An improved molecular test system for the screening of human PPAR transactivation by conjugated linoleic acid isomers and their precursor fatty acids

Abstract

An improved molecular test system for the screening of human PPAR transactivation by conjugated linoleic acid isomers and their precursor fatty acidsTo investigate the potentials of cis-9,trans-11 and trans-10,cis-12 conjugated linoleic acid (9-CLA and 10-CLA, respectively) isomers and their precursors trans-11 vaccenic (VA), linoleic (LA) and oleic (OA) acids for interactions with genes, we determined their binding affinities to the ligand binding domains of the human peroxisome proliferatoractivated receptor (PPAR) a, b and g subtypes by a fluorescent binding assay. Then, we elaborated a transactivation-chemiluminescent assay using HepG2 cells transfected with full-length cDNAs encoding human PPARs and retinoic acid (RA) receptors (RXRs) and with the ideal PPAR response element (iPPRE)-luciferase reporter. Binding affinity of 9-CLA was two times higher (but weaker than of precursor VA and OA) than that of 10-CLA for PPARa, the opposite was observed with PPARb; binding affinities of CLAs and precursor fatty acids with PPARg were comparable. Unlike in binding studies, transactivation potentials of 9-and 10-CLAs were comparable in the human system. Comparing the transactivation potentials of CLAs and their precursors in toto, those obtained for PPARa (two-to fourfold) in both human and murine systems (the latter was used in this study as reference) were comparable, but for PPARb and g, fold inductions obtained in the human system were unique. Inclusion of the coactivator RXR and its natural ligand RA in the system was found unnecessary and would lead to false positive values. Taken together, the human transactivation-based test system -which was found to be superior to the murine system -comprises only iPPRE and human PPARs for rapid screening of potential CLA and other PPAR agonists.

Effects of conjugated linoleic acid on oxidative stress in rats with sucrose-induced non-alcoholic fatty liver disease

“…Therefore, the discovery of nutrients that ameliorate fatty liver is of interest. The term conjugated linoleic acid (CLA) represents a heterogeneous group of positional and geometric isomers of linoleic acid, which are natural and predominantly found in milk, dairy products, meat, and meat products of ruminants (Benjamin, Hanhoff, Bö rchers, & Spener, 2005;Steinhart, Rickert, & Winkler, 2003). Currently well-known as a nutraceutical, CLA has generated wide interest in research pertaining to alleviate major killer diseases such as cancer, atherosclerosis, and diabetes in humans (Milner, 1999;Park & Pariza, 2007).…”

Gene expression after dietary intervention with trans fatty acids (trans‐11/trans‐12 18:1) in humans

“…There is evidence that cis-9,trans-11 CLA and trans-11 18:1 are potent agonists of PPAR subtypes [8]. Despite differences between and within gender subgroups at baseline, probably by random inter-individual differences, there is a notable increase of PPARg and GLUT4 expression during the trans-FA intervention.…”

“…Target genes of PPARa (FA oxidation) and PPARg (storage of FA) are directly implicated in lipogenic pathways such as genes of FA transport protein (FATP), glucose transporter (GLUT1, GLUT4), acyl-CoA oxidase (ACOX1), malic enzyme (ME), and lipoprotein lipase (LPL) [6]. CLA (cis-9,trans-11 CLA and trans-10,cis-12 CLA) as minor dietary FA are ligands and activators of PPAR subtypes [7,8]. Mice fed diets containing CLA showed a regulation of gene expression of lipogenic enzymes (e.g.…”

Bioactive Conjugated Linoleic Acid (CLA) in Milk

“…Bioactive lipid components with health beneficial properties are seen widely in bovine milk lipids (Park, 2009) and ruminant meat products such as beef (Benjamin et al, 2005;Benjamin and Spener, 2009). Among the several milk bioactive lipid components conjugated linoleic acids (CLA) has gained more importance to nutritionists and researchers in recent years due to enhancement of health benefits, which includes anticarcinogenic, antidiabetic and antiatherogenic (Benjamin and Spener, 2009;Carvalho et al, 2010;Reynolds and Roche, 2010).…”