Diet-induced Paternal Obesity Impairs Cognitive Functions In Offspring Through Epigenetic Modifications In Spermatozoa

PART ? Establishment of diet-induced paternal obesity mouse model and the phenotype of offspringObjective:To determine the effects of a high fat diet-induced paternal obesity on cognitive functions in mice offspring.Materials and Methods:We established a mouse model of diet-induced paternal obesity.We examined body weight and blood biochemical in F1 and F2 offspring.Using behavioral tests,we examined cognitive functions in F1 and F2 offspring.Results:HFD induced obesity and dyslipidemia in FO fathers,with no changes in cognition or sperm parameters.There were no significant differences in body weight and blood biochemicals between two groups both in F1 and F2 offspring.Paternal HFD resulted in cognitive deficits and hippocampal neurogenesis impairment in F1 offspring.However,cognitive functions were unaffected in the F2 generation.Conclusion:Paternal HFD results in impaired hippocampus-dependent learning and memory with reduced hippocampal neurogenesis in F1 offspring.However,cognitive functions were unaffected in the F2 generation.PART ? Paternal HFD reprograms DNA methylation patterns in FO spermatozoaObjective:To explore the epigenetic mechanism by which paternal HFD exerts the intergenerational effects on cognitive function in F1 offspring.Materials and Methods:We collected spermatozoa from CD and HFD fathers and examined DNA methylation patterns using reduced representation bisulfite sequencing(RRBS).Using Ingenuity Pathway Analysis(IPA)to identify potential genes associated with cognitive phenotypes in F1 offspring.Using pyrosequencing to validate CpG methylation status at BDNF promoter region in FO spermatozoa and F1 hippocampus.Results:Using RRBS,we found 793 differentially methylated genes at promoter regions.We further performed IPA using the terms "spatial learning" and "cognitive impairment" and found that BDNF showed a strong relationship with both spatial learning and cognitive impairment.Using pyrosequencing analysis,we confirmed an elevated CpG methylation at BDNF promoter both in HFD FO spermatozoa and F1 hippocampus.Moreover,qPCR revealed that HFD F1 hippocampus showed reduced BDNF mRNA expression.Conclusion:Collectively,these data indicate that elevated BDNF methylation status in HFD FO spermatozoa can transmit to the offspring's hippocampus,thereby affecting BDNF expression in HFD F1 hippocampus.PART ? BDNF/TrkB signaling is involved in cognitive impairments in HFD F1 offspringObjective:To investigate the effects of BDNF/TrkB signal transduction on paternal HFD-induced cognitive impairments in HFD F1 offspring.Materials and Methods:BDNF,TrkB,pErk/Erk and pAkt/Akt protein levels in F1 hippocampus were determined by Western blot.Results:Our results showed decreased BDNF,TrkB as well as downstream pErk/Erk and pAkt/Akt protein levels in the HFD F1 hippocampus.Conclusion:BDNF/TrkB signal transduction is involved in paternal HFD-induced cognitive impairments in HFD F1 offspring.