Relationship between lipoprotein subfraction cholesterol and residual risk for cardiovascular outcomes: A post hoc analysis of the AIM-HIGH trial

A homogeneous assay to determine high-density lipoprotein subclass cholesterol in serum

Existing methods to measure high-density lipoprotein cholesterol (HDL-C) subclasses (HDL₂-C and HDL₃-C) are complex and require proficiency, and thus there is a need for a convenient, homogeneous assay to determine HDL-C subclasses in serum. Here, cholesterol reactivities in lipoprotein fractions [HDL₂, HDL₃, low-density lipoprotein (LDL), and very-low-density lipoprotein (VLDL)] toward polyethylene glycol (PEG)-modified enzymes were determined in the presence of varying concentrations of dextran sulfate and magnesium nitrate. Particle sizes formed in the lipoprotein fractions were measured by dynamic light scattering. We optimized the concentrations of dextran sulfate and magnesium nitrate before assay with PEG-modified enzymes to provide selectivity for HDL₃-C. On addition of dextran sulfate and magnesium nitrate, the sizes of particles of HDL₂, LDL, and VLDL increased, but the size of HDL₃ fraction particles remained constant, allowing only HDL₃-C to participate in coupled reactions with the PEG-modified enzymes. In serum from both healthy volunteers and patients with type 2 diabetes, a good correlation was observed between the proposed assay and ultracentrifugation in the determination of HDL-C subclasses. The assay proposed here enables convenient and accurate determination of HDL-C subclasses in serum on a general automatic analyzer and enables low-cost routine diagnosis without preprocessing.

Niacin for treatment of nonalcoholic fatty liver disease (NAFLD): novel use for an old drug?

Niacin has been widely used clinically for over half a century for dyslipidemia. Recent new evidence indicates that niacin may be useful in the treatment of nonalcoholic fatty liver disease (NAFLD) and its sequential complications including nonalcoholic steatohepatitis and fibrosis. There is an urgent unmet need for a cost-effective solution for this public health problem affecting nearly one in three adults. Niacin inhibits and reverses hepatic steatosis and inflammation in animals and liver cell cultures. It prevents liver fibrosis in animals and decreases collagen in cultured human stellate cells. Its mechanism of action is by oxidative stress reduction and inhibition of diacylglycerol acyltransferase 2 and other possible targets. An uncontrolled clinical trial in 39 hypertriglyceridemic patients with steatosis showed reduction of liver fat by 47% and reductions in liver enzymes and C-reactive protein from the baseline when treated with niacin extended-release for 6 months These hypothesis-generating data indicate a novel repurposed use of niacin for NAFLD. Niacin beneficially affects NAFLD at 3 major stages directly and, by affecting steatosis, it indirectly decreases the cascade effect on inflammation and fibrosis. It offers the advantage potentially of combination with other drugs in development for evolving synergistically more intense and broader efficacy. In select patients, it may benefit frequently associated atherogenic dyslipidemia. A randomized placebo-controlled double-blind parallel trial (with niacin alone or in combination with another drug in development) to assess the safety and efficacy of niacin on steatosis, inflammation, and fibrosis in patients with nonalcoholic steatohepatitis/NAFLD is warranted.

Current Therapies Focused on High-Density Lipoproteins Associated with Cardiovascular Disease

High-density lipoproteins (HDL) comprise a heterogeneous family of lipoprotein particles divided into subclasses that are determined by density, size and surface charge as well as protein composition. Epidemiological studies have suggested an inverse correlation between High-density lipoprotein-cholesterol (HDL-C) levels and the risk of cardiovascular diseases and atherosclerosis. HDLs promote reverse cholesterol transport (RCT) and have several atheroprotective functions such as anti-inflammation, anti-thrombosis, and anti-oxidation. HDLs are considered to be atheroprotective because they are associated in serum with paraoxonases (PONs) which protect HDL from oxidation. Polyphenol consumption reduces the risk of chronic diseases in humans. Polyphenols increase the binding of HDL to PON1, increasing the catalytic activity of PON1. This review summarizes the evidence currently available regarding pharmacological and alternative treatments aimed at improving the functionality of HDL-C. Information on the effectiveness of the treatments has contributed to the understanding of the molecular mechanisms that regulate plasma levels of HDL-C, thereby promoting the development of more effective treatment of cardiovascular diseases. For that purpose, Scopus and Medline databases were searched to identify the publications investigating the impact of current therapies focused on high-density lipoproteins.