Unveiling the role of APOM gene in liver cancer: Investigating the impact of hsa-miR-4489/MUC1-mediated ferroptosis on the advancement of hepatocellular carcinoma cells.

Primary liver cancer has consistently exhibited a high prevalence and fatality rate, necessitating the investigation of associated diagnostic markers and inhibition mechanisms to effectively mitigate its impact. The significance of apolipoprotein M (ApoM) in impeding the progression of neoplastic ailments is progressively gaining recognition. However, a comprehensive understanding of its underlying mechanism in liver cancer advancement remains to be elucidated. Recent evidence indicates a potential association between ApoM and polyunsaturated fatty acids (PUFAs), with the peroxidation of phospholipids (PLs) containing PUFAs being recognized as a crucial element in the occurrence of ferroptosis. This prompts us to investigate the impact of the APOM gene on the progression of liver cancer through the ferroptosis pathway and elucidate its underlying mechanisms. The findings of this study indicate that the liver cancer cell model, which was genetically modified to overexpress the APOM gene, demonstrated a heightened ferroptosis effect. Moreover, the observed inhibition of the GSH (Glutathione) - GPX4 (Glutathione Peroxidase 4) regulatory axis suggests that the role of this axis in inhibiting ferroptosis is weakened. Through intersection screening and validation, we found that Mucin 1,cell surface associated (MUC1) can inhibit ferroptosis and is regulated by the APOM gene. Bioinformatics analysis and screening identified miR-4489 as a mediator between the two. Experimental results using the dual luciferase reporter gene confirmed that has-miR-4489 targets MUC1's 3'-UTR and inhibits its expression. In conclusion, this study provides evidence that the APOM gene induces a down-regulation in the expression of the ferroptosis-inhibiting gene MUC1, mediated by miR-4489, thereby impeding the advancement of liver cancer cells through the facilitation of ferroptosis.

ApoM suppresses kidney renal clear cell carcinoma growth and metastasis via the Hippo-YAP signaling pathway.

Renal cell carcinoma is one of the most common malignancies worldwide, and kidney renal clear cell carcinoma (KIRC) is the most common histopathological type of renal cell carcinoma. However, the mechanism of KIRC progression remains poorly understood. Apolipoprotein M (ApoM) is a plasma apolipoprotein and a member of the lipid transport protein superfamily. Lipid metabolism is essential for tumor progression, and its related proteins can be used as therapeutic targets for tumors. ApoM influences the development of several cancers, but its relationship with KIRC remains unclear. In this study, we aimed to investigate the biological function of ApoM in KIRC and to reveal its potential molecular mechanisms. We found that ApoM expression was significantly reduced in KIRC and was strongly correlated with patient prognosis. ApoM overexpression significantly inhibited KIRC cell proliferation in vitro, suppressed the epithelial mesenchymal transition (EMT) of KIRC cells, and decreased their metastatic capacity. Additionally, the growth of KIRC cells was inhibited by ApoM overexpression in vivo. In addition, we found that overexpression of ApoM in KIRC attenuated Hippo-YAP protein expression and YAP stability and thus inhibited KIRC growth and progression. Therefore, ApoM may be a potential target for the treatment of KIRC.

Apolipoprotein M supports S1P production and conservation and mediates prolonged Akt activation via S1PR1 and S1PR3.

Sphingosine 1-phosphate (S1P) is one of the lipid mediators involved in diverse physiological functions. S1P circulates in blood and lymph bound to carrier proteins. Three S1P carrier proteins have been reported, albumin, apolipoprotein M (ApoM) and apolipoprotein A4 (ApoA4). The carrier-bound S1P exerts its functions via specific S1P receptors (S1PR1-5) on target cells. Previous studies showed several differences in physiological functions between albumin-bound S1P and ApoM-bound S1P. However, molecular mechanisms underlying the carrier-dependent differences have not been clarified. In addition, ApoA4 is a recently identified S1P carrier protein, and its functional differences from albumin and ApoM have not been addressed. Here, we compared the three carrier proteins in the processes of S1P degradation, release from S1P-producing cells and receptor activation. ApoM retained S1P more stable than albumin and ApoA4 in the cell culture medium when compared in the equimolar amounts. ApoM facilitated theS1P release from endothelial cells most efficiently. Furthermore, ApoM-bound S1P showed a tendency to induce prolonged activation of Akt via S1PR1 and S1PR3. These results suggest that the carrier-dependent functional differences of S1P are partly ascribed to the differences in the S1P stability, S1P-releasing efficiency and signaling duration.

