Exogenous supplement of N-acetylneuraminic acid improves macrophage reverse cholesterol transport in apolipoprotein E-deficient mice

Natural products in atherosclerosis therapy by targeting PPARs: a review focusing on lipid metabolism and inflammation

Inflammation and dyslipidemia are critical inducing factors of atherosclerosis. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors and control the expression of multiple genes that are involved in lipid metabolism and inflammatory responses. However, synthesized PPAR agonists exhibit contrary therapeutic effects and various side effects in atherosclerosis therapy. Natural products are structural diversity and have a good safety. Recent studies find that natural herbs and compounds exhibit attractive therapeutic effects on atherosclerosis by alleviating hyperlipidemia and inflammation through modulation of PPARs. Importantly, the preparation of natural products generally causes significantly lower environmental pollution compared to that of synthesized chemical compounds. Therefore, it is interesting to discover novel PPAR modulator and develop alternative strategies for atherosclerosis therapy based on natural herbs and compounds. This article reviews recent findings, mainly from the year of 2020 to present, about the roles of natural herbs and compounds in regulation of PPARs and their therapeutic effects on atherosclerosis. This article provides alternative strategies and theoretical basis for atherosclerosis therapy using natural herbs and compounds by targeting PPARs, and offers valuable information for researchers that are interested in developing novel PPAR modulators.

Metabolite Neu5Ac triggers SLC3A2 degradation promoting vascular endothelial ferroptosis and aggravates atherosclerosis progression in ApoE-/-mice

Background: Atherosclerosis (AS) is still the major cause of cardiovascular disease (CVD) as well as stroke. Endothelial metabolic disorder has been found to be activated and then promote endothelial cells (ECs) injury, which is regarded to initiate AS progression. N-acetylneuraminic acid (Neu5Ac), a metabolite produced by hexosamine-sialic acid pathway branching from glucose metabolism, was presented as a notable biomarker of CVD and is positively correlated with ECs function. However, few studies explain whether Neu5Ac regulate AS progression by affecting EC function as well as its involved mechanisms are still unknown. Methods: Here, we mimicked an animal model in ApoE-/- mice which displaying similar plasma Neu5Ac levels with AS model to investigate its effect on AS progression. Results: We found that Neu5Ac exacerbated plaques area and increased lipids in plasma in absence of HFD feeding, and ECs inflammatory injury was supposed as the triggering factor upon Neu5Ac treatment with increasing expression of IL-1β, ICAM-1, and promoting ability of monocyte adhesion to ECs. Mechanistic studies showed that Neu5Ac facilitated SLC3A2 binding to ubiquitin and then triggered P62 mediated degradation, further leading to accumulation of lipid peroxidation in ECs. Fer-1 could inhibit ECs injury and reverse AS progression induced by Neu5Ac in ApoE-/- mice. Interestingly, mitochondrial dysfunction was also partly participated in ECs injury after Neu5Ac treatment and been reversed by Fer-1. Conclusions: Together, our study unveils a new mechanism by which evaluated metabolite Neu5Ac could promote SLC3A2 associated endothelial ferroptosis to activate ECs injury and AS plaque progression, thus providing a new insight into the role of Neu5Ac-ferroptosis pathway in AS. Also, our research revealed that pharmacological inhibition of ferroptosis may provide a novel therapeutic strategy for premature AS.

Triglyceride and Triglyceride-Rich Lipoproteins in Atherosclerosis

Cardiovascular disease (CVD) is still the leading cause of death globally, and atherosclerosis is the main pathological basis of CVDs. Low-density lipoprotein cholesterol (LDL-C) is a strong causal factor of atherosclerosis. However, the first-line lipid-lowering drugs, statins, only reduce approximately 30% of the CVD risk. Of note, atherosclerotic CVD (ASCVD) cannot be eliminated in a great number of patients even their LDL-C levels meet the recommended clinical goals. Previously, whether the elevated plasma level of triglyceride is causally associated with ASCVD has been controversial. Recent genetic and epidemiological studies have demonstrated that triglyceride and triglyceride-rich lipoprotein (TGRL) are the main causal risk factors of the residual ASCVD. TGRLs and their metabolites can promote atherosclerosis via modulating inflammation, oxidative stress, and formation of foam cells. In this article, we will make a short review of TG and TGRL metabolism, display evidence of association between TG and ASCVD, summarize the atherogenic factors of TGRLs and their metabolites, and discuss the current findings and advances in TG-lowering therapies. This review provides information useful for the researchers in the field of CVD as well as for pharmacologists and clinicians.

