Are overall adiposity and abdominal adiposity separate or redundant determinants of blood viscosity?

Body fat and blood rheology: Evaluation of the association between different adiposity indices and blood viscosity

BACKGROUND

In recent years, new measures of body adiposity have been introduced: lipid accumulation product (LAP), body adiposity index (BAI) and body shape index (ABSI). These indices have been demonstrated to better associate with cardiovascular disease than other measures of adiposity.

OBJECTIVES

The aim of the present study was to evaluate if LAP or BAI better associate with blood viscosity than other measures of adiposity (body mass index, BMI; waist circumference, WC; waist-to-hip ratio, W/HR; waist-to-height ratio, W/HtR).

METHODS

344 subjects were recruited for the present investigation. Exclusion criteria were: diabetes, elevated triglycerides, smoking and drug use. Blood lipids and glucose were measured by routine methods. Blood and plasma viscosity were measured by a cone-plate viscometer. Adiposity measures were computed as previously described.

RESULTS

In simple correlation analyses, blood viscosity (BV) correlated with BMI, BAI, and LAP in males and with LAP in females. Correlations between plasma viscosity and adiposity indices were weak and not statistically significant. Other variables significantly related with BV were: gender, HDL- and LDL-Cholesterol, and triglycerides (p < 0.05). In multiple regression analysis only LAP was associated with BV.

CONCLUSIONS

Our data suggest that LAP index is strongly associated to blood viscosity. This result, along with previous evidence, identifies LAP index as a potential cardiovascular risk marker.

Association of whole blood viscosity with non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is an independent risk factor for increased cardiovascular disease. Altered hemorheological parameters have also been shown to play a crucial role in atherogenesis. Moreover, increased viscosity is observed in insulin resistance, metabolic syndrome, hypertension, diabetes, ischemic heart disease, and stroke. A recent study confirmed that whole blood viscosity (WBV) is a predictor of cardiovascular events.

AIMS

This study aimed to investigate the association of WBV with NAFLD.

METHODS

In this cross-sectional study, we investigated the relationship between WBV and NAFLD in 1329 subjects (962 men and 367 women) in a general health examination.

RESULTS

WBV at low shear stress was elevated in patients with NAFLD. In addition, the prevalence of metabolic syndrome and NAFLD increased as WBV quartiles increased both in men and in women. Multiple regression analysis further identified WBV as an independent and significant determinant for NAFLD.

CONCLUSIONS

The findings showed that WBV at low shear stress is increased in NAFLD. Moreover, WBV at low shear stress is independently associated with NAFLD even after adjusting other cardiovascular risk factors.

« Optimal » vs actual hematocrit in obesity and overweight

Equations of blood viscosity provide a prediction of the 'optimal' hematocrit' (hct) as the hct resulting in the highest value of the bell-shaped curve of hematocrit/viscosity ratio h/η. We investigated if overweight and obesity have an influence on these parameters. We compared 32 normal weight subjects, 40 overweight (BMI 25-30) and 38 obese subjects. There was no difference in the theoretical curve of h/η. The actual h/η is the same in the 3 groups but is always higher than the theoretical h/η in all groups. The actual h/η is lower in overweight than controls (p = 0.011). Modeling yields the same value of theoretical optimal hct across BMI classes. The 3 groups have the same values of actual hct, but actual is significantly lower than optimal in all cases (p < 0.001). Hematocrit is lower than predicted due to a discrepancy between predicted and actual h/η which is due to the inter-subject variability of RBC rigidity ...   The discrepancy between optimal and actual h/η is negatively correlated to RBC rigidity indexes even if the model uses a fixed value of these indexes. Thus keeping in mind that the optimal hct should not be the same in the various parts of the vascular bed, its theoretical prediction with Quemada's equation appears to predict a value higher than actual hematocrit but well correlated to it, and the agreement between optimal and actual hct is dependent on RBC flexibility. This leads to think that the body sets hematocrit below its ideal value in sedentary subjects in order to cope with the need of increasing blood viscosity factors in case of exercise without impairing O2 supply to tissues.

Elevated whole blood viscosity in patients with lumbar disc herniation

BACKGROUND

Various vascular risk factors such as smoking, obesity, and diabetes mellitus are associated with hyperviscosity and lumbar disc herniation (LDH). However, the changes of viscosity in LDH have not been examined.

AIMS

The present study was to elucidate 1) the rheological parameter levels in patients with LDH, 2) the risk factors that were related to rheological parameters.

METHODS

Our study evaluated the rheological parameters in 307 cases with LDH and in 307 control subjects. Multiple linear regression analysis was conducted to assess the significant factors for whole blood viscosity (WBV) at low shear rate.

RESULTS

LDH patients had markedly lower physical activity and significantly higher WBV 3 s-1 compared with non-LDH subjects (p < 0.001). Moreover, WBV (3 s-1) tended to increase as physical activity decreased. Multiple linear regression analysis revealed that reduced physical activity was a significant factor contributing to elevated WBV (3 s-1).

CONCLUSIONS

WBV (3 s-1) is elevated in patients with LDH. In addition, reduced physical activity is a significant factor for WBV (3 s-1). Further studies are warranted to determine the role of WBV (3 s-1) in LDH.