The influence of progesterone on bovine uterine fluid energy, nucleotide, vitamin, cofactor, peptide, and xenobiotic composition during the conceptus elongation-initiation window

Abstract

Conceptus elongation coincides with one of the periods of greatest pregnancy loss in cattle and is characterized by rapid trophectoderm expansion, commencing ~ Day 13 of pregnancy, i.e. before maternal pregnancy recognition. The process has yet to be recapitulated in vitro and does not occur in the absence of uterine gland secretions in vivo. Moreover, conceptus elongation rates are positively correlated to systemic progesterone in maternal circulation. It is, therefore, a maternally-driven and progesterone-correlated developmental phenomenon. This study aimed to comprehensively characterize the biochemical composition of the uterine luminal fluid on Days 12-14 -the elongationinitiation window -in heifers with normal vs. high progesterone, to identify molecules potentially involved in conceptus elongation initiation. Specifically, nucleotide, vitamin, cofactor, xenobiotic, peptide, and energy metabolite profiles of uterine luminal fluid were examined. A total of 59 metabolites were identified, of which 6 and 3 displayed a respective progesterone and day effect, whereas 16 exhibited a day by progesterone interaction, of which 8 were nucleotide metabolites. Corresponding pathway enrichment analysis revealed that pyridoxal, ascorbate, tricarboxylic acid, purine, and pyrimidine metabolism are of likely importance to to conceptus elongation initiation. Moreover, progesterone reduced total metabolite abundance on Day 12 and may alter the uterine microbiome.One-third of viable bovine blastocysts are estimated to fail to elongate 1-3 , rendering them unable to secrete sufficient interferon tau (IFNτ), the pregnancy recognition signal 4-7 , resulting in pregnancy failure on account of a lack of uterine oxytocin receptor upregulation for luteolysis prevention 6,8 . Any insights into the mechanisms driving conceptus elongation, therefore, offer scope to improve ruminant fertility.Conceptus elongation is a maternally-driven and progesterone-correlated developmental phenomenon 9 ; it can neither be recapitulated in vitro 10 nor can occur in vivo in uterine gland absence 11 . Moreover, the rate of conceptus elongation is positively related to maternally circulating progesterone (P4) 12,13 , though this relationship is indirect -in vitro derived embryos transferred on Day 7 into heifers previously (Days 3-6) supplemented with P4 exhibit advanced elongation on Day 14, regardless of identical systemic P4 during in utero embryo development 14 .Whilst the amino acid 15-20 , carbohydrate 20-23 and lipid 2,24,25 composition of bovine uterine luminal fluid (ULF) has been interrogated to some degree, analyses extending to additional biochemicals (e.g. nucleotide, cofactor and vitamin, xenobiotic, peptide, and energy metabolites) have received very little attention, if any, despite their known importance to, and/or potential impact on, central cellular processes.Nucleotides serve a variety of functions such as in substrate activation and anabolism, in addition to being necessary for DNA replication and RNA production to support protein ...

Aspects of embryo-maternal communication in establishment of pregnancy in cattle

“…These findings combined, coupled with previous data on the enzymatic profile of bovine ULF (Muñoz et al, 2012;Forde et al, 2014), give rise to the hypothesis that conceptus elongation internally hinges on 5' adenosine monophosphate-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor gamma (PPARγ) activity, and is modulated by glucose, adenine, and adenosine mono-(AMP), di-(ADP), and tri-phosphate (AMP) influx (discussed in Simintiras et al, 2019d). Additional observations worth highlighting include: (i) that total ULF metabolite abundance ( Fig.…”

“…Thirdly, P4 supplementation amplified the total mean metabolite abundance on Day 14 (P ≤ 0.0001); however, just 19 metabolites (8.2% of total) were elevated (P ≤ 0.05) on Day 14 in high vs. normal P4 heifers, and are, therefore, largely responsible for raising the mean (Simintiras et al, 2019d). The biochemical properties of the these 'selectively' amplified 19 metabolites -including glucose (primary fuel source), trimethylamine-N-oxide (proteinstabilizing osmolyte), and phenol sulfate (relatively metabolically inert yet acidic molecule) -(i) support the notion that optimal conceptus elongation is contingent on biophysical and physicochemical, in addition to metabolic, cues, and (ii) contribute to the generation of our hypothesis pertinent to the molecular bases of conceptus elongation initiation, discussed below.…”

“…Given that conceptus elongation coincides with a period of significant bovine pregnancy loss, our aim was to achieve a better understanding of the biochemical landscape surrounding the peri-elongation conceptus. Over 5000 metabolites were screened for by highthroughput untargeted ultra-high-performance liquid chromatography tandem mass spectroscopy, with 233 consistently identified, clustering within 8 superpathways: amino acids, carbohydrates (Simintiras et al, 2019a), lipids (Simintiras et al, 2019b), cofactors, vitamins, nucleotides, peptides, energy substrates, and xenobiotics (Simintiras et al, 2019c). A global analysis of this dataset revealed three core 'strategies' likely utilised by the bovine endometrium to facilitate conceptus elongation, discussed below.…”

“…Firstly, indicative of the changing biochemical requirements of the conceptus around the initiation of elongation, a metabolic shift in the ULF of normal P4 heifers after Day 12 was observed (Simintiras et al, 2019d), to which fructose and mannitol/sorbitol were central. More specifically, only these two metabolites increased on Days 13 and 14 vs. 12 within the normal P4 group.…”

“…2C), or day by P4 interactions (Fig. 2D), and (ii) the identification of a plethora of microbiome-associated molecules in ULF, some of which were responsive to P4 (Simintiras et al, 2019c), highlights a need for further research into the influence of the uterine microbiome in uterine metabolism and maternal-embryo communication.…”