Atherosclerosis - Research

Research

An indication of the role of HDL on atherosclerosis has been with the rare Apo-A1 Milano human genetic variant of this HDL protein. A small short-term trial using bacterial synthetized human Apo-A1 Milano HDL in people with unstable angina produced fairly dramatic reduction in measured coronary plaque volume in only 6 weeks vs. the usual increase in plaque volume in those randomized to placebo. The trial was published in JAMA in early 2006. Ongoing work starting in the 1990s may lead to human clinical trials—probably by about 2008. These may use synthesized Apo-A1 Milano HDL directly. Or they may use gene-transfer methods to pass the ability to synthesize the Apo-A1 Milano HDLipoprotein.

Methods to increase high-density lipoprotein (HDL) particle concentrations, which in some animal studies largely reverses and remove atheromas, are being developed and researched.

Niacin has HDL raising effects (by 10–30%) and showed clinical trial benefit in the Coronary Drug Project and is commonly used in combination with other lipoprotein agents to improve efficacy of changing lipoprotein for the better. However most individuals have nuisance symptoms with short term flushing reactions, especially initially, and so working with a physician with a history of successful experience with niacin implementation, careful selection of brand, dosing strategy, etc. are usually critical to success.

However, increasing HDL by any means is not necessarily helpful. For example, the drug torcetrapib is the most effective agent currently known for raising HDL (by up to 60%). However, in clinical trials it also raised deaths by 60%. All studies regarding this drug were halted in December 2006. See CETP inhibitor for similar approaches.

The ERASE trial is a newer trial of an HDL booster, which has shown promise.

The ASTEROID trial used a high-dose of rosuvastatin—the statin with typically the most potent dose/response correlation track record (both for LDLipoproteins and HDLipoproteins.) It found plaque (intima + media volume) reduction. Several additional rosuvastatin treatment/placebo trials for evaluating other clinical outcomes are in progress.

The actions of macrophages drive atherosclerotic plaque progression. Immunomodulation of atherosclerosis is the term for techniques that modulate immune system function to suppress this macrophage action. Immunomodulation has been pursued with considerable success in both mice and rabbits since about 2002. Plans for human trials, hoped for by about 2008, are in progress.

Research on genetic expression and control mechanisms is progressing. Topics include

• PPAR, known to be important in blood sugar and variants of lipoprotein production and function;
• The multiple variants of the proteins that form the lipoprotein transport particles.

Some controversial research has suggested a link between atherosclerosis and the presence of several different nanobacteria in the arteries, e.g., Chlamydophila pneumoniae, though trials of current antibiotic treatments known to be usually effective in suppressing growth or killing these bacteria have not been successful in improving outcomes.

The immunomodulation approaches mentioned above, because they deal with innate responses of the host to promote atherosclerosis, have far greater prospects for success.