Smoking is bad for your sperm

By Sally Robertson, B.Sc.Aug 13 2012

In men with varicocele, smoking alters semen quality and sperm function as well as inducing seminal oxidative stress (OS), report researchers.

In a cross-sectional study of 110 patients with varicocele, smokers showed increased seminal lipid peroxidation compared with nonsmokers, as well as decreases in mitochondrial activity and DNA integrity of sperm.

There were also changes in the expression of proteins in seminal plasma, some of which have been related to male fertility, report Ricardo Pimenta Bertolla (Sao Paulo Federal University, Brazil) and team.

In their analysis of patients with varicocele, the team found that heavy smokers (20 or more cigarettes/day) had a significantly lower mean percentage of sperm with progressive motility compared with moderate smokers (1-19/day) and nonsmokers, at 42.8% versus 51.5% and 49.8%.

Heavy smokers also had a significantly lower mean volume of sperm than nonsmokers, at 2.9 mL versus 3.7 mL.

In addition, assessment by Comet assays showed that nonsmokers had a significantly higher mean percentage of sperm with high DNA integrity than the moderate and heavy smokers, at 46.6% versus 34.3% and 35.4%, respectively. They also had a lower mean percentage of sperm with obvious DNA damage, at 10.9% versus 14.6% and 14.2%.

Furthermore, assessment by 3,3-diaminobenzidine deposition showed that nonsmokers versus heavy smokers had a significantly higher mean proportion of sperm with high mitochondrial activity, at 13.2% versus 8.3%, while they had a significantly lower percentage of sperm with low mitochondrial activity, at 13.2% versus 20.4%.

Using malondialdehyde quantification, the team also determined that the mean level of lipid peroxidation was significantly lower in nonsmokers than in moderate and heavy smokers, at 232.7 ng/mL versus 259.8 ng/mL and 341.6 ng/mL, respectively.

Writing in Human Reproduction, Bertolla et al explain: "Since varicocele promotes a decrease in testicular blood renewal with a consequent accumulation of toxic substances, it can potentiate the toxic effects of environmental exposure to genotoxic substances."

However, "Importantly, there were no differences between the rates of DNA fragmentation, mitochondrial activity and lipid peroxidation levels when comparing the groups of varicocele regardless of smoking," they remark.

"This suggests that our results are due predominantly to smoking."

Analysis of seminal plasma proteins also showed that seven of nine proteins expressed across the entire study population had higher expression levels in nonsmokers than the other two groups.

"Because alterations in seminal plasma protein profiles are also present, these may explain pathways leading to the altered semen phenotypes," suggests the team.

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