SREBP2 mediates the modulation of intestinal NPC1L1 expression by curcumin

Targeted Degradation of PCSK9 In Vivo by Autophagy-Tethering Compounds

Proprotein convertase subtilisin/kexin type-9 (PCSK9), a secreted protein that is synthesized and spontaneously cleaved in the endoplasmic reticulum, has become a hot lipid-lowering target chased by pharmaceutical companies in recent years. Autophagosome-tethering compounds (ATTECs) represent a new strategy to degrade targeted biomolecules. Here, we designed and synthesized PCSK9·ATTECs that are capable of lowering PCSK9 levels via autophagy in vivo, providing the first report of the degradation of a secreted protein by ATTECs. OY3, one of the PCSK9·ATTECs synthesized, shows greater potency to reduce plasma low-density lipoprotein cholesterol (LDL-C) levels and improve atherosclerosis symptoms than treatment with the same dose of simvastatin. OY3 also significantly reduces the high expression of PCSK9 caused by simvastatin administration in atherosclerosis model mice and subsequently increases the level of low-density lipoprotein receptor, promoting simvastatin to clear plasma LDL-C and alleviate atherosclerosis symptoms. Thus, we developed a new candidate compound to treat atherosclerosis that could also promote statin therapy.

Curcumin protects against bisphenol A-induced hepatic steatosis by inhibiting cholesterol absorption and synthesis in CD-1 mice

Curcumin is a polyphenol extracted from the rhizome of turmeric, and our previous research showed that curcumin inhibited cholesterol absorption and had cholesterol-lowering effect. Bisphenol A (BPA), a common plasticizer, is widely used in the manufacture of food packaging and is associated with non-alcoholic fatty liver disease (NAFLD). We hypothesized that curcumin could protect against BPA-induced hepatic steatosis by inhibiting cholesterol absorption and synthesis. Male CD-1 mice fed BPA-contaminated diet with or without curcumin for 24 weeks were used to test our hypothesis. We found that chronic low-dose BPA exposure significantly increased the levels of serum triglyceride (TG), total cholesterol (TC), and low-density lipoprotein cholesterol and the contents of liver TG and TC, resulting in liver fat accumulation and hepatic steatosis while curcumin supplementation could alleviate BPA-induced dyslipidemia and hepatic steatosis. Moreover, the anti-steatosis and cholesterol-lowering effects of curcumin against BPA coincided with a significant reduction in intestinal cholesterol absorption and liver cholesterol synthesis, which was modulated by suppressing the expression of sterol regulatory element-binding protein-2 (SREBP-2), Niemann-Pick C1-like 1 (NPC1L1), and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) in the small intestine and liver. In addition, the expression levels of liver lipogenic genes such as liver X receptor alpha (LXRα), SREBP-1c, acetyl-CoA carboxylase 1 (ACC1), and ACC2 were also markedly down-regulated by curcumin. Overall, our findings indicated that curcumin inhibited BPA-induced intestinal cholesterol absorption and liver cholesterol synthesis by suppressing SREBP-2, NPC1L1, and HMGCR expression, subsequently reducing liver cholesterol accumulation and fat synthesis, thereby preventing hepatic steatosis and NAFLD.

Lipid-Lowering Nutraceuticals for an Integrative Approach to Dyslipidemia

Dyslipidemia is a treatable risk factor for atherosclerotic cardiovascular disease that can be addressed through lifestyle changes and/or lipid-lowering therapies. Adherence to statins can be a clinical challenge in some patients due to statin-associated muscle symptoms and other side effects. There is a growing interest in integrative cardiology and nutraceuticals in the management of dyslipidemia, as some patients desire or are actively seeking a more natural approach. These agents have been used in patients with and without established atherosclerotic cardiovascular disease. We provide an updated review of the evidence on many new and emerging nutraceuticals. We describe the mechanism of action, lipid-lowering effects, and side effects of many nutraceuticals, including red yeast rice, bergamot and others.

The role of cholesterol and mitochondrial bioenergetics in activation of the inflammasome in IBD

Inflammatory Bowel Disease (IBD) is characterized by a loss of intestinal barrier function caused by an aberrant interaction between the immune response and the gut microbiota. In IBD, imbalance in cholesterol homeostasis and mitochondrial bioenergetics have been identified as essential events for activating the inflammasome-mediated response. Mitochondrial alterations, such as reduced respiratory complex activities and reduced production of tricarboxylic acid (TCA) cycle intermediates (e.g., citric acid, fumarate, isocitric acid, malate, pyruvate, and succinate) have been described in in vitro and clinical studies. Under inflammatory conditions, mitochondrial architecture in intestinal epithelial cells is dysmorphic, with cristae destruction and high dynamin-related protein 1 (DRP1)-dependent fission. Likewise, these alterations in mitochondrial morphology and bioenergetics promote metabolic shifts towards glycolysis and down-regulation of antioxidant Nuclear erythroid 2-related factor 2 (Nrf2)/Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) signaling. Although the mechanisms underlying the mitochondrial dysfunction during mucosal inflammation are not fully understood at present, metabolic intermediates and cholesterol may act as signals activating the NLRP3 inflammasome in IBD. Notably, dietary phytochemicals exhibit protective effects against cholesterol imbalance and mitochondrial function alterations to maintain gastrointestinal mucosal renewal in vitro and in vivo conditions. Here, we discuss the role of cholesterol and mitochondrial metabolism in IBD, highlighting the therapeutic potential of dietary phytochemicals, restoring intestinal metabolism and function.

