While conducting a systematic review to identify proteins and metabolites associated with three different diseases, I am planning to build networks to investigate interactions among these proteins/metabolites. I intend to use BioGRID to expand the networks. My question is: should I create separate networks for the genes of each disease and then integrate them, or can I build a single network including all genes found in the three diseases? What would be the best approach when constructing networks from data collected from other studies?