The Effect of Dietary Fat on Behavior in Mice

Purpose Obesity is linked to cognitive dysfunction in humans and rodents, and its effects can be passed on to the next generation. However, the extent of these effects is not well understood. The purpose of this study was to determine the effect of a prenatal maternal high-fat diet and an individual high-fat diet in inbred mice. Methods We varied maternal diet and offspring diet to test the hypothesis that a high-fat diet would increase anxiety, reduce activity levels, and impair nest-building. First, we fed a high-fat (HF) or low-fat (LF) diet to genetically identical female Small (SM/J) mice and mated them with LF males. We cross-fostered all offspring to LF-fed SM/J nurses and weaned them onto an HF or LF diet. We weighed the mice weekly and we tested anxiety with the Open Field Test, activity levels with instantaneous scan sampling, and nest building using the Deacon Scale. Results Diet significantly affected weight, with HF females weighing 28.2 g (± 1.4 g SE) and LF females weighing 15.1 g (± 1.6 g SE) at 17 weeks old. The offspring’s own diet had major behavioral effects. HF mice produced more fecal boli and urinations in the Open Field Test, built lower-quality nests, and had lower activity in adulthood than LF mice. The only trait that a prenatal maternal diet significantly affected was whether the offspring built their nests inside or outside of a hut. Conclusions Offspring diet, but not prenatal maternal diet, affected a wide range of behaviors in these mice

Maternal high-fat diet associated with altered gene expression, DNA methylation, and obesity risk in mouse offspring.

We investigated maternal obesity in inbred SM/J mice by assigning females to a high-fat diet or a low-fat diet at weaning, mating them to low-fat-fed males, cross-fostering the offspring to low-fat-fed SM/J nurses at birth, and weaning the offspring onto a high-fat or low-fat diet. A maternal high-fat diet exacerbated obesity in the high-fat-fed daughters, causing them to weigh more, have more fat, and have higher serum levels of leptin as adults, accompanied by dozens of gene expression changes and thousands of DNA methylation changes in their livers and hearts. Maternal diet particularly affected genes involved in RNA processing, immune response, and mitochondria. Between one-quarter and one-third of differentially expressed genes contained a differentially methylated region associated with maternal diet. An offspring high-fat diet reduced overall variation in DNA methylation, increased body weight and organ weights, increased long bone lengths and weights, decreased insulin sensitivity, and changed the expression of 3,908 genes in the liver. Although the offspring were more affected by their own diet, their maternal diet had epigenetic effects lasting through adulthood, and in the daughters these effects were accompanied by phenotypic changes relevant to obesity and diabetes

Top 10 significant GO biological processes affected by maternal diet.

<p>A negative logFC value indicates that the process was downregulated in mice with high-fat-fed mothers.</p

Diagram of the long bone lengths that were measured with calipers.

<p>A description of the measurements can be found in Table D in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192606#pone.0192606.s001" target="_blank">S1 File</a>.</p

Distribution of DMRs in genes.

<p>The number of genes in the mouse liver with at least one differentially methylated region (DMR) associated with maternal diet within the gene body, more than one DMR in the gene body, and at least one DMR in the promoter region (within 2 kb upstream of the transcription start site (p < 0.05). HF = High-fat diet, LF = Low-fat diet, first diet listed is maternal diet and second diet (after the hyphen) is the offspring diet.</p

The multidimensional scaling plot.

<p>(A) Gene expression libraries clustered by sex (dimension 1) and offspring diet (dimension 2), but not maternal diet. (B) There were no discernable patterns in dimensions 3 or 4. HF = High-fat diet, and LF = Low-fat diet, N = 10 per group.</p

Diet content.

<p>Diet content.</p

Weekly weights of offspring (± SE).

<p>High-fat diet offspring weigh more than low-fat diet offspring by 4 weeks of age (1 week after being weaned onto the diet) (♀ p = 1.66 x 10⁻¹⁰, ♂ p = 9.10 x 10⁻¹³). Maternal diet does not affect body weight in the sons, but it does in the daughters. The ANOVA indicated that maternal diet had a significant effect on weight in daughters starting at week 9 (p = 0.041). Asterisks (*) indicate where pairwise comparisons showed significant p values < 0.05. As adults, high-fat daughters weigh even more if their mothers were also on a high-fat diet. HF = High-fat diet, LF = Low-fat diet, N = 10 per group, the first diet listed (before the hyphen) indicates the maternal diet, and the second diet (after the hyphen) indicates offspring diet.</p

Experimental design.

<p>Experimental design.</p

Effect of diet on leptin regulation.

<p>(A) High-fat mice had more serum leptin (♀ p = 5.27 x 10⁻⁶, ♂ p = 2.38 x 10⁻⁸), however (B) high-fat mice still consumed more food as adults (♀ p = 2.66 x 10⁻¹⁵, ♂ p = 1.67 x 10⁻¹⁵). (C) They also had reduced expression of the leptin receptor (♀ p = 4.53 x 10⁻¹², ♂ p = 8.64 x 10⁻⁸) in the liver, although it is unknown if there was a similar reduction in the hypothalamus. Maternal high-fat diet further increased the serum leptin levels and food consumption in high-fat-fed daughters, but did not have this effect in sons (see p-values of pairwise comparisons on the graphs). HF = High-fat diet, LF = Low-fat diet, N = 10 per group, the first diet listed (before the hyphen) indicates the maternal diet, and the second diet (after the hyphen) indicates offspring diet.</p