Cholesterol Biosynthesis In Liver Research Articles

Early life exposure to vitamin D deficiency impairs molecular mechanisms that regulate liver cholesterol biosynthesis, energy metabolism, inflammation, and detoxification.

Emerging data suggests liver disease may be initiated during development when there is high genome plasticity and the molecular pathways supporting liver function are being developed. Here, we leveraged our Collaborative Cross mouse model of developmental vitamin D deficiency (DVD) to investigate the role of DVD in dysregulating the molecular mechanisms underlying liver disease. We defined the effects on the adult liver transcriptome and metabolome and examined the role of epigenetic dysregulation. Given that the parental origin of the genome (POG) influences response to DVD, we used our established POG model [POG1-(CC011xCC001)F1 and POG2-(CC001xCC011)F1] to identify interindividual differences. We found that DVD altered the adult liver transcriptome, primarily downregulating genes controlling liver development, response to injury/infection (detoxification & inflammation), cholesterol biosynthesis, and energy production. In concordance with these transcriptional changes, we found that DVD decreased liver cell membrane-associated lipids (including cholesterol) and pentose phosphate pathway metabolites. Each POG also exhibited distinct responses. POG1 exhibited almost 2X more differentially expressed genes (DEGs) with effects indicative of increased energy utilization. This included upregulation of lipid and amino acid metabolism genes and increased intermediate lipid and amino acid metabolites, increased energy cofactors, and decreased energy substrates. POG2 exhibited broader downregulation of cholesterol biosynthesis genes with a metabolomics profile indicative of decreased energy utilization. Although DVD primarily caused loss of liver DNA methylation for both POGs, only one epimutation was shared, and POG2 had 6.5X more differentially methylated genes. Differential methylation was detected at DEGs regulating developmental processes such as amino acid transport (POG1) and cell growth & differentiation (e.g., Wnt & cadherin signaling, POG2). These findings implicate a novel role for maternal vitamin D in programming essential offspring liver functions that are dysregulated in liver disease. Importantly, impairment of these processes was not rescued by vitamin D treatment at weaning, suggesting these effects require preventative measures. Substantial differences in POG response to DVD demonstrate that the parental genomic context of exposure determines offspring susceptibility.

Abstract 2799: Intestinal Akkermansia muciniphila complements the therapeutic efficacy of PD1 therapy by reshaping the immunosuppressive microenvironment in nonalcoholic fatty liver disease (NAFLD)-induced hepatocellular carcinoma

Abstract Objectives: Nonalcoholic fatty liver disease (NAFLD)-induced hepatocellular carcinoma (HCC) is an emerging malignancy in the developed world. However, immune checkpoint inhibitors (ICIs) are ineffective for patients with this disease. Advances in research have shown that gut-liver communication contributes to NAFLD progression. Therefore, identifying a key gut microbiota for predicting ICIs response and an effective combinatorial strategy is urgently needed. Design: 16S rRNA sequencing was employed to identify key gut microbiota crucial in developing the mouse NAFLD-induced HCC model. The in vivo roles of Akkermansia muciniphila (Akk) were evaluated by immunofluorescence staining, qPCR, mass spectrometry analysis, ELISA assay, and single-cell RNA sequencing (scRNA-seq) coupled with immune profiling analysis. The clinical and therapeutic value of Akk alone in combination with PD1 treatment was investigated. Results: Akk was decreased from healthy to HCC tissues during HCC tumor development, and daily administration of Akk not only ameliorates liver steatosis and cholesterol biosynthesis but could effectively attenuate the development of NAFLD-induced HCC. Akk repairs the intestinal lining, with a concurrent decrease in the serum concentration of lipopolysaccharide (LPS) and bile acid metabolites. Using scRNA-seq coupled with immune profiling analyses, we found that Akk suppressed the populations of immunosuppressive cells, including monocytic myeloid-derived suppressor cells (m-MDSCs) and M2 macrophages, by suppressing the differentiation of these cells from monocytes, which leads to T cell proliferation and activation. Consistent with this finding, Akk administration, combined with PD1 treatment, exerted a maximal growth-suppressive effect, accompanied by increased infiltration and activation of T cells. Clinically, the fecal level of Akk in HCC patients was decreased in NAFLD-induced HCC patients and serves as a potential biomarker for predicting PD1 response in HCC patients. Conclusions: Akk regulates the immune tumor environment by regulating two key immune suppressive cells via regulation of the LPS flux to develop NALFD-induced HCC. This finding provides a solid therapeutic basis for a rational combination with PD1 for the treatment of this deadly disease. Interestingly, Akk may serve as a predictive biomarker for PD1 response in HCC patients. Citation Format: Xueqian Wu, Fan Ying, Katherine Po Sin Chung, Carmen Oi Ning Leung, Terence Kin Wah Lee. Intestinal Akkermansia muciniphila complements the therapeutic efficacy of PD1 therapy by reshaping the immunosuppressive microenvironment in nonalcoholic fatty liver disease (NAFLD)-induced hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2799.

