Hepatic Cholesterol Biosynthesis Research Articles

Statins: a role in breast cancer therapy?

Statin drugs have been used for more than two decades to treat hypercholesterolemia and as cardio‐preventive drugs, resulting in a marked decrease in cardiovascular morbidity and mortality worldwide. Statins halt hepatic cholesterol biosynthesis by inhibiting the rate‐limiting enzyme in the mevalonate pathway, hydroxymethylglutaryl‐coenzyme A reductase (HMGCR). The mevalonate pathway regulates a host of biochemical processes in addition to cholesterol production. Attenuation of these pathways is likely responsible for the myriad benefits of statin therapy beyond cholesterol reduction – the so‐called pleiotropic effects of statins. Chief amongst these purported effects is anti‐cancer activity. A considerable body of preclinical, epidemiologic and clinical evidence shows that statins impair proliferation of breast cancer cells and reduce the risk of breast cancer recurrence. Potential mechanisms for this effect have been explored in laboratory models, but remain poorly understood and require further investigation. The number of clinical trials assessing the putative clinical benefit of statins in breast cancer is increasing. Currently, a total of 30 breast cancer/statin trials are listed at the global trial identifier website clinicaltrials.gov. Given the compelling evidence from performed trials in a variety of clinical settings, there have been calls for a clinical trial of statins in the adjuvant breast cancer setting. It would be imperative for such a trial to incorporate tumour biomarkers predictive of statin response in its design and analysis plan. Ongoing translational clinical trials aimed at biomarker discovery will help identify, which breast cancer patients are most likely to benefit from adjuvant statin therapy, and will add valuable clinical knowledge to the field.

The CD36-PPARγ Pathway in Metabolic Disorders.

Uncovering the biological role of nuclear receptor peroxisome proliferator-activated receptors (PPARs) has greatly advanced our knowledge of the transcriptional control of glucose and energy metabolism. As such, pharmacological activation of PPARγ has emerged as an efficient approach for treating metabolic disorders with the current use of thiazolidinediones to improve insulin resistance in diabetic patients. The recent identification of growth hormone releasing peptides (GHRP) as potent inducers of PPARγ through activation of the scavenger receptor CD36 has defined a novel alternative to regulate essential aspects of lipid and energy metabolism. Recent advances on the emerging role of CD36 and GHRP hexarelin in regulating PPARγ downstream actions with benefits on atherosclerosis, hepatic cholesterol biosynthesis and fat mitochondrial biogenesis are summarized here. The response of PPARγ coactivator PGC-1 is also discussed in these effects. The identification of the GHRP-CD36-PPARγ pathway in controlling various tissue metabolic functions provides an interesting option for metabolic disorders.

Long noncoding RNA lncARSR promotes hepatic cholesterol biosynthesis via modulating Akt/SREBP-2/HMGCR pathway

AimsDisruption of cholesterol homeostasis has been identified as a major factor in the pathogenesis of atherosclerosis, myocardial infarction, and strokes. Long noncoding RNAs (lncRNAs) have emerged as critical players in cellular cholesterol metabolism, but their functions are still largely unknown. Materials and methodsC57BL6/j mice were fed with high cholesterol diet (containing 4% cholesterol) or chow diet. Adenoviruses-lncARSR and lncARSR shRNA were used to overexpress or knockdown lncARSR expression. Key findingsThe expression of lncARSR were increased both in patients with hypercholesterolemia and mice with high cholesterol diet feeding. Overexpression of lncARSR in mice resulted in elevated lipid levels in both serum and liver fragments. However, knockdown of lncARSR in mice fed with high cholesterol diet showed decreased lipid levels in serum and liver fragments compared with control mice. Furthermore, we found that the expression of HMG-CoA reductase (HMGCR), the rate-limiting enzyme of cholesterol synthesis was increased with lncARSR overexpression, which was accompanied with the increase of hepatic de novo cholesterol synthesis rate. Mechanistically, we found that lncARSR increased the expression of mature SREBP-2, which is a primary transcription factor of HMGCR. And lncARSR activated the PI3K/Akt pathway. When PI3K/Akt pathway was blocked by LY294002, the inhibitor of PI3K, the effect of lncARSR on SREBP-2 and HMGCR disappeared. SignificanceOur data indicated upregulated lncARSR promotes hepatic cholesterol biosynthesis via modulating Akt/SREBP-2/HMGCR pathway, and implied that lncARSR may serve as a therapeutic target for cholesterol disorder.

