Liver molecular networks associated with drinking behavior in nonhuman primates

To test the hypothesis that molecular changes in the induction phase when rhesus macaques consume the same escalating doses of alcohol in a 3-month period are predictive of drinking behavior as light drinkers (LD) or very heavy drinkers (VHD) when they have free access to alcohol. The sirtuin signaling pathway and a molecular network regulated by the estrogen receptor were enriched with differentially expressed genes and proteins in liver biopsy samples of VHD vs. LD when animals were alcohol naïve. After consuming the same amount of alcohol for 3 months by LD and VHD, the sirtuin signaling pathway and MYC regulatory network were most significantly enriched with differentially expressed genes and proteins in both groups in response to alcohol. However, majority of the differentially abundant genes and proteins in this pathway and network differed between LD and VHD. Moreover, the epigenetic mechanisms regulating the response to alcohol are primarily through microRNAs in LD and primarily through DNA methylation in VHD. Overall design: Rhesus monkeys (~4.6 years old, males) were used for the study. Before and after the induction phase, liver biopsies were performed. During the induction phase, monkeys consumed the same amount of alcohol. After the induction phase, monkeys had free access to alcohol for 12 months, and they were classifiied as LD or VHD based on daily alcohol consumption. Liver samples from three LD that consumed 1.5 g ethanol/kg/day and three VHD that consumed 4.0 g ethanol/kg/day at the end of the free access period were used for mRNA and microRNA (miRNA) sequencing. Gene and protein expression in VHD livers was compared to that in LD livers before the induction phase. Also, gene and protein expression after induction was compared to that before induction to determine the molecular response to alcohol in LD and VHD livers. Differential DNA methylation sites associated with differentially expressed genes were also analyzed.