Regional Hemodynamic Abnormalities in Overweight Men

Blood pressure, forearm hemodynamic data, and red blood cell (RBC) cation transport measurements were obtained in 27 men with body mass indexes (BMI) greater than 26.6 kg/m2 and 21 men with BMI less than 26.6 kg/m2. Subjects with higher BMI had significantly higher systolic and diastolic pressure measured both noninvasively and invasively, P less than .02-.001. Baseline forearm blood flow (FABF) was substantially higher in the heavier subjects, P less than .02, whereas forearm vascular resistance (FAVR) levels were not different, P greater than .10. Despite the higher baseline forearm blood flow, the high BMI group displayed a greater rise in flow, P less than .01, in response to a regional phentolamine infusion, an index of vascular alpha-tone. Results of multiple regression analysis suggested that overweight was indirectly correlated with vascular alpha-tone via a relationship with arterial plasma norepinephrine concentration, a marker of sympathetic drive, and bumetanide-sensitive RBC Na+-K+ cotransport activity. These data indicate that in overweight men (1) higher FABF is not fully counter-balanced by lower FAVR; (2) increased vascular alpha-tone contributes to the altered flow-resistance relationship and thereby to the elevated blood pressure; and (3) greater sympathetic drive and Na+-K+ cotransport activity may explain the elevated vascular alpha-tone.