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The two kinds of small LDL

Posted Dec 27 2010 9:57am
You won't find this in any publication nor description (at least ones that I've come across) about the ubiquitous small LDL particles. It's an observation I've made having obtained thousands of advanced lipoprotein panels of the sort that break lipoproteins down by size. I've discussed this issue previously here . But small LDL is so ubiquitous, not addressed by conventional strategies like statin drugs or fat restriction (it is made worse, in fact, but reducing fat in the diet), that it is worth keeping at the top of everyone's consciousness.

(Because most of the lipoprotein analyses performed in my office are done via NMR, I will discuss in terms relevant to NMR. This does not necessarily mean that similar observations cannot be made with centrifugation, i.e, VAP from Atherotech, or gel electropheresis from Berkeley, Boston Heart Lab, Spectracell, and others).

There are two basic varieties of small LDL particles
1) Genetically-programmed--e.g., via cholesteryl-ester transfer protein (CETP) activity
2) Acquired--via carbohydrate consumption

It means that people with acquired small LDL from carbohydrate consumption can reduce small LDL to zero with reduction of carbohydrates, especially the most small LDL-provoking foods of all: wheat, cornstarch, and sucrose.

It also means that people who have small LDL for genetically-determined reasons can only minimize, not eliminate, small LDL. By NMR, we struggle to keep small LDL in the 300-600 nmol/L range when genetically-determined. (People typically start with 1400-3000 nmol/L small LDL particles prior to diet changes and other efforts.) We can only presumptively identify genetically-determined small LDL when all the appropriate efforts have been made, including reduction in weight to ideal, yet small LDL persists.

Here is where we need better tools: when you've done everything possible, yet small LDL persists.

While we break LDL particles (NOT LDL cholesterol, the crude and misleading way of viewing atherosclerosis causation) down by size, it's really about all the undesirable characteristics that accompany small size
--Distortion of Apo B conformation--i.e., the primary protein that directs LDL particle fate is distorted, making it less likely to be cleared by the liver but more likely to be taken up by inflammatory (macrophages) in the artery wall, creating plaque. It means that small LDL particles linger for a longer time than larger particles.

--Small LDLs are more oxidation-prone. Oxidized LDL are more avidly taken up by inflammatory macrophages.

--Small LDLs are more glycation -prone.

--Small LDLs are more adherent to structural tissues, e.g., glycosaminoglycans, that reside in the artery wall.

You and I cannot measure such phenomena, so we resort to distinguishing LDL particles by size.

The drug industry believes it may have a solution to small LDL in the form of CETP-inhibiting drugs, like anacetrapib . In the way of nutritional solutions beyond carbohydrate reduction, weight loss/exercise, niacin, vitamin D normalization, and omega-3 fatty acid supplementation, there are exciting but very preliminary data surrounding the possibility that anthocyanins may inhibit CETP activity. Having toyed with this concept for the past 6 months, I remain uncertain how meaningful the effect truly is, but it is harmless, since we obtain anthocyanins from foods colored purple or purplish, such as blackberries, blueberries, cherries, red leaf lettuce, red cabbage, etc.

I welcome any unique observations on this issue.

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