DEHP低剂量慢性暴露对雌性大鼠糖代谢的影响
Effects of chronic exposure to low-dose DEHP on glucose metabolism in female rats
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摘要:
目的 观察邻苯二甲酸二（2-乙基己基）酯（DEHP）低剂量慢性暴露对雌性大鼠糖代谢的影响。
方法 将24只SPF级雌性SD大鼠随机分为4组，分别为0、3、30、300 mg/kg（以体重计，后同）DEHP染毒组，每组6只，采用喂饲的方式连续染毒46周，定期测量大鼠空腹血糖，并记录体重变化。于末次染毒24 h后，称量大鼠体重，分别进行口服葡萄糖耐量试验（OGTT）、胰岛素耐量实验（ITT），计算曲线下面积（AUC）；随后水合氯醛麻醉，心尖取血处死，取肝脏、胰腺、生殖器周围白色脂肪、腓肠肌称重，并保存于10%（体积分数）中性福尔马林中固定，用于组织病理形态观察（腓肠肌除外）。
结果 DEHP染毒期间，各组大鼠均未出现明显毒作用表现。与0 mg/kg组比较：① 各实验组大鼠体重差异均无统计学意义（P > 0.05）。② 300 mg/kg组大鼠肝脏脏器系数升高（P<0.05），其余剂量组均无统计学差异（P > 0.05）；各实验组胰腺、生殖器周围白色脂肪、腓肠肌脏器系数差异均无统计学意义（P > 0.05）。③ DEHP暴露18周后，300 mg/kg大鼠空腹血糖升高（P<0.05），其他时点各组差异均无统计学意义（P > 0.05）；各组HOMA-IR、ISI、血清胰岛素水平差异均无统计学意义（P > 0.05）。④ OGTT结果显示，雌性大鼠300 mg/kg组服糖后血糖浓度峰值出现早15 min出现峰值（P=0.004），而服糖后60、120 min时血糖浓度明显下降（P=0.038，P=0.039），且服糖后120 min血糖浓度低于空腹水平，血糖AUC降低（P=0.040）；ITT实验结果显示，30 mg/kg组血糖值在15 min时明显低于0 mg/kg组（P=0.029），300 mg/kg组血糖值下降较为明显，在60、120 min时血糖值下降超过空腹血糖的50%（P=0.017，P=0.038），且恢复至空腹血糖值缓慢，300 mg/kg组血糖AUC降低（P=0.028）。肝脏病理形态结果显示：各DEHP染毒组大鼠肝细胞出现不同程度增大、水肿，间质疏松，可见不同程度胆管周围炎。胰腺病理形态结果显示：各DEHP染毒组大鼠胰岛面积减小、细胞数量减少。生殖器周围白色脂肪病理形态结果显示各DEHP染毒组大鼠脂肪细胞不同程度缩小、大小不一，细胞排列不整齐。
结论 DEHP低剂量慢性暴露可能导致雌性大鼠发生胰岛素抵抗。
Abstract:Objective To observe the effects of chronic exposure to low-dose di (2-ethylhexyl) phthalate (DEHP) on glucose metabolism in female rats.
Methods Twenty-four female SPF SD rats were randomly divided into four groups0, 3, 30, and 300 mg/kg (in terms of body weight) DEHP groups, respectively, with six rats in each group, and exposed to DEHP by gavage for continuous 46 weeks. Fasting blood glucose of rats and body weight change were measured regularly. Twenty-four hours after the last exposure, rats' body weight was measured, and oral glucose tolerance test (OGTT) was conducted to estimate area under curve (AUC) of blood glucose over time. Insulin tolerance test (ITT) was also carried out. Then the rats were given chloral hydrate anesthesia and sacrificed to collect samples of heart apex, weigh liver, pancreas, gastrocnemius muscle, and white fat around genital organs, and to observe histopathological changes of the tissues after fixed in 10% neutral formalin (except muscle sample).
Results During the DEHP exposure, no obvious toxic effect was observed in any groups. Compared with the 0 mg/kg group, there was no significant difference in the body weight of the experimental groups (P > 0.05). The liver organ coefficients of the 300 mg/kg group was elevated (P < 0.05) and the other experimental groups showed no differences (P > 0.05) compared with the 0 mg/kg group. There were no significant differences in the organ coefficients of pancreas, white fat around genital, and gastrocnemius muscle among the experimental groups (P > 0.05). Compared with the 0 mg/kg group, elevated fasting blood glucose was observed in the 300 mg/kg group treated with DEHP for 18 weeks (P < 0.05), while there was no significant difference in the fasting blood glucose at different exposure time (P>0.05). The homeostasis model assessment of insulin resistance (HOMA-IR), insulin sensitivity index (ISI), and serum insulin levels showed no differences among all groups (P > 0.05). The OGTT results showed that, for the 300 mg/kg group, blood glucose reached peak value at 15 min after administration with glucose (P=0.004) then was significantly decreased at 60 min and 120 min after the administration (P=0.038, P=0.039), and the value at 120 min was lower than the fasting level; in addition, the blood glucose AUC was decreased (P=0.040). The ITT results showed that the blood glucose of the 30 mg/kg group at 15 min was significantly lower than that of the 0 mg/kg group (P=0.029); the blood glucose of the 300 mg/kg group was decreased more obviously with a reduction more than 50% at 60 min and 120 min (P=0.017, P=0.038), and returned to the fasting blood glucose value slowly; the blood glucose AUC of the 300 mg/kg group was also decreased (P=0.028). The liver cells of each DEHP exposure group showed edema, interstitial loose, and varied degrees of bile duct inflammation. Shrinkages in area of pancreatic islets and count of islet cells were observed in each DEHP group. The changes of white fat around genitalia of each DEHP group included shrunk cell morphology, different cell sizes, and irregular cell arrangement.
Conclusion Chronic exposure to low-dose DEHP can lead to insulin resistance in female rats.
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