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GERR Physiology > Carbohydrate metabolism and blood glucose control > Flashcards

Carbohydrate metabolism and blood glucose control Flashcards

1
Q

Explain Carbohydrate Metabolism

A

1- Dietary sugar and starch ingested are transformed to fructose, galactose and glucose
2- metabolized in liver
3- then used via glycolysis & TCA cycle to generate energy

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2
Q

what happens in the case of no glucose in body from food

A

Glucose can be synthesized through fat or amino acids , if there is no glucose available to use

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3
Q

How does the liver convert fructose and galactose to glucose ?
Why must it be converted ?

A
  • the enzyme glucose 6-phosphatase , which hepatocytes contain in large amounts converts them to glucose
  • glucose is the final pathway for carbs to be transported into tissue cells
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4
Q

How does glucose transport through the cell membrane

A
  • Glucose is transported by facilitated diffusion across the cell membrane
  • this involves protein transporters binding with glucose to move it across the membrane
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5
Q

What are GLUT proteins, what is the difference between the types and what is their function

A
  • glucose transporters that mediate the concentration of glucose uptake in tissues
  • some are more efficient than others, those are often found in tissue that requires a lot of energy ( ex: brain , RBC, cornea, CNS ) GLUT 1&3 > GLUT 2&4
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6
Q

How is glucose absorption in GI different

A

requires active sodium-glucose co-transport

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7
Q

What is the main regulator of glucose concentration

A

Insulin

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8
Q

Describe Insulin, why it is secreted and it’s degradation

A
  • large polypeptide hormone of 2 amino acid chains
  • produced by pancreatic B-cells in islets of langerhans
  • secretion is stimulated by increase of blood glucose levels
  • degraded in liver after 6 min
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9
Q

How is insulin secreted

A
  • high levels of ATP close potassium channels in Beta cell
  • membrane depolarization opens Calcium channels
  • calcium is insulin secretion signal
  • preformed insulin is produced by ER , gets processed through Golgi and then insulin is released into blood stream
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10
Q

What are Sulfonylureas

A

drugs used to treat type 2 diabetes , close potassium channels to increase insulin secretion

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11
Q

what is Glucagon-like peptide

A

drug that increases insulin secretion by opening calcium channels

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12
Q

What is the effect of Somatostatin and Norepinephrine on Insulin

A

reduce insulin secretion

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13
Q

When are insulin levels highest , how long does it last

A

after a meal , 2-3 hours

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14
Q

Graph relationship with insulin secretion and glucose

A

linear relation

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15
Q

Minor factors regulating insulin secretion

A
  • levels of circulating amino acids in blood: can stimulate insulin which increases protein tissue uptake
  • GI hormones : while eating
  • Autonomic nervous system: stress decreases secretion , eating / relaxing increases secretion
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16
Q

Effect of insulin on adipose tissue

A 
increase glucose uptake = lipogenesis ( store fat) 
decrease lipolysis ( breakdown of fat )
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17
Q

Effect of High insulin on liver

A

Increase glucokinase and thus glucose uptake
increase glycogen synthesis , storing glycogen
decrease gluconeogenesis ( break down of glucose)

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18
Q

Effect of insulin on striated muscle

A

increase glucose uptake, glycogen synthesis, protein synthesis

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19
Q

Effect of Insulin on glucose facilitated diffusion

A
  • in fasting conditions : muscle GLUT4 does not take up glucose at low levels, will use fat instead
  • GLUT4 in insulin presence will increase glucose uptake , increasing facilitated diffusion
20
Q

Exercise effect on Glucose facilitated diffusion

A

muscles active = glucose diffused to be used for energy

muscles inactive = glucose turned to glycogen

21
Q

Effect of low insulin on liver

A
  • increase glycogen phosphorylase which increases glycogen breakdown
  • increase glucose 6 phosphatase which increase glucose release from liver
22
Q

Effect of insulin on Brain

A
  • Insulin has minimal effect on brain glucose uptake

- GLUT 1 is always readily taking up glucose

23
Q

What happens due to hypoglycaemia ( symptoms )

A

nervous irritability, fainting, convulsions , coma

24
Q

What is the major site of glucose uptake

A

muscle

25
Q

If Boy suffering from hyperglycaemia is given insulin and potassium chloride , what will the rapid effect of insulin stimulate

