Human sperm anatomy: ultrastructural localization of 1alpha,25-dihydroxyvitamin D receptor and its possible role in the human male gamete

Causal association between 25-Hydroxyvitamin D and risk of abnormal spermatozoa: A bidirectional Mendelian randomization study

Previous studies indicated conflicting findings regarding the association between vitamin D and abnormal spermatozoa. Herein, we assessed the causal association between circulating 25-Hydroxyvitamin D (25OHD) levels and the risk of abnormal spermatozoa by utilizing bidirectional Mendelian randomization (MR) analysis. Genome-wide association study summary statistics for 25OHD and abnormal spermatozoa were obtained from publicly accessible databases. Single nucleotide polymorphisms (SNPs) associated with 25OHD and SNPs associated with abnormal spermatozoa were used as instrumental variables (IVs) for forward MR analysis and reverse MR analysis, respectively. Inverse variance weighted (IVW) was the main MR approach, while weighted median, MR-Egger, and maximum likelihood methods were employed to supplement IVW. In addition, several sensitivity tests assessed the reliability of MR analysis. Forward MR analysis showed that elevated 25OHD levels significantly reduced abnormal spermatozoa risk (odds ratio [OR] = 0.75, 95 % confidence interval [CI]: 0.56-1.00, P = 4.98E-02), and the effect remained statistically significant after excluding SNPs associated with confounders (OR = 0.73, 95 % CI: 0.54-0.98, P = 3.83E-02) or only utilizing SNPs located near 25OHD-associated genes only as IVs (OR = 0.58, 95 % CI: 0.41-0.81, P = 1.67E-03). Reverse MR analysis indicated abnormal spermatozoa not affecting 25OHD level (P > 0.05). Sensitivity tests showed that MR analyses were not affected by heterogeneity and horizontal polytropy. Overall, the present MR study supports that elevated 25OHD levels reduce the risk of abnormal spermatozoa. Therefore, ensuring adequate vitamin D intake and maintaining stable levels of 25OHD may be effective strategies to optimize reproductive outcomes.

Calcium and vitamin D homoeostasis in male fertility

Calcium and vitamin D have well-established roles in maintaining calcium balance and bone health. Decades of research in human subjects and animals have revealed that calcium and vitamin D also have effects on many other organs including male reproductive organs. The presence of calcium-sensing receptor, vitamin D receptor, vitamin D activating and inactivating enzymes and calcium channels in the testes, male reproductive tract and human spermatozoa suggests that vitamin D and calcium may modify male reproductive function. Functional animal models have shown that vitamin D deficiency in male rodents leads to a decrease in successful mating and fewer pregnancies, often caused by impaired sperm motility and poor sperm morphology. Human studies have to a lesser extent validated these findings; however, newer studies suggest a positive effect of vitamin D supplementation on semen quality in cases with vitamin D deficiency, which highlights the need for initiatives to prevent vitamin D deficiency. Calcium channels in male reproductive organs and spermatozoa contribute to the regulation of sperm motility and capacitation, both essential for successful fertilisation, which supports a need to avoid calcium deficiency. Studies have demonstrated that vitamin D, as a regulator of calcium homoeostasis, influences calcium influx in the testis and spermatozoa. Emerging evidence suggests a potential link between vitamin D deficiency and male infertility, although further investigation is needed to establish a definitive causal relationship. Understanding the interplay between vitamin D, calcium and male reproductive health may open new avenues for improving fertility outcomes in men.

In vitro effects of the combination of serotonin, selenium, zinc, and vitamins D and E supplementation on human sperm motility and reactive oxygen species production

Infertility affects 15% of all couples worldwide and 50% of cases of infertility are solely due to male factors. A decrease in motility in the semen is considered one of the main factors that is directly related to infertility. The use of supplementation to improve the overall sperm quality has become increasingly popular worldwide. The purpose of this study was to evaluate whether sperm motility was affected by the combination of serotonin (5-HT), selenium (Se), zinc (Zn), and vitamins D, and E supplementation. Semen samples were incubated for 75 min at 37°C in medium containing varying concentrations of 5-HT, Se, Zn, vitamin D, and E. 5-HT (200 μM), Se (2 μg/ml), Zn (10 μg/ml), vitamin D (100 nM), and vitamin E (2 mmol) have also been shown to increase progressive sperm motility. Three different mixtures of supplements were also tested for their combined effects on sperm motility and reactive oxygen species (ROS) production. While the total motility in the control group was 71.96%, this was found to increase to 82.85% in the first mixture. In contrast the average ROS level was 8.97% in the control group and decreased to 4.23% in the first mixture. Inclusion of a supplement cocktail (5-HT, Se, Zn, vitamins D and E) in sperm processing and culture medium could create an overall improvement in sperm motility while decreasing ROS levels during the incubation period. These molecules may enhance the success of assisted reproduction techniques when present in sperm preparation medium.

The role of the transsulfuration pathway in spermatogenesis of vitamin D deficient mice

Vitamin D deficiency is a global health problem and has been linked to defective spermatogenesis and male infertility. In this study, we aimed to investigate the main enzymes involved in the transsulfuration pathway of 1-carbon metabolism, and spermatogenesis function. Therefore, sixteen male C57 mice were addressed to a control (standard diet) or vitamin D deficient (VDD) diet for 14 weeks. The results show that compared to the standard diet, VDD increased final body weight and reduced sperm quality, caused damage to the testicular structure, and decreased the serum levels of testosterone. In addition, serum concentrations of homocysteine, vitamin B12, and sperm oxidative stress markers increased. In testicular tissues, the CBS and CSE protein levels were down-regulated whereas HO-1 was up-regulated at both mRNA and protein expression levels. Within a mice deprivation model, VDD deeply suppressed testosterone and impaired spermatogenesis with oxidative stress-mediated mechanisms. The effects of the deprivation appeared to be at least in part independent of genomic and receptor-mediated vitamin D actions and suggest a specific impairment of the alternative transsulfuration pathway.

The Association between Vitamin D and the Components of Male Fertility: A Systematic Review

OBJECTIVE

Previous systematic reviews of the effects of vitamin D on the components of male fertility have been inconclusive. This article systematically reviews the latest research to examine the relationship between vitamin D, semen quality parameters, and sex hormones production.

METHODS

MEDLINE, Cochrane, and Web of Science databases were searched using the appropriate keywords.

RESULTS

Observational studies indicate significant correlation between vitamin D levels and sperm parameters, with a particular emphasis on sperm motility, and partially suggest a relationship between higher serum testosterone and vitamin D levels. Additionally, interventional studies confirmed that vitamin D supplementation has a positive effect on sperm motility, especially progressive. However, most randomized clinical trials indicate that vitamin D treatment does not have any significant effect on testosterone or other hormone levels.

CONCLUSIONS

Although our findings add to the discussion regarding the effect of vitamin D on male fertility, there is still no solid evidence to support the use of vitamin D supplementation to improve the outcomes of patients with impaired sperm parameters and hormonal disorders. Additional dedicated clinical studies are needed to clarify the relationship between vitamin D and male fertility, along with its components.

Vitamin D Receptor affects male mouse fertility via regulation of lipid metabolism and testosterone biosynthesis in testis

Vitamin D and vitamin D receptor (VD/VDR) plays a vital role in the development of spermatozoa, which is largely determined by the testosterone level in serum. Testosterone biosynthesis is closely related to lipid metabolism in gonadal adipose around testes. VDR could regulate lipid metabolism in adipocytes as well. However, it still remains unknown how VDR regulates lipid metabolism to impact testosterone biosynthesis in testis. Hereby, various parameters of male fertility were compared between wildtype (WT) and Vdr knockout (Vdr-KO) male mouse. For Vdr-KO mice, the size of testis and gonadal adipose was smaller than that of WT, and the sperm quality and testosterone level were lower than WT. Subsequently, testis proteome data between Vdr-KO and WT mice indicated that dysregulation of lipid metabolism was closely associated with decreased testosterone biosynthesis in Vdr-deficient mouse. And further evaluation of VDR functions in Leydig cells verified that VDR impacted lipid metabolism and regulated the expression of a range of genes involved in testosterone biosynthesis. Knockdown VDR could significantly decrease testosterone synthesis and secretion in Leydig cells. Meanwhile, expression of genes involved in androgen synthesis was decreased but genes related to lipolysis were up-regulated. Collectively, the present study unveiled the relationship between lipid metabolism and testosterone biosynthesis mediated by VDR in mouse testis and its effect on male fertility. These findings will greatly enhance our current understanding of VDR intermediate in lipid metabolism and androgen synthesis.

