men) was designed to compare the effects of a high-fat load (50 g fat), rich in palmitic acid from both plant (palm olein) or animal source (lard) versus an oleic acid-rich fat (virgin olive oil) on lipemia, plasma glucose, insulin and adipocytokines. Serum triacylglycerol (TAG) concentrations were significantly lower after the lard meal than after the olive oil and palm olein meals (meal effect P = 0.003; time effect P < 0.001). The greater reduction in the plasma non-esterified free fatty acids levels in the lard group compared to the olive oil meal was mirrored by the changes observed for serum TAG levels (P < 0.05). The magnitude of response for plasma glucose, insulin and adipocytokines [interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and leptin] were not altered by the type of dietary fats. A significant difference in plasma IL-1β was found over time following the three high fat loads (time effect P = 0.036). The physical characteristics and changes in TAG structure of lard may contribute to the smaller increase in postprandial lipemia compared with palm olein. A high fat load but not the type of fats influences concentrations of plasma IL-1β over time but had no effect on other pro-inflammatory markers tested in the postprandial state.     

Daily Intake of Cod or Salmon for 2?Weeks Decreases the 18:1n-9/18:0 Ratio and Serum Triacylglycerols in Healthy Subjects

Intake of fish and omega-3 (n-3) fatty acids is associated with a reduced concentration of plasma triacylglycerols (TAG) but the mechanisms are not fully clarified. Stearoyl-CoA desaturase-1 (SCD1) activity, governing TAG synthesis, is affected by n-3 fatty acids. Peripheral blood mononuclear cells (PBMC) display expression of genes involved in lipid metabolism. The aim of the present study was to estimate whether intake of lean and fatty fish would influence n-3 fatty acids composition in plasma phospholipids (PL), serum TAG, 18:1n-9/18:0 ratio in plasma PL, as well as PBMC gene expression of SCD1 and fatty acid synthase (FAS). Healthy males and females (n = 30), aged 20–40, consumed either 150 g of cod, salmon, or potato (control) daily for 15 days. During intervention docosahexaenoic acid (DHA, 22:6n-3) increased in the cod group (P < 0.05), while TAG concentration decreased (P < 0.05). In the salmon group both eicosapentaenoic acid (EPA, 20:5n-3) and DHA increased (P < 0.05) whereas TAG concentration and the 18:1n-9/18:0 ratio decreased (P < 0.05). Reduction of the 18:1n-9/18:0 ratio was associated with a corresponding lowering of TAG (P < 0.05) and an increase in EPA and DHA (P < 0.05). The mRNA levels of SCD1 and FAS in PBMC were not significantly altered after intake of cod or salmon when compared with the control group. In conclusion, both lean and fatty fish may lower TAG, possibly by reducing the 18:1n-9/18:0 ratio related to allosteric inhibition of SCD1 activity, rather than by influencing the synthesis of enzyme protein.     

Effect of Dietary Cholesterol and Fat on Cell Cholesterol Transfer to Postprandial Plasma in Hyperlipidemic Men

Postprandial chylomicrons are potent ultimate acceptors of cell membrane cholesterol and are believed to accelerate reverse cholesterol transport (RCT). We compared the effects of meals rich in polyunsaturated fat (PUFA) and either high (605 mg) or low (151 mg) in cholesterol and a meal rich in dairy fat (DF) in the form of cream on net in vitro transport of red blood cell (RBC) membrane cholesterol to 4 and 6 h postprandial plasma in eight normotriglyceridemic (NTG-H) and eight hypertriglyceridemic (HTG-H) men with mild to moderate hypercholesterolemia. In HTG-H men, cell cholesterol accumulation in 6-h postprandial plasma was significantly (P = 0.02) less after the PUFA-HC meal compared with the other meals. The significant (P < 0.001) increase in cell plus endogenous cholesterol accumulation in the triglyceride-rich lipoprotein (TRL) fraction of 4 h postprandial plasma incubated with RBC was significantly (P = 0.007) higher after the PUFA-HC meal compared with DF meal in HTG-H men. In NTG-H men, cholesterol accumulation in plasma and plasma lipoproteins in the presence and absence of RBC was not significantly affected by the type of meal ingested. These data suggest that addition of large amounts of cholesterol to a PUFA meal may impair diffusion-mediated transport of cell membrane cholesterol to postprandial plasma and that replacing DF with PUFA in a meal increases postprandial lipemia and may potentially increase cholesterol accumulation in atherogenic postprandial TRL in HTG-H men.     

