Associations between platelet monoamine oxidase-B activity and acquired colour vision loss in a fish-eating population

Platelet monoamine oxidase-B (MAO-B) has been considered a surrogate biochemical marker of neurotoxicity, as it may reflect changes in the monoaminergic system in the brain. Colour vision discrimination, in part a dopamine dependent process, has been used to identify early neurological effects of some environmental and industrial neurotoxicants. The objective of this cross-sectional study was to explore the relationship between platelet MAO-B activity and acquired colour discrimination capacity in fish-consumers from the St. Lawrence River region of Canada. Assessment of acquired dyschromatopsia was determined using the Lanthony D-15 desaturated panel test. Participants classified with dyschromatopsia (n = 81) had significantly lower MAO-B activity when compared to those with normal colour vision (n = 32) (26.5 ± 9.6 versus 31.0 ± 9.9 nmol/min/20 μg, P = 0.030)). Similarly, Bowman's Colour Confusion Index (CCI) was inversely correlated with MAO-B activity when the vision test was performed with the worst eye only (r = − 0.245, P = 0.009), the best eye only (r = − 0.188, P = 0.048) and with both eyes together (r = − 0.309, P = 0.001). Associations remained significant after adjustment for age and gender when both eyes (P = 0.003) and the worst eye (P = 0.045) were tested. Adjustment for heavy smoking weakened the association between MAO-B and CCI in the worst eye (P = 0.140), but did not alter this association for both eyes (P = 0.006). Adjustment for blood-mercury concentrations did not change the association. This study suggests a relationship between reduced MAO-B activity and acquired colour vision loss and both are associated with tobacco smoking. Therefore, results show that platelet MAO-B may be used as a surrogate biochemical marker of acquired colour vision loss.