Deposition of Free Cholesterol in the Blood Vessels of Patients with Coronary Artery Disease: a Possible Novel Mechanism for Atherogenesis

A cholesterol-rich nanoemulsion (LDE) that mimics the composition of low-density lipoprotein (LDL) acquires apoE in the plasma and is taken-up by the cells by LDL receptors. In this study, to verify whether free cholesterol (FC) and the cholesteryl ester (CE) components of LDL are taken-up differently by the vessels. LDE labeled with ³H-cholesterol and ¹⁴C-cholesteryl oleate was injected into 20 coronary artery disease patients 24 h before a scheduled myocardial coronary artery bypass grafting. The plasma kinetics of both radiolabels was determined from plasma samples collected over 24 h, and fragments of vessels discarded during surgery were collected and analyzed for radioactivity. LDE FC was removed faster than CE. The radioactive counting of LDE CE was greater than that of LDE FC in the blood, but the uptake of FC was markedly greater than that of CE in all fragments: fivefold greater in the aorta (p = 0.04), fourfold greater in the internal thoracic artery (p = 0.03), tenfold greater in the saphenous vein (p = 0.01) and threefold in the radial artery (p = 0.05). In conclusion, the greater removal from plasma of FC compared with CE and the remarkably greater vessel tissue uptake of FC compared with CE suggests that, in the plasma, FC dissociates from the nanoemulsion particles and precipitates in the vessels. Considering LDE as an artificial nanoemulsion model for LDL, our results suggest that dissociation of FC from lipoprotein particles and deposition in the vessel wall may play a role as an independent mechanism in atherogenesis.     

Rosuvastatin Enhances the Catabolism of LDL apoB‐100 in Subjects with Combined Hyperlipidemia in a Dose Dependent Manner

Dose‐associated effects of rosuvastatin on the metabolism of apolipoprotein (apo) B‐100 in triacylglycerol rich lipoprotein (TRL, d < 1.019 g/ml) and low density lipoprotein (LDL) and of apoA‐I in high density lipoprotein (HDL) were assessed in subjects with combined hyperlipidemia. Our primary hypothesis was that maximal dose rosuvastatin would decrease the apoB‐100 production rate (PR), as well as increase apoB‐100 fractional catabolic rate (FCR). Eight subjects received placebo, rosuvastatin 5 mg/day, and rosuvastatin 40 mg/day for 8 weeks each in sequential order. The kinetics of apoB‐100 in TRL and LDL and apoA‐I in HDL were determined at the end of each phase using stable isotope methodology, gas chromatography‐mass spectrometry, and multicompartmental modeling. Rosuvastatin at 5 and 40 mg/day decreased LDL cholesterol by 44 and 54 % (both P < 0.0001), triacylglycerol by 14 % (ns) and 35 % (P < 0.01), apoB by 30 and 36 % (both P < 0.0001), respectively, and had no significant effects on HDL cholesterol or apoA‐I levels. Significant decreases in plasma markers of cholesterol synthesis and increases in cholesterol absorption markers were observed. Rosuvastatin 5 and 40 mg/day increased TRL apoB‐100 FCR by 36 and 46 % (both ns) and LDL apoB‐100 by 63 and 102 % (both P < 0.05), respectively. HDL apoA‐I PR increased with low dose rosuvastatin (12 %, P < 0.05) but not with maximal dose rosuvastatin. Neither rosuvastatin dose altered apoB‐100 PR or HDL apoA‐I FCR. Our data indicate that maximal dose rosuvastatin treatment in subjects with combined hyperlipidemia resulted in significant increases in the catabolism of LDL apoB‐100, with no significant effects on apoB‐100 production or HDL apoA‐I kinetics.     

