Effects of Obesity and Diabetes on Sperm Cell Proteomics in Rats

In silico approach uncovers the shared genetic landscape of type 2 diabetes mellitus and asthenozoospermia

Asthenozoospermia (AZS) is one of the most common types of male infertility. Current evidence revealed that type 2 diabetes mellitus (T2DM) is closely associated with declining semen quality, especially for poor sperm motility. This study aimed to uncover the genetic interrelationships and important biomarkers between AZS and T2DM. Transcriptome data regarding AZS and T2DM were downloaded from the Gene Expression Omnibus (GEO) database. We performed GO and pathway analysis, and protein-protein interaction (PPI) network construction for T2DM-related differentially expressed genes (DMRGs). Moreover, we calculated receiver operator characteristic (ROC) curve and conducted external independent validation. Expression of hub DMRGs was assessed for patients using the qPCR method. MiRNA interaction and immune infiltration were subsequently characterized. A total of 554 overlapping DMRGs were identified between the AZS/T2DM and healthy groups. These overlapping DMRG participated in the DNA damage-, energy metabolism-, and immune-related biological pathways. Module function analysis discovered that the top three PPI modules were tightly correlated with DNA damage-related processes. After external validation in other independent datasets, two hub DMRGs (TBC1D12 and SCG5) were obtained. ROC analysis revealed that TBC1D12 and SCG5 had good diagnostic performance (area under the curve > 0.75). Immune infiltration profile showed that the level of T cell co-stimulation and CD8+_T_cells were negatively related to the hub DMRGs expression. Mirna interaction analysis showed 15 significant hub DMRGs-miRNA interactions. The qPCR results showed that expression of TBC1D12 and SCG5 were significantly different between sperm samples from diabetic patients with AZS and controls. The present study revealed molecular signatures and critical pathways between the AZS and T2DM, and identified two hub DMRGs of TBC1D12 and SCG5. The data would provide novel understandings of shared pathogenic mechanisms in T2DM-associated AZS.

Hyperglycemia adversely affects critical physiological events related to rat sperm capacitation

Hyperglycemia, the hallmark of diabetes mellitus (DM), is the main cause of DM-related systemic complications, including reproductive issues. Furthermore, the incidence of DM in males of reproductive ages is becoming an increasing concern, as the complexity of sperm capacitation (an essential process for fertilizing the egg) extends beyond conventional sperm parameters such as count, viability, and motility. Capacitation defects cause male infertility, and DM-related hyperglycemia may affect this process. We explore the effects of uncontrolled hyperglycemia on sperm using alloxan-induced hyperglycemic Wistar rats. In addition to assessing conventional sperm parameters, we also evaluated functional indicators, including hyperactivation (HA) with a pharmacological approach and assessed its effects with a computer-assisted sperm analysis (CASA); fluorescence indicators to monitor membrane potential (EmR, DiSC3(5)) and mitochondrial membrane potential (Ψ, JC-1); CatSper activity, using its ability to permeate Na+ ions, and ATP levels with the luciferin-luciferase reaction. We confirmed previous findings with our hyperglycemic model, which replicated the typical reduction on conventional sperm parameters. In sperm from hyperglycemic rats, we observed increased motility and HA levels after pharmacological treatment. Additionally, CatSper activity was unaffected by hyperglycemia, while EmR was hyperpolarized under non-capacitating condition. Finally, we noted a low percentage of hyperpolarized Ψ and reduced ATP content. This study highlights the significance of impact of hyperglycemia on sperm physiology and capacitation. We proposed that low ATP levels perturb energy state, signaling pathways, ion channels activity, motility, and HA. Our findings offer insight into DM-associated infertility and potential treatment strategies.

Testicular fat deposition attenuates reproductive performance via decreased follicle-stimulating hormone level and sperm meiosis and testosterone synthesis in mouse

OBJECTIVE

Testicular fat deposition has been reported to affect animal reproduction. However, the underlying mechanism remains poorly understood. The present study explored whether sperm meiosis and testosterone synthesis contribute to mouse testicular fat depositioninduced reproductive performance.

METHODS

High fat diet (HFD)-induced obesity CD1 mice (DIO) were used as a testicular fat deposition model. The serum hormone test was performed by agent kit. The quality of sperm was assessed using a Sperm Class Analyzer. Testicular tissue morphology was analyzed by histochemical methods. The expression of spermatocyte marker molecules was monitored by an immuno-fluorescence microscope during meiosis. Analysis of the synthesis of testosterone was performed by real-time polymerase chain reaction and reagent kit.

RESULTS

It was found that there was a significant increase in body weight among DIO mice, however, the food intake showed no difference compared to control mice fed a normal diet (CTR). The number of offspring in DIO mice decreased, but there was no significant difference from the CTR group. The levels of follicle-stimulating hormone were lower in DIO mice and their luteinizing hormone levels were similar. The results showed a remarkable decrease in sperm density and motility among DIO mice. We also found that fat accumulation affected the meiosis process, mainly reflected in the cross-exchange of homologous chromosomes. In addition, overweight increased fat deposition in the testis and reduced the expression of testosterone synthesis-related enzymes, thereby affecting the synthesis and secretion of testosterone by testicular Leydig cells.