Novel metabolic phenotypes in lecithin cholesterol acyltyransferase-deficient mice.

Lecithin cholesterol acyltyransferase (LCAT) deficiency is a rare monogenic disorder causing lipoprotein dysregulation and multiple organ dysfunctions, including renal impairment. LCAT knockout mice have been shown informative in elucidating mechanisms of many major clinical morbid phenotypes. Extended characterization of the LDL receptor/LCAT double knockout (Ldlr/Lcat-DKO or DKO) mice had led to the discovery of a number of novel protective metabolic phenotypes, including resistance to obesity, nonalcoholic steatohepatitis (NASH) and insulin resistance. We seek to integrate the findings to explore novel pathogenic pathways. The chow fed DKO mice were found more insulin sensitive than their Ldlr-KO controls. Joint analyses of the three strains (DKO, Ldlr-KO and wild-type) revealed differential metabolic responses to a high cholesterol diet (HCD) vs. high-fat diet (HFD). DKO mice are protected from HFD-induced obesity, hepatic endoplasmic reticulum (ER) stress, insulin resistance, ER cholesterol and NASH markers (steatosis and inflammasomes). Joint analysis revealed the HFD-induced NASH is dependent on de-novo hepatic cholesterol biosynthesis. DKO mice are protected from HCD-induced hepatic ER stress, ER cholesterol, but not NASH, the latter likely due to cholesterol crystal accumulation. DKO mice were found to develop ectopic brown adipose tissue (BAT) in skeletal muscle. Ectopic BAT derived in part from myoblast in utero and from adult satellite cells. Primed expression of PRDM16 and UCP in quiescent satellite cell caused by LCAT deficiency synergizes with cell cholesterol depletion to induce satellite cell-to-BAT transdifferentiation. Metabolic phenotyping of selective LCAT null mice led to the discovery of novel metabolically protective pathways.

Sprouty2 loss-induced IL6 drives castration-resistant prostate cancer through scavenger receptor B1.

Metastatic castration‐resistant prostate cancer (mCRPC) is a lethal form of treatment‐resistant prostate cancer and poses significant therapeutic challenges. Deregulated receptor tyrosine kinase (RTK) signalling mediated by loss of tumour suppressor Sprouty2 (SPRY2) is associated with treatment resistance. Using pre‐clinical human and murine mCRPC models, we show that SPRY2 deficiency leads to an androgen self‐sufficient form of CRPC. Mechanistically, HER2‐IL6 signalling axis enhances the expression of androgen biosynthetic enzyme HSD3B1 and increases SRB1‐mediated cholesterol uptake in SPRY2‐deficient tumours. Systemically, IL6 elevated the levels of circulating cholesterol by inducing host adipose lipolysis and hepatic cholesterol biosynthesis. SPRY2‐deficient CRPC is dependent on cholesterol bioavailability and SRB1‐mediated tumoral cholesterol uptake for androgen biosynthesis. Importantly, treatment with ITX5061, a clinically safe SRB1 antagonist, decreased treatment resistance. Our results indicate that cholesterol transport blockade may be effective against SPRY2‐deficient CRPC.

Statins and inflammation in cardiovascular disease.

