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nutr 3330 midterm > Vit D and Ca > Flashcards

Vit D and Ca Flashcards

1
Q

is Vit D a water soluble vitamin

A

no, it is fat soluble

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2
Q

where is Vit D synthesized
what is it synthesized from
what does it require

A

in the skin, from cholesterol…need sunlight

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3
Q

what is the main form of Vit D that is utilized by humans

A

D3

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4
Q

what is the active form of Vit D

A

calcitriol

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5
Q

Vit D food sources

A

found naturally in very few foods
…..fatty fish, fish liver oils
….mushrooms
….milk and a lot of dairy products are fortified

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6
Q

Vit D absorptions and transport

A
  • absorbed involves incorporation into chylomicron
  • transported in plasma BOUND to a PROTEIN (DBP-vitamin D Binding Protien)
  • converted to active form (calcitriol) in kidney
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7
Q

where can Vit D be stored

A

in liver, other tissues, especially adipose (bc its fat soluble)

vit D produced in the skin in the spring summer and fall can be stored for winter

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8
Q

Overall metabolic role of Vit D

A

maintain calcium and phosphorus homeostasis

  • ensure Ca and Phosphorus are available in the blood that “bathes” the bones
  • acts as a STEROID hormone
  • sometimes referred to as the Vit D Endocrine System

main thing it keep Ca in check…Phosphorus follows along

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9
Q

Vit D as steroid hormone

A

targets specific organs and their Vit D Receptor (VDR)

main target organs are INTESTINE and BONE
Also, brain and nervous system, pancreas, muscle, cartilage, repro organs, cancer cells

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10
Q

list the steps of Vit D acting as a steroid hormone

A

(1) 1,25(OH)2-D3 travels to specific cell
(2) enters cell and binds to nuclear VDR
(3) binds to the actual DNA
(4) alters transcription rate of mRNA which code for synthesis of specific proteins, which will alter metabolic function

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11
Q

Vit D and Ca homeostasis

A

tight regulation of Ca important for:

  • bone growth
  • maintenance of bone density
  • nervous system
  • blood clotting

also important to keep phosphorus in normal range
comple system..involved:
-vit D (steroid hormone)
-parathyroid hormone (PTH)

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12
Q

PTH

A

-peptie hormone
produced by parathyroid glands

  • key role in Ca homeostasis….also regulates phosphorus
  • parathyroid gland contains a protein that acts as a SENSOR of blood calcium

-dec blood Ca
(sensor PRO detects this, inc PTH synthesis)

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13
Q

PTH Effects…what is the goal

A

GOAL:

to restore normal blood Ca and maintain phosphorus homeostasis via negative feeedback loop

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14
Q

what are the primary target organs of PTH and what happens

A 
KIDNEY
(A) stimulates activation o fVit D
(B) inc Ca reabsorption
  -dec urinary Ca
  - inc blood Ca
(C) dec phosphate reabsorption
   -prevents hyperphosphatemia; whic can inhibit conversion of Vit D to its active form 
-when Ca removed from bone, P is as well
-inc urinary phosphate
BONE
(A) inc osteoclast activity
   -inc bone resorption (breakdown)
   -Ca and  P are released
  -inc blood Ca and P
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15
Q

Hyperparathyroidism

A
  • parathyroid gland tumour

- high blood Ca…bone will be broken down

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16
Q

hypoparathyroidism

A
  • removal of parathyroid or thyroid glands

- Ca not being homeostatic

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17
Q

what is the goal of Calcitriol 1,25(OH)2-D3?

A

-to restore normal blood calcium

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18
Q

where is calcitriol produced and what is production stimulated by

A

kidney

PTH

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19
Q

where in the body does calcitriol act?

A

intestine and bone

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20
Q

what are the effects of calcitriol on the intestine?

A

(A) stimulates Ca absorption

  • also need Mg
  • inc blood Ca

(B)stimulates phosphorus absorption
-inc blood phosphorus

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21
Q

what are the effects of calcitriol on bones

A

increased osteoclast activity (same as PTH)

  • inc bone resorption (breakdown)
  • Ca and P are released
  • inc blood calcium and P
22
Q

what is the most abundant mineral in the body

A

calcium

23
Q

outline the two types of Ca absorption

A

PASSIVE

  • does not depend on Vit D
  • concentration dependent
  • we can absorb Ca without vit D, but we dont always get enough, or sources are being inhibited

ACTIVE TRANSPORT absorption

  • Depends on Vit D
  • requires a transporter and energy
  • requires calbindin (Ca binding protein)
  • Vit D increases synthesis of calbindin therefore increases Ca absorption
24
Q

what is the purpose of Calbindin

A

free Ca is very toxic to inside of cells so the Ca needs to move across cell. The Ca needs to be BOUND in order to shuttle it across the cell
CALBINDIN binds Ca and acts as a shuttle for Ca through the cell
Calbindin facilitates Ca absorption across the intestinal cell

