Effect of Compounds Affecting ABCA1 Expression and CETP Activity on the HDL Pathway Involved in Intestinal Absorption of Lutein and Zeaxanthin

The antioxidant xanthophylls lutein and zeaxanthin are absorbed from the diet in a process involving lipoprotein formation. Selective mechanisms exist for their intestinal uptake and tissue‐selective distribution, but these are poorly understood. We investigated the role of high‐density lipoprotein (HDL), apolipoprotein (apo) A1 and ATP‐binding cassette transporter (ABC) A1 in intestinal uptake of lutein in a human polarized intestinal cell culture and a hamster model. Animals received dietary lutein and zeaxanthin and either a liver X receptor (LXR) agonist or statin, which up‐ or down‐regulate intestinal ABCA1 expression, respectively. The role of HDL was studied following treatment with the cholesteryl ester transfer protein (CETP) modulator dalcetrapib or the CETP inhibitor anacetrapib. In vitro, intestinal ABCA1 at the basolateral surface of enterocytes transferred lutein and zeaxanthin to apoA1, not to mature HDL. In hamsters, plasma lutein and zeaxanthin levels were markedly increased with the LXR agonist and decreased with simvastatin. Dalcetrapib, but not anacetrapib, increased plasma and liver lutein and zeaxanthin levels. ABCA1 expression and apoA1 acceptor activity are important initial steps in intestinal uptake and maintenance of lutein and zeaxanthin levels by an HDL‐dependent pathway. Their absorption may be improved by physiological and pharmacological interventions affecting HDL metabolism.     

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.     

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.     

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.     

Effect of liposome-encapsulated hemoglobin on triglyceride, total cholesterol, low-density lipoprotein, and high-density lipoprotein cholesterol measurements

The present study investigated the effect of liposome-encapsulated hemoglobin (LEH), an experimental oxygen-carrying resuscitation fluid, on triglyceride, total cholesterol, and low density lipoprotein (LDL), and high density lipoprotein (HDL) cholesterol measurements. In vivo, the intravenous infusion of LEH (5.6 mL/kg, n=6) elevated serum triglycerides (+92% vs. baseline, P<.05), total cholesterol (+25% vs. baseline, P<.01), LDL cholesterol (+72% vs. baseline, P<.01) and had no effect on serum HDL cholesterol. In addition, LEH did not alter the elevation in serum triglycerides (+302% vs. baseline, P<.01) and LDL cholesterol (+86% vs. baseline, P<.01) induced by lipopolysaccharide (3.6 mg/kg, i.v., n=6). Ex vivo, measurements of triglycerides and total cholesterol as well as LDL and HDL cholesterol in whole blood from naive rats were not changed by the addition of LEH (0–50%, n=6). In vitro, the addition of a fixed concentration of LEH (50%, n=6) to varying concentrations of cholesterol solution (0–50%), or vice versa, had no effect on cholesterol determination. It is therefore concluded that LEH only minimally affects serum levels of triglycerides, total cholesterol, LDL cholesterol, and HDL cholesterol and does not interfere with their measurement.     

Changes in cholesteryl ester transfer protein concentration during normal gestation

Background: It has been shown that endogenous estrogen may affect the concentration of cholesteryl ester transfer protein (CETP) and that the gestation in women is accompanied by increased levels of endogenous estrogen. Objectives: To examine the changes in CETP concentration and to investigate the relationship between CETP and estrogen levels during normal pregnancy. Methods: Serum concentrations of CETP, estrogen and lipid traits were determined from 296 healthy women at different times during gestation. Results: Pregnant women exhibited a significant elevation in the concentration of CETP as compared with non‐pregnant women (3.11 ± 1.51 mg/L vs. 2.64 ± 1.25 mg/L, p <0.001). The CETP concentration was highest in the first trimester (3.85 ± 1.33 mg/L, compared with controls, p <0.0001), declined progressively from the first to the third trimester and still remained elevated in the third trimester as compared with non‐pregnant subjects (p <0.05). A negative correlation was noted between serum CETP and estradiol (E₂) levels in pregnant women (r = –0.288, p <0.0001). In addition, significantly negative correlations between the serum CETP concentration and all the lipid traits examined were found in gestating women. Conclusion: CETP concentrations were significantly elevated in pregnancy and decreased progressively from early to late gestation. The results suggest that endogenous E₂ is either not involved or its effect on CETP is dominated by elevated lipid levels or some other factors during mid and late pregnancy.     

