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Information about Adipose Tissue

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Adipose tissue is one of the main types of connective tissue.


In anatomy, adipose tissue or fat is loose connective tissue composed of adipocytes. Its main role is to store energy in the form of fat, although it also cushions and insulates the body. Obesity in humans and most animals is not dependent on the amount of body weight, but on the amount of body fat—specifically adipose tissue. Two types of adipose tissue exist: white adipose tissue (WAT) and brown adipose tissue (BAT). Adipose tissue also serves as an important endocrine organ[1] by producing recently-discovered hormones such as leptin, resistin and the cytokine TNFα. The formation of adipose tissue appears to be controlled by the adipose gene.

Anatomical features

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Gonadal adipose tissue in a female mouse
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Gonadal adipose tissue in a male mouse
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Retroperitoneal adipose tissue in a male mouse
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Mesenteric adipose tissue in a male mouse; in situ
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Mesenteric adipose tissue from a male mouse
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Inguinal adipose tissue in a male mouse


In humans, adipose tissue is located beneath the skin and is also found around internal organs. Adipose tissue is found in specific locations, which are referred to as 'adipose depots'. Adipose tissue contains several cell types, with the highest percentage of cells being adipocytes, which contain fat droplets. Other cell types include fibroblasts, macrophages and endothelial cells. Adipose tissue contains many small blood vessels. In the integumentary system, which includes the skin, it accumulates in the deepest level, the subcutaneous layer, providing insulation from heat and cold. Around organs, it provides protective padding. However, its main function is to be a reserve of lipids, which can be burned to meet the energy needs of the body. Adipose depots in different parts of the body have different biochemical profiles.

In a severely obese person, excess adipose tissue hanging downward from the abdomen is referred to as a panniculus (or pannus). A panniculus complicates surgery of the morbidly obese. The panniculus may remain as a literal "apron of skin" if a severely obese person quickly loses large amounts of weight (a common result of gastric bypass surgery). This condition cannot easily be corrected through diet and exercise, as the panniculus consists of adipocytes and other supporting cell types shrunken to their minimum volume and diameter. Reconstructive surgery is one way to fix the problem.

In mice, there are eight major adipose depots, four of which are within the abdominal cavity: the paired gonadal depots are attached to the uterus and ovaries in females and the epididymis and testes in males, the paired retroperitoneal depots are found along the dorsal wall of the abdomen, surrounding the kidney, and when massive extend into the pelvis. The mesenteric depot forms a glue-like web that supports the intestines, and the omental depot, which originates near the stomach and spleen and when massive extends into the ventral abdomen. Both the mesenteric and omental depots incorporate much lymphoid tissue as lymph nodes and milky spots respectively. The two superficial depots are the paired inguinal depots, which are found anterior to the upper segment of the hind limbs (underneath the skin) and the subscapular depots, paired medial mixtures of brown adipose tissue adjacent to regions of white adipose tissue, which are found under the skin between the dorsal crests of the scapulae. The layer of brown adipose tissue in this depot is often covered by a “frosting” of white adipose tissue, sometimes these two types of fat (brown and white) are hard to distinguish. The inguinal depots enclose the inguinal group of lymph nodes. Minor depots include the pericardial which surrounds the heart, and the paired popliteal depots, between the major muscles behind the knees, each containing one large lymph node(Pond 1998). Of all the depots in the mouse, the gonadal depots are the largest and the most easily dissected (Cinti, 1999), comprising about 30% of dissectible fat, e.g., (Bachmanov et al. 2001).

Physiology

Free fatty acid is "liberated" from lipoproteins by lipoprotein lipase (LPL) and enters the adipocyte, where it is reassembled into triglycerides by esterising it onto glycerol. Human fat tissue contains about 87% lipids.

In humans, lipolysis is controlled though the balanced control of lipolytic B-adrenergic receptors and a2A-andronergic receptor mediated antilipolysis.

Fat is not laid down when there is a surplus available and stored passively until it is needed; rather it is constantly being stored in and released from each cell.

Fat cells have an important physiological role in maintaining triglyceride and free fatty acid levels, as well as determining insulin resistance. Abdominal fat has a different metabolic profile—being more prone to induce insulin resistance. This explains to a large degree why central obesity is a marker of impaired glucose tolerance and is an independent risk factor for cardiovascular disease (even in the absence of diabetes mellitus and hypertension).

Recent advances in biotechnology have allowed for the harvesting of adult stem cells from adipose tissue, allowing stimulation of tissue regrowth using a patient's own cells. The use of a patient's own cells reduces the chance of tissue rejection and avoids the ethical issues associated with the use of human embryonic stem cells.

