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.

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.

Nutrigenetic Interaction of Spontaneously Hypertensive Rat Chromosome 20 Segment and High-Sucrose Diet Sensitizes to Metabolic Syndrome.

Several corresponding regions of human and mammalian genomes have been shown to affect sensitivity to the manifestation of metabolic syndrome via nutrigenetic interactions. In this study, we assessed the effect of sucrose administration in a newly established congenic strain BN.SHR20, in which a limited segment of rat chromosome 20 from a metabolic syndrome model, spontaneously hypertensive rat (SHR), was introgressed into Brown Norway (BN) genomic background. We mapped the extent of the differential segment and compared the genomic sequences of BN vs. SHR within the segment in silico. The differential segment of SHR origin in BN.SHR20 spans about 9 Mb of the telomeric portion of the short arm of chromosome 20. We identified non-synonymous mutations e.g., in ApoM, Notch4, Slc39a7, Smim29 genes and other variations in or near genes associated with metabolic syndrome in human genome-wide association studies. Male rats of BN and BN.SHR20 strains were fed a standard diet for 18 weeks (control groups) or 16 weeks of standard diet followed by 14 days of high-sucrose diet (HSD). We assessed the morphometric and metabolic profiles of all groups. Adiposity significantly increased only in BN.SHR20 after HSD. Fasting glycemia and the glucose levels during the oral glucose tolerance test were higher in BN.SHR20 than in BN groups, while insulin levels were comparable. The fasting levels of triacylglycerols were the highest in sucrose-fed BN.SHR20, both compared to the sucrose-fed BN and the control BN.SHR20. The non-esterified fatty acids and total cholesterol concentrations were higher in BN.SHR20 compared to their respective BN groups, and the HSD elicited an increase in non-esterified fatty acids only in BN.SHR20. In a new genetically defined model, we have isolated a limited genomic region involved in nutrigenetic sensitization to sucrose-induced metabolic disturbances.

Sphingosine-1-phosphate: metabolism, transport, atheroprotection and effect of statin treatment.

PURPOSE OF REVIEW: To better define the metabolism of sphingosine-1-phosphate (S1P), its transport in plasma and its interactions with S1P receptors on vascular cells, and to evaluate the effect of statin treatment on the subnormal plasma levels of high-density lipoprotein (HDL)-bound S1P characteristic of the atherogenic dyslipidemia of metabolic syndrome (MetS). RECENT FINDINGS: Neither clinical intervention trials targeted to raising high-density lipoprotein-cholesterol (HDL-C) levels nor human genome-wide association studies (GWAS) studies have provided evidence to support an atheroprotective role of HDL. Recently however a large monogenic univariable Mendelian randomization on the N396S mutation in the gene encoding endothelial lipase revealed a causal protective effect of elevated HDL-C on coronary artery disease conferred by reduced enzyme activity. Given the complexity of the HDL lipidome and proteome, components of HDL other than cholesterol may in all likelihood contribute to such a protective effect. Among HDL lipids, S1P is a bioactive sphingolipid present in a small proportion of HDL particles (about 5%); indeed, S1P is preferentially enriched in small dense HDL3. As S1P is bound to apolipoprotein (apo) M in HDL, such enrichment is consistent with the elevated apoM concentration in HDL3. When HDL/apoM-bound S1P acts on S1P1 or S1P3 receptors in endothelial cells, potent antiatherogenic and vasculoprotective effects are exerted; those exerted by albumin-bound S1P at these receptors are typically weaker. When HDL/apoM-bound S1P binds to S1P2 receptors, proatherogenic effects may potentially be induced. Subnormal plasma levels of HDL-associated S1P are typical of dyslipidemic individuals at high cardiovascular risk and in patients with coronary heart disease. International Guidelines recommend statin treatment as first-line lipid lowering therapy in these groups. The cardiovascular benefits of statin therapy are derived primarily from reduction in low-density lipoprotein (LDL)-cholesterol, although minor contributions from pleiotropic actions cannot be excluded. Might statin treatment therefore normalize, directly or indirectly, the subnormal levels of S1P in dyslipidemic subjects at high cardiovascular risk? Our unpublished findings in the CAPITAIN study (ClinicalTrials.gov: NCT01595828), involving a cohort of obese, hypertriglyceridemic subjects (n = 12) exhibiting the MetS, showed that pitavastatin calcium (4 mg/day) treatment for 180days was without effect on either total plasma or HDL-associated S1P levels, suggesting that statin-mediated improvement of endothelial function is not due to normalization of HDL-bound S1P. Statins may however induce the expression of S1P1 receptors in endothelial cells, thereby potentiating increase in endothelial nitric oxide synthase response to HDL-bound S1P, with beneficial downstream vasculoprotective effects. SUMMARY: Current evidence indicates that S1P in small dense HDL3 containing apoM exerts antiatherogenic effects and that statins exert vasculoprotective effects through activation of endothelial cell S1P1 receptors in response to HDL/apoM-bound S1P.