Liver transcriptome analysis reveal the metabolic and apoptotic responses of Trachinotus ovatus under acute cold stress

Trachinotus ovatus is an economically important fish and has been recommended as a high-quality aquaculture fish breed for the high-quality development of sea ranches in the South China Sea. However, T. ovatus shows intolerance to low temperature, greatly limiting the extension of farming scale, reducing production efficiency in winter, and increasing farming risks. In this study, liver transcriptome analysis was investigated in T. ovatus under acute low temperature conditions (20 and 15 °C) using RNA sequencing (RNA-Seq) technology. Inter-groups differential expression analysis and trend analysis screened 1219 DEGs and four significant profiles (profiles 0, 3, 4, and 7), respectively. GO enrichment analysis showed that these DEGs were mainly related to metabolic process and cell growth and death process. KEGG enrichment analysis found that DEGs were mainly associated with lipid metabolism, carbohydrate metabolism, and cell growth and death, such as gluconeogenesis, glycolysis, fatty acid oxidation, cholesterol biosynthesis, p53 signaling pathway, cell cycle arrest, and apoptotic cell death. Moreover, protein–protein interaction networks identified two hub genes (FOS and JUNB) and some important genes related to metabolic process and cell growth and death process, that corresponding to enrichment analysis. Overall, gluconeogenesis, lipid mobilization, and fatty acid oxidation in metabolic process and cell cycle arrest and apoptotic cell death in cell growth and death process were enhanced, while glycolysis, liver glycogen synthesis and cholesterol biosynthesis in metabolic process were inhibited. The enhancement or attenuatment of metabolic process and cell growth and death process is conducive to maintain energy balance, normal fluidity of cell membrane, normal physiological functions of liver cell, enhancing the tolerance of T. ovatus to cold stress. These results suggested that metabolic process and cell growth and death process play important roles in response to acute cold stress in the liver of T. ovatus. Gene expreesion level analysis showed that acute cold stress at 15 °C was identified as a critical temperature point for T. ovatus in term of cellular metabolism alteration and apoptosis inducement, and rewarming intervention should be timely implemented above 15 °C. Our study can provide theoretical support for breeding cold-tolerant cultivars of T. ovatus, which is contributed to high-quality productions fish production.

Effect of Gender on Cholesterol Levels in Type 2 Diabetes Mellitus Patients

In women aged 17-50 years, a decrease in Follicle-stimulating hormone (FSH) levels will increase the hormone estrogen which requires cholesterol, so that cholesterol becomes low through inhibition of liver cholesterol biosynthesis. The purpose of this study was to determine differences in cholesterol levels between women and men with Type 2 Diabetes Mellitus. The study design was a cross-sectional analytic observational and purposive sampling technique with inclusion criteria of HbA1c > 6.5%. As a result, the average age of the male respondents was 44 years (SD±18.4), HbA1c 8.5% (SD±2.4), and cholesterol 212 mg/dL (SD±40), the average age of females was 58 years old (SD ± 7.7, HbA1c 10.6% (SD ± 3.4), and cholesterol 181 mg/dL (SD ± 37.6). The results of the Mann- Whitney test with p = 0.038 (p <0.05) mean that there is a significant difference in cholesterol levels between men and women, which means there are differences in how the brain works between men and premenopausal women who suffer from type 2 Diabetes Mellitus Suggestions for future researchers, it is necessary to conduct research on High-sensitivity C-reactive protein (hs-CRP) and low-density lipoprotein (LDL) cholesterol in premenopausal women regarding the role of estrogen and FSH in regulating cholesterol.

