White Adipose Tissue Flashcards
White adipose tissue
characterizes obesity, based on the excess amount
Adipocyte
a fat cell, that stores triglycerides. It’s a fat droplet, that is considered to be an energy storage
3 compartments of adipocyte:
Nucleus, cytoplasm, and fat reservoir
Are adipocytes present in other species:
Yes and no! The more complex the species became, like chickens, fish, frogs, and rats.
Worms Fat distribution:
stores fat droplets inside of the intestinal cells
Flies fat distribution
have fat bodies, and serve as dual organs for liver and adipose tissue. Humans can also store in the liver (not common though)
Evolution of Adipose depots:
lower organisms have evolved specialized cells to hold lipids but they are not adipocytes.
Amphibians and Reptiles:
have dedicated visceral (intra-abdominal) WAT depots
Mammals:
have specialized subcutaneous and visceral WAT depots
Why do we have specialized locations to store fat?:
So that way we have a safe harbor for excess energy. Furthermore, it is also viewed as an active endocrine organ / complex tissue that controls energy metabolism and lipid homeostasis
Why is WAT an active endocrine organ:
Its because it helps with energy storage, appetite, glucose, and fatty acid metabolism. Involved in thermogenesis, fecundity (fertility), and reproduction. Immune responses and storage of toxins. [Growth factors, complement factors, cytokines, hormones adipokines, and oxidized fatty acids.
Mammalian WAT:
has adipose tissues which contain connective tissue matrix, nerve tissue, stromovascular cells, and immune cells. All these components are integrated and control metabolism
Behavioral Fat
Male orangutan has adipose flanges and the females lack them. The females look for males with the flanges for mating purposes. This leads to reproductive success
Mechanical Fat:
elephants have plantar adipose tissues which cause pressure dissipation when they are walking because of their weight
Energy Suppling Fat:
camels have hump adipose tissue. It uses the energy from the tissues to mobilize fats and generate water
Metabolic WAT:
the color is yellow/orange because of Vitamin A (hydrophobic)
Is WAT higly plastic ?
yes it can range from 4-70% of someone’s total body weight because it’s a soft/connective tissue. Collagen allows for it to expand and contract based on the amount of energy
Anatomy of White adipose tissue:
- 30-40% adipocytes
- 60-70% other cells fraction is called stromal vascular compartment
- SV compartment contains: Vascular endothelium, Vascular smooth muscle cells, Fibrolast, Immune Cells, and Adipose stem cells
Mammalian Adipocyte Compartments
lipid droplet, nucleus, and mitochondria
2 Distributions of Adipose:
Subcutaneous fat and Visceral Fat
Dermal vs Subcutaneous:
dermal supports hair follicle growth and skin health.
Subcutaneous Fat:
- not uniformed shaped
- fat below the skin
- Heterogeneous adipocytes- small adipocytes interspersed with larger adipocytes
- High metabolic activity
- High vascularized
- Better immunological outcome
- Healthy fat/metabolically protective
Visceral Fat:
- bad fat!
- uniformed shape
- Abdominal fat
- Homogenous adipocytes- same-sized adipocytes
- Decreased stimulated lipolysis but increased triglyceride synthesis
- Less vascularization
- Poor immunological outcome
Does having a specific fat type matter?
Yes. Those with the same BMI, the person with more subcutaneous fat [pear shape] had a lower risk of health problems versus the person with more visceral fat [apple shape]
Gynoid -Type (pear shape):
- Lower body obesity, more subcutaneous fat storage
- More metabolically active {insulin sensitive}
- Protective role
Android-Type (apple shape):
- Abdominal obesity
- Decreased stimulated lipolysis but increased triglyceride synthesis. Increased lipoprotein lipase activity
- Greater risks of: metallic disease, chronic inflammation, and coagulation
- Men tend to accumulate this fat in the abdominal region
How to test which fat is worse:
transplantation studies, transplantation of subcutaneous fat to the visceral cavity. They found if you switch it becomes more like what it was switched to [sub to vis the vis became more sub]
What accounts for differences in fat distribution:
sex steroids (testosterone and estrogen). Those with low testosterone have more vis fat because it’s not being used towards building muscle. Estrogen promotes subcutaneous fat and burns visceral. But when they go through menopause they have more visceral fat and are more at risk of metabolic problems
Cushing Syndromes:
- High levels of cortisol
- Increase in fat in shoulder blades
- Activation of nuclear hormone receptor, glucocorticoid receptor
Deposition of fat between the scapula
Is there a single gene that contributes fat distriubtion ?
No single gene contributes to fat distribution. It’s been difficult to determine between mouse and humans because mouse have different fat storages .