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.

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.

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.

Endothelial Spns2 and ApoM Regulation of Vascular Tone and Hypertension Via Sphingosine-1-Phosphate.

Background Most of the circulating sphingosine-1-phosphate (S1P) is bound to ApoM (apolipoprotein M) of high-density lipoprotein (HDL) and mediates many beneficial effects of HDL on the vasculature via G protein-coupled S1P receptors. HDL-bound S1P is decreased in atherosclerosis, myocardial infarction, and diabetes mellitus. In addition to being the target, the endothelium is a source of S1P, which is transported outside of the cells by Spinster-2, contributing to circulating S1P as well as to local signaling. Mice lacking endothelial S1P receptor 1 are hypertensive, suggesting a vasculoprotective role of S1P signaling. This study investigates the role of endothelial-derived S1P and ApoM-bound S1P in regulating vascular tone and blood pressure. Methods and Results ApoM knockout (ApoM KO) mice and mice lacking endothelial Spinster-2 (ECKO-Spns2) were infused with angiotensin II for 28 days. Blood pressure, measured by telemetry and tail-cuff, was significantly increased in both ECKO-Spns2 and ApoM KO versus control mice, at baseline and following angiotensin II. Notably, ECKO-Spns2 presented an impaired vasodilation to flow and blood pressure dipping, which is clinically associated with increased risk for cardiovascular events. In hypertension, both groups presented reduced flow-mediated vasodilation and some degree of impairment in endothelial NO production, which was more evident in ECKO-Spns2. Increased hypertension in ECKO-Spns2 and ApoM KO mice correlated with worsened cardiac hypertrophy versus controls. Conclusions Our study identifies an important role for Spinster-2 and ApoM-HDL in blood pressure homeostasis via S1P-NO signaling and dissects the pathophysiological impact of endothelial-derived S1P and ApoM of HDL-bound S1P in hypertension and cardiac hypertrophy.

Apolipoprotein M Gene Polymorphism Rs805297 (C-1065A): Association With Type 2 Diabetes Mellitus and Related Microvascular Complications in South Egypt.

BACKGROUND: Apolipoprotein M (ApoM) may have a role in the susceptibility of type 2 diabetes mellitus (T2DM). Polymorphisms in the promoter region of the ApoM gene were found to be significantly associated with diabetes. The aim of this study was to investigate the association of ApoM SNP rs805297 (C-1065A) with the susceptibility of T2DM and related microvascular complications in South Egypt. METHODS: We conducted a case-control study of 60 T2DM patients and 60 healthy control subjects. Lipid profile, fasting, and 2 hours postprandial glucose and creatinine levels were estimated. Patients were subjected to general and Fundus examinations, and screening for nephropathy by urinary albumin levels. ApoM level was assayed by ELISA. Genotyping of the human ApoM gene polymorphism SNP rs805297 (C-1065A) was done by PCR-restriction fragment length polymorphism followed by sequencing to confirm the polymorphism results. RESULTS: ApoM was not different between T2DM and the control group (p=0.075) and was negatively correlated with LDL-c (p=0.029). There were significant differences in ApoM genotypes (p=0.001) and allele frequencies (p=0.019) between T2DM and the control group. A significant reduction in FBG, 2hPPG, and HbA1c levels in the heterozygous than the wild genotype in the group with diabetes with no difference in other lab parameters and microvascular complications. The C-allele is associated with lower blood glucose levels and retinopathy. The wild (CC) genotype is considered as a risk factor for developing T2DM in South Egyptians but not CA+AA genotypes. CONCLUSIONS: In South Egyptians the ApoM polymorphism rs805297 (C-1065A) wild type (CC) was associated with T2DM susceptibility and may have a role in controlling hyperglycemia in these patients. The A-allele is associated with hyperglycemia and diabetic retinopathy.

