Investigating the reproductive, metabolic and developmental programming effects of caloric and non-caloric sweeteners in combination with high fat diets in mice

Infertility is rising globally with up to 50% of cases contributed to male factor infertility. Growing rates of obesity have resulted in increased awareness of the concerns posed by sugar-sweetened beverages. Non-caloric sweeteners (NCS) are promoted as a ‘healthier’ option. Limited information exists on the impact of NCS intake on paternal transmission of disease and adverse health effects in the offspring. The aims were to systematically review the literature on preconception consumption of NCS on male reproductive outcomes in rodents, investigate the impact of paternal diet during gestation on offspring anthropometric measurements in a Finnish retrospective cohort study, investigate the impact of paternal preconception intakes of HFD and AceK, RebA and fructose on paternal metabolic and reproductive health and on glucose homeostasis and reproductive health in offspring mice. To investigate the impact of NCS on paternal and offspring outcomes C57BL/6 male mice received 10%kcal low fat chow with water (CD) or 45% high fat diet chow (HF) and supplemented with water (CDCon/HFCon) RebA (CDRebA/HFRebA) Ace K (CDAceK/HFAcek) or fructose (CDFr/HFFr) and reproductive and metabolic outcomes were assessed and the impact of paternal NCS exposure in offspring was examined.
After reviewing the literature 44% of studies showed a negative effect of NCS on male reproductive parameters. Analysis of the STEPS study showed paternal BMI was associated with increased male weight and height z-scores at 13 months and BMI z-scores at 5 years. Paternal diet was associated with increased female BMI z-scores at ages 2 and 3 years. The NCS in the preclinical mouse study induced subtle metabolic and reproductive effects on adult male mice. HFD and NCS increased glucose AUC and RebA and AceK and HFFr induced gene expression associated with muscle atrophy in the skeletal muscle and IR and testosterone pathways in the testes. There was an overall sweetener effect of RebA on decreased sperm viability and an overall HFD effect of Fr on sperm viability. CDRebA, HFRebA, HFAceK and HFFr increased abnormal morphology. Fr decreased plasma testosterone concentrations. RebA, HFAceK and HFFr decreased testes gene expression markers relating to spermatogenesis and CDAceK increased expression of genes associated with improved spermatogenesis. There was an overall change in 8 testicular miRNAs in response to HFD or sweetener. There was increased expression of 4 miRNAs driven by HFFR, decreased expression of five miRNAs driven by RebA, AceK downregulated 1 miRNA and HFAceK upregulated 1 miRNA associated with reproduction. Paternal HFAceK reduced offspring pup survival. In offspring, paternal NCS and Fr induced subtle negative reproductive effects with CDRebA increasing male offspring gonadal AT and RebA decreasing female offspring adult weight and baseline glucose concentrations. Overall, RebA females had earlier onset puberty while HFAceK females had altered estrus cycles. HFAceK and HFFr had poorer sperm morphology outcomes in offspring males. This thesis shows paternal diet and BMI subtly influence offspring outcomes and that NCS exacerbates HFD-induced metabolic disease while NCS regardless of diet induced altered skeletal muscle gene expression. NCS and Fr negatively affected sperm parameters, while Fr decreased testosterone. CDAceK appeared to improve testicular gene expression however HFAceK, RebA and HFFr did not. There were subtle sex-specific reproductive effects of paternal NCS on offspring outcomes, with HFAceK reducing pup survival after birth. In adulthood, there was mostly reproductive effects of paternal NCS observed, with HFAceK affecting female estrous cyclicity and RebA inducing earlier onset puberty. HFAceK and HFFr negatively affecting sperm morphology. This work highlights the necessity of undertaking further research into the effects of NCS and fructose intake in those most at risk of metabolic and reproductive disturbances.