PPARD and escherichia coli infection: Moreover, we knocked down the expression of PPARβ/δ or PPARγ in hBMECs using Small interfering RNA (siRNA) (Figure 2E,H) and found that either the PPARβ/δ knockdown or the PPARγ knockdown significantly reduced the ANGPTL4 expression in hBMECs (Figure 2F,I), which largely supported the notion that meningitic E. coli infection induced the upregulation of ANGPTL4 through the PPARβ/δ- and PPARγ-mediated signaling.