Cholesterol and bile acid-mediated regulation of autophagy in fatty liver diseases and atherosclerosis

The DHCR7 is the key target of lipotoxic liver injury caused by matrine through abnormal activation of the cholesterol synthesis pathway

BACKGROUND

Matrine, the main active ingredient in Sophora flavescens and Sophorae tonkinensis radix et rhizome, is a highly effective insecticide. However, its hepatotoxicity to some extent affects its application value. This study aimed to explore the mechanism underlying matrine-induced liver injury.

METHODS

The zebrafish (Danio rerio) and L02 cell model were utilized to investigate the toxic dose of matrine and its effects on liver tissue damage, liver cell morphology and activity, and expression levels of ALT and AST. Zebrafish and L02 cell samples were then collected for transcriptomic testing to further explore the possible mechanism by which matrine induced liver injury. Finally, integrated bioinformatics methods and experiments were used to elucidate the possible mechanisms behind matrine-induced liver injury.

RESULTS

The result presented solid in vivo evidence of matrine-induced hepatotoxicity, supported by abnormal changes of liver morphological, disturbed liver cell structure, obvious apoptosis, as well as elevated levels of ALT and AST in zebrafish. In addition, in vitro L02 cell experiments also showed that matrine can produce significant liver cell damage effects. The integrated bioinformatics analysis results revealed that differentially expressed genes (DEGs) were substantially enriched in multiple pathways related to lipid regulation. Among which, the steroid biosynthesis was the most key signaling pathway, evidenced by the enhanced expression of eight genes, including DHCR7, SQLE, CYP51, CYP24A1, SC5D, LSS, MSMO1 and SOAT1. Furthermore, AY9944, the targeted inhibitor of DHCR7, could offset the toxic effect, as reflected by diminished liver phenotype damage, steatosis, and cholesterol accumulation caused by matrine.

CONCLUSIONS

Matrine can upregulate the expression of key genes in steroid biosynthesis pathway, resulting in cholesterol accumulation and then inducing hepatotoxicity. Among them, targeted inhibition of DHCR7 gene expression can alleviate matrine-induced liver injury.

Role of CETP, PCSK-9, and CYP7-alpha in cholesterol metabolism: Potential targets for natural products in managing hypercholesterolemia

Cardiovascular diseases (CVDs) are a leading cause of mortality worldwide, primarily affecting the heart and blood vessels, with atherosclerosis being a major contributing factor to their onset. Epidemiological and clinical studies have linked high levels of low-density lipoprotein (LDL) emanating from distorted cholesterol homeostasis as its major predisposing factor. Cholesterol homeostasis, which involves maintaining the balance in body cholesterol level, is mediated by several proteins or receptors, transcription factors, and even genes, regulating cholesterol influx (through dietary intake or de novo synthesis) and efflux (by their conversion to bile acids). Previous knowledge about CVDs management has evolved around modulating these receptors' activities through synthetic small molecules/antibodies, with limited interest in natural products. The central roles of the cholesteryl ester transfer protein (CETP), proprotein convertase subtilisin/kexin type 9 (PCSK9), and cytochrome P450 family 7 subfamily A member 1 (CYP7A1), among other proteins or receptors, have fostered growing scientific interests in understanding more on their regulatory activities and potential as drug targets. We present up-to-date knowledge on the contributions of CETP, PCSK9, and CYP7A1 toward CVDs, highlighting the clinical successes and failures of small molecules/antibodies to modulate their activities. In recommendation for a new direction to improve cardiovascular health, we have presented recent findings on natural products (including functional food, plant extracts, phytochemicals, bioactive peptides, and therapeutic carbohydrates) that also modulate the activities of CETP, PCSK-9, and CYP7A1, and emphasized the need for more research efforts redirected toward unraveling more on natural products potentials even at clinical trial level for CVD management.

Polymethoxyflavones in citrus extract has a beneficial effect on hypercholesterolemia rats by promoting liver cholesterol metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

Hyperlipidemia is characterized by the disorder of lipid metabolism accompanied by oxidative stress damage, and low-grade inflammation, with the pathway of cholesterol and bile acid metabolic are an important triggering mechanism. Polymethoxyflavones (PMFs) are the active constituents of Aurantii Fructus Immaturus, which have many biological effects, including anti-inflammatory, antioxidant activities, anti-obesity, suppressing adipogenesis in adipocytes, and ameliorate type 2 diabetes, with potential roles for regulation of lipid metabolism. However, its associated mechanisms on hyperlipidemia remain unclear.

AIM OF THE STUDY

This study aims to identify the anti-hypercholesterolemia effects and mechanisms of PMFs in a hypercholesterolemia model triggered by high-fat compounds in an excessive alcohol diet (HFD).

MATERIALS AND METHODS

A hypercholesterolemia rat model was induced by HFD, and PMFs was intragastric administered at 125 and 250 mg/kg daily for 16 weeks. The effects of PMFs on hypercholesterolemia were assessed using serum lipids, inflammatory cytokines, and oxidative stress levels. Hematoxylin & eosin (H&E) and Oil Red O staining were performed to evaluate histopathological changes in the rat liver. The levels of total cholesterol (TC) and total bile acid (TBA) in the liver and feces were determined to evaluate lipid metabolism. RAW264.7 and BRL cells loaded with NBD-cholesterol were used to simulate the reverse cholesterol transport (RCT) process in vitro. The signaling pathway of cholesterol and bile acid metabolic was evaluated by Western Blotting (WB) and qRT-PCR.

RESULTS

Lipid metabolism disorders, oxidative stress injury, and low-grade inflammation in model rats were ameliorated by PMFs administration. Numerous vacuoles and lipid droplets in hepatocytes were markedly reduced. In vitro experiments results revealed decreased NBD-cholesterol levels in RAW264.7 cells and increased NBD-cholesterol levels in BRL cells following PMFs intervention. PMFs upregulated the expression of proteins associated with the RCT pathway, such as LXRα, ABCA1, LDLR, and SR-BI, thereby promoting TC entry into the liver. Meanwhile, the expression of proteins associated with cholesterol metabolism and efflux pathways such as CYP7A1, CYP27A1, CYP7B1, ABCG5/8, ABCB1, and BSEP were regulated, thereby promoting cholesterol metabolism. Moreover, PMFs treatment regulated the expression of proteins related to the pathway of enterohepatic circulation of bile acids, such as ASBT, OSTα, NTCP, FXR, FGF15, and FGFR4, thereby maintaining lipid metabolism.

CONCLUSIONS

PMFs might ameliorate hypercholesterolemia by promoting the entry of cholesterol into the liver through the RCT pathway, followed by excretion via metabolism pathways of cholesterol and bile acid. These findings provide a promising therapeutic potential for PMFs to treat hypercholesterolemia.

Maternal nutrient metabolism in the liver during pregnancy

The liver plays pivotal roles in nutrient metabolism, and correct hepatic adaptations are required in maternal nutrient metabolism during pregnancy. In this review, hepatic nutrient metabolism, including glucose metabolism, lipid and cholesterol metabolism, and protein and amino acid metabolism, is first addressed. In addition, recent progress on maternal hepatic adaptations in nutrient metabolism during pregnancy is discussed. Finally, the factors that regulate hepatic nutrient metabolism during pregnancy are highlighted, and the factors include follicle-stimulating hormone, estrogen, progesterone, insulin-like growth factor 1, prostaglandins fibroblast growth factor 21, serotonin, growth hormone, adrenocorticotropic hormone, prolactin, thyroid stimulating hormone, melatonin, adrenal hormone, leptin, glucagon-like peptide-1, insulin glucagon and thyroid hormone. Our vision is that more attention should be paid to liver nutrient metabolism during pregnancy, which will be helpful for utilizing nutrient appropriately and efficiently, and avoiding liver diseases during pregnancy.