Apolipoprotein M/sphingosine 1-phosphate protects against diabetic nephropathy.

Diabetic nephropathy remains a common cause of end-stage renal failure and its associated mortality around the world. Sphingosine 1-phosphate (S1P) is a multifunctional lipid mediator and binds to HDL via apolipoprotein M (ApoM). Since HDL has been reported to be epidemiologically associated with kidney disease, we attempted to investigate the involvement of the ApoM/S1P axis in the pathogenesis/progression of diabetic nephropathy. In type 2 diabetic patients, the serum ApoM levels were inversely correlated with the clinical stage of diabetic nephropathy. The decline in the eGFR over a 5-year observation period proceeded more rapidly in subjects with lower serum ApoM levels. In a mouse model of streptozotocin-induced diabetes, deletion of ApoM deteriorated the phenotypes of diabetic nephropathy: the urinary albumin and plasma creatinine levels increased, the kidneys enlarged, and renal fibrosis and thickening of the basement membrane progressed. On the other hand, overexpression of ApoM ameliorated these phenotypes. These protective effects of ApoM were partially inhibited by treatment with VPC23019, an antagonist of S1P1 and S1P3, but not by treatment with JTE013, an antagonist of S1P2. ApoM/S1P axis attenuated activation of the Smad3 pathway, while augmented eNOS phosphorylation through the S1P1 pathway. Moreover, ApoM/S1P increased the SIRT1 protein levels and enhanced mitochondrial functions by increasing the S1P content of the cell membrane, which might cause selective activation of S1P1. ApoM might be a useful biomarker for predicting the progression of diabetic nephropathy, and the ApoM/S1P-S1P1 axis might serve as a novel therapeutic target for preventing the development/progression of diabetic nephropathy.

Association of apolipoprotein M and sphingosine-1-phosphate with brown adipose tissue after cold exposure in humans.

The HDL-associated apolipoprotein M (apoM) and its ligand sphingosine-1-phosphate (S1P) may control energy metabolism. ApoM deficiency in mice is associated with increased vascular permeability, brown adipose tissue (BAT) mass and activity, and protection against obesity. In the current study, we explored the connection between plasma apoM/S1P levels and parameters of BAT as measured via 18F-FDG PET/CT after cold exposure in humans. Fixed (n = 15) vs personalized (n = 20) short-term cooling protocols decreased and increased apoM (- 8.4%, P = 0.032 vs 15.7%, P < 0.0005) and S1P (- 41.0%, P < 0.0005 vs 19.1%, P < 0.005) plasma levels, respectively. Long-term cooling (n = 44) did not affect plasma apoM or S1P levels. Plasma apoM and S1P did not correlate significantly to BAT volume and activity in the individual studies. However, short-term studies combined, showed that increased changes in plasma apoM correlated with BAT metabolic activity (ß: 0.44, 95% CI [0.06-0.81], P = 0.024) after adjusting for study design but not BAT volume (ß: 0.39, 95% CI [- 0.01-0.78], P = 0.054). In conclusion, plasma apoM and S1P levels are altered in response to cold exposure and may be linked to changes in BAT metabolic activity but not BAT volume in humans. This contrasts partly with observations in animals and highlights the need for further studies to understand the biological role of apoM/S1P complex in human adipose tissue and lipid metabolism.

The FoxOs are in the ApoM house.

The prevalence of metabolic syndrome continues to increase globally and heightens the risk for cardiovascular disease (CVD). Insulin resistance is a core pathophysiologic mechanism that causes abnormal carbohydrate metabolism and atherogenic changes in circulating lipoprotein quantity and function. In particular, dysfunctional HDL is postulated to contribute to CVD risk in part via loss of HDL-associated sphingosine-1-phosphate (S1P). In this issue of the JCI, Izquierdo et al. demonstrate that HDL from humans with insulin resistance contained lower levels of S1P. Apolipoprotein M (ApoM), a protein constituent of HDL that binds S1P and controls bioavailability was decreased in insulin-resistant db/db mice. Gain- and loss-of-function mouse models implicated the forkhead box O transcription factors (FoxO1,3,4) in the regulation of both ApoM and HDL-associated S1P. These data have important implications for potential FoxO-based therapies designed to treat lipid and carbohydrate abnormalities associated with human metabolic disease and CVD.

