Sex-specific effects of leptin administration to pregnant mice on the placentae and the metabolic phenotypes of offspring

Genetic Obesity in Pregnant Ay Mice Does Not Affect Susceptibility to Obesity and Food Choice in Offspring

Maternal diet and obesity (MO) may influence taste preferences and increase the susceptibility to obesity in offspring, but the impact of MO per se to these influences is poorly understood. We evaluated the influence of MO on food choice and susceptibility to obesity in offspring when mothers consumed a standard diet (SD). Mice with the Lethal yellow mutation (Ay/a) develop obesity consuming an SD. Metabolic parameters were assessed in pregnant and lactating Ay/a (obesity) and a/a (control) mothers. Metabolic response to the consumption of a sweet–fat diet (SFD: SD, lard, and sweet biscuits) and the choice of components of this diet were evaluated in their male and female offspring. Compared to control mothers, pregnant obese mothers had higher levels of insulin, leptin, and FGF21. MO increased food intake and liver expression of lipogenesis genes in male offspring consuming the SD. SFD consumption caused obesity development and insulin resistance, increased liver expression of glycolytic and lipogenesis genes, and affected hypothalamic expression of anorexigenic and orexigenic genes. In offspring of both sexes, MO had no effect on food choice and metabolic response to SFD intake. Therefore, when obese mothers consume a balanced diet, MO does not affect food choice and development of diet-induced obesity in offspring.

Inducible knockout of syncytin-a leads to poor placental glucose transport in mice

INTRODUCTION

Cell-cell fusion of cytotrophoblasts into the syncytiotrophoblast layer is a key process in placental development. Syncytin, an endogenous retroviral envelope protein, is expressed in placental trophoblasts and specifically mediates syncytiotrophoblast layer formation. Syncytin deficiency has been observed in fetal growth-restricted placentas. Abnormal fetal growth, especially fetal growth restriction, is associated with the decreased expression of glucose transporters. Here, we aimed to determine the role of syncytin in fetal growth restriction in placental glucose transport capacity.

METHODS

To better explore the function of syncytin in fetal growth-restricted placenta, we generated an inducible knockout mouse model of syncytin-a gene. The expression levels of glucose transporters in BeWo cells were measured before and after HERV-W knockdown.

RESULTS

Syncytin-A disruption was associated with significant abnormalities in placental and fetal development in mice. Syncytin-A destruction causes extensive abnormalities in the maternal-fetal exchange structures in the labyrinth, including an extremely reduced number and dramatically irregular distribution of fetal vessels. Moreover, glucose transporter 1, glucose transporters 3, and connexin 26 expression levels decreased after E14.5. Consistently, low glucose transporter 1, glucose transporter 3, and connexin 26 levels were observed in HERV-W-silenced BeWo cells.

DISCUSSION

Syncytin-A is crucial for both syncytiotrophoblast layer development and morphogenesis, suggesting that syncytin-A disruption leads to fetal growth restriction associated with abnormalities in the maternal-fetal exchange barrier and decreased glucose transport.

Amino Acid Nanofibers Improve Glycemia and Confer Cognitive Therapeutic Efficacy to Bound Insulin

Diabetes poses a high risk for debilitating complications in neural tissues, regulating glucose uptake through insulin-dependent and predominantly insulin-independent pathways. Supramolecular nanostructures provide a flexible strategy for combinatorial regulation of glycemia. Here, we compare the effects of free insulin to insulin bound to positively charged nanofibers comprised of self-assembling amino acid compounds (AACs) with an antioxidant-modified side chain moiety (AAC2) in both in vitro and in vivo models of type 1 diabetes. Free AAC2, free human insulin (hINS) and AAC2-bound-human insulin (AAC2-hINS) were tested in streptozotocin (STZ)-induced mouse model of type 1 diabetes. AAC2-hINS acted as a complex and exhibited different properties compared to free AAC2 or hINS. Mice treated with the AAC2-hINS complex were devoid of hypoglycemic episodes, had improved levels of insulin in circulation and in the brain, and increased expression of neurotransmitter taurine transporter, Slc6a6. Consequently, treatment with AAC2-hINS markedly advanced both physical and cognitive performance in mice with STZ-induced and genetic type 1 diabetes compared to treatments with free AAC2 or hINS. This study demonstrates that the flexible nanofiber AAC2 can serve as a therapeutic platform for the combinatorial treatment of diabetes and its complications.

