Apolipoprotein-CIII O-Glycosylation Is Associated with Micro- and Macrovascular Complications of Type 2 Diabetes.

Apolipoprotein-CIII (apo-CIII) inhibits the clearance of triglycerides from circulation and is associated with an increased risk of diabetes complications. It exists in four main proteoforms: O-glycosylated variants containing either zero, one, or two sialic acids and a non-glycosylated variant. O-glycosylation may affect the metabolic functions of apo-CIII. We investigated the associations of apo-CIII glycosylation in blood plasma, measured by mass spectrometry of the intact protein, and genetic variants with micro- and macrovascular complications (retinopathy, nephropathy, neuropathy, cardiovascular disease) of type 2 diabetes in a DiaGene study (n = 1571) and the Hoorn DCS cohort (n = 5409). Mono-sialylated apolipoprotein-CIII (apo-CIII1) was associated with a reduced risk of retinopathy (ß = -7.215, 95% CI -11.137 to -3.294) whereas disialylated apolipoprotein-CIII (apo-CIII2) was associated with an increased risk (ß = 5.309, 95% CI 2.279 to 8.339). A variant of the GALNT2-gene (rs4846913), previously linked to lower apo-CIII0a, was associated with a decreased prevalence of retinopathy (OR = 0.739, 95% CI 0.575 to 0.951). Higher apo-CIII1 levels were associated with neuropathy (ß = 7.706, 95% CI 2.317 to 13.095) and lower apo-CIII0a with macrovascular complications (ß = -9.195, 95% CI -15.847 to -2.543). In conclusion, apo-CIII glycosylation was associated with the prevalence of micro- and macrovascular complications of diabetes. Moreover, a variant in the GALNT2-gene was associated with apo-CIII glycosylation and retinopathy, suggesting a causal effect. The findings facilitate a molecular understanding of the pathophysiology of diabetes complications and warrant consideration of apo-CIII glycosylation as a potential target in the prevention of diabetes complications.

Drug target Mendelian randomization supports apolipoprotein C3-lowering for lipoprotein-lipid levels reductions and cardiovascular diseases prevention.

BACKGROUND AND AIMS: Inhibitors of apolipoprotein C-III (apoC3) are currently approved for the reduction of triglyceride levels in patients with Familial Chylomicronemia Syndrome. We used drug target Mendelian randomization (MR) to assess the effect of genetically predicted decrease in apoC3 blood protein levels on cardiometabolic traits and diseases. METHODS: We quantified lifelong reductions in apoC3 blood levels by selecting all genome wide significant and independent (r2<0.1) single nucleotide polymorphisms (SNPs) in the APOC3 gene region ±1 Mb, from three genome-wide association studies (GWAS) of apoC3 blood protein levels (deCODE, n = 35,378, Fenland, n = 10,708 and ARIC, n = 7213). We included the largest GWASes on 18 cardiometabolic traits and 9 cardiometabolic diseases as study outcomes. RESULTS: A one standard deviation lowering in apoC3 blood protein levels was associated with lower triglycerides, apolipoprotein B, low-density lipoprotein cholesterol, alanine aminotransferase, and glomerular filtration rate as well as higher high-density lipoprotein cholesterol levels. ApoC3 lowering was also associated with lower risk of acute pancreatitis (odds ratio [OR] = 0.91 95% CI = 0.82 to 1.00), aortic stenosis (OR = 0.82 95% CI = 0.73 to 0.93), and coronary artery disease (OR = 0.86 95% CI = 0.80 to 0.93), and was associated with increased parental lifespan (0.06 95% CI = 0.03-0.09 years). These results were concordant across robust MR methods, the three protein datasets and upon adjustment for APOA1, APOA4 and APOA5 using a multivariable MR framework. CONCLUSIONS: These results provide evidence that apoC3 lowering could result in widespread benefits for cardiometabolic health and encourage the launch of trials on apoC3 inhibition for coronary artery disease prevention.

A novel mouse model of familial combined hyperlipidemia and atherosclerosis.

