APOC3 Expression Research Articles

A novel lncRNA GM47544 modulates triglyceride metabolism by inducing ubiquitination-dependent protein degradation of APOC3

ObjectiveEmerging evidence highlights the pivotal roles of long non-coding RNAs (lncRNAs) in lipid metabolism. Apoprotein C3 (ApoC3) is a well-established therapeutic target for hypertriglyceridemia and exhibits a strong association with cardiovascular disease. However, the exact mechanisms via which the lncRNAs control ApoC3 expression remain unclear. MethodsWe identified a novel long noncoding RNA (lncRNA), GM47544, within the ApoA1/C3/A4/A5 gene cluster. Subsequently, the effect of GM47544 on intracellular triglyceride metabolism was analyzed. The diet-induced mouse models of hyperlipidemia and atherosclerosis were established to explore the effect of GM47544 on dyslipidemia and plaque formation in vivo. The molecular mechanism was explored through RNA sequencing, immunoprecipitation, RNA pull-down assay, and RNA immunoprecipitation. ResultsGM47544 was overexpressed under high-fat stimulation. GM47544 effectively improved hepatic steatosis, reduced blood lipid levels, and alleviated atherosclerosis in vitro and in vivo. Mechanistically, GM47544 directly bound to ApoC3 and facilitated the ubiquitination at lysine 79 in ApoC3, thereby facilitating ApoC3 degradation via the ubiquitin-proteasome pathway. Moreover, we identified AP006216.5 as the human GM47544 transcript, which fulfills a comparable function in human hepatocytes. ConclusionsThe identification of GM47544 as a lncRNA modulator of ApoC3 reveals a novel mechanism of post-translational modification, with significant clinical implications for the treatment of hypertriglyceridemia and atherosclerosis.

Abstract 3054: Proinflammatory Phenotypes And Role Of Ly-6c Low Monocytes In Atherosclerosis With Hypertriglyceridemia

Background: Monocytes play pivotal roles in atherosclerosis. Ly-6C low monocytes, also known as patrolling monocytes, become foamy in the circulation of mice with hyperlipidemia. However, the role of Ly-6C low monocytes in atherosclerosis with hypertriglyceridemia (HTG) remains to be determined. Aim: To examine the phenotypes and role of Ly-6C low monocytes in atherosclerosis in HTG. Method: Ldlr -/- ApoC3Tg (transgenic expression of human ApoC3) mice fed a western high-fat diet (WD) were used to examine the effects of HTG on monocyte lipid accumulation (foamy monocyte formation), phenotypes, and contributions to atherosclerosis. Results: Plasma triglycerides in Ldlr -/- ApoC3Tg mice were 5.1 times higher than in Ldlr -/- controls at 6 weeks on WD, correlating with more than twice the increase in aortic atherosclerosis (P<0.01). Consistently, Ly-6C low compared to Ly-6C high monocytes in Ldlr -/- mice had increased lipid accumulation and exhibited elevated levels of TNFα, IL-6, IL-1β, Plin2, and PPAR-γ. In Ldlr -/- ApoC3Tg mice, Ly-6C low (also CD11c + ) monocytes demonstrated even greater lipid accumulation and adhesion to VCAM-1 and had further elevations in levels of TNFα, IL-6, IL-1β, Plin2, and PPAR-γ than CD11c + (Ly-6C low ) monocytes in Ldlr -/- controls, indicating an enhanced inflammatory response and lipid accumulation under HTG. Furthermore, compared to Ldlr -/- control mice, Ldlr -/- ApoC3Tg mice had an increase in the level of SIRPα (a ligand of the “don’t-eat me” signal CD47) on Ly-6C low monocytes, indicative of impairment in efferocytosis and clearance of apoptotic cells. Additionally, nuclear c-Rel mRNA and protein levels were upregulated in Ly-6C low monocytes of Ldlr -/- ApoC3Tg mice compared to Ldlr -/- controls, suggesting activation of the NF-κB pathway in Ly-6C low monocytes by HTG. Finally, depletion of Ly-6C low monocytes reduced atherosclerosis by 45% (P<0.05) in Ldlr -/- ApoC3Tg mice, indicating a role of Ly-6C low monocytes in atherosclerosis in HTG. Conclusions: HTG accelerates atherogenesis in Ldlr -/- mice, possibly by increasing lipid accumulation and inflammatory phenotypic changes in monocytes, primarily CD11c + Ly-6C low monocytes.

FoxO6-mediated ApoC3 upregulation promotes hepatic steatosis and hyperlipidemia in aged rats fed a high-fat diet.

