Erythrocyte rheological changes in obese patients: influence of hyperinsulinism

OBJECTIVE

To investigate the rheological properties of RBC in obese subjects and the factors associated with their changes.

SUBJECTS

Two consecutive studies of non diabetic obese subjects.

MEASUREMENTS

Filtration index of RBC using the Hanss hemorheometer, RBC filterability using a cell transit time analyser and RBC aggregation measured on the Myrenne aggregometer.

RESULTS

In both studies an increase in the filtration index of RBC, namely a reduction in their deformability, was found. In the first study the filtration index correlated negatively with hematocrit and positively with plasma C peptide levels. In the second study RBC filterability was also studied by the cell transit time analyzer in which there is no aggregate formation. The RBC transit time was not found to be different in the obese patients and in the controls, but RBC aggregation was increased and correlated significantly with body weight and BMI. RBC aggregation worsened after four days of hypocaloric diet.

CONCLUSION

(1) obesity, independently of the other cardiovascular risk factors, is associated with significant changes in RBC rheology; (2) these changes are probably related for the most part to plasma factors, possibly via hyperinsulinemia, even if changes in the chemical composition of the RBC membrane are not excluded, (3) RBC aggregation worsens during the first days of a hypocaloric diet; (4) rheological changes in RBC seem to be another component of the insulin resistance syndrome.

Angiography contrast agents interact with serine proteinases. The molecular structure of the model system elastase/iohexol

Pancreatic elastase was co-crystallised with iohexol, a tri-iodo benzenic contrast agent used in angiography analyses. The X-ray analysis of the complex reveals the presence of three molecules of iohexol associated with the proteinase with low occupancy factors. Two iohexol molecules are located in and near the active site of the enzyme and provide a model for explaining the inhibition of the hemostatic system, one of the major and inconvenient side effect associated with these chemicals.

Glucagon and noradrenaline reduce erythrocyte deformability

An impairment in red blood cell (RBC) deformability has been reported in several diseases and might be involved in the pathogenesis of atherosclerosis. The aim of the present study was to test in vitro the effect of two "stress hormones," norepinephrine and glucagon, on the filterability of RBCs from healthy subjects. Measurements were performed with the Hanss hemorrheometer, and results were expressed as the rigidity index (RI). All concentrations of norepinephrine from 10(-7) to 10(-4) mol/L induced a significant increase in RI compared with Hanks buffer, with the maximal effect being reached using 10(-6) mol/L. All concentrations of glucagon from 0.01 to 5 ng/mL also induced a significant increase in RI, with the maximal effect being achieved using 1 ng/mL. These data suggest that these two stress hormones could be involved in the rheologic impairments found in several diseases and therefore in the pathogenesis of atherosclerosis.

Erythrocyte deformability in diabetes and erythrocyte membrane lipid composition

Erythrocyte deformability was assessed in 40 diabetic patients, 24 insulin-dependent (IDD) and 16 non-insulin-dependent (NIDD), by measuring the initial filtration flow rate of whole blood, isolated red blood cells (RBC), and isolated RBC membranes with the Hanss hemorheometer, and its relationship to the plasma and ghost membrane lipid composition was investigated. RBC deformability was significantly reduced, whereas the deformability of the isolated RBC membranes did not differ significantly from the controls. In the plasma, the triglycerides were high, the high-density lipoprotein (HDL) cholesterol was reduced, and the ratio of total cholesterol over HDL cholesterol was high as compared with the controls. The RBC lipid composition expressed in mumol lipids/10(10) RBC showed significantly lower levels of free cholesterol, sphingomyelines, and phosphatidylcholine, which are the lipids principally located on the outer layer of the RBC membranes. These data suggest that in both IDD and NIDD patients, there may be a relation between these modifications in the RBC lipid composition and rheological impairment of the RBC.