【作者】 严翊；

【导师】 谢敏豪；

【作者基本信息】 北京体育大学 ， 运动人体科学， 2006， 博士

【摘要】 纵观运动性血睾酮降低的动物实验报道,在训练的安排中,多未明确训练属于有氧还是无氧;对于造成的运动性血睾酮降低状态,多未指出其属于生理性还是病理性;在Leydig细胞水平的机制研究中,对LH/CG受体、β2-肾上腺素受体、StAR蛋白、胆固醇侧链裂解酶等环节的改变均有报道,而对睾酮生成的初始原料胆固醇代谢变化的研究所见甚少。本研究针对上述问题开展了如下实验:一、确定运动负荷。通过乳酸最小试验,确定4.5%体重的负重是雄性SD大鼠游泳运动时的最大乳酸稳态负荷,对应血乳酸为10.4±2.5mmol/l,提示负重大于4.5%体重的游泳血乳酸将会堆积。二、建立间歇性无氧训练下大鼠血睾酮降低模型。大鼠进行5%负重的间歇游泳训练五周(游泳5分钟-休息1分钟,6组/日,6次/周)。末次训练后第24小时、48小时和1周末,分批宰杀训练大鼠与对照大鼠,检测血睾酮(T)、皮质酮(C)、肌酸激酶(CK)、血尿素(BU),观察心、肝、肾等脏器组织形态学的变化。结果显示:五周训练导致血T显著降低,血CK、BU显著升高,心、肝、肾组织出现病理性变化,睾丸组织未出现病理性变化。一周停训后,血T、CK、BU变化以及心、肝、肾组织的病理性变化均未完全回复。三、运动性血睾酮降低大鼠Leydig细胞胆固醇代谢变化。大鼠训练、宰杀同前,检测血T、总胆固醇(TC)、高密度脂蛋白胆固醇酯(HDL-CE)、低密度脂蛋白胆固醇酯(LDL-CE),血白细胞的低密度脂蛋白受体(LDL-R)和清道夫受体(SR-BI)、Leydig细胞的HMG-CoA还原酶、LDL-R、SR-BI和StAR基因的mRNA表达。结果显示:五周训练后血T显著降低时, Leydig细胞LDL-R mRNA表达显著增加,SR-BI和HMG-CoA还原酶、StARmRNA表达无明显变化。一周停训后,血T回复但仍处于较低水平,血HDL-CE显著升高,Leydig细胞SR-BI mRNA表达量也显著增加,其余指标均无明显变化。四、运动性血睾酮降低发生、发展过程的研究。在运动性血T降低(TA组)的基础上,大鼠停训一周(TC组),大鼠继续训练一周:负荷不变(TD组)、负荷量加倍(5%体重的负重,2组/日,TE组)或强度增加(6%体重的负重,1组/日, TF组),并与同龄血T正常的不训练大鼠(Sc组)或训练一周大鼠(TG组)进行比较。结果显示:TD组,血睾酮进一步降低,Leydig细胞LDL-R mRNA表达出现显著降低;TF组,血T进一步降低,Leydig细胞LDL-R、SR-BI、HMG-CoA还原酶的mRNA表达量出现显著性降低;TE组,血T进一步、显著性降低,Leydig细胞LDL-R、SR-BI、HMG-CoA还原酶以及StAR的mRNA表达量均发生显著性降低。另外,TD、TE、TF组的心、肝、肾和睾丸组织均发生了不同程度的病理性变化。相比之下,TG组只出现了血T降低,影响Leydig细胞胆固醇代谢的关键环节均未出现变化,同时大鼠心、肝、肾、睾丸组织器官均未发生显著的病理性变化。血白细胞的LDL-R mRNA的表达量随运动负荷增加而显著降低, SR-BI mRNA表达量则随运动负荷的增加有升高的趋势。结论:(1)间歇性无氧游泳训练1周能导致大鼠血睾酮降低,但心、肝、肾、睾丸组织的形态学不会发生改变;训练5周引起血T持续降低并伴有心、肝、肾重要脏器的病理性变化,此时睾丸组织未发生病理性变化;训练5周后停训一周、血T恢复过程中,重要脏器病理变化亦有所缓解;对运动性低血T大鼠强化训练,重要脏器病理变化加剧,睾丸的组织形态也发生了病理性变化。显然,伴随有重要脏器的病理性变化的运动性血T降低,应属病理性的变化。(2) 1周间歇性无氧游泳训练,Leydig细胞胆固醇代谢的关键步骤不受影响;5周间歇性游泳训练,Leydig细胞首先通过加强LDL-R介导的内吞作用加强自身摄取胞外胆固醇的能力;停训一周后,SR-BI介导的胆固醇选择性摄取途径加强;对运动性低血T大鼠强化训练,将引起Leydig细胞内胆固醇的合成、摄取与转运等关键步骤的抑制。(3) Leydig细胞内胆固醇代谢关键环节的障碍不一定是导致运动性血睾酮降低的起始原因,但细胞内HMG-CoA还原酶、LDL-R、SR-BI、StAR mRNA表达量的降低会加速运动引起的血睾酮降低。(4)在运动性血睾酮降低发生、发展过程中,LDL-R mRNA在Leydig细胞与白细胞的表达量在变化趋势上有相似之处,能否利用白细胞的LDL-R、SR-BI mRNA表达量间接反映Leydig细胞摄取外源性胆固醇的功能状态,尚有待进一步研究。更多还原