Recent advances in the screening methods of NPC1L1 inhibitors

NPC1L1 is a crucial protein involved in sterol lipid absorption and has been shown to play an important role in intestinal cholesterol absorption. Hypercholesterolemia is a significant risk factor for cardiovascular diseases such as coronary heart disease. Screening of NPC1L1 inhibitors is critical for gaining a full understanding of lipid metabolism, developing new cholesterol-lowering medicines, and treating cardiovascular diseases. This work summarized existing methodologies for screening NPC1L1 inhibitors and evaluated their challenges, and will assist the development of novel cholesterol-lowering medications and therapeutic strategies for hypercholesterolemia and other cholesterol-related metabolic disorders.

Nutraceuticals in Paediatric Patients with Dyslipidaemia

Coronary heart disease (CHD) is the main cause of death and morbidity in the world. Childhood is a critical period during which atherosclerosis may begin to develop; in the presence of familial hypercholesterolaemia (FH), the lifelong elevation of LDL cholesterol levels greatly accelerates atherosclerosis. Lowering LDL-C levels is associated with a well-documented reduction in cardiovascular disease risk. Current guidelines support the dietary and lifestyle approach as the primary strategy of intervention in children and adolescents with FH. Nutraceuticals (functional foods or dietary supplements of plant or microbial origin) are included in the EU guidelines as lifestyle interventions and may provide an additional contribution in reducing LDL levels when pharmacological therapy is not yet indicated. Meta-analyses of randomised clinical trials have demonstrated that the same nutraceuticals improve lipid profile, including lowering LDL-C, total cholesterol and triglyceride levels. In this narrative review, starting from current scientific evidence, we analyse the benefits and limitations of the nutraceuticals in children and adolescents with dyslipidaemia, and we try to evaluate their use and safety in clinical practice.

Effect of NPC1L1 polymorphism on warfarin stable dose in Chinese patients under heart valve replacement surgery

Warfarin is the most often anticoagulant choice for preventable thromboembolism. Notably, vitamin K plays a vital role in the process of warfarin's anticoagulant effect. Therefore, we presume NPC1L1, a key transporter of vitamin K (VK) intestinal absorption, may modulate the anticoagulant effect of warfarin. Studies have shown that NPC1L1(-762T>C, rs2073548) and p53 (P72R, rs1042522) variations are implicated in influencing NPC1L1 expression. This study aimed to assess the association between these two variants and warfarin stable dose (WSD). A two-stage extreme phenotype design was used to explore the influence of these two variants (rs2073548, rs1042522) on WSD variance in 655 Chinese patients undergoing heart valve replacement surgery. NPC1L1 rs2073548, p53 rs1042522, VKORC1 rs9923231 and CYP2C9*1/*3 polymorphisms were genotyped by polymerase chain reaction-restriction fragment polymorphism (PCR-RFLP) or Sanger sequencing, respectively. WSD was identified when target monitoring international normalized ratio (INR) value at 2.0-3.0. In the discovery phase, NPC1L1 rs2073548 A allele carriers occupied a significantly higher rate in the low dose group (P = .019). However, in the validation group, warfarin dosage in patients with the rs2073548 AA, AG and GG genotypes were 2.91 ± 0.97 mg/day, 3.02 ± 1.00 mg/day and 3.00 ± 1.06 mg/day, respectively. Multiple linear regression analysis results suggested that CYP2C9*3 and VKORC1 rs9923231, but not NPC1L1 rs2073548, were independent predictors of WSD in Chinese heart valve replacement (HVR) surgical patients.

The Anti-Obesity Effect of Traditional Chinese Medicine on Lipid Metabolism

With the improvement of living conditions and the popularity of unhealthy eating and living habits, obesity is becoming a global epidemic. Obesity is now recognized as a disease that not only increases the risk of metabolic diseases such as type 2 diabetes (T2D), non-alcoholic fatty liver disease (NAFLD), cardiovascular disease (CVD), and cancer but also negatively affects longevity and the quality of life. The traditional Chinese medicines (TCMs) are highly enriched in bioactive compounds and have been used for the treatment of obesity and obesity-related metabolic diseases over a long period of time. In this review, we selected the most commonly used anti-obesity or anti-hyperlipidemia TCMs and, where known, their major bioactive compounds. We then summarized their multi-target molecular mechanisms, specifically focusing on lipid metabolism, including the modulation of lipid absorption, reduction of lipid synthesis, and increase of lipid decomposition and lipid transportation, as well as the regulation of appetite. This review produces a current and comprehensive understanding of integrative and systematic mechanisms for the use of TCMs for anti-obesity. We also advocate taking advantage of TCMs as another therapy for interventions on obesity-related diseases, as well as stressing the fact that more is needed to be done, scientifically, to determine the active compounds and modes of action of the TCMs.

