Nuclear Magnetic Resonance (NMR)
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Lipoprotein Analysis: An Advanced User's Guide
Lipoprotein testing is one of the cornerstones of the Track Your Plaque program, one of the reasons that we enjoy such enormous success in dropping so many people's heart scan scores.
Lipoprotein testing uncovers patterns that are simply not detected by conventional cholesterol testing. It does require an intellectual commitment to understand some unique measures. However, the rewards can be substantial: better control over heart disease.
Ideally, your doctor possesses insights into lipoprotein testing and treatment that can help you navigate the important points and subtleties of lipoprotein patterns. Unfortunately, that is rarely true. So, for the motivated and curious participant, here is the Advanced User's Guide.
The Advanced User's Guide is intended for the seasoned participant in the Track Your Plaque; however, even beginners new to the program can benefit from the issues discussed here. Because some of the measures made in NMR lipoprotein testing are unique to NMR and not shared by other lipoprotein testing methods (electrophoresis on the Berkeley panel, ultracentrifugation on the Atherotech Vertical Auto Profile, or VAP), this Guide is best used after a NMR panel is obtained and the results are in hand.
Let's first discuss a bit of background on what NMR is and how the measures are obtained.
NMR: An ingenious technological advance
Nuclear Magnesium Resonance, or NMR, has been evolving since the early 1970s. The Nobel prize for Medicine was awarded to two scientists in 2003 for their contributions in developing the original science behind the technique. Although best known for its ability for medical imaging of the human body (often called Magnetic Resonance Imaging, or MRI, for this use), it involves the application of a magnetic field to an object to amplify and detect the signal produced by its unique "molecular signature."
To image a human brain, for instance, the head is positioned within a large set of powerful magnets. Different molecules from various portions of the brain and skull each respond by emitting their unique molecular signature. These responses are detected in three dimensions and an image is constructed using specialized software permitting analysis of both structure and quantity. (Image courtesy of Wikipedia)
Biochemist Dr. James Otvos was among the first to apply magnetic fields to human plasma (the clear portion of human blood that remains when the red blood cells have been removed). By subjecting plasma with specific proteins of known composition to MRI, Dr. Otvos created a library of signals unique to various human proteins.
Here's where the technique achieves true genius. When the smorgasbord of proteins in real-life human plasma is subjected to a magnetic field, a composite signal from hundreds or thousands of human proteins results. Dr. Otvos' library of isolated signals allowed him to develop a computer program that dissected, or "deconvoluted," the various signals within the total. Dr. Otvos likens this to a large number of bells, all ringing simultaneously. The result: a great cacophony of noise. But, if the frequency of each individual bell is known, the relative contribution of each bell to the total sound can be determined. This is similar to the deconvolution process of the NMR signals for analysis of lipoproteins.
NMR provides detailed analysis of actual lipoprotein particles. They can be evaluated by type (LDL cholesterol particles, HDL cholesterol particles, VLDL and others), size, and number.
Contrast this to conventional cholesterol values, in which the amount of various lipoproteins are gauged based on the cholesterol content of blood. LDL cholesterol, for instance, is meant to tell us what fraction of cholesterol resides on a low-density particle, regardless of whether it's small or large. But LDL particles are not all the same: There are big particles, small particles, and particles in between. Thus, a person with pure small LDL particles will be indistinguishable from a person with pure large LDL particles by standard cholesterol testing, yet the risk for heart disease differs dramatically between these two patterns. And although LDL cholesterol can be measured, it is nearly always calculated using an antiquated method called the Friedewald equation, named after the National Institutes of Health researcher who developed this "cheap and easy" method to obtain a crude estimation of LDL cholesterol in the 1960s. But, in our view, like bell bottoms and tail fins, the time for calculated LDL is over. It's time for new and better technology.
Since Dr. Otvos' early efforts, hundreds of clinical studies have been published to validate this enormously clever technology. Studies have compared NMR lipoprotein analysis to other techniques like electrophoresis and ultracentrifugation. Other studies have demonstrated that measures obtain through NMR are superior to conventional lipids. In particular, LDL particle number of NMR has proven considerably superior to conventionally calculated LDL cholesterol (Cromwell WC, Otvos JD 2004).
Is NMR better than other techniques for lipoprotein analysis? This is a contentious and presently unsettled question. Each technique has its proponents. NMR is the preferred technology for the Track Your Plaque program, but in truth all the techniques represent substantial improvements over conventional lipids of the sort relied upon (unfortunately) by the majority of practicing physicians.
