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Biochemistry > Obesity > Flashcards

Obesity Flashcards

1
Q

Why is studying obesity important?

A

Predisposes development of type II diabetes

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2
Q

Define obesity

A

Excess accumulation of fat in the body

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3
Q

What are the 4 ways obesity can be measured?

A

> BMI
Waist to hip ratio
Skin fold calliper test
Calculate proportions of muscle to fat to water

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4
Q

What is BMI?

What do the different ranges indicate?

A

Body mass index
= mass/height^2

20-25 = normal
25-30 = grade I
30-40 = grade II
40+ = morbidly obese = increase risk of death
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5
Q

What are the 3 causes of obesity?

A

> Increased food consumption + reduced energy expenditure
Genetic causes
Pathological = disease causing process that results in obesity

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6
Q

What is leptin?

A

Protein w/ 167 amino acids

  • acts like a hormone (reduces Neuropeptide Y production)
  • produced by adipocytes
  • controls appetite
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7
Q

What is the name of the gene that encodes leptin?

A

OB gene

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8
Q

How can the OB gene cause obesity?

What is this condition known as?

A

Homozygous mutation in OB gene

  • -> leptin not produced/ non-functional
  • -> appetite never sated

Ob/Ob

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9
Q

Describe how appetite is controlled

A
  1. Adipocytes secrete leptin into blood stream
  2. Leptin reaches hypothalamus + binds to leptin receptor
  3. -> reduced production of Neuropeptide Y
  4. -> increased energy expenditure + reduced food intake
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10
Q

How does Ob/Ob lead to a patient always being hungry?

A
  1. Don’t produce leptin
  2. Neuropeptide Y produced all the time
  3. Decreased energy expenditure + increased food intake
  4. Always hungry
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11
Q

Give an example of a pathological cause of obesity

A

Cushing’s disease

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12
Q

Describe a cushingoid appearance

A 
> moon face
> truncal obesity 
> striae (stretch marks)
> thin extremities/ limbs due to muscle wasting  
> diabetic 
> buffalo hump
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13
Q

What can Cushing’s be due to?

A

Adenoma in pituitary gland

Adrenal tumour

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14
Q

What is an adenoma?

A

Benign tumour of epithelial origin

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15
Q

What are the 2 types of adenomas?

A

Microadenoma
= less than 10mm

Macroadenoma
= more than 10mm

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16
Q

What are the 2 regions of the pituitary gland?

A

Anterior

Posterior

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17
Q

What does the anterior region of the pituitary gland secrete and by which cells?

A 
Basophilic cells:
> FSH
> LH
> ACTH
> TSH

Acidophilic cells:
> GH
> prolactin

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18
Q

What does FSH stand for?

A

Follicle stimulating hormone

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19
Q

What does LH stand for?

A

Luteinising hormone

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20
Q

What does ACTH stand for?

A

Adrenocorticotropic hormone

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21
Q

What does TSH stand for?

A

Thyroid stimulating hormone

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22
Q

What does GH stand for?

A

Growth hormone

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23
Q

What does the posterior region of the pituitary gland secrete?

A

Oxytocin

Vasopressin

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24
Q

What are the regions of the adrenal gland?

A

Cortex

Medulla

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25
Q

What does the medulla of the adrenal gland do?

A

Produces catecholamines: epinephrine + norepinephrine

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26
Q

What does the cortex of the adrenal gland do?

A

Corticosteroids:
> cortisol
> mineralocorticoids
> sex steroids

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27
Q

What are the 3 layers of the cortex from outside to the medulla?

A

 Zona Glomerulosa
 Zona Fasciculata
 Zona Reticularis

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28
Q

What is the normal function of cortisol?

A

Raises blood glucose levels

29
Q

What happens in normal circumstances when the pituitary gland secretes ACTH?

What is this an example of?

A
  1. Causes cortex of adrenal gland to secrete cortisol
  2. Prevents ACTH secretion

Negative feedback

30
Q

How can a pituitary adenoma lead to Cushing’s?

A
  1. Increase in ACTH
  2. Increase in cortisol
  3. Cells in tumour don’t respond to cortisol
    -> cortisol levels remain high
    =hypercortisolaemia
31
Q

How can adrenal tumours lead to Cushing’s?

A

Increase cortisol levels

=hypercortisolaemia

32
Q

What are the 4 clinical presentations of Cushing’s disease?

A

> cushingoid appearance
headache
bitemporal hemianopia
hypercortisolaemia

33
Q

What are headaches in Cushing’s caused by?

A

Stretching of dura matter

-> Swelling of the meninges

34
Q

What are the meninges?

A 
3 layers of protective tissue:
> dura 
> arachnoid
> pia 
...that surround the brain + spinal cord
35
Q

What is bitemporal hemianopia?

A

Loss of 1/2 field of vision

36
Q

How are optic nerves orientated?

