Apelin-13 modulates the endometrial transcriptome of the domestic pig during implantation.

BACKGROUND: The peri-implantation period is a critical time during pregnancy that mostly defines the overall litter size. Most authors agree that the highest percentage of embryo mortality occurs during this time. Despite the brevity of the peri-implantation period, it is the most dynamic part of pregnancy in which the sequential and uninterrupted course of several processes is essential to the animal's reproductive success. Also then, the maternal uterine tissues undergo an intensive remodelling process, and their energy demand dramatically increases. It is believed that apelin, a member of the adipokine family, is involved in the control of female reproductive functions in response to the current metabolic state. The verified herein hypothesis assumed the modulatory effect of apelin on the endometrial tissue transcriptome on days 15 to 16 of gestation (beginning of implantation). RESULTS: The analysis of data obtained during RNA-seq (Illumina HiSeq2500) of endometrial slices treated and untreated with apelin (n = 4 per group) revealed changes in the expression of 68 genes (39 up-regulated and 29 down-regulated in the presence of apelin), assigned to 240 gene ontology terms. We also revealed changes in the frequency of alternative splicing events (397 cases), as well as single nucleotide variants (1,818 cases) in the presence of the adipokine. The identified genes were associated, among others, with the composition of the extracellular matrix, apoptosis, and angiogenesis. CONCLUSIONS: The obtained results indicate a potential role of apelin in the regulation of uterine tissue remodelling during the peri-implantation period.

Chemerin affects the cytokine production and the expression of their receptors in the porcine endometrium during early pregnancy and the estrous cycle: an in vitro study.

Interactions between female metabolic status, immune response, and reproductive system functioning are complex and not fully understood. We hypothesized that chemerin, considered a hormonal link between the above-mentioned processes, influences endometrial functions, particularly cytokine secretion and signalling. Using porcine endometrial explants collected during early pregnancy and the estrous cycle, we investigated chemerin effects on the secretion of interleukins (IL-1ß, IL-6, IL-8), leukaemia inhibitory factor (LIF), tumour necrosis factor α (TNFα), transforming growth factor α (TGFα), and protein abundances of their respective receptors. Our results demonstrate chemerin modulation of cytokine secretion and receptor expression, with effects dependent on the stage of pregnancy and dose of chemerin. Furthermore, chemerin influences the phosphorylation of stress-activated protein kinase/Jun-amino-terminal kinase (SAPK/JNK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κß) in the endometrium. Chemerin multifaceted actions, such as involvement in immune response, cell proliferation, and tissue remodelling seem to be mediated by cytokines, at least in the endometrium. These findings underscore the potential crosstalk between chemerin and hormonal signalling pathways, providing insights into the complex mechanisms underlying early pregnancy establishment and maintenance.

Visfatin Affects the Transcriptome of Porcine Luteal Cells during Early Pregnancy.

Visfatin/NAMPT (VIS), the hormone exerting a pleiotropic effect, is also perceived as an important factor in the regulation of reproductive processes and pregnancy maintenance. Previous studies confirmed its involvement in the control of porcine pituitary and ovary function. In this study, we hypothesized that VIS may affect the global transcriptome of luteal cells and thus regulate the functioning of the ovaries. Illumina's NovaSeq 6000 RNA sequencing was performed to investigate the differentially expressed genes (DEGs) and long non-coding RNAs (DELs) as well as the occurrence of differential alternative splicing events (DASs) in the porcine luteal cells exposed to VIS (100 ng/mL) during the implantation period. The obtained results revealed 170 DEGs (99 up- and 71 downregulated) assigned to 45 functional annotations. Moreover, we revealed 40 DELs, of which 3 were known and 37 were described for the first time. We identified 169 DASs events. The obtained results confirmed a significant effect of VIS on the transcriptome and spliceosome of luteal cells, including the genes involved in the processes crucial for successful implantation and pregnancy maintenance as angiogenesis, steroidogenesis, inflammation, cell development, migration, and proliferation.

