Can we talk about your endothelium for a minute? Don’t be shy – we all have one! The endothelium is simply (or not so simply) the tissue that lines your blood vessels, heart, and lymphatic vessels. It is sensitive and easily damaged by high cholesterol or homocysteine (an amino acid that is strongly linked to heart disease) levels, high blood sugar, high blood pressure, smoking, obesity, a sedentary lifestyle, inflammation, and aging.
The endothelium releases nitric oxide, so if it becomes damaged, the nitric oxide levels in your body become imbalanced. Nitric oxide relaxes the vessels and keeps them flexible, increasing blood flow and helping to keep a lid on blood pressure. Nitric oxide also has anti-inflammatory properties and reduces the risk of plaque sticking to the lining of blood vessels, which can cause a heart attack or stroke. A deficiency in nitric oxide production can reduce blood flow to the brain and increase both inflammation and oxidative stress, all of which may cause cognitive problems. Loss of nitric oxide in the small blood vessels of muscle causes less oxygen to be delivered during times of increased demand, like during physical activity. Recent research hints that nitric oxide is also crucial to respiratory health.
The Endothelium and Diabetes
The endothelium is damaged by insulin resistance, high blood sugar, inflammation, and other risk factors of heart disease common in individuals who have diabetes. It is important that endothelial cells remain in the tissues that line vessels; you don’t want them floating around your body. Unfortunately, the number of endothelial cells moving through the body outside of the endothelium is higher among individuals with diabetes, regardless of how well blood glucose levels are controlled. These cells release microparticles that are predictive of the presence of coronary artery lesions. In fact, these microparticles are a more powerful risk factor for heart disease than the duration of diabetes, lipid level, or the presence of high blood pressure.
Endothelial Progenitor Cells and Diabetes
Endothelial progenitor cells (EPC) repair the endothelium in cases of injury or tissue death; this is why the size of your EPC pool reflects your heart health. Individuals with either type 1 or type 2 diabetes have a decreased number of circulating EPCs compared to individuals without diabetes. Patients with both diabetes and peripheral arterial disease (a circulatory disease) have notably low EPC levels, especially if they also have an ischemic foot ulcer at the time that EPC level is measured.
Researchers recently discovered that when EPCs are injected into the muscle of rats, there is a reversal of damage to the sciatic nerve (a large nerve that runs from the lower back down the back of both legs) and recovery of blood flow within the nerve. The researchers who made this finding believe that bone marrow-derived EPCs might be able to reverse different types of nerve damage associated with diabetes in humans.
The decreased level of EPC in people with diabetes seems likely to play a role in the development of diabetic heart disease, kidney disease, and eye disease, as well. The kidneys contain many different types of endothelia, and acute or chronic kidney damage can result from endothelial injury.
Treatment of Endothelial Dysfunction
- Beta-blockers won’t improve endothelial function, but an ACE/ARB will, and individuals with diabetes should be on one of these medications to protect their kidney function anyways.
- Cardioprotective drugs including statins and ACE inhibitors increase nitric oxide availability.
- Aspirin treatment might help to improve endothelial function, but there is some controversy about this subject at this time.
- Nitrate consumption has been proven to have beneficial effects on blood pressure, arterial stiffness, platelet function, and cerebral blood flow. Nitric oxide production is increased by eating nitrate-rich vegetables, especially leafy green vegetables and beets. Other foods, including grape juice, chocolate, black tea, walnuts, and red wine contain substances, such as polyphenols, that also increase the production of nitric oxide in the body.
- The amino acid arginine, found in high protein foods including nuts, beans, seeds, poultry, seafood, and dairy products boost production of nitric oxide. Please don’t purchase arginine supplements, though – they dramatically increased the number of deaths among heart attack patients in a recent study, and they may worsen peripheral artery disease.
- High levels of free fatty acids in the body impair endothelial function, in fact, immediately after eating a high-fat meal, researchers can see impaired endothelium-dependent vasodilation.
- Oxidative stress is thought to cause endothelial dysfunction and atherosclerosis (the hardening and narrowing of arteries); antioxidants protect the endothelium from this damage and also increase the availability of nitric oxide. Folic acid has also been determined to have a positive effect on endothelial function, and antioxidants are found in many of the same foods including leafy green vegetables, citrus fruits, berries, apples, cherries, plums, okra, artichokes, brussels sprouts, asparagus, bell peppers, potatoes, beans, and nuts,
- Magnesium deficiency is believed to contribute to a pro-inflammatory state, damage to the endothelium, and an increased risk for blood clot formation in the arteries. Magnesium is found in whole grains, green leafy vegetables, and nuts.
- Coenzyme Q10 also helps to reduce oxidative stress and increases the availability of nitric oxide. It is also believed to reduce oxidation of LDL cholesterol, which accumulates in places where the endothelial has been damaged and contributes to the development of atherosclerosis.
Endothelial dysfunction has recently been identified as a hindrance to cardiovascular health, but the recommendations for treatment are mostly the same as those for most modern diseases plaguing us. Namely, control of blood sugar, blood pressure, and cholesterol levels; weight loss if necessary; smoking cessation; a focus on eating plenty of whole foods, and exercise.