Recent Molecular Mechanisms and Beneficial Effects of Phytochemicals and Plant-Based Whole Foods in Reducing LDL-C and Preventing Cardiovascular Disease

Abnormal lipid metabolism leads to the development of hyperlipidemia, a common cause of multiple chronic disorders, including cardiovascular disease (CVD), obesity, diabetes, and cerebrovascular disease. Low-density lipoprotein cholesterol (LDL-C) currently remains the primary target for treatment of hyperlipidemia. Despite the advancement of treatment and prevention of hyperlipidemia, medications used to manage hyperlipidemia are limited to allopathic drugs, which present certain limitations and adverse effects. Increasing evidence indicates that utilization of phytochemicals and plant-based whole foods is an alternative and promising strategy to prevent hyperlipidemia and CVD. The current review focuses on phytochemicals and their pharmacological mode of actions for the regulation of LDL-C and prevention of CVD. The important molecular mechanisms illustrated in detail in this review include elevation of reverse cholesterol transport, inhibition of intestinal cholesterol absorption, acceleration of cholesterol excretion in the liver, and reduction of cholesterol synthesis. Moreover, the beneficial effects of plant-based whole foods, such as fresh fruits, vegetables, dried nuts, flax seeds, whole grains, peas, beans, vegan diets, and dietary fibers in LDL-C reduction and cardiovascular health are summarized. This review concludes that phytochemicals and plant-based whole foods can reduce LDL-C levels and lower the risk for CVD.

NPC1L1-dependent transport of 27-alkyne cholesterol in intestinal epithelial cells

Niemann-Pick C1 Like-1 (NPC1L1) mediates the uptake of micellar cholesterol by intestinal epithelial cells and is the molecular target of the cholesterol-lowering drug ezetimibe (EZE). The detailed mechanisms responsible for intracellular shuttling of micellar cholesterol are not fully understood due to the lack of a suitable NPC1L1 substrate that can be traced by fluorescence imaging and biochemical methods. 27-Alkyne cholesterol has been previously shown to serve as a substrate for different cellular processes similar to native cholesterol. However, it is not known whether alkyne cholesterol is absorbed via an NPC1L1-dependent pathway. We aimed to determine whether alkyne cholesterol is a substrate for NPC1L1 in intestinal cells. Human intestinal epithelial Caco2 cells were incubated with micelles containing alkyne cholesterol in the presence or absence of EZE. Small intestinal closed loops in C57BL/6J mice were injected with micelles containing alkyne cholesterol with or without EZE. Alkyne cholesterol esterification in Caco2 cells was significantly inhibited by EZE and by inhibitor of clathrin-mediated endocytosis Pitstop 2. The esterification was similarly reduced by inhibitors of the acyl-CoA cholesterol acyltransferase (ACAT). Alkyne cholesterol efficiently labeled the apical membrane of Caco2 cells and the amount retained on the membrane was significantly increased by EZE as judged by accessibility to exogenous cholesterol oxidase. In mouse small intestine, the presence of EZE reduced total alkyne cholesterol uptake by ∼75%. These data show that alkyne cholesterol acts as a substrate for NPC1L1 and may serve as a nonradioactive tracer to measure cholesterol absorption in both in vitro and in vivo models.

Curcumin inhibits the proteolytic process of SREBP-2 by first inhibiting the expression of S1P rather than directly inhibiting SREBP-2 expression

