Certain fat cells can switch on heat-generating pathways directly, without being prompted by the nervous system.

Known for its ability to convert chemical energy to heat, brown fat warms up when cold-sensing neural circuits release the neurotransmitter noradrenaline. Without β-adrenergic receptors to sense these signals, the response of brown fat to the cold is limited.

A team led by Bruce Spiegelman at the Dana–Farber Cancer Institute in Boston, Massachusetts, found that other types of fat cell can activate genes to boost heat production in chilly environments — even if they lack β-adrenergic receptors. When exposed to temperatures 33 °C or below, these white and beige fat cells sharply increased their expression of two thermogenesis genes within a matter of hours.

A large part of cold-induced heat production from fat could come from subcutaneous fat tissue that senses temperature directly, the authors say.

Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1310261110 (2013)