Vitamin D

What Percentage of Available (Pre-Vitamin D3) 7-Dehydrocholesterol is actually converted to active Vitamin D in the skin? What is this affected by?

Only 5-15% of the available (Pre-Vitamin D3) 7-Dehydrocholesterol is converted to active forms of Vitamin D3. This amount of activity is affected mainly by the intrinsic properties of the skin, the environment, the time of day and the current season.

What stimulates the production of 1,25 dihydroxy D3 1-hydroxylase

Parathyroid Hormone, and low calcium status both stimulate the production of 1,25 dihydroxy D3 1-hydroxylase.

What are some diseases and phenomenon commonly caused by a chronic ongoing Vitamin D deficiency?

Rickets (softening of bone in children), Osteomalacia (softening of bone in adults), osteoporosis (brittle bones in adults).

What factors can lead to Vitamin D deficiency?

Some factors which can promote a vitamin D deficiency include the lack of sunlight, lack of dietary Vitamin D, malabsorptive syndromes, liver disease, kidney disease, and chronic use of anti-convulsant drugs.

What factors affect the amount of Vitamin D3 (Cholecalciferol) found in an animal source?

The amount of Vitamin D3 (Cholecalciferol) obtained from animal sources depends primarily on the diet of the animal as well as its exposure to sunlight.

What are the two most prominent forms of Vitamin D?

The two most prominent forms of Vitamin D are Vitamin D3 (Cholecalciferol), and Vitamin D2 (ergocalciferol).

Pre-Mature infants are at higher risk for Vitamin E deficiency due to:

Their increased risk for hemolytic anemia, generally have lower Vitamin E levels than normal infants, and require forumulas that provide adequate Vitamin E intake in relation to PUFAs.

How many stereoisomers are there for Vitamin E?

There are eight different stereoisomers for Vitamin E.

What are some symptoms of Vitamin D Toxicity?

Vitamin D Toxicity can result in a rapid increase in serum calcium, as well as the calcification of soft tissues, and demineralization of bones as well.

How does vitamin D affect calcium and phosphorous homeostasis in the intestines?

Vitamin D acts in increasing the absorption of Calcium in the small intestine by increasing the synthesis of albindin (CBP) and subsequently opens calcium channels as a result, allowing more calcium to become absorbed through the small intestine.

How does Vitamin D act in increasing the mineralization and demineralization of bone?

Vitamin D increases the mineralization and demineralization of bone by increasing the activity of osteoclasts and osteoblasts in the bones.

How does vitamin D affect the kidneys in Calcium and phosphorous homeostasis mechanisms?

Vitamin D increases the re-absorption of both phosphate and calcium in the renal tubule.

How is Vitamin D first digested and absorbed from food sources?

Vitamin D is absorbed from fat soluble compounds, its efficiency absorption is approximately 50%, an it is absorbed the fastes in the duodenum, while most is absorbed in the ileum.

What are the major dietary sources of Vitamin D?

Vitamin D is mainly found in animal foods, most food sources have very low amounts of vitamin D, and other sources include the fortification of baked goods, grain products, milk and infant foods

How is Vitamin D metabolized after it has been transported by chylomicrons and DBP?

Vitamin D is taken up by the liver with chylomicrons and DBP and is then hydroxylated to 25-OH-D3.

What is the mechanism of action for Vitamin D?

Vitamin D's mechanism of action follows the typical model of steroid hormones, including specific receptors on specific cells in target organs. Receptor-ligand moves into the nucleus where it binds to DNA and then stimulates or represses transcription of particular genes which then produce mRNA as a result.

What are the main sources of Vitamin D2 (Ergocalciferol)

Vitamin D2 (Ergocalciferol) is obtained through the diet mainly from plants, and in the major synthetic form used in nutrition, it is produced primarily by irradiation of ergosterol.

What are some of the main functions of Vitamin E?

Vitamin E also functions in protecting fats and vitamin A form free-radical destruction (Antioxidant activity), it also exerts protective effects in all vital tissues including: the eyes, lungs, skin, heart, muscles, and positively effects the immune system, and lastly defends red blood cells and may also prevent a form of anemia known as hemolytic anemia.

What are some major causes of Vitamin E deficiency?

Vitamin E deficiency is mainly caused by the malabsorption of lipids in the diet due to celiac disease, pancreatitis, sprue, biliary cirrhosis, or also from genetic diseases that impair fat absorption for example cystic fibrosis or biliary atresia.

Vitamin E has the ability to do what to unpaired electrons?

