The relative atherogenicity of VLDL and LDL is dependent on the topographic site

Increased Remnant Lipoproteins in Apo E Deficient Mice Induce Coronary Atherosclerosis following Transverse Aortic Constriction and Aggravate the Development of Pressure Overload-Induced Cardiac Hypertrophy and Heart Failure

Murine coronary arteries are very resistant to the development of atherosclerosis, which may be related to their intramyocardial course. Blood pressure promotes atherosclerotic plaque formation by acting as a physical force that potentiates the migration of pro-atherogenic lipoproteins across the endothelium. C57BL/6N apolipoprotein (apo) E deficient mice have increased remnant lipoproteins that are a risk factor for coronary atherosclerosis. In this study, our aim was to quantify coronary atherosclerosis and artery remodeling following transverse aortic constriction (TAC) in C57BL/6N apo E−/− mice and to evaluate the impact of increased remnant lipoproteins on the development of pressure overload-induced cardiac hypertrophy and heart failure. Advanced atherosclerotic lesions were observed in the left coronary artery of C57BL/6N apo E−/− TAC mice but not in C57BL/6N TAC mice. Pressure overload resulted in markedly increased cardiac hypertrophy and more pronounced heart failure in C57BL/6N apo E−/− TAC mice in comparison to C57BL/6N TAC mice. Pathological hypertrophy, as evidenced by increased myocardial fibrosis and capillary rarefaction, was more prominent in C57BL/6N TAC apo E−/− than in C57BL/6N TAC mice and led to more marked cardiac dysfunction. In conclusion, TAC in apo E deficient mice induces coronary atherosclerosis and aggravates the development of pathological cardiac hypertrophy and heart failure.

Thirty-Five-Year History of Desialylated Lipoproteins Discovered by Vladimir Tertov

Atherosclerosis is one of the leading causes of death in developed and developing countries. The atherogenicity phenomenon cannot be separated from the role of modified low-density lipoproteins (LDL) in atherosclerosis development. Among the multiple modifications of LDL, desialylation deserves to be discussed separately, since its atherogenic effects and contribution to atherogenicity are often underestimated or, simply, forgotten. Vladimir Tertov is linked to the origin of the research related to desialylated lipoproteins, including the association of modified LDL with atherogenicity, autoimmune nature of atherosclerosis, and discovery of sialidase activity in blood plasma. The review will briefly discuss all the above-mentioned information, with a description of the current situation in the research.

Blood flow patterns regulate PCSK9 secretion via MyD88-mediated pro-inflammatory cytokines

AIMS

Blood flow patterns play an important role in the localization of atherosclerosis in the sense that low-flow state is pro-atherogenic, and helical flow is protective against atherosclerosis. Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates cholesterol metabolism via low-density lipoprotein receptor (LDLr) degradation and is highly expressed in the atherosclerotic tissues. This study was designed to investigate the role of different blood flow patterns in the regulation of PCSK9 expression.

METHODS AND RESULTS

We designed an experimental model guider to generate stable helical flow. Our data showed that compared with normal flow, low-flow state induces whereas helical flow inhibits PCSK9 expression in the rabbit thoracic aorta in an inflammatory state. Our data also identified that TLR4-MyD88-NF-κB signalling plays an important role in PCSK9 expression. On the other hand, TRIF pathway had almost no effect. Further studies showed that the signals downstream of NF-κB, such as pro-inflammatory cytokines (IL-1β, IL-18, MCP-1, IL-6, TNF-α, IL-12, IFNγ, and GM-CSF) directly influence PCSK9 expression. Interestingly, high fat diet further enhanced PCSK9 expression in an inflammatory milieu.

CONCLUSIONS

These observations suggest a link between abnormal flow patterns and PCSK9 expression in inflammatory states, which may qualify helical flow and pro-inflammatory cytokines as potential targets to treat PCSK9-related cardiovascular diseases.

