HMG-CoA Reductase Activity Research Articles

Amelioration of Diabetic Dyslipidemia by GTF – 231 (Gymnemic acid, Trigonelline and Ferulic acid- 2:3:1), a phytochemical preparation Studied in High Fat Diet Fed-Low Dose STZ Induced Experimental Type 2 Diabetes in Rats

Background: Persistent hyperglycemia in diabetes is associated with profound changes in lipid and lipoprotein abnormalities which result in particle distribution within lipoprotein classes. Recently, we have reported the antidiabetic properties of GTF-231 (Gymnemic acid, Trigonelline and Ferulic acid- 2:3:1) a phytochemical preparation in experimental type 2 diabetic rats. The present study was aimed to evaluate the effect of GTF-231 on the regulation of lipid homeostasis in T2DM induced rats.Materials and methods: High fat diet fed-low dose STZ induced experimental type 2 diabetes was used as the animal model. GTF at a concentration of 300 mg/kg.b.w./rat/day was orally administered for 30 days to experimental type 2 diabetic rats. The alterations in the levels of lipid profile in plasma, hepatic and renal tissues were studied. The activities of HMG CoA reductase was assayed in liver and kidney tissues of control and experimental groups of rats. The levels of lipid metabolizing enzymes such as lipoprotein lipase and lecithin cholesterol acyltransferase in the plasma and hepatic tissues were assayed.Results: Oral administration of GTF-231 significantly normalized the altered levels of lipid profile in plasma, hepatic and renal tissues. Likewise, the decreased levels of HDL-c and increased levels of LDL-c and VLDL-c in plasma of diabetic rats were normalized upon treatment with GTF. Additionally, GTF-231 treatment significantly decreased the activity HMG-CoA reductase in the liver and kidney tissues. Decreased activities of lipid metabolizing enzymes such as lipoprotein lipase and lecithin cholesterol acyltransferase in the plasma and hepatic tissues were normalized upon oral treatment with GTF-231.Conclusion: The data obtained are claimed to display synergistic, efficacious and agonistic/antagonistic actions of GTF-231 and the mixture of species in the phytochemical preparation shows better therapeutic effects at a relatively less concentration than either species on its own and the ameliorative potential of GTF-231 in diabetic dyslipidemia was comparable with metformin (200 mg/kg.b.w.).

CSA13 inhibits colitis-associated intestinal fibrosis via a formyl peptide receptor like-1 mediated HMG-CoA reductase pathway

Many Crohn’s disease (CD) patients develop intestinal strictures, which are difficult to prevent and treat. Cationic steroid antimicrobial 13 (CSA13) shares cationic nature and antimicrobial function with antimicrobial peptide cathelicidin. As many functions of cathelicidin are mediated through formyl peptide receptor-like 1 (FPRL1), we hypothesize that CSA13 mediates anti-fibrogenic effects via FPRL1. Human intestinal biopsies were used in clinical data analysis. Chronic trinitrobenzene sulfonic acid (TNBS) colitis-associated intestinal fibrosis mouse model with the administration of CSA13 was used. Colonic FPRL1 mRNA expression was positively correlated with the histology scores of inflammatory bowel disease patients. In CD patients, colonic FPRL1 mRNA was positively correlated with intestinal stricture. CSA13 administration ameliorated intestinal fibrosis without influencing intestinal microbiota. Inhibition of FPRL1, but not suppression of intestinal microbiota, reversed these protective effects of CSA13. Metabolomic analysis indicated increased fecal mevalonate levels in the TNBS-treated mice, which were reduced by the CSA13 administration. CSA13 inhibited colonic HMG-CoA reductase activity in an FPRL1-dependent manner. Mevalonate reversed the anti-fibrogenic effect of CSA13. The increased colonic FPRL1 expression is associated with severe mucosal disease activity and intestinal stricture. CSA13 inhibits intestinal fibrosis via FPRL1-dependent modulation of HMG-CoA reductase pathway.