Chemerin affects the expression of angiogenesis-related factors in the porcine endometrium during early pregnancy and the oestrous cycle: an in vitro study.

CONTEXT: The appropriate course of angiogenesis in the endometrium is crucial for pregnancy establishment and maintenance. Very little is known about the factors linking vessel formation and immune system functioning. AIMS: We hypothesised that chemerin, an adipokine known for its involvement in the regulation of energy balance and immunological functions, may act as a potent regulator of endometrial angiogenesis during early pregnancy in pigs. METHODS: Porcine endometrial tissue explants were obtained from pregnant pigs on days 10-11, 12-13, 15-16 and 27-28, and on days 10-12 of the oestrous cycle. The explants were in vitro cultured for 24h in the presence of chemerin (100, 200ng/mL) or in medium alone (control). We evaluated the in vitro effect of chemerin on the secretion of vascular endothelial growth factors A-D (VEGF-A-D), placental growth factor (PlGF), basic fibroblast growth factor (bFGF) and angiopoietin 1 and 2 (ANG-1, ANG-2) with the ELISA method. The protein abundance of angiogenesis-related factor receptors, VEGF receptors 1-3 (VEGFR1-3), FGF receptors 1 and 2 (FGFR1-2) and ANG receptor (TIE2) was evaluated with the Western blot (WB) method. We also analysed the influence of chemerin on the phosphorylation of AMPK using WB. KEY RESULTS: We found that in the studied endometrial samples, chemerin up-regulated the secretion of VEGF-A, VEGF-B and PlGF, and protein expression of VEGFR3. The adipokine caused a decrease in VEGF-C, VEGF-D and ANG-1 release. Chemerin effect on bFGF and ANG-2 secretion, and protein content of VEGFR1, VEGFR2, FGFR1, FGFR2 and TIE2 were dependent on the stage of pregnancy. Chemerin was found to down-regulate AMPK phosphorylation. CONCLUSIONS: The obtained in vitro results suggest that chemerin could be an important factor in the early pregnant uterus by its influence on angiogenic factors' secretion and signalling. IMPLICATIONS: The obtained results on the role of chemerin in the process of endometrial angiogenesis may, in the long term perspective, contribute to the elaboration of more effective methods of modifying reproductive processes and maintaining energy homeostasis in farm animals.

Adaptation of the Porcine Pituitary Transcriptome, Spliceosome and Editome during Early Pregnancy.

The physiological mechanisms of the porcine reproduction are relatively well-known. However, transcriptomic changes and the mechanisms accompanying transcription and translation processes in various reproductive organs, as well as their dependence on hormonal status, are still poorly understood. The aim of this study was to gain a principal understanding of alterations within the transcriptome, spliceosome and editome occurring in the pituitary of the domestic pig (Sus scrofa domestica L.), which controls basic physiological processes in the reproductive system. In this investigation, we performed extensive analyses of data obtained by high-throughput sequencing of RNA from the gilts' pituitary anterior lobes during embryo implantation and the mid-luteal phase of the estrous cycle. During analyses, we obtained detailed information on expression changes of 147 genes and 43 long noncoding RNAs, observed 784 alternative splicing events and also found the occurrence of 8729 allele-specific expression sites and 122 RNA editing events. The expression profiles of the selected 16 phenomena were confirmed by PCR or qPCR techniques. As a final result of functional meta-analysis, we acquired knowledge regarding intracellular pathways that induce changes in the processes accompanying transcription and translation regulation, which may induce modifications in the secretory activity of the porcine adenohypophyseal cells.

Chemerin effect on transcriptome of the porcine endometrium during implantation determined by RNA-sequencing†.