Within the context of residual cardiovascular risk in post-statin era, emerging evidence from epidemiologic and human genetic studies have demonstrated that triglyceride (TG)-rich lipoproteins and their remnants are causally related to cardiovascular risk. While, carriers of loss-of-function mutations of ApoC3 have low TG levels and are protected from cardiovascular disease (CVD). Of translational significance, siRNAs/antisense oligonucleotide (ASO) targeting ApoC3 is beneficial for patients with atherosclerotic CVD. Therefore, animal models of atherosclerosis with both hypercholesterolemia and hypertriglyceridemia are important for the discovery of novel therapeutic strategies targeting TG-lowering on top of traditional cholesterol-lowering. In this study, we constructed a novel mouse model of familial combined hyperlipidemia through inserting a human ApoC3 transgene (hApoC3-Tg) into C57BL/6 J mice and injecting a gain-of-function variant of adeno-associated virus-proprotein convertase subtilisin/kexin type 9 (AAV-PCSK9)-D377Y concurrently with high cholesterol diet (HCD) feeding for 16 weeks. In the last 10 weeks, hApoC3-Tg mice were orally treated with a combination of atorvastatin (10 mg·kg-1·d-1) and fenofibrate (100 mg·kg-1·d-1). HCD-treated hApoC3-Tg mice demonstrated elevated levels of serum TG, total cholesterol (TC) and low density lipoprotein-cholesterol (LDL-C). Oral administration of atorvastatin and fenofibrate significantly decreased the plaque sizes of en face aorta, aortic sinus and innominate artery accompanied by improved lipid profile and distribution. In summary, this novel mouse model is of considerable clinical relevance for evaluation of anti-atherosclerotic drugs by targeting both hypercholesterolemia and hypertriglyceridemia.

APOC3 siRNA and ASO therapy for dyslipidemia.

PURPOSE OF REVIEW: The aim of this review is to present the clinical indications of apolipoprotein C-III (apoC3) inhibition in the therapeutic arsenal for the treatment of lipid disorders and associated risks and to compare the most advanced modalities of apoC3 inhibition currently available or in development, specifically APOC3 antisense oligonucleotides (ASO) and small interfering RNA (siRNA). RECENT FINDINGS: ApoC3 inhibition significantly decreases triglyceride levels by mechanisms coupling both lipoprotein lipase (LPL) upregulation and LPL-independent mechanisms. The main apoC3 inhibitors in advanced clinical development are the GalNAc-ASO olezarsen and the GalNAc-siRNA plozasiran. Clinical studies conducted with volanesorsen, the olezarsen precursor, showed a favorable effect on hepatic steatosis (nonalcoholic fatty liver disease, NAFLD). Olezarsen does not appear to be associated with the main side effects attributed to volanesorsen including thrombocytopenia. Plozasiran is in advanced clinical development and requires subcutaneous injection every 3 months and present to-date an efficacy and safety profile comparable to that of the monthly ASO. SUMMARY: Inhibition of apoC3 is effective across all the spectrum of hypertriglyceridemia, might have a favorable effect on hepatic steatosis (NAFLD) and the effect of apoC3 inhibition on cardiovascular risk is not limited to its effect on plasma triglycerides. APOC3 GalNAc-conjugated ASO and siRNA are both effective in decreasing plasma apoC3 and triglyceride levels.

Exploring apolipoprotein C-III: pathophysiological and pharmacological relevance.

The availability of pharmacological approaches able to effectively reduce circulating LDL cholesterol (LDL-C) has led to a substantial reduction in the risk of atherosclerosis-related cardiovascular disease (CVD). However, a residual cardiovascular (CV) risk persists in treated individuals with optimal levels of LDL-C. Additional risk factors beyond LDL-C are involved, and among these, elevated levels of triglycerides (TGs) and TG-rich lipoproteins are causally associated with an increased CV risk. Apolipoprotein C-III (apoC-III) is a key regulator of TG metabolism and hence circulating levels through several mechanisms including the inhibition of lipoprotein lipase activity and alterations in the affinity of apoC-III-containing lipoproteins for both the hepatic receptors involved in their removal and extracellular matrix in the arterial wall. Genetic studies have clarified the role of apoC-III in humans, establishing a causal link with CVD and showing that loss-of-function mutations in the APOC3 gene are associated with reduced TG levels and reduced risk of coronary heart disease. Currently available hypolipidaemic drugs can reduce TG levels, although to a limited extent. Substantial reductions in TG levels can be obtained with new drugs that target specifically apoC-III; these include two antisense oligonucleotides, one small interfering RNA and an antibody.

Inhibition of Angiopoietin-Like Protein 3 or 3/8 Complex and ApoC-III in Severe Hypertriglyceridemia.