VDR mediated HSD3B1 to regulate lipid metabolism and promoted testosterone synthesis in mouse Leydig cells

BACKGROUND

The vitamin D receptor (VDR) mediates the pleiotropic biological actions that include osteoporosis, immune responses and androgen synthesis wherein the VDR transcriptionally regulates expression of the genes involved in this complex process. 3β-Hydroxysteroid dehydrogenase-1 (HSD3B1) is an absolutely necessary enzyme for androgen synthesis.

OBJECTIVE

The purpose of the present study was to explore the molecular mechanism of VDR mediated HSD3B1 regulation of lipid metabolism and testosterone synthesis.

METHODS

The levels of VDR, HSD3B1 and lipid metabolism associated protein were determined by quantitative real-time polymerase chain reaction (RT-qPCR) or western blot. The levels of testosterone concentrations in cell culture media serum by enzyme-linked immunosorbent assay (ELISA). Targeted relationship between VDR and Hsd3b1 was evaluated by dual-luciferase reporter assay.

RESULTS

Based on the data analysis of mouse testicular proteome, we found that the expression of HSD3B1 was significantly reduced after VDR deletion. Here, we identified that Hsd3b1 was widely expressed in different tissues of mice by RT-qPCR, and was highly expressed in testis, and mainly located in testicular Leydig cells. Dual-luciferase assay confirmed that VDR could bind candidate vitamin D responsive elements (VDREs) in upstream region of Hsd3b1, and enhance gene expression. Furthermore, over-expression VDR and HSD3B1 significantly increased testosterone synthesis in mice Leydig cells. Meanwhile, Lpl expression was significantly down-regulated and Angptl4 expression was significantly up-regulated in the present of HSD3B1 overexpression. Both LPL and ANGPTL4 play important roles in regulating lipid metabolism.

CONCLUSIONS

The present study unveiled VDR mediated HSD3B1 to regulate lipid metabolism and promoted testosterone synthesis in mouse Leydig cells. These findings will greatly help us to understand the roles of VDR and HSD3B1 in testosterone synthesis and lipid metabolism.

Manipulation of Dietary Intake on Changes in Circulating Testosterone Concentrations

Elevations in the circulating concentration of androgens are thought to have a positive effect on the anabolic processes leading to improved athletic performance. Anabolic-androgenic steroids have often been used by competitive athletes to augment this effect. Although there has been concerted effort on examining how manipulating training variables (e.g., intensity and volume of training) can influence the androgen response to exercise, there has been much less effort directed at understanding how changes in both macronutrient and micronutrient intake can impact the androgen response. Thus, the focus of this review is to examine the effect that manipulating energy and nutrient intake has on circulating concentrations of testosterone and what the potential mechanism is governing these changes.

Novel Insights into the Antagonistic Effects of Losartan against Angiotensin II/AGTR1 Signaling in Glioblastoma Cells

Simple Summary

Patients with high-grade glioma (HGG) such as glioblastoma (GBM) who undergo surgical resection with adjuvant therapy have a mean overall survival of 14.6 months and 100% of recurrence. Thus, these disappointing outcomes in terms of glioblastoma life expectancy require seeking novel pharmacological tools, including drug repurposing. In the present study, we identify a novel molecular mechanism through which Losartan antagonizes Angiotensin II (Ang II)/Angiotensin II type I receptor (AGTR1) signaling, overexpressed in GBM cells. For instance, we demonstrate how Losartan drastically inhibits the stimulatory effects of Ang II on aromatase activity and consequently reduces local estrogen production, sustaining cancer progression. Thus, it is reasonable to repurpose Losartan as an adjuvant pharmacological tool to be implemented prospectively in the novel therapeutic strategies adopted in GBM patients.

Abstract

New avenues for glioblastoma therapy are required due to the limited mortality benefit of the current treatments. The renin-angiotensin system (RAS) exhibits local actions and works as a paracrine system in different tissues and tumors, including glioma. The glioblastoma cell lines U-87 MG and T98G overexpresses Angiotensin II (Ang II)/Angiotensin II type I receptor (AGTR1) signaling, which enhances in vitro and in vivo local estrogen production through a direct up-regulation of the aromatase gene promoters p I.f and p I.4. In addition, Ang II/AGTR1 signaling transactivates estrogen receptor-α in a ligand-independent manner through mitogen-activated protein kinase (MAPK) activation. The higher aromatase mRNA expression in patients with glioblastoma was associated with the worst survival prognostic, according to The Cancer Genome Atlas (TCGA). An intrinsic immunosuppressive glioblastoma tumor milieu has been previously documented. We demonstrate how Ang II treatment in glioblastoma cells increases programmed death-ligand 1 (PD-L1) expression reversed by combined exposure to Losartan (LOS) in vitro and in vivo. Our findings highlight how LOS, in addition, antagonizes the previously documented neoangiogenetic, profibrotic, and immunosuppressive effects of Ang II and drastically inhibits its stimulatory effects on local estrogen production, sustaining glioblastoma cell growth. Thus, Losartan may represent an adjuvant pharmacological tool to be repurposed prospectively for glioblastoma treatment.

Effects of vitamin D supplementation in extender on sperm kinematics and apoptosis following the freeze-thaw process in normozoospermic and asthenozoospermic Holstein bulls

Background

Asthenozoospermia is a usual male infertility factor, characterized by decreased semen quality. It has been revealed that antioxidants improve sperm function, enhance endogenous antioxidant activities, and protect spermatozoa against oxidative damage during cryopreservation. This aimed to evaluate the effects of vitamin D on sperm kinematics and apoptosis in the semen of bulls with normozoospermia and asthenozoospermia after the freeze-thaw process. For this purpose, 32 semen samples of four Holstein bulls (normozoospermic, progressive motility > 70 %) and 32 semen samples of four bull (asthenozoospermic progressive motility < 40 %) were collected and pooled separately (normozoospermic and asthenozoospermic). Samples were then diluted into four equal aliquots of extender containing different vitamin D concentrations (0, 5, 10, and 50 ng/mL) and aspirated into a 0.5 mL straw.

Results

The percentages of sperm progressive motility and viability were significantly higher (P < 0.05) in 50 ng/mL of vitamin D in normozoospermic group. Sperm kinematics parameters including curvilinear velocity (VCL), straight-line velocity (VSL), and average path velocity (VAP) were significantly higher in the high dose (50 ng/mL) vitamin D-treated group compared to the low dose vitamin D-treated group (5ng/mL) in normozoospermic bull semen samples. The supplementation of the semen extender with different concentrations of vitamin D could not increase the rate of acrosome integrity in normozoospermic bulls compared to the control group (P < 0.05). In the asthenozoospermic group, 10 ng/mL vitamin D-treated group could increase the rate of plasma membrane integrity compared to 5 ng/mL vitamin D-treated group (P < 0.05). The percentages of early-apoptosis (P = 0.049) and late-apoptosis (P = 0.005) were significantly higher in the asthenozoospermic than the normozoospermic group.

Conclusions

The present study revealed that a high dose (50 ng/mL) of vitamin D protected normozoospermic bulls’ sperms from the freezing procedure and lead to higher quality of frozen-thawed bull sperm.

Male vitamin D status and male factor infertility

OBJECTIVE

To determine the association between vitamin D levels in the male partner and fertility outcomes in couples with mild male factor infertility.

DESIGN

Secondary analysis of a randomized, controlled trial.

SETTING

Nine fertility centers in the United States.

PATIENT(S)

Men (n = 154) with sperm concentration between 5 and 15 million/mL, motility ≤40%, or normal morphology ≤4% were eligible. Female partners were ovulatory, ≤40 years old, and had documented tubal patency.

INTERVENTION(S)

Men provided semen and blood at baseline for semen analysis and 25-hydroxyvitamin D (25(OH)D) levels. They were randomly assigned to receive a vitamin formulation including vitamin D 2,000 IU daily or placebo for up to 6 months. Couples attempted to conceive naturally during the first 3 months and with clomiphene citrate with intrauterine insemination of the female partner in months 4 through 6.

MAIN OUTCOME MEASURE(S)

Primary: sperm concentration, motility, morphology, and DNA fragmentation at baseline. Secondary: cumulative pregnancy, miscarriage, and live birth rates.

RESULT(S)

Semen parameters and sperm DNA fragmentation were not statistically significantly different between men with vitamin D deficiency and men with 25(OH)D levels ≥20 ng/mL. In addition, clinical pregnancy and live birth rates were similar. Male 25(OH)D level <20 ng/mL was associated with a higher rate of pregnancy loss (adjusted odds ratio 9.0; 95% confidence interval 1.3 to 61.3).

