Insulin and glucagon
Insulin
and glucagon are
work oppositely. Like, one is agonist another one is antagonist. When body
doesn’t maintain enough glucose level in body & remain the blood glucose
level high. Insulin are reduced blood glucose level & provide energy to
body.
Whenever the blood glucose level low pancreas secreted the glucagon that
increase blood glucose level & decrease the body glucose level. so, insulin and glucagon are work as a agonsit and antagonist.
There are
the four type of cells of islet of Langerhans : β cell secreted
insulin, α cell secreted glucagon, d cell secreted somatostatin & F
cell secreted pancreatic polypeptide.
Insulin
Insulin are
discovered in 1921 by banting & best. It was extracting the beta cell of
pancreatic islet. It produces the hypoglycemic action. First obtain as a
crystalline form in 1926 after many years in 1956 fully structure developed by
sanger.
In starting
preproinsulin produce that is 110 amino acid contain, after 24 amino acid
removed produce proinsulin. Main insulin is formed by the removal of C peptide
from the proinsulin by the proteolysis.
Insulin consists 2 peptide chain one is
A chain & another one is B. both are connected through disulphide bridge. Insulin
are producing the hypoglycemic effect.
Glucagon
after the
discovery of the insulin, in 1923 around two year after one component discover
that antagonize the insulin, produce the hyperglycemic effect. That called as a
‘glucagon’. Glucagon containing 29 amino acids.
It is a single chain polypeptide chain. Molecular
weight of the glucagon is 3500. Its secreted by the alpha cells of islet of
Langerhans. And also, a commercially produce by the recombinant DNA technology.
Another
hyperglycemic agents growth hormones, corticosteroids, catecholamines,
thyroxine etc.…
insulin vs glucagon (difference between insulin and glucagon) :
INSULIN
|
GLUCAGON
|
It produce
by the β cell of pancreas
|
It produce
by the a cell of pancreas.
|
it secreted by the red color β islet.
|
it secreted by the green color of a islet.
|
when
blood glucose level high its active
|
When blood
glucose level low its active.
|
Inhibit the gluconeogenesis
|
Stimulate the gluconeogenesis & release
of glucose from liver.
|
It increases
a body energy level. (body glucose level)
|
Decrease
a body energy level. (body glucose level)
|
it stimulates the uptake & storage of
glucose in skeletal muscle.
|
It produces no effect on skeletal muscle.
|
insulin deficiency
cause type 1 & type 2 diabetes.
|
Glucagon
deficiency cause glucagonoma & hypoglycemia.
|
Mechanism of action of insulin and glucagon (mao) :
Insulin
and glucagon are
opposite effect so, its mechanism of action is also opposite.
mechanism of action of insulin :
insulin
binds to tyrosine kinase receptor that present on the cell membrane. tyrosine
kinase receptor consists 2 alpha and 2 beta subunits. Alpha subunit is
extravascular & beta subunit is transmembrane protein.
Insulin
bind to alpha subunit it activates the tyrosine kinase receptor & also a
bind to beta subunit that produce the complex series like phosphorylation –
dephosphorylation reaction. That promote the entry of the glucose in the cell
& also a decrease the blood glucose level.
Mediated
various action of insulin. But entry of glucose into RBCs, WBCs, brain &
liver are not depending on insulin. Also, an exercise also facilitates entry of
glucose into muscle cell without use of insulin.
Insulin are
also a inhibit the gluconeogenesis & glycogenolysis, also a inhibit the
lipolysis in adipose tissue.
Insulin are
enhancing the protein synthesis in muscle & muscle glycogenesis. increase
the entry of amino acid into muscles & cell.
Mechanism of action of glucagon :
Glucagon
are producing a hyperglycemic effect, most of its function are opposite
the insulin. Glucagon are decrease the
body glucose level. But it is increasing the blood glucose level. Its play a
major role in development of diabetes ketoacidosis.
