Study on comparative analysis of differential metabolites in Guanzhong dairy goat semen before and after freezing

Liquid chromatograph-mass spectrometry metabolomics uncovers potential biomarkers of semen cryo-injury in goats

OBJECTIVE

Semen cryopreservation acts a crucial role in enhancing breed improvement and conserving genetic resources. However, it often leads to decreased sperm activity and reduced pregnancy rates. Despite significant advancements in semen freezing techniques for goats, the precise factors and mechanisms causing cryo-injury remain unclear.

METHODS

In this study, we examined the motility characteristics of fresh semen versus frozen-thawed semen and investigated changes in the metabolite profiles of seminal plasma using liquid chromatograph-mass spectrometry.

RESULTS

A total of 364 differentially expressed metabolites (DEMs) were identified between fresh and frozen-thawed semen samples. Among these, 185 metabolites were significantly up-regulated, while 179 were down-regulated (p<0.05). The majority of these DEMs belonged to lipids and lipid-like molecules, as well as organic acids and derivatives. The Kyoto encyclopedia of genes and genomes indicated that these DEMs were primarily involved in pathways related to amino acid synthesis and metabolism. Additionally, metabolite set enrichment analysis underscored the critical role of amino acid synthesis and metabolic pathways in semen cryopreservation. Specific metabolites such as alanine, proline, phenylalanine, tryptophan, tyrosine, adenosine, citric acid, flavin adenine dinucleotide, and choline emerged as potential biomarkers for sperm cryo-injury in goats.

CONCLUSION

These findings provide valuable insights into enhancing the quality of semen cryopreservation in goats, contributing to improved breeding and genetic resource conservation efforts.

Integrated analyses of transcriptomes, metabolomes, and proteomes unveil the role of FoXO signaling axis in buck semen cryopreservation

Sperm cryopreservation is a complex process involving gene expression, protein synthesis, membrane stability, and metabolic adaptation. However, molecular alterations in sperm cryopreservation and the mechanisms defending against freezing damage remain poorly understood. This study investigates these changes and defense mechanisms using transcriptomics, proteomics, and metabolomics data. During sperm cryopreservation, the expression level of G protein subunit alpha i3 (GNAI3) was significantly downregulated in post-thaw sperm (P < 0.001), while matrix metallopeptidase 9 (MMP9) was upregulated compared to FS groups (P < 0.01). Additionally, interleukin 6 (IL6) expression in the CS group showed an approximate increase (P < 0.05), whereas ribosomal protein S27a (RPS27A) expression decreased markedly (P < 0.05). Other important molecules such as macrophage stimulating 1 receptor (MST1R), hypoxia-inducible factor 1 subunit alpha (HIF1A), fibroblast growth factor 8 (FGF8), CD9 molecule (CD9), peptidase D (PEPD) and terminal nucleotidyltransferase 5B (TENT5B) also exhibited significant changes in expression (P < 0.05). Moreover, the study revealed the regulatory roles of metabolites such as glucose and glutamic acid during sperm cryopreservation. The involvement of catalase (CAT) protein in antioxidant defense was also noted. The interactions among mRNAs, miRNAs, proteins, and metabolites highlight the critical role of the FoxO signaling pathway in modulating responses to freezing. Our study reveals the molecular regulatory mechanisms of sperm during cryopreservation, emphasizing the importance of the FoxO pathway and specific metabolites in response to cryo-injury. These findings provide deeper insights into the complexity of sperm cryobiology and offer practical guidance for optimizing sperm cryopreservation.

