Effects of paternal overnutrition and interventions on future generations

In the last two decades, evidence from human and animal studies suggests that paternal obesity around the time of conception can have adverse effects on offspring health through developmental programming. This may make significant contributions to the current epidemic of obesity and related metabolic and reproductive complications like diabetes, cardiovascular disease, and subfertility/infertility. To date, changes in seminal fluid composition, sperm DNA methylation, histone composition, small non-coding RNAs, and sperm DNA damage have been proposed as potential underpinning mechanism to program offspring health. In this review, we discuss current human and rodent evidence on the impact of paternal obesity/overnutrition on offspring health, followed by the proposed mechanisms, with a focus on sperm DNA damage underpinning paternal programming. We also summarize the different intervention strategies implemented to minimize effects of paternal obesity. Upon critical review of literature, we find that obesity-induced altered sperm quality in father is linked with compromised offspring health. Paternal exercise intervention before conception has been shown to improve metabolic health. Further work to explore the mechanisms underlying benefits of paternal exercise on offspring are warranted. Conversion to healthy diets and micronutrient supplementation during pre-conception have shown some positive impacts towards minimizing the impact of paternal obesity on offspring. Pharmacological approaches e.g., metformin are also being applied. Thus, interventions in the obese father may ameliorate the potential detrimental impacts of paternal obesity on offspring.

Paternal Obesity and SGLT2 Inhibition Alter Expression of Placental Regulatory Genes

We previously demonstrated that paternal obesity is associated with offspring metabolic risk during later life, and that paternal SGLT2i treatment improves offspring metabolic phenotypes. Since the placenta is a key determinant of prenatal growth and development, we hypothesized the placenta could mediate the impact of paternal obesity and paternal SGLT2i treatment. Male C57BL/6J mice were fed standard chow (Purina 9F) or 60% high-fat diet (HFD, D12492, Research Diet), or 60% HFD plus the SGLT2 inhibitor canagliflozin (CANA, 25 mg/kg/d) for 4 weeks before mating with chow-fed females. Placenta were collected on E16.5, and RNA-seq was performed on placenta from male offspring (paternal chow, pChow, n=4, pHFD, n=5, and pHFD+CANA, n=4), and differentially expressed genes were identified using Limma. Placenta weight was significantly lower in pHFD (0.089±0.004 g, 7 litters from 6 fathers) vs. both pChow (0.108±0.011 g, 4 litters, 4 fathers) and pHFD+CANA (0.107±0.013 g, 5 litters, 5 fathers)(p<0.05). Litter size, fetal or liver weight, or fetal/placental weight ratio did not differ between groups. No genes were differentially expressed in pHFD vs. pChow (FDR<0.1). Gene set enrichment analysis (GSEA) identified significance (FDR<0.05, NES>1.8) for gene sets in steroid metabolic, drug catabolic, and protein-containing complex remodeling processes. Genes responsible for enrichment included cholesterol biosynthesis (Hmgcs1), transport (Apob, Apoa1/2/4, Apom, Apoc1, Vldlr, Pcsk9) and steroid hormone biosynthesis genes (Hsd3b1, Cyp11b1), all upregulated in pHFD by 1.5-3-fold. These results suggest pHFD could potentially affect maternal and fetal cholesterol homeostasis. pHFD+CANA altered expression of 154 genes vs. pHFD (7 up-, 147 down, FDR <0.1, FC >|1.5|); 18 gene sets were downregulated by pHFD+CANA (GSEA NES<-1.8 and FDR<0.05), including the 3 sets upregulated by pHFD. ChEA3 enrichment analysis (ENCODE library) predicted regulation by transcription factors important for cholesterol and sterol biosynthesis (Srebf1/2), embryonic development (Foxa2), & glucose homeostasis (Hnf4g), suggesting these pathways could mediate the “rescue” effect of pHFD+CANA (FDR<0.05). Expression of Foxa2 was significantly downregulated (4-fold) in pHFD+CANA vs. pHFD. We independently analyzed expression of the 78 detected imprinted genes. None were significantly different in pHFD, but both paternally expressed (Nnat) and maternally expressed genes (H19, Phlda2, Meg3, Meg8) were downregulated in pHFD+CANA vs. pHFD by 1.4 to 3.8 fold in pHFD+CANA (p<0.001,FDR<0.1). In summary, paternal SGLT2i reversed the impact of pHFD on placental weight. Robust impact of both pHFD and pSGLT2i on the transcriptome suggests that the placenta is a key mediator of paternal metabolic effects on offspring development and metabolic disease risk, potentially via modification of lipid transport.