Aspergillus terreus treated rice straw suppresses methane production and enhances feed digestibility in goats.

The objectives of this study were to test the efficacy of producing lovastatin in rice straw treated with Aspergillus terreus in larger laboratory scale following the procedure previously reported and to investigate the effectiveness of the treated rice straw containing lovastatin on methane mitigation in goats. The concentration of lovastatin in the treated rice straw was 0.69 ± 0.05g/kg dry matter (DM) rice straw. Our results showed that supplementation of lovastatin at 4.14mg/kg BW reduced methane production by 32% while improving the DM digestibility by 13% (P < 0.05) in goats fed fermented rice straw compared to those fed untreated rice straw. Populations of total methanogens and Methanobacteriales species were significantly reduced (P < 0.05) while the population of total bacteria and Ruminococcus albus were increased in the treatment group (P < 0.05). Our results demonstrated that lovastatin in the treated rice straw acted specifically on the methanogens by inhibiting the activity of HMG-CoA reductase in the methanogens' cell membrane biosynthesis pathway and thus the growth of rumen methanogens as previously reported. This study provides a simple yet practical approach to mitigate enteric methane production particularly in the developing countries which depend heavily on the use of agro-biomass such as rice straw to feed their ruminant animals.

Bioconversion of mevastatin to pravastatin by various microorganisms and its applications – A review

Hypercholesterolemia is considered to be an important risk factor in coronary heart disease. Statins has received a lot of attention in recent years due to control of cholesterol biosynthesis and level of cholesterol in the body, by inhibiting the enzyme 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase. Inhibition results in reduced levels of mevalonate in the body, leading to pleiotropic effects. Compactin and its hydroxy derivative pravastatin are natural statins and are used as hypocholesterolemic agents which are potent inhibitors of HMG-CoA reductase activity. Pravastatin was more effective drug than compactin. Various fungi and bacteria have been used for the commercial production of pravastatin. Using different strategies for improving production levels, yields have been increased more than the amount originally produced. Recently, the gene sequencing is responsible for pravastatin production has been cloned and sequenced. It has been incorporated into other fungal or bacterial species for better compactin resistant as well as for maximum bioconversion rate. This review deals with the structure and chemistry, applications, mode of action, bioconversion, and production of pravastatin. This review is an effort to compile the available information on various aspects of pravastatin.

Double emulsion‐encapsulated guggul exhibits improved in vivo hypocholesterolaemic action in rats

SummaryGuggul tree or Commiphora mukul is a small thorny herb having remarkable hypocholesterolaemic properties. Its therapeutic effects are because of its biocomponent guggulsterones, especially guggulsterone E and Z. In this research, double emulsion‐based spread was tried to improve the bioavailability of the herb guggul in in vivo rat model. The effect of the different diets with encapsulated and nonencapsulated guggul was evaluated and compared after 6 weeks, based on the final body weight and analysis of organs, serum and faeces of normal and hypercholesterolaemic (H) rats. It was evident from the results that double emulsion‐encapsulated guggul showed better control on weight of H rats (25.98% lower), inhibition of HMG CoA reductase (3.95 times less) activity and reduction in atherosclerotic index (47.2%), as compared to diet with unencapsulated guggul. Encapsulation of guggul also improved faecal excretion of bile acids, lipids and total cholesterol in H and normal rats.

Development of Wheat Bran Oil Concentrates Rich in Bioactives with Antioxidant and Hypolipidemic Properties.

Wheat bran, an abundant byproduct of the milling industry, comprises fat-soluble bioactives and fibers. In the present study, two concentrates were prepared from wheat bran oil (WBO) using silicic acid coupled with acetone (WBA) and hexane (WBH). WBA extract had enhanced color and viscosity and was enriched with fat-soluble bioactives (sterols, oryzanol-like compounds, tocopherols, and carotenoids) as evidenced from NMR and other techniques. In in vitro studies, WBA exhibited significant free radical scavenging activity, limited DNA and LDL oxidation, and inhibiting HMG-CoA reductase and lipase activity better than WBH and WBO. Further, an in vivo study with WBA 2 or 3.5% containing high fat diet ameliorated malonaldehyde (MDA) level, lipid profile, and antioxidant enzyme (SOD, catalase, GPx, and GR) activities in liver. A possible reason for this effect is downregulation of HMG-CoA reductase expression with WBA. Thus, WBA has significant potential as an ingredient in health food formulations.

