The Effect Of Hypothyroxinemia Induced By Maternal Iron Deficiency During Pregnancy On Learning Memory And Behavior Of Adult Offspring In Rats

ObjectiveTo investigate the effect of maternal hypothyroxinemia induced by iron deficiency without anemia in pregnancy on the learning memory and behavior of adult offspring rats.In the present study,the rat model of maternal hypothyroxinemia induced by iron deficiency without anemia during pregnancy was established.MethodsNinety Sprague-Dawley female rats,weighing about 200 g,were divided into iron deficiency group(ID group)and control normal group(CN group)randomly.45 Sprague-Dawley male rats,weighing about 220 g,the mating rate of male and female is 2:1.The diet was produced according to the AIN-93 G standard,replacing the ferric citrate with ferrous sulfate heptahydrate,and the iron content was 30 ppm and 70 ppm respectively.Adaptive feed for a week later,all rats were fed defferent iron concentration diets(30 ppm and 70ppm)according to different groups until postnatal day 1(PND1),then all rats were fed diets with normal iron concentration diet(60ppm).Different iron concentration diet feeding for two weeks later,they mated.All litters wereculled to 10 pups per litter by PND2.The maternal weight was measured per five days during pregnancy.Maternal rats were killed after abdominal anesthesia to measure hemoglobin,liver iron,serum ferritin,serum total triiodothyronine(TT3),serum total thyroxine(TT4),serum thyroid stimulating hormone(TSH)at gestational day 0(GD0),gestational day 13(GD13),postnatal day 1(PND1).Normal growth conditions,open eyes time,fur development,ear development and activity of offsprings should be observed.Weight,hemoglobin,liver iron,serum ferritin,serum TT3,serum TT4,serum TSH,iron concentration in cerebral cortex and hippocampus,iron response gene expression and thyroid hormone response gene expression in cerebral cortex and hippocampus,Long-term potentiation test(LTP),Morris water maze,Elevated plus maze,Elevated zero maze,Three chamber test were measured in offsprings.SPSS 21.0 statistical software was used to analyze data.The measurement data was expressed as mean±SEM(x±s),After normal testing,the data is in a normal distribution,and the comparison between the two sets of data is conducted by two independent sample t tests.Data that do not conform to normal distribution are tested by Mann Whitney U.P < 0.05 was considered statistically significant.Results1.General growth and development:There were no fur removal,irritability and abnormal day and night activity in the two groups.There were no differences between the two groups of offsprings in the development of body weight,open eye time,fur and ear development,day and night activity,etc.2.The hemoglobin of the maternal rats in the ID group did not decrease during pregnancy,the concentration of liver iron and serum ferritin did not decrease at GD0,while decreased in GD13 and continued to PND1.Serum TT3 and TSH of maternal rats in the ID group did not decrease during gestation,serum TT4 did not decrease in GD0,while decreased in GD13 andcontinued to PND1.3.At PND1,the liver iron of the offsprings in ID group was decreased,and the content of hemoglobin and iron in cerebral cortex and hippocampus were not decreased,and serum TT4 level decreased.4.At PND1,there was no significant difference in the expression of iron reaction gene(Dmt1)in the hippocampus and cortex of the two groups(P>0.05).The expression of thyroid hormone response gene(Rc3,Reelin)in the hippocampus and cortex was significantly lower than that in the CN group,and the difference was statistically significant(P<0.05).5.At PND40,the percentage of f EPSP slope in group D was significantly lower than that of CN group at LTP test,and the difference was statistically significant(P<0.05).6.At Morris water maze,there was no significant difference between the two groups at PND41 and PND42.The escape latency of ID group was significantly longer than that of CN group,and the difference was statistically significant(P < 0.05)at PND43 and PND44.In the probe test,the target quadrant swimming time and wearing ring number of the ID group were lower than CN group,and the difference was statistically significant(P<0.05).7.At Elevated plus maze,there was no significant difference in the number of open arms of the ID group and CN group,the percentage of open arms and the total number of entering arms.The percentage of open arm time and open arm of ID group was significantly lower than that of CN group,and the difference was statistically significant(P<0.05).8.At Elevated zero maze,the percentage of open arm time and open arm of ID group was significantly lower than that of CN group,and the difference was statistically significant(P<0.05).9.At Three chamber test,in the stage of social approsch,the CN group was longer in chamber 1 for longer than chamber 3,and the difference was statistically significant(P < 0.05).In the ID group there was no statistically significant difference between the tie spent in chamber 1 of the ID group andthe time spent in chamber 3.In the stage of Social novelty,the CN group spent longer in chamber 3 than chamber 1,and the difference was statistically significant(P < 0.05).In the ID group there was no statistically significant difference between the time spent in chamber 1 and the time spent in chamber3.Conclusions1.Iron deficiency without anemia can lead to Maternal hypothyroxinemia.2.Maternal hypothyroxinemia due to iron deficiency without anemia during pregnancy can damage the fetal brain development.3.The damage caused by Maternal hypothyroxinemia due to iron deficiency without anemia during pregnancy will continue into adulthood of offsprings.Adulthood of offsprings have poor learning and memory ability,anxiety behavior tendency and declined social skills.