It is well known that the body's metabolism and reproduction are closely related. Chemerin (CHEM) is one of many biologically active proteins secreted by the adipose tissue involved in the regulation of the energy homeostasis of the organism. In the present study, RNA-sequencing was performed to investigate the differentially expressed genes (DEGs), long non-coding RNAs (lncRNAs), and alternatively spliced (AS) transcripts in the cultured porcine endometrium exposed to chemerin for 24 hours (CHEM; 400 ng/mL) collected during the implantation period (15-16 days of gestation). High-throughput sequencing of transcriptomes was performed on the Illumina NovaSeq 6000 platform (Illumina, USA). In the current study, among all 130 DEGs, 58 were upregulated and 72 were downregulated in the CHEM-treated group. DEGs were assigned to 73 functional annotations. Twelve identified lncRNAs indicated a difference in the expression profile after CHEM administration. Additionally, we detected 386 differentially AS events encompassed 274 protein-coding genes and 2 lncRNAs. All AS events were divided into five alternative splicing types: alternative 3' splice site (A3SS), 5' splice site (A5SS), mutually exclusive exons (MXE), retention intron (RI), and skipping exon (SE). Within all AS events, we identified 42 A3SS, 43 A5SS, 53 MXE, 9 RI, and 239 SE. In summary, CHEM affects the transcriptomic profile of the porcine endometrium, controlling the expression of numerous genes, including those involved in the cell migration and adhesion, angiogenesis, inflammation, and steroidogenesis. It can be assumed that CHEM may be an important factor for a proper course of gestation and embryo development.

Chemerin Affects P4 and E2 Synthesis in the Porcine Endometrium during Early Pregnancy.

Chemerin, belonging to the adipokine family, exhibits pleiotropic activity. We hypothesised that the adipokine could be involved in the regulation of steroidogenesis in the porcine endometrium. Thus, the aim of this study was to determine the effect of chemerin on the key steroidogenic enzyme proteins' abundance (Western blot), as well as on P4 and E2 secretion (radioimmunoassay) by the porcine endometrium during early pregnancy and the mid-luteal phase of the oestrous cycle. Moreover, we investigated the hormone impact on Erk and Akt signalling pathway activation (Western blot). Chemerin stimulated E2 production on days 10 to 11 of pregnancy. On days 10 to 11 and 15 to 16 of gestation, and on days 10 to 11 of the cycle, chemerin enhanced the expression of StAR and all steroidogenic enzyme proteins. On days 12 to 13 of pregnancy, chemerin decreased StAR and most of the steroidogenic enzyme proteins' abundance, whereas the P450C17 abundance was increased. On days 27 to 28 of pregnancy, chemerin increased StAR and P450C17 protein contents and decreased 3ßHSD protein amounts. It was noted that the adipokine inhibited Erk1/2 and stimulated Akt phosphorylation. The obtained results indicate that chemerin affected P4 and E2 synthesis through the Erk1/2 and Akt signalling pathways.

Chemerin as a modulator of angiogenesis and apoptosis processes in the corpus luteum of pigs: an in vitro study†.

The corpus luteum (CL) undergoes rapid changes, and its functional capabilities are influenced by processes such as angiogenesis and apoptosis. According to the literature, chemerin-a protein that participates in the regulation of energy homeostasis and the immune response, may also affect angiogenesis and apoptosis. Therefore, the aim of this study was to investigate the in vitro effect of chemerin on angiogenesis and apoptosis in porcine luteal cells (Lc) during specific phases related to CL physiology. Luteal cells were harvested from gilts during the early-, mid-, and late-luteal phases of the estrous cycle. The cells were preincubated for 48 h and incubated for 24 h with chemerin or a serum-free medium (controls). The abundance of angiogenesis- and apoptosis-related proteins was determined by enzyme-linked immunosorbent assay (ELISA) in spent culture media, or by ELISA and Western blot in protein extracts. The current study demonstrated that chemerin stimulates the production of vascular endothelial growth factor A (VEGF-A) and basic fibroblast growth factor (bFGF) by porcine Lc and increases the protein abundance of angiogenic factors' receptors (VEGFR1, VEGFR2, VEGFR3, FGFR1, FGFR2) in these cells. The study also revealed that chemerin exerts a modulatory effect (stimulatory/inhibitory, depending on the phase of the cycle) on the protein abundance of first apoptosis signal (Fas), Fas ligand, B-cell lymphoma 2, and caspase-3 in porcine Lc. These results imply that chemerin may affect angiogenesis and apoptosis processes in the porcine CL, as evidenced by its modulatory effect of chemerin on the protein abundance of crucial angiogenesis- and apoptosis-related factors, observed in an in vitro study of porcine Lc.

