Paternal over- and under-nutrition program fetal and placental development in a sex-specific manner

Under- and over-nutrition are directly linked to poor physiological, metabolic and reproductive health. While the association between paternal diet and offspring well-being is becoming established, the underlying mechanisms are yet to be fully defined. The aim of this study was to establish and compare the impact of over- and under-nutrition on male reproductive fitness and post-fertilisation development, with the additional exploration of the role that specific micronutrient supplementation may play in ameliorating any detrimental effects of poor paternal diet. Male C57/BL6J mice were fed either control diet (CD), isocaloric low protein diet (LPD), ‘Western’ diet (WD) or LPD or WD supplemented with methyl-donors and carriers (MD-LPD or MD-WD respectively) for 8 weeks before mating with virgin C57/BL6J females maintained on standard mouse chow. Placental tissue was collected at embryonic day (E)8.5 to assess early placental morphology and metabolism or E17.5 for sex-specific transcriptomic profiling. Post-mating male tissues were harvested for assessment of testicular morphology, gene expression and metabolic profiling and fecal microbiome was analysed. This study found significant increases in adiposity, hepatic cholesterol and FFAs in WD and MDWD fed males, alongside an increase in the abundance of Defferibacteres, Proteobacteria and reduction TM7 abundance in fecal samples compared to CD fed males. Analysis of testicular gene expression revealed 402 (267 down-regulated, 135 upregulated) genes and 285 (187 down-regulated, 98 up-regulated) genes differentically expressed in WD and MD-WD-fed males, respectively, with minimal changes observed in LPD and MD-LPD groups compared to CD-fed males. Placenta from LPD fed fathers had a significant reduction in lactate production at E8.5 and significant sex-specific influences of paternal diet on late gestation fetal and placental growth were observed in both LPD and MD-LPD groups, which had a significantly higher proportion of fetuses with weights below the 10th centile when compared to CD fetuses. We also identified a significant reduction in sexually dimorphic gene expression in response to paternal diet, with 301, 13, 0, 14 and 15 placental genes to be differentially expressed between males and females in the CD, LPD, MD-LPD, WD and MD-WD. We observed that males consuming a high fat/sugar diet (WD and MD-WD), displayed a series of physiological changes in their metabolic health, gut bacterial profiles and testicular morphology and gene expression. While both over- and under-nutritional regimens had no impact on fundamental male fertility, we observed a significant loss in sexual-dimorphism in the late gestation placenta in response to our experimental diets. Such loss of sexual- dimorphism could provide one process through which poor paternal diet programs offspring ill-health in adulthood.