IL18 and metabolic disease: To verify these hypotheses, we analyzed the role of IL-18 in the regulation of lipid concentration and cell growth in BAs and BAT as follows: (i) histopathological examination of BAs and BAT from Il18+/+ and Il18−/− mice; (ii) analysis of primary cell cultures was performed in vitro, and thermogenic and adipogenic genes were compared; (iii) we analyzed the molecular mechanisms affected during metabolic diseases; and (iv) we assessed the lipid-normalizing effect of recombinant IL-18 (rIL-18).