A High Legume Low Glycemic Index Diet Improves Serum Lipid Profiles in Men

Clinical studies have shown that fiber consumption facilitates weight loss and improves lipid profiles; however, the beneficial effects of high fermentable fiber low glycemic index (GI) diets under conditions of weight maintenance are unclear. In the Legume Inflammation Feeding Experiment, a randomized controlled cross-over feeding study, 64 middle-aged men who had undergone colonoscopies within the previous 2 years received both a healthy American (HA) diet (no legume consumption, fiber consumption = 9 g/1,000 kcal, and GI = 69) and a legume enriched (1.5 servings/1,000 kcal), high fiber (21 g/1,000 kcal), low GI (GI = 38) diet (LG) in random order. Diets were isocaloric and controlled for macronutrients including saturated fat; they were consumed each for 4 weeks with a 2–4 week break separating dietary treatments. Compared to the HA diet, the LG diet led to greater declines in both fasting serum total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) (P < 0.001 and P < 0.01, respectively). Insulin-resistant (IR) subjects had greater reductions in high density lipoprotein cholesterol (HDL-C; P < 0.01), and triglycerides (TAG)/HDL-C (P = 0.02) after the LG diet, compared to the HA diet. Insulin-sensitive (IS) subjects had greater reductions in TC (P < 0.001), LDL-C (P < 0.01), TC/HDL-C (P < 0.01), and LDL-C/HDL-C (P = 0.02) after the LG diet, compared to the HA diet. In conclusion, a high legume, high fiber, low GI diet improves serum lipid profiles in men, compared to a healthy American diet. However, IR individuals do not achieve the full benefits of the same diet on cardiovascular disease (CVD) lipid risk factors.     

Incubation of lipid emulsions with plasma lipoproteins modifies the fluidity of each particle

Lipid emulsions (LE) contain triglyceride (TG)-rich particles (TGRP) and phospholipid-rich particles (PLRP). Various lipid and protein exchanges take place during in vitro incubations of LE with lipoproteins. These composition changes affect physical properties of particles. The aim of this study was to determine the role of different LE particles and the effect of TG composition on physical modifications. Low density lipoproteins (LDL: 1.025<d<1.040 g/mL) or high density lipoproteins (HDL: 1.085<d<1.150 g/mL) were incubated with the following four LE or their TGRP or PLRP, which were manufactured with the same phospholipid emulsifier: long-chain triglycerides (LCT): 100% soybean oil; medium-chain triglycerides (MCT)/LCT (MCT/LCT, 5∶5, w/w); FO (100% fish oil); and MLF541 (MCT/LCT/FO, 5∶4∶1, by wt). After incubation, modified LE particles and lipoproteins were analyzed by fluorescence polarization. Observed physical modifications were significant in emulsion particles (ordering effect) but not in lipoporteins and also were significant for TG composition effect. Since intact emulsion contained a large excess of TGRP over PLRP, it is not surprising that intact emulsion had the same behavior as TGRP alone, and that PLRP had the same physical characteristics as lipoproteins. TG loss and cholesterol and protein acquisitions by emulsion particles rigidify their envelope. The two emulsions containing FO were less ordered after incubation. In conclusion, incubation of LE with lipoproteins changes physical properties of each kind of particle, and TG composition of the emulsion affects emulsion particle changes but has no effect on LDL and HDL. These order modifications induce more effective exchanges between LE particles and lipoproteins and modify their metabolism; HDL changes may increase the reverse cholesterol transport.     

