Cholesterol, Oxysterols and LXRs in Breast Cancer Pathophysiology.

Breast cancer is the most frequent cancer among women. In 2018, it is estimated that 627,000 women died from breast cancer. This is approximately 15% of all cancer deaths among women (WHO 2018). Breast cancer is a multifactorial chronic disease. While important progress has been made to treat patients, many questions regarding aspects of this disease relating to carcinogenesis are still open. During carcinogenesis, cells exhibit cholesterol homeostasis deregulation. This results in an accumulation of intracellular cholesterol, which is required to sustain their high growth rate. Cholesterol efflux and influx are two metabolic pathways that are necessary to prevent cholesterol accumulation in the cells. Liver X receptors (LXRs) are nuclear receptors that, upon activation, induce the expression of ABC transporters, responsible for promoting cholesterol efflux, and the expression of IDOL (inducible degrader of low-density lipoprotein receptor), in charge of reducing cholesterol influx. Oxysterols, oxygenated derivatives of cholesterol formed through different pathways, have been discovered as LXR-specific ligands. Some oxysterols are involved in tumor formation while others are considered anti-tumor agents. In the present review, we discuss the involvement of cholesterol, oxysterols and LXRs in breast cancer pathophysiology, with an emphasis on the biological effects of LXR ligands.

Effect of Carotenoids from Phaeodactylum tricornutum on Palmitate-Treated HepG2 Cells.

Non-alcoholic fatty liver disease represents the most common liver disease and is characterized by an excess of lipid accumulation in hepatocytes, mainly stored as triglycerides. Phaeodactylum tricornutum is a marine microalga, which is rich in bioactive molecules known to be hepatoprotective, such as n-3 long-chain polyunsaturated fatty acids and fucoxanthin. The aim of this study was to investigate the effects of a carotenoid extract from P. tricornutum in a cellular model of non-alcoholic fatty liver disease induced by palmitate treatment. The combined effects of carotenoids and lipids, especially n-3 long-chain polyunsaturated fatty acids, were also investigated by using a total lipophilic extract. HepG2 cells were exposed for 24 h to 250 µM palmitate with or without the addition of carotenoid extract (6 µg/mL) or total lipophilic extract (100 µg/mL). The addition of carotenoid extract or total lipophilic extract prevented the accumulation of triglycerides, total cholesterol and cholesterol esters. The carotenoid extract and total lipophilic extract also decreased the mRNA expression levels of genes involved in lipogenesis (ACACA, FASN, SCD and DGAT1) and cholesterol esterification (ACAT1/SOAT1). In addition, the total lipophilic extract also downregulated the LXR/NR1H3 and SREBF1 genes, which are involved in lipogenesis regulation. By contrast, the carotenoid extract increased the mRNA level of CPT1A, a ß-oxidation related gene, and reduced the lipid droplet accumulation. In conclusion, this study highlights the preventive effects against non-alcoholic fatty liver disease of the two microalga extracts.

4-cholesten-3-one decreases breast cancer cell viability and alters membrane raft-localized EGFR expression by reducing lipogenesis and enhancing LXR-dependent cholesterol transporters.

BACKGROUND: The alteration of lipid metabolism in cancer cells is recognized as one of the most important metabolic hallmarks of cancer. Membrane rafts defined as plasma membrane microdomains enriched in cholesterol and sphingolipids serve as platforms for signaling regulation in cancer. The main purpose of this study was to evaluate the effect of the cholesterol metabolite, 4-cholesten-3-one, on lipid metabolism and membrane raft integrity in two breast cancer cell lines, MCF-7 and MDA-MB-231. Its ability to reduce cell viability and migration has also been investigated. METHODS: RT-qPCR was performed to evaluate the expression of enzymes involved in lipogenesis and cholesterol synthesis, and ABCG1 and ABCA1 transporters involved in cholesterol efflux. Its effect on cell viability and migration was studied using the MTT assay, the wound healing assay and the Transwell migration assay, respectively. The effect of 4-cholesten-3-one on membrane rafts integrity was investigated by studying the protein expression of flotillin-2, a membrane raft marker, and raft-enriched EGFR by western blot. RESULTS: Interestingly, we found that 4-cholesten-3-one treatment decreased mRNA expression of different enzymes including ACC1, FASN, SCD1 and HMGCR. We further demonstrated that 4-cholesten-3-one increased the expression of ABCG1 and ABCA1. We also found that 4-cholesten-3-one decreased the viability of MCF-7 and MDA-MB-231 cells. This effect was neutralized after treatment with LXR inverse agonist or after LXRß knockdown by siRNA. As a result, we also demonstrated that 4-cholesten-3-one disrupts membrane rafts and cell migration capacity. CONCLUSION: Our results show that 4-cholesten-3-one exerts promising antitumor activity by altering LXR-dependent lipid metabolism in breast cancer cells without increasing lipogenesis.