Influence of leptin administration to pregnant female mice on obesity development, taste preferences, and gene expression in the liver and muscles of their male and female offspring

. The consumption of food rich in sugar and fat provokes obesity. Prenatal conditions have an impact on taste preferences and metabolism in the adult offspring, and this impact may manifest differently in different sexes. An increase in blood leptin level in pregnant females reduces the risk of obesity and insulin resistance in the offspring, although the mechanisms mediating this effect are unknown. Neither is it known whether maternal leptin affects taste preferences. In this study, we investigated the effect of leptin administration to pregnant mice on the development of diet-induced obesity, food choice, and gene expression in the liver and muscles of the offspring with regard to sex. Leptin was administered to female mice on days 11, 12, and 13 of pregnancy. In male and female offspring, growth rate and intake of standard chow after weaning, obesity development, gene expression in the liver and muscles, and food choice when kept on a high-calorie diet (standard chow, lard, sweet cookies) were recorded. Leptin administration to pregnant females reduced body weight in the female offspring fed on the standard diet. When the offspring were given a high-calorie diet, leptin administration inhibited obesity development and reduced the consumption of cookies only in males. It also increased the consumption of standard chow and the mRNA levels of genes for the insulin receptor and glucose transporter type 4 in the muscles of both male and female offspring. The results demonstrate that an increase in blood leptin levels in pregnant females has a sex-specif ic effect on the metabolism of the offspring increasing resistance to obesity only in male offspring. The mechanism underlying this effect includes a shift in food preference in favor of a balanced diet and maintenance of insulin sensitivity in muscle tissues.

The Placenta's Role in Sexually Dimorphic Fetal Growth Strategies

Fetal sex affects the risk of pregnancy complications and the long-term effects of prenatal environment on health. Some have hypothesized that growth strategies differ between the sexes, whereby males prioritize growth whereas females are more responsive to their environment. This review evaluates the role of the placenta in such strategies, focusing on (1) mechanisms underlying sexual dimorphism in gene expression, (2) the nature and extent of sexual dimorphism in placental gene expression, (3) sexually dimorphic responses to nutrient supply, and (4) sexual dimorphism in morphology and histopathology. The sex chromosomes contribute to sex differences in placental gene expression, and fetal hormones may play a role later in development. Sexually dimorphic placental gene expression may contribute to differences in the prevalence of complications such as preeclampsia, although this link is not clear. Placental responses to nutrient supply frequently show sexual dimorphism, but there is no consistent pattern where one sex is more responsive. There are sex differences in the prevalence of placental histopathologies, and placental changes in pregnancy complications, but also many similarities. Overall, no clear patterns support the hypothesis that females are more responsive to the maternal environment, or that males prioritize growth. While male fetuses are at greater risk of a variety of complications, total prenatal mortality is higher in females, such that males exposed to early insults may be more likely to survive and be observed in studies of adverse outcomes. Going forward, robust statistical approaches to test for sex-dependent effects must be more widely adopted to reduce the incidence of spurious results.

Fetal Brain Elicits Sexually Conflicting Transcriptional Response to the Ablation of Uterine Forkhead Box A2 (Foxa2) in Mice

In this study, we investigated the effects of ablation of uterine Forkhead Box A2 (Foxa2) on gene expression of fetal brain relative to placenta. Using a conditional knockout mouse model for uterine Foxa2, here we show that the lack of uterine Foxa2 elicits a sexually-conflicting transcriptional response in the fetal brain relative to placenta. The ablation of Foxa2 in the uterus altered expression of genes related to growth, nutrient sensing, aging, longevity and angiogenesis among others. In the wildtype mice, these genes were expressed higher in the fetal brain and placenta of males compared to females. However, in mice lacking uterine Foxa2, the same genes showed the opposite pattern i.e., higher expression in the fetal brain and placenta of females compared to males. Based on the known marker genes of mice placenta and fetal brain cells, we further predicted that the genes exhibiting the sexually conflicting expression were associated with vascular endothelial cells. Overall, our study suggests that uterine Foxa2 plays a role in the regulation of the brain-placental axis by influencing the fetoplacental vascular changes during pregnancy.

Assessment of autism-relevant behaviors in C57BKS/J leptin receptor deficient mice

Gestational diabetes mellitus (GDM) was associated with greater autism risk in epidemiological studies. Disrupted leptin signaling may contribute to their coincidence, as it is found in both disorders. Given this we examined leptin receptor (Lepr) deficient (BKS.Cg-Dock7^m +/+ Lepr^db/J diabetic (db)) heterozygous (db/+) mice for autism-relevant behaviors. BKS db/+ females are lean with normal blood glucose, but they develop GDM while pregnant. We hypothesized BKS db/+ offspring might exhibit physiological and behavior traits consistent with autism. Adolescent body weight, fasting blood glucose, serum corticosterone, social preferences, self-grooming, marble burying, social dominance and cognitive flexibility of BKS db/+ mice was compared to C57BLKS/J (BKS) and C57BL/6J (BL6) mice. Male db/+ weighed more and had higher blood glucose and corticosterone relative to BL6, but not BKS mice. Also, male db/+ lacked social interaction preference, explored arenas less, and buried more marbles than BL6, but not BKS males. Male and female db/+ were more dominant and made more mistakes in water T-mazes locating a sunken platform after its position was reversed than BL6, but not BKS mice. Overall BKS db/+, particularly males, exhibited some autism-like social deficits and restrictive-repetitive behaviors relative to BL6, but BKS strain contributions to BKS db/+ behaviors were evident. Since BKS db/+ and BKS behavioral and physiological phenotypes are already so similar, it will be difficult to use these models in studies designed to detect contributions of fetal GDM exposures to offspring behaviors.