CONCLUSION(S)

Vitamin D deficiency in the male partner did not significantly impact semen parameters or treatment outcomes. Further study is warranted to better characterize the rate of miscarriage in couples with male vitamin D deficiency.

The effects of Vitamin D3 supplementation on Spermatogram and endocrine factors in asthenozoospermia infertile men: a randomized, triple blind, placebo-controlled clinical trial

OBJECTIVE

Evaluate the effects of vitamin D3 (VD3) on sperm parameters and endocrine markers in infertile men with asthenozoospermia.

MATERIALS AND METHODS

This randomized, triple-masking, placebo-controlled clinical trial conducted on 86 asthenozoospermia infertile men with serum 25 hydroxy vitamin D3 (25(OH)VD3) < 30 ng/ml in the infertility clinic of Ahvaz Jahad daneshgahi, Iran. Patients were randomly allocated to groups A and B, who received daily 4000 IU VD3 and matching placebo respectively for 3 months. Demographic data, dietary intake, physical activity, sun exposure, anthropometric indices, serum 25(OH)VD3, luteinizing hormone (LH), follicle-stimulating hormone (FSH), total testosterone (T), estradiol (E2),, sex hormone-binding globulin (SHBG), free androgen index (FAI = T/SHBG. 100), T/LH and T/E2 ratios, prolactin (PRO), parathyroid hormone (PTH), osteocalcin (OCN), phosphorus and sperm parameters were assessed.

RESULTS

Three months VD3 supplementation with 4000 IU/day had no significant effects body weight, body mass index (BMI), waist circumference (WC), body fat (BF), serum, OCN, LH, FSH, T, E2, SHBG, PRO, T/E2 ratio, FAI, semen volume, sperm count and normal sperm morphology. It increases serum 25(OH)VD3, PTH and phosphorus and seminal and serum calcium, T/LH ratio and total and progressive sperm motility and decreased significantly compared to the baseline and placebo group.

CONCLUSION

VD3 supplementation may affect sperm motility in men with asthenozoospermia and serum 25(OH)VD3 < 30 ng/ml.

TRIAL REGISTRATION

Iran Clinical Trials Registry, ID: IRCT20151128025274N4, registered on 28 March 2018, URL of trial registry record: https://www.irct.ir/trial/29983.

Seasonal Variations in Sex Steroids in a Young Male Population and Their Relationship with Plasma Levels of Vitamin D

Purpose

Vitamin D (VD) acts on sperm motility, capacitation and survival but its role in steroidogenesis is less clear. Aims: To analyze seasonal variations in sex steroids and VD in a healthy male population.

Materials and Methods

Twenty-nine healthy males, 34.0±4.8 years were included. Blood collection in winter (W) and summer (S) was performed to measure: 25OHD, total testosterone (TT), free testosterone (FT), estradiol (E2), luteinizing hormone (LH), and sex hormone binding globulin (SHBG). Testosterone/estradiol (T/E2) ratio was calculated.

Results

In W, lower levels of 25OHD: 18.8±7.2 ng/mL vs. 38.8±11.9 ng/mL (p<0.0001) and LH: 3.5±1.2 mU/mL vs. 3.9±1.5 mU/mL (p=0.05), and higher levels of TT: 501.9±157.7 ng/dL vs. 405.0±128.0 ng/dL (p=0.0003), FT: 11.8±4.1 ng/dL vs. 10.2±3.7 ng/dL (p=0.017), SHBG: 28.5±10.9 nmol/L vs. 23.6±7.9 nmol/L (p=0.002) and T/E2 ratio: 30.7±19.7 ng/dL/pg/mL vs. 17.3±3.6 ng/dL/pg/mL (p=0.0015) with no variation in E2 levels were observed. A positive correlation between 25OHD and E2 (r=0.28, p=0.04) and negative correlations between 25OHD and TT (r=−0.27, p=0.049), 25OHD and FT (r=−0.32, p=0.01), and 25OHD and T/E2 (r=−0.44, p=0.0008) were found.

Conclusions

In healthy young male population, seasonal variations were observed in 25OHD and LH levels (higher in S) and in TT, FT, SHBG levels, and T/E2 (higher in W). Lower values of TT and FT in S are accompanied by higher levels of LH, which rules out a central mechanism for lowering testosterone. 25OHD negatively correlated with TT, FT, and T/E2 and positively correlated with E2, suggesting a relationship between VD status and changes in gonadal steroids.

Association of Vitamin D and Reproductive Hormones With Semen Parameters in Infertile Men

Background

Hypovitaminosis D has been linked with poor semen parameters and endocrinological factors in male infertility. This study aimed to analyze the association of serum vitamin D levels and reproductive hormones such as follicle-stimulating hormone (FSH), luteinizing hormone (LH), and total testosterone (TT) with the semen parameters in a cohort of infertile men.

Methodology

In this study, 224 infertile men (aged 18-45 years) were recruited after applying inclusion and exclusion criteria. Semen analysis was performed as per the 2010 World Health Organization (WHO) criteria. The patients were divided into two groups on the basis of semen parameters: normozoospermic men and men with one or more altered semen parameters as per the WHO 2010 guidelines for all the analysis. Vitamin D and hormone levels were evaluated by quantitative competitive immunoassay by chemiluminescent microparticle immunoassay technology with flexible assay protocols (Architect, Abbott Diagnostics, Lake Forest, IL, USA). The patients were further divided into three groups on the basis of vitamin D levels: Sufficient (>20 ng/mL), insufficient (12-20 ng/mL), and deficient (<12 ng/mL). These groups were compared for different semen and hormonal parameters.

Results

Out of the 224 infertile men included, 124 were normozoospermic while 100 patients had one or more altered semen parameters. The median age of the participants was 30 years (minimum = 18 years, maximum = 45 years). The serum vitamin D and TT levels were significantly lower (p < 0.0001) and FSH (p = 0.001) and LH levels (p < 0.0001) were significantly higher in those with one or more altered semen parameters compared to the normozoospermic men. The sperm concentration, total motility, linear progressive motility, percentage normal morphology, and serum TT levels were significantly lower in the patients with serum vitamin D levels of <12 ng/mL in both the normozoospermic men and those with one or more altered semen parameters compared to patients with higher vitamin D levels. Semen parameters such as sperm concentration, total motility, linear progressive motility, and morphology were positively correlated with the levels of serum vitamin D and TT.

Conclusions

Vitamin D deficiency was examined in a large proportion of infertile men. Serum vitamin D and TT levels were positively associated with semen parameters evident from lower levels of vitamin D and TT in men with altered semen parameters compared to normozoospermic men. However, further comprehensive studies with larger sample sizes should be conducted to further validate the role of vitamin D in male infertility by checking the effect of vitamin D supplementation on semen parameters.

Serum vitamin D content is associated with semen parameters and serum testosterone levels in men

The present study aimed to evaluate the influence of serum vitamin D levels on semen quality and testosterone levels. This is a cross-sectional study conducted at Androscience, Science and Innovation Center in Andrology and High-Complex Clinical and Andrology Laboratory in Sao Paulo, Brazil, with 508 male patients, aged 18-60 years, from 2007 to 2017. Seminal parameters and serum sexual hormones were correlated with serum vitamin D concentrations in 260 men selected by strict selection criteria. Patients were divided into normozoospermic group (NZG, n = 124) and a group with seminal abnormalities (SAG, n = 136). Evaluation included complete physical examination, past medical history, habits and lifestyle factors, two complete seminal analysis with sperm functional tests, serum levels of 25-hydroxy-vitamin D3(25(OH)VD3), total and free testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), sex hormone-binding globulin (SHBG), total cholesterol, homeostatic model assessment of insulin resistance (HOMA-IR) index, and karyotype. The mean concentration of 25(OH)VD3was significantly lower in the SAG (P < 0.001) and positively correlated with all baseline seminal parameters and total testosterone levels. In addition, serum vitamin D3concentration was found to be positively correlated with sperm concentration (β= 2.103; P < 0.001), total number of spermatozoa with progressive motility (β = 2.069; P = 0.003), total number of motile spermatozoa (β = 2.571; P = 0.015), and strict morphology (β = 0.056; P = 0.006), regardless of other variables. This is the first comparative study to address the issue of serum vitamin D3content between normozoospermic patients and those with sperm abnormalities. It clearly demonstrates a direct and positive relationship between serum vitamin D level and overall semen quality, male reproductive potential, and testosterone levels.

