Lipids data interpretation

This chapter gives an overview of GC/MS analytical procedures used for lipid determination, and a summary of the complex issue of lipid chromatographic data interpretation in paintings and archaeological objects. Some examples and case studies are also included. 

RECOGNITION OF LIPID METABOLISM PATHWAYS FOR DATA INTERPRETATION... 

In addition to those cellular lipid functions introduced earlier, some classes of these lipids possess some other unique functions in cellular processes, which should be recognized and are very useful for data interpretation. In this section, some examples of these lipid classes and their cellular functions (Table 16.1) are overviewed. 

There are many other lipid classes in this category. For instance, acyl CoA species are involved in all the cellular processes related to lipid metabolism in addition to the involvement of energy metabolism vitamins are the essential nutrients of mammals wax serves as both chemical and physical barriers for plants PA and DAG species are key intermediates for lipid biosynthesis in addition to their role in biomembrane, signal transduction, and energy metabolism as stated earlier. In summary, there is no doubt that recognition of the specific role(s) that an individual lipid class plays can clearly make the data interpretation better and insightful. 

The existence of sample inhomogeneity and cellular compartments could lead to complications for data interpretation. In Chapter 13, we discussed the importance of careful sample preparation for accurate analysis of lipids and for developing the strategies to overcome the effects of sample inhomogeneity on acquisition of... 

Similar to the effects of different cell types in a sample on interpreting lipidomics data, different lipid profiles present in different cellular compartments and microdomains are also a factor making data interpretation complicated. We extensively discuss the subcellular lipidomics in Chapter 20, which may aid in the understanding of this complication and interpreting the lipidomics data better. 

Biological membranes provide the essential barrier between cells and the organelles of which cells are composed. Cellular membranes are complicated extensive biomolecular sheetlike structures, mostly fonned by lipid molecules held together by cooperative nonco-valent interactions. A membrane is not a static structure, but rather a complex dynamical two-dimensional liquid crystalline fluid mosaic of oriented proteins and lipids. A number of experimental approaches can be used to investigate and characterize biological membranes. However, the complexity of membranes is such that experimental data remain very difficult to interpret at the microscopic level. In recent years, computational studies of membranes based on detailed atomic models, as summarized in Chapter 21, have greatly increased the ability to interpret experimental data, yielding a much-improved picture of the structure and dynamics of lipid bilayers and the relationship of those properties to membrane function [21]. 

Hepatic reperfusion injury is not a phenomenon connected solely to liver transplantation but also to situations of prolonged hypoperfusion of the host s own liver. Examples of this occurrence are hypovolemic shock and acute cardiovascular injur) (heart attack). As a result of such cessation and then reintroduction of blood flow, the liver is damaged such that centrilobular necrosis occurs and elevated levels of liver enzymes in the serum can be detected. Particularly because of the involvement of other organs, the interpretation of the role of free radicals in ischaemic hepatitis from this clinical data is very difficult. The involvement of free radicals in the overall phenomenon of hypovolemic shock has been discussed recently by Redl et al. (1993). More specifically. Poll (1993) has reported preliminary data on markers of free-radical production during ischaemic hepatitis. These markers mostly concerned indices of lipid peroxidation in the serum and also in the erythrocytes of affected subjects, and a correlation was seen with the extent of liver injury. The mechanisms of free-radical damage in this model will be difficult to determine in the clinical setting, but the similarity to the situation with transplanted liver surest that the above discussion of the role of XO activation, Kupffer cell activation and induction of an acute inflammatory response would be also relevant here. It will be important to establish whether oxidative stress is important in the pathogenesis of ischaemic hepatitis and in the problems of liver transplantation discussed above, since it would surest that antioxidant therapy could be of real benefit. 

---