Maternal zinc metabolism and changes of metallothionein-1 and zinc transporter-1 in fetal congenital heart diseases

Abstract

Objective To investigate maternal zinc metabolism and the changes of zinc-related factors as metallothionein-1(MT1) and zinc transporter-1(ZnT1) in certain types of congenital heart diseases (CHD). Methods Fifteen infants with interventricular septal defect, 12 infants with atrial septal defect and 7 infants with tetralogy of Fallot, together with their mothers were enrolled, and normal infants and their mothers were enrolled by a ratio of 1∶1 with the above three types of CHD diseases. General conditions of the mothers, along with their diets and zinc-containing drug supplementation during the pregnancy, were surveyed. Maternal blood zinc levels and serum alkaline phosphatase activities at gestation week 32 and delivery or induced abortion, and the protein and mRNA expressions of MT1 and ZnT1 in maternal serum and placental tissue at delivery or induced abortion were assayed. Results The general conditions were comparable between the CHD group and control group. The ratio of the mothers taking more zinc-rich food was significantly lower in the CHD group than in the control group. Circulating zinc levels in interventricular septal defect (73.55±5.79 μmol/L), atrial septal defect (72.66±5.82 μmol/L) and tetralogy of Fallot (68.72±6.72 μmol/L) groups were significantly lower than those in the control groups (82.77±7.88, 84.58±7.55 and 85.66±7.30 μmol/L) at delivery (P all <0.05). Similar change patterns were seen for serum alkaline phosphatase activities. The relative quantities of serum MT1 and ZnT1 proteins in interventricular septal defect (73.22±36.54 and 68.55±27.82), atrial septal defect (64.29±38.26 and 74.55±29.67) and tetralogy of Fallot (67.88±30.50 and 70.13±29.65) groups were significantly lower than those in their corresponding control groups (166.31±67.43 and 97.67±30.22, 182.56±71.40 and 111.65±32.70, and 173.81±62.36 and 108.27±28.52, P<0.01 or P<0.05). The relative quantities of placental MT1 and ZnT1 proteins and mRNA expressions in interventricular septal defect (protein quantities 0.438±0.096 and 0.384±0.061, mRNA expressions 1.23±0.82 and 0.96±0.39), atrial septal defect (0.427±0.093 and 0.377±0.059, 1.17±0.70 and 0.85±0.40) and tetralogy of Fallot (0.414±0.111 and 0.336±0.066, 1.31±0.97 and 0.90±0.38) groups were significantly lower than those in their corresponding control groups (protein quantities 0.565±0.083 and 0.541±0.090, mRNA expressions 2.78±1.06 and 1.67±0.33; protein quantities 0.622±0.136 and 0.493±0.079, mRNA expressions 2.85±0.89 and 1.72±0.38; protein quantities 0.637±0.125 and 0.521±0.089, mRNA expressions 3.21±0.99 and 1.61±0.29; P<0.01 or P<0.05). Conclusion Mothers with their fetus of certain types of CHD are found zinc deficiency, and down-regulation of MT1 and ZnT1 expressions in the serum and placenta may involve in the pathogenesis of CHD when maternal zinc deficiency. Key words: Zinc deficiency; Congenital heart disease; Pregnancy; Metallothionein-1; Zinc transporter-1