Chylomicrons triacylglycerol

The clearance of labeled chylomicrons from the blood is rapid, the half-time of disappearance being under 1 hour in humans. Larger particles are catabolized more quickly than smaller ones. Fatty acids originating from chylomicron triacylglycerol are delivered mainly to adipose tissue, heart, and muscle (80%), while about 20% goes to the liver. However, the liver does not metabolize native chylomicrons or VLDL significantly thus, the fatty acids in the liver must be secondary to their metabolism in extrahepatic tissues. 

Heart Pumping of blood Aerobic pathways, eg, P-oxidation and citric acid cycle Free fatty acids, lactate, ketone bodies, VLDL and chylomicron triacylglycerol, some glucose Lipoprotein lipase. Respiratory chain well developed. 

Zinder, O., Mendelson, C.R., Blanchette-Mackie, E.J., Scow, R.O. 1976. Lipoprotein lipase and uptake of chylomicron triacylglycerol and cholesterol by perfused rat mammary tissue. Biochim. Biophys. Acta 431, 526-537. 

Apo-H (also known as /S-2-glycoprotein I) Chylomicrons Triacylglycerol metabolism... 

C. The chylomicron triacylglycerol is digested by lipoprotein lipase, and the palmitate enters a fat cell and is stored as triacylglycerol. It is released as free palmitate and carried, complexed with albumin, to a muscle cell, where it is oxidized. 

The glycerol released from chylomicron triacylglycerols by LPL may be used for triacylglycerol synthesis in the liver in the fed state. 

Taguchi, H.,Watanabe, H., Onizawa, K., Nagao,T., Gotoh,N.,Ya-sukawa, T., Tsushima, R., Shimazaki, H., and Itakura, H. (2000) Douhle-Blind Controlled Study on the Effects of Dietary Diacyl-glycerol on Postprandial Serum and Chylomicron Triacylglycerol Responses in Healthy Humans, J. Am. Coll. Nutr. 19,789-796. 

Fig. 4. Changes in chylomicron-triacylglycerol (TAG) (NS) and very low density lipoprotein-TAG (P> 0.05) after fat loading. Values are means SEM, n = 6. NS, not significant.

Apoprotein C-II, which activates lipoprotein lipase at the cell surface, permitting uptake of fatty acids from chylomicron triacylglycerol. The triacylglycerols are hydrolysed extracellularly, and the free fatty acids are then taken into the cell and re-esterified to triacylglycerol. In the fed state the major site of lipoprotein lipase activity is adipose tissue, but other tissues can also hydrolyse chylomicron triacylglycerol as required. 

Yli-Jokipii, K.M., Schwab, U.S., Tahvonen, R.L., Kurvinen, J.P, Mykkanen, H.M. and Kallio, H.P., Triacylglycerol molecular weight and to a lesser extent, fatty acid positional distribution, affect chylomicron triacylglycerol composition in women. J. Nutr, 132, 924—929 (2002). 

In Man, up to 300 g of chylomicron triacylglycerols can be hydrolysed by lipoprotein lipase each day, although less than 1% of dietary lipids may be found in the blood at any given time. 

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