Many studies have demonstrated that curcumin can downregulate mRNA levels of sterol regulatory element-binding proteins (SREBP-2); however, our study did not find similar results. This study was designed to demonstrate that curcumin inhibits the proteolytic process of SREBP-2 by first inhibiting the expression of membrane-bound transcription factor site-1 protease (S1P) rather than directly inhibiting SREBP-2 expression. After curcumin treatment, Caco-2 cells were collected to observe the dose- and time-dependent dynamics of precursor and mature SREBP-2, transcription factor-specific protein 1 (SP-1), and SREBP cleavage-activating protein (SCAP). After curcumin treatment, SREBP-2 distribution was detected in the cells and S1P protein expression was examined. Curcumin could downregulate mRNA levels of SREBP2, SP-1 and SCAP, but it did not simultaneously downregulate the expression of precursor SREBP-2 (pSREBP-2) and SCAP. Curcumin can inhibit the proteolytic process of SREBP-2, reduce the production of mature SREBP-2 (mSREBP-2), and change the cellular distribution of SREBP-2. The inhibitory effect of curcumin on SP-1 protein expression is short-acting. Curcumin could downregulate the mRNA and protein expression of S1P, but has no obvious inhibitory effect on the mRNA and protein expression of S2P (site-2 protease). Curcumin can inhibit the SREBP-2 proteolytic process to reduce mSREBP-2 which functions as a transcription factor, affecting the regulation of cholesterol metabolism-related genes. Curcumin does not directly inhibit the expression of mSREBP-2 protein, and it has no such inhibitory effect for at least a short period of time, although curcumin does reduce the amount of mSREBP-2 protein. S1P is a key protease in the hydrolysis of pSREBP-2 into mSREBP-2. Therefore, curcumin may decrease the amount of mSREBP-2 by directly inhibiting the expression of S1P mRNA and protein.

Novel Lactobacillus reuteri HI120 Affects Lipid Metabolism in C57BL/6 Obese Mice

Intestinal probiotics are a primary focus area of current medical research. Probiotics such as bifidobacteria and lactobacilli can positively impact obesity and other metabolic diseases by directly or indirectly affecting lipid metabolism. However, the precise mechanisms of these effects remain unclear. In our previous work, the novel strain Lactobacillus reuteri HI120 was isolated and identified. HI120 expresses high levels of linoleic isomerase, resulting in the production of large amounts of conjugated linoleic acid (CLA) when mixed with linoleic acid (LA). As HI120 can efficiently transform LA into CLA, the effect of HI120 on the lipid metabolism in C57BL/6 obese mice was studied and the underlying molecular mechanism was explored in vitro. The results revealed no significant change in the diet, body weight, and serum triglyceride levels in mice. However, serum cholesterol levels were significantly decreased. The underlying mechanism may involve a CLA-mediated reduction in the gene expression levels of NPC1L1, SREBP-2, and HMG-CR, resulting in reduced cholesterol synthesis and absorption. Thus, HI120 can be developed as a potential probiotic formulation. After oral administration, LA from certain food sources can be converted into CLA in the human intestine to contribute to the prevention and treatment of obesity and hyperlipidemia.

The intestinal microbiota regulates host cholesterol homeostasis

BACKGROUND

Management of blood cholesterol is a major focus of efforts to prevent cardiovascular diseases. The objective of this study was to investigate how the gut microbiota affects host cholesterol homeostasis at the organism scale.

RESULTS

We depleted the intestinal microbiota of hypercholesterolemic female Apoe^-/- mice using broad-spectrum antibiotics. Measurement of plasma cholesterol levels as well as cholesterol synthesis and fluxes by complementary approaches showed that the intestinal microbiota strongly regulates plasma cholesterol level, hepatic cholesterol synthesis, and enterohepatic circulation. Moreover, transplant of the microbiota from humans harboring elevated plasma cholesterol levels to recipient mice induced a phenotype of high plasma cholesterol levels in association with a low hepatic cholesterol synthesis and high intestinal absorption pattern. Recipient mice phenotypes correlated with several specific bacterial phylotypes affiliated to Betaproteobacteria, Alistipes, Bacteroides, and Barnesiella taxa.

CONCLUSIONS

These results indicate that the intestinal microbiota determines the circulating cholesterol level and may thus represent a novel therapeutic target in the management of dyslipidemia and cardiovascular diseases.

Mechanisms of Niemann-Pick type C1 Like 1 protein degradation in intestinal epithelial cells

Intestinal Niemann-Pick C1 Like 1 (NPC1L1) protein plays a key role in cholesterol absorption. A decrease in NPC1L1 expression has been implicated in lowering plasma cholesterol and mitigating the risk for coronary heart disease. Little is known about the mechanisms responsible for NPC1L1 protein degradation that upon activation may lead to a reduction in NPC1L1 protein levels in intestinal epithelial cells (IECs). In current studies, the human intestinal Caco-2 and HuTu-80 cell lines expressing NPC1L1-hemagglutinin fusion protein were used to investigate the mechanisms of NPC1L1 protein degradation. Incubation with the proteasome inhibitors MG-132 and lactacystin (10 μM, 24 h) significantly increased NPC1L1 protein levels in IECs. Also, the inhibition of the lysosomal pathway with bafilomycin A1 (80 nM, 24 h) resulted in a significant increase in NPC1L1 protein levels. Immunoprecipitation studies showed that NPC1L1 protein is both a poly- and monoubiquinated polypeptide and that the inhibition of the proteasomal pathway remarkably increased the level of the polyubiquinated NPC1L1. The surface expression of NPC1L1 was increased by the inhibition of both proteasomal and lysosomal pathways. Furthermore, the pharmacological inhibition of mitogen-activated protein kinase pathway (PD-98059, 15 μM, 24 h) and siRNA silencing of ERK1/2 resulted in a significant decrease in NPC1L1 protein levels in IECs. In conclusion, our results showed that basal level of intestinal cholesterol transporter NPC1L1 protein is modulated by both ubiquitin proteasome- and lysosome-dependent degradation as well as by ERK1/2-dependent pathway. The modulation of these pathways may provide novel clues for therapeutic intervention to inhibit cholesterol absorption and lower plasma cholesterol.

