BACKGROUND The global obesity epidemic has paralleled a decrease in semen quality. Yet, the association between obesity and sperm parameters remains controversial. The purpose of this report was to update the evidence on the association between BMI and sperm count through a systematic review with meta-analysis. METHODS A systematic review of available literature (with no language restriction) was performed to investigate the impact of BMI on sperm count. Relevant studies published until June 2012 were identified from a Pubmed and EMBASE search. We also included unpublished data (n = 717 men) obtained from the Infertility Center of Bondy, France. Abstracts of relevant articles were examined and studies that could be included in this review were retrieved. Authors of relevant studies for the meta-analysis were contacted by email and asked to provide standardized data. RESULTS A total of 21 studies were included in the meta-analysis, resulting in a sample of 13 077 men from the general population and attending fertility clinics. Data were stratified according to the total sperm count as normozoospermia, oligozoospermia and azoospermia. Standardized weighted mean differences in sperm concentration did not differ significantly across BMI categories. There was a J-shaped relationship between BMI categories and risk of oligozoospermia or azoospermia. Compared with men of normal weight, the odds ratio (95% confidence interval) for oligozoospermia or azoospermia was 1.15 (0.93-1.43) for underweight, 1.11 (1.01-1.21) for overweight, 1.28 (1.06-1.55) for obese and 2.04 (1.59-2.62) for morbidly obese men. CONCLUSIONS Overweight and obesity were associated with an increased prevalence of azoospermia or oligozoospermia. The main limitation of this report is that studied populations varied, with men recruited from both the general population and infertile couples. Whether weight normalization could improve sperm parameters should be evaluated further.

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BMI in relation to sperm count: an updated systematic review and collaborative meta-analysis

The results of several studies point to an increased likelihood of abnormal semen parameters among overweight men, and an elevated risk for subfertility among couples in which the male partner is obese. Obesity is, therefore, associated with a higher incidence of male factor infertility. Several mechanisms might account for the effect of obesity on male infertility, both directly and indirectly, by inducing sleep apnea, alterations in hormonal profiles (reduced inhibin B and androgen levels accompanied by elevated estrogen levels) and increased scrotal temperatures, ultimately manifesting as impaired semen parameters (decreased total sperm count, concentration and motility; increased DNA fragmentation index). Neither the reversibility of obesity-associated male infertility with weight loss nor effective therapeutic interventions have been studied in-depth. The increasing prevalence of obesity calls for greater clinical awareness of its effects on fertility, better understanding of underlying mechanisms, and exploration into avenues of treatment.

https://www.clevelandclinic.org/reproductiveresearchcenter/docs/scipubs2009_01.pdf

The effect of obesity on sperm disorders and male infertility.

DNA fragmentation is an important factor in the aetiology of male infertility. However, it is still underevaluated and its inclusion in routine semen analysis is debated. DNA fragmentation has been shown to be a robust indicator of fertility potential, more so than conventional semen parameters. Men with high DNA fragmentation levels have significantly lower odds of conceiving, naturally or through procedures such as intrauterine insemination and IVF. Couples may be counselled to proceed directly to intracytoplasmic sperm injection as it is more successful in this group, avoiding costly procedures, recurrent failures or pregnancy losses; however, this treatment is not without limitations or risks. Ideally DNA fragmentation should be minimized where possible. Oxidative stress is the major cause of DNA fragmentation in spermatozoa. Endogenous and exogenous factors that contribute to oxidative stress are discussed, and in many cases are shown to be easily modifiable. Antioxidants play a protective role, although a delicate balance of reduction and oxidation is required for essential functions, including fertilization. Reducing oxidative stress may improve a couple's chances of conception either naturally or via assisted reproduction. Sources of oxidative stress therefore should be thoroughly examined in men with high levels of DNA fragmentation and modified where possible. DNA fragmentation is an important factor in the aetiology of male infertility. However it is still underevaluated and its inclusion in routine semen analysis is still debated. DNA fragmentation has been shown to be a robust indicator of fertility potential, more so than conventional semen parameters. Men with high levels of DNA fragmentation will have significantly lower odds of conceiving naturally or through procedures such as intrauterine insemination and IVF. Intracytoplasmic sperm injection (ICSI) may be much more successful in this group, and couples may be counselled to proceed directly to ICSI, avoiding costly procedures, recurrent failures or pregnancy losses. However, ICSI is not without its limitations or risks. Ideally, DNA fragmentation should be investigated and minimized where possible in men trying to conceive naturally or through assisted reproduction technology. Oxidative stress is the major cause of DNA fragmentation in spermatozoa. Endogenous and exogenous factors that contribute to oxidative stress are discussed and in many cases are easily modifiable. Antioxidants play a protective role, although a delicate balance of reduction and oxidation is required for essential sperm function, including fertilization. Reducing oxidative stress may improve a couple's chances of conception either naturally or via assisted reproduction treatment. Sources of oxidative stress therefore should be thoroughly examined in men with high levels of DNA fragmentation and modified where possible.

https://www.rbmojournal.com/article/S1472-6483(14)00118-7/pdf

Sperm DNA damage caused by oxidative stress: modifiable clinical, lifestyle and nutritional factors in male infertility.

