Adipose Tissue Overview

Study Notes

Adipose tissue is connective tissue primarily composed of adipocytes (fat cells)
Adipocytes store lipids, mainly triglycerides
Two main types: white adipose tissue and brown adipose tissue

Function: Primarily for long-term energy storage
Structure: Uni-locular, meaning a single large lipid droplet fills most of the cell; this gives it a white appearance
Location: Throughout the body; subcutaneous layers, visceral fat, and other locations.
Role: Energy storage, insulation, cushioning, and organ support.
Lipids: triglycerides, cholesterol, and other lipids; these are insoluble in water, allowing for efficient storage
Hormonal regulation: responds to hormones and nervous stimuli; releases hormones and other substances, functioning as an endocrine organ
Important: important for nutritional homeostasis; plays a significant role in regulating energy balance
Medical application: Lipomas (benign tumors) can develop from these cells

Function: Primarily for thermogenesis (heat production); important for maintaining body temperature
Structure: Multilocular, meaning multiple small lipid droplets are present along with abundant mitochondria, which is why it has a darker appearance
Location: Abundant in newborns; concentrated in the neck, back, and around certain organs in the body
Role: Crucial for thermoregulation, especially in newborns.
UCP1: uncoupling protein-1 (also called thermogenin); these proteins in the inner mitochondrial membrane enable the transport of protons, which releases heat energy from these organelles rather than ATP
Hormonal regulation: norepinephrine stimulates thermogenesis in brown fat cells
Medical application: These cells are sometimes referred to as 'hibernomas' in fetal tissue

Adipocytes are derived from mesenchymal stem cells
White adipocytes and brown adipocytes originate from different progenitor cells, and arise from the mesoderm in the embryo
Beige adipocytes are generally intermediate between white and brown adipocytes, which can switch between these states depending on the environmental conditions.

Lipids enter adipocytes from three sources: dietary fats, lipids synthesized by the liver (VLDL), and fatty acids
Mobilization of lipids from adipocytes is stimulated by norepinephrine, promoting the release of fatty acids
Proteins and hormones like albumin aid the transport of mobilized lipids out of the cells

Adipocyes function as an endocrine organ and release various hormones and other factors
Leptin released by adipocytes, impacts eating behavior and energy expenditure.
Insulin is involved with glucose uptake by the adipocytes and promotes triglyceride synthesis
Other peptide hormones and growth hormone (GH) contribute to balancing lipid synthesis and mobilization.

Adipose tissue plays an important role in obesity and related health conditions.
Obesity is associated with chronic low-grade inflammation, with the release of factors from visceral fat.