Adipose tissue

Summary

Adipose tissue is a type of connective tissue that is composed mainly of adipocytes. It is found throughout the body and fulfills a number of important functions: it provides structural support and protective padding for major organs (e.g., kidneys), it serves as an insulating layer that prevents cutaneous heat loss, and it stores energy for longer periods of fasting. While the insulating and energy storage functions of adipose tissue provide decisive evolutionary advantages, their roles have diminished in modern times. Today, humans also rely on clothing for insulation and, in industrialized societies where food is readily available and affordable, its positive role as an energy reservoir has reversed to become a major health concern (obesity). However, in infants, adipose tissue continues to play a central role in the maintenance of body heat, and in individuals with severe illness, energy stores within the body make an essential contribution to sustaining the body.

There are two types of adipose tissue. Brown adipose tissue is abundant in neonates but recedes in adulthood. Its primary function is to prevent hypothermia through thermogenesis. White adipose tissue remains present throughout a lifetime and serves as the body's most important energy reservoir and also produces hormones.

White adipose tissue

Structure

Function

Individuals with congenital leptin deficiency (e.g., due to leptin gene mutations) present with constant hunger, hyperphagia, and severe obesity beginning in the first few months of life.

Blocking aromatase activity is the mechanism of treatment of estrogen-dependent diseases such as breast cancer, endometriosis, and endometrial cancer. Obese women are more prone to develop these conditions due to higher circulating levels of estrogens synthesized by their adipose tissue.

Occurrence

Development

Mesoderm germ layer → mesenchymal stem cells → preadipocytes (mitotically active) → adipocytes (ripe, mitotically inactive)

A persistently high-calorie intake that exceeds daily needs can lead to a pathological increase of white adipose tissue, causing obesity.

Brown adipose tissue

Structure

Function

Nonshivering thermogenesis (heat production)

Occurrence

Development

  • Embryonic: mesoderm germ layer → mesenchymal stem cellsbrown adipose tissue
  • In adult organism: regression over the course of a lifetime

Clinical significance

last updated 11/28/2019
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