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ADIPOSE TISSUE

Adipose tissue is a term which is used to describe connective tissues that are made up of adipocytes. Its primary function is one of fat energy storage, however, it is also known to provide insulation and act as a cushion to the body.

Adipose tissue is usually described as body fat and is present all around the human body. The majority of it is located underneath the skin in the form of subcutaneous fat, however, it can also be found around internal organs in the form of visceral fat, within bone marrow, in breast tissue and between muscles. There are two types of adipose tissue; brown adipose tissue and white adipose tissue.

[A]. Brown Adipose Tissue (BAT)


Characteristics of BAT cells include:
- Large number of tiny fat (lipid) droplets present.
- Greater number of mitochondria present.
- More iron being stored by the mitochondria.
- Cells appear brown in colour.

[B]. White Adipose Tissue (WAT)


Characteristics of WAT include:
- Single drop of fat (lipid) present.
- Fewer mitochondria present.
- Less iron being stored by the mitochondria.
- Cells appear white in colour.

Over the last few years, scientists have discovered that the adipose tissue plays a vital function in the secretion of many bioactive substances which are called adipokines or adipocytokines. These are found to play vital functions by affecting directly on distant or adjacent organs in the body. Majority of adipocytokines have a pro-inflammatory action, whilst only a few display anti-inflammatory properties.

ADIPOCYTOKINES
Adipocytokines are bioactive substances which are produced by adipose tissue, that are then released into the blood stream. In order to maintain good health it is necessary to have the right balance of adipocytokines within the body. There are also many adipocytokines in the blood that also function in the modulation of blood pressure and sugar metabolism.


Both “beneficial” and “harmful” adipocytokines have now been identified within the human body.
[1]. Individuals who have normal body fat present have been found to have a greater number of “beneficial” adipocytokine (mainly adiponectin) present in their blood.
[2]. On the other hand, individuals who have excess amounts of visceral fat present experience a reduction in the levels of adiponectin and an increase in “harmful” adipocytokines present [PAI-1, Leptin, TNF-alpha, MCP-1,  IL-6 and IL-18]. This process leads to a disruption in the natural balance of adipocytokines being secreted into the blood stream.

There is now conclusive evidence to suggest that the increase in “harmful” adipocytokines leads to atherosclerotic diseases, diabetes, cardiovascular condition (including stroke and heart attack).

ADIPONECTIN:
- Adiponectin is a 244 amino acid protein hormone which is known to function in the modulation of many metabolic processes that include fatty acid oxidation and glucose regulation.
- It is known to be only secreted by adipose tissues into the blood and accounts for 0.01% of all plasma protein.
- The levels of its expression are found to be inversely correlated with body fat percentage in adults. Dramatic weight loss has also been found to result in a significant increase in the amount of circulating adiponectin.
- This hormone also has vital functions in the suppression of metabolic derangements that may result in: type 2 diabetes, obesity, NAFLD and atherosclerosis.
- In the presence of leptin it has been found to cause an increase in insulin sensitivity.

PAI-1:
- PAI-1 (Plasminogen Activator Inhibitor 1) is produced in the endothelium cells which are known to line the blood vessels, however, it is also found to be secreted by adipose tissues.
- It can function by inhibiting the process that degrades blood clots (fibrinolysis).
- Blot clots are generally found to be more frequent in individuals who have a much higher level of PAI-1 in there blood when compared to those with normal levels.
- Matrix metalloproteinases activity is also inhibited by PAI-1, this is important for the invasion of malignant cells that are found across the basal lamina.
- The amount of PAI-1 in the blood increases with excessive accumulation of visceral fat. This leads to a greater potential risk of one having a stroke or a heart attack because of the increase in difficulty for the body to be able to dissolve blood clots.

LEPTIN:
- Leptin has a vital function in the regulation of body weight and appetite.
- It has been discovered to bind leptin receptors which are located in the hypothalamus. This specific binding activity stimulates an intracellular signal pathway which causes the down regulation of leptin receptors that are important for increasing appetite. The net effect of this action is the inhibition of excess feeding.
- During obesity, however, the amount of leptin present is constantly at an elevated level because of excess eating. This causes a permanent down-regulation of leptin receptors and makes them less sensitive to leptin. Abnormal production of leptin has been linked to uncontrollable eating habits and even a risk to obesity.

TNF-ALPHA:
- TNF-alpha is a 17kDa non-glycosylated protein which is 157 amino acids in length.
- TNF-alpha is mainly made by macrophages but it can also be produced by a number of other cells which include; mast cells, adipose tissue, endothelial cells, neurons, fibroblast cells and lymphoid cells.
- It has a number of functions which include; appetite suppression, acute phase response, increasing insulin resistance, stimulation of phagocytosis.
- TNF-alpha was initially identified as a substance that has the ability to attack tumour cells.
- However, scientist later discovered that elevated levels of TNF-alpha can disrupt insulin action. This can lead to the blood sugar levels being reduced and the potential of having diabetes increasing.

FINAL THOUGHTS
[1]. Visceral fat is found to build-up in the membrane of the abdomen [mesentery] and is a visual sign of an obese body type where the abdomen protrudes markedly.
[2]. Individual with an excess of visceral fat have been found to have elevated levels of PAI-1, TNF-alpha, Leptin, MCP-1, IL-6 and IL-18 in the blood but lower concentration of adiponectin.
[3]. It has now been well documented that dysfunctional adipocytes leads to the dysregulation of adipocytokines which could be related to a number of lifestyle related diseases that are linked to obesity.
[4]. As researchers make further progress in the understanding of adipocytokines and how they function, the better we will be become at dealing with the large number of metabolic syndromes which currently exist.

Products available to study some of the adipocytokines mentioned above are listed below.

Product Name

Cat. No.#

Size

Price

Adiponectin ELISA Kit

DEE009

96 wells

£430

Adiponectin (Acrp30) Human

CYT-024

10ug

£160

Adiponectin Human

CYT-280

25ug

£160

Angiotensin I EIA Kit

EK-002-01

96 wells

£430

Angiotensin II EIA Kit

EK-002-12

96 wells

£430

Angiopoietin 1 (ANGPT1) Human

CYT-074

5ug

£160

IL-6 ELISA Kit (Human)

EL10023

96 wells

£390

IL-6 sR ELISA Kit (Human)

EL10043

96 wells

£410

Leptin EIA Kit (Mouse)

EK-003-13

96 wells

£430

Leptin Human

CYT-228

1mg

£160

Leptin His Human

CYT-287

25ug

£160

MCAF / MCP-1 ELISA Kit (Human)

EL10009

96 wells

£390

MCP-3 ELISA Kit (Human)

EL10016

96 wells

£390

MCP 1 Human (CCL2)

CHM-271

20ug

£160

MCP 2 Human (CCL8)

CHM-316

10ug

£160

MCP 3 Human (CCL7)

CHM-317

10ug

£160

Resistin EIA Kit (Mouse)

EK-028-35

96 wells

£430

Resistin ELISA Kit (Human)

EK-028-36

96 wells

£430

Resistin Mutant Human

CYT-585

10ug

£160

Resistin Human

CYT-456

25ug

£160

Resistin Mouse

CYT-457

25ug

£160

Resistin Rat

CYT-458

25ug

£160

TNF alpha Human

CYT-223

50ug

£160

TNF alpha ELISA Kit (Human)

EL10019

96 wells

£380

TNF Alpha ELISA Kit (Mouse)

EK-072-24

96 wells

£430


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