Fat-soluble substances

Persistent and semi-persistent lipophilic (fat soluble) substances known to accumulate in fatty tissue. 

The vitamin and metabolic derivatives of a fat-soluble substance calciferol. These antirachitic vitamins are produced from A -unsaturated sterols upon irradiation with ultraviolet light. Population biologists have adduced strong evidence for the hypothesis that lighter skin color, the primary characteristic of race, is related to the lower solar radiance in northern climes. Vitamin D plays a central role in calcium metabolism, both in terms of... 

Figure 6.13 shows the concentrations of organic compounds in water that are sufficient to immobilize tadpoles, and their values of log P or the partition coefficient between octanol and water. Thymol, with a log P of 1000, is 10,000 times more toxic than ethanol, which has a log P of around 0.3. A plausible explanation of this phenomenon lies in the structure of the membranes of cells, which are made of two layers of lipid, or fat, so that a more fat-soluble substance would find it easier to penetrate the cell and to cause damage. 

Studies have shown that Clenbuterol reduces fat, which would help rid lipid tissue of THC metabolities. Clenbuterol also increases metabolism. No studies have directly shown that Clenbuterol will help pass a drug test. However, provided that it reduces fat, 1 would assume that the fat breakdown would result in less fat soluble substances in the system. Caution Clenbuteral is labeled as a performance enhancer, and it s on the banned list for athlete testing. If are being tested as an athlete, avoid Clenbuterol ... 

The provision of fat-soluble vitamins and lipids is difficult, if not impossible, in various diseases. This is especially true for diseases that are accompanied by a lot of oxidative stress, for example, mucoviscidosis. The requirements of fat-soluble antioxidative substances are certainly high in these cases and can barely be covered by intramuscular injections because fat-soluble vitamins can hardly, if at all, be absorbed from oily preparations. Alternatively, the vitamins can administered via the buccal mucosa the fat-soluble substances have to be packaged in such a way that they can be transported in a watery compartment and are thus able to largely dissolve in the saliva. When they have an adequate size, they can then penetrate the buccal mucosa. One approach is the development of the so-called nanocolloids, that is, particles with a polar nucleus, in which the fat-soluble vitamin is dissolved, and an apolar wrapping (monolayer). This structure makes an oral application of fat-soluble substances possible. First tests demonstrated that vitamin A palmitate, a-tocopherol, as well as coenzyme Qio are thus able to enter the systemic circulation via the buccal mucosa. 

Various factors are required for regular fat digestion. Sublingual lipase and eventually a gastric lipase — which are both stable in an acidic environment — start digesting dietary fats in the stomach. In the intestine, pancreatic bicarbonate as well as bile acids are essential for emulsification of fats and fat-soluble substances which are then cleaved by pancreatic lipases. The cleavage products are incorporated into micelles and can then penetrate the unstirred water layer (UWL) which covers the intestinal surface. There, they can deliver the cleavage products of dietary fats as well as fat-soluble substances (e.g., carotenoids, vitamin E, vitamin A) to the luminal surface of the enterocytes. 

The regular digestion of dietary fats and fat-soluble substances and/or their absorption via the lipid route is compromised in the frame of various diseases such as cystic fibrosis, short bowel syndrome, cholestasis, and chronic inflammatory bowel diseases. 

FIGURE 5.7 Absorption of dietary fat-soluble substances via the lipid route affected by insufficiently emulsified and micellised lipids. 

Vitamin confers biologic activity upon prothrombin and factors VII, IX, and X by participating in their postribosomal modification. Vitamin is a fat-soluble substance found primarily in leafy green vegetables. The dietary requirement is low, because the vitamin is additionally synthesized by bacteria that colonize the human intestine. Two natural forms exist vitamins Ki and K2. Vitamin K1 (phytonadione Figure 34-5) is found in food. Vitamin K2 (menaquinone) is found in human tissues and is synthesized by intestinal bacteria. 

Further studies have extended this promotion of auxin and gibberellin action to other fat-soluble substances, in particular some isoprenoid vitamins and related compounds (I). For instance, vitamin E, vitamin Kl9 and phytol are quite comparable in their growth-promoting ability to the fatty acid ester, methyl linoleate. But some fat-soluble vitamins are not active—for instance, vitamin A, -carotene, and vitamin D2. 

Albumin Maintains plasma oncotic pressure. Transports fat-soluble substances, e.g. bilirubin, drugs Reduced levels Low levels cause ascites and increase free plasma concentration of albumin-bound drugs, e.g. oestradiol, phenytoin Albumin is a useful clinical indicator of the liver s synthetic function. The liver produces and exports up to 12 g of albumin per day. Low levels are also seen in malnutrition, hypercatabolism and nephrotic syndrome. Half-life of 20 days, therefore indicator of chronic liver disease... 