Organ-specific metabolic pathways distinguish prediabetes, type 2 diabetes, and normal tissues

SummaryEnvironmental and genetic factors cause defects in pancreatic islets driving type 2 diabetes (T2D) together with the progression of multi-tissue insulin resistance. Mass spectrometry proteomics on samples from five key metabolic tissues of a cross-sectional cohort of 43 multi-organ donors provides deep coverage of their proteomes. Enrichment analysis of Gene Ontology terms provides a tissue-specific map of altered biological processes across healthy, prediabetes (PD), and T2D subjects. We find widespread alterations in several relevant biological pathways, including increase in hemostasis in pancreatic islets of PD, increase in the complement cascade in liver and pancreatic islets of PD, and elevation in cholesterol biosynthesis in liver of T2D. Our findings point to inflammatory, immune, and vascular alterations in pancreatic islets in PD that are hypotheses to be tested for potential contributions to hormonal perturbations such as impaired insulin and increased glucagon production. This multi-tissue proteomic map suggests tissue-specific metabolic dysregulations in T2D.

Peroxisomal β-oxidation stimulates cholesterol biosynthesis in the liver in diabetic mice

Although diabetes normally causes an elevation of cholesterol biosynthesis and induces hypercholesterolemia in animals and human, the mechanism linking diabetes to the dysregulation of cholesterol biosynthesis in the liver is not fully understood. As liver peroxisomal β-oxidation is induced in the diabetic state and peroxisomal oxidation of fatty acids generates free acetate, we hypothesized that peroxisomal β-oxidation might play a role in liver cholesterol biosynthesis in diabetes. Here, we used erucic acid, a specific substrate for peroxisomal β-oxidation, and 10,12-tricosadiynoic acid, a specific inhibitor for peroxisomal β-oxidation, to specifically induce and suppress peroxisomal β-oxidation. Our results suggested that induction of peroxisomal β-oxidation increased liver cholesterol biosynthesis in streptozotocin-induced diabetic mice. We found that excessive oxidation of fatty acids by peroxisomes generated considerable free acetate in the liver, which was used as a precursor for cholesterol biosynthesis. In addition, we show that specific inhibition of peroxisomal β-oxidation decreased cholesterol biosynthesis by reducing acetate formation in the liver in diabetic mice, demonstrating a crosstalk between peroxisomal β-oxidation and cholesterol biosynthesis. Based on these results, we propose that induction of peroxisomal β-oxidation serves as a mechanism for a fatty acid-induced upregulation in cholesterol biosynthesis and also plays a role in diabetes-induced hypercholesterolemia.

Organ-Specific Metabolic Pathways Distinguish Prediabetes, Type 2 Diabetes and Normal Tissues