Hepatic FoxOs link insulin signaling with plasma lipoprotein metabolism through an apolipoprotein M/sphingosine-1-phosphate pathway.

Multiple beneficial cardiovascular effects of HDL depend on sphingosine-1-phosphate (S1P). S1P associates with HDL by binding to apolipoprotein M (ApoM). Insulin resistance is a major driver of dyslipidemia and cardiovascular risk. However, the mechanisms linking alterations in insulin signaling with plasma lipoprotein metabolism are incompletely understood. The insulin-repressible FoxO transcription factors mediate key effects of hepatic insulin action on glucose and lipoprotein metabolism. This work tested whether hepatic insulin signaling regulates HDL-S1P and aimed to identify the underlying molecular mechanisms. We report that insulin-resistant, nondiabetic individuals had decreased HDL-S1P levels, but no change in total plasma S1P. This also occurred in insulin-resistant db/db mice, which had low ApoM and a specific reduction of S1P in the HDL fraction, with no change in total plasma S1P levels. Using mice lacking hepatic FoxOs (L-FoxO1,3,4), we found that hepatic FoxOs were required for ApoM expression. Total plasma S1P levels were similar to those in controls, but S1P was nearly absent from HDL and was instead increased in the lipoprotein-depleted plasma fraction. This phenotype was restored to normal by rescuing ApoM in L-FoxO1,3,4 mice. Our findings show that insulin resistance in humans and mice is associated with decreased HDL-associated S1P. Our study shows that hepatic FoxO transcription factors are regulators of the ApoM/S1P pathway.

Isoform-Dependent Effects of Apolipoprotein E on Sphingolipid Metabolism in Neural Cells.

BACKGROUND: Sphingosine 1-phosphate (S1P) and ceramides have been implicated in the development of Alzheimer's disease. Apolipoprotein E (ApoE) isoforms are also involved in the development of Alzheimer's disease. OBJECTIVE: We aimed at elucidating the potential association of the ApoE isoforms with sphingolipid metabolism in the central nervous system. METHODS: We investigated the modulations of apolipoprotein M (apoM), a carrier of S1P, S1P, and ceramides in Apoeshl mice, which spontaneously lack apoE, and U251 cells and SH-SY5Y cells infected with adenovirus vectors encoding for apoE2, apoE3, and apoE4. RESULTS: In the brains of Apoeshl mice, the levels of apoM were lower, while those of ceramides were higher. In U251 cells, cellular apoM and S1P levels were the highest in the cells overexpressing apoE2 among the apoE isoforms. The cellular and medium contents of ceramides decreased in the order of the cells overexpressing apoE3 > apoE2 and increased in the cells overexpressing apoE4. In SH-SY5Y cells, apoM mRNA and medium S1P levels were also the highest in the cells overexpressing apoE2. The cellular contents of ceramides decreased in the order of the cells overexpressing apoE3 > apoE2 = apoE4 and those in medium decreased in the order of the cells overexpressing apoE3 > apoE2, while increased in the cells overexpressing apoE4. CONCLUSION: The modulation of apoM and S1P might partly explain the protective effects of apoE2 against Alzheimer's disease, and the modulation of ceramides might be one of the mechanisms explaining the association of apoE4 with the development of Alzheimer's disease.

Regulation of the apolipoprotein M signaling pathway: a review.

Apolipoprotein M (apoM), an apolipoprotein predominantly associated with high-density lipoprotein (HDL), is considered a mediator of the numerous roles of HDL, including reverse cholesterol transport, anti-atherosclerotic, anti-inflammatory and anti-oxidant, and mediates pre-ß-HDL formation. ApoM expression is known to be regulated by a variety of in vivo and in vitro factors. The transcription factors farnesoid X receptor, small heterodimer partner, liver receptor homolog-1, and liver X receptor comprise the signaling cascade network that regulates the expression and secretion of apoM. Moreover, hepatocyte nuclear factor-1α and c-Jun/JunB have been demonstrated to exert opposing regulatory effects on apoM through competitive binding to the same sites in the proximal region of the apoM gene. Furthermore, as a carrier and modulator of sphingosine 1-phosphate (S1P), apoM binds to S1P within its hydrophobic-binding pocket. The apoM/S1P axis has been discovered to play a crucial role in the apoM signaling pathway through its ability to regulate glucose and lipid metabolism, vascular barrier homeostasis, inflammatory response and other pathological and physiological processes. Using the findings of previous studies, the present review aimed to summarize the regulation of apoM expression by various factors and its role in different physiological and pathological conditions, and provide a new perspective for the further treatment of these diseases.

