Oxidized lipids, dietary, role

Koch et al. (2007a) found that the dietary oxidized lipids cause upregulation of the insulin-induced gene (Insig)-l in the liver in a PPARa-dependent manner. Insigs are membrane proteins that reside in the endoplasmic reticulum and play a central role in the regulation of SREBP activation, because they prevent the translocation of inactive SREBPs from the endoplasmic reticulum to the Golgi, where proteolytic activation of SREBPs and subsequent release of transcriptionally active forms of SREBPs occur (Yabe et al. 2002). As a result, the synthesis of cholesterol declines in response to PPARa activation. 

Witztum, 1994). Dietary antioxidants, such as lycopene, can protect lipids, proteins, and DNA from oxidation and play a role in the prevention of such diseases. 

First, several reports over the last 25 yr show that carbon recycling from a-linolenate in neonatal rats and near-term primate fetuses consumes the majority of a-linolenate that is not used as a fuel. Second, a-linolenate cannot be synthesized de novo by mammals and is the main dietary precursor to the n-3 long-chain polyunsaturated fatty acids (LC-PUFAs), eicosapentaenoate (20 5n-3) and docosahexaenoate (22 6n-3), which have important regulatory and membrane functions, respectively. Thus, a-linolenate is a vitamin-like nutrient that would not be expected to be easily p-oxidized or extensively carbon recycled into other lipids when it already has an important precursor role for membrane components needed for normal development of the visual and nervous systems. 

Bartsch, H., Nair, J., and Owen, R.W., Exocyclic DNA adducts as oxidative stress markers in colon carcinogenesis potential role of lipid peroxidation, dietary fat and antioxidants, Biol Chem., 383,915-921,2002. 

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