Study On The Changes Of Bone Microstructure In Mice With Fatty Liver Disease

Objective:The aim of this study was to evaluate the effect of non-alcoholic fatty liver disease(NAFLD)induced by high fat diet in C57BL/6J mice on bone microstructures and the possible mechanism.Methods:20 C57BL/6J male mice(4 weeks old)were enrolled and divided into two groups,fed for 12 weeks either with standard chow(Control,n=9)or with high-fat diet to induce NAFLD(HFD,n=11).Blood plasma,femur,tibia and liver samples were collected after sacrifice.Plasma alanine aminotransferase(ALT)and aspartate aminotransferase(AST)concentration were examined.The liver was stained with H&E and Oil red-O to determine if the mice were suffering from fatty liver and to measure the amount of triglyceride(TG)and cholesterol(Tch).The bone samples were scanned using a Micro-CT system in a high-resolution scanning mode.Total volume(TV),bone volume(BV),total bone volume fraction(BV/TV),connectivity density(Conn.D),structural model index(SMI),trabecular number(Tb.N),trabecular thickness(Tb.Th),trabecular spacing(Tb.Sp),apparent density(Ap.Dens),material density(Mat.Dens)and degree of anisotropy(DA)were compared between Control and HFD groups.The number of marrow fat drops were measured by some of the femur with H&E staining.Results:In HFD group,all mice were proved with fatty liver disease by liver H&E and oil red O staining.Compared to control group,HFD group had lower levels of TV(2.128±0.591 mm3 vs.3.570±0.330 mm3,P<0.001),Tb.N(1.769±0.218 mm-1 vs.2.284±0.726 mm-1,P=0.030),SMI(2.950±0.242 vs.3.820±0.729,P=0.004)and higher levels of Tb.Sp(0.595±0.083 mm vs.0.472±0.116 mm,P=0.013)in femur.HFD group also had lower levels of TV(1.127±0.338 mm3 vs.1.741±0.683 mm3,P=0.017)and SMI(2.431±0.501 vs.3.188±0.465,P=0.003)in tibia.Bone marrow histomorphological analysis showed that the number of adipose drop(AD)per mm2 bone marrow was significantly higher in HFD group compared with Control mice(5.5±2.2 vs.2.6±0.5,P=0.042).AD was positively with TV(Femur:r=-0.756,P=0.030;Tibia:r=-0.771,P=0.025).Conclusion:Our results suggested an adverse effect of fatty liver disease on bone microstructure in C57BL/6J mice.Bone marrow adiposity may be a factor underlying this physiopathologic process.