25 Gastrointestinal Peptides Chan

Question 1

What are the characteristics of Gut Peptide Hormones?

Answer 1

Diverse cellular sources. Wide scope of biological activities. Multiple structural forms. Multiple receptor subtypes. Multiple ligand-receptor specificity. Few therapeutic applications

Question 2

What is Gastrin secreted by?

Answer 2

G cells in the stomach

Question 3

What are the effects of Gastrin?

Answer 3

Increases acid secretion, increases mucus growth

Question 4

What is the stimulus for Gastrin release?

Answer 4

Peptides and amino acids in lumen; Gastrin releasing peptide and ACh in nervous reflexes

Question 5

What is Cholecystokinin (CCK) secreted by?

Answer 5

Endocrine cells of the small intestine (Duodenum/Jejunum); neurons of the brain and gut

Question 6

What are the effects of Cholescystokinin (CCK)?

Answer 6

Stimulates pancreatic enzyme and HCO3 secretion. Stimulates bladder contractions; inhibits stomach emptying (promotes satiety)

Question 7

What is the stimulus for Cholescystokinin (CCK) release?

Answer 7

Fatty Acids and some Amino Acids

Question 8

What is Secretin secreted by?

Answer 8

Endocrine cells of the small intestine (Duodenum/Jejunum)

Question 9

What are the effects of Secretin?

Answer 9

Stimulates pancreatic and hepatic HCO3 secretion; inhibits acid secretion; Pancreatic growth. Stimulates gallbladder contraction; inhibits stomach emptying

Question 10

What is the stimulus for Secretin release?

Answer 10

Acid in small intestine

Question 11

What is Gastric Inhibitory Peptide secreted by?

Answer 11

Endocrine K Cells of the small intestine

Question 12

What are the effects of Gastric Inhibitory Peptide?

Answer 12

Stimulates pancreatic insulin release. Inhibits Acid secretion. Satiety and lipid metabolism

Question 13

What is the stimulus for Gastric Inhibitory Peptide release?

Answer 13

Glucose, Fatty Acid, and Amino Acids in small intestine

Question 14

What is Motilin secreted by?

Answer 14

Endocrine cells in the small intestine (Duodenum/Jejunum)

Question 15

What are the effects of Motilin?

Answer 15

Stimulates migrating motor complex for motility

Question 16

What is the stimulus for Motilin release?

Answer 16

Fasting: cyclic release every 1.5-2 hours by neural stimulus

Question 17

What is Glucagon Like Peptide 1 secreted by?

Answer 17

Endocrine cells in small intestine

Question 18

What are the effects of Glucagon Like Peptide 1?

Answer 18

Stimulates insulin release; inhibits glucagon release. Possibly inhibits acid secretion. Slows gastric emptying. Satiety

Question 19

What is the stimulus for Glucagon Like Peptide 1 release?

Answer 19

Mixed meals of fats and carbohydrates

Question 20

What secretes Somatostatin and where are they located?

Answer 20

D cells, located throughout the GI tract

Question 21

Which GI regulatory peptide has endocrine, paracrine, neurocrine, and autocrine activity?

Answer 21

Somatostatin

Question 22

Where are GI regulatory peptides with neurocrine activity secreted?

Answer 22

Synpatic cleft

Question 23

How does Gastrin release regulate itself?

Answer 23

When released from G cells, Gastrin can act on the CCK2R on the D cell which releases Somatostatin. Somatostatin can then bind to SSTR2 on the G cell which inhibits further Gastrin release

Question 24

Besides Gastrin release from the G cell, what else can stimulate Somatostatin release from the D cell?

Answer 24

ACh acting on the GRP nerve can activate the GRP receptor on D cells which causes Somatostatin release. This same nerve can also act on GRP receptors on G cells which can cause Gastrin release

Question 25

How does Gastrin increase acid release?

Answer 25

Gastrin acts on CCK2R's on Parietal cells which cause H+ release

Question 26

How can Somatostatin decrease acid release?

Answer 26

Somatostatin released from D cells can act on the SSTR2's on Parietal cells which inhibit H+ release

Question 27

How can Histamine cause acid release?

Answer 27

Histamine acts on the HRH2's on parietal cells, causing H+ release (also act on the HRH2's on D cells, causing Somatostatin release)

Question 28

What are the effects of Octreotide on plasma levels of growth hormone in acromegaly?

Answer 28

By 108 weeks of treatment, the amount of growth hormone is normalized

Question 29

How are GI Peptides and Body Weight Control related?

Answer 29

Obesity is associated with the metabolic syndrome, chronic diseases like DM, HTN, and heart disease. Highly resistant to treatment with most of the weight lost regained within 5 years after dieting. Binge eating is implicated for more than 25% of the over weight population and is related to dysfunction of GI peptide signaling

Question 30

What are the Incretins?

Answer 30

A group of GI hormones (GLP-1, GIP) that lower blood glucose by: increasing insulin release and inhibiting glucagon release after eating, slowing the rate of nutrient absorption and reducing food intake by reducing gastric emptying

Question 31

What is the GI peptide control of food intake (GLP-1)?

Answer 31

Released in the lower gut. Decreases food intake by slowing gastric emptying; reduced hunger and increased fullness ratings

Question 32

How is GLP-1 degraded?

Answer 32

Rapidly by dipeptidyl peptidase 4 (DPP-4). Half-life of 1-2 minutes

Question 33

What are some synthetic analogues of GLP-1?

Answer 33

Extenatide (Byetta): injectable, with a half life of 2.4 hours; multiple injections required. Liraglutide (Victoza): injectable, with a half-life of 11-15 hours; once a day injection

Question 34

What are some Dipeptidyl Peptidase-4 (DPP-4) Inhibitors?

Answer 34

Sitagliptin (Januvia): effective in improving blood glucose control when used alone or with other diabetes meds. Saxagliptin (Onglyza): used alone or in combination with other oral diabetes medicines; may worsen peripheral edema when used with TDZ

Question 35

What is the GI peptide control of food intake (Ghrelin)?

Answer 35

Produced mainly by the stomach. Increased food intake when administered to humans. Level rises before meals and falls following meals. The higher the energy value of a meal the larger the postprandial decline. Level increases from the morning to the evening, reaches higher peak before dinner than before breakfast. Level rises following weight loss in obese subjects. Insulin and somatostatin strongly inhibit Ghrelin expression and secretion

Question 36

What is the GI peptide control of food intake (Cholecystokinin (CCK))?

Answer 36

After a meal, CCK is released from endocrine 1 cells of the duodenum and the jejunum. Reduces the sensation of hunger in part by inhibiting gastric emptying. Administration to humans inhibits food intake. A decrease in plasma CCK correlates with a decreased fullness and increased hunger

Question 37

What is the GI peptide control of food intake (Peptide YY (3-36))?

Answer 37

Secreted from specialized endocrine L cells of the large bowel. Circulating levels suppressed during fasting. Released into circulation within 15 minutes after meals and peaks in about 1 hour. Infusion of PYY in normal weight humans reduced 24-hour food intake. PYY levels in obese humans are reduced but anorectic effect is preserved

Question 38

What is known as the "hunger hormone"?

Answer 38

Ghrelin. When this hormone level is high it indicates the need to eat. Causes an increase in food intake