Metabolic Syndrome

By Stacey Waring, M.D., M.S.

During the last 15 years a new disorder known as metabolic syndrome has become widespread in this country. It affects approximately 47 million Americans 1 and puts them at increased risk of death from heart disease. There are several different ways to define metabolic syndrome. The National Cholesterol Education Program publishes guidelines that all physicians use to treat cholesterol and included in their most recent publication a definition of metabolic syndrome. 2 Metabolic syndrome is diagnosed when three out of five of these criteria are met:

•  Abdominal obesity . This is a waist size in men greater than 40 inches and a waist size in women greater than 35 inches.

•  High-density lipoprotein (HDL) less than 40 in men and 50 in women . HDL is commonly known as the "good cholesterol" and is involved in transporting fat from different parts of the body to the liver. Low HDL is also a major risk factor for heart disease.

•  Triglycerides greater that 150 . Triglycerides are another type of blood fat that may be related to heart disease

•  Blood pressure greater than 130/85.

•  Fasting glucose greater than 100 . Diabetes is defined as a fasting glucose greater than 126. Impaired fasting glucose is the medical term for a prediabetic state and is defined as a fasting glucose greater than 100 but less than 126.

Obesity is the single biggest contributor to metabolic syndrome. Metabolic syndrome is essentially a complication of obesity. Gaining weight increases your cholesterol, blood pressure and blood sugar levels. Insulin resistance is another condition that increases the risk for metabolic syndrome. Insulin is a hormone released by the pancreas that is necessary to allow glucose to enter the cells of the body. Insulin resistance is a condition where organs and tissues do not respond appropriately to insulin. This causes the body to release more insulin to get blood sugars down to a normal level. Insulin resistance is a major contributor to the metabolic syndrome and is closely related to obesity. However, some people who are not obese have insulin resistance. This is most likely related to genetic factors.

WHAT ARE THE CONSEQUENSES OF METABOLIC SYNDROME?

Metabolic syndrome increases the likelihood of inflammation in the body. One way to determine the level of inflammation in the body is by measuring the level of C-reactive protein (CRP) in the blood. CRP has been found to be a risk factor for heart attack and stroke in healthy people. Individuals with metabolic syndrome also are more likely to have alterations in certain cholesterol subparticles, including changes in sizes and numbers, which increase the risk for arteriosclerosis.

Most notably metabolic syndrome increases the risk for heart disease. In one study individuals with metabolic syndrome were three times more likely to die from heart disease than people without metabolic syndrome. This held true even after they had adjusted for conventional risk factors for heart disease. 3

Additionally, metabolic syndrome is highly predictive of new onset diabetes. It can increase the risk for polycystic ovary disease, which can decrease fertility. Metabolic syndrome also promotes fatty liver, which can, although rare, lead to liver cirrhosis.

WHO IS AFFECTED?

WHAT CAN BE DONE?

The cornerstones of therapy are weight loss and physical activity. This cannot be stressed enough. Together they treat the underlying reason for metabolic syndrome. Weight loss and physical activity decrease cholesterol and triglycerides; raise good cholesterol, lower blood pressure and glucose; and reduce insulin resistance. They also decrease CRP and other markers of inflammation.

Treating insulin resistance with medication would be an attractive means of treating metabolic syndrome. Two classes of drugs, metformin and thiazolidinediones, are used for people with diabetes mellitus. Both classes of drugs treat insulin resistance. They act at the receptor for insulin to help the body use insulin more effectively. However, neither is approved for use in people without diabetes. Management of hypertension, cholesterol abnormalities and blood glucose will also help prevent the consequences of metabolic syndrome.

1. Ford ES, Giles WH. Dietz WH. Prevelance of the metabolic syndrome among US adults: findings of the Third National Health and Nutrition Examination Survey. JAMA. 2002;287:356-359.

2. Third report of the National Cholesterol Education Progam (NCEP) expert panel on detection, evaluation and treatment of high blood cholesterol in adults (Adult Treatment Panel III). Final report. Circulation. 2002; 106; 3143-3421.

3. The metabolic syndrome and total and Cardiovascular disease mortality in middle-aged men. JAMA. 2002;288:2709-2716.

Stacey Waring, M.D. is an internist with Louisville Internal Medicine. She is a former collegiate tennis player. She completed her M.D. and Master of Science in exercise physiology at the University of Louisville . She also completed her residency and chief residency in internal medicine at the University of Louisville . Her office phone is 502- 895-4772.