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BIOL0027 > Age-Related Decline in Peripheral Metabolic Tissue Homeostasis > Flashcards

Age-Related Decline in Peripheral Metabolic Tissue Homeostasis Flashcards

1
Q

Name the main metabolic diseases

A

Obesity
Type 2 diabetes
Metabolic syndrome

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2
Q

Define obesity

A

Excess body fat - resulting from chronic imbalance of energy

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3
Q

What is a limitation of BMI as a proxy measure of adiposity?

A

Ignores types of fat and where fat stored - requires imaging

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4
Q

What are the 4 key features of metabolic syndrome?

A

Central obesity - fat around waist
Dyslipidemia - improperly regulated fat metabolism (increased triglycerides, increased LDL, decreased HDL)
Increased blood pressure
Increased blood glucose - linked to insulin resistance

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5
Q

What is the vicious circle with obesity, diabetes, and ageing?

A

Ageing predisposes to obesity and diabetes

Obesity and diabetes cause damage - accelerates ageing

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6
Q

Which hormone controls carbohydrate homeostasis?

A

Insulin

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7
Q

Which hormone controls lipid homeostasis?

A

Leptin

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8
Q

Which cell type detects glucose and what does this cause?

A

Beta-cells in islets of Langerhans

Secrete insulin into blood

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9
Q

What are the metabolic effects of insulin?

A

CNS - anorexigenic effect - promotes satiety
Liver - prevents gluconeogenesis - decreases liver glucose output
Skeletal muscle - increases glucose uptake and glycogen synthesis
Adipose tissue - decreases lipolysis (fatty acid store breakdown)

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10
Q

Which tissue type produces leptin?

A

Adipose tissue

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11
Q

What are the metabolic effects of leptin?

A

Hypothalamus - decreases appetite and food intake

Skeletal muscle - increases fatty acid B-oxidation

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12
Q

Name the 2 types of body fat depots

A

Visceral

Subcutaneous

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13
Q

What are the characteristics of viseral body fat depots?

A

Within abdominal cavity
Close to organs - can impair function
More harmful

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14
Q

What are the characteristics of subcutaneous body fat depots?

A

Not harmful

Some positive effects

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15
Q

Name the 2 types of adipose tissue

A

White adipose tissue (WAT)

Brown adipose tissue (BAT)

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16
Q

What are the characteristics of WAT?

A

Most space in adipocytes taken up by fat droplet

17
Q

What are the characteristics of BAT?

A

Many mitochondria, highly vascularised
UCP1 only expressed in BAT mitos - uncouples fatty acid oxidation from ATP production
Energy released as heat - instead of ATP - prevents increased biomass - prevents obesity
Good adipose tissue type
Important for thermogenesis

18
Q

What might explain the age-related decrease in BAT?

A

Sex hormones maintain BAT - cortisol promotes shrinking of BAT
Young adults - increased sex hormones - most energy stored in BAT
Ageing - decreased sex hormones - most energy stored in WAT
Stress - increased cortisol - decreased BAT - more energy stored in WAT

19
Q

How does fat distribution change with age?

A

Young - most subcutaneous - small depots
Middle age - more of both depots - larger increase in visceral depots
Old age - less of both depots - larger decrease in subcutaneous - ectopic fat forms in organs (e.g. liver) - mot specialised for fat storage - toxic effect

20
Q

What is the process of adipocyte development?

A

Mesenchymal progenitor cells - undergo determination - become preadipocytes (stem cells)
Preadipocytes replicate
Preadipocytes differentiate - become developing adipocytes
Developing adipocytes undergo lipid accumulation - become mature adipocytes
Mature adipocytes undergo apoptosis - replaced by preadipocytes

21
Q

How is adipocyte development altered with age?

A

Same/slightly more preadipocytes
Decreased developing adipocytes - due to transcriptional factor changes
Decreased mature adipocytes - due to decreased maturation potential of developing adipocytes

22
Q

What is the adipose tissue expandability hypothesis?

A

Adipose tissue has finite capacity for fat storage

Point when capacity reached - fat deposited ectopically - lipotoxicity

23
Q

What is fat stored as in adipose tissue?

A

Triglycerides

24
Q

What are triglycerides released as into the blood?

A

Fatty acids

25
Q

What are the steps of insulin receptor signalling?

A

Insulin binds to receptor
Association of IRS (adaptor protein)
Recruits p85 (kinase) - phosphorylates PIP2 - forms PIP3 (second messenger)
Akt and PDK1 bind PIP3
Akt and PDK1 in close proximity - PDK1 phosphorylates Akt - activates

26
Q

What is Akt?

A

Master kinase

27
Q

What are the effects of Akt?

A

Glucose uptake
Glycogen synthesis
Decreased hepatic glucose output
Decreased lipolysis

28
Q

How are fatty acids toxic?

A

Can be metabolised to other lipid products - e.g. ceramide, diacylglycerol - activate pro-inflammatory signalling kinases

29
Q

How does a feedback loop downregulate insulin signalling?

A

Akt activates mTORC1 - leads to IRS phosphorylation - marked for proteasomal degradation - physiological
Proinflammatory signalling kinases phosphorylate IRS1 - marked for proteasomal degradation - pathological - insulin resistance

30
Q

What are the effects of insulin resistance?

A

Hyperglycaemia (high blood glucose) - due to decreased glucose uptake by muscle, increased liver glucose output
Lipidemia (high blood fatty acid) - due to lipolysis by adipose tissue

31
Q

How does glucose distribution differ between insulin-sensitive and insulin-resistant individuals?

A

Decreased muscle glycogen content in insulin-resistant
Increased liver lipid content in insulin-resistant - glucose stored in liver instead of muscle - due to increased lipogenesis in liver

32
Q

What is non-alcoholic fatty liver disease (NAFLD)?

A

Accumulation of fat in liver with low/no alcohol consumption

33
Q

Which traits increase the risk of NAFLD?

A

High BMI
Age
More metabolic syndrome criteria

34
Q

What is the overall effect of ageing on metabolic syndromes?

A

Ageing limits adipose tissue expandability - worsens lipotoxicity caused by obesity
Excess fat stored in non-adipose tissues - exerts lipotoxic effect
Lipotoxicity contributes to insulin resistance in peripheral metabolic tissues
Muscle insulin resistance impairs energy storage as glycogen - promotes lipogenesis in liver - NAFLD development

BIOL0027 (20 decks)

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