Dietary L-arginine supplementation during early gestation of gilts affects conceptuses development

Supplementation of l-arginine in pregnant gilts affects the protein abundance of DNMT1 in 35-day fetuses

Maternal nutrition is one of the main environmental factors regulating gene expression during fetal development through epigenetic modifications. Some nutrients, such as the amino acid l-arginine, are added to maternal diets to modulate gene expression, improve the reproductive performance of females, and enhance conceptus development. This study investigated the hypothesis that supplementation of pregnant gilts with l-arginine regulates gene expression in conceptuses through epigenetic mechanisms. For this, fetal programming phenotypic markers, the expression of key epigenetic genes, and the abundance of DNA methylation proteins (DNMT3A and DNMT1) were evaluated in 25- and 35-day conceptuses from gilts supplemented (ARG) or not (CON) with 1.0 % l-arginine during early gestation. At 25 days, there were no significant differences in phenotypic markers between CON and ARG embryos (P > 0.05). Similarly, no differences were found between CON and ARG fetuses at 35 days (P > 0.05). Maternal supplementation with l-arginine did not influence the expression of the evaluated key epigenetic genes in pig embryos or fetuses, nor DNMT3A protein abundance (P > 0.05); on the other hand, DNMT1 protein abundance was lower in ARG fetuses (P = 0.002). It is concluded that supplementation of l-arginine in pregnant gilts affects epigenetic mechanisms, such as DNA methylation, in 35-day fetuses through regulation of DNMT1 levels. Further studies using transcriptomic and proteomic analysis could reveal additional epigenetic modifications in embryos and fetuses following maternal supplementation with l-arginine.

Long Non-Coding RNAs Differentially Expressed in Swine Fetuses

Long non-coding RNAs (lncRNAs) are non-coding transcripts involved in various biological processes. The Y chromosome is known for determining the male sex in mammals. LncRNAs on the Y chromosome may play important regulatory roles. However, knowledge about their action mechanisms is still limited, especially during early fetal development. Therefore, we conducted this exploratory study aiming to identify, characterize, and investigate the differential expression of lncRNAs between male and female swine fetuses at 35 days of gestation. RNA-Seq libraries from 10 fetuses were prepared and sequenced using the Illumina platform. After sequencing, a data quality control was performed using Trimmomatic, alignment with HISAT2, and transcript assembly with StringTie. The differentially expressed lncRNAs were identified using the limma package of the R software (4.3.1). A total of 871 potentially novel lncRNAs were identified and characterized. Considering differential expression, eight lncRNAs were upregulated in male fetuses. One was mapped onto SSC12 and seven were located on the Y chromosome; among them, one lncRNA is potentially novel. These lncRNAs are involved in diverse functions, including the regulation of gene expression and the modulation of chromosomal structure. These discoveries enable future studies on lncRNAs in the fetal stage in pigs.

L-Arginine Supplementation for Nulliparous Sows during the Last Third of Gestation

We evaluated the effects of L-arginine supplementation during the last third of gestation on molecular mechanisms related to skeletal muscle development of piglets and litter traits at birth. Twenty-three nulliparous sows averaging 205.37 ± 11.50 kg of body weight were randomly assigned to the following experimental treatments: control (CON), where pregnant sows were fed diets to meet their nutritional requirements; arginine (ARG), where sows where fed CON + 1.0% L-arginine. Skeletal muscle from piglets born from sows from ARG group had greater mRNA expression of MYOD (p = 0.043) and MYOG (p ≤ 0.01), and tended to present greater mRNA expression (p = 0.06) of IGF-2 gene compared to those born from CON sows. However, there were no differences (p > 0.05) in the histomorphometric variables of fetuses' skeletal muscle. The total weight of born piglets, total weight of born alive piglets, piglet weight at birth, coefficient of variation of birth weight, and the incidence of intrauterine growth restriction (IUGR) piglets did not differ between groups. No stillborn piglets (p < 0.01) were verified in the ARG sows compared to CON group. The blood levels of estradiol (p = 0.035) and urea (p = 0.03) were higher in ARG sows compared to those from the CON group. In summary, our data show that arginine supplementation of nulliparous sows at late gestation enhance mRNA expression of key myogenic regulatory factors, which likely contribute to improve animal growth rates in later stages of development.