PURPOSE OF REVIEW: The role of the inhibition of ANGPTL3 in severe or refractory hypercholesterolemia is well documented, less in severe hyperTG. This review focuses on the preclinical and clinical development of ApoC-III inhibitors and ANGPTL3, 4, and 3/8 complex inhibitors for the treatment of severe or refractory forms of hypertriglyceridemia to prevent cardiovascular disease or other morbidities. RECENT FINDINGS: APOC3 and ANGPTL3 became targets for drug development following the identification of naturally occurring loss of function variants in families with a favorable lipid profile and low cardiovascular risk. The inhibition of ANGPTL3 covers a broad spectrum of lipid disorders from severe hypercholesterolemia to severe hypertriglyceridemia, while the inhibition of ApoC-III can treat hypertriglyceridemia regardless of the severity. Preclinical and clinical data suggest that ApoC-III inhibitors, ANGPTL3 inhibitors, and inhibitors of the ANGPTL3/8 complex that is formed postprandially are highly effective for the treatment of severe or refractory hypertriglyceridemia. Inhibition of ANGPTL3 or the ANGPTL3/8 complex upregulates LPL and facilitates the hydrolysis and clearance of triglyceride-rich lipoproteins (TRL) (LPL-dependent mechanisms), whereas ApoC-III inhibitors contribute to the management and clearance of TRL through both LPL-dependent and LPL-independent mechanisms making it possible to successfully lower TG in subjects completely lacking LPL (familial chylomicronemia syndrome). Most of these agents are biologicals including monoclonal antibodies (mAb), antisense nucleotides (ASO), small interfering RNA (siRNA), or CRISPR-cas gene editing strategies.

[The role of apolipoprotein C3 in the regulation of nonalcoholic fatty liver disease, glucose and lipid metabolism, and islet ß cell function].

As a member of the apolipoprotein C (ApoC) family with a relatively high content, ApoC3 plays a major role in the regulation of triglyceride metabolism, and plays an important role in the occurrence and development of cardiovascular diseases, glucose and lipid metabolism disorders. Nonalcoholic fatty liver disease (NAFLD) refers to the accumulation of a large amount of fat in the liver in the absence of a history of chronic alcohol consumption or other damage to the liver. A large number of previous studies have shown that there is a correlation between the gene polymorphism and high expression of ApoC3 and NAFLD. In the context of hypertriglyceridemia (HTG), this article reviews the relationship between ApoC3 and NAFLD, glucose and lipid metabolism, and islet ß cell function, showing that ApoC3 can not only inhibit lipoprotein lipase (LPL) and hepatic lipase (HL) activity, delay the decomposition of triglyceride in plasma to maintain the body's energy metabolism during fasting, but also be significantly increased under insulin resistance, prompting the liver to secrete a large amount of very low-density lipoprotein (VLDL) to induce HTG. Therefore, targeting and inhibiting ApoC3 might become a new approach to treat HTG. Increasing evidence suggests that ApoC3 does not appear to be an independent "contributor" to NAFLD. Similarly, our previous studies have shown that ApoC3 is not an independent factor triggering islet ß cell dysfunction in ApoC3 transgenic mice, but in a state of excess nutrition, HTG triggered by ApoC3 high expression may exacerbate the effects of hyperglycemia and insulin resistance on islet ß cell function, and the underlying mechanism remains to be further discussed.

Apolipoprotein-CIII O-Glycosylation, a Link between GALNT2 and Plasma Lipids.