Chronic inflammation and immune system activation underlie a variety of seemingly unrelated cardiac conditions including not only atherosclerosis and the subsequent coronary artery disease but also peripheral artery disease, hypertension with target organ damage and heart failure. The beneficial effects of HMG-CoA reductase inhibitors or statins are mainly attributed to their ability to inhibit hepatic cholesterol biosynthesis. Beyond their lipid lowering activity, ample evidence exists in support of their potent anti-inflammatory properties which initiate from the inhibition of GTPase isoprenylation, activating a cataract of secondary pathways and extend to the inhibition and blocking of immune cell activation and interaction. To summarize the anti-inflammatory mechanisms of statins in clinical and experimental settings in cardiovascular disease. A systematic search of PubMed and the Cochrane Database was conducted in order to identify the majority of trials, studies, current guidelines and novel articles related to the subject. In vitro, statins have immuno-modulatory and anti-inflammatory effects, and they can exert anti-atherosclerotic effects independently of their hypolipidemic actions. In addition, positive results have emerged from mechanistic and experimental studies on the active role of HMG-CoA reductase inhibitors in HF. By extrapolating those data in clinical setting, we further understand how HMG-CoA reductase inhibitors can beneficially affect not only systolic but also diastolic HF. In this review article, we present the basic pathophysiologic data supporting the anti-inflammatory actions of statins in clinical and experimental settings and we link these mechanisms with confirmatory clinical data on the potent non lipid lowering effects of HMG-CoA reductase inhibitors.

Rab8a Deficiency in Skeletal Muscle Causes Hyperlipidemia and Hepatosteatosis by Impairing Muscle Lipid Uptake and Storage.

Skeletal muscle absorbs long-chain fatty acids (LCFAs) that are either oxidized in mitochondria or temporarily stored as triglycerides in lipid droplets (LDs). So far, it is still not fully understood how lipid uptake and storage are regulated in muscle and whether these are important for whole-body lipid homeostasis. Here we show that the small GTPase Rab8a regulates lipid uptake and storage in skeletal muscle. Muscle-specific Rab8a deletion caused hyperlipidemia and exacerbated hepatosteatosis induced by a high-fat diet. Mechanistically, Rab8a deficiency decreased LCFA entry into skeletal muscle and inhibited LD fusion in muscle cells. Consequently, blood lipid levels were elevated and stimulated hepatic mammalian target of rapamycin, which enhanced hepatosteatosis by upregulating hepatic lipogenesis and cholesterol biosynthesis. Our results demonstrate the significance of lipid uptake and storage in muscle in regulating whole-body lipid homeostasis, and they shed light on the roles of skeletal muscle in the pathogenesis of hyperlipidemia and hepatosteatosis.

Lipogenic transcription factor ChREBP mediates fructose-induced metabolic adaptations to prevent hepatotoxicity.

Epidemiologic and animal studies implicate overconsumption of fructose in the development of nonalcoholic fatty liver disease, but the molecular mechanisms underlying fructose-induced chronic liver diseases remain largely unknown. Here, we have presented evidence supporting the essential function of the lipogenic transcription factor carbohydrate response element-binding protein (ChREBP) in mediating adaptive responses to fructose and protecting against fructose-induced hepatotoxicity. In WT mice, a high-fructose diet (HFrD) activated hepatic lipogenesis in a ChREBP-dependent manner; however, in Chrebp-KO mice, a HFrD induced steatohepatitis. In Chrebp-KO mouse livers, a HFrD reduced levels of molecular chaperones and activated the C/EBP homologous protein-dependent (CHOP-dependent) unfolded protein response, whereas administration of a chemical chaperone or Chop shRNA rescued liver injury. Elevated expression levels of cholesterol biosynthesis genes in HFrD-fed Chrebp-KO livers were paralleled by an increased nuclear abundance of sterol regulatory element-binding protein 2 (SREBP2). Atorvastatin-mediated inhibition of hepatic cholesterol biosynthesis or depletion of hepatic Srebp2 reversed fructose-induced liver injury in Chrebp-KO mice. Mechanistically, we determined that ChREBP binds to nuclear SREBP2 to promote its ubiquitination and destabilization in cultured cells. Therefore, our findings demonstrate that ChREBP provides hepatoprotection against a HFrD by preventing overactivation of cholesterol biosynthesis and the subsequent CHOP-mediated, proapoptotic unfolded protein response. Our findings also identified a role for ChREBP in regulating SREBP2-dependent cholesterol metabolism.

