Sperm DNA damage in non-familial sporadic heritable retinoblastoma (NFSHRb)

Investigating the association between alcohol intake and male reproductive function: A current meta-analysis

Background

Alcohol use and alcohol-related health problems are on the rise in developing countries. This meta-analysis was conducted to determine the effects of alcohol consumption on human male reproductive function through semen parameters, antioxidants in semen, sperm DNA fragmentation, and sex hormones.

Methods

Studies regarding the effects of alcohol consumption on male reproductive function were searched on databases. Based on the random-effects model, STATA software was used to analyze and synthesize the selected studies. Alcoholics, moderate alcoholics, heavy alcoholics, and no alcoholics values were compared using the standard mean difference. Publications were assessed for publication bias by the Egger test.

Result

Forty studies were selected from databases examining the effect of alcohol consumption on male reproductive health in 23,258 people on five continents of the world. The meta-analysis revealed that alcohol intake reduced semen volume during each ejaculation (SMD = -0.51; 95% CI -0.77, -0.25). However, there were no significant associations with other semen indicators such as density, mobility, and normal and abnormal sperm count from this analysis. In addition, drinking alcohol lowered antioxidant enzymes in semen (SMD = -7.93; 95% CI -12.59, -3.28) but had no effect on sperm DNA fragmentation. Finally, the results showed a decrease in general testosterone levels (SMD = -1.60; 95% CI -2.05, -1.15), Follicle Stimulating Hormone (SMD = -0.47; 95% CI -0.88, -0.05), Luteinizing Hormone (SMD = -1.35; 95% CI -1.86, -0.83), but no effect in other sex hormones named as estradiol, Inhibin B and Sex Hormone-Binding Globulin. Furthermore, when analyzing subgroups at different drinking levels, the results showed that the moderate alcoholic group (less than 7 units/week) had no change in the semen index. Meanwhile, the group of heavy alcoholics (more than 7 units/week) harmed the semen index and sex hormones, especially by increasing estradiol.

Conclusion

There is evidence that alcohol consumption affected semen volume and antioxidant, reproductive hormones thus negatively affecting male reproductive function. This study might be necessary to make recommendations regarding alcohol consumption for men.

Exposure to polycyclic aromatic hydrocarbons and nicotine, and associations with sperm DNA fragmentation

Background

Tobacco smoking has been reported to cause DNA fragmentation and has been suggested to cause mutations in spermatozoa. These effects have been ascribed to the action of polycyclic aromatic hydrocarbons (PAH) present in the smoke. Simultaneously, DNA fragmentation has been associated with mutagenesis.

Objective

The aim of this study was to investigate whether levels of urinary biomarkers of PAH and nicotine exposure were associated with sperm DNA fragmentation.

Methods

In the urine of 381 men recruited from two cohorts of young men (17–21 years old) from the general Swedish population, the PAH metabolites 1‐hydroxypyrene and 2‐hydroxyphenanthrene, as well as the nicotine metabolite cotinine, were measured. The sperm DNA fragmentation index (DFI) was analysed using the sperm chromatin structure assay. Associations between the DFI, and PAH metabolite levels as continuous variables as well as in quartiles, were studied by general linear models adjusted for abstinence time. A similar analysis was carried out for cotinine levels, according to which the men were categorised as “non‐smoking” (n = 216) and “smoking” (n = 165).

Results

No association was found between levels of any of the three biomarkers and DFI, either as a continuous variable (p = 0.87–0.99), or when comparing the lowest and the highest quartiles (p = 0.11–0.61). The same was true for comparison of men categorised as non‐smoking or smoking (DFI 11.1% vs. 11.8%, p = 0.31).

Discussion

We found no evidence of PAH or nicotine exposure to be associated with DFI, which does not exclude that these exposures may have other effects on sperm DNA.

Conclusion

In these young men, levels of biomarkers of nicotine and PAH exposure were not associated with DFI.

From sperm to offspring: Assessing the heritable genetic consequences of paternal smoking and potential public health impacts

Individuals who smoke generally do so with the knowledge of potential consequences to their own health. What is rarely considered are the effects of smoking on their future children. The objective of this work was to review the scientific literature on the effects of paternal smoking on sperm and assess the consequences to offspring. A literature search identified over 200 studies with relevant data in humans and animal models. The available data were reviewed to assess the weight of evidence that tobacco smoke is a human germ cell mutagen and estimate effect sizes. These results were used to model the potential increase in genetic disease burden in offspring caused by paternal smoking, with specific focus on aneuploid syndromes and intellectual disability, and the socioeconomic impacts of such an effect. The review revealed strong evidence that tobacco smoking is associated with impaired male fertility, and increases in DNA damage, aneuploidies, and mutations in sperm. Studies support that these effects are heritable and adversely impact the offspring. Our model estimates that, with even a modest 25% increase in sperm mutation frequency caused by smoke-exposure, for each generation across the global population there will be millions of smoking-induced de novo mutations transmitted from fathers to offspring. Furthermore, paternal smoking is estimated to contribute to 1.3 million extra cases of aneuploid pregnancies per generation. Thus, the available evidence makes a compelling case that tobacco smoke is a human germ cell mutagen with serious public health and socio-economic implications. Increased public education should be encouraged to promote abstinence from smoking, well in advance of reproduction, to minimize the transmission of harmful mutations to the next-generation.