Abstract
Porcine liver decomposition product (PLDP) is a functional food that enhances delayed memory recall and frontal lobe function in humans and exerts antidepressant and anxiolytic effects. In the present study, the previously unexplored anti-inflammatory effects of PLDP were investigated both in vitro and in vivo. The effects of PLDP on interleukin (IL)-1β production were examined in lipopolysaccharide (LPS)-stimulated Raw 264.7 cells and on their transition to an M1 or M2 phenotype. The effects of PLDP administered 30 min before the initiation of a formalin-induced inflammation-related behavior were also evaluated. Furthermore, the effects of PLDP on LPS-induced inflammation related to cytokine production and behavior in vivo were examined. PLDP was orally administered for five consecutive days and 24 h after LPS administration the mice were evaluated in an open field test and plasma cytokine production was measured. PLDP and its lipid fraction, PLDP extracted lipids (PEL) suppressed LPS-induced IL-1β production. Flow cytometry revealed that PEL shifted Raw 264.7 cells to the M2 phenotype. Moreover, PEL reduced phase 2 inflammation-related behavior in formalin-induced inflammation. In the LPS-induced inflammation model, PLDP improved the LPS-attenuated locomotor activity and exploratory behavior and reduced the increased plasma interferon-γ levels. These results suggest that PLDP exerts anti-inflammatory effects and shifts macrophages to the M2 phenotype. Furthermore, our results indicate that the lipid components in PLDP, especially phospholipids, could exert considerable central neuroprotective effects.