营养诱导性追赶生长大鼠骨密度与体重和瘦素的相关性研究

The study of the relattionship among bone mineral density,body weight,and leptin level in nutrition-induced catch up growth rats

目的动态观察营养诱导性追赶生长过程中大鼠股骨骨密度(Bone mineral density,BMD)的变化。方法 5周龄wistar大鼠限食4周后给予开放普通和高脂饲料建立追赶生长模型,记录体重、进食量并计算出食物热卡量及蛋白和钙量,ELISA检测血清leptin水平,双能X线检测BMD。结果限食4周的半量限食组(semi-starvation,S组)BMD明显受损,随着营养状态恢复,普通追赶组(refeeding normal chow group,RN组)BMD持续增加,而高脂追赶组(refeeding high-fat diet group,RH组)出现升高后又再度下降趋势;开放喂养后,RN组和RH组体重迅速增长到实验终点与未经限食的对照组(normal chow group,NC组)和高脂组(high-fat diet group,HF组)无明显差异;血清leptin在S组明显降低,在开放喂养后持续上升,在RH组上升幅度更高,8周时RH和RN血清leptin明显高于NC组,12周明显高于HF组;整个试验期中,HF组与RH组摄入的食物热卡明显高于NC组和RN组,但摄入的蛋白及钙质明显低于NC组和RN组;食物热卡与BMD无相关性,而蛋白和钙量则与BMD呈正相关,体重与BMD呈正相关,且体重是影响BMD最主要的因素,leptin与BMD呈负相关,但leptin只在排除体重影响下作用才得以凸显。结论追赶生长个体更倾向于出现内脏肥胖和高leptin血症,因此可能导致骨形成障碍。对于出现追赶生长的个体应该尽量给与足够但不过量的食物热卡,过多的食物热卡对BMD恢复并无太大帮助,反而多余的热卡可能蓄积为脂肪组织影响BMD;应该以补充高蛋白和高钙食物为主,帮助体重尤其是非脂肪组织的生长,以带来机体骨质更好的恢复。

Objective To investigate the change of bone mineral density （BMD） in nutrition-induced catch up growth rats. Methods Five-week-old male Wistar rats were fed with normal or high fat diet to establish catch up growth model after 4-week semi-starvation. Their body weight and daily food intake were recorded. Total amount of food calories, protein, and calcium were calculated. Serum leptin were detected using ELISA method. BMD was detected using DXA. Results After 4-week semi- starvation, BMD was damaged significantly in rats of semi-starvation group （ S ）. After refeeding, BMD in rats of refeeding normal chow group （RN） recovered continually, but in the refeeding high-fat diet group （RH） the recovery decreased again. After refeeding, the body weight of rats in RN and RH group catch up their same age rats in normal chow group （NC） and high-fat diet group （HF）. Serum leptin decreased significantly in S group. After refeeding, the leptin level increased, especially in RH group. The leptin level in RH and RN group was higher than that in NC group in 8 weeks, and was higher than that in HF group in 12 weeks. During the whole research, the food calorie intake in HF group and RH group was higher than that in NC group and in RN group, but the intake of protein and calcium was lower. Food calorie was not correlated with BMD, but food protein and calcium were positively correlated with BMD. Body weight was positively correlated with BMD, and was an important influential factor of BMD. Leptin was negatively correlated with BMD. The effect of leptin was more obvious when the influence of body weight was excluded. Conclusion Abdominal obesity and high leptin level occur more likely in individuals with catch up growth, leading to damaged bone growth. Efficient but not over dosed food calorie should provide to those individuals. Over intake of food calorie may not help the BMD recovery. The supplement should be mainly food with high protein and calcium to help growth of body weight especially non-fat tissues, thus to contribute better recovery of the bone.