Effects of Vitamin D on Apoptosis and Quality of Sperm in Asthenozoospermia

OBJECTIVE

Vitamin D receptor (VDR) is expressed in human spermatozoa. However, the role of vitamin D (VD) in human male reproduction has not yet been clarified. In this study, effects of VD on sperm parameters and its apoptosis in asthenozoospermic and healthy men were evaluated.

METHODS

The study was carried out on discharged semen samples of 80 asthenozoospermic and healthy men. The samples were divided into control and experimental groups (received 20 µMol of VD). This study assessed sperm motility using the Makler chamber, their morphology by Diff quick, apoptosis and necrosis by Annexin-V and TUNEL assays, and their chromatin integrity was assessed by Aniline blue and Toluidine blue staining, according to WHO guidelines.

RESULTS

The results revealed that: 1) the total number of motile sperms was increased by VD in both groups, but it was only significant in the asthenozoospermia group. 2) The progressive motility was increased with significant difference in both groups.3) Morphology of sperm did not show any changes due to VD in any of the groups. 4) Early apoptosis and necrosis of sperms were reduced in both groups, but the results of late apoptosis showed no statistical difference in these groups. 5) The percentage of positive toluidine blue was significantly decreased after using VD in the asthenozoospermia group.

CONCLUSION

VD could improve motility, early apoptosis, and sperm necrosis, especially in asthenozoospermic men and it could be used for therapeutic opportunities.

Impact of vitamin D deficiency on mouse sperm structure and function

BACKGROUND

In rodents and humans, vitamin D deficiency (VDD) is associated with altered sperm structure and function (primarily decreased motility and morphological abnormalities) that are primarily attributed to VDD-induced hypocalcemia. However, it is suspected that VDD has much more drastic effects on mammalian spermatozoa.

OBJECTIVES

The purpose of this study was to illustrate that VDD, depending on its severity and duration, can alter sperm nuclear integrity and can also lead to the loss of spermatozoa's ability to support embryonic development.

MATERIALS AND METHODS

A mouse model of induced VDD combining the action of a vitamin D-deficient diet, UV exposure limitation, and paricalcitol injections; a vitamin D2 analog that catabolizes endogenous vitamin D by increasing the expression of CYP24A, a member of the cytochrome P450 family, has been used to create different grades of VDD.

RESULTS

We show that the most significant sperm defect recorded concerns the integrity of the paternal nucleus, which is both decondensed and fragmented in moderate-to-severe VDD situations. Consistent with the known consequences of fertilization with DNA-damaged spermatozoa, we show that paternal VDD decreases the ability of spermatozoa to optimally support fertilization and embryonic development.

DISCUSSION AND CONCLUSION

Given the worldwide high prevalence of VDD in humans, and although obtained in an animal model, the data presented here suggest that subfertile/infertile males may benefit from VDD testing and that attempts to correct serum vitamin D levels could be considered prior to conception, either naturally or through ART.

Normal fertilisation rates and serum 25-OHD levels among couples undergoing in-vitro fertilisation: a prospective cohort study

Background

The aim of this study was to explore the correlation between serum vitamin D levels in couples undergoing in-vitro fertilisation (IVF) and normal fertilisation process.

Methods

Between March 2016 and March 2017, we performed a prospective cohort study at an academic reproductive medicine centre to measure serum 25-hydroxyvitaminD (25-OHD) levels of 1232 couples before controlled ovarian stimulation. Generalized linear regression and binary multivariate logistic regression were employed to assess whether 25-OHD levels in men and women correlated with normal fertilisation rates and low fertilisation rate (LFR).

Results

Serum 25-OHD levels in women were classified into three groups: Group A, less than 10%; Group B, between 10 and 90%; and Group C, greater than 90%. Using generalized linear regression, we observed that female 25-OHD levels were related to normal fertilisation rates. Adjusted normal fertilisation rates from Group A to Group C in women were 59.50, 62.72, and 66.13%, respectively (P = 0.007). After binary logistic regression analysis, for women, compared with Group C, the ORs for LFR were 4.814 in Group A (95% CI, 1.266–18.309, P = 0.021) and were 3.204 in Group B (95% CI, 0.949–10.812, P = 0.061). Male 25-OHD levels were not related to the probability of low fertilisation rate (P > 0.05).

Conclusions

Circulating 25-OHD concentrations in women appear to be associated with normal fertilisation rates and low fertilisation rates in IVF cycles, but not in men. A further randomized controlled trial with vitamin D supplementation is needed to demonstrate whether female vitamin D levels exert an effect on the normal fertilisation process.

Trial registration

https://clinicaltrials.gov/;NCT03305510; Registered 08 October 2017 - Retrospectively registered.

Effect of serum 25-hydroxyvitamin D levels on sperm quality and assisted reproductive technology outcomes for men of infertile Chinese couples

INTRODUCTION

Vitamin D insufficiency/deficiency is highly prevalent in China, but its effect on sperm quality and outcomes of assisted reproductive technology (ART) in men from infertile couples is not clear. This study aimed to explore the association of serum 25-hydroxyvitamin D (25OHD) levels and semen parameters, as well as ART outcomes for men from infertile couples.

MATERIALS AND METHODS

This study recruited 1308 men from infertile couples who attended the Reproductive Medicine Center of Peking University Third Hospital for first time from February to August 2019 (NCT03804294). Reproductive hormones levels, semen parameters, and clinical outcomes of ART were compared between vitamin D-deficient group (serum 25OHD ≤ 10 ng/mL), insufficient group (serum 25OHD 10-20 ng/mL), and sufficient group (serum 25OHD ≥ 20 ng/mL).

RESULTS

We found 27.7% of participants were vitamin D sufficient, suggesting high prevalence of vitamin D insufficiency/deficiency in China. Reproductive hormone levels were similar between the three groups. The total number of morphologically normal spermatozoa was significantly different between the three groups in all participants, impaired semen quality subgroup, and normozoospermia subgroup (P < .05) with the adjustment of confounders (age, BMI, alcohol consumption, cigarette smoking, and physical exercise). The percentage of normal sperm morphology significantly increased with elevated serum 25OHD levels in all participants and the participants with impaired semen quality (P < .05), and the total sperm count showed significant difference in participants with impaired semen quality (P = .026). For routine in vitro fertilization and intracytoplasmic sperm injection cycles, there were no differences in fertilization rate, top-quality embryo rate, biochemical pregnancy rate, and clinical pregnancy rate between serum 25OHD < 20 ng/mL and serum 25OHD ≥ 20 ng/mL groups.

CONCLUSIONS

Males of infertile couples with higher serum 25OHD levels exhibit better results in sperm morphology, and serum 25OHD levels may contribute to total sperm number in participants with impaired semen quality, but show no effects on the ART outcomes.

The effect of vitamin D on sperm motility and the underlying mechanism

Vitamin D deficiency is a common health issue around the world. We therefore evaluated the associations of semen quality with both serum and seminal plasma vitamin D levels and studied the mechanisms underlying these by incubating spermatozoa with 1,25(OH)₂D in vitro. Two hundred and twenty-two men were included in our study. Vitamin D was detected using an electrochemiluminescence method. Spermatozoa used for in vitro experiments were isolated by density gradient centrifugation. Positive relationships of serum 25(OH)D with semen volume and seminal plasma fructose were identified. Seminal plasma 25(OH)D level showed no relationship with serum 25(OH)D level, while it was inversely associated with sperm concentration and positively correlated with semen volume and sperm kinetic values. In vitro, sperm kinetic parameters increased after incubation with 1,25(OH)₂D, especially upon incubation for 30 min with it at a concentration of 0.1 nmol l⁻¹. Under these incubation conditions, the upward migration of spermatozoa increased remarkably with increasing adenosine triphosphate (ATP) concentration. The concentration of cyclic adenosine monophosphate (cAMP) and the activity of protein kinase A (PKA) were both elevated, and the PKA inhibitor, N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride (H89) reversed the increase of ATP production. The concentrations of cytoplasmic calcium ions and nicotinamide adenine dinucleotide (NADH) were both enhanced, while mitochondrial calcium uniporter (MCU) inhibitor, Ruthenium 360 (Ru360) did not reverse the increase of ATP production. Therefore, seminal plasma vitamin D may be involved in regulating sperm motility, and 1,25(OH)₂D may enhance sperm motility by promoting the synthesis of ATP both through the cAMP/PKA pathway and the increase in intracellular calcium ions.

