Effects Of Pre-pregnancy Obesity On The Level Of Vitamin D In Maternal And Fetal Mice And The Related Mechanism

Objective:In this study,high-fat diet was used to establish model of pre-pregnancy obese mice.The purpose of this study was to investigate the possible mechanism of the influence of pre-pregnancy obesity on the level of vitamin D by detecting the levels of vitamin D and the expression of vitamin Danabolic enzymes and placenta transport in pregnant and fetal mice.Methods:Four-week-old C57BL/6J mice were fed adaptively for one week and then divided into groups.The control group(CON)continued to be fed with normal diet,while the high-fat group(HFD)was fed with high-fat diet.After 10 weeks,the high-fat dietgroups were divided into diet-induced obesity resistance(DIR),diet-induced overweight(DIW),and(Diet-Induced Obesity)DIOgroup according to their weight were less than 10%,10% to 20%,andmore than 20% of the average body weight of the CON group,and a normal diet-fed group(CON)was also established.After grouping,the mice in each group were caged according to the ratio of male and female 2:1,and the diet of the mice remained unchanged after conception.The food,vitamin D intake and weight gain of the mice in each group was recorded.The mice were anesthetized on the 18 th day of pregnancy(GD18).The blood,liver and kidney of the mice were taken.The fetal mice and placenta were stripped and dried.The fetal mice body length and placental diameter were measured,and the fetal mice body and placental weight were weighed.The plasma was collected after centrifugation.Total 25(OH)Dlevel in plasma was measured by radioimmunoassay and 1,25(OH)2D3 by enzyme-linked immunosorbent assay.q RT-PCR was used to detect vitamin D anabolic enzymes m RNA expression of CYP2R1,CYP27B1,CYP24A1,VDR and LRP2-CUBN.The expression levels of vitamin D anabolic enzymes protein were detected by Western Blot.Results: After 10 weeks,the body weight of the four groups of mice was statistically significant(F= 58.090,P<0.01).The average body weight of the DIR group was not different from the CON group(P=0.448).The average body weight of the DIW and the DIO group was significantly higher than that of the CON and the DIR group,and the differences were statistically significant(P<0.05).Compared with the CON and the DIR group,the carcass ratios of the DIW and the DIO group were significantly decreased(P<0.05).Compared with the CON group,the maternal plasma total25(OH)D level of the DIR,DIW and DIO groups decreased significantly(P<0.05);compared with the DIR group,the plasma total 25(OH)D level of the DIW and DIO groups decreased significantly(P<0.05).Compared with the CON group,the total25(OH)D level in the fetal plasma of the DIR,DIW and DIO groups decreased significantly(P<0.05);compared with the DIR group,the total 25(OH)D level in the fetal plasma of the DIW and DIO groups decreased significantly(P<0.05).Compared with the CON group,the level of 1,25(OH)2D3 in the maternal plasma of the DIW and DIO group decreased significantly(P<0.05);compared with the DIR group,the level of 1,25(OH)2D3 in the plasma of the DIW and DIO groups decreased significantly(P<0.05).In maternal liver,compared with the CON group,the gene and protein expressions of CYP2R1 and VDR in the DIR,DIW and DIO group decreased significantly(P<0.05).In maternal kidney,compared with the CON group,the gene and protein expressions of CYP27B1,LRP2-CUBNand VDR in the DIR,the DIW and the DIO group decreased significantly(P<0.05);while CYP24A1 had opposite trend.In the placenta,compared with the CON group,the gene and protein expressions of CYP27B1,LRP2-CUBNand VDR in the DIR,the DIW and the DIO group decreased(P<0.05);while CYP24A1 had opposite trend.In fetal liver,compared with the CON group,gene and protein expressions of CYP2R1 and VDR in the DIR,DIW and DIO group decreased significantly(P<0.05).In fetal kidney,compared with CON group,the protein expressions level of CYP27B1 and VDR in DIO group was downregulated(P<0.05);there was no difference in the protein expression level of CYP24A1(P<0.05);compared with CON group,the protein expressions level of LRP2-CUBN in DIR,DIW and DIO group were down regulated(P<0.05).Conclusions:The result of this experiment showed that pre-pregnancy obesity may affect fetal vitamin D level by down-regulating the abundance of CYP2R1 in the liver and CYP27B1 in the kidney of pregnant miceand up-regulating CYP24A1 expression which caused the insufficiency of vitamin D synthesis and the increase of vitamin D decomposition,down-regulating the abundance of CYP27B1 and LRP2-CUBN expression in placenta,which caused the limitation of vitamin D synthesis and transportation,adding to abnormal expression of CYP2R1 in liver,CYP27B1 and CYP24A1 in kidney of fetus,which eventually brought about the insufficiency of vitamin D nutrition level in maternal and fetal mice.