Plasma kinetic behavior in hyperlipidemic subjects of a lipidic microemulsion that binds to low density lipoprotein receptors

It was previously reported that a protein-free microemulsion (LDE) with structure roughly resembling that of the lipid portion of low density lipoprotein (LDL) was presumably taken up by LDL receptors when injected into the bloodstream. In contact with plasma, LDE acquires apolipoproteins (apo) including apo E that would be the ligand for receptor binding. Currently, apo were associated to LDE by incubation with high density lipoprotein (HDL). LDE-apo uptake by mononuclear cells showed a saturation kinetics, with an apparent K _m of 13.1 ng protein/mL. LDE-apo is able to displace LDL uptake by mononuclear cells with a K _i of 11.5 ng protein/mL. LDE without apo is, however, unable to displace LDL. The uptake of ¹⁴C-HDL is not dislocated by increasing amounts of LDE-apo, indicating that HDL and LDE-apo do not bind to the same receptor sites. In human hyperlipidemias, LDE labeled with ¹⁴C-cholesteryl ester behaved kinetically as expected for native LDL. LDE plasma disappearance curve obtained from eight hypercholesterolemic patients was markedly slower than that from 10 control normolipidemic subjects [fractional clearance rate (FCR)=0.02±0.01 and 0.12±0.04 h⁻¹, respectively; P<0.0001]. On the other hand, in four severely hypertriglyceridemic patients, LDE FCR was not significantly different from the controls (0.07±0.03 h⁻¹). These results suggest that LDE can be a useful device to study lipoprotein metabolism.     

The Expression of Lipoprotein Receptors Is Increased in the Infarcted Area After Myocardial Infarction Induced in Rats With Cardiac Dysfunction

Left ventricular (LV) remodeling after myocardial infarction constitutes the structural basis for ventricular dysfunction and heart failure. The characterization underlying the expression of lipoprotein receptors in cardiac dysfunction is scarcely explored. The aim of this study was to analyze the status of lipoprotein receptors on the infarcted and noninfarcted areas of LV and to verify whether nanoparticles that mimic the lipid structure of low‐density lipoprotein (LDL) and have the ability to bind to LDL receptors (LDE) are taken up more avidly by the noninfarcted LV. 13 male Wistar rats with left coronary artery ligation (myocardial infarction [MI]) and 12 animals with SHAM operation (SHAM) were used in this study. 6 weeks after the procedure, the quantification of low‐density lipoprotein receptor (LDLR), LDL receptor‐related protein 1 (LRP1), scavenger receptor‐class B type I (SR‐BI) lipoprotein receptors, and PCNA proliferation marker, and tissue uptake of radioactively labeled LDE were performed. Immunohistochemistry and Western blot analysis showed that LDLR, LRP1, SR‐BI, and PCNA, expression in infarcted area of MI was remarkably higher than SHAM and noninfarcted subendocardial (SEN) and interstitial (INT) areas. In addition, in SEN noninfarcted area of MI, the presence of LDLR was about threefold higher than in SHAM SEN and INT noninfarcted areas. The LDE uptake of noninfarcted LV of MI group was about 30% greater than that of SHAM group. In conclusion, these findings regarding the status of lipoprotein receptors after MI induction could help to establish mechanisms on myocardial repairing. In conclusion, infarcted rats with LV dysfunction showed increased expression of lipoprotein receptors mainly in the infarcted area.     

A micro‐method for lipoprotein cholesterol profiles: Impact of CETP in KKAy mice

The aim of the present study was to assess cholesterol‐containing lipoprotein profiles in minute serum samples. The lipoprotein profiles of KKA^y and transgenic KKA^y‐CETP mice and of other species were determined. The transgenic KKA^y‐CETP mice express the simian enzyme cholesteryl ester transfer protein (CETP). The serum profile of the cholesterol‐containing high‐density (HDL), low‐density (LDL) and very‐low‐density lipoproteins (VLDL) was monitored on a Superose 6 column using fast protein liquid chromatography. Serum from several mouse and rat strains, rabbit, hamster, pig and man was included for comparative and method validation purposes. The chromatograms showed that the transgenic KKA^y‐CETP mice had significantly decreased relative levels of HDL vs. VLDL and LDL cholesterol (p <0.001). Introduction of the CETP gene shifted the serum profile of the cholesterol‐containing lipoproteins of the KKA^y‐CETP mice closer to the human profile in a dose‐dependent manner, thus making these mice an interesting model for man. The described lipoprotein separation technology offers promising and reliable opportunities for studies of blood lipoprotein profiles with minute serum samples, in both animals and man.     

