Regulation of cholesterol homeostasis by liver X receptors

Association between the Mediterranean Diet and Vitamin C and the Risk of Head and Neck Cancer

Diet may modulate the risk of head and neck cancer (HNC) through antioxidant and anti-inflammatory effects. To date, there is limited evidence regarding the effects of the Mediterranean diet on HNC risk. The purpose of the study was to assess the association between Mediterranean diet adherence, type of diet, and vitamin C and the risk of HNC. A case-control study was conducted at the Dentistry Hospital, University of Barcelona, including 101 cases of HNC and 101 controls matched by age and sex. Dietary habits were assessed using a 14-question Mediterranean diet score that classified the type of diet into healthy diet (10-14 points), regular diet (5-9 points), and unhealthy diet (≤4 points). Multivariate logistic regression models were used to assess the association between Mediterranean diet adherence, type of diet, and vitamin C and the risk of HNC. Higher adherence to the Mediterranean diet was significantly associated with a lower risk of HNC (OR = 0.88, 95% CI: 0.79-0.98). A healthy diet (OR = 0.29, 95% CI: 0.10-0.84) and vitamin C intake (OR = 0.25, 95% CI: 0.10-0.62) were strongly associated with lower odds of HNC. Moderate egg intake was the only type of food significantly associated with a lower risk of HNC. Dietary patterns that emphasize a high intake of antioxidant and anti-inflammatory bioactive components may have a protective effect on the risk of HNC.

Egg and cholesterol intake, apolipoprotein E4 phenotype and risk of venous thromboembolism: findings from a prospective cohort study

The impact of egg consumption, a major source of dietary cholesterol, with the risk of atherosclerotic cardiovascular diseases (ASCVDs) is controversial. Venous thromboembolism (VTE) is a CVD which shares common risk factors and mechanistic pathways with ASCVD. However, there is no data on the relationship between egg or cholesterol intake and VTE risk. Therefore, we evaluated the prospective associations of egg and cholesterol intakes with VTE risk and whether the apolipoprotein E4 (apoE4) phenotype, which influences cholesterol metabolism, could modify the associations. Data involving 1,852 men aged 42-61 years at baseline without a history of VTE or coronary heart disease in the population-based Kuopio Ischaemic Heart Disease Risk Factor Study were analysed. Dietary intakes were assessed with 4-day food records. Incident VTE events were identified by record linkage to hospital discharge registries. Hazard ratios (95% confidence intervals [CIs]) for incident VTE were estimated using Cox regression. During a median follow-up of 28.8 years, 132 VTE events occurred. Comparing the top (>38 g/d) versus bottom (<20 g/d) tertiles of egg consumption, the HR (95% CI) for VTE was 0.99 (0.64-1.53) in analysis adjusted for several established risk factors and other dietary factors. There was also no evidence of an association between cholesterol intake and VTE risk. Imputed results were consistent with the observed results. The apoE4 phenotype did not modify the associations. In middle-aged and older Finnish men, egg or cholesterol intakes were not associated with future VTE risk. Other large-scale prospective studies are needed to confirm or refute these findings.

Cholesterol Dysmetabolism in Alzheimer's Disease: A Starring Role for Astrocytes?

In recent decades, the impairment of cholesterol metabolism in the pathogenesis of Alzheimer’s disease (AD) has been intensively investigated, and it has been recognized to affect amyloid β (Aβ) production and clearance, tau phosphorylation, neuroinflammation and degeneration. In particular, the key role of cholesterol oxidation products, named oxysterols, has emerged. Brain cholesterol metabolism is independent from that of peripheral tissues and it must be preserved in order to guarantee cerebral functions. Among the cells that help maintain brain cholesterol homeostasis, astrocytes play a starring role since they deliver de novo synthesized cholesterol to neurons. In addition, other physiological roles of astrocytes are to modulate synaptic transmission and plasticity and support neurons providing energy. In the AD brain, astrocytes undergo significant morphological and functional changes that contribute to AD onset and development. However, the extent of this contribution and the role played by oxysterols are still unclear. Here we review the current understanding of the physiological role exerted by astrocytes in the brain and their contribution to AD pathogenesis. In particular, we focus on the impact of cholesterol dysmetabolism on astrocyte functions suggesting new potential approaches to develop therapeutic strategies aimed at counteracting AD development.

Impaired cholesterol metabolism in the mouse model of cystic fibrosis. A preliminary study

This study aims to investigate cholesterol metabolism in a mouse model with cystic fibrosis (CF) by the comparison of affected homozygous versus wild type (WT) mice. In particular, we evaluated the effects of a diet enriched with cholesterol in both mice groups in comparison with the normal diet. To this purpose, beyond serum and liver cholesterol, we analyzed serum phytosterols as indirect markers of intestinal absorption of cholesterol, liver lathosterol as indirect marker of de novo cholesterol synthesis, liver cholestanol (a catabolite of bile salts synthesis) and the liver mRNA levels of LDL receptor (LDLR), 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoAR), acyl CoA:cholesterol acyl transferase 2 (ACAT2), cytochrome P450 7A1 (CYP7A1) and tumor necrosis factor alpha (TNFα). CF mice showed lower intestinal absorption and higher liver synthesis of cholesterol than WT mice. In WT mice, the cholesterol supplementation inhibits the synthesis of liver cholesterol and enhances its catabolism, while in CF mice we did not observe a reduction of LDLR and HMG-CoAR expression (probably due to an altered feed-back), causing an increase of intracellular cholesterol. In addition, we observed a further increase (5-fold) in TNFα mRNA levels. This preliminary study suggests that in CF mice there is a vicious circle in which the altered synthesis/secretion of bile salts may reduce the digestion/absorption of cholesterol. As a result, the liver increases the biosynthesis of cholesterol that accumulates in the cells, triggering inflammation and further compromising the metabolism of bile salts.