Lipoprotein sialylation in atherosclerosis: Lessons from mice

Sialylation is a dynamically regulated modification, which commonly occurs at the terminal of glycan chains in glycoproteins and glycolipids in eukaryotic cells. Sialylation plays a key role in a wide array of biological processes through the regulation of protein-protein interactions, intracellular localization, vesicular trafficking, and signal transduction. A majority of the proteins involved in lipoprotein metabolism and atherogenesis, such as apolipoproteins and lipoprotein receptors, are sialylated in their glycan structures. Earlier studies in humans and in preclinical models found a positive correlation between low sialylation of lipoproteins and atherosclerosis. More recent works using loss- and gain-of-function approaches in mice have revealed molecular and cellular mechanisms by which protein sialylation modulates causally the process of atherosclerosis. The purpose of this concise review is to summarize these findings in mouse models and to provide mechanistic insights into lipoprotein sialylation and atherosclerosis.

Characterization and Extraction Influence Protein Profiling of Edible Bird's Nest

The edible bird nest (EBN) from Aerodramus fuciphagus has been consumed as a Chinese traditional food for health and medicinal purposes due to its elevated nutritional value. The present study focused on the influence of characterization and extraction methods on protein profiling, which could be a guideline for grading the EBN. The proposed extraction method is similar to the common food preparation methods of consumers and thus can accurately establish the bioactive protein available upon human consumption. The characterization includes physicochemical analysis (physical, morphology, elemental composition, and microbial content) and chemical analysis (crude protein and amino acid). The morphology of half-cup EBN was found to be uniformly shaped and rich in calcium as compared to rough surface of stripe-shaped EBN, and there was no significant microbial growth in both types of EBN. The crude protein and amino acid content in half-cup EBN were significantly higher than stripe-shaped EBN. The full stew (FS) and stew (SE) extraction methods produced a maximal yield of soluble protein. Sialic acid content in SE extract (8.47%, w/w) and FS extract (7.91%, w/w) were recorded. About seven parent proteins (39.15 to 181.68 kDa) were identified by LC-MS/MS Q-TOF, namely 78 kDa glucose-regulated protein, lysyl oxidase-3, Mucin-5AC-like, acidic mammalian chitinase-like, 45 kDa calcium-binding protein, nucleobindin-2, and ovoinhibitor-like. In conclusion, the characteristics and extraction methods influence the availability of bioactive protein and peptides, demonstrating the potential usage of EBN in improving its biological activities and nutritional properties.

TCA Cycle and Fatty Acids Oxidation Reflect Early Cardiorenal Damage in Normoalbuminuric Subjects with Controlled Hypertension

Moderately increased albuminuria, defined by an albumin to creatinine ratio (ACR) > 30 mg/g, is an indicator of subclinical organ damage associated with a higher risk of cardiovascular and renal disease. Normoalbuminuric subjects are considered at no cardiorenal risk in clinical practice, and molecular changes underlying early development are unclear. To decipher subjacent mechanisms, we stratified the normoalbuminuria condition. A total of 37 hypertensive patients under chronic renin–angiotensin system (RAS) suppression with ACR values in the normoalbuminuria range were included and classified as control (C) (ACR < 10 mg/g) and high-normal (HN) (ACR = 10–30 mg/g). Target metabolomic analysis was carried out by liquid chromatography and mass spectrometry to investigate the role of the cardiorenal risk urinary metabolites previously identified. Besides this, urinary free fatty acids (FFAs), fatty acid binding protein 1 (FABP1) and nephrin were analyzed by colorimetric and ELISA assays. A Mann–Whitney test was applied, ROC curves were calculated and Spearman correlation analysis was carried out. Nine metabolites showed significantly altered abundance in HN versus C, and urinary FFAs and FABP1 increased in HN group, pointing to dysregulation in the tricarboxylic acid cycle (TCA) cycle and fatty acids β-oxidation. We showed here how cardiorenal metabolites associate with albuminuria, already in the normoalbuminuric range, evidencing early renal damage at a tubular level and suggesting increased β-oxidation to potentially counteract fatty acids overload in the HN range.

Electroacupuncture Inhibits Atherosclerosis through Regulating Intestinal Flora and Host Metabolites in Rabbit

Methods

In this study, general rabbit conditions, vascular histology, metabolites, and intestinal flora structures were analyzed. Integrated analysis of metabolomics and 16S rRNA sequencing were performed. All the rabbits were randomly divided into four groups. The rabbit model of atherosclerosis was established. The histopathological change in the common carotid artery was assessed by HE staining and the structural change in the flora by 16S rRNA sequencing. HPLC-TOF-MS and Agilent MPP 12.1 were integrated to identify and screen out differential metabolites. Correlational analyses of every differential metabolite with intestinal flora were integrated on Omicshare platform.