Metabolomics-Driven Discovery of Meroterpenoids from a Mussel-Derived Penicillium ubiquetum.

Penicillium ubiquetum MMS330 isolated from the blue mussel Mytilus edulis collected on the Loire estuary in France was here investigated. As very few secondary metabolites have been documented for this species, its metabolome was studied following the OSMAC approach to enhance as many biosynthetic pathways as possible. Interestingly, HPLC-HRMS based hierarchical clustering analysis together with MS/MS molecular networking highlighted the selective overproduction of some structurally related compounds when the culture was performed on seawater CYA (Czapek Yeast extract Agar) medium. Mass-guided purification from large scale cultivation on this medium led to the isolation of nine meroterpenoids including two new analogues, 22-deoxyminiolutelide A (1) and 4-hydroxy-22-deoxyminiolutelide B (2), together with seven known compounds (3-9). The structures of 1 and 2 were elucidated on the basis of HR-ESIMS and NMR spectroscopic data analysis. Furthermore, NMR signals of 22-deoxyminiolutelide B (3) were reassigned.

Intestinal Proportion of Blautia sp. is Associated with Clinical Stage and Histoprognostic Grade in Patients with Early-Stage Breast Cancer.

Improving knowledge about breast cancer etiology is crucial in order to propose prevention strategies for this pathology. Gut microbiota is involved in numerous physiopathological situations including cancers. Although its potential involvement in breast cancer through the alteration of the enterohepatic circulation of estrogens and/or the metabolism of phytoestrogens has been discussed for some time, it remains to be demonstrated. The present study seeks to strengthen this hypothesis by identifying possible links between the fecal microbiota composition and clinical characteristics in breast cancer patients. Bacterial DNA was extracted from the feces of 31 patients with early-stage breast cancer and amplified by real-time polymerase chain reaction (qPCR), targeting 16S rRNA sequences specific to bacterial groups, and then analyzed in relation to clinical characteristics. The absolute numbers of total bacteria and of three bacterial groups (Firmicutes, Faecalibacterium prausnitzii, and Blautia) differed significantly according to the patient's body mass index. The percentage and the absolute numbers of certain bacterial groups, namely C. coccoides, F. prausnitzii, and Blautia, differed significantly according to the clinical stages and the histoprognostic grades. Our study highlighted that intestinal microbiota composition in these patients differs according to clinical characteristics and BMI. Further studies are required to clarify the link between breast cancer and intestinal microbiota.

The Marine-Derived Fungus Clonostachys rosea, Source of a Rare Conjugated 4-Me-6E,8E-hexadecadienoic Acid Reducing Viability of MCF-7 Breast Cancer Cells and Gene Expression of Lipogenic Enzymes.

A marine-derived strain of Clonostachys rosea isolated from sediments of the river Loire estuary (France) was investigated for its high lipid production. The fungal strain was grown on six different culture media to explore lipid production changes. An original branched conjugated fatty acid, mainly present in triglycerides and mostly produced when grown on DCA (23% of total fatty acid composition). It was identified as 4-Me-6E,8E-hexadecadienoic on the basis of spectroscopic analyses. This fatty acid reduced viability of MCF-7 breast cancer cells in a dose dependent manner (up to 63%) at physiological free fatty acid human plasma concentration (100 µM). Reduction of gene expression of two lipogenic enzymes, the acetyl CoA carboxylase (ACC) and the fatty acid synthase (FAS) was evaluated to explore the mechanisms of action of 4-Me-6E,8E-16:2 acid. At 50 µM, 50% and 35% of mRNA gene expression inhibition were observed for ACC and FAS, respectively.