The association of 14-year dietary cholesterol trajectories with the risk of cardio-metabolic diseases, all-cause mortality and serum lipids

OBJECTIVES

The effect of dietary cholesterol consumption on health effects and serum lipids remains controversial. This study aimed to examine the association of dietary cholesterol trajectories over 14 years in China with the risk of cardio-metabolic diseases and all-cause mortality and serum lipids.

METHODS

This study used weighted longitudinal data of 8952 adults from the China Health and Nutrition Survey, and subgroup analyses included 5466 adults who provided blood samples. Latent class trajectory modelling was performed to examine cholesterol trajectories. Cox regression models and general linear regressions were performed to examine the association between trajectories and outcomes.

RESULTS

Compared to the participants with persistently low dietary cholesterol intake, participants with gradually increasing cholesterol intake throughout adulthood were more likely to have hypertension (HR = 1.14, 95% CI: 1.03, 1.28) and to die due to all causes (HR = 2.19, 95% CI: 1.57, 3.05). Moreover, participants with persistently high cholesterol intake were more likely to die due to all causes (HR = 2.26, 95% CI 1.47, 3.47). The total cholesterol (TC):HDL-cholesterol (HDL-C) ratio and apolipoprotein B (ApoB) in these two groups were also significantly elevated compared to the group with persistently low dietary cholesterol intake (all P < 0.05). An association between trajectories of cholesterol and the incidence of diabetes was also observed; however, such an association became non significant after additional adjustment for other nutrients, food consumption and social environment.

CONCLUSIONS

Gradually increasing or persistently high cholesterol consumption throughout adulthood was significantly associated with an increased risk of hypertension and all-cause mortality with elevated serum lipids.

LncRNA kcnq1ot1 promotes lipid accumulation and accelerates atherosclerosis via functioning as a ceRNA through the miR-452-3p/HDAC3/ABCA1 axis

Kcnq1 overlapping transcript 1 (kcnq1ot1), an imprinted antisense lncRNA in the kcnq1 locus, acts as a potential contributor to cardiovascular disease, but its role in atherosclerosis remains unknown. The aim of this study was to explore the effects of kcnq1ot1 on atherogenesis and the underlying mechanism. Our results showed that kcnq1ot1 expression was significantly increased in mouse aorta with atherosclerosis and lipid-loaded macrophages. Lentivirus-mediated kcnq1ot1 overexpression markedly increased atherosclerotic plaque area and decreased plasma HDL-C levels and RCT efficiency in apoE^-/- mice fed a Western diet. Upregulation of kcnq1ot1 also reduced the expression of miR-452-3p and ABCA1 but increased HDAC3 levels in mouse aorta and THP-1 macrophages. Accordingly, kcnq1ot1 overexpression inhibited cholesterol efflux and promoted lipid accumulation in THP-1 macrophages. In contrast, kcnq1ot1 knockdown protected against atherosclerosis in apoE^-/- mice and suppressed lipid accumulation in THP-1 macrophages. Mechanistically, kcnq1ot1 enhanced HDAC3 expression by competitively binding to miR-452-3p, thereby inhibiting ABCA1 expression and subsequent cholesterol efflux. Taken together, these findings suggest that kcnq1ot1 promotes macrophage lipid accumulation and accelerates the development of atherosclerosis through the miR-452-3p/HDAC3/ABCA1 pathway.

Targeting SREBP-2-Regulated Mevalonate Metabolism for Cancer Therapy

Recently, targeting metabolic reprogramming has emerged as a potential therapeutic approach for fighting cancer. Sterol regulatory element binding protein-2 (SREBP-2), a basic helix-loop-helix leucine zipper transcription factor, mainly regulates genes involved in cholesterol biosynthesis and homeostasis. SREBP-2 binds to the sterol regulatory elements (SREs) in the promoters of its target genes and activates the transcription of mevalonate pathway genes, such as HMG-CoA reductase (HMGCR), mevalonate kinase and other key enzymes. In this review, we first summarized the structure of SREBP-2 and its activation and regulation by multiple signaling pathways. We then found that SREBP-2 and its regulated enzymes, including HMGCR, FPPS, SQS, and DHCR4 from the mevalonate pathway, participate in the progression of various cancers, including prostate, breast, lung, and hepatocellular cancer, as potential targets. Importantly, preclinical and clinical research demonstrated that fatostatin, statins, and N-BPs targeting SREBP-2, HMGCR, and FPPS, respectively, alone or in combination with other drugs, have been used for the treatment of different cancers. This review summarizes new insights into the critical role of the SREBP-2-regulated mevalonate pathway for cancer and its potential for targeted cancer therapy.

