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BMR 603 Test 1 > Integration of Metabolism. > Flashcards

Integration of Metabolism. Flashcards

1
Q

How much oxygen does the Brain use at rest?

A

20% of resting O2

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2
Q

In the fed state, the brain relies primarily on ____ for energy?

A

Glucose

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3
Q

How is glucose transported in the endothelial cells of capillary walls?

A

GLUT1

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4
Q

How is glucose transported in neurons?

A

GLUT3

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5
Q

What is the mechanism of GLUT1 and GLUT3?

A

Facilitated Diffusion

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6
Q

During a fast what is the main alternative fuel for the brain?

A

Ketones

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7
Q

How do ketones enter the brain?

A

Monocarboxylate transporters [MCT]

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8
Q

During starvation what proportion of fuel does glucose make up for the brain?

A

1/3rd of the Brain’s fuel is glucose even in starvation.

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9
Q

What is the route that all nutrients take to get to the liver following ingestion?

A

Portal Vein

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10
Q

Why is the Liver in metabolism?

A

It plays a central role in glucose homeostasis.

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11
Q

How does the liver control glucose homeostasis:

A
  • Synthesizes glycogen from glucose
  • Gluconeogenesis: Makes glucose from non-carb precursors.
  • Releases glucose during the post-absorptive state.
  • Responds to insulin and glucagon that regulate blood glucose levels.
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12
Q

What is the energy utilization of Skeletal muscle at rest and during vigorous exercise.

A
  • At Rest: 30% total oxygen
  • Vigorous Exercise: 90% total oxygen
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13
Q

What are the major characteristics of Brown Adipose Tissue (BAT)?

A
  • Utilize uncoupling protein 1
  • Plays an important role in thermogenesis.
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14
Q

What are the major characteristics of White adipose Tissue (WAT)?

A
  • Principle function: Storage of Triglycerides
  • Two forms:
    • ​Subcutaneous (under skin)
    • Visceral (Abdominal cavity and around organs): VERY BAD
  • Beige Adipocytes
    • WAT cells that gain traits of BAT
  • Secrete adipokines that have signal functions.
    • Example: Leptin
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15
Q

What are two major regulators of Fuel Homeostasis?

A

Insulin and Glucagon

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16
Q

Role of insulin?

A

Promotes utilization and storage of nutrients following ingestion of a meal.

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17
Q

Role of Glucagon?

A

Acts primarily on the liver to mobilize glucose when exogenous nutrients are unavailable.

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18
Q

Insulin follows a daily pattern with _____ following a meal, and a sustained _______ that occurs in the abscence of stimuli.

A

Episodic Peaks

Low Basal Level

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19
Q

What is the principle physiological stimulus for insulin release?

A

Glucose

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20
Q

Insulin is released by what cells?

A

Pancreatic Beta-cells

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21
Q

How does glucose enter into B-cells to induce insulin release?

A

GLUT2

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22
Q

What happens to glucose once it enters into the B-cell and what is the mechanism for insulin release?

A
  • Glucose is phosphorylated into glucose 6-phosphate
  • G6P is then metabolized which results in an increase in intracellular concentration of ATP
  • Increasing ATP levels inhibit K+ efflux through ATP-Sensitive K+ Channels.
    • Plasma membrane depolarized
  • Ca+ channels opened and it floods in. This triggers the release of insulin by exocytosis.
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23
Q

B-Cell ATP-sensitive K+ channels have what special subunits?

A
  • Sulfonylurea receptor (SUR)
    • Activated by sulfonylureas
      • ​which are used to treat Type 2 diabetes mellitus.
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24
Q

What is the role of incretins and what are the two good canidates for this at physiological conditions?

A
  • Incretins: hormones released by cells in the intestinal mucosa that promotes glucose stimulated insulin release.
    • Responsible for about half of insulin release.
  • Candidates:
    • GIP
    • GLP-1​
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25
Q

What inhibits insulin release by sympathetic stimulation?