Vitamin D status is not associated with reproductive parameters in young Spanish men

BACKGROUND

Relatively low sperm count was reported among young Spanish men in 2013. Several potential culprits have been suggested as explanations for reported trends in sperm counts in Western men, including lifestyles. Although controversial, some studies suggest that semen parameters, such as low sperm motility or abnormal morphology, may be associated with low serum vitamin D levels.

OBJECTIVES

To evaluate associations between semen parameters and reproductive hormones and serum 25-hydroxyvitamin D (25OHD) status in young Spanish men and to examine these associations in relation to dietary intake of vitamin D.

MATERIALS AND METHODS

This cross-sectional study includes 198 university students recruited in 2010-2011 in southern Spain, who provided samples of blood and semen and food frequencies. Semen quality was evaluated by measuring volume, concentration, sperm counts, motility, and morphology, according to the WHO guidelines. Serum samples were analyzed for total 25OHD and reproductive hormones, including FSH, LH, testosterone, inhibin B, and estradiol. Dietary vitamin D intake was assessed using a validated food frequency questionnaire. Associations with semen quality and reproductive hormones were examined using linear regression, adjusting for potential confounders.

RESULTS

Almost all men had adequate levels of serum vitamin D - only three men (1.5%) were vitamin D deficient (<30 nmol/L) and 17% were insufficient (<50 nmol/L). However, dietary vitamin D intakes were relatively low (below recommended 600 IU/day in 99% of men). Neither dietary intake nor serum vitamin D levels were associated with any sperm parameter or any reproductive hormone (all p ≥ 0.09).

DISCUSSION

We did not observe an association between vitamin D status and any reproductive parameter in our study population.

CONCLUSIONS

Our results suggest that serum vitamin D levels are sustained in Spanish men despite low dietary intake and therefore low vitamin D does not explain the poor semen quality previously observed in these young Spanish men.

Effects of Diet-Induced Obesity and Deficient in Vitamin D on Spermatozoa Function and DNA Integrity in Sprague-Dawley Rats

Obesity has adverse effects on male fertility and usually is diagnosed with a prevalence of vitamin D deficiency (VD⁻). Discussion on the impact of obesity/VD⁻ on sperm function has been limited. This study analyzed the effects of diet-induced obesity/VD⁻ on viability and plasma membrane integrity (PMI), superoxide anion (O₂⁻) level, and DNA fragmentation (DNA_frag) in sperm Sprague-Dawley rats. The males were randomized into four groups and fed for a period of 12 weeks: G1: control diet with vitamin D (C/VD⁺), G2: control diet without vitamin D (C/VD⁻), G3: high-fat diet with vitamin D (HF/VD⁺), and G4: high-fat diet without vitamin D (HF/VD⁻). Sperm function parameters were analyzed by flow cytometry. PMI percentages and O₂⁻ levels were not affected by any of the diets. DNA fragmentation was increasing significantly (p<0.05) in the spermatozoa of animals with diets vitamin D deficient (G2) and diet-induced obesity (G4). Our results allow us to point out that diet-induced obesity and VD⁻ produce greater damage in DNA sperm of rats. The use of nutraceuticals containing vitamin D could be reducing the risk of fragmentation of DNA in spermatozoa.

Association of serum content of 25-hydroxy vitamin D with semen quality in normozoospermic and oligoasthenoteratozoospermic men

BACKGROUND

Vitamin D has multifaceted function in human reproductive physiology. It has been revealed that vitamin D is involved in spermatogenesis, and semen quality can be linked to vitamin D status in men.

OBJECTIVE

Evaluating the correlation of 25-hydroxy vitamin D (25-OHD) levels in serum with basic and advanced semen parameters and essential determinants of spermatozoa function.

MATERIALS AND METHODS

Participants were categorized, based on semen parameters, into normozoospermic (NS) and oligoasthenoteratozoospermic (OAT) men. Serum level of 25-OHD was measured. Apoptotic status of spermatozoa, mitochondrial membrane potential and reactive oxygen species content of semen were assessed.

RESULTS

Difference of 25-OHD concentration in serum of NS men versus OAT ones did not meet significance threshold. DNA fragmentation, reactive oxygen species content of semen and mitochondrial membrane potential state revealed significant difference between NS and OAT subjects. There were no significant differences in basic and functional semen parameters when men were stratified based on serum 25-OHD level. Taking both 25-OHD and semen categories (NS and OAT) into consideration did not indicate any significant difference in studied parameters. Total motility of spermatozoa was positively correlated with serum concentration of 25-OHD in all studied subjects. In addition, normal morphology of spermatozoa in NS men revealed a positive and significant correlation with levels of 25-OHD in serum.

CONCLUSION

Vitamin D may affect motility and morphology of spermatozoa. Lower content of serum vitamin D may affect fertility of men and should be considered in examination of men with abnormal spermogram.

Possible influence of vitamin D on male reproduction

Vitamin D is a versatile signaling molecule with an established role in the regulation of calcium homeostasis and bone health. In recent years the spectrum of vitamin D target organs has expanded and a reproductive role is supported by the presence of the vitamin D receptor (VDR) and the vitamin D metabolizing enzymes in the gonads, reproductive tract, and human spermatozoa. Interestingly, expression levels of VDR and the vitamin D inactivating enzyme CYP24A1 in human spermatozoa serve as positive predictive markers of semen quality and are higher expressed in spermatozoa from normal than infertile men. VDR mediates a non-genomic increase in intracellular calcium concentration, sperm motility, and induces the acrosome reaction. Furthermore, functional animal model studies have shown that vitamin D is important for sex steroid production, estrogen signaling, and semen quality. Cross-sectional clinical studies have supported the notion of a positive association between serum 25-hydroxyvitamin D (25-OHD) level and semen quality in both fertile and infertile men. However, it remains to be determined whether this association reflects a causal effect. The VDR is ubiquitously expressed and activated vitamin D is a regulator of insulin, aromatase, and osteocalcin. Hence, it is plausible that the influence of vitamin D on gonadal function may be mediated indirectly through other vitamin D regulated endocrine factors. Recent studies have indicated that vitamin D supplementation may be beneficial for couples in need of assisted reproductive techniques as high serum vitamin D levels were found to be associated with a higher chance of achieving pregnancy. Randomized clinical trials are needed to determine whether systemic changes in vitamin D metabolites can influence semen quality, fertility, and sex steroid production in infertile men. In this review known and possible future implications of vitamin D in human male reproduction function will be discussed.

The role of vitamin D in male fertility: A focus on the testis

In the last decade, vitamin D has emerged as a pleiotropic molecule with a multitude of autocrine, paracrine and endocrine functions, mediated by classical genomic as well as non-classical non-genomic actions, on multiple target organs and systems. The expression of vitamin D receptor and vitamin D metabolizing enzymes in male reproductive system, particularly in the testis, suggests the occurrence of vitamin D synthesis and regulation as well as function in the testis. The role of vitamin D in the modulation of testis functions, including hormone production and spermatogenesis, has been investigated in animals and humans. Experimental studies support a beneficial effect of vitamin D on male fertility, by modulating hormone production through genomic and non-genomic actions, and, particularly, by improving semen quality essentially through non-genomic actions. However, clinical studies in humans are controversial. Indeed, vitamin D seems to contribute to the modulation of the bioavailable rather than total testosterone. Moreover, although an increased prevalence or risk for testosterone deficiency was reported in men with vitamin D deficiency in observational studies, the majority of interventional studies demonstrated the lack of effect of vitamin D supplementation on circulating levels of testosterone. The most consistent effect of vitamin D was reported on semen quality. Indeed, vitamin D was shown to be positively associated to sperm motility, and to exert direct actions on spermatozoa, including non-genomic driven modulation of intracellular calcium homeostasis and activation of molecular pathways involved in sperm motility, capacitation and acrosome reaction. The current review provides a summary of current knowledge on the role of vitamin D in male fertility, by reporting clinical and experimental studies in humans and animals addressing the relationship between vitamin D and testis function.

Interactions between oestrogen and 1α,25(OH)2-vitamin D3 signalling and their roles in spermatogenesis and spermatozoa functions

Oestrogens and 1α,25(OH)₂-vitamin D₃ (1,25-D₃) are steroids that can provide effects by binding to their receptors localised in the cytoplasm and in the nucleus or the plasma membrane respectively inducing genomic and non-genomic effects. As confirmed notably by invalidation of the genes, coding for their receptors as tested with mice with in vivo and in vitro treatments, oestrogens and 1,25-D₃ are regulators of spermatogenesis. Moreover, some functions of ejaculated spermatozoa as viability, DNA integrity, motility, capacitation, acrosome reaction and fertilizing ability are targets for these hormones. The studies conducted on their mechanisms of action, even though not completely elicited, have allowed the demonstration of putative interactions between their signalling pathways that are worth examining more closely. The present review focuses on the elements regulated by oestrogens and 1,25-D₃ in the testis and spermatozoa as well as the interactions between the signalling pathways of both hormones.

