Adiponectin links maternal metabolism to uterine contractility

Maternal PM2.5 exposure is associated with preterm birth and gestational diabetes mellitus, and mitochondrial OXPHOS dysfunction in cord blood

Maternal exposure to fine particulate matter (PM2.5) is associated with adverse pregnancy and neonatal health outcomes. To explore the mechanism, we performed mRNA sequencing of neonatal cord blood. From an ongoing prospective cohort, Air Pollution on Pregnancy Outcome (APPO) study, 454 pregnant women from six centers between January 2021 and June 2022 were recruited. Individual PM2.5 exposure was calculated using a time-weighted average model. In the APPO study, age-matched cord blood samples from the High PM2.5 (˃15 ug/m3; n = 10) and Low PM2.5 (≤ 15 ug/m3; n = 30) groups were randomly selected for mRNA sequencing. After selecting genes with differential expression in the two groups (p-value < 0.05 and log2 fold change > 1.5), pathway enrichment analysis was performed, and the mitochondrial pathway was analyzed using MitoCarta3.0. The risk of preterm birth (PTB) increased with every 5 µg/m3 increase of PM2.5 in the second trimester (odds ratio 1.391, p = 0.019) after adjusting for confounding variables. The risk of gestational diabetes mellitus (GDM) increased in the second (odds ratio 1.238, p = 0.041) and third trimester (odds ratio 1.290, p = 0.029), and entire pregnancy (odds ratio 1.295, p = 0.029). The mRNA-sequencing of cord blood showed that genes related to mitochondrial activity (FAM210B, KRT1, FOXO4, TRIM58, and FBXO7) and PTB-related genes (ADIPOR1, YBX1, OPTN, NFkB1, HBG2) were upregulated in the High PM2.5 group. In addition, exposure to high PM2.5 affected mitochondrial oxidative phosphorylation (OXPHOS) and proteins in the electron transport chain, a subunit of OXPHOS. These results suggest that exposure to high PM2.5 during pregnancy may increase the risk of PTB and GDM, and dysregulate PTB-related genes. Alterations in mitochondrial OXPHOS by high PM2.5 exposure may occur not only in preterm infants but also in normal newborns. Further studies with larger sample sizes are required.

Excessive Pregestational Weight and Maternal Obstetric Complications: The Role of Adipokines

There is a high frequency of overweight and obesity in women of reproductive age. Women who start pregnancy with overweight or obesity have an increased risk of developing maternal obstetric complications such as gestational hypertension, pre-eclampsia, gestational diabetes mellitus, postpartum hemorrhage, and requiring C-section to resolve the pregnancy with a higher risk of C-section surgical site infection. Excessive weight in pregnancy is characterized by dysregulation of adipokines, the functions of which partly explain the predisposition of pregnant women with overweight or obesity to these maternal obstetric complications. This review compiles, organizes, and analyzes the most recent studies on adipokines in pregnant women with excess weight and the potential pathophysiological mechanisms favoring the development of maternal pregnancy complications.

The Pathophysiology of Labor Dystocia: Theme with Variations

Abnormally prolonged labor, or labor dystocia, is a common complication of parturition. It is the indication for about half of unplanned cesarean deliveries in low-risk nulliparous women. Reducing the rate of unplanned cesarean birth in the USA has been a public health priority over the last two decades with limited success. Labor dystocia is a complex disorder due to multiple causes with a common clinical outcome of slow cervical dilation and fetal descent. A better understanding of the pathophysiologic mechanisms of labor dystocia could lead to new clinical opportunities to increase the rate of normal vaginal delivery, reduce cesarean birth rates, and improve maternal and neonatal health. We conducted a literature review of the causes and pathophysiologic mechanisms of labor dystocia. We summarize known mechanisms supported by clinical and experimental data and newer hypotheses with less supporting evidence. We review recent data on uterine preparation for labor, uterine contractility, cervical preparation for labor, maternal obesity, cephalopelvic disproportion, fetal malposition, intrauterine infection, and maternal stress. We also describe current clinical approaches to preventing and managing labor dystocia. The variation in pathophysiologic causes of labor dystocia probably limits the utility of current general treatment options. However, treatments targeting specific underlying etiologies could be more effective. We found that the pathophysiologic basis of labor dystocia is under-researched, offering wide opportunities for translational investigation of individualized labor management, particularly regarding uterine metabolism and fetal position. More precise diagnostic tools and individualized therapies for labor dystocia might lead to better outcomes. We conclude that additional knowledge of parturition physiology coupled with rigorous clinical evaluation of novel biologically directed treatments could improve obstetric quality of care.