Tissue distribution of transcription for 29 lipid metabolism-related genes in Takifugu rubripes, a marine teleost storing lipid predominantly in liver

The tissue distribution pattern of lipid is highly diverse among different fish species. Tiger puffer has a special lipid storage pattern, storing lipid predominantly in liver. In order to better understand the lipid physiology in fish storing lipid in liver, the present study preliminarily investigated the tissue distribution of transcription for 29 lipid metabolism-related genes in tiger puffer, which are involved in lipogenesis, fatty acid oxidation, biosynthesis and hydrolysis of glycerides, lipid transport, and relevant transcription regulation. Samples of eight tissues, brain, eye, heart, spleen, liver, intestine, skin, and muscle, from fifteen juvenile tiger puffer were used in the qRT-PCR analysis. The intestine and brain had high transcription of lipogenic genes, whereas the liver and muscle had low expression levels. The intestine also had the highest transcription level of most apolipoproteins and lipid metabolism-related transcription factors. The transcription of fatty acid β-oxidation-related genes was low in the muscle. The peroxisomal fatty acid oxidation may dominate over mitochondrial β-oxidation in the liver and intestine of tiger puffer, and the MAG pathway probably predominates over the G3P pathway in re-acylation of absorbed lipids in the intestine. The intracellular glyceridases were highly transcribed in the brain, eye, and heart. In conclusion, in tiger puffer, the intestine could be a center of lipid metabolism whereas the liver is more likely a pure storage organ for lipid. The lipid metabolism in the muscle could also be inactive, possibly due to the very low level of intramuscular lipid.

Mulberry Fruit Extract Promotes Serum HDL-Cholesterol Levels and Suppresses Hepatic microRNA-33 Expression in Rats Fed High Cholesterol/Cholic Acid Diet

Serum high-density lipoprotein cholesterol (HDL-C) levels and cholesterol excretion are closely associated with the risk of cardiovascular complications. The specific aim of the present study was to investigate the cholesterol lowering effect of mulberry fruit in rats fed a high cholesterol/cholic acid diet. Four-week supplementation with mulberry fruit extract significantly decreased serum and hepatic cholesterol (TC), serum low-density lipoprotein cholesterol (LDL-C), and fecal bile acid levels without changes in body weight and food intake (p < 0.05). Mulberry fruit extract significantly inhibited hepatic sterol-regulatory element binding protein (Srebp) 2 gene expression and upregulated hepatic mRNA levels of liver X receptor alpha (Lxr-α), ATP-binding cassette transporter 5 (Abcg5), and cholesterol 7 alpha-hydroxylase (Cyp7a1), which are involved in hepatic bile acid synthesis and cholesterol metabolism (p < 0.05). In addition, hepatic microRNA-33 expression was significantly inhibited by supplementation of mulberry fruit extract (p < 0.05). These results suggest the involvement of miR-33, its associated hepatic bile acid synthesis, HDL formation, and cholesterol metabolism in mulberry fruit-mediated beneficial effects on serum and hepatic lipid abnormalities.

Association of egg intake with blood lipids, cardiovascular disease, and mortality in 177,000 people in 50 countries

BACKGROUND

Eggs are a rich source of essential nutrients, but they are also a source of dietary cholesterol. Therefore, some guidelines recommend limiting egg consumption. However, there is contradictory evidence on the impact of eggs on diseases, largely based on studies conducted in high-income countries.

OBJECTIVES

Our aim was to assess the association of egg consumption with blood lipids, cardiovascular disease (CVD), and mortality in large global studies involving populations from low-, middle-, and high-income countries.

METHODS

We studied 146,011 individuals from 21 countries in the Prospective Urban Rural Epidemiology (PURE) study. Egg consumption was recorded using country-specific validated FFQs. We also studied 31,544 patients with vascular disease in 2 multinational prospective studies: ONTARGET (Ongoing Telmisartan Alone and in Combination with Ramipril Global End Point Trial) and TRANSCEND (Telmisartan Randomized Assessment Study in ACEI Intolerant Subjects with Cardiovascular Disease). We calculated HRs using multivariable Cox frailty models with random intercepts to account for clustering by study center separately within each study.

RESULTS

In the PURE study, we recorded 14,700 composite events (8932 deaths and 8477 CVD events). In the PURE study, after excluding those with history of CVD, higher intake of egg (≥7 egg/wk compared with <1 egg/wk intake) was not significantly associated with blood lipids, composite outcome (HR: 0.96; 95% CI: 0.89, 1.04; P-trend = 0.74), total mortality (HR: 1.04; 95% CI: 0.94, 1.15; P-trend = 0.38), or major CVD (HR: 0.92; 95% CI: 0.83, 1.01; P-trend = 0.20). Similar results were observed in ONTARGET/TRANSCEND studies for composite outcome (HR 0.97; 95% CI: 0.76, 1.25; P-trend = 0.09), total mortality (HR: 0.88; 95% CI: 0.62, 1.24; P-trend = 0.55), and major CVD (HR: 0.97; 95% CI: 0.73, 1.29; P-trend = 0.12).

CONCLUSIONS

In 3 large international prospective studies including ∼177,000 individuals, 12,701 deaths, and 13,658 CVD events from 50 countries in 6 continents, we did not find significant associations between egg intake and blood lipids, mortality, or major CVD events. The ONTARGET and TRANSCEND trials were registered at clinicaltrials.gov as NCT00153101. The PURE trial was registered at clinicaltrials.gov as NCT03225586.