Sex as a Biological Variable in Atherosclerosis

Atherosclerosis is a chronic inflammatory vascular disease and the predominant cause of heart attack and ischemic stroke. Despite the well-known sexual dimorphism in the incidence and complications of atherosclerosis, there are relatively limited data in the clinical and preclinical literature to rigorously address mechanisms underlying sex as a biological variable in atherosclerosis. In multiple histological and imaging studies, overall plaque burden and markers of inflammation appear to be greater in men than women and are predictive of cardiovascular events. However, while younger women are relatively protected from cardiovascular disease, by the seventh decade, the incidence of myocardial infarction in women ultimately surpasses that of men, suggesting an interaction between sex and age. Most preclinical studies in animal atherosclerosis models do not examine both sexes, and even in those that do, well-powered direct statistical comparisons for sex as an independent variable remain rare. This article reviews the available data. Overall, male animals appear to have more inflamed yet smaller plaques compared to female animals. Plaque inflammation is often used as a surrogate end point for plaque vulnerability in animals. The available data support the notion that rather than plaque size, plaque inflammation may be more relevant in assessing sex-specific mechanisms since the findings correlate with the sex difference in ischemic events and mortality and thus may be more reflective of the human condition. Overall, the number of preclinical studies directly comparing plaque inflammation between the sexes is extremely limited relative to the vast literature exploring atherosclerosis mechanisms. Failure to include both sexes and to address age in mechanistic atherosclerosis studies are missed opportunities to uncover underlying sex-specific mechanisms. Understanding the mechanisms driving sex as a biological variable in atherosclerotic disease is critical to future precision medicine strategies to mitigate what is still the leading cause of death of men and women worldwide.

The Correlation of Dyslipidemia with the Extent of Coronary Artery Disease in the Multiethnic Study of Atherosclerosis

Background

The extent of coronary artery calcium (CAC) improves cardiovascular disease (CVD) risk prediction. The association between common dyslipidemias (combined hyperlipidemia, simple hypercholesterolemia, metabolic Syndrome (MetS), isolated low high-density lipoprotein cholesterol, and isolated hypertriglyceridemia) compared with normolipidemia and the risk of multivessel CAC is underinvestigated.

Objectives

To determine whether there is an association between common dyslipidemias compared with normolipidemia, and the extent of coronary artery involvement among MESA participants who were free of clinical cardiovascular disease at baseline.

Methods

In a cross-sectional analysis, 4,917 MESA participants were classified into six groups defined by specific LDL-c, HDL-c, or triglyceride cutoff points. Multivessel CAC was defined as involvement of at least 2 coronary arteries. Multivariate Poisson regression analysis evaluated the association of each group with multivessel CAC after adjusting for CVD risk factors.

Results

Unadjusted analysis showed that all groups except hypertriglyceridemia had statistically significant prevalence ratios of having multivessel CAC as compared to the normolipidemia group. The same groups maintained statistical significance prevalence ratios with multivariate analysis adjusting for other risk factors including Agatston CAC score [combined hyperlipidemia 1.41 (1.06-1.87), hypercholesterolemia 1.55 (1.26-1.92), MetS 1.28 (1.09-1.51), and low HDL-c 1.20 (1.02-1.40)].

Conclusion

Combined hyperlipidemia, simple hypercholesterolemia, MetS, and low HDL-c were associated with multivessel coronary artery disease independent of CVD risk factors and CAC score. These findings may lay the groundwork for further analysis of the underlying mechanisms in the observed relationship, as well as for the development of clinical strategies for primary prevention.

Atherogenic subfractions of lipoproteins in the treatment of metabolic syndrome by physical activity and diet - the RESOLVE trial

Background

We aimed to comprehensively evaluate lipoprotein profile including lipid particle size following a lifestyle intervention in metabolic syndrome (MetS) volunteers and to assess the associations between lipoprotein subfractions and carotid-intima-media-thickness (CIMT) – a surrogate indicator of atherogenesis.

Methods

100 participants (50–70 years) from the RESOLVE trial, underwent a one-year follow-up beginning with a three-week residential program combining high exercise volume (15-20 h/week), restrictive diet (-500 kcal/day), and education. For baseline references, 40 aged-matched healthy controls were recruited. Independent associations between subfractions of lipoproteins and CIMT were evaluated using a generalized estimating equations model accounting for variation in correlations between repeated measures. The lipoprotein subfractions profile was assessed using Lipoprint® electrophoresis allowing to separate: the very low-density lipoprotein (VLDL) fraction, then the intermediate-density lipoprotein (IDL) C, B and A, the low-density lipoprotein (LDL) with subfractions 1 and 2 as large LDL and subfractions 3 to 7 as small dense LDL (sdLDL), and the high density lipoprotein (HDL) subfractions categorized into large, intermediate, and small HDL. Apolipoproteins A1 and B were also measured.

Results

78 participants completed the program. At baseline, apolipoproteins B/A1, VLDL, sdLDL and small HDL were higher in MetS than in healthy controls; IDL, LDL size, large and intermediate HDL were lower. Despite time-related regains during the follow-up, lipoprotein subfractions traditionally involved in cardiovascular risk, such as sdLDL, improved immediately after the residential program with values closest to those of healthy controls. CIMT improved throughout the lifestyle intervention. Using a generalized estimating equations model, none of the subfractions of lipoproteins nor apolipoproteins were linked to CIMT.

