Adipose tissue adaptive response to trans-10, cis-12-conjugated linoleic acid engages alternatively activated M2 macrophages

In mice, nutritional supplementation with the trans-10, cis-12 isomer of linoleic acid (t10, c12-CLA) promotes lipoatrophy, hyperinsulinemia, and macrophage infiltration in white adipose tissue (WAT). We explored the dynamics of these interrelated responses over 2 consecutive 7 d periods of t10, c12-CLA administration and withdrawal. t10, c12-CLA down-regulated lipogenic and lipolytic gene expression and increased collagen deposition, but with no evidence of cross-linking. An abundant CD45(+) cell infiltrate, comprising prominently CD206(+)CD11c(-) macrophages, was found in WAT in association with an anti-inflammatory gene signature. Infiltration of natural killer (NK) and dendritic cells contributed to WAT's innate immune response to t10, c12-CLA. Less abundant adaptive immune cells colonized WAT, including B, NK T, gamma delta T, and alpha beta T cells. By contrast, T-regulatory cell abundance was not affected. Interruption of treatment allowed recovery of WAT mass and normalization of insulinemia, coincident with regain of WAT homeostasis owing to a coordinated reversion of genic, structural, and immune deregulations. These data revealed a striking resilience of WAT after a short-term metabolic injury induced by t10, c12-CLA, which relies on alternatively activated M2 macrophage engagement. In addition, the temporal links between variations in WAT alterations and insulinemia upon t10, c12-CLA manipulation strengthen the view that WAT dysfunctional status is critically involved in altered glucose homeostasis.