Lasting effects on body weight and mammary gland gene expression in female mice upon early life exposure to n-3 but not n-6 high-fat diets

Abstract

Exposure to an imbalance of nutrients prior to conception and during critical developmental periods can have lasting consequences on physiological processes resulting in chronic diseases later in life. Developmental programming has been shown to involve structural and functional changes in important tissues. The aim of the present study was to investigate whether early life diet has a programming effect on the mammary gland. Wild-type mice were exposed from 2 weeks prior to conception to 6 weeks of age to a regular low-fat diet, or to high-fat diets based on either corn oil or flaxseed oil. At 6 weeks of age, all mice were shifted to the regular low-fat diet until termination at 10 weeks of age. Early life exposure to a high-fat diet, either high in n-6 (corn oil) or in n-3 (flaxseed oil) polyunsaturated fatty acids, did not affect birth weight, but resulted in an increased body weight at 10 weeks of age. Transcriptome analyses of the fourth abdominal mammary gland revealed differentially expressed genes between the different treatment groups. Exposure to high-fat diet based on flaxseed oil, but not on corn oil, resulted in regulation of pathways involved in energy metabolism, immune response and inflammation. Our findings suggest that diet during early life indeed has a lasting effect on the mammary gland and significantly influences postnatal body weight gain, metabolic status, and signaling networks in the mammary gland of female offspring.

Figure 1. Schematic overview of experimental study design.

Wild-type FVB mice were exposed from two weeks prior to conception to 6 weeks of age to a low-fat (5%) regular mouse diet, or to high-fat (24%) diets based on either corn oil or flaxseed oil. At 6 weeks of age, all mice were shifted to the regular low-fat diet until terminal sacrifice at 10 weeks of age.

Figure 2. Body weight trajectories in F1 female mice, perinatally exposed to a low-fat (5%) regular mouse diet (indicated in black), or to high-fat (24%) diets based on either corn oil (red) or flaxseed oil (blue). Graph plots mean (and 95% confidence intervals) body weights of F1 female pups with age.

The increased body weights of mice fed high-fat diets were significant versus regular diet at 3 weeks of age and beyond (P<0.001; nonlinear repeated measures model); however, mice fed the high-fat corn oil diet shifted to the regular trajectory between 6 and 10 weeks of age. The slight dip in the growth curves at 3 weeks of age in all three groups is accounted for by the removal of male pups, which are slightly heavier than females.

Figure 3. Gene expression changes in the mammary gland.

Test diets were given from two weeks prior to conception to 6 weeks of age, and regular diet thereafter. Microarray analysis was performed at 10 weeks of age. After removing litter-size and batch effects the source of variance was plotted for regular diet (red; n = 12), high-fat diet based on corn oil (green, n = 8) and high-fat diet based on flaxseed oil (magenta, n = 8) using PCA. The heat-map shows clustering of 670 differentially-regulated genes (horizontal) and samples (vertical).