Defects in pancreatic islets and the progression of multi-tissue insulin resistance in combination with environmental factors are the main causes of type 2 diabetes (T2D). Mass spectrometry-based proteomics of five key-metabolic tissues on a cohort of 42 multi-organ donors provided deep coverage of the proteomes of pancreatic islets, visceral adipose tissue (VAT), liver, skeletal muscle and serum. Enrichment analysis of gene ontology (GO) terms built a tissue-specific map of the chronological order of altered biological processes across healthy controls (CTRL), pre-diabetes (PD) and T2D subjects. This unique dataset allowed us to explore alterations of entire biological pathways and individual proteins in multiple tissues. We confirmed the significant decrease of the citric acid cycle and the respiratory electron transport in VAT and muscle of T2D and we provided a thorough visual representation of the complete set of downregulated proteins. Importantly, we found widespread novel alterations in relevant biological pathways including the increase in hemostasis in pancreatic islets of PD, the increase in the complement cascade in liver and pancreatic islets of PD and the elevation in cholesterol biosynthesis in liver of T2D. Overall, our findings suggest inflammatory, immune and vascular impairments in pancreatic islets as potentially causal factors of insufficient insulin production and increased glucagon levels in the early stages of T2D. In contrast alterations in lipid metabolism and mitochondrial function in the liver and VAT/muscle, respectively, became evident later in manifest T2D. This first multi-tissue proteomic map indicates the temporal order of tissue-specific metabolic dysregulation in T2D development.

Recent insights into low-density lipoprotein metabolism and therapy.

Elevated levels of low-density lipoprotein cholesterol (LDL-C) are causal to atherosclerosis and, thus, the reduction of LDL-C represents a major objective for the prevention of cardiovascular disease. Aim of this review is to provide an overview on novel strategies to lower LDL-C. Although inhibiting liver cholesterol biosynthesis by statins is used as the main therapeutic approach to increase hepatic LDL-receptor expression and lower plasma cholesterol levels, novel insights into lipid and lipoprotein biology have led to the development of additional lipid-lowering therapies that can be used in combination with or as an alternative to statins in patients with statin-intolerance. New approaches include bempedoic acid, proprotein convertase subtilisin/kexin type 9 inhibitors, and angiopoietin-like protein 3 inhibitors. In the last decade, several novel therapeutic approaches have been tested and some of them have been approved as lipid-lowering agents. Some drugs are already available in clinical practice, whereas others are at late stages of development.

Diets enriched with coconut, fish, or olive oil modify peripheral metabolic effects of ozone in rats

Dietary factors may modulate metabolic effects of air pollutant exposures. We hypothesized that diets enriched with coconut oil (CO), fish oil (FO), or olive oil (OO) would alter ozone-induced metabolic responses. Male Wistar-Kyoto rats (1-month-old) were fed normal diet (ND), or CO-, FO-, or OO-enriched diets. After eight weeks, animals were exposed to air or 0.8 ppm ozone, 4 h/day for 2 days. Relative to ND, CO- and OO-enriched diet increased body fat, serum triglycerides, cholesterols, and leptin, while all supplements increased liver lipid staining (OO > FO > CO). FO increased n-3, OO increased n-6/n-9, and all supplements increased saturated fatty-acids. Ozone increased total cholesterol, low-density lipoprotein, branched-chain amino acids (BCAA), induced hyperglycemia, glucose intolerance, and changed gene expression involved in energy metabolism in adipose and muscle tissue in rats fed ND. Ozone-induced glucose intolerance was exacerbated by OO-enriched diet. Ozone increased leptin in CO- and FO-enriched groups; however, BCAA increases were blunted by FO and OO. Ozone-induced inhibition of liver cholesterol biosynthesis genes in ND-fed rats was not evident in enriched dietary groups; however, genes involved in energy metabolism and glucose transport were increased in rats fed FO and OO-enriched diet. FO- and OO-enriched diets blunted ozone-induced inhibition of genes involved in adipose tissue glucose uptake and cholesterol synthesis, but exacerbated genes involved in adipose lipolysis. Ozone-induced decreases in muscle energy metabolism genes were similar in all dietary groups. In conclusion, CO-, FO-, and OO-enriched diets modified ozone-induced metabolic changes in a diet-specific manner, which could contribute to altered peripheral energy homeostasis.

Heterozygous Disruption of Beclin 1 Alleviates Zinc Oxide Nanoparticles-Induced Disturbance of Cholesterol Biosynthesis in Mouse Liver.

