Introduction to ArtificiaI Intelligence in Higher Education
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Vitamin-D--sims 2020
1. SIMS 305- Clinical Biochemistry
Dr. Ali Raza
Senior Lecturer
Centre for Human Genetics and Molecular Medicine (CHGMM),
Sindh Institute of Medical Sciences (SIMS), SIUT.
3. Dietary Sources of Vitamin-D
⢠Fish liver oil
⢠Egg-yolk
⢠Margarine
⢠Butter
⢠Cheese
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4. Vitamin D and Immunity
⢠Increases the activity of natural killer cells (cytotoxic lymphocytes).
⢠Increases the phagocytic ability of macrophages
⢠Reduces the risk of
⢠Virus-causing diseases (colds, flu).
⢠Cancers (Colon, reast and ovarian cancer).
⢠Cardiovascular disease
(Positive impact on the composition of plasma lipids)
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5. Vitamin D
⢠Need natural precursors of the vitamin D, called as âProvitaminsâ
⢠Only two Provitamins have been found in nature.
⢠Provitamin D2: Ergosterol, found in plants.
⢠Provitamin D3: 7-dehydrocholesterol, found in the skin.
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7. Biologically Active Form of Vitamin D
⢠Calcitriol is the biologically active form of vitamin D
⢠Synthesized involve
liver : Synthesis of 25-OH-D3 in Liver (Calcidiol)
kidneys : Synthesis of 1, 25-di âOH-D3 (Calcitriol)
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9. Vitamin-D Regulation
Calcitriol synthesis is regulated by:
⢠Feedback inhibition of 1 ι-hydroxylase
⢠Parathyroid hormone (PTH)
⢠Serum phosphate level
⢠Calcitriol regulates its own concentration since high levels of
calcitriol (1) Inhibit â1 Îą-hydroxylaseâ and
(2) Stimulates 24,25-di-OH-D3 (storage form)
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10. FUNCTIONS OF VITAMIN D
⢠Vitamin D is found to regulate calcium and phosphate
metabolisms by acting on
⢠Bones,
⢠kidneys,
⢠Intestinal mucosa
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11. FUNCTIONS OF VITAMIN D
Intestinal absorption of calcium and phosphate:
⢠Vit D binds to the chromatin of target tissue and
expresses the genes for Osteocalcin (Ca ++ binding
protein) & Ca++ ATPase in intestinal cells.
⢠This increases the Ca++ absorption by actively transporting
Ca++ across the plasma membrane against electrochemical
gradients.
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12. FUNCTIONS OF VITAMIN D
Mineralization of bones:
⢠Mineralization of bones is promoted by
1, 25, (OH)2D3
24,25(OH)2D3.
⢠Synthesis of Ca++-binding proteins (osteocalcin) and
alkaline phosphatase is promoted which increases calcium
and phosphate ions in the bone.
⢠These ions enhance the mineral deposition in the bone.
⢠24, 25(OH)2D3 helps the deposition of hydroxyapatite in
bone. 12
13. Deficiency of Vitamin DâClinical
Aspect
⢠Bow legs /knock knees:
Bending of long bones giving
rise to deformities.
⢠Hot-cross bun appearance of
head: fontanelles do not close
properly
⢠Pigeon breast appearance:
deformity of the chest
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14. Deficiency of Vitamin DâClinical Aspect
Deficiency produces
(1) Rickets: Children
(2)Osteomalacia : Adults
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15. Types of vitamin D deficiency Rickets
(i) Type I:
Inherited autosomal recessive disorder
1-Îą-Hydroxylase deficiency
Defect in conversion of 25-OH-D3 to calcitriol
(ii) Type II :
Inherited autosomal recessive disorder
a single amino acid change in one of the zinc fingers of
the DNA binding sites for receptors.
makes the receptors non-functional.
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16. 2. Osteomalacia
Deficiency of vitamin D in adults is rare.
