Fish oil fat emulsion alleviates traumatic brain injury in mice by regulation of microglia polarization

Microglia activation, a hallmark of brain neuroinflammation, contributes to the secondary damage following traumatic brain injury (TBI). To explore the potential roles of different fat emulsions-long chain triglyceride (LCT) / medium chain triglyceride (MCT) and fish oil (FO) fat emulsion in neuroprotection and neuroinflammation in TBI, in this study, we first generated the controlled cortical impact (CCI) model of TBI mice. Then either LCT/MCT or FO fat emulsion treated mice were studied by Nissl staining to assess the lesion volume. Sham and TBI mice treated with 0.9% saline were used as controls. The fatty acid composition in different TBI mouse brains was further evaluated by gas chromatography. Immunofluorescent staining and quantitative RT-PCR both demonstrated the suppression of pro-inflammatory microglia and upregulated anti-inflammatory microglia in FO fat emulsion treated TBI brain or primary microglia induced by lipopolysaccharide (LPS) in vitro. Furthermore, motor and cognitive behavioral tests showed FO fat emulsion could partially improve the motor function in TBI mice. Together, our results indicate that FO fat emulsion significantly alleviates the TBI injury and neuroinflammation probably by regulating microglia polarization.