Aortic stenosis and lipids: does intervention work?

Elevated Lipoprotein(a): Background, Current Insights and Future Potential Therapies

Lipoprotein(a) forms a subfraction of the lipid profile and is characterized by the addition of apolipprotein(a) (apo(a)) to apoB100 derived particles. Its levels are mostly genetically determined inversely related to the number of protein domain (kringle) repeats in apo(a). In epidemiological studies, it shows consistent association with cardiovascular disease (CVD) and most recently with extent of aortic stenosis. Issues with standardizing the measurement of Lp(a) are being resolved and consensus statements favor its measurement in patients at high risk of, or with family histories of CVD events. Major lipid-lowering therapies such as statin, fibrates, and ezetimibe have little effect on Lp(a) levels. Therapies such as niacin or cholesterol ester transfer protein (CETP) inhibitors lower Lp(a) as well as reducing other lipid-related risk factors but have failed to clearly reduce CVD events. Proprotein convertase subtilisin kexin-9 (PCSK9) inhibitors reduce cholesterol and Lp(a) as well as reducing CVD events. New antisense therapies specifically targeting apo(a) and hence Lp(a) have greater and more specific effects and will help clarify the extent to which intervention in Lp(a) levels will reduce CVD events.

Disease-inspired tissue engineering: Investigation of cardiovascular pathologies

Once focused exclusively on the creation of tissues to repair or replace diseased or damaged organs, the field of tissue engineering has undergone an important evolution in recent years. Namely, tissue engineering techniques are increasingly being applied to intentionally generate pathological conditions. Motivated in part by the wide gap between 2D cultures and animal models in the current disease modeling continuum, disease-inspired tissue-engineered platforms have numerous potential applications, and may serve to advance our understanding and clinical treatment of various diseases. This review will focus on recent progress toward generating tissue-engineered models of cardiovascular diseases, including cardiac hypertrophy, fibrosis, and ischemia reperfusion injury, atherosclerosis, and calcific aortic valve disease, with an emphasis on how these disease-inspired platforms can be used to decipher disease etiology. Each pathology is discussed in the context of generating both disease-specific cells as well as disease-specific extracellular environments, with an eye toward future opportunities to integrate different tools to yield more complex and physiologically relevant culture platforms. Ultimately, the development of effective disease treatments relies upon our ability to develop appropriate experimental models; as cardiovascular diseases are the leading cause of death worldwide, the insights yielded by improved in vitro disease modeling could have substantial ramifications for public health and clinical care.

Elastolytic activity of cysteine cathepsins K, S, and V promotes vascular calcification

Elastin plays an important role in maintaining blood vessel integrity. Proteolytic degradation of elastin in the vascular system promotes the development of atherosclerosis, including blood vessel calcification. Cysteine cathepsins have been implicated in this process, however, their role in disease progression and associated complications remains unclear. Here, we showed that the degradation of vascular elastin by cathepsins (Cat) K, S, and V directly stimulates the mineralization of elastin and that mineralized insoluble elastin fibers were ~25–30% more resistant to CatK, S, and V degradation when compared to native elastin. Energy dispersive X-ray spectroscopy investigations showed that insoluble elastin predigested by CatK, S, or V displayed an elemental percentage in calcium and phosphate up to 8-fold higher when compared to non-digested elastin. Cathepsin-generated elastin peptides increased the calcification of MOVAS-1 cells acting through the ERK1/2 pathway by 34–36%. We made similar observations when cathepsin-generated elastin peptides were added to ex vivo mouse aorta rings. Altogether, our data suggest that CatK-, S-, and V-mediated elastolysis directly accelerates the mineralization of the vascular matrix by the generation of nucleation points in the elastin matrix and indirectly by elastin-derived peptides stimulating the calcification by vascular smooth muscle cells. Both processes inversely protect against further extracellular matrix degradation.

IMPROVE-IT: what have we learned?

PURPOSE OF REVIEW

Recent studies and dyslipidemia treatment guidelines indicate that combination lipid-lowering therapy is frequently needed and its use has increased in recent years. Ezetimibe and simvastatin as a fixed dose is an efficacious treatment choice based on positive results of the recent IMProved Reduction of Outcomes: Vytorin Efficacy International Trial (IMPROVE-IT). In this review, we discuss recent controversies surrounding ezetimibe and provide clinical perspective on the results of the IMPROVE-IT study.

