Lipid accumulation biochemistry

The role that fatty liver plays in liver injury is not clearly understood, and fatty liver in itself does not necessarily mean liver dysfunction. The onset of lipid accumulation in the liver is accompanied by changes in blood biochemistry, and for this reason blood chemistry analysis can be a useful diagnostic tool. 

Koppaka, V. and P.H. Axelsen Accelerated accumulation of amyloid beta proteins on oxidatively damaged lipid membranes. Biochemistry 39 (2000) 10011-6. 

Bafor, M., Wiberg, E. and Stymne, S. (1990c) Palm kernel (Elaeis guineensis), lipid accumulation, fatty acid changes and acyltransferase activities, in Plant Lipid Biochemistry, Structure and Utilization, eds. P.J. Quinn and J.L. Harwood, Portland, London, pp. 198-200. 

Microorganisms lacking ATP citrate lyase do not accumulate lipid much above 10-15%, although the corollary, that organisms with ATP citrate lyase activity will accumulate lipid may not always hold because other enzymes, such as AMP deaminase, AMP-dependent isocitrate dehydrogenase or malic enzyme, may be lacking or may not be under sufficiently stringent control to allow extensive lipid accumulation. There is clearly much still to be learnt about lipid accumulation and its attendant biochemistry to explain all these variations at the fundamental level. 

Contrary to the accumulated knowledge on the static or quasi-static characteristics of thin lipid films at air/water interface, less attention has been paid to the dynamical or nonequilibrium behavior of the film. Studies on the dynamical characteristics of thin lipid films may be quite important, because the life phenomena are maintained under nonequilibrium conditions. According to the modern biochemistry [11,12], thin lipid membrane in living cells is not a rigid wall but a thermally fluctuating barrier with high fluidity. In the present section, we will show that thin lipid film exhibits the various interesting dynamical tc-A characteristics, such as the "overshoot hump", the "zero surface pressure", and the "flat plateau". 

Comparative biochemistry. Some researchers believe that the proper role of comparative biochemistry is to put evolution on a molecular basis, and that detoxication enzymes, like other enzymes, are suitable subjects for study. Xenobiotic-metabolizing enzymes were probably essential in the early stages of animal evolution because secondary plant products, even those of low toxicity, are frequently lipophilic and as a consequence would, in the absence of such enzymes, accumulate in lipid membranes and lipid depots. The evolution of cytochrome P450 isoforms, with more than 2000 isoform cDNA sequences known, is proving a useful tool for the study of biochemical evolution. 

Much of my previous research experience had been in lipid biochemistry and DMBA, a polycyclic hydrocarbon, is essentially a lipid xenobiotic. The suggestion had been made by Dao et al O) that the specific induction of mammary tumors by DMBA and other polycyclic hydrocarbons might be due to their tendency, as lipids, to accumulate and persist in the adipose tissue of the mammary gland, thereby increasing the exposure to the susceptible mammary epithelial tissue. If this were indeed a factor in the ability of these compounds to produce mammary tumors, it seemed to us that it might be possible to influence their effectiveness by altering fat metabolism in the body. 

In the last ten years, considerable information has accumulated on the biochemistry of the archaea. Some aspects of this subject, such as bioenergetics, molecular biology and genetics, membrane lipids, etc., have been dealt with in individual book chapters and review articles in various treatises, but the subject as a whole has not yet been treated in a comprehensive maimer. 

Table 12.5 Summary of enzyme deficiencies and accumulating lipids in the sphingolipidoses. Reproduced with permission from the Annual Review of Biochemistry, 47, 1978 by Annual Reviews Inc.

Both somatic and microspore-derived embryos of oil plants are valuable tools in applied lipid biochemistry. It is well known from the Uterature that cultured embryos of various oil plants accumulate triaeylglycerols during maturation and that they synthesize unusual fatty adds found in the seeds. The capacity of cultured embryos and embryogenic cells of oil plants as model systems is, therefore, reviewed with respect to their usefulness in studying the mechanisms of genetic control of biosynthesis and assembly of triacylglycerols in oil seeds. 

Projects in oil-crop breeding as well as bioreactor development projects have to face competition from petrochemical intermediates and Increasing sophistication of traditional chemistry. However, in some areas of biotechnological research on lipids it has become visible that biotransformation reactions will lead to products hitherto unavailable from industrial chemistry. In order to further develop this field, the accumulation of more basic knowledge of molecular biochemistry of fatty acids In plants will be as Important as more efforts to master the commercial biotransformation of sparingly water-soluble compounds. 

Being at the end of the food chain, carnivorous marine mammals accumulate in their blubber chlorinated pesticides of anthropic origin, especially DDT, chlordanes, PCBs (polychlorinated biphenyls) and heptachlor, at concentrations that may be toxic to the animals. The lipid and chlorinated pesticide compositions are related to the diet the diet may be deduced, at least in part, from the detailed composition of the blubber. This approach to the biochemistry of marine mammals has produced a great number of publications, the most recent of which include the following Maruya and Lee (1998) Aguilar, Borrell, and Pastor (1999) Kannan et al. (2000) Ross et al. (2000) Watanabe et al. (2000) Kajiwara et al. (2001) Kubota, Kunito, andTanabe (2001) Le Boeuf et al. (2002) Hoekstra et al. (2003) Vetter, Jun, and Althoff (2003) Hansen et al. 

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