Risk Factors for Thyroid Dysfunction in Pregnancy: An Individual Participant Data Meta-Analysis.

Background: International guidelines recommend targeted screening to identify gestational thyroid dysfunction. However, currently used risk factors have questionable discriminative ability. We quantified the risk for thyroid function test abnormalities for a subset of risk factors currently used in international guidelines. Methods: We included prospective cohort studies with data on gestational maternal thyroid function and potential risk factors (maternal age, body mass index [BMI], parity, smoking status, pregnancy through in vitro fertilization, twin pregnancy, gestational age, maternal education, and thyroid peroxidase antibody [TPOAb] or thyroglobulin antibody [TgAb] positivity). Exclusion criteria were pre-existing thyroid disease and use of thyroid interfering medication. We analyzed individual participant data using mixed-effects regression models. Primary outcomes were overt and subclinical hypothyroidism and a treatment indication (defined as overt hypothyroidism, subclinical hypothyroidism with thyrotropin >10 mU/L, or subclinical hypothyroidism with TPOAb positivity). Results: The study population comprised 65,559 participants in 25 cohorts. The screening rate in cohorts using risk factors currently recommended (age >30 years, parity ≥2, BMI ≥40) was 58%, with a detection rate for overt and subclinical hypothyroidism of 59%. The absolute risk for overt or subclinical hypothyroidism varied <2% over the full range of age and BMI and for any parity. Receiver operating characteristic curves, fitted using maternal age, BMI, smoking status, parity, and gestational age at blood sampling as explanatory variables, yielded areas under the curve ranging from 0.58 to 0.63 for the primary outcomes. TPOAbs/TgAbs positivity was associated with overt hypothyroidism (approximate risk for antibody negativity 0.1%, isolated TgAb positivity 2.4%, isolated TPOAb positivity 3.8%, combined antibody positivity 7.0%; p < 0.001), subclinical hypothyroidism (risk for antibody negativity 2.2%, isolated TgAb positivity 8.1%, isolated TPOAb positivity 14.2%, combined antibody positivity 20.0%; p < 0.001) and a treatment indication (risk for antibody negativity 0.2%, isolated TgAb positivity 2.2%, isolated TPOAb positivity 3.0%, and combined antibody positivity 5.1%; p < 0.001). Twin pregnancy was associated with a higher risk of overt hyperthyroidism (5.6% vs. 0.7%; p < 0.001). Conclusions: The risk factors assessed in this study had poor predictive ability for detecting thyroid function test abnormalities, questioning their clinical usability for targeted screening. As expected, TPOAb positivity (used as a benchmark) was a relevant risk factor for (subclinical) hypothyroidism. These results provide insights into different risk factors for gestational thyroid dysfunction.

Triglycerides Mediate the Relationship Between Maternal Free Thyroxine and Birth Weight: A Prospective Cohort Study from China.

Background: Fetal overgrowth (large for gestational age, LGA) is associated with an increased risk of maternal and fetal morbidity and adverse health outcomes. Thyroid hormones are key regulators of metabolism during pregnancy and fetal development. Lower maternal free thyroxine (fT4) and higher maternal triglyceride (TG) levels during early pregnancy are associated with higher birth weight. We aimed at examining the mediating role of maternal TG in the association between maternal fT4 and birth weight. Methods: We performed a large prospective cohort study including pregnant Chinese women who were treated at a tertiary obstetric center during the period of January 2016 to December 2018. We included 35,914 participants with complete medical records. We performed causal mediation analysis to decompose the overall effect of fT4 on birth weight and LGA with maternal TG as the mediator. Results: We observed statistically significant associations between maternal fT4, TG levels, and birth weight (all p < 0.0001). Using a four-way decomposition model, we identified a controlled direct effect (coefficient [confidence interval, CI], -0.038 [-0.047 to -0.029], p < 0.0001) that accounted for 63.9% of the total effect, in addition to the other three estimated effects (reference interaction, coefficient [CI] = -0.006 [-0.009 to -0.001], p = 0.008; mediated interaction, coefficient [CI] = 0.0004 [0.000 to 0.001], p = 0.008; and pure indirect effect, coefficient [CI] = -0.009 [-0.013 to -0.005], p < 0.0001) of TG on the association between fT4 and birth weight Z score. Moreover, maternal TG accounted for 21.6% and 20.7% (via mediation) and 13.6% and 41.6% (via maternal fT4 and TG interaction) of the total effect of maternal fT4 on fetal birth weight and LGA, respectively. The proportions of the total associations that could be reduced by "eliminating" the effect of maternal TG were 36.1% for birth weight and 65.1% for LGA, respectively. Conclusions: High maternal TG levels may play substantial mediating roles in the relationship between low fT4 levels in early pregnancy and increased birth weight and a higher risk of LGA. Further, the occurrence of fetal overgrowth may also be influenced by possible synergistic effects between fT4 and TG.