Comprehensive lipidomics in apoM-/- mice reveals an overall state of metabolic distress and attenuated hepatic lipid secretion into the circulation.

Apolipoprotein M (apoM) participates in both high-density lipoprotein and cholesterol metabolism. Little is known about how apoM affects lipid composition of the liver and serum. In this study, we systemically investigated the effects of apoM on liver and plasma lipidomes and how apoM participates in lipid cycling, via apoM knockout in mice and the human SMMC-7721 cell line. We used integrated mass spectrometry-based lipidomics approaches to semiquantify more than 600 lipid species from various lipid classes, which include free fatty acids, glycerolipids, phospholipids, sphingolipids, glycosphingolipids, cholesterol, and cholesteryl esters (CEs), in apoM-/- mouse. Hepatic accumulation of neutral lipids, including CEs, triacylglycerols, and diacylglycerols, was observed in apoM-/- mice; while serum lipidomic analyses showed that, in contrast to the liver, the overall levels of CEs and saturated/monounsaturated fatty acids were markedly diminished. Furthermore, the level of ApoB-100 was dramatically increased in the liver, whereas significant reductions in both ApoB-100 and low-density lipoprotein (LDL) cholesterol were observed in the serum of apoM-/- mice, which indicated attenuated hepatic LDL secretion into the circulation. Lipid profiles and proinflammatory cytokine levels indicated that apoM-/- leads to hepatic steatosis and an overall state of metabolic distress. Taken together, these results revealed that apoM knockout leads to hepatic steatosis, impaired lipid secretion, and an overall state of metabolic distress.

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.

Increased expression levels of inflammatory cytokines and adhesion molecules in lipopolysaccharide­induced acute inflammatory apoM­/­ mice.

Apolipoprotein M (apoM) may serve a protective role in the development of inflammation. Nuclear factor­κB (NF­κB) and its downstream factors (including a number of inflammatory cytokines and adhesion molecules) are essential for the regulation of inflammatory processes. In the present study, the importance of apoM in lipopolysaccharide (LPS)­induced acute inflammation and its potential underlying mechanisms, were investigated using an apoM­knockout mouse model. The levels of inducible nitric oxide synthase (iNOS), NF­κB, interleukin (IL)­1ß, intercellular adhesion molecule 1 (ICAM­1) and vascular cell adhesion protein 1 (VCAM­1) were detected using reverse transcription­quantitative PCR and western blotting. The serum levels of IL­6 and IL­10 were detected using Luminex technology. The results demonstrated that the protein levels of iNOS, NF­κB, IL­1ß, ICAM­1 and VCAM­1 were significantly increased in apoM­/­ mice compared with those in apoM+/+ mice. In addition, two­way ANOVA revealed that the interaction between apoM and LPS had a statistically significant effect on a number of factors, including the mRNA expression levels of hepatic iNOS, NF­κB, IL­1ß, ICAM­1 and VCAM­1. Notably, the effects of apoM and 10 mg/kg LPS on the levels of IL­6 and IL­10 were the opposite of those induced by 5 mg/kg LPS, which could be associated with the dual anti­ and pro­inflammatory effects of IL­6 and IL­10. Collectively, the results of the present study revealed that apoM is an important regulator of inflammatory cytokine and adhesion molecule production in LPS­induced inflammation, which may consequently be associated with the severity of inflammation. These findings indicated that the anti­inflammatory effects of apoM may partly result from the inhibition of the NF­κB pathway.

Apolipoprotein M and Risk of Type 2 Diabetes.

