A TRIANGULAR GLAND, WHICH HAS BOTH EXOCRINE AND ENDOCRINE CELLS, LOCATED BEHIND THE STOMACHACINAR CELLS PRODUCE AN ENZYME-RICH JUICE USED FOR DIGESTION (EXOCRINE PRODUCT)PANCREATIC ISLETS (ISLETS OF LANGERHANS) PRODUCE HORMONES INVOLVED IN REGULATING FUEL STORAGE AND USE.

1. ENDOCRINE
PANCREAS

2. PANCREAS
• A TRIANGULAR GLAND, WHICH HAS BOTH EXOCRINE AND
ENDOCRINE CELLS, LOCATED BEHIND THE STOMACH
• ACINAR CELLS PRODUCE AN ENZYME-RICH JUICE USED
FOR DIGESTION (EXOCRINE PRODUCT)
• PANCREATIC ISLETS (ISLETS OF LANGERHANS) PRODUCE
HORMONES INVOLVED IN REGULATING FUEL STORAGE AND
USE.

4. ISLETS OF LANGERHANS
• PAUL LANGERHANS – German medical student, 1st
discovered in dogs in1869
• 1-2% of the pancreatic mass
• 1- 2 million islets in humans
• Beta (β) cells produce INSULIN
• Alpha (α) cells produce GLUCAGON
• Delta (δ) cells produce SOMATOSTATIN
• F cells produce PANCREATIC POLYPEPTIDE

5. INSULIN

6. Frederick G. Banting and John
Macleod were awarded the Nobel
Prize in Physiology or Medicine in
1923 "for the discovery of insulin."
SOURCE- http://www.nobelprize.org/educational/medicine/insulin/discovery-
insulin.html

7. INSULIN STRUCTURE
• Large polypeptide 51 AA (MW 6000)
• Two chains linked by disulfide bonds.
• A chain (21AA)
• B chain (30 AA)
• The hydrophobic character of the amino acids at the C-
terminal of B-chain is important for biological activity of
Insulin

8. INSULIN STRUCTURE

9. Insulin Synthesis
• Insulin gene is located on the short arm of the
chromosome 11
• Synthesized as Preprohormone containing 110
amino acids

10. DNA (chromosome 11) in β cell
mRNA
Preproinsulin – 110 aa (signal peptide, A
chain,B chain, and peptide C)
Proinsulin – 86 aa

11. •Insulin gene encodes a large
precursor of insulin (preproinsulin)
•During translation, the signal
peptide is cleaved (proinsulin)
•During packaging in granules by
golgi, proinsulin is cleaved into
insulin and C peptide

13. C - PEPTIDE
Connects A & B chains
Facilitates folding of A & B chains
Retained in granules
No biological activity, but secreted in equimolar
ratio with Insulin
Hence its concentration in plasma directly
reflects β–cells activity

14. Regulation of insulin secretion
Mainly regulated by feed back control signal
provided by nutrients level in plasma
“ Hormone of Abundancy”

16. PLASMA GLUCOSE

17. MECHANISM OF GLUCOSE
INDUCED INSULIN
SECRETION

19. METABOLISM OF
INSULIN
• Insulin circulates freely in plasma
• Its half life is 5-8 min.
• Metabolic clearance is 800ml/min
• Basal insulin release to the circulation is about
0.5-1 unit/hr
• Total release into peripheral circulation in a day is
30 units
• Metabolized mainly in Liver & Kidney

20. MECHANISM OF ACTION
INSULIN RECEPTOR
• A glycoprotein tetramer having 2 α
and 2 β subunits
• Gene located on chromosome 19
• Insulin binds with α subunit resulting in
conformational change of receptor
• The HR complex is then internalized by
endocytosis

21. MECHANISM OF ACTION
Binding of Insulin to α subunit
Conformational change in Receptor (β subunit)
Activation of tyrosine kinase activity of β
subunit
Autophosphorylation of β subunit on tyrosine
residues
Phosphorylation of intracellular proteins that
brings about alteration in cell functions

22. MECHANISM OF ACTION
 The active tyrosine kinase phosphorylates tyrosines on
Insulin Receptor Substrates (IRS1 & IRS2)
 IRSs are docking proteins to which a variety of
downstream proteins bind
 Phosphorylation of IRS causes translocation of GLUTs
(Glucose Transport Proteins) to the cell membrane
 GLUTS facilitate glucose entry into the cell
 Different protein channels are also inserted into the
plasma membrane leading to increased entry of amino
acids, K+, Mg+ & P+

23. GLUCOSE TRANSPORTERS

24. MECHANISM OF ACTION

25. PHYSIOLOGICAL
ACTIONS OF
INSULIN

26. 27
Ganong Review of Medical Physiology 1985 12th ed #258

27. INSULIN ACTION ON
LIVER
CARBOHYDRATEMETABOLISM
•Stimulates glucose oxidation
•Promotes glucose storage as glycogen
•Inhibits glycogenolysis
•Inhibits gluconeogenesis
MUSCLE
•Stimulates glucose uptake (GLUT4)
•Promotes glucose storage as glycogen

28. INSULIN ACTION ON
CARBOHYDRATE METABOLISM
ADIPOSE TISSUE
• Stimulates glucose transport into
adipocytes
• Promotes the conversion of glucose into
triglycerides and fatty acids
“ANTI-DIABETOGENIC”

29. INSULIN ACTION ON PROTEIN
METABOLISM
• Facilitates amino acids entry into muscle
cells
• Facilitates protein synthesis in ribosomes
by induction of gene transcription
• Inhibits proteolysis by decreasing
lysosomal activity
“ANABOLIC HORMONE”