Molecular actions of vitamin D in reproductive cell biology

Vitamin D (VitD) is an important secosteroid and has attracted attention in several areas of research due to common VitD deficiency in the population, and its potential to regulate molecular pathways related to chronic and inflammatory diseases. VitD metabolites and the VitD receptor (VDR) influence many tissues including those of the reproductive system. VDR expression has been demonstrated in various cell types of the male reproductive tract, including spermatozoa and germ cells, and in female reproductive tissues including the ovaries, placenta and endometrium. However, the molecular role of VitD signalling and metabolism in reproductive function have not been fully established. Consequently, the aim of this work is to review current metabolic and molecular aspects of the VitD–VDR axis in reproductive medicine and to propose the direction of future research. Specifically, the influence of VitD on sperm motility, calcium handling, capacitation, acrosin reaction and lipid metabolism is examined. In addition, we will also discuss the effect of VitD on sex hormone secretion and receptor expression in primary granulosa cells, along with the impact on cytokine production in trophoblast cells. The review concludes with a discussion of the recent developments in VitD–VDR signalling specifically related to altered cellular bioenergetics, which is an emerging concept in the field of reproductive medicine.

Vitamin D and male reproductive system

Vitamin D deficiency is a highly prevalent worldwide condition and affects people of all ages. The most important role of vitamin D is the regulation of intestinal calcium absorption and metabolism of calcium and phosphorus to maintain muscle and bone homeostasis. Furthermore, in recent years it has been discovered that the vitamin D receptor (VDR) is widely distributed in many organs and tissues where vitamin D can perform other actions that include the modulation of the immune response, insulin secretion, anti-proliferative effect on cells of vascular smooth muscle, modulation of the renin-angiotensin-aldosterone system and regulates cell growth in several organs. The VDR is widely distributed in the male reproductive system. Vitamin D induces changes in the spermatozoa's calcium and cholesterol content and in protein phosphorylation to tyrosine/threonine residues. These changes could be involved in sperm capacitation. Vitamin D seems to regulate aromatase expression in different tissues. Studies analyzing seasonal variations of sex steroids in male populations yield conflicting results. This is probably due to the wide heterogeneity of the populations included according to age, systemic diseases and obesity.

CORRELATIONS BETWEEN POLYMORPHISMS OF ESTROGEN 1, VITAMIN D RECEPTORS AND HORMONAL PROFILE IN INFERTILE MEN

Objective

Estrogen receptor alpha (ESR1) polymorphisms (XbaI and PvuII) and vitamin D receptor (VDR) polymorphisms (FokI, BsmI, ApaI and TaqI) are the most frequently studied regarding the correlations with the infertility in males, but the results are controversial.The purpose of this study is to evaluate possible correlations between hormonal markers, VDR and ESR1 genotypes and semen analysis, in order to bring new data for a better understanding of male infertility.

Subjects and Methods

42 infertile men and 28 controls were enrolled. The polymorphisms of VDR gene (ApaI, TaqI, BsmI and FokI) and ESR1 (XbaI and PvuII) were performed by PCR-RFLP, along with hormonal markers.

Results

An important correlation between PvuII polymorphism and infertility status was revealed. A significant difference between control and infertility group regarding the presence of BsmI (A>G) and ApaI (G>T) polymorphisms was observed in infertile group, prolactin and DHEA were found to correlate significantly statistic with BsmI GG genotype, whereas ApaI AA genotype correlates with prolactin and SHBG levels.

Conclusions

By a multivariate analysis, we demonstrated a cumulative effect of some genetic variants in the hormonal status of infertile patients. Therefore, we show that specific genetic variants of ESR1 and VDR genes may jointly influence human spermatogenesis.

Serum 25-hydroxyvitamin D levels and testosterone deficiency in middle-aged Korean men: a cross-sectional study

Previous studies have demonstrated that male hypogonadism is associated with a low level of vitamin D. However, no reports have investigated the effects of vitamin D on testosterone levels in Korean men. Our aim was to investigate whether testosterone levels are associated with serum vitamin D levels and whether seasonal variation exists. This cross-sectional study analyzed serum 25-hydroxyvitamin D [25(OH)D], total testosterone (TT), and free testosterone (FT) in 652 Korean men over 40 years of age who had undergone a comprehensive medical examination. The average age of the subjects was 56.7 ± 7.9 years, and the mean serum 25(OH)D, TT and FT levels were 21.23 ± 7.9 ng ml⁻¹, 4.70 ± 1.6 ng ml⁻¹, and 8.12 ± 3.3 pg ml⁻¹, respectively. In the multiple linear regression model, 25(OH)D showed positive association with TT (β =0.137, P < 0.001) and FT (β =0.103, P = 0.008). 25(OH)D and FT showed similar seasonal or monthly variation after adjustment for age. A vitamin D deficiency [25(OH)D < 20 ng ml⁻¹] was associated with an increased risk of deficiencies of TT (<2.30 ng ml⁻¹) (odds ratio [OR]: 2.65; 95% confidence interval [CI]: 1.21–5.78, P = 0.014) and FT (<6.50 pg ml⁻¹) (OR: 1.44; 95% CI: 1.01–2.06 P = 0.048) after adjusting for age, season, body mass index, body composition, chronic disease, smoking, and alcohol use. In conclusion, we demonstrated a positive correlation between 25(OH)D and testosterone, which showed similar seasonal variation in Korean men.

Males with low serum levels of vitamin D have lower pregnancy rates when ovulation induction and timed intercourse are used as a treatment for infertile couples: results from a pilot study

BACKGROUND

Vitamin D (Vit D) is important for the regulation of reproductive physiology. In humans, maternal Vit D deficiency has been implicated in several reproductive- and pregnancy-related disorders. Very few data are available regarding the Vit D status in male partners of couples attempting pregnancy. This observational study (IRB Prot. N. 078/13) aimed to evaluate whether low Vit D serum levels in males might decrease the rate of successful conception in couples attempting pregnancy.

METHODS

Male and female partners of infertile couples (n = 102) were classified into 2 GROUPS according to normal (≥30 ng/ml) or low (below 30 ng/ml) serum Vit D levels in male partners. Semen analysis was performed in each male participant based on the WHO reference criteria. The female partners of both groups were subjected to 3 consecutive cycles of gonadotropin-induced mono-ovulation. The main outcome measures included the clinical pregnancy rate, delivery per patient and per cycle, and miscarriage rate between the 2 groups evaluated at the end of the three-month period of the study.

RESULTS

In male partners of both groups, standard semen analysis did not highlight substantial differences in sperm concentration, sperm progressive motility, or typical form. The pregnancy rates per patient and per cycle and delivery rates per patient and per cycle were all significantly higher (p< 0.05) in couples with normal Vit D levels.

CONCLUSIONS

These results suggest the existence of a relationship between male Vit D serum levels and semen ability to begin a pregnancy during cycles of timed vaginal intercourse.

Expression of Vitamin D Receptor in Seminal Vesicles of Cholesterol Formula Mice

Objectives

Genomic function of vitamin D receptor (VDR) indicates spermatogenesis that is important for in male reproductive organ authors evaluated the VDR expression in seminal vesicles with high cholesterol (HC) formula diet rat, because there is no report about relationship or difference in VDR in seminal vesicles between HC and control.

Methods

Male C57BL/6 mice aged 5 weeks were raised for 13 weeks. After one week of adaptation-period, they were fed different diet on normal AIN-93G diet, or HC diet containing 2% cholesterol for 12 weeks. The antibodies used were rabbit anti-VDR primary polyclonal.

Results

There was no significant difference in VDR reactivity in seminal vesicles, body weight of rat and weight of seminal vesicles between HC group and normal control group.

Conclusion

Our data give the no difference in expression of VDR of seminal vesicles rat between HC formula diet and normal AIN-93G diet. But we confirmed the VDR expression in seminal vesicles.

