| Objective:To observe the behavior of mice with diabetes mellitus and pathological change and the expression ofγ-secrete enzyme andβ-amyloid protein in hippocampus. By testing insulin-like growth factor-1 and the expression of insulin, insulin receptor, to analyze the relationship between the main molecules of insulin signal pathway andγ-secrete enzyme/β-amyloid protein in hippocampus and explore the pathogenesis mechanism of glucose metabolic dysfunction for Alzheimer's disease.Method:Animal model of diabetes mellitus was established by high fat and suger and streptozocin with lateral cerebral ventricle injection.(the constituents of the fodder: 10% pig oil, 20% sucrose, 2.5%cholesterol, 1%cholate, and 6.5% regulated feeding stuff ) . Wistar rats were randomly divided into control group (N), 4 week diabetes mellitus model group (M4),6 week diabetes mellitus model group (M6) and 8 week diabetes mellitus model group (M8).. Behaviour was tested by Morris water maze task. Congo red detected deposition of beta-amyloid in the brain tissues. Bielschowsky stained silver determined senile plaques and neurofibillary tangles in the brain tissues. Biochemistry method detected blood sugar, cholesterol and , radioimmunoassay detected the viscosity of insulin, immunohistochemistry detected the expression of insulin-like growth factor-1 and insulin receptor in hippocampus, enzyme linked immunosorbent assay to testγ-secrete enzyme andβ-amyloid protein40/42. In addition, image analyzing machine is made use of to test the density value of light.Result1. Models of diabetes and behavioral testCompared with the weight(453.2±15.4)g of the N group,ther is a striking reduce of weight in model groups(P<0.05)with no distinct discrepancies.The density of blood sugar has risen from (5.96±0.49) mmol/dl in N group to (13.32±2.55) mmol/dl(P<0.01) in model groups,the serum hemoglobin from 4.32±0.18% L to 13.11±0.58% L (P<0.01),the serum insulin density from (325.6±19.7) pmol/l to (553.1±18.6) pmol/l (P<0.01)with no differences of weight, blood sugar, serum hemoglobin, and serum insulin density in the groups. The level of blood sugar is abovel 9mmol/dl. The antibody of insulin as well as the rise of level of cholesterol all signify the success of model-building.Morris water maze experiment tested the learning capacity of mice in space discernment:the latency of searching for the platform in diabetes mellitus is obviously longer than that of N group and ther is a striking difference between them±.Space exploring experiment tested special memory of mice: the number of mice in M groups crossing the platform is greatly reduced(p<0.01)with no striking differences within the model groups. All of the results demonstrate that there is a distinct barrier in learning and memorizing as well as an obvious decline in learning memory.2. Histopathological changesSlight deposits of powder-like substances in the brains of mice in N group by Congo red. The organization and cell serum are both dyed red and slight deposit of powder-like substances in brain tissues of mice in M groups. The brain tissues of the sample rats are positive when stained by Congo red. In the brain tissue slice of 3 groups that are dyed red with Congo and have no demonstration of senile plaques scattering among the molecule layers of hippocampus and can't find senile plaques. The mice's response to the Congo red is positive. .No features of pathological changes in Alzheimer's disease are observed.3. Analysis of Aβandγ-secrete enzymeN groups'sβ-amyloid protein andγ-secret enzyme are obviously highly expressed (P<0.01). Within the three model groups there are no notable difference, andβ-amyloid protein is positively correlated toγ-secret enzyme, learning and memory impairment.Obvious increase in the level ofβ-amyloid protein 40 in brain tissues of mice with diabetes mellitus by enzyme linkedimmunosorbent assay is employed to testβ-amyloid protein 40 andβ-amyloid protein 42. Increased from (66.13±6.83 pg/mg of the normal groups to the (88.33±6.73) pg/mg of the model groups (P<0.01). the level ofβ-amyloid protein 42 is also distinctly increased, from (63.46±6.17) pg/mg of the normal groups to (90.44±6.88) pg/mg of the model groups (P<0.01).Obvious increase in the level ofγ-secrete enzyme in the brain tissues of mice with diabetes mellitus. It is increased from (90.54±11.12)pg/mg of B groups to the (134.59±14.12)pg/mg of M groups (P<0.01) by enzyme linked immunosorbent assay,the level ofβ-amyloid protein expression is negatively correlated to learning and memory impairment。1. Test of IGF-1and INR in the signal molecule of insulin signal access INS: The level is increased from 325.6±19.7pmol/lof N group to 553.1±18.6pmol/l by radioimmunoassay (P<0.01) ,No distinct differences of the test results are observed among the behavior of mice of different groups(P>0.05).IGF-1: The OD value is from 0.61±0.11 to 3.52±0.16 by immunohistochemistry (P<0.01).No distinct differences of the test results are observed among the behavior of mice of different groups.INR: The OD value is from 1.56±0.23 to 0.52±0.14 by immunohistochemistry (P<0.01). No distinct differences of the test results are observed among the behavior of mice of different groups.γ-secret enzyme expression is negatively correlated to inslulin growth factor-1(P<0.05).γ-secret enzyme expression is also negatively correlated to insulin receptor(P<0.05);β-amyloid protein 40/42 expression is negatively correlated to inslulin growth factor-1(P<0.05),β-amyloid protein 40/42 expression is negatively correlated to insulin receptor(P<0.05)。Conclusion1. We have success to establish the animal models of diabetes mice by injecting streptozocin into the lateral cerebral ventricle and by high fat and suger.2.β-amyloid protein is one of the factors that cause the outbreak of Alzheimer's disease, and it has negative influence upon the function of mice's cognitive behavior. The viscosity ofβ-amyloid protein blood plasma is positively correlated to the seriousness of Alzheimer's disease.3.INS/INR,IGF-1message access may adjust the expression ofγ-secrete enzyme, influence the metabolism ofβ-amyloid protein, and participate in the outbreak of Alzheimer's disease.4. To prevent and positively treat 2-type diabetes mellitus can reduce the occurrence of Alzheimer's disease. Furthermore, the exploration of INS/INR,IGF-1message access's mechanism that leads to the increase of plasma concentration ofβ-amyloid protein can provide the new theories to the treatment of Alzheimer's disease.
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