Changes in Plasma LDL and HDL Composition in Patients Undergoing Cardiac Surgery

Changes of lipoprotein composition have been mainly reported in conditions of sepsis. This study characterized compositional changes in LDL and HDL during the acute phase response following cardiac surgery with cardiopulmonary bypass. Twenty-one patients undergoing cardiac surgery were included in this study. Blood samples were drawn before operation and on day 2 post-surgery. In parallel to plasma lipids and antioxidant status, lipoproteins were analyzed for lipid, apolipoprotein (apo), hydroperoxide and alpha-tocopherol content. Beyond decreases in lipid concentrations and antioxidant defenses, cardiac surgery induced substantial modifications in plasma lipoproteins. ApoB decrease in LDL fraction (−46%; P < 0.0001) reflected a marked reduction in the circulating particle number. LDL cholesteryl ester content relative to apoB concentration remained unchanged post-surgery while triglyceride (+113%; P < 0.001), free cholesterol (+22%; P < 0.05) and phospholipid (+23%; P < 0.025) were raised relative to apoB indicating increased particle size. In HDL, an abrupt rise of apoSAA (P < 0.05) was observed together with a decrease of apoA1 (−22%; P < 0.005). Cholesteryl ester content in HDL fraction decreased in parallel to apoA1 concentration while triglycerides, free cholesterol and phospholipids increased relative to apoA1. In contrast to unchanged alpha-tocopherol content, hydroperoxide content was increased in LDL and HDL. By comparison to sepsis, cardiac surgery induces a comparable reduction in circulating LDL but a more limited decrease in HDL particles. Furthermore, in contrast, cardiac surgery induces an increase in polar and non-polar lipids, as well as of particle size in both LDL and HDL. M. Hacquebard is recipient of a fellowship from the Danone Institute, Belgium.     

High Density Lipoprotein Level is Negatively Associated With the Increase of Oxidized Low Density Lipoprotein Lipids After a Fatty Meal

Recent reports show that a fatty meal can substantially increase the concentration of oxidized lipids in low density lipoprotein (LDL). Knowing the LDL‐specific antioxidant effects of high density lipoprotein (HDL), we aimed to investigate whether HDL can modify the postprandial oxidative stress after a fatty meal. Subjects of the study (n = 71) consumed a test meal (a standard hamburger meal) rich in lipid peroxides, and blood samples were taken before, 120, 240, and 360 min after the meal. The study subjects were divided into four subgroups according to the pre‐meal HDL cholesterol value (HDL subgroup 1, 0.66–0.91; subgroup 2, 0.93–1.13; subgroup 3, 1.16–1.35; subgroup 4, 1.40–2.65 mmol/L). The test meal induced a marked postprandial increase in the concentration of oxidized LDL lipids in all four subgroups. The pre‐meal HDL level was associated with the extent of the postprandial rise in oxidized LDL lipids. From baseline to 6 h after the meal, the concentration of ox‐LDL increased by 48, 31, 24, and 16 % in the HDL subgroup 1, 2, 3, and 4, respectively, and the increase was higher in subgroup 1 compared to subgroup 3 (p = 0.028) and subgroup 4 (p = 0.0081), respectively. The pre‐meal HDL correlated with both the amount and the rate of increase of oxidized LDL lipids. Results of the present study show that HDL is associated with the postprandial appearance of lipid peroxides in LDL. It is therefore likely that the sequestration and transport of atherogenic lipid peroxides is another significant mechanism contributing to cardioprotection by HDL.     

