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Year 2 Gastro > Appetite > Flashcards

Appetite Flashcards

1
Q

How many people die everywhere as a result of being overweight or obese?

A

2.8 million people

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2
Q

What are the three triggers for regulation of thirst?

A

Body fluid osmolality
Blood volume is reduced
Blood pressure is reduced

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3
Q

Which of the three thirst triggers is the most potent?

A

Plasma osmolality increase is the more potent stimulus – change of 2-3% induces strong desire to drink

Decrease of 10-15% in blood volume or arterial pressure is required to produce the same response

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4
Q

How does ADH regulate osmolality?

A

Antidiuretic hormone (ADH) or vasopressin

Acts on the kidneys to regulate the volume & osmolality of urine
Collecting duct - Aquaporin 2 channel

When plasma ADH is low a large volume of urine is excreted (water diuresis)

When plasma ADH is high a small volume of urine is excreted (anti diuresis).

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5
Q

Where is ADH stored?

A

Posterior pituitary

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6
Q

What are the features of osmoreceptors?

A

Sensory receptors
Osmoregulation
Found in the hypothalamus

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7
Q

In which region of the hypothalamus are osmoreceptors found?

A

Organum vasculosum of the lamina terminalis (OVLT)

Subfornical Organ (SFO)

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8
Q

How do Osmoreceptors cause ADH release?

A

Cells shrink when plasma more concentrated

Proportion of cation channels increases – membrane depolarizes

Send signals to the ADH producing cells to increase ADH

Fluid retention
Invokes drinking

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9
Q

What is thirst decreased by?

A

Thirst is decreased by drinking even before sufficient water has been absorbed by the GI tract to correct plasma osmolality

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10
Q

What receptors are involved in thirst?

A

Receptors in mouth, pharynx, oesophagus are involved

Relief of thirst sensation via these receptors is short lived

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11
Q

When is thirst completely satisfied?

A

Thirst is only completely satisfied once plasma osmolality is decreased or blood volume or arterial pressure corrected.

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12
Q

How does changes is pressure regulate thirst?

A

Renin-angiotensin-aldosterone system

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13
Q

How does Aldosterone achieve water retention?

A

H2O retention via

Na+CL- absorption and K+ excretion

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14
Q

What does Angiontensin II do to increase water retention?

A

Vasoconstriction, increase sympathetic activity

ADH secretion

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15
Q

What occurs in a weight reduced - underfed state?

A 
Decreased sympathetic nervous activity 
Decreased energy expenditure
Increased hunger and food intake
Decreased thyroid activity
Weight gain
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16
Q

What occurs in a weight augmented - overfed state?

A

Increased sympathetic nervous activity
Increased energy expenditure
Decreased hunger and food intake
Weight loss

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17
Q

What is involved in appetite regulation?

A

Hypothalamus
Ghrelin
Leptin

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18
Q

What does hypothalamus do to regulate appetite?

A

Arcuate nucleus is an aggregation of neurons in the medial basal path

Produces appetite increasing (Orexigenic) and appetite decreasing (anorectic) peptides

Lateral hypothalamus - orexigenic

Ventrolmedial hypothalamus - associated with satiety

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19
Q

What do lesions in the ventromedial hypothalamus lead to?

A

Decreased satiety

Obesity

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20
Q

What are other hyporthalmic factors implicated in appetite regulation?

A

Endocannabinoids

AMP activated protein kinase

Protein thyrosine phosphatase

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21
Q

What are the main features of the arcuate nucleus?

A

Brain area involved in the regulation of food intake

Incomplete blood brain barrier, allows access to peripheral hormones.

Integrates peripheral and central feeding signals

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22
Q

What are the two neuronal populations in the arcuate nucleus?

A

Two neuronal populations:

Stimulatory (NPY/Agrp neuron)
Inhibitory (POMC neuron)

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23
Q

What can the arcuate nucleus neurons be affected by?

A

Leptin

Insulin

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24
Q

What do POMC neuron activation do?

