for bachelor mbbs, nursing and paramedics

1. Gastrointestinal Hormone
and Disorders -I
Binaya Tamang
UCMS-TH

2. Introduction
• There are more than 30 peptides expressed within the digestive tract.
• Making the gut the largest endocrine organ in the body.
• Secreted by pancreatic islet cell ( somatostatin), GUT mucosa ( CCK)
and nerve of intestine ( VIP)
• They can act as
• Regulatory peptide hormone
• Peptide neurotransmitters
• Growth factors
• Collectively, they influence motility secretion digestion and absorption in
the GUT.
• Regulate bile flow and secretion of pancreatic hormones

3. Principal GUT regulatory protein: Two Family
üGastrin family
• Cholecystokinin
• Gastrin ( little-17aa and big-34aa)
üSecretin-Glucagon family
• Secretin
• vasoactive intestinal polypeptide (VIP)
• Glucose dependent insulinotropic polypeptide (GIP)
Lets describe some important types

4. Cholecystokinin (CCK):
• Linear peptide hormone (33aa).
• Preprocholecystokinin ( 115aa) by
cleavage àCCK
• Secreted by C or I cells of duodenum
and jejunum.
• Main stimulus: mix polypeptides with
aa ( Trp and Phe), gastric juice and FA
>9C
Fxn:
• stimulates gallbladder contraction
and bile flow
• To reach inside intestineà relaxes
sphincter of Oddi
• Increases secretion of digestive
enzymes from pancreas.
• Increases small intestine motility.
• Has a role as indicating satiety ( I am
not hungry anymore)

5. Gastrin
• Secreted by G cells of the stomach and proximal part of duodenum.
• Preprogastrin by cleavage (101 aa) à gastrin.
• Big gastrin (34 aa) and Small gastrin (17aa)
• Biologically active part is C terminal pentapeptide (5aa).
• In market, synthetic peptide called as Pentagastrin à used in gastric
function test.
• Stimulated by : meals, aa (Gly, Trp, Phe), alcohol, caffeine, smelling,
chewing, tasting (vagal stimulation).
• FXN: stimulates acid (HCL) and prorenin, pepsin secretion, also
stimulates pancreatic secretion, intrinsic factor.
• Excessive gastrin secretion: gastrin producing tumors as Zollinger-Ellison
syndromeà resulting in very high level of acidity and chronic gastric
ulcers

6. Secretin (HCO3-)
• Linear polypeptide (27aa), secreted by S cell of the duodenum and
jejunum.
• Primarily released on contact of S cell with gastric HCL.
• Not released until pH is < 4.5.
• FXN: Stimulates pancreatic bicarbonate secretion so that gastric HCL is
maintained ( neutralized) à optimum pH is maintained for the action of
pancreatic enzymes.
• It also inhibits gastric secretion
• Acts synergistically with CCK

7. Glucose dependent insulinotropic polypeptide
(GIP)
• Old name : Gastric inhibitory peptide (42 aa).
• Secreted by neuroendocrine K cells of duodenum and proximal jejunum.
• Stimulated by glucose, TG taken orally not IV.
üFxn:
• stimulates insulin release by hyperglycemia,
• inhibits gastric acid, pepsin and gastrin secretion ( OLD name)
• reduces gastric and intestinal motility;
• increase fluid and electrolyte secretion from small intestine.
• Overall regulates glucose and lipid metabolism by increasing release of
insulin.
• Response to GIP is defective in type 2 DM.

8. Vasoactive intestinal polypeptide ( VIP)
• Linear polypeptide (28 aa)
• is a neuropeptide released by enteric neurons.
• Present throughout the body but highest in nervous system and GUT.
• No evidence of its release during digestion
üFXN:
• Acts as neurotransmitter in central and autonomous nervous system,
• Vasodilation and relaxation of smooth muscle of GUT.
• Secretion of water and electrolytes from the pancreas and GUT as
well.
• Release of hormones from the hypothalamus, pancreas and GUT.

9. Glucagon like peptides ( GLP-1)
• Polypeptide (31aa)
• Site of origin: L cells in ileum and colon
ü FXN:
• It potentiates Glucose dependent insulin secretion
• Simple: Insulin production is 70% greater when when glucose is
administered orally than when similar conc is reached after IV.
• BUT WHY?
• This increment is due to intestinal factors, termed incretins ( most imp is
GLP1)à AUGMENTATION EFFECT
• USEFULALSO
• Good target for treating DMà increases the level of insulin significantly.
• GLP-2 acts as enterocyte-specific growth hormone.

10. Ghrelin
• Site of origin: stomach and hypothalamus
• 28 aa, acylated on ser3 with octanoic acid.
• Stimulates the release of GH ( so the name Growth-hormone release)
üFxn: Ghrelin stimulates to release neuropeptide Y (NPY)à NPY
enhances appetite (increases)
üREGUATED:
• Its production is increased by fasting, hypoglycemia and leptin.
• Conversely inhibited by food intake, hyperglycemia and obesity
• High before meal but falls rapidly after taking meal.

11. Somatostatin
• Secreted mainly by delta cells of pancreas, also by GUT and
hypothalamus.
• It is the main inhibitory peptide of GI tract.
• Fxn;
• Inhibits the production of numerous GUT peptides
• Like: gastrin, CCK, Secretin, VIP ,Insulin,
• Pancreatic enzymes and electrolytes into intestine

12. Other hormones

13. 👍THANK YOU 🙏