Postpartum Weight Retention is Associated with Elevated Ratio of Oxidized LDL Lipids to HDL-Cholesterol

Oxidized LDL lipids (ox‐LDL) are associated with lifestyle diseases such as cardiovascular diseases, metabolic syndrome and type 2 diabetes. The present study investigated how postpartum weight retention effects on ox‐LDL and serum lipids. The study is a nested comparative research of a cluster‐randomized controlled trial, NELLI (lifestyle and counselling during pregnancy). During early pregnancy (8–12 weeks) and 1 year postpartum, 141 women participated in measurements for determining of plasma lipids: total cholesterol (T‐C), LDL‐cholesterol (LDL‐C), HDL‐cholesterol (HDL‐C), triacylglycerols (TAG) and ox‐LDL. Subjects were stratified into tertiles (weight loss, unaltered weight and weight gain groups) based on their weight change from baseline to follow‐up. Ox‐LDL was determined by baseline level of conjugated dienes in LDL lipids. Among the group of weight gainers, concentration of TAG reduced less (?0.14 vs. ?0.33, p = 0.002), HDL‐C reduced more (?0.31 vs. ?0.16, p = 0.003) and ox‐LDL/HDL‐C ratio increased (3.0 vs. ?0.2, p = 0.003) when compared to group of weight loss. Both T‐C and LDL‐C elevated more (0.14 vs. ?0.21, p = 0.008; 0.31 vs. 0.07, p = 0.015) and TAG and ox‐LDL reduced less (?0.33 vs. 0.20, p = 0.033; ?3.33 vs. ?0.68, p = 0.026) in unaltered weight group compared to weight loss group. The women who gained weight developed higher TAG and ox‐LDL/HDL‐C ratio as compared to those who lost weight. Postpartum weight retention of 3.4 kg or more is associated with atherogenic lipid profile.     

Xanthophylls, Phytosterols and Pre-β1-HDL are Differentially Affected by Fenofibrate and Niacin HDL-Raising in a Cross-Over Study

Fenofibrate and extended‐release (ER) niacin similarly raise high‐density lipoprotein cholesterol (HDL‐C) concentration but their effects on levels of potent plasma antioxidant xanthophylls (lutein and zeaxanthin) and phytosterols obtained from dietary sources, and any relationship with plasma lipoproteins and pre‐β1‐HDL levels, have not been investigated. We studied these parameters in 66 dyslipidemic patients treated for 6 week with fenofibrate (160 mg/day) or ER‐niacin (0.5 g/day for 3 week, then 1 g/day) in a cross‐over study. Both treatments increased HDL‐C (16 %) and apolipoprotein (apo) A‐I (7 %) but only fenofibrate increased apoA‐II (28 %). Lutein and zeaxanthin levels were unaffected by fenofibrate but inversely correlated with percentage change in apoB and low‐density lipoprotein cholesterol and positively correlated with end of treatment apoA‐II. ApoA‐II in isolated HDL in vitro bound more lutein than apoA‐I. Xanthophylls were increased by ER‐niacin (each ~30 %) without any correlation to lipoprotein or apo levels. Only fenofibrate markedly decreased plasma markers of cholesterol absorption; pre‐β1‐HDL was significantly decreased by fenofibrate (?19 %, p < 0.0001), with little change (3.4 %) for ER‐niacin. Although fenofibrate and ER‐niacin similarly increased plasma HDL‐C and apoA‐I, effects on plasma xanthophylls, phytosterols and pre‐β1‐HDL differed markedly, suggesting differences in intestinal lipidation of HDL. In addition, the in vitro investigations suggest an important role of plasma apoA‐II in xanthophyll metabolism.     

Metabolic behavior in rats of a nonprotein microemulsion resembling low-density lipoprotein

A protein-free microemulsion (LDE) with a lipid composition resembling that of low-density lipoprotein (LDL) was used in metabolic studies in rats to compare LDE with the native lipoprotein. LDE labeled with radioactive lipids was injected into the bloodstream of male Wistar rats, and plasma kinetics of the labeled lipids were followed on plasma samples collected at regular intervals for 12 h after injection. The 24-h LDE uptake by different tissues was also measured in tissue samples excised after the animals had been sacrificed. We found that LDE plasma kinetics were similar to those described for native LDL [fractional clearance rate (FCR) of cholesteryl ester, 0.42±0.11 h⁻¹]. The major site for LDE uptake was the liver, and the tissue distribution of the LDE injected radioactivity was as one would expect for LDL. To test whether LDE was taken up by the specific LDL receptors, the LDE emulsion was injected into rats treated with 17α-ethinylestradiol, which is known to increase the activity of these receptors; as expected, removal of LDE from the bloodstream increased (FCR=0.90±0.35 h⁻¹). On the other hand, saturation of the receptors that remove remnants by prior infusion of massive amounts of lymph chylomicrons did not change LDE plasma kinetics. These results indicate that LDE is cleared from plasma by B,E receptors and not by the E receptors that remove remnants. Incorporation of free cholesterol into LDE increased LDE plasma clearance. Incubation studies also showed that LDE incorporates a variety of apolipoproteins, including apo E, a ligand for recognition of lipoproteins by specific receptors. Our data suggest that LDE can be a useful tool to test LDL metabolism and B,E receptor function.     