A

Decreases feeding

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25
Q

What do NPY/Agrp neurone activation do?

A

Increases feeding

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26
Q

How does the melanocortin system work?

A

Melanocortins are products of the POMC gene

Regulates energy balance in feeding behviours and energy expenditures

MC4R receptors are stimulated by serotonin

Leads to reduction in appetitis

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27
Q

What does POMC deficiency and MC4-R mutations cause?

A

Obesity

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28
Q

What higher brain regions also play a role in appetite?

A

Higher centres.

Amygdala- emotion, memory.

Other parts of the hypothalamus, e.g. lateral hypothalamus

Vagus to brain stem to hypothalamus.

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29
Q

What is the adipostat mechanism?

A

Circulating hormone produced by fat

More fat, more hormones

Hypothalamus senses the concentration of hormone.

Hypothalamus then alters neuropeptides to increase or decrease food intake.

Perhaps a problem with the regulation of the adipostat mechanism leads to obesity ?

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30
Q

What is the ob/ob mouse?

A

Obese mouse

Unable to produce leptin leading to obesity

Identification of the gene in the mouse led to discovery of leptin significance

31
Q

What are the features of leptin?

A

Meaning - thin
Discovered in 1994.
Missing in the ob/ob mouse.
Made by adipocytes in white adipose tissue.
Circulates in plasma.
Acts upon the hypothalamus regulating appetite (intake) and thermogenesis (expenditure).
Plays a role in atherosclerosis

32
Q

What is congenital leptin deficiency?

A

Very rare
Causes severe obesity early in life
Constant hunger

33
Q

What is the systemic effects of leptin?

A

Low when low body fat

High when high body fat

Replacement in the ob/ob mouse decreases weight

Hormone that decreases food intake and increases thermogenesis

34
Q

What are the three mechanisms of action of leptin?

A

Insufficient production

Defective receptor signalling

Decreased sensitivity of leptin

35
Q

What are the features of leptin resistance?

A

Leptin circulates in plasma in concentrations proportional to fat mass

Fat humans have high leptin

Obesity due to leptin resistance- hormone is present but doesn’t signal effectively

Leptin is ineffective as a weight control drug.

36
Q

Why do we feel less hungry after a meal?

A

Hormonal signals from gastrointestinal hormones

37
Q

What secretes the gastrointestinal hormones?

A

Enteroendocrine cells of stomach

38
Q

What are the two main gastrointestinal hormones?

A

Ghrelin
Stimulates appetite, increases gastric emptying

Peptid YY
Inhibits food intake

39
Q

When are the blood levels of ghrelin highest?

A

Blood levels of ghrelin are highest before meals

help prepare for food intake by increasing gastric motility and acid secretion

40
Q

What does ghrelin do?

A

Directly modulates neurons in the arcuate nucleus
Stimulates NPY/Agrp neurons.
Inhibits POMC neurons

41
Q

What are the affects of ghrelin?

A

Increases appetite

Regulation of reward, taste sensation, memory, circadian rhythm

42
Q

What is PPY?

A

Short peptide released in the terminal ileum (TI) and colon in response to feeding (36 Amino acids)

43
Q

What are the affects of PPY?

A

Reduces appetite – can be digested or injected IV

Food arriving to the TI and colon results in PYY release

Inhibits NPY release

Stimulates POMC neurons

44
Q

What is the affect of PPY when taken?

A

Experience less hunger
Early fullness
Nausea

45
Q

What are co-morbidities associated with obesity?

A 
Depression
Stroke
MI
Hypertension
Diabetes
Peripheral vascular disease
Gout
Osteoarthritis
Bowel cancer
Sleep apnoea
46
Q

What is adipisia?

A

Inappropriate lack of thirst

with consequent failure in order to correct hyperosmolarity

47
Q

What are the types of polydipsia?

A

Primary

Secondary

48
Q

What are the main features of secondary polydipsia?