Vitamin E has the ability to accomodate Unpaired electrons as its resonance structure of the ring allows it to act as a free radical quencher (anti-oxidant).

Where is Vitamin E primarily stored in the body?

Vitamin E is mainly stored within the liver and adipose tissues, both of which have the most highest concentrations of Vitamin E of any other organ.

How Toxic is Vitamin E in higher doses?

Vitamin E is one of the least toxic of the Vitamins.

What are the two forms of storage pools for Vitamin E?

Vitamin E is stored in the Labile or Fixed Position. In the Labile Form, it can be mobilized quickly, while in the fixed which occurs in the adipose tissue of the body, secretion and mobilization is more minor.

Is Vitamin E synthesized by animals or plants?

Vitamin E is synthesized only by plants.

What is the primary function of Vitamin E in the body?

Vitamin E's primary function is to maintain cell membrane integrity, it also mainly acts as an antioxidant in the body and prevents oxidation of unsaturated fatty acids in the cell membrane. Mitochondrial membrane and endoplasmic reticulum have high amounts of PUFAs in their phospholipids

How is 25-Hydroxylase enzyme activity affected during the deficiency of Vitamin D?

25-hydroxylase enzyme activity is increased during a deficiency of Vitamin D.

In what process/mechanism in Vitamin E mainly absorbed?

Absorption is governed by the same intraluminal and membrane events as other fat soluble substances including Emulsification Solubilization in mixed micelles Diffusion across unstirred water layer Permeation of enertocytic membrane Incorporation into chylomicrons Transportation via lymphatic ducts

How is Vitamin D transported in the body after its absorption?

After it is absorbed, Vitamin D is transported in the form Chylomicrons Transcalciferol (DBP).

After it has been hydroxylated to 25-OH-D3 in the liver, how is Vitamin D further metabolized?

After its hydroxylation, Vitamin D is then transported to the kidneys, where the second hydroxyl group is added at carbon 1, then producing 1,25 dihydroxyl-D3 1-hydroxylase as a result.

Why do green plants often contain more higher concentrations of Vitamin E than other plant sources?

Alpha-Tocopherol is contained mainly in the chloroplasts of plant cells so therefore green plants tend to contain more Vitamin E as a result. Also, Tocotrienols are found in bran in germ fractions.

How is Cholecalciferol (Vitamin D3) produced in by the body?

Cholecalciferol (Vitamin D3) is primarily produced endogenously by ultraviolet light, which is converted from 7-dehydrocholesterol (Previtamin D3) in the epidermal layer of the skin

What various processes destroy Vitamin E activity?

Drying, milling, refining, sunlight, irradiation and canning all destroy Vitamin E activity obtained from foods.

What are the major carriers of Vitamin E? Is it specific to certain target organs or tissues?

HDL and LDL are the most major carriers of Vitamin E, and the two mechanisms of uptake are lipoprotein receptors and lipoprotein lipase in the intestines.

What typically occurs along with higher intakes of Vitamin E?

High doses are antagonistic to other fat soluble vitamins, typically resulting in impaired bone mineralization, reduced liver storage of Vitamin A, and the inhibition of Vitamin K hydroxylation reactions from occuring as a result.

What decreases the production of 1,25-dihydroxy D3 1-hydroxylase

High phosphorous status decreases the production of 1,25 dihydroxy D3 1-hydroxylase activity in the body via feedback inhibition mechanisms.

What role does Vitamin D play in the body's response to hypocalcemia, or low levels of calcium in the blood?

Hypocalcemia results in an increase in parathyroid hormone which is released. Parathyroid hormone causes an increaseed production of 1,25-OH2-D, which then induces calbindin (CBD) synthesis and bone demineralization which occurs as a result of the decreased calcium levels in the blood.

Synthetic preparations of Vitamin E compounds contain how many of the stereoisomers of Vitamin E? What is it called?

All synthetic preparations of Vitamin E presently contain all eight stereoisomers and are designed with the prefix "all-rac"

What are some major sources of Vitamin E in the diet?

Main dietary sources of Vitamin E include vegetable oils, wheat germ oil (richest natural source), and some cereals

What is the major function that Vitamin D plays a role in the body?

Main function of Vitamin D is in calcium and phosphorus homeostasis, which acts on the kidneys, intestines, and bones

Vitamin E is the generic name for what kind of molecules?

Vitamin E is the generic name for all toco (saturated side chain) and tocotrienol (unsaturated side chain) derivatives that exhibit the qualitative biological activity of a-tocopherol.