Soft tissue
Adipose tissue
Normal brown fat

Author: Vijay Shankar, M.D. (see Authors page)

Revised: 27 July 2016, last major update August 2012

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Brown fat [title]

Cite this page: Normal brown fat. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/softtissueadiposebrownfat.html. Accessed December 8th, 2016.
Terminology
  • Also called Brown Adipose Tissue (BAT)
Sites
  • More conspicuous in infants (5% of body weight) and children; replaced with white fat over time
  • Persists in adults in interscapular region, neck, mediastinum, axilla, retroperitoneum (perirenal)
  • Substantial amounts of metabolically active brown fat are present in healthy adults (N Engl J Med 2009;360:1518)
Pathophysiology
  • Main function is heat production (nonshivering thermogenesis), mediated through a dense vascular system and sympathetic nerves (Physiol Rev 2004;84:277)
  • Brown fat mitochondria express uncoupling protein (UCP1), which uncouples fatty oxidation from ATP generation, which causes energy to be dissipated as heat
  • Cold exposure leads to sympathetic stimulation of brown fat via norepinephrine binding to beta adrenergic receptors, then oxidation of fatty acids and heat production
  • Protein-tyrosine phosphatase 1B is a modulator of brown fat adipogenesis (PLoS One 2011;6:e16446)
  • Moderate intermittent stress can stimulate brown adipose tissue growth and thermogenic activity
Diagrams / Tables

Images hosted on other servers:

Sites of brown fat

Clinical Features
  • Increased presence is associated with alcohol abuse, malnourishment and cachexia (may maintain body temperature in those with diminished subcutaneous fat), cardiovascular disease (Arch Pathol Lab Med 1992;116:1152); also Duchenne‚Äôs muscular dystrophy (Arch Pathol Lab Med 1988;112:550)
  • Brown fat thermogenesis is visible with a thermal (infrared) camera in infants over neck and interscapular area
  • Also important in animals coming out of hibernation, allowing them to rewarm quickly
Gross Description
  • Red-brown (less lipid) to tan (more lipid) due to vascularity and numerous mitochondria
  • Has glandular and lobular appearance
Micro Description
  • Lobules of adipocytes, capillaries, nerves and connective tissue
  • Adipocytes are smaller (25 - 40 microns) than in white fat, are polygonal with acidophilic multivacuolated and granular cytoplasm and central spherical nucleus with fine indentations
Micro Images

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Multivacuolated cytoplasm

CD31

Positive Stains
Electron Microscopy Description
  • Numerous mitochondria and smaller amounts of lipid droplets
Additional References