Apolipoprotein C-I genotype and serum levels of triglycerides, C-reactive protein and coronary heart disease

Role of apolipoprotein C1 in lipoprotein metabolism, atherosclerosis and diabetes: a systematic review

Apolipoprotein C1 (apoC1) is a small size apolipoprotein whose exact role is not totally clarified but which seems to modulate significantly the metabolism of lipoproteins. ApoC1 is involved in the metabolism of triglyceride-rich lipoproteins by inhibiting the binding of very low density lipoproteins (VLDL) to VLDL-receptor (VLDL-R), to low density lipoprotein receptor (LDL-R) and to LDL receptor related protein (LRP), by reducing the activity of lipoprotein lipase (LPL) and by stimulating VLDL production, all these effects leading to increase plasma triglycerides. ApoC1 takes also part in the metabolism of high density lipoproteins (HDL) by inhibiting Cholesterol Ester Transfer Protein (CETP). The functionality of apoC1 on CETP activity is impaired in diabetes that might account, at least in part, for the increased plasma CETP activity observed in patients with diabetes. Its different effects on lipoprotein metabolism with a possible role in the modulation of inflammation makes the net impact of apoC1 on cardiometabolic risk difficult to figure out and apoC1 might be considered as pro-atherogenic or anti-atherogenic depending on the overall metabolic context. Making the link between total plasma apoC1 levels and the risk of cardio-metabolic diseases is difficult due to the high exchangeability of this small protein whose biological effects might depend essentially on its association with VLDL or HDL. The role of apoC1 in humans is not entirely elucidated and further studies are needed to determine its precise role in lipid metabolism and its possible pleiotropic effects on inflammation and vascular wall biology. In this review, we will present data on apoC1 structure and distribution among lipoproteins, on the effects of apoC1 on VLDL metabolism and HDL metabolism and we will discuss the possible links between apoC1, atherosclerosis and diabetes.

Cholesterol-related gene variants are associated with diabetes in coronary artery disease patients

Coronary artery disease (CAD) which is a complex cardiovascular disease is the leading cause of death worldwide. The changing prevalence of the disease in different ethnic groups pointing out the genetic background of CAD. In this study, we aimed to evaluate the contribution of selected cholesterol metabolism-related gene polymorphisms to CAD presence. A total of 493 individuals who underwent coronary angiography were divided into 2 groups: normal coronary arteries (≤ 30% stenosis) and critical disease (≥ 50% stenosis). Individuals were genotyped for APOC1 (rs11568822), APOD (rs1568565), LIPA (rs13500), SORL1 (rs2282649), and LDLR (rs5930) polymorphisms using hydrolysis probes in Real-Time PCR. Blood samples were drawn before coronary angiography and biochemical analyses were done. The results were statistically evaluated. When the study group was stratified according to CAD, the minor allele of APOD polymorphism was found related to decreased risk for T2DM in the non-CAD group. In logistic regression analysis adjusted for several confounders, LDLR rs5930 polymorphism was found associated with T2DM presence in the male CAD group [OR = 0.502, 95%CI (0.259-0.974), p = 0.042]. Besides, APOD and LIPA polymorphisms were shown to affect serum lipid levels in non-CAD T2DM patients (p < 0.05). The minor allele of APOC1 was found associated with triglyceride levels in males independent of CAD status. Besides, LDLR minor allele carrier females had elevated HbA1c and glucose levels independent from CAD status in the whole group. The cholesterol metabolism-related gene polymorphisms were found associated with T2DM and biochemical parameters stratified to sex, CAD, and T2DM status.

Similarities and Differences in Extracellular Vesicle Profiles between Ischaemic Stroke and Myocardial Infarction

