Scientists have found that diabetes damages DNA in men's sperm and may affect fertility.
The researchers from Belfast, Northern Ireland showed that the DNA in the nuclei of the sperm cells had greater levels of fragmentation in diabetic men (52%, versus 32% in non-diabetic men) and that there were more deletions of DNA in the tiny, energy-generating structures in the cells called mitochondria (4 versus 3).
"As far as we know, this is the first report of the quality of DNA in the nucleus and mitochondria of sperm in diabetes. Our study identifies important evidence of increased DNA fragmentation of nuclear DNA and mitochondrial DNA deletions in sperm from diabetic men. These findings cause concern, as they may have implications for fertility,” said Dr Ishola Agbaje who undertook the research
Dr Agbaje and his colleagues examined sperm from 27 diabetic men, with an average age of 34 and 29 non-diabetic men with an average age of 33. They found that although semen volume was significantly less in diabetic men (2.6 versus 3.3 ml), there were no significant differences in sperm concentration, total sperm output, form and structure of the sperm or their ability to move.
When they measured DNA damage they found that the percentage of fragmented nuclear DNA was significantly higher in sperm from the diabetic men and that the number of deletions in mitochondrial DNA was also higher – the number of deletions ranged from three to six (average four) in the diabetic men and from one to four (average three) in the non-diabetic men.
"Our study shows increased levels of sperm DNA damage in diabetic men. From a clinical perspective this is important, particularly given the overwhelming evidence that sperm DNA damage impairs male fertility and reproductive health.
Other studies have already shown that, while the female egg has a limited ability to repair damaged sperm DNA, fragmentation beyond this threshold may result in increased rates of embryonic failure and pregnancy loss.
In the context of spontaneous conception, sperm DNA quality has been found to be poorer in couples with a history of miscarriages," said Professor Sheena Lewis, scientific director of the Reproductive Medicine Research Group.
However, Prof Lewis said that it was not possible to say from this current study whether the DNA damage caused by diabetes would have the same effect on men’s fertility and the health of future children as DNA damage caused by other factors such as smoking.
"This is just one, relatively small study that highlights a possible concern. Further studies need to be carried out in order to understand the precise nature of the diabetes-related damage, the causal mechanisms and the clinical significance.
Given the global rise in the prevalence of diabetes, it is also vital to examine the reproductive outcomes of pregnancies fathered by diabetic men, and the prevalence of diabetes amongst men attending for infertility treatment," she concluded. The study is published in the 3 May edition of the journal Human Reproduction.