Trends in sperm quality by computer-assisted sperm analysis of 49,189 men during 2015-2021 in a fertility center from China.

Background: Sperm quality, including semen volume, sperm count, concentration, and total and progressive motility (collectively, "semen parameters"), has declined in the recent decades. Computer-assisted sperm analysis (CASA) provides sperm kinematic parameters, and the temporal trends of which remain unclear. Our objective is to examine the temporal trend of both semen parameters and kinematic parameters in Shanghai, China, in the recent years. Methods: This retrospective study analyzed semen parameters and kinematic parameters of 49,819 men attending our reproductive center by using CASA during 2015-2021. The total sample was divided into two groups: samples that surpassed the WHO guideline (2010) low reference limits ("above reference limit" group, ARL; n = 24,575) and samples that did not ("below reference limit" group, BRL; n = 24,614). One-way analysis of variance, Kruskal-Wallis test, independent samples t-test, and covariance analysis were used to assess the differences among groups. Year, age, and abstinence time were included in the multiple linear regression model of the ARL group to adjust the confounders and depict the trends in sperm quality. Results: Among all the total sample and the ARL and BRL groups, the age of subjects increased in recent years. Semen volume and sperm count showed declined tendency with years in the total sample, the ARL and BRL groups, and the subgroup of age or abstinence time, whereas sperm velocities showed increased tendency with years on the contrary. The multiple linear regression model of the ARL group, adjusting for age and abstinence time, confirmed these trends. Semen volume (ß1= -0.162; CI: -0.172, -0.152), sperm count (ß1= -9.97; CI: -10.813, -9.128), sperm concentration (ß1 = -0.535; CI: -0.772, -0.299), motility (ß1 = -1.751; CI: -1.830, -1.672), and progressive motility (ß1 = -1.12; CI: -0.201, -0.145) decreased with year, whereas curvilinear line velocity (VCL) (ß1 = 3.058; CI: 2.912, 3.203), straight line velocity (VSL) (ß1 = 2.075; CI: 1.990, 2.161), and average path velocity (VAP) (ß1 = 2.305; CI: 2.224, 2.386) increased over time (all p < 0.001). In addition, VCL, VSL, and VAP significantly declined with age and abstinence time. Conclusion: The semen parameters declined, whereas the kinematic parameters increased over the recent years. We propose that, although sperm count and motility declined over time, sperm motion velocity increased, suggesting a possible compensatory mechanism of male fertility.

IKBA phosphorylation governs human sperm motility through ACC-mediated fatty acid beta-oxidation.

The nuclear factor-κB (NF-κB) signaling pathway regulates specific immunological responses and controls a wide range of physiological processes. NF-κB inhibitor alpha (IKBA) is an NF-κB inhibitory mediator in the cytoplasm that modulates the nuclear translocation and DNA binding activities of NF-κB proteins. However, whether the upstream cascade of the canonical NF-κB signaling pathway has physiological roles independent of IKBA-mediated transcriptional activation remains unclear. Herein we investigated the function of IKBA in mature sperm in which transcriptional and translational events do not occur. IKBA was highly expressed in human sperm. The repression of IKBA phosphorylation by its inhibitor Bay117082 markedly enhanced sperm motility. On the contrary, lipopolysaccharide-stimulated IKBA phosphorylation significantly decreased sperm motility. Nevertheless, Bay117082 treatment did not affect the motility of IKBA-knockout sperm. Further, untargeted metabolomic analysis and pharmacological blocking assays revealed that the Bay117082-induced increase in sperm motility was attributable to fatty acid ß-oxidation (FAO) enhancement. In addition, we found that IKBA phosphorylation inhibition resulted in a significant reduction of acetyl-CoA carboxylase levels in the FAO metabolic pathway. Our findings indicate that IKBA-mediated signaling orchestrates sperm motility program and improves our understanding of transcription-independent NF-κB signaling pathway in cells.

Lysophosphatidic Acid Improves Human Sperm Motility by Enhancing Glycolysis and Activating L-Type Calcium Channels.

Until now, the molecular mechanisms underlining sperm motility defect causing male infertility are still poorly understood. Safe and effective compounds or drugs that can improve sperm motility are also very limited. Lysophosphatidic acid (LPA) is a naturally occurring phospholipid and a bioactive intermediate with multiple biological activities. It has been detected in various body fluids such as serum, plasma, saliva, tears, blister fluids, hen egg white, and ascites from patients with ovarian cancer. LPA is also abundant in seminal plasma and follicular fluid. It enhances follicle stimulation, improves oocyte fertilization, and promotes early embryonic development and embryo implantation. However, the physiological role of LPA in the male reproductive system remains unknown. Here, our study showed that LPA significantly improved the motility parameters of human sperm hyperactivation in a dose-dependent manner. The LPA-induced elevation of sperm motility is dependent on bovine serum albumin (BSA) but independent of the classical BSA-induced sAC/cAMP/PKA signaling pathway. The enhancement of sperm motility by LPA could not be blocked by CCCP, a respiratory inhibitor suppressing mitochondrial ATP production. Moreover, LPA improved the activity of triosephosphate isomerase in glycolysis. Meanwhile, LPA treatment significantly increased ATP and phosphoenolpyruvate levels and decreased ADP content during sperm glycolysis. Notably, none of known or identified LPA receptors was detected in human sperm. Further investigations showed that LPA promoted sperm motility through L-type calcium channels. In summary, this study revealed the involvement of LPA in the regulation for human sperm motility by enhancing glycolysis and activating L-type calcium channels. The current findings may shed new light on the understanding of causes of asthenozoospermia, and indicate that LPA could be used as a novel therapeutic agent to improve sperm function and fertilizing capacity.

