Plasma levels of catecholamine metabolites and serum levels of brain-derived neurotorophic factor in smokers with schizophrenia treated with varenicline: A pilot study

Objective: The present study sought to determine changes in plasma levels of catecholamine metabolites and serum levels of brain-derived neurotorophic factor (BDNF) among smokers with schizophrenia who were treated with varenicline. Methods: We compared plasma homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) levels and serum BDNF levels across 4 groups, divided as follows: smokers with schizophrenia (S-Sc), nonsmokers with schizophrenia (NS-Sc), smokers who were otherwise healthy (S-HC) and nonsmokers who were otherwise healthy (NS-HC). In addition, we also examined plasma HVA and MHPG levels and serum BDNF levels prior to study initiation (T0) and 8 weeks after varenicline treatment (T8) in the S-Sc and S-HC groups. Results: Plasma HVA levels in the S-Sc group at T0 were significantly higher than in the NS-Sc, S-HC and NS-HC groups at the same time point (S-Sc at T0; 7.6 ± 1.6 ng/mL, NS-Sc; 4.8 ± 1.0 ng/mL, S-HC; 4.3 ± 0.9 ng/mL, NS-HC; 3.4 ± 1.4 ng/mL, p < 0.0001). Plasma MHPG levels in the S-Sc group at T0 were significantly higher than in the NS-Sc and S-HC groups; in addition, plasma MHPG levels in the NS-HC group were significantly higher than in the S-HC group (S-Sc at T0; 5.2 ± 0.7 ng/mL, NS-Sc; 2.8 ± 1.2 ng/mL, S-HC; 1.9 ± 0.8 ng/mL, NS-HC; 3.6 ± 1.3 ng/mL, p < 0.0002). Serum BDNF levels did not differ between the S-Sc and NS-Sc groups. In contrast, no difference in plasma HVA levels, plasma MHPG levels or serum BDNF levels was observed between T0 and T8. Conclusions: In conclusion, plasma levels of HVA and MHPG in the S-Sc group were significantly higher than in the NS-Sc group. Serum BDNF levels did not differ between the S-Sc and NS-Sc groups. Plasma HVA and MHPG levels and serum BDNF levels did not change after treatment with varenicline.