Dietary Omega-3 Fatty Acids Differentially Impact Acute Ethanol-Responsive Behaviors and Ethanol Consumption in DBA/2J Versus C57BL/6J Mice

Abstract

Background: Complex interactions between environmental and genetic factors influence the risk of developing alcohol use disorder (AUD) in humans. To date, studies of the impact of environment on AUD risk have primarily focused on psychological characteristics or on the effects of developmental exposure to ethanol (EtOH). We recently observed that modifying levels of the long-chain ω-3 (LC ω-3) fatty acid, eicosapentaenoic acid (EPA), alters acute physiological responses to EtOH in Caenorhabditis elegans. Because mammals derive ω-3 fatty acids from their diet, here we asked if manipulating dietary levels of LC ω-3 fatty acids can affect EtOH-responsive behaviors in mice.

Methods: We used 2 well-characterized inbred mouse strains, C57BL/6J (B6) and DBA/2J (D2), which differ in their responses to EtOH. Age-matched young adult male mice were maintained on isocaloric diets that differed only by being enriched or depleted in LC ω-3 fatty acids. Animals were subsequently tested for acute EtOH sensitivity (locomotor activation and sedation), voluntary consumption, and metabolism. Fat deposition was also determined.

Results: We found that dietary levels of LC ω-3s altered EtOH sensitivity and consumption in a genotype-specific manner. Both B6 and D2 animals fed high LC ω-3 diets demonstrated lower EtOH-induced locomotor stimulation than those fed low LC ω-3 diets. EtOH sedation and EtOH metabolism were greater in D2, but not B6 mice on the high LC ω-3 diet. Conversely, LC ω-3 dietary manipulation altered EtOH consumption in B6, but not in D2 mice. B6 mice on a high LC ω-3 diet consumed more EtOH in a 2-bottle choice intermittent access model than B6 mice on a low LC ω-3 diet.

Conclusions: Because EtOH sensitivity is predictive of risk of developing AUD in humans, our data indicate that dietary LC ω-3 levels should be evaluated for their impact on AUD risk in humans. Further, these studies indicate that genetic background can interact with fatty acids in the diet to significantly alter EtOH-responsive behaviors.

Keywords: Eicosapentaenoic Acid; EtOH Consumption; EtOH Locomotor Activation; EtOH Sensitivity; ω-3 Fatty Acid.

Figure 1. Ethanol locomotor activation is lower in B6 and D2 mice fed a high ω-3 diet

Mean +/− SEM cumulative locomotor activity of B6 mice on (A) high ω-3 diet or (B) low ω-3 diet after saline, or ethanol at 1.5 and 2.0 g/kg. Mean +/− SEM cumulative locomotor activity of D2 mice on (C) high ω-3 or (D) low ω-3 diet after saline, or ethanol at 1.5 or 2.0 g/kg. *p<0.05 vs. saline, main effect of diet by RM ANOVA.

Figure 2. The level of dietary ω-3 fatty acids alters ethanol intake in B6, but not D2 mice

Daily ethanol intake (A), preference (B) and total fluid intake (C) in B6 mice. Daily ethanol intake (D), preference (E), and total fluid intake (F) in D2 mice. Ethanol intake and total fluid were greater in B6 mice on a high ω-3 diet relative to B6 on a low ω-3 diet. Ethanol preference showed a trend towards increased preference in B6 mice on a high ω-3 diet relative to B6 on a low ω-3 diet. Ethanol intake, preference and total fluid intake were not altered by diet in D2 mice. Data are presented as mean +/− SEM.*p<0.05, main effect of diet by two-way RM ANOVA.

Figure 3. Sensitivity to a high dose of ethanol is greater in D2 mice on a high ω-3 diet

Latency to lose the righting reflex (in seconds) in (A) B6 and (C) D2 mice was not significantly altered by diet. The duration of sleep time (in minutes) was significantly greater in D2 mice (D) on high ω-3 diet relative to D2 mice on low ω-3 diet, but not in B6 mice (B). Data are reported as mean +/− SEM. *p<0.05 by t-Test in high vs. low ω-3 diet.

Figure 4. Ethanol metabolism is faster in D2 mice on high ω-3 diet

Mean +/− SEM of blood ethanol concentrations at 15, 30, 60 and 90 minutes after 3.8g/kg ethanol (i.p.) in (A) B6 and (B) D2 mice. Data are reported as mean +/− SEM. *p<0.05 for main effect of diet by two-way RM ANOVA.

Figure 5. D2 mice on high ω-3 diet have more intrascapular brown fat

Mean +/− SEM of body weight (A, E), body density (B, F), body length (C, G) and fat pads (D, H) in B6 (A–D) and D2 mice. Body weight, body length and intrascapular brown fat were lower in D2 mice on low ω-3 diet (E–H). *p<0.05 by t-test in high vs. low ω-3 diet.