Pleiotropic Effects of Statins on the Cardiovascular System

The statins have been used for 30 years to prevent coronary artery disease and stroke. Their primary mechanism of action is the lowering of serum cholesterol through inhibiting hepatic cholesterol biosynthesis thereby upregulating the hepatic low-density lipoprotein (LDL) receptors and increasing the clearance of LDL-cholesterol. Statins may exert cardiovascular protective effects that are independent of LDL-cholesterol lowering called pleiotropic effects. Because statins inhibit the production of isoprenoid intermediates in the cholesterol biosynthetic pathway, the post-translational prenylation of small GTP-binding proteins such as Rho and Rac, and their downstream effectors such as Rho kinase and nicotinamide adenine dinucleotide phosphate oxidases are also inhibited. In cell culture and animal studies, these effects alter the expression of endothelial nitric oxide synthase, the stability of atherosclerotic plaques, the production of proinflammatory cytokines and reactive oxygen species, the reactivity of platelets, and the development of cardiac hypertrophy and fibrosis. The relative contributions of statin pleiotropy to clinical outcomes, however, remain a matter of debate and are hard to quantify because the degree of isoprenoid inhibition by statins correlates to some extent with the amount of LDL-cholesterol reduction. This review examines some of the currently proposed molecular mechanisms for statin pleiotropy and discusses whether they could have any clinical relevance in cardiovascular disease.

Statins redux: A re-assessment of how statins lower plasma cholesterol.

Obesity associated dyslipidemia and its negative effects on the heart and blood vessels have emerged as a major healthcare challenge around the globe. The use of statins, potent inhibitors of hydroxyl-methyl glutaryl (HMG) Co-A reductase, a rate-limiting enzyme in cholesterol biosynthesis, has significantly reduced the rates of cardiovascular and general mortality in patients with coronary artery disease. How statins lower plasma cholesterol levels presents a mechanistic conundrum since persistent exposure to these drugs in vitro or in vivo is known to induce overexpression of the HMG Co-A reductase gene and protein. In an attempt to solve this mechanistic puzzle, Schonewille et al, studied detailed metabolic parameters of cholesterol synthesis, inter-organ flux and excretion in mice treated with 3 common statins, rosuvastatin, atorvastatin or lovastatin, each with its unique pharmacokinetics. From the measurements of the rates of heavy water (D2O) and [13C]-acetate incorporation into lipids, the authors calculated the rates of whole body and organ-specific cholesterol synthesis in control and statin-treated mice. These analyses revealed dramatic enhancement in the rates of hepatic cholesterol biosynthesis in statin-treated mice that concomitantly elicited lower levels of cholesterol in their plasma. The authors have provided strong evidence to indicate that statin treatment in mice led to induction of compensatory metabolic pathways that apparently mitigated an excessive accumulation of cholesterol in the body. It was noted however that changes in cholesterol metabolism induced by 3 statins were not identical. While sustained delivery of all 3 statins led to enhanced rates of biliary excretion of cholesterol and its fecal elimination, only atorvastatin treated mice elicited enhanced trans-intestinal cholesterol excretion. Thus, blockade of HMGCR by statins in mice was associated with profound metabolic adaptations that reset their cholesterol homeostasis. The findings of Schonewille et al, deserve to be corroborated and extended in patients in order to more effectively utilize these important cholesterol-lowering drugs in the clinic.

