Abnormal erythrocyte rheology in patients with morbid obesity.

The objectives of this study were to investigate the rheological properties of the erythrocyte in patients with morbid obesity and to follow them up after a short-term weight loss. A fluorescent polarization method was used to assess erythrocyte membrane biorheology and to measure its fluidity. Eighteen subjects participated in the study: 8 healthy controls and 10 patients with morbid obesity. The erythrocyte membrane fluidity was obtained in the healthy subjects and in the patients with morbid obesity prior to and after a ten-day zero-calorie diet. Fluidity was determined by steady-state fluorescence polarization after incorporation of the lipophilic probe 1,6-diphenyl-1,3,5 hexatriene (DPH). With this method, the anisotropy parameter at 37 degrees C, which is inversely related to membrane fluidity, was obtained. The patients with morbid obesity revealed an abnormal erythrocyte rheology. The exhibited an abnormally low erythrocyte membrane fluidity as compared with normal subjects. The anisotropy parameter at 37 degrees C was 1.417 +/- 0.093 in these obese patients compared with 1.279 +/- 0.043 in normal-weight controls (p < 0.01). Upon a short-term significant weight loss from a body mass index (BMI) (weight/height2) of 39 +/- 5 to 36 +/- 5 kg/m2 (p < 0.05), the anisotropy parameter did not change (1.401 +/- 0.190). Thus, fluidity measurements permit recognition of an abnormal erythrocyte rheology in patients with morbid obesity. This abnormality may partially explain the excess cardiovascular and thromboembolic morbidity in morbid obesity.