Propofol promotes migration, alleviates inflammation, and apoptosis of lipopolysaccharide-induced human pulmonary microvascular endothelial cells by activating PI3K/AKT signaling pathway via upregulating APOM expression.

Propofol (PRO), a clinical potent intravenous anesthetic, plays a significant role in relieving inflammatory diseases by repressing the release of inflammatory cytokines. The present study was aimed to reveal a novel mechanism by which PRO alleviates acute lung injury (ALI). Lipopolysaccharide (LPS) was utilized to induce human pulmonary microvascular endothelial cells (HPMECs) so as to simulate the microenvironment of ALI, and the expression of apolipoprotein M (APOM) was examined with western blotting. Then, APOM was silenced and profopol was used to treat the LPS-injured HPMECs. The cell viability, migration, and apoptosis were respectively observed after the processes of cell counting kit-8, wound healing, transwell, and TUNEL assay. Meanwhile, the inflammatory response was detected by determining the contents of inflammatory cytokines. Subsequently, the relationship between phosphoinositide-3 kinase (PI3K)/protein kinase B (AKT) signaling pathway and PRO was analyzed by western blotting. PI3K/AKT inhibitor LY294002 was employed to evaluate whether the effects of PRO on LPS-challenged HPMECs injury were mediated by this pathway. Results revealed that APOM was notably downregulated in HPMECs after LPS exposure. PRO treatment promoted cell proliferation and migration while alleviated inflammation and apoptosis of LPS-treated HPMECs, which was reversed by APOM-downregulation. PRO brought about the upregulation of proteins in PI3K/AKT signaling pathway, and LY294002 intervention further accentuated the impacts of APOM-knockdown on LPS-challenged HPMECs injury. To conclude, PRO promotes migration and alleviates inflammation and apoptosis of LPS-treated HPMECs by PI3K/AKT signaling pathway via upregulating APOM, which laid an experimental foundation for the future study and clinical application of PRO.

The effects and possible mechanism of action of apolipoprotein M on the growth of breast cancer cells.

BACKGROUND: To investigate the effects and mechanism of action of apolipoprotein M (ApoM) on the growth of breast cancer (BC) cells. METHODS AND RESULTS: Bioinformatics, cell experiments and animal experiments were used to verify the effect of ApoM on breast cancer cell lines and breast tumor growth in vivo. ApoM expression was significantly reduced in BC tissues, and patients with lower ApoM mRNA expression had a poorer prognosis (P < 0.0001). Besides, ApoM can partially inhibit the proliferative, migratory and invasive processes of BC cells. In vivo, the difference between ApoM-OE and NC groups was no significant. The level of vitamin D receptor (VDR) protein in MDA-MB-231 cells was increased by overexpression of ApoM (P < 0.05), while in MCF-7 cells, VDR levels decreased (P < 0.05). CONCLUSIONS: ApoM can partially inhibit the growth of BC cells. VDR may play a role, but is not the main pathway.

Adipose-Derived Lipid-Binding Proteins: The Good, the Bad and the Metabolic Diseases.

