Adipose tissue, which classically has been considered as an energy-storing organ, is now viewed as a massive source of bioactive substances such as
leptin,
tumor necrosis factor (
TNF)-alpha, and
adiponectin.
Adiponectin was discovered to be the most abundant adipose-specific transcript. Its function had been unclear, but epidemiological and clinical studies have demonstrated that serum levels of
adiponectin are inversely associated with
body weight, especially abdominal visceral fat accumulation. In addition,
adiponectin was inversely related to cardiovascular risk factors, such as
insulin resistance, blood pressure, and
low-density lipoprotein (
LDL) cholesterol and
triglyceride levels, and was positively related to
high-density lipoprotein (
HDL) cholesterol levels. Moreover, low
adiponectin concentration is associated with a high incidence of
cardiovascular disease (CVD), diabetes, some kinds of
cancer, and other various diseases. These associations suggest the clinical significance of
adiponectin, and a number of investigations are now being conducted to clarify the
biological functions of
adiponectin. Recent studies have revealed that
adiponectin exhibits antiinflammatory, antiatherogenic, and
antidiabetic properties. In addition,
adiponectin has been thought to be a key molecule in "
metabolic syndrome," which is an epidemiological target for preventing
cardiovascular disease. Various functions of
adiponectin may possibly serve to prevent and treat
obesity-related diseases and CVD. Furthermore, enhancement of
adiponectin secretion or action may become a promising therapeutic target.