30. INSULIN ACTION ON FAT
METABOLISM
LIVER
• Anti ketogenic & Lipogenic
• Stimulates HMG-CoA reductase
ADIPOSE TISSUE
• Promotes storage of fat
• Inhibits lipolysis by inhibiting Hormone
sensitive lipase
• Promotes lipogenesis by stimulating
lipoprotein lipase

31. INSULIN ACTION ON PLASMA K+
CONCENTRATION
• Facilitates rapid entry of K+ into cell by
simulating Na-K ATPase activity
• Thus decreases plasma concentration of
K+
• APPLIED: Insulin is given along with
glucose in the treatment of Hyperkalemia
that occurs in Acute Renal Failure
“PHYSIOLGICAL REGULATOR OF PLASMA

32. INSULIN ACTION (SUMMARY):
CELLS
•  GLUCOSE USE & STORAGE
•  PROTEIN SYNTHESIS
•  FAT SYNTHESIS
Dominates in Fed State Metabolism
•  GLUCOSE UPTAKE IN MOST Anti-
Diabetogenic
Anabolic
Anti-ketogenic
Lipogenic

33. GLUCAGON

34. • A 29-amino-acid polypeptide hormone that is a
potent hyperglycemic agent
• Produced by α cells in the pancreas
• Its major target is the liver, where it promotes:
• Glycogenolysis – the breakdown of glycogen to
glucose
• Gluconeogenesis – synthesis of glucose from
lactic acid and non carbohydrates
• Release of glucose to the blood from liver cells

35. DNA in α cells
mRNA
Preproglucagon
Proglucagon
Glucagon

37. PHYSIOLOGICAL ACTIONS OF
GLUCAGON
•Stimulates glycogenolysis, gluconeogenesis
& inhibits glycogenesis
•Promotes lipolysis & ketogenesis
•Increases calorigenesis
“Prodiabetogenic and Ketogenic”

38. INSULIN-GLUCAGON
RATIO
• Insulin is hormone of energy storage
• Glucagon is hormone of energy release
• A balance should be maintained for normal
metabolic functions
• After a normal balance diet is 3
• After overnight fasting decreases to 1, may
decrease to as low as 0.4 after prolonged fasting
• Physiological significance – during neonatal
period a low I/G ratio is critical for survival of the

39. INSULIN & GLUCAGON REGULATE
METABOLISM

40. NORMAL PLASMA GLUCOSE LEVELS
•Fasting : 70 – 100mg%
•Postprandial : 100 – 140mg%
•RBS : 80 – 120mg%

41. GLUCOSE
HOMEOSTASIS

42. GLUCOSE
HOMEOSTASIS

43. SOMATOSTATIN
•Secreted from D
cells of pancreas
•Also secreted in
hypothalamus & GIT
•A peptide hormone
with 2 forms, one
with 14 AAs & the
other with 28 AAs
Functions:
•Inhibits secretion of
insulin & glucagon
•Inhibits GI motility* & GI
secretions
•Regulates feedback
control of gastric
emptying

44. PANCREATIC
•Secreted from F
Pc
Oe
Llls
YPof
Ep
Pa
Tn
Ic
Dre
Eas
•Polypeptide with 36 amino acids
•Structurally similar to Neuropeptide Y
secreted from hypothalamus
•Secreted in response to food intake
•Inhibits exocrine pancreatic secretion
•Slows the absorption of food from the GI
tract

45. APPLIED PHYSIOLOGY
INSULIN DEFICIENCY – DIABETES MELLITUS
INSULIN EXCESS – INSULINOMA
GLUCAGON EXCESS – GLUCAGONOMA
SOMATOSTATIN EXCESS –
SOMATOSTATINOMA
CARCINOMA OF PANCREAS

46. DIABETES
•A serious diso
Mrde
Er
Lo
Lfc
ITar
Ubo
Shydrate
metabolism
•Most common endocrine disorder
•Results from hyposecretion or hypoactivity
of insulin
•The three cardinal signs of DM are:
• Polyuria – huge urine output
• Polydipsia – excessive thirst

47. Classification of DM
Type 1 or IDDM - Insulin Dependent Diabetes
Mellitus
Type 2 or NIDDM - Non-Insulin Dependent
Diabetes Mellitus
Other Types of Diabetes Mellitus – MODY, pancreatic
diseases, drug induced (corticosteroids, thiazide
diuretics, phenytoin)

50. 52
Polyphagia – decreased activity of
satiety center removes its inhibitory
effect on feeding center in brainPolyuria – is due to osmotic diuresis
Polydipsia – dehydration due to
polyuria stimulates thirst

51. 53
Glycosuria - because when insulin is
not present, glucose is not taken up
out of the blood at the target cells.
So blood glucose is very highly
increased → increased glucose is
filtered and excreted in the urine
(exceeds transport maximum)

52. 54
Ketosis -
Fats and proteins are metabolized
excessively, and byproducts known as
ketone bodies are produced. These are
released into the bloodstream and
cause:
Decreased pH (so increased acidity)
Compensations for metabolic
acidosis
Acetone given off in breath

53. 55
Weight loss - patient eats, but nutrients
are not taken up by the cells and/or
are not metabolized properly
“Disease of Starvation midst of
Plenty”

55. DIAGNOSIS
•Demonstrating persistent hyperglycemia &
glycosuria
•Glucose Tolerance Test (GTT) – oral is
preferred
•Estimation of Fasting Blood Glucose (FBS)
•FBS more than 126mg% in more than two
occasions confirms DM

56. TREATMENT
•Insulin therapy
•Oral hypoglycemic agents
•Life style modifications

57. COMPLICATIO
NS
•Microvascular – diabetic retinopathy,
diabetic nephropathy
•Macrovascular – Myocardial Infarction &
Stroke
•Diabetic neuropathy
•Chronic ulcer & gangrene formation due to
decreased resistance to infection