Orexin B affects the transcriptome of incubated in vitro porcine endometrial explants from the early-implantation period.

This study determined the effect of orexin B (OXB) on the porcine endometrial transcriptome during the embryo attachment phase. Microarray analyses of gene ontology (GO), biological pathways, networks and differentially expressed genes (DEG) were performed. Orexin B influenced the expression of 887 genes (fold change > 1.2; p < .05): 620 genes were up-regulated, and 267 were down-regulated. The analysis of the relationship between DEG revealed that OXB interacts with genes linked with processes such as cell hormone binding, regulation of hormone levels, lipid transport, steroid metabolic processes, the apoptotic signalling pathway and the acute inflammatory response, which are pivotal for reproductive success. Orexin B played a bivalent role in the early-pregnant uterus by limiting the pregnancy outcome, promoting embryo development, suppressing the immune system and, consequently, preventing embryo rejection. These findings suggest that OXB could be responsible for the proper course of gestation by adapting litter size to the metabolic status of the maternal organism.

Expression of chemerin and its receptors in the ovaries of prepubertal and mature gilts.

Recent studies have demonstrated that chemerin participates in the regulation of female reproductive function at the level of the ovaries. Due to the lack of data concerning the presence of the chemerin system (chemerin and its receptors: CMKLR1, GPR1, CCRL2) in the ovaries of pigs, one of the most economically important livestock species, the aim of this study was to investigate the expression and localization of chemerin and its receptors in the ovaries of prepubertal and mature gilts. We also aimed to examine the concentrations of chemerin in the follicular fluid of prepubertal and mature animals. In the present study, we have demonstrated the expression patterns of chemerin system components in the porcine follicles of different sizes of prepubertal and mature animals, as well as in corpora lutea of mature gilts during the estrous cycle and early pregnancy. The obtained results suggest that the expression of chemerin system components is influenced by the reproductive stage, cell type, and the hormonal status of gilts (the estrous cycle/pregnancy). We have also presented the localization of the chemerin system components in various ovarian structures, and also showed changes in the concentration of chemerin in the follicular fluid of pigs. The presented findings not only confirm that chemerin is produced locally in the porcine ovary but they also demonstrate that chemerin directly affects ovarian cells, as confirmed by the presence of chemerin receptors in all ovarian structures. Therefore, chemerin appears to be an important intra-ovarian factor that could regulate ovary function in pigs.

Sex- and season-dependent differences in the expression of adiponectin and adiponectin receptors (AdipoR1 and AdipoR2) in the hypothalamic-pituitary-adrenal axis of the Eurasian beaver (Castor fiber L.).

Adiponectin, a product of the Adipoq gene, is an adipocyte-derived protein hormone of the cytokine family and the most abundantly expressed adipokine. Adiponectin and its receptors AdipoR1 and AdipoR2 (collectively referred to as the adiponectin system) are widely expressed in the central nervous system and other tissues, which suggests that this hormone has pleiotropic effects. Adiponectin could also play a role in the modulation of the hypothalamic-pituitaryadrenal (HPA) hormonal regulatory axis. There is a general scarcity of data on the adiponectin system in wild animals where annual changes in reproductive activity are linked with fluctuations in the activity of the HPA axis. The Eurasian beaver (Castor fiber L.) could be an interesting and suitable model for investigating the above processes. We hypothesized that the expression of the adiponectin system in the tissues of the beaver HPA axis is sex- and season-dependent. The study was performed on adult animals harvested during three different stages of reproductive activity: April ('breeding'), July ('post-breeding') and November ('pre-breeding'). The expression of the adiponectin system was confirmed in all branches (mediobasal hypothalamus, pituitary, adrenal cortex) of the HPA axis in both sexes and during all periods of reproductive activity. The expression of Adipoq, AdipoR1 and AdipoR2 was generally dependent on sex and the period of the reproductive season. The expression of adiponectin system genes was particularly pronounced in the adrenal cortex. These findings suggest that the adiponectin system in the Eurasian beaver could link reproductive processes with stress responses and energy metabolism.