FoxO6, an identified factor, induces hyperlipidemia and hepatic steatosis during aging by activating hepatic lipoprotein secretion and lipogenesis leading to increased ApoC3 concentrations in the bloodstream. However, the intricate mechanisms underlying hepatic steatosis induced by elevated FoxO6 under hyperglycemic conditions remain intricate and require further elucidation. In order to delineate the regulatory pathway involving ApoC3 controlled by FoxO6 and its resultant functional impacts, we employed a spectrum of models including liver cell cultures, aged rats subjected to HFD, transgenic mice overexpressing FoxO6 (FoxO6-Tg), and FoxO6 knockout mice (FoxO6-KO). Our findings indicate that FoxO6 triggered ApoC3-driven lipid accumulation in the livers of aged rats on an HFD and in FoxO6-Tg, consequently leading to hepatic steatosis and hyperglycemia. Conversely, the absence of FoxO6 attenuated the expression of genes involved in lipogenesis, resulting in diminished hepatic lipid accumulation and mitigated hyperlipidemia in murine models. Additionally, the upregulation of FoxO6 due to elevated glucose levels led to increased ApoC3 expression, consequently instigating cellular triglyceride mediated lipid accumulation. The transcriptional activation of FoxO6 induced by both the HFD and high glucose levels resulted in hepatic steatosis by upregulating ApoC3 and genes associated with gluconeogenesis in aged rats and liver cell cultures. Our conclusions indicate that the upregulation of ApoC3 by FoxO6 promotes the development of hyperlipidemia, hyperglycemia, and hepatic steatosis in vivo, and in vitro. Taken together, our findings underscore the significance of FoxO6 in driving hyperlipidemia and hepatic steatosis specifically under hyperglycemic states by enhancing the expression of ApoC3 in aged rats.

Abstract 17091: ARO-APOC3, an Investigational RNAi Therapeutic, Silences APOC3 and Reduces Atherosclerosis-Associated Lipoproteins in Patients With Mixed Dyslipidemia: MUIR Study Results

Background: Despite the availability of potent LDL-C-lowering therapies, patients with mixed dyslipidemia (MD) remain at high risk of cardiovascular (CV) disease due to residual risk from triglyceride (TG)-rich atherogenic lipoproteins (TRLs), ie, remnant cholesterol and/or VLDL-C. Inhibition of APOC3 has emerged as a promising therapeutic strategy for reducing this residual CV risk. Aim: We report interim results through Week 24 from MUIR, an ongoing, randomized, placebo-controlled, Phase 2b study (NCT04998201) evaluating the effects of ARO-APOC3 in patients with MD (fasting TGs 150 to 499 mg/dL and either LDL-C ≥70 mg/dL or non-HDL-C ≥100 mg/dL). Methods: Eligible subjects (n=353) were randomized 3:1 to receive either subcutaneous injections of 10, 25, or 50 mg ARO-APOC3 or matched placebo on Day 1 and at Week 12 or 50 mg ARO-APOC3 on Day 1 and Week 24. Subjects were on a stable diet and optimal lipid-lowering therapies. The primary endpoint was the percent change from baseline in fasting TGs at Week 24. Statistically significant differences were determined using mixed model repeat measures analysis. Results: At Week 24, when dosed on Day 1 and Week 12, ARO-APOC3 significantly decreased APOC3 in a dose-dependent manner up to 80% (p<0.0001). Least squares (LS) mean TGs were significantly reduced by 52 to 64% (p<0.0001). Least squares (LS) mean atherogenic lipoproteins were reduced by up to 27% for non-HDL-C, 19% for apolipoprotein B, and 55% for remnant cholesterol. LS mean HDL-C was increased by up to 51%. The most frequent adverse events were COVID-19 infection, worsening of glycemic control, and upper respiratory infection. Conclusions: By silencing APOC3 expression, ARO-APOC3 significantly reduced circulating TGs and atherogenic TRLs in patients with MD. The effect of ARO-APOC3 on CV relative risk reduction will be evaluated in an upcoming outcomes trial.

Apolipoprotein C-III itself stimulates the Syk/cPLA2-induced inflammasome activation of macrophage to boost anti-tumor activity of CD8+ T cell.

Increased prevalence of cancer in obese individuals is involved with dyslipidemia- induced chronic inflammation and immune suppression. Although apolipoprotein C-III (ApoC3)-transgenic mice (ApoC3TG mice) or poloxamer 407 (P407)-treated mice had hyperlipidemia, CD8+ T cells with upregulated antitumor activities were observed in ApoC3TG mice, and decreased CD8+ T cell activities were observed in P407-treated mice. Increased ApoC3 expression in hepatocellular carcinoma was associated with increased infiltration of CD8+ T cells and predicted survival. Recombinant ApoC3 had no direct effects on CD8+ T cells. The upregulation of CD8+ T cells in ApoC3TG mice was due to cross-talk with context cells, as indicated by metabolic changes and RNA sequencing results. In contrast to dendritic cells, the macrophages of ApoC3TG mice (macrophagesTG) displayed an activated phenotype and increased IL-1β, TNF-α, and IL-6 production. Coculture with macrophagesTG increased CD8+ T cell function, and the adoptive transfer of macrophagesTG suppressed tumor progression in vivo. Furthermore, spleen tyrosine kinase (Syk) activation induced by TLR2/TLR4 cross-linking after ApoC3 ligation promoted cellular phospholipase A2 (cPLA2) activation, which in turn activated NADPH oxidase 2 (NOX2) to promote an alternative mode of inflammasome activation. Meanwhile, mitochondrial ROS produced by increased oxidative phosphorylation of free fatty acids facilitated the classical inflammasome activation, which exerted an auxiliary effect on inflammasome activation of macrophagesTG. Collectively, the increased antitumor activity of CD8+ T cells was mediated by the ApoC3-stimulated inflammasome activation of macrophages, and the mimetic ApoC3 peptides that can bind TLR2/4 could be a future strategy to target liver cancer.