Apolipoprotein-CIII (apo-CIII) is involved in triglyceride-rich lipoprotein metabolism and linked to beta-cell damage, insulin resistance, and cardiovascular disease. Apo-CIII exists in four main proteoforms: non-glycosylated (apo-CIII0a), and glycosylated apo-CIII with zero, one, or two sialic acids (apo-CIII0c, apo-CIII1 and apo-CIII2). Our objective is to determine how apo-CIII glycosylation affects lipid traits and type 2 diabetes prevalence, and to investigate the genetic basis of these relations with a genome-wide association study (GWAS) on apo-CIII glycosylation. We conducted GWAS on the four apo-CIII proteoforms in the DiaGene study in people with and without type 2 diabetes (n = 2318). We investigated the relations of the identified genetic loci and apo-CIII glycosylation with lipids and type 2 diabetes. The associations of the genetic variants with lipids were replicated in the Diabetes Care System (n = 5409). Rs4846913-A, in the GALNT2-gene, was associated with decreased apo-CIII0a. This variant was associated with increased high-density lipoprotein cholesterol and decreased triglycerides, while high apo-CIII0a was associated with raised high-density lipoprotein-cholesterol and triglycerides. Rs67086575-G, located in the IFT172-gene, was associated with decreased apo-CIII2 and with hypertriglyceridemia. In line, apo-CIII2 was associated with low triglycerides. On a genome-wide scale, we confirmed that the GALNT2-gene plays a major role i O-glycosylation of apolipoprotein-CIII, with subsequent associations with lipid parameters. We newly identified the IFT172/NRBP1 region, in the literature previously associated with hypertriglyceridemia, as involved in apolipoprotein-CIII sialylation and hypertriglyceridemia. These results link genomics, glycosylation, and lipid metabolism, and represent a key step towards unravelling the importance of O-glycosylation in health and disease.

SP1 transcriptionally upregulates the expression of APOC3 in KGN cells to promote disease progression by regulating TLR2/NF-κB signalling pathway.

INTRODUCTION: Apolipoprotein C3 (APOC3) is known for its important functions in metabolism-related diseases. However, the function and molecular mechanism of APOC3 in polycystic ovarian syndrome (PCOS) have not been reported. MATERIAL AND METHODS: Quantitative polymerase chain reaction and western blot assays were used to detect the expression of APOC3 in KGN cells. Small interference APOC3 (siAPOC3) was applied to reduce APOC3 expression, and the proliferation ability of human granulosa cell line (KGN cells) was measured by cell counting kit-8 and colony formation assays. The protein levels of key genes related to apoptosis were detected by western blot assay. The transcriptional regulator of APOC3 was predicted by the UCSC and PROMO website, and verified by dual luciferase assay. siAPOC3 and pcDNA3.1-specific protein 1 (SP1) vector were co-transfected into KGN cells to detect the function of SP1 and APOC3 in KGN cells. RESULTS: APOC3 was overexpressed in KGN cells, and siAPOC3 transfection significantly reduced the growth ability of KGN cells and increased the apoptosis ability of KGN cells. SP1 directly bound to the promoter of APOC3 and transcriptional regulated APOC3 expression. Overexpression of SP1 increased the growth ability of KGN cells and decreased the apoptosis ability of KGN cells, which were reversed after siAPOC3 transfection. The increased levels of toll-like receptor 2 (TLR2) and p65 phosphorylation (p-P65) nuclear factor kappa B (NF-κB) caused by SP1 overexpression were inhibited by siAPOC3 transfection. APOC3, transcriptionally regulated by SP1, promoted the growth of KGN cells, and inhibited the apoptosis by regulating TLR2/NF-κB signalling pathway.

[Association Between Apolipoprotein C-3 Sstâ Polymorphism and Serum Lipids in Patients With Gestational Diabetes Mellitus].

Objective: To investigate the apolipoprotein C-3 (APOC3) gene Sst Ⅰ polymorphism and its relationship with changes in serum lipids in patients with gestational diabetes mellitus (GDM). Methods: A total of 630 pregnant women with GDM and 1027 normal pregnant controls were covered in the study. The genotype and allele frequencies of APOC3 Sst Ⅰ polymorphism were analyzed by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). Total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and glucose (Glu) were measured by enzymatic methods. Plasma insulin (INS) was measured by chemiluminescence. Apolipoproteins A 1 (apoA1) and B (apoB) levels were measured by turbidimetric immunoassay. Results: The allele frequencies of S1 and S2 of the APOC3 polymorphism at the SstⅠ locus were 0.704 and 0.296 in the GDM group and 0.721 and 0.279 in the control group, respectively. There was no significant difference in genotype frequency and allele frequency of APOC3 Sst Ⅰ polymorphism between the GDM and the control groups ( P>0.05). In the GDM group, those with S2S2 and S1S2 genotypes had higher plasma HDL-C levels and lower atherogenic index (AI) values than those with S1S1 genotype did, with the differences being statistically significant (all P<0.05). GDM patients were then divided into obesity and non-obesity subgroups. Further subgroup analysis showed that the association of APOC3 genotype with changes in HDL-C levels was observed only in obese GDM patients, while the association of APOC3 genotype with changes in AI values was observed in both obese and nonobese patients. In addition, in obese GDM patients, those with S2S2 genotype had significantly higher plasma TG levels than those with S1S1 and S1S2 genotypes did ( P<0.05 and P<0.01, respectively). In non-obese GDM patients, those with S2S2 genotype had significantly lower apoB/apoA1 ratio than S2S2 carriers did ( P<0.05). No genotype-related effect on lipid and apolipoprotein variations was evident in the normal controls. Conclusion: APOC3 Sst Ⅰ polymorphism in GDM patients is associated with HDL-C and TG levels as well as AI value and apoB/apoA1 ratio. The changes in lipid levels and apolipoprotein ratio showed BMI-dependent features. However, association between polymorphism at the locus and the development of GDM was not observed.

