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GI 2018 > Physiology of feeding and satiety > Flashcards

Physiology of feeding and satiety Flashcards

(61 cards)

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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
Where is peptide YY secreted from?
Endocrine mucosal L-cells of the GI tract
26
When do peptide YY levels increase?
Post-prandially
27
What does peptide YY do?
Inhibits gastric motility, slows emptying and reduces food intake (Hypo)
28
What is obestatin produced as a result of?
Gene that encodes ghrelin
29
Where is obestatin released from?
cells lining stomach/small intestine
30
What does obestatin do?
reduce food intake - may act to antagonise the actions of ghrelin - actions unclear at present.
31
What is ghrelin?
Octanoylated peptide
32
Where is ghrelin produced and released from?
produced and secreted by oxyntic cells in stomach
33
When do ghrelin levels increase?
before meals and decrease after meals
34
What raises ghrelin levels?
Fasting and hypoglycaemia
35
What does peripheral ghrelin do?
stimulates food intake (Hypo) and decreases fat utilization
36
What is the role of ghrelin containing neurones in the hypothalamus?
help control fat metabolism, increase lipogenesis (liver and adipose)
37
Which two hormones- produced in peripheral tissues can act on hypothalamic neurones?
Leptin | Insulin
38
Where is leptin made and released from?
Fat cells
39
Where is insulin made and released from?
pancreatic cells
40
What do insulin and leptin do?
inform the brain to alter energy balance, eat less and increase energy burn- this malfunctions in obesity
41
What does reduced leptin mimic?
Starvation, causing unrestrained appetite
42
Describe the structure of leptin?
member of the cytokine family, 146 aa long, made & secreted from adipocytes
43
Where is leptin found?
circulates in proportion to body adiposity
44
Where are there high levels of leptin and insulin receptors?
In the hypothalamus
45
What does intracerebroventricular leptin inhibit and cause?
inhibits food intake and decreases body weight
46
List the biological roles of leptin?
> Food intake/energy expenditure/fat deposition > Peripheral glucose homeostasis/insulin sensitivity > Maintenance of immune system > Maintenance of reproductive system > Angiogenesis > Tumourigenesis > Bone formation
47
What does insulin circulate in proportion to?
Adiposity
48
What does high intracerebroventricular (icv) insulin do?
inhibits food intake and decreases body weight of rodents
49
What are the hedonistic aspects of food linked to?
Sugar and fat
50
What areas are implicated in the hedonistic aspects of food?
>Ventral tegmental area >Nucleus accumbens >Striatum >Substantia nigra
51
What is the vast majority of human obesity characterised by?
High leptin levels
52
What does diet induced obesity result in?
Leptin resistance 1. defective transport to brain 2. altered signal transduction following leptin binding to its receptor
53
Which appetite suppressant drug is approved in USA?
Phentermine
54
Which drug is supposed to be marketed in feb 2018?
Mysimba
55
What is liraglutide mechanism?
unclear - has to be injected Some concerns remain regarding thyroid and pancreatic cancer
56
What does bariatric surgery induce?
high level of complete resolution of Type 2 Diabetes (reverses insulin resistance in most cases)
57
What is the mechanism of bariatric surgery success?
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
Do adults possess BAT?
yes | Neck, clavicle and spinal chord
59
What does BAT do?
Disperse energy as hear
60
What do thermogenic adipocytes do?
Increase energy expenditure uncoupling of oxidative metabolism from ATP production
61
What is the key function of UCP1?
"short circuits" proton gradient in mitochondria - accelerates fuel oxidation - produce heat

GI 2018 (10 decks)

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