HMG-CoA Reductase Inhibitory Activity of Gnetum gnemon Seed Extract and Identification of Potential Inhibitors for Lowering Cholesterol Level

Objectives: Melinjo (Gnetum gnemon) seeds have been known to have some biological properties. One of them is ant hypercholesterolemia. The present study investigated in vitro and in silico methods to predict potential antihypercholesterolemic of the Melinjo seed extracts of through HMG-CoA reductase inhibitory activity. Methods: Melinjo seed powders were successively extracted by reflux method using five solvents with gradient polarity including: n-hexane, dichloromethane, ethyl acetate and methanol. All extracts were evaluated in vitro using HMG-CoA Reductase assay kit, to analyze the inhibitory activity. Molecular docking of the phytochemical content of the seeds were carried out using Auto Dock Vina, and also Ligand Scout to analyses interaction between ligand and receptor. Results: Dichloromethane extract demonstrated the highest inhibitory activity against HMG-CoA reductase with IC50 value is 0.40 μg/mL, followed by that of ethyl acetate extract. UPLC-MS analyses showed that dichloromethane extract contained trans-resveratrol, piceid, gnetin C, gnetol, isorhapontigenin, ɛ-viniferin, gnemonol L, and gnemonol M. Molecular docking studies demonstrated that dimer of resveratrol such as gnemonol L, gnemosida, and ɛ-viniferin have better free binding energy than that of monomer. piceid, gnetin C, gnemonol L, and gnemonol M could be considered as HMG-CoA reductase inhibitor. Conclusion: Gnetum gnemon seed extract showed strong HMG-CoA reductase activity. Resveratrol dimer promises as a potential lead compound to design/synthesize anti-cholesterol. Key words: Gnetum gnemon, Melinjo, HMG-CoA Reductase, Resveratrol, Stilbene, Molecular Docking.

Regulation of hepatic hydroxy methyl glutarate – CoA reductase for controlling hypercholesterolemia in rats

Hypercholesterolemia is a major risk factor upon developing cardiovascular diseases. This study is aiming to investigate the inhibition role of quercetin on hydroxy methyl glutarate − CoA reductase activity and its gene for attenuating hypercholesterolemia. The kinetic characteristics of HMG-CoA reductase activity were evaluated on extracellular rat liver microsomes. For studying the effect of quercetin by inducing hypercholesterolemia rats by Tyloxapol (i.v.). In addition, rats were treated with different doses of quercetin according to the inhibition constant of this inhibitor. Our results showed that in quercetin rats groups plasma cholesterol, triglycerides, LDL −cholesterol and total lipids levels and hepatic (TBARS) level were significantly decreased as compared with negative control. However, plasma HDL level, hepatic total thiol level, catalase activity and total protein level significantly increased groups as compared with negative control. In addition, HMG-CoA reductase activity was decreased in quercetin groups and this confirmed in gene expression that these groups caused downregulation for HMG-CoA reductase. However, LDL receptor (LDLr) gene expression was upregulated by quercetin. Moreover, histopathological examination of rat liver showed the ameliorative effect of quercetin on hypercholesterolemic effect of triton. In conclusion, quercetin may consider as a new saving candidate for the future development of hypocholesterolemia agents.

Hypolipidemic effects of total flavonoide extracted from the leaves of Actinidiakolomikta in rats fed a high-fat diet.