CONCLUSION

Fat accumulation in the testes causes testicular cell dysfunction, which affects testosterone hormone synthesis and ultimately affects sperm formation.

Proteomic Analysis of Intracellular and Membrane-Associated Fractions of Canine (Canis lupus familiaris) Epididymal Spermatozoa and Sperm Structure Separation

Simple Summary

Epididymal spermatozoa have great potential in current dog reproductive technologies. In the case of azoospermia or when the male dies, the recovery of epididymal spermatozoa opens new possibilities for reproduction. It is of great importance to analyze the quality of the sperm in such cases. Proteomic studies contribute to explaining the role of proteins at various stages of epididymal sperm maturation and offer potential opportunities to use them as markers of sperm quality. The present study showed, for the first time, mass spectrometry and bioinformatic analysis of intracellular and membrane-associated proteins of canine epididymal spermatozoa. Additionally, sonication was used for the separation of dog epididymal sperm morphological elements (heads, tails and acrosomes). The results revealed the presence of differentially abundant proteins in both sperm protein fractions significant for sperm function and fertilizing ability. It was also shown that these proteins participate in important sperm metabolic pathways, which may suggest their potential as sperm quality biomarkers.

Abstract

This study was provided for proteomic analysis of intracellular and membrane-associated fractions of canine (Canis lupus familiaris) epididymal spermatozoa and additionally to find optimal sonication parameters for the epididymal sperm morphological structure separation and sperm protein isolation. Sperm samples were collected from 15 dogs. Sperm protein fractions: intracellular (SIPs) and membrane-associated (SMAPs) were isolated. After sonication, sperm morphology was evaluated using Spermac Stain™. The sperm protein fractions were analyzed using gel electrophoresis (SDS-PAGE) and nanoliquid chromatography coupled to quadrupole time-of-flight mass spectrometry (NanoLC-Q-TOF/MS). UniProt database-supported identification resulted in 42 proteins identified in the SIPs and 153 proteins in the SMAPs. Differentially abundant proteins (DAPs) were found in SIPs and SMAPs. Based on a gene ontology analysis, the dominant molecular functions of SIPs were catalytic activity (50%) and binding (28%). Hydrolase activity (33%) and transferase activity (21%) functions were dominant for SMAPs. Bioinformatic analysis of SIPs and SMAPs showed their participation in important metabolic pathways in epididymal sperm, which may suggest their potential as sperm quality biomarkers. The use of sonication 150 W, 10 min, may be recommended for the separation of dog epididymal sperm heads, tails, acrosomes and the protein isolation.

Effect of spermidine on ameliorating spermatogenic disorders in diabetic mice via regulating glycolysis pathway

Diabetes mellitus (DM), a high incidence metabolic disease, is related to the impairment of male spermatogenic function. Spermidine (SPM), one of the biogenic amines, was identified from human seminal plasma and believed to have multiple pharmacological functions. However, there exists little evidence that reported SPM's effects on moderating diabetic male spermatogenic function. Thus, the objective of this study was to investigate the SPM's protective effects on testicular spermatogenic function in streptozotocin (STZ)-induced type 1 diabetic mice. Therefore, 40 mature male C57BL/6 J mice were divided into four main groups: the control group (n = 10), the diabetic group (n = 10), the 2.5 mg/kg SPM-treated diabetic group (n = 10) and the 5 mg/kg SPM-treated diabetic group (n = 10), which was given intraperitoneally for 8 weeks. The type 1 diabetic mice model was established by a single intraperitoneal injection of STZ 120 mg/kg. The results showed that, compare to the control group, the body and testis weight, as well the number of sperm were decreased, while the rate of sperm malformation was significantly increased in STZ-induced diabetic mice. Then the testicular morphology was observed, which showed that seminiferous tubule of testis were arranged in mess, the area and diameter of which was decreased, along with downregulated anti-apoptotic factor (Bcl-2) expression, and upregulated pro-apoptotic factor (Bax) expression in the testes. Furthermore, testicular genetic expression levels of Sertoli cells (SCs) markers (WT1, GATA4 and Vimentin) detected that the pathological changes aggravated observably, such as the severity of tubule degeneration increased. Compared to the saline-treated DM mice, SPM treatment markedly improved testicular function, with an increment in the body and testis weight as well as sperm count. Pro-apoptotic factor (Bax) was down-regulated expression with the up-regulated expression of Bcl-2 and suppression of apoptosis in the testes. What's more, expression of WT1, GATA4, Vimentin and the expressions of glycolytic rate-limiting enzyme genes (HK2, PKM2, LDHA) in diabetic testes were also upregulated by SPM supplement. The evidence derived from this study indicated that the SMP's positive effect on moderating spermatogenic disorder in T1DM mice's testis. This positive effect is delivered via promoting spermatogenic cell proliferation and participating in the glycolytic pathway's activation.

