Adipose Tissue

  • Adipocytes - fat-storing cells

    • Adipocytes function as key regulators of the body’s overall energy metabolism

    • Adipocytes specialize in concentrating triglycerides as lipid droplet(s)

  • Adipose Tissue - compromised by adipocytes

2 Major Types of Adipose Tissue:

  1. White Adipose Tissue - more common type specialized for fat storage, consists of cells each containing one large cytoplasmic droplet of whitish-yellow fat

  2. Brown Adipose Tissue - contains cells with multiple lipid droplets interspersed among abundant mitochondria, which helps give this tissue a darker appearance

A. WHITE ADIPOSE TISSUE

  • Specialized for relatively long-term energy storage

  • Unilocular - what white adipocytes are called due to its single large droplet of triglycerides

white adipose tissue

a. STORAGE AND MOBILIZATION OF LIPIDS

  • White adipocytes can store triglycerides derived from three sources:

    1. Dietary fats brought to the cells via the circulation as chylomicrons

    2. Lipids synthesized in the liver and transported in blood with very low-density lipoproteins (VLDLs)

    3. Free fatty acids and glycerol synthesized by the adipocytes

  • Lipoprotein lipase - an enzyme that hydrolyzes chylomicrons and VLDLs at the luminal surfaces of blood capillaries

  • Insulin - stimulates glucose uptake by adipocytes and accelerates its conversion into triglycerides, and the production of lipoprotein lipase

  • Leptin - the 16-kDa polypeptide hormone that is produced by hormonal activity of white adipocytes

b. HISTOGENESIS OF WHITE ADIPOSE TISSUE

  • Preadipocytes - first developed in adipose development

    • Preadipocytes then develop into three namely: White Adipocytes, Beige Adipocytes, and Brown Adipocytes

B. BROWN ADIPOSE TISSUE

  • Brown adipose tissue constitutes 2%–5% of the newborn body weight, located mainly in the back, neck, and shoulders

  • Becomes greatly reduced during childhood and adolescence

  • Multilocular - what brown adipocytes are called because of many small lipid inclusions it has

  • The color of brown adipose tissue is due to the very abundant mitochondria that contains cytochrome pigment

  • Heat production is the principal function of brown adipose tissue

brown adipose tissue

a. FUNCTION OF BROWN ADIPOCYTES

  • Thermogenesis - the main function of these multilocular adipose cells (brown adipocytes)

    • Thermogenin - transmembrane protein of brown adipocyte’s mitochondrial membrane

b. HISTOGENESIS OF BROWN ADIPOSE TISSUE

  • Brown adipocytes emerge earlier than white fat during fetal development

  • The number of brown adipocytes increases during cold adaptation