Long-Term Effects of Prenatal Exposure to Undernutrition on Cannabinoid Receptor-Related Behaviors: Sex and Tissue-Specific Alterations in the mRNA Expression of Cannabinoid Receptors and Lipid Metabolic Regulators

Maternal malnutrition causes long-lasting alterations in feeding behavior and energy homeostasis in offspring. It is still unknown whether both, the endocannabinoid (eCB) machinery and the lipid metabolism are implicated in long-term adaptive responses to fetal reprogramming caused by maternal undernutrition. We investigated the long-term effects of maternal exposure to a 20% standard diet restriction during preconceptional and gestational periods on the metabolically-relevant tissues hypothalamus, liver, and perirenal fat (PAT) of male and female offspring at adulthood. The adult male offspring from calorie-restricted dams (RC males) exhibited a differential response to the CB1 antagonist AM251 in a chocolate preference test as well as increased body weight, perirenal adiposity, and plasma levels of triglycerides, LDL, VLDL, bilirubin, and leptin. The gene expression of the cannabinoid receptors Cnr1 and Cnr2 was increased in RC male hypothalamus, but a down-expression of most eCBs-metabolizing enzymes (Faah, Daglα, Daglβ, Mgll) and several key regulators of fatty-acid β-oxidation (Cpt1b, Acox1), mitochondrial respiration (Cox4i1), and lipid flux (Pparγ) was found in their PAT. The female offspring from calorie-restricted dams exhibited higher plasma levels of LDL and glucose as well as a reduction in chocolate and caloric intake at post-weaning periods in the feeding tests. Their liver showed a decreased gene expression of Cnr1, Pparα, Pparγ, the eCBs-degrading enzymes Faah and Mgll, the de novo lipogenic enzymes Acaca and Fasn, and the liver-specific cholesterol biosynthesis regulators Insig1 and Hmgcr. Our results suggest that the long-lasting adaptive responses to maternal caloric restriction affected cannabinoid-regulated mechanisms involved in feeding behavior, adipose β-oxidation, and hepatic lipid and cholesterol biosynthesis in a sex-dependent manner.

Novel Role for Matrix Metalloproteinase 9 in Modulation of Cholesterol Metabolism.

BackgroundThe development of atherosclerosis is strongly linked to disorders of cholesterol metabolism. Matrix metalloproteinases (MMPs) are dysregulated in patients and animal models with atherosclerosis. Whether systemic MMP activity influences cholesterol metabolism is unknown.Methods and ResultsWe examined MMP‐9–deficient (Mmp9 −/−) mice and found them to have abnormal lipid gene transcriptional responses to dietary cholesterol supplementation. As opposed to Mmp9 +/+ (wild‐type) mice, Mmp9 −/− mice failed to decrease the hepatic expression of sterol regulatory element binding protein 2 pathway genes, which control hepatic cholesterol biosynthesis and uptake. Furthermore, Mmp9 −/− mice failed to increase the expression of genes encoding the rate‐limiting enzymes in biliary cholesterol excretion (eg, Cyp7a and Cyp27a). In contrast, MMP‐9 deficiency did not impair intestinal cholesterol absorption, as shown by the 14C‐cholesterol and 3H‐sitostanol absorption assay. Similar to our earlier study on Mmp2 −/− mice, we observed that Mmp9 −/− mice had elevated plasma secreted phospholipase A2 activity. Pharmacological inhibition of systemic circulating secreted phospholipase A2 activity (with varespladib) partially normalized the hepatic transcriptional responses to dietary cholesterol in Mmp9 −/− mice. Functional studies with mice deficient in other MMPs suggested an important role for the MMP system, as a whole, in modulation of cholesterol metabolism.ConclusionsOur results show that MMP‐9 modulates cholesterol metabolism, at least in part, through a novel MMP‐9–plasma secreted phospholipase A2 axis that affects the hepatic transcriptional responses to dietary cholesterol. Furthermore, the data suggest that dysregulation of the MMP system can result in metabolic disorder, which could lead to atherosclerosis and coronary heart disease.

Effects of long-term supplementation of policosanol on blood cholesterol/glucose levels and 3-hydroxy-3-methylglutaryl coenzyme a reductase activity in a rat model fed high cholesterol diets.