Gestational cholestyramine treatment protects adult offspring of ApoE-deficient mice against maternal-hypercholesterolemia-induced atherosclerosis.

AIM: Perinatal hypercholesterolemia exacerbates the development of atherosclerotic plaques in adult offspring. Here, we aimed to study the effect of maternal treatment with cholestyramine, a lipid-lowering drug, on atherosclerosis development in adult offspring of hypercholesterolemic ApoE-deficient (ApoE-/-) mice. METHODS: ApoE-/- mice were treated with 3% cholestyramine (CTY) during gestation (G). After weaning, offspring (CTY-G) were fed control diet until sacrificed at 25weeks of age. Atherosclerosis development in the aortic root of offspring was assessed after oil-red-o staining, along with some of predefined atherosclerosis regulators such as LDL and HDL by high-performance liquid chromatography (HPLC), and bile acids (BA) and trimethylamine N-oxide (TMAO) by liquid chromatography-mass spectrometry (LC-MS/MS). RESULTS: In pregnant dams, cholestyramine treatment resulted in significantly lower plasma total- and LDL-cholesterol as well as gallbladder total BA levels. In offspring, both males and females born to treated dams displayed reduced atherosclerotic plaques areas along with less lipid deposition in the aortic root. No significant change in plasma total cholesterol or triglycerides was measured in offspring, but CTY-G males had increased HDL-cholesterol and decreased apolipoproteins B100 to A-I ratio. This latter group also showed reduced gallbladder total and specifically tauro-conjugated bile acid pools, whereas for CTY-G females, hydrophilic plasma tauro-conjugated BA pool was significantly higher. They also benefited from lower plasma TMAO. CONCLUSION: Prenatal cholestyramine treatment reduces atherosclerosis development in adult offspring of ApoE-/- mice along with modulating the plaques' composition as well as some related biomarkers such as HDL-C, bile acids and TMAO.

Deep phenotyping and biomarkers of various dairy fat intakes in an 8-week randomized clinical trial and 2-year swine study.

Health effects of dairy fats (DF) are difficult to evaluate, as DF intakes are hard to assess epidemiologically and DF have heterogeneous compositions that influence biological responses. We set out to find biomarkers of DF intake and assess biological response to a summer DF diet (R2), a winter DF diet (R3), and a R3 supplemented with calcium (R4) compared to a plant-fat-based diet (R1) in a randomized clinical trial (n=173) and a 2-year study in mildly metabolically disturbed downsized pigs (n=32). Conventional clinical measures were completed by LC/MS plasma metabolomics/lipidomics. The measured effects were modeled as biological functions to facilitate interpretation. DF intakes in pigs specifically induced a U-shaped metabolic trajectory, reprogramming metabolism to close to its initial status after a one-year turnaround. Twelve lipid species repeatably predicted DF intakes in both pigs and humans (6.6% errors). More broadly, in pigs, quality of DF modulated the time-related biological response (R2: 30 regulated functions, primarily at 6 months; R3: 26 regulated functions, mostly at 6-12 months; R4: 43 regulated functions, mostly at 18 months). Despite this heterogeneity, 9 functions overlapped under all 3 DF diets in both studies, related to a restricted area of amino acids metabolism, cofactors, nucleotides and xenobiotic pathways and the microbiota. In conclusion, over the long-term, DF reprograms metabolism to close to its initial biological status in metabolically-disrupted pigs. Quality of the DF modulates its metabolic influence, although some effects were common to all DF. A resilient signature of DF consumption found in pigs was validated in humans.

Link between Omega 3 Fatty Acids Carried by Lipoproteins and Breast Cancer Severity.