The anti-hyperlipidemic effects of Poria cocos (Schw.) Wolf extract: Modulating cholesterol homeostasis in hepatocytes via PPARα pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Poria cocos (Schw.) Wolf (Polyporaceae, P.cocos), which is born on the pine root, has a history of more than two thousand years of medicine in China. P.cocos was first recorded in the Shennong's Herbal Classic, studies have proved its lipid-lowering effect.

AIM OF STUDY

The aim of study was to investigate the underlying mechanism of P.cocos extract on hyperlipidemia.

MATERIALS AND METHODS

Male Sprague-Dawley (SD) rats aged 9-12 weeks were intraperitoneally (IP) injected with Triton-WR 1339 to establish an acute hyperlipidemia model. At 0 h and 20 h after the model was established, low and high doses of P.cocos extract or simvastatin were given twice. After 48 h, the rats were sacrificed, and liver and serum samples were collected for analysis. The cell model was constructed by treating L02 cells with 1% fat emulsion-10% FBS-RPMI 1640 medium for 48 h. At the same time, low and high doses of P.cocos extract and simvastatin were administered. Oil red O staining was used to evaluate the lipid accumulation in the cells, and H&E staining was used to evaluate the liver lesions of rats. Real-time quantitative PCR and western blotting were used to detect the expressions of lipid metabolism-related genes.

RESULTS

P.cocos extract relieved lipid accumulation in vitro and alleviated hyperlipidemia in vivo. Both gene and protein expressions of peroxisome proliferator-activated receptor α (PPARα) were shown to be up-regulated by P.cocos extract. Additionally, P.cocos extract down-regulated the expressions of fatty acid synthesis-related genes sterol regulatory element-binding protein-1 (SREBP-1), Acetyl-CoA Carboxylase 1 (ACC1) and fatty acid synthase (FAS), while up-regulated the expressions of cholesterol metabolism-related genes liver X receptor-α (LXRα), ATP-binding cassette transporter A1 (ABCA1), cholesterol 7alpha-hydroxylase (CYP7A1) and low density lipoprotein receptor (LDLR), which were reversed by the treatment with the PPARα inhibitor GW6471.

CONCLUSION

P.cocos extract ameliorates hyperlipidemia and lipid accumulation by regulating cholesterol homeostasis in hepatocytes through PPARα pathway. This study provides evidence that supplementation with P.cocos extract could be a potential strategy for the treatment of hyperlipidemia.

HuangQi ChiFeng decoction maintains gut microbiota and bile acid homeostasis through FXR signaling to improve atherosclerosis

Huangqi Chifeng Decoction (HQCFT), a traditional Chinese medicine preparation, has long been used to treat cardiovascular and cerebrovascular diseases. However, the mechanism of the beneficial effect of HQCFT on atherosclerosis remains to be explored. In this work, to investigate the effects of HQCFT on bile acid (BA) metabolism and the gut microbiome in atherosclerosis, ApoE-/- mice were fed a with high-fat diet for 16 weeks to establish the AS model. HQCFT(1.95 g kg-1 and 3.9 g kg-1 per day) was administered intragastrically for 8 weeks to investigate the regulatory effects of HQCFT on gut microbiota and bile acid metabolism and to inhibit the occurrence and development of AS induced by a high-fat diet. Histopathology, liver function and blood lipids were used to assess whether HQCFT can reduce plaque area, regulate lipid levels and alleviate liver steatosis in AS mice. In addition, 16S rDNA sequencing was used to screen the gut microbiota structure, and ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC‒MS/MS) was used to determine the bile acid profile. The mRNA and protein expression levels of bile acid metabolism were detected by RT‒PCR and WB to find the potential correlation. Results: HQCFT can regulate gut microbiota disorders, which was achieved by increasing gut microbiota diversity and altering Proteobacteria, Desulfobacterota, Deferribacteres, Rodentibacter, Parasutterella, and Mucispirillum interference abundance to improve AS-induced gut microbiota. HQCFT can also adjust the content of bile acids (TCA, LCA, DCA, TDCA, TLCA, UDCA, etc.), regulate bile acid metabolism, relieve liver fat accumulation, and inhibit the process of AS. In addition, HQCFT can restore the abnormal metabolism of bile acid caused by AS by regulating the expression of farnesoid X receptor (FXR), liver X receptor α (LXRα), ABCA1, ABCG1 and CYP7A1. Conclusion: HQCFT may play a part in the prevention of atherosclerosis by inhibiting the FXR/LXRα axis, increasing the expression of CYP7A1 in the liver, and regulating the interaction between the gut microbiota and bile acid metabolism.

The modulatory effects on enterohepatic cholesterol metabolism of novel cholesterol-lowering peptides from gastrointestinal digestion of Xuanwei ham

The aim of this study was to investigate the effects and mechanism of in vitro protein digestive products of Xuanwei ham with different ripening periods on cholesterol metabolism and hypercholesterolemia. The results showed that compared with other gastrointestinal digestion (GID) groups, the GID group of Xuanwei ham with 3-year ripening period (XWH3-GID) inhibited the expression of Niemann-Pick C1-like 1 (NPC1L1) and acetyl-CoA acetyltransferase 2 (ACAT2) through hepatocyte nuclear factor 1-alpha (HNF-1α), which in turn effectively inhibited cholesterol absorption in Caco-2 cell monolayers. Following absorption by Caco-2 cell monolayers, the XWH3-GID group suppressed the expression and secretion of proprotein convertase subtilisin/kexin type 9 (PCSK9) via HNF-1α, which enhanced the protein expression and fluorescence intensity of low density lipoprotein receptor (LDLR) on the HepG2 cell membrane, and thus promoted the uptake of low density lipoprotein (LDL). Importantly, three novel peptides (LFP, PKF and VPFP) derived from titin were identified after intestinal epithelial transport in the XWH3-GID group, which could exert cholesterol-lowering effects through inhibiting intestinal cholesterol absorption and promoting peripheral hepatic LDL uptake, and effectively ameliorate western diet-induced hypercholesterolemia in ApoE-/- mice. These results suggest that Xuanwei ham with 3-year ripening period can be used as a source of cholesterol-lowering peptides and has potential to intervene in hypercholesterolemia.

Hepatic steatosis is associated with dysregulated cholesterol metabolism and altered protein acetylation dynamics in chickens

BACKGROUND

Hepatic steatosis is a prevalent manifestation of fatty liver, that has detrimental effect on the health and productivity of laying hens, resulting in economic losses to the poultry industry. Here, we aimed to systematically investigate the genetic regulatory mechanisms of hepatic steatosis in laying hens.

METHODS

Ninety individuals with the most prominent characteristics were selected from 686 laying hens according to the accumulation of lipid droplets in the liver, and were graded into three groups, including the control, mild hepatic steatosis and severe hepatic steatosis groups. A combination of transcriptome, proteome, acetylome and lipidome analyses, along with bioinformatics analysis were used to screen the key biological processes, modifications and lipids associated with hepatic steatosis.

RESULTS

The rationality of the hepatic steatosis grouping was verified through liver biochemical assays and RNA-seq. Hepatic steatosis was characterized by increased lipid deposition and multiple metabolic abnormalities. Integration of proteome and acetylome revealed that differentially expressed proteins (DEPs) interacted with differentially acetylated proteins (DAPs) and were involved in maintaining the metabolic balance in the liver. Acetylation alterations mainly occurred in the progression from mild to severe hepatic steatosis, i.e., the enzymes in the fatty acid oxidation and bile acid synthesis pathways were significantly less acetylated in severe hepatic steatosis group than that in mild group (P < 0.05). Lipidomics detected a variety of sphingolipids (SPs) and glycerophospholipids (GPs) were negatively correlated with hepatic steatosis (r ≤ -0.5, P < 0.05). Furthermore, the severity of hepatic steatosis was associated with a decrease in cholesterol and bile acid synthesis and an increase in exogenous cholesterol transport.