Policosanol is a well-defined nutraceutical for the management of blood cholesterol levels. The present study examined (i) the effect of policosanol supplementation on blood cholesterol and glucose levels and (ii) changes in hepatic cholesterol biosynthesis using 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase) activity in Wistar rats fed high cholesterol diets. The Wistar rats were assigned randomly to high-cholesterol diets (1.25% cholesterol) with or without policosanol (8.0 mg/kg body weight) for 6 weeks. Compared with the control group, dietary treatment with policosanol resulted in a significant decrease of blood cholesterol (p<0.01), blood glucose (p<0.01), triglyceride (p<0.001), and low density lipoprotein-cholesterol levels (p<0.01) and HMG-CoA reductase activity (p<0.001) in the liver. These results indicate that policosanol decreases blood cholesterol levels by suppressing cholesterol biosynthesis via decrease of HMG-CoA activity. Policosanol has the potential to be developed into an effective dietary strategy for both postprandial hyperglycemia and hypercholesterolemia.

Fármacos hipolipemiantes y PCSK9

PCSK9 is a protease, synthesized mainly in the liver, which promotes the hepatic degradation of the LDL receptor and consequently decreases LDL receptor density and clearance of LDL particles. Statins inhibit HMG-CoA-reductase activity, an enzyme that catalyses an important step in hepatic cholesterol biosynthesis. The decrease of the hepatic intracellular cholesterol pool produced by these drugs upregulates the activity of the SREBP2 transcription factor, which subsequently stimulates the expression of the LDL receptor gene, an effect that is followed by an increase in the serum concentration of PCSK9. This article aims to review the effects of different lipid-lowering drugs on plasma PCSK9 concentrations. Overall, statins increase blood PCSK9 levels, an effect that is enhanced by ezetimibe. In contrast, others drugs, such as fibrates and niacin, could decrease PCSK9 levels.

Increase of circulating cholesterol in vitamin D deficiency is linked to reduced vitamin D receptor activity via the Insig-2/SREBP-2 pathway.

Individuals deficient in vitamin D are more likely to have higher circulating cholesterol levels and cardiovascular diseases. However, the underlying mechanisms are still unclear. A cross-sectional survey, animal study, and in vitro experiments were conducted to investigate the effect and mechanisms of vitamin D deficiency on endogenous cholesterol metabolism. We demonstrated that vitamin D deficiency was positively associated with an increase of total serum cholesterol and low-density lipoprotein cholesterol levels in northern Chinese individuals. The vitamin D deficiency-induced increase of cholesterol concentration was mainly due to enhanced cholesterol biosynthesis rather than reduced catabolism. Under vitamin D deficiency, the transcriptional activity of vitamin D receptor (VDR) was decreased, leading to the downregulation of insulin-induced gene-2 (Insig-2) expression and thus its inhibitory role on sterol regulatory element-binding protein 2 activation; 3-hydroxy-3-methylglutaryl-coenzyme A reductase expression was accordingly increased. Vitamin D3 was protective against vitamin D deficiency-induced cholesterol increase by maintaining the transcriptional activity of VDR and Insig-2 expression. Vitamin D deficiency is associated with the increase of circulating cholesterol in the people of northern China by enhancing hepatic cholesterol biosynthesis, which was linked to the reduction of transcriptional activity of VDR.

Association of Statin Therapy and Risks of Cholelithiasis, Biliary Tract Diseases, and Gallbladder Procedures: Retrospective Cohort Analysis of a US Population.