A

Exercise and Stress

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26
Q

How do Stress and Exercise inhibit insulin release?

A

Sympathetic Stimulation

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27
Q

What is the most important physiological stimulus for the release of glucagon?

And what two conditions cause this?

A

Hypoglycemia

Stress and exercise.

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28
Q

What is BMR and how may it be measured both directly or indirectly?

A
  • Basal Metabolic Rate
  • Directly: Heat Production
  • Indirectly: Oxygen consumption
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29
Q

What is an example of another hormone besides insulin and glucagon that also effects the mobilization and utilization of nutrients?

A
  • Thyroid Hormones
    • ​T4: Inactive form
    • T3: Active form
      • Increase in T3 in bloodstream, increases BMR
  • ​​Epinephrine
    • Promotes glucose release by the liver and stimulates lipolysis.
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30
Q

What is the absorptive state?

A

Period of time during and after the ingestion of a meal when cell metabolism is fueled primarily by the nutrients absorved from that meal.

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31
Q

Where does Carbohydrate metabolism occur duing the absorptive state?

A

Liver

32
Q

What does insulin-to-glucagon ratio help indicate?

A

It is an important determinant of hepatic function.

33
Q

What does GLUT2 do? and how?

A
  • It is a bidirectional transporter, with a low affinity for glucose.
    • ​Absorptive State: Glucose enters liver cells due to elevated glucose levels in the portal vein.
    • When plasma glucose levels are low: GLUT2 limits entry into liver cells.
    • When hepatic glucose production is stimulated: Glucose exits the GLUT2 transporter.
34
Q

When glucose enters the liver it is converted to _____ by _______.

A

Glucose 6-phosphate

Glucokinase

35
Q

What hormone increases glucokinase expression?

A

Insulin

36
Q

When fasting why is glucose not converted to G6P.

A
  • Glucose is spared for use by other tissues during interdigestive periods​
37
Q

What role does insulin have in the liver?

A
  • Promotes storage of glucose as glycogen
  • Promotes glycolysis
  • Promotes FA synthesis
  • ​​Inhibits:
    • Release of Glucose​
    • ​Glycogenolysis
    • Gluconeogenesis
38
Q

How does insulin promote glycolysis in the liver?

A
  • Pyruvate -> Acetyl CoA
  • Acetyl CoA is oxidized via the TCA cycle.
  • High glucose levels = Acetyl CoA used for FA synthesis.
39
Q

How does insulin inhibit release of glucose in the liver?

A

Repressing the expression of the gene for G6P.

40
Q

How does insulin inhibit gluconeogenesis in the liver?

A

Inhibit protein catabolism

41
Q

Liver glycogen levels peak ______ after the ingestion of a meal

A

4 to 6 hours

42
Q

How does the liver change in response to a change in the composition of ones diet?

A
  • High in carbohydrate = produce more enzymes for carb metabolization and fat synthesis.
  • High Protein Content = produce more enzymes for amino acid metabolism and gluconeogenesis.
43
Q

How does insulin promote glucose uptake in skeletal muscle?

A
  • By stimulating the translocation of GLUT4
    • ​Exercise also does this.
44
Q

Can glycogen in skeletal muscle be used to maintain blood glucose levels? Detail?

A
  • No it cannot assit.
    • Skeletal muscle lacks Glucose 6-Phosphatase.
45
Q

Describe Lipid Metabolism during the Absorptive State?

A
  • FA are converted by chylomicrons into TAGs.
46
Q

What role does insulin play in lipid metabolism?

A

Insulin induces the synthesis and secretion of Lipoprotein lipase (LPL).

47
Q

What does lipoprotein lipase do?

A

It catalyzes the breakdown of Triacylglycerols into VLDLs to monoglycerides & fatty acids.

48
Q

Insulin inhibits _____ in fat cells by acting __________.

A

basal and hormone-stimulated lipolysis

Hormone-sensitive lipase

49
Q

What catalyzes the breakdown of intracellular TAGs to fatty acids and glycerols?

