APP17-mer peptide in regulation of neuronal mitochondrial transmembrane potentials and apoptosis in the hippocampus of diabetic rats

Hongxing LI; Rong WANG; Yifeng DU; Zhijuan JI; Shuli SHENG

ABSTRACT

BACKGROUND:

Learning and memory disorder exist in diabetic rats,which can be improved by APP 17-mer peptide. However, it is unclear whether learning and memory disorder in diabetes mellitus is caused by influencing neuronal mitochondrial transmembrane potentials and apoptosis in hippocampus or not and what is the related action mechanism of APP17-mer peptide.

OBJECTIVE:

To observe the effects of APP17-mer peptide on neuronal mitochondrial transmembrane potentials (△ψm) and apoptosis in hippocampal area of diabetic rats.

DESIGN:

A completely randomized, grouping and controlled trial.

SETTING:

Beijing Research Laboratory for Brain Aging, Beijing Xuanwu Hospital, Capital University of Medical Sciences; the Department of Endocrine, the First Central Hospital of Baoding.MATERIALS The data measurement of the experiment was carried out in the Instrument Testing Center, the General Hospital of Chinese PLA between May 2002 and August 2002. The modeling and intervention of the experiment was carried out in the Animal Laboratory of Xuanwu Hospital, Capital University of Medical Sciences. Eighteen male Wistar rats were enrolled and randomized into control group, model group and APP17-mer peptide group with 6 rats in each group.

METHODS:

① Diabetic models in the model and APP17-mer peptide groups were established by intraperitoneal injection of 60 mg/kg streptozotocin (pH=4.4) in fasted rats(fasting for 12 hours). Three days later, modeling was successful if blood sugar level in caudal vein was more than 15 mmol/L. Rats in the control group were not subjected to modeling.Then, the rats in the APP17-mer peptide group were subjected to the subcutaneous injection of APP17-mer peptide (3.4 μg for each rat once) three times a week and totally for ten weeks, whereas rats in the other groups were given saline of the same volume. ② After ten weeks, rats were anesthetized and decapitated to take out brain tissues, and then hippocampal tissues were isolated in ice bath for preparation of single cell suspension.JC-1 labeled mitochondrial transmembrane potentials and cell apoptosis in hippocampal area were measured by means of flow cytometry. ③ One-way analysis of variance was adopted in the comparison among groups.

RESULTS:

Eighteen rats were involved in the results analysis. ①Neuronal mitochondrial transmembrane potential was lower in the model group as compared with the control group [(551.91±53.36) vs (809.88±82.41) △ψm,P＜0.01] while it was higher in the APP17-mer peptide group as compared with the model group [(705.99±89.92) vs (551.91±53.36) △ψm, P ＜ 0.05].There was no difference between the APP17-mer peptide group and control group (P=0.146). ②) Apoptotic percentage of single cell in hippocampus was significantly higher in the model group than in the control and APP17-mer peptide groups [(5.32±1.37)%, (1.03±0.55)%, (2.80±0.92)%, P＜0.01, 0.05].

CONCLUSION:

Neuronal mitochondrial transmembrane potential and cell apoptosis in hippocampus may be involved in the occurrence and development of diabetes mellitus, and APP17-mer peptide plays an improved role in the process.