The Mechanism Of Low Birth Weight In Adult Diabetes Mellitus And Insulin Resistance

Low birth weight(LBW)is one of the important markers of fetal growth environment damage in utero.LBW not only exposes newborns to a higher risk of morbidity and mortality during the perinatal period,but also increases the risk of metabolic diseases in adulthood.Pre-pregnancy body mass index(BMI)and pregnancy weight gain(GWG)are important factors affecting pregnancy outcome and newborn birth.Therefore,the relationship between GWG during pregnancy,maternal PRE-pregnancy BMI and newborn birth weight has attracted increasing clinical attention,and the control and management of maternal pre-pregnancy body mass index and pregnancy weight are particularly important.The "catch-up growth" of low birth weight infants can improve the quality of life and promote the healthy growth of body and mind.However,studies have found that catch-up growth can also promote the occurrence and development of IR,and increase the risk of insulin resistance,type 2 diabetes,obesity and other metabolic diseases after adulthood.Skeletal muscle is the main peripheral tissue of islet stimulating glycolipid metabolism and plays an important role in maintaining the balance of mechanical energy and quantity.IR in skeletal muscle is an important feature of type 2 diabetes.The imbalance between fatty acid uptake and oxidation is the main cause of lipid deposition and IR in skeletal muscle.However,the mechanism of LBW inducing IR and diabetes is still unclear.Long chain fatty acids(LCFA)can be transported to the nucleus via the CD36-FABP4 pathway and can be activated to promote glycolysis and lipid metabolism and increase insulin sensitivity.Adenosine-activated protein kinase(AMPK)regulates PGC-1α-CPT1 signaling pathway to increase mitochondrial oxidation and utilization of fatty acids,thereby reducing fatty acid content in the body.This study first investigated the effects of prepregnancy BMI and GWG on newborn birth weight and pregnancy outcome.To establish a low birth weight mouse model,explore the key roles of CD36-FABP4-PPAR γ and AMPK-PGC-1α-CPT1 signaling pathways in the pathogenesis of insulin resistance and type 2 diabetes in low birth weight mice in adulthood,and bring new theoretical breakthroughs and promising therapeutic targets for the prevention and treatment of metabolic diseases.Part One Influence of pre-pregnancy body mass index and pregnancy weight gain on newborn birth weightObjective: To investigate the effects of pre-pregnancy body mass index(BMI)and pregnancy weight gain(GWG)on newborn birth weight and pregnation-related outcomes,and to provide a reasonable theoretical basis for the scientific management of pre-pregnancy and pregnancy weight control,so as to avoid the birth of SGA or LGA newborn and reduce the risk of metabolic diseases in adulthood.Methods: From July 2020 to August 2021,679 single pregnant women who gave birth in Baoding Boye County Hospital were selected.According to BMI level before pregnancy,they were divided into three groups: low BMI group(46 cases),normal BMI group(450 cases)and overweight and obese group(183 cases).According to different levels of GWG during pregnancy,they were divided into GWG excessive group(265 cases),GWG suitable group(289 cases),GWG insufficient group(125 cases).The birth weight and related outcomes of newborns in each group were analyzed,and the correlation between BMI and GWG before pregnancy and birth weight and pregnancy-related outcomes of newborns was analyzed.Results:1.Correlation analysis of pre-pregnancy BMI and GWG with birth weight of newborn The incidence of SGA in low BMI group and LGA in over weight and obese group were higher than those in other groups.The incidence of LGA in wo men with excessive GWG and the incidence of SGA in women with insufficie nt GWG were higher than those in other groups(P < 0.05).The incidence of LGA in pregnant women with excessive GWG in normal BMI group and overweight and obese group was higher than that in other groups,while the incidence of SGA in pregnant women with insufficient GWG significantly was higher in low BMI group and normal BMI group than in other groups(P< 0.05).After adjusting for confounding factors,the risk of LGA was increased in overweight and obese women before pregnancy and excessive GWG women(P<0.05),while the risk of SGA was increased in women with insufficient GWG women(P<0.001)..2.Effects of pregnancy weight gain and neonatal outcomes Excessive GWG increased the incidence of cesarean section,hypertension during pregnancy and premature rupture of membranes in pregnant women compared with other groups(P < 0.05).Compared with other groups,the incidence of gestational diabetes,anemia,premature delivery and fetal distress in pregnant women with insufficient GWG was higher(P < 0.05).3.Influence of different levels of pregnancy weight gain and neonatal outcomes according to pre-pregnancy BMI groups The incidence of premature rupture of membranes,anemia,neonatal preterm delivery and fetal distress caused by insufficient GWG was significantly higher in low BMI group than in other groups(P < 0.05).The incidence of gestational diabetes,neonatal preterm delivery and fetal distress with insufficient in insufficient GWG was higher in normal BMI group than in other groups(P < 0.05).Compared with the other two groups,excessive GWG increased the incidence of premature rupture of membranes and cesarean section.