Identification of a novel apolipoprotein, ApoN, in ovarian follicular fluid

Tandem mass tag-based proteomic analysis of granulosa and theca interna cells of the porcine ovarian follicle following in vitro treatment with vitamin D3 and insulin alone or in combination

This study was performed to investigate the proteomic basis underlying the interaction between vitamin D3 (VD) and insulin (I) within ovarian follicle using the pig as a model. Porcine antral follicles were incubated in vitro for 12 h with VD alone and I alone or in combination (VD + I) or with no treatment as the control (C). In total, 7690 and 7467 proteins were identified in the granulosa and theca interna compartments, respectively. Comparative proteomic analysis revealed 97 differentially abundant proteins (DAPs) within the granulosa layer and 11 DAPs within the theca interna layer. In the granulosa compartment, VD affected proteome leading to the promotion of cell proliferation, whereas I influenced mainly proteins related to cellular adhesion. The VD + I treatment induced granulosa cell proliferation probably via the DAPs involved in DNA synthesis and the cell cycle regulation. In the theca interna layer, VD alone or in co-treatment with I affected DAPs associated with cholesterol transport and lipid and steroid metabolic processes that was further confirmed by diminished lipid droplet accumulation. SIGNIFICANCE: The application of quantitative proteomics demonstrated for the first time the complexity of VD and I interactions in porcine ovarian follicle, providing a framework for understanding the molecular mechanisms underlying their cross-talk. Although identified DAPs were related to crucial ovarian processes, including the granulosa cell proliferation and cholesterol transport in the theca interna layer, novel molecular pathways underlying these processes have been proposed. The identified unique proteins may serve as indicators of VD and I interactions in both follicle layers, and could be useful biomarkers of ovarian pathologies characterized by impaired VD and I levels, such as polycystic ovary syndrome.

Evaluation of the molecular response of corpora lutea to manganese-amino acid complex supplementation in gilts

Porcine pregnancy establishment and maintenance are dependent on the formation of functional corpora lutea (CL). Manganese (Mn) is critical for CL function as it is a cofactor for Mn superoxide dismutase and enzymes involved in cholesterol synthesis. Previously, we have shown that luteal Mn content increased and luteal progesterone (P₄) concentration decreased in the CL of gilts fed diets supplemented with an Mn–amino acid complex (Availa-Mn; Zinpro Corporation) compared with controls fed Mn sulfate. Importantly, serum P₄ increased from 0 (estrus onset) to 12 d post estrus (dpe), as expected, but P₄ abundance in circulation was not affected by dietary Mn source (P = 0.15). We hypothesized that a more bioavailable Mn source (which results in increased luteal Mn content) would alter the luteal proteome and abundance of mRNA associated with steroid biogenesis during the mid-luteal phase of the estrous cycle. Postpubertal gilts (n = 32) were assigned to one of the four gestation diets. The control diet (CON) contained 20 ppm of supplemental Mn in the form of Mn sulfate. Three additional diets included 20 (TRT1), 40 (TRT2), or 60 (TRT3) ppm of supplemental Mn in the form of a Mn–amino acid complex instead of Mn sulfate. Dietary treatment began at estrus synchronization (approximately 20 d before estrus) and continued through 12 dpe when gilts were euthanized and tissues were collected. Protein and total RNA extracts from the CL were used for proteomic analysis via label-free liquid chromatography with tandem mass spectrometry to assess global protein abundance and quantitative real-time polymerase chain reaction (qRT-PCR) to assess specific mRNA abundance, respectively. Compared with CON, 188, 382, and 401 proteins were differentially abundant (P < 0.10) in TRT1, TRT2, and TRT3, respectively. Gene Ontology enrichment software revealed that proteins involved in P₄ signaling and cholesterol synthesis were downregulated in CL of gilts fed Mn–amino acid complex compared with controls. Quantitative RT-PCR showed that relative transcript abundance of genes encoding steroidogenic enzymes (CYP11A1 and StAR) in CL tissue was decreased in gilts from TRT2 compared with CON (P = 0.02), but TRT1 and TRT3 were not affected (P ≥ 0.30). Collectively, these data support our hypothesis that a more bioavailable dietary Mn source may influence luteal function by altering the abundance of protein and mRNA involved in steroidogenesis.