CONTEXT: Recent studies have discovered a role of apolipoprotein M (apoM) in energy metabolism, and observational analyses in humans suggest an association with type 2 diabetes. The causal relationship remains however elusive. OBJECTIVE: To investigate whether reduced plasma apoM concentrations are causally linked to increased risk of type 2 diabetes. DESIGN: Prospective study design analyzed by Mendelian randomization. SETTING AND PARTICIPANTS: Two cohorts reflecting the Danish general population: the Copenhagen City Heart Study (CCHS, n = 8589) and the Copenhagen General Population Study (CGPS; n = 93 857). Observational analyses included a subset of participants from the CCHS with available plasma apoM (n = 725). Genetic analyses included the complete cohorts (n = 102 446). During a median follow-up of 16 years (CCHS) and 8 years (CGPS), 563 and 2132 participants developed type 2 diabetes. MAIN OUTCOME MEASURES: Plasma apoM concentration, genetic variants in APOM, and type 2 diabetes. RESULTS: First, we identified an inverse correlation between plasma apoM and risk of type 2 diabetes in a subset of participants from the CCHS (hazard ratio between highest vs lowest quartile (reference) = 0.32; 95% confidence interval = 0.1-1.01; P for trend = .02). Second, genotyping of specific single nucleotide polymorphisms in APOM further revealed a 10.8% (P = 6.2 × 10-5) reduced plasma apoM concentration in participants with variant rs1266078. Third, a meta-analysis including data from 599 451 individuals showed no association between rs1266078 and risk of type 2 diabetes. CONCLUSIONS: The present study does not appear to support a causal association between plasma apoM and risk of type 2 diabetes.

Aging Suppresses Sphingosine-1-Phosphate Chaperone ApoM in Circulation Resulting in Maladaptive Organ Repair.

Here, we show that the liver-derived apolipoprotein M (ApoM) protects the lung and kidney from pro-fibrotic insults and that this circulating factor is attenuated in aged mice. Aged mouse hepatocytes exhibit transcriptional suppression of ApoM. This leads to reduced sphingosine-1-phosphate (S1P) signaling via the S1P receptor 1 (S1PR1) in the vascular endothelial cells of lung and kidney. Suboptimal S1PR1 angiocrine signaling causes reduced resistance to injury-induced vascular leak and leads to organ fibrosis. Plasma transfusion from Apom transgenic mice but not Apom knockout mice blocked fibrosis in the lung. Similarly, infusion of recombinant therapeutics, ApoM-Fc fusion protein enhanced kidney and lung regeneration and attenuated fibrosis in aged mouse after injury. Furthermore, we identified that aging alters Sirtuin-1-hepatic nuclear factor 4α circuit in hepatocytes to downregulate ApoM. These data reveal an integrative organ adaptation that involves circulating S1P chaperone ApoM+ high density lipoprotein (HDL), which signals via endothelial niche S1PR1 to spur regeneration over fibrosis.

LncRNA TUG1 regulates ApoM to promote atherosclerosis progression through miR-92a/FXR1 axis.

This study aims to explore the possible mechanism of TUG1 regulating ApoM in AS. To this end, expression levels of TUG1 and ApoM were measured in high fat dieted C57BL/6J mice, normal dieted C57BL/6J mice, ob/ob mice and db/db mice. LV-TUG1 or sh-TUG1 was injected into C57BL/6J mice before isolating peritoneal macrophages to measure cholesterol efflux (CE) and expression levels of ABCA1, ABCG1 and SR-BI. Meanwhile, CE in RAW264.7 cells was also measured after cell transfection. Dual luciferase reporter assay and anti-AGO2 RIP were applied to verify the relationship among TUG1, FXR1 and miR-92a. Total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterin (LDL-C), high-density lipoprotein cholesterol (HDL-C) as well as expressions of inflammatory cytokines (TNF-α, IL-1ß and IL-6) in plasma were measured. Knock-down or expressed TUG1, FXR1 or miR-92a in NCTC 1469 cells or in ApoE-/- AS mice to determine the alteration on ApoM and plaque size. TUG1 was highly expressed while ApoM was down-regulated in high fat dieted C57BL/6J mice, b/ob and db/db mice. Overexpression of TUG1 could reduce the expression of ApoM, ABCA1 and ABCG1 in addition to slowing down CE rate. Reversed expression pattern was found in cells with knock-down of TUG1. TUG1 can compete with FXR1 to bind miR-92a. FXR1 negatively target ApoM. Overexpression of TUG1 in ApoE-/- mice can increase plaque size and enhance macrophage contents accordingly. TUG1 can inhibit ApoM in both liver tissues and plasma to inhibit CE through regulating miR-92a/ FXR1 axis. TUG1 is a promising target for AS treatment.

