Monoamine oxidase activity (MAO) has been related to neuronal damage,
since the oxidative deamination of biogenic amines produces free
radicals that may enhance oxidative stress. Elevated enzyme activities
in brain (MAO-A and MAO-B forms) and in platelets (MAO-B form) have been
reported in several degenerative diseases, indicating that MAO activity
may be involved in the disease progression. We estimated platelet MAO
activity in a group of 59 patients (34 males) with HD, 20 subjects (7
males) at risk, and 29 (14 males) healthy subjects with positive family
history for HD, categorized according to clinical features and the
number of CAG repeat units (CAG-RN) at the Huntington gene. A group of
64 subjects (36 males) with negative family history for HD served as
controls. In contrast to some previous studies, platelet MAO activities
in both male and female patients (CAG-RN 40 to 62) with overt
symptomatology, were not different compared to same sex control
subjects. Subjects at risk (CAG-RN 39 to 52), though, showed
significantly lower activities compared to same sex patients or
controls. MAO activities seem to increase with disease progression, and
tend to be higher in patients with dementia. The increases may be an
epiphenomenon of disease pathology, but the possibility that an increase
in the expression of the enzyme precedes the onset of the disease and
contributes to enhanced oxidative stress should be considered in future
longitudinal studies as a possible mechanism that accelerates disease
progression