Omics and Male Infertility: Highlighting the Application of Transcriptomic Data

Male infertility is a multifaceted disorder affecting approximately 50% of male partners in infertile couples. Over the years, male infertility has been diagnosed mainly through semen analysis, hormone evaluations, medical records and physical examinations, which of course are fundamental, but yet inefficient, because 30% of male infertility cases remain idiopathic. This dilemmatic status of the unknown needs to be addressed with more sophisticated and result-driven technologies and/or techniques. Genetic alterations have been linked with male infertility, thereby unveiling the practicality of investigating this disorder from the “omics” perspective. Omics aims at analyzing the structure and functions of a whole constituent of a given biological function at different levels, including the molecular gene level (genomics), transcript level (transcriptomics), protein level (proteomics) and metabolites level (metabolomics). In the current study, an overview of the four branches of omics and their roles in male infertility are briefly discussed; the potential usefulness of assessing transcriptomic data to understand this pathology is also elucidated. After assessing the publicly obtainable transcriptomic data for datasets on male infertility, a total of 1385 datasets were retrieved, of which 10 datasets met the inclusion criteria and were used for further analysis. These datasets were classified into groups according to the disease or cause of male infertility. The groups include non-obstructive azoospermia (NOA), obstructive azoospermia (OA), non-obstructive and obstructive azoospermia (NOA and OA), spermatogenic dysfunction, sperm dysfunction, and Y chromosome microdeletion. Findings revealed that 8 genes (LDHC, PDHA2, TNP1, TNP2, ODF1, ODF2, SPINK2, PCDHB3) were commonly differentially expressed between all disease groups. Likewise, 56 genes were common between NOA versus NOA and OA (ADAD1, BANF2, BCL2L14, C12orf50, C20orf173, C22orf23, C6orf99, C9orf131, C9orf24, CABS1, CAPZA3, CCDC187, CCDC54, CDKN3, CEP170, CFAP206, CRISP2, CT83, CXorf65, FAM209A, FAM71F1, FAM81B, GALNTL5, GTSF1, H1FNT, HEMGN, HMGB4, KIF2B, LDHC, LOC441601, LYZL2, ODF1, ODF2, PCDHB3, PDHA2, PGK2, PIH1D2, PLCZ1, PROCA1, RIMBP3, ROPN1L, SHCBP1L, SMCP, SPATA16, SPATA19, SPINK2, TEX33, TKTL2, TMCO2, TMCO5A, TNP1, TNP2, TSPAN16, TSSK1B, TTLL2, UBQLN3). These genes, particularly the above-mentioned 8 genes, are involved in diverse biological processes such as germ cell development, spermatid development, spermatid differentiation, regulation of proteolysis, spermatogenesis and metabolic processes. Owing to the stage-specific expression of these genes, any mal-expression can ultimately lead to male infertility. Therefore, currently available data on all branches of omics relating to male fertility can be used to identify biomarkers for diagnosing male infertility, which can potentially help in unravelling some idiopathic cases.

Influence of Risk Factors for Male Infertility on Sperm Protein Composition

Male infertility is a common health problem that can be influenced by a host of lifestyle risk factors such as environment, nutrition, smoking, stress, and endocrine disruptors. These effects have been largely demonstrated on sperm parameters (e.g., motility, numeration, vitality, DNA integrity). In addition, several studies showed the deregulation of sperm proteins in relation to some of these factors. This review inventories the literature related to the identification of sperm proteins showing abundance variations in response to the four risk factors for male infertility that are the most investigated in this context: obesity, diabetes, tobacco smoking, and exposure to bisphenol-A (BPA). First, we provide an overview of the techniques used to identify deregulated proteins. Then, we summarise the main results obtained in the different studies and provide a compiled list of deregulated proteins in relation to each risk factor. Gene ontology analysis of these deregulated proteins shows that oxidative stress and immune and inflammatory responses are common mechanisms involved in sperm alterations encountered in relation to the risk factors.

Human sperm functioning is related to the aquaporin-mediated water and hydrogen peroxide transport regulation

Aquaporins (AQPs) are transmembrane water channels and some of them are permeable in addition to water to other small solutes including hydrogen peroxide. The sperm cells of mammals and fishes express different AQPs, although there is no agreement in the literature on their localization. In humans, AQP3 and AQP11 are expressed mainly in the tail, AQP7 in the head and AQP8 in the midpiece. Thanks to the results of experiments with KO mice and to data obtained by comparing sub-fertile patients with normospermic subjects, the importance of AQPs for the normal functioning of sperms to ensure normal fertility emerged. AQP3, AQP7 and AQP11 appeared involved in the sperm volume regulation, a key role for fertility because osmoadaptation protect the sperm against a swelling and tail bending that could affect sperm motility. AQP8 seems to have a fundamental role in regulating the elimination of hydrogen peroxide, the most abundant reactive oxygen species (ROS), and therefore in the response to oxidative stress. In this review, the human AQPs expression, their localization and functions, as well as their relevance in normal fertility are discussed. To understand better the AQPs role in human sperm functionality, the results of studies obtained in other animal species were also considered.