nonshivering thermogenesis

Nonshivering thermogenesis is a biological process where specialized tissue generates heat without muscle contraction. This is crucial for mammals, especially newborns and hibernating animals, to prevent hypothermia.1

Brown adipose tissue (BAT), or brown fat, is key to this process. It contains mitochondria that produce heat by uncoupling electron transport from ATP production, a mechanism facilitated by a protein called thermogenin (UCP1). Newborns have significant BAT in their necks and backs to help maintain body temperature, as they have a larger surface area-to-volume ratio and less insulating white adipose tissue than adults.1

In response to cold, hormones like TSH and epinephrine activate BAT. This process is more efficient in brown fat cells due to their higher number of mitochondria and thermogenin. While BAT is prominent in infants, it can transform into white adipose tissue during development, though precursors may remain in adults. Hibernating animals also utilize nonshivering thermogenesis, stimulated by factors like reduced daylight and cold.1