Fatty acid medium chain

GOR40 Medium chain fatty acids Insulin regulation... 

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). 

Hajjaj, H. et al.. The biosynthetic pathway of citrinin in the filamentous fungi Monascus ruber as revealed by C-NMR, Appl. Env. Microbiol, 65, 311, 1999. Hajjaj, H. et al.. Medium-chain fatty acids affect citrinin production in the filamentous fungus Monascus ruber, Appl. Env. Microbiol, 66, 1120, 2000. 

K Morimoto, T Nakamura, K Morisaka. (1989). Effect of medium-chain fatty acid salts on penetration of a hydrophilic compound and a macromolecular compound across rabbit corneas. Arch Int Pharmacodyn 302 18-26. 

Lindmark T, Kimura Y, Artursson P (1998) Absorption enhancement through intracellular regulation of tight junction permeability by medium chain fatty acids in Caco-2 cells. J Pharmacol Exp Ther 284 362-369... 

Medium-chain fatty acid albumin bound diet (especially dairy produce) cardiac muscle, liver... 

Medium-chain fatty acids are also present in bovine milk and some plant oils (e.g. coconut). After digestion of the triacylglycerol, they are taken up by the enterocytes in the small intestine but are not esterified. Instead they pass directly into the hepatic portal blood, from where they are taken up by the liver for complete oxidation or conversion to ketone bodies. 

This latter situation is particularly beneficial for patients who are being fed intravenously because, if triacylglycerols containing medium-chain fatty acids are included in parenteral feeds, they are readily converted into ketone bodies so that a soluble fat fuel is rapidly made available in the blood that can be oxidised by most tissues. 

There are three isoenzymes (see p. 98) of acyl CoA dehydrogenase that are specialized for long-chain fatty acids (12-18 C atoms), medium-chain fatty acids (4-14), and short-chain fatty acids (4-8). 

Diagnosis of medium-chain acyl-coenzyme A dehydrogenase deficiency in the neonatal period by measurement of medium-chain fatty acids in plasma and filter paper blood samples. 

Perret, J. P., N. Guiffray, and P. Mottaz. Stimulation of insulin secretion by medium-chain fatty acids in the diet of young rabbits. Ann Nutr Metab 1983 27(2) 153-161. 

Ruminant milk fats are also rich in medium-chain fatty acids. These are synthesized in the mammary gland via the usual malonyl CoA pathway (section 3.5) and are released from the synthesizing enzyme complex by thioacylases presumably, the higher levels of medium chain acids in ruminant milk fats compared with those of monogastric animals reflect higher thioacylase activity in the mammary tissue of the former. 

FIGURE 17-16 The fatty acids in the endoplasmic reticulum. This alternative to /3 oxidation begins with oxidation of the carbon most distant from the a carbon—the oj (omega) carbon. The substrate is usually a medium-chain fatty acid shown here is lauric acid (laurate). This pathway is generally not the major route for oxidative catabolism of fatty acids... 

Entry of short- and medium-chain fatty acids into the mitochondria... 

The synthesis of fatty acids for incorporation into milk fat within the mammary gland is similar to that seen in other tissues. There are two basic reactions the conversion of acetyl-coenzyme A (CoA) to malonyl-CoA, followed by incorporation of the latter into a growing acyl chain via the action of the fatty acid-synthetase complex. However, the product of these reactions in lactating mammary tissue from many species is short and medium chain fatty acids. In most other tissues the product is palmitate. For more complete details see Moore and Christie, (1978), Bauman and Davis (1974), and Patton and Jensen (1976). 

Both goat and cow mammary tissue synthesize medium-chain fatty acids. However, attempts to isolate thioesterase II from the cytosol of ruminant mammary tissues have not been successful (Grunnet and Knudsen 1979). In contrast to the nonruminant, the fatty acid-... 