Unanticipated Enhancement of Intestinal TG Output by Apoc3 ASO Inhibition.

BACKGROUND: The objective of this study was to investigate whether apoC3 (apolipoprotein C3) inhibition with an antisense oligonucleotide (ASO) modulates intestinal triglyceride secretion. METHODS: 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 (apolipoprotein B48) 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). RESULTS: 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. CONCLUSIONS: 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.

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

BACKGROUND: Polycystic 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. OBJECTIVE: Aimed to investigate ApoC3 expression in ovary of PCOS, and to discuss its potential role in PCOS progression. METHODS: ApoC3 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. RESULTS: ApoC3 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. CONCLUSIONS: We identified ApoC3 expression in oocyte. It may be involved in PCOS progression and possibly participate in the regulation of oocyte development.

Updates in Drug Treatment of Severe Hypertriglyceridemia.

PURPOSE OF REVIEW: To provide an insight into the new pharmacological options for the treatment of severe hypertriglyceridemia (sHTG). RECENT FINDINGS: sHTG is difficult to treat. The majority of the traditional pharmacological agents available have limited success in both robustly decreasing triglyceride levels and/or in reducing the incidence of acute pancreatitis (AP), the most severe complication of sHTG. Therapeutic options with novel mechanisms of action have been developed, such as antisense oligonucleotides (ASO) and small interfering RNA (siRNA) targeting APOC3 and ANGPTL3. The review discusses also 2 abandoned drugs for sHTG treatment, evinacumab and vupanorsen. The ASO targeting APOC3, volanesorsen, is approved for use in patients with familial chylomicronemia syndrome (FCS) in Europe. Olezarsen, an N-acetylgalactosamine (GalNAc)-conjugated ASO with the same target, seems to have a better safety and efficacy profile. siRNA targeting APOC3 and ANGPTL3, namely ARO-APOC3 and ARO-ANG3, are also promising for the treatment of sHTG. However, the ultimate clinical goal of any sHTG treatment, the decrease in the risk of AP, has not been definitively achieved till now by any pharmacotherapy, either approved or in development.

Silencing ApoC3 alleviates LPS-induced acute lung injury by inhibiting TLR signaling pathway.

This study aims to confirm whether apolipoprotein C3 (ApoC3) can regulate the inflammatory response and tissue damage in acute lung injury (ALI) and explore its regulatory pathway. ALI mouse model was established by intraperitoneal injection of lipopolysaccharide (LPS). ApoC3 levels were detected by real-time quantitative polymerase chain reaction, immunohistochemistry, and western blot assays. The levels of various inflammatory factors were detected by enzyme-linked immunosorbent assay and western blot analysis. Finally, the expression of toll-like receptor (TLR)/nuclear factor kappa B (NF-κB) signaling pathway-related protein [TLR2, myeloid differentiation primary response protein 88 (MyD88), IL-1 receptor-associated kinase 1 (IRAK1), NF-κB p65, and inhibitor of kappa B alpha (IκBα)], SLP adaptor and CSK interacting membrane protein (SCIMP), spleen tyrosine kinase (Syk), and phosphorylated (p)-Syk was detected by western blot analysis. ApoC3 was overexpressed in ALI mouse lung tissue and cell inflammation model. Silencing ApoC3 reduced inflammatory factors and alleviated lung tissue damage in ALI mice. Silencing ApoC3 reduced inflammatory factors and downregulated the expression of TLR2, MyD88, IRAK1, NF-κB p65, and increased IκBα expression in LPS-treated RAW264.7 cells. Moreover, co-transfection of si-TLR2 and shApoC3 further enhanced the inhibitory effects on the levels of inflammatory factors induced by silencing ApoC3. ApoC3 overexpression increased the levels of inflammatory factors and protein expression of SCIMP and p-Syk, while silencing TLR2 reversed the promotive effects of ApoC3 overexpression on above factors. In LPS-induced ALI mouse model and inflammatory cell model, downregulation of ApoC3 reduced inflammatory factors and relieved tissue damage. This process might be achieved through the TLR pathway.