Vitamin D and Evening Primrose Oil Administration Improve Glycemia and Lipid Profiles in Women with Gestational Diabetes

Limited data are available assessing the effects of vitamin D and evening primrose oil (EPO) administration on markers of insulin resistance and lipid concentrations in gestational diabetes mellitus (GDM). This study was designed to evaluate the effects of vitamin D and EPO administration on insulin resistance and lipid concentrations among women with GDM. In this prospective randomized, double‐blind, placebo‐controlled clinical trial, 60 participants with GDM were divided into 2 groups of either 1000 IU vitamin D3 and 1000 mg EPO or placebo for 6 weeks. At the beginning and end of the study, fasting blood samples were obtained from the participants to measure related variables. After 6 weeks of intervention, changes in fasting plasma glucose (?3.6 ± 7.5 vs. +1.5 ± 11.4 mg/dL, P = 0.04), serum insulin concentrations (?2.0 ± 5.3 vs. +4.6 ± 10.7 µIU/mL, P = 0.004), homeostasis model of assessment (HOMA) insulin resistance (?0.5 ± 1.1 vs. +1.1 ± 2.5, P = 0.003), HOMA‐B cell function (?7.7 ± 23.3 vs. +17.4 ± 42.9, P = 0.007) and the quantitative insulin sensitivity check index (+0.01 ± 0.02 vs. ?0.01 ± 0.02, P = 0.007) in the vitamin D plus EPO group were significantly different from the placebo group. In addition, compared with the placebo, vitamin D and EPO supplementation resulted in significant reductions in serum TAG (?20.0 ± 54.3 vs. +34.3 ± 38.2 mg/dL, P < 0.001), VLDL (?4.0 ± 10.9 vs. +6.9 ± 7.6 mg/dL, P < 0.001), TC (?22.1 ± 32.6 vs. +5.3 ± 20.1 mg/dL, P < 0.001), LDL concentrations (?18.0 ± 25.5 vs. +1.8 ± 15.7 mg/dL, P = 0.001) and TC/HDL (?0.3 ± 0.4 vs. +0.3 ± 0.5 mg/dL, P < 0.001). We did not observe any significant effect of vitamin D and EPO supplementation on serum HDL concentrations. Clinical trial registration number: http://www.irct.ir : IRCT201509115623N52.     

Maternal Flaxseed Oil During Lactation Enhances Bone Development in Male Rat Pups

Flaxseed oil is an alpha linolenic acid source important in the growth and body development stage; furthermore, this acid acts on adipose tissue and bone health. The aim of this study was to evaluate body composition, fatty acid composition, hormone profile, retroperitoneal adipocyte area and femur structure of pups at weaning, whose mothers were fed a diet containing flaxseed oil during lactation. After birth, pups were randomly assigned: control (C, n = 12) and flaxseed oil (FO, n = 12), rats whose mothers were treated with diet containing soybean or flaxseed oil. At 21 days, the pups were weaned and body mass, length, body composition, biochemical parameter, leptin, osteoprotegerin, osteocalcin, fatty acids composition, intra‐abdominal fat mass and femur structure were analyzed. FO showed (p < 0.05): higher body mass (+12 %) and length (+9 %); body fat mass (g, +45 %); bone mineral density (+8 %), bone mineral content (+55 %) and bone area (+35 %), osteocalcin (+173 %) and osteoprotegerin (+183 %). Arachidonic acid was lower (p < 0.0001), alpha‐linolenic and eicosapentaenoic were higher (p < 0.0001). Intra‐abdominal fat mass was higher (+25 %), however, the retroperitoneal adipocytes area was lower (?44 %). Femur mass (+10 %), distance between epiphyses (+4 %) and bone mineral density (+13 %) were higher. The study demonstrates that adequate flaxseed oil content during a lactation diet plays an important role in the development of pups.     

n‐3 PUFA Esterified to Glycerol or as Ethyl Esters Reduce Non‐Fasting Plasma Triacylglycerol in Subjects with Hypertriglyceridemia: A Randomized Trial

