营养变迁模型体脂变化及与骨密度的关系

Changes of body fat and its relationship with bone mineral density in nutritional transition model

目的 观察能量限制后不同饮食模式重饲的营养变迁模型体脂的改变以及与骨密度(bone mineral density,BMD)的关系。方法 8周龄雄性 SD 大鼠分为正常饮食(normal chow for 4/12 weeks, NC4/NC12)组、限制饮食(calorie restriction for 4 weeks,R4)组、限食后普通饮食重饲(RN)组、限食后高脂饮食重饲(high-fat diet after calorie restriction,RH)组、高脂饮食(high-fat diet,HF)组。实验 4周、12周检测大鼠四肢、躯干及全身的体脂含量及BMD。结果 (1)与同期NC组相比,大鼠各部位脂肪含量在热卡限制期变化不明显( P >0.05),但四肢/躯干脂肪比例显著下降(分别为0.418和0.327),差异有统计学意义( P <0.05)。重饲后,RN及RH组除上肢外,其他部位脂肪含量(大腿、躯干及全身脂肪含量RN组为22.80、15.77、16.17,RH组为23.80、18.55、20.90)均明显升高(NC12组3部位脂肪含量分别为20.32、10.93、12.47),同时躯干/全身脂肪比例显著增加( P <0.05),尤以RH组为著(NC12、RN及RH组分别为0.720、0.753及0.765, P <0.01),达到HF组(0.768)水平。大腿/全身脂肪比例在重饲后呈下降趋势,其中RH组(0.115)差异有统计学意义(NC12为0.150, P <0.05)。四肢/躯干脂肪比例在RN(0.237)、RH(0.205)及HF(0.210)组均明显降低(NC12为0.320),但3组间比较,差异无统计学意义。(2)热卡限制使全身(0.111 g/cm^2)、躯干(0.094 g/cm^2)及大腿(0.098 g/cm^2)BMD呈显著下降趋势(NC4分别为0.120、0.109及0.107 g/cm^2, P <0.05)。恢复饮食后,RN及RH组的BMD均有不同程度的提升,RN 组3个部位的BMD均恢复至正常水平( P >0.05),RH 组全身(0.145 g/cm^2)、躯干(0.127 g/cm^2)及大腿(0.121 g/cm^2)3个部位的BMD仍明显低于 NC12组(3个部位BMD分别为0.150、 0.136及0.130 g/cm^2)。HF 组躯干(0.141 g/cm^2)及全身BMD(0.153 g/cm^2)均明显高于NC12 组( P <0.01)。(3)多元逐步回归结果显示,体质量是影响全身、大腿及躯干BMD的最重要因素, r 值分别为0.894,0.754,0.914( P <0.001);除体质量外,大腿/全身脂肪比例是影响全身BMD( r =-0.583, P <0.001)、躯干脂肪含量是影响躯干BMD( r =-0.675, P < 0.001)的另一重要因素。结论 营养变迁可导致全身不同部位脂质含量增加,躯干部脂肪堆积明显,以限食后开放高脂饮食为著;各部位骨密度在营养变迁过程中,呈现先降低后升高的动态改变,高脂饮食重饲骨密度恢复程度较正常饮食重饲为差;体质量、大腿/全身脂肪比例及躯干脂肪含量是影响全身及局部骨密度的重要因素。

Objective To investigate the changes of body fat and its relationship with bone mineral density (BMD) in the nutritional transition models of refeedings with different dietary patterns after calorie restriction. Methods Male SD rats,aged 8 weeks,were divided into normal chow (containing normal chow for 4/12 weeks, NC4/NC12) group,calorie restriction (calorie restriction for 4 weeks,R4) group,refeeding with normal chow after calorie restriction (RN) group,refeeding with high-fat diet after calorie restriction (RH) group,and high-fat diet (HF) group. Body fat content and BMD of limbs,trunk and the whole body skeleton(WBS) were detected at the end of 4 and 12 weeks, along with body weight. Results (1)Compared with NC4 group, the fat content of each part did not change significantly during the calorie restriction period,but the fat ratio of limb to trunk decreased significantly (the values were 0.418 and 0.327, respectively, P <0.05). After refeeding,in addition to the upper limbs, the fat content in other parts (the thigh, trunk and whole boby in RN group were 22.80, 15.77, 16.17, and in RH group were 23.80, 18.55, 20.90, respectively) increased significantly (in NC12 group were 20.32, 10.93, 12.47, respectively),along with the fat ratio of trunk to whole body,especially in the RH group(0.720, 0.753 and 0.765 correspond to groups NC12, RN and RH respectively, P < 0.01),and it even reached the level of HF (0.768) group. The fat ratio of femur to whole body showed a downward trend after refeeding,and the difference was significant in the RH group ( vs. NC12 group, the values were 0.115 and 0.150, respectively, P < 0.05). The fat ratio of limb to trunk decreased significantly in RN(0.237),RH(0.205) and HF (0.210) groups (NC12 was 0.320)( P <0.05),but there was no significant difference among the three groups.(2)The BMD of the whole body (0.111 g/cm^2), trunk (0.094 g/cm^2) and thigh (0.098 g/cm^2) were significantly decreased by calorie restriction (0.120, 0.109 and 0.107 g/cm^2 in NC4 group respectively, P < 0.05). After refeeding,BMD in the whloe body (0.145 g/cm^2), trunk (0.127 g/cm^2) and thigh (0.121 g/cm^2)in RH group was still significantly lower than that in the NC12 group (0.150, 0.136 and 0.130 g/cm^2, respectively),while the recovery degree of BMD in RN group was higher than that in RH group ( P <0.05),which reached the level of NC12 group. The BMD of trunk (0.141 g/cm^2) and WBS (0.153 g/cm^2) in HF group was significantly elevated at the end of the experiment ( vs. NC12 group, P <0.01).(3) Multiple stepwise regression analysis showed that body weight was the most important factor affecting BMD of the whole body,femur and trunk,with r values of 0.894,0.754 and 0.914 respectively ( P < 0.001). In addition to body weight,the fat ratio of femur to whole body was another important factor affecting the BMD of WBS ( r =-0.583 , P < 0.001),and trunk fat content also had an important influence on the BMD of trunk ( r =-0.675, P < 0.001). Conclusions Nutritional transition can lead to increased fat content in different parts of the body and abdominal fat accumulation,especially when refeeding with high-fat diet. Along with the changes of nutrition,the BMD in different parts shows a dynamic change of increase after decline,and the recovery degree of BMD in refeeding with high-fat diet is worse than that with the normal diet. Body weight,the fat ratio of femur to whole body and trunk fat content are important factors affecting the whole body and local BMD.