Analysis of Fecal Microbiota in Patients with Hypertension Complicated with Ischemic Stroke.

Ischemic stroke is a disease with a very high incidence in the clinic, and hypertension is the most important variable risk factor of ischemic stroke. Studies have shown that intestinal microbes are involved in the occurrence and development of various diseases. This study aims to explore whether intestinal microbes play an important role in the pathogenesis of ischemic stroke in a hypertensive population. In this study, the inpatients in the Department of Neurology and Cardiology of the Second Affiliated Hospital of Shandong First Medical University in April 2021 were selected, including seven patients with hypertension complicated with ischemic stroke and only seven patients with hypertension. After collecting the stool samples of patients, the gene sequence of the samples was detected by 16S rRNA sequencing technology, and the double-ended 2 × 150bp sequencing was carried out. After sequencing, the results were analyzed by diversity analysis, species difference analysis, species function difference analysis, and other bioinformatics tests. According to the test results, serum proteomics and biochemical blood tests were carried out to verify. There was no significant difference in α diversity and β diversity between hypertension complicated with the cerebral infarction and hypertension groups. LEfSe analysis showed that at the genus level, compared with the hypertension group, Bacteroides, UCG_009, and Eisenbergiella had significantly increased relative abundance. The genera with relatively significantly reduced abundance are Ruminococcus_gnavus_group, Sutterellaceae, Burkholderia, and Prevotella and the LDA score of Prevotella is < - 4, which indicates that there are significant differences. Compared with the blood biochemical indexes, the results showed that the level of APOA1 in hypertensive patients with ischemic stroke was significantly higher than that in hypertensive patients (p < 0.05), but there was no significant difference in total cholesterol (CHOL), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), apolipoprotein B (APOB), and free fatty acid (NEFA). Proteomic analysis showed that there were 89 up-regulated genes and 51 down-regulated genes in the serum of the two groups, and the expression of APOC2 and APOC3 in the cerebral infarction group with hypertension was significantly higher than that in the hypertension group (p < 0.05). The intestinal diversity of patients with hypertension complicated with stroke is similar to that of patients with hypertension, but there are differences in microbiota, among which Prevotella is the most significant. Prevotella could affect lipid metabolism so that APOC2 and APOC3 in the blood are significantly increased, leading to cerebral artery atherosclerosis and, finally, ischemic stroke. This provides a new idea for preventing and treating ischemic stroke in patients with hypertension, but the mechanism of Prevotella acting on apolipoprotein needs further verification by basic medical research.

ApoC3 is expressed in oocytes and increased expression is associated with PCOS progression

BackgroundPolycystic ovary syndrome (PCOS) is a lifelong metabolic disorder and the most common cause of anovulatory infertility affecting women in reproductive age. Our recent study reported that apolipoprotein C3 (ApoC3) could be a potential diagnostic serum marker for metabolism disturbance in PCOS patients, but whether it is present in the ovaries and what role it plays has not yet been described.ObjectiveAimed to investigate ApoC3 expression in ovary of PCOS, and to discuss its potential role in PCOS progression.MethodsApoC3 expression in ovarian tissue samples from 12 PCOS patients along with 12 healthy controls were measured via immunohistochemistry (IHC). Also, the level of ApoC3 in follicular fluid from 14 patients diagnosed with PCOS and 13 control subjects were detected by ELISA. The expression and location of ApoC3 in ovaries of PCOS mice were tested weekly for three consecutive weeks during PCOS formation using real time PCR, Western Blot, IHC and immunofluorescence. The relation of ApoC3 and sex hormones was analyzed in mouse plasma. Additionally, the dynamic changes of ApoC3 level in ovaries of healthy mice during postnatal development was also investigated.ResultsApoC3 levels in ovarian tissue and follicular fluid were significantly higher in PCOS patients than in controls (33.87 ± 4.11 vs. 27.71 ± 3.65, P < 0.01; 0.87 ± 0.09 vs. 0.51 ± 0.32 ng/mL, P < 0.05), respectively. In ovary, ApoC3 was found to be located in the cytoplasm of oocyte, and its expression gradually increased with PCOS progression (P < 0.05). Furthermore, correlation analysis showed that plasma ApoC3 level was closely associated with luteinizing hormone (r = 0.709, P = 0.001), testosterone (r = 0.627, P = 0.005) and anti-mullerian hormone (r = 0.680, P = 0.002) in PCOS mice. In addition, ApoC3 level in oocyte was physiologically increased and peaked on postnatal age 21 (P21), then decreased following P21 in healthy mice.ConclusionsWe identified ApoC3 expression in oocyte. It may be involved in PCOS progression and possibly participate in the regulation of oocyte development.