Threshold-Effect Association of Dietary Cholesterol Intake with Dyslipidemia in Chinese Adults: Results from the China Health and Nutrition Survey in 2015

The association of dietary cholesterol intake with dyslipidemia and subtypes is controversial. This study aimed to examine the association of dietary cholesterol intake with dyslipidemia and subtypes in Chinese adults. Using data from the China Health and Nutrition Survey (CHNS) in 2015, the present study selected 4383 participants aged 18–59 years who were free of diabetes, apoplexy, and myocardial infarction disease. Information was obtained on dietary intake, anthropometric measurements, and blood laboratory measurements. Dietary cholesterol intake was calculated based on the data collected by consecutive 3 days 24 h recalls combined with the weighing of household seasonings and categorized by 11 levels: The first 10 levels in ranges of 50 mg/day and the 11th level at ≥500 mg/day. Dyslipidemia, hypercholesterolemia, hypertriglyceridemia, low-density lipoprotein (LDL)-hypercholesterolemia, and high-density lipoprotein (HDL)-hypocholesterolemia were defined based on the Chinese adult dyslipidemia prevention guide (2016 edition). Multivariable logistic regressions were performed to examine the association of dietary cholesterol intake levels with dyslipidemia and subtypes. The prevalence of dyslipidemia was 37.5% among Chinese adults in 2015 (hypercholesterolemia 9.6%, HDL-hypocholesterolemia 21.1%, LDL-hypercholesterolemia 12.7%, and hypertriglyceridemia 15.2%). The lowest prevalence of hypercholesterolemia and LDL-hypercholesterolemia was 6.7% and 9.4%, respectively, which was relative to a dietary cholesterol intake level of 100.0 to <150.0 mg/day. After adjusting for all potential confounders, adults with the highest dietary cholesterol intake level of ≥500 mg/day compared with the dietary cholesterol intake of 100.0 to <150.0 mg/day showed one-time higher odds of hypercholesterolemia (odds ratios (OR) 2.0, 95% confidence intervals (CI) 1.3–3.3), as well as LDL-hypercholesterolemia (OR 2.0, 95% CI 1.3–3.0), but a null association of dietary cholesterol intake with dyslipidemia, hypertriglyceridemia, and HDL-hypocholesterolemia. The study suggested that a dietary cholesterol intake level of 500 mg/day and above may be a threshold point for high odds of hypercholesterolemia and LDL-hypercholesterolemia.

Oxysterols and the NeuroVascular Unit (NVU): A far true love with bright and dark sides

The brain is isolated from the whole body by the blood-brain barrier (BBB) which is located in brain microvessel endothelial cells (ECs). Through physical and metabolic properties induced by brain pericytes, astrocytes and neurons (these cells and the ECs referred to as the neurovascular unit (NVU)), the BBB hardly restricts exchanges of molecules between the brain and the bloodstream. Among them, cholesterol exchanges between these two compartments are very limited and occur through the transport of LDLs across the BBB. Oxysterols (mainly 24S and 27-hydroxycholesterol) daily cross the BBB and regulate molecule/cholesterol exchanges via Liver X nuclear Receptors (LXRs). In addition, these oxysterols have been linked to pathological processes in neurodegenerative diseases such as Alzheimer's disease. Here we propose an overview of the actual knowledge concerning oxysterols and the NVU cells in physiological and in Alzheimer's disease.

Upregulation of Nuclear Factor IA Suppresses Oxidized Low-Density Lipoprotein-Induced Endoplasmic Reticulum Stress and Apoptosis in Human Umbilical Vein Endothelial Cells

Background

Endoplasmic reticulum stress (ERS) is part of the cardiovascular pathological processes, including atherosclerosis. Nuclear factor IA (NFIA) influences atherosclerosis development; however, its effects on ERS remain unknown. This study investigated the effect of NFIA on oxidized low-density lipoprotein (ox-LDL)-induced ERS and apoptosis in endothelial cells.

Material/Methods

Ox-LDL was used to induce lipotoxicity in human umbilical vein endothelial cells (HUVECs) to establish an in vitro oxidative injury model transfected with pcDNA3.0-NFIA. The cytotoxic response was detected using an assay to determine the release of lactate dehydrogenase (LDH). Morphological changes in cell apoptosis were detected using Hoechst 33258 staining. The proportion of apoptotic cells, releases of reactive oxygen species (ROS), and mitochondrial membrane potential (ΔΨm) were determined using flow cytometry. The expression levels of apoptosis- and ERS-related molecules were detected through Western blotting.

Results

NFIA expression was downregulated in the in vitro oxidative cell-injury model. Exposure of HUVECs to ox-LDL resulted in a significant increase in apoptosis, decrease in ROS levels, and loss of ΔΨm. Overexpression of NFIA remarkably inhibited ERS and mitochondrial-mediated apoptosis induced by ox-LDL in HUVECs by reversing the effect of ox-LDL on the expression of JNK1, p-JNK1, CHOP, Cyt C, and Bax.

Conclusions

These results demonstrated that NFIA might have beneficial effects in the prevention of ox-LDL-induced ERS and apoptosis in vascular endothelial cells. This study provided new insights into the mechanism of atherosclerosis.

Formulation and Characterization of Quercetin-loaded Oil in Water Nanoemulsion and Evaluation of Hypocholesterolemic Activity in Rats

Due to poor water solubility and high susceptibility to chemical degradation, the applications of quercetin have been limited. This study investigated the effects of pH on the formation of quercetin-loaded nanoemulsion (NQ) and compared the hypocholesterolemic activity between quercetin and NQ to utilize the quercetin as functional food ingredient. NQ particle size exhibited a range of 207⁻289 nm with polydispersity index range (<0.47). The encapsulation efficiency increased stepwise from 56 to 92% as the pH increased from 4.0 to 9.0. Good stability of NQ was achieved in the pH range of 6.5⁻9.0 during 3-month storage at 21 and 37 °C. NQ displayed higher efficacy in reducing serum and hepatic cholesterol levels and increasing the release of bile acid into feces in rats fed high-cholesterol diet, compared to quercetin alone. NQ upregulated hepatic gene expression involved in bile acid synthesis and cholesterol efflux, such as cholesterol 7 alpha-hydroxylase (CYP7A1), liver X receptor alpha (LXRα), ATP-binding cassette transporter A1 (ABCA1) and ATP-binding cassette sub-family G member 1 (ABCG1). These results suggest at least partial involvement of hepatic bile acid synthesis and fecal cholesterol excretion in nanoemulsion quercetin-mediated beneficial effect on lipid abnormalities.

