Adipose tissue is composed mainly of lipid-filled fat cells (adipocytes) that are
surrounded by immune cells, fibroblasts, blood vessels, and collagen fibers. On the
basis of histology, adipose tissue can be classified into two types: white and brown.
White adipose tissue is the predominant type in humans and is characterized by adipocytes
with a single, large lipid inclusion and a peripherally-located nucleus. The main
function of white adipose tissue is to provide an efficient storage site for energy
in the form of triglycerides (metabolically active adipose tissue); it also can serve
protective or cushioning function in many vital areas (mechanical adipose tissue)
[
[1]
] (Table 1). Brown adipose tissue, so-called because of the characteristic color that is imparted
by the rich vascular supply and abundant mitochondria, uses triglycerides for thermogenesis
and plays an important role in energy expenditure (see Table 1). In most mammals, the brown adipose tissue is prominent in the newborn period. In
small mammals (eg, mice, rats), it persists in the postnatal period and is detectable
throughout life. In humans, brown adipose tissue is expressed only in the immediate
postnatal period, regresses subsequently, and does not play a significant role in
metabolism. For this article, white adipose tissue will be referred to as adipose
tissue.
Table 1Classification of adipose tissue
| White adipose tissue | Brown adipose tissue |
|---|---|
| Metabolically active | Interscapular |
| Subutaneous sites other than mechanical | Perirenal |
| Intra-abdominat (omental, mesenteric, and retroperitoneal) | Paravertebral |
| Intrathoracic | |
| Bone marrow | |
| Mechanical | |
| Subcutaneous (scalp, buccal, palm, sole, vulvar) | |
| Orbital | |
| Periarticular | |
| Epidural | |
| Crista galli | |
| Perineal | |
| Pericalyceal |
a Brown adipose tissue is only present in humans in the early postnatal period.
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Article info
Footnotes
☆Dr. Garg has received research grant support from Amgen Inc.
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© 2004 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
