Energy Balance Flashcards
(39 cards)
what are the two types of fat? how are they functionally different?
brown and white
white- energy storage as triglyceride
brown- oxidizes FA for heat using mitochondrial uncoupling
how is fat energy stored?
triglycerides
how does white fat receive FAs?
VLDLs- liver
chylomicrons- intestines
uses lipoprotein lipase to break TGs into FAs that can be taken into cells
how does white fat make glycerol?
it needs glucose
glycolysis to DHAP
DHAP to glycerol-3-phosphate
glycerol 3 phosphate gets two acyl-CoAs esterified, forming phosphatidic acid
phosphatidic acid gets dephosphorylated to diacylglycerol
diacylglycerol is esterified w/ third acyl glycerol to TG
how does glucose get into adipose tissues?
GLUT4
how does TG leave the cell?
it gets broken down, first by adipocyte triglyceride lipase (ATGL), then Hormone sensitive lipase
both of which are regulated
finally, monoglyceride lipase frees the final FA
how does insulin affect adipocytes?
increases LPL
increases GLUT4
decreases ATGL and HSL
decreases perilipin, decreasing HSL activity
how is glucose uptake different in muscle and adipocytes relative to other tissues
in RBCs, CNS, etc., GLUT channels are always activated
muscle and fat have GLUT4, which is highly regulated by insulin
what property of GLUT4 does insulin regulate?
the amount of it expressed on the enzyme- does not regulate it affinity
causes the fusion of GLUT4 containing vesicles w/ plasma membrane
why do muscle cells uptake glucose?
to use as energy immediately or to store as glycogen
why do fat cells uptake glucose?
for fuel or to convert to glycerol for fat storage
describe brown fat
many small lipid droplets
lots of mitochondria (high oxidative capacity)
fatty acid oxidation can be uncoupled for heat (UCP)
mainly found in infants, but also in adults (cold adaptation, inverse w/ obesity)
describe white fat
one very large lipid droplet
low oxidative capacity
most FA returns to circulatoin
job is to store energy as TG
belly fat may be more dangerous than limb fat
what determines FA uptake one it has been removed from TG by LPL
concentration gradients.
- following a meal, the blood will have a lot of FA, and so it will push FA into cells
- at the same time, adipocytes will be internally creating TG, creating a low FA gradient
these two mechanisms work together
what hormones interact w/ perilipin and HSL?
perilipin and HSL are activated via phosphorylation in PKA dependent manner
PKA is caused by glucagon, catecholamines
PKA inhibited by insulin (phosphodiesterase)
what happens to the glycerol after it is broken down during lipolysis?
it leaves the cell and goes to the liver for gluconeogenesis
describe the role of inflammation in diabetes?
adipocytes only make up 20-40% of cells in fat. immune cells, including macrophages, help make up the remaining cells.
when adipocytes get sufficiently enlarged, they become stressed, releasing signals that convert M2 macrophages to M1. These newly proinflammatory macrophages secrete cytokines that play a role in insulin resistance
what mechanisms are used to regulate energy balance oh a
second to second basis
hour to hour basis
week to week basis
- phosphorylation/allostery
- transcription
- . transcription/neuronal
describe your metabolic status prior to breakfast (healthy)
low insulin
low GLUT4 on membrane
low glucose uptake
increased HSL activity,
releasing FA to blood for muscle
low ACC activity- meaning
- low FA synthesis in liver
- low malonyl-CoA allows CAT allow FA oxidation
RESULT: FA oxidation is primary energy source
describe your metabolic response to food intake (healthy)
high insulin
high GLUT4
high glucose uptake
low HSL and perilipin activity
high ACC activity-
- FA synthesis
- no FA oxidation
RESULT: glucose oxidation favored
which is faster to get into circulation: glucose or FAs?
glucose
glucose is taken immediately to liver
FAs are taken through lymphatics to thoracic duct and hit the heart first
how does insulin prepare the adipocytes based off the speed at which fat arrives?
insulin activates LPL on multiple levels: transcription, transport, processing
these take time. but FA is slow to get into the blood so the timing is apporpriate
why are your primary uses of energy?
basal metabolic rate: energy to keep muscle, brain, liver, kidney, heart happy. adipose uses relatively little
physical activity
diet-induced- energy it takes to digest food
where are the neurons responsible for appetite control found?
arcuate nucleus of hypothalamus 2 types
POMC- appetite suppressing
release MSH
NPY- appetite activating
1 inhibits downstream neurons that POMC neurons activate
2. inhibits POMC neurons