Objective(s):This study was to investigate the antihyperlipidemic and antioxidant effect of total flavonoid extract from Actinidiakolomikta (TFAK) in hyperlipidemia induced by a high-fat diet.Materials and Methods:Male SD rats were randomly divided into 6 groups: normal group, model (hyperlipidemic diet) group, hyperlipedemic diet supplemented with TFAK (50, 100 and 200 mg/kg) and simvastatin (30 mg/kg) groups. The rats were administrated TFAK by oral for 28 days. Body weight, total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), superoxide dismutase (SOD), catalase(CAT), glutathione peroxidase(GSH-Px) and malondialdehyde (MDA) were measured. The atherogenic index (AI) and coronary risk index (CRI) were calculated. The activity of hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase in hepatic tissue was examined. Histopathologic changes were also checked.Results:The levels of TC, TG and LDL-c were increased in model group. Compared to the model group, TFAK reduced significantly the body weight, TC, TG, LDL-c, AI, CRI and elevated the level of HDL-c. Moreover, the activity of SOD was elevated significantly, whereas the content of MDA decreased. The activity of HMG-CoA reductase was also decreased. Morphological evaluation found that rats in model group developed a severe steatosis, but the severity of liver steatosis was ameliorated in TFAK treated groups. The possible mechanism may be associated with decrease HMG-CoA reductase activity.Conclusion:Our results suggest that TFAK exerts strong antioxidant and lipid-lowering effects, prevents hepatic fatty deposition and regulates the HMG-CoA reductase.

Regeneration of NADPH Coupled with HMG-CoA Reductase Activity Increases Squalene Synthesis in Saccharomyces cerevisiae.

Although overexpression of the tHMG1 gene is a well-known strategy for terpene synthesis in Saccharomyces cerevisiae, the optimal level for tHMG1p has not been established. In the present study, it was observed that two copies of the tHMG1 gene on a dual gene expression cassette improved squalene synthesis in laboratory strain by 16.8-fold in comparison to single-copy expression. It was also observed that tHMG1p is limited by its cofactor (NADPH), as the overexpression of NADPH regenerating genes', viz., ZWF1 and POS5 (full length and without mitochondrial presequence), has led to its increased enzyme activity. Further, it was demonstrated that overexpression of full-length POS5 has improved squalene synthesis in cytosol. Finally, when tHMG1 and full-length POS5 were co-overexpressed there was a net 27.5-fold increase in squalene when compared to control strain. These results suggest novel strategies to increase squalene accumulation in S. cerevisiae.

Copper-Catalyzed Regioselective Monodefluoroborylation of Polyfluoroalkenes en Route to Diverse Fluoroalkenes.

Monodefluoroborylation of polyfluoroalkenes has been achieved in a regioselective manner under mild conditions via copper catalysis. The method has shown an extremely broad scope of substrates, including (difluorovinyl)arenes, tetrafluoroethylene (TFE), (trifluorovinyl)arenes, and trifluoromethylated monofluoroalkenes. The choice of boron source was important for the efficient transformation of (difluorovinyl)arenes; (Bpin)2 was suitable for substrates with an electron-deficient aryl group and (Bnep)2 for those with an electron-rich aryl group. Derivatization of the (fluoroalkenyl)boronic acid esters to the corresponding potassium trifluoroborate salts has rendered the products easily isolable, which greatly improved the synthetic practicality of the monodefluoroborylation reaction. Stoichiometric experiments indicate that the fate of the regioselectivity depends on the mode of β-fluorine elimination, which depends on the substrate. Further transformation of the boryl group has allowed facile preparation of fluoroalkene derivatives as exemplified by the synthesis of a fluoroalkene mimic of atorvastatin, which potently inhibited the enzyme activity of HMG-CoA reductase.

