Soraphen A enhances macrophage cholesterol efflux via indirect LXR activation and ABCA1 upregulation

Association of a Novel Homozygous Variant in ABCA1 Gene with Tangier Disease

Tangier disease (TD) is a rare autosomal recessive disorder caused by a variant in the ABCA1 gene, characterized by significantly reduced levels of plasma high-density lipoprotein cholesterol (HDL-C) and apolipoprotein A-1 (ApoA-I). TD typically leads to accumulation of cholesterol in the peripheral tissues and early coronary disease but with highly variable clinical expression. Herein, we describe a case study of a 59-year-old male patient with features typical of TD, in whom a likely pathogenic variant in the ABCA1 gene was identified by whole-exome sequencing (WES), identified for the first time as homozygous (NM_005502.4: c.4799A>G (p. His1600Arg)). In silico analysis including MutationTaster and DANN score were used to predict the pathogenicity of the variant and a protein model generated by SWISS-MODEL was built to determine how the homozygous variant detected in our patient may change the protein structure and impact on its function. This case study describes a homozygous variant of the ABCA1 gene, which is responsible for a severe form of TD and underlines the importance of using bioinformatics and genomics for linking genotype to phenotype and better understanding and accounting for the functional impact of genetic variations.

Role of ABCA1 in Cardiovascular Disease

Cholesterol homeostasis plays a significant role in cardiovascular disease. Previous studies have indicated that ATP-binding cassette transporter A1 (ABCA1) is one of the most important proteins that maintains cholesterol homeostasis. ABCA1 mediates nascent high-density lipoprotein biogenesis. Upon binding with apolipoprotein A-I, ABCA1 facilitates the efflux of excess intracellular cholesterol and phospholipids and controls the rate-limiting step of reverse cholesterol transport. In addition, ABCA1 interacts with the apolipoprotein receptor and suppresses inflammation through a series of signaling pathways. Thus, ABCA1 may prevent cardiovascular disease by inhibiting inflammation and maintaining lipid homeostasis. Several studies have indicated that post-transcriptional modifications play a critical role in the regulation of ABCA1 transportation and plasma membrane localization, which affects its biological function. Meanwhile, carriers of the loss-of-function ABCA1 gene are often accompanied by decreased expression of ABCA1 and an increased risk of cardiovascular diseases. We summarized the ABCA1 transcription regulation mechanism, mutations, post-translational modifications, and their roles in the development of dyslipidemia, atherosclerosis, ischemia/reperfusion, myocardial infarction, and coronary heart disease.

Newly-found functions of metformin for the prevention and treatment of age-related macular degeneration

Metformin (MET), a first-line oral agent used to treat diabetes, exerts its function mainly by activating adenosine monophosphate-activated protein. The accumulation of oxidized phospholipids in the outer layer of the retina plays a key role in retinal pigment epithelium (RPE) cells death and the formation of choroidal neovascularization (CNV), which mean the development of age-related macular degeneration (AMD). Recent studies have shown that MET can regulate lipid metabolism, inhibit inflammation, and prohibit retinal cell death and CNV formation due to various pathological factors. Here, newly discovered functions of MET that may be used for the prevention and treatment of AMD were reviewed.

Recent developments in the regulation of cholesterol transport by natural molecules

The dysregulation of cholesterol metabolism is a high-risk factor for non-alcoholic fatty liver disease (NAFLD), dyslipidemia, and atherosclerosis (AS). Cholesterol transport maintains whole-body cholesterol homeostasis. Low-density apolipoprotein receptor (LDLR) mediates cholesterol uptake in cells and plays an important role in the primary route of circulatory cholesterol clearance in liver cells. Caveolins 1 is an integral membrane protein and shuttle between the cytoplasm and cell membrane. Caveolins 1 not only plays a role in promoting cholesterol absorption in cells but also in the transport of cellular cholesterol efflux by interacting with the ATP-binding cassette transporter A1 (ABCA1) and scavenger receptor class B type I (SR-BI). These proteins, which are associated with reverse cholesterol transport (RCT), are potential therapeutic targets for NAFLD and AS. Many studies have indicated that natural products have lipid-lowering effects. Moreover, natural molecules, derived from natural products, have the potential to be developed into novel drugs. However, the mechanisms underlying the regulation of cholesterol transport by natural molecules have not yet been adequately investigated. In this review, we briefly describe the process of cholesterol transport and summarize the mechanisms by which molecules regulate cholesterol transport. This article provides an overview of recent studies and focuses on the potential therapeutic effects of natural molecules; however, further high-quality studies are needed to firmly establish the clinical efficacies of natural molecules.

Myxobacteria and their products: current trends and future perspectives in industrial applications

Myxobacteria belong to a group of bacteria that are known for their well-developed communication system and synchronized or coordinated movement. This typical behavior of myxobacteria is mediated through secondary metabolites. They are capable of producing secondary metabolites belonging to several chemical classes with unique and wide spectrum of bioactivities. It is predominantly significant that myxobacteria specialize in mechanisms of action that are very rare with other producers. Most of the metabolites have been explored for their medical and pharmaceutical values while a lot of them are still unexplored. This review is an attempt to understand the role of potential metabolites produced by myxobacteria in different applications. Different myxobacterial metabolites have demonstrated antibacterial, antifungal, and antiviral properties along with cytotoxic activity against various cell lines. Beside their metabolites, these myxobacteria have also been discussed for better exploitation and implementation in different industrial sectors.