Transcriptome, Spliceosome and Editome Expression Patterns of the Porcine Endometrium in Response to a Single Subclinical Dose of Salmonella Enteritidis Lipopolysaccharide.

Endometrial infections at a young age can lead to fertility issues in adulthood. Bacterial endotoxins, such as lipopolysaccharide (LPS), can participate in long-term molecular changes even at low concentrations. Lipopolysaccharide plays a crucial role in the progression of septic shock, inflammation and auto-immune diseases. The aim of this study was to describe transcriptomic modulations in the porcine endometrium, induced in vivo by a single subclinical dose of LPS from Salmonella Enteritidis. which did not produce clinical symptoms of toxicity. The RNA-seq methodology was applied to reveal 456 differentially expressed regions, including 375 genes, four long noncoding RNAs, and 77 other unclassified transcripts. Two independent methods confirmed 118 alternatively spliced genes that participate i.a., in the formation of the MHC-I complex and the adaptive immune response. Single nucleotide variant-calling algorithms supported the identification of 3730 allele-specific expression variants and 57 canonical A-to-I RNA editing sites. The results demonstrated that the differential expression of genes involved in inflammation, immune response, angiogenesis and endometrial development may be maintained for up to 7 days after exposure to LPS. RNA editing sites and long noncoding RNAs (lncRNAs) play an important role in transcriptional regulatory machinery in the porcine endometrium in response to LPS administration.

The In Vitro Effect of Prostaglandin E2 and F2α on the Chemerin System in the Porcine Endometrium during Gestation.

Chemerin belongs to the group of adipocyte-derived hormones known as adipokines, which are responsible mainly for the control of energy homeostasis. Adipokine exerts its influence through three receptors: Chemokine-like receptor 1 (CMKLR1), G protein-coupled receptor 1 (GPR1), and C-C motif chemokine receptor-like 2 (CCRL2). A growing body of evidence indicates that chemerin participates in the regulation of the female reproductive system. According to the literature, the expression of chemerin and its receptors in reproductive structures depends on the local hormonal milieu. The aim of this study was to investigate the in vitro effect of prostaglandins E2 (PGE2) and F2α (PGF2α) on chemerin and chemerin receptor (chemerin system) mRNAs (qPCR) and proteins (ELISA, Western blotting) in endometrial tissue explants collected from early-pregnant gilts. Both PGE2 and PGF2α significantly influenced the expression of the chemerin gene, hormone secretion, and the expression of chemerin receptor genes and proteins. The influence of both prostaglandins on the expression of the chemerin system varied between different stages of gestation. This is the first study to describe the modulatory effect of PGE2 and PGF2α on the expression of the chemerin system in the porcine uterus during early gestation.

Transcriptomic Analysis of Porcine Endometrium during Implantation after In Vitro Stimulation by Adiponectin.

Comprehensive understanding of the regulatory mechanism of the implantation process in pigs is crucial for reproductive success. The endometrium plays an important role in regulating the establishment and maintenance of gestation. The goal of the current study was to determine the effect of adiponectin on the global expression pattern of genes and relationships among differentially expressed genes (DE-genes) in the porcine endometrium during implantation using microarrays. Diverse transcriptome analyses including gene ontology (GO), biological pathway, networks, and DE-gene analyses were performed. Adiponectin altered the expression of 1286 genes with fold-change (FC) values greater than 1.2 (p < 0.05). The expression of 560 genes were upregulated and 726 downregulated in the endometrium treated with adiponectin. Thirteen genes were selected for real-time PCR validation of differential expression based on a known role in metabolism, steroid and prostaglandin synthesis, interleukin and growth factor action, and embryo implantation. Functional analysis of the relationship between DE-genes indicated that adiponectin interacts with genes that are involved in the processes of cell proliferation, programmed cell death, steroid and prostaglandin synthesis/metabolism, cytokine production, and cell adhesion that are critical for reproductive success. The presented results suggest that adiponectin signalling may play a key role in the implantation of pig.