Role of APOC3 3238C/G polymorphism in HIV-associated neurocognitive disorder.

Apolipoprotein not only have a role in cholesterol metabolism but also play a role in normal brain function. Apolipoprotein gene polymorphisms are known risk factors for a number of mental and neurological disorders. The expression of brain apolipoproteins is significantly altered in several brain disorders. Therefore, we assed ApoC33238 C/G polymorphism in a total of 248 patient infected with HIV (45 with HAND, 89 without HAND, 114 without ART) and 134 healthy controls using PCR-RFLP. ApoC3 3238CG, 3238 GG genotypes and 3238G allele showed a non-significant increased risk for severity of HAND (P = 0.16, OR = 1.83; P = 0.32, OR = 2.78; P = 0.10, OR = 1.65) while comparing individuals with and without HAND. ApoC3 3238 GG genotype and 3238G allele revealed an increased risk for disease progression when compared between HIV patients with and without ART (P = 0.55, OR = 1.76; P = 0.65, OR = 1.12) though risk could not reach statistical significance. ApoC3 3238 GG genotype and 3238G allele were associated with the reduced risk of acquiring HIV infection when comparing HIV patients who are not on ART with healthy controls (P = 0.05, OR = 0.29; P = 0.04, OR = 0.66). In HIV patients on ART,ApoC3 3238 GG genotype showed an increased susceptibility to development of HAND (P = 0.48, OR = 2.24) when comparing alcohol drinkers and non-drinkers however risk could not reach statistical significance. In conclusion, the genotype ApoC33238GG displayed an inclination of risk for the severity of HAND and HIV disease progression. The polymorphism of APOC3 3238C/G may have a role to reduce the risk for acquisition of HIV infection. ApoC33238GG genotype in presence of alcohol may increase susceptibility to development of HAND.

APOC3 and ABCA1 variants in unusual combined hypolipidaemia showing premature peripheral vascular disease.

BACKGROUND: Familial combined hypolipidaemia is a condition characterised by very low concentrations of circulating very-low-density lipoprotein (VLDL), low-density lipoprotein cholesterol (LDL), and high-density lipoprotein cholesterol (HDL). It is thought that low LDL/combined hypolipidaemia can protect from cardiovascular disease (CVD), but this is not what we found in a case we present. OBJECTIVE: We report on a 57-years-old male patient with combined hypolipidaemia who presented with premature peripheral vascular disease. We investigated also his two sons, 32- and 27-years-old, who manifested a tendency to low lipid levels. METHODS AND RESULTS: We used Illumina exome analysis in all three individuals and in all of them we could exclude the major effect of the variants within the genes most frequently mutated in hypolipidaemia, including recently reported LIPC gene variant. Instead, in all three individuals we identified a novel ABCA1 variant, possibly responsible for the decreased HDL levels. The proband and one of his sons also share the splicing APOC3 variant rs138326449, known to be associated with decreased TG levels. CONCLUSION: The heterogeneous nature and the risk of atherosclerosis in combined hypolipidaemia seems to be variable, based on an interplay between low HDL and LDL levels, and it depends on the combination of variants that cause it (Tab. 2, Ref. 38).

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

BACKGROUND: Both 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. METHODS: A 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. RESULTS: Participants 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 ß = -0.144, t = -2.392, P < 0.05; female: standardized ß = -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. CONCLUSIONS: In 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.

Investigation of associations between apolipoprotein A5 and C3 gene polymorphisms with plasma triglyceride and lipid levels.

