Adipose Tissue

What is Adipose Tissue?

Adipose tissue, otherwise known as body fat, is a connective tissue derived from fibroblasts, called adipocytes that are specialized for storage of fats. The cell fills up with a single, large triglyceride droplet, and cytoplasm and nucleus are pushed to the periphery of the cell. With weight gain, the amount of adipose tissue increases and new blood vessels form. Thus, an obese person has many more blood vessels than does a lean person, a situation that can cause high blood pressure, since the heart has to work harder. It primarily serves as the fat storage area and energy reserve, but also provides insulation, thermoregulation, and hormone production.

Types of Adipose Tissue

Adipose tissue is categorised into three types:

White Adipose Tissue

• Composed mainly of large, unilocular adipocytes (cells with a single large fat droplet).

• Storages energy in the form of triglycerides.

• Most adipose tissue in adults is white adipose tissue.

• Insulates and cushions internal organs to protect them.

• Secretes hormones like leptin, which works by regulating hunger levels and energy balance.

Brown Adipose Tissue

• It is darker due to rich blood supply and numerous pigmented mitochondria that participate in aerobic cellular respiration.

• Specialised in heat production through nonshivering thermogenesis.

• It is widespread in the fetus, infant and hibernating animals, adults have only small amounts composed primarily of adipocytes

Beige Adipose Tissue

• Intermediate in nature between white adipose tissue and brown adipose tissue.

• May be induced through various stimuli, such as cold exposure, to change from white-like to brown-like cells, a process called browning.

• Plays a role in thermoregulation and energy expenditure.

Structure and Composition of Adipose Tissue

Adipose tissue is very complex in structure, composed of several cellular and extracellular elements. It is composed mainly of adipocytes, stroma vascular fraction and extracellular matrix.

Adipocytes (Unilocular vs Multilocular)

• Primary fat-storing cells

• Unilocular adipocytes in white adipose tissue store a single large fat droplet.

• Multilocular adipocytes in brown adipose tissue store several small fat droplets.

Stromal Vascular Fraction

• Pre-adipocytes, fibroblasts, vascular endothelial cells, and immune cells.

• Provides support to the growth and maintenance of adipocytes.

• Participates in the regenerative capacity of the tissue.

Extracellular Matrix Components

The ECM provides structural support to the adipose tissue

Collagen

• The major component of ECM.

• Provides tensile strength and structural integrity.

• Involved in the formation of the tissue's supportive network

Fibronectin

• Glycoprotein that binds to collagen and cell surface integrins.

• Facilitates cell adhesion, growth and wound healing.

Distribution of Adipose Tissue

Adipose tissue is distributed in different regions of the body with variations in its distribution.

Subcutaneous Fat

• Located beneath the skin.

• Provides insulation and energy storage.

• Visible as body contours and can be measured using skinfold callipers.

Visceral Fat

• Surrounds internal organs within the abdominal cavity.

• Linked to metabolic and cardiovascular risks.

• Cannot be seen directly but can be measured using CT or MRI imaging.

Differences By Gender and Age

• Men have more visceral fat, while women have more subcutaneous fat

• Ageing is characterised by a change in adipose tissue distribution, with a greater increase in visceral fat

Physiological Roles of Adipose Tissue

Adipose tissue has several crucial roles in the human body

Energy Storage and Mobilisation

• Stores energy in excess by converting it into triglycerides.

• Mobilises stored fat during energy deficits

Insulation and Thermoregulation

• Provides thermal insulation to maintain body temperature.

• Brown adipose tissue generates heat through thermogenesis.

Endocrine Functions (Leptin, Adiponectin, Cytokines)

• Produces hormones and cytokines which regulate metabolism, appetite and inflammation.

• Hormones Produced: e.g. Leptin, Adiponectin

• Leptin helps to mediate satiety and energy balance

• Adiponectin increases insulin sensitivity and exerts anti-inflammatory effects.

Adipose Tissue in Health and Disease

Adipose tissue contributes to a wide array of health disorders and diseases

Obesity and BMI

• Results from an imbalance between calorie intake and expenditure

• This leads to increased fat mass and associated health risks

• Body mass index is a measure of body fat based on height and weight.

• High value of BMI—excess adipose tissue, potential health risks

Metabolic Syndrome

• The cluster of conditions including insulin resistance, hypertension, dyslipidemia

• Linked to excess visceral fat

Insulin Resistance and Type 2 Diabetes

• Excess adipose tissue, in particular visceral fat, potentiates insulin resistance.

Cardiovascular Diseases

• Excess adipose tissue, specifically visceral fat, is associated with an increased risk for heart disease and stroke.

• Contributes to the pathogenesis of atherosclerosis.

Adipose Tissue Across Life Stages

Properties and functions of adipose tissue change during the lifetime

Foetal and Postnatal Development

• Starts in the fetus and continues after birth.

• Growth can refer to hypertrophy, an increase in cell size, and hyperplasia, an increase in cell number.

Puberty Changes

• Changes to body fat distribution occur with changes in hormone levels during puberty.

• Females generally gain more subcutaneous fat while males gain more visceral fat.

Ageing and Adipose Tissue

• Ageing is associated with changes in body fat distribution and a decrease in the activity of brown adipose tissue.

• The accumulation of visceral fat, and a concomitant loss of subcutaneous fat, contribute to metabolic disease.

Adipose Tissue NEET MCQs (With Answers & Explanations)

Important topics that can be asked in NEET exam are:

• Types of Adipose Tissues

• Structure and Composition

• Distribution of AdiposeTissue

• Endocrine Role (Leptin, Adiponectin)

Practice Questions for NEET

Q1. What is the contributing factor to the brown colouration in brown fat?

1. Its enhanced ability to generate heat.

2. Abundance of mitochondria.

3. High concentration of iron-containing cytochrome pigments.

4. Presence of chromatophores.

Correct answer: 3) High concentration of iron-containing cytochrome pigments.

Explanation:

Brown adipose tissue (brown fat) does contain a high concentration of mitochondria, which is correct. However, the brown colouration in brown fat is primarily due to its higher content of iron-containing proteins, particularly cytochromes referred to as iron-containing cytochrome pigments. These iron-containing proteins in the mitochondria contribute to the brown colour and are involved in the process of generating heat.

Hence, the correct answer is option 3) High concentration of iron-containing cytochrome pigments.

Q2. What is the location of Adipose tissue?

1. Limbs and nose

2. Under your skin and between your internal organs

3. In the inner cavities of bones.

4. Both (b) and (c)

Correct answer: Both (b) and (c)

Explanation:

Adipose tissue, otherwise known as body fat, is a connective tissue that extends throughout your body. It's found under your skin (subcutaneous fat), between your internal organs (visceral fat), and even in the inner cavities of bones (bone marrow adipose tissue).

Hence, the correct answer is option 4) Both (b) and (c).

Q3. Which statement/s are true for white Adipose tissue?

I. It is Multilocular

II. Present in Babies

III. Few Mitochondria

IV. Seen in Adults

1. I and II

2. III and IV

3. I and III

4. II and IV

Correct answer: 2) III and IV

Explanation:

Adipose tissue can be white or brown.

White Adipose tissue(WAT)

→ Unilocular

→ Few mitochondria

→ Seen in Adults

BAT

→ Multilocular and more mitochondria

→ In babies

→ In hibernating animals

Hence, the correct answer is option 2) III and IV.

Also Read:

• MCQs on Adipose Tissue

• Epithelial Tissue

• Types of Neurons

Recommended Video On 'Adipose Tissue'