page_title: Brown adipose tissue
section_title: Adults
hierarchical_section_title: Brown adipose tissue / Function / Adults
caption_attribution_description: English: Intermediate magnification micrograph of a hibernoma, an uncommon benign soft tissue tumour, that is thought to arise from brown fat. H&amp;E stain. Features: Large polygonal/oval cells: Nucleus - central location, small. Cytoplasm - multivacuolated, oval, eosinophilic, granular. See also Image:Hibernoma1.jpg - high magnification. Image:Hibernoma3.jpg - low magnification.
context_page_description: Brown adipose tissue or brown fat makes up the adipose organ together with white adipose tissue. Brown adipose tissue is found in almost all mammals.
  Classification of brown fat refers to two distinct cell populations with similar functions. The first shares a common embryological origin with muscle cells, found in larger "classic" deposits. The second develops from white adipocytes that are stimulated by the sympathetic nervous system. These adipocytes are found interspersed in white adipose tissue and are also named 'beige' or 'brite'.
  Brown adipose tissue 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, brown adipose tissue produces heat by non-shivering thermogenesis.
  In contrast to white adipocytes, which contain a single lipid droplet, brown adipocytes contain numerous smaller droplets and a much higher number of mitochondria, which gives the tissue its color. Brown fat also contains more capillaries than white fat.
context_section_description: It was believed that after infants grow up, most of the mitochondria (which are responsible for the brown color) in brown adipose tissue disappear, and the tissue becomes similar in function and appearance to white fat.  In rare cases, brown fat continues to grow, rather than involuting; this leads to a tumour known as a hibernoma. More recent research has shown that brown fat is related not to white fat, but to skeletal muscle.
  Studies using positron emission tomography scanning of adult humans have shown that brown adipose tissue is still present in most adults in the upper chest and neck (especially paravertebrally). The remaining deposits become more visible (increasing tracer uptake, meaning more metabolically active) with cold exposure, and less visible if an adrenergic beta blocker is given before the scan. These discoveries could lead to new methods of weight loss, since brown fat takes calories from normal fat and burns it. Scientists have been able to stimulate brown fat growth in mice. One study of APOE knock out mice showed cold exposure could promote atherosclerotic plaque growth and instability. The study mice were subjected to sustained low temperatures of 4 °C for 8 weeks which may have caused a stress condition, due to rapid forced change rather than a safe acclimatisation, that can be used to understand the effect on adult humans of modest reductions of ambient temperature of just 5 to 10 °C.  Furthermore, several newer studies have documented the substantial benefits of cold exposure in multiple species including humans, for example researchers concluded that "activation of brown adipose tissue is a powerful therapeutic avenue to ameliorate hyperlipidaemia and protect from atherosclerosis" and that brown fat activation reduces plasma triglyceride and cholesterol levels and attenuates diet-induced atherosclerosis development.
  Long term studies of adult humans are needed to establish a balance of benefit and risk, in combination with historical research of living conditions of recent human generations prior to the current increase of poor health related to excessive accumulation of white fat. Pharmacological approaches using β3-adrenoceptor agonists have been shown to enhance glucose metabolic activity of brown adipose tissue in rodents.
  Additionally research has shown:
  Brown adipose tissue activation improves glucose homeostasis and insulin sensitivity in humans suggesting that anyone with impaired insulin function might benefit from BAT activation, however there is broader application given research showing even mildly elevated blood glucose in healthy non-diabetic humans is associated with damage over time of many organs such as eyes, tendons, endothelial/cardiovascular system and brain, and results in higher levels of damaging advanced glycation end products.
  Brown adipose tissue activation may play an important role in bone health and bone density.
  Brown adipose tissue activation through cold exposure increases adiponectin levels, just two hours of cold exposure resulted in a 70% increase in circulating adiponectin in adult men. Centenarians (both men and women) and their offspring have been found to have genetics that boost adiponectin, and they have higher circulating adiponectin, suggesting a link between longevity and adiponectin production. In addition, high concentrations of plasma adiponectin in centenarians was associated with favorable metabolic indicators, and with lower levels of C-reactive protein and E-selectin.
  Cold exposure increases circulating irisin. Irisin improves insulin sensitivity, increases bone quality and quantity, is involved in the building of lean muscle mass, and helps reduce obesity by converting white fat to brown fat, providing many of the same benefits of exercise. Healthy centenarians are characterized by increased serum irisin levels, whereas levels of this hormone were found to be significantly lower in young patients with myocardial infarction. These findings may prompt further research into the role played by irisin not only in vascular disorders but also in li
caption: Micrograph of a hibernoma, a benign tumour thought to arise from brown fat (haematoxylin and eosin stain)
exif: {"Image Make": "Canon", "Image Model": "Canon EOS DIGITAL REBEL XSi", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image DateTime": "2009:07:15 08:16:03", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "192", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "9118", "Thumbnail JPEGInterchangeFormatLength": "9604", "EXIF ExposureTime": "1/160", "EXIF FNumber": "0", "EXIF ExposureProgram": "Shutter Priority", "EXIF ISOSpeedRatings": "200", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2009:07:08 11:29:41", "EXIF DateTimeDigitized": "2009:07:08 11:29:41", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ShutterSpeedValue": "59/8", "EXIF ApertureValue": "2147483648", "EXIF ExposureBiasValue": "0", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "0", "EXIF SubSecTime": "93", "EXIF SubSecTimeOriginal": "93", "EXIF SubSecTimeDigitized": "93", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "4272", "EXIF ExifImageLength": "2848", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "8994", "EXIF FocalPlaneXResolution": "2136000/439", "EXIF FocalPlaneYResolution": "356000/73", "EXIF FocalPlaneResolutionUnit": "2", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Manual", "EXIF SceneCaptureType": "Standard"}