Results

Atherosclerotic rabbits showed obvious changes in general conditions, significant fibrous cap and necrotic center on carotid artery, abnormal intestinal bacteria structure, and metabolites levels. Electroacupuncture improved the conditions, reduced lipid deposition on the carotid artery wall, diversified intestinal flora, and normalized host metabolism. Integrated analysis showed that 149 altered metabolites were related to 22 intestinal flora, among which eight intestinal floras and 21 metabolites have relationships with atherosclerosis.

Conclusion

Electroacupuncture can effectively reverse atherosclerosis through manipulating the structural feature of intestinal flora to influence the host metabolites. The possible mechanisms involved activating signal pathways through host metabolites or affecting the activity of cardiovascular-related enzymes, or regulating host lipid metabolism directly.

Setosphapyrone C and D accelerate macrophages cholesterol efflux by promoting LXRα/ABCA1 pathway

LXRα agonists have attracted significant attention due to their potential biological activities on promoting cholesterol efflux. This study was designed to investigate whether setosphapyrone C and D have potential lipid-lowering capacity and the underlying mechanisms in vitro. Our data showed that setosphapyrone C and D had weak cytotoxicity compared to the liver X receptor α (LXRα) agonist T0901317. In RAW 264.7 macrophages, setosphapyrone C and D significantly enhanced [³H]-cholesterol efflux by ~ 21.3% and 32.4%, respectively; furthermore, setosphapyrone C and D enhanced the protein levels of ATP-binding cassette transporter (ABC) A1 and LXRα by 58% and 69%, and 60% and 70% (8 µM), respectively; however, they had no effect on the protein levels of ABCG1 and scavenger receptor B type 1; additionally, they had minor effect on the mRNA expression of lipogenic genes. Of note, setosphapyrone C and D significantly enhanced LXRα/ABCA1pathway in mice primary macrophages. In BRL cells, setosphapyrone C and D significantly improved the protein levels of ABCA1 and ABCG1; setosphapyrone D significantly enhanced the protein expression of low-density lipoprotein. Collectively, setosphapyrone C and D with weak cytotoxicity exhibited effective lipid-lowering effect via enhancing LXRα/ABC pathways. Setosphapyrones possess potential application for the treatment of hyperlipidemic diseases.

The marine-derived furanone reduces intracellular lipid accumulation in vitro by targeting LXRα and PPARα

Recent studies have demonstrated that commercially available lipid‐lowering drugs cause various side effects; therefore, searching for anti‐hyperlipidaemic compounds with lower toxicity is a research hotspot. This study was designed to investigate whether the marine‐derived compound, 5‐hydroxy‐3‐methoxy‐5‐methyl‐4‐butylfuran‐2(5H)‐one, has an anti‐hyperlipidaemic activity, and the potential underlying mechanism in vitro. Results showed that the furanone had weaker cytotoxicity compared to positive control drugs. In RAW 264.7 cells, the furanone significantly lowered ox‐LDL‐induced lipid accumulation (~50%), and its triglyceride (TG)‐lowering effect was greater than that of liver X receptor (LXR) agonist T0901317. In addition, it significantly elevated the protein levels of peroxisome proliferator‐activated receptors (PPARα) and ATP‐binding cassette (ABC) transporters, which could be partially inhibited by LXR antagonists, GSK2033 and SR9243. In HepG2 cells, it significantly decreased oleic acid‐induced lipid accumulation, enhanced the protein levels of low‐density lipoprotein receptor (LDLR), ABCG5, ABCG8 and PPARα, and reduced the expression of sterol regulatory element‐binding protein 2 (~32%). PPARα antagonists, GW6471 and MK886, could significantly inhibit the furanone‐induced lipid‐lowering effect. Furthermore, the furanone showed a significantly lower activity on the activation of the expression of lipogenic genes compared to T0901317. Taken together, the furanone exhibited a weak cytotoxicity but had powerful TC‐ and TG‐lowering effects most likely through targeting LXRα and PPARα, respectively. These findings indicate that the furanone has a potential application for the treatment of dyslipidaemia.

The fucoidan A3 from the seaweed Ascophyllum nodosum enhances RCT-related genes expression in hyperlipidemic C57BL/6J mice

