Body weight changes and bipolar disorder: a molecular pathway analysis.

Background: There is evidence suggesting a link between weight-related disorders and bipolar disorder (BD). The pathophysiology of the association includes psychological, social and psychotropic treatment-related variables, together with psychiatric comorbidity. Weight changes during BD may influence compliance to the treatment, quality of life and prognosis, and can modulate risk of death associated with, for example, diabetes or cardiovascular disorders.

Methods: The STEP-BD sample is analyzed through a hypothesis-free molecular pathway analysis in order to detect the molecular pathways that distinguish individuals who experience weight change during BD treatment from those who do not. A total of 618 individuals were available for the analysis, mean age = 41.19 ± 12.58, females = 351 (56.8%). Socioeconomic variables and treatment-related variables were included as clinical covariates. A cluster analysis in the genetic dataset provided the genetic covariate input to the study to avoid stratification factors.

Result: After applying the quality analysis that is typical for this kind of investigation, no Genome Wide Association Study significant finding was retrieved. Six molecular pathways were found to be significantly associated with weight change during the first 3 months of treatment after correction for multiple testing. Of those, CDC42 (R-HSA-9013148) participates in insulin synthesis and secretion and contributes to the pathogenesis of insulin resistance and Rac Family Small GTPase 1 (R-HSA-9013149) is involved in metabolic regulation of pancreatic islet β-cells and in diabetes pathophysiology.

Discussion: Pathways that are central in energy homeostasis may play a role to separate individuals with BD that will experience weight changes during treatment from those who will not. If confirmed, such finding can be instrumental in the identification of the correct preventive strategies and most correct treatment to increase compliance and efficacy in the treatment of BD.