Gallstone disease is a leading cause of morbidity in Western countries and carries a high economic burden. Statin medications decrease hepatic cholesterol biosynthesis and may, therefore, lower the risk of cholesterol cholelithiasis by reducing the cholesterol concentration in the bile. Population-based evidence, however, is sparse. To assess the risk of gallbladder diseases among statin users compared with nonusers in an American patient cohort. We performed a retrospective cohort study of patients enrolled in the San Antonio Tricare health system using data between October 2003 and March 2012. We defined 2 groups: statin users (use for 90 days or greater) and nonusers (no prior statin). A propensity score based on 82 variables was generated to match statin users and nonusers 1:1. Outcomes included incidence of cholelithiasis, biliary tract diseases, and gallbladder procedures. A total of 43 438 patients were identified; 13 626 (31.4%) were statin users, and 29 812 (68.6%) were nonusers. We matched 6342 pairs of statin users and nonusers based on propensity score. The odds ratios (ORs) in statin users in comparison to nonusers were similar for cholelithiasis (OR = 0.86; 95% CI = 0.73, 1.02), biliary tract disease (OR = 0.85; 95% CI = 0.67-1.08), and gall bladder procedures (OR = 0.85; 95% CI = 0.69, 1.04). Statin use was not significantly associated with either an increased or decreased risk of cholelithiasis or gallbladder disease.

Plasma cholesterol-lowering and transient liver dysfunction in mice lacking squalene synthase in the liver

Squalene synthase (SS) catalyzes the biosynthesis of squalene, the first specific intermediate in the cholesterol biosynthetic pathway. To test the feasibility of lowering plasma cholesterol by inhibiting hepatic SS, we generated mice in which SS is specifically knocked out in the liver (L-SSKO) using Cre-loxP technology. Hepatic SS activity of L-SSKO mice was reduced by >90%. In addition, cholesterol biosynthesis in the liver slices was almost eliminated. Although the hepatic squalene contents were markedly reduced in L-SSKO mice, the hepatic contents of cholesterol and its precursors distal to squalene were indistinguishable from those of control mice, indicating the presence of sufficient centripetal flow of cholesterol and/or its precursors from the extrahepatic tissues. L-SSKO mice showed a transient liver dysfunction with moderate hepatomegaly presumably secondary to increased farnesol production. In a fed state, the plasma total cholesterol and triglyceride were significantly reduced in L-SSKO mice, primarily owing to reduced hepatic VLDL secretion. In a fasted state, the hypolipidemic effect was lost. mRNA expression of liver X receptor α target genes was reduced, while that of sterol-regulatory element binding protein 2 target genes was increased. In conclusion, liver-specific ablation of SS inhibits hepatic cholesterol biosynthesis and induces hypolipidemia without increasing significant mortality.

Adverse effects of long-term exposure to bisphenol A during adulthood leading to hyperglycaemia and hypercholesterolemia in mice.

Bisphenol A (BPA) is a suspected endocrine disruptor highly prevalent in our environment since it is used as monomer of polycarbonate plastics and epoxy resins. Recent epidemiological and animal studies have suggested that BPA exposure may influence the development of obesity and related pathologies such as type 2 diabetes, and cardiovascular diseases. However, experimental studies have often focused on short-term exposures. In this study, we investigated the effect of several months of BPA exposure on hepatic and plasma metabolic markers in adult mice. Male CD1 mice were exposed during 8 months to five different BPA doses below or equivalent to the current no observed adverse effect level (NOAEL: 5000 μg/kg/day) through drinking water. Plasma lipid profiles and liver transcriptomic analysis were performed in control and BPA-treated animals. We report a specific impact of BPA exposure on glycaemia, glucose tolerance and cholesterolemia. Consistent with the hypercholesterolemia in BPA-treated animals, RT-qPCR performed on hepatic mRNA from same animals demonstrated an overexpression of key genes involved in cholesterol biosynthesis, namely, Mvd, Lss Hmgcr, and Sqle. BPA also induced the expression of the sterol regulatory element-binding proteins 2, a master regulator of hepatic cholesterol biosynthesis. As shown by the plasma lathosterol to cholesterol ratio, a surrogate marker for cholesterol biosynthesis, whole body cholesterol de novo synthesis was also increased in BPA-exposed animals. These original results are consistent with many epidemiological studies reporting on a link between BPA exposure and the onset of cardiovascular diseases.

