Plasma Fatty Acids During Pregnancy And Risk Of Gestational Diabetes Mellitus

Gestational diabetes mellitus(GDM)is one of the most common complications of pregnancy.According to the latest data from the International Diabetes Federation,14%of all the pregnant women worldwide were affected by GDM in 2017.Although most women with GDM would regain normal glucose tolerance after delivery,GDM can also lead to considerable short and long-term risks to both mothers and developing fetus.Thus,the prevention of GDM has become a major public health issue of global concerns.The main risk factors of GDM include obesity,advanced age,family history of diabetes and so on.Besides,many studies have indicated that reasonable diet may be an effective means of GDM prevention.Dietary modifications that have occurred during the past decades include increased consumption of saturated animal fat and simultaneously decreased intake of unsaturated fat.This change in dietary pattern could significantly affect the composition of fatty acid in human tissues,which have further impact on metabolism and health.Fatty acids are important composition of fat,and the profile of fatty acids in tissues can reflect both fatty acids intake and metabolism without being affected by recall bias.Compared to traditional dietary intake assessment methods,using plasma,serum or adipose tissue fatty acids as biological markers has obvious advantages and has been considered as a better choice for epidemiologic studies.Recent years,dietary fat intake and fatty acid composition of blood and tissue have been shown to be associated with the development of insulin resistance and type 2diabetes.However,to date,few epidemiologic studies have explored the difference of fatty acid profile between women with and without GDM and yielded inconsistent results,and none of these studies was conducted in China.Moreover,different types of desaturases and elongase play a major role in fatty acid metabolism,and their relationships with metabolic diseases have gained extensive attention.Thus,the aim of our study was to investigate the association of plasma fatty acid subtypes,individual fatty acids and related enzyme activity with odds of GDM initially,and further explore the novel fatty acid patterns associated with GDM odds in a Chinese population.The main contents of this study are as follows:Part One:Quantification of Plasma Fatty Acids by Gas Chromatography-mass SpectrometryObjective:To develop a gas chromatography-mass spectrometry(GC-MS)method with simple pretreatment,high sensitivity,high specificity and high throughput to quantify plasma fatty acids concentrations.Methods:We used the modified direct transesterification method to achieve the derivation of fatty acids.Plasma samples were analyzed on an Agilent 7890B gas chromatography coupled with an Agilent 5977A Series mass spectrometry.The internal standard curve method was used for quantitative determination.Finally,validation of the analytical method was performed according to European Medicine Agency Guideline on bioanalytical method validation.Results:The optimization of the GC-MS method provided chromatography separation efficiency and sensitivity to analyze 38 individual fatty acids within 35 min.There was no significant endogenous interference at the retention times of the analytes and internal standard.The lower limit of quantification of individual fatty acids was between 0.01?g/mL and 0.10?g/mL,and the linearity was acceptable for all fatty acids in the specified range of concentrations(all r~2>0.998).The intra-day and inter-day precision of target fatty acids in spiked samples ranged from 0.63%to 7.58%and 1.15%to 12.28%,and the intra-day and inter-day accuracy ranged from 86.04%to 114.78%and 86.11%to 114.11%,respectively.Conclusion:The GC-MS method established in this study is an accurate,stable method with simple pretreatment and high sensitivity,which is suitable for metabolomics studies of plasma fatty acids with large sample size.Part Two:Association of Plasma Fatty Acids and Related Enzyme Activity During Pregnancy with Gestational Diabetes MellitusObjective:To investigate the association of plasma fatty acid subtypes,individual fatty acids and related enzyme activity with odds of GDM in a Chinese population.Methods:A case-control study of 217 GDM cases and 217 age-,gestational age-and parity-matched controls was conducted in Wuhan,China between August 2012 and April 2015.All the