Lipids bile salts

Muranishi, S., N. Muranishi, and H. Sezaki. 1979. Improvement of absolute bioavailability of normally poorly absorbed drugs Inducement of the intestinal absorption of streptomycin and gentamicin by lipid-bile salt mixed micelles in rat and rabbit. Int J Pharm 2 101. 

Muranishi, N., et al. 1980. Mechanism for the inducement of the intestinal absorption of poorly absorbed drugs by mixed micelles. I. Effects of various lipid-bile salt mixed micelles on the intestinal absorption of streptomycin in rat. Int J Pharm 4 271. 

Q9 Lipid in the diet is present mostly in the form of triglycerides, which are digested by pancreatic lipase to yield fatty acids and monoglycerides bile salts are also required for digestion and absorption of the dietary lipids. Bile salts interact with the fatty acids and monoglycerides in the gut lumen to form micelles, which can be absorbed by the epithelial cells. In the epithelial cell the triglyceride is resynthesized to form droplets, or chylomicrons, which enter the lacteals and are carried by the lymphatic system into the general circulation. 

Fat-soluble vitamins such as retinol and )3-carotene are readily dissolved in mixed lipid-bile salt micelles in vitro. Retinol is approximately 10 times more readily dissolved in such micelles than /3-carotene [105]. It is likely that these two substances occupy different regions of the micelle. The difference in solubility, therefore, may reflect the limited capacity of the nonpolar core of the micelle for the relatively bulky /3-carotene molecule. Retinol, on the other hand, may occupy a more hydrophilic region of the micelle. In a mixed oil/micellar system, a-tocopherol distributes between the two phases, its concentration in the micellar phase being enhanced by expansion of the micelles with monoglycerides and lecithin of long-chain fatty acids. However, lipids containing medium-chain fatty acids do not expand the micelles as effectively as their long-chain counterparts such that there is less solubilization of a-tocopherol in the micellar phase [106]. 

The answer to this question has already been given above. Bile salts are not necessary for absorption of triglycerides but may be necessary for absorption of other lipids such as cholesterol and some nonpolar lipids. Bile salts can, however, be... 

The structure of cholic acid helps us understand how bile salts such as sodium tauro cholate promote the transport of lipids through a water rich environment The bot tom face of the molecule bears all of the polar groups and the top face is exclusively hydrocarbon like Bile salts emulsify fats by forming micelles m which the fats are on the inside and the bile salts are on the outside The hydrophobic face of the bile salt associates with the fat that is inside the micelle the hydrophilic face is m contact with water on the outside... 

Resistant to ether, chloroform, and bile salts, indicating lack of essential lipids... 

We turn now to the biosynthesis of lipid structures. We begin with a discussion of the biosynthesis of fatty acids, stressing the basic pathways, additional means of elongation, mechanisms for the introduction of double bonds, and regulation of fatty acid synthesis. Sections then follow on the biosynthesis of glyc-erophospholipids, sphingolipids, eicosanoids, and cholesterol. The transport of lipids through the body in lipoprotein complexes is described, and the chapter closes with discussions of the biosynthesis of bile salts and steroid hormones. 

In general, the sterols perform a structural function, for example as components of the lipid layers of membranes. The Cis, C19 and C21 steroids mainly perform an endocrine function. In other words they are hormones. The bile salts (C24-steroids) fulfil a functional role in digestion in animals. 

Irrespective of the physical form of the carotenoid in the plant tissue it needs to be dissolved directly into the bulk lipid phase (emulsion) and then into the mixed micelles formed from the emulsion droplets by the action of lipases and bile. Alternatively it can dissolve directly into the mixed micelles. The micelles then diffuse through the unstirred water layer covering the brush border of the enterocytes and dissociate, and the components are then absorbed. Although lipid absorption at this point is essentially complete, bile salts and sterols (cholesterol) may not be fully absorbed and are not wholly recovered more distally, some being lost into the large intestine. It is not known whether carotenoids incorporated into mixed micelles are fully or only partially absorbed. 

Nutrients lipids, fibers, other carotenoids Bile salts pH... 

The reaction was started by transferring 1 mL of the enzyme/buffer/bile salt solution (pH=7.2, 37 C) to each flask placed in a thermostated shaker at 37°C. Experiments were carried out without lipid and bile salt as well, and in these experiments equal amounts of stock solutions of the enzyme in buffer and peptide in buffer were mixed in the flasks at time zero, to give the indicated concentrations (see Table III). The reactions in the flasks were stopped by adding 0.5 ml acetonitrile at different times. The total amount of intact peptide remaining in a flask was determined by HPLC, after the content was dissolved by adding ethanol. 

Penetration enhancers are low molecular weight compounds that can increase the absorption of poorly absorbed hydrophilic drugs such as peptides and proteins from the nasal, buccal, oral, rectal, and vaginal routes of administration [186], Chelators, bile salts, surfactants, and fatty acids are some examples of penetration enhancers that have been widely tested [186], The precise mechanisms by which these enhancers increase drug penetration are largely unknown. Bile salts, for instance, have been shown to increase the transport of lipophilic cholesterol [187] as well as the pore size of the epithelium [188], indicating enhancement in both transcellular and paracellular transport. Bile salts are known to break down mucus [189], form micelles [190], extract membrane proteins [191], and chelate ions [192], While breakdown of mucus, formation of micelles, and lipid extraction may have contributed predominantly to the bile salt-induced enhancement of transcellular transport, chelation of ions possibly accounts for their effect on the paracellular pathway. In addition to their lack of specificity in enhancing mem-... 

P. E. Luner, D. V. Kamp. Wetting behavior of bile salt-lipid dispersions and dissolution media patterned after intestinal fluids. J. Pharm. Sci. 2001,... 

In addition to the common pathways, glycolysis and the TCA cycle, the liver is involved with the pentose phosphate pathway regulation of blood glucose concentration via glycogen turnover and gluconeogenesis interconversion of monosaccharides lipid syntheses lipoprotein formation ketogenesis bile acid and bile salt formation phase I and phase II reactions for detoxification of waste compounds haem synthesis and degradation synthesis of non-essential amino acids and urea synthesis. 

ATP-dependent process, aided by the bile-salt excretion pump (BSEP) expression in the canalicular membrane. Conjugation increases the aqueous solubility of the bile adds, and renders these bile adds largely impermeable to the cell membranes of the intestine and duodenum hence, they are unable to leave the intestinal lumen. This allows bile-add levels to rise in the lumen, ultimately reaching sufficient concentrations to form micelles, which allow lipid emulsification and subsequent absorption. 

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