The Role of Statins in the Osteogenesis on Bone Fusion Using Bone Marrow-Derived and Adipose-Derived Stem Cells

Introduction Statins are commonly prescribed drugs that inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG Co-A) reductase, decreasing hepatic cholesterol biosynthesis by reducing serum cholesterol concentrations. Several studies demonstrated statins enhance new bone formation and increase bone volume in an animal. In this study, simvastatin and lovastatin were employed to elucidate the osteogenic effects of stains on the culture system of two stem cells; human bone marrow-derived (hMSC) and adipose-derived stem cell (hADSC). Materials and Methods In this study, simvastatin and lovastatin were employed to elucidate the osteogenic effects of stains on the culture system of two stem cells; human bone marrow-derived (hMSC) and adipose-derived stem cell (hADSC). There are two experimental conditions: (1) statins supplemented along with other osteoinductive supplements and (2) without them. The statins increased the expression of the osteogenic markers, such as alkaline phosphatase (ALP) activity and alizarin red S staining(ARS) on both conditions. These results were verified with gene mRNA levels using PCR. Finally, ex vivo calvaria organ culture model was investigated by H&amp;E and Masson trichrome staining. Results The statins increased the expression of the osteogenic markers, such as alkaline phosphatase (ALP) activity and alizarin red S staining (ARS) on both conditions. These results were verified with gene mRNA levels using PCR. There were almost the same trends in the expression of osteogenic makers induced from stem cell, although MSC was differentiated slower than ADSC. Also, neonatal murine calvarial was introduced to find the osteogenic effects of statins in ex vivo. It is observed that the bone density and thickness in the dissected calvarial tissue was enhanced in culture system including statins. Conclusion Our results suggests that statins could stimulate the differentiation of stem cell into osteoblasts and also affect the process of bone formation, resulting in the increase of mineralization induced by them. It implies that statins can be candidates as osteoinductive materials for bone fusion Disclosure of Interest None declared

Omega-3 phospholipids from fish suppress hepatic steatosis by integrated inhibition of biosynthetic pathways in dietary obese mice

Non-alcoholic fatty liver disease (NAFLD) accompanies obesity and insulin resistance. Recent meta-analysis suggested omega-3 polyunsaturated fatty acids DHA and EPA to decrease liver fat in NAFLD patients. Anti-inflammatory, hypolipidemic, and insulin-sensitizing effects of DHA/EPA depend on their lipid form, with marine phospholipids showing better efficacy than fish oils. We characterized the mechanisms underlying beneficial effects of DHA/EPA phospholipids, alone or combined with an antidiabetic drug, on hepatosteatosis. C57BL/6N mice were fed for 7weeks an obesogenic high-fat diet (cHF) or cHF-based interventions: (i) cHF supplemented with phosphatidylcholine-rich concentrate from herring (replacing 10% of dietary lipids; PC), (ii) cHF containing rosiglitazone (10mg/kg diet; R), or (iii) PC+R. Metabolic analyses, hepatic gene expression and lipidome profiling were performed. Results showed that PC and PC+R prevented cHF-induced weight gain and glucose intolerance, while all interventions reduced abdominal fat and plasma triacylglycerols. PC and PC+R also lowered hepatic and plasma cholesterol and reduced hepatosteatosis. Microarray analysis revealed integrated down-regulation of hepatic lipogenic and cholesterol biosynthesis pathways by PC, while R-induced lipogenesis was fully counteracted in PC+R. Gene expression changes in PC and PC+R were associated with preferential enrichment of hepatic phosphatidylcholine and phosphatidylethanolamine fractions by DHA/EPA. The complex down-regulation of hepatic lipogenic and cholesterol biosynthesis genes and the antisteatotic effects were unique to DHA/EPA-containing phospholipids, since they were absent in mice fed soy-derived phosphatidylcholine. Thus, inhibition of lipid and cholesterol biosynthesis associated with potent antisteatotic effects in the liver in response to DHA/EPA-containing phospholipids support their use in NAFLD prevention and treatment.