PurposeLiver is regarded as one of the primary target organs for zinc oxide nanoparticles (ZnONPs) toxicity. Since liver represents the leading site for de novo cholesterol biosynthesis in mammals, the injuries of liver could result in the disruption of cholesterol biosynthesis. In this study, we aimed to investigate whether pulmonary ZnONPs exposure induces disturbance of cholesterol biosynthesis in mouse liver.Methods and resultsOur data demonstrated intratracheally instilled with a single dose of 3, 6, and 12 μg/animal ZnONPs could induce histopathological deterioration in mouse liver in a dose-related manner at 3 days, but remission was observed at 7 days after treatment. Moreover, ZnONPs caused the disturbance of cholesterol biosynthesis by increasing both 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase and sterol regulatory element-binding protein 2 (SREBP2) protein expressions. To further reveal the underlying toxic mechanisms, we detected the biomarkers of autophagy and found that pulmonary ZnONPs exposure led to the elevation of LC3B-II and Beclin 1, suggesting ZnONPs might trigger autophagy in liver tissues. By using both beclin 1+/+ and beclin 1+/- mice, we demonstrated that inhibition of autophagy by heterozygous disruption of beclin 1 attenuated the disturbance of cholesterol biosynthesis induced by ZnONPs in liver.ConclusionPulmonary exposure of ZnONPs would induce the cholesterol biosynthesis disturbance in mouse liver through Beclin-1-dependent autophagy activation, suggesting that inhibition of autophagy may contribute to preventing the cholesterol biosynthesis disturbance and its associated pathologies induced by ZnONPs in liver.

RNA-Sequencing Analysis of Paternal Low-Protein Diet-Induced Gene Expression Change in Mouse Offspring Adipocytes

Increasing evidence indicates that parental diet affects the metabolism and health of offspring. It is reported that paternal low-protein diet (pLPD) induces glucose intolerance and the expression of genes involved in cholesterol biosynthesis in mouse offspring liver. The aim of the present study was to determine the effect of a pLPD on gene expression in offspring white adipose tissue (WAT), another important tissue for the regulation of metabolism. RNA-seq analysis indicated that pLPD up- and down-regulated 54 and 274 genes, respectively, in offspring WAT. The mRNA expression of many genes involved in lipogenesis was down-regulated by pLPD feeding, which may contribute to metabolic disorder. The expression of carbohydrate response element-binding protein β (ChREBP-β), an important lipogenic transcription factor, was also significantly lower in the WAT of pLPD offspring, which may have mediated the down-regulation of the lipogenic genes. By contrast, the LPD did not affect the expression of lipogenic genes in the WAT of the male progenitor, but increased the expression of lipid oxidation genes, suggesting that a LPD may reduce lipogenesis using different mechanisms in parents and offspring. These findings add to our understanding of how paternal diet can regulate metabolism in their offspring.

Deregulation of Acanthamoeba castellanii steroidogenesis is amoebicidal and protects cultured corneal cells from Ac attack

Human infections by amoeba represent rare diseases, yet they are an emerging health problem that can develop into rapid death, as in cases involving the spinal cord or amoeba that penetrate the brain. Our recent papers highlighted in J. Lipid Res, 2017 and ASBMB Today magazine, 2018 focus on development of new sterol methyltransferase (SMT) inhibitors to prevent steroidogenesis in the parasitic amoeba Acanthamoeba castellanii (Ac). Now we show, Ac cultured on unexplored sterol C24‐methyltransferase (SMT) inhibitors 25‐azalanosterol and 25‐thialanosterol iodine salt are highly potent anti‐amoeba drugs exhibiting IC50 25 nM and 15 nM, respectively and a minimum amoebicidal concentration of 1 μM. Both analogs inhibited the cloned 24‐AcSMT and 28‐AcSMT yielding Ki values of 13 nM/37nM and 9nM/16nM, respectively and blocked Ac steroidogenesis at the target enzyme. Against human epithelial kidney cell growth these drugs had no effect to 40 μM or effected cholesterol biosynthesis (selective index greater than 103); in mice at 50 mg/kg, 3H‐analog could rapidly cross the blood brain barrier with minimal effect on liver cholesterol biosynthesis. Against human corneal epithelial cultures infected with Ac, the drugs protected the eye at doses of 500 nM. These new amoeba sterol biosynthesis inhibitors are currently under investigation for their therapeutic potential.Support or Funding InformationThis research was funded through a grant from the National Institutes of Health.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Modulating liver cholesterol metabolism by 3-Iodothyronamine

