Transgenerational Hangovers: A Rat Model for Behavioural and Epigenetic Changes Across Generations due to Paternal Preconceptual Alcohol Consumption

Abstract

<p><strong>Alcohol is the most harmful drug of abuse, making alcoholism a major economic and public health crisis. Unsurprisingly, this has led to the majority of neurobiological research on alcohol focussing on its direct effects on an individual. This includes those affected by foetal alcohol spectrum disorders (FASDs). However, research has shown that heavy paternal drinking predicts earlier and heavier adolescent drinking in the offspring, accompanied with other behavioural and molecular changes. While alcohol use disorder (AUD) is highly heritable, research on genetic variants alone does not sufficiently account for its risk and the FASDs like symptoms seen in the offspring of alcoholic fathers. Recently, there has been an increase in appreciation of the importance of epigenetic mechanisms of inheritance, which transfer changes due to parental experiences through the germline. This thesis aimed to assess both the inter and transgenerational impacts of preconceptual paternal alcohol consumption (PPAC) using a rat model. Sprague Dawley male rats (F0) underwent chronic voluntary ethanol intake and at the end of the drinking paradigm were kept for one spermatogenesis cycle before being mated with ethanol naïve females. The litters and matched controls were behaviourally assessed, and a cohort of F1 males mated to observe a F2 generation.</strong></p><p>PPAC caused behavioural changes in both the F1 and F2 generations, including altering litter sizes and delaying development. The F1 also show a reduction in sensitivity to the motor impairing effects of ethanol compared to controls. Sexually dimorphic effects of PPAC were seen with female offspring having a reduced preference to ethanol in both the F1 and F2, while tolerance to ethanol in motor coordination was again seen in the F2 females but not F2 males. Likewise, F1 males presented reductions in locomotor activity but these effects did not persist in the F2.</p><p>Analysis of liver mitochondrial DNA copy number (mtDNA-CN) found that drinking F0 fathers had reduced mtDNA-CN at the end of the ethanol intake paradigm and 12 weeks post-drinking relative to controls. The livers of F1 showed lower mtDNA-CN in the offspring of ethanol sired rats compared to offspring of non-drinkers after undergoing ethanol consumption, suggesting differences in liver metabolism. Finally, livers of F0 drinkers had reduced expression of Peroxisome proliferator-activated receptor γ coactivator 1α (Pgc1a), relating to mitochondrial biogenesis, and methyl-CpG-binding protein 2 (Mecp2), indicating putative changes in methylation signalling, together suggesting epigenetic inheritance of changes due to xenotoxic stress.</p><p>The findings show PPAC induces developmental delays, causes transgenerational changes in drinking behaviour, ethanol sensitivity and liver mitochondrial function in a sexually dimorphic manner. These changes may be protective to the female offspring of PPAC to modify their ethanol intake. The alterations in F1 liver mtDNA-CN demonstrate potential far-reaching consequences for the metabolism of xenotoxic substances extending beyond ethanol and provides evidence to support behavioural and epigenetic changes across generations due to PPAC.</p>