According to the International Agency for Research on Cancer (IARC) more than 10% of cancers can be explained by inadequate diet and excess body weight. Breast cancer is the most common cancer affecting women. The goal of our study is to clarify the relationship between ω3 fatty acids (FA) carried by different lipoproteins and breast cancer (BC) severity, according to two approaches: through clinic-biological data and through in vitro breast cancer cell models. The clinical study has been performed in sera from a cohort of BC women (n = 140, ICO, France) whose tumors differed by their hormone receptors status (HR− for tumors negative for estrogen receptors and progesterone receptors, HR+ for tumors positive for either estrogen receptors or progesterone receptors) and the level of proliferation markers (Ki-67 ≤ 20% Prolif− and Ki-67 ≥ 30% Prolif+). Lipids and ω3FA have been quantified in whole serum and in apoB-containing lipoproteins (Non-HDL) or free of it (HDL). Differences between Prolif− and Prolif+ were compared by Wilcoxon test in each sub-group HR+ and HR−. Results are expressed as median [25th−75th percentile]. Plasma cholesterol, triglycerides, HDL-cholesterol and Non-HDL cholesterol did not differ between Prolif− and Prolif+ sub-groups of HR− and HR+ patients. Plasma EPA and DHA concentrations did not differ either. In the HR− group, the distribution of EPA and DHA between HDL and Non-HDL differed significantly, as assessed by a higher ratio between the FA concentration in Non-HDL and HDL in Prolif− vs. Prolif+ patients (0.20 [0.15−0.36] vs. 0.04 [0.02−0.08], p = 0.0001 for EPA and 0.08 [0.04−0.10] vs. 0.04 [0.01−0.07], p = 0.04 for DHA). In this HR− group, a significant increase in Non-HDL EPA concentration was also observed in Prolif− vs. Prolif+ (0.18 [0.13−0.40] vs. 0.05 [0.02−0.07], p = 0.001). A relative enrichment on Non-HDL in EPA and DHA was also observed in Prolif− patients vs. Prolif+ patients, as assessed by a higher molar ratio between FA and apoB (0.12 [0.09−0.18] vs. 0.02 [0.01−0.05], p < 0.0001 for EPA and 1.00 [0.73−1.69 vs. 0.52 [0.14−1.08], p = 0.04 for DHA). These data were partly confirmed by an in vitro approach of proliferation of isolated lipoproteins containing EPA and DHA on MDA-MB-231 (HR−) and MCF-7 (HR+) cell models. Indeed, among all the studied fractions, only the correlation between the EPA concentration of Non-HDL was confirmed in vitro, although with borderline statistical significance (p = 0.07), in MDA-MB-231 cells. Non-HDL DHA, in the same cells model was significantly correlated to proliferation (p = 0.04). This preliminary study suggests a protective effect on breast cancer proliferation of EPA and DHA carried by apo B-containing lipoproteins (Non-HDL), limited to HR− tumors.

Circulating HDL and Non-HDL Associated Apolipoproteins and Breast Cancer Severity.

Plasma lipids are carried within lipoproteins with various apolipoprotein content. This study evaluates the interest of measuring the apolipoproteins of circulating lipoproteins in breast cancer. Patients with early-stage breast cancer (n = 140) were included. Tumors differed by the expression of estrogen and progesterone receptor (HR- and HR+ for negative and positive expression) and the proliferation marker Ki-67 (≤20% or ≥30%). Apolipoprotein concentrations were determined in plasma, HDL and non-HDL fractions, and results are given in mg/dL, median (25th-75th). Patients did not differ in their plasma and lipoprotein lipid concentrations. HDL apoC-I and non-HDL apoC-II were reduced (1.34 (1.02-1.80) vs. 1.61 (1.32-2.04), p = 0.04; 0.31 (0.18-0.65) vs. 0.63 (0.39-1.02), p = 0.01; respectively), in RH-/high Ki-67 patients in comparison to RH-/low Ki-67 patients, while plasma apoD and HDL apoD were higher (3.24 (2.99-4.16) vs. 3.07 (2.39-3.51), p = 0.04; 2.74 (2.36-3.35) vs. 2.45 (2.01-2.99), p = 0.04; respectively). When RH+/high Ki-67 patients were compared with RH+/low Ki-67 patients, HDL apoC-I and HDL apoC-III were higher (1.56 (1.20-1.95) vs. 1.35 (1.10-1.62), p = 0.02; 2.80 (2.42-3.64) vs. 2.38 (1.69-2.96), p = 0.02; respectively). The distribution of exchangeable apolipoproteins, such as apoC-I, apoC-II, apoC-III, apoD, between lipoproteins is linked to the severity of breast cancer.