Triacylglycerols and Polar Lipids in Cow and Goat Milk are Differentially Affected by Various Lipid Supplemented Diets

This study characterizes milk triacylglycerol (TAG) and polar lipid (PL) fractions from cows and goats fed various lipid supplements modulating milk fat content. Twelve Holstein cows and 12 Alpine goats, at 86 ± 24.9 and 61 ± 1.8 days in milk, respectively, are allocated to one of 4 groups to receive diets supplemented with either corn oil [5% dry matter intake (DMI)] plus wheat starch (COS), marine algae powder (MAP; 1.5% DMI) or hydrogenated palm oil (HPO; 3% DMI), or a no-added-lipid control diet (CTL), according to a 4 × 4 Latin square design with 28 d experimental periods. Milk TAG and PL contents are determined by liquid chromatography-mass spectrometry (LC-MS). Multivariate analysis and ANOVA demonstrate major between-species differences in diet effects. In cows, COS specifically increases TAG 54:3 and 54:4 associated with milk fat depression (MFD), and increases the sum of phosphatidylcholines (PC) and phosphatidylinositols (PI). In addition to causing a MFD, MAP diet increases long-chain polyunsaturated TAG in both species, with higher magnitude in cows than in goats, and decreases the sum of PI in goats. HPO increases TAG 52:1 and the sum of PI in cows, but not in goats. Practical applications: Feed strategies can quickly and efficiently modulate the ruminant milk fat production and composition to improve nutritional quality for consumers. Certain starch-rich diets supplemented with polyunsaturated fatty acids (PUFA)-rich vegetable oils and diets supplemented with marine products (long-chain PUFA) reduce milk fat secretion and modify the milk fatty acid (FA) profile in cows, but not—or less so—in goats. Advanced analysis of both the TAG and PL fractions of milk fat is required to unravel these differences in lipid metabolism between cows and goats fed various lipid-supplemented diets. This study brings new insight on using nutritional strategies to control milk lipid composition according to ruminant species.     

Soluble fiber and soybean protein reduce atherosclerotic lesions in guinea pigs. Sex and hormonal status determine lesion extension

These studies were undertaken to assess guinea pigs as potential models for early atherosclerosis development. For that purpose, male, female, and ovariectomized (to mimic menopause) guinea pigs were fed a control or a TEST diet for 12 wk. Differences between diets were the type of protein (60% casein/40% soybean vs. 100% soybean) and the type of fiber (12.5% cellulose vs. 2.5% cellulose/5% pectin/5% psyllium) for control and TEST diets, respectively. Diet had no effect on plasma cholesterol or triacylglycerol (TAG) concentrations; however, there were significant effects related to sex/hormonal status. Ovariectomized guinea pigs had higher plasma cholesterol and TAG concentrations than males or females (P<0.01). In contrast to effects on plasma lipids, hepatic cholesterol and TAG were 50% lower in the TEST groups (P<0.01) compared to controls. Low density lipoproteins (LDL) from guinea pigs fed the TEST diet had a lower number of cholesteryl ester (CE) molecules and a smaller diameter than LDL from controls. Atherosclerotic lesions were modulated by both diet (P<0.0001) and sex (P<0.0001). Guinea pigs fed the TEST diet had 25% less lesion extension whereas males had 20% larger occlusion of the arteries compared to both female and ovariectomized guinea pigs. Significant positive correlations were found between LDL CE and atherosclerotic lesions (r=0.495, P<0.05) and LDL size and fatty streak area (r=0.56, P<0.01). In addition, females fed the TEST diet had the lowest plasma and hepatic cholesterol concentrations, the smallest LDL particles, and the least atherosclerosis involvement compared to the other groups. These data indicate that dietary factors and sex/hormonal status play a role in determining plasma lipids and atherosclerosis in guinea pigs.     