Ground Beef High in Total Fat and Saturated Fatty Acids Decreases X Receptor Signaling Targets in Peripheral Blood Mononuclear Cells of Men and Women

We hypothesized that consumption of saturated fatty acids in the form of high‐fat ground beef for 5 weeks would depress liver X receptor signaling targets in peripheral blood mononuclear cells (PBMC) and that changes in gene expression would be associated with the corresponding changes in lipoprotein cholesterol (C) concentrations. Older men (n = 5, age 68.0 ± 4.6 years) and postmenopausal women (n = 7, age 60.9 ± 3.1 years) were assigned randomly to consume ground‐beef containing 18% total fat (18F) or 25% total fat (25F), five patties per week for 5 weeks with an intervening 4‐week washout period. The 25F and 18F ground‐beef increased (p < 0.05) the intake of saturated fat, monounsaturated fat, palmitic acid, and stearic acid, but the 25F ground‐beef increased only the intake of oleic acid (p < 0.05). The ground‐beefs 18F and 25F increased the plasma concentration of palmitic acid (p < 0.05) and decreased the plasma concentrations of arachidonic, eicosapentaenoic, and docosahexaenic acids (p < 0.05). The interventions of 18F and 25F ground‐beef decreased very low‐density lipoprotein C concentrations and increased particle diameters and low‐density lipoprotein (LDL)‐I‐C and LDL‐II‐C concentrations (p < 0.05). The ground‐beef 25F decreased PBMC mRNA levels for the adenosine triphosphate (ATP) binding cassette A, ATP binding cassette G1, sterol regulatory element binding protein‐1, and LDL receptor (LDLR) (p < 0.05). The ground‐beef 18F increased mRNA levels for stearoyl‐CoA desaturase‐1 (p < 0.05). We conclude that the increased LDL particle size and LDL‐I‐C and LDL‐II‐C concentrations following the 25F ground‐beef intervention may have been caused by decreased hepatic LDLR gene expression.     

The influence of plasma apolipoprotein A‐II concentrations on HDL subclass distribution

Background and aims: To investigate the impact of plasma apoA‐II concentrations on the alteration of HDL subclass distribution, and the cooperative effect of apoA‐I and apoA‐II on it. Methods and results: The apoA‐I contents of plasma HDL subclasses were quantified by two‐dimensional gel electrophoresis associated with immunodetection for 292 Chinese people. These subjects were divided according to the mean ± 1 SD of apoA‐II and apoA‐I levels as two cut‐points, respectively. Compared with the low‐apoA‐II group, the apoA‐I contents of HDL_3a (in the high group), HDL_3b, and HDL_2b increased strikingly, both in the middle‐ and high‐apoA‐II group. The apoA‐I contents of all HDL subclasses increased progressively when the apoA‐I and apoA‐II levels simultaneously or the apoA‐I/apoA‐II ratio increased, and in comparison to the low‐apoA‐I–A‐II levels group, the apoA‐I contents of HDL_2b (115%) increased more significantly than those of preβ₁‐HDL (39%) in the high‐apoA‐I–A‐II levels group. Multiple analyses also indicated that the three HDL subclasses, HDL_3a, HDL_3b and HDL_2b, were independently predicted by apoA‐II. Conclusion: Excess apoA‐II can cause the accumulation of both large‐sized HDL_2b and small‐sized HDL₃, which implies that apoA‐II plays a double role in the HDL maturation metabolism. Meanwhile, the degree of HDL_2b increased significantly relative to that of preβ₁‐HDL when apoA‐I and apoA‐II levels were elevated simultaneously, suggesting that the maturation and metabolism of HDL might be promoted and reverse cholesterol transport might be enhanced.     

