Paternal under and over nutrition modify semen composition and preimplantation embryo developmental kinetics in mice
The importance of parental diet in relation to eventual offspring health is increasing in prominence due to the increased frequency of reproductive age adults consuming poor diets. Whilst maternal health and offspring outcome have been studied in some detail, the paternal impacts are not as well understood. A father's poor nutritional status has been shown to have negative consequences on fetal growth and development and ultimately impact the long-term adult health of the offspring.  In this study we examined sperm and seminal plasma mediated mechanisms of preimplantation embryo development alterations in response to sub-optimal paternal diets. Male mice were fed a diet to model either under (low protein diet (LPD)) or over (high fat/sugar (Western) diet (WD)) nutrition, LPD or WD supplemented with methyl-donors or a control diet before mating with age-matched control fed females. Male metabolic health was influenced by WD and MD-WD; with significant changes in serum lipids and hepatic 1-carbon metabolites. Sperm RNA sequencing revealed significant changes to mRNA profiles in all groups when compared to CD (LPD: 32, MD-LPD: 17, WD: 53, MD-WD: 35). In vitro embryo development was revealed all sub-optimal diets with and without methyl-donors increased the rate of embryo development. As embryo development can be directed by sperm and seminal plasma mediated mechanism, we also examined the proteomic profile of the seminal plasma, revealing a significant number of changes in all groups compared to control (LPD: 13, MD-LPD: 27, WD: 24, MD-WD: 19). Male diet also altered uterine gene expression examined via qPCR, specifically alterations in Cd14 and Ptgs1 were observed in response to male WD matings. Our current study shows that paternal nutritional status has the potential to influence male metabolic and reproductive factors, which can ultimately alter embryonic development and the post-mating maternal environment. This study highlights potential direct (sperm mediated) and indirect (semen mediated) pathways in which a father's poor diet could shape the long-term health of his offspring. Overall design: To investigate murine sperm RNA profile changes in response to sub-optimal diets and dietary supplementations. We fed male mice either control diet (NPD; 18% casein, 21% sugar, 0% milk fat, 0% cholesterol), isocaloric low protein diet (LPD; 9% casein, 24% sugar, 0% milk fat, 0% cholesterol), 'Western' diet (WD; 19% casein, 34% sugar, 20% milk fat, 0.15% cholesterol) or LPD or WD supplemented with methyl-donors [an addition of 5 g/kg diet choline chloride, 15 g/kg diet betaine, 7.5 g/kg diet methionine, 15 mg/kg diet folic acid, 1.5 mg/kg diet vitamin B12 to either LPD (MDL) or WD (MDWD)] for a minimum of 8 weeks before live caudal sperm was retrieved for total RNA extraction.