participants were recruited from pregnant women who screened for GDM at the outpatient clinics of the Department of Endocrinology,Tongji Hospital.Basic information was collected by trained investigators with structured questionnaires.Plasma fatty acids were quantified by GC-MS as previously described.We estimated desaturase and elongase activity by using fatty acid product-to-precursor ratios.Multivariable conditional logistic regression and restrict cubic spline model were used to evaluate the association of fatty acid subtypes,individual fatty acids and related enzyme activity with odds of GDM.Adjustments were made for potential counding factors,including age,prepregnancy body mass index,gestational age,parity,smoking and drinking status and family history of diabetes.Results:Women with GDM displayed significantly higher concentrations of plasma total fatty acids than control subjects(median:2624.96(2073.66-3472.03)?mol/L and 2458.38(1857.25-2985.84)?mol/L,respectively,P=0.001).Compared with women the lowest quantile,women in the highest quantile of plasma odd-chain fatty acid had decreased odds of GDM(adjusted OR,0.45;95%CI,0.25-0.83).Among the 20 individual fatty acids included in the analyses,13 fatty acids were considered to be negatively associated with odds of GDM.After adjustment,the ORs(95%CIs)of GDM comparing the highest with lowest quantiles were as follows:C14:0,0.55(0.31-0.99);C15:0,0.48(0.25-0.91);C17:0,0.43(0.23-0.78);C18:0,0.32(0.16-0.63);C24:0,0.41(0.22-0.79);C16:1n-7,0.49(0.27-0.88);C20:1n-9,0.25(0.12-0.52);C18:3n-6,0.48(0.25-0.92);C20:2n-6,0.30(0.15-0.59);C18:3n-3,0.37(0.19-0.73);C20:3n-3,0.26(0.13-0.50);C20:5n-3,0.47(0.25-0.89);C22:5n-3,0.33(0.17-0.66).In addition,significant positive association with GDM odds was observed in the highest compared with lowest quantiles of C24:1n-9(OR,2.05;95%CI,1.12-3.76).There was no interaction between total and individual fatty acids on GDM development(all P>0.05).As to fatty acid metabolism enzymes,?9-16 desaturase and?6 desaturase activity were inversely associated with GDM odds in multivariable-adjusted models.Comparing extreme quantiles,OR(95%CI)of GDM was 0.50(0.27-0.93)for?9-16 desaturase and0.35(0.19-0.65)for?6 desaturase.Conclusions:The present study indicated that higher concentrations of C24:1n-9and lower concentrations of odd-chain fatty acids,C14:0,C15:0,C17:0,C18:0,C24:0,C16:1n-7,C20:1n-9,C18:3n-6,C20:2n-6,C18:3n-3,C20:3n-3,C20:5n-3 and C22:5n-3were significantly associated with higher odds of GDM.As to enzyme activity,?9-16desaturase and?6 desaturase activity were inversely associated with GDM odds.Further studies are warranted to explore the combined effects of various fatty acids on the development of GDM.Part Three:Novel Plasma Fatty Acid Patterns and Odds of Gestational Diabetes Mellitus:Exploration Based on Principal Component AnalysisObjective:To investigate the association between fatty acid patterns and odds of GDM.Methods:Methods related to participant recruiment,basic information acquisition and fatty acids determination were described in parts one and two.Principal component analysis was used to derive fatty acid patterns(eigenvalue>1)from 20 plasma fatty acids in 434 pregnant women.A score of each pattern was calculated by multiplying coefficient with each fatty acid for each participant.Multivariable conditional logistic regression and restrict cubic spline model were used to evaluate the association of fatty acid pattern and odds of GDM.Results:Four fatty acid patterns were identified and explained 31.41%,18.47%,13.56%and 9.68%of the overall variability,respectively.Two novel fatty acid patterns were associated with lower odds of GDM.The first pattern was partly characterized by higher concentrations of odd-chain fatty acids,C18:0,C18:3n-3,C20:2n-6,C20:3n-6and lower concentrations of C24:1n-9 and C18:2n-6.The second pattern was characterized by higher concentrations of n-3 polyunsaturated fatty acids,C24:0,C18:3n-6 and lower concentrations of C16:0 and C20:4n-6.After adjustment,the ORs(95%CIs)of GDM comparing extreme quartiles of the first and second pattern scores were 0.42(0.23-0.76)and 0.48(0.26-0.90),respectively.Conclusion:The combination of individual fatty acids might have potentially important effects on the development of GDM.Identifying specific fatty acid patterns during pregnancy may contribute to early diagnosis and prevention of GDM,which need further verification in prospective studies.