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A cost for high levels of sperm competition in rodents: increased sperm DNA fragmentation.

ABSTRACT: Sperm competition, a prevalent evolutionary process in which the spermatozoa of two or more males compete for the fertilization of the same ovum, leads to morphological and physiological adaptations, including increases in energetic metabolism that may serve to propel sperm faster but that may have negative effects on DNA integrity. Sperm DNA damage is associated with reduced rates of fertilization, embryo and fetal loss, offspring mortality, and mutations leading to genetic disease. We tested whether high levels of sperm competition affect sperm DNA integrity. We evaluated sperm DNA integrity in 18 species of rodents that differ in their levels of sperm competition using the sperm chromatin structure assay. DNA integrity was assessed upon sperm collection, in response to incubation under capacitating or non-capacitating conditions, and after exposure to physical and chemical stressors. Sperm DNA was very resistant to physical and chemical stressors, whereas incubation in non-capacitating and capacitating conditions resulted in only a small increase in sperm DNA damage. Importantly, levels of sperm competition were positively associated with sperm DNA fragmentation across rodent species. This is the first evidence showing that high levels of sperm competition lead to an important cost in the form of increased sperm DNA damage.

SUBMITTER: delBarco-Trillo J

PROVIDER: S-EPMC4810851 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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A cost for high levels of sperm competition in rodents: increased sperm DNA fragmentation.

delBarco-Trillo Javier J García-Álvarez Olga O Soler Ana Josefa AJ Tourmente Maximiliano M Garde José Julián JJ Roldan Eduardo R S ER

Proceedings. Biological sciences 20160301 1826

Sperm competition, a prevalent evolutionary process in which the spermatozoa of two or more males compete for the fertilization of the same ovum, leads to morphological and physiological adaptations, including increases in energetic metabolism that may serve to propel sperm faster but that may have negative effects on DNA integrity. Sperm DNA damage is associated with reduced rates of fertilization, embryo and fetal loss, offspring mortality, and mutations leading to genetic disease. We tested w ...[more]

PMID: 26936246

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Project description:Sperm competition favors increases in relative testes mass and production efficiency, and changes in sperm phenotype that result in faster swimming speeds. However, little is known about its effects on traits that contribute to determine the quality of a whole ejaculate (i.e., proportion of motile, viable, morphologically normal and acrosome intact sperm) and that are key determinants of fertilization success. Two competing hypotheses lead to alternative predictions: (a) sperm quantity and quality traits co-evolve under sperm competition because they play complementary roles in determining ejaculate's competitive ability, or (b) energetic constraints force trade-offs between traits depending on their relevance in providing a competitive advantage. We examined relationships between sperm competition levels, sperm quantity, and traits that determine ejaculate quality, in a comparative study of 18 rodent species using phylogenetically controlled analyses. Total sperm numbers were positively correlated to proportions of normal sperm, acrosome integrity and motile sperm; the latter three were also significantly related among themselves, suggesting no trade-offs between traits. In addition, testes mass corrected for body mass (i.e., relative testes mass), showed a strong association with sperm numbers, and positive significant associations with all sperm traits that determine ejaculate quality with the exception of live sperm. An "overall sperm quality" parameter obtained by principal component analysis (which explained 85% of the variance) was more strongly associated with relative testes mass than any individual quality trait. Overall sperm quality was as strongly associated with relative testes mass as sperm numbers. Thus, sperm quality traits improve under sperm competition in an integrated manner suggesting that a combination of all traits is what makes ejaculates more competitive. In evolutionary terms this implies that a complex network of genetic and developmental pathways underlying processes of sperm formation, maturation, transport in the female reproductive tract, and preparation for fertilization must all evolve in concert.

Project description:BACKGROUND:Sperm DNA integrity is considered essential for successful transmission of the paternal genome, fertilization and normal embryo development. DNA fragmentation index (DFI, %) has become a key parameter in the swine artificial insemination industry to assess sperm DNA integrity. Recently, in some elite Norwegian Landrace boars (boars with excellent field fertility records), a higher level of sperm DFI has been observed. In order to obtain a better understanding of this, and to study the complexity of sperm DNA integrity, liquid preserved semen samples from elite boars with contrasting DFI levels were examined for protamine deficiency, thiol profile and disulphide bonds. Additionally, the DNA methylation profiles of the samples were determined by reduced representation bisulphite sequencing (RRBS). RESULTS:In this study, different traits related to sperm DNA integrity were investigated (n = 18 ejaculates). Upon liquid storage, the levels of total thiols and disulphide bonds decreased significantly, while the DFI and protamine deficiency level increased significantly. The RRBS results revealed similar global patterns of low methylation from semen samples with different levels of DFI (low, medium and high). Differential methylation analyses indicated that the number of differentially methylated cytosines (DMCs) increased in the low-high compared to the low-medium and the medium-high DFI groups. Annotating the DMCs with gene and CpG features revealed clear differences between DFI groups. In addition, the number of annotated transcription starting sites (TSS) and associated pathways in the low-high comparison was greater than the other two groups. Pathway analysis showed that genes (based on the closest TSS to DMCs) corresponding to low-high DFI comparison were associated with important processes such as membrane function, metabolic cascade and antioxidant defence system. CONCLUSION:To our knowledge, this is the first study evaluating DNA methylation in boar sperm cells with different levels of DFI. The present study shows that sperm cells with varying levels of DNA fragmentation exhibit similar global methylation, but different site-specific DNA methylation signatures. Moreover, with increasing DNA fragmentation in spermatozoa, there is an increase in the number of potentially affected downstream genes and their respective regulatory pathways.