The NMR Lipoprotein Report - Page 1
The report format and even some of the measures have changed over the years. This has been a source of confusion for Track Your Plaque Members. The people at Liposcience are constantly exploring ways to improve their test and report format, but it has resulted in some confusion. Hopefully, we can help you negotiate the common tripping points.
Now, let's walk you through a typical NMR report. However, be aware that we use the information from the NMR report somewhat differently than that provided. We believe that our approach puts the wealth of information in the NMR report to full use.
LDL particle number is the very first value you encounter on the first page and probably the most important number on the entire report. As the name suggests, it represents a count of LDL particles in the blood. Think of it as the number of LDL particles per cubic centimeter of blood. (It's not really that, but it's a convenient way to think about it.)
An easy way to put this number to use is to take the value (e.g. "856 nmol/l" as pictured above) and drop the last digit (i.e. divide by 10). This gives you an idea of what the "real" measured LDL cholesterol should be (about "85").
Greater numbers of cholesterol-containing particles in the blood means more opportunity for deposition into the artery wall to create plaque. The amount of cholesterol contained per particle can vary widely. If LDL particles have less cholesterol in each particle but there are many of them, standard (Friedewald) LDL cholesterol will be low, but heart disease risk will be high. LDL particle number will remove this inaccuracy and reveal real risk.
The Quebec Cardiovascular Study demonstrated that heart attacks still occurred when a person's LDL cholesterol is low but particle number is high. In other words, LDL particle number is a better indicator of heart attack potential, even when LDL cholesterol is low. High LDL particle number responds to the same treatments as LDL cholesterol, but provides greater precision.
In addition to prescription medicines, there are many nutritional strategies that lower LDL particle number.
The Track Your Plaque LDL particle number target: 700 nmol/l
The line below LDL particle number is small LDL. However, we're going to wait until we get to the second page before we discuss small LDL.
Also listed on the most recent version (above) of the NMR report are conventional lipids: LDL cholesterol, HDL cholesterol, triglycerides, and total cholesterol. These are the same as the values obtained in most local laboratories and will not be discussed further here. Note that the LDL cholesterol is calculated by the conventional Friedewald calculation. Although you are also provided the much more accurate LDL particle number, the calculated LDL can be useful to 1) demonstrate how inaccurate your calculated LDL cholesterol can be compared to LDL particle number, and 2) can be useful for future comparative purposes when you obtain only conventional lipid values without NMR analysis.
After basic lipids, there are a number of measures listed on the first page. IGNORE THEM. Yes, we know that there's important information in the NMR lipoprotein analysis, but these values are "composites," values provided for simplification that, in our view, substantially dilute the accuracy of the information. The information we need is on page 2.
If page 2 is unavailable to you because your blood was drawn by LabCorp, then you will have to rely on the less quantitative values for "LDL Particle Size," "Large HDL," and "Large VLDL" on page 1. The pitfall will be that the information is more of an average of particle size within each class, rather than a graphic representation of the true range of particle sizes. We have urged LabCorp to change this procedure. If page 2 is not being made available to you be sure to express your dissatisfaction to your laboratory. If you are a LabCorp customer, contact the following company representative:
Director of Marketing
Laboratory Corporation of America
1904 Alexander Drive
Research Triangle Park, NC 27709
919-361-7700 Main
919-361-7149 Facsimile
(contact information courtesy of Track Your Plaque Member, Eugene. Thanks, Eugene!)
Some Members may have an older version of the NMR report that looks like this:
In this version, we are only interested in the LDL particle number on this page.
The NMR Lipoprotein Report - Page 2
Here's the second page of the NMR Lipoprofile (from a different person than the others used above).
Let's look at the classes of very low-density lipoproteins, VLDL, the three blue bars at the far left of the chart. These are simply lipoprotein particles that tend to be abundant when triglycerides are excessive. There's nothing to do specifically for these particles, since all efforts to reduce triglycerides to <60 mg/dl will automatically take care of VLDL. Thus, the Track Your Plaque goal for VLDL is just the same as that for triglycerides. That said, you may be impressed with how plentiful VLDL classes can be even when triglycerides are only modestly elevated, say, at only 90 mg/dl.
