[The metabolic syndrome. Part II: its mechanisms of development and its complications]

The metabolic syndrome is a cluster of interrelated metabolic factors such as insulin resistance, hyperinsulinemia, abdominal obesity, impaired glucose tolerance, dyslipidemia, hypertension, and a proinflammatory and prothrombotic state. It is a common cause of the development of atherosclerotic vascular disease and type 2 diabetes. Genetic predisposition and environmental factors such as physical inactivity and increased caloric intake are responsible for the predisposition to metabolic syndrome. Available studies on the pathogenesis of metabolic syndrome are discrepant. Insulin resistance and abdominal obesity are the dominant causes of metabolic syndrome. Increased visceral adipose tissue mass and its proinflammatory activity are thought to underlie all the changes observed in metabolic syndrome. Adipose tissue is a dynamic endocrine and paracrine organ that produces and secretes inflammatory factors called adipokines, which link obesity, insulin resistance, atherosclerosis, and type 2 diabetes. Recent data suggest that oxidative stress is a primary pathogenic mechanism leading to the development of insulin resistance associated with over-nutrition. In this study the authors analyze the association between abdominal obesity, hyperinsulinemia, and insulin resistance and show some pathogenic mechanisms which may be responsible for the proatherogenic action of insulin resistance, hyperinsulinemia, and impaired glucose tolerance. Here the association among the disorders mentioned in the definitions of metabolic syndrome is discussed in more detail and it is shown that their clustering is not accidental in patients with insulin resistance. The role of adipose tissue in the development of insulin resistance and metabolic syndrome leading to overt cardiovascular disease and type 2 diabetes is also described.