The Safety and Anti‐Hypercholesterolemic Effect of Coptisine in Syrian Golden Hamsters

Current work was conducted to evaluate the cholesterol‐lowering effect of coptisine extracted from Rhizomacoptidis in Syrian golden hamsters. The safety results indicated that coptisine was a safe and low‐toxic compound. Coptisine showed a beneficial effect in the abnormal serum lipid levels induced by a high‐fat and high‐cholesterol diet (HFHC): at a concentration of 70.05 mg/kg, coptisine significantly led to a decrease in total cholesterol, triglycerides, and low‐density lipoprotein cholesterol (LDL‐c) levels by 26.70, 15.38, and 22.22 %, respectively, and high‐density lipoprotein cholesterol (HDL‐c) was increased by 41.74 % in serum of hamsters (p < 0.01). In addition, total bile acid (TBA) levels in feces of hamsters were elevated after coptisine administration. Further investigation has suggested that the mRNA and protein expression of 3‐hydroxy‐3‐methyl‐glutaryl‐CoA reductase (HMGCR) in the liver of hamsters was down‐regulated by high‐dosage coptisine treatment (p < 0.05); mRNA and protein expression of low‐density lipoprotein receptor (LDLR) and cholesterol 7α‐hydroxylase (CYP7A1) were dramatically up‐regulated by coptisine administration. The apical sodium‐dependent bile salt transporter expression was down‐regulated in the coptisine‐treated animals, but showed no significant differences from the HFHC groups. Taken together, our results demonstrate that a high dosage of coptisine could inhibit cholesterol synthesis via suppressing the HMGCR expression and promoting the use and excretion of cholesterol via up‐regulating LDLR and CYP7A1 expression. These findings suggest a critical role for coptisine in anti‐ hypercholesterolemia, and thus it needs to be considered as a potential natural cholesterol lowering agent.     

Low-Density Lipoproteins,High-Density Lipoproteins (HDL), and HDL-Associated Proteins Differentially Modulate Chronic Myelogenous Leukemia Cell Viability

Cellular lipid metabolism, lipoprotein interactions, and liver X receptor (LXR) activation have been implicated in the pathophysiology and treatment of cancer, although findings vary across cancer models and by lipoprotein profiles. In this study, we investigated the effects of human-derived low-density lipoproteins (LDL), high-density lipoproteins (HDL), and HDL-associated proteins apolipoprotein A1 (apoA1) and serum amyloid A (SAA) on markers of viability, cholesterol flux, and differentiation in K562 cells—a bone marrow-derived, stem-like erythroleukemia cell model of chronic myelogenous leukemia (CML). We further evaluated whether lipoprotein-mediated effects were altered by concomitant LXR activation. We observed that LDL promoted higher K562 cell viability in a dose- and time-dependent manner and increased cellular cholesterol concentrations, while LXR activation by the agonist TO901317 ablated these effects. LXR activation in the presence of HDL, apoA1 and SAA-rich HDL suppressed K562 cell viability, while robustly inducing mRNA expression of ATP-binding cassette transporter A1 (ABCA1). HDL and its associated proteins additionally suppressed mRNA expression of anti-apoptotic B-cell lymphoma-extra large (BCL-xL), and the erythroid lineage marker 5′-aminolevulinate synthase 2 (ALAS2), while SAA-rich HDL induced mRNA expression of the megakaryocytic lineage marker integrin subunit alpha 2b (ITGA2B). Together, these findings suggest that lipoproteins and LXR may impact the viability and characteristics of CML cells.     