Effects of 17β-estradiol and starvation on trout plasma lipoproteins

Administering 17β-estradiol (E₂) to juvenile trout results in plasma hyperlipidemia and hyperlipoproteinemia associated with significant increases in the concentrations of triglycerides (TG), free cholesterol, phospholipids, free fatty acids and proteins, both postprandial and during starvation. TG undergo the greatest increase (9 times control level 96 h after feeding). The concentration differences between E₂-treated and control trout increase during starvation, primarily by progressive decreases in the concentrations of various lipids in controls. E₂-induced hypertriglyceridemia is mainly caused by an increase in the concentration of very low density lipoproteins (VLDL) during both the postprandial period (6 times control level at 24 h) and during starvation (15 times control level at 96 h); hyperlipoproteinemia lasts up to at least 7 d after the last feeding. E₂ treatment does not change the concentration of high density lipoproteins, but does increase plasma concentrations of a very high density lipoprotein, vitellogenin (VTG). In E₂-treated VLDL, cholesteryl esters are depleted while proteins are enriched. During the postprandial phase, the apolipoprotein (apo) profile of VLDL (d< 1.015 g/mL) is comparable in E₂-treated and control trout. Starvation of E₂-treated trout is accompanied by an enrichment in apo B₂₄₀, A-I and A-II. The secretion levels of TG and VLDL-TG, as determinedin vivo, by injecting Triton WR-1339 to starving animals, are significantly higher in E₂-treated trout than in controls. In trout, as in chicks, E₂ administration significantly increases the concentration and hepatic secretion of plasma VLDL independent of the nutritional status and the appearance of VTG in the plasma. This suggests the existence of similar mechanisms for the regulation of lipoprotein metabolism by estrogens in oviparous vertebrates.     

Effect of Diacylglycerol on Postprandial Serum Triacylglycerol Concentration: A Meta-analysis

Diacylglycerol (DAG) supplementation has been shown to be associated with the reduction of postprandial triacylglycerol (TAG) concentration, although the extent of the association is uncertain. We quantitatively examined the effect of dietary DAG on postprandial serum TAG concentration by conducting a meta-analysis of randomized controlled trials. Potential papers were initially searched for in the electronic databases of Medline, Embase and Cochrane library. Inclusion criteria required the trial to be randomized with DAG as the treatment group, and TAG as the control group. Information was extracted independently by two investigators and the effect of DAG on postprandial TAG concentration was examined in Review Manager 4.2. Seven papers were included in the statistic pooling. DAG supplementation reduced the increment of postprandial TAG concentration significantly at postprandial 2 h (Weighted mean difference (WMD) −0.07 mmol/L; 95% CI −0.13 to 0.00 mmol/L; P = 0.05), 4 h (WMD −0.15 mmol/L; 95% CI −0.24 to −0.06 mmol/L; P = 0.002) and 6 h (WMD −0.14 mmol/L; 95% CI −0.23 to −0.05 mmol/L; P = 0.002). Linear regression showed that the effect of DAG was positively correlated with the daily dosage at 2 h (P = 0.095) and 6 h (P = 0.053) after lipid loading. In conclusion, compared with TAG oil, DAG reduced the postprandial serum TAG concentration at 2 h, 4 h and 6 h postprandial and was positively correlated with daily dosage.     

Paraoxonase 1 Activity in Chylomicrons and VLDL: The Effect of Type 2 Diabetes and Meals Rich in Saturated Fat and Oleic Acid