Extracellular vesicles (EVs) are involved in intercellular signalling through the transfer of molecules during physiological and pathological conditions, such as ischaemic disease. EVs might therefore play a role in ischaemic stroke (IS) and myocardial infarction (MI). In the present study, we analysed the similarities and differences in the content of circulating EVs in patients with IS and MI. This prospective observational study enrolled 140 participants (81 patients with IS, 37 with MI and 22 healthy controls [HCs]). We analysed the protein and microRNA content from EVs using proteomics and reverse transcription quantitative real-time polymerase chain reaction and compared it between the groups. In the patients with IS and MI, we identified 14 common proteins. When comparing IS and MI, we found differences in the protein profiles (apolipoprotein B, alpha-2-macroglobulin, fibronectin). We also found lower levels of miR-340 and miR-424 and higher levels of miR-29b in the patients with IS and MI compared with the HCs. Lastly, we found higher miR-340 levels in IS than in MI. In conclusion, proteomic and miRNA analyses suggest a relationship between circulating EV content and the patient’s disease state. Although IS and MI affect different organs (brain and heart) with distinct histological characteristics, certain EV proteins and miRNAs appear to participate in both diseases, while others are present only in patients with IS.

Apolipoprotein C1: Its Pleiotropic Effects in Lipid Metabolism and Beyond

Apolipoprotein C1 (apoC1), the smallest of all apolipoproteins, participates in lipid transport and metabolism. In humans, APOC1 gene is in linkage disequilibrium with APOE gene on chromosome 19, a proximity that spurred its investigation. Apolipoprotein C1 associates with triglyceride-rich lipoproteins and HDL and exchanges between lipoprotein classes. These interactions occur via amphipathic helix motifs, as demonstrated by biophysical studies on the wild-type polypeptide and representative mutants. Apolipoprotein C1 acts on lipoprotein receptors by inhibiting binding mediated by apolipoprotein E, and modulating the activities of several enzymes. Thus, apoC1 downregulates lipoprotein lipase, hepatic lipase, phospholipase A2, cholesterylester transfer protein, and activates lecithin-cholesterol acyl transferase. By controlling the plasma levels of lipids, apoC1 relates directly to cardiovascular physiology, but its activity extends beyond, to inflammation and immunity, sepsis, diabetes, cancer, viral infectivity, and-not last-to cognition. Such correlations were established based on studies using transgenic mice, associated in the recent years with GWAS, transcriptomic and proteomic analyses. The presence of a duplicate gene, pseudogene APOC1P, stimulated evolutionary studies and more recently, the regulatory properties of the corresponding non-coding RNA are steadily emerging. Nonetheless, this prototypical apolipoprotein is still underexplored and deserves further research for understanding its physiology and exploiting its therapeutic potential.

Variable cartilage degradation in mice with diet-induced metabolic dysfunction: food for thought

OBJECTIVE

Human cohort studies have demonstrated a role for systemic metabolic dysfunction in osteoarthritis (OA) pathogenesis in obese patients. To explore the mechanisms underlying this metabolic phenotype of OA, we examined cartilage degradation in the knees of mice from different genetic backgrounds in which a metabolic phenotype was established by various dietary approaches.

DESIGN

Wild-type C57BL/6J mice and genetically modified mice (hCRP, LDLr^-/-. Leiden and ApoE*3Leiden.CETP mice) based on C57BL/6J background were used to investigate the contribution of inflammation and altered lipoprotein handling on diet-induced cartilage degradation. High-caloric diets of different macronutrient composition (i.e., high-carbohydrate or high-fat) were given in regimens of varying duration to induce a metabolic phenotype with aggravated cartilage degradation relative to controls.

RESULTS

Metabolic phenotypes were confirmed in all studies as mice developed obesity, hypercholesteremia, glucose intolerance and/or insulin resistance. Aggravated cartilage degradation was only observed in two out of the twelve experimental setups, specifically in long-term studies in male hCRP and female ApoE*3Leiden.CETP mice. C57BL/6J and LDLr^-/-. Leiden mice did not develop HFD-induced OA under the conditions studied. Osteophyte formation and synovitis scores showed variable results between studies, but also between strains and gender.

CONCLUSIONS

Long-term feeding of high-caloric diets consistently induced a metabolic phenotype in various C57BL/6J (-based) mouse strains. In contrast, the induction of articular cartilage degradation proved variable, which suggests that an additional trigger might be necessary to accelerate diet-induced OA progression. Gender and genetic modifications that result in a humanized pro-inflammatory state (human CRP) or lipoprotein metabolism (human-E3L.CETP) were identified as important contributing factors.