Inhibition of Angiotensin II-Induced Cardiac Fibrosis by Atorvastatin in Adiponectin Knockout Mice

Adiponectin is a polypeptide known to inhibit cardiac fibrosis via the activation of ?adenosine monophosphate‐activated protein kinase (AMPK). Statins can also activate AMPK, resulting in the secretion of adiponectin. We determined whether atorvastatin inhibits angiotensin II‐induced cardiac fibrosis (AICF) in the presence or absence of adiponectin. Adiponectin knockout (APN‐KO, n = 44) and wild type (WT, n = 44) mice were received subcutaneous angiotensin II (1.5 mg/kg/day), and atorvastatin (10 mg/kg/day) was administered orally for 15 days. The mRNA expression levels of collagen type I and III, as well as AMPK phosphorylation levels in cardiac tissue were then measured. In the APN‐KO mice, collagen type I (p < 0.001) and type III (p = 0.001) expression was significantly greater when treated with angiotensin II, while their expression was significantly reduced in the presence of angiotensin II and atorvastatin. Relative AMPK phosphorylation levels in APN‐KO mice were also significantly higher in the angiotensin II + atorvastatin group when compared with angiotensin II group alone. We conclude that atorvastatin attenuates AICF independently from adiponectin by activating AMPK. These data suggest potential cardioprotection beyond lipid modulation potentially supporting statin pleiotropic hypothesis.     

Do not use the Friedewald formula to calculate LDL‐cholesterol in hypercholesterolaemic rats

Reputable calculations such as the Friedewald formula are used extensively to determine LDL‐cholesterol (LDL‐C) values from known total cholesterol, triacylglycerol and HDL‐cholesterol (HDL‐C) levels. To the best of our knowledge, however, the validity of this equation has not yet been confirmed in rats. The aim of the present study is to give some insights as to why this formula must be used carefully in rats, and to find cut‐off points below which this formula can be considered reliable. Sera of 54 rats with different cholesterol, triacylglycerol and HDL‐C levels were tested. LDL was isolated by ultracentrifugation and LDL‐C measured by an enzymatic colorimetric method and compared against LDL‐C obtained by the formula. In rats whose serum cholesterol was <100 mg/dL, or whose HDL‐C constituted ≥75% of total cholesterol, or whose cholesterol/phospholipids ratio was <1, or whose serum did not contain β‐VLDL, LDL‐C obtained by both methods did not significantly differ. Under other conditions, however, and particularly in hypercholesterolaemic rats who did present β‐VLDL, the results clearly show that the Friedewald formula overestimates LDL‐C levels. In conclusion, (VLDL + LDL)‐C instead of VLDL‐C and LDL‐C must be used when ultracentrifugation or other alternative methods are not available to measure LDL‐C in hypercholesterolaemic rats.     

Lipid transfers to HDL are diminished in long-term bedridden patients: association with low HDL-cholesterol and increased inflammatory markers

Plasma lipids have been extensively studied in sedentary and in subjects practicing exercise training, but not in extreme inactivity as occurs in bedridden patients. This is important for the care of bedridden patients and understanding the overall plasma lipid regulation. Here, we investigated plasma lipids, lipid transfers to HDL and inflammatory markers in bedridden patients. Fasting blood samples were collected from 23 clinically stable bedridden patients under long‐term care (>90 days) and 26 normolipidemic sedentary subjects, paired for age and gender. In vitro transfer of four lipids to HDL was performed by incubating plasma with donor nanoparticles containing radioactive lipids. Total (193 ± 36 vs 160 ± 43, p = 0.005), LDL (124 ± 3 vs 96 ± 33 p = 0.003) and HDL‐cholesterol (45 ± 10 vs 36 ± 13, p = 0.008), apolipoprotein A‐I (134 ± 20 vs 111 ± 24, p = 0.001) and oxidized LDL (53 ± 13 vs 43 ± 12, p = 0.011) were lower in bedridden patients, whereas triglycerides, apolipoprotein B, CETP and LCAT were equal in both groups. Transfers of all lipids, namely unesterified cholesterol, cholesterol esters, triglycerides and phospholipids, to HDL were lower in bedridden patients, probably due to their lower HDL‐cholesterol levels. Concentrations of IL‐1β, IL‐6, IL‐8, HGF and NGF were higher in bedridden patients compared to sedentary subjects. In conclusion, inactivity had great impact on HDL, by lowering HDL‐cholesterol, apolipoprotein A‐I and thereby cholesterol transfers to the lipoprotein, which suggests that inactivity may deteriorate HDL protection beyond the ordinary sedentary condition.     

