Humanized diet and thermoneutral housing enable sex-aware dissection of the MASLD-T2D-CVD triad

Metabolic dysfunction-associated steatotic liver disease (MASLD), type 2 diabetes (T2D), and cardiovascular disease (CVD) constitute a tightly interconnected axis that drives global cardiometabolic mortality. Yet their causal and temporal relationships remain difficult to disentangle. Here, we introduce a humanized mouse platform that integrates a fast-food mimicking diet (FFMD), thermoneutral housing, and genetic diversity within a sex-aware framework to resolve the hierarchy between MASLD, T2D, and CVD. FFMD feeding increases liver weight fourfold and rapidly induces severe, fully penetrant steatohepatitis (MASH) and marked hyperinsulinemia in wild-type mice, outperforming standard Western diets. Despite comparable body weight, liver fat, and liver enzymes, weight-matched diabetic db/db mice, develop MASH in only 27% of cases, compared to 100% in FFMD-fed wild-type mice, thereby uncoupling advanced liver disease from overt diabetes. Longitudinal and crossover studies in CVD-prone mice further reveal that ambient temperature dictates the transition from early MASLD to cirrhosis and aortic mineralization, implicating MASH - rather than T2D - as the main driver of advanced cardiohepatic injury. Together, this model positions ambient temperature as a tunable determinant of disease progression and provides a translational platform to interrogate and therapeutically target the MASLD-T2D-CVD triad.