[Metabolic syndrome]

About 20 years ago, Reaven presented the concept that a series of related factors such as hyperinsulinemia, hypertension, low high-density lipoprotein (HDL)-cholesterol levels, and hypertriglyceridemia tended to co-occur in the same individual and that this risk-factor clustering and its association with insulin resistance might be of critical importance in the underlying cause of cardiovascular disease. This risk-factor clustering called as "syndrome X" has now become "metabolic syndrome" (METS). Nowadays, METS is becoming well known as a condition of high-risk for the subsequent development of ischemic cardiovascular disease in Western population as well as Japanese population and it is proved that the prevalence of METS is very common. There are several different diagnostic definitions for METS. In Japanese definition, waist circumference is essential for criterion of METS because visceral fat accumulation is believed to be associated with METS more closely than the body mass index (BMI) itself or the amount of subcutaneous fat. Therefore treatment strategy to reduce visceral fat seems to be crucial for management of patients with METS. Adipose tissue is not simply an energy storage organ, but also a secretary organ, producing a variety of bioactive substances, including adiponectin. Adiponectin is paradoxically reduced in obesity and elevated adiponectin concentration is associated with greater insulin sensitivity. Therefore hypoadiponectinemia can be considered a key factor of the development of METS. We believe that detection, prevention and treatment of METS are important clinical and public health challenges.