Enhanced susceptibility of obese mice to glycidamide-induced sperm chromatin damage without increased oxidative stress

Abstract

Diet-induced obesity is known to impair male reproduction and may aggravate the male reproductive toxicity of the food contaminant acrylamide. Exposure of male mice to acrylamide induces paternally mediated pre- and post-implantation losses because of spermatozoal toxicity and these effects are potentiated in mice fed a high-fat diet. Glycidamide - an acrylamide metabolite - is the primary mediator of reproductive effects in males. The mechanisms causing the interaction between diet and acrylamide are not clear. However, diet-induced obesity is associated with oxidative stress in male reproductive tissues which might contribute to increased germ cell susceptibility. In this study, we investigated whether a moderate diet-induced obesity regimen could interfere with glycidamide-induced spermatozoal toxicity and increase oxidative stress. For this purpose, sperm chromatin integrity, oxidised DNA and protein levels, transcript levels of oxidative stress responsive genes and glycidamide-induced DNA and haemoglobin adducts were analysed in samples from male mice exposed to a high-fat diet for 6 weeks in combination with a single glycidamide exposure 7 days prior to sacrifice. We found that glycidamide-induced sperm DNA fragmentation was markedly higher in obese than in lean mice. However, the levels of oxidised DNA and/or protein in blood, liver and testicular tissue was lower in obese than in lean mice. Accompanying the reduced level of oxidised macromolecules, the transcript levels of several oxidative stress-related genes were altered in the liver and testis from obese mice suggesting induction of an antioxidant response in these animals. The haemoglobin-glycidamide adduct levels were higher in obese than in lean animals, whereas obesity did not seem to increase the level of glycidamide-induced DNA adducts. These findings show that a moderate diet-induced obesity regimen may potentiate glycidamide-induced sperm cells toxicity and suggest that the increase in glycidamide-induced sperm toxicity observed in obese mice does not depend on overt oxidative stress.

Keywords: DNA damage; gene expression; glycidamide; obesity; oxidative stress; sperm chromatin integrity.