Knudsen and Grunnet (1982) have proposed an interesting system for the control of medium-chain fatty acid synthesis by ruminant mammary tissue. Their proposal is based on their observations that ruminant mammary tissue fatty acid-synthetase exhibits both medium-chain thioesterase (Grunnet and Knudsen 1978) and transacylase (Knudsen and Grunnet 1980) activity and that medium-chain fatty acids synthesized de novo can be incorporated into TG without an intermediate activation step (Grunnet and Knudsen 1981). They proposed that the synthesis of the medium-chain fatty acids is controlled by their incorporation into TG (Grunnet and Knudsen 1981). Further work will be needed to substantiate transacylation as a chain-termination mechanism in fatty acid synthesis by ruminant mammary tissue. 

In many in vitro studies the acylation of the sn-3 position appears to be the rate-limiting step in TG synthesis. It has been suggested that the intracellular concentration of medium chain fatty acids may limit the final acylation reaction in TG synthesis (Dimmena and Emery 1981). Another theory is that the concentration of phosphatidate phosphatase, the enzyme that hydrolyzes the phosphate bond in phospha-tidic acid, yielding DG, may be the limiting factor (Moore and Christie 1978). The DG acyltransferase responsible for the final acylation of milk TG has been studied in mammary tissue from lactating rats (Lin et al. 1976). It was observed to be specific for the sn-1,2 DG, with very little activity observed with the sn-1,3 or sn-2,3 DG. It exhibited a broad specificity for acyl donors. The acyl-CoA specificity was not affected by the type of 1,2 DG acceptor offered, which implies that the type of fatty acid introduced into the glycerol backbone was not influenced by the specificity of subsequent acylation steps. However, the concentration of acyl donors will affect the final acylation. It was ob-... 

Kuksis et al. (1973) have extensively analyzed the structure of milk TGs and have summarized their results as follows there are three types of TGs. The first has acyl carbons totaling 48-54, composed of long-chain 1,2-DGs containing 18 0, 18 1, and 18 2. In type 2 the carbon numbers are 36-46 and the sn-3 position acids are 4 0, 6 0, and 8 0. These TGs are enantiomers. In type 3, the carbon numbers are 26-34, the 1,2-DGs contain medium chain fatty acids, and the 3-posi-tion acids are short and medium chain. Those TGs in type 3 that have short-or medium-chain acids in the sn-3 position that are different from those in sn-1 are also enantiomers. 

Grunnet, I. and Knudsen, J. 1979. Fatty-acid synthesis in lactating goat mammary gland, I. Medium chain fatty acid synthesis. Evr. J. Biochem. 95, 497-502. 

Smith, S. and Ryan, P. 1979. Asynchronous appearance of two enzymes concerned with medium chain fatty acid synthesis in developing rat mammary gland. J. Biol. Chem. 254, 8932-8936. 

Smith, S. and Stern, A. 1981. Development of the capacity of mouse mammary glands for medium chain fatty acid synthesis during pregnancy and lactation. Biochim. Biophys. Acta 664, 611-615. 

Constantinides, P.P., et al., Water-in-oil microemulsions containing medium-chain fatty acids/salts formulation and intestinal absorption enhancement evaludfibarm. Res., 13, 210, 1996. 

It is important to bear in mind when discussing the effect of dairy fat in association to heart disease that dairy products contain many different saturated fatty acids that do not exert the same biological response in terms of, for example, cholesterol levels. The saturated fatty acids in milk fat include shorter and medium chain fatty acids (2 0-10 0), lauric acid (12 0), myristic acid (14 0), palmitic acid (16 0), and stearic acid (18 0). Other fatty acids in milk fat are oleic acid (18 1) and linoleic acid (18 2n-6) as indicated in Table 1.2. 

An important issue that has been recognized recently concerns the potential adverse effect of absorption enhancers on the rectal mucosa, as shown in rats after a single application [61,62], Safety evaluation of the applicability of absorption enhancers is imperative. In clinical application, medium-chain fatty acids such as sodium caprate are used only for suppositories containing antibiotics [36],... 

Lindmark, T., T. Nikkila, and P. Artursson. 1995. Mechanisms of absorption enhancement by medium chain fatty acids in intestinal epithelial Caco-2 cell monolayers. J Pharmacol Exp Ther 275 958. 

Van Hoogdalem, E.J., et al. 1988. Absorption enhancement of rectally infused cefoxitin sodium by medium-chain fatty acids in conscious rats Concentration-effect relationship. Pharm Res 5 453. 

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