Decreased serum activity of semicarbazide-sensitive amine oxidase (SSAO) in patients treated with second generation antipsychotics: a link to impaired glucose metabolism?

Objective: Although the treatment of schizophrenia with many second generation antipsychotics is known to be associated with metabolic changes, such as hyperglycemia or hypercholesterolemia, the underlying mechanisms of these adverse reactions remain unclear. In light of the recent focus on the involvement of semicarbazide-sensitive amine oxidase (SSAO) in glucose metabolism, we investigated SSAO serum activity in schizophrenic patients treated with antipsychotics with the objective of determining a possible link between SSAO and impaired glucose metabolism.

Methods: Blood samples were drawn from 44 schizophrenic patients (24 receiving second generation antipsychotics known to disturb glucose metabolism) on day 1 and day 5 of inpatient treatment. Forty-one healthy adults with no medical condition known to influence SSAO served as controls.

Results: Of the 44 schizophrenic patients, the 24 treated with second generation antipsychotics known to disturb glucose metabolism showed significantly lower SSAO serum activity [day 1 (mean +/- SD): 477 +/- 105 mU/L; day 5: 438 +/- 86 mU/L] than the 20 patients treated with other antipsychotics not known to influence glucose metabolism (day 1: 513 +/- 124 mU/L, p = 0.359; day 5: 542 +/- 204 mU/L, p = 0.021) only after 5 days of treatment and compared to healthy controls (526 +/- 142 mU/L, p = 0.021). No differences were observed between schizophrenic patients treated with first generation antipsychotics and the controls.

Conclusion: We found decreased SSAO serum activity exclusively in schizophrenic patients treated with second generation antipsychotics known to disturb glucose metabolism. In terms of the role of SSAO in glucose metabolism, the observed decrease in SSAO serum activity may be linked to metabolic changes that are known to occur in schizophrenic patients being treated with many second generation antipsychotics.