Lipid homeostasis

Dietary lipid consists mostly of triacylglycerol from plant and animal sources. It supplies about 45% of the energy in a typical Western diet. Except for the essential polyene fatty acids (Chapter 18), the dietary requirement for lipid can be met by carbohydrate or protein. However, the Eskimo has a satisfactory diet consisting of 80-90% lipid. Digestion of triacylglycerol is discussed in Chapter 12. A 

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Unsaturations of lipids play a key role in lipid homeostasis, where organisms adapt to temperature variations of the environment. Plants and animals maintain physiological functions by reversibly altering the composition and conformation of lipid molecules of the cell membrane. To achieve this, they extensively and elegantly use the unsaturations (double bonds) present in their side chains. This is the process by which cell membranes adjust their flexibility (fluidity) of the bilayer and adapt themselves to perturbations in temperature, pressure, and other variations in the natural environment [11-14]. They remain indispensable for the poikilothermism exhibited by fishes, invertebrates, and amphibians [15, 16]. Commercially,... 

Zhang, Y.-M. and Rock, C.O. (2008) Membrane lipid homeostasis in bacteria. Nature Reviews Microbiology, 6, 222-233. 

Another example in which literature results were reanalyzed in view of the PSSC concept concerns the development of ligands for the farnesoid X receptor. The farnesoid X receptor is a transcriptional sensor for bile acids, the primary products of cholesterol metabolism, and plays an important role in lipid homeostasis. The farnesoid X receptor was, until recently, an orphan receptor, which means that no specific ligands existed for this receptor. Selective ligands for this receptor have been found in natural product libraries described by Nicolaou et al. The group of Nicolaou developed solid phase synthesis methods to make combinatorial libraries based on a benzopyran core structure. " A 10,000-membered combinatorial library based on the benzopyran core structure was synthesized and screened for activity on the farnesoid X receptor. The first specific ligands for the... 

Nicotinic acid disturbs the normal cornification of the skin, occasionally leading to reversible ichthyosis and acanthosis nigricans (SEDA-19, 206). Two mechanisms are advanced to explain this effect insulin resistance induced by nicotinic acid, with compensatory hyperinsu-linemia (which in turn leads to increased insulin binding to insulin-like growth factor receptors and stimulation of keratinocytes), or a disturbance of epidermal lipid homeostasis. 

Klappacher GW, Glass CK. Roles of peroxisome proliferator-activated receptor gamma in lipid homeostasis and inflammatory responses of macrophages. Curr Opin Lipidol 2002 13 305-312. 

Yu,Y. H., and Ginsberg,H.N. 2005. Adipocyte signaling and lipid homeostasis sequelae of insulin-resistant adipose tissue. Circ. Res., 96,1042-1052. 

Figure 9.10. Regulation of target genes by PPAR RXR heterodimers. Fatty acids serve as transcriptional inducers and substrates of enzymes involved in lipid homeostasis. (From Handschin, C., and Meyer, U. A. Induction of drug metabolism The role of nuclear receptors. Pharmacol. Rev. 55 649-673, 2003.)...

Cell Membranes, Dynamics of Lipid Homeostasis, Chemistry of Membrane Trafficking... 

Lipid homeostasis is maintained through the multilayered regulatory networks of lipid metabolism, transport, and signal transduction. These processes are dynamic and respond to nutritional and environmental cues, which includes interplay between fatty... 

FATP5 reveals multiple functions in liver metabolism alterations in hepatic lipid homeostasis. Gastroenterology 2006 130 1245-1258. 

Glucose Homeostasis, Chemistry of Lipid Homeostasis, Chemistry of Metabolic Labelling of Sugars Metabolism, Cellular Organisation Nucleic Acid Metabolism, Chemistry of... 

The nature of the fatty acids in TAGs determines their hydrophobicity/hydrophih-city and diffusional mobility. In an aqueous/hpid environment, such as adipose tissue or lipoproteins in plasma, the relative hydrophihcity of the TAGs determines their partitioning between the interfacial phase and the apolar phase. This may have far stretching consequences. For instance, the rate and selectivity of fatty acid mobilization from fat cells may affect levels and composition of the nonester-ified fatty acids in plasma. These in mrn affect lipid homeostasis. Rate and selectivity of fatty acid mobilization from adipose stores are not related to the positional distribution of fatty acids on the glycerol backbone (75). They are related, however, to triacylglycerol hydrophihcity and thus to TAG structure (76). 

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