(P < 0.05)Summary: BMI before pregnancy and pregnancy weight gain are the important influencing factors of newborn birth weight,and are also related to pregnancy outcomes.Therefore,women’s weight changes before pregnancy and during pregnancy should be closely monitored and controlled within a reasonable range,so as to avoid SGA or LGA newborn babies as much as possible and reduce the risk of metabolic diseases in adulthood.Part Two Changes of glycolipid metabolism in low birth weight mice during adulthoodObjective: To observe the changes of body weight and length of mice with low birth weight caused by malnutrition during pregnancy,as well as the changes of metabolic indexes such as blood glucose,insulin and blood lipid in adult mice.In order to further explore the effects of catch-up growth of low birth weight on adult diabetes and insulin resistance.Methods: There were 20 female and 10 male ICR mice,respectively.After adaptive feeding,pregnant females were randomly divided into normal diet group(NBW)and restricted diet group(IUGR).Between 12.5 and 18.5days of gestation,the NBW group was given a normal amount of food and the IUGR group was given 50% dietary restriction.Male progeny mice were weaned 3 weeks after birth,and were randomly divided into control group(Con,n=9)and low birth weight group(LBW,n=9)according to the weight of the mice after birth.The mice were fed with normal diet,and blood samples were collected for glucose tolerance test(IPGTT)at 19 weeks of age.Activity,food intake and water intake of mice at 24 hours were measured by metabolic cage at 21 weeks of age.Blood samples were collected at the age of 21 weeks for the determination of fasting glucose,fasting insulin,total cholesterol(TC)and triglyceride(TG)levels.Results:1.Establishment of low birth weight animal model: the body weight of mice in the restricted diet group(IUGR)was significantly lower than that of mice with normal birth weight(NBW),the difference was statistically significant(P<0.05),and the low birth weight mouse model was successfully established.2.Comparison of water intake,food intake and total activity of mice:During 18 weeks of normal diet,there was no difference in total food intake,water intake,standing times,total distance of exercise and 24-hour diet between Con and LBW groups(P>0.05).3.Comparison of body weight,bod length and proportion of skeletal muscle weight between the two groups: compared with Con group,LBW group had similar body weight on day 14 and 21 after birth,but increased significantly on day 14 and 21 after birth,while The body length of mice in LBW group was significantly lower than that in Con group at 5 months after birth(P<0.05).4.Experimental results of IPGTT of mice in the two groups Compared with Con group,blood glucose in LBW group(19 weeks of age)was significantly increased at 30 min,60min and 120 min,and AUCglu in LBW group was also significantly increased(P<0.05).5.Comparison of fasting glucose,fasting insulin and HOMA-IR between the two groups of mice Blood glucose and fasting insulin were detected at the age of 21 weeks.Compared with the Con group,fasting blood glucose and fasting insulin in LBW group at 21 weeks of age and HOMA-IR calculated were significantly increased(P<0.05).6.Comparison of total cholesterol and triglyceride levels between the two groups Compared with Con group,serum total cholesterol and triglyceride levels levels in LBW group at 21 weeks of age were increased(P<0.05).Summary: A low birth weight mouse model was successfully established by dietary restriction during pregnancy.Low-birth-weight mice developed catch-up growth early in life,impaired glucose regulation and insulin resistance in adulthood.Part Three Changes in protein expression of skeletal muscle related pathways in low birth weight miceObjective: To investigate the molecular mechanism of adult diabetes induced by low birth weight and provide a new theoretical basis and potential target for the treatment of type 2 diabetes by quantitative analysis of total protein TMT markers in skeletal muscle tissue of mice using proteomic technique based on mass spectrometry.Methods: Using mass spectrometry based proteomic technology to all mice skeletal muscle protein TMT LBW tag quantitative analysis and Con protein expression spectrum,screening of low birth weight differences of adipose tissue in mice modified protein,protein