Adipose tissue releases a large range of bioactive factors called adipokines, many of which are involved in inflammation, glucose homeostasis and lipid metabolism. Under pathological conditions such as obesity, most of the adipokines are upregulated and considered as deleterious, due to their pro-inflammatory, pro-atherosclerotic or pro-diabetic properties, while only a few are downregulated and would be designated as beneficial adipokines, thanks to their counteracting properties against the onset of comorbidities. This review focuses on six adipose-derived lipid-binding proteins that have emerged as key factors in the development of obesity and diabetes: Retinol binding protein 4 (RBP4), Fatty acid binding protein 4 (FABP4), Apolipoprotein D (APOD), Lipocalin-2 (LCN2), Lipocalin-14 (LCN14) and Apolipoprotein M (APOM). These proteins share structural homology and capacity to bind small hydrophobic molecules but display opposite effects on glucose and lipid metabolism. RBP4 and FABP4 are positively associated with metabolic syndrome, while APOD and LCN2 are ubiquitously expressed proteins with deleterious or beneficial effects, depending on their anatomical site of expression. LCN14 and APOM have been recently identified as adipokines associated with healthy metabolism. Recent findings on these lipid-binding proteins exhibiting detrimental or protective roles in human and murine metabolism and their involvement in metabolic diseases are also discussed.

Apolipoprotein M and Sphingosine-1-Phosphate Receptor 1 Promote the Transendothelial Transport of High-Density Lipoprotein.

Objective: ApoM enriches S1P (sphingosine-1-phosphate) within HDL (high-density lipoproteins) and facilitates the activation of the S1P1 (S1P receptor type 1) by S1P, thereby preserving endothelial barrier function. Many protective functions exerted by HDL in extravascular tissues raise the question of how S1P regulates transendothelial HDL transport. Approach and Results: HDL were isolated from plasma of wild-type mice, Apom knockout mice, human apoM transgenic mice or humans and radioiodinated to trace its binding, association, and transport by bovine or human aortic endothelial cells. We also compared the transport of fluorescently-labeled HDL or Evans Blue, which labels albumin, from the tail vein into the peritoneal cavity of apoE-haploinsufficient mice with (apoE-haploinsufficient mice with endothelium-specific knockin of S1P1) or without (control mice, ie, apoE-haploinsufficient mice without endothelium-specific knockin of S1P1) endothelium-specific knockin of S1P1. The binding, association, and transport of HDL from Apom knockout mice and human apoM-depleted HDL by bovine aortic endothelial cells was significantly lower than that of HDL from wild-type mice and human apoM-containing HDL, respectively. The binding, uptake, and transport of 125I-HDL by human aortic endothelial cells was increased by an S1P1 agonist but decreased by an S1P1 inhibitor. Silencing of SR-BI (scavenger receptor BI) abrogated the stimulation of 125I-HDL transport by the S1P1 agonist. Compared with control mice, that is, apoE-haploinsufficient mice without endothelium-specific knockin of S1P1, apoE-haploinsufficient mice with endothelium-specific knockin of S1P1 showed decreased transport of Evans Blue but increased transport of HDL from blood into the peritoneal cavity and SR-BI expression in the aortal endothelium. Conclusions: ApoM and S1P1 promote transendothelial HDL transport. Their opposite effect on transendothelial transport of albumin and HDL indicates that HDL passes endothelial barriers by specific mechanisms rather than passive filtration.

Apolipoprotein M-A Marker or an Active Player in Type II Diabetes?

Apolipoprotein M (apoM) is a member of the lipocalin superfamily and an important carrier of the small bioactive lipid sphingosine-1-phosphate (S1P). The apoM/S1P complex is attached to all lipoproteins, but exhibits a significant preference for high-density lipoproteins. Although apoM, S1P, and the apoM/S1P complex have been discovered more than a decade earlier, the overall function of the apoM/S1P complex remains controversial. Evidence suggests that the complex plays a role in inflammation and cholesterol metabolism and is important for maintaining a healthy endothelial barrier, regulating the turnover of triglycerides from lipoproteins, and reducing cholesterol accumulation in vessel walls. Recent studies have also addressed the role of apoM and S1P in the development of diabetes and obesity. However, limited evidence is available, and the data published so far deviates. This review discusses the specific elements indicative of the protective or harmful effects of apoM, S1P, and the apoM/S1P complex on type 2 diabetes development. Since drugs targeting the S1P system and its receptors are available and could be potentially used for treating diabetes, this research topic is a pertinent one.

Revealing the Role of High-Density Lipoprotein in Colorectal Cancer.

