brown adipose tissue

Introduction

Anatomy:

• thermogenic adipose tissue found in interscapular regions, the mediastinum & other regions
• in human adults, the largest depot of brown fat is stored above the clavicles

Physiology

• it is most abundant in hibernating animals but also occurs in humans, especially newborns.
• the thermogenic properties & brown color may be due to mitochondria in which electron transport is uncoupled from production of stored energy in the form of ATP.
• brown fat protects against glucose intolerance & vascular disease
• humans with brown fat have
  • lower blood glucose & serum triglyceride levels & higher HDL cholesterol levels
  • lower rates of type 2 diabetes, dyslipidemia, coronary artery disease, atrial fibrillation/flutter, cerebrovascular disease, congestive heart failure, & hypertension
• benefits of having brown fat are most pronounced in overweight or obese persons
• sympathetic innervation of browm fat occurs via the Edinger-Westfall nucleus & oculomotor nerve (cranial nerve-3) & maybe the trochlear nerve (cranial nerve 4)
• KLF15 maintains white adipocytes selectively within white adipose tissue
  • deletion of KLF15 is sufficient to induce beige adipocytes (brown fat)
  • direct regulation of ADRB1 is a molecular mechanism for this

Clinical significance

• brown fat deposits in human adults are highly metabolically active but small in size, thus likely contribute little to whole body energy metabolism

More general terms

• adipose tissue

Additional terms

• mitochondrial brown fat uncoupling protein 1; UCP 1; thermogenin (UCP1, SLC25A7)