Human sperm liver receptor homolog-1 (LRH-1) acts as a downstream target of the estrogen signaling pathway

In the last decade, the study of human sperm anatomy, at molecular level, has revealed the presence of several nuclear protein receptors. In this work, we examined the expression profile and the ultrastructural localization of liver receptor homolog-1 (LRH-1) in human spermatozoa. We evidenced the presence of the receptor by Western blotting and real time-RT-PCR. Furthermore, we used immunogold electron microscopy to investigate the sperm anatomical regions containing LRH-1. The receptor was mainly located in the sperm head, whereas its expression was reduced in the neck and across the tail. Interestingly, we observed the presence of LRH-1 in different stages of testicular germ cell development by immunohistochemistry. In somatic cells, it has been suggested that the LRH-1 pathway is tightly linked with estrogen signaling and the important role of estradiol has been widely studied in sperm cells. To assess the significance of LRH-1 in male gametes and to deepen understanding of the role of estrogens in these cells, we investigated important sperm features such as motility, survival and capacitation. Spermatozoa were treated with 10 nm estradiol and the inhibition of LRH-1 reversed the estradiol stimulatory action. From our data, we discovered that human spermatozoa can be considered a new site of expression for LRH-1, evidencing its role in sperm motility, survival and cholesterol efflux. Furthermore, we may presume that in spermatozoa the LRH-1 effects are closely integrated with the estrogen signaling, supporting LRH-1 as a downstream effector of the estradiol pathway on some sperm functions.

Vitamin D and assisted reproduction: should vitamin D be routinely screened and repleted prior to ART? A systematic review

PURPOSE

To review the current literature regarding the role of vitamin D status in pregnancy outcomes in women undergoing assisted reproductive technology (ART) and to assess cost-effectiveness of routine vitamin D deficiency screening and repletion prior to initiation of ART.

METHODS

A systematic literature review was conducted using PubMed. Relevant study outcomes were compared among the selected studies. A cost-benefit analysis was performed using a decision tree mathematical model with sensitivity analyses from the perspective of direct societal cost. Published data were used to estimate probabilities and costs in 2014 US dollars.

RESULTS

Thirty-four articles were retrieved, of which eight met inclusion criteria. One study demonstrated a negative relationship between vitamin D status and ART outcomes, while two studies showed no association. The remaining five studies concluded that ART outcomes improved after vitamin D repletion.

CONCLUSION

The majority of reviewed studies reported a decrement in ART outcomes in patients with vitamin D deficiency. Cost-benefit analyses suggested that screening and supplementing vitamin D prior to ART might be cost effective, but further evidence is needed. Given the absence of Level I evidence regarding vitamin D status and ART outcomes, full endorsement of routine vitamin D screening and supplementation prior to ART is premature.

The vitamin D receptor localization and mRNA expression in ram testis and epididymis

The objectives of present study were to investigate the presence of vitamin D receptor (VDR) in testis and epididymis of ram by polymerase chain reaction (PCR), to locate VDR in testis and epididymis by immunohistochemistry and to compare difference of VDR expression between testis and epididymis before and after sexual maturation by Real time-PCR and Western blot. The results showed that VDR exists in the testis and epididymis of ram while VDR protein in testis and epididymis was localized in Leydig cells, spermatogonial stem cells, spermatocytes, Sertoli cells and principal cells. For the adult ram, the amounts of VDR mRNA and VDR protein were less (p < 0.01) in testis than compared with caput, corpus and cauda epididymis. For prepubertal ram, the result showed the same trend (p < 0.01). However, the expression levels of VDR mRNA and VDR protein in caput, corpus, cauda epididymis and testis showed no significant difference (p > 0.05) between adult and prepubertal. In conclusion, VDR exists in testis and epididymis of ram, suggesting 1α,25-(OH)(2)VD(3) may play a role in ram reproduction.

Functional Importance of 1α,25(OH)2-Vitamin D3 and the Identification of Its Nongenomic and Genomic Signaling Pathways in the Testis

The 1α,25(OH)2-vitamin D3 (1,25-D3) is known by its classic effects on Ca2+ metabolism and regulation of cellular proliferation and differentiation. The hormone 1,25-D3 acts in the testis through nongenomic and genomic events being implicated in the success of spermatogenesis in rats and in human being. The aim of this review was to highlight the effect and intracellular pathways of 1,25-D3 to modulate the spermatogenesis. The pivotal role of 1,25-D3 in male reproduction is reinforced by the presence of VDR and 1α-hydroxylase in reproductive tract. Also, the marked expression of VDR and the VD metabolizing enzymes in human testis, ejaculatory tract, and mature spermatozoa implicates the 1,25-D3 in spermatogenesis and maturation of human spermatozoa. Among genomic events, 1,25-D3 influences the expression of calcium binding protein and stimulates aromatase gene expression through a nongenomic activation of the membrane-bound VDR receptor involving the PKA pathway in the testis. Also, 1,25-D3 stimulates amino acid transport and exocytosis in testis by nongenomic events coupled to ionic currents triggered at plasma membrane. All together, the demonstration that 1,25-D3 regulates both Sertoli cell and sperm function may be useful for the study and development of new therapeutic strategies for the male reproductive disorders.

Vitamin D and male reproduction

Vitamin D is a versatile signalling molecule with a well-established role in the regulation of calcium homeostasis and bone health. The spectrum of vitamin D target organs has expanded and the reproductive role of vitamin D is highlighted by expression of the vitamin D receptor (VDR) and enzymes that metabolize vitamin D in testis, male reproductive tract and human spermatozoa. The expression levels of VDR and CYP24A1 in human spermatozoa serve as positive predictive markers of semen quality, and VDR mediates a nongenomic increase in intracellular calcium concentration that induces sperm motility. Interestingly, functional animal models show that vitamin D is important for estrogen signalling and sperm motility, while cross-sectional studies support the positive association between serum 25-hydroxyvitamin D level and sperm motility in both fertile and infertile men. Expression of VDR and enzymes that metabolize vitamin D in fetal testis indicates a yet unknown role during development, which may be extrapolated from invasive testicular germ cell tumours where 1α,25-dihydroxyvitamin D induces a mesodermal differentiation of the pluripotent testicular cancer cells. Taken together, vitamin D signalling has a positive effect on semen quality, increases estrogen responsiveness and differentiates germ cell tumours. Future studies are needed to determine when 1α,25-dihydroxyvitamin D acts in a paracrine manner and whether systemic changes, which are subject to pharmacological modulation, could influence male reproductive function.

Vitamin D in human reproduction: a narrative review

BACKGROUND

Special attention has been given to the effect of vitamin D supplementation on fertility outcomes in both sexes.

AIMS

The purpose of this narrative review was to elucidate the role of vitamin D in male and female reproduction, providing current evidence from both animal and human studies.

MATERIALS AND METHODS

Using PubMed and Medline, we searched for publications during the last 30 years regarding the role of vitamin D in human reproduction.

RESULTS

Accumulating evidence from animal and human studies suggests that vitamin D is involved in many functions of the reproductive system in both genders. In women, vitamin D status has been associated with in vitro fertilization (IVF) outcome, features of polycystic ovarian syndrome (PCOS) and endometriosis. Although several data converge towards a beneficial effect of vitamin D supplementation in metabolic disturbances in women with PCOS, a significant knowledge gap precludes the establishment of a clear cause-effect relationship. In men, vitamin D status has been associated with semen quality and sperm count, motility and morphology. There is evidence for a favourable effect of vitamin D supplementation on semen quality, testosterone concentrations and fertility outcomes.

DISCUSSION

Studies with superior methodological characteristics are needed in order to establish a role for vitamin D on the treatment of female and male infertility.

CONCLUSIONS

Recent data on vitamin D provide new insights in the complex pathogenesis and treatment of infertility.

Calcitriol downregulates TNF-α and IL-6 expression in cultured placental cells from preeclamptic women

Placenta is an important source and target of hormones that contribute to immunological tolerance and maintenance of pregnancy. In preeclampsia (PE), placental calcitriol synthesis is low; whereas pro-inflammatory cytokines levels are increased, threatening pregnancy outcome. Previously, we showed that calcitriol inhibits Th-1 cytokines under experimental inflammatory conditions in normal trophoblasts. However, a study of the regulation of inflammatory cytokines by calcitriol in trophoblasts from a natural inflammatory condition, such as PE, is still lacking. Therefore, the aim of the present study was to investigate calcitriol effects upon TNF-α, IFN-γ, IL-6 and IL-1β in cultured placental cells from preeclamptic women by using qPCR and ELISA. Placentas were collected after cesarean section from preeclamptic women and enriched trophoblastic preparations were cultured in the absence or presence of different calcitriol concentrations during 24h. In these cell cultures, pro-inflammatory cytokines TNF-α and IL-6 secretion and mRNA expression were downregulated by calcitriol (P<0.05). No significant effects of calcitriol upon IFN-γ and IL-1β were observed. In addition, basal expression of TNF-α, IL-6 and IL-1β decreased as the cells formed syncytia. Our study supports an important autocrine/paracrine role of placental calcitriol in controlling adverse immunological responses at the feto-maternal interface, particularly in gestational pathologies associated with exacerbated inflammatory responses such as preeclampsia.