Curcumin, Cardiometabolic Health and Dementia

Current research indicates curcumin [diferuloylmethane; a polyphenolic compound isolated from the rhizomes of the dietary spice turmeric (Curcuma longa)] exerts a beneficial effect on health which may be partly attributable to its anti-oxidative and anti-inflammatory properties. The aim of this review is to examine potential mechanisms of the actions of curcumin in both animal and human studies. Curcumin modulates relevant molecular target pathways to improve glucose and lipid metabolism, suppress inflammation, stimulate antioxidant enzymes, facilitate insulin signalling and reduce gut permeability. Curcumin also inhibits Aβ and tau accumulation in animal models and enhances mitochondria and synaptic function. In conclusion, in high-dose animal studies and in vitro, curcumin exerts a potential beneficial effect on cardiometabolic disease. However, human studies are relatively unconvincing. More intervention studies should be conducted with the new curcumin formulation with improved oral bioavailability.

Add-on therapy with traditional Chinese medicine: An efficacious approach for lipid metabolism disorders

Add-on therapy with traditional Chinese medicine (TCM) has been extensively researched in the intractable diseases, such as asthma, cancer, and Alzheimer's disease. As an entirely new concept, add-on therapy of TCM has been also used to prevent and treat hyperlipidemia via lowering cholesterol level. However, the efficacy of add-on therapy with TCM for mediating lipid metabolism disorders remains controversial. In this review, we summarize and provide strong evidence that add-on therapy of TCM as a novel approach is efficacious and safe for hyperlipidemia associated diseases based on the mediation of lipid metabolism disorders.

Gastrointestinal interactions, absorption, splanchnic metabolism and pharmacokinetics of orally ingested phenolic compounds

The positive health effects of phenolic compounds (PCs) have been extensively reported in the literature. An understanding of their bioaccessibility and bioavailability is essential for the elucidation of their health benefits. Before reaching circulation and exerting bioactions in target tissues, numerous interactions take place before and during digestion with either the plant or host's macromolecules that directly impact the organism and modulate their own bioaccessibility and bioavailability. The present work is focused on the gastrointestinal (GI) interactions that are relevant to the absorption and metabolism of PCs and how these interactions impact their pharmacokinetic profiles. Non-digestible cell wall components (fiber) interact intimately with PCs and delay their absorption in the small intestine, instead carrying them to the large intestine. PCs not bound to fiber interact with digestible nutrients in the bolus where they interfere with the digestion and absorption of proteins, carbohydrates, lipids, cholesterol, bile salts and micronutrients through the inhibition of digestive enzymes and enterocyte transporters and the disruption of micelle formation. PCs internalized by enterocytes may reach circulation (through transcellular or paracellular transport), be effluxed back into the lumen (P-glycoprotein, P-gp) or be metabolized by phase I and phase II enzymes. Some PCs can inhibit P-gp or phase I/II enzymes, which can potentially lead to drug-nutrient interactions. The absorption and pharmacokinetic parameters are modified by all of the interactions within the digestive tract and by the presence of other PCs. Undesirable interactions have promoted the development of nanotechnological approaches to promote the bioaccessibility, bioavailability, and bioefficacy of PCs.

Nutraceutical approaches to metabolic syndrome

Metabolic Syndrome (MetS), affecting at least 30% of adults in the Western World, is characterized by three out of five variables, from high triglycerides, to elevated waist circumference and blood pressure. MetS is not characterized by elevated cholesterolemia, but is rather the consequence of a complex interaction of factors generally leading to increased insulin resistance. Drug treatments are of difficult handling, whereas well-characterized nutraceuticals may offer an effective alternative. Among these, functional foods, e.g. plant proteins, have been shown to improve insulin resistance and reduce triglyceride secretion. Pro- and pre-biotics, that are able to modify intestinal microbiome, reduce absorption of specific nutrients and improve the metabolic handling of energy-rich foods. Finally, specific nutraceuticals have proven to be of benefit, in particular, red-yeast rice, berberine, curcumin as well as vitamin D. All these can improve lipid handling by the liver as well as ameliorate insulin resistance. While lifestyle approaches, such as with the Mediterranean diet, may prove to be too complex for the single patient, better knowledge of selected nutraceuticals and more appropriate formulations leading to improved bioavailability will certainly widen the use of these agents, already in large use for the management of these very frequent patient groups. Key messages Functional foods, e.g. plant proteins, improve insulin resistance. Pro- and pre-biotics improve the metabolic handling of energy-rich foods. Nutraceutical can offer a significant help in handling MetS patients being part of lifestyle recommendations.