Treatment of Hyperlipidemia Changes With Level of Kidney Function-Rationale

Lipoprotein abnormalities such as low levels of high-density lipoprotein (HDL) and high triglycerides (TGs), associated with the metabolic syndrome, are also associated with subsequent decline in kidney function. Patients with end-stage kidney disease also exhibit low HDL and high TGs and a modest reduction in low-density lipoprotein (LDL), although the mechanisms responsible for these changes differ when patients with end-stage kidney disease are compared with those having metabolic syndrome with normal kidney function, as do lipoprotein structures. Among dialysis patients, oxidized LDL, levels of TG-rich intermediate-density lipoprotein, and low HDL are associated with aortic pulsewave velocity and other markers of atherosclerosis. Statins are effective in reducing LDL and do decrease risk of cardiovascular events in patients with CKD not requiring dialysis but have no significant effect on outcomes, including all-cause mortality among dialysis patients. Similarly gemfibrozil and other fibrates lower TGs, increase HDL, and reduce cardiovascular events, but not mortality, among patients with CKD not requiring dialysis but have no significant effect on cardiovascular outcomes in dialysis patients. There is potential clinical benefit in treating elevated LDL, TGs, and low HDL in patients with CKD using statins or fibrates in those not yet requiring dialysis.

Double Filtration Plasma Apheresis Shortens Hospital Admission Duration of Patients With Severe Hypertriglyceridemia-Associated Acute Pancreatitis

OBJECTIVES

The treatment effectiveness of double filtration plasma apheresis (DFPP) on severe hypertriglyceridemia-associated acute pancreatitis (STAP) has been questioned because the currently defined serum triglyceride level--1000 mg/dL--is too low for STAP. Given this, we aimed to investigate DFPP effectiveness when we elevated STAP definition to 5000 mg/dL serum triglyceride.

METHODS

We performed nested case-control studies for STAP patients and divided them into groups "with" or "without" DFPP. We further recruited outpatient asymptomatic hypertriglyceridemia patients with STAP history, then divided them into groups "with" or "without" prophylactic DFPP once every 3 to 6 months for 2 years. We observed hospitalization duration and STAP recurrence between patients with and patients without DFPP.

RESULTS

Twelve STAP patients receiving DFPP had a median hospitalization of 5 days, whereas 24 patients without DFPP had 10 days (P = 0.009). Six outpatient referrals with STAP history receiving prophylactic DFPP showed no STAP recurrences whereas 6 without DFPP showed 3 recurrences (P = 0.046). For the 25 patients whose serum triglyceride exceeded 5000 mg/dL, 11 receiving DFPP had median hospitalization of 5 days while 14 without DFPP had 11 days (P = 0.012).

CONCLUSIONS

When applied to serum triglyceride in excess of 5000 mg/dL, DFPP removes oxidized and inflammatory lipoproteins, shortens hospitalization duration, and minimizes STAP recurrence.

Bioprospecting the American alligator (Alligator mississippiensis) host defense peptidome

Cationic antimicrobial peptides and their therapeutic potential have garnered growing interest because of the proliferation of bacterial resistance. However, the discovery of new antimicrobial peptides from animals has proven challenging due to the limitations associated with conventional biochemical purification and difficulties in predicting active peptides from genomic sequences, if known. As an example, no antimicrobial peptides have been identified from the American alligator, Alligator mississippiensis, although their serum is antimicrobial. We have developed a novel approach for the discovery of new antimicrobial peptides from these animals, one that capitalizes on their fundamental and conserved physico-chemical properties. This sample-agnostic process employs custom-made functionalized hydrogel microparticles to harvest cationic peptides from biological samples, followed by de novo sequencing of captured peptides, eliminating the need to isolate individual peptides. After evaluation of the peptide sequences using a combination of rational and web-based bioinformatic analyses, forty-five potential antimicrobial peptides were identified, and eight of these peptides were selected to be chemically synthesized and evaluated. The successful identification of multiple novel peptides, exhibiting antibacterial properties, from Alligator mississippiensis plasma demonstrates the potential of this innovative discovery process in identifying potential new host defense peptides.

