HMG-CoA Reductase mRNA Levels Research Articles

Cadmium chloride induces non-alcoholic fatty liver disease in rats by stimulating miR-34a/SIRT1/FXR/p53 axis

Cadmium (Cd) is associated with non-alcoholic fatty liver disease (NAFLD). The hepatic activation of p53/miR-43a-induced suppression of SIRT1/FXR axis plays a significant role in the development of NAFLD. In this study, we have investigated CdCl2-induced NAFLD in rats involves activation of miR34a/SIRT1/FXR axis. Adult male rats were divided into 4 groups (n-8/each) as a control, CdCl2 (10 mg/l), CdCl2 + miR-34a antagomir (inhibitor), and CdCl2 + SRT1720 (a SIRT1 activator) for 8 weeks, daily. With no effect on fasting glucose and insulin levels, CdCl2 significantly reduced rats' final body, fat pads, and liver weights, and food intake. Concomitantly, it increased the circulatory levels of liver markers (ALT, AST, and γ-GTT), increased the serum and hepatic levels of total cholesterol and triglycerides coincided with increased hepatic lipid accumulation. Besides, it increased the mRNA and protein levels of SREBP1, SREBP2, FAS, and HMGCOA reductase but reduced mRNA levels of PPARα, CPT1, and CPT2. Interestingly, CdCl2 also increased mRNA levels of miR34 without altering mRNA levels of SIRT1 but with a significant reduction in protein levels of SIRT1. These effects were associated with increased total protein levels of p53 and acetylated protein of p53, and FXR. Of note, suppressing miR-34a with a specific anatomic or activating SIRT1 by SRT1720 completely prevented all these effects and reduced hepatic fat accumulations in the livers of rats. In conclusion, CdCl2 induced NAFLD by increasing the transcription of miR-34a which in turn downregulates SIRT1 at the translational level.

Beneficial effects of primidone in Niemann-Pick disease type C (NPC)-model cells and mice: Reduction of unesterified cholesterol levels in cells and extension of lifespan in mice

Niemann-Pick disease type C (NPC) is caused by a loss of function of either NPC1 or NPC2 protein, resulting in the accumulation of unesterified, free-cholesterol (free-C) in cells/tissues and thus leading to cell/tissue damage. In the brain of patients/animals with NPC, as a consequence of the accumulation of free-C in late endosomes/lysosomes (LE/LY) in cells, multiple lipids including complex sphingolipids are accumulated, and almost all patients/animals ultimately develop progressive/fatal neurodegeneration. Several reagents that are considered to act in the brain show beneficial effects on NPC-model animals. In the present study, we investigated the effects of antiepileptic drugs, such as primidone and valproic acid, on the accumulation of free-C in NPC1-null CHO cells and NPC1* fibroblasts, human fibroblasts established from a patient with NPC1 mutation. Like valproic acid, treatment with primidone reduced free-C levels in LE/LY in NPC1-null/mutant cells. Down-regulation of cholesterol ester levels in NPC1-null cells and up-regulation of HMG-CoA reductase and low-density lipoprotein receptor mRNA levels in NPC1* cells were partially recovered by primidone treatment. Thus, primidone was suggested to enhance free-C trafficking from LE/LY to endoplasmic reticulum in NPC1-null/mutant cells. In NPC1-null mice, oral application of primidone (100 mg/kg/day) extended lifespan by approximately 5 days, although the first days showing ataxia, a typical symptom of neuromotor dysfunction, were not affected. Our findings suggest the potential of primidone for the treatment of NPC.