To date, treatment of hypertriglyceridemia with long‐chain n‐3 polyunsaturated fatty acids (n‐3 PUFA) has been investigated solely in fasting and postprandial subjects. However, non‐fasting triacylglycerols are more strongly associated with risk of cardiovascular disease. The objective of this study was to investigate the effect of long‐chain n‐3 PUFA on non‐fasting triacylglycerol levels and to compare the effects of n‐3 PUFA formulated as acylglycerol (AG‐PUFA) or ethyl esters (EE‐PUFA). The study was a double‐blinded randomized placebo‐controlled interventional trial, and included 120 subjects with non‐fasting plasma triacylglycerol levels of 1.7–5.65 mmol/L (150–500 mg/dL). The participants received approximately 3 g/day of AG‐PUFA, EE‐PUFA, or placebo for a period of eight weeks. The levels of non‐fasting plasma triacylglycerols decreased 28 % in the AG‐PUFA group and 22 % in the EE‐PUFA group (P < 0.001 vs. placebo), with no significant difference between the two groups. The triacylglycerol lowering effect was evident after four weeks, and was inversely correlated with the omega‐3 index (EPA + DHA content in erythrocyte membranes). The omega‐3 index increased 63.2 % in the AG‐PUFA group and 58.5 % in the EE‐PUFA group (P < 0.001). Overall, the heart rate in the AG‐PUFA group decreased by three beats per minute (P = 0.045). High‐density lipoprotein (HDL) cholesterol increased in the AG‐PUFA group (P < 0.001). Neither total nor non‐HDL cholesterol changed in any group. Lipoprotein‐associated phospholipase A2 (LpPLA2) decreased in the EE‐PUFA group (P = 0.001). No serious adverse events were observed. Supplementation with long‐chain n‐3 PUFA lowered non‐fasting triacylglycerol levels, suggestive of a reduction in cardiovascular risk. Regardless of the different effects on heart rate, HDL, and LpPLA2 that were observed, compared to placebo, AG‐PUFA, and EE‐PUFA are equally effective in reducing non‐fasting triacylglycerol levels.     

Regulation by long-chain fatty acids of the expression of cholesteryl ester transfer protein in HepG2 cells

Cholesteryl ester transfer protein (CETP) is an important determinant of lipoprotein function, especially high density lipoprotein (HDL) metabolism, and contributes to the regulation of plasma HDL levels. Since saturated and polyunsaturated fatty acids (FA) appear to influence the CETP activity differently, we decided to investigate the effects of FA on the expression of CETP mRNA in HepG2 cells using an RNA blot hybridization analysis. Long-chain FA (>18 carbons) at a 0.5 mM concentration were added to the medium and incubated with cells for 48 h at 37°C under 5% CO₂. After treatment with 0.5 mM arachidonic (AA), eicosapentaenoic (EPA), and docosahexaenoic acid (DHA), the levels of CETP mRNA were less than 50% of the control levels (AA, P=0.0005; EPA, P<0.01; DHA, P<0.0001), with a corresponding significant decrease in the CETP mass. These results suggest that FA regulate the gene expression of CETP in HepG2 and this effect is dependent upon the degree of unsaturation of the acyl carbon chain in FA.     

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.     

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.     

Occurrence of dyslipidemia in spontaneous intracerebral hemorrhage

Background: Dyslipidemia, mainly hypocholesterolemia is considered to be a risk factor (RF) for spontaneous intracerebral hemorrhage (SICH). The aim of our study was to assess its role in our SICH patients. Methods: In a hospital‐based cross‐section study, laboratory assessments of total cholesterol (TC), triglycerides (TG), high‐density cholesterol (HDL‐C) and low‐density cholesterol (LDL‐C) plasma levels were performed in 80 SICH patients without vascular malformation and in a control group (CG) of 80 age‐ and sex‐matched patients with low back pain. All patients were treated at the Departments of Neurology and Neurosurgery, University Hospital, Olomouc, Czech Republic. Two‐sample t‐test and Mann‐Whitney test were applied when assessing statistical significance. Results: The following mean lipid plasma levels were found in SICH patients versus CG subjects (in mmol/L): TC, 5.89 vs. 5.48 (p = 0.007); TG, 1.31 vs. 2.10 (p <0.0001); HDL‐C, 1.58 vs. 1.33 (p = 0.0001); LDL‐C, 3.70 vs. 3.18 (p = 0.0004). Conclusions: TC and LDL‐C plasma levels were higher in SICH patients in the Olomouc region of the Czech Republic.     

