trans-10,cis-12-Conjugated Linoleic Acid Instigates Inflammation in Human Adipocytes Compared with Preadipocytes

Abstract

We showed previously in cultures of primary human adipocytes and preadipocytes that lipopolysaccharide and trans-10,cis-12-conjugated linoleic acid (10,12-CLA) activate the inflammatory signaling that promotes insulin resistance. Because our published data demonstrated that preadipocytes are the primary instigators of inflammatory signaling in lipopolysaccharide-treated cultures, we hypothesized that they played the same role in 10,12-CLA-mediated inflammation. To test this hypothesis, we employed four distinct models. In model 1, a differentiation model, CLA activation of MAPK and induction of interleukin-8 (IL-8), IL-6, IL-1␤, and cyclo-oxygenase-2 (COX-2) were greatest in differentiated compared with undifferentiated cultures. In model 2, a cell separation model, the mRNA levels of these inflammatory proteins were increased by 10,12-CLA compared with bovine serum albumin vehicle in the adipocyte fraction and the preadipocyte fraction. In model 3, a co-culture insert model, inserts containing ϳ50% adipocytes (AD50) or ϳ100% preadipocytes (AD0) were suspended over wells containing AD50 or AD0 cultures. 10,12-CLA-induced IL-8, IL-6, IL-1␤, and COX-2 mRNA levels were highest in AD50 cultures when co-cultured with AD0 inserts. In model 4, a conditioned medium (CM) model, CM collected from CLAtreated AD50 but not AD0 cultures induced IL-8 and IL-6 mRNA levels and activated phosphorylation of MAPK in naive AD0 and AD50 cultures. Consistent with these data, 10,12-CLA-mediated secretions of IL-8 and IL-6 from AD50 cultures were higher than from AD0 cultures. Notably, blocking adipocytokine secretion prevented the inflammatory capacity of CM from 10,12-CLA-treated cultures. These data suggest that CLA instigates the release of inflammatory signals from adipocytes that subsequently activate adjacent preadipocytes.

Efficacy of Gamma-glutamylcysteine (GGC) in Ischemia-reperfusion Injury

“…In fact, CLA has been reported to down-regulate NF-jB p50/p65 activation and the expression of its target gene COX-2 as a ROS generator (Iwakiri et al, 2002;Cheng et al, 2004;Ringseis et al, 2006;Park et al, 2010). Although other investigators have reported that the trans-10, cis-12 CLA isomer induces prooxidative and inflammatory effects through NF-jB p50/p65 activation (Kennedy et al, 2009;Martinez et al, 2010), this does not appear to be a factor at the 50 lmol/L dose used under the conditions of the current study. In contrast, our data at the 10 lmol/L dose of CLA with GGC is consistent with previous reports of prooxidant effects of CLA as mentioned above.…”

“…The objectives of this study were to investigate a synergistic antioxidant role of CLA as an adjuvant and the effects of mixtures of compounds/co-administration seeking an optimal concentration range for beneficial effects by comparing co-administration of GGC and CLA to treatment with GGC alone on oxidative stress and GSH synthesis in human endothelial cells. Since CLA-induced adverse effects, such as increases in insulin resistance and inflammation, have been observed mainly by use of single purified CLA isomer (in particular the trans-10, cis-12-CLA isomer, but not the cis-9, trans-11-CLA isomer) (Halade et al, 2010;Kennedy et al, 2010;Martinez et al, 2010), a mixture of CLA isomers was chosen in this study. We assessed changes in levels of 8-epi-PGF 2a , thiobarbituric acid reactive substances (TBARS), GSH, total antioxidants, GSS expression, and PPARc and NF-jB DNA binding in human umbilical vein endothelial cells (HUVEC) treated with GGC alone (100 lmol/L: constant) or GGC together with CLA (the cis-9, trans-11 and trans-10, cis-12 CLA isomer mixture; 50% each) at graded concentrations.…”

Relationships between adiponectin levels, the metabolic syndrome, and type 2 diabetes: a literature review

“…CLA can cause resistance to insulin action by reducing plasma levels of adiponectin (80). The mRNA levels of adiponectin were reduced after CLA supplementation in rats (81) and in cultured human adipocyte cells (82).…”

Conjugated linoleic acid reduces adiposity and increases markers of browning and inflammation in white adipose tissue of mice

“…This would have important medical implications, because an increased brown fat-like signature is associated with lower risk of developing obesity in mice ( 11 ) and humans ( 12 ). We have shown that 10,12 CLA increases cyclooxygenase (COX)-2 expression and prostaglandin (PG) production in human adipocytes ( 13 ), which have been associated with induction of brown fat-like adipocytes in WAT ( 14,15 ), suggesting a link between infl ammation and browning. Consistent with this hypothesis, relatively high levels of an equal mixture of 10,12 and 9,11 CLA [1.5% ( 16 )] or 10,12 CLA alone [0.5% ( 17 ); 1% ( 18 )] increase markers of brown fat-like adipocytes, including uncoupling protein 1 (UCP1) in WAT in mice.…”

“…The samples were homogenized on ice and centrifuged at 15,000 g for 15 min at 4°C; then the protein concentration was determined in the supernatant using the bicinchoninic acid assay. Equal amounts of protein were separated using 4-12% NuPage mini precast gels (Invitrogen Inc.), and transferred to PVDF membranes (Bio-Rad Inc.) as previously described ( 13 ). Membranes were then blocked with 5% milk in TBST for 30 min and washed with TBST 5 min three times.…”