Identifying Non-Linear Association Between Maternal Free Thyroxine and Risk of Preterm Delivery by a Machine Learning Model.

Objective: Preterm delivery (PTD) is the primary cause of mortality in infants. Mounting evidence indicates that thyroid dysfunction might be associated with an increased risk of PTD, but the dose-dependent association between the continuous spectrum maternal free thyroxine (FT4) and PTD is still not well-defined. This study aimed to further investigate this relationship using a machine learning-based model. Methods: A hospital-based cohort study was conducted from January 2014 to December 2018 in Shanghai, China. Pregnant women who delivered singleton live births and had first-trimester thyroid function data available were included. The generalized additive models with penalized cubic regression spline were applied to explore the non-linear association between maternal FT4 and risk of PTD and also subtypes of PTD. The time-to-event method and multivariable Cox proportional hazard model were further applied to analyze the association of abnormally high and low maternal FT4 concentrations with the timing of PTD. Results: A total of 65,565 singleton pregnancies with completed medical records and no known thyroid disease before pregnancy were included for final analyses. There was a U-shaped dose-dependent relationship between maternal FT4 in the first trimester and PTD (p <0.001). Compared with the normal range of maternal FT4, increased risk of PTD was identified in both low maternal FT4 (<11.7 pmol/L; adjusted hazard ratio [HR] 1.34, 95% CI [1.13-1.59]) and high maternal FT4 (>19.7 pmol/L; HR 1.41, 95% CI [1.13-1.76]). The association between isolated hypothyroxinemia and PTD was mainly associated with spontaneous PTD (HR 1.33, 95% CI [1.11-1.59]) while overt hyperthyroidism may be attributable to iatrogenic PTD (HR 1.51, 95% CI [1.18-1.92]) when compared with euthyroid women. Additionally, mediation analysis identified that an estimated 11.80% of the association between overt hyperthyroidism and iatrogenic PTD risk was mediated via the occurrence of hypertensive disorders in pregnancy (p <0.001). Conclusions: We revealed a U-shaped association between maternal FT4 and PTD for the first time, exceeding the clinical definition of maternal thyroid function test abnormalities. Our findings provide insights towards the need to establish optimal range of maternal FT4 concentrations for preventing adverse outcomes in pregnancy.

Association of Maternal Thyroid Function with Gestational Hypercholanemia.

Background: High bile acid concentration is associated with adverse perinatal outcomes (i.e., stillbirth and preterm birth) and experimental studies indicate that thyroid hormone regulates bile acid metabolism, but this has not yet been translated to clinical data in pregnant women. We aim to explore the association of thyroid function with bile acid concentrations and the risk of gestational hypercholanemia. Methods: This study comprised 68,016 singleton pregnancies without known thyroid or hepatobiliary diseases before pregnancy and thyroid medication based on a prospective cohort. Thyroid function and serum total bile acid (TBA) were routinely screened in both early (9-13 weeks) and late pregnancy (32-36 weeks). Hypercholanemia was defined as serum TBA concentration ≥10 µmol/L. Multiple linear regression models and multiple logistic regression models were performed. Results: A higher free thyroxine (fT4) during both early or late pregnancy was associated with a higher TBA concentration and a higher risk of hypercholanemia (all p < 0.01). A higher thyrotropin (TSH) in early pregnancy was associated with a higher TBA concentration in early pregnancy (p = 0.0155), but with a lower TBA concentration during later pregnancy (p < 0.0001), and there was no association of TSH with hypercholanemia. Overt hyperthyroidism in late pregnancy was associated with a 2.12-fold higher risk of hypercholanemia ([confidence interval; CI 1.12-4.03], p = 0.021) and subclinical hyperthyroidism during later pregnancy was associated with a 1.5-fold higher risk of hypercholanemia ([CI 1.14-1.97], p = 0.0034). Sensitivity analyses indicated that a high fT4 throughout pregnancy was associated with a higher risk of hypercholanemia rather than only in early or late pregnancy. Conclusions: A higher fT4 concentration during either early or late pregnancy, but not the TSH concentration, is associated with higher TBA and a higher risk of gestational hypercholanemia. Furthermore, hyperthyroidism during pregnancy could be a novel risk factor for hypercholanemia.

