The effects of trivalent chromium on hormonal regulation in ovariohysterectomized rats

Abstract

節育已經被證實是導致伴侶動物肥胖的主要風險因素之一。造成節育後肥胖的影響因素有許多，其中有些研究探討節育後賀爾蒙的變化，發現節育會造成影響葡萄糖及脂肪代謝賀爾蒙的平衡發生改變。三價鉻離子是一種動物體內不可或缺的微量元素，其對於葡萄糖、脂質及蛋白質代謝很重要。此外，有研究顯示三價鉻離子可藉由像是減少攝食量及增加代謝速率的機制進而減少體重。故本研究欲探討給予三價鉻離子對於節育動物體重和身體組成的變化及節育後賀爾蒙的影響。本實驗將8週齡的雌性大鼠分為4組 (n=6/組)，給予生理食鹽水之大鼠為控制組 (C)，給予三價鉻離子之大鼠為鉻離子組 (Cr)，給予生理食鹽水及進行子宮卵巢摘除手術之大鼠為子宮卵巢摘除手術組 (OHE)，給予三價鉻離子及進行子宮卵巢摘除手術之大鼠為鉻離子及子宮卵巢摘除手術組 (Cr+OHE)，每天給予並在給予後一週進行子宮卵巢摘除手術，之後持續給予13週。每週秤量各組大鼠的體重及攝食量，並在實驗大鼠14、18及22週齡時採集血液檢測生長激素、第一型類胰島素生長因子 (IGF-I)、胰島素及醣皮質固醇的濃度。在實驗的最後，進行腹腔注射葡萄糖耐受性試驗 (IPGTT)。結果顯示子宮卵巢摘除手術組 (OHE) 和鉻離子及子宮卵巢摘除手術組 (Cr+OHE) 的生長激素濃度在三個時間點都較控制組低，其中鉻離子及子宮卵巢摘除手術組 (Cr+OHE) 的生長激素濃度有隨著實驗的時間較久而呈下降的趨勢，甚至在22週齡時達顯著差異 (P < 0.05)。而子宮卵巢摘除手術組 (OHE) 和鉻離子及子宮卵巢摘除手術組 (Cr+OHE)的血中第一型類胰島素生長因子在14週齡及18週齡均顯著高於控制組。子宮卵巢摘除手術組 (OHE) 和鉻離子及子宮卵巢摘除手術組 (Cr+OHE) 的血中醣皮質固醇的濃度在14週齡時均較控制組低，但只有子宮卵巢摘除手術組 (OHE) 具顯著差異。而在14週齡時，子宮卵巢摘除手術組 (OHE)、鉻離子組 (Cr) 和鉻離子及子宮卵巢摘除手術組 (Cr+OHE)，血中胰島素濃度都較控制組高，其中鉻離子及子宮卵巢摘除手術組 (Cr+OHE) 具顯著差異 (P < 0.05)。在葡萄糖耐受性試驗中，雖然子宮卵巢摘除手術組 (OHE) 和鉻離子及子宮卵巢摘除手術組 (Cr+OHE) 的葡萄糖曲線下面積都低於對照組，但只有鉻離子及子宮卵巢摘除手術組 (Cr+OHE) 具顯著差異 (P < 0.05)。然而，子宮卵巢摘除手術組 (OHE) 的胰島素曲線下面積顯著高於控制組。綜合以上結果，本實驗顯示給予三價鉻離子具有調節子宮卵巢摘除手術大鼠體內荷爾蒙的作用，並可改善節育後的胰島素敏感性。

Neutering has been identified as an important risk factor of obesity. Many factors seem to be involved, but a number of studies have shown that neutering modifies hormone balance, and these modifications of hormonal factors involved in glucose and fat metabolism. Trivalent chromium (Cr3+) is an essential nutrient required for glucose, lipid and protein metabolism, and is necessary for insulin function. Cr3+ has also been suggested to reduce body weight by a number of mechanisms, such as reduce food intake and increasing metabolic rate. In this study, all 8-week-old SD female rats were divided into four groups (n=6): (1) control group, (2) ovariohysterectomy (OHE) group, (3) Cr3+ supplement group, (4) OHE with Cr3+ supplement group. OHE was performed after one week of supplemental Cr3+, the regimen of supplemental Cr3+ were continued for 13 weeks. Body weight and food intake were recorded weekly. Evaluation of circulating growth hormone (GH), insulin-like growth factor-I (IGF-I), insulin and corticosterone (CORT) concentrations at different time points. At the end of experiment, intraperitoneal glucose tolerance tests (IPGTTs) were conducted after overnight fasting. In results, both OHE groups had lower GH levels than control group. And the GH levels of OHE with Cr3+ supplement group were gradually decreased and even were significantly lower compared with control group at 22-week-old. The IGF-I levels in both OHE groups were significantly higher than that in control group at 14- and 18-week-old. The levels of insulin at 14-week-old were higher in OHE group, Cr3+ group and OHE with Cr3+ supplement group, however the insulin level of OHE with Cr3+ supplement group was significantly higher than that in control group. Lower CORT levels were found in both of OHE groups than that in control group, but only significantly lower in OHE group at 14-week-old. During the GTTs, the area under the curve (AUC) glucose in OHE and OHE with Cr3+ supplement group were lower than that in control group, but only OHE with Cr3+ supplement group had significant difference. However, AUC insulin was significantly higher in OHE group than in control group. According to the results of this study, the daily supplementation of Cr3+ to OHE rats affects hormone status and can improve insulin sensitivity.