Glucagon
activate adenyl cyclase by Gs coupling receptor & increase the cAMP in
heart cell, fat cell & liver cell & other tissue. It inactivates
orally, that release from pancreas is broken down in kidney, plasma, liver
& other tissue. Its half life is 3 to 6 min.
Insulin secretion regulation:
·
Hormonal
· Neural
·
Chemical
Insulin hormone:
many hormones like, corticosteroids, growth hormones &
thyroxine modify insulin release in response to glucose. PGE are the inhibit the
insulin release. The different islet of pancreas is produced different hormone
like, β
cell are the core of the islet & that are most abundant cell type.
- The α cell comprise the 25 % of its islet mass. d cell is secreted a somatostatin.
- Somatostatins are inhibiting the release of insulin & glucagon.
- Glucagon are stimulating the release of somatostatins & insulin.
- Insulin are inhibiting the glucagon secretion. Amylin & another β cell polypeptide release insulin. Inhibit the glucagon secretion through a central site of action in brain.
Insulin neural:
- Islet of Langerhans are richly supplied by vagal & sympathetic nerves.
- Adrenergic beta2 receptor increase the insulin release trough adenyl cyclase.
- Adrenergic alpha2 receptor reduced the insulin release through inhibit the beta cell adenyl cyclase.
- Also, a vagal stimulation or cholinergic – muscarinic activation by acetyl choline cause insulin secretion through IP3 – DAG – increase intracellular calcium in the b cells.
Insulin chemical:
its phosphorylation by glucokinase. Glucose metabolism &
its entry leads to activate the glucosensor which is indirectly inhibit the K+
channel resulting produce the partial depolarization of β cell.
The increase the influx of calcium ion & decrease the efflux
® increase the
intracellular ca2+ ®
exocytic release of insulin also other nutrients that stimulate the insulin release
like, fatty acid, amino acid & ketone bodies. glucose is the principle of
the regulator & it stimulate the synthesis of insulin.
Glucose & other nutrients are more effecting in
stimulate the insulin release when it given orally than i.v.
Function of insulin and glucagon
Insulin function
Diabetes mellitus syndrome by hyperglycaemia due to
deficiency of insulin. Insulin also affect the protein, fat, carbohydrate
metabolism.
Insulin are mainly effective in all forms of diabetes
mellitus & is must for type 1 cases, also a useful in gastrational diabetes
& pancreatectomy diabetes. Another one many of diabetes type 2 case can be
control by diet. Proper diet & exercise can also recover,
insulin needed
some patient who,Not controlled by exercise & diet.
- Failure of primary & secondary oral hypoglycaemics.
- Underweight patient.
- Patients in coma
- Complication of diabetes like nonketotic, ketoacidosis, gangrene etc.
- Mostly type 1 diabetes patients required a 0.4 to 0.8 U/Kg/day & diabetes type 2 patients required a 0.2 to 1.6 U/kg/day. Also, a depend on the body weight. Obese patients required a higher dose.
Glucagon function
Hypoglycaemia due to insulin; use of glucagon is; it measures
for the emergency & followed by oral glucose/blood glucose level stabilize.
Its not work if hepatic glycogen is already depleted.
Cardiogenic shock to stimulate heart in beta adrenergic
blocker treated patients. Its action is not marketed.
To facilitate radiography examination of lower / upper
gastro track by relaxing & intestine.
They generate the chemical signals from gut (incretins) that
act on β
cell in the pancreas to cause an anticipatory release of insulin.
The incretin involves in various like glucose dependent
insulinotropic polypeptide (GLP), glucagon like polypeptide – 1 (GLP-1), vasoactive
intestinal peptide (VIP), pancreozymin – cholecystokinin etc...
Various incretin is may mediate signal from various nutrient.
So, glucagon & some of these peptides enhance the
insulin release by increasing cyclic AMP formation in the β
cells.
conclusion :
here, all details of insulin and glucagon like its mechanism of action, use, regualtion of insulin, difference between insulin and glucagon, i hope you like my article everything about insulin and glucagon, if you like comment out.
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