Differences in short-chain fatty acids (SCFs) such as propionate, butyrate, acetate and isovaleric acid, tryptophan metabolism, neurotrophins, and synthesis/degradation of neurotransmitters such as GABA, glutamate, and nitric oxide are known as schizophrenia-associated GBMs [134]. The gene discussed is BDNF; the disease is schizophrenia.