Identification of HMG-CoA Reductase Inhibitor Active Compound in Medicinal Forest Plants

Cardiovascular disease is a leading cause of death worldwide, hypercholesterolemia is one of the causes. Three medicinal forest plants are potential natural resources to be developed as cholesterol-reducing herbal product, but scientific informations on their mechanism is still limited. The objective of this research is to explore the potency of the leaf of Jati Belanda (Guazuma ulmifolia), Jabon (Antocephalus macrophyllus), and Mindi (Melia azedarach) as inhibitor of HMG-CoA reductase (HMGR), a key enzyme in the regulation of cholesterol biosynthesis. Samples were macerated in ethanol 96% and the filtrate was partitioned using n-hexane and chloroform to obtain the ethanolic flavonoid extract. The effect of each extracts on the HMG-CoA reductase activity were analyzed using HMGR assay kit. At concentration of 10 ppm the G.ulmifolia ethanolic extract showed the highest inhibitory activity as well as pravastatin control inhibitor. The phenolic content of the ethanolic extracts of G.ulmifolia, A.macrophyllus, and M.azedarach were: 11.00, 34.83, and 13.67 mg gallic acid AE/g dried leaves, respectively. The flavonoid content of the ethanolic extracts of G.ulmifolia, A.macrophyllus, and M.azedarach were: 0.22, 0.64, and 0.78 mg QE/g dried leaves, respectively. Interestingly, G.ulmifolia extract the lowest concentration of phenolic and flavonoid content. HPLC analysis showed that all samples contain quercetin at similiar small concentrations (6.7%, 6.6%, and 7.0% for G.ulmifolia, A.macrophyllus, and M.azedarach, respectively). This indicating other active compounds may play some roles in this inhibitory action on HMG-CoA reductase activity. Further identification using LC-MS/MS showed that G.ulmifolia flavonoid extract contained an unidetified coumpound with molecural weight of 380.0723 Da.

Cholesterol-lowering effect of Aralia elata (Miq.) Seem via the activation of SREBP-2 and the LDL receptor

BackgroundHyperlipidemia causes arteriosclerosis, a risk factor for coronary heart disease. Prevention of hyperlipidemia by improving dietary habits has recently attracted attention. In this regard, we investigated whether Aralia elata (Miq.) Seem (AE) extract inhibits hepatic cholesterol accumulation and modulate the cellular signaling pathway. MethodsTo determine AE's cholesterol regulating mechanism, we measured cholesterol level, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity and cholesterol regulating-related gene expression in HepG2 cells and in high-fat diet (HFD)-induced mice using ELISA and RT-PCR assay. ResultsThe AE extract reduced cholesterol levels and HMG-CoA reductase activity in hepatocellular carcinoma HepG2 cells. In addition, it also reduced the plasma cholesterol concentrations in HFD-induced mice. Furthermore, the AE extract increased the gene expression of the LDL-receptor (LDL-R); sterol-regulatory-element binding protein-2 (SREBP-2); ATP-binding cassette, sub-family A, member 1 (ABCA1); and scavenger receptor class B member 1 (SR-B1) in a dose-dependent manner. However, the AE extract did not affect the gene expression of acetyl-coenzyme A acetyltransferase (ACAT) in either the HepG2 cells or mice. ConclusionWe demonstrated that the AE extract activated genes related to cholesterol metabolism, such as SREBP-2 and LDL-R, which resulted in hypocholesterolemic activities.

Evaluation of DNA damage in Wistar rat tissues with hyperlipidemia induced by tyloxapol

Hyperlipidemia is characterized by high levels of plasma triglycerides and LDL-cholesterol, accompanied by reduced HDL-cholesterol levels, and is often associated with an increased risk of cardiovascular diseases. However, few studies have shown the effects of hyperlipidemia on genomic stability. The aim of this study was to evaluate DNA damage provided by tyloxapol induced hyperlipidemia. Tyloxapol, a non-ionic surfactant, which increases the activity of the enzyme HMG-CoA reductase and decreases clearance of lipoproteins, was used to induce hyperlipidemia in Wistar rats. Genomic instability was assessed using the comet assay which evaluates DNA strand breaks in several tissues, and the micronucleus assay in bone marrow to detect chromosomal mutagenicity for clastogenic and/or aneugenic effects. Biochemical analyses confirmed hyperlipidemia in tyloxapol-treated rats, accompanied by hyperglycemia. Higher creatinine and urea levels were observed, suggesting kidney injury. The comet assay indicated increased DNA damage in blood, liver, and kidney, but not in brain tissue. However, no increase in micronucleus frequency was observed, indicating lack of mutagenic effects. Simvastatin, used as lipid lowering drug, decreased cholesterol and triglycerides in rats treated with tyloxapol. Those findings indicate that tyloxapol-induced hyperlipidemia is able to increase genomic instability, which is associated with higher cancer risk. Therefore, this surfactant might be used in models to evaluate new hypolipidemic drugs with associated chemopreventive properties.

