Adipogenesis Flashcards
Brown adipose tissue and white adipose tissue are originated from __________ ____________.
Distinct progenitors
Where is brown adipose tissue derived from?
Derived from paraxial mesoderm and Myf5+ progenitors (same as skeletal muscle)
Where is white adipose tissue derived from?
Derived from lateral mesoderm and Myf- progenitors
What does Myf5 stand for? What does it regulate?
- Myf5 = Myogenic factor 5
- Regulates muscle differentiation or myogenesis
What is adipogenesis?
Adipogenesis = the formation of adipocytes (fat cells) from stem cells.
Describe the FIRST step of adipogenesis.
1) Mesenchymal stem cells go through determination, which is where stem cells become specialized (also known as precursor cells). After determination, the mesenchymal stem cells turn into adipoblast.
Describe the SECOND step of adipogenesis.
2) The adipoblast goes through commitment, which is a process during which stem or precursory cells set their fate and become a preadipocyte.
Describe the THIRD step of adipogenesis.
3) The preadipocyte goes through proliferation, which expands the cell population and increases the number of preadipocytes.
Describe the FOURTH step of adipogenesis.
4) The preadipocytes go through differentiation and become “developing adipocytes,” which are a few small lipid droplets that express some lipogenic enzymes.
Describe the FIFTH step of adipogenesis.
5) The developing adipocytes then go through maturation and become mature adipocytes. Mature adipocytes are large lipid droplets, express abundant lipogenic enzymes, and have an enlarged cell size.
What are mesenchymal stem cells (MSCs)?
- are multipotent stem cells
- can differentiate into adipocytes, osteoblasts, chondrocytes, and myoblasts.
What are adipoblasts?
- precursor of preadipocytes
- does not contain lipogenic enzymes or lipid droplets
What are preadipocytes?
- fat cell progenitors with only the potential to differentiate into adipocytes.
- low lipogenic gene expression
- no lipid droplets
Adipocytes collect together to form ______ that eventually develop into larger ________.
Lobules, lobes
Lobules of fat are separated and supported by _________ connective tissue called __________.
loose, septa
True or False: Septa carries blood vessels and neurons to adipose tissue.
FALSE - Septa carries blood vessels and NERVES to adipose tissue.
For the molecular regulation of adipogenesis, there are “master” ____________ factors for adipocyte differentiation.
Transcription
What are the “master” transcription factors for adipocyte differentiation?
- CCAAT/Enhancer Binding Proteins (C/EBPs)
- Peroximose Proliferator-Activated Receptors y (PPARy)
What is lipogenesis?
Lipogenesis = synthesis or absorption of fatty acids (FA) from blood and subsequent esterification to form triacylglycerol (TAG).
What is lipogenesis efficient at?
Very efficient at storing fat
What is lipolysis?
Lipolysis = release of fatty acids from the adipocytes, which involves the breakdown of triacylglycerols (TAG) within adipocytes and results in diffusion of fatty acids across cell membranes.
What is the formula for calculating the net lipid accretion rate?
Lipogenesis rate minus lipolysis rate
What do triacylglycerols do?
- Stores fat as TAGs
- Accumulates FAs to produce TAGs by:
1) FAS from blood, which comes from diet and hepatic synthesis.
2) De novo (from new) synthesis of FAs
How does diet contribute to lipogenesis?
- TAGs (From the diet) are transported from the small intestine attached to ________. These structures are called ____________.
- Endothelial cell walls of capillaries contain the enzyme _______ that hydrolyses TAgs in chylomicrons to glycerol and free fatty acids for uptake by adipocytes.
- lipoproteins, chylomicrons
- lipoprotein lipase
What are the locations where diet-contributed lipogenesis occurs for cattle, sheep, and pigs? What about for avian species?
- For cattle, sheep, and pigs = occurs mostly in the adipose tissue.
- For avian species = occurs mostly in the liver
A component of lipogenesis is the dietary fatty acids used to assemble TAGs in adipocytes.
What’s the difference between ruminants and monogastrics?
- For ruminants, rumen microbes modify FA before absorption - therefore, fatty acids in feed and adipose are DIFFERENT.
- For monogastrics, unmodified FAs absorbed from the diet enter the blood stream - therefore, FA in feed and adipose is SIMILAR.
A component of lipogenesis is the substrate for de novo synthesis of fatty acids in adipocytes.
What’s the difference between ruminants and monogastrics?
- For ruminants, they have acetate.
- For monogastrics, they have glucose.
Lipolysis is the breakdown of TAG within adipocytes and results in diffusion of FA across the cell membrane.
What is it controlled and stimulated by?
- Controlled by hormone-sensitive lipases.
- Stimulated by hormones with catabolic actions.
For the regulation of lipogenesis and lipolysis, ________, _________, and ___________ trigger to increase cAMP, which results in ________ lipolysis and _________ lipogenesis.
Starvation, exercise, catecholamines, increasing, decreasing
In lipolysis, fatty acids are targeted to various processes including…
- Catabolized for energy
- Used for membrane synthesis
For the regulation of lipogenesis and lipolysis, ________, and _________ trigger to decrease cAMP, which results in ________ lipolysis and _________ lipogenesis.
Insulin, feeding, decreasing, increasing