CONCLUSIONS

In addition to acquiring a global and thorough picture of hepatic steatosis in laying hens, we were able to reveal the role of acetylation in hepatic steatosis and depict the changes in hepatic cholesterol metabolism. The findings provides a wealth of information to facilitate a deeper understanding of the pathophysiology of fatty liver and contributes to the development of therapeutic strategies.

Unbalanced Redox With Autophagy in Cardiovascular Disease

Precise redox balance is essential for the optimum health and physiological function of the human body. Furthermore, an unbalanced redox state is widely believed to be part of numerous diseases, ultimately resulting in death. In this review, we discuss the relationship between redox balance and cardiovascular disease (CVD). In various animal models, excessive oxidative stress has been associated with increased atherosclerotic plaque formation, which is linked to the inflammation status of several cell types. However, various antioxidants can defend against reactive oxidative stress, which is associated with an increased risk of CVD and mortality. The different cardiovascular effects of these antioxidants are presumably due to alterations in the multiple pathways that have been mechanistically linked to accelerated atherosclerotic plaque formation, macrophage activation, and endothelial dysfunction in animal models of CVD, as well as in in vitro cell culture systems. Autophagy is a regulated cell survival mechanism that removes dysfunctional or damaged cellular organelles and recycles the nutrients for the generation of energy. Furthermore, in response to atherogenic stress, such as the generation of reactive oxygen species, oxidized lipids, and inflammatory signaling between cells, autophagy protects against plaque formation. In this review, we characterize the broad spectrum of oxidative stress that influences CVD, summarize the role of autophagy in the content of redox balance-associated pathways in atherosclerosis, and discuss potential therapeutic approaches to target CVD by stimulating autophagy.

Relationship between Cholesterol-Related Lipids and Severe Acute Pancreatitis: From Bench to Bedside

It is well known that hypercholesterolemia in the body has pro-inflammatory effects through the formation of inflammasomes and augmentation of TLR (Toll-like receptor) signaling, which gives rise to cardiovascular disease and neurodegenerative diseases. However, the interaction between cholesterol-related lipids and acute pancreatitis (AP) has not yet been summarized before. This hinders the consensus on the existence and clinical importance of cholesterol-associated AP. This review focuses on the possible interaction between AP and cholesterol-related lipids, which include total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and apolipoprotein (Apo) A1, from the bench to the bedside. With a higher serum level of total cholesterol, LDL-C is associated with the severity of AP, while the persistent inflammation of AP is allied with a decrease in serum levels of cholesterol-related lipids. Therefore, an interaction between cholesterol-related lipids and AP is postulated. Cholesterol-related lipids should be recommended as risk factors and early predictors for measuring the severity of AP. Cholesterol-lowering drugs may play a role in the treatment and prevention of AP with hypercholesterolemia.

Quercetin 7-rhamnoside protects against alpha-naphthylisothiocyanate (ANIT)-induced in cholestatic hepatitis rats by improving biliary excretion and inhibiting inflammatory responses

Objective: To explore the pharmacological effects and molecular mechanism of quercetin 7-rhamnoside (Q7R) in the treatment of cholestatic hepatitis induced by alpha-naphthylisothiocyanate (ANIT). Methods: ANIT-induced cholestatic hepatitis rat model was used to investigate the hepatoprotective effects of three different doses of Q7R (1.25 mg/kg; 2.5 mg/kg; 5 mg/kg). Serum biochemical indices were detected using commercial kits. H&E and masson staining were used to observe hepatic tissue damage and collagen deposition in hepatocytes. The metabolism of bile acid-related substances was detected via HPLC-MS/MS by 5-(diisopropylamino) amylamine (DIAAA) derivative method. Hepatocyte injury, cholestasis, and inflammation were detected at the mRNA and protein levels using reverse transcription-polymerase chain reaction (RT-PCR) and western blotting, respectively. Results: Q7R can decrease the level of CYP7A1, and increase FXR, CYP27A1 so then improving abnormal bile acid secretion. Furthermore, Q7R can also ameliorating inflammation by reduce TNF-α, IL-1β, PTGS1, PTGS2, NCOA2, NF-κB level. Therefore, Q7R had an effective therapeutic effect on ANIT-induced cholestatic hepatitis, improving abnormal bile acid secretion, and inhibiting inflammatory responses. Conclusion: The results demonstrated that Q7R treat cholestatic hepatitis by regulating bile acid secretion and alleviating inflammation.

Metabolic Role of Autophagy in the Pathogenesis and Development of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of liver disease, ranging from simple steatosis to hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Liver fibrosis, which portends a poor prognosis in NAFLD, is characterized by the excessive accumulation of extracellular matrix (ECM) proteins resulting from abnormal wound repair response and metabolic disorders. Various metabolic factors play crucial roles in the progression of NAFLD, including abnormal lipid, bile acid, and endotoxin metabolism, leading to chronic inflammation and hepatic stellate cell (HSC) activation. Autophagy is a conserved process within cells that removes unnecessary or dysfunctional components through a lysosome-dependent regulated mechanism. Accumulating evidence has shown the importance of autophagy in NAFLD and its close relation to NAFLD progression. Thus, regulation of autophagy appears to be beneficial in treating NAFLD and could become an important therapeutic target.

Metabolomic Approach to Screening Homozygotes in Chinese Patients with Severe Familial Hypercholesterolemia

Homozygous familial hypercholesterolemia (HoFH) is a rare inborn-errors-of-metabolism disorder characterized by devastatingly elevated low-density lipoprotein cholesterol (LDL-C) and premature cardiovascular disease. The gold standard for screening and diagnosing HoFH is genetic testing. In China, it is expensive and is always recommended for the most likely HoFH subjects with aggressive LDL-C phenotype. However, the LDL-C levels of HoFH patients and a substantial proportion of heterozygous FH (HeFH) patients overlapped considerably. Here, we performed a cost-effective metabolomic profiling on genetically diagnosed HoFH (n = 69) and HeFH patients (n = 101) with overlapping LDL-C levels, aiming to discovery a unique metabolic pattern for screening homozygotes in patients with severe FH. We demonstrated a differential serum metabolome profile in HoFH patients compared to HeFH patients. Twenty-one metabolomic alterations showed independent capability in differentiating HoFH from severe HeFH. The combined model based on seven identified metabolites yielded a corrected diagnosis in 91.3% of HoFH cases with an area under the curve value of 0.939. Collectively, this study demonstrated that metabolomic profiling serves as a useful and economical approach to preselecting homozygotes in FH patients with severe hypercholesterolemia and may help clinicians to conduct selective genetic confirmation testing and familial cascade screening.

Long noncoding RNA lincsc5d regulates hepatic cholesterol synthesis by modulating sterol C5 desaturase in large yellow croaker

Although long noncoding RNA (lncRNA) plays a vital role in cholesterol metabolism, very little information is available in fish. Thus, a 10-week feeding experiment was performed to estimate the effects of lncRNA on cholesterol metabolism in large yellow croaker fed with fish oil (FO), soybean oil (SO), olive oil (OO), and palm oil (PO) diets. Results showed that fish fed with OO and PO diets had higher liver total cholesterol (TC) and cholesterol ester (CE) contents compared with fish fed with FO diets. Analysis of the KEGG pathway showed that the steroid biosynthesis pathway was enriched in comparisons FO vs SO, FO vs OO, and FO vs PO. Meanwhile, sterol C5 desaturase (SC5D), a cholesterol synthase, was up-regulated in the steroid biosynthesis pathway. SC5D was widely expressed in all tissues examined, and the highest expression of SC5D was detected in brain. More importantly, a novel lncRNA associated with sc5d gene was identified by RNA sequencing and named as lincsc5d. The tissue distribution of lincsc5d was similar to that of sc5d. A nuclear/cytoplasmic RNA separation assay showed that lincsc5d was a nucleus-enriched lncRNA. qRT-PCR results demonstrated that lincsc5d was markedly up-regulated in the SO, OO, and PO groups. Furthermore, the results of TC content and the lincsc5d and sc5d expression in hepatocytes agreed with in vivo results. In conclusion, this study indicated that vegetable oils, especially OO and PO, increased hepatic cholesterol levels by promoting cholesterol synthesis, and lncRNA lincsc5d and sc5d might be involved in cholesterol synthesis.