Project description:Limited data exists on possible approaches to improve sperm DNA fragmentation index (DFI) when no identifiable cause is found. The effect of short abstinence on sperm parameters has been extensively studied, but rarely reported on the effect on DFI in infertile men. In this study, we aimed to determine whether a second ejaculate provided after very short abstinence demonstrates lower DFI rates in infertile men. This prospective cohort study was conducted at Mount Sinai Hospital, Toronto, Canada, a tertiary university affiliated hospital. All men having DFI testing in addition to the standard semen analysis were identified via a prospectively collected database. Infertile men were instructed to provide two semen samples 3-4 hours apart (the first sample was given after 2-5 days of abstinence) to test the effect on DFI levels. Data analysis was performed for the comparison of the change in sperm parameters and DFI between samples and between men with DFI above and under 30%. A total of 52 men provided double ejaculates 3-4 hours apart. In the entire group, DFI decreased from 38.9%±21.4% to 35.1%±21.6% in the second sample (P<0.001). Semen volume was lower on the second sample (2.3±1.4 vs. 1.5±0.9 mL, P<0.001), while the remaining parameters did not change. Forty out of 52 patients (76.9%) had improved DFI (average of 6.0±4.0 percentage points). Change in DFI varied with 22/52 (42.3%) and 7/52 (13.5%) of patients found to have decreases in DFI >5% and >10% in the second ejaculate, respectively. For men with DFI of 30-40%, 64% (7/11) of DFIs reduced to the under 30% range. First DFI value was the only parameter associated with DFI decrease to under 30% in multivariate models [odds ratio (OR), 0.62; 95% confidence interval (CI): 0.39-0.98; P=0.04]. This study identified significant improvements in DFI in infertile men providing a second sample after 3-4 hours. Controlled trials are needed to determine if reproductive outcomes are improved using a second ejaculate for infertile men with high initial sperm DFI values.

Project description:Men in couples that have experienced pregnancy loss have a higher risk of sexual dysfunction. Semen quality impairment is common in men of couples with pregnancy loss. The objective of this article is to evaluate the differences in the incidence of male sexual dysfunction in a cohort of pregnancy loss couples with different types of semen quality impairment. A cross-sectional analysis of 426 men who attended our outpatient clinic for couples' pregnancy loss, those without genetic abnormalities were included in the final analysis covering June 2021 to October 2021. The patients were divided into 5 groups according to type of semen quality impairment: normozoospermia group (group normal; N = 161), high sperm DNA fragmentation group (group high-SDF; N = 87), isolated asthenozoospermia group (group iAstheno; N = 45), isolated teratozoopermia group (group iTerato; N = 44), and ≥ 2 abnormal sperm parameters group (group multiple; N = 89). All subjects underwent a complete physical inspection, including palpation of the male genitalia and semen analysis. Validated assessment tools for erectile dysfunction (the International Index of Erectile Function -IIEF-5) and anxiety (the seven-item Generalized Anxiety Disorder Scale- GAD-7) were also used. Men with high sperm DNA fragmentation and isolated teratozoopermia were associated with increased erectile dysfunction risk when compared with normozoospermic men, with an OR of 2.75 [1.49-5.09; p = 0.001] and 2.44 [1.22-5.31; p = 0.024], respectively. It is interesting to note that there was no difference in prevalence of erectile dysfunction between Group iAstheno and Group normal (20.0% vs. 18.0%; OR = 1.24 [0.52-2.97]; P = 0.625). More than half (50.6%) of the participants in Group high-SDF reported sexual intercourse less than once per week, much more than those in the normozoospermia group (23.2%, p < 0.05), followed by Group iTerato (44.4%) and Group multiple (46.1%). GAD-7 scores increased slightly but significantly among groups when compared with Group normal. Not surprisingly, GAD-7 scores remained higher in Group high-SDF. In males of pregnancy loss couples, men with high sperm DNA fragmentation and teratozoopermia suffer from a higher incidence of erectile dysfunction. This phenomenon is not significant in men with isolated asthenozoospermia. Proper counseling and treatment of impaired semen quality are warranted.

Dataset Information

A cost for high levels of sperm competition in rodents: increased sperm DNA fragmentation.

Publications

A cost for high levels of sperm competition in rodents: increased sperm DNA fragmentation.

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