Changes of lipid levels in mice with hypoxic pulmonary arterial hypertension

To observe the changes of lipid levels in mice with pulmonary hypertension induced by hypoxia. The animal model of hypoxic pulmonary hypertension was established by exposing the mice to isobaric hypoxic chamberfor 3 weeks (23 h/d, regular chow feed). Twenty male C57BL/6 mice were randomlydivided into normoxia group and hypoxia group (n=10). The concentrations of total cholesterol, low density lipoprotein (LDL) and high density lipoprotein (HDL) in plasma were detected by Elisa method.The mRNA levels of HMG-CoAreductase (HMGCR), low density lipoprotein receptor (LDLR), scavenger receptor class B1 (SR-B1), and sterol regulatory element-binding factor-2 (SREBF2) in liverwere measured by real-time PCR. ① The right ventricular systolic pressure (RVSP) and the weight ratio of right ventricle (RV) to left ventricle plus septum (LV+S) of hypoxia group were significantly higher than those of normoxia group (P<0.05).② The concentrations of HDL and HDL/LDL in plasma were significantly higher in hypoxia group, compared with normoxia group (P<0.05).③The mRNA levels of LDLR and SR-B1in liver were significantly down-regulated in hypoxia group(P<0.05).④RVSP were significantly negative correlated with HDL/LDL, the gene expression of LDLR and SR-B1 (P<0.05). Abnormal lipid metabolism participates in the pathological proceeding of pulmonary hypertension induced by hypoxia.

Coenzyme Q10 첨가 급여가 산란계의 지방대사 연관 유전자 발현에 미치는 영향

Department of Animal Science and Biotechnology, Gyeongnam National University of Science and Technology, Jinju 52725, Korea ABSTRACT The aim of this study was to investigate the expression patterns of key genes involved in lipid metabolism in response to dietary Coenzyme Q10 (CoQ10) in hens. A total of 36 forty week-old Lohmann Brown were randomly allocated into 3 groups consisting of 4 replicates of 3 birds. Laying hens were subjected to one of following treatments: Control (BD, basal diet), T1 (BD+ CoQ10 100 mg/kg diet) and T2 (BD+ micellar of CoQ10 100 mg/kg diet). Birds were fed ad libitum a basal diet or the basal diet supplemented with CoQ10 for 5 weeks. Total RNA was extracted from the liver for quantitative RT-PCR. The mRNA levels of HMG-CoA reductase(HMGCR) and sterol regulatory element-binding proteins(SREBP)2 were decreased more than 3050% in the liver of birds fed a basal diet supplemented with CoQ10 (p<0.05). These findings suggest that dietary CoQ10 can reduce cholesterol levels by the suppression of the hepatic HMGCR and SREBP2 genes. The gene expressions of liver X receptor (LXR) and SREBP1 were down regulated due to the addition of CoQ10 to the feed (p<0.05). The homeostasis of cholesterol can be regulated by LXR and SREBP1 in cholesterol-low-conditions. The supplement of CoQ10 caused a decreased expression of lipid metabolism-related genes including PPARγ, XBP1, FASN, and GLUTs in the liver of birds (p<0.05). These data suggest that CoQ10 might be used as a dietary supplement to reduce cholesterol levels and to regulate lipid homeostasis in laying hens.(Key words : Coenzyme Q10, gene expressions, cholesterol, lipids, chickens)

Lipid Lowering Effects of Hydroalcoholic Extract of Anethum graveolens L. and Dill Tablet in High Cholesterol Fed Hamsters

Objective. This study was aimed to determine the effect of Anethum graveolens extract and Anethum graveolens (dill) tablet on lipid profile, liver enzymes, and gene expression and enzymatic activity of HMG-CoA reductase in high cholesterol fed hamsters. Materials and Methods. Golden Syrian male hamsters (130 ± 10 g) were randomly divided into 6 groups (n = 6) and received daily the following: group 1 received chow + 2% cholesterol + 0.5% cholic acid (HCD), groups 2 and 3 received HCD diet plus 100 and 200 mg/kg hydroalcoholic extract of dill, respectively, and groups 4 and 5 received HCD diet plus 100 and 200 mg/kg dill tablet, respectively. Group 6 received only chow. After 1 month feeding serum biochemical factors were determined. HMG-CoA reductase mRNA level was measured (real-time PCR) and its activity was determined spectrophotometrically. Results. Compared with hypercholesterolemic group 1, lipid profile, blood glucose, and liver enzymes significantly decreased in all dill tablet or dill extract treated groups (p < 0.05). The changes in HMG-CoA reductase gene expression level and enzyme activity significantly reduced in animals that received 200 mg/kg of extract or tablet. Conclusion. Dill extract and dill tablet showed potential hypocholesterolemic properties in hamsters by inhibition of HMG-CoA reductase activity.