variations associated with low birth weight and the analysis of the function of the differences between the modified protein,then pick the key targets and pathways.Results:1 Overview of sample protein identification In this study,a total of 3039 proteins were identified,of which 2633 proteins had quantitative information.In this study,differentially expressed proteins in skeletal muscle tissues of LBW mice and Con mice were compared.Compared with Con group,113 proteins were up-regulated and 142 proteins were down-regulated in LBW group.In this study,3039 proteins were identified,of which 2633 contained annotations with quantitative information.In this study,differentially expressed proteins in skeletal muscle tissues of LBW mice and Con mice were compared.In this study,3039 proteins were identified,of which 2633 contained annotations with quantitative information.In this study,differentially expressed proteins in skeletal muscle tissues of LBW mice and Con mice were compared.Compared with Con group,142 proteins were down-regulated and 113 proteins were up-regulated in LBW group.Compared with Con group,142 proteins were down-regulated and 113 proteins were up-regulated in LBW group.2 Bioinformatics analysis of differentially expressed proteins in LBW and Con groups2.1 Functional classification of differentially expressed proteins:In this study,DEPs in the LBW/Con group are involved in cellular process,single-organism process,and cellular process.Metabolic process and biological regulation account for about 12% of DEPs.2.2 Functional enrichment analysis of differentially expressed proteins In this study,differentially expressed protein KEGG was mainly enriched in fatty acid degradation,fatty acid metabolism,PPAR and other energy metabolic pathways.2.3 Cluster analysis In this study,in PPAR and fatty acid metabolism pathways,compared with Con group,CD36,Fabp4,ACC1 and FAS expressions were up-regulated in LBW group,while CPT1 expression was down-regulated in LBW group.Summary: TMT labeled quantitative proteomic technique was used to screen out differential proteins associated with low birth weight diabetes and insulin resistance in adulthood.It is speculated that fatty acid transport pathway CD36-Fabp4-PPARγ and fatty acid synthesis and oxidation pathway may be important to reveal the molecular mechanism..Part Four Molecular mechanism of insulin resistance in adulthood due to low birth weightObjective: To further verify the function of CD36-Fabp4-PPARγ and AMPK-PGC-1α-CPT1 pathways and explore their mechanisms,the m RNA and protein expressions of PPAR and AMPK pathway related genes in skeletal muscle tissue of low birth weight mice were determined.To provide new ideas and intervention targets for the prevention and treatment of insulin resistance.Methods: Animal grouping and specimen collection were the same as in the second part.The protein and molecular expression levels of CD36,Fabp4,PPARγ,ACC1,FAS,CPT1,PGC-1α and GLUT4 of AMPK were detected by reverse transcription-polymerase chain reaction(RT-PCR)and Western blot.Results:1.Comparison of m RNA levels and protein expression of fatty acid transport-related genes in skeletal muscle of mice Rt-pcr results showed that the expression levels of CD36,Fabp4 and PPARγ m RNA in skeletal muscle tissue of LBW group were significantly higher than those in Con group(P<0.05).Compared with Con group,the protein expression levels of CD36,Fabp4 and PPARγ in skeletal muscle tissue of mice in LBW group were significantly increased,and the difference was statistically significant(P<0.05).2.Comparison of m RNA levels and protein expression of genes related to fatty acid synthesis in skeletal muscle of mice The expression levels of ACC1 and FAS mrna in LBW group were significantly higher than those in Con group,and the expression levels of ACC1 and FAS protein in skeletal muscle tissue of LBW group were significantly higher than those in Con group,with statistical difference(P<0.05).3.Comparison of fatty acid oxidation and glucose metabolism-related gene protein expression in skeletal muscle of mice Compared with Con group,the protein expression levels of P-AMPK/AMPK,PGC-1α,CPT1 and GLUT4 in skeletal muscle tissue of mice in LBW group were significantly decreased,with statistical significance(P<0.05).Summary: Changes in CD36-Fabp4-PPARγ and AMPK-PGC-1α-CPT1 signaling pathways may be involved in insulin resistance and type 2 diabetes mellitus induced by catch-up growth at low birth weight.Conclusion:1.BMI before pregnancy and gestational weight gain are the important factors affecting newborn birth weight.2.Mice with low birth weight showed catch-up growth in early life,impaired glucose regulation and insulin resistance in adulthood.3.Changes in CD36-Fabp4-PPARγ and AMPK-PGC-1α-CPT1 signaling pathways may be associated with insulin resistance and type 2 diabetes mellitus induced by catch-up growth of low birth weight.