RECENT FINDINGS

IMPROVE-IT is the first trial that demonstrates a significant clinical benefit of a nonstatin hypolipidemic agent (ezetimibe) used in combination with statin (simvastatin) therapy in patients who have experienced an acute coronary syndrome. For almost a decade, the use of ezetimibe was limited by a relative lack of definitive evidence. However, the most recent Plaque Regression With Cholesterol Absorption Inhibitor or Synthesis Inhibitor Evaluated by Intravascular Ultrasound study showed greater coronary plaque regression by statin/ezetimibe combination compared with statin monotherapy. The results of the IMPROVE-IT trial are fostering new debate about the value of adjunctive low-density lipoprotein cholesterol lowering over and above a statin.

SUMMARY

Ezetimibe/simvastatin combination, either as a single pill or as the combined use of the individual compounds, represents a well-tolerated and efficacious choice for dyslipidemia treatment in high-risk subjects, including patients with diabetes. Limited additional risk for adverse events compared with simvastatin monotherapy is observed, and an individualized, patient-centered approach to therapy is recommended.

Improving the odds: ezetimibe and cardiovascular disease

The beauty of science is that well-conducted experiments provide answers to questions which were posed in times of greater ignorance. Cardiovascular disease (CVD) is the leading cause of death worldwide and will be for some time. Cholesterol is a critical player which drives the underlying pathophysiological process of atherosclerosis. Statins are the first line treatment for lipids in CVD given their ability to low-density lipoprotein cholesterol (LDL-C) by up to 50%, and their proven benefits in both primary and secondary intervention . Despite the unprecedented efficacy of statins, additional treatments are sought to potentially reduce the residual risk that remains despite statin treatment such as that associated with reduced high-density lipoprotein cholesterol levels (HDL-C) or triglycerides . In the last 5 years, several trials have reported on their potential additional benefit beyond statin therapy. These include omega-3 fatty acids in patients with prediabetes or diabetes , fibrates in diabetes , nicotinic acid/niacin in cardiovascular disease and cholesterol ester transfer protein inhibitors in cardiovascular disease . Despite their promise, none of these treatments were able to demonstrate benefit beyond baseline statin therapy when compared with placebo . The idea that benefit beyond statin treatment may be an unachievable goal has dogged the medical community working on CVD prevention. The phrase, 'Statins for atherosclerosis - as good as it gets?' was coined in 2005 and has rung true up until now .

Vascular calcification: an update on mechanisms and challenges in treatment

Vascular calcification is highly associated with cardiovascular disease mortality, particularly in high-risk patients with diabetes and chronic kidney diseases (CKD). In blood vessels, intimal calcification is associated with atherosclerosis, whereas medial calcification is a nonocclusive process which leads to increased vascular stiffness and reduced vascular compliance. In the valves, calcification of the leaflets can change the mechanical properties of the tissue and result in stenosis. For many decades, vascular calcification has been noted as a consequence of aging. Studies now confirm that vascular calcification is an actively regulated process and shares many features with bone development and metabolism. This review provides an update on the mechanisms of vascular calcification including the emerging roles of the RANK/RANKL/OPG triad, osteoclasts, and microRNAs. Potential treatments adapted from osteoporosis and CKD treatments that are under investigation for preventing and/or regressing vascular calcification are also reviewed.

Progress in perioperative medicine: focus on statins

Beyond cholesterol reduction, statins have multiple beneficial influences on vascular endothelial function, atherosclerotic plaque stability, inflammation, and thrombosis. These favorable pleiotropic effects may be the basis for their perioperative risk reduction in cardiothoracic and vascular procedures. The published evidence suggests that statins offer significant outcome benefits throughout perioperative practice. Because statin therapy significantly reduces the perioperative risk for patients undergoing cardiovascular procedures, they already are recommended in published guidelines. Beyond cardiac risk reduction, statin therapy also may protect the brain and the kidney in the perioperative setting, both in cardiac and vascular surgery. The pleiotropic effects of statins also appear to have therapeutic roles in the progression of valve disease, sepsis, and venous thrombosis. Further trials are required to provide data to drive their safe and comprehensive perioperative application for optimal patient outcome both in the short term and the long term. Because there are multiple randomized trials currently in progress throughout perioperative medicine, it is very likely that the indications for statins will be expanded significantly.