High cholesterol levels are seen as a cause of dangerous deposits in the bloodstream, which lead to hardening of the arteries (atherosclerosis). As a consequence, thrombosis, strokes, and heart attacks can develop, which are among the leading causes of death in Western society. Low-density lipoprotein (LDL) is commonly referred to as the “bad cholesterol,” because it promotes atherosclerosis. In contrast, the “good cholesterol,” high-density lipoprotein (HDL), helps transport excess cholesterol out of the bloodstream and can counteract an inflammatory reaction in damaged vessel walls.
“It has long been known that HDL has a protective function in cardiovascular diseases that are based on atherosclerosis,” reports Prof. Eicke Latz, Director of the Institute of Innate Immunity at the University of Bonn and who is further affiliated with the German Center for Neurodegenerative Diseases (DZNE) and the University of Massachusetts Medical School in the USA. “The molecular causes to which this protective effect of HDL can be attributed were unclear until now.” For instance, studies had shown that therapies that simply increase HDL levels in the blood of patients are not sufficient to reduce the incidence of atherosclerosis. HDL has anti-inflammatory effects on immune cells — however the mechanisms have remained unclear until now. The research group has now investigated how HDL acts upon inflammatory processes.
Bioinformatics approach revealed a candidate gene
Principle investigators Dr. Dominic De Nardo and Larisa I. Labzin are both Australians currently training in the lab of Prof. Eicke Latz. In collaboration with other working groups of the University of Bonn, an international research team from Japan, Australia, China, the USA, and Germany has identified how HDL acts to prevent chronic inflammation. In a very extensive study over a period of about three years, the group performed experiments in human and mouse cells, to determine which genes are regulated by high HDL levels. “At first, we were really just feeling around in the dark,” reports Prof. Latz. Close cooperation with the working group of Prof. Joachim L. Schultze of the Life and Medical Sciences (LIMES) Institute of the University of Bonn finally got the scientists on the right track. “With the aid of genomic and bioinformatics approaches, we were able to filter out a candidate gene from the wealth of regulated genes,” adds Prof. Schultze.
This gene is found in phagocytes, which act in the body like police on the beat and, as part of the innate immune defense system, arrest intruders. These patrolmen are supported by a kind of “criminal file,” the so-called Toll-like receptors (TLR). With their help, the phagocytes can distinguish between “good” and “bad.” If it is a dangerous intruder, the TLR can also trigger the release of inflammatory substances via biochemical signaling pathways. The transcriptional regulator, ATF3, plays a key role in this process. “It reduces the transcription of the inflammatory genes and prevents further stimulation of inflammatory processes via the Toll-like receptors,” explains Dr. Dominic De Nardo.
Sustained inflammatory reactions can lead to organ failure
The immune system uses inflammatory processes to keep pathogens in check, to detect damaged tissue, and then repair it. In sustained inflammatory reactions, however, there are dangerous consequences -including blood poisoning or organ failure. “The transcriptional regulator ATF3 acts to reduce these inflammatory reactions by suppressing the activation of inflammatory genes following excessive stimulation of immunoreceptors,” reports Dr. De Nardo. In the end, high-density lipoprotein (HDL) is responsible for down regulating the inflammatory reactions, via the activation of ATF3. “To put it simply, high HDL levels in blood are an important protective factor against sustained inflammation,” summarizes Prof. Latz.
“Our studies also indicate that the amount of HDL in blood alone is not decisive for the protective function of HDL, but that the anti-inflammatory function is probably more important. These results also suggest a molecular approach for treating inflammation in other widespread diseases, such as diabetes,” sums up Prof. Latz .
HDL plays such a crucial role in so many of the bodies functions that increasing your HDL can improve overall health and can help alleviate inflammatory reactions in the body. This can help you live a longer and healthier life just by making some small nutritional changes to your diet. Here are some suggestions on how to improve your HDL levels.
- Don’t smoke. If you smoke, quit. Quitting smoking can increase your HDL cholesterol by up to 10 percent. Quitting isn’t easy, but you can increase your odds of success by trying more than one strategy at a time. Talk with your doctor about your options for quitting.
