Is Homocysteine a Marker or a Risk Factor: A Question Still Waits for an Answer

Abstract

Homocysteine, a non-proteinogenic sulfur-containing amino acid, was discovered in 1932, and 30 years passed until, in 1969, for the first time, its involvement in pathology was reported. It was only in the last two decades that homocysteine has become a subject of scientific interest and has begun to be intensively studied. A large number of scien tists consider homocysteine as an independent risk factor particularly for cardiovascular disease, while others indicate homocysteine as a marker of this disease. Both sides bring scientific arguments for their opinions, yet the dilemma of homocysteine characterization still persists. Although the reported studies do not lead to a unique answer, it is generally accepted that homocysteine is associated with vascular dysfunction. Numerous scien- tific data show that the link between homocysteine and inflammation is achieved via the reactive oxygen species (ROS) pathway. The latest data indicate hydrogen peroxide as a possible messenger in cellular signaling in physiological or pathological processes and present the consequences of disturbing the oxidation-reducing balance . In this chapter, we present the latest scientific evidences gathered from the literature for both hypotheses regarding homocysteine involvement in pathology, and we propose a possible mecha- nism of action for homocysteine, based on our preliminary (yet unpublished) work. to the activity of reactive species, and recent data indicate protein-tyrosine phosphatases as key factors in regulating intracellular signaling pathways. These proteins allow regulation because they can undergo reversible oxidation phenomena due to the presence in their structure of cysteine residues bearing SH groups. The structural similarity of Cys with homocysteine draws attention to the possibility that Hcy may interfere with cysteine functions. In conclu sion, the recent association of Hcy with both inflammation and the reactive species involved in cellular signaling indicates that homocysteine remains a topic of interest and attention in current research. It is obvious that HHcy is an issue of interest in contemporary medicine.