Triglycerides tissue distribution

Olive oil was the original model lipid for partition studies, and was used by Overton in his pioneering research [518,524], It fell out of favor since the 1960s, over concerns about standardizing olive oil from different sources. At that time, octanol replaced olive oil as the standard for partition coefficient measurements. However, from time to time, literature articles on the use of olive oil appear. For example, Poulin et al. [264] were able to demonstrate that partition coefficients based on olive oil-water better predict the in vivo adipose-tissue distribution of drugs, compared to those from octanol-water. The correlation between in vivo log Kp (adipose tissue-plasma) and log (olive oil-water) was 0.98 (r2), compared to 0.11 (r2) in the case of octanol. Adipose tissue is white fat, composed mostly of triglycerides. The improved predictive performance of olive oil may be due to its triglyceride content. 

R. C. Johnson, S. K. Young, R. Cotter, L. Lin and W. B. Rowe, Medium-chain-triglyceride lipid emulsion metaboUsm and tissue distribution. Am.. Clin. Nutr., 52, 502-508 (1990). 

The assumption of a characteristic line pattern for lipids is justified by the fact that IMCL, EMCL, and other adipose tissue in subcutaneous fat tissue or in tibial bone marrow are known to consist mainly of a very similar composition of fatty acid triglycerides. The characteristic line pattern A is indirectly determined by recording a reference lipid spectrum (R) out of a lipid compartment with a relatively homogenous magnetic field described by a normal distribution, i.e., a Gaussian function G. That means R can be written as... 

Lipid samples from natural sources generally contain various classes of lipid compounds in which concentration of individual lipid class varies substantially. Lipids from fat-rich tissues of biological samples are usually dominated by triglycerides. On the other hand, those from low-fat tissues tend to have even distribution of compounds among lipid classes. The range of calibration standard solutions described in this unit is the same for all lipid classes. To improve the accuracy in lipid-class quantification, it would always be a good approach to adjust the range of individual calibration standards based on the lipid class profile of lipids from particular sources. 

In considering the distribution of particular lipids, it must be emphasized that there is wide variation in the lipid composition of various cells (see section entitled An Excursion into the Complexities of Phospholipids Found in Certain Cells Defining the Problem ). Of the three classes of lipids depicted in Figure 1-1, triglycerides (triacylglycerols) form the chief lipid constituent of adipose tissue in the mammal and also are found in plasma. 

After a carbohydrate-rich meal, glucose is distributed into tissues and then subsequently converted to the fuel stores of glycogen (glycogenesis) and triglyceride (lipogenesis), or catabolized by oxidation to carbon dioxide (via glycolysis and the Krebs cycle). 

Studies investigating stereoselective binding and distribution of NSAIDs to extrasynovial tissues are scarce. In rats, etodolac displays less stereoselectivity in tissue concentrations than in plasma and was thought to be due to a greater unbound fraction of S enantiomer in plasma relative to antipode [275]. For 2-aryl propionates, which undergo in vivo unidirectional inversion from R to S enantiomer (e.g., ibuprofen), the presence of these NSAIDs in the adipose tissue as hybrid triglycerides has been reported [276]. 

Shapiro el al. (1960) studied the distribution of labeled fatty acids in the triglycerides synthesized by rat mesenteric fat incubated with palmitate-1-C and concluded that the newly synthesized triglycerides primarily resulted from a process involving the total esterification of a-glycerophosphate with 3 molecules of fatty acid, and that esterification of preformed tissue diglycerides, or a lipase-activated exchange between triglycerides and free fatty acid did not make a major contribution. 

Table 3.168 Positional distribution of fatty acids in triglycerides isolated from pig tissues (Christie and Moore, 1970)... 

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