Paraoxonase 1 (PON 1) has antioxidant and cardioprotective properties and is abnormally low in type 2 diabetic serum. This study aimed to determine the effect of type 2 diabetes and meals rich in saturated fat and oleic acid on PON1 activity in chylomicrons and very low density lipoproteins (VLDL). PON1 arylesterase activity was measured in chylomicrons and VLDL that were isolated in serum from 20 patients with type 2 diabetes and 20 age- and gender-matched, overweight controls 3 h after meals rich in cream or olive oil in a randomized, cross-over study. Chylomicron–PON1 activity (45%, P = 0.02), ratio chylomicron–PON1/chylomicron–triacylglycerides (TAG) (42%, P = 0.03) and chylomicron–protein content (46%, P < 0.001) were significantly lower in patients with type 2 diabetes compared with controls after the olive oil meal with comparable findings after the meal rich in cream. After ingestion of olive oil, chylomicron–PON1 activity was significantly higher in controls (P = 0.01) and marginally higher (P = 0.06) in diabetic patients and chylomicron–TAG were significantly (P < 0. 05) higher in both groups of subjects, compared with values after ingestion of cream. VLDL–PON1 increased (two-fold) significantly (P < 0.003) during both meals. Chylomicron-PON1 activity was correlated significantly with chylomicron–protein (P < 0.001, n = 40) and with postprandial serum PON1 activity (P ≤ 0.001, n = 40). Our data suggest that type 2 diabetes is associated with abnormally low chylomicron–PON1 activity after fatty meals and this may be linked to lower chylomicron–protein content and serum PON1 activity. Switching from saturated fat to olive oil in the meal increases PON1 activity in the chylomicron fraction largely due to increased numbers of chylomicron particles.     

ABCG5/G8 Deficiency in Mice Reduces Dietary Triacylglycerol and Cholesterol Transport into the Lymph

The adenosine triphosphate‐binding cassette (ABC) transporter G5/G8 is critical in protecting the body from accumulating dietary plant sterols. Expressed in the liver and small intestine, it transports plant sterols into the biliary and intestinal lumens, thus promoting their excretion. The extent to which G5/G8 regulates cholesterol absorption remains unclear. G5/G8 is also implicated in reducing the absorption of dietary triacylglycerols (TAG) by unknown mechanisms. We hypothesized that G5/G8 suppresses the production of chylomicrons, and its deficiency would enhance the absorption of both dietary TAG and cholesterol. The aim of this study was to investigate the effects of G5/G8 deficiency on lipid uptake and secretion into the lymph under steady‐state conditions. Surprisingly, compared with wild‐type mice (WT) (n = 9), G5/G8 KO (n = 13) lymph fistula mice given a continuous intraduodenal infusion of [3H]‐TAG and [14C]‐cholesterol showed a significant (P < 0.05) reduction in lymphatic transport of both [³H]‐TAG and [¹⁴C]‐cholesterol, concomitant with a significant (P < 0.05) increase of [³H]‐TAG and [¹⁴C]‐cholesterol accumulated in the intestinal lumen. There was no difference in the total amount of radiolabeled lipids retained in the intestinal mucosa between the two groups. G5/G8 KO mice given a bolus of TAG showed reduced intestinal TAG secretion compared with WT, suggesting an independent role for G5/G8 in facilitating intestinal TAG transport. Our data demonstrate that G5/G8 deficiency reduces the uptake and secretion of both dietary TAG and cholesterol by the intestine, suggesting a novel role for the sterol transporter in the formation and secretion of chylomicrons.     

Positional distribution of decanoic acid: Effect on chylomicron and VLDL TAG structures and postprandial lipemia

Although medium-chain FA (MCFA) are mainly absorbed via the portal venous system, they are also incorporated into chylomicron TAG; therefore, the positional distribution of MCFA in TAG is likely to affect their metabolic fate. We studied chylomicron and VLDL TAG structures, as well as the magnitude of postprandial lipemia, after two oral fat loads containing decanoic acid (10∶0) predominantly at the sn-1(3),2 (MML) or at the sn-1,3 positions (MLM) of TAG in a randomized, double-blind, crossover clinical trial with 10 healthy, normal-weight volunteers. An MS-MS method was used to analyze TAG regioisomers. The position of decanoic acid in chylomicron TAG reflected its position in the TAG ingested, and TAG with none, one, two, or three decanoic acid residues were detected after ingestion of both fats. More (P<0.05) 30∶0 and 38∶1 TAG (acyl carbons:double bonds) and fewer 46∶5, 54∶5 and 54∶4 TAG were found in chylomicrons after ingestion of MML than after MLM. The VLDL TAG composition did not differ between the fat loads but did change (P<0.05) 2 to 6 h after ingestion of both fats. No statistical differences were seen between the fat loads in areas under the plasma, chylomicron, or VLDL TAG response curves or in FFA concentrations. Thus, the positional distribution of MCFA in TAG affects their metabolic, fate, but the magnitude of postprandial lipemia does not seem to be dependent on the positional distribution of MCFA in the ingested fat.     

