The relationship between serum adiponectin concentration and hypertension or cardiac hypertrophy is still controversial. We have previously proposed that tissue-bound adiponectin possibly plays an important role against metabolic syndrome. In this study, we investigated the relationship between heart-bound adiponectin and hypertension or cardiac hypertrophy, compared with serum adiponectin in hypertensive rats.Design and Method:
Six-, 12-, and 20-week-old Wistar-Kyoto rats (WKY); 2 subspecies (strains C and B2, characterized by having lower and higher blood pressure, respectively) of spontaneously hypertensive rats (SHR); and stroke-prone SHR (SHRSP) were used. Blood pressure, heart/body ratio, serum adiponectin, and heart-bound adiponectin were measured. Histopathological analyses of the heart were also carried out.Results:
The heart/body ratio strongly correlated with blood pressure in 12- and 20-week-old rats, as expected. Serum adiponectin concentration, however, was positively correlated with blood pressure in 12- and 20-week-old rats, and the heart/body ratio and heart muscle cross-sectional area in 20-week-old rats, indicating that there is no relationship between serum adiponectin and blood pressure or cardiac hypertrophy in these rats. In contrast, heart-bound adiponectin in SHRSP was significantly decreased than that in other species of all ages. This results from a decrease in T-cadherin expression, which induces adiponectin binding to tissues. Heart-bound adiponectin inversely correlated with the heart muscle cross-sectional area, but not with blood pressure, indicating that heart-bound adiponectin is more closely related with cardiac hypertrophy than serum adiponectin concentration in these rats.Conclusions:
Some researches have reported that serum adiponectin concentration is a useful parameter for evaluating the health condition. Some patients, however, showed hypertension and cardiac hypertrophy despite having high adiponectin concentrations in blood. Our results suggest the possibility that such patients would have decreased heart-bound adiponectin mediated by T-cadherin, and a high adiponectin concentration in blood.