VIT D INCREASES CALBINDIN SYNTHESIS

25
Q

Factors enhancing Ca absorption

A 
Vit D
presence of calbindin
stomach acid
supplements best absorbed with a meal
optimal ratio of Ca to Phosphorus
26
Q

factors inhibiting Ca absorption

A

Vit D deficiency

  • lack of stomach acid
  • excess phosphorus
  • high fiber diet
  • phytic acid
  • oxalate
27
Q

metabolic role of Ca

A

bone health

  • Ca’s major role
  • bone is dynamic….losing and gaining minerals all the time
  • goal is balance

regulator of cellular processes (minor role)

  • muscle contraction, blood clotting
  • transmission of nerve impulses
  • membrane excitability
  • second messenger
28
Q

Ca as a second messenger

A
  • signal transduction
  • intracellular messenger of hormone action
  • peptide hormone action
    • calmodulin is an intracellular protein (Ca receptor) that binds Ca allowing for activation of intracellular proteins and enzymes
29
Q

Calmodulin

A
  • intracellular protein/Ca receptor
  • also called Ca-dependent regulatory protein
  • found in all cells
  • binds intracellular Ca
  • allows for signal transduction to occur
  • activated proteins and enzymes
  • key in the mechanism of action of numerous peptide hormones
30
Q

calcitonin acts in the opposite of _____

A

PTH

31
Q

what are the hormones involved in the regulation of Ca homeostasis

A

PTH
calcitriol
calcitonin

32
Q

Calcitonin

A
  • peptide hormone
  • produced in thyroid gland
  • acts in OPPOSITION to PTH
  • production stimulated by INC in blood calcium
  • production inhibited by derease in blood calcium

overall hypocalcemic effect

33
Q

where in the body does calcitonin act

A

kidney and bone

34
Q

what are the effects of calcitonin in kidney

A

inhibits activation of Vit D
-inhibits 1-hydroxylase

stimulates Ca excretion OR decreases Ca reabsorption
-inc urinary Ca

35
Q

what are the effects of Calcitonin on bone

A

inhibits activity of osteoclasts

  • inhibits bone resorption
  • hypocalcemic effect
36
Q

what hormone is used to treat diseases with high rates of bone resorption

A

calcitonin

37
Q

in a vit D deficiency,

production of _____, and _____ absorption is decreased

A

calbindin

Ca

38
Q

list 3 syndromes related to Vit D and Ca deficiencies

A

Rickets(children)
osteomalacia
osteoporosis

39
Q

rickets

A

vit D deficiency
low blood Ca
impaired mineralization of growing bones
muscle weakness and nervousness

40
Q

factors contributing to development of rickets

A

poor diet

low UV light exposure

41
Q

Osteomalacia

A

Vit D deficiency
low blood Ca
looking at composition and quality of bone
(remember bone is in constant state of turnover)

new bone matrix is laid down but NOT mineralized properly (amount not affected, COMPOSITION affected)

RARE

softening of bones

defect in mineralization of the bone matrix

42
Q

osteoporosis

A

Ca deficiency
looks at AMOUNT of bone

reduced bone density

43
Q

what are the 2 compartments of bone

A

cortical

  • 80% of skeleton
  • dense bone tissue, shafts of long bone, outer hard shell of flat bones
  • Ca loss is slow

trabecular

  • inner structural matric
  • at ends of long bones, inside the cortical shell of flat bones
  • loses Ca readily (faster)
44
Q

Type I osteoporosis

A

rapid bone loss
50-70y/o
due to rapid loss of estrogen in women following menopause
due to dec in testosterone in men with advancing age
more common in women
primarily TRABECULAR BONE
wrist and spine fractures

45
Q

Type II osteoporosis

A 
slower bone loss
>70y/o
due to aging factors 
  -reduced Ca absorption
   -inc risk of falling
  -increased bone mineral loss

BOTH trabecular and cortical bone
hip fractures

46
Q

what is used as an indicator of Vit D and Ca status?

A

bone health

47
Q

what is Vit D and Ca toxicity called

A

hypervitaminosis D

48
Q

Vit D and Calcium- toxicity

A

results in Ca absorption
Symptoms:
-hypercalcemia**
-Calcinosis

-not due to excess sun (this is self limiting)

49
Q

what is calcinosis

A

results from Vit D and Ca- toxicity

  • deposition of Ca in soft tissues
  • blood vessels
  • heart kidney lungs
  • kidney stones
  • tissues around joints
50
Q

Ca and disease prevention

A

osteoporosis

colon cancer

hypertension
-inverse relationship between Ca and blood pressure

obesity

nutr 3330 midterm (13 decks)

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