The Adaptive Characteristics of Cholesterol and Bile Acid Metabolism in Nile Tilapia Fed a High-Fat Diet

Since high-fat diet (HFD) intake elevates liver cholesterol and enhanced cholesterol-bile acid flux alleviates its lipid deposition, we assumed that the promoted cholesterol-bile acid flux is an adaptive metabolism in fish when fed an HFD. The present study investigated the characteristic of cholesterol and fatty acid metabolism in Nile tilapia (Oreochromis niloticus) after feeding an HFD (13% lipid level) for four and eight weeks. Visually healthy Nile tilapia fingerlings (average weight 3.50 ± 0.05 g) were randomly distributed into four treatments (4-week control diet or HFD and 8-week control diet or HFD). The liver lipid deposition and health statue, cholesterol/bile acid, and fatty acid metabolism were analyzed in fish after short-term and long-term HFD intake. The results showed that 4-week HFD feeding did not change serum alanine transaminase (ALT) and aspartate transferase (AST) enzyme activities, along with comparable liver malondialdehyde (MDA) content. But higher serum ALT and AST enzyme activities and liver MDA content were observed in fish fed 8-week HFD. Intriguingly, remarkably accumulated total cholesterol (mainly cholesterol ester, CE) was observed in the liver of fish fed 4-week HFD, along with slightly elevated free fatty acids (FFAs) and comparable TG contents. Further molecular analysis in the liver showed that obvious accumulation of CE and total bile acids (TBAs) in fish fed 4-week HFD was mainly attributed to the enhancement of cholesterol synthesis, esterification, and bile acid synthesis. Furthermore, the increased protein expressions of acyl-CoA oxidase 1/2 (Acox1 and Acox2), which serve as peroxisomal fatty acid β-oxidation (FAO) rate-limiting enzymes and play key roles in the transformation of cholesterol into bile acids, were found in fish after 4-week HFD intake. Notably, 8-week HFD intake remarkably elevated FFA content (about 1.7-fold increase), and unaltered TBAs were found in fish liver, accompanied by suppressed Acox2 protein level and cholesterol/bile acid synthesis. Therefore, the robust cholesterol-bile acid flux serves as an adaptive metabolism in Nile tilapia when fed a short-term HFD and is possibly via stimulating peroxisomal FAO. This finding enlightens our understanding on the adaptive characteristics of cholesterol metabolism in fish fed an HFD and provides a new possible treatment strategy against metabolic disease induced by HFD in aquatic animals.

The Hypolipidemic Effect of Hawthorn Leaf Flavonoids through Modulating Lipid Metabolism and Gut Microbiota in Hyperlipidemic Rats

Objective. The purpose of this study was to explore the potential mechanisms of the lipid-regulating effects and the effect on modulating the gut microbiota of hawthorn leaf flavonoids (HLF) in the high-fat diet-induced hyperlipidemic rats. Methods. The hypolipidemic effect of HLF was investigated in the high-fat diet-induced hyperlipidemic rats. The action targets of HLF in the treatment of hyperlipidemia were predicted by network pharmacology and KEGG enrichment bubble diagram, which were verified by the test of western blotting. Meanwhile, we used 16S rRNA sequencing to evaluate the effects of HLF on the microbes. Results. The results of animal experiments showed that HLF could reduce the body weight and regulate the levels of serum lipid in high-fat diet (HFD) rats. Meanwhile, for the related targets of cholesterol metabolism, HLF could significantly upregulate the expression of LDLR, NR1H3, and ABCG5/ABCG8; reduce the expression of PCSK9; and increase the level of CYP7A1 in the intestinal tissue, whereas cholesterol biosynthetic protein expressions including HMGCR and SCAP were lowered by HLF. In addition, HLF increased the activities of plasma SOD, CAT, and GSH-Px and decreased the levels of Casp 1, NLRP3, IL-1β, IL-18, and TNF-α, improving the degree of hepatocyte steatosis and inflammatory infiltration of rats. Notably, HLF significantly regulated the relative abundance of major bacteria such as g_Lactobacillus, g_Anaerostipes, g_[Eubacterium]_hallii_group, g_Fusicatenibacter, g_Akkermansia, and g_Collinsella. Synchronously, we found that HLF could regulate the disorder of plasma HEPC and TFR levels caused by HFD. Conclusion. This study demonstrates that HLF can regulate metabolic hyperlipidemia syndromes and modulate the relative abundance of major bacteria, which illustrated that it might be associated with the modulation of gut microbiota composition and metabolites.

ATF3 in atherosclerosis: a controversial transcription factor

Atherosclerosis, the pathophysiological basis of most malignant cardiovascular diseases, remains a global concern. Transcription factors play a key role in regulating cell function and disease progression in developmental signaling pathways involved in atherosclerosis. Activated transcription factor (ATF) 3 is an adaptive response gene in the ATF/cAMP response element binding (CREB) protein family that acts as a transcription suppressor or activator by forming homodimers or heterodimers with other ATF/CREB members. Appropriate ATF3 expression is vital for normal physiological cell function. Notably, ATF3 exhibits distinct roles in vascular endothelial cells, macrophages, and the liver, which will also be described in detail. This review provides a new perspective for atherosclerosis therapy by summarizing the mechanism of ATF3 in atherosclerosis, as well as the structure and pathophysiological properties of ATF3. KEY MESSAGES: • In endothelial cells, ATF3 overexpression aggravates oxidative stress and inflammation. • In macrophages and liver cells, ATF3 can act as a negative regulator of inflammation and promote cholesterol metabolism. • ATF3 can be used as a potential therapeutic factor in the treatment of atherosclerosis.

Di(2-ethylhexyl) phthalate disturbs cholesterol metabolism through oxidative stress in rat liver

Di(2-ethylhexyl) phthalate (DEHP) is widely used and has been implicated in hepatotoxicity, although the mechanism is unclear. Here, we investigated the effect of DEHP on hepatic cholesterol metabolism in SD rats exposed to 0 and 300 mg/kg/day DEHP for 12 weeks. An RNA-Seq analysis was performed to describe the hepatic responses to long-term DEHP exposure in combination with serological and oxidative stress parameter measurements. DEHP increased the serum levels of total cholesterol (TC), high-density lipoprotein (HDL), and alanine transaminase (ALT). Moreover, DEHP increased the content of malondialdehyde (MDA) and decreased antioxidant enzyme activities in the liver. Transcriptomic results revealed that DEHP dramatically changed the cholesterol metabolism pathway and oxidation-reduction process and depressed gene expression involved in cholesterol efflux and monooxygenase activity. Total antioxidant capacity (T-AOC) positively correlated with Abcg5 and Abcg8. Overall, this study showed the mechanisms underlying hepatotoxicity caused by DEHP, providing new insights into understanding DEHP poisoning.