황국곡자 투여가 지방질 대사에 미치는 영향

본 연구에서는 Asp. terreus를 접종하여 제조한 황국곡자를 이용하여 지질대사와 관련 조절유전자 및 심혈관질환에 미치는 효능을 확인하고, 고지혈증 개선에 미치는 황국곡자의 효능을 검증하고자 하였다. SD rat을 사용하여 8주 동안 고콜레스테롤 식이와 황국곡자 0.5, 2 g을 경구투여 하였다. 그 결과 간조직에서 황국곡자 투여군은 총 지질의 함량이 감소하였으나 황국곡자가 콜레스테롤 배출에는 크게 영향을 주지 않음을 확인하였다. 간조직 내 LDL 및 HDL 관련 유전자 발현 확인 결과, 콜레스테롤 합성의 가장 중요한 기작인 HMG-CoA reductase, LDL receptor와 SREBP2 발현에서는 고콜레스테롤군보다 유의적으로 모두 증가하여 체내의 콜레스테롤을 낮추는 것으로 판단된다. 또한 간조직의 형태학적 특징을 관찰해본 결과 황국곡자 투여군이 고콜레스테롤군에 비해 간 손상의 정도가 현저히 감소되어 있으며 간세포 내 작은 공포 모양의 지방구가 현저히 줄어들어 있는 것을 확인하였으며 황국곡자를 투여한 군 모두 지방세포 침윤과 같은 지방간 병변의 치료효과를 확인하였다. 결과적으로 황국곡자는 체내의 지질대사에 영향을 끼침에 따라 고지혈증의 개선을 위한 소재로 이용될 수 있을 것으로 판단된다. The aim of this study was to investigate the effects of rice contatining Aspergillus terreus (Hwangkuk, HK) on lipid metabolism in male Sprague-Dawley (SD) rats fed a high-cholesterol diet (HCD) for 8 weeks. SD rats were divided into five groups: Normal, [Negative Control (HCD), Positive Control (lovastatin)], [HK 0.5 g/kg and HK 2 g/kg]. Hepatic total lipids significantly decreased following treatment with rice contatining Asp. terreus. Furthermore, this treatment led to higher expression levels of HMG-CoA reductase, LDL receptor and SREBP2 mRNA in the liver compared with the HCD group. In addition, histopathologic evaluation showed that feeding rats with rice containing Asp. terreus suppressed hepatic steatosis. These results suggest that rice containing Asp. terreus may be able to regulate of cholesterol synthesis and prevent hyperlipidemia.

Cholesterol in brain disease: sometimes determinant and frequently implicated.

Cholesterol is essential for neuronal physiology, both during development and in the adult life: as a major component of cell membranes and precursor of steroid hormones, it contributes to the regulation of ion permeability, cell shape, cell-cell interaction, and transmembrane signaling. Consistently, hereditary diseases with mutations in cholesterol-related genes result in impaired brain function during early life. In addition, defects in brain cholesterol metabolism may contribute to neurological syndromes, such as Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD), and even to the cognitive deficits typical of the old age. In these cases, brain cholesterol defects may be secondary to disease-causing elements and contribute to the functional deficits by altering synaptic functions. In the first part of this review, we will describe hereditary and non-hereditary causes of cholesterol dyshomeostasis and the relationship to brain diseases. In the second part, we will focus on the mechanisms by which perturbation of cholesterol metabolism can affect synaptic function.

