1. PENGANTAR METABOLISME ZAT GIZI MIKRO PROGRAM STUDI ILMU GIZI-FIKES
PERTEMUAN 3
DUDUNG ANGKASA
PROGRAM STUDI ILMU GIZI-FIKES

2. VISI DAN MISI UNIVERSITAS ESA UNGGUL

3. Materi Sebelum UTS 03. Vitamin D 04. Vitamin E dan K
01. Pengantar metabolisme mikro
02. Vitamin A
03. Vitamin D
04. Vitamin E dan K
05. Vitamin Larut Air- C
06. Vitamin Larut Air-B kompleks
07. Vitamins Interaction

4. Materi Setelah UTS 10. Mineral-Mn, Cr, Cl 11. Mineral-Co, Mo, Cu, F
08. Mineral-Ca, Mg, Na, K, P, S
09. Mineral-Fe, Zn, I
10. Mineral-Mn, Cr, Cl
11. Mineral-Co, Mo, Cu, F
12. Mineral Interactions
13. Mineral-Vitamins Interactions
14. Review

5. KEMAMPUAN AKHIR YANG DIHARAPKAN
Mahasiswa dapat menjelaskan metabolisme vitamin D yang meliputi pencernaan, penyerapan, distribusi (sirkulasi), utilisasi, dan eksresinya serta tingkat kebutuhan dan resiko keracunannya.

6. METABOLISM OF VITAMIN D (“The Sunshine vitamin)
Esa Unggul University

10. Chemical form of Vitamin D

11. Source of vitamin D

12. Source of vitamin D
The two most prominent members of this group are ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3).
Ergocalciferol is derived from a common plant steroid, ergosterol,
Cholecalciferol is the form of vitamin D obtained when radiant energy from the sun strikes the skin and converts the precursor 7-dehydrocholesterol into vitamin D3.

18. Absorption (Diet)
Vitamin D obtained from the diet is absorbed from the intestinal tract
Ingested vitamin D is solubilized within mixed micelles in the duodenum
Vitamin D is absorbed from the intestinal tract in association with fats, it requires the presence of bile salts for absorption.
The micelles dissociate in the acidic microclimate of the unstirred layer and the liberated vitamin D is absorbed in the jejunum by simple diffusion, along with other lipids
Duodenum most rapid absorption, the distal is the largest.
Vitamin D is incorporated into chylomicrons within the enterocytes and, when released, the chylomicrons convey the vitamin in the mesenteric lymph to the systemic circulation.

19. Absorption (Diet)
During the journey in the lymph, an appreciable amount of the vitamin D in the chylomicrons is transferred to the DBP
only 50% of a dose of vitamin D is absorbed.
The same with other fat soluble vitamin

20. Absorption (Skin)
Cholecalciferol, slowly diffuse from the the skin to blood, picked up by DBP.
About 60% plasma cholecal– is bound to DBP
It will travels to muscle, adipose tissue, prior to liver

21. Transpor
In the plasma, 25(OH)D, and indeed all vitamin D metabolites, are mainly bound to a specifi c glycoprotein, known as the vitamin D-binding protein (DBP).
The binding affinities of the DBP for vitamin D and its metabolites are 25(OH)D3 = 24R,25(OH)2D3 = 25,26(OH)2D3 > 1α,25(OH)2D3 > vitamin D3.

22. In the Liver
Cholecal from DBP or CR is hydroxylated at carbon 25 25-OH D3 (calcidiol) by 25-hydroxylase (monoxygenase)
This enzym is NADPH-dependent, and more efficient during vitamin D deficiency
Most 25-OH D3 synthesized in the liver is secreted into blood by DBP
The blood is the largest single pool of 25-OH D3, which has a half-life of 3 weeks
When blood 25-OH D3 decrease, skin reservoir is activated

24. Wimalawansa, S. J. , 2016. Non-musculoskeletal benefits of vitamin D
Wimalawansa, S.J., Non-musculoskeletal benefits of vitamin D. The Journal of steroid biochemistry and molecular biology.

25. Three key enzymes are involved in the conversion of vitamin D:
Vitamin D-25-hydroxylase in the liver converts vitamin D to 25(OH)D;
a multicatalytic 1α-hydroxylase in the kidney converts 25(OH)D to 1α,25(OH)2D; and
24Rhydroxylase, another renal multicatalytic enzyme, converts 25(OH)D to 24R,25(OH)2D

26. DBP:Vitamin D binding protein

31. Excretion
Excretion of absorbed vitamin D and its metabolites occurs primarily in feces with the aid of bile salts. Very little vitamin D appears in urine.

32. Calcitriol and Intestine
Primary function is to increase absorption of calcium and phosporus
This vitamer is believed function as a steroid hormone as well as to function in signal transduction

33. Calcitriol and Calcium
Calcitriol, as a hormone, interact with high affinity receptors in the enterocyts and is carried to nucleus
It will interact with specific protein mRNA
mRNA endoplasmic reticulum into selected protein in brush border High calcium absorption

34. Calcitriol and P
Calcitriol, will increase the activity of brush border alkaline phospatase, which hydrolize phospate ester bond  increase P abs
Calcitriol modulate the Na-dependent layer

38. Vitamin D-related diseases
Rickets
Ricket (infant) failure of bone to mineralize
Epiphyseal cartilage continues to grow and enlarge without replacement of bone matrix and mineral
The spine becomes curved, pelvic and thoraic deformities occur

39. Toxicity
hypervitaminosis D results from the excessive consumption of vitamin D supplements, and not from the consumption of usual diets.
Toxic concentrations of vitamin D have not resulted from unlimited exposure to sunshine.
Vitamin D intoxication can be a concern in patients with specifi c diseases being treated with unusual amounts of vitamin D or analogues of the vitamin.