Mechanisms Underlying Abnormal Cardiac And Pericardial Fat Metabolism In Sheep Fetuses Resulting From Maternal Undernutrition During Late Pregnancy

Fetal pericardial fat is the main energy supply tissue for the heart during late pregnancy and after birth,and the normal development of fetal cardiac fat is crucial for the functioning of the fetal heart.The development of fetuses with maternal undernutrition is retarded,and the increased incidence and mortality rate of cardiovascular diseases are found after birth.However,the mechanism of the impact of abnormal fetal pericardial development on cardial fat metabolism is unclear.Therefore,this thesis selects 18 Mongolian ewes,carrying single fetuses during late pregnancy（90 to 130 days of pregnancy）,were randomly divided into three treatment groups:the control group(CG,ad libitum,0.63 MJ ME/kg BW^0.75/d),the maternal undernutrition group 1(MU1,0.33 MJ ME/kg BW^0.75/d),and the maternal undernutrition group 2(MU2,0.20 MJ ME/kg BW^0.75/d).At 130 days of pregnancy,the fetal heart and its cardiac fat were collected for investigating mechanisms underlying abnormal cardiac and pericardial fat metabolism in sheep fetuses resulting from maternal undernutrition during late pregnancy.The results are as follows:Experiment 1:Effect of development during late pregnancy in IUGR fetal heartMaternal undernutrition resulted in significant reductions in the fetal weight of MU1 and MU2 groups（P<0.01）.The results showed that the area and diameter of myocardial cells in the MU1 and MU2 groups were significantly reductions than those in the control group（P<0.05）.And the fetal heart tissue weight of MU2 group was significantly reductions than that of the control group（P<0.01）,fetal cardiac cell cycle arrest in G1 phase;The total amount of protein in MU2 group was significantly lower than that in CG group（P<0.05）,and the development of myocardial cells in IUGR fetus was blocked.Experiment 2:Effect of damage during late pregnancy in IUGR fetal heartMaternal undernutrition resulted in significant increase in the contents of MDA in the MU1 and MU2 groups（P<0.05）.The ER-related degradation gene ERdj in the MU1 and MU2 groups was significantly reductions than that in the control group（P<0.01）;the gene expression levels of XBP1（P<0.05）and CHOP（P<0.05）nonfolding protein reaction genes in fetal heart tissue in the MU2 group were significantly increasing than those in the control group;the expression of the autophagy endoplasmic reticulum gene RB1CC1 in the MU1and MU2 groups was significantly reductions than that in the control group（P<0.05）,and the expression of P62 gene was significantly reductions than that in the control group（P<0.01）.The activity of mitochondrial respiratory chain complex III enzyme in MU1 and MU2 groups was significantly reductions than that in the control group（P<0.01）;The activity of complexⅣenzyme in MU2 group was significantly reductions than that in control group（P<0.05）.Experiment 3:Effect of damage during late pregnancy in IUGR fetal Pericardial fatMaternal undernutrition resulted in significant reductions in the weight of fetal Pericardial fat in the MU1（P<0.05）and MU2 groups（P<0.01）;the pericardial fat growth rate of the MU2 group fetus was significantly reductions than that of the control group（P<0.01）.The expression of the UCP1 gene in the MU1 and MU2 groups was significantly reductions than that in the control group（P<0.05）.The enzyme activities of mitochondrial respiratory chain complexes I,IV,I+III in MU1 and MU2 groups were significantly reductions than those in the control group（P<0.01）.Experiment 4:Lipomics analysis fatty acid metabolism in IUGR fetal Pericardial fatLipomics analysis indicates that MU1 significant differences in 102 lipid types,including 2 types of acyl carnitine,6 types of triacylglycerol,and 7 types of glycerol phospholipids.A total of 197 significantly different lipid substances were found in the MU2group,including 4 acylcarnitine,8 diacylglycerols and analogs,15 triacylglycerols and analogs,and 11 glycerol phospholipids.These lipid substances are mainly related to long-chain saturated fatty acids.In this experiment,with the deepening of feeding restriction,the types and quantities of differentiated metabolites between the MU2 group and the control group significantly increased compared to the MU1 group.The content of long-chain saturated fatty acid related fatty acyls,triglycerides,and various glycerol phospholipids in the pericardial fat of low nutritional fetuses during late pregnancy significantly increased.Experiment 5:Transcriptomic analysis the mechanism of abnormal fat metabolism in IUGR fetal pericardial fatThe results of pericardial adipose tissue transcriptome showed that the differential genes of differentially expressed gene intersection between restriction group and control group were mainly enriched in ECM receptor interaction,inositol phosphate metabolism,Notch signaling pathway,glycerol ester metabolism,cancer pathway and other signaling pathways.Changes in genes such as CDH5,VEGFA,PDGF,Notch1,DLL4,PLEC,and RPL37A are key genes that affect the effects of maternal malnutrition on pericardial adipose tissue.Changes in lipid content in maternal IUGR fetal pericardial adipose tissue may be caused by increased expression of angiogenic genes,abnormal ribosome genes,increased regulation of cardiac lipid metabolism genes.Experiment 6:Effect of abnormal fat metabolism in IUGR fetal heartMaternal undernutrition resulted the free fatty acid NEFA andβ-HB in fetal heart tissue of MU1 and MU2 groups was significantly increasing than that of the control group（P<0.05）;TG and T-CHO was significantly reductions in the control group（P<0.05）.The content of lipid metabolism related genes in the three groups showed that the expression levels of fatty acid transporter related gene CD36（P<0.01）and fatty acid kinase related gene ACSL1（P<0.01）in fetal heart tissue of MU1 and MU2 groups were significantly increasing than those in the control group.MU2 group mitochondriaβ-oxidase related gene LCAD（P<0.05）,ACAT1（P<0.01）,TCA cycle related gene IDH（P<0.01）,and fatty acid esterase related gene GPAT（P<0.01）were significantly reductions than those in the control group.In summary,IUGR during late pregnancy can lead to retardation and morphological changes in the development of the fetal heart and Pericardial adipose tissue.The heart may experience abnormal myocardial development,oxidative stress,endoplasmic reticulum stress,mitochondrial stress,and abnormal lipid metabolism.Additionally,the development of fetal pericardial fat may be inhibited,resulting in reduced expression of UCP1 and abnormal function of mitochondrial complex enzymes.The pericardial fat content of long-chain saturated fatty acids related to acyls,triglycerides,and various glycerol phospholipids increases significantly,while the polyunsaturated fat decreases.The genes regulating angiogenesis factors in pericardial fat are activated,while genes related to abnormal ribosome synthesis may contribute to the excessive accumulation of long-chain saturated fatty acids.IUGR can also cause abnormal lipid metabolism in the fetal heart and pericardial fat,leading to an imbalance between the supply and metabolic damage of saturated long-chain fatty acids.This may be a significant contributor to the increased risk of postnatal cardiovascular disease in IUGR fetuses.These findings are important for understanding the mechanisms of maternal malnutrition on pericardial fat metabolism,IUGR-related pericardial fat dysplasia,and postnatal cardiovascular disease incidence and mortality,and providing a scientific reference for preventing postnatal cardiovascular disease,disaster prevention and animal protection,and related medical research.