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Medicine Unit 8 > Liver And Adipose Tissue > Flashcards

Liver And Adipose Tissue Flashcards

1
Q

Functions of adipose tissue

A

Mechanical cushioning
Thermal insulation
Energy store
EndocrIne organ

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2
Q

2 types of adipose tissue

A

Brown
White

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3
Q

Brown adipose tissue

A

Mitochondria
Fat droplets
Develops from muscle cell progenitors

Metabolism generates heat so is important in children because of their high surface area to body mass ratio
No significant levels in adults

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4
Q

White adipose tissue

A

Fewer mitochondria
One single fat droplet
Controlled storage and release of fat

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5
Q

Where are fatty acids stored

A

In all cells
Primarily adipocytes
Stored for future use of triacylglycerols

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6
Q

Triacylglycerols

A

Molecules of glycerol and 3 fatty acids
Esterified
Predominantly saturated

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7
Q

Development of fat cell

A

Fibroblast like precursor cells receive hormone signals that trigger differentiation into sdipocytes
Cells alter gene expression pattern and accumulate lipid droplets
As lipids accumulate they. Edge to form mature fat cell (triglyceride droplet and nucleus)
Mature fat cells can’t divide but early stages are reversible

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8
Q

Thrifty genes

A

Permit more efficient food utilisation and fat deposition in times of abundance
Resulting in better survival in times of subsequent famine

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9
Q

Adipocytes in obesity

A
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10
Q

White adipose tissue as an organ

A

Metabolic integration
EndocrIne activity

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11
Q

What does white adipose tissue produce

A

Production of
Steroid hormones: oestrogen from androgens and cortisol from cortisone
Proteins of energy metabolism blood clotting And complement pathway
Cytokines for signalling
Peptide hormones including leptin

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12
Q

Leptin

A

Mutation in ob/ob mice was identified in gene producing protein called leptin
Produced primarily in adipose tissue in proportion of adipose mass
Leptin treatment reduces food intake and increases energy expenditure and reverses obesity in ob/ob mice

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13
Q

Why isn’t leptin an anti obesity drug

A

Leptin administration only effective in individuals who are obese due to leptin deficiency
Most obese people have high leptin concentration but fail to respond normally so have leptin resistance

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14
Q

Hormones secreted by adipocytes

A

Adiponectin
Resistin
TNF
IL6
fatty acids

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15
Q

Leptin function

A

Metabolic rate
Reproduction

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16
Q

Adiponectin function

A

Liver glucose production
Muscle glucose oxidation

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17
Q

Resistin function

A

Promotes insulin resistance

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18
Q

TNF function

A

Impairs insulin signalling

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19
Q

Il 6 function

A

Increases lipolysis
Glucose uptake

20
Q

Fatty acids function

A

Impairs insulin production in pancreas
Sensitivity

21
Q

Role of the CNS in weight regulation

A

2 regions
Lateral hypothalamus.
Ventromedial hypothalamus

22
Q

Lateral hypothalamus

A

Hunger centre
Animals with lesions in this area become anorectic and lose weight

23
Q

Ventromedial hypothalamus

A

Satiety centre
Animals with lesions in this area overeat and become obese

24
Q

Appetite signals

A
25
Q

Hormones involved in appetite

A

NPY
AgRP
POMC

26
Q

Hormones involved in appetite

A

NPY
AgRP
POMC

27
Q

NPY function

A

Neuropeptide Y – Neurotransmitter (Brain and ANS); INCREASE Food intake (orexigenesis), DECREASE physical activity.

28
Q

AgRP function

A

Agouti-related peptide – Neuropeptide (Brain); INCREASE Appetite, DECREASE metabolism.

29
Q

POMC function

A

Pro-opiomelanocortin – Hormone precursor (Pituitary); Regulates MSH (melanocyte stimulating hormone) which then regulates appetite and sexual behaviour!!

30
Q

Where do hormones regulating appetite act

A

act at the hypothalamus
•leptin and insulin decrease appetite by inhibitory actions on NPY/AgRP neurons. They signal the well-fed state
•ghrelin, from the empty stomach, activates NPY/AgRP neurons.

31
Q

Fat fat cells

A

Promote insulin resistance
Trigger low grade chronic inflammation
Leads to type 2 diabetes
High blood pressure
Cardiovascular disease
Increased cancer risk

32
Q

Thin fat cells

A

More benignly regulate metabolic interplay between tissues
Release Adiponectin promotes glucose uptake into tissues

33
Q

Major metabolic pathways in the adipocytes

A

Carbohydrate metabolism

34
Q

Carbohydrate metabolism in the adipocyte in the fed state

A

Increased glucose transport — Elevated insulin levels in fed state leads to influx of glucose through insulin- sensitive transporter.
(2)Increased glycolysis — Increased intracellular glucose results in enhanced glycolysis. Glycolysis supplies glycerol phosphate for triglyceride synthesis.
(3)Increased hexose monophosphate pathway (HMP)— Metabolism of glucose through this pathway produces NADPH, which is essential for fat synthesis.

35
Q

Fat metabolism in the fed state in adipocytes

A

Increased fatty acid synthesis — De novo synthesis from acetyl CoA is a major source of fatty acids in human adipose tissue only when re-feeding after a fast.
(6) Decreased triglyceride hydrolysis — Elevated insulin levels favors the dephosphorylated (inactive) state of hormone-sensitive lipase, preventing TG degradation and promoting storage.

36
Q

Carbohydrate metabolism in adipocytes in fasting state

A

Glucose transport and metabolism are depressed due to low insulin levels. This leads to a decrease in fatty acid and triglyceride synthesis

37
Q

Fat metabolism in fasting state of adipocyte

A

Increased triglyceride hydrolysis — The activation of hormone-sensitive lipase via phosphorylation leads to hydrolysis of stored TG. This activation is enhanced by noradrenaline released from sympathetic nerve endings in adipose tissue.
(2)Increased fatty acid release — Fatty acids liberated by TG hydrolysis are released into the circulation and transported to other tissues for use as fuel. The glycerol released by TG hydrolysis is used by liver for gluconeogenesis.

38
Q

Where may fat be stored

A

Visceral
Subcutaneous

39
Q

Visceral fat

A

Around abdominal organs
Particularly problematic
Signals sent to liver

40
Q

Subcutaneous fat

A

Under skin
Metabolically less active
Less signalling molecules

41
Q

Android

A

Upper body density
More common in men and post menopausal women
Risk for diabetes and hypertension
Larger fat cells
More easily mobilised fat stores

42
Q

Ovoid

A

Overall obesity
Most common in people with genetic predisposition to obesity

43
Q

Gynoid

A

Lower body density
More common in pre menopausal women
Fat stores not easily mobilised
Harder to lose weight
Relatively benign health wise except arthritis and varicose veins

44
Q

Long term body weight regulation

A

Integration of hormonal metabolic and neural signals

45
Q

BMI calculation

A

Weight in kg/ height in m2

<18.5 underweight
18.4-24.9 normal
25-29.9 overweight
>30 obese

Medicine Unit 8 (24 decks)

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