Latest Advances in Sow Nutrition during Early Gestation

In the pig, the establishment and maintenance of luteal function in early gestation is crucial to endometrial function, embryo development, and survival. The level of feed intake has a positive effect on formation of luteal tissue and progesterone secretion by the ovaries in the pre-implantation period, which is important for endometrial remodeling and secretion. These effects are independent of luteinising hormone (LH) and probably driven by metabolic cues, such as insulin and insulin-like growth factor (IGF-1), and seem to support progesterone secretion and delivery to the endometrium, the latter which occurs directly, bypassing the systemic circulation. Even after implantation, a high feed intake seems to improve embryo survival and the maintenance of pregnancy. In this stage, luteal function is LH-dependent, although normal variations in energy intake may not result in pregnancy failure, but may contribute to nutrient supply to the embryos, since in this phase uterine capacity becomes limiting. Feed incidents, however, such as unintended fasting of animals or severe competition for feed, may result in embryo or even pregnancy loss, especially in periods of seasonal infertility. Specific nutrients such as arginine have a role in the vascularisation of the placenta and can improve the uterine capacity in the period after implantation.

Transcription Landscape of the Early Developmental Biology in Pigs

Since pre- and postnatal development are programmed during early prenatal life, studies addressing the complete transcriptional landscape during organogenesis are needed. Therefore, we aimed to disentangle differentially expressed (DE) genes between fetuses (at 35 days old) and embryos (at 25 days old) through RNA-sequencing analysis using the pig as model. In total, 1705 genes were DE, including the top DE IBSP, COL6A6, HBE1, HBZ, HBB, and NEUROD6 genes, which are associated with developmental transition from embryos to fetuses, such as ossification, skeletal muscle development, extracellular matrix organization, cardiovascular system, erythrocyte differentiation, and neuronal system. In pathway analysis, embryonic development highlighted those mainly related to morphogenic signaling and cell interactions, which are crucial for transcriptional control during the establishment of the main organs in early prenatal development, while pathways related to myogenesis, neuronal development, and cardiac and striated muscle contraction were enriched for fetal development, according to the greater complexity of organs and body structures at this developmental stage. Our findings provide an exploratory and informative transcriptional landscape of pig organogenesis, which might contribute to further studies addressing specific developmental events in pigs and in other mammals.

l-Arginine supplementation of gilts during early gestation modulates energy sensitive pathways in pig conceptuses

Dietary l-arginine (ARG) supplementation has been studied as a nutritional strategy to improve reproductive performance of pregnant sows, since arginine is a conditionally essential amino acid. However, reports addressing the molecular mechanisms that mediate supplementation effects on embryos and fetuses development are still scarce. Therefore, we aimed to evaluate the effects of 1.0% ARG supplementation of commercial pregnant gilts on genes and proteins from energy metabolism and antioxidant defense pathways in embryos and fetuses. We also analyzed the global transcriptome profile of 25- and 35-day-old conceptuses. At Day 25, we observed a lower abundance of phospho-AMP-activated protein kinase (phospho-AMPK) protein and downregulation of oxidative phosphorylation system genes in ARG embryos. On the other hand, ARG fetuses showed greater expression of MLST8 and lower expression of MTOR genes, in addition to lower abundance of phospho-AMPK and phospho-mammalian target of rapamycin (phospho-mTOR) proteins. Transcriptome analysis at Day 35 did not present differentially expressed genes. For the antioxidant defense pathway, no differences were found between CON and ARG conceptuses, only trends. In general, supplementation of gilts with 1.0% ARG during early gestation affects energy sensitive pathways in 25- and 35-day conceptuses; however, no effects of supplementation were found on the antioxidative defense pathway in 25-day embryos.

Sex Determination Using RNA-Sequencing Analyses in Early Prenatal Pig Development

Sexual dimorphism is a relevant factor in animal science, since it can affect the gene expression of economically important traits. Eventually, the interest in the prenatal phase in a transcriptome study may not comprise the period of development in which male and female conceptuses are phenotypically divergent. Therefore, it would be interesting if sex differentiation could be performed using transcriptome data, with no need for extra techniques. In this study, the sex of pig conceptuses (embryos at 25 days-old and fetuses at 35 days-old) was determined by reads counts per million (CPM) of Y chromosome-linked genes that were discrepant among samples. Thus, ten genes were used: DDX3Y, KDM5D, ZFY, EIF2S3Y, EIF1AY, LOC110255320, LOC110257894, LOC396706, LOC100625207, and LOC110255257. Conceptuses that presented reads CPM sum for these genes (ΣCPM_chrY) greater than 400 were classified as males and those with ΣCPM_chrY below 2 were classified as females. It was demonstrated that the sex identification can be performed at early stages of pig development from RNA-sequencing analysis of genes mapped on Y chromosome. Additionally, these results reinforce that sex determination is a mechanism conserved across mammals, highlighting the importance of using pigs as an animal model to study sex determination during human prenatal development.