1. Department of Internal Medicine, Medical School, University of Ioannina, Ioannina, Greece
2. Laboratory of Physiology, Medical School, University of Ioannina, Ioannina, Greece
3. Laboratory of Biochemistry, Department of Chemistry, University of Ioannina, Ioannina, Greece
4. Department of Clinical Biochemistry, Royal Free Campus, University College London (UCL), London, UK