Insulin resistance is one of the major risk factors associated with development of
hypertension and
atherosclerosis. Recent studies have shown that
adiponectin, an adipocyte-derived
hormone, may be involved in
insulin resistance and development of
atherosclerosis in diabetes patients. The aim of this study was to examine
adiponectin levels in patients with
essential hypertension to determine the relationships between
adiponectin levels and
insulin sensitivity and to examine the relationship of
adiponectin with pulse wave velocity (PWV) in a general population based on the results of an epidemiological survey in Japan. In a clinical study, 20 normotensives (NT) and 30 non-treated essential hypertensives (EHT) were hospitalized, and euglycemic hyperinsulinemic
glucose clamp (GC) was performed to evaluate
insulin sensitivity defined as M value. EHT were divided into
insulin-resistant EHT (EHT-R) and
insulin-nonresistant EHT (EHT-N) according to the mean -1 SD of the M value of NT as a cut-off point. Fasting plasma
glucose (FPG), immunoreactive
insulin (IRI), and
adiponectin concentrations were measured. There were no significant differences in body mass index (BMI) or FPG among the NT, EHT-N, and EHT-R groups. The M value and
adiponectin concentration in EHT-R were significantly lower than those in the NT or EHT-N. The IRI level in the EHT-R was significantly higher than those in the other groups. A positive correlation between
adiponectin concentration and M value was found in all subjects, and
adiponectin concentration and M value were found to be significant determinants of each other in multiple regression analysis. In an epidemiological study, we studied 391 male inhabitants of rural communities in Hokkaido, Japan. Systolic blood pressure (SBP), BMI, FPG, IRI, and
adiponectin were measured in all subjects early in the morning. Homeostasis model assessment (HOMA) values were calculated as an index of
insulin sensitivity, and PWV was used as an index of
atherosclerosis. A negative correlation between HOMA values and
adiponectin concentration was found in all of the subjects. Multiple regression analysis revealed that
adiponectin was a significant determinant for PWV in subjects less than 70 years of age. The results of the clinical study indicate that EHT-R had not only
hyperinsulinemia but also a low concentration of
adiponectin. The results of multiple regression analysis for determinants of degree of PWV using data obtained in the epidemiological study suggest that
adiponectin plays a role in antiatherosclerosis, partly through improvement of
insulin resistance.