Low protein diet fed exclusively during mouse oocyte maturation leads to behavioural and cardiovascular abnormalities in offspring

Abstract

Early embryonic development is known to be susceptible to maternal undernutrition, leading to a disease-related postnatal phenotype. To determine whether this sensitivity extended into oocyte development, we examined the effect of maternal normal protein diet (18% casein; NPD) or isocaloric low protein diet (9% casein; LPD) restricted to one ovulatory cycle (3.5 days) prior to natural mating in female MF-1 mice. After mating, all females received NPD for the remainder of gestation and all offspring were litter size adjusted and fed standard chow. No difference in gestation length, litter size, sex ratio or postnatal growth was observed between treatments. Maternal LPD did, however, induce abnormal anxiety-related behaviour in open field activities in male and female offspring (P < 0.05). Maternal LPD offspring also exhibited elevated systolic blood pressure (SBP) in males at 9 and 15 weeks and in both sexes at 21 weeks (P < 0.05). Male LPD offspring hypertension was accompanied by attenuated arterial responsiveness in vitro to vasodilators acetylcholine and isoprenaline (P < 0.05). LPD female offspring adult kidneys were also smaller, but had increased nephron numbers (P < 0.05). Moreover, the relationship between SBP and kidney or heart size or nephron number was altered by diet treatment (P < 0.05). These data demonstrate the sensitivity of mouse maturing oocytes in vivo to maternal protein undernutrition and identify both behavioural and cardiovascular postnatal outcomes, indicative of adult disease. These outcomes probably derive from a direct effect of protein restriction, although indirect stress mechanisms may also be contributory. Similar and distinct postnatal outcomes were observed here compared with maternal LPD treatment during post-fertilization preimplantation development which may reflect the relative contribution of the paternal genome.

Figure 1. Maternal low protein diet (LPD) during oocyte maturation causes an elevation in birth weight in male offspring at a trend level (P = 0.073) independent of maternal origin and gestational litter size

Mean (±s.e.m.) for males (n = 82–96) and females (n = 101–105) from 19 litters per treatment group.

Figure 2. Maternal LPD during oocyte maturation has no effect on postnatal growth

Mean (±s.e.m.) body mass for male (A, n = 42–60) and female (B, n = 48–57) offspring for 3–28 weeks from 19 litters per treatment group.

Figure 3. Maternal LPD during oocyte maturation leads to changes in postnatal behaviour

Mean open field behaviour for male (A, n = 52–59 per treatment) and female (B, n = 54–57) offspring from 19 litters. *P < 0.01 independent of maternal origin and gestational litter size. ‡Difference at a trend level (P = 0.071).

Figure 4. Maternal LPD during oocyte maturation induces an elevation in postnatal SBP

Mean (±s.e.m.) SBP of male (A, n = 45–59 per treatment) and female (B, n = 51–56) offspring from 19 litters per treatment group. *P < 0.05 independent of maternal origin and gestational litter size. ‡Difference at a trend level (P = 0.09).

Figure 5. Maternal LPD during oocyte maturation reduces the vasoreactivity of isolated male offspring mesenteric arteries at 22 weeks

Cumulative additions of phenylephrine (PE; A) and, after preconstriction with PE, of the vasodilators acetylcholine (ACh; B), isoprenaline (ISO, C) and sodium nitroprusside (SNP; D). No difference is observed in responsiveness to PE or SNP between treatments; however, LPD arteries display attenuated responses to ACh and ISO when compared to NPD arteries. Values are mean ±s.e.m.; n = 7 males, each from different litters, from each treatment group; *P < 0.015.

Figure 6. Maternal LPD during oocyte maturation alters the correlation between organ : body weight ratios and Life SBP in offspring

A and B, LPD males have a positive correlation (continuous line) between both left and right kidney : body weight ratio and Life SBP (P < 0.015) which differs from NPD males (dashed line, P < 0.015). C, LPD males have a positive correlation (continuous line) between heart : body weight ratio and Life SBP (P = 0.004) which differed from that of NPD males (dashed line, P = 0.05). All differences were independent of maternal origin and gestational litter size.

Figure 7. Maternal LPD during oocyte maturation increases kidney mean glomerular number (GN) in female LPD offspring at 28 weeks

A, GN in whole left kidney, GN (g kidney mass)⁻¹ and GN (cm³ kidney tissue)⁻¹. Values are mean ±s.e.m., n = 6 kidneys per treatment, *P < 0.05 independent of maternal origin and gestational litter size. ‡P = 0.091. B, analysis of glomerular number : Life SBP correlation.