Genome-wide identification and expression analysis of ammonium transporter 1 (AMT1) gene family in cassava (Manihot esculenta Crantz) and functional analysis of MeAMT1;1 in transgenic Arabidopsis.

Nitrogen (N), a fundamental macronutrient for plant growth and development, is absorbed from the soil primarily in the form of ammonium (NH4 +) and uptaken through a plant's ammonium transporters (AMTs). While AMT proteins have been documented within diverse plant taxa, there has been no systematic analysis of their activity in cassava (Manihot esculenta Crantz), which is highly resistant to nitrogen deficiency. Here, we perform a comprehensive genome-wide analysis to identify and characterize the functional dynamics of cassava ammonium transporters 1 (MeAMT1). We identified a total of six AMT1 genes in the cassava genome (MeAMT1;1 to MeAMT1;6), the phylogenetic analysis of which fell into three distinct subgroups based on the conserved motifs and gene structures. Collinearity analysis showed that segmental duplication events played a key role in expansion of the MeAMT1 gene family. Synteny analysis indicated that two MeAMT1 genes were orthologous to Arabidopsis and rice. MeAMT1 promoters were additionally found to include various cis-acting elements related to light responsiveness, hormones, stress, and development processes. According to the RNA-seq data, the majority of MeAMT1 genes displayed specific patterns in the tested tissues. qRT-PCR revealed that all the tested MeAMT1 genes were up-regulated by low ammonium exposure. Furthermore, Arabidopis transformed with MeAMT1;1 gene grew well than wild-type plants in response to ammonium deficiency, suggesting that MeAMT1s play important role in response to low ammonium. Overall, our work lays the groundwork for new understanding of the AMT1 gene family in cassava and provides a basis for breeding efficient nitrogen use in other plants. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-03070-6.

Cooling Kinetic Characteristics of Temperature Difference between Cadaver Temperature and Ambient Temperature.

OBJECTIVES: To study the cooling reaction kinetic characteristics of the temperature difference between cadaver temperature and ambient temperature (hereinafter referred to as "cadaver temperature difference") according to the reaction kinetics method. METHODS: Thirty rabbits were randomly divided into 5 groups with 6 rabbits in each group. The rabbits were injected with 10% potassium chloride solution intravenously. After death, the rabbits were placed at 5 ℃, 10 ℃, 15 ℃, 20 ℃ and 25 ℃ environment condition, respectively, and the rectal temperature was measured every minute for 20 hours. The measured cadaver temperature was subtracted from ambient temperature, and the cadaver temperature difference data was calculated using the reaction kinetics formula. The linear regression equation was fitted for analysis, and the experimental results were applied to the temperature difference data of human body after death for verification. RESULTS: Under different environmental conditions, the linear coefficient determination of temperature difference -ln(C/C0) in rabbits was 0.99, showing a good linear relationship with time t. The application of human body temperature data after death was consistent with the results of animal experiments. CONCLUSIONS: Under stable conditions, the temperature difference cooling process after death in rabbits is a first-order kinetic response. The method can also be used to study the temperature difference in human body after death.

Pregnancy and Neonatal Outcomes With Levothyroxine Treatment in Women With Subclinical Hypothyroidism Based on New Diagnostic Criteria: A Systematic Review and Meta-Analysis.

Background: Subclinical hypothyroidism (SCH) during pregnancy has been associated with multiple adverse maternal and neonatal outcomes. However, the potential benefits of levothyroxine (LT4) supplementation remain controversial. Variations across studies in diagnostic criteria for SCH may, in part, explain the divergent findings on the subject. This study aimed to assess the effect of LT4 treatment on pregnancy and neonatal outcomes among pregnant women who were diagnosed as SCH based on the most recent diagnostic criteria. Methods: We conducted a systematic review and meta-analysis of the literature published from inception to January 2020. The search strategy targeted the studies on pregnancy and neonatal outcomes following LT4 treatment in women with SCH based on 2017 American Thyroid Association diagnostic criteria. Pooled effect sizes were estimated using fixed and random effect models, according to the absence or presence of heterogeneity which was assessed using the I-squared statistic. Sources of heterogeneity and the stability of results were evaluated through sensitivity analysis. Results: Of the 2781 identified references, 306 full-text articles were screened for eligibility. Finally, 6 studies including a total of 7955 participants were retained for analysis. Summary effect estimates indicated that pregnant women with SCH treated with LT4 had a lower risk of pregnancy loss [odds ratio (OR) = 0.55, 95% confidence interval (CI): 0.43-0.71], preterm birth (OR=0.63, 95% CI: 0.41-0.98) and gestational hypertension (OR = 0.78, 95% CI: 0.63-0.97) than those in control group. Conclusion: LT4 treatment in pregnant women with SCH may reduce the risk of pregnancy loss, preterm delivery and gestational hypertension.