It can occur:
⢠In pregnancy and lactation
⢠In women who observe purdah
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17. 3. Renal Osteodystrophy
⢠When renal parenchyma is lost, it is unable to
form calcitriol and
calcium absorption is impaired.
⢠Hypocalcemia leads to increase in PTH which acts on bone to
increase Ca++.
⢠Results in excessive bone turnover and structural changes,
condition known as Renal osteodystrophy.
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18. Hypervitaminosis D
⢠Serious deleterious effects may be produced if large doses (500
to 1000 times) of vit D is taken for prolonged periods.
1. Immediate effects: Anorexia, thirst, constipation and polyuria.
Followed by nausea, vomiting and diarrhoea.
2. Delayed effects: Persistent hyper Calcaemia and phosphataemia
may produce
(a) Urinary lithiasis
(b) Metastatic calcification (deposition of calcium salts )
kidneys, bronchi, pulmonary alveoli, muscles, arteries and
gastric mucosa.
⢠Renal failure may develop and can lead to death. 18
19. CLINICAL ASPECTS
Recently low vitamin D level has been correlated with
certain diseases:
⢠Heart ailments
⢠Diabetes
⢠Breast cancer
⢠Peripheral artery disease
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20. Heart Ailments
⢠Low vitamin D levels (i.e. below 15 ng/ml) had double the
risk of developing heart problems
⢠Most organs and tissues of human body have vitamin D
receptors. E.g. smooth muscles of the heart and the blood
vessels.
⢠Causes these smooth muscles to relax and this in turn
prevents heart attacks/strokes.
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21. Diabetes: Vitamin-D in preventing diabetes.
⢠Vitamin D receptors are located in the β-cells of Islet of
Langerhans of pancreas.
⢠Association of Vitamin D and diabetes came from
population studies that insulin dependent Type-1 diabetes
occurred commonly in areas which receive less sunlight.
⢠Vitamin-D probably stimulates not only the release of
insulin but also the expression of insulin receptors.
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22. Breast Cancer
⢠Maintaining vitamin-D levels may actually prevent certain
types of cancers particularly breast cancer.
⢠Breast cancer cells have vitamin-D receptors, when these
receptors are activated with vitamin-D
⢠Vitamin-D brings some molecular reactions that can make
the cancer cells slow down their growth rate or quite
often even die or at least become less aggressive.
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23. Peripheral Artery Disease (PAD)
⢠Vitamin D may protect against an
PAD disease (fatty deposits restrict
blood flow to the limbs)
⢠Individuals with low levels of vit-D
experience an increase risk of PAD.
⢠Most often reduces blood flow to
the legs causing
pains,
numbness,
impairing the ability to work and
may lead to amputation. 23
Editor's Notes
Ergosterol is widely distributed in plants. It is not absorbed well hence is not of nutritional importance.
Calciferol is readily absorbed. 7-dehydrocholesterol is formed from cholesterol in the intestinal mucosa, and principally liver, passed on to the skin where it undergoes activation to vitamin D3 by the action of solar UV rays.
Transformation from inactive provitamin to the active vitamin is accomplished by the ultraviolet rays.
The photochemical activation, photolysis results only in intramolecular rearrangement
Regulation of calcitriol synthesis is done by:
⢠feedback inhibition of 1 ι-hydroxylase. (Its own concentration)
⢠Parathyroid hormone (PTH)
⢠Serum phosphate level.
Hypocalcaemia leads to marked increase in 1 Îą-hydroxylase activity, the effect requires PTH.
Calcitriol regulates its own concentration since high levels of calcitriol inhibit â1 Îą-hydroxylaseâ and
stimulates the formation of 24,25-di-OH-D3 which is not potent as calcitriol and now supposed to be a storage form.
The DNA + histone = chromatin definition: The DNA double helix in the cell nucleus is packaged by special proteins termed histones. The formed protein/DNA complex is called chromatin. The basic structural unit of chromatin is the nucleosome.
hydroxyapatite: a complex phosphate of calcium Ca5(PO4)3OH that occurs as a mineral and is the chief structural element of vertebrate bone.
