What is Metabolic Syndrome?

Are You at Risk for Diabetes and Heart Disease?

Sep 30, 2008 Stephen Allen Christensen

Trends in America's demographics are placing many individuals at risk for diabetes and cardiovascular disease. Certain traits identify those at highest risk.

Metabolic syndrome (previously called syndrome X) is a combination of traits that increase one’s risk for heart disease and type 2 diabetes mellitus. Metabolic syndrome is characterized by elevated blood pressure, impaired glucose tolerance, central obesity, and dyslipidemia (high triglyceride and low HDL levels).

The incidence of metabolic syndrome increases with age. Prevalence varies among ethnic groups, ranging from 16% of black men to 37% of Hispanic women (Ford ES, Giles WH, Dietz WH. JAMA 2002:287:358).

Since the US population is aging, and since over half of American adults are overweight, metabolic syndrome is becoming more frequent; it may soon overtake cigarette smoking as the number one risk factor for cardiovascular disease. (Eckel and Krauss, Circulation 1998:97:2099-2100)

Traits of Metabolic Syndrome

• Hypertension: Blood pressure ≥140/90 (World Health Organization criterion); ≥130/85 (Adult Treatment Panel criterion). Individuals on medication for hypertension fulfill this criterion
• Impaired glucose tolerance: Fasting glucose ≥100, abnormal glucose tolerance test, or documented diabetes
• Central obesity: Waist-to-hip ratio >0.9 for men, >.0.85 for women or BMI >30 (WHO); waist circumference >102 cm for men, >88 cm for women (ATP)
• Dyslipidemia: Triglyceride level ≥150 mg/dl for men and women (WHO and ATP); HDL cholesterol <35 mg/dl for men, <39 mg/dl for women (WHO); <40 mg/dl for men, <50 mg/dl for women (ATP)
• The World Health Organization has also added a diagnostic criterion for relative values of albumin and protein in urine.

(NIH publication no. 01-3670; Alberti KG, Zimmet PZ. Diabet Med 1998;15:539-53).

The Physiology of Metabolic Syndrome

Human physiology is essentially a process of maintaining internal balance amidst an ever-changing external environment. While myriad hormones work to maintain this homeostasis, insulin—rather, the body’s resistance to insulin—appears to be the driving force behind metabolic syndrome.

When a person’s blood glucose rises after a meal, insulin is secreted by the pancreas to prevent the glucose from rising too high. Insulin stimulates the body’s cells to absorb and burn glucose as fuel, or to store it as glycogen or fat.

In addition to controlling glucose levels, insulin prevents fat cells from releasing lipids into the bloodstream; insulin also acts to raise blood pressure and increase body fat stores.

Unfortunately, cells that are repeatedly exposed to insulin gradually become resistant to the hormone’s effects—a phenomenon called “insulin resistance” or “glucose intolerance.” Some people are genetically inclined to develop insulin resistance. The chronic ingestion of too many calories—particularly in the form of carbohydrates—leads to insulin resistance as well.

As cells become resistant to insulin, blood glucose levels rise. More lipids are released into the bloodstream. The pancreas must secrete more insulin to maintain homeostasis. The cells then become even more insulin-resistant.

Over time, a vicious cycle is established. Without intervention, metabolic syndrome worsens until a person develops overt diabetes or cardiovascular disease...or both.

Interrupting the Cycle of Metabolic Syndrome

Theoretically, aggressive management of the individual components of metabolic syndrome should delay its complications. This predicates the use of medications for controlling blood pressure, dyslipidemia, or, in the case of documented diabetes, blood glucose.

However, lifestyle changes are the bases of management strategies for those diagnosed with metabolic syndrome. First-line therapy includes changes in diet and activity levels. Weight loss improves all aspects of metabolic syndrome. For those individuals who have trouble losing weight, dietary changes and exercise that improve lipid levels and lower blood pressure will lead to lowered insulin resistance, even when weight loss does not occur. (Duncan GE, et al. Diabetes Care 2003:26:557-562)

As with many disease conditions, lifestyle interventions—and, for our children, establishing good habits at an early age—are the keys to longer, healthier lives.

The copyright of the article What is Metabolic Syndrome? in General Medicine is owned by Stephen Allen Christensen. Permission to republish What is Metabolic Syndrome? in print or online must be granted by the author in writing.

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