Metabolic syndrome is a term to describe a set of symptoms that often occur together and are related to the development of heart disease. The characteristic symptoms include excess abdominal fat, abnormal glucose metabolism (conversion of a sugar called glucose to energy), hypertension (high blood pressure), and abnormal blood levels of the fatty substances cholesterol and triglycerides. Metabolic syndrome is also referred to as syndrome x, insulin resistance syndrome, or the deadly quartet.
Metabolic syndrome is associated with a higher risk for coronary artery disease (CAD), heart attack, and stroke. Many of the individual components of metabolic syndrome also increase the risk for CAD. However, the risk associated with metabolic syndrome is greater than the risk associated with any individual component of the syndrome alone.
Symptoms.
Many of the characteristic symptoms of metabolic syndrome are related to obesity, particularly in the abdomen, which leads to abnormal glucose metabolism. Insulin, a hormone produced by the pancreas, promotes the uptake of glucose into muscle and fat tissue, where it is used as fuel. However, in some individuals, muscles and fat cells become resistant to insulin. Such insulin resistance is more common in people who are obese—that is, who have an excessive amount of body fat, particularly around the abdomen. In response, the pancreas produces more insulin, thereby leading to hyperinsulinemia, an excess amount of insulin in the blood.
Insulin resistance and hyperinsulinemia cause reactions in tissues that are sensitive to insulin, particularly the blood vessels. The reactions are responsible for many conditions associated with metabolic syndrome, such as hypertension. About half of all patients who have hypertension are insulin-resistant with hyperinsulinemia. In addition, metabolic syndrome patients often have an abnormal tendency to form blood clots. Such patients have a higher risk of coronary thrombosis, a condition in which a clot blocks the passage of blood in an artery of the heart.
In some people with insulin resistance, the body cells fail to use glucose efficiently. The amount of glucose in the blood remains abnormally high, a condition called Type 2 diabetes. High levels of glucose in the blood damage many organ systems and increase risk of atherosclerosis, a condition that narrows arteries, especially those that carry blood to the heart, brain, kidneys, and legs. See Diabetes.
Abnormal levels of cholesterol and triglycerides accompany insulin resistance in patients with metabolic syndrome. Both substances are carried through the bloodstream in large molecules called lipoproteins. There are two chief types of cholesterol-carrying lipoproteins, low-density lipoprotein (LDL) and high-density lipoprotein (HDL). Patients with metabolic syndrome often have higher than normal levels of triglycerides, low levels of HDL, and an increase in small, dense LDL particles. All of these conditions are linked to coronary artery disease when they occur independently.
Treatment.
For physicians treating patients with metabolic syndrome, the main goal is to reduce the underlying risk factors of the syndrome, particularly obesity. For most patients, weight reduction and increased physical activity will lessen symptoms and reduce the risk of cardiovascular disease. If weight loss is not achieved, physicians may prescribe drugs to treat the various components of the syndrome.
Physicians may prescribe drugs called thiazolidinediones (TZD’s) to reduce insulin resistance. For many patients, a combination of medications is necessary to control hypertension. Drugs called statins are often used to control cholesterol levels. A small daily dose of aspirin can be effective in reducing the risk of blood clots.
Many of the drugs used to treat metabolic syndrome also reduce inflammation. Researchers are investigating the possibly significant role of inflammation in the development of metabolic syndrome and other diseases.
See also Cholesterol; Heart (Coronary artery disease); Insulin; Obesity.
