Evidence for possible period 2 gene mediation of the effects of alcohol exposure during the postnatal period on genes associated with maintaining metabolic signaling in the mouse hypothalamus

Abstract

Background: Animals exposed to alcohol during the developmental period develop circadian disturbances and metabolic problems that often persist during their adult period. In order to study whether alcohol and the circadian clock interact to alter metabolic signaling in the hypothalamus, we determined whether postnatal alcohol feeding in mice permanently alters metabolic sensing in the hypothalamus. Furthermore, we evaluated whether the effect of circadian disruption via Period 2 (Per2) gene mutation prevents alcohol's effects on metabolic signaling in the hypothalamus.

Methods: Per2 mutant and wild-type male and female mice of the same genetic background were given a milk formula containing ethanol (EtOH; 11.34% vol/vol) from postnatal day (PD) 2 to 7 and used for gene expression and peptide level determinations in the hypothalamus at PD7 and PD90.

Results: We report here that postnatal alcohol feeding reduces the expression of proopiomelanocortin (Pomc) gene and production of β-endorphin and α-melanocyte stimulating hormone (α-MSH) in the hypothalamus that persists into adulthood. In addition, expressions of metabolic sensing genes in the hypothalamus were also reduced as a consequence of postnatal alcohol exposure. These effects were not sex-specific and were observed in both males and females. Mice carrying a mutation of the Per2 gene did not show any reductions in hypothalamic levels of Pomc and metabolic genes and β-endorphin and α-MSH peptides following alcohol exposure.

Conclusions: These data suggest that early-life exposure to alcohol alters metabolic sensing to the hypothalamus possibly via regulating Per2 gene and/or the cellular circadian clock mechanism.

Figure 1

Effect of postnatal ethanol exposure on levels of POMC mRNA (A), β-endorphin (B) and α-MSH (C) and Per2 (D) in the mediobasal hypothalamus (MBH) at PD7 and PD90 in C57BL/6 and Per2^Brdml Mice. Pups fed with milk formula containing alcohol (AF), pair-fed isocaloric milk formula (PF) or left in the litter (AD) between PD2–PD7. Data are mean ± SE. N = 6. Two-way ANOVA identified significant interaction between feeding effects and genotypes (P<0.05). Bonferroni posttest identified differences between control groups (AD & PF) vs. AF treated group within the same mice strain (*, P <0.05, **, P <0.01, ***, P <0.001) or between C57BL/6 and Per2 mutant mice in each feeding group (^a, P <0.05, ^aa, P <0.01, ^aaa, P <0.001).

Fig. 2

Effect of postnatal ethanol exposure on mRNA levels of Stat3 (A), Sirt1 (B) and Pgc1α (C) and Asb4 (D) in the mediobasal hypothalamus (MBH) at PD7 and PD90 in C57BL/6 and Per2^Brdml Mice. Pups were fed with a milk formula containing alcohol (AF), pair-fed isocaloric milk formula (PF) or left in the litter (AD) between PD2–PD7. Data are mean ± SE. N = 6. Two-way ANOVA identified significant interaction between feeding effects and genotypes (P<0.05). Bonferroni posttest identified differences between control groups (AD & PF) vs. AF treated group within the same mice strain (*, P <0.05, **, P <0.01, ***, P <0.001) or between C57BL/6 and Per2 mutant mice in each feeding group (^a, P <0.05, ^aa, P <0.01, ^aaa, P <0.001).