A Nested Case-Control Study of Allopregnanolone and Preterm Birth in the Healthy Start Cohort

Context

Chronic stress is a risk factor for preterm birth; however, objective measures of stress in pregnancy are limited. Maternal stress biomarkers may fill this gap. Steroid hormones and neurosteroids such as allopregnanolone (ALLO) play important roles in stress physiology and pregnancy maintenance and therefore may be promising for preterm birth prediction.

Objective

We evaluated maternal serum ALLO, progesterone, cortisol, cortisone, pregnanolone, and epipregnanolone twice in gestation to evaluate associations with preterm birth.

Methods

We performed a nested case-control study using biobanked fasting serum samples from the Healthy Start prebirth cohort. We included healthy women with a singleton pregnancy and matched preterm cases with term controls (1:1; N = 27 per group). We used a new HPLC-tandem mass spectrometry assay to quantify ALLO and five related steroids. We used ANOVA, Fisher exact, χ², t test, and linear and logistic regression as statistical tests.

Results

Maternal serum ALLO did not associate with preterm birth nor differ between groups. Mean cortisol levels were significantly higher in the preterm group early in pregnancy (13w0d-18w0d; P < 0.05) and higher early pregnancy cortisol associated with increased odds of preterm birth (at 13w0d; odds ratio, 1.007; 95% CI, 1.0002-1.014). Progesterone, cortisone, pregnanolone, and epipregnanolone did not associate with preterm birth.

Conclusion

The findings from our pilot study suggest potential utility of cortisol as a maternal serum biomarker for preterm birth risk assessment in early pregnancy. Further evaluation using larger cohorts and additional gestational timepoints for ALLO and the other analytes may be informative.

Adiponectin affects uterine steroidogenesis during early pregnancy and the oestrous cycle: An in vitro study

Reproduction in females is an energetically demanding process. We assumed that adiponectin (ADPN), known for its role in energy balance maintenance, is also engaged in the regulation of uterine steroidogenesis in the pig. We determined the impact of ADPN alone or in combination with insulin (INS) on testosterone (T), estrone (E₁) and estradiol (E₂) secretion by porcine endometrium and myometrium, uterine expression of CYP17A1 and CYP19A3 genes, and endometrial abundance of P450_C17 and P450_AROM proteins during the peri-implantation period and the oestrous cycle, using radioimmunoassay, qPCR, and Western Blot, respectively. During pregnancy, in the endometrial explants from days 10-11, ADPN decreased CYP17A1 gene expression, P450_C17 protein abundance and T secretion, whereas increased E₁ secretion. On days 12-13 of pregnancy, ADPN decreased CYP17A1 and CYP19A3 expression, P450_C17 and P450_AROM protein abundance and E₁ secretion, but stimulated T secretion. On days 15-16 of pregnancy, ADPN decreased P450_C17 protein accumulation but enhanced CYP19A3 expression and E₁ secretion. On days 27-28 of pregnancy, ADPN increased CYP17A1 and CYP19A3 mRNA content and T secretion in this tissue and decreased P450_C17 content. ADPN effect on myometrial explants was dependent on stage of gestation or oestrous cycle. Moreover, INS treatment modulated basal and ADPN-affected steroidogenic enzymes gene and protein expression and steroids secretion. The results obtained indicate that ADPN may affect processes required for successful implantation such as steroidogenesis. ADPN and INS were also shown to modulate each other action, which indicates that the proper course of uterine steroidogenesis may be dependent on both hormones' interaction.

The ontogenies of endometrial and myometrial leptin and adiponectin receptors in pregnant rats: Their putative impact on uterine contractility

AIMS

Limited data are available about the functions and expressions of leptin and adiponectin receptors (LEPR, AdipoRs) in the uterus. Our aim was to investigate the effects of leptin and adiponectin on the contractions of intact and denuded nonpregnant and pregnant uteri, as well as the changes in mRNA and protein expressions of LEPR and AdipoRs during the gestational period.

MAIN METHODS

Contractions of nonpregnant and 5-, 15-, 18-, 20- or 22-day pregnant uterine rings were measured in an isolated organ bath system. The tissue contractions were stimulated with KCl and modified by cumulative concentrations of leptin or adiponectin. The mRNAs, protein expressions and localizations of LEPR and AdipoRs were determined by RT-PCR, Western blot and immunohistochemistry, respectively.