Where does the pituitary gland sit?

A

Optic nerves cross over
-> optic chiasma = point of cross

Sits at optic chiasma

37
Q

How do pituitary adenomas cause bitemporal hemianopia?

A

Pituitary gland sits below optic chiasma

->swelling of adenoma presses on it

38
Q

What are the 3 effects of Hypercortisolaemia?

A

> increases gluconeogeneis
redistribution of body fat
muscle wasting

39
Q

Describe the Cori cycle

A
  1. lactate in contracting muscles carried to liver
  2. converted into glucose
  3. glucose can go back to liver (as glycogen) or back to muscle
40
Q

How does Hypercortisolaemia increase gluconeogenesis?

A

Cortisol stimulates production of more enzymes for gluconeogenesis

41
Q

How does Hypercortisolaemia cause redistribution of body fat?

A

Cortisol may cause lipid breakdown

42
Q

How does Hypercortisolaemia cause muscle wasting?

A

Cortisol inhibits protein synthesis + increases protein degradation

43
Q

Define iatrogenic

A

Unwanted side-effects due to drugs

44
Q

Why might somebody take cortisol?

A

> adrenal glands removed
reduced ATCH/cotrisol
anti-inflammatory

45
Q

What are the side effects of taking cortisol?

A

Can produce cushingoid characteristics

- as produce own cortisol endogenously + taking extra cortisol

46
Q

What are the most likely deaths due to obesity?

A 
> coronary heart disease
> diabetes 
> arthritis 
> gall stones
> varicose veins + haemorrhoids
> increased risk of death during surgery 
> decreased lung capacity
47
Q

Why are obese people more likely to die during surgery?

A

Surgery takes longer due to being bigger

Difficult to maintain anaesthetic as it dissolves into fat over time

48
Q

How can obesity lead to AAGA in surgery?

A
  1. Anaesthetic dissolves into fat over time
  2. anaesthetic levels in blood decreases
  3. patient wakes up
49
Q

What is AAGA?

A

Accidental awareness of general anaesthesia

50
Q

How can obesity lead to decreased lung capacity?

A

Fat presses on lungs

  • > reduces lung capacity
  • > reduces lung function
51
Q

What can a reduced lung capacity predispose?

A

Bronchitis

Pneumonia

52
Q

What are the 2 things that can result from coronary heart disease?

A

Heart attack

Stroke

53
Q

What are the 2 types of cells that respond to insulin + take up glucose?

A

Adipocytes
Muscle cells
- cardiac
- skeletal

54
Q

Describe what happens to a fat/muscle cell when glucose levels are low

A

Insulin levels are also low

->GLUT4 remain within the cell

55
Q

Describe what happens to a fat/muscle cell when glucose levels are high

A 
High insulin levels 
-> binds to insulin receptor
-> GLUT4 moves to membrane
(translocation)
-> glucose enters cell
56
Q

What happens in obese people in terms of insulin?

A

Insulin resistance
= cells unable to sense insulin
= type II diabetes

57
Q

How can Cushing’s lead to diabetes?

A

Increased cortisol
-> inhibits affect of insulin on GLUT4 movement to membrane
-> blood glucose levels increase
= diabetes

58
Q

What is the function of insulin?

A

Lowers blood glucose conc

- stimulates body to store glucose for when needed

59
Q

Why are obese people at a higher risk of developing diabetes?

A

Have increased levels of fatty acids
-> decrease in glucose uptake into muscle + decrease in glucose utilisation
-> increase in blood glucose
= diabetes

60
Q

Why do obese people get arthritis?

A

Increased pressure on weight-bearing joints e.g. knees + hips

(exacerbates issue as can’t exercise)

61
Q

How do gall stones form?

A

When bile salts + cholesterol precipitate

62
Q

What are varicose veins?

A

Tortuous blood vessels on legs

63
Q

How do varicose veins form?

A

Increased pressure on veins
-> leaky valves
-> blood pools
= tortuous blood vessels on surface of leg

64
Q

What are haemorrhoids?

A

Enlargement of spongy blood vessels around anus

65
Q

What are the causes of haemorrhoids?

A

Increase in intra-abdominal pressure

Decrease in fibre intake
-> increased straining on defecation

66
Q

What are the 3 degrees of haemorrhoids?

A

1st - bleed at end of defecation
2nd - protrude + return
3rd - remain outside

67
Q

What are the treatments for haemorrhoids?

A

Non-surgical:

  • inject irritant fluid
  • -> shrivel up

Surgical:
- elastic band OR cut off

68
Q

What is muscle wasting in Cushing’s due to?

A

Increased cortisol levels on protein metabolism

69
Q

How does cortisol affect protein metabolism?

A

Reduces protein synthesis

Increases protein breakdown

Biochemistry (14 decks)

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