Lipid-soluble vitamins vitamin

However, it was not until 1924, when Steenbock and Hess showed that irradiation of certain foods generated protective activity against the disease, that vitamin D (calciferol) was recognized as a second lipid-soluble vitamin. Vitamin D is a family of compounds formed by the irradiation of A5/7-unsaturated sterols such as ergosterol and 7-dehydrocholesterol. The former yields ergocalciferol (vitamin D2) and the latter cholecalciferol (vitamin D3). 

Lipid-Soluble Vitamins Vitamin A Vision, growth, and reproduction (see supplement 2). 

See also Antioxidants, Reactive Oxygen, Oxygen Metabolism and Human Disease, P-Carotene, G Proteins in Vision, Lipid-Soluble Vitamins, Vitamins... 

See also / -Carotene, Lipid-Soluble Vitamins, Vitamins... 

See also Lipid-Soluble Vitamins, Vitamin A, G Proteins in Vision... 

Selected applications of coupled SEE-SEC consider the analysis of tocopherols in plants and oil by-products (65) or the analysis of lipid-soluble vitamins (66) by using a dynamic on-line SEE-SEC coupling, integrated in the SE chromatograph, based on the use of micropacked columns. 

In vitro and ex vivo studies have shown that FATPs transport LCFAs and very long-chain fatty acids (VLCFAs) but no medium-chain fatty acids, fatty acid esters, or lipid-soluble vitamins [4]. LCFA transport is inhibited by prior protease treatment. Synthetic substrates for FATPs include 14C-labeled fatty acids and the fluorescently labeled fatty acid analogue C1 -BODEP Y-Cl 2. Using the latter substrate, differences in fatty acid uptake kinetics between FATP expressing 3T3 LI adipocytes and 3T3 LI fibroblasts, which are devoid of FATPs, can be readily appreciated (Fig. 2). 

There are four important lipid-soluble vitamins, D, A, K, and E. Two of these vitamins, A and D, work through enhancer mechanisms similar to those for lipid-soluble hormones. In addition, all four lipid-soluble vitamins have more specialized mechanisms through which they act. Table 1-10-2 lists their major functions. 

Vitamin D is a lipid-soluble vitamin, as is vitamin A. Lipid-soluble vitamins are stored in the body, in contrast to water-soluble vitamins such as vitamin C. Excess consumption of lipid-soluble vitamins can result in excess storage and resultant toxicity. The UL for vitamin D is 50 micrograms/day. Excess consumption may raise the blood level of calcium to the extent that calcification of organs (particularly the kidneys), occurs, and formation of kidney stones may follow. 

The food components resorbed by the epithelial cells of the intestinal wall in the region of the jejunum and ileum are transported directly to the liver via the portal vein. Fats, cholesterol, and lipid-soluble vitamins are exceptions. These are first released by the enterocytes in the form of chylomicrons (see p. 278) into the lymph system, and only reach the blood via the thoracic duct. 

Drugs that may interact with laxatives include mineral oil, milk or antacids, H2 antagonists, proton pump inhibitors, lipid soluble vitamins (A, D, E, and K), and tetracycline. 

Boso, R.L., Bellini, M.S., Miksik, I., Deyl, Z. (1995). Microemulsion electrokinetic chromatography with different organic modifiers separation of water-and lipid-soluble vitamins. J. Chromatogr. 709 11 — 19. 

A lack of lipid-soluble vitamins can be detrimental, but so can excessive amounts, particularly of vitamins A and D, which can accumulate to dangerous levels. Too much vitamin A causes dry skin, irritability, and headaches. Excessive amounts of vitamin D lead to diarrhea, nausea, and calcification of joints and other body parts. Vitamins E and K are less harmful in large quantities because they are readily metabolized. 

Ascorbic Acid Is Required to Maintain the Enzyme that Forms Hydroxyproline Residues in Collagen Vitamin B12 Coenzymes Are Associated with Rearrangements on Adjacent Carbon Atoms Iron-Containing Coenzymes Are Frequently Involved in Redox Reactions Metal Cofactors Lipid-Soluble Vitamins... 

In general, less is known about the mechanisms of action of the lipid-soluble vitamins than about the coenzymes derived from water-soluble vitamins. The structures and functions of vitamins D, K, E, and A are discussed briefly. 

Like other fat-soluble vitamins, vitamin D is absorbed in the gut with other lipids. The two major natural sources of vitamin D are cholecalciferol... 

Steatorrhea, the clinical result of insufficient intraluminal lipid hydrolysis, is the most important digestive malfunction in pancreatic exocrine insufficiency. As a rule, concomitant malabsorption of the lipid-soluble vitamins A, D, E, and K must be suspected in these patients. Naturally, potential differential diagnoses have to be considered in patients who present with steatorrhea (Table 26-1). The pivotal role of fat malabsorption in chronic pancreatitis is due to several interacting mechanisms ... 

In fact, we found that a-tocopherol, an antioxidant lipid-soluble vitamin, prevented geranylgeranoic acid-induced apoptotic cell death of human hepatoma cells. These results are presented in Figure 1 (Shidoji et al 1997). 

Sulfolipids Free fatty acids Lipid-soluble vitamins Pigments Phenolic compounds Metals and Metalloproteins... 

Cancer The increased risk of cancer in vitamin deficiency is thought to be the result of depletion in beta-carotene. Beta-carotene is a very effective antioxidant and is suspected to reduce the risk of cancer is known to be initiated, by the production of free radicals. Of particular interest is the potential benefit of increased b-carotene intake to reduce the risk of lung cancer in smokers. However, caution needs to be taken when increasing the intake of any of the lipid soluble vitamins. 

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