Phenotyping small animals as models for the human metabolic syndrome: thermoneutrality matters.

It is standard practice in preclinical biomedical research to house mammalian model organisms at an ambient temperature substantially below the thermoneutral zone. These experimental studies are performed using animals that are chronically challenged by mild cold stress. This condition increases food intake, metabolic rate, sympathetic activity, blood pressure and heart rate. Furthermore, this condition alters the behavioral and physiological responses to drug administration, energy restriction and overfeeding. This paper will review these observations, which must be understood in the context of phenotyping small mammals to enhance our understanding of the biology of human disease.