The Effects Of High Protein Feeding On The Brain Development Of IUGR Rats

Objectives: To make intrauterine grow retardation(IUGR) rat model by feeding pregnant rats 6% low protein diet. The IUGR rats were fed by 30% high-protein diet and 21% normal-protein diet after birth, to observe the growth rule, brain structure changes, dynamics expression of myelin basic protein (MBP) in brain for two IUGR group rats, and assess their learning and memory ability. To discuss the influence of 30% high-protein postnatal feeding on the brain development of IUGR rats.Methods: Fifteen healthy three-month Sprague-Dawley rats were enrolled in the study. Male and female rats were put into a cage at the proportion of 1:1. The pregnant rats were divided into two groups: the control group and IUGR group. The rats of control group were fed by 21% normal protein diet to the pregnants. The rats of IUGR group were fed by 6% low protein diet to the pregnant rats. During the loctation of 21d, for offspring rats for control group (CC), all the female rats were fed by 21% normal protein diet and running water. The offsprings of IUGR group were randomly divided into 30% high-protein feeding group (SH ) and 21% normal protein feeding group (SC).During the loctation of 21d, the female rats of two groups were separately fed by 30% protein diet and 21% normal protein diet, running water. After 21d, the offspring rats were separated from female, then given 21% normal protein diet to the CC group and SC group, 30% high protein diet to the SH group ,and running water until 32d. We chose 1d, 7d, 15d and 21d as for 4 different time points. There were six rats in every time point. In every time point, we observe the offspring body weight, crown-rump length, brain weight and take brain for study. For the brain samples, hippocampus structure was observed with HE stain method, while dynamics expression of myelin basic protein in corpus callosum, internal capsule and external capsule was observed with immunohistochemistry method. Morris water maze test was performed to assess learning and memory ability during P 26-32.All the date was analyzed using the software SPSS 18.0.Results: 1. The dynamics expression of growth and brain weight for three groups: At 1d, the rats of SH,SC group were thinner and shorter, and their body weight , crown-rump and brain weight was lower than control(sP<0.05); At 7d, body weight , crown-rump and the brain weight of the SH,SC groups were lower than controls(P<0.01);After catch-up growing, at 21d, body weight , crown-rump of the three groups had no differences(P>0.05), but the brain weight of them was still obviously different(P<0.05).2. The changes of HE stain in the hippocampus for three groups: At 1d, the neurons in the hippocampus of IUGR rats arrange raritas and disorder, some neurons were dropsy, chromatospherite pyknosis cell appeared, there were more apoptosis cell and the numbers of neurons decreased compared with normal group. At 7d, 15d, 21d, the dropsy degree of the neurons in SH, SC groups was improved ,but the arrange of neurons was still disorder and there was no obviously increase of the numbers of neurons in the hippocampus. Cell shape of SH group was better than that of SC group. At 32d, the numbers of neurons in the hippocampus for the SH and SC group were still less than that for CC group, but the cell shape of SH group was similar with CC group ,while the shape of cell in SC group was irregular.3. The dynamics expression of MBP in corpus callosum, internal capsule and external capsule for three groups:At 7d, there was no expression of myelin basic protein in these brain area. At 15d,the expression of three brain area was obvious, and higher with the time increasing .At 15d,21d,32d, the expression of myelin basic protein in control group was higher than that in SH and SC groups(P<0.01),and there was no difference between SH group and SC group(P>0.05),whereas the expression of myelin basic protein in the SH group was higher than that in the SC group.4.Morris water test (1)The average latencies of all rats were reduced by degree from D1 to D5.The escape latency was significantly longer in rats of SC group than that of control at D5(P<0.05). The escape latency was significantly shorter in rats of SH group than that of SC group at D5(P<0.05) .However ,there were no significantly difference of SH group and control group (P>0.05).(2) As far as search strategy is concerned ,rats of SC group performed worse than those in SH group and control group at D5,with statistically significant difference.(3)The frequency of passing through the platform quadrant in rats had no significant difference among the three groups (P>0.05).Conclusions: 1.Feeding 6% low protein diet to the pregnant rat was an effective method to make IUGR rat model.2. The IUGR rats induced by feeding 6% low protein diet during the pregnancy, demonstrated reduced the numbers of neurons in the hippocampus and the low brain weight. After birth, by feeding normal protein diet, they could achieve the catch-up growth, but the numbers of neurons in the hippocampus, the brain weight and the expression of MBP failed. Then the ability of learning and memory decreased.3. After birth,30% high-protein diet could also make the IUGR rats achieve catch-up growth as normal protein diet .At the same time, it could improve the neurons shape in the hippocampus, increase brain weight and the expression of MBP, then improve the ability of learning and memory in some extend.