Dietary long-chain n-3 PUFAs mitigate CD4+ T cell/adipocyte inflammatory interactions in co-culture models of obese adipose tissue

Abstract

Obese adipose tissue (AT) inflammation is partly driven by accumulation of CD4⁺ T helper (Th)1 cells and reduced Th2 and T regulatory subsets, which promotes macrophage chemotaxis and ensuing AT metabolic dysfunction. This study investigated CD4⁺ T cell/adipocyte cytokine-mediated paracrine interactions (cross talk) as a target for dietary intervention to mitigate obese AT inflammation. Using an in vitro co-culture model designed to recapitulate CD4⁺ T cell accumulation in obese AT (5% of stromal vascular cellular fraction), 3T3-L1 adipocytes were co-cultured with purified splenic CD4⁺ T cells from C57Bl/6 mice consuming one of two isocaloric diets containing either 10% w/w safflower oil (control, CON) or 7% w/w safflower oil+3% w/w fish oil (FO) for 4 weeks (n=8-11/diet). The FO diet provided 1.9% kcal from the long-chain (LC) n-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid and docosahexaenoic acid, a dose that can be achieved by supplementation. Co-cultures were stimulated for 48 h with lipopolysaccharide (LPS) to mimic in vivo obese endotoxin levels or with conditioned media collected from LPS-stimulated visceral AT isolated from CON-fed mice. In both stimulation conditions, FO reduced mRNA expression and/or secreted protein levels of Th1 markers (T-bet, IFN-γ) and increased Th2 markers (GATA3, IL-4), concomitant with reduced inflammatory cytokines (IL-1β, IL-6, IL-12p70, TNF-α), macrophage chemokines (MCP-1, MCP-3, MIP-1α, MIP-2) and levels of activated central regulators of inflammatory signaling (NF-κB, STAT-1, STAT-3) (P<.05). Therefore, CD4⁺ T cell/adipocyte cross talk represents a potential target for LC n-3 PUFAs to mitigate obese AT inflammation.

Keywords: Adipocytes; CD4(+) T cells; Inflammation; N-3 polyunsaturated fatty acids; Obesity.