The Track Your Plaque goal for VLDL: Triglycerides 60 mg/dl or less
Intermediate-density lipoprotein, IDL, is the first (left-most) red bar. This is a very important measure, a reflection of the persistence of after-meal lipoproteins in the blood. Blood is usually drawn 8 or more hours after eating. At this point, IDL should show 0 mg/dl—i.e., there should be nothing here at all. (Unfortunately, the Liposcience report often shows a small bar even when 0 mg/dl are present; just look at the number at the top of the bar.) Increased levels of IDL above zero have been associated with coronary plaque, carotid disease, and aneurysms. A level of 75 nmol/l or more is considered very high. IDL is very easy to reduce or eliminate. Fish oil is an immensely effective agent to reduce IDL, though doses required may be higher than our minimum of 4000 mg/day (providing 1200 mg EPA +DHA). Niacin, high-fiber foods, the fibrates (Tricor® and Lopid®), reduction of processed carbohydrates like wheat products, and weight loss all help to reduce IDL.
Track Your Plaque IDL goal: 0 mg/dl
Now let's look at the two red bars that represent the distribution of large and small LDL (Large LDL-P and Small LDL-P).
Small LDL
The two right-most red bars represent the amount of LDL cholesterol particles that are large and small. We put more weight on the numbers (in nmol/l) of small LDL than the actual size of the bar.
To calculate the percentage small LDL, divide the number above the small LDL bar by the total LDL particle number (or just add the total of small and large LDL to calculate the total LDL particle number). In the example, small LDL comprises 1354 ÷ 1429 = 94.8%, a very severe small LDL pattern. (Those of you without page 2 can use the same numbers on page 1.)
Small LDL's are a more destructive force than their larger counterparts. It is the number one most common cause of heart disease, found in >60% of all people who experience heart attacks. They persist in the circulation longer than large LDL particles, allowing more opportunity to cling like little magnets to artery walls. Smaller particles are better able to penetrate the cellular barrier. Once they penetrate, they are more adherent than large particles. In the arterial wall, small LDL's are more prone to oxidation and stimulate release of inflammatory and adhesive proteins.
An excess of small LDL is sometimes called "LDL pattern B." When small LDL exceeds some percentage of total LDL (e.g. 18%), then this is arbitrarily designated "pattern B." (We do not use this confusing designation. We just say that 'you have x percent small LDL' to minimize confusion)
Small LDL holds a world of information. Not only is risk for heart attack three- to six-fold higher, but resistance to insulin tends to be greater, metabolic syndrome and diabetes are much more likely to develop, particularly when excess weight is present. It also tells you that a very low-fat diet (<20% of calories) may paradoxically worsen heart disease risk. When small LDL occurs alongside other abnormalities, such as high total cholesterol or high c-reactive protein (a measure of inflammation), heart attack risk is six-fold higher.
Weight loss is a powerful method of increasing LDL size. Exercise also has a modest benefit. Niacin (vitamin B3) effectively corrects LDL size in doses of 1000-1500 mg per day.
Dietary strategies that slow or reduce sugar release (i.e., lower glycemic index) can be helpful, such as high fiber foods or supplements like flaxseed, glucomannan, oat bran (beta-glucan), psyllium seed, raw nuts like almonds and walnuts, and the starch-blocker white bean extract. We have used wheat-free diets with great success, eliminating all breads, pastas, wheat-based breakfast cereals, pretzels, crackers, and other wheat flour-containing foods.
Track Your Plaque small LDL target: <10% small LDL (<70 nmol/l)
HDL Cholesterol and HDL subclasses
HDL is our friend, a protective class of lipoproteins that is responsible for "reverse cholesterol transport", or removing cholesterol from plaque. A low HDL (below 40) is exceptionally common, affecting >50% of people with heart disease. Many of these people have been told that they have no reason for heart disease, or they have a cause that is untreatable. Both statements are simply untrue.
Like LDL, HDL is really a family of different HDL particles. The truly beneficial HDL is "large" HDL (sometimes also known as "HDL2b"). The smaller HDL fractions can sometimes comprise a major portion of the total HDL, and a seemingly favorable total HDL of, say, 56 can sometimes conceal a real lack of effective large HDL. Low HDL commonly accompanies small LDL particles, elevated triglycerides, and triglyceride-rich lipoproteins like VLDL.
On the NMR report, large HDL is represented by the left-most green bar, followed by medium and small HDL to the right. The quantity of HDL in each class is shown in units of µmol/l. Unfortunately, it has been the recent conversion from a weight-based HDL measurement in mg/dl to the particle-count based measurement in µmol/l that has been a source of confusion.