The more soluble in water a chemical or its products are, the more quickly and efficiently it will be eliminated in the urine. The function of metabolism is to convert a chemical from a fat-soluble substance, for example the benzene present in petrol (see Figure 5 and box), into a water-soluble one. If the process is successful, the substance is eliminated quickly into the urine within a few hours. The process of metabolism ensures that the body is protected from prolonged exposure to a potentially hazardous chemical. The process has evolved over millions of years to allow humans and other animals to eliminate chemicals absorbed from food. 

Once a compound has entered the systemic circulation it can be distributed aroimd the body in a matter of minutes. Whether or not it actually enters a particular tissue depends upon a variety of factors, but some tissues may be particularly susceptible whereas others may have extra protection. For instance, the central nervous system is surrounded by layers of lipid and protein collectively called the "blood-brain barrier" which protects it from water-soluble ionic compounds but it is readily pemeable to many fat-soluble substances. In different circumstances, depending upon the toxicity of the compounds involved, this may be either beneficial or damaging. 

Food lipids usually contain small amounts of other fat-soluble substances, including flavor components and some vitamins. Animal fats may contain vitamins A and D, and varying amounts of cholesterol, while vegetable fats may contain carotenes, vitamin E, and sitosterol, but not cholesterol. 

Polysorbate-20, 60, and SO. These have the same acceptable daily intake as sorbitan esters but are characterized by the property of enhancing the absorption of fat-soluble substances (38). This property can be an advantage or an adverse effect depending on the drug. Furthermore, poly-sorbates can also provoke hypersensitivity following topical application. They may disrupt normal membrane structures (39). 

Since the discovery by Evans and Bishop (1923) of a fat-soluble substance necessary for reproduction in the rat, extensive investigation in laboratory and domestic animals has revealed many pathologic states which result from dietary deficiency of vitamin E (Mason, 1954). Despite numerous studies, the mechanism of action of tocopherol and its importance in human nutrition have not been clearly defined. 

Carbon tetrachloride Diacetone alcohol Dibutyl ether 1,4-Dioxane Ethyl chloride Ethyl ether 2-Hexanone Isophorone Isopropyl acetate 2-Methoxy-1-propanol acetate 1-Nitropropane Paraldehyde Propylene dichloride Tetrabromoethane Tetrahydronaphthalene 1,1,2-Trichloroethane solvent, fat-soluble antioxidants Sucroglycerides Sucrose fatty acid esters solvent, fat-soluble substances pharmaceuticals Sesamol... 

Cell membrane. This encloses the cell and regulates the passage of ions, nutrients, lipid-soluble ( fat-soluble ) substances, metabolic products, toxicants, and toxicant metabolites into and out of the cell interior because of its varying permeability for different substances. The cell membrane protects the contents of the cell from undesirable outside... 

The mechanism by which pesticides exert their toxic effects on mammals has been characterized for only a few groups of compounds [17,18]. For example, the mechanism for organophosphorus and carbamate insecticides involves inhibition of cholinesterase also, nitrophenols and higher chlorinated phenols are inhibitors for oxidative phosphorylation [10]. Fat-soluble substances (e.g., organochlorines such as DDT, HCH, and other persistent substances) accumulate in the body and, when stored in fatty tissues, cannot be... 

Studies on the fat-soluble substances required by the beetles have been most interesting. FraenkeF and Fraenkel and Blewett made an extensive investigation of the sterol requirement of several beetles. They found that all five beetles studied required a sterol, although some appeared to be less adversely affected on sterol low diets than others. It is of interest that,... 

The maximum degree of esterification gives a mixture in which hexa, hepta and octa sucrose esters prevail. The product Olestra is a lipid-like substance that was developed as a non-energy (nonabsorbable) fat substitute, since ester bonds are not hydrolysed by enzymes of the digestive tract. However, it was found that Olestra has some adverse gastrointestinal effects and depletes blood levels of many valuable fat-soluble substances, including carotenoids. 

A fat-soluble substance, found in many plants, especially carrots. It can be hydrolysed in the intestine to give vitamin A. 

Carotene derives its name from the carrot, from which it was first isolated 100 years ago. It is the yellow-colored, fat-soluble substance that gives the characteristic color to carrots and butter. 

Properties—Vitamin A (retinol) is an almost colorless (pale yellow) fat-soluble substance. It is insoluble in water hence, there is no loss by extraction from cooking. Although the esters of vitamin A are relatively stable compounds, the alcohol, aldehyde, and acid forms are rapidly destroyed by oxidation when they are exposed to air and light Since vitamin A occurs in the stable form (the ester) in most foods, normal preparation procedures do not destroy much vitamin A activity. However, fats that undergo oxidative rancidity, can lose their vitamin A rapidly. We depend mainly on storage in a cool, dark place (refrigeration) and on added antioxidants, such as vitamin E, to protect fats and oils from vitamin A loss. 

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