KEY FINDINGS

Both adipokines relaxed the nonpregnant intact uterus more effectively than the denuded myometrium. Leptin inhibited the contractions of endometrium-denuded uteri throughout pregnancy, while its action was weakened on intact uteri towards term. The changes in LEPR receptor densities were independent of the relaxing effect. Adiponectin inhibited contractions, but this effect ceased on pregnancy day 22, while a gradual decrease was detected towards term on denuded myometria. These modifications were in harmony with changes in the expressions of AdipoRs.

SIGNIFICANCE

Both leptin and adiponectin play a role in the relaxation of the pregnant uterus, but their efficacy significantly decreases towards the end of gestation. Their endometrial receptors may have a fine-tuning role in uterine contractions, predicting the importance of these adipokines in uterine contractions under altered adipokine level conditions.

Adiponectin and the regulation of gastric content volume in the newborn rat

BACKGROUND

Oral intake is dependent on the gastric ability to accommodate the food bolus. Comparatively, neonates have a smaller gastric capacity than adults and this may limit the volume of their milk intake. Yet, we previously reported that the newborn rat gastric milk volume is greatest after birth and, when normalized to body weight, decreases with postnatal age. Such age-dependent changes are not the result of intake differences, but greater gastric accommodation and reduced emptying rate.

AIM

Hypothesizing that breastmilk-derived adiponectin is the factor regulating gastric accommodation in neonates, we comparatively evaluated its effects on the rat fundic muscle tone at different postnatal ages.

METHODS

In freshly dispersed smooth muscle cells (SMC), we measured the adiponectin effect on the carbachol-induced length changes.

RESULTS

Adiponectin significantly reduced the carbachol-stimulated SMC shortening independently of age. In the presence of the inhibitor iberiotoxin, the adiponectin effect on SMC shortening was suppressed, suggesting that it is mediated via large-conductance Ca²⁺ sensitive K⁺ channel activation. Lastly, we comparatively measured the newborn rat gastric milk curd adiponectin content in one- and two-week-old rats and found a 50% lower value in the latter.

CONCLUSION

Adiponectin, a major component of breastmilk, downregulates fundic smooth muscle contraction potential, thus facilitating gastric volume accommodation. This rodent’s adaptive response maximizes breastmilk intake volume after birth.

Adiponectin as a Potential Biomarker for Pregnancy Disorders

Adiponectin is an adipocyte-derived hormone that plays a critical role in energy homeostasis, mainly attributed to its insulin-sensitizing properties. Accumulating studies have reported that adiponectin concentrations are decreased during metabolic diseases, such as obesity and type 2 diabetes, with an emerging body of evidence providing support for its use as a biomarker for pregnancy complications. The identification of maternal factors that could predict the outcome of compromised pregnancies could act as valuable tools that allow the early recognition of high-risk pregnancies, facilitating close follow-up and prevention of pregnancy complications in mother and child. In this review we consider the role of adiponectin as a potential biomarker of disorders associated with pregnancy. We discuss common disorders associated with pregnancy (gestational diabetes mellitus, preeclampsia, preterm birth and abnormal intrauterine growth) and highlight studies that have investigated the potential of adiponectin to serve as biomarkers for these disorders. We conclude the review by recommending strategies to consider for future research.

Estrogen Regulates Local Cysteine Metabolism in Mouse Myometrium

Sulfur amino acid metabolism influences reproductive physiology, and transsulfuration in particular may be critical for normal cellular function. The sex hormone estrogen (E2) modulates gene expression and redox balance in some tissues by inducing the transsulfuration enzymes cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). The role of sex hormones in sulfur amino acid metabolism by uterine smooth muscle is not known. Here, we show that CBS and CSE proteins increase in the mouse myometrium during estrus and diestrus, respectively, suggesting that E2 reciprocally regulates myometrial CBS and CSE expression. In ovariectomized mice, exogenous E2 upregulates CBS and downregulates CSE levels. E2 promotes CBS mRNA and protein expression but attenuates CSE protein expression without affecting CSE mRNA. This pattern of E2-stimulated changes in transsulfuration enzyme expression is specific to the uterine smooth muscle. E2 does not change vaginal or cervical expression of CBS or CSE significantly, and E2 decreases expression of CSE in the liver without affecting CBS. E2 also downregulates myometrial cysteinesulfinic acid decarboxylase (CSAD) and decreases myometrial biochemical synthesis of the gaso-transmitter hydrogen sulfide (H2S). These findings suggest that myometrial sulfur amino acid metabolism may regulate uterine redox homeostasis, with implications for the source and metabolism of myometrial cysteine in high E2 states such as estrus and pregnancy.