Nitric oxide synthase (NOS) single nucleotide polymorphisms are associated with coronary heart disease and hypertension in the INTERGENE study

OBJECTIVE

Nitric oxide synthase (NOS) exists in three distinct isoforms, each encoded by a specific gene: neuronal NOS (NOS1 gene), inducible NOS (NOS2 gene) and endothelial NOS (NOS3 gene). Single nucleotide polymorphisms (SNPs) in NOS genes have been associated with cardiovascular pathology. We aimed to comprehensively investigate which NOS gene variants are most strongly associated with coronary heart disease (CHD) and hypertension, using a set of tagging SNPs with good coverage across the 3 genes.

METHOD AND RESULTS

CHD cases (n=560) and randomly selected population controls (n=2791) were genotyped at 58 SNPs in the NOS genes. Control individuals with systolic blood pressure ≥140, diastolic blood pressure ≥90 or on antihypertensive medication were defined as hypertensive. A structured stepwise logistic regression approach was used to select the SNPs most strongly associated with CHD and hypertension. NOS1 SNP rs3782218 showed the most consistent association with both phenotypes, odds ratio 0.59 (95% confidence interval 0.44-0.80) and 0.81 (0.67-0.97) per T-allele for CHD and hypertension respectively. For CHD, another NOS1 SNP (rs2682826) and a NOS3 SNP (rs1549758) also showed effect. For hypertension associations were seen for additional SNPs including NOS3 SNP rs3918226, previously associated with hypertension in genome-wide association study (GWAS) data.

CONCLUSION

We found a previously unreported association between NOS1 SNP rs3782218 and both CHD and hypertension, and confirmed NOS1 as the most important NOS risk gene for CHD. In contrast, variants in all three NOS genes were seen to be associated with hypertension in the same source population.

The association between plasma homocysteine and coronary heart disease is modified by the MTHFR 677C>T polymorphism

OBJECTIVE

An elevated level of total plasma homocysteine (tHcy) has been associated with risk of coronary heart disease (CHD). The level of tHcy is affected by lifestyle, in addition to genetic predisposition. The methylene tetrahydrofolate reductase (MTHFR) 677C>T polymorphism (rs1801133) is among the strongest genetic predictors of tHcy. We examined whether the association between tHcy and CHD is modified by the MTHFR 677C>T polymorphism.

DESIGN AND SETTING

Data from two case-control studies of first-time myocardial infarction (MI), Stockholm Heart Epidemiology Programme (SHEEP), and for MI and unstable angina, INTERGENE, were analysed in parallel.

PATIENTS

THcy was determined in a total of 1150 cases and 1753 controls.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The outcome comprised first-time MI and unstable angina, subsumed as CHD. Logistic regression was used to investigate the association between tHcy and CHD, and its modification by genotype.

RESULTS

High tHcy was confirmed to be a risk factor for CHD in both studies. In SHEEP, the association between tHcy and MI was observed in MTHFR 677 C-homozygotes (OR=1.4, 95% CI 1.2 to 1.6, for a difference by 1 SD of log tHcy) and in heterozygotes (OR=1.3, 95% CI 1.1 to 1.6) but not in T-homozygotes, independent of smoking, physical activity and obesity. An effect modification of similar magnitude was observed but not statistically significant in the smaller INTERGENE study, and confirmed in a meta-analysis of both studies.

CONCLUSIONS

Two Swedish case-control studies showed that the association between elevated tHcy and CHD was confined to carriers of the MTHFR 677 C-allele, which could have implications for the efficiency of tHcy-lowering treatment.

The identification of apolipoprotein C-I in rare minnow (Gobiocypris rarus) and its expression following cadmium exposure

Cadmium (Cd) is a ubiquitous environment contaminant that has been detected in a variety of terrestrial and aquatic organisms. In our study, rare minnow were exposed to 0.4 mg/L Cd(2+) solution, fish tissues including gill, intestine, kidney, liver, muscle, and spleen were collected at 1, 6, 12, 24 and 48 h after exposure. Differential expression sequence tags (ESTs) were screened and an EST similar to Hemibarbus mylodon apolipoprotein C-I (ApoC-I) was identified. The ApoC-I cDNA had been obtained with the sequence of 583 bp, which can code 84 amino acids. The transcription expression patterns of ApoC-I were compared after Cd exposure with the real-time PCR in the above tissues. ApoC-I regulation was prominent in spleen, muscle, gill and liver and moderate in kidney and intestine. This suggests a complex transcriptional regulation of ApoC-I expression following Cd exposure.