12 Pancreas Flashcards
Where is insulin produced
β-cells of pancreas
What is the precursor to the active form of insulin
proinsulin
What are the two chains of insulin
Alpha chain and beta chain linked by disulfide bonds
C-peptide is cut out of the proinsulin molecule but also secreted
Is insulin similar across species
Yes; highly conserved
What fragment of the proinsulin molecule is used to monitor endogenous insulin secretion post-injection
C-peptide fragment
Why is the C molecule useful
released in equimolar amounts with insulin
Is a ‘record’ of endogenous secretion
Is a way of measuring endogenous insulin levels
What are the actions of insulin?
Glucose metabolism
1) facilitates glucose uptake by most tissues
- exceptions: RBCs, most of the brain, intestinal mucosa, lens of the eye, kidney tubules
2) facilitates glucose storage as glycogen
3) lowers blood glucose
4) fat metabolism
5) protein metabolism
6) mineral metabolism
What does insulin do to blood glucose levels? How?
lowers blood glucose by:
- transports glucose into cells by carrier-mediated facilitated diffusion
- converts glucose to glycogen in liver
- converts glucose to TGs in adipose
- inhibits gluconeogenesis in liver
What is glucose converted into in the liver
glycogen
What is glucose converted to in adipose tissue
Triglycerides
What does insulin do to the liver
inhibits gluconeogenesis
What does insulin do to fat metabolisim
inhibits hormone-sensitive lipase (decreases lipolysis)
Promote fat deposition
Triglyceride synthesis
What does insulin do to protein metabolism
Increase AA transport into cells
Increase protein synthesis
Synergizes with GH
What does insulin do to mineral metabolism
transports K+ into cells
Is insulin anabolic or catabolic
anabolic (builds things up)
How is glucose metabolism maintained when blood glucose is high (hyperglycemia)
Increase glucose > increase insulin secretion > glucose cellular uptake (in muscle, fat)
decrease endogenous production of glucose > increased utilization of glucose (muscle & adipose cells) AND increased storage of glucose (in liver a glycogen), fat and aa arriving in the blood from GI tract
What are three major consequences of Insulin deprivation on CHO metabolisim
Glycosuria
Polyuria
Polydypsia
What are some consequences of insulin deprivation on fatty acid metabolism
lipolysis stimulated > formation of acetoacetic acid > formation of ketone bodies >
Ketoaciduria
Ketoacidosis: fruity breath > COMA > DEATH
What 3 conditions release insulin
High glucose
High AA
High FFA
What inhibits insulin
epinephrine
Where is glucagon produced
α-cells of pancreas
Is glucagon similar across species
yes; highly conserved in various species
What does glucagon do in the liver?
5 things
Increase gluconeogeneis
- increases every rate limiting enzyme
Increase glycogenolysis
- if glycogen is present it is mobilized
Decreases glyconeogenesis
Increase protein catabolism
Increase lipolysis
What does glucagon do in the liver
overall Increases glucose output
What stimulates glucagon secretion?
Decreased glucose Elevated AA (also stimulates insulin)
What inhibits glucagon secretion?
High free fatty acids (FFA)
What does glucagon do to muscle
Increase FFA
indirectly inhibits glucose uptake by muscle and fat
What does glucagon do to adipose tissue
Promotes lypolisis
What is a normal blood glucose level 4mM
between 70-110mg/dl (90 is the mean)
below 70 = hypoglycemia
above 180 = hyperglycemia
What does somatostatin do to insulin and glucagon
inhibits release
What stimulates somatostatin
increased AA
glucose
What is the overall effect of somatostatin
Decrease glucose
decreased glucose transport across gut wall
- decreased gut blood flow
What hormone is hypoglycemic
insulin (only one)
α- cells of the pancreas make
glucagon (mobilizes glucose)
β-cells of the pancreas make
insulin (stores glucose)
δ-cells of the pancreas make
somatostatin (regulatory, inhibits endocrine pancreas)
What hormones are hypoglycemic?
ONLY insulin
there is no plan-B
gluconeogenesis
the synthesis of glucose from noncarbohydrate sources, such as amino acids and glycerol. It occurs primarily in the liver and kidneys whenever the supply of carbohydrates is insufficient to meet the body’s energy needs.
stimulated by cortisol and other glucocorticoids and by the thyroid hormone thyroxine.
What are the major actions of insulin
↑ glucose transport into muscle & adipose cells
↓ blood glucose
↑ intracellular metabolic use of glucose
↑ glycogen synthesis in liver and muscle cells
↓ gluconeogenesis (in the liver)
↑ intracellular transport of aa & lipids and protein & triglyceride synthesis
↑ overall body growth (general effect)
How does insulin deprivation affect CHO metabolism?
insulin deficiency blocks glucose uptake & increases liver glycogenolysis > increase in serum glucose > increased glucose filtration in kidneys > glucose overload in kidneys
this causes:
glycosuria, polyuria, and polydypsia
define glycosuria (glucosuria)
glucose in the urine
when you loose glucose in the urine it drags water with it
polyuria
excessive urination
polydypsia
excessive thirst
Is glucagon anabolic or catabolic in terms of glycogen metabolism?
catabolic
it is used in situations where there is no fuel coming in but continued need for energy
If the body is hyperglycemic (high blood glucose) how does it normalize?
β-cells of pancreas release insulin
liver takes up glucose and stores it as glycogen
body / fat cells take in glucose from the blood
normal blood glucose levels are acheived
If the body is hypoglycemic (low blood glucose) how does it normalize?
α-cells of the pancreas release glucagon
liver breaks down glycogen and releases glucose into the blood
normal blood glucose levels are achieved
Where is somatostatin produced?
δ-cells of pancreas
GI tract
hypothalamus
(multiple forms 14 or 28 aa)
What happens to your blood sugar after you eat 10 chocolate chip cookies for lunch? How long does it take for insulin to be secreted?
blood sugar increases
insulin quickly released
- stored in pancreas and ready for release
You are on an 8-hr hike and you miss lunch. Does your blood sugar crash as you expend energy all day? What hormone would be increased in this metabolic situation?
no
glucagon
