At a glance
- In the United States, approximately 34% of adults carry the diagnosis of metabolic syndrome.
Obesity, lipid levels, BP, and insulin resistance should be considered when diagnosing metabolic syndrome.
Screening should include a physical examination, a dietary history, and laboratory workup.
The goal of treatment is to delay or prevent CVD and diabetes.
The National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) report identified a constellation of factors that increased an individual’s risk of developing cardiovascular disease (CVD).1 Metabolic syndrome is a general diagnosis given to a set of disorders that a patient experiences simultaneously, including hyperglycemia, elevated BP, dyslipidemia and abdominal obesity.
In the United States, approximately 34% of adults have been diagnosed with metabolic syndrome.2 As obesity rates increase, the incidence of metabolic syndrome is also expected to rise. The damaging effects of metabolic syndrome may place affected patients at a higher risk of developing CVD and type 2 diabetes mellitus (T2DM).3
The exact societal cost of the syndrome is unknown because the disorder can vary so much. However, given that the annual projected costs associated with hypertension, diabetes, cholesterol disorders and obesity are escalating, one can expect that the annual cost associated with metabolic syndrome will be astronomical. Sullivan and colleagues estimated the loss in productivity resulting from metabolic risk factors was $17.3 billion annually.4
Boudreau et al studied the health-care utilization of patients with metabolic syndrome and found that the cost of care for patients with diabetes who were obese and had dyslipidemia and hypertension was almost twice that of patients with prediabetes who had the same risk factors ($8,067 compared with $4,638).5
Major organizations, such as the American Heart Association (AHA) and the American Diabetes Association (ADA), do not agree on the usefulness of metabolic syndrome in clinical practice. Several studies have testified to the significance of the syndrome as a diagnostic predictor of CVD.6,7 Yet many highly acclaimed scientists refute the validity of the syndrome to predict cardiovascular or diabetes risk as postulated by others in the medical community.8,9 Reaven adamantly believes the syndrome is a “pathological process” and challenges the scientific world to stop “spinning” the notion that it is anything more.9
Despite the rather intense battles about the utility of a diagnosis of metabolic syndrome in clinical practice, most parties agree that the risk factors associated with the syndrome are problematic for the patient, public health, and health-care providers.10-12
Components of metabolic syndrome
While not all organizations agree on the requirements for diagnosing metabolic syndrome (Table 1), there is consensus about the factors that should be considered. These include whether the patient is obese or overweight, lipid levels, BP and the presence or absence of insulin resistance.
Obesity. In women, the metabolic syndrome affects 33.1% of overweight persons and 56.1% of obese and extremely obese individuals; slightly more than 10% of normal-weight and underweight persons have the syndrome.2 In men with metabolic syndrome, only 6% were in the normal-weight category, with more than 93% in the overweight or obese category. Metabolic syndrome is linked more to central visceral obesity than to overall obesity. Several studies cite central obesity as the pivotal component in development of the syndrome.13,14
The proposed connection between obesity and the risk factors for metabolic syndrome are complex. Increase in visceral fat leads to central obesity and has been linked to increased insulin resistance as a result of hormonal influences.15 Also, cortisol has been widely studied as a culprit in stimulating the appetite for high-carbohydrate, fatty foods that lead to increased deposition of fat around the abdomen.
The hormones thought to play the greatest role in the development of obesity-related metabolic syndrome are the adipokines, leptin, and adiponectin.16 The hormone leptin helps regulate appetite and storage of fat and influences thermogenesis to burn calories. Sudden increase in weight or extreme weight gain disturbs the leptin regulation, thereby allowing deposition of fat in the visceral areas as well as inciting an increase in triglyceride storage in vital organs, such as the heart, muscles and liver.13
Dyslipidemia. In obese patients with metabolic syndrome, deregulation of the hormonal system often leads to dyslipidemia. Levels of the hormone adiponectin were found to be inversely related to visceral fat and lower in patients with coronary artery disease.14 Adiponectin promotes insulin sensitivity and has an antiatherogenic effect.17 The patient with metabolic syndrome usually has normal levels of LDL, although the lipoproteins themselves are believed to be denser and smaller in nature, which makes them more atherogenic. Levels of triglycerides and HDL are often elevated in the patient with metabolic syndrome.12
Insulin resistance. In insulin resistance, the body produces insulin, but it is not used properly. This cyclic dysfunction leads to higher glucose levels in the bloodstream, which causes more insulin production (hyperinsulinemia).
An increase in total body fat is independently related to insulin resistance. Scientists believe that adipose tissue releases additional adipokines that are insulin antagonists, such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and resistin.17 These inflammatory factors are responsible for insulin resistance, the production of C-reactive protein (CRP), and increased adhesion of WBCs and molecules to endothelial cells.18
Hypertension. Hyperinsulinemia and obesity in metabolic syndrome raises patients’ risk for elevated BP. Elevated insulin levels increase the kidney’s absorption of sodium and water, which in turns increases blood volume and elevates the BP.19 Obese patients require a larger-than-normal cardiac output because of increased blood volume. In addition, sympathetic system in obese patients is overactive, leading to constriction of peripheral arteries, sodium retention and vascular resistance. The presence of any of these actions, alone or synergistically, can lead to hypertension.
In 2009, a group of organizations released a set of diagnostic criteria on which they agreed (Table 2).20
The organizations involved were the International Diabetes Federation (IDF) Task Force on Epidemiology and Prevention; the National Heart, Lung, and Blood Institute; the AHA; the World Heart Federation; International Atherosclerosis Society; and the International Association for the Study of Obesity.