Gut Parabacteroides merdae protects against cardiovascular damage by enhancing branched-chain amino acid catabolism

Obesity, dyslipidemia and gut dysbiosis are all linked to cardiovascular diseases. A Ganoderma meroterpene derivative (GMD) has been shown to alleviate obesity and hyperlipidemia through modulating the gut microbiota in obese mice. Here we show that GMD protects against obesity-associated atherosclerosis by increasing the abundance of Parabacteroides merdae in the gut and enhancing branched-chain amino acid (BCAA) catabolism. Administration of live P. merdae to high-fat-diet-fed ApoE-null male mice reduces atherosclerotic lesions and enhances intestinal BCAA degradation. The degradation of BCAAs is mediated by the porA gene expressed in P. merdae. Deletion of porA from P. merdae blunts its capacity to degrade BCAAs and leads to inefficacy in fighting against atherosclerosis. We further show that P. merdae inhibits the mTORC1 pathway in atherosclerotic plaques. In support of our preclinical findings, an in silico analysis of human gut metagenomic studies indicates that P. merdae and porA genes are depleted in the gut microbiomes of individuals with atherosclerosis. Our results provide mechanistic insights into the therapeutic potential of GMD through P. merdae in treating obesity-associated cardiovascular diseases.

Targets of statins intervention in LDL-C metabolism: Gut microbiota

Increasing researches have considered gut microbiota as a new “metabolic organ,” which mediates the occurrence and development of metabolic diseases. In addition, the liver is an important organ of lipid metabolism, and abnormal lipid metabolism can cause the elevation of blood lipids. Among them, elevated low-density lipoprotein cholesterol (LDL-C) is related with ectopic lipid deposition and metabolic diseases, and statins are widely used to lower LDL-C. In recent years, the gut microbiota has been shown to mediate statins efficacy, both in animals and humans. The effect of statins on microbiota abundance has been deeply explored, and the pathways through which statins reduce the LDL-C levels by affecting the abundance of microbiota have gradually been explored. In this review, we discussed the interaction between gut microbiota and cholesterol metabolism, especially the cholesterol-lowering effect of statins mediated by gut microbiota, via AMPK-PPARγ-SREBP1C/2, FXR and PXR-related, and LPS-TLR4-Myd88 pathways, which may help to explain the individual differences in statins efficacy.

The role of lactoferrin in atherosclerosis

Atherosclerosis (AS) is a common pathological basis for many cardiovascular diseases (CVDs) and result in high mortality and immense health and economic burdens worldwide. Early prevention, diagnosis, and treatment are promising approaches for stemming the development and progression of AS. Lactoferrin (Lf) is an iron-binding glycoprotein belonging to the transferrin family. It is widely found in body fluids such as digestive tract fluids, tears, and milk. Lf possesses anti-inflammatory, antibacterial, immunoregulatory, antioxidant and many other physiological functions. The serum Lf level is reportedly associated with the risk of AS and AS-related CVDs. Lf administration is closely involved in several mechanisms, including cholesterol metabolism, foam cell formation, ICAM-1 expression, homocysteine and leptin levels, anti-inflammatory and antioxidant function. Moreover, Lf has also been applied in the sythesis of magnetic resonance imaging (MRI) contrast agents to detect AS. Lf plays an important role in AS and may therefore be used in its diagnosis and treatment. Thus, this article aims to review the association between Lf and the risk of AS and AS-related CVDs, the mechanisms of Lf administration on AS, and its potential application in AS diagnosis.

Liver PP2A-Cα Protects From Parenteral Nutrition-associated Hepatic Steatosis

BACKGROUND & AIMS

Parenteral nutrition (PN) is a lifesaving therapy for patients with intestinal failure. Hepatic steatosis is a potentially fatal complication of long-term PN, but the involved pathological mechanisms are incompletely unclarified. Herein, we identify the role of protein phosphatase 2A (PP2A) in the pathogenesis of parenteral nutrition-associated hepatic steatosis (PNAHS).

METHODS

Proteomic/phosphoproteomic analyses of liver samples from patients with PNAHS were applied to identify the mechanism of PNAHS. Total parenteral nutrition (TPN) mice model, in vivo, and in vitro experiments were used to assess the effect of PP2A-Cα on liver fatty acid metabolism.

RESULTS

Reduced expression of PP2A-Cα (catalytic subunit) enhanced activation of serine/threonine kinase Akt2 and decreased activation of adenosine monophosphate-activated protein kinase (AMPK) were associated with hepatic steatosis in patients with PNAHS. Mice given PN for 14 days developed hepatic steatosis, down-regulation of PP2A-Cα, activation of Akt2, and inhibition of AMPK. Hepatocyte-specific deletion of PP2A-Cα in mice given PN exacerbated Akt2 activation, AMPK inhibition, and hepatic steatosis through an effect on fatty acid degradation, whereas hepatocyte-specific PP2A-Cα overexpression significantly ameliorated hepatic steatosis accompanied with Akt2 suppression and AMPK activation. Additionally, pharmacological activation of Akt2 in mice overexpressing PP2A-Cα led to the aggravation of hepatic steatosis.

CONCLUSIONS

Our findings demonstrate that hepatic PP2A-Cα serves as a protective factor of PNAHS due to ameliorating hepatic steatosis and improving liver function. Our study provides a strong rationale that PP2A-Cα may be involved in the pathogenesis of PNAHS.

Metabolomics analysis of the effects of quercetin on Cd-induced hepatotoxicityin rats

Cadmium(Cd) is known to cause damage to the liver. In this study, metabolomics technology was used to investigate the effect of quercetin(QE) on Cd-induced hepatotoxicity. A total of 60 male SD rats were randomly divided into the following 6 groups: control group (C), low and high dose QE group (Q1: 10 mg/kg·bw, Q2: 50 mg/kg·bw), Cd group (D), low and high dose QE and Cd combined intervention group (DQ1, DQ2). The rats were given Cd chloride (CdCl₂) at a concentration of 40 mg/L through free drinking water. After 12 weeks of treatment, liver samples of rats were collected for metabonomic analysis. A total of 12 metabolites were identified, the intensities of PC(18:0/14:1(9Z)) and Arachidonate acid were decreased in the Cd-treated group (p < 0.01), whereas the intensities of Chenodeoxyglycocholic acid, Cholic acid, Taurochenodesoxycholic acid, Glycocholic acid, Prostaglandin D2, 15-Deoxy-d-12,14-PGJ2, Oxidized glutathione, Cholesterol, Protoporphyrin IX, Bilirubinwere increased significantly in the Cd-treated group compared with group C(p < 0.01). When rats were given high doses of QE and Cd at the same time, the intensity of the above metabolites was significantly restored in group DQ2. Results suggest that The protective effect of QE on Cd-induced liver injury is associated with antioxidant activity of QE, as well as QE can regulates hepatic bile acid metabolism by affecting FXR and BSEP, and regulates AA metabolism by inhibiting Cd-induced activities of COX-2 and PLA2.

Liver proteome profiling in dairy cows during the transition from gestation to lactation: Effects of supplementation with essential fatty acids and conjugated linoleic acids as explored by PLS-DA

This study aimed at investigating the synergistic effects of essential fatty acids (EFA) and conjugated linoleic acids (CLA) on the liver proteome profile of dairy cows during the transition to lactation. 16 Holstein cows were infused from 9 wk. antepartum to 9 wk. postpartum into the abomasum with either coconut oil (CTRL) or a mixture of EFA (linseed + safflower oil) and CLA (EFA + CLA). Label-free quantitative proteomics was performed in liver tissue biopsied at days -21, +1, +28, and + 63 relative to calving. Differentially abundant proteins (DAP) between treatment groups were identified at the intersection between a multivariate and a univariate analysis. In total, 1680 proteins were identified at each time point, of which between groups DAP were assigned to the metabolism of xenobiotics by cytochrome P450, drug metabolism - cytochrome P450, steroid hormone biosynthesis, glycolysis/gluconeogenesis, and glutathione metabolism. Cytochrome P450, as a central hub, enriched with specific CYP enzymes comprising: CYP51A1 (d - 21), CYP1A1 & CYP4F2 (d + 28), and CYP4V2 (d + 63). Collectively, supplementation of EFA + CLA in transition cows impacted hepatic lipid metabolism and enriched several common biological pathways at all time points that were mainly related to ω-oxidation of fatty acids through the Cytochrome p450 pathway. SIGNIFICANCE: In three aspects this manuscript is notable. First, this is among the first longitudinal proteomics studies in nutrition of dairy cows. The selected time points are critical periods around parturition with profound endocrine and metabolic adaptations. Second, our findings provided novel information on key drivers of biologically relevant pathways suggested according to previously reported performance, zootechnical, and metabolism data (already published elsewhere). Third, our results revealed the role of cytochrome P450 that is hardly investigated, and of ω-oxidation pathways in the metabolism of fatty acids with the involvement of specific enzymes.