Examining Sex Differences in the Human Placental Transcriptome During the First Fetal Androgen Peak

Sex differences in human placenta exist from early pregnancy to term, however, it is unclear whether these differences are driven solely by sex chromosome complement or are subject to differential sex hormonal regulation. Here, we survey the human chorionic villus (CV) transcriptome for sex-linked signatures from 11 to 16 gestational weeks, corresponding to the first window of increasing testis-derived androgen production in male fetuses. Illumina HiSeq RNA sequencing was performed on Lexogen Quantseq 3' libraries derived from CV biopsies (n = 11 females, n = 12 males). Differential expression (DE) was performed to identify sex-linked transcriptional signatures, followed by chromosome mapping, pathway analysis, predicted protein interaction, and post-hoc linear regressions to identify transcripts that trend over time. We observe 322 transcripts DE between male and female CV from 11 to 16 weeks, with 22 transcripts logFC > 1. Contrary to our predictions, the difference between male and female expression of DE autosomal genes was more pronounced at the earlier gestational ages. In females, we found selective upregulation of extracellular matrix components, along with a number of X-linked genes. In males, DE transcripts centered on chromosome 19, with mitochondrial, immune, and pregnancy maintenance-related transcripts upregulated. Among the highest differentially expressed autosomal genes were CCRL2, LGALS13, and LGALS14, which are known to regulate immune cell interactions. Our results provide insight into sex-linked gene expression in late first and early second trimester developing human placenta and lay the groundwork to understand the mechanistic origins of sex differences in prenatal development.

Placental microRNA expression associates with birthweight through control of adipokines: results from two independent cohorts

MicroRNAs are non-coding RNAs that regulate gene expression post-transcriptionally. In the placenta, the master regulator of foetal growth and development, microRNAs shape the basic processes of trophoblast biology and specific microRNA have been associated with foetal growth. To comprehensively assess the role of microRNAs in placental function and foetal development, we have performed small RNA sequencing to profile placental microRNAs from two independent mother-infant cohorts: the Rhode Island Child Health Study (n = 225) and the New Hampshire Birth Cohort Study (n = 317). We modelled microRNA counts on infant birthweight percentile (BWP) in each cohort, while accounting for race, sex, parity, and technical factors, using negative binomial generalized linear models. We identified microRNAs that were differentially expressed (DEmiRs) with BWP at false discovery rate (FDR) less than 0.05 in both cohorts. hsa-miR-532-5p (miR-532) was positively associated with BWP in both cohorts. By integrating parallel whole transcriptome and small RNA sequencing in the RICHS cohort, we identified putative targets of miR-532. These targets are enriched for pathways involved in adipogenesis, adipocytokine signalling, energy metabolism, and hypoxia response, and included Leptin, which we further demonstrated to have a decreasing expression with increasing BWP, particularly in male infants. Overall, we have shown a robust and reproducible association of miR-532 with BWP, which could influence BWP through regulation of adipocytokines Leptin and Adiponectin.

Leprdb/+ Dams Protect Wild-type Male Offspring Bone Strength from the Detrimental Effects of a High-Fat Diet

The prevalence of maternal obesity is increasing at an alarming rate and increases the life-long risk of developing cardiometabolic disease in adult offspring. Leptin, an adipokine, is systemically elevated in the obese milieu. We recently showed that maternal hyperleptinemia without obesity improves offspring insulin sensitivity and glucose tolerance while protecting against weight gain on a high-fat, high-sugar (HFD). Here, we investigate the effect of maternal hyperleptinemia on offspring bone by using 2 independent maternal models. First, we compared wild-type (WT) offspring from severely hyperleptinemic Leprdb/+ (DB/+) dams with those from WT dams. In the second model, WT females were implanted with miniosmotic pumps that released either saline (group SAL) or leptin (group LEP; 650ng/hour) and the WT offspring were compared. At 23 weeks of age, a subset of offspring were challenged with a HFD for 8 weeks. When the offspring were 31 weeks of age, bone geometry, strength, and material properties were investigated. The HFD increased trabecular bone volume but decreased both total breaking strength and material strength of femora from the offspring of WT dams. However, male offspring of DB/+ dams were protected from the detrimental effects of a HFD, while offspring of LEP dams were not. Further material analysis revealed a modest decrease in advanced glycation end product accumulation coupled with increased collagen crosslinking in male offspring from DB/+ dams on a HFD. These data suggest that while maternal leptin may protect bone quality from the effects of a HFD, additional factors of the maternal environment controlled by leptin receptor signaling are likely also involved.

Role of adipose tissue in regulating fetal growth in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a global health issue with significant short and long-term complications for both mother and baby. There is a strong need to identify an effective therapeutic that can prevent the development of GDM. A better understanding of the pathophysiology of GDM and the relationship between the adipose tissue, the placenta and fetal growth is required. The placenta regulates fetal growth by modulating nutrient transfer of glucose, amino acids and fatty acids. Various factors secreted by the adipose tissue, such as adipokines, adipocytokines and more recently identified extracellular vesicles, can influence inflammation and interact with placental nutrient transport. In this review, the role of the placental nutrient transporters and the adipose-derived factors that can influence their function will be discussed. A better understanding of these factors and their relationship may make a potential target for therapeutic interventions to prevent the development of GDM and its consequences.