Lipid-lowering nutraceuticals in clinical practice: position paper from an International Lipid Expert Panel

In recent years, there has been growing interest in the possible use of nutraceuticals to improve and optimize dyslipidemia control and therapy. Based on the data from available studies, nutraceuticals might help patients obtain theraputic lipid goals and reduce cardiovascular residual risk. Some nutraceuticals have essential lipid-lowering properties confirmed in studies; some might also have possible positive effects on nonlipid cardiovascular risk factors and have been shown to improve early markers of vascular health such as endothelial function and pulse wave velocity. However, the clinical evidence supporting the use of a single lipid-lowering nutraceutical or a combination of them is largely variable and, for many of the nutraceuticals, the evidence is very limited and, therefore, often debatable. The purpose of this position paper is to provide consensus-based recommendations for the optimal use of lipid-lowering nutraceuticals to manage dyslipidemia in patients who are still not on statin therapy, patients who are on statin or combination therapy but have not achieved lipid goals, and patients with statin intolerance. This statement is intended for physicians and other healthcare professionals engaged in the diagnosis and management of patients with lipid disorders, especially in the primary care setting.

Hypocholesterolemic Activity of Curcumin Is Mediated by Down-regulating the Expression of Niemann-Pick C1-like 1 in Hamsters

We previously demonstrated that curcumin reduces cholesterol absorption in Caco-2 cells through down-regulating Niemann-Pick C1-like 1 (NPC1L1) expression, but the in vivo effect of curcumin on intestinal cholesterol absorption remains unknown. The present study aimed to investigate the effects and mechanisms of curcumin consumption on cholesterol absorption in hamsters. Male hamsters were fed a high-fat diet supplemented with or without curcumin (0.05% w/w) for 12 weeks. Curcumin supplementation significantly decreased serum total cholesterol (TC) (from 6.86 ± 0.27 to 3.50 ± 0.24 mmol/L), triglyceride (TG) (from 5.07 ± 0.34 to 3.72 ± 0.40 mmol/L), and low-density lipoprotein cholesterol (from 2.58 ± 0.19 to 1.71 ± 0.15 mmol/L) levels as well as liver TC (from 11.6 ± 0.05 to 7.2 ± 0.03 mg/g) and TG (from 30.3 ± 0.22 to 25.2 ± 0.18 mg/g) levels (P < 0.05 for all). In contrast, curcumin treatment markedly enhanced fecal cholesterol output (P < 0.01). Moreover, curcumin supplementation down-regulated the mRNA and protein expressions of sterol regulatory element binding protein-2 (SREBP-2) and NPC1L1 in the small intestine (P < 0.05). Our current results indicate that curcumin inhibits cholesterol absorption in hamsters by suppressing SREBP-2 and subsequently down-regulating NPC1L1 expression, which may be responsible for the hypocholesterolemic effects of curcumin.

Antihyperlipidemic effect of Acanthopanax senticosus (Rupr. et Maxim) Harms leaves in high-fat-diet fed mice

BACKGROUND

Metabolic syndrome is a major risk factor for a variety of obesity-related diseases. Recently, the effects of functional foods have been investigated on lipid metabolism as a means to reduce lipid content in the blood, liver and adipose tissues associated with carnitine O-palmitoyltransferase (CPT) activity. Acanthopanax senticosus (Rupr. et Maxim) Harms (AS) is a medicinal herb possessing a wide spectra of functions including antioxidant, anti-inflammatory and anti-fatigue actions. Despite much research being focused on the cortical roots of AS, little information is available regarding its leaves, which are also expected to promote human health, for example by improving abnormal lipid metabolism. Here, we explored whether AS leaves affect lipid metabolism in mice fed a high-fat diet.

RESULTS

The administration of AS to BALB/c mice fed a high-fat diet significantly decreased plasma triglycerides (TG). CPT activity in the liver of these mice was significantly enhanced by AS treatment.

CONCLUSION

These findings indicate that AS leaves have the potential to alleviate increase in plasma TG levels due to high-fat diet intake in mice, possibly by increasing mitochondrial fatty acid β-oxidation, especially via CPT activation. Consequently, daily intake of AS leaves could promote beneficial health effects including the prevention of metabolic syndrome. © 2015 Society of Chemical Industry.

Combination of curcumin and piperine prevents formation of gallstones in C57BL6 mice fed on lithogenic diet: whether NPC1L1/SREBP2 participates in this process?

