Elevated plasma level of apolipoprotein D in schizophrenia and its treatment and outcome

Recently, apolipoprotein D (apoD), a protein that is involved in the essential polyunsaturated fatty acid (EPUFA) transport and metabolism, and neuronal growth and regeneration was reported to have increased in the postmortem brain and decreased in the serum of schizophrenia patients. We studied the plasma apoD levels in never-medicated schizophrenic patients at the onset of psychosis and in chronic patients with clozapine treatment. Plasma apoD levels were elevated in never-medicated patients at the first-episode of psychosis compared to normals (P = 0.047). Interestingly, the increase in apoD level was even more significant in chronic patients treated with clozapine compared to normals and first-episode patients (P = 0.008 and P = 0.03, respectively). The increased apoD level in never-medicated first-episode patients indicate that this increase probably predates the illness, since the duration of illness was < 5 days. Similarly, an even larger increase in apoD after clozapine treatment may be associated with its prophylactic effects, since the psychopathological scores were significantly reduced and the clozapine treatment has been found to increase the EPUFA membrane levels. These altered levels of apoD may help to understand the nature and possible mechanism of phospholipid membrane pathology in schizophrenia.