Adipose tissue is the greatest peripheral source of aromatase in both males and females contributing to the production of estradiol.

Hormones secreted by adipose tissue include: Adipose tissues also secrete a type of cytokines (cell-to-cell signalling proteins) called adipokines (adipocytokines) which play a role in obesity-associated complications.

Brown fat

A specialised form of adipose tissue in human infants, and some animals, is brown fat or brown adipose tissue. It is located mainly around the neck and large blood vessels of the thorax. This specialised tissue can generate heat by "uncoupling" the respiratory chain of oxidative phosphorylation within mitochondria, leading to the breakdown of fatty acids. This thermogenic process may be vital in neonates exposed to the cold, who then require this thermogenesis to keep warm as they are unable to shiver, or take other actions to keep themselves warm.[2]

Attempts to stimulate this process pharmacologically have so far been unsuccessful, but might in the future be a target of weight loss therapy.

Genetics

In 2007, researchers isolated the adipose gene, which ap­par­ently serves to keep animals lean dur­ing times of plen­ty. Increased adipose gene activity was associated with slimmer individuals.[3]

Cultural and social role

Excess adipose tissue on a human can lead to medical problems; however, a round or large figure does not of itself imply a medical problem, and is sometimes not primarily caused by adipose tissue. For a discussion of the aesthetic and medical significance of body shape, see dieting and obesity.

Additional images


diagrammatic sectional view of the skin (magnified).

Yellow adipose tissue in paraffin section


References

1. ^ Kershaw EE, Flier JS (2004). "Adipose tissue as an endocrine organ". J. Clin. Endocrinol. Metab. 89 (6): 2548-56. DOI:10.1210/jc.2004-0395. PMID 15181022. 
2. ^ Himms-Hagen, J. (August 1990) "Brown adipose tissue thermogenesis: interdisciplinary studies" The FASEB Journal (Federation of American Societies for Experimental Biology) 4(11): pp. 2890-2898
3. ^ Suh, Jae Myoung et al. (September 2007) "Adipose Is a Conserved Dosage-Sensitive Antiobesity Gene" Cell Me­tab­o­lism 6(3): pp. 195-207
  2. Bachmanov AA, Reed DR, Tordoff MG, Price RA, Beauchamp GK (2001) Nutrient preference and diet-induced adiposity in C57BL/6ByJ and 129P3/J mice. Physiology and Behavior 72, 603-613
  3. Cinti S (1999) The adipose organ. Editrice Kurtis, Milano
  4. Pond CM (1998) The fats of life. Cambridge University Press, Cambridge

See also

 •  • [ e]
Human anatomy, endocrine system: endocrine glands
Hypothalamic/pituitary axesAdrenal axis (Adrenal gland) • Thyroid axis (Thyroid gland, Parathyroid gland) • Gonadal axis (Testes, Ovaries, Corpus luteum)
OtherPineal gland • Islets of pancreas
 •  • [ e]
Histology: connective tissue
Classificationproper (loose/areolar, dense, adipose brown and white, reticular) embryonic (mucous, mesenchymal) specialized (cartilage, bone, blood)
Extracellular matrixground substance (tissue fluid) fibers (collagen, reticular fiber, elastic fibers)
Cellsresident (fibroblast, adipocyte, chondroblast, osteoblast), wandering cell
Anatomy (from the Greek ἀνατομία anatomia, from ἀνατέμνειν
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Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, muscle, and nervous tissue.) It is largely a category of exclusion rather than one with a precise definition, but all or most tissues in this category are similarly:
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Adipocytes are the cells that primarily compose adipose tissue, specialized in storing energy as fat.

Description

There are two types of adipose tissue, white adipose tissue (WAT) and brown adipose tissue (BAT), which are also known as white fat and brown fat,
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energy (from the Greek ενεργός, energos, "active, working")[1] is a scalar physical quantity that is a property of objects and systems of objects which is conserved by nature.
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Fat

Fat may refer to:
  • Fat, a group of compounds that are generally soluble in organic solvents and largely insoluble in water
  • Adipose tissue, an anatomical term for loose connective tissue composed of adipocytes

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thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer.

