Effects of insulin on muscle Flashcards Preview

E: Regulatory Physiology & Pharmacology > Effects of insulin on muscle > Flashcards

Flashcards in Effects of insulin on muscle Deck (31):
1

What two classes of glucose carrier transfers glucose across the plasma membrane?

Sodium-coupled glucose transporters

Facilitative glucose transporters

2

Where is sodium-dependent glucose cotransporter expressed?

In absorptive and reabsorptive epithelia such as intestine and kidney.

3

How is glucose transport from the lumen of the intestine or nephrons?

They have to actively uptake glucose against its concentration gradient.

By coupling sodium uptake with glucose

4

Structure of the SGLT1?

14 TM domains.

Mutations affecting the transporter. 

Loss the capacity to absorb glucose

5

What is the conditions glucose-galactose malabsorption?

Glucose-galactose malabsorption is a condition in which the cells lining the intestine cannot take in the sugars glucose and galactose, which prevents proper digestion of these molecules and larger molecules made from them.

6

SGLT1 transport mechanism?

Bind to sodium ion.

Sugar then binds and thus a confirmational change. 

New site present. 

Sugar unbinds and thus so does sodium. 

Causing a confirmational change.

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7

How is glucose absorbed across the intestinal membrane?

Gut lumen to cells by SGLT1 

From cells into blood: GLUT2

Na:K symporter used to generate ATP

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8

Faciliative glucose transporters

Integral membrane protein

Present on the surface of all cell membranes.

Transports glucose down its gradient.

Bi-directionally

 

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9

The 3 classes on facilitative GLUT family?

Class 1->3

7TM domain.

10

Class 1 GLUT transport includes?

High affinity binding protein: GLUT 1, 3 4.

Low-affinity binding protein: GLUT2.

11

Class 2 GLUT transport includes?

Very low affinity: GLUT 5, 7, 9, 11.

Myoinositol transporter HMIT1

12

Class 3 GLUT transport includes?

GLUT 6, 8, 10, 12

13

GLUT1 transporter?

Low Km

High affinity.

Garage door.

Tissues involved in absorption, reabsorption and glucose sensing

14

GLUT 2 transporter?

High Km

Low affinity.

Role in sensing glucose conc. in islets.

Kidney, pancreatic beta cells, liver

15

GLUT 3 transporters?

High affinity

Placenta so the child will always receive the glucose it requires even if the mother is fasting

16

GLUT4 transporter?

Insulin responsive

Skeletal and cardiac muscle, adipose tissues

Responsible for mediating insulin-sensitive glucose transport.

17

Cytochlasin B?

Fungal metabolite.

Specifically binds to facilitative glucose transporters

Non-competitive. 

Inhibits cell functions such as division and movement

Binds to the cytoplasmic domain of the transporter

 

18

What does insulin do to the glucose transporters?

Stimulates the movement or translocation of glucose transporters from the intracellular membrane to the plasma membrane.

GLUT4

19

Use of green fluorescent protein in testing that insulin effects the translocation of glut4?

its a gene

Chrimetic protein can be produced of GLUT4.

Insulin comes in: can see the GLUT4 vesicles (as they are green) translocating to the plasma membrane

20

Insulin post-receptor signalling?

Insulin binds to the tyrosine kinase receptor at the alpha subunit.

Can activate the signalling pathways by the activation of: P13-kinase, PKB, MAP kinase, p70S6 kinase. 

Important for glucose transport, glycogen synthesis, protein synthesis etc.

21

Insulin Pathway 

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22

Action of insulin on muscle?

Increase of glucose uptake by increasing GLUT4 at cell surface.

Increase glucose effects: glucogen synthesis, glycolysis.

Increase amino acid uptake.

Increase protein synthesis. 

23

Regulation of skeletal muscle glucose uptake during exercise?

Regulated by:

Glucose supply

Glucose transport

Glucose phosphorylation

24

What is glucose phosphorylated into and how is this important?

GLUT4 allows transport of glucose

Glucose phosphorylated by hexokinase (HK) to form G6P.

G6P enters glycolysis

Maitains the concentration gradient for glucose to passively enter the cell.

As it cannot diffuse out of the cell.

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25

Why is G6P and HK important for type 2 dibaetes?

In type 2 diabetes: stimulation of flucose uptake is impaired in muscle..

However, exercise still stimualtes glucose uptake despite reduction in insulin-stimulated glucose

26

Name the 6 methods to study exercise and muscle contraction?

Cultured myotubes

Electrical stimulation

Nerve stimulation

Treadmill

Wheel running

Biopsies (From humans)

27

How does insulin and exercise differ when enhancing muscle glucose uptake

Exercise stimulates AMPK (kinase)

Senses the reduction in cellular levels.

Becomes activated when levels become too low.

28

Metformin?

Oral antidiabetic drug

Activates AMPK.

stimualtes the GLUT4 translocation.

29

AICAR?

another drug

resembles AMPK

30

What is the metabolic effects of AICAR and Metformin?

Inhibit hepatic glucose production

Stimulate muslce glucose uptake

Increase Lactic acid production

31

GLUT class receptor characteristics?

12 transmembrane domains

NH2 and COOH are facing the cytoplasm face.