Interaction Between Apolipoprotein M Gene Single-Nucleotide Polymorphisms and Obesity and its Effect on Type 2 Diabetes Mellitus Susceptibility.

This study investigated the correlation of four single nucleotide polymorphisms (SNPs) in Apolipoprotein M (ApoM) with the risk of type 2 diabetes mellitus (T2DM) and effects of the interactions of this gene and obesity. The effects of SNP and obesity interaction on T2DM was examined by generalized multifactor dimensionality reduction (GMDR) combined with the logistic regression model. T2DM patient-control haplotype was analyzed in silico using the haplotype analysis algorithm SHEsis. The rs805296-C allele or 724-del allele indicted high risk of T2DM. The incidence of T2DM in individuals with rs805296-C allele polymorphism (TC + CC) was higher than those without (TT), adjusted OR (95%CI) = 1.29 (1.10-1.66) (p < 0.001). Moreover, the individuals with 724-delallele have a higher risk of T2DM compared to those with 724-ins variants, adjusted OR (95%CI) = 1.66 (1.40-2.06), p < 0.001. GMDR analysis suggested that the interaction model composed of the two factors, rs805296 and obesity, was the best model with statistical significance (P value from sign test [Psign]=0.0107). The T2DM risk in obese individuals having TC or CC genotype was higher than non-obese individuals with TT genotype (OR = 2.38, 95% CI = 1.58-3.53). Haplotype analysis suggests that rs805297-C and rs9404941-C alleles haplotype indicate high risk of T2DM, OR (95%CI) = 1.62 (1.29-2.16), p < 0.001. Our results suggested that rs805296 and 724-del minor allele of ApoM gene, interaction of rs805296 and obesity, rs805297-C and rs9404941-C alleles haplotype were indicators of high T2DM risk.

Apolipoprotein M overexpression through adeno-associated virus gene transfer improves insulin secretion and insulin sensitivity in Goto-Kakizaki rats.

AIMS/OBJECTIVE: The development of type 2 diabetes is a result of insulin resistance in various tissues, including skeletal muscle and liver. Apolipoprotein M (ApoM) plays an important role in the function of high-density lipoprotein, and also affects hepatic lipid and glucose metabolism. In this study, we aimed to investigate whether ApoM overexpression modulates glucose metabolism and improves insulin sensitivity. MATERIALS AND METHODS: The Goto-Kakizaki (GK) rats were transfected with adeno-associated virus (AAV) encoding rat ApoM gene or control blank. The oral glucose tolerance test (OGTT) and hyperinsulinemic-euglycemic clamp (HEC) experiment were used to assess the insulin sensitivity of GK rats. RESULTS: The results show that ApoM messenger ribonucleic acid and protein were significantly overexpressed in the pancreatic tissues. Overexpression of ApoM decreased fasting blood glucose and random blood glucose, improved glucose tolerance, and increased bodyweight and insulin levels in GK rats. The glucose infusion rate of rats in the AAV encoding rat ApoM gene group during HEC test was 1.04-, 1.23- and 1.95-fold higher than that in the AAV control blank group at 1-3 weeks after injection of AAV, respectively. A Wes-ProteinSimple assay and quantification was carried out to assess phosphorylated protein kinase B/protein kinase B protein levels in the muscle tissues of ApoM-overexpressing GK rats, and they were found to be higher than those of the control group at the seventh week after AAV injection. CONCLUSIONS: ApoM overexpression through adeno-associated virus gene transfer might improve insulin secretion and insulin sensitivity in GK rats.

LncRNA HCG11 suppresses laryngeal carcinoma cells progression via sponging miR-4469/APOM axis.