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.     

Mifepristone Treatment Results in Differential Regulation of Glycerolipid Biosynthesis in Baby Hamster Kidney Cells Expressing a Mifepristone-Inducible ABCA1

ATP binding cassette A1 (ABCA1) transports cholesterol, phospholipids and lipophilic molecules to and across cellular membranes. We examined if ABCA1 expression altered cellular de novo glycerolipid biosynthesis in growing Baby hamster kidney (BHK) cells. Mock BHK cells or cells expressing a mifepristone-inducible ABCA1 (ABCA1) were incubated plus or minus mifepristone and then with [³H]serine or [³H]inositol or [³H]ethanolamine or [methyl-³H]choline or [³H]glycerol or [¹⁴C]oleate and radioactivity incorporated into glycerolipids determined. Mifepristone did not affect [1,3-³H]glycerol or [¹⁴C]oleate or [³H]ethanolamine or [methyl-³H]choline uptake in BHK cells. In contrast, [³H]glycerol and [¹⁴C]oleate incorporated into phosphatidylserine (PtdSer) were elevated 2.4-fold (p < 0.05) and 54% (p < 0.05), respectively, upon ABCA1 induction confirming increased PtdSer biosynthesis from these precursors. However, mifepristone inhibited [³H]serine uptake and incorporation into PtdSer indicating that PtdSer synthesis from serine in BHK cells is dependent on serine uptake. Mifepristone stimulated [³H]inositol uptake in mock and ABCA1 cells but not its incorporation into phosphatidylinositol indicating that its synthesis from inositol is independent of inositol uptake in BHK cells. [³H]glycerol and [¹⁴C]oleate incorporated into triacylglycerol were reduced and into diacylglycerol elevated only in mifepristone-induced ABCA1 expressing cells due to a decrease in diacylglycerol acyltransferase-1 (DGAT-1) activity. The presence of trichostatin A, a class I and II histone deacetylase inhibitor, reversed the ABCA1-mediated reduction in DGAT-1 activity but did not affect DGAT-1 mRNA expression. Thus, mifepristone has diverse effects on de novo glycerolipid synthesis. We suggest that caution should be exercised when using mifepristone-inducible systems for studies of glycerolipid metabolism in cells expressing glucocorticoid responsive receptors.     

Phospholipid Transfer Protein Deficiency Decreases the Content of S1P in HDL via the Loss of its Transfer Capability

Sphingosine‐1‐phosphate (S1P) is an amphiphilic signaling molecule, which is enriched in functional high density lipoprotein (HDL) and shows arterial protection. The distribution of S1P is changed with increased plasma phospholipid transfer protein (PLTP) activity and impaired HDL function in patients with coronary heart diseases. Therefore, we hypothesized that PLTP might transfer S1P among cells or lipoproteins. We found that plasma S1P contents were decreased by 60.1 % in PLTP knockout mice (PLTP?/?, N = 5) compared with their wild type littermates (WT, N = 5) (151.70 ± 38.59 vs. 379.32 ± 59.90 nmol/l, P<0.01). S1P content in HDL fraction (HDL‐S1P) from PLTP?/? was decreased by 64.7 % compared with WT (49.36 ± 1.49 vs. 139.76 ± 2.94 nmol/l, P<0.01). The results of the S1P transfer assay indicated that PLTP could facilitate S1P transport from erythrocytes to HDL at 37 °C in D‐Hanks buffer. Plasma content of apolipoprotein M, a specific adaptor of S1P, was not changed in PLTP?/? compared with WT. Therefore, we concluded that PLTP was a key factor to maintain plasma HDL‐S1P, and PLTP deficiency could decrease the S1P content in plasma lipoproteins, which involves its capability of transferring S1P from erythrocyte to HDL.     

