S. Khazaipoul, Kondwani G H Katundu, Claudia A. Blindauer
Apr 1, 2018
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Cardiovascular Research
Abstract
Funding Acknowledgements: British Heart Foundation Background/Introduction: Zinc ions are a key regulator of haemostasis. The concentration of labile zinc in plasma is tightly regulated through binding to human serum albumin (HSA). The zinc binding capacity of HSA is altered in disease conditions such as diabetes, obesity and cancer, which are associated with increased plasma free fatty acid (FFA) levels. FFAs can allosterically disrupt binding of zinc to HSA. Chronic elevation of fatty acids is associated with the development of thrombotic complications. Purpose: The aim of this study was to explore how FFAs influence Zn2þ binding characteristic of albumin and to explore how this dynamic may influence blood clotting Methods: Isothermal titration calorimetry (ITC) was used to examine zinc-binding to HSA and bovine serum albumin (BSA) in the presence of different concentrations of fatty acid (myristic acid: C14:0). In addition platelet aggregation assays were carried out on platelet rich plasma (PRP) prepared from the blood sample taken from healthy individuals in the presence of different zinc and/or myristic acid concentrations, where aggregation was initiated by the addition of thrombin. Results: The ITC data showed that 1 molecular equivalent (mol. eq.) of myristic acid was sufficient to significantly affect zinc binding to albumin. Addition of 4-5 mol. eq. of myristic acid had a dramatic effect on Zn2þ binding to both BSA and HSA. Measurement of thrombin-mediated platelet aggregation parameters in PRP revealed dose-dependent increases both in maximum aggregation and rate of aggregation in the presence of zinc. Addition of 20 mM zinc increased maximum aggregation by 1.1-fold and the rate of aggregation by 3-fold. Furthermore, maximum aggregation was greatly exacerbated in the presence of 20 lM zinc upon addition of myristic acid (4 mol. eq.), where maximum aggregation was increased by 4-fold. Conclusions: The results support the concept that elevated levels of FFAs, as associated with certain disease states impact upon haemostasis through modulation of plasma zinc dynamics. This mechanism, is likely to contribute to the development of thrombotic complications in these individuals.