OBJECTIVE: Longnon-coding RNAs (lncRNAs) have been reported to participate in the regulatory mechanisms of various cancers. Therefore, the aim of this study was to investigate the functional role of lncRNA HLA complex group 11 (HCG11) in laryngeal carcinoma. MATERIALS AND METHODS: The laryngeal carcinoma cell lines SNU46, SNU899, AMC-HN-8, and normal human nasopharyngeal epithelial cells NP69 were purchased. The expression of HCG11, miR-4469, and apolipoprotein M (APOM) was detected by quantitative Real Time-PCR (qRT-PCR) in tissues and cells. Cell proliferation was detected by Cell Counting Kit-8 (CCK-8) assay and colony formation assays. The protein expression of Bax and Bcl-2 was detected by Western blot. Besides, the mechanism assays were conducted to observe the interaction between miR-449 and HCG11 or APOM. The apoptosis in each group was detected by TUNEL assay. RESULTS: In this research, low expression of HCG11 was discovered in laryngeal carcinoma tissues and cells. Overexpression of HCG11 retarded cell proliferation and enhanced cell apoptosis. Later, we found that APOM was also downregulated in laryngeal carcinoma tissues and cell lines, and inhibited laryngeal carcinoma progression. HCG11 positively regulated APOM at the post-transcriptional level. MiR-4469 was predicted to have the binding sites of HCG11 and APOM. Furthermore, it was demonstrated that HCG11 absorbed miR-4469 to upregulate APOM expression. Finally, it was indicated that the repression of APOM rescued the effects of HCG11 overexpression on cell proliferation and cell apoptosis. CONCLUSIONS: This study uncovered that HCG11 sponged miR-4469 to suppress laryngeal carcinoma progression by upregulating APOM expression.

Apolipoprotein M, identified as a novel hepatitis C virus (HCV) particle associated protein, contributes to HCV assembly and interacts with E2 protein.

Hepatitis C virus (HCV) infection is a major cause of chronic liver diseases such as steatosis, cirrhosis, and hepatocellular carcinoma. HCV particles have been found to associate with apolipoproteins, and apolipoproteins not only participate in the HCV life cycle, but also help HCV escape recognition by the host immune system, which pose challenges for the development of both HCV treatments and vaccines. However, no study has reported on the comprehensive identification of apolipoprotein associations with HCV particles. In the present study, we performed proteome analysis by affinity purification coupled with mass spectrometry (AP-MS) to comprehensively identify the apolipoprotein associations with HCV particles, and ApoM was first identified by AP-MS besides the previously reported ApoE, ApoB, ApoA-I and ApoC-I. Additionally, three assays further confirmed that ApoM was a novel virus particle associated protein. We also showed that ApoM was required for HCV production, especially for the assembly/release step of HCV life cycle. Furthermore, ApoM interacted with the HCV E2 protein. Finally, HCV infection reduced ApoM expression both in vitro and in vivo. Collectively, our study demonstrates that ApoM, identified as a novel HCV particle associated protein, contributes to HCV assembly/release and interacts with HCV E2 protein. It provides new insights on how HCV and the host apolipoproteins are reciprocally influenced and lays a basis for research in developing innovative antiviral strategies.

Protection Against Insulin Resistance by Apolipoprotein M/Sphingosine-1-Phosphate.

Subjects with low serum HDL cholesterol levels are reported to be susceptible to diabetes, with insulin resistance believed to be the underlying pathological mechanism. Apolipoprotein M (apoM) is a carrier of sphingosine-1-phosphate (S1P), a multifunctional lipid mediator, on HDL, and the pleiotropic effects of HDL are believed to be mediated by S1P. In the current study, we attempted to investigate the potential association between apoM/S1P and insulin resistance. We observed that the serum levels of apoM were lower in patients with type 2 diabetes and that they were negatively correlated with BMI and the insulin resistance index. While deletion of apoM in mice was associated with worsening of insulin resistance, overexpression of apoM was associated with improvement of insulin resistance. Presumably, apoM/S1P exerts its protective effect against insulin resistance by activating insulin signaling pathways, such as the AKT and AMPK pathways, and also by improving the mitochondrial functions through upregulation of SIRT1 protein levels. These actions of apoM/S1P appear to be mediated via activation of S1P1 and/or S1P3. These results suggest that apoM/S1P exerts protective roles against the development of insulin resistance.