Investigating The Role of Novel Bioactive Compound from Ficus Virens Ait on Cigarette Smoke Induced Oxidative Stress and Hyperlipidemia in Rats.

The present study is premeditated to extenuate the role of Ficus virens extract and its bioactive compound on cigarette smoke, an important risk factor for CVD, induced oxidative stress and hyperlipidemia. Cigarette smoke (CS) exposure to rats results in significant loss of body weight and increases blood carbon monoxide saturation (carboxyhemoglobin), nicotine, plasma TC, TG, and LDL-C levels but reduced level of antiatherogenic HDL-C. Moreover, owing to substantial oxidative stress generated in rats due to cigarette smoke a significant increase in plasma and erythrocytes lipid peroxidation products were observed which was well correlated with increase in ex-vivo BDC (48%) and MDA (53%) level (p < 0.001). Simultaneous administration of FVBM extract at higher dose (100 mg/rat) and F18 (n-Octadecanyl-O-α-D-glucopyranosyl(6'→1'')-O-α-D-glucopyranoside) compound to CS-exposed rats effectively blocked the increase in plasma lipid and lipoprotein levels (p < 0.001) which was due to the marked suppression in the hepatic HMG-CoA reductase activity (p < 0.001) and significantly inhibit the lipid peroxidation process thus preventing the membrane damage, LDL oxidation, and in turn subsequent atherosclerosis. Thus, the results clearly demonstrated the protective role of FVBM extract and F18 compound in risk factor induced cardiovascular disease.

Hypocholesterolemic activity of cornelian cherry (Cornus mas L.) fruits

Background Lipid profile disturbances are important risk factors for cardiovascular events in patients with diabetes mellitus and finding safe and multifaceted agents is persuaded in this regard. This study aimed to evaluate the effect of cornelian cherry dried powder (CCDP) on serum lipid profile as well as liver antioxidant capacity, HMG-CoA reductase level and activity, and LDL receptor level in streptozotocin-induced diabetic rats. Methods Forty-eight male adult Wistar rats were randomly allocated into eight equal groups and were treated for 4 weeks as follows: negative control (normal rats, basic diet); positive control (diabetic rats, basic diet), T1 to T4 groups: diabetic rats fed with basic diet containing 0.25, 0.5, 1 and 2 g/ 100 g BW CCDP, respectively; T5: diabetic rats fed with basic diet plus 10 mg/kg lovastatin in drinking water and T6: normal rats fed with basic diet containing 1 g/ 100 g BW CCDP. Results Administration of CCDP had no significant effect on serum glucose levels in diabetic rats however decreased total cholesterol, low-density lipoprotein cholesterol (LDL-C) and increased high-density lipoprotein cholesterol (HDL-C) levels and liver antioxidant capacity as compared to positive control rats (p<0.05). Although HMG-CoA reductase level showed a significant decrease only in T3 group, its activity was reduced in all diabetic CCDP and lovastatin-treated groups as compared to positive control. LDL receptor level remained statistically the same among positive control and CCDP-treated groups. Conclusions In conclusion, the present study confirms hypocholesterolemic effect of CCDP in diabetic rats and demonstrated that this effect was at least partly due to inhibition of liver HMG-CoA reductase activity.