Dietary Cholesterol and the Lack of Evidence in Cardiovascular Disease

Cardiovascular disease (CVD) is the leading cause of death in the United States. For years, dietary cholesterol was implicated in increasing blood cholesterol levels leading to the elevated risk of CVD. To date, extensive research did not show evidence to support a role of dietary cholesterol in the development of CVD. As a result, the 2015–2020 Dietary Guidelines for Americans removed the recommendations of restricting dietary cholesterol to 300 mg/day. This review summarizes the current literature regarding dietary cholesterol intake and CVD. It is worth noting that most foods that are rich in cholesterol are also high in saturated fatty acids and thus may increase the risk of CVD due to the saturated fatty acid content. The exceptions are eggs and shrimp. Considering that eggs are affordable and nutrient-dense food items, containing high-quality protein with minimal saturated fatty acids (1.56 gm/egg) and are rich in several micronutrients including vitamins and minerals, it would be worthwhile to include eggs in moderation as a part of a healthy eating pattern. This recommendation is particularly relevant when individual’s intakes of nutrients are suboptimal, or with limited income and food access, and to help ensure dietary intake of sufficient nutrients in growing children and older adults.

Recent development of signaling pathways inhibitors of melanogenesis

Human skin, eye and hair color rely on the production of melanin, depending on its quantity, quality, and distribution, Melanin plays a monumental role in protecting the skin against the harmful effect of ultraviolet radiation and oxidative stress from various environmental pollutants. However, an excessive production of melanin causes serious dermatological problems such as freckles, solar lentigo (age spots), melasma, as well as cancer. Hence, the regulation of melanin production is important for controlling the hyper-pigmentation. Melanogenesis, a biosynthetic pathway to produce melanin pigment in melanocyte, involves a series of intricate enzymatic and chemical catalyzed reactions. Several extrinsic factors include ultraviolet radiation and chemical drugs, and intrinsic factors include molecules secreted by surrounding keratinocytes or melanocytes, and fibroblasts, all of which regulate melanogenesis. This article reviews recent advances in the development of melanogenesis inhibitors that directly/indirectly target melanogenesis-related signaling pathways. Efforts have been made to provide a description of the mechanism of action of inhibitors on various melanogenesis signaling pathways.

Oral intake of 7-dehydrocholesterol increases vitamin D3 concentrations in the liver and kidney

INTRODUCTION

Due to the high prevalence of vitamin D deficiency, strategies are needed to improve vitamin D status. Food components can affect vitamin D metabolism and have to be considered when estimating the efficacy of vitamin D supplements. 7-dehydrocholesterol (7-DHC) occurs naturally in food, but its impact on vitamin D metabolism has not yet been examined.

METHODS

Three groups of male C57BL/6 mice (n=12 per group) were placed on a diet that contained 0, 2.5 or 5mg 7-DHC per kg diet over a period of 6 weeks. Vitamin D and other sterols in the serum, skin, liver and kidney were quantified by LC-MS/MS. The relative mRNA abundance of hepatic genes encoding vitamin D hydroxylation enzymes and transporters was analyzed by real-time RT-PCR.

RESULTS

We found a substantial dose-dependent increase of non-hydroxylated vitamin D₃ in the liver and kidney of mice fed a diet containing 7-DHC. The vitamin D₃ content in the liver was 2.80±0.61pmol/g, 7.34±4.28pmol/g and 12.9±3.58pmol/g in groups that received 0, 2.5 and 5mg/kg 7-DHC, respectively. In the kidney, the vitamin D₃ content of these groups was 1.78±1.17pmol/g, 3.55±1.06 and 6.36±2.29pmol/g, respectively. The serum and tissue concentrations of 25-hydroxyvitamin D₃ (25(OH)D₃) remained unaffected by 7-DHC. The relative mRNA data provided no plausible mechanism for the observed effects of 7-DHC on vitamin D₃. All groups of mice had similar concentrations of cholesterol, desmosterol and 7-DHC in their serum and tissues.

CONCLUSION

The current findings provide the first evidence that dietary 7-DHC seems to affect vitamin D metabolism. The underlying mechanism remains elusive and needs further investigation.

Systems Analysis of the Complement-Induced Priming Phase of Liver Regeneration

Liver regeneration is a well-orchestrated process in the liver that allows mature hepatocytes to reenter the cell cycle to proliferate and replace lost or damaged cells. This process is often impaired in fatty or diseased livers, leading to cirrhosis and other deleterious phenotypes. Prior research has established the role of the complement system and its effector proteins in the progression of liver regeneration; however, a detailed mechanistic understanding of the involvement of complement in regeneration is yet to be established. In this study, we have examined the role of the complement system during the priming phase of liver regeneration through a systems level analysis using a combination of transcriptomic and metabolomic measurements. More specifically, we have performed partial hepatectomy on mice with genetic deficiency in C3, the major component of the complement cascade, and collected their livers at various time points. Based on our analysis, we show that the C3 cascade activates c-fos and promotes the TNF-α signaling pathway, which then activates acute-phase genes such as serum amyloid proteins and orosomucoids. The complement activation also regulates the efflux and the metabolism of cholesterol, an important metabolite for cell cycle and proliferation. Based on our systems level analysis, we provide an integrated model for the complement-induced priming phase of liver regeneration.