- Lose weight. Extra pounds take a toll on HDL cholesterol. If you’re overweight, losing even a few pounds can improve your HDL level. For every 6 pounds (2.7 kilograms) you lose, your HDL may increase by 1 mg/dL (0.03 mmol/L). If you focus on becoming more physically active and choosing healthier foods — two other ways to increase your HDL cholesterol — you’ll likely move toward a healthier weight in the process.
- Get more physical activity. Within two months of starting, frequent aerobic exercise can increase HDL cholesterol by about 5 percent in otherwise healthy sedentary adults. Your best bet for increasing HDL cholesterol is to exercise briskly for 30 minutes five times a week. Examples of brisk, aerobic exercise include walking, running, cycling, swimming, playing basketball and raking leaves — anything that increases your heart rate. You can also break up your daily activity into three 10-minute segments if you’re having difficulty finding time to exercise.
- Choose healthier fats. A healthy diet includes some fat, but there’s a limit. In a heart-healthy diet, between 25 and 35 percent of your total daily calories can come from fat — but saturated fat should account for less than 7 percent of your total daily calories. Avoid foods that contain saturated and trans fats, which raise LDL cholesterol and damage your blood vessels.Monounsaturated and polyunsaturated fats — found in olive, peanut and canola oils — tend to improve HDL’s anti-inflammatory abilities. Nuts, fish and other foods containing omega-3 fatty acids are other good choices for improving your LDL cholesterol to HDL cholesterol ratio.
- Drink alcohol only in moderation. Moderate use of alcohol has been linked with higher levels of HDL cholesterol. If you choose to drink alcohol, do so in moderation. For healthy adults, that means up to one drink a day for women of all ages and men older than age 65, and up to two drinks a day for men age 65 and younger. If you don’t drink alcohol, don’t start just to try raising your HDL levels.
Medications and foods that may help
Some medications used to lower LDL cholesterol may also increase HDL cholesterol, including:
- Niacin. Niacin (Niaspan) is usually the best medication to increase HDL cholesterol. Various prescription and over-the-counter preparations are available, but prescription niacin is preferred, as it has the least side effects. Dietary supplements containing niacin that are available over-the-counter are not effective for lowering triglycerides and may damage your liver.You may have heard that a large study that examined the effect of niacin to raise HDL cholesterol was stopped early. This study examined how niacin worked when used with statin medications for people who have a history of heart disease. The trial was stopped because no difference was seen between people who took prescription-strength niacin and people who took a placebo. The study also found there may be a small increase in the risk of stroke for people who take niacin to increase their HDL cholesterol level. More research is necessary to see how effective niacin might be compared with other heart disease medications. You shouldn’t stop taking niacin unless you get your doctor’s OK. Talk to your doctor if you’re concerned about taking niacin.
- Fibrates. The medications fenofibrate (Lofibra, Tricor) and gemfibrozil (Lopid) can help increase your HDL cholesterol level.
- Statins. Statins block a substance your liver needs to make cholesterol. This reduces cholesterol in your liver cells, which causes your liver to remove cholesterol from your blood. Statins may also help your body reabsorb cholesterol from built-up deposits on your artery walls. Choices include atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Altoprev, Mevacor), pravastatin (Pravachol), rosuvastatin (Crestor) and simvastatin (Zocor).
If your doctor prescribes medication to help control your cholesterol, take it as directed while you continue to focus on a healthy lifestyle.
Some foods may have a healthy effect on blood cholesterol levels. Some options include:
- Whole grains, such as oatmeal, oat bran and whole-wheat products
- Nuts, such as walnuts, almonds and brazil nuts
- Plant sterols such as beta-sitosterol and -sitostanol (typically found in margarine spreads such as Promise Activ or Benecol)
- Omega-3 fatty acids, such as fatty fish, fish oil supplements, flaxseeds and flaxseed oil
If you’re currently taking medications, talk to your doctor before starting any supplement to avoid potential harmful interactions.