LDL-C levels in older people: Cholesterol homeostasis and the free radical theory of ageing converge

The cardiovascular disease (CVD) risk factor, low density lipoprotein cholesterol (LDL-C) increases with age, up until the midpoint of life in males and females. However, LDL-C can decrease with age in older men and women. Intriguingly, a recent systematic review also revealed an inverse association between LDL-C levels and cardiovascular mortality in older people; low levels of LDL-C were associated with reduced risk of mortality. Such findings are puzzling and require a biological explanation. In this paper a hypothesis is proposed to explain these observations. We hypothesize that the free radical theory of ageing (FRTA) together with disrupted cholesterol homeostasis can account for these observations. Based on this hypothesis, dysregulated hepatic cholesterol homeostasis in older people is characterised by two distinct metabolic states. The first state accounts for an older person who has elevated plasma LDL-C. This state is underpinned by the FRTA which suggests there is a decrease in cellular antioxidant capacity with age. This deficiency enables hepatic reactive oxidative species (ROS) to induce the total activation of HMG-CoA reductase, the key rate limiting enzyme in cholesterol biosynthesis. An increase in cholesterol synthesis elicits a corresponding rise in LDL-C, due to the downregulation of LDL receptor synthesis, and increased production of very low density lipoprotein cholesterol (VLDL-C). In the second state of dysregulation, ROS also trigger the total activation of HMG-CoA reductase. However, due to an age associated decrease in the activity of cholesterol-esterifying enzyme, acyl CoA: cholesterol acyltransferase, there is restricted conversion of excess free cholesterol (FC) to cholesterol esters. Consequently, the secretion of VLDL-C drops, and there is a corresponding decrease in LDL-C. As intracellular levels of FC accumulate, this state progresses to a pathophysiological condition akin to nonalcoholic fatty liver disease. It is our conjecture this deleterious state has the potential to account for the inverse association between LDL-C level and CVD risk observed in older people.

DENV up-regulates the HMG-CoA reductase activity through the impairment of AMPK phosphorylation: A potential antiviral target.

Dengue is the most common mosquito-borne viral disease in humans. Changes of lipid-related metabolites in endoplasmic reticulum of dengue virus (DENV) infected cells have been associated with replicative complexes formation. Previously, we reported that DENV infection inhibits HMGCR phosphorylation generating a cholesterol-enriched cellular environment in order to favor viral replication. In this work, using enzymatic assays, ELISA, and WB we found a significant higher activity of HMGCR in DENV infected cells, associated with the inactivation of AMPK. AMPK activation by metformin declined the HMGCR activity suggesting that AMPK inactivation mediates the enhanced activity of HMGCR. A reduction on AMPK phosphorylation activity was observed in DENV infected cells at 12 and 24 hpi. HMGCR and cholesterol co-localized with viral proteins NS3, NS4A and E, suggesting a role for HMGCR and AMPK activity in the formation of DENV replicative complexes. Furthermore, metformin and lovastatin (HMGCR inhibitor) altered this co-localization as well as replicative complexes formation supporting that active HMGCR is required for replicative complexes formation. In agreement, metformin prompted a significant dose-dependent antiviral effect in DENV infected cells, while compound C (AMPK inhibitor) augmented the viral genome copies and the percentage of infected cells. The PP2A activity, the main modulating phosphatase of HMGCR, was not affected by DENV infection. These data demonstrate that the elevated activity of HMGCR observed in DENV infected cells is mediated through AMPK inhibition and not by increase in PP2A activity. Interestingly, the inhibition of this phosphatase showed an antiviral effect in an HMGCR-independent manner. These results suggest that DENV infection increases HMGCR activity through AMPK inactivation leading to higher cholesterol levels in endoplasmic reticulum necessary for replicative complexes formation. This work provides new information about the mechanisms involved in host lipid metabolism during DENV replicative cycle and identifies new potential antiviral targets for DENV replication.