In this study, we attempt to find out whether chronic low dose 3-Iodothyronamine (an endogenous metabolite of thyroid hormone) administration could modulate liver de novo cholesterol synthesis, the same as thyroid hormones. Eighteen male mice were divided randomly into treatment (n=10) and control (n=8) groups. The experimental procedure was applied for 7 days during which test group received T1AM whereas the control group received dimethyl sulfoxide and normal saline. The liver was analyzed for HMG-CoA reductase concentration and hepatic lipase activity whiles cholesterol, LDL and HDL concentrations were measured in the blood serum. There was non-significant decrease in HMG-CoA reductase concentration (224±21.2 versus 187±32.5) in test group compared to control. Interestingly LDL and cholesterol concentrations exhibited significant decrease in test group versus the control. There was non-significant decrease in hepatic lipase activity (771±316 versus 645±317) in test group versus the control. It appears that T1AM reduced serum LDL and cholesterol just like T 3 , in contrast, it decreased liver cholesterol biosynthesis contrary to THs.

Effects of different sub-lethal concentrations of plasticizer-Diethyl phthalate on Fresh water murrel, Channa striatus (Bloch)

In the present study, effects of exposure to different sub lethal concentrations of diethyl phthalate on hematological, biochemical and histological parameters of fresh water murrel, Channa striatus were evaluated. LC50 of DEP was determined and was found to be 70ppm for the present study. The experimental fishes were divided into control and DEP exposed groups. DEP exposed fish species were subjected to 0.4 ppm, 4 ppm and 40ppm concen-trations of DEP and observed after an interval of 7, 14 and 21days. Exposure to sub lethal levels of DEP revealed significant decrease in haematological parameters due to anemic condition induced by impaired haem synthesis. Exposure to DEP caused reduction in level of protein in muscle (*182.5, *180.7, *176.7, *176.1, *173.4,*167.5 and *165.7) and liver (*104.7, *98.6, *92.7, *87.7, *87.4, *86.4, *80.8, *75.6 and*68.6) due to impairment of protein synthesis. Levels of cholesterol in muscle and liver of DEP exposed fish were found to be decreased after treatment indicating either an inhibition of cholesterol biosynthesis in liver or reduced absorption of dietary cholesterol. Histo-pathological examination of liver of DEP exposed fish species showed necrosis in hepatocytes and cytoplasmic vacuolization. Histoarchitecture of kidney of DEP exposed fish species revealed shrinkage of glomeruli, glomerular distortion, vacuolization of tubular cells, necrosis and atrophy of renal tubules. As an endocrine disruptor, DEP interferes with the haematopoietic system metabolic machinery and histoarchitecture of organs of Channa striatus.

Abstract 13674: Feedback Regulation of Cholesterol Metabolism by Lexis, a Lipid-responsive Non-coding RNA

The LXR and SREBP transcription factors are key regulators of cellular and systemic cholesterol homeostasis in animals. The molecular mechanisms that integrate these pathways are incompletely understood. Here we show that ligand activation of LXR in liver not only promotes cholesterol efflux, but also simultaneously inhibits the cholesterol biosynthesis pathway. We further identify the long non-coding RNA LeXis as an unexpected mediator of this effect. LeXis is the most robustly induced transcript in mouse liver in response to western diet feeding or pharmacologic LXR activation. Tissue-specific overexpression of LeXis inhibits liver cholesterol biosynthesis and lowers plasma cholesterol levels. Reciprocally, knockdown of LeXis increases hepatic cholesterol content and raises plasma cholesterol levels. These studies outline a regulatory role for a non-coding RNA in lipid metabolism and advance our understanding of the mechanisms by which LXRs orchestrate systemic sterol homeostasis.