The Marine Microalga, Tisochrysis lutea, Protects against Metabolic Disorders Associated with Metabolic Syndrome and Obesity.

Long-chain polyunsaturated fatty acids n-3 series and especially docosahexaenoic acid are known to exert preventive effects on metabolic disturbances associated with obesity and decrease cardiovascular disease risk. n-3 LC-PUFAs are mainly consumed in the form of fish oil, while other sources, such as certain microalgae, may contain a high content of these fatty acids. The aim of this study was to evaluate the effects of Tisochrysis lutea (Tiso), a microalga rich in DHA, on metabolic disorders associated with obesity. Three male Wistar rat groups were submitted for eight weeks to a standard diet or high-fat and high fructose diet (HF), supplemented or not with 12% of T. lutea (HF-Tiso). The supplementation did not affect plasma alanine aminotransferase (ALAT). Bodyweight, glycemia and insulinemia decreased in HF-Tiso rats (ANOVA, p < 0.001), while total plasma cholesterol, high-density lipoprotein-cholesterol (HDL-C) increased (ANOVA, p < 0.001) without change of low-density lipoprotein-cholesterol (LDL-C) and triacylglycerol (TAG) levels. Tiso supplementation decreased fat mass and leptinemia as well as liver TAG, cholesterol and plasma tumor necrosis factor-alpha levels (ANOVA, p < 0.001) while it did not affect interleukin 6 (IL-6), IL-4 and lipopolysaccharides levels. HF-Tiso rats showed an increase of IL-10 level in abdominal adipose tissue (ANOVA, p < 0.001). In conclusion, these results indicated that DHA-rich T. lutea might be beneficial for the prevention of obesity and improvement of lipid and glucose metabolism.

Basolateral Secretion from Caco-2 Cells Pretreated with Fecal Waters from Breast Cancer Patients Affects MCF7 Cell Viability.

We hypothesized that the role of microbiota in breast cancer relates to its influence on gut lipid metabolism. This was tested in an in vitro model combining MCF-7 and Caco-2 cells. A total of 32 women newly diagnosed for breast cancer before any treatment and 28 healthy women provided their stools. Bacterial DNA was amplified by qPCR targeting 16s rRNA specific to Bacteroidetes and Firmicutes phyla, Lactobacillales sp., Clostridium cluster IV, Faecalibacterium prausnitzii, Clostridium cluster XIVa, Roseburia intestinalis, Blautia sp., Lactonifactor longoviformis, Bifidobacterium sp., Coriobacteriaceae, Eggertella lenta, Escherichia, and Shigella. Fecal waters (FW) were quantified for short chain fatty acids (SCFA). Caco-2 cells grown on filter inserts were incubated apically with 10% FW for 24 h, and LXR, apolipoproteins AIV, and E gene expression were estimated by real time (RT) qPCR. Then, MCF-7 cells were incubated with the whole basolateral medium for 24 h, and their viability was estimated by 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) test. Regression models were used to determine the correlation between MCF-7 viability and bacteria relative abundance, Caco-2 cells lipid metabolism gene expression and stool composition, as well as microbiota composition and short chain fatty acids. Logistic regression models established disease odds ratios (OR) for MCF-7 viability and Caco-2 gene expression. The OR of MCF-7 viability was 1.05 (1.01-1.10) (OR (5th-95th), p = 0.04), while that of apo AIV gene expression was 0.63 (0.39-1.01), p = 0.055). Viability correlated with % Bifidobacterium sp. (21.18 ± 7.66, p = 0.008) and valerate (-2.849 ± 1.048, p = 0.009) (ß ± s.d.). This study suggests that microbiota interacts with intestine cell lipid metabolism. Since these metabolites can reach breast cells by systemic circulation, we hypothesized that they may influence cancer disease.

