Physiology of feeding and satiety

Question 1

What is energy homeostasis?

Answer 1

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

Question 2

How is energy primarily stored?

Answer 2

Promotes body fuel stability

Question 3

What leads to obesity

Answer 3

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

Question 4

What are some consequences of metabolic stress?

Answer 4

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

Question 5

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

Answer 5

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

Question 6

What has a dramatic increase in obesity caused?

Answer 6

A global epidemic

Question 7

Describe obesity as a general disorder

Answer 7

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

Question 8

What are the major influencing factors on obesity

Answer 8

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

Question 9

What are some of the consequences of obesity?

Answer 9

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

Question 10

Name 3 reasons of why we need fat?

Answer 10

Energy storage
Prevention of starvation
Energy buffer during prolonged illness

Question 11

why is obesity described as a disease of the brain?

Answer 11

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

Question 12

How does the CNS influence energy balance and body weight?

Answer 12

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

Question 13

Where is the site of integration

Answer 13

The brain

Question 14

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

Answer 14

Hypothalamus

Question 15

Lesioning ventromedial hypothalamus causes what?

Answer 15

Obesity

Question 16

Lesioning lateral hypothalamus causes what?

Answer 16

Leanness

Question 17

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

Answer 17

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

Question 18

What happens to the satiation signals during a meal

Answer 18

They increase to limit the meal size

Question 19

Where is Cholecystokinin (CCK) secreted?

Answer 19

From enteroendocrine cells in the duodenum and jejunum

Question 20

How is the volume of CCK regulated?

Answer 20

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

Question 21

Where is Peptide YY (PYY3-36) secreted?

Answer 21

From endocrine mucosal L cells of GI tract.

Question 22

How are the levels of PYY3-36 monitored?

Answer 22

They increase rapidly pst prandially

Question 23

What is the role of PYY

Answer 23

To inhibit gastric motility, slow emptying and reduce food intake

Question 24

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

Answer 24

Product of pro-glucagon gene.

Question 25

Where is GLP-1 released from?

Answer 25

L cells in response to food ingestion

Question 26

What does GLP-1 do?

Answer 26

Inhibits gastric emptying and reduces food intake

Question 27

Where is Oxyntomodulin (OXM) released from?

Answer 27

Oxyntic cells of the small intestine after a meal

Question 28

How does OXM act?

Answer 28

Acts to suppress appetite - although the mechanism is unnclear

Question 29

What is OXM

Answer 29

A product of pro-glucagon gene

Question 30

What is obestatin

Answer 30

Peptide produced from the gene that encodes ghrelin

Question 31

Where is obestatin released from?

Answer 31

cells lining the stomach and the small intestin

Question 32

What is the roll of obestatin?

Answer 32

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

Question 33

What is Ghrelin?

Answer 33

A hunger signal | Octanoylated peptide

Question 34

Where is Ghrelin secreted?

Answer 34

Oxyntic cells in the stomach

Question 35

What happens to ghrelin levels?

Answer 35

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

Question 36

What do feedback loops(s) do?

Answer 36

Act to maintain constancy of total body energy stores

Question 37

To control amount of body fat, what occurs?

Answer 37

status of fat stores must be communicated to the brain

Question 38

What 2 hormones report fat status to the brain?

Answer 38

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

Question 39

What is the function of insulin and leptin?

Answer 39

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

Question 40

what are some of the roles of leptin?

Answer 40

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

Question 41

What are some of the rolls of insulin

Answer 41

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

Question 42

Describe the food reward

Answer 42

Pleasure derived from eating - chocolate makes us feel good

Question 43

What is a treatment for leptin resistant obese individuals

Answer 43

Leptin therapy

Question 44

What does diet-induced obesity result in?

Answer 44

Leptin resistance

Question 45

Why does diet-induced obesity result in leptin resistance?

Answer 45

Defective leptin transport into brain | Altered signal transduction following leptin binding to its receptor

Question 46

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

Answer 46

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

Question 47

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

Answer 47

Orlistat (Xenical or Alli)

Question 48

How does orlistat work?

Answer 48

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

Question 49

What type of surgery can be done for obese individuals?

Answer 49

Gastric by-pass

Question 50

What are the benefits of fastric by-pass surgery?

Answer 50

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