Expression of Chemerin and Its Receptors in the Porcine Hypothalamus and Plasma Chemerin Levels during the Oestrous Cycle and Early Pregnancy.

Chemerin (CHEM) may act as an important link integrating energy homeostasis and reproductive functions of females, and its actions are mediated by three receptors: chemokine-like receptor 1 (CMKLR1), G protein-coupled receptor 1 (GPR1), and C-C motif chemokine receptor-like 2 (CCRL2). The aim of the current study was to compare the expression of CHEM and its receptor (CHEM system) mRNAs (quantitative real-time PCR) and proteins (Western blotting and fluorescent immunohistochemistry) in the selected areas of the porcine hypothalamus responsible for gonadotropin-releasing hormone production and secretion: the mediobasal hypothalamus, preoptic area and stalk median eminence during the oestrous cycle and early pregnancy. Moreover, plasma CHEM concentrations were determined using ELISA. The expression of CHEM system has been demonstrated in the porcine hypothalamus throughout the luteal phase and follicular phase of the oestrous cycle, and during early pregnancy from days 10 to 28. Plasma CHEM levels and concentrations of transcripts and proteins of CHEM system components in the hypothalamus fluctuated throughout pregnancy and the oestrous cycle. Our study was the first experiment to demonstrate the presence of CHEM system mRNAs and proteins in the porcine hypothalamus and the correlations between the expression levels and physiological hormonal milieu related to the oestrous cycle and early pregnancy.

Modulation of adiponectin system expression in the porcine uterus during early pregnancy by prostaglandin E2 and F2α.

Studies have demonstrated that adiponectin could be a link between reproductive functions and energy metabolism in animals. The aim of the present study was to investigate the effects of prostaglandin (PG) E2 and PGF2α (10, 50, 100, 250 and 500ngmL-1) on the expression and secretion of adiponectin and its receptor genes and proteins by cultured in vitro porcine endometrial and myometrial tissues on Days 10-28 of pregnancy and Days 10-11 of the oestrous cycle. The gene expression was analysed using the real-time PCR method. Adiponectin protein secretion was determined by ELISA, whereas the receptors proteins content was defined using Western Blot analysis. Both PGE2 and PGF2α modulated the expression of adiponectin system genes and proteins in the uterus during early pregnancy. PGE2 and PGF2α had similar effects on the adiponectin system, which differed between the stages of gestation and between pregnancy and the oestrous cycle. On Days 10-11 of gestation, PGE2 and PGF2α generally increased adiponectin secretion by endometrial and myometrial tissues. Both PGs decreased levels of endometrial adiponectin receptor type 1 (AdipoR1), whereas only PGF2α decreased myometrial levels of AdipoR1. Both PGs increased myometrial adiponectin receptor type 2 (AdipoR2) levels. On Days 12-13 of gestation, PGE2 decreased AdipoR1 concentrations in both tissues and AdipoR2 levels in the endometrium. PGF2α decreased myometrial concentrations of both receptors. On Days 15-16 of gestation, both PGE2 and PGF2α increased concentrations of AdipoR1 and AdipoR2 in the endometrium and myometrium. PGE2 stimulated the secretion of adiponectin in the endometrium, but not in the myometrium. On Days 27-28 of pregnancy, both PGE2 and PGF2α inhibited the expression of AdipoR1 and AdipoR2 in endometrial and myometrial tissues and decreased the secretion of endometrial adiponectin. Both PGE2 and PGF2α had tissue-specific and dose-dependent effects on the adiponectin system.

The influence of adiponectin on the transcriptomic profile of porcine luteal cells.