Acetone Fraction of the Red Marine Alga Laurencia papillosa Reduces the Expression of Bcl-2 Anti-apoptotic Marker and Flotillin-2 Lipid Raft Marker in MCF-7 Breast Cancer Cells.

Marine macroalgae have attracted much attention in recent years as a valuable source of bioactive metabolites. The cytotoxic potential of the Laurencia papillosa red alga collected from the Lebanese coast has been investigated on human breast cancer cells MCF-7. The crude extract of Laurencia papillosa (L. papillosa) was fractionated by column chromatography using a series of increasingly polar solvents (methylene chloride, acetone and methanol). Cytotoxicity of the crude extract and fractions was determined by MTT assay in MCF-7 cells. Apoptosis was detected by annexin V/propidium iodide assay and by measurement of Bcl-2 expression. Flotillin-2 expression was examined using RT-qPCR and Western blot. The crude extract, and the fractions of CH2Cl2 and acetone exhibited a dose-dependent cytotoxic effect on MCF-7 cells. Apoptosis was specifically induced by one of the acetone fractions having the highest cytotoxicity. It has been demonstrated by an increase in late phase apoptotic cell populations, and a decrease in Bcl-2 anti-apoptotic marker expression on mRNA and protein levels in a dose- and time- dependent manner. Furthermore, this active fraction decreased Flotillin-2 expression associated with cancer progression. Our data suggest that L. papillosa is an important source of cytotoxic metabolites. Further studies are needed for the chemical characterization of the metabolite associated with observed biological activities.

Unusual sterolic mixture, and 24-isopropylcholesterol, from the sponge Ciocalypta sp. reduce cholesterol uptake and basolateral secretion in Caco-2 cells.

An unusual sterolic mixture (82.3% of 24-isopropylated sterols) and its major component, 24-isopropylcholesterol, isolated from a marine sponge, Ciocalypta sp. (Halichondriidae), reduce cholesterol uptake, basolateral secretion and ACAT-2 mRNA expression and increase the expression of ABCA1 mRNA in Caco-2 cells. The decreases of cholesterol uptake and secretion induced by 24-isopropylcholesterol alone were more than that of both the sterolic mixture and beta-sitosterol. These data add a new sterol, 24-isopropylcholesterol, to sterols that may reduce intestinal cholesterol absorption.

Preventive Effects of the Marine Microalga Phaeodactylum tricornutum, Used as a Food Supplement, on Risk Factors Associated with Metabolic Syndrome in Wistar Rats.

Long-chain polyunsaturated fatty acids, n-3 series (n-3 LC-PUFA), are known for their preventive effects against cardiovascular disease. In an unfavourable economic and environmental context of fish oil production, marine microalgae could be an alternative source of n-3 LC-PUFA and are of interest for human nutrition. The aim of this study was to evaluate the effects of P. tricornutum, a microalga rich in eicosapentaenoic acid and used as a food supplement, on the metabolic disorders associated with metabolic syndrome and obesity development. Three male Wistar rat groups (n = 6) were submitted for eight weeks to a standard diet or high-fat diet (HF) with 10% fructose in drinking water, supplemented or not with 12% of P. tricornutum (HF-Phaeo). Supplementation led to n-3 LC-PUFA enrichment of lipids in the liver, plasma and erythrocytes. Plasma transaminases showed no difference between the HF and HF-Phaeo groups. Body weight, fat mass, inflammatory markers and insulinemia decreased in HF-Phaeo rats versus the HF group. Plasma total cholesterol, triacylglycerols and leptine diminished in HF-Phaeo rats, while HDL-cholesterol increased. In conclusion, this study highlights the beneficial effects of P. tricornutum in reducing the metabolic disorders associated with metabolic syndrome.

Lithocholic bile acid inhibits lipogenesis and induces apoptosis in breast cancer cells.

