Vit D

Question 1

List all fat soluble vit and where they are found

Answer 1

Fat soluble vit are A,D,E and K and can be found in the fat or fatty tissue and liver

Question 2

describe absorption of fats

Answer 2

Transporting into blood in chylomicrons — lymphatic system – taken up by hydrolysis

Question 3

Biological functions of Vit D

Answer 3

Calcium balance
Immunomodulator
Regulates cell growth (anti-proliferation)
Reduces hypertension

Question 4

what are the 2 ways we can get Vit D

Answer 4

7-dehydrocholesterol in skin from the sun
D3 absorption by digestive tract

Question 5

How does Vit D increase calcium absorption

Answer 5

In the intestine it can increase from basal 10-15% to 30-80%
In the bones and kidney: induce formation and activation of osteoclasts and increase renal distal tubule reabsorption of calcium

Question 6

What is the purpose of calcium as a feedback

Answer 6

To increase or decrease formation of Vit D in the kidney

Question 7

2 conversion that take place to get calcitriol

Answer 7

D3 to 25-OH D3 by liver enzymes
25-OH D3 to calcitriol by kidney enzymes

Question 8

Most of the effects of Vit D increase or decrease are mediated though?

Answer 8

Gene expression: CPY27B1 + CPY4A1

Question 9

What are the 3 extra things to consider with Vit D from the sun vs from the diet

Answer 9

The sun Vit D requires UV light to be actived to previt D\
Thermal isomerization (Heat) is needed to convert previt to D3
D3 requires VDBP to enter the bloodstream

Question 10

CYP27B1

Answer 10

Stim by PTH - highly regulated, gene that increased with low expression of calcium

Question 11

CYP24A1

Answer 11

Gene that provides Neg feedback for CYP27B or increases when theres to much calcium

Question 12

Tachysterol

Answer 12

Inactive metabolite of Vit D that decreases Vit D synthesis

Question 13

How long of sun exposure is needed to obtain enough Vit D

Answer 13

5-15 min from 10AM - 3PM during summer (june-sep)

Question 14

What factors could affect getting enough sun exposure

Answer 14

Higher latitudes, winter months, time, body temperature, skin color, aging (decreased 7 DHC), sun screen, clothing, obesity (more stored less acessible)

Question 15

Why would oral supplementation of Vit D3 or injections be prescribed If the person has renal disease

Answer 15

Kidney uses enzymes (CYP27B) and is the synthesizer of Vit D3 to calcitriol. If the kidney isn’t working you’re rather fucked isn;t it

Question 16

What would chronic liver disease cause

Answer 16

decreases vit D metabolism

Question 17

Where is vit d2 and d3 found in the diet

Answer 17

D2 is found in plants (mushrooms)
D3 is found in animals (fatty fish, egg yolk, liver)
Fortified food products: Cows milk, yogurt, soy, OJ, Cereal, butter, formula

Question 18

What is the difference in bioactivity between D2 and D3

Answer 18

D2 contains a Double bound which makes it 20-40% less bioactive than D3

Question 19

DRI for VIT D: lifestages

Answer 19

Infant: 400 IU
Children: 600 IU
Adults/Prego/Lactating: 600 IU
Over 70: 800 IU

Question 20

Which groups of people are at risk for inadequacy

Answer 20

Breastfed infant - Mother
Older / Dark skin
Fat malabsorption
Bypass surgery - serum levels may rise

Question 21

Why is Serum [25(OH)D] > 1,25(OH)2D for indication of vit D status

Answer 21

Serum: long half life 15 days, indicates both sources. (Does not indicate amount stored)

Calcitriol: short half life 15 hr, regulated by PTH/calcium/phosphate. Does not decrease until deficiency is server (always in balance)

Question 22

IS toxicity possible for Vit D

Answer 22

Not in the skin (regulated)
can be with excessive Vit D 4-5K IU supplementation –> hypercalcemia / soft tissue calcification (deposits of calcium in soft tissue)

Question 23

Describe what occurs with the following serum levels of 25OHD3; less than 12ng, 12-20ng, >20ng, >50ng

Answer 23

<12 — Vit D deficiency, rickets in children and osteomalacia in adults
12-20 — inadequate for bone and overall health
>20 - adequate
>50 - potential adverse affects

Question 24

Rickets

Answer 24

Vit D deficiency in children, epiphyseal plates do not close,
hypertrophy of chondrocytes
Symptoms: Soft bones, short, bone deforms

Question 25

Osteomalacia

Answer 25

Vit D deficiency in adults: poor mineralization of collagen
Symptoms: osteopenia (decrease opacity), increase bone fractures, bone pain