Hemostatic abnormalities associated with obesity and the metabolic syndrome
Article first published online: 29 APR 2005
Journal of Thrombosis and Haemostasis
Volume 3, Issue 5, pages 1078–1080, May 2005
How to Cite
STRATMANN, B. and TSCHOEPE, D. (2005), Hemostatic abnormalities associated with obesity and the metabolic syndrome. Journal of Thrombosis and Haemostasis, 3: 1078–1080. doi: 10.1111/j.1538-7836.2005.01302.x
- Issue published online: 29 APR 2005
- Article first published online: 29 APR 2005
The role of platelets and anti-platelet therapy
Obesity is associated with accelerated atherothrombosis and an increased incidence of cardiovascular morbidity and mortality [1,2]. Numerous observations suggest that it is the interplay of the metabolic disorders frequently accompanying excess body weight that promotes the progression of atherosclerotic lesions in obese individuals [3,4]. Platelet hyperactivity, besides hypertension, dyslipidemia, decreased fibrinolysis, and increased procoagulation factors is a consequence of the metabolic syndrome and one of the most central problems obese patients have to face [5–7].
The mechanism by which obesity leads to the development of these vascular and metabolic disorders is the development of insulin resistance which is defined as reduced insulin action in peripheral tissues, such as skeletal muscle, adipose tissue, and liver.
Obesity with a body mass index (BMI) ≥ 35 kg m−2 has been shown to increase the risk of developing Type 2 diabetes by more than 60-fold in women and by 42-fold in men . Steinberg and coworkers showed that severely obese insulin-resistant individuals (mean BMI 34 kg m−2) with normal glucose tolerance have the same degree of impairment in blood flow and vascular reactivity as those with established Type 2 diabetes . Thus, most of the diabetes-specific characteristics of platelets and antiplatelet therapy are attributable to obese patients.
Endothelial dysfunction is considered to be a key element in the development of atherosclerosis and has also been closely associated with obesity/insulin resistance [9,10]. Endothelial dysfunction is defined as the partial or complete loss of balance between vasoconstrictors (endothelin, angiotensin II) and vasodilators [nitric oxide (NO), prostacyclin], growth promoting and inhibiting factors, proatherogenic and anti-atherogenic factors, and procoagulant and anticoagulant factors . The reduced production of NO from L-arginine by NO synthase is remarkable in the stetting of insulin resistance and is a clear marker in diabetes. Cyclic nucleotides are the main effectors of platelet antiaggregation, the platelet hyperactivity can be attributed to the resistance to these vasodilating agents.
Impaired fibrinolysis and enhanced coagulation contribute to the hemotactic disorders in obesity. Plasminogen activator inhibitor-1 (PAI-1) is typically increased in the obesity/insulin-resistance state and plays an important role in the genesis of vascular abnormalities. PAI levels are strongly correlated with BMI and fasting plasma insulin levels in Type 2 diabetes and also with triglyceride levels in non-diabetic obese patients. PAI-I levels decrease and fibrinolytic activity improves when insulin resistance and hyperinsulinemia are reduced by weight loss [12–16].
Platelets and antiplatelet therapy
The physiological function of platelets is to plug local damage within the blood vessel. In pathological conditions, such as atherosclerosis, arterial thrombus formation may limit local blood supply, causing local ischemia and the progression of atherosclerosis.
Antiplatelet drugs are divided into four classes:
- 1Inhibition of thromboxane production by acetylsalicylic acid (aspirin). By decreasing the synthesis of thromboxane A2 aspirin administered at a useful dosage of 70–100 mg represents the antiplatelet drug of choice for prevention of vascular complications [17–19]. Obese insulin-resistant non-diabetic patients, however, have a blunted response to the platelet inhibitory effect of acetylsalicylic acid .
- 2Blockage of the ADP receptor by ticlopidine and clopidogrel. Thienopyridine antiplatelet agents prevent the activation of the GPIIb/IIIa receptor and the subsequent binding of fibrinogen. In the corresponding study analysing the effects of ticlopidine the progression of overall retinopathy was significantly less severe in the ticlopidine group due to its antithrombotic action . The CAPRIE study revealed that clopidogrel (75 mg daily) was more effective than aspirin (325 mg daily) in reducing the elevated risk for recurrent ischemic events in diabetic patients with a history of diabetes .
- 3Antagonists of the GP IIb/IIIa fibrinogen receptor. RGD-analogs and monoclonal antibodies to GP IIb/IIIa such as abciximab inhibit platelet aggregation by preventing the binding of von Willebrand factor, fibrinogen and adhesive molecules to the GP IIb/IIIa receptor. Treatment with abciximab reduced the number of deaths and myocardial infarctions as well as the number of emergency revascularization procedures in both diabetic and non-diabetic patients [23–24].
- 4Inhibition of platelet cyclic AMP breakdown by phosphodiesterase inhibitors. Dipyridamole inhibits phosphodiesterase and thus raises platelet cyclic AMP levels. It potentiates the platelet inhibitory action of prostacyclin and stimulates prostacyclin synthesis .
Clinical circumstances with a known association with higher levels of prolactin and leptin such as pregnancy or obesity show an elevated risk of thromboembolic events . Prolactin as well as leptin have been identified as co-activators of ADP-dependent platelet aggregation or P-selectin expression . Therefore, they are suspected of being additional risk factors for both arterial and venous thrombosis. Wallaschofski and coworkers were able to show that prolactin has a stronger effect on platelet activation than leptin in vitro and in vivo. They speculate that the stronger effect of prolactin on ADP-stimulated platelet aggregation, compared with leptin, depends on higher stimulation of CD62p expression by prolactin and that hormonal factors in platelet aggregation and venous or arterial thrombosis should be considered for risk stratification of patients with venous and arterial thrombosis [28,29].
Platelet aggregation plays an essential role in thrombus formation, therefore treatment strategies using antiplatelet agents to prevent subsequent ischemic events are developed. Hormonal aspects should be considered in future. Low-dose enteric-coated aspirin therapy is recommend by the American Diabetes Association as a primary prevention strategy for diabetic people with high risk for cardiovascular events. Also, obese patients benefit from antiplatelet therapy, besides weight loss.
- 23Long-term protection from myocardial ischemic events in a randomized trial of brief integrin beta3 blockade with percutaneous coronary intervention. EPIC Investigator Group. Evaluation of Platelet IIb/IIIa Inhibition for Prevention of Ischemic Complication. JAMA 1997; 278: 479–84.DOI: 10.1001/jama.278.6.479, , , , , , , , , , .
- 24Sustained suppression of ischemic complications of coronary intervention by platelet GP IIb/IIIa blockade with abciximab: one-year outcome in the EPILOG trial. Evaluation in PTCA to Improve Long-term Outcome with abciximab GP IIb/IIIa blockade. Circulation 1999; 99: 1951–8., , , , , , , , , , , , .