Colorectal cancer (CRC) is a highly prevalent malignancy with multifactorial etiology, which includes metabolic alterations as contributors to disease development. Studies have shown that lipid status disorders are involved in colorectal carcinogenesis. In line with this, previous studies have also suggested that the serum high-density lipoprotein cholesterol (HDL-C) level decreases in patients with CRC, but more recently, the focus of investigations has shifted toward the exploration of qualitative properties of HDL in this malignancy. Herein, a comprehensive overview of available evidences regarding the putative role of HDL in CRC will be presented. We will analyze existing findings regarding alterations of HDL-C levels but also HDL particle structure and distribution in CRC. In addition, changes in HDL functionality in this malignancy will be discussed. Moreover, we will focus on the genetic regulation of HDL metabolism, as well as the involvement of HDL in disturbances of cholesterol trafficking in CRC. Finally, possible therapeutic implications related to HDL will be presented. Given the available evidence, future studies are needed to resolve all raised issues concerning the suggested protective role of HDL in CRC, its presumed function as a biomarker, and eventual therapeutic approaches based on HDL.

Apolipoprotein M promotes cholesterol uptake and efflux from mouse macrophages.

Apolipoprotein M (ApoM) exhibits various anti-atherosclerotic functions as a component of high-density lipoprotein (HDL) particles. Scavenger receptor class B type I (SR-BI) is a classic HDL receptor that mediates selective cholesterol uptake and enhances the efflux of cellular cholesterol to HDL. However, the effect of ApoM on cholesterol transport in macrophages remains unclear. In this study, we identified for the first time that ApoM is expressed in mouse macrophages and is involved in cholesterol uptake, similar to SR-BI. NBD-cholesterol uptake and efflux in cells were characterized using fluorescence spectrophotometry. The uptake ratios of cholesterol by macrophages from ApoM-/- SR-BI-/- mice were significantly lower than those from ApoM+/+ SR-BI-/- and ApoM-/- SR-BI+/+ mice. Real-time fluorescence quantitative PCR was used to analyze the expression of cholesterol transport-related genes involved in cholesterol uptake. ApoM-enriched HDL (ApoM+ HDL) facilitated more cholesterol efflux from murine macrophage Ana-1 cells than ApoM-free HDL (ApoM- HDL). However, recombinant human ApoM protein inhibited the ability of ApoM- HDL to induce cholesterol efflux. In conclusion, ApoM promotes cholesterol uptake and efflux in mouse macrophages. A better understanding of ApoM function may lead to the development of novel therapeutic strategies for treating atherosclerotic diseases.

Glycation of HDL Polymerizes Apolipoprotein M and Attenuates Its Capacity to Bind to Sphingosine 1-Phosphate.

AIM: Recently, it has been established that most of the pleiotropic effects of high-density lipoprotein (HDL) are attributed to sphingosine 1-phosphate (S1P), which rides on HDL via apolipoprotein M (ApoM). In subjects with diabetes mellitus, both the pleiotropic effects of HDL and its role in reverse cholesterol transport are reported to be impaired. To elucidate the mechanisms underlying the impaired pleiotropic effects of HDL in subjects with diabetes, from the aspects of S1P and ApoM. METHODS: The incubation of HDL in a high-glucose condition resulted in the dimerization of ApoM. Moreover, the treatment of HDL with methylglyoxal resulted in the modulation of the ApoM structure, as suggested by the results of western blot analysis, isoelectric focusing electrophoresis, and two-dimensional gel electrophoresis, which was reversed by treatment with anti-glycation reagents. RESULTS: The glycation of HDL resulted in impaired binding of the glycated HDL to S1P, and the S1P on glycated HDL degraded faster. In the case of human subjects, on the other hand, although both the serum ApoM levels and the ApoM content in HDL were lower in subjects with diabetes, we did not observe the polymerization of ApoM. CONCLUSIONS: Modulation of the quantity and quality of ApoM might explain, at least in part, the impaired functions of HDL in subjects with diabetes mellitus. ApoM might be a useful target for laboratory testing and/or the treatment of diabetes mellitus.

Apolipoprotein M inhibits proliferation and migration of larynx carcinoma cells.

