Trans Fatty acids turnover

Trans fatty acids occur mainly in positions 1 and 3 of triacylglycerols, the predominant lipids in adipose tissue. The concentration of trans fatty acids in adipose tissue is approximately proportional to long-term dietary intake, and determination of the concentrations in storage fat is one method used to estimate trans fatty acid intake. However, this is not entirely straightforward as variation has been reported in the composition of adipose tissue obtained from different sites and depths, and factors that influence adipose tissue turnover rates such as dieting and exercise are also complicating factors. Trans-18 l isomers account for approximately 70% of the trans fatty acids found in adipose tissue, and trans-18 2 isomers (trans,trans, trans,cis, and cisytrans) account for about 20%. 

The turnover of trans fatty acids parallels that of other types of fatty acids in the body, and trans fatty acids are readily removed from the tissues for oxidation. Studies in which hmnan subjects were fed labelled carbon-13 isotope have demonstrated... 

Current research on changes in the stracture of the cytoplasmic membrane shows the involvement of 1) the composition of the fatty acids of the phospholipids like the cis/trans isomerization of unsaturated fatty acids 2) composition of phospholipid headgroups and 3) rate of turnover of membrane components. 

The concentration of CLA in plasma lipids is determined by bioavailability from the gut, and subsequent partitioning between p-oxidation, incorporation into tissue lipids, secretion from the gut and liver, and turnover within the plasma compartment. There is only limited information available about the metabolic fate of CLA in humans. Using deuterated fatty acid ethyl esters, Emken et al. (2002) showed that the bioavailability of cis-9,tram- CLA and trans- 0,cis- 2 CLA after a bolus was lower than that of oleic acid. However, since the fatty acids were not ingested as TAG any effect of the conjugated double bonds... 

The immobilized enzymes can, therefore, be easily separated by filtration and they are recyclable several times without loss of activity. Actually, total turnovers as high as 2 x 105 moles of product per mole of catalyst have been recorded. Nevertheless, as a drawback, it is worth highlighting that these systems are very sensitive to the kind of substrate employed and hence they can be unsuitable and less versatile for some particular oleochemical applications. For instance, fatty compounds with the C=C in the trans configuration, such as elaidic acid, react very slowly, and the epoxidation of polyunsaturated oleochemicals proceeds step by step. This means that the formation of di-epoxides takes place only after the nearly complete formation of monoepoxides. 

---