Reproductive functions are closely related to nutritional status. Recent studies suggest that adiponectin may be a hormonal link between them. Adiponectin is an adipocytokine, abundantly expressed in adipose tissues. It plays a dominant role in lipid and carbohydrate metabolism by stimulating fatty acid oxidation, decreasing plasma triglycerides, and increasing cells' sensitivity to insulin and has direct antiatherosclerotic effects. The hormone is also postulated to play a modulatory role in the regulation of the reproductive system. The aim of this study was to identify differentially expressed genes (DE-genes) in response to adiponectin treatment of porcine luteal ovarian cells. The global expression of genes in the porcine ovary was investigated using the Porcine (V2) Two-color gene expression microarray, 4 × 44 (Agilent, USA). Analysis of the microarray data showed that 701 genes were differentially expressed and 389 genes showed a fold change greater than 1.2 (p < 0.05). Among this number, 186 genes were up-regulated and 203 were down-regulated. The list of DE-genes was used for gene ontology analyses. The biological process list was generated from up-regulated and down-regulated DE-genes. We found that up-regulated products of DE-genes take part in 30 biological processes and down-regulated products in 9. Analysis of the interaction network among DE-genes showed that adiponectin interacts with genes involved in important processes in luteal cells. These results provide a basis for future work describing the detailed interactions and relationships explaining local regulation of adiponectin actions in the ovary of pigs.

Adiponectin expression in the porcine pituitary during the estrous cycle and its effect on LH and FSH secretion.

Female reproductive success is closely associated with nutritional status and energy balance. In this context, adiponectin appears to be a key hormone connecting reproductive system function and metabolism regulation. It is hypothesized that adiponectin expression in the pituitary depends on the phase of the estrous cycle. The effect of adiponectin on luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion is also postulated. Changes in the adiponectin gene and protein expression in the porcine anterior (AP) and posterior (NP) pituitaries as well as the effect of in vitro administration of adiponectin on basal and gonadotropin-releasing hormone (GnRH)- and/or insulin-stimulated LH and FSH secretion were investigated on days 2-3, 10-12, 14-16, and 17-19 of the estrous cycle. Adiponectin gene was more pronounced on days 2-3 in AP but on days 10-12 in NP. Protein concentration in AP was the highest on days 10-12 and in NP on days 10-12 and 17-19 of the cycle. In vitro, adiponectin did not affect basal LH secretion but increased FSH release by AP cells. Adiponectin administration affected GnRH- and/or insulin-induced LH and FSH output in a manner dependent on the phase of the estrous cycle. In this study we indicated for the first time adiponectin expression in the porcine AP and NP that was dependent on the phase of the estrous cycle. In vitro studies indicated that adiponectin may affect gonadotropin secretion. The above suggests that the studied adipokine may influence female reproductive functions via its effect on LH and FSH secretion by gonadotrophs, but the cellular mechanism of its action remains unknown.

Expression of adiponectin receptors 1 and 2 in the ovary and concentration of plasma adiponectin during the oestrous cycle of the pig.

The aim of this study was to compare the expression levels of adiponectin receptor 1 and adiponectin receptor 2 mRNAs and proteins in porcine ovaries during four stages (days 2 to 3, 10 to 12, 14 to 16, 17 to 19) of the oestrous cycle and to measure adiponectin plasma concentrations during the same phases of the cycle. Higher mRNA expression of adiponectin receptor 1 was detected in porcine granulosa cells than in corpora lutea and theca cells (P < 0.01). In contrast, higher gene expression of adiponectin receptor 2 occurred in newly developed and mature corpora lutea (P < 0.01). The adiponectin receptor 1 protein content was the highest in corpora lutea isolated on days 2 to 3 of the cycle and was the lowest in theca interna cells (P < 0.01). The profile of adiponectin receptor 2 protein was similar to that of adiponectin receptor 1. Adiponectin plasma concentrations were significantly higher throughout the luteal phase than in the follicular phase (P < 0.01). In conclusion, the presence of adiponectin receptor 1 and adiponectin receptor 2 mRNAs and proteins in the porcine ovary suggests that adiponectin may directly affect ovarian functions through its own specific receptors. The expression of both receptors and adiponectin plasma concentration were dependent on hormonal status related to the stage of the cycle.