Lecture 34 - Starvation Flashcards

1
Q

What are the key concepts of metabolic homeostasis under starvation

A
  • Maintenance of blood glucose levels
  • Sparing to glucose by multiple tissues
  • Making alternative fuels available
  • Provision of special fuels need of each tissue
  • Sparing of structural body proteins
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2
Q

Why must blood glucose be maintained during starvation

A

The brain relied on glucose for energy and function, particularly before ketone bodies become the primary fuel source

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3
Q

What happens to fuels levels in blood during starvation

A
  • Ketone production increases
  • Glucose levels maintaines
  • Increase in FFAs
  • Protein utilised initially then conserved
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4
Q

Source of glucose from fed to starving
1 stage

A
  • Tissues using glucose: all
  • Major fuel for the brain: glucose
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5
Q

5th stages

A

Origin of glucose: Gluconeogenesis
Tissues using glucose: Brain, RBCs
Major fuel of brain: Ketone bodies and glucose

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6
Q

How long do glycogen stored last after fasting begins

A

Glycogen lasts for approx 24 hrs

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7
Q

How does the body’s fuel source change during starvation

A

The body shifts from using glycogen to mobilising FAs and producing Ketone Bodies after glycogen depleted

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8
Q

What is the primary hormone regulating metabolism during starvations

A

Glucagon

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9
Q

Which hormones potentiate glucagons effects during starvations

A

Cortisol and adrenaline

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10
Q

How are fatty acids mobilised during starvations

A

Fat is broken down in adipose tissue and FAs are release unit the bloodstream for use by other tissues

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11
Q

Which tissue primarily use fatty acids during starvation

A

Muscles and liver utilise for energy

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12
Q

What role does gluconeogenesis play during starvation

A

It synthesises glucose to maintain blood levels, especially for the brain and RBC

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13
Q

What are the main substrate for gluconeogensis

A
  • Lactate from RBC
  • Alanine from muscle proteins
  • Glycerol from fats
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14
Q

When does ketone body production increase

A

Ketone production increases after prolonged starvation when glycogen stores are depleted and gluconeogenesis sloes down

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15
Q

Where are ketone bodies synthesises

A

Ketone bodies are synthesised in the liver from acetyl coA derived from fatty acids

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16
Q

What fuels the brain after glycogen stores are depleted

A

The brain primarily uses ketone bodies

17
Q

How does alcohol consumption affect gluconeogenesis

A

Alcohol increases the NADH/NAD+ ratio, which inhibits gluconeogensis by shifting pyruvate to lactate and oxaloacetate to malate, reducing glucose production

18
Q

What can excessive alcohol consumption lead to during starvation

A

It can lower blood glucose, leading to hypoglycaemia, potentially coma due to impaired gluconeogenesis

19
Q

What are some factors that allowed individuals to survive for extended period without food

A

Large fat stores, glucose sparing, and the ability to utilise ketone for brain function played key roles in survival

20
Q

Starvation metabolism

A
  • Gluconeogenesis in liver prominent
  • Fat becomes a prominent fuel for many tissues
  • Ketones made in liver from catabolism of fat becomes alternative and efficient for brain
  • Mobilisation of muscle protein is spared
21
Q

what are the two Ketone bodies

A

Synthesised in the liver from FAs
- Acetoacetate
- B-hydroxybutyrate

22
Q

What happens to the muscle during starvation

A

Proteolysis of amino acids to provide carbon backbones for energy and glucose production