Male obesity in reproductive-age men has nearly tripled in the past 30 y and coincides with an increase in male infertility worldwide. There is now emerging evidence that male obesity impacts negatively on male reproductive potential not only reducing sperm quality, but in particular altering the physical and molecular structure of germ cells in the testes and ultimately mature sperm. Recent data has shown that male obesity also impairs offspring metabolic and reproductive health suggesting that paternal health cues are transmitted to the next generation with the mediator mostly likely occurring via the sperm. Interestingly the molecular profile of germ cells in the testes and sperm from obese males is altered with changes to epigenetic modifiers. The increasing prevalence of male obesity calls for better public health awareness at the time of conception, with a better understanding of the molecular mechanism involved during spermatogenesis required along with the potential of interventions in reversing these deleterious effects. This review will focus on how male obesity affects fertility and sperm quality with a focus on proposed mechanisms and the potential reversibility of these adverse effects.

https://www.tandfonline.com/doi/pdf/10.4161/spmg.21362

Impact of obesity on male fertility, sperm function and molecular composition.

Consistent age-dependent declines in human semen quality: A systematic review and meta-analysis

Summary

Obesity can adversely affect human health, including fertility. While obesity can disturb the hormonal profile of the female organism and is associated with fertility loss, little is known about what effect male obesity has on fertility. The present study analysed sperm samples of 153 donors. The men were selected from couples attending an infertility clinic, who had tried for 12 months or more to achieve pregnancy without success. The age of the men under investigation was recorded, and their body mass index (BMI) was calculated. All semen samples were assessed for volume, concentration, motility and morphology. Sperm chromatin integrity was measured by sperm chromatin structure assay. Quality of sperm chromatin condensation was assessed by toluidine blue, aniline blue and chromomycin A3 staining. We can conclude that the impact of elevated BMI on the parameters investigated (basic semen parameters, chromatin integrity and chromatin condensation) was not proven in this study. On the other hand, ejaculate quality appeared to be affected by ageing. The impact was reflected by chromatin integrity, which is a factor that can substantially affect fertility in men, rather than by basic sperm parameters.

Male obesity and age in relationship to semen parameters and sperm chromatin integrity

Purpose
To analyse relationships between semen parameters, sperm chromatin integrity and frequencies of chromosomally unbalanced, disomic and diploid sperm in 13 Robertsonian and 37 reciprocal translocation carriers and to compare the results with data from 10 control donors.

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Balanced chromosomal translocations in men: relationships among semen parameters, chromatin integrity, sperm meiotic segregation and aneuploidy

A considerable proportion of male factor infertility cases are associated with inflammatory processes. The most common sexually transmissible agents causing sexually transmitted diseases in industrial countries are Chlamydia trachomatis, genital Ureaplasma and Mycoplasma spp. This study was undertaken to investigate whether these bacterial contaminants in semen affect sperm quality parameters and particularly DNA integrity (detected by sperm chromatin structure assay) in males from infertile couples (n = 293). The results showed that semen contaminations with the investigated bacterial species were not associated with sperm DNA fragmentation. However, contaminations with Mycoplasma spp. and C. trachomatis were associated with decreased sperm concentrations. Total sperm numbers in contaminated semen samples tended to be decreased, but not significantly. Mycoplasma had the highest adverse effect on sperm quality (concentration, motility, morphology and DNA condensation). Antibiotic therapy of the selected 47 men was successful in 55%, but semen quality parameters did not improve at least up to 3 months after the therapy. The presence of pathogenic bacteria in semen is primarily associated with low sperm production. Our data showed that Mycoplasma spp. contamination of semen had the highest adverse effect on sperm quality. Sperm chromatin integrity assessed by the presence of DNA breaks was not disturbed.

The effect of bacterial contamination of semen on sperm chromatin integrity and standard semen parameters in men from infertile couples

background: The swim-up and hyaluronan (HA)-binding methods are used for the selection of good quality spermatozoa to improve pregnancy rates and embryo quality and to reduce the number of miscarriages after IVF. We evaluated whether the processing of sperm by these methods reduces the frequency of spermatozoa with abnormal karyotypes and altered chromatin quality in balanced translocation carriers.

The effect of the swim-up and hyaluronan-binding methods on the frequency of abnormal spermatozoa detected by FISH and SCSA in carriers of balanced chromosomal translocations

Globozoospermia, characterised by the presence of round spermatozoa lacking acrosomes in an ejaculate, is a known cause of male infertility. Semen analysis, including sperm chromatin structure assay, toluidine blue, chromomycin A3 and aniline blue staining and fluorescence in situ hybridisation, was performed in an infertile globozoospermic patient to establish to which extent these genetic factors contributed to his infertility. No spermatozoa capable of hyaluronan (HA) binding were detected in the HA binding assay. Increased rates of immature spermatozoa with defective replacement of histones by protamines, DNA breaks and disturbed chromatin integrity and sperm aneuploid for the sex chromosomes were observed. Intracytoplasmic sperm injection (ICSI) was used in three in vitro fertilisation (IVF) cycles, and enough morphologically well-developing embryos were obtained in each cycle. However, no pregnancy was achieved. The infertility of our couple, resistant to IVF/ICSI treatment, was most probably caused by a combination of male and female factors.

R. Rybar

Papers

Male obesity and age in relationship to semen parameters and sperm chromatin integrity

Balanced chromosomal translocations in men: relationships among semen parameters, chromatin integrity, sperm meiotic segregation and aneuploidy

The effect of bacterial contamination of semen on sperm chromatin integrity and standard semen parameters in men from infertile couples

The effect of the swim-up and hyaluronan-binding methods on the frequency of abnormal spermatozoa detected by FISH and SCSA in carriers of balanced chromosomal translocations

Total globozoospermia associated with increased frequency of immature spermatozoa with chromatin defects and aneuploidy: a case report.