A

Glucose transport in muscle

26
Q

What raises glucose levels ( 4 hormones )

A

1- glucagon
2- adrenaline/noradrenaline
3- Growth hormone
4- cortisol

27
Q

What is Glucagon , what stimulates its secretion, what does it counteract

A
  • large polypeptide produces by pancreatic alpha cells in islets of langerhans
  • stimulated by low blood glucose
  • counteract actions of insulin
28
Q

Effect of low blood glucose in liver

A
  • increase glycogenolysis to produce more glucose
  • increase gluconeogenesis
  • decrease glycogen storage
29
Q

Explain how glycogen breaks down into glucose

A
  • glucagon receptor signalling increases cyclic AMP and Protein kinase
  • stimulating glycogen phosphorylase
    promoting glycogen breakdown and glucose release
30
Q

How is glucagon secretion regulated ( stimulation / inhibition )

A
  • increased by low blood glucose and increased amino acids ( lead to gluconeogenesis )
  • exercise increases glucagon secretion
  • inhibited by somatostatin produced by pancreatic delta cells
31
Q

Describe somatostatin mode of action

A

general suppressive action on metabolism thus extending time nutrients are used

32
Q

Effect of adrenaline/noradrenaline on glucose metabolism ( in liver and adipose tissue )

A

increases glycogenolysis & lipolysis

33
Q

Effect of Cortisol and Growth hormone on glucose metabolism ( in liver, muscle and adipose tissue )

A

stimulates gluconeogenesis, decreases tissue glucose uptake and increases lipolysis

34
Q

Relationship of hypoglycaemia and stress

A

stress hormones will increase blood glucose levels to prevent hypoglycaemia

35
Q

Explain Type 1 diabetes, cause, onset and its frequency

A
  • caused by B-cell dysfunction in pancreas
  • due to viral infection, hereditary or autoimmune disease
  • insulin-dependent
  • 10% of cases
  • juvenile onset ( 14 y)
36
Q

Explain Type 2 diabetes, cause, onset and its frequency

A
  • tissues become resistant to insulin
  • non insulin dependent
  • obesity related
  • adult onset ( 30y)
37
Q

Hyperglycaemia symptoms ( 8)

A
  • always hungry
  • tiredness
  • frequent urination.
  • sudden weight loss
  • wounds not healing
  • blurry vision
  • numb feet or hands
  • thirsty
38
Q

Glucose filteration in kidneys

A

glucose is filtered out & reabsorbed in proximal tubule using GLUT2

39
Q

Effect of hyperglycaemia on urine

A

if blood glucose is at a higher concentration than 10 mmol/L the proximal tubule is overwhelmed and glucose will be excreted in urine

40
Q

What are Gliflozins

A

drugs that decrease renal glucose reabsorption and thus decrease blood glucose levels

41
Q

How does hyperglycaemia cause dehydration ( Explain effect in cells, kidney & brain )

A
  • high blood glucose increases osmolarity of ECF and thus cells loose water
  • high blood glucose increases osmolarity in renal tubular fluid decreasing water absorption and thus water is excessively lost in urine
  • increased blood osmolarity activates osmoreceptors to secrete ADH and activate the hypothalamus
42
Q

What is glucotoxicity and its effect

A

high concentration of glucose will cause glucose to react with proteins and signalling pathways which can result in tissue damage

43
Q

Diabetes effect on fat metabolism ( 2 possible conditions)

A
  • increased lipase increases lipolysis ( since insulin is what usually inhibits lipase )
  • fatty acids will be metabolized to keto acids which decrease blood PH = diabetic keto acidosis ( can be smelled on breath )
  • can also cause hyperkaelemia
44
Q

Effect of diabetes on body protein

A
  • decrease insulin increases protein and fat use and thus rapid weight loss
  • especially type 1 diabetes
45
Q

How is Diabetes diagnosed

A

1- Urinary glucose level ( over 10 mmol/L)
2- Fasting blood glucose
3- Fasting plasma insulin ( different for T1 &T2 diabetes)
4- Glucose tolerance test ( if blood glucose is not decreased after glucose is given )
5- keto acidosis ( nail varnish smell on breath )

46
Q

If someone is severely hypoglycaemic what additional condition might occur

A

keto acidosis since the hypoglycaemia will decrease insulin levels and increase glucagon

GERR Physiology (18 decks)

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