Cirsium brevicaule A. GRAY leaf inhibits adipogenesis in 3T3-L1 cells and C57BL/6 mice

BackgroundVarious flavonoids obtained from the genus Cirsium have been reported to exhibit beneficial effects on health. The present study evaluated the antiobesity effects of Cirsium brevicaule A. GRAY leaf (CL) by using 3T3-L1 cells and C57BL/6 mice that were fed a high-fat diet (HFD).MethodsDried CL powder was serially extracted with solvents of various polarities, and these extracts were tested for antiadipogenic activity using 3T3-L1 adipocytes. Mice were fed experimental HFD supplemented with dried CL powder for 4 wk. Lipid levels and mRNA levels of genes related to lipid metabolism were determined in 3T3-L1 adipocytes and the white adipose tissue (WAT) and liver of mice fed on a HFD.ResultsTreatment of 3T3-L1 adipocytes with a hexane extract of CL significantly reduced cellular lipid accumulation and expression of the fatty acid synthase (FASN) gene. Dietary CL reduced the serum levels of non-esterified fatty acids in HFD-fed mice. Significant decreases in subcutaneous WAT weight and associated FASN gene expression were observed in the mice fed the experimental CL diet. Dietary CL also reduced the hepatic lipid and serum levels of a hepatopathic indicator in the HFD-fed mice. A significant reduction in mRNA levels of FASN and HMG-CoA reductase were observed in the livers of the CL-diet group. Dietary CL, on the other hand, increased in the hepatic mRNA levels of genes related to β-oxidation, namely peroxisome proliferator-activated receptor α, calnitine palmitoyltrasferase 1A, and uncoupling protein 2. Expression of the insulin receptor gene was also significantly increased in the livers of mice-fed the CL diet.ConclusionsThe present study therefore demonstrated that CL suppresses lipid accumulation in the WAT and liver partly through inhibiting mRNA levels of FASN gene and enhancing the lipolysis-related gene expression.

The inhibitory effect of black soybean on hepatic cholesterol accumulation in high cholesterol and high fat diet-induced non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is defined as excess of fat in the liver. We investigated the effects of black soybean on the cholesterol metabolism and insulin resistance of mice fed high cholesterol/fat diets. Mice were randomly allocated into four groups that were fed different diets: the normal cholesterol/fat diet; high cholesterol/fat diets (HCD); and HCD with 1%, and 4% black soybean powder (1B-HCD, and 4B-HCD). Liver total cholesterol and triglyceride concentrations were significantly lower in the black soybean-supplemented groups than that in the HCD group. PCR revealed significantly lower hepatic SREBP2 and HMG-CoA reductase mRNA levels of black soybean-supplemented mice. Real-time PCR revealed significantly higher hepatic ABCA1 mRNA level of black soybean-supplemented mice, which may increase cholesterol efflux. Liver bile acids concentration was significantly high in the 4B-HCD group. Black soybean stimulated secretion of adiponectin, activation of pAMPK, and eliminated free fatty acids in the liver. Black soybean supplementation decreased MDA and nitrate level. The activities of SOD, catalase, and GPx were restored by black soybean supplementation. Our data strongly indicate that black soybean influences the balance between oxidative and antioxidative stress. We suggest that black soybean improves cholesterol metabolism, insulin resistance, and alleviates oxidative damage in NAFLD.

On the regulatory role of side-chain hydroxylated oxysterols in the brain. Lessons from CYP27A1 transgenic and Cyp27a1−/− mice

The two oxysterols, 27-hydroxycholesterol (27OH) and 24S-hydroxycholesterol (24OH), are both inhibitors of cholesterol synthesis and activators of the liver X receptor (LXR) in vitro. Their role as physiological regulators under in vivo conditions is controversial, however. In the present work, we utilized a previously described mouse model with overexpressed human sterol 27-hydroxylase (CYP27A1). The levels of 27OH were increased about 12-fold in the brain. The brain levels of HMG-CoA reductase mRNA and HMG-CoA synthase mRNA levels were increased. In accordance with increased cholesterol synthesis, most of the cholesterol precursors were also increased. The level of 24OH, the dominating oxysterol in the brain, was decreased by about 25%, most probably due to increased metabolism by CYP27A1. The LXR target genes were unaffected or slightly changed in a direction opposite to that expected for LXR activation. In the brain of Cyp27(-/-) mice, cholesterol synthesis was slightly increased, with increased levels of cholesterol precursors but normal mRNA levels of HMG-CoA reductase and HMG-CoA synthase. The mRNA levels corresponding to LXR target genes were not affected. The results are consistent with the possibility that both 24OH and 27OH are physiological suppressors of cholesterol synthesis in the brain. The results do not support the contention that 27OH is a general activator of LXR target genes in this organ.