BACKGROUND: It has amply been documented that mammary tumor cells may exhibit an increased lipogenesis. Biliary acids are currently recognized as signaling molecules in the intestine, in addition to their classical roles in the digestion and absorption of lipids. The aim of our study was to evaluate the impact of lithocholic acid (LCA) on the lipogenesis of breast cancer cells. The putative cytotoxic effects of LCA on these cells were also examined. METHODS: The effects of LCA on breast cancer-derived MCF-7 and MDA-MB-231 cells were studied using MTT viability assays, Annexin-FITC and Akt phosphorylation assays to evaluate anti-proliferative and pro-apoptotic properties, qRT-PCR and Western blotting assays to assess the expression of the bile acid receptor TGR5 and the estrogen receptor ERα, and genes and proteins involved in apoptosis (Bax, Bcl-2, p53) and lipogenesis (SREBP-1c, FASN, ACACA). Intracellular lipid droplets were visualized using Oil Red O staining. RESULTS: We found that LCA induces TGR5 expression and exhibits anti-proliferative and pro-apoptotic effects in MCF-7 and MDA-MB-231 cells. Also, an increase in pro-apoptotic p53 protein expression and a decrease in anti-apoptotic Bcl-2 protein expression were observed after LCA treatment of MCF-7 cells. In addition, we found that LCA reduced Akt phosphorylation in MCF-7 cells, but not in MDA-MB-231 cells. We also noted that LCA reduced the expression of SREBP-1c, FASN and ACACA in both breast cancer-derived cell lines and that cells treated with LCA contained low numbers of lipid droplets compared to untreated control cells. Finally, a decrease in ERα expression was observed in MCF-7 cells treated with LCA. CONCLUSIONS: Our data suggest a potential therapeutic role of lithocholic acid in breast cancer cells through a reversion of lipid metabolism deregulation.

Human lecithin:cholesterol acyltransferase deficiency: in vivo kinetics of low-density lipoprotein and lipoprotein-X.

OBJECTIVE: Lecithin:cholesterol acyltransferase deficiency (LCAT-def) is characterized by low levels of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) and the accumulation of lipoprotein-X (LpX). Despite the low HDL, atherosclerosis is uncommon in LCAT-def. The decreased LDL would be a possible explanation but the underlying mechanism is not clear. In addition, the mechanism(s) for LpX accumulation is not known. The aim of the present study is to elucidate the mechanism(s) responsible for the low LDL and determine the plasma kinetics of LpX in LCAT-def. METHODS AND RESULTS: We conducted a radiotracer study in LCAT-def (n=2) and normal controls (n=10) and a stable isotope study in one patient and other controls (n=7). LCAT-def LDL was catabolized faster than control LDL in the control subjects as well as in LCAT-def patients. Control LDL was catabolized faster in LCAT-def patients than the controls. The production rate of LDL apolipoprotein B-100 was normal in LCAT-def. The increased LDL apoB-100 catabolism was confirmed by a stable isotope study. LpX was catabolized more slowly in LCAT-def. CONCLUSIONS: The decreased LDL in LCAT-def is attributable to an increased catabolism caused by a rapid catabolism of abnormal LDL and an upregulation of LDL receptor pathway. The decreased catabolism of LpX contributes to its accumulation in LCAT-def.

LXR Activation Down-regulates Lipid Raft Markers FLOT2 and DHHC5 in MCF-7 Breast Cancer Cells.

BACKGROUND/AIM: Lipid rafts are cholesterol-enriched microdomains of the plasma membrane. Recent studies have underlined that their integrity is critical for cancer cell survival. Liver X receptor (LXR) has a central role in cellular cholesterol homeostasis and its stimulation inhibits proliferation of several cancer cell lines. This study investigated whether LXR could modulate lipid rafts integrity and consequently alter proliferation of the MCF-7 breast cancer cell line. MATERIALS AND METHODS: Effect of LXR agonist T0901317 on integrity of MCF-7 lipid rafts was examined by studying the expression of rafts marker flotillin-2 (FLOT2) and DHHC5, which palmitoylates FLOT2, and by studying the expression of phospho-Akt. RESULTS: We demonstrated that LXR stimulation decreases mRNA and protein expression of FLOT2 and DHHC5 in MCF-7 cells. LXR stimulation also reduces Akt phosphorylation and its localization at the plasma membrane. CONCLUSION: We showed, for the first time, that LXR regulates transcription of specific proteins of lipid rafts in a breast cancer model.