Unanticipated Enhancement of Intestinal TG Output by Apoc3 ASO Inhibition.

The objective of this study was to investigate whether apoC3 (apolipoprotein C3) inhibition with an antisense oligonucleotide (ASO) modulates intestinal triglyceride secretion. Sprague-Dawley rats were treated with subcutaneous injections of apoC3 ASO 25 mg/kg twice weekly or inactive ASO for 4 weeks before the assessment of lymph flow, triglyceride and apoB48 appearance in the lymph. Rats were surgically implanted with catheters in the mesenteric lymph duct and duodenum. Following an overnight fast, an intraduodenal lipid bolus (1.5-mL intralipid) was administered. Lymph fluid was collected for the following 4 hours to compare effects on lymph flow, lymph triglyceride and apoB48 concentration, and secretion. To assess suppression of apoC3 expression and protein abundance by apoC3 ASO compared with inactive ASO (placebo), intestinal and hepatic tissues were collected from a subset of animals before (fasting) and after an enteral lipid bolus (post-lipid). ApoC3 ASO significantly reduced apoC3 mRNA expression in the liver compared with inactive ASO (fasting: 42%, P=0.0048; post-lipid: 66%, P<0.001) and in the duodenum (fasting: 29%, P=0.0424; post-lipid: 53%, P=0.0120). As expected, plasma triglyceride also decreased significantly (fasting: 74%, P<0.001; post-lipid: 33%, P=0.0276). Lymph flow and cumulative lymph volume remained unchanged following apoC3 ASO therapy; however, lymph triglyceride, but not apoB48 output, increased by 38% (ANOVA, P<0.001). Last, no changes were observed in stool triglyceride, intestinal fat (quantified via oil red O staining), and expression of mRNAs involved in triglyceride synthesis, lipid droplet formation, and chylomicron transport and secretion. Despite the marked reduction in plasma triglyceride concentration that occurs with apoC3 ASO inhibition, intestinal triglyceride output surprisingly increased rather than decreased. These data demonstrate that the reduction of intestinal triglyceride output does not contribute to the potent plasma triglyceride-lowering observed with this novel therapy for hypertriglyceridemia. Further studies are required to explore the mechanism of this intestinal effect.

Apolipoprotein C3 is negatively associated with estrogen and mediates the protective effect of estrogen on hypertriglyceridemia in obese adults

BackgroundBoth estrogen and apolipoprotein C3 (ApoC3) play crucial roles in lipid metabolism. But the link between them remains unclear, and it is unknown whether estrogen regulates triglyceride (TG) levels via ApoC3. Researchers hypothesized that estrogen exerts a regulatory effect on ApoC3 metabolism, and that this regulation could play a significant role in lipid metabolism. To explore this potential link, the present investigation aimed to examine the associations between estradiol (E2), ApoC3, and TG levels in both males and females.MethodsA total of 519 obese people (133 males and 386 premenopausal females) were recruited. Based on their TG levels, the participants were split into two groups [hypertriglyceridemia (HTG) group: TG ≥ 1.7 mmol/L; control group: TG < 1.7 mmol/L]. Serum ApoC3, E2, and TG levels were measured and compared in those two groups for both sexes separately. To ascertain the connection among E2, ApoC3, and TG, linear regression and mediation analysis were used.ResultsParticipants in the HTG group presented higher levels of ApoC3 (P < 0.001). In contrast, they tend to have lower E2 levels than the control. Linear regression analysis proposed that in both sexes, E2 was negatively associated with ApoC3 levels. The relationship remained significant after adjustment for confounding factors (male: standardized β = -0.144, t = -2.392, P < 0.05; female: standardized β = -0.077, t = -2.360, P < 0.001). Furthermore, mediation analysis revealed the relationship between reduced E2 levels and elevated TG levels is directly mediated by ApoC3.ConclusionsIn obese men and premenopausal women, ApoC3 was negatively and linearly correlated with serum E2 levels. The findings showed that estrogen may suppress ApoC3 expression and thus lower TG levels.