Clinical Nomogram to Predict Major Adverse Cardiac Events in Acute Myocardial Infarction Patients within 1 Year of Percutaneous Coronary Intervention

The purpose of this study was to summarize the clinical characteristics and risk factors of major adverse cardiovascular events (MACEs) in patients who had had acute myocardial infarction (AMI) within 1 year of percutaneous coronary intervention (PCI). A total of 421 AMI patients who were treated with PCI and experienced MACEs within 1 year of their admission were included in this retrospective study. In addition, patients were matched for age, sex, and presentation with 561 patients after AMI who had not had MACEs. The clinical characteristics and risk factors for MACEs within 1 year in AMI patients were investigated, to develop a nomogram for MACEs based on univariate and multivariate analyses. The C statistic was used to assess the discriminative performance of the nomogram. In addition, calibration curve and decision curve analyses were conducted to validate the calibration performance and utility, respectively, of the nomogram. After univariate and multivariate analyses, a nomogram was constructed based on age (odds ratio (OR): 1.030; 95% confidence interval (CI): 1.014–1.047), diabetes mellitus (OR: 1.667; 95% CI: 1.151–2.415), low-density lipoprotein cholesterol (OR: 1.332; 95% CI: 1.134–1.565), uric acid (OR: 1.003; 95% CI: 1.001–1.005), lipoprotein (a) (OR: 1.003; 95% CI: 1.002–1.003), left ventricular ejection fraction (OR: 0.929; 95% CI: 0.905–0.954), Syntax score (OR: 1.075; 95% CI: 1.053–1.097), and hypersensitive troponin T (OR: 1.002; 95% CI: 1.002–1.003). The C statistic was 0.814. The calibration curve showed good concordance of the nomogram, while decision curve analysis demonstrated satisfactory positive net benefits. We developed a convenient, practical, and effective prediction model for predicting MACEs in AMI patients within 1 year of PCI. To ensure generalizability, this model requires external validation.

Therapeutic regulation of autophagy in hepatic metabolism

Metabolic homeostasis requires dynamic catabolic and anabolic processes. Autophagy, an intracellular lysosomal degradative pathway, can rewire cellular metabolism linking catabolic to anabolic processes and thus sustain homeostasis. This is especially relevant in the liver, a key metabolic organ that governs body energy metabolism. Autophagy's role in hepatic energy regulation has just begun to emerge and autophagy seems to have a much broader impact than what has been appreciated in the field. Though classically known for selective or bulk degradation of cellular components or energy-dense macromolecules, emerging evidence indicates autophagy selectively regulates various signaling proteins to directly impact the expression levels of metabolic enzymes or their upstream regulators. Hence, we review three specific mechanisms by which autophagy can regulate metabolism: A) nutrient regeneration, B) quality control of organelles, and C) signaling protein regulation. The plasticity of the autophagic function is unraveling a new therapeutic approach. Thus, we will also discuss the potential translation of promising preclinical data on autophagy modulation into therapeutic strategies that can be used in the clinic to treat common metabolic disorders.

Hepatic Lipid Metabolism Disorder and Atherosclerosis

Lipid metabolism disorder plays a fundamental role in the pathogenesis of atherosclerosis. As the largest metabolic organ of the human body, liver has a key role in lipid metabolism by influencing fat production, fat decomposition, and the intake and secretion of serum lipoproteins. Numerous clinical and experimental studies have indicated that the dysfunction of hepatic lipid metabolism is closely tied to the onset of atherosclerosis. However, the identity and functional role of hepatic lipid metabolism responsible for these associations remain unknown. This review presented that cholesterol synthesis, cholesterol transport, and the metabolism of triglyceride, lipoproteins, and fatty acids are all associated with hepatic lipid metabolism and atherosclerosis. Moreover, we also discussed the roles of gut microbiota, inflammatory response, and oxidative stress in the pathological association between hepatic lipid metabolism and atherosclerosis. These significant evidences support strongly that hepatic lipid metabolism disorders may increase the risk of atherosclerosis.

Myocardial Infarction and Coronary Artery Disease in Menopausal Women With Type 2 Diabetes Mellitus Negatively Correlate With Total Serum Bile Acids

Background

As metabolic molecules, bile acids (BAs) not only promote the absorption of fat-soluble nutrients, but they also regulate many metabolic processes, including the homeostasis of glucose and lipids. Although total serum BA (TBA) measurement is a readily available clinical test related to coronary artery disease (CAD), myocardial infarction (MI), and type 2 diabetes mellitus (T2DM), the relationship between TBA and these pathological conditions remain unclear, and research on this topic is inconclusive.

Methods

This study enrolled 20,255 menopausal women aged over 50 years, including 6,421 T2DM patients. The study population was divided into different groups according to the median TBA level in order to explore the clinical characteristics of menopausal women with different TBA levels. Spline analyses, generalized additive model (GAM) model and regression analyses based on TBA level were used to explore the relationship between TBA and different diseases independently, including CAD and MI, or in combination with T2DM.

Results

Both in the general population and in the T2DM subgroup, the TBA level was significantly lower in CAD patients than in non-CAD patients. Spline analyses indicated that within normal clinical range of TBA concentration (0-10 µmol/L), the presence of CAD and MI showed similar trends in total and T2DM population. Similarly, the GAM model indicated that within the 0-10 μmol/L clinical range, the predicted probability for CAD and MI alone and in combination with T2DM was negatively correlated with TBA concentration. Multivariate regression analysis suggested that low TBA level was positively associated with the occurrence of CAD combined with T2DM (OR: 1.451; 95%CI: 1.141-1.847).

Conclusions

In menopausal women, TBA may represent a valuable clinical serum marker with negative correlation for CAD and MI in patients with T2DM.

Hypolipidemic Effects and Preliminary Mechanism of Chrysanthemum Flavonoids, Its Main Components Luteolin and Luteoloside in Hyperlipidemia Rats

This study aimed to investigate the key constituents and preliminary mechanism for the hypolipidemic activity of chrysanthemum flavonoids. Hyperlipidemia (HPL) rats were divided into five groups: the model control group (MC); Chrysanthemum flavone intervention group (CF); luteolin intervention group; luteoloside intervention group and simvastatin intervention group. The body weight, organ coefficient, serum lipids, antioxidant activity, and lipid metabolism enzymes were detected. Hematoxylin and eosin (H&E) staining was used to observe the liver and adipose tissue. Chrysanthemum flavonoids, luteolin, and luteoloside can reduce the weight and levels of total cholesterol (TC), triglycerides (TG), and LDL-C, and increase the level of HDL-C in the blood and reduce liver steatosis. Indicators of liver function (AST, ALT, and ALP) improved. The antioxidant activity (GSH-Px, CAT, SOD) and enzymes associated with lipid catabolism (FAβO, CYP7A1, and HL) increased, while lipid peroxidation products (MDA) and enzymes associated with lipid synthesis (FAS, HMG-CoA, and DGAT) decreased. Chrysanthemum flavonoids had a better effect on the antioxidant level and lipid metabolism-related enzyme activity. There was no significant difference in the effects of the chrysanthemum flavonoids, luteolin, and Luteoloside on improving blood lipids and hepatic steatosis—mechanisms that may be related to antioxidant levels and regulating enzymes involved in the metabolism of fatty acids, cholesterol, and triglycerides in the liver. However, chrysanthemum flavonoids had a stronger antioxidant and lipid metabolism regulation ability, and the long-term effects may be better.

