Cell Signaling Vitamin D3

Question 1

Where do we get most of our vitamin D?

Answer 1

the sun and our diet

Question 2

Children with vitamin D deficiency tend to have …

Answer 2

cavities

Question 3

Which step of vitamin D3 synthesis does the sun catalyze?

Answer 3

Pro (7-dehydrocholesterol) to previtamin D3

Question 4

What is the biologically active form of vitamin D3?

Answer 4

1,25(OH)2D3

Question 5

What organ provides the majority of the circulating 1,25(OH)2D3?

Answer 5

kidney

Question 6

Serum levels measure what vitamin D molecule?

Answer 6

25(OH)D3 because it is the main circulatory form

Question 7

What protein usually binds thing in the blood?

Answer 7

Albumin

Question 8

What is another name for 1,25(OH)2D3?

Answer 8

calcitriol

Question 9

What is another name for vitamin D2?

Answer 9

Ergocalciferol

Question 10

What is another name for vitamin D3?

Answer 10

cholecalciferol

Question 11

Vitamin D2

Answer 11

Plant/fungi form; most commonly found in dietary supplements and fortified foods. Less absorbable, less potent, shorter acting.

Question 12

Vitamin D receptor (VDR)

Answer 12

• Transcription factor widely distributed in the body
• Upon binding 1,25-(OH)2D3, VDR forms a heterodimeric complex with other nuclear hormone receptors, particularly the Retinoid-X-Receptor.

Question 13

Vitamin D3 is modified by what organ before the kidney?

Answer 13

Liver

Question 14

Vitamin D3 is required for proper ____ and ____ absorption needed to build strong bones and teeth.

Answer 14

calcium; phosphorus

Question 15

Vitamin D metabolites are transported in the blood bound to?

Answer 15

Vitamin D binding protein and serum albumin

Question 16

Vitamin D3 induces what in the gut?

Answer 16

Calcium absorption

Question 17

Calmodulin

Answer 17

Binding protein that helps calcium be absorbed into the body.

Question 18

Vitamin D Receptor affects:

Answer 18

1. Genes regulating Ca transport (TRPV6)
2. Genes needed to form bone
3. RANKL/ osteoclast formation
4. Antimicrobial peptides like defensins/cathelicidin

Question 19

Name an antimicrobial peptide that is vitamin D3 dependent

Answer 19

defensins and cathelicidin

Question 20

Rickets

Answer 20

• Vitamin D/calcium/phosphate deficiency
• Most common in countries that do not fortify their foods and have low exposure to sunlight
• Prominence of the costochondrial junction, deformities of the back, bowing of the legs, parietal flattening, delayed eruption of the permeant dentition and enamel defects

Question 21

Type I rickets

Answer 21

• Manifests by age 2, usually by 6mo
• Low circulating 1,25(OH)2D3
• Defect in 1-hydrolase

Question 22

Type II Rickets

Answer 22

• Normal at birth, bone disease before age 2
• Normal or high circulating levels of 1,25(OH)2D3
• Due to mutations in VDR receptor
• Alopecia

Question 23

Osteomalacia

Answer 23

Similar to rickets; Softening of the bones due to inadequate levels of calcium and phosphate which are most commonly due to vitamin D deficiency

Question 24

Vitamin D resistant rickets

Answer 24

caused by an inactivating mutation in the nuclear vitamin D receptor.

Question 25

Plaque Psoriasis

Answer 25

Immune mediated disease affecting the skin with no cure however vitamin D3 can help control symptoms.

Question 26

Parathyroid Hormone (PTH)

Answer 26

- Increases calcium levels and stimulates production of 1,25(OH)2D3 - Synthesized and secreted by chief cells of the parathyroid gland

Question 27

Calcitonin

Answer 27

Decreases calcium levels

Question 28

Cathelicidin

Answer 28

- Found in lysosomes of macrophages and polymorphonuclear leukocytes (PMNs). - Serve a critical role in mammalian innate immune defense against invasive bacterial infection.

Question 29

What foods are high in vitamin D3?

Answer 29

fish oil, milk

Question 30

What regulates the expression of 1-hydroxylase?

Answer 30

PTH

Question 31

What kind of receptor does vitamin D3 use to mediate its effects?

Answer 31

intracellular but some effects are thought to be mediated through membrane receptor

Question 32

Vitamin D deficiency is associated with...

Answer 32

cancer, cardiovascular disease, hypertension, stroke, diabetes, multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, osteoporosis, periodontal disease, macular degeneration, mental illness, propensity to fall, and chronic pain.

Question 33

TRPV6

Answer 33

positively regulates intracellular calcium transport