VNN1 promotes atherosclerosis progression in apoE-/- mice fed a high-fat/high-cholesterol diet

Accumulated evidence shows that vanin-1 (VNN1) plays a key part in glucose metabolism. We explored the effect of VNN1 on cholesterol metabolism, inflammation, apoptosis in vitro, and progression of atherosclerotic plaques in apoE^−/− mice. Oxidized LDL (Ox-LDL) significantly induced VNN1 expression through an ERK1/2/cyclooxygenase-2/PPARα signaling pathway. VNN1 significantly increased cellular cholesterol content and decreased apoAI and HDL-cholesterol (HDL-C)-mediated efflux by 25.16% and 23.13%, respectively, in THP-1 macrophage-derived foam cells (P < 0.05). In addition, VNN1 attenuated Ox-LDL-induced apoptosis through upregulation of expression of p53 by 59.15% and downregulation of expression of B-cell lymphoma-2 127.13% in THP-1 macrophage (P < 0.05). In vivo, apoE^−/− mice were divided randomly into two groups and transduced with lentivirus (LV)-Mock or LV-VNN1 for 12 weeks. VNN1-treated mice showed increased liver lipid content and plasma levels of TG (124.48%), LDL-cholesterol (119.64%), TNF-α (148.74%), interleukin (IL)-1β (131.81%), and IL-6 (156.51%), whereas plasma levels of HDL-C (25.75%) were decreased significantly (P < 0.05). Consistent with these data, development of atherosclerotic lesions was increased significantly upon infection of apoE^−/− mice with LV-VNN1. These observations suggest that VNN1 may be a promising therapeutic candidate against atherosclerosis.

Pleiotropic effects of antitumour alkylphospholipids on cholesterol transport and metabolism

BACKGROUND

Alkylphospholipid (APL) analogs are a new class of membrane-directed synthetic compounds with a variety of biological actions and clinical applications. In particular, these agents are promising candidates in cancer treatment. We have demonstrated that after prolonged treatment APLs alter intracellular cholesterol traffic and metabolism in human tumor-cell lines, leading to an accumulation of cholesterol inside the cell. After further investigation concerning the mode of action of APLs, we have explored the influence of several APLs on novel aspects of cholesterol and lipoprotein homeostasis using hepatoma HepG2 cells and THP1-derived macrophages.

METHODS

Quantitative real-time PCR analysis with a pathway-focused PCR array system was performed to measure relative changes in the mRNA expression of a number of genes related to cholesterol transport and metabolism. We compared the gene-expression profiles of HepG2 cells treated with miltefosine, edelfosine or perifosine for 6h and 24h with the profile of control cells. We also analysed particular genes of interest in both HepG2 and macrophage-like THP1 cells using specific PCR assays. Immunoblots were used to confirm protein-expression changes. Measurement of ABCA1-mediated cholesterol efflux was determined using apoA1 as cholesterol acceptor.

RESULTS

We found global changes in gene-expression patterns to maintain cholesterol homeostasis after exposure of cells to APLs. The pathways for cholesterol biosynthesis and LDL-cholesterol uptake were both transcriptionally upregulated by the three APLs assayed. Conversely, major pathways involved in the catabolism of cholesterol to bile acids and lipoprotein-associated cholesterol export were impaired after APL incubation, which may well contribute to the higher cell-cholesterol levels induced by these compounds.

CONCLUSION

Incubation of cells with different APLs stimulated cholesterol biosynthesis and uptake at the same time as it depressed common pathways for excess cholesterol removal in tumor cells, ultimately leading to altered cholesterol homeostasis.

RP5-833A20.1/miR-382-5p/NFIA-dependent signal transduction pathway contributes to the regulation of cholesterol homeostasis and inflammatory reaction

OBJECTIVE

Cardiovascular disease caused by atherosclerosis is the number one cause of death in Western countries and threatens to become the major cause of morbidity and mortality worldwide. Long noncoding RNAs are emerging as new players in gene regulation, but how long noncoding RNAs operate in the development of atherosclerosis remains unclear.

APPROACH AND RESULTS

Using microarray analysis, we found that long noncoding RNA RP5-833A20.1 expression was upregulated, whereas nuclear factor IA (NFIA) expression was downregulated in human acute monocytic leukemia macrophage-derived foam cells. Moreover, we showed that long noncoding RNA RP5-833A20.1 may decreases NFIA expression by inducing hsa-miR-382-5p expression in vitro. We found that the RP5-833A20.1/hsa-miR-382-5p/NFIA pathway is essential to the regulation of cholesterol homeostasis and inflammatory responses in human acute monocytic leukemia macrophages. Lentivirus-mediated NFIA overexpression increased high-density lipoprotein cholesterol circulation, reduced low-density lipoprotein cholesterol, and very-low-density lipoprotein cholesterol circulation, decreased circulation of inflammatory cytokines, including interleukin-1β, interleukin-6, tumor necrosis factor-α, and C-reactive protein, enhanced reverse cholesterol transport, and promoted regression of atherosclerosis in apolipoprotein E-deficient mice.

CONCLUSIONS

Our findings indicated that the RP5-833A20.1/miR-382-5p/NFIA pathway was essential to the regulation of cholesterol homeostasis and inflammatory reactions and suggested that NFIA may represent a therapeutic target to ameliorate cardiovascular disease.