Aspergillus awamoriFeeding Modifies Lipid Metabolism in Rats

In the present study, an experiment was conducted to show that A. awamori modifies lipid metabolism in mammals. A total number of 24 rats at 6 weeks of age were divided into 2 groups (10% and 30% fat dietary groups), and each group was further divided into control and experimental groups (6 rats per group). Rats in the experimental groups were given diets containing 0.05% A. awamori. The diets were administered for 3 weeks to evaluate the effects of A. awamori on growth, plasma lipid profile, and the expressions of genes related to lipid metabolism in the liver. After the rats were fed A. awamori, body weight gain was increased, while food intake was decreased; therefore, food efficiency was increased in both A. awamori groups. Plasma triglycerides, LDL cholesterol, and glucose levels were decreased, but plasma HDL cholesterol levels were increased. Furthermore, saturated fatty acids were decreased while; unsaturated fatty acids were increased in the liver. The liver mRNA levels of FAS, ACC, delta-6-desaturase, and HMG-CoA reductase were increased, while the mRNA level of LDL receptor was decreased. From these data, it is proposed that A. awamori could be used as an effective probiotic to prevent lifestyle-related diseases in humans.

Blockade of cholesterol absorption by ezetimibe reveals a complex homeostatic network in enterocytes

Enterocyte cholesterol homeostasis reflects aggregated rates of sterol synthesis, efflux, and uptake from plasma and gut lumen. Cholesterol synthesis and LDL uptake are coordinately regulated by sterol regulatory element-binding proteins (SREBP), whereas sterol efflux is regulated by liver X receptors (LXR). How these processes are coordinately regulated in enterocytes, the site of cholesterol absorption, is not well understood. Here, we treat mice with ezetimibe to investigate the effect of blocking cholesterol absorption on intestinal SREBPs, LXRs, and their effectors. Ezetimibe increased nuclear SREBP-2 8-fold. HMG-CoA reductase (HMGR) and LDL receptor (LDLR) mRNA levels increased less than 3-fold, whereas their protein levels increased 30- and 10-fold, respectively. Expression of inducible degrader of LDLR (IDOL), an LXR-regulated gene that degrades LDLRs, was reduced 50% by ezetimibe. Coadministration of ezetimibe with the LXR agonist T0901317 abolished the reduction in IDOL and prevented the increase in LDLR protein. Ezetimibe-stimulated LDLR expression was independent of proprotein convertase subtilisin/kexin type 9 (PSCK9), a protein that degrades LDLRs. To maintain cholesterol homeostasis in the face of ezetimibe, enterocytes boost LDL uptake by increasing LDLR number, and they boost sterol synthesis by increasing HMGR and other cholesterologenic genes. These studies reveal a hitherto undescribed homeostatic network in enterocytes triggered by blockade of cholesterol absorption.

