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BRS 4: Endocrinology > 4.7: Glucose homeostasis > Flashcards

4.7: Glucose homeostasis Flashcards

1
Q

What kind of substrate is glucose

A

Energy substrate

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2
Q

What are normal blood glucose concentration levels

A

4-5mmol/L

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3
Q

What occurs when blood glucose concentration falls below normal levels (hypoglycaemia)

A

Cerebral function is increasingly impaired

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4
Q

What happens if blood glucose concentration falls below 2mmol/L

A

Unconsciousness
Coma
Ultimately death

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5
Q

Glucose regulation

A

Closely regulated
Feedback system required for regulation
High blood glucose releases insulin, blood glucose decreases and glucagon cortisol GH and catecholamines secreted to increase it

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6
Q

Persistent hyperglycaemia results in

A

Diabetes mellitus

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7
Q

What % of people are affected with diabetes mellitus in the UK?

A

7%

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8
Q

What is the % risk increase risk of a person with diabetes mellitus dying relative to aged-matched control without diabetes?

A

34%

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9
Q

What is the most prevalent form of diabetes

A

Type 2 diabetes mellitus

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10
Q

What structure does the pancreas gland have

A

Retroperitonael structure

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11
Q

What cells are present in the pancreas

A

Islets of Langerhans

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12
Q

98% of the pancreas generates

A

Exocrine secretions via duct to small intestine

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13
Q

What proportion of pancreatic blood supply is delivered to the islets of Langerhans

A

10-15%

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14
Q

3 types of islet cells and what they secrete

A

Alpha cells - glucagon
Beta cells - insulin
Delta cells - somatostatin

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15
Q

Communication between islet cells is called

A

Paracrine communication

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16
Q

Gap junctions between islet cells allow for

A

Small molecules to pass directly between cells

17
Q

Function of Tight junctions in islet cells

A

Create small intercellular spaces

18
Q

Broad function of insulin

A

Stimulates growth and development and reduces blood glucose
Growth and development in utero

19
Q

Broad function of glucagon

A

Increases blood glucose

20
Q

Function of somatostatin

A

Negative feedback effect on both insulin and glucagon

21
Q

Increase in blood glucose results in :

A

Stimulation of B-cells
Increased insulin secretion
Somatostatin inhibits glucagon
A-cells secrete glucagon to control insulin concentrations to ensure hyperglycaemia

22
Q

During high blood glucose insulin causes (3 main, 2 independent of glucose)

A

Build up of glycogen stores
Break down glucose
Increased glucose uptake

Increase protein synthesis
Reduction in breakdown of fat (glycolysis)

23
Q

As blood glucose decreases :

A

A-cells stimulated to produce glucagon
Somatostatin regulates insulin (stops secretion completely)
Some amino acids, GI hormones, SNS activity and PNS activity all regulate blood glucose

24
Q

Function of glucagon during low blood glucose levels

A

Increases lipolysis,
Increases amino acid transport in liver
Increases gluconeogenesis and hepatic glycogenolysis which increases blood glucose

25
Q

GLUT2 transporter sensitivity for insulin

A

Not insulin sensitive
Has a high capacity but not affinity for glucose

26
Q

Glucokinase is

A

The main glucose sensor (aka hexokinase IV)

27
Q

What happens as glucose binds to GLUT-2 receptor

A

Glucose enters cell, glucokinase converts glucose into Glucose-6-phosphate which produces ATP which inhibits K+ transporter, leading to influx of K+ and membrane depolarisation .
Ca channels open, causing influx of Ca2+ which causes mobilisation of insulin

28
Q

Effects of high glucose on c-peptide in healthy individuals

A

C-peptide increases

29
Q

Effects of high glucose on c-peptide in a person with type 1 diabetes, why?

A

Low C-peptide
Not enough insulin to immobilise into c-peptide

30
Q

How is c-peptide formed

A

Insulin is cleaved into c-peptide
Can be used much easier for testing

31
Q

Where is glucokinase (hexokinase IV) found in the body (4)?

A

Liver
Pancreas
Small intestine
Hypothalamus

32
Q

Main difference between actions of hexokinase I and hexokinase IV

A

Hexokinase IV is not subjective to -ve feedback from glucose-6-P

33
Q

What is the gastrointestinal “incretin” effect

A

Increased stimulation of insulin secretion elicited by oral as compared with intravenous administration of glucose under similar plasma glucose levels

34
Q

What is glucagon like peptide-1 (GLP-1) and what is it secreted in response to?

A

Gut hormone
Secreted in response to nutrients in gut

35
Q

What effects does GLP-1 have on the hormones secreted by the islets of langerhans?

A

Stimulates insulin
Suppresses glucagon

36
Q

What effect does GLP-1 have on satiety?

A

Increases satiety (feeling of fullness)
Delays gastric emptying

37
Q

Why does GLO-1 have a short half-life?

A

Rapid degradation from enzyme dipeptidyl peptidase-4 (DPPG-4 inhibitor)

38
Q

Which subunit does insulin bind to on the insulin receptors?

A

Alpha subunit

39
Q

What happens to the tyrosine kinase domains of beta subunits of the insulin receptors after insulin is bound to the receptor?

A

They undergo conformational change

BRS 4: Endocrinology (10 decks)

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