Autophagy in liver diseases: A review

The liver is a highly dynamic metabolic organ that plays critical roles in plasma protein synthesis, gluconeogenesis and glycogen storage, cholesterol metabolism and bile acid synthesis as well as drug/xenobiotic metabolism and detoxification. Research from the past decades indicate that autophagy, the cellular catabolic process mediated by lysosomes, plays an important role in maintaining cellular and metabolic homeostasis in the liver. Hepatic autophagy fluctuates with hormonal cues and the availability of nutrients that respond to fed and fasting states as well as circadian activities. Dysfunction of autophagy in liver parenchymal and non-parenchymal cells can lead to various liver diseases including non-alcoholic fatty liver diseases, alcohol associated liver disease, drug-induced liver injury, cholestasis, viral hepatitis and hepatocellular carcinoma. Therefore, targeting autophagy may be a potential strategy for treating these various liver diseases. In this review, we will discuss the current progress on the understanding of autophagy in liver physiology. We will also discuss several forms of selective autophagy in the liver and the molecular signaling pathways in regulating autophagy of different cell types and their implications in various liver diseases.

Reconstruction and analysis of correlation networks based on GC-MS metabolomics data for hypercholesterolemia

BACKGROUND AND AIMS

Hypercholesterolemia is characterized by the elevation of plasma total cholesterol level, especially low-density lipoprotein (LDL) cholesterol. This disease is usually caused by a mutation in genes such as LDL receptor, apolipoprotein B, or proprotein convertase subtilisin/kexin type 9. However, a considerable number of patients with hypercholesterolemia do not have any mutation in these candidate genes. In this study, we examined the difference in the metabolic level between patients with hypercholesterolemia and healthy subjects, and screened the potential biomarkers for this disease.

METHODS

Analysis of plasma metabolomics in hypercholesterolemia patients and healthy controls was performed by gas chromatography-mass spectrometry and metabolic correlation networks were constructed using Gephi-0.9.2.

RESULTS

First, metabolic profile analysis confirmed the distinct metabolic footprints between the patients and the healthy ones. The potential biomarkers screened by orthogonal partial least-squares discrimination analysis included l-lactic acid, cholesterol, phosphoric acid, d-glucose, urea, and d-allose (Variable importance in the projection > 1). Second, arginine and methionine metabolism were significantly perturbed in hypercholesterolemia patients. Finally, we identified that l-lactic acid, l-lysine, l-glutamine, and l-cysteine had high scores of centrality parameters in the metabolic correlation network.

CONCLUSION

Plasma l-lactic acid could be used as a sensitive biomarker for hypercholesterolemia. In addition, arginine biosynthesis and cysteine and methionine metabolism were profoundly altered in patients with hypercholesterolemia.

Function of the endolysosomal network in cholesterol homeostasis and metabolic-associated fatty liver disease (MAFLD)

Background

Metabolic-associated fatty liver disease (MAFLD), also known as non-alcoholic fatty liver disease, has become the leading cause of chronic liver disease worldwide. In addition to hepatic accumulation of triglycerides, dysregulated cholesterol metabolism is an important contributor to the pathogenesis of MAFLD. Maintenance of cholesterol homeostasis is highly dependent on cellular cholesterol uptake and, subsequently, cholesterol transport to other membrane compartments, such as the endoplasmic reticulum (ER).

Scope of review

The endolysosomal network is key for regulating cellular homeostasis and adaptation, and emerging evidence has shown that the endolysosomal network is crucial to maintain metabolic homeostasis. In this review, we will summarize our current understanding of the role of the endolysosomal network in cholesterol homeostasis and its implications in MAFLD pathogenesis.

Major conclusions

Although multiple endolysosomal proteins have been identified in the regulation of cholesterol uptake, intracellular transport, and degradation, their physiological role is incompletely understood. Further research should elucidate their role in controlling metabolic homeostasis and development of fatty liver disease.

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The intracellular cholesterol transport is tightly regulated by the endocytic and lysosomal network.

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Dysfunction of the endolysosomal network affects hepatic lipid homeostasis.

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The endosomal sorting of lipoprotein receptors is precisely regulated and is not a bulk process.

Therapeutic potential of natural products against atherosclerosis: Targeting on gut microbiota

Gut microbiota (GM) has emerged as an essential and integral factor for maintaining human health and affecting pathological outcomes. Metagenomics and metabolomics characterization have furthered gut metagenome's understanding and unveiled that deviation of specific GM community members and GM-dependent metabolites imbalance orchestrate metabolic or cardiovascular diseases (CVDs). Restoring GM ecosystem with nutraceutical supplements keenly prebiotics and probiotics relatively decreases CVDs incidence and overall mortality. In Atherosclerosis, commensal and pathogenic gut microbes correlate with atherogenesis events. GM-dependent metabolites-trimethylamine N-oxide and short-chain fatty acids regulate atherosclerosis-related metabolic processes in opposite patterns to affect atherosclerosis outcomes. Therefore, GM might be a potential therapeutic target for atherosclerosis. In atherogenic animal models, natural products with cardioprotective properties could modulate the GM ecosystem by revitalizing healthier GM phylotypes and abrogating proatherogenic metabolites, paving future research paths for clinical therapeutics.

Autophagy, Hyperlipidemia, and Atherosclerosis

Autophagy is an evolutionarily conserved process in eukaryotes that processes the turnover of intracellular substances. Atherosclerosis is a disease caused by multiple factors, it mainly occurs on the walls of large and medium blood vessels and atherosclerotic plaques form in the intima of the blood vessels. Hyperlipidemia is considered to be a very dangerous factor leading to cardiovascular and cerebrovascular diseases, especially atherosclerosis. This chapter mainly introduces the key role of autophagy in hyperlipidemia and atherosclerosis, that is, impaired lipophagy affects the degradation of triacylglycerol, cholesterol, etc., leading to hyperlipidemia in atherosclerosis. In patients, excessive levels of autophagy accelerate the rupture of atherosclerotic plaque. This chapter also describes the advances in the treatment of atherosclerosis and hyperlipidemia by targeted autophagy.

α7nAChR Deletion Aggravates Myocardial Infarction and Enhances Systemic Inflammatory Reaction via mTOR-Signaling-Related Autophagy

Alpha7 nicotinic acetylcholine receptor (α7nAChR) has been previously reported to play an alleviative role in myocardial infarction (MI). In this study, we investigated its specific mechanism. α7nAChR^-/- mice and its control (α7nAChR^+/+) were used for the study of α7nAChR. Left anterior descending coronary artery occlusion was conducted for the creation of mice MI model and lipopolysaccharide (LPS) was used as inflammatory stressor in murine peritoneal macrophages. Triphenyltetrazolium chloride (TTC) staining and echocardiography was used for the detection of infarct size and cardiac function, respectively. Western blot was conducted for the testing of autophagy-related proteins and enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-PCR) was used for the testing of proinflammatory cytokines. Rapamycin was used for the induction of autophagy through inhibiting mammalian target of rapamycin (mTOR)-related signaling. We found that knocking out α7nAChR enhanced the cardiac infarct size and damaged cardiac function in MI. α7nAChR deficiency increased the levels of several proinflammatory cytokines in serum and spleen from MI mice as well as murine macrophages under inflammatory stress. α7nAChR deletion decreased the level of autophagy in spleen from MI mice and macrophages under inflammatory stress. Rapamycin alleviated the cardiac function and systemic inflammatory reaction in MI mice as well as inflammatory reaction in macrophages under inflammatory stress, which was attenuated by knocking out α7nAChR. Our current study investigated the mechanism of α7nAChR-mediated cardio-protective and anti-inflammatory effect related to mTOR-related autophagy, which might provide a novel insight in the treatment of MI.