Hypolipidemic effects of a new piperine derivative GB-N from Piper longum in high-fat diet-fed rats

Context: Long pepper, Piper longum Linn. (Piperaceae), is widely used in traditional Mongolian medicine for treating hyperlipidemia and coronary heart disease.Objective: To investigate the hypolipidemic effects of a new piperine derivative GB-N isolated from long pepper in high-fat diet-fed rats.Methods: The levels of serum total cholesterol, triacylglycerols (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were determined by enzymatic colorimetric method. The levels of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA), CYP7A1, lecithin cholesterol acyltransferase (LCAT) and LDL receptor (LDLR) mRNA and protein expression were detected by real-time polymerase chain reaction and western blot analysis.Results and discussion: Compared with model rats, oral administration of GB-N at doses of 2.5–10 mg/kg to hyperlipidemic rats could significantly decrease the levels of serum TG from 1.54 mmol/L in hyperlipidemic rats to 0.94–1.02 mmol/L, with an increase in serum HDL-C levels from 0.40 mmol/L in hyperlipidemic rats to 1.21–2.26 mmol/L. Treatment with GB-N (10 mg/kg) could also significantly upregulate levels of hepatic HMG-CoA reductase, CYP7A1, LCAT and LDLR mRNA and protein expression.Conclusion: GB-N had hypolipidemic activity via regulating lipid metabolism pathways in liver of hyperlipidemic rats and could be explored as a potential agent for the prevention of hyperlipidemia diseases.

Aronia melanocarpa (chokeberry) polyphenol rich extract reduces plasma cholesterol and improves antioxidant function in Apolipoprotien E knockout mice

The objective of this work was to evaluate the effect of polyphenol‐rich chokeberry extract (CBE) on lipid metabolism and antioxidant function in a mouse model for atherosclerosis. Male apoE−/− mice were fed a high fat/high cholesterol diet (15% fat, 0.2% cholesterol by wt) supplemented with 0.005% or 0.05% of CBE by wt for 4 weeks (n = 10/group). The 0.05% CBE diet provided daily doses of 0.19 mg anthocyanins, 0.17 mg phenolic acids, 0.06 mg proanthocyanidins, and 0.02 mg flavonoids. Mice consuming 0.05% CBE had ~20% lower plasma total cholesterol concentrations compared with control, without altering triglyceride levels. Despite the hypercholesterolemic effect of CBE, mRNA levels of low‐density lipoprotein receptor and HMG‐CoA reductase in CBE‐fed mice were not significantly different from controls. Dietary CBE did not alter hepatic lipids or expression of genes involved in lipogenesis and fatty acid β‐oxidation. Dietary 0.05% CBE increased plasma paraoxonase‐1 (PON1) activity 39%, but did not affect glutathione peroxidase and superoxide dismutase activities. Thus, dietary CBE improves antioxidant function and its cholesterol‐lowering effect may be independent of hepatic cholesterol metabolism. Supported by College of Agriculture and Natural Resources and Research Foundation at the University of Connecticut.

Early gestational gene transfer with targeted ATP7B expression in the liver improves phenotype in a murine model of Wilson's disease

The ideal gene therapy for metabolical liver disorders would target hepatocytes before the onset of disease and be durable, non-toxic and non-immunogenic. Early gestational gene transfer can achieve such goals. Here, we demonstrate that prenatal gene transfer of human Atp7b reduces liver pathology and improves biochemical markers in Atp7b(-/-) mice, a murine model of Wilson's disease (WD). Following prenatal injection of lentivirus vector containing the human Atp7b gene under the transcriptional control of a liver-specific promoter, the full-length ATP7B was detectable in mouse livers for the entire duration of experiments (20 weeks after birth). In contrast to a marked pathology in non-injected animals, livers from age-matched treated mice consistently demonstrated normal gross and histological morphology. Hepatic copper content was decreased in the majority of treated mice, although remaining copper levels varied. Improvement of hepatic copper metabolism was further apparent from the presence of copper-bound ceruloplasmin in the sera and normalization of the mRNA levels for HMG CoA-reductase. With this approach, the complete loss of copper transport function can be ameliorated, as evident from phenotypical improvement in treated Atp7b(-/-) mice. This study provides proof of principle for in utero gene therapy in WD and other liver-based enzyme deficiencies.