An octimibate derivative, Oxa17, enhances cholesterol efflux and exerts anti-inflammatory and atheroprotective effects in experimental atherosclerosis

Atherosclerotic cardiovascular diseases (ASCVDs), associated with vascular inflammation and lipid dysregulation, are responsible for high morbidity and mortality rates globally. For ASCVD treatment, cholesterol efflux plays an atheroprotective role in ameliorating inflammation and lipid dysregulation. To develop a multidisciplinary agent for promoting cholesterol efflux, octimibate derivatives were screened and investigated for the expression of ATP-binding cassette transporter A1 (ABCA1). Western blotting and qPCR analysis were conducted to determine the molecular mechanism associated with ABCA1 expression in THP-1 macrophages; results revealed that Oxa17, an octimibate derivative, enhanced ABCA1 expression through liver X receptors alpha (LXRα) activation but not through the microRNA pathway. We also investigated the role of Oxa17 in high-fat diet (HFD)-fed mice used as an in vivo atherosclerosis-prone model. In ldlr^-/- mice, Oxa17 increased plasma high-density lipoprotein (HDL) and reduced plaque formation in the aorta. Plaque stability improved via reduction of macrophage accumulation and via narrowing of the necrotic core size under Oxa17 treatment. Our study demonstrates that Oxa17 is a novel and potential agent for ASCVD treatment with atheroprotective and anti-inflammatory properties.

Taurine-Mediated IDOL Contributes to Resolution of Streptococcus uberis Infection

Metabolic alterations occur in pathogenic infections, but the role of lipid metabolism in the progression of bacterial mastitis is unclear. Cross talk between lipid droplets (LDs) and invading bacteria occurs, and targeting of de novo lipogenesis inhibits pathogen reproduction. In this study, we investigate the role(s) of lipid metabolism in mammary cells during Streptococcus uberis infection. Our results indicate that S. uberis induces the synthesis of fatty acids and production of LDs. Importantly, taurine reduces fatty acid synthesis, the abundance of LDs and the in vitro bacterial load of S. uberis These changes are mediated, at least partly, by the E3 ubiquitin ligase IDOL, which is associated with the degradation of low-density lipoprotein receptors (LDLRs). We have identified a critical role for IDOL-mediated fatty acid synthesis in bacterial infection, and we suggest that taurine may be an effective prophylactic or therapeutic strategy for preventing S. uberis mastitis.

Hypolipidemic Roles of Casein-Derived Peptides by Regulation of Trans-Intestinal Cholesterol Excretion and Bile Acid Synthesis

Hyperlipidemia, a syndrome characterized by an abnormal elevation of blood lipids, causes chronic lethal metabolic disorders. Although statins are regularly prescribed to patients, an alternative to treat the burden of excessive lipids is required for cholesterol control. In this study, it was found that the treatment of casein hydrolyzed by pepsin and trypsin induced trans-intestinal cholesterol excretion (TICE) through ATP-binding cassette subfamily G members 5 (ABCG5) expression. Next, we analyzed sequences of the peptides responsible for TICE induction, synthesized artificial peptides based on the sequences, and the hypolipidemic effects of the peptide treatments were assessed in both in vitro and in vivo models. We determined that two bioactive peptides contained in casein hydrolysates (SQSKVLPVPQK and HPHPHLSF) induced TICE through the expression of ABCG5 in enterocytes and suppressed hepatic mRNA expression of cytochrome P450 family 7 subfamily A member 1 (CYP7A1) and CYP8B1by ileal FGF19 expression both in an liver X receptor α (LXRα)-mediated manner. In the hyperlipidemic mouse models, the oral administration of peptides reduced serum cholesterol levels through elevation of the ABCG5 expression in proximal intestine and fecal cholesterol secretion. Besides this, peptides induced ileal expression of fibroblast growth factor 15/19 (FGF15/19) and inhibited hepatic bile acid synthesis. We found that the oral treatment of casein-derived bioactive peptides could improve hyperlipidemia by regulating intestinal excretion and hepatic synthesis of cholesterols.

Celastrol suppresses lipid accumulation through LXRα/ABCA1 signaling pathway and autophagy in vascular smooth muscle cells

The uptake of modified low-density lipoprotein (LDL) and the accumulation of lipid droplets induce the formation of vascular smooth muscle cells (VSMCs)-derived foam cells, thereby promoting the development and maturation of plaques and accelerating the progression of atherosclerosis. Celastrol is a quinine methide triterpenoid isolated from the root bark of traditional Chinese herb Tripterygium wilfordii. It possesses various biological properties, including anti-obesity, cardiovascular protection, anti-inflammation, etc. In the present study, we found that celastrol significantly reduced lipid accumulation induced by oxidized LDL (ox-LDL) in VSMCs. Mechanistically, celastrol up-regulated adenosine triphosphate-binding cassette transporter A1 (ABCA1) expression through activating liver X receptor α (LXRα) expression, which contributed to inhibit lipid accumulation in VSMCs. Meanwhile, celastrol decreased lipid accumulation by triggering autophagy in VSMCs. Therefore, these findings supported celastrol as a potentially effective agent for the prevention and therapy of atherosclerosis.