Simvastatin treatment aggravates the glucocorticoid insufficiency associated with hypocholesterolemia in mice

Background and aimsStatin treatment disrupts HMG-CoA reductase-mediated endogenous cholesterol synthesis and lowers plasma LDL-cholesterol levels. Although statin treatment can theoretically impair adrenal steroid hormone synthesis, thus far, no effect on glucocorticoid output has been described, as LDL-cholesterol levels usually remain within the physiological range. However, novel statin-based treatment regimens that dramatically decrease LDL-cholesterol levels are currently employed. Here, we assessed whether inhibition of cholesterol synthesis under these relatively hypocholesterolemic conditions may alter adrenal glucocorticoid output. MethodsHypocholesterolemic apolipoprotein A1 (apoA1) knockout mice were administered high dose simvastatin twice daily for 3 days. ResultsSimvastatin treatment did not change plasma cholesterol levels or modify the adrenal expression levels of genes involved in cholesterol metabolism. However, simvastatin treatment lowered basal plasma levels of the primary glucocorticoid corticosterone (−62%; p < 0.05). Upon injection with adrenocorticotropic hormone, control-treated apoA1 knockout mice already showed only a mild increase in plasma corticosterone levels, indicative of relative glucocorticoid insufficiency. Importantly, simvastatin treatment further diminished the adrenal glucocorticoid response to adrenocorticotropic hormone exposure (two-way ANOVA p < 0.05 for treatment). Peak corticosterone levels were 49% lower (p < 0.01) upon simvastatin treatment. ConclusionsWe have shown that simvastatin treatment aggravates the glucocorticoid insufficiency associated with hypocholesterolemia in mice. Our data suggest that (1) HMG-CoA reductase activity controls the adrenal steroidogenic capacity under hypocholesterolemic conditions and (2) imply that it might be important to monitor adrenal function in humans subjected to statin-based treatments aimed at achieving sub-physiological LDL-cholesterol levels, as these may potentially execute a negative impact on the glucocorticoid function in humans.

Treatment with the natural FXR agonist chenodeoxycholic acid reduces clearance of plasma LDL whilst decreasing circulating PCSK9, lipoprotein(a) and apolipoprotein C-III.

The natural farnesoid X receptor (FXR) agonist chenodeoxycholic acid (CDCA) suppresses hepatic cholesterol and bile acid synthesis and reduces biliary cholesterol secretion and triglyceride production. Animal studies have shown that bile acids downregulate hepatic LDL receptors (LDLRs); however, information on LDL metabolism in humans is limited. Kinetics of autologous 125 I-LDL were determined in 12 male subjects at baseline and during treatment with CDCA (15 mg kg-1 day-1 ). In seven patients with gallstones treated with CDCA for 3 weeks before cholecystectomy, liver biopsies were collected and analysed for enzyme activities and for specific LDLR binding. Serum samples obtained before treatment and at surgery were analysed for markers of lipid metabolism, lipoproteins and the LDLR modulator proprotein convertase subtilisin/kexin type 9 (PCSK9). Chenodeoxycholic acid treatment increased plasma LDL cholesterol by ~10% as a result of reduced clearance of plasma LDL-apolipoprotein (apo)B; LDL production was somewhat reduced. The reduction in LDL clearance occurred within 1 day after initiation of treatment. In CDCA-treated patients with gallstones, hepatic microsomal cholesterol 7α-hydroxylase and HMG-CoA reductase activities were reduced by 83% and 54%, respectively, and specific LDLR binding was reduced by 20%. During treatment, serum levels of fibroblast growth factor 19 and total and LDL cholesterol increased, whereas levels of 7α-hydroxy-4-cholesten-3-one, lathosterol, PCSK9, apoA-I, apoC-III, lipoprotein(a), triglycerides and insulin were reduced. Chenodeoxycholic acid has a broad influence on lipid metabolism, including reducing plasma clearance of LDL. The reduction in circulating PCSK9 may dampen its effect on hepatic LDLRs and plasma LDL cholesterol. Further studies of the effects of other FXR agonists on cholesterol metabolism in humans seem warranted, considering the renewed interest for such therapy in liver disease and diabetes.