【Abstract】 Making a comprehensive view in experimental reports in rats with lower serum testosterone due to exercise, it was found that there were ambiguous statements on the training character (aerobic or anaerobic). And so was on the state of lower serum testosterone due to exercise (physiological or pathological). In studies of the mechanism of Leydig’s cells there were reports on the changes of such links as the LH/CG receptor,β2-adrenoceptor, StAR protein and cholesterol side change cleavage. As to the study of cholesterol metabolic changes of the incipient substrate for testosterone production there were rare reports. The experiments of this study were carried out in allusion to the above problems.1. Selection of training loads. Through lactate maximum tests, the load of the maximal lactate state during swimming was fixed on a load of 4.5% of the male SD rat’s body weight, corresponding to the blood lactate of 10.4±2.5mmol/L. It is indicated that in swimming if the load is greater than 4.5% of the body weight, blood lactate will be accumulated.2. Establishment of the rat model with lower serum testosterone due to intermittent anaerobic training. The rats were forced to have their intermittent swimming training (exercising 5 minutes with a rest of 1 minute, 6 groups per day and 6 times a week) for 5 weeks with a load equivalent to 5% of their body weight. At the 24th hour (TA group), the 48th hour (TB group) after the last training and at the end of a week (TC group), the training rats and the sedentary rats were killed in batches to examine the changes of serum testosterone (T), corticosterone (C), creatine kinase (CK) and blood urea (BU) and to observe the histomorphologic changes of the heart, liver, and kidney. The results showed that the training of the five weeks induced a remarkable decrease of serum testosterone, but serum CK and BU increased significantly. There were pathological changes in hearts, livers and kidneys the rats, but there was no in testis. After stopping training for one week, the changes of serum T, CK, BU and the histomorphologic changes of hearts, livers and kidneys were not recovered at all.3. Changes of cholesterol metabolism in Leydig’s cells of rats with lower serum testosterone due to exercise. The training mode applied and the methods used to kill the rats were the same as the above mentioned. The serum testosterone (T), total cholesterol (TC), high density lipoprotein- cholesterol (HDL-CE), low density lipoprotein-cholesterol (LDL-CE), the mRNA expression of low density lipoprotein receptor (LDL-R) and scavenger receptor class B type I (SR-BI) in leukocytes of the blood as well as the mRNA expression of3-hydroxyl-3-methylglutaryl-coenzyme A reductase(HMG-CoA reductase), LDL-R, SR-BI and steroidgenic acute regulatory (StAR) protein in Leydig’s cells were examined by the real-time fluorescence quantification PCR with the Taq-man probe technique. The results showed that when serum T decreased significantly due to the five-week training, the LDL-R mRNA in Leydig’s cells increased significantly. After one-week recovery, the concentration of serum T was up, but still under the normal level. The serum HDL-CE increased significantly, and the SR-BI mRNA expression in Leydig’s cells increased as well. But there was no change of the rest indexes.4. Research on the occurrence and development of lower serum T due to exercise. After the five-week intermittent anaerobic swimming training, a group of the rats (TC group) stopped training for one week, while the other groups were forced to continue training. The TD group trained with the same load. The load of the TE group was doubled, that is bearing a weight of 5% of their body weight and the rats trained 2 times per day. The intensity of the TF group was increased and the rats trained once a day with the load of 6% of their body weight. By comparing with the sedentary rats of the same age (Sc group) or those of the rats trained once a day with the load of 5% of their body weight for one week (TG group), it was found that the level of serum T in TD groups had a further decrease, and the mRNA expression of LDL-R、SR-BI、HMG-CoA reductase in Leydig’s cells decreased remarkably. As for the TE group the level of serum T decreased remarkably, too. And so did the LDL-R、SR-BI、HMG-CoA reductase and mRNA expression of StAR in Leydig’s cells. In addition, in TD, TE and TF groups there were pathological changes to different extent in hearts, livers, kidneys and testis of the rats. In the TG group there was decrease only in serum T, but the key links influencing the cholesterol metabolism in Leydig’s cells were not changed. And there were not remarkable pathological changes in hearts, livers, kidneys and testis of the rats. The mRNA expression of LDL-R in leukocytes of the blood decreased with the increase of the training load. But the mRNA expression of SR-BI tended to increase.Conclusion:(1) The one-week intermittent anaerobic swimming training induced lower serum testosterone, but there was no histomorphologic change in the heart, liver, kidney, adrenal gland and testis. The five-week training caused lower serum testosterone, accompanying with pathological changes in the above-mentioned organs except testis. When stopping training for a week after the five-week training, the serum T recovered and pathological changes of the above -mentioned organs were retarded. Pathological changes were aggravated in organs of rats with lower serum testosterone having had their intensive training and so did the morphology of testis. It is obvious that the decrease of serum testosterone due to exercise accompanying with pathological changes in some organs belongs to pathological character. (2) The key processes of cholesterol metabolism in Leydig’s cells were not affected by the one-week intermittent anaerobic training. In 5-week intermittent swimming training the ability of Leydig’s cells to intake their extracellular cholesterol was strengthened firstly by reinforcing the endocytosis mediated by LDL-R. After stopping training for one week the pathway for selective intake of the cholesterol mediated by SR-BI was strengthened. The intensive training in rats with lower serum testosterone due to exercise will inhibit the cholesterol synthesis, intake and transport in Leydig’s cells. (3) The original reason for inducing lower serum testosterone was not always the obstacle of the key links of cholesterol metabolism in Leydig’s cells. Nevertheless, the decrease of mRNA level of HMG-CoA reductase, LDL-R, SR-BI and StAR in Leydig’s cells will accelerate the decrease of serum T due to exercise. (4) In the process of the occurrence and development of lower serum testosterone due to exercise there was similar tendency on the expression of LDL-R in Leydig’s cells and blood leucocytes. But whether the mRNA expressions of LDL-R and SR-BI in blood leucocytes can be used to indirectly reflect the functional state of the intake of exogenous cholesterol in Leydig’s cells remains to be further studied.更多还原