A lincRNA-DYNLRB2-2/GPR119/GLP-1R/ABCA1-dependent signal transduction pathway is essential for the regulation of cholesterol homeostasis

Accumulated evidence shows that G protein-coupled receptor 119 (GPR119) plays a key role in glucose and lipid metabolism. Here, we explored the effect of GPR119 on cholesterol metabolism and inflammation in THP-1 macrophages and atherosclerotic plaque progression in apoE(-/-) mice. We found that oxidized LDL (Ox-LDL) significantly induced long intervening noncoding RNA (lincRNA)-DYNLRB2-2 expression, resulting in the upregulation of GPR119 and ABCA1 expression through the glucagon-like peptide 1 receptor signaling pathway. GPR119 significantly decreased cellular cholesterol content and increased apoA-I-mediated cholesterol efflux in THP-1 macrophage-derived foam cells. In vivo, apoE(-/-) mice were randomly divided into two groups and infected with lentivirus (LV)-Mock or LV-GPR119 for 8 weeks. GPR119-treated mice showed decreased liver lipid content and plasma TG, interleukin (IL)-1β, IL-6, and TNF-α levels, whereas plasma levels of apoA-I were significantly increased. Consistent with this, atherosclerotic lesion development was significantly inhibited by infection of apoE(-/-) mice with LV-GPR119. Our findings clearly indicate that, Ox-LDL significantly induced lincRNA-DYNLRB2-2 expression, which promoted ABCA1-mediated cholesterol efflux and inhibited inflammation through GPR119 in THP-1 macrophage-derived foam cells. Moreover, GPR119 decreased lipid and serum inflammatory cytokine levels, decreasing atherosclerosis in apoE(-/-) mice. These suggest that GPR119 may be a promising candidate as a therapeutic agent.

Nur77 decreases atherosclerosis progression in apoE(-/-) mice fed a high-fat/high-cholesterol diet

Rationale

It is clear that lipid disorder and inflammation are associated with cardiovascular diseases and underlying atherosclerosis. Nur77 has been shown to be involved in inflammatory response and lipid metabolism.

Objective

Here, we explored the role of Nur77 in atherosclerotic plaque progression in apoE^−/− mice fed a high-fat/high cholesterol diet.

Methods and Results

The Nur77 gene, a nuclear hormone receptor, was highly induced by treatment with Cytosporone B (Csn-B, specific Nur77 agonist), recombinant plasmid over-expressing Nur77 (pcDNA-Nur77), while inhibited by treatment with siRNAs against Nur77 (si-Nur77) in THP-1 macrophage-derived foam cells, HepG2 cells and Caco-2 cells, respectively. In addition, the expression of Nur77 was highly induced by Nur77 agonist Csn-B, lentivirus encoding Nur77 (LV-Nur77), while silenced by lentivirus encoding siRNA against Nur77 (si-Nur77) in apoE^−/− mice fed a high-fat/high cholesterol diet, respectively. We found that increased expression of Nur77 reduced macrophage-derived foam cells formation and hepatic lipid deposition, downregulated gene levels of inflammatory molecules, adhesion molecules and intestinal lipid absorption, and decreases atherosclerotic plaque formation.

Conclusion

These observations provide direct evidence that Nur77 is an important nuclear hormone receptor in regulation of atherosclerotic plaque formation and thus represents a promising target for the treatment of atherosclerosis.

Dihydrocapsaicin Attenuates Plaque Formation through a PPARγ/LXRα Pathway in apoE(-/-) Mice Fed a High-Fat/High-Cholesterol Diet

Aims

Atherosclerosis is a chronic inflammatory disease and represents the major cause of cardiovascular morbidity and mortality. There is evidence that dihydrocapsaicin (DHC) can exert multiple pharmacological and physiological effects. Here, we explored the effect of DHC in atherosclerotic plaque progression in apoE^−/− mice fed a high-fat/high-cholesterol diet.

Methods and Results

apoE^−/− mice were randomly divided into two groups and fed a high-fat/high-cholesterol diet with or without DHC for 12 weeks. We demonstrated that cellular cholesterol content was significantly decreased while apoA1-mediated cholesterol efflux was significantly increased following treatment with DHC in THP-1 macrophage-derived foam cells. We also observed that plasma levels of TG, LDL-C, VLDL-C, IL-1β, IL-6, TNF-α and CRP were markedly decreased while plasma levels of apoA1 and HDL-C were significantly increased, and consistent with this, atherosclerotic lesion development was significantly inhibited by DHC treatment of apoE^−/− mice fed a high-fat/high-cholesterol diet. Moreover, treatment with both LXRα siRNA and PPARγ siRNA made the up-regulation of DHC on ABCA1, ABCG1, ABCG5, SR-B1, NPC1, CD36, LDLR, HMGCR, apoA1 and apoE expression notably abolished while made the down-regulation of DHC on SRA1 expression markedly compensated. And treatment with PPARγ siRNA made the DHC-induced up-regulation of LXRα expression notably abolished while treatment with LXRα siRNA had no effect on DHC-induced PPARγ expression.

Conclusion

These observations provide direct evidence that DHC can significantly decrease atherosclerotic plaque formation involving in a PPARγ/LXRα pathway and thus DHC may represent a promising candidate for a therapeutic agent for the treatment or prevention of atherosclerosis.

Pathogenesis, modulation, and therapy of Alzheimer’s disease: A perspective on roles of liver-X receptors

The pathogenesis of Alzheimer’s disease (AD) has been mostly linked to aberrant amyloid beta (Aβ) and tau proteins metabolism, disturbed lipid/cholesterol homeostasis, and progressive neuroinflammation. Liver X receptors (LXR) are ligand-activated transcription factors, best known as the key regulators of cholesterol metabolism and transport. In addition, LXR signaling has been shown to have significant anti-inflammatory properties. In this brief review, we focus on the outcome of studies implicating LXR in the pathogenesis, modulation, and therapy of AD.