Altered lipid, apolipoprotein, and lipoprotein profiles in inflammatory bowel disease: consequences on the cholesterol efflux capacity of serum using Fu5AH cell system.

Epidemiological data suggest a link between chronic inflammation condition and atherosclerosis. Infection and inflammation can also impair lipoprotein metabolism and produce a wide variety of changes in plasma concentrations of lipids and lipoproteins. Twenty-one patients with inflammatory bowel diseases (IBDs) and 28 healthy subjects were recruited. Serum concentrations of lipids, lipoproteins, apolipoproteins, leptin, ghrelin, and inflammation markers (C-reactive protein and serum amyloid A) were measured, and subjects' lipoproteins were characterized. The ability of patients with serum IBD to efflux free cell cholesterol was measured. Serum cholesterol, high-density lipoprotein cholesterol, apolipoprotein (apo) A-I, apoC-II, apoC-III bound to apoB, phospholipid, and phospholipids not bound to apoB levels were significantly lower, whereas serum triglyceride, serum amyloid A, and C-reactive protein levels were significantly higher in patients with active IBD. Apolipoprotein A-I immunoreactivity (pre-beta small particles and small alpha-high-density lipoprotein particles) is decreased in patients with IBD. In contrast, apoE immunoreactivity (slow/small apoE containing lipoprotein particles [LpE particle]) increased in these patients. The efflux capacity of serum from patients with IBD using [(3)H]-cholesterol-labeled Fu5AH cells was reduced (P < .005). Our results demonstrate that, in subjects with active IBD, inflammation leads to alterations in lipid, apolipoprotein, and lipoprotein profiles and reduced cholesterol efflux. These changes are similar to those proposed to promote atherogenesis and may contribute to the development of cardiovascular events.

Nicotinic Acid Accelerates HDL Cholesteryl Ester Turnover in Obese Insulin-Resistant Dogs.

AIM: Nicotinic acid (NA) treatment decreases plasma triglycerides and increases HDL cholesterol, but the mechanisms involved in these change are not fully understood. A reduction in cholesteryl ester transfer protein (CETP) activity has been advanced to explain most lipid-modulating effects of NA. However, due to the central role of CETP in reverse cholesterol transport in humans, other effects of NA may have been hidden. As dogs have no CETP activity, we conducted this study to examine the specific effects of extended-release niacin (NA) on lipids and high-density lipoprotein (HDL) cholesteryl ester (CE) turnover in obese Insulin-Resistant dogs with increase plasma triglycerides. METHODS: HDL kinetics were assessed in fasting dogs before and four weeks after NA treatment through endogenous labeling of cholesterol and apolipoprotein AI by simultaneous infusion of [1,2 13C2] acetate and [5,5,5 2H3] leucine for 8 h. Kinetic data were analyzed by compartmental modeling. In vitro cell cholesterol efflux of serum from NA-treated dogs was also measured. RESULTS: NA reduced plasma total cholesterol, low-density lipoprotein cholesterol, HDL cholesterol, triglycerides (TG), and very-low-density lipoprotein TG concentrations (p < 0.05). The kinetic study also showed a higher cholesterol esterification rate (p < 0.05). HDL-CE turnover was accelerated (p < 0.05) via HDL removal through endocytosis and selective CE uptake (p < 0.05). We measured an elevated in vitro cell cholesterol efflux (p < 0.05) with NA treatment in accordance with a higher cholesterol esterification. CONCLUSION: NA decreased HDL cholesterol but promoted cholesterol efflux and esterification, leading to improved reverse cholesterol transport. These results highlight the CETP-independent effects of NA in changes of plasma lipid profile.