Reverse cholesterol transport (RCT) has been demonstrated to reduce hyperlipidemia, and fucoidans are found to possess hypolipidemic effect. This study was designed to investigate the lipid-lowering effect of the fucoidan from the brown seaweed A. nodosum and whether it improves RCT-related genes expression in C57 BL/6J mice. Our results indicated that fucoidan A3 (100 mg/kg/day) intervention significantly reduced plasma total cholesterol (~23.2%), triglyceride (~48.7%) and fat pad index. This fucoidan significantly increased the mRNA expression of low-density lipoprotein receptor (LDLR), scavenger receptor B type 1 (SR-B1), cholesterol 7 alpha-hydroxylase A1 (CYP7A1), liver X receptor (LXR) β, ATP-binding cassette transporter (ABC) A1 and sterol regulatory element-binding protein (SREBP) 1c, and decreased the expression of peroxisome proliferator-activated receptor (PPAR) γ, however, it had no effect on the expression of proprotein convertase subtilisin/kexin type 9, PPARα, LXRα, SREBP-2, ABCG1, ABCG8 and Niemann-Pick C1-like 1. These results demonstrated that this fucoidan improved lipid transfer from plasma to the liver by activating SR-B1 and LDLR, and up-regulated lipid metabolism by activating LXRβ, ABCA1 and CYP7A1. In conclusion, this fucoidan lowers lipid by enhancing RCT-related genes expression, and it can be explored as a potential candidate for prevention or treatment of lipid disorders.

The fucoidan from the brown seaweed Ascophyllum nodosum ameliorates atherosclerosis in apolipoprotein E-deficient mice

Hyperlipidemia is a major cause of atherosclerosis. Reverse cholesterol transport (RCT) is believed to attenuate hyperlipidemia and the progression of atherosclerosis. Although fucoidans are reported to have hypolipidemic effects, the underlying mechanisms are unclear. Furthermore, few reports have revealed the anti-atherosclerotic effects and the underlying mechanisms of fucoidans. This study was designed to investigate the anti-atherosclerotic effect and mechanisms of the fucoidan from seaweed A. nodosum. Our results demonstrated that the fucoidan administration ameliorated atherosclerotic lesion and lipid profiles in a dose-dependent manner in the apolipoprotein E-deficient (apoE-/-) mice fed a high-fat diet. In the apoE-/- mice liver, the fucoidan treatment significantly increased the expression of scavenger receptor B type 1 (SR-B1), peroxisome proliferator-activated receptor (PPAR) α and β, liver X receptor (LXR) α, ATP-binding cassette transporter (ABC) A1 and ABCG8; and markedly decreased the expression of PPARγ and sterol regulatory element-binding protein (SREBP) 1c, but not low-density lipoprotein receptor, proprotein convertase subtilisin/kexin type 9, cholesterol 7 alpha-hydroxylase A1, LXRβ and ABCG1. In the small intestine of the apoE-/- mice, the fucoidan treatment significantly reduced the expression of Niemann-Pick C1-like 1 (NPC1L1) and dramatically improved ABCG8 levels. These results demonstrated for the first time that the fucoidan from A. nodosum attenuated atherosclerosis by regulating RCT-related genes and proteins expression in apoE-/- mice. In summary, this fucoidan from A. nodosum may be explored as a potential compound for prevention or treatment of hyperlipidemia-induced atherosclerosis.

Fucoidan A2 from the Brown Seaweed Ascophyllum nodosum Lowers Lipid by Improving Reverse Cholesterol Transport in C57BL/6J Mice Fed a High-Fat Diet

Reverse cholesterol transport (RCT) is a physiological process, in which excess peripheral cholesterol is transported to the liver and further excreted into the bile and then feces. Recently, fucoidans are reported to have a lipid-lowering effect. This study was designed to investigate whether fucoidan from the brown seaweed Ascophyllum nodosum lowers lipid by modulating RCT in C57BL/6J mice fed a high-fat diet. Our results indicated that fucoidan intervention significantly reduced plasma triglyceride, total cholesterol, and fat pad index and markedly increased high-density lipoprotein cholesterol in a dose-dependent manner. In the liver, fucoidan significantly increased the expression of peroxisome proliferator-activated receptor (PPAR)α, PPARγ, liver X receptor (LXR)β, adenosine triphosphate (ATP) binding cassette (ABC)A1, ABCG8, low-density lipoprotein receptor (LDLR), scavenger receptor B type 1 (SR-B1), and cholesterol 7-α-hydroxylase A1 (CYP7A1) and decreased the triglyceride level and expression of proprotein convertase subtilisin/kexin type 9 (PCSK9) and PPARβ but had no effect on LXRα, ABCG1, and ABCG5. In the small intestine, the fucoidan treatment significantly reduced the expression of Niemann-Pick C1-like 1 (NPC1L1) and improved ABCG5 and ABCG8. These results demonstrated that fucoidan can improve lipid transfer from plasma to the liver by activating SR-B1 and LDLR and inactivating PCSK9 and upregulate lipid metabolism by activating PPARα, LXRβ, ABC transporters, and CYP7A1. In the small intestine, this fucoidan can decrease cholesterol absorption and increase cholesterol excretion by activating NPC1L1 and ABCG5 and ABCG8, respectively. In conclusion, fucoidan from A. nodosum may lower lipids by modulating RCT-related protein expression and can be explored as a potential compound for prevention or treatment of hyperlipidemia-related diseases.