神经肽Y与限食后重饲大鼠骨状态的关系

Relationship between neuropeptide Y and bone status in rats refeeding after dietary restriction

目的观察限食后重饲大鼠骨组织中神经肽Y(neuropeptide Y,NPY)基因表达变化及与骨状态的关系。方法8周龄雄性SD大鼠随机分为4组:正常饮食4周(NC4)组,热卡限制4周(R4)组,正常饮食12周(NC12)组,热卡限制4周后重饲8周(RN)组,每组8只大鼠。实验4周、12周末检测大鼠股骨骨密度、骨矿盐含量及骨面积,股骨骨组织NPY mRNA基因表达变化,同时检测血清NPY、碱性磷酸酶及骨钙素水平。结果R4组大鼠股骨骨密度、骨矿盐含量及骨面积较NC4组显著下降,差异有统计学意义(P<0.05);RN组骨矿盐含量低于NC12组(P<0.05),但骨密度及骨面积与NC12组比较差异无统计学意义(P>0.05)。R4组骨组织NPY mRNA基因表达较NC4组显著上调(NC4与R4组2-△△Ct分别为1.1637±0.0889和3.2947±0.1164,P<0.01),重饲后RN组骨组织NPY mRNA基因表达呈下降趋势,但至12周末实验结束仍明显高于NC12组(NC12与RN组2-△△Ct分别为1.2041±0.0632和2.0658±0.0965,P<0.01)。R4组较NC4组血清NPY水平明显升高、碱性磷酸酶及骨钙素水平显著下降,差异有统计学意义(均P<0.01);重饲后,RN组血清NPY水平仍高于NC12组,碱性磷酸酶及骨钙素水平有所提升,但低于NC12组,差异有统计学意义(P<0.01)。相关分析显示,股骨NPY的mRNA表达水平与股骨骨密度、骨矿盐含量、骨面积、血清碱性磷酸酶、骨钙素均呈显著负相关(r值分别为-0.759、-0.728、-0.755、-0.819、-0.848,P<0.01);以股骨骨密度为因变量,逐步回归结果显示,股骨骨密度与股骨NPY的mRNA表达水平、体质量密切相关(R2=0.865,P<0.01)。结论限食后重饲大鼠股骨NPY mRNA表达与股骨骨参数及血清骨转换标志物呈显著负相关,是影响骨状态的重要因素。

Objective To observe the changes of neuropeptide Y(NPY)expression in bone tissue and its relationship with bone status in rats refeeding after dietary restriction.Methods Male SD rats,aged 8 weeks,were randomly divided into 4 groups:normal controls for 4 weeks(NC4)group,caloric restriction for 4 weeks(R4)group,normal controls for 12 weeks(NC12)group,refeeding with normal chow for 8 weeks after calorie restriction for 4 weeks(RN)group.Bone mineral density(BMD),bone mineral content,and bone area of femur,NPY gene expression in bone tissue were detected at the end of 4 and 12 weeks,along with serum NPY,alkaline phosphatase,and osteocalcin levels.Results Compared with NC4 group,BMD,bone mineral content,and bone area of femur decreased significantly in the R4 group(P<0.05).After refeeding,BMD and bone area in RN group were restored to the level of NC12 group(P>0.05),but the bone mineral content of RN group was still lower than that of NC12 group(P<0.05).NPY mRNA expression of bone tissue in R4 group was significantly increased(the values of 2-△△Ct in R4 and NC4 were 3.2947±0.1164,1.1637±0.0889,respectively,P<0.01).After refeeding,NPY mRNA expression of bone tissue in RN group showed a downward trend,but it was still significantly higher than that of NC12 group(the values of 2-△△Ct in RN and NC12 group were 2.0658±0.0965,1.2041±0.0632,respectively,P<0.01).The serum NPY level increased significantly in R4 group,alkaline phosphatase and osteocalcin levels decreased significantly,and compared with NC4,the difference was statistically significant(P<0.01);After refeeding,the serum NPY level in RN group was still slightly increased,and the levels of alkaline phosphatase and osteocalcin were also increased,but did not return to the level of NC12 group(P<0.01).The correlation analysis showed that NPY mRNA expression of bone tissue in femur was negatively correlated with BMD,bone mineral content and bone area of femur,alkaline phosphatase and osteocalcin levels(r values were-0.759,-0.728,-0.755,-0.819,-0.848,respectively;all P<0.01).With femoral BMD as dependent variable,the stepwise regression results showed that NPY mRNA expression of bone tissue in femur and body weight were closely correlated with femoral BMD(R2=0.865,P<0.01).Conclusion The expression of NPY mRNA in femur of rats refeeding after dietary restriction is negatively correlated with bone parameters of femur and serum markers of bone turnover,which is an important factor affecting bone status.