Explore The Relationship Between Mouse Brown Adipose Tissue And Bone Microstructures With 7.0T MRI And MicroCT

Objective: Quantitative evaluation of mouse brown adipose tissue(BAT)by 7.0T magnetic resonance imaging(MRI)using T2*mapping technology,and the correlation study with bone microstructures of middle femoral cortical bone and distal cancellous bone measured by micro-computed tomography(micro CT).The analysis aims to verify the relationship between brown adipose tissue and bone quality.Methods: 24 female Kunming mice were imaged at 7T MRI that measured T2* relaxation time on the deep and superficial of interscapular BAT(i BAT)and subcutaneous WAT(s BAT).Hematoxylin-eosin staining was performed on the interscapular area and subcutaneous fat and detecting the the expression of uncoupling protein 1(UCP1)m RNA by fluorescence quantitative real time polymerase chain reaction(Q-PCR)experiment.Bone microarchitectures BMD,BV/TV,Tb.Th,Tb.Sp,Tb.N,SMI,Ct.Th,Tt.Ar,Ct.Po of trabecular bone of distal femur and cortical bone of middle femur were examined by micro CT.The paired t-test was used to differentiate T2*relaxation time between deep and superficial i BAT.The paired t-test was used to differentiate T2* relaxation time between deep and superficial i BAT vs s WAT.BAT T2* was compared with all bone microstructures using Pearson’s correlation.Pearson correlation analysis was used to compare the relationship between the expression of UCP1 m RNA of deep i BAT and all bone microstructures.P < 0.05 was considered statistically significant.Results:1.There was no significant difference in T2 * between deep and superficial i BAT(t = 0.427,P > 0.05).2.T2* values of the deep and superficial of i BAT differed significantly from that of the s WAT(t =-10.816,P < 0.001;t =-12.276,P < 0.001,respectively).3.Deep iBAT T2* values was significantly negatively correlated with BV/TV,Tb.Th and Tb.N of distal femur(r =-0.554,P = 0.005;r =-0.413,P= 0.045;r =-0.542,P = 0.006,respectively),Deep i BAT T2* values was significantly positively correlated with distal femur SMI(r = 0.465,P =0.022).No significant correlation between Deep i BAT T2* values and BMD and Tb.Sp of the distal femur(P > 0.05).Superficial i BAT T2* values was significantly negatively correlated with the distal femur Tb.N(r =-0.406,P =0.049).No significant correlation between superficial i BAT T2* values and other trabecular bone microstructures BMD,BV/TV,Tb.Th,Tb.Sp,SMI of distal femur(P > 0.05).4.Deep iBAT T2* values was significantly negatively correlated with the middle femur BMD(r =-0.483,P = 0.017).No significant correlation between deep i BAT T2* values and other cortical bone microstructures BV /TV,Ct.Th,Tt.Ar,Ct.Po of the middle femur(P > 0.05).No significant correlation between superficial i BAT T2* values and all cortical bone microstructures of middle femur(P > 0.05).5.No significant correlation between s WAT T2* values and all bone microstructures BMD,BV/TV,Tb.Th,Tb.Sp,Tb.N,SMI,Ct.Th,Tt.Ar,Ct.Po of distal femur and middle femur(P > 0.05).6.There was no significant correlation between the expression of UCP1 m RNA in deep i BAT and bone microstructures BMD,BV/TV,Tb.Th,Tb.Sp,Tb.N,SMI of distal femur(P > 0.05).The expression of UCP1 m RNA in deep i BAT was significantly positively correlated with Tt.Ar in the middle femur(r = 0.468,P = 0.023).There was no significant correlation between the expression of UCP1 m RNA in deep i BAT and other cortical bone microstructures BMD,BV/TV,Ct.Th,Ct.Po in the middle femur(P > 0.05).Conclusions:7.0TMRI quantitative T2* can quantitatively reflect the histological difference between white adipose tissue and brown adipose tissue.There is a correlation between brown adipose tissue and bone quality.