Recent updates on therapeutic targeting of lipoprotein(a) with RNA interference.

PURPOSE OF REVIEW: RNA interference (RNAi)-based therapies that target specific gene products have impacted clinical medicine with 16 FDA approved drugs. RNAi therapy focused on reducing plasma lipoprotein(a) [Lp(a)] levels are under evaluation. RECENT FINDINGS: RNAi-based therapies have made significant progress over the past 2 decades and currently consist of antisense oligonucleotides (ASO) and small interfering RNA (siRNA). Chemical modification of the RNA backbone and conjugation of siRNA enables efficient gene silencing in hepatocytes allowing development of effective cholesterol lowering therapies. Multiple lines of evidence suggest a causative role for Lp(a) in atherosclerotic cardiovascular disease, and recent analyses indicate that Lp(a) is more atherogenic than low density lipoprotein- cholesterol (LDL-C). These findings have led to the 'Lp(a) hypothesis' that lowering Lp(a) may significantly improve cardiovascular outcomes. Four RNAi-based drugs have completed early phase clinical trials demonstrating >80% reduction in plasma Lp(a) levels. Phase 3 clinical trials examining clinical outcomes with these agents are currently underway. SUMMARY: Currently, four RNAi-based drugs have been shown to be effective in significantly lowering plasma Lp(a) levels. Clinical outcome data from phase 3 trials will evaluate the Lp(a) hypothesis.

Food for Thought or Feeding a Dogma? Diet and Coronary Artery Disease: a Clinician's Perspective.

PURPOSE OF REVIEW: To provide an overview of nutrition studies evaluating the association of dietary saturated fat and meat intake with the development of coronary artery disease (CAD) and discuss implications of recent data. RECENT FINDINGS: Recent studies have led to the re-evaluation of the role of saturated fat in CAD. Randomized controlled trials (RCTs) support Mediterranean diet to reduce cardiovascular risk. Recent data revealed significant association of intake of meat or poultry with increased risk, but fish consumption was associated with lower risk of incident CAD. In this review, we provide a brief overview of the studies and data that have led to the re-evaluation of the link between saturated fat and CAD. Due to conflicting data from long-term prospective cohort studies and significant heterogeneity, associations of unprocessed meat with CAD are less clear compared to the role of processed meat. Pooled data from prospective cohort studies have overcome some of these limitations and show association of both processed and unprocessed meat and poultry intake but not fish consumption with incident CAD. These findings were also validated recently in a large UK Biobank prospective study. While recognizing the limitations of these cohort studies, we discuss relevant landmark RCTs. We finally consider the challenges with RCTs in nutrition research to improve the quality of evidence and need for evidence-based dietary guidelines with respect to saturated fat intake from a clinical perspective.

Separation of Quadruplex Polymorphism in DNA Sequences by Reversed-Phase Chromatography.

This unit describes a method for the separation of a mixture of quadruplex conformations formed from the same parent sequence via reversed-phase chromatography (RPC). Polymorphism is inherent to quadruplex formation and even relatively simple quadruplex-forming sequences can fold into a cornucopia of possible conformations and topologies. Isolation of a specific conformation for study can be problematic. This is especially true for conformations of the human telomere sequence d(GGG(TTAGGG)3). High performance liquid chromatography (HPLC), especially reversed-phase chromatography, has been a mainstay of nucleic acid research and purification for many decades. We have successfully applied this method to the problem of separating individual quadruplex species in the ensemble from the same parent sequence.

Release kinetics of paclitaxel and cisplatin from two and three layered gold nanoparticles.

Gold nanoparticles functionalized with biologically compatible layers may achieve stable drug release while avoiding adverse effects in cancer treatment. We study cisplatin and paclitaxel release from gold cores functionalized with hexadecanethiol (TL) and phosphatidylcholine (PC) to form two-layer nanoparticles, or TL, PC, and high density lipoprotein (HDL) to form three-layer nanoparticles. Drug release was monitored for 14 days to assess long term effects of the core surface modifications on release kinetics. Release profiles were fitted to previously developed kinetic models to differentiate possible release mechanisms. The hydrophilic drug (cisplatin) showed an initial (5-h) burst, followed by a steady release over 14 days. The hydrophobic drug (paclitaxel) showed a steady release over the same time period. Two layer nanoparticles released 64.0±2.5% of cisplatin and 22.3±1.5% of paclitaxel, while three layer nanoparticles released the entire encapsulated drug. The Korsmeyer-Peppas model best described each release scenario, while the simplified Higuchi model also adequately described paclitaxel release from the two layer formulation. We conclude that functionalization of gold nanoparticles with a combination of TL and PC may help to modulate both hydrophilic and hydrophobic drug release kinetics, while the addition of HDL may enhance long term release of hydrophobic drug.

Mechanistic insights into editing-site specificity of ADARs.

Adenosine deaminases that act on RNA (ADARs) deaminate adenosines in dsRNA to produce inosines. ADARs are essential in mammals and are particularly important in the nervous system. Altered levels of adenosine-to-inosine (A-to-I) editing are observed in several diseases. The extent to which an adenosine is edited depends on sequence context. Human ADAR2 (hADAR2) has 5' and 3' neighbor preferences, but which amino acids mediate these preferences, and by what mechanism, is unknown. We performed a screen in yeast to identify mutations in the hADAR2 catalytic domain that allow editing of an adenosine within a disfavored triplet. Binding affinity, catalytic rate, base flipping, and preferences were monitored to understand the effects of the mutations on ADAR reactivity. Our data provide information on the amino acids that affect preferences and point to a conserved loop as being of key importance. Unexpectedly, our data suggest that hADAR2's preferences derive from differential base flipping rather than from direct recognition of neighboring bases. Our studies set the stage for understanding the basis of altered editing levels in disease and for developing therapeutic reagents.