4_1Adipose Flashcards
What are the functions of adipose?
1) insulation and organ protection; 2) drug metabolism; 3) energy storage/expenditure; 4) endocrine
What are the endocrine functions of adipose?
1) regulation of body weight; 2) insulin sensitivity; 3) inflammation
From what does adipose protect organs?
protects from intertial injury and excessive movement
Where is brown fat stored?
1) supraclavicular; 2) subscapular
What are the types of adipose?
WAT (SQ and Visceral) and BAT
How does adipose tissue vary?
by type and location
Describe the cellularity of VAT
mostly unilocular
Describe the cellularity of BAT
multilocular and uniform
Describe the cellularity of SAT.
unilocular with some multilocular (more heterogeneous than VAT)
What are pericytes?
adipocyte stem cells
Where are pericytes located?
lining of vasculature with mature adipocytes
What is the function of WAT?
storage and endocrine
What is the function of BAT?
non-shivering thermogenesis
What was dinitrophenolamine (DNP)?
a former drug that induced beiging by uncoupline the H+ gradient; no longer on market due to abuse and OD
Which adipocytes are associated with the healthy pear-shape?
SAT
Which adipocytes are associated with the unhealthy apple shape?
VAT
What are the 2 types of WAT?
SAT and VAT
What type of fat is associated with inflammation and metabolic disease?
VAT!
How do adipocytes vary?
cellularity and function
Describe the presence of BAT throughout life.
abundant in newborns and declines with age; induced by constant cold
What are beige adipocytes?
an intermediate phenotype that is susceptible to environmental and pharmacologial induction
What is the function of uncoupling proteins (UCPs)?
uncouple the ATP/H+ gradient to allow H+ travel from intermembrane space to matrix
What proteins are upregulated in beige adipocytes?
UCP1 (also UCP-2 and -3)
What cells do Myf5+ cells differentiate to?
white or beige adipocytes
What cells do Myf5- cell differentiate to?
brown adipocytes
What is transdifferentiation?
the induction of white fat to beige fat
What substances induce transdifferentiation in animal models?
norepi and beta-3 agonists
What is the precursor to Myf5+/- cells?
mesenchymal cell
What is DGAT?
diacylglycerol transferase
What is ATGL?
adipocyte TG lipase
What are the pathways for TG synthesis in adipose?
1) from FFAs (major); 2) de novo from glucose (minor)
How is TG synthesis stimulated in adipose?
insulin
What reaction is catalyzed by ATGL?
TG – DAG
What reaction is catalyzed by HSL?
DAG – MAG – FA + glycerol
What is the function of perilipin?
when de-phosphorylated, it prevents lipase access to TGs
What substances stimulate the phosphorylation of perilipin?
catecholamines
What is the function of catecholamines in adipose?
phosphorylation of perilipin and HSL
Which form of HSL is active?
phosphorylated
What form of perilipin allows ATGL access to TGs?
phosphorylated
How do catecholamines initiate signal transduction?
bind to G-alpha-S to initate the cAMP/PKA pathway
What is the primary function of leptin?
long-term regulation of body weight to limit weight gain/loss during positive/negative energy balances
What are the effects of leptin?
increased energy expenditure: 1) decreased SNS activity; 2) decreased TSH; 3) decreased GnRH; 4) increased glucocorticoids;;; decreased food intake
When is leptin released?
more released during positive energy balance
How do leptin levels vary?
levels of synthesis and secretion correlate with changes in adipose mass (no oscillation between meals)
How is adipose defended (with regard to liposuction report)?
removal of SQ fat yields decreased leptin. Decreased leptin decreases energy expenditure. Fat returns as VAT
Why do most fatty acids leave the adipose for beta-oxidation?
adipose lacks lots of mitochondria
What is the de novo pathway for TG synthesis?
glucose yields G3P and pyruvate. Pyruvate converted to acetyl-CoA and to fatty acids. Fatty acids are activated and esterified via DGAT to G3P
What are the anabolic fates of DAG?
1) TG, 2) phospholipid synthesis
