Decreasing Hippocampal Apoptosis and Improvement of Spatial Memory After High-Intensity Interval Training in Male Adult Diabetic Rats

to this aim, 48 eight-week-old male Wistar rats with 150 ± 10 g weight were categorized in 4 groups: control (n=12), diabetic (n = 12), exercise diabetic (n=12), exercise (n = 12). Peritoneal injection of STZ so-lution (50 mg / kg) was used to induce diabetes. After familiarization with the environment and training for a week, HIIT protocol was performed 3 times/week for 6-weeks, with 50-110% vo2max intensity. MWM protocols were applied to assess spatial memory and learning. Finally, BDNF, FOXO-1, CASPASE-3 gene expression was evaluated by using Real Time PCR technique. . High intensity interval training The HIIT started after the animals were acclimatized and familiarized with the exercise training with the intensity of 30-50% of VO2max (According to Høydala, 2007 article) within a three-day period. The repetitions during the three sessions were ranged from 6 to 8 repetitions in one minute with 2-min rest between the sets. As shown in figure, the main HIIT protocol was progressive during six weeks (3 sessions a week) (50-110% VO2max) (53). The HIIT started with a 5-min warm-up (45- 50% VO2max). The rats performed 10 repetitions of a 1-min run. However, the speed and degree of incline varied from week to another week, and 2- min inactive rest time be-tween the sets. Time-to-exhaustion The time-to-exhaustion test was performed on two groups (HIIT & DIIT) to com-pare pre- and post-training results. The rats run on the treadmill as the speed gradual-ly increased to evaluate time, distance and speed with respect to their performance. To start, the treadmill was set at the speed of 10m/min with a fixed incline of zero and the speed increased by 2m/min for every 2 min until the rats were exhausted or the maxi-mum speed was achieved. The result of the post-test indicated that the rats improved their performance. Morris water maze is a circular pool (150 cm diameter, 60 cm height) which was divided into four quadrants and was filled with water (20±1 °C, 55±5% humidity), es-cape platform, and camera which was suspended above the maze and recorded escape latency, distance to reach the platform, and the percentage of time which rat spent in target. Then, the surface of escape platform was covered in a fixed position of 1 cm under the water. The MWM was in the laboratory surrounded by various signs. Each rat was given 8trials per day for 3 consecutive days. Each release point was randomly changed for every trial. To be accustomed to the maze, the mice were placed in water without platform for three minutes to swim three hours before training. Each trial lasted until the rat discovered the hidden platform or for a maximum duration of 60 seconds and then it was to rest on it for 30 seconds. if rat which failed to find the plat-form, it was placed on the platform by the experimenter. To assess memory retention, a spatial probe test was performed in 4th day, and the platform was removed from the maze. Each rat spent 60 seconds searching for the water maze.为实现本研究目标，本实验选取48只8周龄、体重为150±10g的雄性Wistar大鼠，随机分为4组：对照组（n=12）、糖尿病组（n=12）、运动干预糖尿病组（n=12）及单纯运动组（n=12）。采用腹腔注射链脲佐菌素（Streptozocin, STZ）溶液（剂量为50mg/kg）的方式构建糖尿病模型。在完成环境适应与一周适应性训练后，所有大鼠每周进行3次高强度间歇训练（High-intensity Interval Training, HIIT），持续6周，训练强度为50%~110%最大摄氧量（VO2max）。采用莫里斯水迷宫（Morris Water Maze, MWM）实验方案评估大鼠的空间学习与记忆能力。最终采用实时荧光定量聚合酶链式反应（Real Time PCR）检测各组大鼠脑源性神经营养因子（Brain-derived neurotrophic factor, BDNF）、叉头框转录因子O1（Forkhead box O1, FOXO-1）及半胱天冬酶-3（CASPASE-3）的基因表达水平。 一、高强度间歇训练方案 本次HIIT方案的适配阶段为3天，期间让大鼠适应运动训练，训练强度设定为30%~50% VO2max（参考Høydala等人2007年的研究文献）。适配阶段的每次训练包含6~8组1分钟运动单元，组间休息2分钟。如附图所示，正式HIIT方案在6周内逐步递进（每周3次训练），强度区间为50%~110% VO2max（参考文献53）。正式训练前先进行5分钟热身，热身强度为45%~50% VO2max；大鼠需完成10组1分钟跑台运动，组间休息2分钟。各周的跑速与坡度均有所调整。 二、力竭运动测试 本研究选取HIIT组与DIIT组进行力竭运动测试，以对比训练前后的运动表现。测试时大鼠在跑台运动，跑速逐步提升，以此记录大鼠的运动时长、运动距离与运动速度，评估其运动能力。测试初始阶段，跑台速度设为10m/min，坡度固定为0；之后每2分钟跑速提升2m/min，直至大鼠力竭或达到预设最大速度。后续测试结果显示，大鼠的运动能力得到显著提升。 三、莫里斯水迷宫实验 莫里斯水迷宫为直径150cm、高60cm的圆形水池，被均分为四个象限，池内水温控制为20±1℃，环境湿度为55±5%。实验包含逃生平台与悬挂于迷宫上方的摄像系统，用于记录大鼠的逃生潜伏期、抵达平台的运动距离及在目标象限的停留时间占比。逃生平台固定于某一象限的水下1cm处，平台表面被水覆盖。整个水迷宫实验置于带有多种视觉线索的实验室中。 训练阶段：每只大鼠每日进行8次训练，连续训练3天，每次训练的释放点随机调整。正式训练前3小时，需将大鼠置于无逃生平台的水池中游泳3分钟，以适应迷宫环境。每次训练时长上限为60秒，若大鼠成功发现逃生平台，则允许其在平台上停留30秒；若大鼠未在60秒内找到平台，则由实验人员将其放置于平台上，同样停留30秒。 记忆保留评估：于第4天进行空间探索测试，此时移除逃生平台，每只大鼠在水池中游泳60秒以评估其空间记忆保留能力。