Abnormalities in mitochondrial energy metabolism induced by cryopreservation negatively affect goat sperm motility

The motility of sperm decreases following cryopreservation, which is closely associated with mitochondrial function. However, the alterations in mitochondrial metabolism after sperm freezing in goats remain unclear. This experiment aimed to investigate the impact of ultra-low temperature freezing on goat sperm's mitochondrial energy metabolism and its potential correlation with sperm motility. The results revealed that goat sperm exhibited mitochondrial vacuolization, reduced matrix density, and significantly decreased levels of high-membrane potential mitochondria and adenosine triphosphate content, accompanied by a substantial increase in reactive oxygen species levels, ultimately leading to a significant decline in sperm viability. Further investigations unveiled that energy-related differential metabolites (capric acid, creatine, and D-glucosamine-6-phosphate) and differential metabolites with antioxidant effects (saikosaponin A, probucol, and cholesterol sulfate) were significantly downregulated. In addition, the activity of key rate-limiting enzymes involved in very long-chain fatty acid biosynthesis and β-oxidation-specifically acetyl-CoA carboxylase, fatty acid synthase, and carnitine palmitoyltransferase I related to capric acid metabolism-was considerably reduced. Furthermore, supplementation of differential metabolite capric acid (500 μM) significantly enhanced the motility of frozen-thawed goat sperm. These findings indicated that the mitochondrial ultrastructure of goat sperm is damaged and energy metabolism becomes abnormal after cryopreservation, potentially affecting sperm viability. The addition of different metabolites such as capric acid to the freezing extender can alleviate the decrease in sperm motility induced by cryopreservation.

Exploring the full potential of sperm function with nanotechnology tools

Sperm quality is essential to guarantee the success of assisted reproduction. However, selecting high-quality sperm and maintaining it during (cryo)preservation for high efficiency remains challenging in livestock reproduction. A comprehensive understanding of sperm biology allows for better assessment of sperm quality, which could replace conventional sperm analyses used today to predict fertility with low accuracy. Omics approaches have revealed numerous biomarkers associated with various sperm phenotypic traits such as quality, survival during storage, freezability, and fertility. At the same time, nanotechnology is emerging as a new biotechnology with high potential for use in preparing sperm intended to improve reproduction in livestock. The unique physicochemical properties of nanoparticles make them exciting tools for targeting (e.g., sperm damage and sexing) and non-targeting bioapplications. Recent advances in sperm biology have led to the discovery of numerous biomarkers, making it possible to target specific subpopulations of spermatozoa within the ejaculate. In this review, we explore potential biomarkers associated with sperm phenotypes and highlight the benefits of combining these biomarkers with nanoparticles to further improve sperm preparation and technology.

Metabolites assay offers potential solution to improve the rooster semen cryopreservation

Semen cryopreservation represents a promising technology utilized for preserving high-quality chicken varieties in husbandry practices. However, the efficacy of this methodology is significantly impeded by the diminished quality of sperm. Metabolites, as the end products of metabolic reactions, serve as indicators of biological processes and offer insights into physiological conditions. In this study, we investigaged the sperm quality and alteration in metabolic profiles during the cryopreservation of Longyou Partridge Chicken semen. Following artificial semen collection, four groups of semen samples were established based on four points of the cryopreservation process (Ⅰ, fresh semen; Ⅱ, semen added extender and chilled at 4 °C for 30 min; Ⅲ, semen added cryoprotectants; Ⅳ, semen gradient freezed and stored in liquid nitrogen). Semen cryopreservation has a negative effect on the percentage of sperm in a straight-line trajectory (LIN), has no significant effect on total motile sperms (TM) or the proportion of sperm with typical morphology (NM). Metabolites were identified using LC-MS technique and analyses including Principal Component Analysis (PCA), Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA), Univariate statistical analysis, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database were employed to identify metabolites. A total of 2471 metabolites had been identified, with the majority of the list being made up of amino acids and their metabolites as well as benzene and substituted derivatives. Group II exhibits 882 metabolites with significantly elevated abundance relative to Group I, alongside 37 metabolites displaying decreased abundance. In Group III, 836 metabolites demonstrate notably augmented abundance compared to Group II, while 87 metabolites exhibit reduced abundance. Furthermore, Group IV showcases 513 metabolites with markedly heightened abundance in comparison to Group III, and 396 metabolites with decreased abundance. Specific metabolites such as 5-Hydroxylysine, Phosphocholine, and alpha-d-glucose-6-phosphate exhibited a progressive decline during the cryopreservation process, correlating with either dilution and chilling, cryoprotectant addition, or freezing. In conclusion, our investigation systematically examined the changes of seminal metabolome and sperm quality throughout the cryopreservation process of rooster semen.