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Phase 2a - Endocrinology > Regulation of appetite > Flashcards

Regulation of appetite Flashcards

1
Q

The obesogenic environment

A

Physical activity is discouraged and unhealthy food consumption is encouraged. Homes, schools communities ay encourage this environment; food industry – recipes high in sugar, salt and fat, large portion sizes, poor nutritional labelling, aggressive marketing of unhealthy food especially to children.

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2
Q

Define appetite

A

Desire to eat food

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3
Q

Define hunger

A

Need of eating

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4
Q

Define anorexia

A

Lack of appetite

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5
Q

Define satiety

A

Feeling of fullness - disappearance of appetite after a meal

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6
Q

Define BMI

A

weight (kg) / ht (m^2)

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7
Q

BMI <18.5

A

Underweight

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8
Q

BMI 18.5 - 24.9

A

Normal

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9
Q

BMI 25.0 - 29.9

A

Overweight

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10
Q

BMI 30 - 39.9

A

Obese

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11
Q

BMI >40

A

Morbidly obese

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12
Q

What are the risks of obesity?

A

Type II diabetes
Hypertension
Coronary artery disease
Stroke
Osteoarthritis
Obstructive sleep apnoea

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13
Q

What carcinomas are linked with obesity?

A

Breast
Endometrium
Prostate
Colon

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14
Q

Visceral:subcutaneous fat ratio (V:S)

A

L1/L2 cuts above and below - volume calculated.

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15
Q

What does weight regulation depend on?

A

Genes
Environment
Maintenance (homeostasis) system
Normal fat mass (-ve FB to maintenance)

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16
Q

In an individual, weight is normally…

A

Remarkably constant - hardwired to maintain a specific weight.

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17
Q

Maintaining fat mass

A

CNS increased food intake

Energy expenditure is reduced

Maintains a positive energy balance = fat stored which signals to CNS via insulin and leptin.

Lepin switches off Anabolic signals and on catabolic signals. No food intake and metabolic rate and physical activity is increased.

Fat is broken down.

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18
Q

The satiety cascade

A

Internal physiological drive to eat
Feeling that prompts thought of food and motivates food consumption

External psychological drive to eat
Sometimes even in the absence of hunger (e.g buffet)

19
Q

Energy balance is influenced by

A

Insulin
Leptin
Adiponectin

TONIC

20
Q

Sensory and cognitive factors influencing satiety

A

Sensory and cognitive: sensation + prior beliefs + associations

Meal quality

21
Q

Post ingestive factors influencing satiety

A

Meal quantity

Stretch
Osmotic load
CCK
GLP-1
PYY
Ghrelin

22
Q

Post absorptive factors influencing satiety

A

Liver and metabolites
Nutrient status

Insulin
Oxidation
Glucose
AAs

23
Q

Which part of the brain plays a central role in appetite regulation?

A

Hypothalamus

24
Q

The hunger centre is located in

A

The Lateral hypothalamus

25
Q

The satiety centre is located in

A

The ventromedial hypothalamic nucleus

26
Q

Examples of central appetite controllers that increase appetite

A

NPY
MCH
AgRP (Agouti-related poeptide)
Orexin
Endocannabinoid

27
Q

Examples of central appetite controllers that decrease appetite

A

alpha -MSH
CART (cocaine and amphetamine regulated transcript)
GLP-1
Serotonin

28
Q

Leptin stimulates what?

A

POMC (pro-opiomelanocortin) /CART

Inhibits PVN and PFA

29
Q

Leptin inhibits

A

NPY /AGRP

Stimulates PVN and PFA

30
Q

Arcuate nucleus

A

It has fenestrated BBB - able to sample peripheral hormones.

31
Q

Leptin

A

Isolated in 1994
Greek ‘leptos’ - thin
Expressed in white fat
Binds to leptin receptor
- cytokine receptor family
- in hypothalamus

Switches off appetite and is
immunostimulatory

ob/ob mouse - leptin deficient
hyperphagic
hyperinsulinaemic
very obese
Blood levels increase after meal
Blood levels decrease after fasting

32
Q

Peptide YY

A

36 amino acids
Structurally similar to NPY
Binds NPY receptors
secreted by neuroendocrine cells in ileum, pancreas and colon
in response to food
inhibits gastric motility
reduces appetite

33
Q

CCK

A

1973 - administration - reduced feeding in rodents

Receptors in pyloric sphincter
- delays gastric emptying
- gall bladder contraction
- insulin release

and via vagus - satiety

34
Q

Ghrelin

A

Isolated in 1999
28 amino acid
Acyl side chain
Expressed in stomach

Action: stimulates - Growth hormone release
- appetite - orexigenic

Blood levels high when fasting, fall on re-feeding
Levels lower after gastric bypass surgery

?use in anorexia/cachexia

35
Q

MCR1

A

Melanocytes

Skin pigmentation

(POMC deficiency = pale skin)

36
Q

MCR2

A

Adrenal

Adrenal cortex - steroids

(POMC deficiency = adrenal insufficiency)

37
Q

MCR3 and MCR4

A

Brain

Satiety signalling

(POMC deficiency = hyperphagia and obesisty)

38
Q

MCR5

A

Skin

39
Q

Leptin and insulin

A

Leptin and insulin:
1. Stimulate- POMC/CART neurons -> increased CART and alpha-MSH levels

  1. Inhibit NPY/AgRP neurons -> decreased NPY and AgRPNet effect : ↑ Satiety and decreased Appetite
40
Q

Ghrelin

A

Stimulates NPY/AgRP = increased NPY and AgRP secretion

Increased appetite

41
Q

PYY3-36 (homolog of NPY)

A

Binds to an inhibitory receptor on NPY/AgRP = decrease the secretion of NPY and AgRP therefore decrease appetite

42
Q

Fasted state

A

NYP up
Glucose down
Insuling down
Ghrelin up
Lepton down
a-MSH down
AgRP up

Activated AMPK increased appetite and decreased Malonyl CoA.

43
Q

Fed state

A

NPY down
Glucose up
Insulin up
Ghrelin down
Leptin up
a-MSH up
AgRP down

Deactivate AMPK decreased appetite and increased Malonyl CoA.

44
Q

The effects of incretins include

A
  1. Blunting of glucagon
  2. Beta-cell stimulation of insulin production
  3. Improved satiety
  4. Decreased gastric motility

Phase 2a - Endocrinology (11 decks)

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