Homocysteine imbalance: a pathological metabolic marker.

Perturbations in methyl group metabolism and homocysteine balance have emerged over the past few decades as having defining roles in a number of pathological conditions. Numerous nutritional, hormonal, and genetic factors that are characterized by elevations in circulating homocysteine concentrations are also associated with specific pathological conditions, including cancer development, autoimmune diseases, vascular dysfunction, and neurodegenerative disease. Although much remains to be explored, our understanding of the relationship between disease, methyl balance, and epigenetic control of gene expression has steadily progressed. However, homocysteine balance and its role in health and disease are not as clearly understood. This review presents our current understanding of homocysteine metabolism and its link to specific pathologies.