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Antipsychotic-induced weight gain (AIWG) is a common adverse event in schizophrenia. Genome-wide association studies (GWAS) and polygenic risk scores (PRS) for other diseases or traits are recent approaches to disentangling the genetic architecture of AIWG. 200 patients with schizophrenia treated monotherapeutically with antipsychotics were included in this study. A multiple linear regression analysis with ten-fold crossvalidation was performed to predict the percentage weight change after five weeks of treatment. Independent variables were sex, age, body mass index (BMI) at baseline, medication-associated risk, and PRSs (BMI, schizophrenia, diabetes, and metabolic syndrome). An explorative GWAS analysis was performed on the same subjects and traits. PRSs for BMI (β = 3.78; p = 0.0041), schizophrenia (β = 5.38; p = 0.021) and diabetes type 2 (β = 13.4; p = 0.046) were significantly associated with AIWG. Other significant factors were sex, baseline BMI and medication. Compared to the model without genetic factors, the addition of PRSs for BMI, schizophrenia, and diabetes type 2 increased the goodness of fit by 6.5 %. The GWAS identified the association of three variants (rs10668573, rs10249381 and rs1988834) with AIWG at a genome-wide level of p < 1 · 10 -6 . Using PRS for schizophrenia, BMI, and diabetes type 2 increased the explained variation of predicted weight gain, compared to a model without PRSs. For more precise results, PRSs derived from other traits (ideally AIWG) should be investigated. Potential risk variants identified in our GWAS need to be further investigated and replicated in independent samples., Competing Interests: Declaration of competing interest SP was supported by the European Union's Horizon Europe research and innovation programme (Psych-STRATA, grant agreement No 101057454). UH was supported by the European Union's Horizon 2020 research and innovation programme (PSY-PGx, grant agreement No 945151) outside the submitted work. MF, MSS, BBB, CG, IS, MR, PZ, TGS, RM declare no conflicts of interest., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The HOMER 1 protein plays a crucial role in mediating glutamatergic neurotransmission. It has previously shown to be a candidate gene for etiology and pathophysiology of different psychiatric diseases such as schizophrenia. To identify genes involved in response to antipsychotics, subgroups of animals were treated with haloperidol (1 mg/kg, n = 11) or saline (n = 12) for one week. By analyzing microarray data, we replicated the observed increase of Homer 1 gene expression. Furthermore, we genotyped 267 schizophrenic patients, who were treated monotherapeutically with different antipsychotics within randomized-controlled trials. Psychopathology was measured weekly using the PANSS for a minimum of four and a maximum of twelve weeks. Correlations between PANSS subscale scores at baseline and PANSS improvement scores after four weeks of treatment and genotypes were calculated by using a linear model for all investigated SNP's. We found an association between two HOMER 1 polymorphisms (rs2290639 and rs4704560) and different PANSS subscales at baseline. Furthermore all seven investigated polymorphisms were found to be associated with therapy response in terms of a significant correlation with different PANSS improvement subscores after four weeks of antipsychotic treatment. Most significant associations have been shown between the rs2290639 HOMER 1 polymorphism and PANSS subscales both at baseline conditions and after four weeks of antipsychotic treatment. This is the first study which shows an association between HOMER 1 polymorphisms and psychopathology data at baseline and therapy response in a clinical sample of schizophrenic patients. Thus, these data might further help in detecting differential therapy response in individuals with schizophrenia., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Drug induced weight gain is a serious side effect of several atypical antipsychotics. As genetic factors play an important role in the homeostasis of hunger/satiety we tried to replicate a preliminary previous finding about an impact of three polymorphisms in the synaptosomal-associated protein of 25kDa (SNAP-25; sites MnlI, TaiI and DdelI in the 3(')-UTR) on clinical response and antipsychotic induced weight gain. We genotyped 162 schizophrenic patients being treated in monotherapy with atypical antipsychotics and 312 healthy control subjects for the three polymorphisms in the SNAP-25 gene using PCR. PANSS scores and weight were measured weekly for a minimum of five weeks. We found significant associations between the TaiI and MnlI polymorphisms and serum triglyceride levels at baseline and for the DdelI polymorphism and weight gain. In conclusion our study can at least partly replicate the previous findings concerning the impact of SNAP-25 gene polymorphisms on weight gain during antipsychotic treatment.