Conclusions

Lipoprotein subfractions traditionally involved in CVR, decreased after the 3-week residential program. During a 12 month follow-up, the time-related regains remained closer to the values of healthy controls than they were at baseline. CIMT improved throughout the lifestyle intervention. However, we failed to demonstrate a link between some lipoprotein subfractions and the atherogenicity directly measured from the wall thickness of arteries (CIMT). Further investigations are required to explore the atherogenicity of lipoprotein subfractions.

Trial registration

NCT00917917

Effect of dietary cholesterol and cholesterol oxides on blood cholesterol, lipids, and the development of atherosclerosis in rabbits

Two studies were conducted to determine the effects of dietary cholesterol (CHO) and cholesterol oxides (COPs) on the development of atherosclerosis and the changes in fatty acid and blood characteristics in rabbits. In the first study, forty male New Zealand white rabbits were divided into 5 groups and fed commercial rabbit chow with no added CHO or COPs, 1 g CHO, 0.9 g CHO + 0.1 g COPs, 0.8 g CHO + 0.2 g COPs, or 0.5 g CHO + 0.5 g COPs per kg diet. In the second study, 24 male New Zealand White rabbits were divided into 3 groups and fed a diet containing 2 g CHO, 1.6 g CHO + 0.4 g COPs, or 1.2 g CHO + 0.8 g COPs per kg diet. All diets induced atherosclerotic lesions in the rabbits' ascending thoracic aorta. The serum CHO and triglyceride levels (p < 0.05) increased significantly with the increased levels of CHO in the diets. Dietary CHO or COPs did not influence high-density lipoprotein CHO levels. The ratio of saturated fatty acid to unsaturated fatty acid increased as the level of dietary CHO and COPs increased.

Correlation of atherosclerosis between different topographic sites is highly dependent on the type of hyperlipidemia

There is a surprising paucity of studies that provide quantitative correlative data on the extent of atherosclerosis between different topographic sites. The impact of cardiovascular risk factors is dependent on the vascular bed, which underlies site-selective effects on progression of atherosclerosis. Therefore, the intraindividual correlation of atherosclerosis between different topographic sites may be dependent on the specific cardiovascular risk profile. The focused objective of the current study is to evaluate whether the correlation of the extent of atherosclerosis between different topographic sites is dependent on the type of hyperlipidemia. Atherosclerosis was quantified at four different topographic locations in the aorta of rabbits with type II or type III hyperlipidemia. Correlation coefficients and semi-partial correlation coefficients adjusted for plasma lipoproteins and sex were determined to compare the degree of atherosclerosis at different topographic sites. Semi-partial correlations adjusted for total plasma cholesterol, plasma triglycerides, and sex of the intima/media ratio between different topographic sites were highly dependent on the type of hyperlipidemia. E.g., the semi-partial correlation coefficient between the intima/media ratio at the level of the ascending aorta and at the level of the descending thoracic aorta was 0.87 (p < 0.0001) in the model of type II hyperlipidemia and was only 0.10 (p = NS) in the model of type III hyperlipidemia. This divergent pattern was also observed for other intersite correlations. Semi-partial Pearson correlation coefficients were very similar to unadjusted Pearson correlation coefficients. Correlation of atherosclerosis between different topographic sites may vary importantly in relation to the type of hyperlipidemia.

Triglyceride lipases and atherosclerosis

PURPOSE OF REVIEW

There are strong epidemiologic connections between plasma triglycerides and atherosclerosis. We will consider to what extent this goes back to derangements of the lipoprotein lipase (LPL) system. The roles of hepatic lipase and endothelial lipase will also be touched upon.

RECENT FINDINGS

Understanding of LPL action has taken major steps with the discovery of lipase maturation factor 1 as a specific endoplasmic reticulum chaperon needed for proper folding of the lipases, glycosylphosphatidylinositol-anchored HDL-binding protein 1 as an endothelial cell protein needed for transport and binding of LPL and some angiopoietin-like proteins that can modulate LPL activity. Studies of genetic variants continue to support the important roles of the lipases in lipoprotein metabolism and in atherosclerosis.

CONCLUSION

There are several ways by which derangement of the lipases may contribute to atherogenesis. Lipase actions are major determinants of plasma lipoprotein patterns. LPL activity must be modulated in relation to the physiological situation (feeding, fasting, exercise, etc.). Fatty acids and monoglycerides generated must be efficiently removed so that they do not endanger the integrity of the endothelium, cause lipotoxic reactions or both. In addition, the lipases may cause binding and endocytosis of lipoprotein particles in the artery wall.