Platelet monoamine oxidase activity and plasma levels of non-catecholic phenylethylamines in insulin-dependent diabetic subjects.

The activity of blood platelets monoamine oxidase (MAO) was significantly reduced in a group of insulin-dependent diabetics when compared to sex- and age-matched controls. This enzymatic change was accompanied by a dramatic increase in the plasma levels of phenylethylamine, whereas no significant changes were observed for the concentration of either p-tyramine or phenylethanolamine. Levels of the o- and m-isomers of tyramine were below detectable limits (less than 0.050 ng/ml). A possible role of the MAO/monoamine system in the pathophysiology of diabetes is discussed.