Acupoint Catgut Embedding Improves Lipid Metabolism in Exercise-Induced Fatigue Rats via the PPAR Signaling Pathway

To improve the phenomenon of exercise-induced fatigue that often occurs during horse racing, we previously studied the improvement in exercise tolerance by acupoint catgut embedding preconditioning in an exercise-induced fatigue rat model. We found that acupoint catgut embedding pretreatment effectively improved animal exercise tolerance. Here, by combining transcriptomics and metabolomics, we aimed to explore the underlying mechanisms of this improvement. We used blood biochemical detection combined with ELISA to detect triglyceride (TG), total cholesterol (TC), lactate dehydrogenase (LDH), high-density lipoprotein (HDL), alanine transaminase (ALT), aspartate aminotransferase (AST), and glucose (GLU), arachidonic acid (AA), and free fatty acid (FFA) content and found that acupoint embedding can correct FFA, AA, TG, LDH, and AST in the blood. We used RT-qPCR to measure the expression of genes in tissue from the quadriceps femoris muscle. We found that solute carrier family 27 member 2 (Slc27a2), fatty acid binding protein 1 (Fabp1), apolipoprotein C3 (Apoc3), and lipoprotein lipase (Lpl) genes in the peroxisome proliferator-activated receptor (PPAR) signaling pathway were important. The regulation of lipid metabolism through the PPAR signaling pathway was important for improving the exercise endurance of rats in our exercise-induced fatigue model. Therefore, we conclude that acupoint catgut embedding can not only promote body fat decomposition and reduce lactic acid accumulation but also promote the repair of tissue damage and liver damage caused by exercise fatigue. Acupoint catgut embedding regulates the PPAR signaling pathway by upregulating Lpl expression and downregulating Slc27a2, Fabp1, and Apoc3 expression to further improve body fat metabolism.

Single-cell RNA sequencing revealed the liver heterogeneity between egg-laying duck and ceased-laying duck

BackgroundIn the late phase of production, ducks untimely cease laying, leading to a lower feed conversion. Liver plays a vital role in the synthesis and transport of yolk materials during egg formation in birds. However, the molecular mechanism of liver in ceased-laying duck is far from clear, higher resolution and deeper analysis is needed. Sing-cell RNA-sequencing of 10 × Genomics platform can help to map the liver single cell gene expression atlas of Shaoxing duck and provide new insights into the liver between egg-laying and ceased-laying ducks.ResultsAbout 20,000 single cells were profiled and 22 clusters were identified. All the clusters were identified as 6 cell types. The dominant cell type is hepatocyte, accounted for about 60% of all the cells. Of note, the heterogeneity of cells between egg-laying duck and ceased-laying duck mainly occurred in hepatocytes. Cells of cluster 3 and 12 were the unique hepatocyte states of egg-laying ducks, while cells of cluster 0 and 15 were the unique hepatocyte states of ceased-laying ducks. The expression mode of yolk precursor transporters, lipid metabolizing enzymes and fibrinogens were different in hepatocytes between egg-laying duck and ceased-laying duck. APOV1, VTG2, VTG1, APOB, RBP, VTDB and SCD might be activated in egg-laying ducks, while APOA1, APOA4, APOC3, FGB and FGG might be activated in ceased-laying ducks.ConclusionsOur study further proofs that APOV1 and APOB play key roles in egg production, rather than APOA1 and APOA4. It is also the first to detect a correlation between the higher expression of APOC3, FGB, FGG and ceased-laying in duck.

The Effects of PPAR Agonists on Atherosclerosis and Nonalcoholic Fatty Liver Disease in ApoE-/-FXR-/- Mice.

Background Farnesoid X receptor (FXR), a bile acid–activated nuclear receptor, is a potent regulator of glucose and lipid metabolism as well as of bile acid metabolism. Previous studies have demonstrated that FXR deficiency is associated with metabolic derangements, including atherosclerosis and nonalcoholic fatty liver disease (NAFLD), but its mechanism remains unclear. In this study, we investigated the role of FXR in atherosclerosis and NAFLD and the effect of peroxisome proliferator-activated receptor (PPAR) agonists in mouse models with FXR deficiency.Methods En face lipid accumulation analysis, liver histology, serum levels of glucose and lipids, and mRNA expression of genes related to lipid metabolism were compared between apolipoprotein E (ApoE)−/− and ApoE−/−FXR−/− mice. The effects of PPARα and PPARγ agonists were also compared in both groups of mice.Results Compared with ApoE−/− mice, ApoE−/−FXR−/− mice showed more severe atherosclerosis, hepatic steatosis, and higher levels of serum cholesterol, low-density lipoprotein cholesterol, and triglycerides, accompanied by increased mRNA expression of FAS, ApoC2, TNFα, IL-6 (liver), ATGL, TGH, HSL, and MGL (adipocytes), and decreased mRNA expressions of CPT2 (liver) and Tfam (skeletal muscle). Treatment with a PPARα agonist, but not with a PPARγ agonist, partly reversed atherosclerosis and hepatic steatosis, and decreased plasma triglyceride levels in the ApoE−/−FXR−/− mice, in association with increased mRNA expression of CD36 and FATP and decreased expression of ApoC2 and ApoC3 (liver).Conclusion Loss of FXR is associated with aggravation of atherosclerosis and hepatic steatosis in ApoE-deficient mice, which could be reversed by a PPARα agonist through induction of fatty acid uptake, β-oxidation, and triglyceride hydrolysis.