Deficiency of Vitamin DâClinical Aspect
Genu valgum, commonly called "knock-knee", is a condition in which the knees angle in and touch one another when the legs are straightened. Individuals with severe valgus deformities are typically unable to touch their feet together while simultaneously straightening the legs.
Deficiency produces (1) Rickets in growing children and
(2)Osteomalacia in adults.
Pectus carinatum (L carÄŤnÄtus, equiv. to carÄŤn(a) keel), also called pigeon chest, is a deformity of the chest characterized by a protrusion of the sternum and ribs
Vitamin D is required for the normal growth and mineralisation of bones. In its absence, instead of growth occurring normally, the osteoblasts proliferation does not take place in an orderly fashion and is not accompanied by vascularisation and mineralisation at the normal rate. This results in irregularity in the zone of provisional calcification.
The cartilage cells do not degenerate as they should and ends of the long bones become bulky and soft. The bone mineral may be reabsorbed away from shaft of long bones making it soft.
⢠Bending of long bones giving rise to deformities such as bow legs and knock knees
occur.
⢠The ankles, knees, wrists and elbows are swollen due to swelling of epiphyseal cartilages.
⢠The fontanelles do not close properly giving hot-cross bun appearance of head.
⢠Ribs give beaded appearance and chest gives a pigeon breast appearance.
Deficiency of Vitamin DâClinical Aspect
Deficiency produces (1) Rickets in growing children and
(2)Osteomalacia in adults. (softening of the bones, typically through a deficiency of vitamin D or calcium.)
Pectus carinatum (L carÄŤnÄtus, equiv. to carÄŤn(a) keel), also called pigeon chest, is a deformity of the chest characterized by a protrusion of the sternum and ribs
Vitamin D is required for the normal growth and mineralisation of bones. In its absence, instead of growth occurring normally, the osteoblasts proliferation does not take place in an orderly fashion and is not accompanied by vascularisation and mineralisation at the normal rate. This results in irregularity in the zone of provisional calcification.
The cartilage cells do not degenerate as they should and ends of the long bones become bulky and soft. The bone mineral may be reabsorbed away from shaft of long bones making it soft.
⢠Bending of long bones giving rise to deformities such as bow legs and knock knees
occur.
⢠The ankles, knees, wrists and elbows are swollen due to swelling of epiphyseal cartilages.
⢠The fontanelles do not close properly giving hot-cross bun appearance of head.
⢠Ribs give beaded appearance and chest gives a pigeon breast appearance.
Osteoid; the unmineralized organic component of bone.
parenchyma. [pah-reng´kÄ-mah] the essential or functional elements of an organ, as distinguished from its framework, which is called the stroma. ... renal parenchyma the functional tissue of the kidney, consisting of the nephrons. That filters blood and make urine
HYPERVITAMINOSIS D
Normally vit D is well tolerated if taken in large doses
but serious deleterious effects may be produced if taken
in extremely large doses, 500 to 1000 times of normal
requirement for prolonged periods.
Effects are mainly due to induced hypercalcaemia.
⢠Immediate effects and
⢠Delayed effects.
1. Immediate effects: Include anorexia, thirst, lassitude,
constipation and polyuria. Followed later on by
nausea, vomiting and diarrhoea.
2. Delayed effects: Persistent hypercalcaemia and
hyperphosphataemia may produce:
⢠Urinary lithiasis
⢠Metastatic calcification (Metastatic calcification is deposition of calcium salts in otherwise normal tissue), which may affect
kidneys, bronchi, pulmonary alveoli, muscles,
arteries and gastric mucosa. Renal failure may
develop and can lead to death.
Anorexia : lack or loss of appetite for food
Peripheral artery disease (P.A.D.) is a disease in which plaque builds up in the arteries that carry blood to your head, organs, and limbs. Plaque is made up of fat, cholesterol, calcium, fibrous tissue, and other substances in the blood