Monascus purpureus-fermented Thai glutinous rice reduces blood and hepatic cholesterol and hepatic steatosis concentrations in diet-induced hypercholesterolemic rats.

BackgroundRed yeast rice (RYR) is a fermented product used as a food supplement to promote blood circulation and lower blood cholesterol levels in eastern Asia. Interestingly, monacolin K is the most active compound in RYR that proved to inhibit HMG-CoA reductase in the cholesterol biosynthesis pathway.MethodsThe hypocholesterolemic effects of oral administration of Thai RYR, produced by fermentation of Thai glutinous rice (Oryza sativa L. var. Niaw San-pah-tawng) with Monascus purpureus CMU 002U, were determined in normal and hypercholesterolemic rats. The rats were divided into six groups, and fed two different kinds of diet. Groups I-II, normal rats fed with a normal diet (SP-diet), were treated with distilled water (SP-control) and 2.0 g/kg/day of RYR extract (SP-2 g). In Groups III-VI, the rats were rendered hypercholesterolemic by feeding them a high fat and cholesterol diet (HFC-diet), and were treated with distilled water (HFC-control), 1.0 g/kg/day (HFC-1 g), 2.0 g/kg/day (HFC-2 g) of RYR extract, and 5.0 mg/kg/day of rosuvastatin (HFC-rosuvastatin) for 30 days, respectively.ResultsThe RYR extract significantly decreased the concentrations of serum total cholesterol and low density lipoprotein cholesterol (LDL-C), atherosclerotic index, LDL-C/HDL-C ratio and hepatic cholesterol levels in both HFC-1 g and HFC-2 g groups (p < 0.05) as compared with the HFC-control group, and with no significant change in high density lipoprotein cholesterol (HDL-C) concentrations among all six groups. The reduction of serum TC and LDL-C also paralleled the observed changes in mRNA expressions of the genes involved in cholesterol biosynthesis and homeostasis in the liver. The hypercholesterolemic rats treated with RYR extract were significantly higher in LDLR and HMGR expression, but lower in CYP7A1 expression when compared to the untreated hypercholesterolemic rats (HFC-control) (p < 0.05). The hepatic injuries in hypercholesterolemic rats were also obviously alleviated by RYR extract.ConclusionsThe extract of Thai RYR possessed potent hypocholesterolemic and anti-atherogenic activities in diet-induced hypercholesterolemic rats. The possible mechanism involving cholesterol-lowering potential of the extract might contribute to its ability to increase LDL-C endocytosis in hepatocyte and to competitively inhibit HMG-CoA reductase, a key enzyme for cholesterol biosynthesis in liver.

Sterol regulatory element binding protein 2 overexpression is associated with reduced adipogenesis and ectopic fat accumulation in transgenic spontaneously hypertensive rats.

It has been reported that the major function of the sterol regulatory element binding protein 2 (SREBP-2) is to activate preferentially cholesterol biosynthesis in liver and adipose tissue rather than fatty acid synthesis. In the current study, we analyzed the effects of overexpression of human dominant-positive SREBP-2 transgene under control of PEPCK promoter in the spontaneously hypertensive rat (SHR) on lipid and glucose metabolism. Transgenic overexpression of SREBP-2 was associated with significantly higher hepatic triglycerides (20.4+/-0.9 vs. 17.0+/-0.05 micromol/g, P<0.05) but not cholesterol (10.6+/-0.4 vs. 10.9+/-0.4 micromol/g) and decreased relative weight of epididymal fat pad (0.73+/-0.03 vs. 0.83+/-0.03, P<0.05). In addition, muscle triglyceride (15.8+/-3.7 vs. 8.5+/-1.2 micromol/g, P<0.001) and cholesterol (3.6+/-0.5 vs. 2.1+/-0.1 micromol/g, P<0.05) concentrations were significantly increased in transgenic rats when compared to SHR controls. Ectopic fat accumulation was associated with significantly increased serum glucose levels (6.4+/-0.1 vs. 5.9+/-0.1 mmol/l, P<0.005) and reduced insulin levels (1.78+/-0.33 vs. 2.73+/-0.37 nmol/l, P<0.05) in transgenic rats. These results provide evidence for important role of SREBP-2 in regulation of lipid and glucose metabolism.

