Maternal dietary imbalance between omega-6 and omega-3 fatty acids triggers the offspring's overeating in mice

Abstract

The increasing prevalence of obesity and its effects on our society warrant intensifying basic animal research for understanding why habitual intake of highly palatable foods has increased due to recent global environmental changes. Here, we report that pregnant mice that consume a diet high in omega-6 (n-6) polyunsaturated fatty acids (PUFAs) and low in omega-3 (n-3) PUFAs (an n-6^high/n-3^low diet), whose n-6/n-3 ratio is approximately 120, induces hedonic consumption in the offspring by upregulating the midbrain dopaminergic system. We found that exposure to the n-6^high/n-3^low diet specifically increases the consumption of palatable foods via increased mesolimbic dopamine release. In addition, neurodevelopmental analyses revealed that this induced hedonic consumption is programmed during embryogenesis, as dopaminergic neurogenesis is increased during in utero access to the n-6^high/n-3^low diet. Our findings reveal that maternal consumption of PUFAs can have long-lasting effects on the offspring's pattern for consuming highly palatable foods.

Fig. 1. Exposure to the n-6^high/n-3^low diet increases the n-6/n-3 ratio in the offspring’s brain without causing obesity.

a Composition of fatty acids in the control and n-6^high/n-3^low diets (n = 3/diet). b Body weight measured in the mothers and offspring in the control and n-6^high/n-3^low groups (n = 10/group). Data were analyzed using a two-way ANOVA (week as repeated measure). c Daily food intake measured for the mothers and offspring in the control and n-6^high/n-3^low groups (n = 10/group). Data were analyzed using a two-way ANOVA (week as repeated measure). d Levels of n-6 and n-3 PUFAs in the offspring’s brain in the control and n-6^high/n-3^low groups (n = 3/group). *P < 2.08 × 10^–3 and ***P < 4.17 × 10⁻⁵, unpaired Student’s t test. e The n-6/n-3 ratio in the offspring’s brain in the control and n-6^high/n-3^low groups (n = 3/group). ***P < 4.17 × 10⁻⁵, unpaired Student’s t test. Data are expressed as the mean (a).

Fig. 2. Exposure to the n-6^high/n-3^low diet increases the consumption of highly palatable foods.

a Cumulative intake of water, 1%, 3%, 10%, or 30% sucrose solution measured in the control and n-6^high/n-3^low groups after water deprivation for 12 h (water, n = 7/control or 8/n-6^high/n-3^low; 1%, n = 7/control or 9/n-6^high/n-3^low; 3%, n = 8/control or 10/n-6^high/n-3^low; 10% and 30%, n = 9/control or 10/n-6^high/n-3^low). *P < 0.05, two-way ANOVA with simple main effect analysis (hour as repeated measure). b Intake of water, 1%, 3%, 10%, or 30% sucrose solution measured in the control and n-6^high/n-3^low groups without water deprivation (water, 10%, and 30%, n = 8/control or 10/n-6^high/n-3^low; 1%, n = 11/control or 12/n-6^high/n-3^low; 3%, n = 8/control or 9/n-6^high/n-3^low). *P < 0.05, Wilcoxon’s rank sum test (for water and 1% and 10% sucrose solutions) or unpaired Student’s t-test (for 3% and 30% sucrose solutions). c, d Mice in the n-6^high/n-3^low group consume more sucrose solution (1% and 10%) than those in the control group when given access to both water and sucrose solution (c, n = 6/group; d, n = 10/group). *P < 0.05 and ***P < 0.001, two-way ANOVA with simple main effect analysis (consumption of water and sucrose solution as repeated measure). e The number of rewards obtained during the training sessions of the PR task (n = 12/control or 16/n-6^high/n-3^low). Data were analyzed using a Wilcoxon’s rank sum test. f The break point in the PR task (n = 12/control or 16/n-6^high/n-3^low). *P < 0.05, Welch’s t-test. g, h Cumulative intake of the indicated diets in the control and n-6^high/n-3^low groups. *P < 0.05, **P < 0.01, and ***P < 0.001, two-way ANOVA with simple main effect analysis (hour as repeated measure). LSD, n = 8/control or 10/n-6^high/n-3^low; HSD, n = 8/control or 7/n-6^high/n-3^low; LFD, n = 9/control or 10/n-6^high/n-3^low; HFD, n = 8/control or 10/n-6^high/n-3^low.

