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GI 2018 > Physiology of feeding and satiety > Flashcards

Physiology of feeding and satiety Flashcards

1
Q

Which factors influence obesity?

A
  • Genetics

- Environment

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2
Q

What diseases does obesity contribute to?

A

type 2 diabetes

hypertension

MI

cancer (colon)

osteoarthritis

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3
Q

Why do we need fat?

A

energy storage

prevention of starvation

energy buffer during prolonged illness

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4
Q

Why is it so difficult to lose fat?

A

re-programmes the brain

brain views it as normal

dieting is viewed as a threat to the body and defends new weight

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5
Q

How does the CNS influence energy balance and body weight?

A
  1. behaviour
  2. ANS activity
  3. Neuroendocrine system
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6
Q

What is the site of integration?

A

Brain

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7
Q

What is the neural centre responsible for the CNS influence over body fat?

A

Hypothalamus

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8
Q

What does lesioning of the ventromedial hypothalamus cause?

A

Obesity

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9
Q

What does lesioning of the lateral hypothalamus cause?

A

Leanness

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10
Q

What are the three factors of the control system for satiation?

A
  1. satiety signalling
  2. adiposity negative feedback signalling
  3. food reward
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11
Q

Define satiation?

A

Sensation of fullness generated during a meal

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12
Q

Define satiety?

A

period of time between termination of one meal and the initiation of the next

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13
Q

Define adiposity?

A

The state of being obese

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14
Q

Where is CCK secreted from?

A

enteroendocrine cells in duodenum and jejunum.

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15
Q

What determines the proportion of CCK released?

A

lipids and proteins in meal

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16
Q

How does CCK work?

A

Signals via sensory nerves to hindbrain and stimulates hindbrain directly (nucleus of solitary tract (NTS)).

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17
Q

What is glucagon-like peptide 1 a product of?

A

of pro-glucagon gene

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18
Q

Where is glucagon-like peptide 1 released from?

A

L cells

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19
Q

What stimulated glucagon-like peptide 1 release?

A

food ingestion

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20
Q

What does glucagon-like peptide 1 do?

A

Inhibits gastric emptying and reduces food intake (Hypo, NTS)

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21
Q

What is Oxyntomodulin a result of?

A

pro-glucagon gene

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22
Q

Where is Oxyntomodulin released from?

A

oxyntic cells of small intestine

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23
Q

When is Oxyntomodulin released in response to?

A

after meal

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24
Q

What does Oxyntomodulin do?

A

Suppress apetite

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25
Q

Where is peptide YY secreted from?

A

Endocrine mucosal L-cells of the GI tract

26
Q

When do peptide YY levels increase?

A

Post-prandially

27
Q

What does peptide YY do?

A

Inhibits gastric motility, slows emptying and reduces food intake (Hypo)

28
Q

What is obestatin produced as a result of?

A

Gene that encodes ghrelin

29
Q

Where is obestatin released from?

A

cells lining stomach/small intestine

30
Q

What does obestatin do?

A

reduce food intake - may act to antagonise the actions of ghrelin - actions unclear at present.

31
Q

What is ghrelin?

A

Octanoylated peptide

32
Q

Where is ghrelin produced and released from?

A

produced and secreted by oxyntic cells in stomach

33
Q

When do ghrelin levels increase?

A

before meals and decrease after meals

34
Q

What raises ghrelin levels?

A

Fasting and hypoglycaemia

35
Q

What does peripheral ghrelin do?

A

stimulates food intake (Hypo) and decreases fat utilization

36
Q

What is the role of ghrelin containing neurones in the hypothalamus?

A

help control fat metabolism, increase lipogenesis (liver and adipose)

37
Q

Which two hormones- produced in peripheral tissues can act on hypothalamic neurones?

A

Leptin

Insulin

38
Q

Where is leptin made and released from?

A

Fat cells

39
Q

Where is insulin made and released from?

A

pancreatic cells

40
Q

What do insulin and leptin do?

A

inform the brain to alter energy balance, eat less and increase energy burn- this malfunctions in obesity

41
Q

What does reduced leptin mimic?

A

Starvation, causing unrestrained appetite

42
Q

Describe the structure of leptin?

A

member of the cytokine family, 146 aa long, made & secreted from adipocytes

43
Q

Where is leptin found?

A

circulates in proportion to body adiposity

44
Q

Where are there high levels of leptin and insulin receptors?

A

In the hypothalamus

45
Q

What does intracerebroventricular leptin inhibit and cause?

A

inhibits food intake and decreases body weight

46
Q

List the biological roles of leptin?

A

> Food intake/energy expenditure/fat deposition
Peripheral glucose homeostasis/insulin sensitivity
Maintenance of immune system
Maintenance of reproductive system
Angiogenesis
Tumourigenesis
Bone formation

47
Q

What does insulin circulate in proportion to?

A

Adiposity

48
Q

What does high intracerebroventricular (icv) insulin do?

A

inhibits food intake and decreases body weight of rodents

49
Q

What are the hedonistic aspects of food linked to?

A

Sugar and fat

50
Q

What areas are implicated in the hedonistic aspects of food?

A

> Ventral tegmental area
Nucleus accumbens
Striatum
Substantia nigra

51
Q

What is the vast majority of human obesity characterised by?

A

High leptin levels

52
Q

What does diet induced obesity result in?

A

Leptin resistance

  1. defective transport to brain
  2. altered signal transduction following leptin binding to its receptor
53
Q

Which appetite suppressant drug is approved in USA?

A

Phentermine

54
Q

Which drug is supposed to be marketed in feb 2018?

A

Mysimba

55
Q

What is liraglutide mechanism?

A

unclear - has to be injected

Some concerns remain regarding thyroid and pancreatic cancer

56
Q

What does bariatric surgery induce?

A

high level of complete resolution of Type 2 Diabetes (reverses insulin resistance in most cases)

57
Q

What is the mechanism of bariatric surgery success?

A

unclear at present - but involve altered secretion of peptides from stomach and gut that affect beta cells and hypothalamus: e.g. GLP-1, PYY3-36, ghrelin

58
Q

Do adults possess BAT?

A

yes

Neck, clavicle and spinal chord

59
Q

What does BAT do?

A

Disperse energy as hear

60
Q

What do thermogenic adipocytes do?

A

Increase energy expenditure uncoupling of oxidative metabolism from ATP production

61
Q

What is the key function of UCP1?

A

“short circuits” proton gradient in mitochondria - accelerates fuel oxidation - produce heat

GI 2018 (10 decks)

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