NON-ALCOHOLIC FATTY LIVER DISEASE (NAFLD) IS THE LEADING CAUSE OF LIVER DISEASE IN ADOLESCENTS AND ADULTS IN THE US AND WORLD, AND ITS RISK HAS INCREASED WITH THE RISE OF OBESITY. USING THE OBESE ZUCKER RAT MODEL, WE PREVIOUSLY REPORTED THAT CONSUMPTION OF SOY PROTEIN DIET REDUCED FATTY LIVER. WE HYPOTHESIZE THAT A SOY PROTEIN DIET WITH HIGH ISOFLAVONE CONTENT COMPARED TO A SOY PROTEIN DIET WITH LOWISOFLAVONE CONTENT WILL 1) REDUCE DEVELOPMENT OF OBESITY-RELATED NAFLD IN YOUNG (ADOLESCENT MODEL) AND ADULT OBESE ZUCKER RATS IN PART BY ALTERING GUT MICROBIOTA AND 2) REVERSE DAMAGE TO LIVER CELLS IN OBESE ZUCKER RATS WITH ESTABLISHED NAFLD IN PART THROUGH GUT MICROBIOTA ALTERATIONS. THE PROPOSAL FOCUSES ON 1) INVESTIGATING THE ROLE OF SOY DIETS AND GUT MICROBIOTA ON PROTECTION FROM NAFLD IN ADOLESCENT AND ADULT RAT MODELS, 2) DETERMINING FOR THE FIRST TIME IF SOY DIETS AND GUTBACTERIAALTERATIONS CAN REVERSE OBESITY-RELATED NAFLD IN THESE MODELS, AND 3) DETERMINING THE EFFECTS OF SOY PROTEIN DIET ON LIVER DAMAGE AND INFLAMMATION MARKERS IN THESE MODELS. WE WILL USE STATE-OF-THE-ART METAGENOMICS AND METAPROTEOMICS TO IDENTIFY THE POPULATION OF GUT MICROORGANISMS AS WELL AS THE FUNCTIONAL BACTERIAL PROTEINS PRESENT. ANALYSIS OF THE MICROBIOTA WILL GENERATE NOVEL DATA ON THE INTERACTION OF OBESITY, SOY PROTEIN DIETS, AND INTESTINAL MICROBIOTA, AND THE POSSIBLE LINK TO PROTECTION FROM NAFLD.