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Gastro > Physiology of feeding and satiety > Flashcards

Physiology of feeding and satiety Flashcards

1
Q

What is energy homeostasis?

A

Physiological process whereby energy intake is matched to energy expenditure over time

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2
Q

How is energy primarily stored?

A

Promotes body fuel stability

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3
Q

What leads to obesity

A

Accessible, tasty calorie dense food and sedentary lifestyle. This is due to a small constant mismatch between energy intake and energy expenditure

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4
Q

What are some consequences of metabolic stress?

A 
Metabolic syndrome
central obesity 
dyslipidemia
insulin resistance 
type 2 diabetes 
cardiovascular disease
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5
Q

At what BMI is a someone classified as overweight and then obese and morbidly obese?

A

Overweight = 25-29.9
Obese is 30-39.9
Morbidly obese is more than 40

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6
Q

What has a dramatic increase in obesity caused?

A

A global epidemic

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7
Q

Describe obesity as a general disorder

A

Not a single disorder, but a heterogeneous group of conditions with multiple causes

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8
Q

What are the major influencing factors on obesity

A

Genetics (fatness through susceptible genes) and environment (compare food in USA to Africa)

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9
Q

What are some of the consequences of obesity?

A 
Stroke
respiratory disease (sleep apnoea)
Heart disease (lipids, diabetes, hypertension)
Gallbladder disease
Osteoarthritis
Dementia
NAFLD (fatty liver) 
Diabetes 
Cancer (uterus, breast, prostate, colon)
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10
Q

Name 3 reasons of why we need fat?

A

Energy storage
Prevention of starvation
Energy buffer during prolonged illness

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11
Q

why is obesity described as a disease of the brain?

A

Difficult to lose weight once gained
Increased body fat alters the brain function
Long term obesity induces brain re-programming
Your brain biews the extra weight (fat) as normal and dieting as a threat to the body’s survival

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12
Q

How does the CNS influence energy balance and body weight?

A

Behaviour - feeding and physical activity
ANS activity - regulates energy expenditure
Neuroendocrine system - secretion of hormones

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13
Q

Where is the site of integration

A

The brain

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14
Q

What is the area responsible for control of energy intake and body weight?

A

Hypothalamus

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15
Q

Lesioning ventromedial hypothalamus causes what?

A

Obesity

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16
Q

Lesioning lateral hypothalamus causes what?

A

Leanness

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17
Q

What 3 basic concepts underlie the control of energy intake and body weight?

A

Satiety signalling (sensation of fullness generated during a meal between termination of one meal and the initiation of the next)
Adiposity negative feedback signalling (state of being obese)
Food reward

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18
Q

What happens to the satiation signals during a meal

A

They increase to limit the meal size

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19
Q

Where is Cholecystokinin (CCK) secreted?

A

From enteroendocrine cells in the duodenum and jejunum

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20
Q

How is the volume of CCK regulated?

A

It is released in proportion to lipids and proteins in a meal

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21
Q

Where is Peptide YY (PYY3-36) secreted?

A

From endocrine mucosal L cells of GI tract.

22
Q

How are the levels of PYY3-36 monitored?

A

They increase rapidly pst prandially

23
Q

What is the role of PYY

A

To inhibit gastric motility, slow emptying and reduce food intake

24
Q

What is glucagon-like peptide 1 (GLP-1)

A

Product of pro-glucagon gene.

25
Q

Where is GLP-1 released from?

A

L cells in response to food ingestion

26
Q

What does GLP-1 do?

A

Inhibits gastric emptying and reduces food intake

27
Q

Where is Oxyntomodulin (OXM) released from?

A

Oxyntic cells of the small intestine after a meal

28
Q

How does OXM act?

A

Acts to suppress appetite - although the mechanism is unnclear

29
Q

What is OXM

A

A product of pro-glucagon gene

30
Q

What is obestatin

A

Peptide produced from the gene that encodes ghrelin

31
Q

Where is obestatin released from?

A

cells lining the stomach and the small intestin

32
Q

What is the roll of obestatin?

A

To reduce food intake or to antagonise the actions of ghrelin (this remains unclear)

33
Q

What is Ghrelin?

A

A hunger signal

Octanoylated peptide

34
Q

Where is Ghrelin secreted?

A

Oxyntic cells in the stomach

35
Q

What happens to ghrelin levels?

A

They increase before meals and decrease after meals. Levels are raised by fasting and hypoglycaemia

36
Q

What do feedback loops(s) do?

A

Act to maintain constancy of total body energy stores

37
Q

To control amount of body fat, what occurs?

A

status of fat stores must be communicated to the brain

38
Q

What 2 hormones report fat status to the brain?

A

Leptin (made and released from fat cells)
Insulin *made and released from pancreatic cells
The levels of these in blood increase as more fat is stored

39
Q

What is the function of insulin and leptin?

A

To inform the brain (hypothalamus) to alter energy balance
Eat less and increase energy burn
This malfunctions in the obese state

40
Q

what are some of the roles of leptin?

A

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

41
Q

What are some of the rolls of insulin

A

Circulates in proportion to body adiposity
Transport system for insulin to enter brain
High levels of insulin receptors in hypothalamus
Intracerebroventricular (ICV) insulin inhibits food intake and decreases body weight of rodents
Neurone specific deletion of the insulin receptor results in obesity
Peripheral actions of insulin are opposite = anabolic

42
Q

Describe the food reward

A

Pleasure derived from eating - chocolate makes us feel good

43
Q

What is a treatment for leptin resistant obese individuals

A

Leptin therapy

44
Q

What does diet-induced obesity result in?

A

Leptin resistance

45
Q

Why does diet-induced obesity result in leptin resistance?

A

Defective leptin transport into brain

Altered signal transduction following leptin binding to its receptor

46
Q

Name 2 types of drugs that have previously been used for obesity?

A

Noradrenergics (appetite suppressors - inhibit noradrenaline uptake)
Serotonergic (appetite suppressors acting on 5-HT system)

47
Q

What is the main type of drug used for obesity currently?

A

Orlistat (Xenical or Alli)

48
Q

How does orlistat work?

A

Inhibits pancreatic lipase decreasing triglyceride absorption
Reduces efficiency of fat absorption in small intestine
Can cause cramping and severe diarrhoea
Need to take vitamin supplements

49
Q

What type of surgery can be done for obese individuals?

A

Gastric by-pass

50
Q

What are the benefits of fastric by-pass surgery?

A

produces substantial weight loss in one year that is sustainable
Induces high level of complete resolution of Type 2 diabetes
Restricts calorie intake and induces malabsorption of nutrients

Gastro (67 decks)

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