Fig. 3From: Cross-talks between gut microbiota and tobacco smoking: a two-sample Mendelian randomization studyThe summary of the key findings in the multivariable MR study. Combining with existing evidence and biological mechanisms, we consistently found that tryptophan, tyrosine, and/or valerate may take part in the action pathways from a Peptococcus and b Actinobacteria to smoking. Black solid arrows indicate known evidence, black dashed arrows indicate biological hypothesis we introduced earlier, and red dashed arrow indicates potentially deducible conclusion. The bold dashed boxes are neurotransmitters that are closely related to corresponding metabolites and are likely involved in the mechanism by which smoking responds to the gut microbiota in a metabolite-dependent mannerBack to article page