Abstract 14605: Paradoxical Reduction of Platelet Activation in Morbid Obesity
Introduction: Post-mortem studies have demonstrated that morbidly obese subjects (MO) show less coronary atherosclerosis than obese subjects (O), but the reasons for this apparent protection from atherosclerosis are not clear yet. Thromboxane A2 (TxA2), a marker of platelet activation, is higher in O compared to lean subjects (L) and this might represent a clue to their increased cardiovascular risk. Data on TxA2 in MO are still lacking, therefore we hypothesized that lower levels of TxA2 in MO might play a role in their lower atherosclerotic burden.
Methods: We measured serum levels of Thromboxane B2(TxB2), a stable metabolite of TxA2, C-reactive protein (hs-CRP) and leptin in 17 L (BMI 22.9±1.6), 25 O (BMI 32.6±2.4) and 23 MO (BMI 48.6±7.1), without insulin resistance, diabetes and overt cardiovascular diseases. Moreover we performed agonist-induced platelet aggregation (PA) in a further population of 30 non diabetic, insulin sensitive individuals, using arachidonic acid, epinephrine, collagen and adenosine diphosphate.
Results: Serum TxB2 levels were lower in L vs O (p=0.046), and in MO vs L and O (p=0.03 and p<0.001 respectively). In contrast, hs-CRP and leptin levels were higher in O vs L (hs-CRP p<0.001; leptin p=0.002) and MO vs L (p<0.001 for both). Leptin was also higher in MO vs O (p<0.001). Although not significant, PA in response to those agonists involved in thromboxane-dependent platelet activation was lower in MO vs O and L. TxB2 negatively correlated with leptin and BMI. Hs-CRP correlated with leptin, and both of them were also correlated with waist circumference, BMI and HOMA-IR.
Conclusions: Insulin sensitive MO show lower levels of TxB2 and a trend toward lower PA in response to TxB2 related agonists, as compared with O and L, suggesting that a reduced platelet activation could play a role in the paradoxical protection of MO from atherosclerosis.
- © 2010 by American Heart Association, Inc.