Non-genomic effects of vitamin D in human spermatozoa

The spectrum for vitamin D (VD) mediated effects has expanded in recent years. Activated VD (1,25(OH)(2)D(3)) binds to the VD receptor (VDR) and mediates non-genomic effects through the alternative ligand binding-pocket (VDR-ap) or regulates gene transcription through the genomic binding-pocket. VDR and VD-metabolizing enzymes are expressed in human testis, male reproductive tract and mature spermatozoa, and VD is considered important for male reproduction. Expression of the VD-inactivating enzyme CYP24A1 at the annulus of human spermatozoa distinguish normal and infertile men with high specificity, and CYP24A1 expression is positively correlated with all semen variables and suggested as a marker for both semen quality and VD responsiveness. Moreover, spermatozoa are transcriptionally silent and are therefore a unique model to study non-genomic effects. 1,25(OH)(2)D(3) induced a rapid increase in intracellular calcium concentration [Ca(2+)](i) in human spermatozoa. The [Ca(2+)](i) increase was abrogated by the non-genomic VDR antagonist 1β,25(OH)(2)D(3), while the specific agonist for VDR-ap (JN) increased [Ca(2+)](i) with similar kinetics as 1,25(OH)(2)D(3). The rise in [Ca(2+)](i) originated as a Ca(2+)-release from intracellular stores since inhibition of phospholipase-C diminished the 1,25(OH)(2)D(3) mediated Ca(2+) response, while suspending spermatozoa in a nominally Ca(2+)-free medium did not affect the VD mediated Ca(2+) rise. The spatio-temporal kinetics of the VD-response differed from the progesterone-mediated increase in [Ca(2+)](i) as the VD-mediated Ca(2+) rise was not observed in the tail region and was independent of extracellular Ca(2+). A functional role of the VD-mediated Ca(2+) increase was supported by showing that 1,25(OH)(2)D(3) increased sperm motility and induced the acrosome reaction in vitro.

Vitamin D metabolism, sex hormones, and male reproductive function

The spectrum of vitamin D (VD)-mediated effects has expanded in recent years, and VD is now recognized as a versatile signaling molecule rather than being solely a regulator of bone health and calcium homeostasis. One of the recently identified target areas of VD is male reproductive function. The VD receptor (VDR) and the VD metabolizing enzyme expression studies documented the presence of this system in the testes, mature spermatozoa, and ejaculatory tract, suggesting that both systemic and local VD metabolism may influence male reproductive function. However, it is still debated which cell is the main VD target in the testis and to what extent VD is important for sex hormone production and function of spermatozoa. This review summarizes descriptive studies on testicular VD metabolism and spatial distribution of VDR and the VD metabolizing enzymes in the mammalian testes and discusses mechanistic and association studies conducted in animals and humans. The reviewed evidence suggests some effects of VD on estrogen and testosterone biosynthesis and implicates involvement of both systemic and local VD metabolism in the regulation of male fertility potential.

Associations between testosterone, bone mineral density, vitamin D and semen quality in fertile and infertile Chinese men

Testosterone (T) and vitamin D (VD) interact in androgen deficient men, however, this interaction and subsequent semen quality and bone mineral density (BMD) status is not clear in infertile men. Our objective was to investigate T, VD, semen quality, BMD and their relationships in Chinese infertile men. We conducted a cross-sectional study of 559 men aged 20-40 years, including 195 fertile men, 9 infertile men with known risk factors for osteoporosis (WR) and 355 infertile men without known risk factors for osteoporosis (WOR). WOR infertile men constituted 314 oligo-, astheno-, teratospermic or normospermic infertile men (OATN men) and 41 non-obstructive azoospermic men (NOA men). Differences of parameters were assessed, and the relationships were adjusted by multiple linear regression. WOR infertile men had significantly lower T, lumbar spine and total hip BMD than fertile men (all p < 0.05). Bioavailable T (Bio-T) and 25-hydroxyvitamin D [25(OH)D] were independent determinants of BMD in WOR infertile men (all p < 0.01) but not in fertile men. After stratifying Bio-T, WOR infertile men had lower BMD than fertile men (all p < 0.05) in low Bio-T subgroups (Bio-T ≤ 11.6 nmol/L), but not high Bio-T subgroups (Bio-T > 11.6 nmol/L). 25(OH)D was an independent determinant of sperm motility and morphology in WOR OATN men (all p < 0.05), with only borderline significance in fertile men(motility: p = 0.047; morphology: p = 0.056). T determined sperm concentration (square root) and morphology in WOR OATN men (all p < 0.001). No correlations between T and 25(OH)D were found in all groups. We suggest that infertile men have lower T and BMD than fertile men. 25(OH)D and T were associated with low BMD and poor semen quality in infertile men.

Vitamin D and fertility: a systematic review

BACKGROUND

Vitamin D has been well-known for its function in maintaining calcium and phosphorus homeostasis and promoting bone mineralization. There is some evidence that in addition to sex steroid hormones, the classic regulators of human reproduction, vitamin D also modulates reproductive processes in women and men.

AIM

The aim of this review was to assess the studies that evaluated the relationship between vitamin D and fertility in women and men as well as in animals.

METHODS

We performed a systematic literature search in Pubmed for relevant English language publications published until October 2011.

RESULTS AND DISCUSSION

The vitamin D receptor (VDR) and vitamin D metabolizing enzymes are found in reproductive tissues of women and men. Vdr knockout mice have significant gonadal insufficiency, decreased sperm count and motility, and histological abnormalities of testis, ovary and uterus. Moreover, we present evidence that vitamin D is involved in female reproduction including IVF outcome (clinical pregnancy rates) and polycystic ovary syndrome (PCOS). In PCOS women, low 25-hydroxyvitamin D (25(OH)D) levels are associated with obesity, metabolic, and endocrine disturbances and vitamin D supplementation might improve menstrual frequency and metabolic disturbances in those women. Moreover, vitamin D might influence steroidogenesis of sex hormones (estradiol and progesterone) in healthy women and high 25(OH)D levels might be associated with endometriosis. In men, vitamin D is positively associated with semen quality and androgen status. Moreover, vitamin D treatment might increase testosterone levels. Testiculopathic men show low CYP21R expression, low 25(OH)D levels, and osteoporosis despite normal testosterone levels.

Expression of the vitamin D metabolizing enzyme CYP24A1 at the annulus of human spermatozoa may serve as a novel marker of semen quality

Vitamin D (VD) is important for male reproduction in mammals and the VD receptor (VDR) and VD-metabolizing enzymes are expressed in human spermatozoa. The VD-inactivating enzyme CYP24A1 titrates the cellular responsiveness to VD, is transcriptionally regulated by VD, and has a distinct expression at the sperm annulus. Here, we investigated if CYP24A1 expression serves as a marker for VD metabolism in spermatozoa, and whether CYP24A1 expression was associated with semen quality. We included 130 men (53 healthy young volunteers and 77 subfertile men) for semen analysis and immunocytochemical (ICC) detection of CYP24A1. Another 40 men (22 young, 18 subfertile) were tested for in vitro effects of 1,25(OH)(2)D(3) on intracellular calcium concentration ([Ca(2+)](i)) and sperm motility. Double ICC staining showed that CYP24A1 and VDR were either concomitantly expressed or absent in 80% of the spermatozoa from young men. The median number of CYP24A1-expressing spermatozoa was 1% in subfertile men and thus significantly (p < 0.0005) lower than 25% in spermatozoa from young men. Moreover, CYP24A1 expression correlated positively with total sperm count, -concentration, -motility and -morphology (all p < 0.004), and the percentage of CYP24A1-positive spermatozoa increased (15 vs. 41%, p < 0.0005) after percoll-gradient-centrifugation. We noticed that the presence of >3% CYP24A1-positive spermatozoa distinguished young men from subfertile men with a sensitivity of 66.0%, a specificity of 77.9% and a positive predictive value of 98.3%. Functional studies revealed that 1,25(OH)(2)D(3) increased [Ca(2+)](i) and sperm motility in young healthy men, while 1,25(OH)(2)D(3) was unable to increase motility in subfertile patients. In conclusion, we suggest that CYP24A1 expression at the annulus may serve as a novel marker of semen quality and an objective proxy for sperm function.