Peanut triacylglycerols activate innate immunity both in insects and mammals

In this study, we investigated immunoreactivity of peanut (Arachis hypogaea) oil using the silkworm (Bombyx mori) model. The peanut oil induced melanin formation when injected to the silkworm hemocoel. We then purified the active substance and identified the triacylglycerols (TAGs) as the responsible molecule for the melanin-forming effect of peanut oil. Also, the peanut TAGs induced the muscle contraction of the silkworm (i.e., cleavage of the insect cytokine BmPP) and the TNF-alpha production by cultured mouse macrophage cells. The muscle contraction activity of the peanut TAGs was reduced by saponification reaction, indicating that the TAG (not the degraded fatty acids) moiety is responsible for the activity. The muscle contraction effects of other TAGs of olive, lard, and beef oil were comparable with that of peanut TAGs. Nevertheless, for the melanin formation, the effect of peanut TAGs was outstanding. The fatty acid composition of peanut TAGs was distinct from that of olive TAGs. These results suggest that TAGs are immunoreactive and induces cytokines both in insect and mammalian immune systems. Also, the differential effects of peanut and olive TAGs for the melanin formation may suggest that TAGs with different fatty acid compositions are distinguished by the immune system.

Automated summary

This study investigated the immunoreactivity of peanut oil using the silkworm model. The results showed that peanut oil induced melanin formation and the triacylglycerols (TAGs) in peanut oil were responsible for this effect. Furthermore, the peanut TAGs caused muscle contraction and TNF-alpha production in the silkworm and mouse macrophage cells, respectively. The muscle contraction activity of peanut TAGs was attributed to the TAG moiety. Additionally, the peanut TAGs exhibited outstanding effects on melanin formation compared to other oils. These findings suggest that TAGs have immunoreactivity and induce cytokine production in insect and mammalian immune systems. Moreover, the different effects of peanut and olive TAGs on melanin formation may be attributed to their distinct fatty acid compositions.