BACKGROUND

A disruption of cholesterol homeostasis characterized by the physical-chemical imbalance of cholesterol solubility in bile often results in formation of cholesterol gallstones. Our earlier studies revealed that curcumin (1000 mg/kg) could prevent formation of gallstones. It has been proved that curcumin is poorly absorbed while piperine is a bioavailability-enhancer. Nevertheless, whether curcumin combined with piperine could enhance the effect of curcumin in preventing gallstones is still awaited.

METHOD

C57BL6 mice were fed on a lithogenic diet concomitant with curcumin at 500 or 1000 mg/kg and/or piperine at 20 mg/kg for 4 weeks. The ratio of gallbladder stone formation was recorded and samples of blood, bile, gallbladder, liver and small intestine were also collected. The volume of gallbladder and weight of liver were calculated, and blood and bile samples were analyzed through biochemical methods. Intestinal NPC1L1 and SREBP2 mRNA and protein expression were detected by real-time PCR and Western blot.

RESULT

Combining with piperine can significantly enhance the effect of curcumin, thus preventing the development of gallbladder stones, lowering the saturation of blood lipids and cholesterol in bile, as well as decreasing the expression of NPC1L1 and SREBP2 in both mRNA and protein levels.

CONCLUSION

Curcumin can prevent the formation of cholesterol gallstones induced by high fat diet in mice and SREBP2 and NPC1L1 may participate in this process. Piperine can increase curcumin's bioavailability, thereby enhancing the effect of curcumin.

Orlistat limits cholesterol intestinal absorption by Niemann-pick C1-like 1 (NPC1L1) inhibition

The known mechanism by which orlistat decreases the absorption of dietary cholesterol is by inhibition of intestinal lipases. The aim of this study was to investigate the ability of orlistat to limit cholesterol absorption by inhibition of the cholesterol transport protein Niemann-Pick C1-like 1 (NPC1L1) as another mechanism of action. In situ rat intestinal perfusion studies were conducted to study the effect of orlistat on jejunal cholesterol absorption. Inhibition kinetic parameters were calculated from in vitro inhibition studies using Caco2 and NPC1L1 transfected cell lines. The in situ studies demonstrated that intestinal perfusion of orlistat (100µM) was able to reduce cholesterol absorption by three-fold when compared to control (i.e. in the absence of orlistat, P<0.01). In vitro studies using Caco2 cells demonstrated orlistat to reduce the cellular uptake of cholesterol by 30%. Additionally, orlistat reduced the cellular uptake of cholesterol in dose dependent manner in NPC1L1 transfected cell line with an IC50=1.2µM. Lineweaver-Burk plot indicated a noncompetitive inhibition of NPC1L1 by orlistat. Beside the already established mechanism by which orlistat reduces the absorption of cholesterol, we demonstrated for the first time that orlistat limits cholesterol absorption by the inhibition of NPC1L1 transport protein.

Fomiroid A, a novel compound from the mushroom Fomitopsis nigra, inhibits NPC1L1-mediated cholesterol uptake via a mode of action distinct from that of ezetimibe

Hypercholesterolemia is one of the key risk factors for coronary heart disease, a major cause of death in developed countries. Suppression of NPC1L1-mediated dietary and biliary cholesterol absorption is predicted to be one of the most effective ways to reduce the risk of hypercholesterolemia. In a screen for natural products that inhibit ezetimibe glucuronide binding to NPC1L1, we found a novel compound, fomiroid A, in extracts of the mushroom Fomitopsis nigra. Fomiroid A is a lanosterone derivative with molecular formula C30H48O3. Fomiroid A inhibited ezetimibe glucuronide binding to NPC1L1, and dose-dependently prevented NPC1L1-mediated cholesterol uptake and formation of esterified cholesterol in NPC1L1-expressing Caco2 cells. Fomiroid A exhibited a pharmacological chaperone activity that corrected trafficking defects of the L1072T/L1168I mutant of NPC1L1. Because ezetimibe does not have such an activity, the binding site and mode of action of fomiroid A are likely to be distinct from those of ezetimibe.

Effects of curcumin on ion channels and transporters

Curcumin [1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione], a polyphenolic compound isolated from the rhizomes of Curcuma longa (turmeric), has been shown to exhibit a wide range of pharmacological activities including anti-inflammatory, anti-cancer, anti-oxidant, anti-atherosclerotic, anti-microbial, and wound healing effects. These activities of curcumin are based on its complex molecular structure and chemical features, as well as its ability to interact with multiple signaling molecules. The ability of curcumin to regulate ion channels and transporters was recognized a decade ago. The cystic fibrosis transmembrane conductance regulator (CFTR) is a well-studied ion channel target of curcumin. During the process of studying its anti-cancer properties, curcumin was found to inhibit ATP-binding cassette (ABC) family members including ABCA1, ABCB1, ABCC1, and ABCG2. Recent studies have revealed that many channels and transporters are modulated by curcumin, such as voltage-gated potassium (Kv) channels, high-voltage-gated Ca(2+) channels (HVGCC), volume-regulated anion channel (VRAC), Ca(2+) release-activated Ca(2+) channel (CRAC), aquaporin-4 (AQP-4), glucose transporters, etc., In this review, we aim to provide an overview of the interactions of curcumin with different types of ion channels and transporters and to help better understand and integrate the underlying molecular mechanisms of the multiple pharmacological activities of curcumin.