Heat is transferred from one material to another by conduction, convection and/or radiation.
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White adipose tissue (WAT) or white fat is one of the two types of adipose tissue found in mammals (compare to brown adipose tissue). In humans, white adipose tissue composes as much as 20% of the body weight in men and 25% of the body weight in women.
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Brown adipose tissue (BAT) or brown fat is one of the two types of adipose tissue (the other being white adipose tissue) that is present in many newborn or hibernating mammals as well as migratory birds. Its primary purpose is to generate body heat.
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1. Pineal gland 2. Pituitary gland 3. Thyroid gland 4. Thymus 5. Adrenal gland 6. Pancreas 7. Ovary 8. Testes]]

The endocrine system
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hormone (from Greek όρμή - "to set in motion") is a chemical messenger that carries a signal from one cell (or group of cells) to another. All multicellular organisms produce hormones (including plants - see phytohormone).
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Identifiers
Symbol LEPR

Entrez 3953
HUGO 6554
OMIM 601007

RefSeq NM_002303
UniProt P48357
Other data

Locus Chr. 1 p31 Leptin
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Resistin is a hormone secreted by adipose tissue. It is also known as "serine/cysteine-rich adipocyte-Specific Secretory Factor" (ADSF or FIZZ3). The length of the resistin pre-peptide in human is 108 aminoacids (in the mouse and rat it's 114 aa); the molecular weight is
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Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. These chemical signals are similar to hormones and neurotransmitters and are used to allow one cell to communicate with another.
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Skin layers: epidermis, dermis, and subcutis, showing a hair follicle, sweat gland & sebaceous gland.]] In zootomy and dermatology, skin is the largest organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs.
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organ (Latin: organum, "instrument, tool") is a group of tissues that perform a specific function or group of functions. Usually there is a main tissue and sporadic tissues. The main tissue is the one that is unique for the specific organ.
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The blood vessels are part of the cardiovascular system and function to transport blood throughout the body. The most important types, arteries and veins, carry blood away from or towards the heart, respectively.
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In zootomy, the integumentary system is the external covering of the body, comprising the skin, hair, feathers, scales, nails, sweat glands and their products (sweat and mucus).
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subcutis is the layer of tissue directly underlying the cutis. It is mainly composed of adipose tissue. Its physiological function includes insulation and storage of nutrients.

Subcutaneous injections are given by injecting a fluid or a solid pellet into the subcutis.
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Obesity
Classification & external resources

Silhouettes representing healthy, overweight, and obese.
ICD-10 E 66.
ICD-9 278

DiseasesDB 9099
MedlinePlus 003101
eMedicine med/1653  

MeSH C23.888.144.699.
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This article or section may contain original research or unverified claims.
Please help Wikipedia by adding references. See the for details.
This article has been tagged since September 2007.

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Panniculus is a medical term describing a dense layer of fatty tissue growth, usually in the abdominal cavity. [1] It can be a result of morbid obesity and can be mistaken for a tumor or hernia.
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For the eye disease in dogs, see .


Pannus is a medical term for a hanging flap of tissue. When involving the stomach, it is called a Panniculus and consists of skin, fat, and sometimes contents of the internal abdomen as part of a hernia.
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Gastric bypass procedures (GBP) are any of a group of similar operations used to treat morbid obesity—the severe accumulation of excess weight as fatty tissue—and the health problems (comorbidities) it causes.
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MOUSE was founded in 1997 by entrepreneur Andrew Rasiej and Founding Executive Director Sarah Holloway. Along with leaders from the "high tech" community in New York City, MOUSE spearheaded the process of wiring public schools for Internet access in New York City.
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The abdominal cavity is the body cavity of the human body (and other animal bodies) that holds the bulk of the viscera and which is located below (or inferior to) the thoracic cavity, and above the pelvic cavity.
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uterus or womb is the major female reproductive organ of most mammals, including humans. One end, the cervix, opens into the vagina; the other is connected on both sides to the fallopian tubes.
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For ovary as part of plants see ovary (plants)
An ovary is an egg-producing reproductive organ found in female organisms. They are usually purple. It is often found in pairs as part of the vertebrate female reproductive system.
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The epididymis is part of the human male reproductive system and is present in all male mammals. It is a narrow, tightly-coiled tube connecting the efferent ducts from the rear of each testicle to its vas deferens.
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The testicle (from Latin testis, meaning "witness",[1] plural testes) or ballock is the male generative gland in animals. This article will concentrate on mammalian testicles unless otherwise noted.
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Dorsal is an adjective which means, being at the back.

Dorsal may refer to:
  • Dorsum (biology), a part of an animal
  • A dorsal consonant, in linguistics
  • The medial longitudinal fasciculus, in neurology
  • The Dorsal stream, in neurology
  • Dorsal fin

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