Permethrin exposure during puberty has the potential to enantioselectively induce reproductive toxicity in mice

Permethrin (PM), as a chiral pesticide, has two asymmetric centers, resulting in two pairs of enantiomers. In China, the commercial formulation of PM contains four enantiomers. The enantiomer-specific activity for endocrine disruption in mice remains unclear. In the present study, the four individual PM enantiomers were separated by preparative HPLC. Then, three week-old male ICR mice (after maternal ablactation) were orally administered (+)-cis, (−)-cis, (+)-trans, and (−)-trans-PM separately daily for 3weeks at doses of 0, 25, 50 and 100mg/kg/day, respectively. The results showed that 100mg/kg of (+)-cis, (−)-cis and (−)-trans-PM treatments resulted in serious testicular histopathological damage, decreases in testis weight and serum testosterone (T) concentrations. Moreover, the transcription status of some key genes involved in cholesterol synthesis and transport as well as T synthesis in the testes were also influenced selectively by PM enantiomers, especially by the (+)-cis-PM. Additionally, peripheral benzodiazepine receptor (PBR) and 17β-hydroxysteroid dehydrogenase (17β-HSD) mRNA levels decreased significantly in the (+)-cis-PM group regardless of the administrated doses, while steroidogenic acute regulatory protein (StAR) levels were significantly down-regulated by (+)-cis and (−)-trans-PM. Moreover, significant differences were mainly found in HMG-CoA reductase, PBR, StAR and 17β-HSD mRNA levels between different enantiomers. Combined with the effects on physiology, histopathology and the expression of genes related to T synthesis, (+)-cis-PM showed the greatest endocrine disruption activities, (−)-cis and (−)-trans-PM were moderate, while (+)-trans-PM exhibited the lowest. These results suggested significant PM enantioselectivity in the reproductive toxicity of mice during puberty exposure.

Hypolipidemic and anti‐oxidant properties of astaxanthin‐rich extract from Haematococcus pluvialis in apolipoprotein E knockout mice

Dyslipidemia and oxidative stress contribute to atherogenesis. Astaxanthin (AST) is a red-colored carotenoid known for high antioxidant capacity. To investigate the effect of AST on lipid metabolism and antioxidant defense, we fed male apolipoprotein E knockout mice, a mouse model for atherosclerosis, an AIN-93M high fat/high cholesterol diet supplemented with AST-rich Hematococcus pluvialis extract (0.03% AST by wt) for 4 wk. Plasma total cholesterol and triglyceride (TG) concentrations were significantly reduced in AST-fed mice compared with control. Realtime PCR analysis demonstrated significantly higher mRNA levels of low density lipoprotein receptor (LDLR), HMG-CoA reductase and sterol regulatory element binding protein 2 (SREBP-2) with elevated mature SREBP-2 protein in the livers of AST-fed mice. The increased LDLR could enhance LDL clearance. Hepatic lipogenic gene expression was not altered but carnithin palmitoyl transferase 1, acylCoA oxidase and uncoupling protein 2 mRNA levels were significantly increased by AST, suggesting TG-lowering effect of AST may be due to increased fatty acid β-oxidation and energy uncoupling. Hepatic expression of antioxidant genes was also induced by AST. Our results suggest that AST supplementation can improve cholesterol and lipid metabolism as well as anti-oxidant status, all of which can be beneficial for the prevention of atherosclerosis development.

Abolished synthesis of cholic acid reduces atherosclerotic development in apolipoprotein E knockout mice

To investigate the effects of abolished cholic acid (CA) synthesis in the ApoE knockout model [apolipoprotein E (apoE) KO],a double-knockout (DKO) mouse model was created by crossbreeding Cyp8b1 knockout mice (Cyp8b1 KO), unable to synthesize the primary bile acid CA, with apoE KO mice. After 5 months of cholesterol feeding, the development of atherosclerotic plaques in the proximal aorta was 50% less in the DKO mice compared with the apoE KO mice. This effect was associated with reduced intestinal cholesterol absorption, decreased levels of apoB-containing lipoproteins in the plasma, enhanced bile acid synthesis, reduced hepatic cholesteryl esters, and decreased hepatic activity of ACAT2. The upregulation of Cyp7a1 in DKO mice seemed primarily caused by reduced expression of the intestinal peptide FGF15. Treatment of DKO mice with the farnesoid X receptor (FXR) agonist GW4064 did not alter the intestinal cholesterol absorption, suggesting that the action of CA in this process is confined mainly to formation of intraluminal micelles and less to its ability to activate the nuclear receptor FXR. Inhibition of CA synthesis may offer a therapeutic strategy for the treatment of hyperlipidemic conditions that lead to atherosclerosis.

