Fig 2: Role of PDK4 in syncytiotrophoblast functions. (A) and (B) The abundance of 11ß-HSD2 mRNA (n = 4, A) and protein (n = 3, B) and ß-hCG mRNA (n = 4, A) was significantly increased by siRNA-mediated knock-down of PDK4 expression. Randomly scrambled siRNA served as negative control (Nc). (C) and (D) Over-expression of PDK4 significantly decreased the abundance of 11ß-HSD2 mRNA (n = 4, C) and protein (n = 3, D) and ß-hCG mRNA (n = 4, C). *P < 0.05; **P < 0.01; ***P < 0.001 against Nc (A and B) or Vehicle (C and D).

Fig 3: The effects of dichloroacetate (DCA) on the PDK2/4-PDHE1a axis and expression of genes related to glucose metabolism in Nile tilapia. (A) The mRNA expression of glucose transport-related genes in the liver (glut2 = glucose transporter 2; glut4 = glucose transporter 4) (n = 9); (B) the mRNA expression of glycolysis-related genes in the liver (gk = glucokinase; pfk = phosphofructokinase; pk = pyruvate kinase) (n = 9); (C) the mRNA expression of gluconeogenesis-related genes in the liver (pepck = phosphoenolpyruvate carboxykinase; g6pase = glucose-6-phosphatase; fbpase = fructose-1,6-bisphosphatase) (n = 9); (D) the mRNA expression of tricarboxylic acids (TCA) cycle-related genes in the liver (idh = isocitrate dehydrogenase; cs = citrate synthase) (n = 9); (E) the mRNA expression of oxidative phosphorylation-related genes in the liver (mtco1 = mitochondrial cytochrome c oxidase 1; sdha = succinate dehydrogenase complex subunit A; ndufa9 = NADH dehydrogenase [ubiquinone] 1a subcomplex subunit 9) (n = 9); (F-G) mRNA and protein expression patterns of pdk1, pdk2, pdk3 and pdk4 in different tissues (pdk1/2/3/4 = pyruvate dehydrogenase kinase 1/2/3/4) (n = 6); (H–I) the protein concentrations of Pdk2, Pdk4, Pdhe1a and p-Pdhe1a in the liver (Pdk2 = pyruvate dehydrogenase kinase 2; Pdk4 = pyruvate dehydrogenase kinase 4; Pdhe1a = pyruvate dehydrogenase E1a subunit) (n = 9); and (J) the mRNA expression of pdk2, pdk4 and pdhe1a genes in the liver (pdhe1a = pyruvate dehydrogenase E1a subunit) (n = 9). Values are means ± SEM. Statistical differences in mean values were evaluated by using either one-way analysis of variance (ANOVA) followed by Tukey test (G), or the independent t-test (others except for G). a, b, c Different letters indicate a significant difference (P < 0.05). * P < 0.05, ** P < 0.01.

Fig 4: Diagram illustrating the switch from glycolysis to OXPHOS via down-regulation of PDK4 expression upon activation of the cAMP pathway by hCG during syncytialization of the trophoblasts.

Fig 5: Role of activation of the cAMP/PKA signaling pathway by hCG in the regulation of PDK4 expression in human placental trophoblasts. (A) and (B) Treatment of trophoblasts with dibutyryl-cAMP (db-cAMP, 200 µM) for 24 hours significantly decreased the amounts of PDK4 mRNA (n = 6, A) and protein (n = 3, B). (C) and (D) Treatment of trophoblasts with ß-hCG antibody (hCGab, 1:100) or PKA inhibitor H89 (20 µM) for 24 hours significantly increased the abundance of PDK4 mRNA (n = 4, C) and protein (n = 3, D). *P < 0.05; **P < 0.01 against Ctr.