Endocrine regulation of energy

Question 1

Glucose levels are regulated by hormones that affect __ and __

Answer 1

Glucose levels are regulated by hormones that affect appetite and cell metabolism

Question 2

What are the major hormones involved in glucose control?

Answer 2

Insulin

Glucagon

Question 3

Other important Hormones of glucose control

Answer 3

Epinephrine 
Cortisol
Growth hormone 
Thyroid hormone 
Secretin 
Cholecystokinin

Question 4

Which hormone is the only hormone that lowers blood glucose?

Answer 4

Insulin

Question 5

What is the class of insulin receptor

Answer 5

RTK

Question 6

What is the class of glucagon receptor

Answer 6

GPCR

Question 7

What is the class of epinephrin receptor

Answer 7

GPCR

Question 8

Which class of enzymes carries out phosphorylation? Dephosphorylation?

Answer 8

phosphorylation (→ kinases) dephosphorylation (→ phosphatases)

Question 9

Which class of biological molecules do Gastrointestinal Hormones belong to?

Answer 9

peptides

Question 10

What do Gastrointestinal Hormones do? apart from regulating glucose levels

Answer 10

Regulate activity of the stomach, the intestine and the pancreas (in addition to the regulation by blood glucose)

Question 11

Where are many of Gastrointestinal Hormones also found? What role do they play there? Where do they get produced?

Answer 11

Many of these hormones are also found in the central or peripheral nervous system (somatostatin, gastrin, cholecystokinine, vasointestinal peptide, insulin, calcitonin)

• Function unknown
• Produced in the cell body of neurons
• May modulate signal transmission

Question 12

What is the most common endocrine disorder?

Answer 12

Diabetes mellitus.

Question 13

How was the function of the islets of Langerhans discovered?

Answer 13

Minkowski (1889) observes diabetes in dogs after pancreatectomy
v Discovery of abnormalities of the islets of Langerhans

Question 14

Apart from insulin, what are some other hormones secreted by pancreas?

Answer 14

glucagon, somatostatin, pancreatic peptide

Question 15

What are the exocrine and endocrine sections of pancreas?

Answer 15

Endocrine: islets of langerhans
Exocrine: duct cells, acinar cells

Question 16

Do islets of langerhans take up a large or a small section of pancreas?

Answer 16

very small (2% of pancreatic mass)

Question 17

role of acinar cells

Answer 17

Secretion of digestive enzymes (proteases, amylase, lipase)

Question 18

role of duct cells

Answer 18

Secretion of NaHCO3 (bicarbonate)

reduces the acidity of food in duodenum

Question 19

Role of islets of langerhans

Answer 19

– α-cells: Glucagon
– β-cells: Insulin
– D-cells: Somatostatin
– E-cell: Ghrelin (mainly produced by the stomach; some by pancreas)
– F-cells (also known as PP cells): PancreaticPolypeptide

Question 20

Where do the products of exocrine section of pancreas empty?

Answer 20

Empties into the duodenum

Question 21

Which hormones that are produced by pancreas are also produced by gastrointestinal mucosa?

Answer 21

Glucagon, somatostatin and pancreatic polypeptide are also produced by cells of the gastrointesinal mucosa

Question 22

What is the localization of various endocrine pancreatic cells?

Answer 22

Alpha and beta cells are the most numerous cell
alpha cells on the periphery; beta in the center
D, PP and E cells are closer to the periphery

Question 23

Describe the blood flow of the pancreas

Answer 23

• islets highly vascularized (5 to 10 x blood flow of exocrine pancreas)
• blood first supplies centrally located B cells i.e. detects glucose levels
• then blood travels to more peripheral A and D cells i.e. exposed to insulin secreted by B cells

Question 24

How are PP, Somatostatin, Insulin and glucagon inter-connected?

Answer 24

Glucagon stimulates insulin and somatostatin; insulin and somatostatin inhibit glucagon
Somatostatin inhibits insulin and PP production

Question 25

glucagon also produced as __; processed to __ to __

Answer 25

glucagon also produced as preproglucagon processed to proglucagon to glucagon

Question 26

Describe insulin synthesis

Answer 26

1) Preproinsulin
removal of its signal peptide ->
2) proinsulin
Proinsulin consists of three domains: A, B and C chains. Within the endoplasmic reticulum, proinsulin is exposed to several specific endopeptidases which excise the C peptide->
3) Active insulin that has a and b chains that are connected by disulphide bond
Insulin and free C peptide are packaged in the Golgi into secretory granules which accumulate in the cytoplasm

Question 27

Describe glucagon synthesis

Answer 27

glucagon is made as (1) proglucagon
- in pancreas, most of the other fragments are removed
in alpha cells 33-61 aa of the gene are retained-> glucagon
- in gut cells and brain different aa of the same gene are retained-> glicentin, GLP-1 and GLP-2 are formed
- active glucagon is a short single amino acid chain

Question 28

Effect of high glucose on alpha and beta cells

Overall effect?

Answer 28

• Inhibition of alpha cells-> decreased glucagon
• Stimulation of beta cells-> increased insulin
  Overall effect: reduction of blood glucose to normal level

Question 29

Effect of low glucose on alpha and beta cells

Overall effect?

Answer 29

• Stimulation of alpha cells-> increased glucagon
• Inhibition of beta cells-> decreased insulin
  Overall effect: increase of blood glucose to normal level