Prior studies have shown that apolipoprotein M (APOM) is involved in the development of some cancers. Here we investigated the effects of APOM on larynx cancer (LC). 20 patients with vocal cord polyps and 18 patients with LC were included in this study. The protein and mRNA levels of the samples were analysed using the Wes-ProteinSimple system (or traditional Western blot) and PCR technology, respectively. APOM protein level in cancer tissues was lower than that in paracarcinomatous (P = 0.0003) and polyp tissues (P < 0.0001). APOM overexpression significantly inhibited TU686 cell proliferation (P < 0.0001) and migration (P < 0.01), and increased expression of vitamin D receptor (VDR, P < 0.0001) as well as nuclear factor erythroid 2-like 3 (NFE2L3, P = 0.0215). In addition, matrix metalloproteinase-10 (MMP-10) mRNA level was significantly reduced in the APOM overexpression group (P = 0.0077). However, Western blot analysis showed that APOM overexpression did not change VDR, NFE2L3 and MMP-10 protein levels (P > 0.05). In summary, APOM inhibits the proliferation and migration of LC cells, but may not be related to VDR, NFE2L3 and MMP-10, which needs further study.

Modulation of sphingosine 1-phosphate by hepatobiliary cholesterol handling.

Hepatobiliary cholesterol handling, mediated by Niemann-Pick C1-like 1 protein (NPC1L1) and ABCG5/8, is well-known to contribute to the homeostasis of cholesterol. We attempted to elucidate the impact of hepatobiliary cholesterol handling on the homeostasis of sphingolipids and lysophospholipids, especially sphingosine 1-phosphate (S1P). We induced the overexpression of NPC1L1 or ABCG5/8 in the mouse liver. Hepatic NPC1L1 overexpression increased the plasma and hepatic S1P levels, while it decreased the biliary S1P levels, and all of these changes were inhibited by ezetimibe. The ability of HDL to activate Akt in the endothelial cells was augmented by hepatic NPC1L1 overexpression. NPC1L1-mediated S1P transport was confirmed by both in vitro and in vivo studies conducted using C17 S1P, an exogenous S1P analog. Upregulation of apolipoprotein M (apoM) was involved in these modulations, although apoM was not necessary for these modulations. Moreover, the increase in the plasma S1P levels also observed in ABCG5/8-overexpressing mice was dependent on the elevation of the plasma apoM levels. In regard to other sphingolipids and lysophospholipids, ceramides were similarly modulated by NPC1L1 to S1P, while other lipids were differently influenced by NPC1L1 or ABCG5/8 from S1P. Hepatobiliary cholesterol handling might also regulate the functional lipids, such as S1P.

Berberine reduces gut-vascular barrier permeability via modulation of ApoM/S1P pathway in a model of polymicrobial sepsis.

AIMS: The hyperpermeability of gut-vascular barrier (GVB) plays a role in gut-derived sepsis. The goal of this study was to evaluate if berberine might improve hepatic apolipoprotein M (ApoM) generation and raise plasma ApoM level to protect the compromised GVB. MATERIALS AND METHODS: The compromised GVB was induced by sepsis. Hepatic ApoM mRNA and phosphoenolpyruvate carboxykinase (PEPCK) mRNA and plasma ApoM level were assayed by qRT-PCR and ELISA, respectively. The permeability of intestinal capillary in vivo and of rat intestinal microvascular endothelial cells (RIMECs) in vitro was assayed by FITC-dextran. The blood glucose was detected by a glucometer. Plasma insulin, TNF-α and IL-1ß were assayed by ELISA. The plasmalemma vesicle-associated protein-1 (PV1), ß-catenin and occludin in RIMECs were assayed by Western blot. KEY FINDINGS: Sepsis decreased hepatic ApoM mRNA and plasma ApoM level, but raised hepatic PEPCK mRNA and plasma glucose, insulin, TNF-α, and IL-1ß levels. The increased vascular endothelial permeability was abrogated by recombinant rat ApoM in vivo or ApoM-bound S1P in vitro. ApoM-bound S1P decreased PV1 but increased occludin and ß-catenin expression in LPS-treated RIMECs. Berberine in a dose-dependent manner raised hepatic ApoM mRNA and plasma ApoM level, but decreased septic hyperglycemia, insulin resistance and plasma TNF-α and IL-1ß levels. Berberine reduced sepsis-induced PEPCK and TLR4 mRNA overexpression in the liver. SIGNIFICANCE: This study demonstrated berberine inhibited TLR4-mediated hyperglycemia, insulin resistance and proinflammatory molecule production, thereby increasing ApoM gene expression and plasma ApoM. Berberine protected the damaged GVB via modulation of ApoM/S1P pathway.