Sperm from diabetic men have greater levels of DNA damage which may affect their fertility

May 8 2007

In the first study to compare the quality of DNA in sperm from diabetic and non-diabetic men, researchers at Queen’s University Belfast showed that the DNA in the nuclei of the sperm cells had greater levels of fragmentation in diabetic men, and that there were more deletions of DNA in the tiny, energy-generating structures in the cells called mitochondria.

Queen’s research fellow, Dr Ishola Agbaje, said: “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.”

Dr Agbaje and his colleagues examined sperm from 27 diabetic men in their thirties and found, that although semen volume was significantly less in diabetic men, there were no significant differences in sperm concentration, total sperm output, form and structure of the sperm or their ability to move. However 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 incidence of type 1 and type 2 diabetes is increasing rapidly worldwide. While diet and obesity are known to be key factors in the increase of type 2 (or late onset) diabetes, type 1 diabetes which is usually diagnosed in childhood or adolescence, is increasing by three per cent a year in European children, although the reason for this is not entirely clear. Genetic factors that make people more susceptible, or environmental factors such as viruses that may trigger the onset of type 1 diabetes, could play a role.

Dr Agbaje, continued: “Infertility is already a major health problem in both the developed and developing world, with up to one in six couples requiring specialist investigation or treatment in order to conceive. Moreover, the last 50 years have seen an apparent decline in semen quality. Sperm disorders are thought to cause or contribute to infertility in 40-50% of infertile couples. The increasing incidence of systemic diseases such as diabetes may further exacerbate this decline in male fertility. However, it is not clear to what extent clinics consider information about the diabetic status of their patients when investigating fertility problems.”

Professor Sheena Lewis, of Queen’s Reproductive Medicine Research Group, said: "Our study shows increased levels of DNA damage in sperm from diabetic men. From a clinical perspective this is important, given the growing body of evidence that sperm DNA damage can impair male fertility and even the health of future generations. 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.”

However, Professor Lewis added: “that it was not possible to determine from this current study whether the DNA damage caused by diabetes would have the same effect on men's fertility 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," she said.

http://www.qub.ac.uk/