Triacylglycerol medium-chain

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. 

Medium-chain acyl-CoA synthetase, which is present within the mitochondrial matrix of the liver, activates fatty acids containing from four to ten carbon atoms. Medium-chain length fatty acids are obtained mainly from triacylglycerols in dairy products. However, unlike long-chain fatty acids, they are not esterified in the epithelial cells of the intestine but enter the hepatic portal vein as fatty acids to be transported to the liver. Within the liver, they enter the mitochondria directly, where they are converted to acyl-CoA, which can be fully oxidised and/or converted into ketone bodies. The latter are released and can be taken up and oxidised by tissues. 

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. 

Correct answer = A. Pancreatic lipase hydrolyzes dietary triacylglycerol primarily to 2-monoacylglycerol plus two fatty acids. These products of hydrolysis can be absorbed by the intestinal mucosal cells. Bile salts do not inhibit release of fatty acids from triacylglycerol, but rather are necessary for the proper solubilization and hydrolysis of dietary triacylglycerol in the small intestine. Short- and medium-chain length fatty acids enter the portal circulation after absorption from the small intestine. Synthesis of apolipoproteins, especially apo B-48, is essential for the assembly and secretion of chylomicrons. 

Studies in vitro and in rats showed that short and medium chain fatty acids and monoacylglycerols hydrolyzed from milk triacylglycerols and digestion products of sphingolipids possess strong anti-bacterial and anti-viral properties. 

Deckelbaum, R. J., Hamilton, J. A., Moser, A., Bengtsson-Olivecrona, G., Butbul, E., Carpentier, Y. A., Gutman, A., and Olivecrona, T. (1990), Medium-chain versus long-chain triacylglycerol emulsion hydrolysis by lipoprotein hpase and hepatic lipase Implications for the mechanisms of lipase action, Biochemistry, 29,1136-1142. 

Acidolysis. This reaction can be acid or enzyme catalyzed and may be used to modify triacylglycerol composition. Acidolysis of an oil containing only Cis and Cjg fatty acids with fatty acids rich in lauric acid (e.g., from palm-kemel oil) results in a triacylglycerol enriched in medium-chain fatty acids. 

Medium-chain fatty acids are saturated fatty acids because of the relatively shorter hydrocarbon chain, which does not facilitate unsaturation. The safety of medium-chain triacylglycerol (MCTs) in dietary oil has been debated, and associated effects on cholesterol metabolism remain unclear. Although some studies have shown that... 

Captex Partially digestible Medium-chain triacylglycerol ABITEC Co. (Columbus, Ohio)... 

In neonate, suckling mammals, short- and medium-chain fatty acids are preferentially split at the sn-3 triacylglycerol position by oral and gastric lipases and are absorbed in the stomach, while the long-chain fatty acids are hydrolyzed at the sn- and sn-2 positions and by pancreatic lipases and are absorbed in the small intestine (50, 51). With growth, the neonate fat digestion system becomes less active, and is replaced by the small intestine-pancreatic lipase pathway. But residual oral and gastric lipase activities and direct absorption of short-chain fatty acids in the... 

Medium chain triacylglycerols Caprylic, capric triacylglycerol Quick skin penetration, emollient, sunscreen solvent, skin, body and hair care... 

Digestion and absorption of triacylglycerols with medium-chain fatty acids 12 carbons) proceed by a different pathway. Medium-chain triacylglycerols are partly water-soluble, are rapidly hydrolyzed by lingual and pancreatic lipases, and do not require the participation of bile acids. Some are absorbed intact and hydrolyzed inside the absorptive cell. Medium-chain fatty acids enter the portal... 

At least three acyl-CoA synthases, each specific for a particular size of fatty acid, exist acetyl-CoA synthase acts on acetate and other low-molecular-weight carboxylic acids, medium-chain acyl-CoA synthase on fatty acids with 4-11 carbon atoms, and acyl-CoA synthase on fatty acids with 6-20 carbon atoms. The activity of acetyl-CoA synthase in muscle is restricted to the mitochondrial matrix. Medium-chain acyl-CoA synthase occurs only in liver mitochondria, where medium-chain fatty acids obtained from digestion of dietary triacylglycerols and transported by the portal blood are metabolized. Acyl-CoA synthase, the major activating enzyme, occurs on the outer mitochondrial membrane surface and in endoplasmic reticulum. The overall reaction of activation is as follows ... 

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