D-Glucose modulates intestinal Niemann-Pick C1-like 1 (NPC1L1) gene expression via transcriptional regulation

The expression of intestinal Niemann-Pick C1-like 1 (NPC1L1) cholesterol transporter has been shown to be elevated in patients with diseases associated with hypercholesterolemia such as diabetes mellitus. High levels of glucose were shown to directly increase the expression of NPC1L1 in intestinal epithelial cells, but the underlying mechanisms are not fully defined. The present studies were, therefore, undertaken to examine the transcriptional regulation of NPC1L1 expression in human intestinal Caco2 cells in response to glucose. Removal of glucose from the culture medium of Caco2 cells for 24 h significantly decreased the NPC1L1 mRNA, protein expression, as well as the promoter activity. Glucose replenishment significantly increased the promoter activity of NPC1L1 in a dose-dependent manner compared with control cells. Exposure of Caco2 cells to nonmetabolizable form of glucose, 3-O-methyl-d-glucopyranose (OMG) had no effect on NPC1L1 promoter activity, indicating that the observed effects are dependent on glucose metabolism. Furthermore, glucose-mediated increase in promoter activity was abrogated in the presence of okadaic acid, suggesting the involvement of protein phosphatases. Glucose effects on several deletion constructs of NPC1L1 promoter demonstrated that cis elements mediating the effects of glucose are located in the region between -291 and +56 of NPC1L1 promoter. Consistent with the effects of glucose removal on NPC1L1 expression in Caco2 cells, 24-h fasting resulted in a significant decrease in the relative expression of NPC1L1 in mouse jejunum. In conclusion, glucose appears to directly modulate NPC1L1 expression via transcriptional mechanisms and the involvement of phosphatase-dependent pathways.

Molecular mechanisms of hypolipidemic effects of curcumin

Recent evidence suggests potential benefits from phytochemicals and micronutrients in reducing the elevated oxidative and lipid-mediated stress associated with inflammation, obesity, and atherosclerosis. These compounds may either directly scavenge reactive oxygen or nitrogen species or they may modulate the activity of signal transduction enzymes leading to changes in the expression of antioxidant genes. Alternatively, they may reduce plasma lipid levels by modulating lipid metabolic genes in tissues and thus reduce indirectly lipid-mediated oxidative and endoplasmic reticulum stress through their hypolipidemic effect. Here we review the proposed molecular mechanisms by which curcumin, a polyphenol present in the rhizomes of turmeric (Curcuma longa) spice, influences oxidative and lipid-mediated stress in the vascular system. At the molecular level, mounting experimental evidence suggests that curcumin may act chemically as scavenger of free radicals and/or influences signal transduction (e.g., Akt, AMPK) and modulates the activity of specific transcription factors (e.g., FOXO1/3a, NRF2, SREBP1/2, CREB, CREBH, PPARγ, and LXRα) that regulate the expression of genes involved in free radicals scavenging (e.g., catalase, MnSOD, and heme oxygenase-1) and lipid homeostasis (e.g., aP2/FABP4, CD36, HMG-CoA reductase, and carnitine palmitoyltransferase-I (CPT-1)). At the cellular level, curcumin may induce a mild oxidative and lipid-metabolic stress leading to an adaptive cellular stress response by hormetic stimulation of these cellular antioxidant defense systems and lipid metabolic enzymes. The resulting lower oxidative and lipid-mediated stress may not only explain the beneficial effects of curcumin on inflammation, cardiovascular, and neurodegenerative disease, but may also contribute to the increase in maximum life-span observed in animal models.

Lack of efficacy of curcumin on neurodegeneration in the mouse model of Niemann-Pick C1

In order to determine the efficacy of curcumin in ameliorating symptoms of neurodegeneration in the mouse model of Niemann-Pick C1, a variety of formulations and dosages of curcumin, one comparable to one previously reported as efficacious, were provided orally to Npc1(-/-)mice. Plasma levels of curcumin, survival, tests of motor performance, and memory (in some cases) were performed. We found variable, but mild, increases in survival (1.5% to 18%). The greatest increased survival occurred with the highest dose (which was unformulated) while the control for the lipidated formulation (containing phosphatidylcholine and stearic acid) had an equivalent impact and other formulations, while not significantly increased, are also not statistically different in effect from the highest dose. We conclude that curcumin is not a highly efficacious treatment for neurodegeneration in Npc1(-/-) mice. Phosphatidylcholine and stearic acid should be studied further.