Observations of the Effects of Maternal Fasting Plasma Glucose Changes in Early Pregnancy on Fetal Growth Profiles and Birth Outcomes.

Introduction: Although the role of maternal hyperglycemia on birth outcomes is clear, literature regarding fetal growth is scarce. We examined the possible associations between maternal fasting plasma glucose (FPG) and fetal growth. Materials and Methods: A total of 35,981 singleton-pregnant women with FPG in the first trimester were included. Fetal growth parameters were measured during pregnancy by ultrasound at mid and late pregnancy. Information on birth characteristics was retrieved from medical records. We used multivariable linear and logistic regression to determine the associations between FPG and z-scores of fetal parameters and risks of birth outcomes and to assess effect modification by maternal characteristics. Results: A per-unit increase in FPG levels was negatively associated with fetal parameters in mid pregnancy but positively correlated with those in late pregnancy and with birth characteristics. The effect estimates in late pregnancy were attenuated by maternal pre-pregnancy body mass index (BMI). A significant relationship between FPG and abdominal circumference (AC), an indicator of fetal adiposity, was sustained in subgroups of women with advanced age, positive family history of diabetes, and multiparity in fully adjusted models. After stratification by BMI, high FPG was associated with accelerated AC only in normal controls (0.044 SD; 95% CI: 0.010, 0.079) and overweight/obese women (0.069 SD; 95% CI: -0.002, 0.140) but not in underweight women. High FPG was an independent risk factor for large-for-gestational age in the whole group and stratified subgroups. Conclusions: Increased FPG in early pregnancy is closely related to fetal growth. Maternal characteristics may modify the associations between FPG and fetal adiposity in late pregnancy.

The Interactive Effect of Prepregnancy Overweight/Obesity and Isolated Maternal Hypothyroxinemia on Macrosomia.

CONTEXT: Prepregnancy overweight/obesity (OWO) and isolated maternal hypothyroxinemia (IMH) may increase the risk of macrosomia, but little is known about their potential combined effect on macrosomia. OBJECTIVE: The aim of this study was to assess whether prepregnancy OWO and first-trimester IMH have a synergistic effect on the risk of macrosomia. METHODS: A large prospective cohort study in a Chinese population from January 2016 to December 2018 in a tertiary care center. In total, 34 930 pregnant women were included. The main outcome measure was macrosomia. RESULTS: A total of 34 930 participants comprising IMH and euthyroid cases was included in this study. Prepregnancy OWO and first-trimester IMH were independently associated with an increased risk of macrosomia (adjusted odds ratio [OR] 2.48, 95% CI 2.22, 2.78, and adjusted OR 1.65, 95% CI 1.34, 2.01, respectively). The coexistence of prepregnancy OWO and IMH was associated with macrosomia, with an adjusted OR of 5.26 (95% CI 3.9, 7.0) compared with pregnant women without either condition. The additive interaction between prepregnancy OWO and IMH was found to be significant with regard to macrosomia. CONCLUSION: Prepregnancy OWO and IMH in the first trimester may synergistically increase the risk of macrosomia.

Associations between Human Chorionic Gonadotropin, Maternal Free Thyroxine, and Gestational Diabetes Mellitus.

Background: Human chorionic gonadotropin (hCG) is a marker of placental function, which also stimulates the maternal thyroid gland. Maternal thyroid function can be associated with the pathophysiology of gestational diabetes mellitus (GDM). We aimed to study whether there is an association of hCG concentrations in early pregnancy with GDM and whether it is mediated through maternal thyroid hormones. Methods: This study included 18,683 pregnant women presenting at a tertiary hospital in Shanghai, China, between January 2015 and December 2016. GDM was diagnosed using a 2-hour, 75-g, oral glucose tolerance test (OGTT) according to the American Diabetes Association guidelines. Multivariable logistic or linear regression models were used to identify associations, adjusting for maternal age, education level, family history of diabetes, parity, fetal sex, thyroperoxidase antibody (TPOAb) status, and prepregnancy body-mass index. Results: Higher hCG concentrations were associated with a lower plasma glucose level during the OGTT, but not with fasting plasma glucose or hemoglobin A1c concentrations tested during early pregnancy. hCG in early pregnancy was negatively associated with GDM risk (p = 0.027). Mediation analysis identified that an estimated 21.4% of the association of hCG-associated GDM risk was mediated through changes in free thyroxine (fT4) concentrations (p < 0.05). In the sensitivity analysis restricted to TPOAb-positive women, hCG was not associated with GDM (p = 0.452). Conclusions: Higher hCG levels in early pregnancy are associated with a lower risk of GDM. Maternal fT4 may act as an important mediator in this association.