Reassessment of the Proteomic Composition and Function of Extracellular Vesicles in the Seminal Plasma.

Seminal plasma contains a high concentration of extracellular vesicles (EVs). The heterogeneity of small EVs or the presence of nonvesicular extracellular matter (NV) pose major obstacles in understanding the composition and function of seminal EVs. In this study, we employed high-resolution density gradient fractionation to accurately characterize the composition and function of seminal EVs and NV. We found that the seminal EVs could be divided into 3 different subtypes-namely, high-density EV (EV-H), medium-density EV (EV-M), and low-density EV (EV-L)-after purification using iodixanol, while NV was successfully isolated. EVs and NV display different features in size, shape, and expression of some classic exosome markers. Both EV-H and NV could markedly promote sperm motility and capacitation compared with EV-M and EV-L, whereas only the NV fraction induced sperm acrosome reaction. Proteomic analysis results showed that EV-H, EV-M, EV-L, and NV had different protein components and were involved in different physiological functions. Further study showed that EV-M might reduce the production of sperm intrinsic reactive oxygen species through glutathione S-transferase mu 2. This study provides novel insights into important aspects of seminal EVs constituents and sounder footing to explore their functional properties in male fertility.

Dietary restriction and/or exercise training impairs spermatogenesis in normal rats.

Dietary restriction and/or exercise has been shown to have multiple benefits for health. However, its effects on reproductive health and the mechanisms by which it regulates reproductive function remain unclear. Here, to evaluate its effects on spermatogenesis and sperm function, rats were divided into 4 groups: ad libitum-fed sedentary control, dietary restriction (DR), exercise training (ET), and dietary restriction plus exercise training (DR+ET) groups. Results indicated that body weight, epididymal fat pad weight, and sperm counts were significantly reduced in the DR, ET, and DR+ET groups. Moreover, sperm motility and capacitation-associated protein tyrosine phosphorylation were suppressed in the DR and DR+ET groups, but not the ET group. Microarray analysis revealed that the number of downregulated genes was higher than that of upregulated genes in the DR and/or ET groups. About half of the downregulated genes are common after exercise training and/or diet restriction. Gene ontology analysis showed that downregulated genes in the DR, ET, and DR+ET groups affected spermatogenesis through overlapping pathways, including glucocorticoid, corticosteroid, extracellular structure organization, and estradiol responses. Our findings suggest that diet restriction and/or exercise training may present potential risks to male reproductive dysfunction by disrupting normal gene expression patterns in the testis. Novelty: Dietary restriction and/or exercise can lead to the damage of spermatogenesis as well as sperm maturation. Sperm functional changes are more sensitive to dietary restriction than exercise training. Dietary restriction and exercise impair spermatogenesis through overlapping biological pathways in the testis.

[Variations of CO2 concentration and δ13C and influencing factors of Quercus variabilis plantation in low hilly area of North China].

The off-axis integrated cavity output spectroscopy technique was used to measure air CO2 concentration and stable carbon isotope ratio (δ13C) above (11 m) and at the bottom (6 m) of canopy of a Quercus variabilis plantation in a low hilly area of North China. The variations of CO2 concentration and δ13C value in Q. variabilis plantation canopy and the influencing factors were analyzed at hourly timescale. The results showed that diurnal variation in the CO2 concentration had a trend, while there was no obvious similar tendency in the diurnal change of δ13C value. Daytime atmosphere stability frequency during the experiment time was 70.2%. With the combined effects of photosynthesis and turbulent in the canopy, CO2 concentration at the bottom of canopy was 1.70 µmol · mol(-1) higher than that above the canopy, while the δ13C value was 0.81 per thousand lower than that above the canopy. Atmosphere stability frequency was 76.2% at night. The CO2 from leaf was not easy to move because of weak turbulent. Thus, CO2 concentration at the bottom of canopy was 1.24 µmol · mol(-1) higher than that above canopy, while the δ13C value was 0.58 per thousand lower than that above canopy. The difference of CO2 concentration between above and at the bottom of the canopy was strongly correlated with their δ13C difference both in daytime and at nighttime. Stepwise regression analysis indicated that solar radiation and relative humidity in daytime were the main environmental factors causing CO2 concentration and δ13C difference between above and at the bottom of the canopy, whereas at nighttime temperature was a key environmental factor influencing δ13C value. The above environmental factors strongly influenced CO2 concentration and δ13C value in air above and at the bottom of Q. variabilis plantation canopy by increasing or decreasing photosynthesis and respiration.