<P> BAT is especially abundant in newborns and in hibernating mammals . It is also present and metabolically active in adult humans, but its prevalence decreases as humans age . Its primary function is thermoregulation . In addition to heat produced by shivering muscle, BAT produces heat by non-shivering thermogenesis . </P> <P> In contrast to white adipocytes, which contain a single lipid droplet, brown adipocytes contain numerous smaller droplets and a much higher number of (iron - containing) mitochondria, which gives BAT its brown appearance . Brown fat also contains more capillaries than white fat, to supply the tissue with oxygen and nutrients and distribute the produced heat throughout the body . </P> <P> The presence of BAT in adult humans was discovered during FDG - PET scans to detect metastatic cancers . Using these scans and data from human autopsies, several BAT depots have been identified . In infants, BAT depots include, but are not limited to: interscapular, supraclavicular, suprarenal, pericardial, para-aortic and around the pancreas, kidney and trachea . These depots gradually get more white fat - like during adulthood . In adults, the depots that are most often detected in FDG - PET scans are the supraclavicular, paravertebral, mediastinal, para-aortic and suprarenal ones . It remains to be determined whether these depots are' classical' BAT or beige / brite fat . </P> <P> Brown fat in humans in the scientific and popular literature refers to two cell populations defined by both anatomical location and cellular morphology . Both share presence of small lipid droplets and numerous iron - rich mitochondria, giving the brown appearance . </P>

Which of the following is known to promote fat storage in adipocytes