A genome-wide scan for selection signatures in Yorkshire and Landrace pigs based on sequencing data

Pigs have experienced dramatic selection due to domestication, which has led to many different phenotypes when compared to their wild counterparts, especially in the last several decades. Currently, genome-wide scans in both cattle and humans showing positive selection footprints have been investigated. However, few studies have focused on porcine selection footprints, particularly on a genome-wide scale. Surveying for selection footprints across porcine genomes can be quite valuable for revealing the genetic mechanisms of phenotypic diversity. Here, we employed a medium sequencing depth (5–20x/site per individual, on average) approach called genotyping by genome reducing and sequencing (GGRS) to detect genome-wide selection signatures of two domestic pig breeds (Yorkshire and Landrace) that have been under intensive selection for traits of muscle development, growth and behavior. The relative extended haplotype homozygosity test, which identifies selection signatures by measuring the characteristics of haplotypes’ frequency distribution within a single population, was also applied to identify potential positively selected regions. As a result, signatures of positive selection were found in each breed. However, most selection signatures were population specific and related to genomic regions containing genes for biological categories including brain development, metabolism, growth and olfaction. Furthermore, the result of the gene set enrichment analysis indicated that selected regions of the two breeds presented a different over-representation of genes in the Gene Ontology annotations and Kyoto Encyclopedia of Genes and Genomes pathways. Our results revealed a genome-wide map of selection footprints in pigs and may help us better understand the mechanisms of selection in pig breeding.

Molecular identification of lyso-glycerophosphocholines as endogenous immunosuppressives in bovine and rat gonadal fluids

The ability of the gametes to escape detection by the immune system is vital to successful human reproduction. Furthermore, the observed capacity of the testis in some species to support tissue grafts without rejection (immunological privilege) indicates that spermatogenic cells are protected by local immunoregulatory mechanisms. One of these mechanisms involves targeting T cells for inactivation and destruction within the testicular environment. Although the fluids of the testis and ovary surrounding the developing gametes contain soluble factors that inhibit T cells, the identity of the molecule(s) responsible for this activity has been unknown. Using a specific T-cell proliferation assay to monitor bioactivity, these molecules were purified from bovine ovarian follicular fluid by methanol extraction and sequential reverse-phase HPLC (RP-HPLC). All purified active fractions coincided with the elution position on RP-HPLC of several small molecules ranging in size from 496 to 522 Da. The same molecules were localized to the immunosuppressive fractions of rat testicular interstitial fluid. The active molecules were identified, using capillary electrophoresis electrospray ionization mass spectroscopy, as lyso-glycerophosphocholines (lyso-GPCs), namely, 1-palmitoyl-sn-glycero-3-phosphocholine, 1-oleoyl-sn-glycero-3-phosphocholine, a 18:2a/lyso-GPC (putatively, 1-linoleoyl-sn-glycero-3-phosphocholine), and a 20:4a/lyso-GPC (putatively, 1-arachidonyl-sn-glycero-3-phosphocholine). Comparison of the bioactivity and mass spectroscopy profiles of two of the purified molecules with their synthetic standards confirmed the identification. These molecules inhibit T-cell proliferation in response to activation and induce apoptosis of these cells in a time- and dose-dependent manner. The emergence of gonadal lyso-GPCs as potential regulators of critical immune events opens up new avenues of inquiry into the origins of autoimmune infertility and more generally into mechanisms of peripheral immunoregulation and the development of novel immunosuppressives.

ApoO, a novel apolipoprotein, is an original glycoprotein up-regulated by diabetes in human heart

Obesity is an independent risk factor for cardiac failure. Obesity promotes excessive deposition of fat in adipose and nonadipose tissues. Intramyocardial lipid overload is a relatively common finding in nonischemic heart failure, especially in obese and diabetic patients, and promotes lipoapoptosis that contributes to the alteration of cardiac function. Lipoprotein production has been proposed as a heart-protective mechanism through the unloading of surplus cellular lipids. We previously analyzed the heart transcriptome in a dog nutritional model of obesity, and we identified a new apolipoprotein, regulated by obesity in heart, which is the subject of this study. We detected this new protein in the following lipoproteins: high density lipoprotein, low density lipoprotein, and very low density lipoprotein. We designated it apolipoprotein O. Apolipoprotein O is a 198-amino acid protein that contains a 23-amino acidlong signal peptide. The apolipoprotein O gene is expressed in a set of human tissues. Confocal immunofluorescence microscopy colocalized apolipoprotein O and perilipins, a cellular marker of the lipid droplet. Chondroitinase ABC deglycosylation analysis or cell incubation with p-nitrophenyl-beta-d-xyloside indicated that apolipoprotein O belongs to the proteoglycan family. Naringenin or CP-346086 treatments indicated that apolipoprotein O secretion requires microsomal triglyceride transfer protein activity. Apolipoprotein O gene expression is up-regulated in the human diabetic heart. Apolipoprotein O promoted cholesterol efflux from macrophage cells. To our knowledge, apolipoprotein O is the first chondroitin sulfate chain containing apolipoprotein. Apolipoprotein O may be involved in myocardium-protective mechanisms against lipid accumulation, or it may have specific properties mediated by its unique glycosylation pattern.