Expression, purification and characterization of the full-length SmpB protein from Mycobacterium tuberculosis.

The trans-translation system is recognized as an excellent target for developing new drugs to rapidly sterilize Mycobacterium tuberculosis (TB) infection and significantly shorten TB treatment duration. As a vital component of the trans-translation system for rescuing stalled ribosomes, the SmpB protein from Mycobacterium tuberculosis (MtbSmpB, 1-160 a. a.) mediates tmRNA binding to stalled ribosomes through forming a complex with tmRNA. So far, few works have been conducted to prepare, characterize biophysical properties and determine three-dimensional structure for the full-length MtbSmpB protein. In the present work, we successfully expressed and purified the His-tagged full-length MtbSmpB protein in Escherichia coli with a yield of 26.9 mg from 1 L of Luria Bertani medium. We also obtained MtbSmpB with a yield of 18.5 mg from 1 L of M9 minimal medium. The MtbSmpB protein showed a single band in SDS-PAGE with a molecular weight of ∼20 kDa consistent with the measurement from MALDI-TOF-mass spectrometry. The dynamic light scattering experiment indicated that MtbSmpB existed in a monomeric form. Moreover, both circular dichroism and nuclear magnetic resonance (NMR) experiments exhibited that MtbSmpB was well structured, suggesting that it could be feasible to determine its solution structure by NMR spectroscopy. NMR titration experiments showed that MtbSmpB specifically bound to tmRNA. This work lays the essential basis for further determining the solution structure and dynamics of the full-length MtbSmpB protein.

Backbone and side-chain resonance assignments for the tmRNA-binding protein, SmpB, from Mycobacterium tuberculosis.

Small protein B (SmpB) is an essential molecule in trans-translation which is a universal biological pathway for protein synthesis in bacteria. Trans-translation can release stalled ribosomes from defective mRNAs and target tag-protein fragments for degradation, and then restart protein synthesis. The SmpB-tmRNA complex coordinating with other components of the trans-translation system, plays vital roles in Mycobacterium tuberculosis under both stress conditions and non-replicating conditions. Thus, elucidation of molecular details and dynamic properties of the SmpB-tmRNA interaction is a crucial step towards effectively blocking trans-translation process to shorten the duration of tuberculosis treatment. Here, we report resonance assignments for 1H, 13C and 15N of M. tuberculosis SmpB (MtSmpB, spanning residues 4-133) protein determined by a suite of 2D/3D heteronuclear NMR experiments along with predicted the secondary structure.

Structural basis for targeting the ribosomal protein S1 of Mycobacterium tuberculosis by pyrazinamide.

Pyrazinamide (PZA) is a first-line drug for tuberculosis (TB) treatment and is responsible for shortening the duration of TB therapy. The mode of action of PZA remains elusive. RpsA, the ribosomal protein S1 of Mycobacterium tuberculosis (Mtb), was recently identified as a target of PZA based on its binding activity to pyrazinoic acid (POA), the active form of PZA. POA binding to RpsA led to the inhibition of trans-translation. However, the nature of the RpsA-POA interaction remains unknown. Key questions include why POA exhibits an exquisite specificity to RpsA of Mtb and how RpsA mutations confer PZA resistance. Here, we report the crystal structures of the C-terminal domain of RpsA of Mtb and its complex with POA, as well as the corresponding domains of two RpsA variants that are associated with PZA resistance. Structural analysis reveals that POA binds to RpsA through hydrogen bonds and hydrophobic interactions, mediated mainly by residues (Lys303, Phe307, Phe310 and Arg357) that are essential for tmRNA binding. Conformational changes induced by mutation or sequence variation at the C-terminus of RpsA abolish the POA binding activity. Our findings provide insights into the mode of action of PZA and molecular basis of PZA resistance associated with RpsA mutations.