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Nutr 301 > Carbs - postprandial > Flashcards

Carbs - postprandial Flashcards

1
Q

what factors regulate glucose metabolism during the absorptive phase

A
  • insulin
  • G6P
  • glucokinase
  • glycogen synthase
  • glycolysis
  • inhibition of gluconeogenesis + glycogenolysis (lack of glucagon)
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2
Q

how does insulin regulate glucose metabolism

A
  • pancreatic B-cells release insulin to promote:
    1) uptake into muscle/adipose cells via GLUT4
    2) conversion of glucose to glycogen in liver (GLUT2) + skeletal muscle cells
    3) protein synthesis in muscle cells
    4) fat synthesis in adipose tissue
  • blood [glucose] decline = homeostasis restored
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3
Q

what cells are independent on insulin?
what cells are dependent on insulin?

A

indep: liver
dep: adipose + muscle

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4
Q

how does glucagon regulate glucose metabolism

A

insulin inhibits secretion = ensures glucose is store/used instead of produced/released

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5
Q

how does glucokinase regulate glucose metabolism

A

increases glucose phosphorylation to G6P for uptake of glucose by the liver = promotes glycogen synthesis + glycolysis

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6
Q

how does glycogen synthase regulate glucose metabolism

A

elevated insulin promotes synthase activity to convert glucose to glycogen for liver/muscle storage

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7
Q

how does glycolysis regulate glucose metabolism

A
  • controls how glucose in broken down by signalling to other pathways to balance levels
  • high ATP demand = accelerated
  • enzymes adjust in response to cellular signals (ie. PFK1 inhib by ATP = will sense cell’s energy/slow rate down)
  • insulin promote/glucagon inhibits
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8
Q

how does inhibition of gluconeogenesis + glycogenolysis regulate glucose metabolism

A

insulin suppresses the release of glucose from the liver by inhibiting them = prevents excess glucose production = balanced maintenance of blood glucose levels

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9
Q

what are the signalling mechanisms in glucose metabolism

A
  • insulin (fed state)
  • glucagon (fasted state)
  • glucose sensor
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10
Q

how does the glucose sensor work

A

adjusts glycolytic flux to plasma glucose concentration in B-cells/hepatocytes
- combo of GLUT2 transport + rate of glycolysis/glucokinase to sense blood glucose levels

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11
Q

in starving state how do glucagon + insulin work together

A

insulin decreases + glucagon increases to stimulate liver to break down glycogen and increase gluconeogenesis = glucose released into plasma

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12
Q

what is the glucose sparing effect

A

glucose uptake by muscle and adipose tissue are decreased = switch to lipid fuels

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13
Q

what are the dysfunctions in glucose metabolism

A
  • insulin resistance
  • T2D
  • hyper/hypoglycemia
  • ketoacidosis
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14
Q

what is insulin resistance

A

a signalling problem where cells respond less effectively to insulin = take up less glucose from blood via GLUT4 translocation/response

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15
Q

what are the impacts of insulin resistance

A

-higher glucose levels = pancreas releases more insulin = more insulin is needed to maintain normal blood glucose levels

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16
Q

how does T2D occur

A

pancreas unable to compensate for sufficient amounts of insulin resistance by secreting more insulin = b-cell fatigue

17
Q

what is GI

A

the incremental area under the blood glucose response curve of a 50g carb portion of a test food expressed as a % of the response to the same amount of carb from a standard food taken by the same subject
- rating foods based on the magnitude + duration of glucose rise in blood after ingestion

18
Q

why does fructose have a lower GI than glucose

A
  • fructose metabolized in liver (GLUT5) + does not enter bloodstream
  • does not trigger insulin response
  • glucose absorbed directly into bloodstream from small intestine
19
Q

what is glycemic load

A

accounts for both GI + amount of food in a serving (quality + quantity)

20
Q

why would Glycogen Storage Disease type 1 (G6P deficiency) cause an enlarged liver, hypoglycemia, and lactic acidosis

A

G6P deficiency = body is not able to release glucose from glycogen or produce it via gluconeogenesis
- enlarged liver because G6P cannot be converted to glucose so glycogen builds up in liver
- hypoglycemia because glucose cannot be released/synthesized so liver cannot supply glucose to maintain normal blood glucose levels
- lactic acidosis because G6P is diverted to glycolysis pathway due to not being able to convert to glucose and all can’t enter TCA so there is an excess production of pyruvate + lactate

21
Q

low blood glucose concentration = 5 steps

A
  1. insulin decreases, glucagon increases
  2. in liver, glucose utilization drops (glycogenesis/lipogenesis)
  3. in liver, glucose production rises (gluconeogenesis/glycogenolysis)
  4. in muscle/adipose, glucose uptake and utilization decreases
  5. plasma glucose level rises
22
Q

high blood glucose concentration = 5 steps

A
  1. insulin increases, glucagon decreases
  2. in liver, glucose utilization rises (glycogenesis/lipogenesis)
  3. in liver, glucose production drops (gluconeogenesis/glycogenolysis)
  4. in muscle/adipose, glucose uptake and utilization increases
  5. plasma glucose level drops
23
Q

~5mmol/L / ~100mg/dL is the normal range for blood glucose levels, T or F

A

false, ~5mmol/L / ~85mg/dL

24
Q

how do catecholamines act on glucose regulation

A
  • secreted by adrenal medulla & stimulate adrenergic receptors = increase glucose production (glycogenolysis/gluconeogenesis)
25
Q

how do glucocorticoids act on glucose regulation

A

secreted by adrenal cortex = increase hepatic glucose output + expression of gluconeogenic genes

26
Q

how do T3s act of glucose regulation

A

modulate/amplify other hormones/actions, increase gene expression for enzymes to regulate metabolism = increase BMR

27
Q

how are glucose metabolism and insulin secretion coupled

A

ATP produced in mitochondria drive insulin secretion = energy from glucose is needed for its signaller to be released

28
Q

a drop in the ATP:ADP ratio results in release of insulin, T or F

A

false, rise in ATP:ADP ratio = insulin release

29
Q

rate of glucose uptake depends on _______ + rate of _______ , ________ , _________

A

rate of glucose uptake depends on # of transporters + rate of transport, phosphorylation, utilization of glucose

30
Q

glucose enters cells through what

A

via facilitated diffusion via GLUT membrane transport proteins

31
Q

what GLUT transporters have high affinities/low capacity for glucose

A

GLUT 1 & 3

32
Q

what GLUT transporters have low affinities/high capacity for glucose

A

GLUT 2 & 4

33
Q

what is important about GLUT 2

A
  • in liver, B-cells, basolateral SI, kidney
  • needs high [glucose] to stimulate = dependent on [glucose]
  • glucose sensor
  • absorption/reabsorption
  • bidirectional transport
34
Q

what is important about GLUT 4

A
  • in skeletal/cardiac muscle & adipose tissue
  • insulin dependent
  • role in energy utilization/glucose homeostasis
  • exercise stimulated (muscle)
35
Q

what is unique about GLUT5

A

is the only one that binds ONLY fructose

36
Q

glucose is both a substrate & regulator of metabolic pathways, T or F

A

true

Nutr 301 (8 decks)

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