Paternal Contributions to Metabolic Disease in Offspring: Environment, Epigenetics, and Sperm

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PROJECT SUMMARY One novel approach to reduce the burden of type 2 diabetes and obesity comes from the recognition that parental obesity or diabetes can increase risk of metabolic disease in offspring via non-genetic effects. This perspective raises the exciting possibility that treatment of parents to improve their metabolism before conception could interrupt vicious intergenerational cycles of obesity and diabetes, thus improving offspring health. In the prior funding cycle, we developed evidence for the impact of paternally-focused interventions on the sperm epigenome and offspring health. We recently demonstrated in humans that paternal obesity is associated with altered DNA methylation in cord blood of offspring7. Our new data in mice indicate (1) paternal obesity and hyperglycemia are key determinants of offspring health, (2) improving paternal metabolism - by treatment with either SGLT2 inhibitors or caloric restriction - can reverse age-associated weight gain, insulin resistance, glucose intolerance, and fatty liver in F1 offspring, (3) paternal metabolism potently modifies the transcriptome in fetal and adult offspring, including oxidative and lipid regulatory genes, and (4) paternal metabolism alters the epigenome in both sperm and offspring tissue. For example, DNA hydroxymethylation (5hmC) at enhancers adjacent to differentially expressed genes is reduced in sperm of HFD-fed males, and reciprocally increased in males treated with SGLT2i or the AMP kinase activator AICAR. In this revised application, we will utilize this innovative mouse model to identify the mechanisms by which paternal health and its treatment modulate the paternal germ cell epigenome to improve offspring health, and to test the hypothesis that the AMPK-Tet2 pathway, a mediator of glucose-mediated epigenetic regulation, mediates observed differences in sperm 5hmC and offspring metabolic disease. In Aim 1, we will define the impact of paternal obesity and hyperglycemia, and its reversal, on the germ cell epigenome (5mC/5hmC, small RNA), and identify key cis-regulating elements. In Aim 2, we will determine the pathogenicity of germ cell epigenetic changes by evaluating offspring outcomes after in vitro fertilization and sperm-derived ncRNA injection. Aim 3 will determine whether paternal effects on offspring are mediated via direct effects on the embryo, or on extraembryonic lineages affecting placental development, using single-cell transcriptomic analysis of blastocysts at a single-cell level and detailed morphometric analysis of placentae derived from control, HFD, and HFD+CANA-treated fathers. Aim 4 will test the hypothesis that the AMPK-Tet2 pathway, a mediator of glucose- mediated epigenetic regulation in somatic cells, also mediates glucose-induced changes in the germ cell epigenome. We will analyze the impact of AMPK activation in vivo on 5hmC in sperm from wild type or Tet2-null mice and on offspring phenotypes. In summary, identification of causal mechanisms in response to paternal hyperglycemia and obesity - and its reversal - will provide critical new information to guide development of new paternally-focused translatable approaches to reduce disease burden in future generations.