A

Hormone-sensitve Lipases

50
Q

In the liver, Insulin surpresses ______, since the liver is the principle provider of ______ bodies.

A

Ketogenesis

Ketone

51
Q

How does insulin supress ketogenesis?

A
  • Decreasing the flow of fatty acids to the liver
  • Stimulates the malonyl CoA which blocks FA transport into the mitochondria.
52
Q

Ketone Disorder?

A

Ketosis

53
Q

The liver is the primary site of _____ FA synthesis

A

De novo

54
Q

In skeletal muscle insulin stimulates?

A
  • Amino acid uptake and protein synthesis.
  • Inhibits Proteolysis of muscle.
55
Q

Liver is the primary source of _____ during a fast.

What is the process called and where else can it occur?

A
  • Glucose
  • Gluconeogenesis
    • Kidneys.
56
Q

What role does glucagon play in the liver during a fast?

A

Stimulates glycogenolysis and inhibits glycogen synthase.

57
Q

Peripheral regulation of gluconeogenesis involves?

A
  • Cortisol: Promotes protein catabolism
  • Insulin: inhibits protein catabolism
58
Q

During the first 3 days to a fast:

A
  • Blood glucose & insulin decreases
  • Blood glucagon increases
    *
59
Q

After about 3 days of fasting:

A
  • Plasma glucose, FFA, and glycerol stabilize.
  • Ketones level continue to increase.
  • Growth hormone levels increase.
60
Q

During a prolonged fast:

A
  • Drop in BMR
    • Decreased Thyroid activity.
      • T4 is same; T3 is lower.
        • Reflects decrease in peripheral conversion of T4 to T3.
  • Brain begins using ketones.
    • Spares proteins.
61
Q

How is Hypoglycemia regulated?

A
  • When: Blood glucose drops
    • Hypothalmus activates the sympathetic NS
    • Stimulates glucagon release and inhibit insulin relase .
  • Epinephrine: inhibits glucose utility by muscle
    • Stimulating Glycogenolysis and gluconeogenesis.
62
Q

What is the primary counter regulator in restoring blood glucose levels.

A

Glucagon.

63
Q

How quick do glucagon and epinephrine elicit responses?

A

Very rapid; provide minute-to-minute regulation.

64
Q

How does the pituitary help with hypoglycemia?

A
  • Releases GH and ACTH
    • ACTH stimulates cortisol
      • Promotes gluconeogenesis and blocks glucose uptake by certain peripheral tissues.
65
Q

What is neuroglycopenia?

A

Deficient supply of gluocse in the CNS

66
Q

What is the “Satiety center”

A

Ventromedial nucleus

67
Q

What is the “hunger center”?

A

Lateral Hypothalamus

68
Q

What are the two neuronal groups that activate the arcuate nucleus of the hypothalmus.

A
  • POMC/CART neurons
  • NPY/AgRP -secreting neurons.
69
Q

What do POMC/CART neurons release and what is the effect?

A
  • Release a-MSH (aka, melanocortin)
    • Decrease food intake
    • increase in energy expenditure
70
Q

What do NPY/AgRP -secreting neurons release and what is the effect?

A
  • Neuropeptide Y (NPY):
    • Promotes feeding behavior
    • Reduce energy expenditure
  • AgRP:
    • antagonist that competes with a-MSH for binding on melanocortin receptors.
71
Q

As the mass of adipose tissue increases, _____ release also increases.

A

Leptin

72
Q

What role does leptin have?

A
  • Inhibits: NPY and AgRP
  • Stimulates: a-MSH

Net effect: Decrease food intake, increase energy expenditure.

73
Q

What does Ghrelin do?

A

Stimulates appetite.

74
Q

What is the role of PPY3-36

A

Appetite surpressant

75
Q

PPY3-36 disorders?

A

PYY3-36 crosses the BBB and can lead to anorexic effects.

76
Q
A

BMR 603 Test 1 (10 decks)

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