Circadian regulation of apolipoprotein gene expression affects testosterone production in mouse testis

The circadian clock system plays an important role in regulating testosterone synthesis in mammals. Male Bmal1−/− mice are infertile with low serum testosterone levels and decreased expression of testicular steroidogenic genes, suggesting that circadian clock genes regulate testosterone biosynthesis by activating steroidogenic gene transcription. However, whether the circadian clock regulates testosterone production via other genes remains unknown. Using Bmal1−/− mice and their wild-type (WT) siblings, we aimed to identify additional genes by which the circadian clock regulates testosterone synthesis. WT and Bmal1−/− mouse testes sections had similar normal morphologies, although there was a decrease in testicular spermatozoa in the Bmal1−/− mice. Low serum testosterone levels were detected in the Bmal1−/− mice. RNA sequencing identified 37 and 48 genes that were differentially expressed between WT and Bmal1−/− mouse testes at circadian time (CT2 and CT14), respectively. The cholesterol metabolism pathway was significantly enriched in the KEGG pathway analysis, and there was lower expression of three apolipoprotein genes (Apoa1, Apoa2, and Apoc3) at CT2 in the testes of Bmal1−/− mice than in those of WT mice. These decreases in Apoa1, Apoa2, and Apoc3 expression were verified by quantitative polymerase chain reaction analysis, which also revealed downregulation of the expression of the circadian clock (Per2, Dbp, and Nr1d1) and steroidogenic (StAR, Cyp11a1, and Hsd17b3) genes. The expression of circadian clock genes was relatively stable in WT mice over a 20-h period, whereas there was clear circadian rhythmic expression of Apoa1, Apoa2, Apoc3, StAR, Cyp11a1, Hsd3b2, and Hsd17b3. Bmal1−/− mice showed severely reduced expression of testicular circadian clock genes at three time points (CT4, CT12, and CT20), and a reduction in mRNA expression levels of Apo (Apoa1, Apoa2, and Apoc3) and steroidogenic (StAR, Cyp11a1, Hsd3b2, and Hsd17b3) genes. Oil Red O staining showed decreased lipid aggregation in the Leydig cells of Bmal1−/− mouse testes. Considering the vital role of Apo genes in high-density lipoprotein formation and cholesterol transport, the present data suggest that the circadian clock system regulates testosterone production by orchestrating the rhythmic expression of Apo genes. These data extend our understanding of the role of the circadian clock in regulating testosterone production in mammals.

Fine genetic mapping of the chromosome 11q23.3 region in a Han Chinese population: insights into the apolipoprotein genes underlying the blood lipid-lipoprotein variances

The unusual chromosome 11q23.3 harboring the apolipoprotein (APO) gene cluster has been well documented for its essential roles in plasma lipid-related traits and atherosclerotic cardiovascular diseases. However, its genetic architecture and the potential biological mechanisms underlying complex phenotypes have not been well assessed. We conducted a study for this target region in a Han Chinese population through a stepwise forward framework based on massive parallel sequencing, association analyses, genetic fine mapping, and functional interpretation. The present study identified new meaningful genetic associations that were not simply determined by statistical significance. In addition to the APOA5 gene, we found robust evidence of the genetic commitments of APOC3 and APOA1 to blood lipids. Several variants with high confidence were prioritized along with the potential biological mechanism interpretations in the wake of adaptive fine-mapping analyses. rs2849174 in the APOC3 enhancer was discovered with an unrivaled posterior probability of causality for triglyceride levels and could mediate APOC3 expression through enhancer activity modulated by a combination of histone modifications and transcription factor accessibility. Similarly, multiple lines of evidence converged in favor of rs3741297 as a causal variant influencing high-density lipoprotein cholesterol. Our findings provided novel insights into this genomic locus in the Chinese population.

MiR-383 ameliorates high glucose-induced β-cells apoptosis and hyperglycemia in high-fat induced diabetic mice

Islet beta-cell dysfunction is an important condition leading to the development of diabetes. Numerous studies have found that miRNA regulates islet β-cell function. In our previous research, the aberrant expression of miR-383 was revealed in type 2 diabetes mellitus (T2DM) serum. Herein, we aimed to assess the function and underlying mechanism of miR-383 in β-cells through in vitro and in vivo experiments. Using high glucose media, the β-cell injury was induced and transfected miR-383 overexpression vector to detect cell function in MIN6. Moreover, miR-383 overexpression lentivirus was administrated into high-fat induced diabetes mice to assess the in vivo effect. Results showed that overexpressing miR-383 reversed the cell apoptosis and oxidative stress, induced by high glucose which targets Toll-like receptors (TLR4) and Apolipoprotein C3 (ApoC3) genes. Furthermore, mechanistic studies demonstrated that miR-383 targeted the TLR4 and ApoC3 3′ UTR consequently inhibiting TLR4 and ApoC3 expression in MIN6 cells. Besides, overexpression of miR-383 ameliorated hyperglycemia and pancreatic apoptosis in high-fat induced diabetic mice. Conclusively, miR-383 potentially alleviate pancreatic β-cell injury induced by high glucose and ameliorates high-fat induced diabetes by suppressing TLR4 and ApoC3 expression.