Paternal obesity results in placental hypoxia and sex-specific impairments in placental vascularization and offspring metabolic function

ABSTRACTPaternal obesity predisposes offspring to metabolic dysfunction, but the underlying mechanisms remain unclear. We investigated whether paternal obesity-induced offspring metabolic dysfunction is associated with placental endoplasmic reticulum (ER) stress and impaired vascular development. We determined whether offspring glucose intolerance is fueled by ER stress-mediated changes in fetal hepatic development. Furthermore, we also determined whether paternal obesity may indirectly affect in utero development by disrupting maternal metabolic adaptations to pregnancy. Male mice fed a standard chow diet (CON; 17% kcal fat) or high fat diet (PHF; 60% kcal fat) for 8-10 weeks were time-mated with control female mice to generate pregnancies and offspring. Glucose tolerance in pregnant females was evaluated at mid-gestation (embryonic day (E) 14.5) and term gestation (E18.5). At E14.5 and E18.5, fetal liver and placentae were collected, and markers of hypoxia, angiogenesis, endocrine function, and macronutrient transport, and unfolded protein response (UPR) regulators were evaluated to assess ER stress. Young adult offspring glucose tolerance and metabolic parameters were assessed at ∼60 days of age. Paternal obesity did not alter maternal glucose tolerance or placental lactogen in pregnancy but did induce placental hypoxia, ER stress, and altered placental angiogenesis. This effect was most pronounced in placentae associated with female fetuses. Consistent with this, paternal obesity also activated the ATF6 and PERK branches of the UPR in fetal liver and altered hepatic expression of gluconeogenic factors at E18.5. Adult offspring of obese fathers showed glucose intolerance and impaired whole-body energy metabolism, particularly in female offspring. Thus, paternal obesity programs sex-specific adverse placental structural and functional adaptations and alters fetal hepatic development via ER stress-induced pathways. These changes likely underpin metabolic deficits in adult offspring.Summary SentencePaternal obesity alters placental vascular structures and is associated with sex-specific compromises in glucose tolerance and metabolism in young offspring

Metabolic Syndrome in Obese Children—Clinical Prevalence and Risk Factors

The prevalence of childhood obesity is increasing worldwide. Some obese children can go on to develop metabolic syndrome (MetS), but exactly who among them remains to be determined. The aim of this study was to indicate predisposing factors for metabolic syndrome, especially those that can be modified. The study comprised 591 obese children aged 10–12 years. They were all Caucasian residents of Gdańsk, Poland, with similar demographic backgrounds. Clinical examination, anthropometry, biometric impedance analysis, blood tests (including oral glucose tolerance tests (OGTT) and insulinemia), and dietary and physical activity evaluation were conducted. The results of our study show that the risk factors for MetS or any of its components include male sex, parental (especially paternal) obesity, low body mass at birth, as well as omitting breakfast or dinner. There are few risk factors for metabolic syndrome both in obese adults and children. Some of these predictors can be modified, especially those in relation to lifestyle. Identifying and then influencing these factors may help to reduce the development of metabolic syndrome and consequently improve health and quality of life.

A genome-wide transcriptomic analysis of embryos fathered by obese males in a murine model of diet-induced obesity

Paternal obesity is known to have a negative impact on the male’s reproductive health as well as the health of his offspring. Although epigenetic mechanisms have been implicated in the non-genetic transmission of acquired traits, the effect of paternal obesity on gene expression in the preimplantation embryo has not been fully studied. To this end, we investigated whether paternal obesity is associated with gene expression changes in eight-cell stage embryos fathered by males on a high-fat diet. We used single embryo RNA-seq to compare the gene expression profile of embryos generated by males on a high fat (HFD) versus control (CD) diet. This analysis revealed significant upregulation of the Samd4b and Gata6 gene in embryos in response to a paternal HFD. Furthermore, we could show a significant increase in expression of both Gata6 and Samd4b during differentiation of stromal vascular cells into mature adipocytes. These findings suggest that paternal obesity may induce changes in the male germ cells which are associated with the gene expression changes in the resulting preimplantation embryos.