TNFα-Induced LDL Cholesterol Accumulation Involve Elevated LDLR Cell Surface Levels and SR-B1 Downregulation in Human Arterial Endothelial Cells

Excess lipid droplets are frequently observed in arterial endothelial cells at sites of advanced atherosclerotic plaques. Here, the role of tumor necrosis factor alpha (TNFα) in modulating the low-density lipoprotein (LDL) content in confluent primary human aortic endothelial cells (pHAECs) was investigated. TNFα promoted an up to 2 folds increase in cellular cholesterol, which was resistant to ACAT inhibition. The cholesterol increase was associated with increased ¹²⁵I-LDL surface binding. Using the non-hydrolysable label, Dil, TNFα could induce a massive increase in Dil-LDL by over 200 folds. The elevated intracellular Dil-LDL was blocked with excess unlabeled LDL and PCSK9, but not oxidized LDL (oxLDL), or apolipoprotein (apoE) depletion. Moreover, the TNFα-induced increase of LDL-derived lipids was elevated through lysosome inhibition. Using specific LDLR antibody, the Dil-LDL accumulation was reduced by over 99%. The effects of TNFα included an LDLR cell surface increase of 138%, and very large increases in ICAM-1 total and surface proteins, respectively. In contrast, that of scavenger receptor B1 (SR-B1) was reduced. Additionally, LDLR antibody bound rapidly in TNFα-treated cells by about 30 folds, inducing a migrating shift in the LDLR protein. The effect of TNFα on Dil-LDL accumulation was inhibited by the antioxidant tetramethythiourea (TMTU) dose-dependently, but not by inhibitors against NF-κB, stress kinases, ASK1, JNK, p38, or apoptosis caspases. Grown on Transwell inserts, TNFα did not enhance apical to basolateral LDL cholesterol or Dil release. It is concluded that TNFα promotes LDLR functions through combined increase at the cell surface and SR-B1 downregulation.     

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.     

Consumption of High-Oleic Soybean Oil Improves Lipid and Lipoprotein Profile in Humans Compared to a Palm Oil Blend: A Randomized Controlled Trial

Partially hydrogenated oils (PHO) have been removed from the food supply due to adverse effects on risk for coronary heart disease (CHD). High-oleic soybean oils (HOSBO) are alternatives that provide functionality for different food applications. The objective of this study was to determine how consumption of diets containing HOSBO compared to other alternative oils, with similar functional properties, modifies LDL cholesterol (LDLc) and other risk factors and biomarkers of CHD. A triple-blind, crossover, randomized controlled trial was conducted in humans (n = 60) with four highly-controlled diets containing (1) HOSBO, (2) 80:20 blend of HOSBO and fully hydrogenated soybean oil (HOSBO+FHSBO), (3) soybean oil (SBO), and (4) 50:50 blend of palm oil and palm kernel oil (PO + PKO). Before and after 29 days of feeding, lipids/lipoproteins, blood pressure, body composition, and markers of inflammation, oxidation, and hemostasis were measured. LDLc, apolipoprotein B (apoB), NonHDL-cholesterol (HDLc), ratios of total cholesterol (TC)-to-HDLc and LDLc-to-HDL cholesterol, and LDL particle number and small LDL particles concentration were lower after HOSBO and HOSBO+FHSBO compared to PO (specific comparisons p < 0.05). Other than TC:HDL, there were no differences in lipid/lipoprotein markers when comparing HOSBO+FHSBO with HOSBO. LDLc and apoB were higher after HOSBO compared to SBO (p < 0.05). PO + PKO increased HDLc (p < 0.001) and apolipoprotein AI (p < 0.03) compared to HOSBO and HOSBO+FHSBO. With the exception of lipid hydroperoxides, dietary treatments did not affect other CHD markers. HOSBO, and blends thereof, is a PHO replacement that results in more favorable lipid/lipoprotein profiles compared to PO + PKO (an alternative fat with similar functional properties).