Already nearing development are longitudinal studies that highlight how these metabolic output encoders can predict downstream pathology: in Alzheimer’s cohorts, ratios of specific serum bile acid ratios were linked to tau accumulation and cognitive declines 2 years later, and in the Parkinson’s prodrome, the loss of SCFA taxa preceded motor or symptom development [31]. The gene discussed is MAPT; the disease is Parkinsonism.