Lactoferrin promotes bile acid metabolism and reduces hepatic cholesterol deposition by inhibiting the farnesoid X receptor (FXR)-mediated enterohepatic axis

BACKGROUND

Lactoferrin (LF) is a multifunctional glycoprotein that can regulate lipid metabolism, lower cholesterol, reduce body weight, and prevent atherosclerosis. Bile acid (BA) metabolism plays an important role in removing excess cholesterol from the body. However, studies on the effects of LF on BA metabolism are limited and inconsistent.

METHODS

Male C57BL/6J mice aged 6-8 weeks were fed with a normal diet (control group), high-fat/high-cholesterol diet containing cholate (HFCCD group), or HFCCD and 1.0% LF in drinking water (LF group) for 8 weeks. Serum and hepatic lipid profiles, and glucose tolerance were measured. Fecal BA composition was determined through ultra-high performance liquid chromatography-tandem mass spectrometry. The gene expression of BA synthase in the liver and farnesoid X receptor (FXR)-mediated BA negative feedback regulation pathway in the liver and ileum were analyzed via RNA analysis.

RESULTS

HFCCD resulted in abnormal cholesterol levels in the serum and liver. LF intervention significantly increased the serum high-density lipoprotein cholesterol level by 24.9% and decreased the hepatic total cholesterol content by 26%. LF treatment significantly increased the BA content per gram by 109.8%, the total amount of BA excretion by 153.5% and conjugated BAs by 87.6% in the feces. Furthermore, LF upregulated the expression of the hepatic sterol 12α-hydroxylase (CYP8B1) gene, which expresses important enzymes in the classical pathway of BA synthesis, and the bile acid-CoA amino acid N-acetyltransferase (BAAT) gene, which is responsible for the formation of conjugated BAs. The FXR-mediated pathways in the enterohepatic axis, including FXR, fibroblast growth factor 15, and fibroblast growth factor receptor 4, were inhibited by LF.

CONCLUSIONS

LF ameliorated hepatic cholesterol deposition in mice fed with a high-fat and high cholesterol diet containing cholate. LF elevated the conjugated BA level, inhibited the ileum FXR and FXR-mediated enterohepatic axis, and increased BA synthesis and excretion.

Lipid Droplet Formation and Lipophagy in Fatty Liver Disease

Lipid droplets (LDs) are key sites of neutral lipid storage that can be found in all cells. Metabolic imbalances between the synthesis and degradation of LDs can result in the accumulation of significant amounts of lipid deposition, a characteristic feature of hepatocytes in patients with fatty liver disease, a leading indication for liver transplant in the United States. In this review, the authors highlight new literature related to the synthesis and autophagic catabolism of LDs, discussing key proteins and machinery involved in these processes. They also discuss recent findings that have revealed novel genetic risk factors associated with LD biology that contribute to lipid retention in the diseased liver.

Leukocyte cell-derived chemotaxin 2 inhibits development of atherosclerosis in mice

Leukocyte cell-derived chemotaxin 2 (LECT2), a multifunctional hepatokine, is involved in many pathological conditions. However, its role in atherosclerosis remains undefined. In this study, we administered vehicle or LECT2 to male Apoe^-/- mice fed a Western diet for 15 weeks. Atherosclerotic lesions were visualized and quantified with Oil-red O and hematoxylin staining. The mRNA expression levels of MCP-1, MMP-1, IL-8, IL-1β, and TNF-α were analyzed by quantitative real-time polymerase chain reaction. Serum TNF-α, IL-1β, IL-8, MCP-1, and MMP-1 concentrations were measured by enzyme-linked immunosorbent assay. CD68, CD31, and α-SMA, markers of macrophages, endothelial cells, and smooth muscle cells, respectively, were detected by immunostaining. Results showed that LECT2 reduced total cholesterol and low-density lipoprotein concentrations in serum and inhibited the development of atherosclerotic lesions, accompanied by reductions in inflammatory cytokines and lower MCP-1, MMP-1, TNF-α, IL-8, and IL-1β mRNA abundance. Furthermore, LECT2 decreased CD68, but increased α-SMA in atherosclerotic lesions, suggesting an increase in smooth muscle cells and reduction in macrophages. In summary, LECT2 inhibited the development of atherosclerosis in mice, accompanied by reduced serum total cholesterol concentration and lower inflammatory responses.

The Role of Autophagy in Liver Epithelial Cells and Its Impact on Systemic Homeostasis

Autophagy plays a role in several physiological and pathological processes as it controls the turnover rate of cellular components and influences cellular homeostasis. The liver plays a central role in controlling organisms’ metabolism, regulating glucose storage, plasma proteins and bile synthesis and the removal of toxic substances. Liver functions are particularly sensitive to autophagy modulation. In this review we summarize studies investigating how autophagy influences the hepatic metabolism, focusing on fat accumulation and lipids turnover. We also describe how autophagy affects bile production and the scavenger function within the complex homeostasis of the liver. We underline the role of hepatic autophagy in counteracting the metabolic syndrome and the associated cardiovascular risk. Finally, we highlight recent reports demonstrating how the autophagy occurring within the liver may affect skeletal muscle homeostasis as well as different extrahepatic solid tumors, such as melanoma.

A sulfated polysaccharide from Gracilaria Lemaneiformis regulates cholesterol and bile acid metabolism in high-fat diet mice

This study aimed to evaluate the regulation of lipid metabolism and mechanism of a sulfated polysaccharide from Gracilaria Lemaneiformis (GLP).

[Lipid-lowering effect of propolis in mice with Triton-WR1339-induced hyperlipidemia and its mechanism for regulating lipid metabolism]

OBJECTIVE

To evaluate the therapeutic effect of propolis against Triton-WR1339-induced hyperlipidemia in mice and explore the underlying mechanism.

METHODS

C57BL/6 mice were randomly divided into 7 groups (n=10), including the control group, hyperlipidemia model group, fenofibrate (30 mg/kg) treatment group, and 4 treatment groups treated with low- (30 mg/kg) or high-dose (60 mg/kg) propolis HB01 or HB02. In all but the control group, acute hyperlipidemia models were established by intramuscular injection of Triton WR-1339, and corresponding treatments were administered via gastric lavage for 7 days. After the treatments, blood samples were collected for testing the levels of total cholesterol (TC), triglycerides (TG), highdensity lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), malondialdehyde (MDA), superoxide dismutase (SOD), alanine aminotransferase (GPT), and aspartate aminotransferase (GOT); Western blotting was used to detect the expressions of the proteins involved in lipid metabolism in the liver tissues including ABCA1, ABCG8, LDLR, and SR-B1.

RESULTS

Compared with the normal control group, the mice with Triton-WR1339-induced hyperlipidemia showed significantly increased levels of TC, TG, LDL, MDA, GPT, and GOT and lowered HDL-C levels and SOD activity (P < 0.05). Treatments with fenofibrate and the 2 propolis at either low or high dose significantly reversed Triton-WR1339-induced changes in blood lipids (P < 0.05), and the effects of propolis were more potent. Triton-WR1339 injection also significantly decreased the expressions levels of ABCA1, ABCG8, LDLR, and SR-B1 in the liver (P < 0.05), and these changes were obviously reversed by treatments with fenofibrate and propolis (P < 0.05), especially by the latter.

CONCLUSIONS

The lipid-lowering effects of propolis are mediated by improving lipid metabolism and regulating the expressions of lipid transport proteins in the liver tissue.