High density lipoprotein subclasses inhibit low density lipoprotein oxidation.

It has been reported earlier that high density lipoprotein (HDL) is a scavenger of superoxide anions, hydroxyl radicals (OH-) and behaves like superoxide dismutase. In the present investigation, we have studied the effect of HDL subclasses: HDL2 and HDL3 on non enzymatically induced oxidation of low density lipoprotein (LDL) by Fe2+ and sodium ascorbate. Both HDL2 and HDL3 showed protection against the oxidative degradation of LDL-lipids, measured as thiobarbituric acid reactive substance, lipid hydroperoxide and conjugated diene. Oxidized LDL was more electronegative, as evidenced by the increase in relative electrophoretic mobility(REM) on agarose gel. HDL3 significantly protected LDL apoprotein as assessed by reversal of REM after oxidation. HDL2 and HDL3 significantly inhibited the generation of OH- in nonenzymic systems in vitro. However, HDL2 was more active against enzymic formation of OH- as compared to HDL3. Alpha-tocopherol could protect LDL lipids and apoprotein components by Fe2+ mediated oxidation but the effects were lower than HDL subclasses. Our findings suggest that HDL subclasses, the potent scavenger of oxygen derived free radicals, play an important role to prevent the oxidative modifications in LDL.

Iron deficiency anemia and catecholamine metabolism.

To assess the effects of iron therapy on platelet monoamine oxidase (MAO) activity and urinary excretion of total metanephrines (MN) in infants and young children with iron deficiency anemia, 24 subjects were tested before and after one month of oral iron treatment. Thirteen healthy children comprised the control group. In the control group, platelet MAO level was 0.21 +/- 0.02 U/mg protein (mean +/- SE), urinary total metanephrine was 2.51 +/- 0.47 micrograms/mg creatinine. In cases with iron deficiency, mean platelet MAO level was 47.6% lower (p less than 0.005) whereas mean urinary metanephrine plus normetanephrine (MN-NMN) was only 20.7% lower (p greater than 0.05) than the control values. After one month, the anemic patients receiving oral iron therapy showed a significant increase in hemoglobin concentration, per cent transferrin saturation and platelet MAO activity (p less than 0.05). However, urinary metanephrine excretion was found to be lower in this group when compared to the metanephrine levels in iron deficiency before the medication (p less than 0.05). Although hemoglobin and transferrin saturation did not return to normal levels, these findings suggested that platelet MAO activity increased and urinary excretion of metanephrines decreased after iron medication.