Fig. 3. Exposure to the n-6^high/n-3^low diet increases DA release in the medial NAc.

a, e Time course of dialysate DA concentration measured in the medial NAc (mNAc); where indicated, water or 10% sucrose was provided. Data were analyzed using a two-way ANOVA (period as repeated measure). b–d, f–h Dialysate DA concentration measured in the mNAc before, during, and after access to either water or 10% sucrose. *P < 0.05 and **P < 0.01, unpaired Student’s t test (b–d, f, h) or Wilcoxon’s rank sum test (g). a–d, n = 6/control or 5/n-6^high/n-3^low; e–h, n = 7/control or 8/n-6^high/n-3^low. i Schematic diagram depicting the infusion of flupenthixol in the mNAc; the location of the VTA is also indicated. j, k The intake of water or 10% sucrose solution measured in mice following an infusion of vehicle or the indicated dose of flupenthixol in each hemisphere (n = 6/control or 8/n-6^high/n-3^low). *P < 0.05, two-way ANOVA with simple main effect analysis (dose as repeated measure).

Fig. 4. Exposure to the n-6^high/n-3^low diet increases the number of dopaminergic neurons in the VTA.

a–d TH-positive dopaminergic neurons measured in the PN, lPBP, and mPBP in the control and n-6^high/n-3^low groups (n = 4/group). *P < 0.05, **P < 0.01, unpaired Student’s t test. e Schematic diagram depicting the injection of cholera toxin B subunit (CTB)-Alexa Fluor 555 into the medial NAc (mNAc) for retrograde tracing. f, g Representative images of the mNAc (f) and the PN and PBP (g) after injecting CTB-Alexa Fluor 555 in the mNAc; the nuclei were counterstained with DAPI (blue, f). Scale bars = 200 μm (a), 500 μm (f), 100 μm (g), and 10 μm (g, inset). aca, anterior commissure; lShell, lateral shell of the NAc; LV, lateral ventricle; ml, medial lemniscus; mPFC, medial prefrontal cortex; mShell, medial shell of the NAc.

Fig. 5. In utero exposure to the n-6^high/n-3^low diet increases the number of dopaminergic neurons in the VTA and induces hedonic consumption.

a Experimental outline showing the timing of exposure to either the control diet or the n-6^high/n-3^low diet. b–g Cumulative intake of 10% sucrose solution (b–d) and TH-positive dopaminergic neurons in the PN and lPBP (e–g) measured in mice in the control group and in mice exposed to the n-6^high/n-3^low diet during gestation (b, e), during lactation (c, f), or after weaning (d, g) (b, n = 9/group; c, n = 8/control or 10/n-6^high/n-3^low; d, n = 7/control or 5/n-6^high/n-3^low; e-g, n = 3/group). **P < 0.01 and ***P < 0.001, two-way ANOVA with simple main effect analysis (hour as repeated measure) (b–d) or unpaired Student’s t test (e–g). Scale bars = 100 μm. lShell, lateral shell of the NAc; ml, medial lemniscus; mShell, medial shell of the NAc.

Fig. 6. Exposure to the n-6^high/n-3^low diet induces dopaminergic neurogenesis in the developing midbrain.

a–d TH-positive dopaminergic neurons measured in the rostral, intermediate, and caudal midbrain at E14.5 (n = 3/group). *P < 0.05 and **P < 0.01, unpaired Student’s t test. e–g, EdU-labeled TH-positive dopaminergic neurons measured in the intermediate midbrain at E14.5 (n = 3/group). ***P < 0.001, unpaired Student’s t test. Scale bars = 100 μm.