The rationality of the hypolipidemic effect of alismatis rhizoma decoction, a classical chinese medicine formula in high-fat diet-induced hyperlipidemic mice.

Alismatis Rhizoma Decoction (ARD) is a classical Traditional Chinese Medicine (TCM) formula for treatment of vertigo with its long history of successful clinical effect. Since vertigo is a symptom of hyperlipidemia, this study aimed at evaluating the hypolipidemic effect of ARD in hyperlipidemic mice induced by high fat diet (HFD) and investigated the rationality of formula combination of Alismatis Rhizoma (AR) and Atractylodis Macrocephalae Rhizoma (AMR). Compared with control group, hyperlipidemic mice in AR and ARD groups displayed a reduction of the following parameters: body weight, liver and serum total cholesterol, triglyceride concentration, liver and spleen coefficients, activities of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT); whereas the serum HDL-cholesterol levels were significantly elevated in both AR and ARD groups. AR and ARD treatments significantly down regulated the expressions of 3-hydroxy-3-methylglutharyl-coenzyme A reductase (HMG-CoA reductase) and sterol regulatory element binding factor-2 (SREBF-2). These findings clearly provided evidences that the suppression on biosynthesis of cholesterol in liver may in part contribute to the hypolipidemic effects of ARD and AR. Since no significantly hypolipidemic effect of AMR was observed, the more prominent effect of ARD than that of AR indicated synergistic effects of AR and AMR, and confirmed the rationality of ARD formula.

Regulation of Hmg-Coa Reductase in Diet-Induced Non-Alcoholic Fatty Liver Disease

Hypercholesterolemia is associated with an increased risk of coronary artery disease, such as atherosclerosis. The liver plays a central role in regulating cholesterol homeostasis. High fat diet has been shown to induce obesity and hyperlipidemia. Despite considerable advance in our understanding of cholesterol metabolism, the regulation of liver cholesterol biosynthesis in response to high fat diet feeding has not been fully addressed. The aim of the present study was to investigate mechanisms by which a high fat diet caused activation of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase), the rate-limiting enzyme, leading to increased cholesterol biosynthesis.

Activation of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase during high fat diet feeding

The liver plays a central role in regulating cholesterol homeostasis. High fat diets have been shown to induce obesity and hyperlipidemia. Despite considerable advances in our understanding of cholesterol metabolism, the regulation of liver cholesterol biosynthesis in response to high fat diet feeding has not been fully addressed. The aim of the present study was to investigate mechanisms by which a high fat diet caused activation of liver 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) leading to increased cholesterol biosynthesis. Mice were fed a high fat diet (60% kcal fat) for 5weeks. High fat diet feeding induced weight gain and elevated lipid levels (total cholesterol and triglyceride) in both the liver and serum. Despite cholesterol accumulation in the liver, there was a significant increase in hepatic HMG-CoA reductase mRNA and protein expression as well as enzyme activity. The DNA binding activity of sterol regulatory element binding protein (SREBP)-2 and specific protein 1 (Sp1) were also increased in the liver of mice fed a high fat diet. To validate the in vivo findings, HepG2 cells were treated with palmitic acid. Such a treatment activated SREBP-2 as well as increased the mRNA and enzyme activity of HMG-CoA reductase leading to intracellular cholesterol accumulation. Inhibition of Sp1 by siRNA transfection abolished palmitic acid-induced SREBP-2 and HMG-CoA reductase mRNA expression. These results suggest that Sp1-mediated SREBP-2 activation contributes to high fat diet induced HMG-CoA reductase activation and increased cholesterol biosynthesis. This may play a role in liver cholesterol accumulation and hypercholesterolemia.