HDL Cholesterol Efflux and Serum Cholesterol Loading Capacity Alterations Associate to Macrophage Cholesterol Accumulation in FH Patients with Achilles Tendon Xanthoma

Achilles tendon xanthoma (ATX) formation involves macrophage cholesterol accumulation within the tendon, similar to that occurring in atheroma. Macrophage cholesterol homeostasis depends on serum lipoprotein functions, namely the high-density lipoprotein (HDL) capacity to promote cell cholesterol efflux (cholesterol efflux capacity, CEC) and the serum cholesterol loading capacity (CLC). We explored the HDL-CEC and serum CLC, comparing 16 FH patients with ATX to 29 FH patients without ATX. HDL-CEC through the main efflux mechanisms mediated by the transporters ATP binding cassette G1 (ABCG1) and A1 (ABCA1) and the aqueous diffusion (AD) process was determined by a cell-based radioisotopic technique and serum CLC fluorimetrically. Between the two groups, no significant differences were found in terms of plasma lipid profile. A trend toward reduction of cholesterol efflux via AD and a significant increase in ABCA1-mediated HDL-CEC (+18.6%) was observed in ATX compared to no ATX patients. In ATX-presenting patients, ABCG1-mediated HDL-CEC was lower (−11%) and serum CLC was higher (+14%) compared to patients without ATX. Considering all the patients together, ABCG1 HDL-CEC and serum CLC correlated with ATX thickness inversely (p = 0.013) and directly (p < 0.0001), respectively. In conclusion, lipoprotein dysfunctions seem to be involved in ATX physiopathology and progression in FH patients.     

Responses of MAC‐T Cells to Inhibited Stearoyl‐CoA Desaturase 1 during cis‐9, trans‐11 Conjugated Linoleic Acid Synthesis

Cis‐9‐conjugated, trans‐11‐conjugated linoleic acid (CLA) is known for its positive activities on human health. The synthesis of cis‐9, trans‐11 CLA in mammary glands is generally thought to be catalyzed by stearoyl‐CoA desaturase 1 (SCD1), but this has not been rigorously established. In this study, we hypothesized that the inhibition of SCD1 (by CAY10566) would block the synthesis of cis‐9, trans‐11 CLA in bovine mammary alveolar cells (MAC‐T) cells. Results showed that MAC‐T cells incubated with 10 nM CAY10566 for 12 h (CAY) produced less cis‐9, trans‐11 CLA (p < 0.01), lower 14:1/(14:1 + 14:0)% (p < 0.01), more trans‐11 18:1 (TVA) accumulation (p < 0.01), and reduced SCD1 mRNA levels (p < 0.01) compared with the control group (CON). Moreover, the mRNA abundances of sterol regulatory element‐binding protein 1 [SREBPF1], acyl‐CoA synthetase short‐chain family member 2 [ACSS2], and lipin 1 [LPIN1] were significantly elevated when SCD1 was inhibited in the CAY group (p < 0.05). Taken together, CAY10566 inhibition of SCD1 resulted in lower cis‐9, trans‐11 CLA synthesis ability, and SREBF1, ACSSS2, and LPIN1 were negatively associated with SCD1. These findings not only provide the direct evidence that cis‐9, trans‐11 CLA synthesis is catalyzed by SCD1, but also help us understand the responses of MAC‐T cells to SCD1 inhibition.     

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.     

Plasma Lipid Transfer Enzymes in Non-Diabetic Lean and Obese Men and Women

There are considerable differences in the plasma lipid profile between lean and obese individuals and between men and women. Little, however, is known regarding the effects of obesity and sex on the plasma concentration of enzymes involved in intravascular lipid remodeling. Therefore, we measured the immunoreactive protein mass of lipoprotein lipase (LPL), hepatic lipase (HL), cholesterol-ester transfer protein (CETP) and lecithin-cholesterol acyl transferase (LCAT) in fasting plasma samples from 40 lean and 40 obese non-diabetic men and premenopausal women. Women, compared with men, had ~5% lower plasma LCAT (p < 0.041), ~35% greater LPL (p = 0.001) and ~10% greater CETP (p = 0.085) concentrations. Obese, compared with lean individuals of both sexes, had ~30% greater plasma LCAT (p < 0.001), ~20% greater CETP (p < 0.001) and ~20% greater LPL (p = 0.071) concentrations. Plasma HL concentration was not different in lean men and women. Obesity was associated with increased (by ~50%) plasma HL concentration in men (p = 0.018) but not in women; consequently, plasma HL concentration was lower in obese women than obese men (p = 0.009). In addition, there were direct correlations between plasma lipid transfer enzyme concentrations and lipoprotein particle concentrations and sizes. There are considerable differences in basal plasma lipid transfer enzyme concentrations between lean and obese subjects and between men and women, which may be partly responsible for respective differences in the plasma lipid profile.