First of all, the Track Your Plaque target for total HDL (all classes) is 60 mg/dl. This value is located on the first page. Next, total the amount of HDL subclasses in µmol/l by adding up the numbers above the 3 bars for HDL (27.9 in the example above). Then, take the number above the large HDL (3.1 in the example above), divide this number by the total from among the three subclasses. This will provide you with a proportion of large HDL (3.1 ÷ 27.9 = 0.11). Lastly, multiply this value (0.11) by your total HDL expressed in mg/dl. This will provide the quantity of large HDL in mg/dl. For example, if HDL was 60mg/dl, then the approximate amount of large HDL would be 6.6mg/dl. We aim for a large HDL of 32 mg/dl or more. However, this goal is a relatively "soft" goal (i.e. probably not an absolute requirement for your plaque control program and one that requires further scientific validation).
To raise total and large HDL, diet can help but a standard low-fat diet does not raise HDL. In fact, strict low-fat diets (<20% of calories from fats) reduce HDL and push HDL to the undesirable smaller size. People with low total and large HDL do better by adding monounsaturated fatty acids (like raw nuts, olive and canola oil), eating low glycemic-index and unprocessed foods, and increasing protein intake. Following a wheat-free diet is one of the most successful strategies we've used. Omega-3 fatty acids (fish oil) have a modest effect in raising total HDL. The medical treatments to raise HDL are identical to those that are used to treat the small LDL particle size.
Track Your Plaque HDL subclass target: Total HDL =60 mg/dl, large HDL =32 mg/dl.
The NMR Lipoprotein Report - Page 3
These are additional measures that can be obtained through NMR or can be obtained through other laboratories. In other words, Liposcience does not need to run these measures, though we do prefer the method used by Liposcience for lipoprotein (a). You can obtain other measures as you and your doctor see fit to add to this page. We generally run lipoprotein(a), homocysteine, C-reactive protein, glucose, and insulin. However, we'll just discuss lipoprotein(a), the one measure that is returned in somewhat unique format.
Lipoprotein (a)
The NMR analysis reports lipoprotein(a), or Lp(a), measured as number of particles, similar to LDL particle number.
This is in contrast to the technique used in most other labs, who report the result in milligrams per deciliter, a measure of weight. The two measures are not interchangeable because of variation in Lp(a) particle size from one person to another (similar to LDL and HDL). It's best to stick to one laboratory or another to avoid inconsistencies when following results on a treatment program.
Lipoprotein (a), or Lp (a) (read "LP little a") is a powerful cause of heart disease. Lp (a) is often responsible for heart attacks in people in their 40's and 50's. About 20% of people with heart disease will have an increased Lp (a). Lp (a) magnifies the dangers of all other abnormalities, especially LDL. Lp(a) also encourages plaque growth and blood clot formation. People who have Lp(a) often have severe high blood pressure in their late 50's or 60's.
Treatment for Lp (a) is controversial. Most experts agree that, at the very least, LDL cholesterol should be lowered to a level no higher than 80, and this results in significantly lower heart attack risk.
Lp(a) itself is most effectively lowered with niacin. In females, the use of estrogen preparations may lower Lp(a), generally around 25%. In men, testosterone lowers Lp(a) by 25%. The nutritional supplement and adrenal gland hormone, DHEA, reduces Lp(a) around 18% females, somewhat less in males. Nutritional strategies that help lower Lp(a) include ground flaxseed (2 tbsp/day), raw almonds (1/4 cup/day), vitamin C (>1000 mg/day), L-carnitine (2 gm/day), and perhaps higher doses of fish oil (3000 mg EPA+DHA or more). All these strategies lower Lp(a) around 7-8% (though are not necessarily additive when combined).
Track Your Plaque Lp(a) target: <75nmol/l (approximately 30 mg/dl)
If you are somewhat frustrated by the complexity of lipoproteins, you're not alone. This is simply an attempt to acquaint you better with this useful and fascinating technology. It cannot replace the judgment of a knowledgeable physician who can interpret your results in the context of your overall health. Nonetheless, we hope that this discussion helps understand this valuable tool.
References:
Blake GJ, Otvos JD, Rifai N, Ridker PM. Low-density lipoprotein particle concentration and size as determined by nuclear magnetic resonance (NMR) spectroscopy as predictors of cardiovascular disease in women. Circulation. 2002;106:1930–1937.
Cromwell WC, Otvos JD. Low-density lipoprotein particle number and risk for cardiovascular disease. Curr Atheroscler Rep 2004 Sep;6(5):381–387.
Groszek E, Grundy SM. Electron-microscopic evidence for particles smaller than 250 Å in very low density Lipoproteins of human plasma. Atherosclerosis 1978;31:241-250.
Grundy SM, Vega GL, Otvos JD, Rainwater DL, Cohen JC. Hepatic lipase influences high density lipoprotein subclass distribution in normotriglyceridemic men: genetic and pharmacological evidence. J Lipid Res 1999;40:229-234.
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