In the literature, it has been reported that reduced concentrations of butyrate-producing bacteria in patients with BD may reduce GLP-1 secretion, and GLP-1 receptors are expressed in brain regions responsible for the regulation of mood and cognition, such as the cerebral cortex, hypothalamus (arcuate nucleus and ventromedial nucleus), and limbic system (amygdala and hippocampus) [38,44]. This evidence concerns the gene GCG and Behcet disease.