A

More common

Medical issues that disrupt any step in osmoregulation or alter ADH can cause secondary polydipsia

49
Q

What are the causes of secondary polydipsia?

A

Chronic medical conditions
Medications
Dehydration

50
Q

What chronic medical conditions cause secondary polydipsia?

A 
Diabetes insipidus & mellitus
Kidney failure
Conn’s syndrome (primary aldosteronism)
Addison's disease (hypoadrenocorticsm)
Sickle cell anaemia
51
Q

What medications cause secondary polydipsia?

A

Diuretics
Laxatives
Both result in dehydration
Antidepressants

52
Q

What causes dehydration?

A 
Acute illness
Sweating
Fevers 
Vomiting 
Diarrhoea
Underhydration
53
Q

What does insipid mean?

A

Tasteless

54
Q

What does Mellitus mean?

A

Sweet tasting

55
Q

What are the main features of diabetes mellitus?

A

General population - common
Related to high blood sugar
Treatment of high blood sugar

56
Q

What are the main features of diabetes insipidus?

A

General population - uncommon
Related to pituitary problems
Impaired ADH production
Treatment with desmopressin

57
Q

What causes primary polydipsia?

A 
Mental illness - psychogenic polydipsia (or acquired)
Schizophrenia
Mood disorders - depressionandanxiety
Anorexia
Drug use

Braininjuries

Organic brain damage

58
Q

Why is polydipsia a problem?

A 
Kidney and bone  damage
Headache
Nausea
Cramps
Slow reflexes
Slurred speech
Low energy
Confusion
Seizures
59
Q

What are the 4 types of polydipsia?

A

Type A
Type B
Type C
Type D

60
Q

Give examples of eating disorders

A 
Binge eating disorder
Anorexia nervosa
Bulimia nervosa
Pica
Rumination syndrome
Avoidant/restrictive food intake disorder
61
Q

Describe global prevalence of eating disorders

A

Global eating disorderprevalence ↑ed from 3.4% to 7.8% between 2000 and 2018.
70 million people live with eating disorder

62
Q

What is Pica?

A

Eating inappropriate things

e.g. hair, soil, dust

63
Q

What is rumination syndrome?

A

Regurgitate and swallow

repeat

64
Q

What are the signs of anorexia?

A

Low BMI, continuous weight loss, amenorrhea, halitosis, mood swings, dry hair, skin & hair thinn

65
Q

What are the different BMI categories for anorexia?

A

Mild: BMI > 17
Moderate: BMI of 16–16.99
Severe: BMI of 15–15.99
Extreme: BMI < 15

66
Q

What are the causes of anorexia?

A

Genetic, environmental, psychological, sociological

67
Q

What is halitosis?

A

Bad breath

68
Q

What is the mechanism of anorexia?

A

Via serotonin release

Increase in CSF

69
Q

What percentage of the worlds population will be obese by 2030?

A

51%

70
Q

Why is obesity increasing?

A

Cheap, calorie rich, readily available food

71
Q

What are the screening tools used for obesity?

A

Height, weight and abdominal girth
Medical history:
Dietary and physical activity patterns, psychosocial factors, weight-gaining medications, familial traits
BMI = kg/m2
BMI of ≥30 or ≥25 + comorbidity or risk factor

72
Q

What surgical treatments are available for obesity?

A

People with a > BMI 40 or 35+ comorbidities

Various procedures

Most common Roux-en-Y gastric bypass & sleeve gastrectomy

WL 5 yrs after BS: 30% - 35%

Remission of comorbidities
Diabetes (80%)
OSA (80%-85%)

73
Q

What are the hormones related to obesity?

A

GLP1 and GLP2:
Stimulate insulin release
Inhibit glucagon release

Ghrelin:
Hunger hormone
NPY activation – initiate appetite

PYY:
Satiety
anorexogenic

74
Q

What hormonal changes are seen after bariatric surgery?

A

Ghrelin reduces

GLP1, GLP2 and PYY elevated

Year 2 Gastro (10 decks)

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