| Background:N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) were common in mammals. Human can not synthesis Neu5Gc due to the mutation of gene CMAH. Neu5Ac is a crucial nutrient in human milk and the major component for gangliosides in brain, The highest content of sialic acid (SA) was in brain tissue of human, and is also the building block for new born brain.As a function of the nervous system, memory is a mirror of external stimuli by different level of reaction, also reflect nervous impulse by different conduction velocity. Information and impulse transmission only be achieved through the synapse, which is a structural basis in memory formation. Sialic acid has been confirmed to be an nutrient that exist in brain membrane and synapse, to further play an important role in neural system, promoting the differentiation, growth, and generation of nerve cells, also play critical roles in synapse transmission, maintaining the normal function of cells, and thus affect on learning and memory. As a result, it is particularly important for low birth weight infants to get sufficient intake of sialic acids to maintain normal brain function. A study has been taken to compare the difference between breast feeding and formula feeding infants, they found that the content of sialic acid in saliva was higher in breast feeding infants. The role of sialic acid on infants’brain development has got increasing attention these years, but much of them were taken on rodents. The innovation of our study is using piglet, a perfect model for infant, which shows more similarity with human in brain development, to detect the impact of sialic acid intake on learning and cognition, and to speculate the possible molecular mechanisms further to show an insight and scientific basis of the nutritional function of sialic acid.Objective:By measuring the number or intensity of different cell markers for nerve cells in hippocampus of38day piglets, to investigate the influence of sialic acid on nerve cells; By measuring the content of brain-derived neurotrophic factor (BDNF) in hippocampus of38day piglets between control group and treatment group, to detect the impact of sialic acid on BDNF cell signaling pathway.Methods:Twenty-nine male3-day-old piglets were allocated to sialic acid treatment group (n=15) and control group (n=14) feeding with sow milk for35days. The control group has the original sialic acid in milk powder, no extra supplementation, content of sialic acid:Neu5Ac77.7±1.6mg/100g milk powder. For treatment group:Neu5Ac486.8±35.2mg/100g milk powder. On postnatal day39, piglets were euthanized with sodium pentobarbital. Using immunofluorescent assay to detect the impact of sialic acid on neuro cell plasticity, mature cells, glia cells and proliferative cells in dentate gyrus. We also used the enzyme-linked immunosorbent assay (ELISA) to measure the BDNF level in hippocampus.Results:(1) No significant effects was found on piglets’body weight and brain weight gain;(2) There is no significant difference on PolySia-NCAM positive expression cells in dentate gyrus in38day old piglets between control group and treatment group, but an increasing trend in treatment group was observed;(3) Neuron-specific nuclear protein (NeuN) positive expression cells are mostly located in granular cell layer of dentate gyrus, hillus and pyramidal cells of Cornu Ammonis, There is no significant effect of sialic acid on mature neuron cells.(4) Glial fibrillary acidic protein (GFAP) positive cells are mostly located on granular cells of dentate gyrus, and it shows a collaborative trends of PolySia-NCAM and GFAP positive cells, which means in38day piglets, the astrocytes still have the capacity of plasticity. No significant effect was found of GFAP intensity between groups, but there is an increasing trend in treatment group.(5) Ki-67labeling cells mostly exist in the subgranular cell layer, in which place newly generated cells exist lifelong. Our results showed no effect of sialic acid was found on proliferative cell numbers.(6) Using ELISA method detecting the BDNF levels in hippocampus of38day piglets, no significant effect was observed, however, there is a rising trend in treatment group.Conclusions:There is no significant impact of sialic acid supplementation on the number of mature neurons and proliferative cells, but sialic acid may affect the plasticity, and astrocytes of dentate gyrus, increase the expression of BDNF levels, further play its role in learning and memory. |
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