Week 7 Flashcards
What are the fat soluble vitamins?
vitamins A, D, E and K
Food sources of Vitamin D
fish and meat
Forms of Vitamin in food sources, supplements and endogenous production?
Food sources: vitamin D3
Supplements: Vitamin D2
endogenous production: D3
How is Vitamin D endogenous produced and activated?
- UVB rays from the sun reactive with 7-dehydrocholesterol in the skin to product Cholecalciferol (Vit D3)
- In the liver, Cholecalciferol is hydrolyzed to 25-hydroxycholecalciferol (hydroxyvitamin D3) by 25-hydroxylase
- In the kidney, this is hydrolyzed again to 1,25 hydroxycholecalciferol or calcitriol which is the active form of vitamin D
How is Vitamin D absorbed?
Via Micelles and enterocytes: bile and pancreatic lipase dependent
Into chylomicrons through the lymphatic system and into the liver
How is Vitamin D transported around the body?
Via lipoproteins
Where is Vitamin D stored?
In adipose tissue, liver, and kidney
How is Vitamin D excreted?
bile and feces
Little in urine
Mechanism of action of Vitamin D in bone health
Vitamin D helps maintain blood calcium homeostasis:
- when blood calcium levels are low this causes the parathyroid hormone (PTH) and calcitriol to mobilize calcium from the bone
- Calcitriol stimulates intestinal calcium absorption
- Increases calcium reabsorption in the distal renal tubules
Discuss deficiency symptoms of Vitamin D, how it is measured and when/why is it likely to occur
Symptoms: rickets in children and osteomalacia in adults
How it occurs: through less sun exposure and absorption of UVB light (season, location, dark skin, aging skin), liver and kidney disease, intestinal disease
How it is measured: measure serum 25-hydroxyvitamin D concentration as this reflects total body vitamin D reserves.
How do you convert international units to the quantity of vitamin D in a supplement?
1UI = 0.025ug cholecalciferol or 0.005ug 25-hydrocholecalciferol (multiply Vit D3 by 40 to get international unit)
What are the symptoms caused by excess consumption of vitamin D as a supplement?
- Over absorption of calcium leading to hypercalcemia, calcium deposit in kidney, joints, blood vessels, heart
- Can lead to bone demineralization via too much bone resorption and can be fatal in chronic excess
Define Free radicals
a molecular that has one or more unpaired electrons and is therefore highly reactive.
Define oxidative stress
An imbalance between pro and antioxidants in favour of prooxidants
Define oxidative damage
Damage to lipids, proteins, and DNA produced by excess production of free radicals
What is Redox Homeostasis
Balance between pro and antioxidants
Define Antioxidants
a substance that donates an electron to free radicals inhibiting oxidation reactions
What is the antioxidant capacity?
The antioxidant capacity defines the synergistic work between the endogenous and the exogenous, enzymatic and non-enzymatic antioxidant systems in keeping free radicals in equilibrium
What is the free radical theory of aging?
The free radical theory of aging states that organisms age because cells accumulate free radical damage over time
What are the endogenous sources of free radicals?
Endogenous: metabolic process requiring oxygen produce ROS; enzymatic oxidation, exercising, systemic oxidation, exercising, obesity.
What are the exogenous sources of free radicals?
Exogenous: Radiation, dietary components prone to oxidation, smoking, cooking methods by-products, air and water pollution, exposure to pesticides, solvent, environmental toxins, and drugs.
Describe the antioxidant defense system of the body
The antioxidant defense system is able to reduce the damage done by free radicals by either being electron donors and stabilizing the free radical or by deactivating free radicals activity by converting them into stable compounds.
What is the role of the Enzymatic antioxidant system
deactivate free radicals by enzymatic activity/converting free radicals into stable products e.g. H2O, O2, H2 (neutralising or turning into stable products)
What is the role of the non-Enzymatic antioxidant system
electron donors to stabilize free radicals to stop the chain reaction of free radicals
What are the components of the Enzymatic antioxidant system and what are the dependant on
SOD1: Cu and Zn dependent SOD2: Mn dependent SOD3: Fe dependent Catalase: Fe GPx: Se
What is the function of superoxide dismutase (SOD), catalase?
SOD: converts superoxide to hydrogen peroxide
Catalase: converts hydrogen peroxide to water and oxygen
What are the components of the Non-Enzymatic antioxidant system and what are the dependant on
Phytochemicals: - exogenous: >activation of nrf2 >Vitamins A, C, E: electron donors - Endogenous > Glutatione: electron donor > albumin > Bilrubin
Outline the difference between water and fat soluble vitamins.
Fat soluble:
- absorbed into the lymphatic system first then blood
- transport via chylomicrons
- stored in cells associated with fat ( adipose tissue and liver)
- toxicity is likely
- periodic doses
Water soluble:
- absorbed straight into the blood
- transported freely in the CVS
- storage in water-filled parts of the body
- toxicity with supplements
- need frequent doses
What is calcitriol?
The active form of Vitamin D
