Methyl donor supplementation prevents transgenerational amplification of obesity

Abstract

Background: The obesity epidemic, recognized in developed nations for decades, is now a worldwide phenomenon. All age groups are affected, including women of childbearing age, fueling concern that maternal obesity before and during pregnancy and lactation impairs developmental establishment of body weight regulatory mechanisms in the fetus or infant, causing transgenerational amplification of obesity prevalence and severity. The biological mechanisms underlying such processes remain unknown.

Methods: We used agouti viable yellow (A(vy)) mice to test the hypothesis that maternal obesity induces transgenerational amplification of obesity. We passed the A(vy) allele through three generations of A(vy)/a females and assessed cumulative effects on coat color and body weight. By studying two separate but contemporaneous populations of mice, one provided a standard diet and the other a methyl-supplemented diet that induces DNA hypermethylation during development, we tested whether potential transgenerational effects on body weight might be mediated by alterations in epigenetic mechanisms including DNA methylation.

Results: The genetic tendency for obesity in A(vy) mice was progressively exacerbated when the A(vy) allele was passed through successive generations of obese A(vy) females. This transgenerational amplification of body weight was prevented by a promethylation dietary supplement. Importantly, the effect of methyl supplementation on body weight was independent of epigenetic changes at the A(vy) locus, indicating this model may have direct relevance to human transgenerational obesity.

Conclusion: Our results show that in a population with a genetic tendency for obesity, effects of maternal obesity accumulate over successive generations to shift the population distribution toward increased adult body weight, and suggest that epigenetic mechanisms are involved in this process.

Figure 1

Methyl supplementation prevents transgenerational increase in adult body weight. (a) Genogram illustrating study design; a/a mice are shown in black and A^vy/a mice in various shades of yellow/brown. (b) Body weight at weaning (P21) in a/a and A^vy/a offspring born to A^vy/a females (n_total=119 (F1), 214 (F2) and 379 (F3)). Box plots indicate median, 25th—75th percentiles (box), and 5th—95th percentiles (whiskers). In unsupplemented A^vy/a offspring only, P21 weight increases with successive generations (P=0.007). (c) Distribution of adult (P180) body weight of A^vy/a offspring by generation and group (n_unsuppl=29 (F1), 36 (F2) and 88 (F3); n_suppl=33 (F1), 62 (F2) and 117 (F3)). The percentages in each panel indicate the proportion of offspring above 50 g (dotted line). Body weight is relatively constant in the supplemented group, but increases transgenerationally in the unsupplemented group (P=0.000006). (d) P180 body weight versus coat color class for A^vy/a animals in the F3 generation (1 = yellow, 2 = slightly mottled, 3 = mottled, 4 = heavily mottled; number of mice in each class is indicated). Body coat color class. weight is not associated with A^vy epigenotype. Supplemented mice tend to weigh less within every coat color class.

Figure 2

Methyl supplementation changes the association between maternal and offspring adult body weight. Adult body weight was measured at P180 for all dams and A^vy offspring in the study. In both the F2 and F3 generations, maternal adult body weight predicts offspring adult body weight in the unsupplemented group only. The P-values of the analysis of covariance are provided.

Figure 3

Adiposity is highly correlated with body weight in isogenic A^vy/a mice. (a) P180 isogenic A^vy/a female mice discordant for body weight. (b) Variation in body weight is mostly explained by variation in adiposity among P180 female (n=24) and male (n=28) A^vy/a mice.

Figure 4

Impact of prior generations on F3 A^vy/a adult body weight. Shown are F3 P180 body weight versus great-grandmaternal (F0, left panel), grandmaternal (F1, center panel) and maternal (F2, right panel) P180 body weight. Heavier mice from F0 and F1 lead to heavier F3 mice, regardless of supplementation. Supplementation abrogates only the effect of maternal body weight on offspring body weight (right panel), rather than prior generational effects. The P-values of the analysis of covariance are provided.