Increased apolipoprotein C3 drives cardiovascular risk in type 1 diabetes.

Type 1 diabetes mellitus (T1DM) increases the risk of atherosclerotic cardiovascular disease (CVD) in humans by poorly understood mechanisms. Using mouse models of T1DM-accelerated atherosclerosis, we found that relative insulin deficiency rather than hyperglycemia elevated levels of apolipoprotein C3 (APOC3), an apolipoprotein that prevents clearance of triglyceride-rich lipoproteins (TRLs) and their remnants. We then showed that serum APOC3 levels predict incident CVD events in subjects with T1DM in the Coronary Artery Calcification in Type 1 Diabetes (CACTI) study. To explore underlying mechanisms, we investigated the impact of Apoc3 antisense oligonucleotides (ASOs) on lipoprotein metabolism and atherosclerosis in a mouse model of T1DM. Apoc3 ASO treatment abolished the increased hepatic Apoc3 expression in diabetic mice - resulting in lower levels of TRLs - without improving glycemic control. APOC3 suppression also prevented arterial accumulation of APOC3-containing lipoprotein particles, macrophage foam cell formation, and the accelerated atherosclerosis in diabetic mice. Our observations demonstrate that relative insulin deficiency increases APOC3 and that this results in elevated levels of TRLs and accelerated atherosclerosis in a mouse model of T1DM. Because serum levels of APOC3 predicted incident CVD events in the CACTI study, inhibiting APOC3 might reduce CVD risk in T1DM patients.

Rosa rugosa flavonoids exhibited PPARα agonist-like effects on genetic severe hypertriglyceridemia of mice

Ethnopharmacological relevanceRosa rugosa Thunb. is a traditional Chinese medicine that was used in the treatment of cardiovascular diseases and relative risk factors such as diabetes, hyperlipidemia, hypertension, and inflammation. Rosa rugosa flavonoids (RRFs) are the main components in Rosa rugosa Thunb. Several studies have demonstrated that RRFs can regulate plasma lipid contents, but the related mechanism of which has not yet been elucidated clearly. Aim of the studyThe goal of this study was to clarify the effects of RRFs on triglyceride metabolism and its related mechanisms. Materials and methodsRRFs were obtained by ethanol extraction from Rosa rugosa Thunb.. Transgenic mice expressing human Apolipoprotein C3 (ApoC3) were used as a mouse model of hypertriglyceridemia. Fenofibrate (FNB), a PPARα agonist, was used as a positive control drug of decreasing high triglyceride. FNB (100 mg/kg) or RRFs (300 mg/kg) were given to the mice by gavage daily. Two weeks later, the changes of plasma lipid levels in the mice were measured by commercial kits, the clearance of triglyceride was evaluated by oral fat load test, and expression of the genes related to lipid β-oxidation and synthesis was detected in the mice livers by real time PCR. ResultsRRFs, as well as FNB, were found to significantly reduce plasma triglyceride (TG) levels in ApoC3 transgenic mice after administration of the drug for two weeks. Plasma lipid clearance rate was increased and lipid content in the mice livers was reduced after administration of RRF. Treatment with RRFs up-regulated mRNA expression of PPARα and its downstream gene of ACOX, while down-regulated mRNA expression of the genes related to fatty acid synthesis (FASN, SREBP-1c, and ACC1). The expression of LPL was raised, while the expression of ApoC3 was decreased, and Foxo1 was inhibited by RRFs in the mice livers. ConclusionRRFs can reduce plasma TG levels by repressing the expression of ApoC3 and inducing the expression of LPL in liver. RRFs could also reduce triglyceride in hepatocytes through increasing β-oxidation and decreasing synthesis of the lipids. These findings show the potency of further clinical application of RRFs as a hypolipidemic drug for treatment of cardiovascular diseases.

RETRACTED: The silencing of ApoC3 suppresses oxidative stress and inflammatory responses in placenta cells from mice with preeclampsia via inhibition of the NF-κB signaling pathway

