(endo) intro to diabetes Flashcards
where is GLUT-4 found?
found in myocytes (muscle) and adipocytes (fat)
- within vesicles
- recruited and enhanced by insulin
how does GLUT-4 compare to GLUT-2?
while GLUT-4 is highly insulin-sensitive, GLUT-2 is not
what is the function of GLUT-4?
increases glucose uptake into cells by 7-fold
describe the structure of GLUT-4 chains
outer hydrophobic chains but inner hydrophilic chains (where glucose will pass to enter the cell)
which type of amino acids are used to form glucose?
gluconeogenic amino acids (e.g. alanine)
how does insulin act on myocytes and affect proteins in the FED state?
insulin stimulates AA conversion into protein (i.e. increases protein synthesis + inhibits proteolysis) for storage
along with insulin, what stimulates protein synthesis in myocytes?
IGF-1 and GH
insulin inhibits proteolysis in myocytes in the FED state
what happens in the FASTING state?
cortisol (and glucagon) act to increase conversion of stored proteins into the gluconeogenic amino acids that they are made up of
= enable gluconeogenesis in the liver to increase blood glucose levels
which hormone stimulates the uptake of gluconeogenic AAs into hepatocytes for gluconeogenesis?
glucagon
what is lipoprotein lipase?
an enzyme that breaks down triglycerides that would otherwise be unable to leave the circulation
= broken down into NEFAs and glycerol (that can be taken up by adipocytes)
what happens to the NEFAs and glycerol taken up by the adipocytes?
converted into triglycerides again and stored
which hormones stimulate and inhibit hepatic gluconeogenesis?
stimulate = glucagon, cortisol
inhibit = insulin
how does insulin act on adipocytes in the FED state?
insulin acts
1) to stimulate conversion of NEFAs and glycerol into triglycerides (for storage)
2) to increase glucose uptake via GLUT-4 that will then act to increase NEFA and glycerol conversion into triglycerides
3) inhibits breakdown of stored triglycerides
what acts on adipocytes in the FASTING state?
both cortisol + GH will act on triglycerides to break them down into NEFAs and glycerol again
what happens with glycerol in the FASTING state?
glycerol is taken up by hepatocytes and converted into glycerol-3-phosphate
gly-3p then undergoes gluconeogenesis to form glucose
= increases HGO
what happens with glycerol in the FED state?
glycerol is taken up by hepatocytes and converted into glycerol-3-phosphate
the gly-3p is then converted into triglycerides for storage
how are cerebral energy requirements met?
glucose (preferred)
ketone bodies
(!! but cannot metabolise NEFAs !!)
what happens with gluconeogenic amino acids in the FED state?
insulin acts to
1) reduce/inhibit hepatic gluconeogenesis
2) promote protein synthesis from gluconeogenic AAs
= reducing HGO
what happens with gluconeogenic amino acids in the FASTING state?
- glucagon only acts to:
1) increase uptake of AAs into hepatocytes
2) promote proteolysis to produce more gluconeogenic AAs for gluconeogenesis
- cortisol + glucagon act to
1) increase hepatic gluconeogenesis
= increasing HGO
explain the process of ketogenesis
- NEFAs are taken up into hepatocytes
- NEFAs are converted into fatty acyl-coAs
- fatty acyl-coAs are converted into ketone bodies
where does ketogenesis take place?
hepatocytes
which ketone bodies are made in hepatocytes during ketogenesis?
- acetyl CoA
- acetoacetate
- acetone + 3 OH-B
what stimulates and what inhibits ketogenesis?
stimulates ketogenesis = glucagon
inhibits ketogenesis = insulin
define hepatic glycogenolysis
the generation of glucose from stored glycogen in the liver