OBJECTIVE: The aim of this study was to determine frequency and associations between APOA5 c.56C>G, -1131T>C, c.553G>T, and APOC3 -482C>T and SstI gene polymorphisms with hypertriglyceridemia. METHODS: Under a case-control study model, 135 hypertriglyceridemic and 178 normotriglyceridemic control participants were recruited. Polymerase chain reaction and restriction fragment length polymorphism methods were utilized for genotyping. Statistical calculations were performed by comparing allele and genotype frequencies between groups. Clinical characteristics were compared between groups and intra-group genotypes. RESULTS: APOC3 gene -482C>T and SstI polymorphic genotypes and allele frequencies were significantly higher in hypertriglyceridemic group (genotype frequencies, p=0.035, p=0.028, respectively). Regression analysis under unadjusted model confirmed that APOC3 -482C>T and SstI polymorphisms were significantly contributing to have hypertriglyceridemia (p=0.02, odds ratio [OR]=1.831 (95% confidence interval [CI] 1.095-3.060); p=0.04, OR=1.812 (1.031-3.183), respectively). APOA5 c.56C>G was in complete linkage disequilibrium with APOA5 c.553G>T polymorphism (D'=1). CONCLUSION: For the first time in a population sample from Turkey, among the five polymorphisms of APOA5 and APOC3 genes investigated, APOC3 -482C>T and SstI polymorphisms were associated with elevated serum TG levels, while APOA5 c.56C>G, -1131T>C, and c.553G>T polymorphisms were not.

Treatment of the metabolic syndrome by siRNA targeting apolipoprotein CIII.

Apolipoprotein CIII (apoCIII) is increased in obesity-induced insulin resistance and type-2 diabetes. Emerging evidences support the advantages of small interfering RNAs (siRNAs) to target disease-causing genes. The aim of this study was to develop siRNAs for in vivo silencing of apoCIII and investigate if this results in metabolic improvements comparable to what we have seen using antisense oligonucelotides against apoCIII. Twenty-four siRNAs were synthesized and tested in a dual luciferase reporter assay. The eight best were selected, based on knockdown at 20 nM, and of these, two were selected based on IC50 values. In vivo experiments were performed in ob/ob mice, an obese animal model for diabetes. To determine the dose-dependency, efficacy, duration of effect and therapeutic dose we used a short protocol giving the apoCIII-siRNA mix for three days. To evaluate long-term metabolic effects mice were treated for three days, every second week for eight weeks. The siRNA mix effectively and selectively reduced expression of apoCIII in liver in vivo. Treatment had to be repeated every two weeks to maintain a suppression of apoCIII. The reduction of apoCIII resulted in increased LPL activity, lower triglycerides, reduced liver fat, ceased weight gain, enhanced insulin sensitivity, and improved glucose homeostasis. No off-target or side effects were observed during the eight-week treatment period. These results suggest that in vivo silencing of apoCIII with siRNA, is a promising approach with the potential to be used in the battle against obesity-induced metabolic disorders.

The role of apolipoprotein C3 in the regulation of nonalcoholic fatty liver disease, glucose and lipid metabolism, and islet β cell function / 生理学报

As a member of the apolipoprotein C (ApoC) family with a relatively high content, ApoC3 plays a major role in the regulation of triglyceride metabolism, and plays an important role in the occurrence and development of cardiovascular diseases, glucose and lipid metabolism disorders. Nonalcoholic fatty liver disease (NAFLD) refers to the accumulation of a large amount of fat in the liver in the absence of a history of chronic alcohol consumption or other damage to the liver. A large number of previous studies have shown that there is a correlation between the gene polymorphism and high expression of ApoC3 and NAFLD. In the context of hypertriglyceridemia (HTG), this article reviews the relationship between ApoC3 and NAFLD, glucose and lipid metabolism, and islet β cell function, showing that ApoC3 can not only inhibit lipoprotein lipase (LPL) and hepatic lipase (HL) activity, delay the decomposition of triglyceride in plasma to maintain the body's energy metabolism during fasting, but also be significantly increased under insulin resistance, prompting the liver to secrete a large amount of very low-density lipoprotein (VLDL) to induce HTG. Therefore, targeting and inhibiting ApoC3 might become a new approach to treat HTG. Increasing evidence suggests that ApoC3 does not appear to be an independent "contributor" to NAFLD. Similarly, our previous studies have shown that ApoC3 is not an independent factor triggering islet β cell dysfunction in ApoC3 transgenic mice, but in a state of excess nutrition, HTG triggered by ApoC3 high expression may exacerbate the effects of hyperglycemia and insulin resistance on islet β cell function, and the underlying mechanism remains to be further discussed.