Incorporation profiles of conjugated linoleic acid isomers in cell membranes and their positional distribution in phospholipids

Abstract

Although the conjugated linoleic acids (CLA) have several isomer-specific biological effects including anti-carcinogenic and anti-adipogenic effects, their mechanisms of action remain unclear. To determine their potential effects on membrane structure and function, we studied the incorporation profiles of four CLA isomers (trans-10 cis-12 (A), trans-9 trans-11 (B), cis-9 trans-11 (C), and cis-9 cis-11 (D)) in CHO and HepG2 cells. All four isomers were incorporated into cellular lipids as efficiently as linoleic acid (LA), with the majority of the incorporated CLA present in membrane rafts. Of the four isomers, only CLA-A increased the cholesterol content of the raft fraction. Over 50% of the incorporated CLAs were recovered in phosphatidylcholine of CHO cells, but in HepG2 the neutral lipids contained the majority of CLA. The desaturation index (18:1/18:0 and 16:1/16:0) was reduced by CLA-A, but increased by CLA-B, the effects being apparent mostly in raft lipids. The Δ 9 desaturase activity was inhibited by CLAs A and C. Unlike LA, which was mostly found in the sn-2 position of phospholipids, most CLAs were also incorporated significantly into the sn-1 position in both cell types. These studies show that the incorporation profiles of CLA isomers differ significantly from that of LA, and this could lead to alterations in membrane function, especially in the raft-associated proteins.

Vaccenic and Elaidic Acid Equally Esterify into Triacylglycerols, but Differently into Phospholipids of Fed Rat Liver Cells

“…This hypothesis however was not relevant under our experimental conditions because the D-9 desaturation of trans-11 into CLA has been shown to be very weak in liver and to take place exclusively in peripheral tissues [52]. Further, contrary to what could be expected, cis-9, trans-11-CLA preferentially esterified as trans-11 onto the sn-1 position of PL [53].…”

Effects of supplemental conjugated linoleic acids (CLA) on fresh and post‐thaw sperm quality of Holstein bulls

“…Conjugated linoleic acid (CLA) is the nomenclature used to define a group of isomers of octadecadienoic acid with double-conjugated bonds that are most abundant in positions 9, 10, 11 and 12, and can be naturally found in dairy products and ruminants meat in both cisand trans-configurations (Pariza, 2004;Soares, Brandelli, Celeghini, de Arruda, & Rodriguez, 2013). CLA, some of essential fatty acids (linoleic and linolenic acids), and other PUFAs are incorporated efficiently into plasma membranes (Sampath & Ntambi, 2005;Subbaiah, Gould, Lal, & Aizezi, 2011). The function of PUFAs in the spermatozoa has been mainly attributed to their possible effect on the fluidity of the sperm cell membrane, particularly after stressful processes like freezing and thawing, and the packing of membrane-bound receptors (Adeel et al, 2009).…”

“…Thus, it has been reported that an increase in CLA, especially trans‐10 cis‐12 CLA, on the raft composition seems to decrease DHA presence. Moreover, one of the known effects of CLA in experimental animals and in cultured cells is the inhibition of the expression, as well as the activity, of Δ 9 desaturase, the enzyme that converts the saturated fatty acids (SFA) to monounsaturated fatty acids (Subbaiah et al., ). Also, it has been reported that CLA feeding may be associated with changes in the expression of key genes for fatty acid metabolism (Rossi, Pastorelli, Cannata, & Corino, ).…”

A trans 10-18:1 enriched fraction from beef fed a barley grain-based diet induces lipogenic gene expression and reduces viability of HepG2 cells

“…In contrast to 18:2n-6, which is located predominantly at the sn-2 position of PL, conjugated 18:2 isomers that contain one cis and one trans double bond (e.g. c 9, t 11-18:2 and t 10, c 12-18:2) are known to be selectively incorporated at the sn-1 position, demonstrating the influence of the trans double bond on the positional distribution of its parent molecule [39] . Furthermore, the incorporation of c 9, t 11-18:2 at the sn-1 position of PL is suggested to increase membrane fluidity since they mainly replace SFA (e.g.…”

“…Furthermore, the incorporation of c 9, t 11-18:2 at the sn-1 position of PL is suggested to increase membrane fluidity since they mainly replace SFA (e.g. 16:0 and 18:0) which typically occupy the sn-1 position of PL [39] . Thus, Δ9 desaturation of t 18:1 that can undergo Δ9 desaturation might to some extent alleviate the reduced membrane fluidity caused by their parent molecules.…”