Liver X receptor activation inhibits melanogenesis through the acceleration of ERK-mediated MITF degradation

Liver X receptors (LXRs) are nuclear receptors that act as ligand-activated transcription factors regulating lipid metabolism and inflammation. In the skin, activation of LXRs stimulates differentiation of keratinocytes and augments lipid synthesis in sebocytes. However, the function of LXRs in melanocytes remains largely unknown. We investigated whether LXR activation would affect melanogenesis. In human primary melanocytes, MNT-1, and B16 melanoma cells, TO901317, a synthetic LXR ligand, inhibited melanogenesis. Small interfering RNA (siRNA) experiments revealed the dominant role of LXRβ in TO901317-mediated antimelanogenesis. Enzymatic activities of tyrosinase were unaffected, but the expression of tyrosinase, tyrosinase-related protein-1 (TRP-1), and TRP-2 was suppressed by TO901317. Expressions of microphthalmia-associated transcription factor (MITF), a master transcriptional regulator of melanogenesis, and cAMP-responsive element-binding activation were not affected. It is noteworthy that the degradation of MITF was accelerated by TO901317. Extracellular signal-regulated kinase (ERK) contributed to TO901317-induced antimelanogenesis, which was evidenced by recovery of melanogenesis with ERK inhibitor. Other LXR ligands, 22(R)-hydroxycholesterol (22(R)HC) and GW3965, also activated ERK and suppressed melanogenesis. The intermediary role of Ras was confirmed in TO901317-induced ERK phosphorylation. Finally, antimelanogenic effects of TO901317 were confirmed in vivo in UVB-tanning model in brown guinea pigs, providing a previously unreported line of evidence that LXRs may be important targets for antimelanogenesis.

Effects of a 2-y dietary weight-loss intervention on cholesterol metabolism in moderately obese men

BACKGROUND

Long-term dietary weight loss results in complex metabolic changes. However, its effect on cholesterol metabolism in obese subjects is still unclear.

OBJECTIVE

We assessed the effects of 2 y of weight loss achieved with various diet regimens on phytosterols (markers of intestinal cholesterol absorption), lanosterol (marker of de novo cholesterol synthesis), and changes in apolipoprotein concentrations.

DESIGN

We conducted the 2-y Dietary Intervention Randomized Controlled Trial (DIRECT-a study of low-fat, Mediterranean, and low-carbohydrate diets). We assessed circulating phytosterol and lanosterol concentrations and their ratios to cholesterol and apolipoproteins A-I and B-100 in 90 DIRECT participants at 0, 6, and 24 mo.

RESULTS

We observed a significant upregulation of the markers of cholesterol absorption (campesterol: +16.8%, P < 0.001) and a downregulation of the markers of cholesterol synthesis (lanosterol: -16.5%, P = 0.008) during the active weight-loss phase (first 6 mo, weight loss of 5%, 6%, and 10% in the 3 diet groups, respectively), followed by a rebound (campesterol: -6.2%, P = 0.045; lanosterol: +43.7%, P < 0.001) during the next 18 mo (weight gain of 1%, 1%, and 2% in the 3 diet groups, respectively). HDL cholesterol continuously increased during the study (17.0%, P < 0.001), whereas LDL cholesterol remained constant. At the end of the 24-mo follow-up period, campesterol (P < 0.001) and lanosterol (P = 0.016) amounts were significantly higher than baseline values. The concentration of apolipoprotein B-100 correlated with cholesterol metabolism (ρ = 0.299 and P = 0.020 for lanosterol; ρ = -0.105 and NS for campesterol), and the homeostasis model assessment of insulin resistance correlated with lanosterol (ρ = 0.09, P = 0.001).

CONCLUSIONS

Long-term weight loss is related to a characteristic response suggestive of altered cholesterol and apolipoprotein metabolism. Various diets have a similar effect on these effects. DIRECT is registered at clinicaltrials.gov as NCT00160108.

Synthetic LXR agonist T0901317 attenuates lipopolysaccharide-induced acute lung injury in rats

OBJECTIVE

To investigate the potential role of synthetic liver X receptors (LXRs) agonists T0901317 in lung of rats with acute lung injury induced by lipopolysaccharide (LPS).

METHODS

Rats infused with LPS served as acute lung injury (ALI) models. Specific mRNA was quantified by semi-quantitative reverse transcription polymerase (RT-PCR) and protein expression by western blotting. Inflammatory cytokine and MPO activity assays were studied by ELISA. Histopathology analysis was evaluated by hematoxylin and eosin.

RESULTS

The expressions of LXRα and LXRβ were gradually decreased after LPS challenge. T0901317 pretreatment efficiently reduced the production of TNF-α, IL-1β, and IL-6, while elevated the level of IL-10 in BALF of rats with ALI. T0901317 also decreased the number of inflammatory cells and the concentration of total proteins in the BALF. Compared with the LPS group, rats with ALI which were pretreated with T0901317 had lower pulmonary tissue MPO activity and lightened histopathologic changes of lung. Furthermore, the expressions of NF-κB and ICAM-1 were markedly reduced after T0901317 administration.

CONCLUSION

The expressions of LXRs were significantly decreased and synthetic agonist T0901317 suppresses lung inflammatory responses and lightened histopathologic changes of lung in rats with ALI. The mechanisms of this action for T0901317 may associate with the inhibition of NF-κB activation and downregulation of adhesion molecules ICAM-1 gene.