Interrelationship of stearic acid content and triacylglycerol composition of lard,beef tallow and cocoa butter in rats

We investigated modes whereby stearic acid (18∶0) exerts a neutral or cholesterol-lowering effect using dietary fats which provided graded levels of 18∶0 and distinct triacylglycerol (TAG) profiles. Male Sprague-Dawley rats (150–175 g) were fed diets containing 0.2% cholesterol and 16% fat from corn oil, or from 1% corn oil plus 15% lard (13.2% 18∶0), beef tallow (19.2% 18∶0) or cocoa butter (34.7% 18∶0) for 3 wk, and then killed in a fasted or fed state. Chylomicron (CM) fatty acid profiles suggested reduced absorption of 18∶0 with greater 18∶0 intake. CM TAG profiles indicated a reduction or loss of two TAG species compared to the TAG profiles of the stearate-rich diets: 1-palmitoyl-2-oleoyl-3-stearoyl glycerol (POS) and 1,3-distearoyl-2-oleoyl glycerol (SOS). Hepatic total cholesterol concentrations were 54–77% lower (P<0.01) in the cocoa butter-fed than the lard- and beef tallow-fed groups. The cocoa butter group showed a significantly lower ratio of high-density lipoprotein esterified/free cholesterol than all other groups. Hepatic stearoyl-CoA and oleoyl-CoA concentrations, the substrate and product for hepatic δ9 desaturase, were not significantly different for corn oil-fed and cocoa butter-fed groups in spite of a large difference in 18∶0 intake. These data suggest that the neutral or cholesterol-lowering effect of 18∶0 is not due to hepatic conversion of stearic to oleic acid, and that POS and SOS are poorly absorbed from stearate-rich dietary fats.     

Lipidemic effects of an interesterified mixture of butter, medium-chain triacylglycerol and safflower oils

The objective of this study was to determine if the positional structure of dietary triacylglycerol affected lipidemic responses. Thirty healthy adults (16 men and 14 postmenopausal women) with low-density lipoprotein cholesterol (LDL-C) concentrations >3.37 mM (130 mg/dl) enrolled in a prospective, single-blind, cross-over outpatient clinical trial that consisted of two 5-wk dietary phases. After baseline screening, subjects were instructed to follow individualized meal plans (weight maintenance diets with 36% of total energy from fat, half of which was from a test oil) and randomized to receive either butter (B) or an interesterified mixture (IM) of butter, medium-chain triacylglycerol (MCI), and safflower oils. Blood drawn during weeks 5 and 10 of feeding was analyzed for total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), LDL-C, and triacylglycerols (TAG). Mean plasma levels of TC (B, 6.98±1.06 mM; IM, 7.09±1.20 mM), HDL-C (B,1.30±0.35 mM; IM, 1.29±0.34 mM), and LDL-C (B, 4.91±0.95 mM; IM, 492±1.10 mM) were not significantly different between the two dietary treatments. Mean TAG levels were higher for the interesterified B-MCT mixture (B, 1.75±0.72 mM; IM, 1.96±0.86 mM, P<0.05). We conclude that an IM of B, MCT and safflower oils as compared to native B has no appreciable effect on plasma cholesterol concentrations but is associated with a modest rise in plasma TAG.