Preeclampsia is one of the three primary causes of maternal morbidity and mortality worldwide. This study evaluated ApoC3 in placenta cells of mice with preeclampsia to explore its therapeutic role in preeclampsia and assess its function on oxidative stress and inflammatory responses involving the NF-κB signaling pathway. A mouse model of preeclampsia was successfully established. APOC3-siRNA with the best silencing effect was screened out. The expression levels of ApoC3, p65, and IkBα were evaluated. The effect of ApoC3 silencing on metabolic activity and apoptosis was measured. The level of high-sensitivity C-reactive protein (hs-CPR), interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α), the activity of matrix metalloproteinase (MMP)-2 and MMP-9, and the expression of malondialdehyde (MDA), 8-isoprostane and oxidized low-density lipoprotein (ox-LDL) were determined. ApoC3-siRNA-3 was the most effective siRNA. The mRNA expression of ApoC3 was scarcely observed, while the expression of p65 decreased and the expression of p-IkBα increased in the ApoC3-siRNA group. Compared with those in the model and empty vector groups, the cell apoptosis rate and the activities of invasion-related factors MMP-2 and MMP-9 increased, while the levels of hs-CPR, IL-6, TNF-α, MDA, 8-isoprostane, and ox-LDL decreased in the ApoC3-siRNA group. Silencing ApoC3 could suppress the NF-κB signaling pathway, thereby exercising a protective effect on cell injury induced by oxidative stress and reducing inflammatory responses.

Apolipoprotein C3 and Cardiovascular Disease in Patients with Type 1 Diabetes and Diabetic Nephropathy

Background and Aims: Apolipoprotein C3 (ApoC3) is a key regulator of triglyceride metabolism via its inhibitory effects on lipolysis and hepatic remnant uptake. Emerging evidence indicate that ApoC3 is an independent risk factor for cardiovascular events. The fact that glucose and insulin regulates ApoC3 expression raises the role of ApoC3 and cardiovascular risk in diabetes. We, therefore, investigated ApoC3 and its association with cardiovascular disease (CVD) in patients with and without diabetic nephropathy. Methods: This cross-sectional and prospective analysis was part of the prospective, ongoing Finnish Diabetic Nephropathy (FinnDiane) Study. Between 1994 and 2015 data were obtained from 3926 type 1 diabetes (T1D) patients at more than 80 hospitals or health centers across Finland. ApoC3 levels were explored by groups of albuminuria, CKD stages, presence of CVD as well as prediction of CVD and death. Survival curves were calculated by Cox regression analysis. Results: At baseline, normo-, micro- and macroalbuminuria were present in 71.7%, 13.8% and 14.5% of the population (n=3926, females 48%, age 37.8±12.2 years, diabetes duration 23.2±13 years, HbA1c 8.4±1.5%). CKD stage 3-5 was diagnosed in 14.3%. Coronary heart disease or stroke (CVD) were present in 5.5% at baseline, while 16.3% developed CVD during 15-year follow-up. Compared to normoalbuminuria ApoC3 was elevated in the presence of micro- (p=0.013) or macroalbumiuria (p&amp;lt;0.001). Increasing ApoC3 levels were observed alongside progression of CKD stage (p&amp;lt;0.001). Notably, higher baseline ApoC3 correlated with presence of CVD at baseline, development of CVD during follow-up and death. Differences in survival of those with the highest quartile of ApoC3 were independent of eGFR, triglycerides or HbA1c. Conclusions: Baseline ApoC3 levels were elevated in T1D patients with micro- and macroalbuminuria, with impaired renal function, and with CVD. ApoC3 also predicted the development of CVD and death during follow-up. Disclosure L. Stechemesser: None. C. Forsblom: None. R. Weitgasser: None. P. Groop: Other Relationship; Self; AstraZeneca, AbbVie Inc., Boehringer Ingelheim GmbH, Eli Lilly and Company, Janssen Pharmaceuticals, Inc., Medscape, Merck Sharp &amp; Dohme Corp., Novartis AG, Novo Nordisk A/S, Sanofi.

Alantolactone suppresses APOC3 expression and alters lipid homeostasis in L02 liver cells

A high level of APOC3 expression is an independent risk factor for some lipid metabolism-related diseases, such as cardiovascular disease (CVD), nonalcoholic fatty liver disease (NAFLD) and atherosclerosis (AS). This suggests that down-regulating APOC3 expression is a potential way of regulating lipid levels. In this study, we used luciferase reporter screening to identify a natural compound, alantolactone (ALA), that can inhibit the promoter activity of APOC3. ALA decreased APOC3 expression at both mRNA and protein levels. Then we pretreated L02 liver cells with oxLDL to investigate the function of ALA in lipid homeostasis. Intriguingly, ALA attenuated oxLDL-induced foam cell formation by reducing total cholesterol (TC) and triglyceride (TG) contents. Furthermore, these results could be reversed by overexpressing APOC3 protein. ALA inhibited tyrosine phosphorylation (Tyr705pho) of STAT3 to down-regulate APOC3 expression. Intriguingly, overexpression of a wild-type STAT3 or a constitutively active form of STAT3 (STAT3-C) up-regulated APOC3 expression and partly reversed the effect of ALA in oxLDL-induced L02 cells. Overexpression of wild-type STAT3 also increased TC but not TG contents in L02 cells. However, overexpression of STAT3-C significantly increased TC and TG contents, and the effect of ALA was partly attenuated by STAT3-C, although this was not statistically significant. These results suggest that ALA attenuates lipid accumulation through down-regulation of APOC3 expression, at least in part by inhibiting STAT3 signaling.