Oxidative Stress Is Increased in Chronic Idiopathic Myelofibrosis (CIMF) Patients, and Is Associated with High Levels of Homocysteine (Hcy) and Depletion of Holotranscobalamin (holoTC).

Abstract

In patients with myeloproliferative disorders, the increased cellular turnover may lead to hyperhomocysteinemia (HH), caused by depletion of folate and/or cobalamin (VitB12). HH represents a cause of oxidative stress, associated with a number of diseases, among which cardiovascular events play an important role. Recently, holoTC, that consist of VitB12 linked to its transport molecule, transcobalamin, has been proposed as a more reliable marker than the dosage of total serum VitB12 to detect the deficiency of this vitamin.The aim of the study was to investigate the clinical role of oxidative stress in CIMF. We performed in 67 CIMF patients (M/F: 38/29; median age 63, range 34–79), the dosage of reactive oxygen species (ROS), total antioxidant capacity (TAC), Hcy, VitB12, folates and holoTC, and correlated the results with the following clinical variables: age, sex, cytogenetics, white blood cells and platelets counts, hemoglobin and LDH levels, splenomegaly and hepatomegaly, hypertension, diabetes, smoking habit, cardiovascular events, secondary tumors, and presence of blasts in peripheral blood. Serum concentrations of VitB12, folates and holoTC were determined by AxSYM B12 or Folate microparticle enzyme immunoassay (MEIA) and new Axis-Shield HoloTC MEIA, respectively; plasma Hcy levels were measured by fluorescence polarization immunoassay (FPIA). All the panel was performed on the Abbott AxSYM analyser. CIMF patients presented increased oxidative stress (lower levels of TAC and higher levels of ROS), compared to a panel of 53 healthy volunteers (Mann Whitney U test, p<0.0001). Higher values of Hcy were detected in the group of CIMF presenting holoTC deficiency (Mann Whitney U test, p=0.03). Consistently, holoTC directly correlated with TAC (Spearman correlation, p=0.01). Interestingly, levels of holoTC and TAC were significantly lower in the group of CIMF patients with blasts in the peripheral blood (Mann Whitney U test, p=0.01 and p=0.009, respectively). Notably, levels of VitB12 and folates did not correlate with Hcy, holoTC, TAC or ROS. No correlations were found between the levels of Hcy, holoTC, TAC, ROS, VitB12 or folates and the remaining clinical variables considered. In conclusion, we demonstrated that CIMF patients present an increase in oxidative stress compared to healthy controls. We observed that holoTC depletion is associated to HH and reduced TAC, consistently with an increased oxidative potential. These findings indicate the presence of a clinically significant VitB12 deficiency, detectable only by holoTC dosage, in the presence of normal levels of total serum VitB12. The other interesting finding is the association of holoTC and TAC deficiency with the presence of blasts in the peripheral blood of the patients, suggesting a role of oxidative damage in CIMF progression. Therefore, our findings suggest that, in CIMF patients, the dosage of ROS, TAC, holoTC, and Hcy, may represent a valuable clinical aid in the diagnosis of unapparent VitB12 deficiency, and provide a rational basis to prevent and/or correct the increase in oxidative potential associated with this disease.