ADIPOSE TISSUE

ADIPOSE TISSUE

Adipose tissue or fat is a loose connective tissue that forms the storage site of fat in the form of triglycerides. It is composed of adipocytes, which are also called fat cells or lipocytes. Obesity does not depend on the body weight, but on the amount of body fat, specifically adipose tissue.

Adipose tissue is of two types, white adipose tissue and brown adipose tissue.

WHITE ADIPOSE TISSUE OR WHITE FAT

White adipose tissue is distributed through the body beneath the skin, forming subcutaneous fat. It also

surrounds the internal organs. This adipose tissue is formed by fat cells which are unilocular, i.e. these cells contain one large vacuole filled with fat.

Functions of White Adipose Tissue

White adipose tissue has three functions:

1. Storage of energy: Main function of white adipose tissue is the storage of lipids. Utilization or storage

of fat is regulated by hormones, particularly insulin, depending upon the blood glucose level. If the

blood glucose level increases, insulin stimulates synthesis and storage of fat in white adipose tissue. On the other hand, if blood glucose level decreases insulin causes release of fat from adipose tissue. Released fat is utilized for energy

2. Heat insulation: Insulation function is due to the presence of adipose tissue beneath the skin

(subcutaneous adipose tissue)

3. Protection of internal organs: White adipose tissue protects the body and internal organs by surrounding them and by acting like a mechanical cushion.

BROWN ADIPOSE TISSUE OR BROWN FAT

Brown adipose tissue is a specialized form of adipose tissue, having the function opposite to that of white

adipose tissue. It is present only in certain areas of the body such as back of neck and intrascapular region. It is abundant in infants forming about 5% of total adipose tissue. After infancy, brown adipose tissue disappears gradually and forms only about 1% of total adipose tissue in adults. It is formed by fat cells which are multilocular, i.e. these cells contain many smallvacuoles filled with fat. The coloration of this adipose tissue is due to high vascularization and large number of iron-rich mitochondria.

Functions of Brown Adipose Tissue

Brown adipose tissue does not store lipids but generates heat by burning lipids. In infants and

hibernating animals, brown adipose tissue plays an import ant role in regulating body temperature via

non-shivering thermogenesis. Heat production in brown fat is very essential for survival of infants and

small animals in cold environment. It is because, the lipid in this tissue releases energy directly as heat.

The mitochondria found in brown adipose tissue contain a unique uncoupling protein called mitochondrial

uncoupling protein 1 (UCP1). Also called thermogenin, this protein allows the controlled entry of protons without adenosine triphosphate (ATP) synthesis, in order to generate heat.

 METABOLISM OF LIPIDS

LIPID PROFILE

Lipid profile is a group of blood tests which are carried out to determine the risk of coronary artery diseases (CAD). Results of lipid profile are considered as good indicators of whether someone is prone to develop stroke or heart attack, caused by atherosclerosis. In order to plan the course of treatment, the results of the lipid profile are correlated with age, sex and other risk factors of heart disease.

Tests included in lipid profile are total cholesterol, triglyceride, HDL, LDL, VLDL and total cholesterol –

HDL ratio. Total cholesterol to HDL ratio is helpful in predicting atherosclerosis and CAD. It is obtained by dividing total cholesterol by HDL. High total cholesterol and low HDL increases the ratio. The increase in the ratio is undesirable. Conversely, high HDL and low total cholesterol lowers the ratio and the decrease in the ratio is desirable.

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