Exercise Enhances Whole-Body Cholesterol Turnover in Mice

Regular exercise reduces cardiovascular risk in humans by reducing cholesterol levels, but the underlying mechanisms have not been fully explored. Exercise might provoke changes in cholesterol and bile acid metabolism and thereby reduce cardiovascular risk. We examined whether voluntary wheel running in mice modulates cholesterol and bile acid metabolism. Male mice (10 wk old) were randomly assigned to have access to a voluntary running wheel for 2 wk (RUN group) or remained sedentary (SED group). Running wheel activity was recorded daily. In a first experiment, fecal sterol outputs, fecal bile acid profiles, plasma parameters, and expression levels of genes involved in cholesterol and bile acid metabolism were determined. In a second experiment, bile flow, biliary bile acid profile, and biliary secretion rates of cholesterol, phospholipids, and bile acids were determined. The RUN group ran an average of 10 km.d and displayed lower plasma cholesterol compared with SED (P = 0.030). Fecal bile acid loss was induced by approximately 30% in running mice compared with SED (P = 0.0012). A approximately 30% increase in fecal cholesterol output in RUN (P = 0.014) was consistent with changes in parameters of cholesterol absorption, such as reduced plasma plant sterol-cholesterol ratio (P = 0.044) and decreased jejunal expression of Npc1l1 (P = 0.013). Supportive of an increased cholesterol synthesis to compensate for fecal sterol loss were increased hepatic mRNA levels of HMGCoA reductase (P = 0.006) and an increased plasma lathosterol-cholesterol ratio (P = 0.0011) in RUN. Voluntary wheel running increased cholesterol turnover in healthy mice owing to an increased fecal bile acid excretion and a decreased intestinal cholesterol absorption. Enhanced cholesterol turnover may contribute to the established reduction of cardiovascular risk induced by regular exercise.

Different effects of pioglitazone and rosiglitazone on lipid metabolism in mouse cultured liver explants

Pioglitazone (PIO) and rosiglitazone (ROSI) are widely used as oral antidiabetic agents for treatment of type 2 diabetes. Although these medications exert similar effects on blood glucose, recent clinical studies indicated that PIO has a more pronounced beneficial effect on lipid parameters than ROSI. In order to get further insight into the lipid effects of both drugs, we tested whether PIO, compared to ROSI, could exert direct effects on lipid liver metabolism in relation with plasma lipids. We performed in vitro studies using mice liver slices incubated 21 h either with ROSI (1 micromol/L) or PIO (7.5 micromol/L). We showed that both glitazones slightly reduced HMG-CoA reductase mRNA levels at the same degree but only PIO reduced intracellular cholesterol content, suggesting an alteration of cholesterol uptake rather than an inhibition of cholesterol biosynthesis. This concept was supported by the reduction of scavenger receptor class B type I expression, hepatic lipase activity and high-density lipoprotein cholesterol uptake in PIO-treated liver explants. Conversely, hepatic lipase mRNA levels were increased 3.5-fold. ROSI, but not PIO, induced acetyl-CoA carboxylase and fatty acid synthase gene expression and increased apoB secretion suggesting a stimulation of lipogenesis. Concurrently, peroxisome proliferator-activated receptor-gamma mRNA levels were induced by ROSI and not significantly changed by PIO. Besides, PIO appeared to be a more potent activator of AMP-Activated Protein Kinase than ROSI. PIO and ROSI exert specific direct effects on liver and extrapolating these data to humans could explain the significant improvements in plasma lipids observed in diabetic patients treated with PIO.