Prolonging the female reproductive lifespan and improving egg quality with dietary omega-3 fatty acids

Abstract

Women approaching advanced maternal age have extremely poor outcomes with both natural and assisted fertility. Moreover, the incidence of chromosomal abnormalities and birth defects increases with age. As of yet, there is no effective and practical strategy for delaying ovarian aging or improving oocyte quality. We demonstrate that the lifelong consumption of a diet rich in omega-3 fatty acids prolongs murine reproductive function into advanced maternal age, while a diet rich in omega-6 fatty acids is associated with very poor reproductive success at advanced maternal age. Furthermore, even short-term dietary treatment with a diet rich in omega-3 fatty acids initiated at the time of the normal age-related rapid decline in murine reproductive function is associated with improved oocyte quality, while short-term dietary treatment with omega-6 fatty acids results in very poor oocyte quality. Thus, omega-3 fatty acids may provide an effective and practical avenue for delaying ovarian aging and improving oocyte quality at advanced maternal age.

Fig. 1

Reproductive and fertility outcomes in long-term diet studies at normal maternal reproductive age (3–6 months). (A) Litter size and viability were not different between F0 generation animals in each of the diet groups (N = 3, 6, 3 litters for SOY, HCO, and DHA groups, respectively). (B) Reproductive function was maintained over six successive generations of animals on the DHA diet with an improvement in viability over successive generations (N = 3, 13, 3 litters for F0, F4, and F5 generations, respectively). Offspring viability assessed at 3 weeks.

Fig. 2

Reproductive and fertility outcomes in long-term diet studies at advanced maternal reproductive age (10–15 months). (A) Reproductive function was maintained in females on the DHA diet at advanced maternal age. (B) Animals on the SOY and (C) CHOW diets had very poor reproductive success at advanced maternal age. Each animal is indicated by a number on the x-axis, and each bar represents one litter. White bars represent total number of offspring, and black bars represent viable offspring. Crosses indicate animals that died or had to be euthanized during the study period. Offspring viability assessed at 2 weeks.

Fig. 3

Fatty acid profiles, ovarian follicle counts, and oocyte quality in acute dietary treatment studies. (A) Serum omega-6/omega-3 fatty acid (dark red bars) and triene/tetraene ratios (light red bars) of animals in each acute dietary treatment group. The serum omega-6/omega-3 fatty acid ratio was more than 7-fold lower in the DHA group compared to the CHOW (P = 0.008) and SOY (P = 0.008) groups, and no animal in any diet group had evidence of biochemical essential fatty acid deficiency (triene/tetraene ratio > 0.2) (N = 5, 5, 5 animals for CHOW, SOY, and DHA groups, respectively). (B) Oocyte characterization demonstrates that a larger percentage of oocytes from animals in the DHA group were fully mature and fewer were atretic compared to the CHOW and SOY groups (N = 53, 23, and 25 oocytes for CHOW, SOY, and DHA groups, respectively). (C) Ovarian follicle counts demonstrate a greater number of total (P = 0.04) and primordial follicles (P = 0.04) in ovaries from animals following acute treatment with the DHA diet compared to the SOY diet (N = 6, 6, and 7 animals for CHOW, SOY, and DHA groups, respectively). (D) Representative mitochondrial staining of oocytes obtained from animals in each of the acute dietary treatment groups. Mitochondria appeared normal in 6/6 (100%) mature oocytes from animals in the DHA group, compared with 0/4 (0%) and 1/3 (33%) mature oocytes in the CHOW and SOY diet groups, respectively (P = 0.006). (E) Representative tubulin (spindle apparatus, green) and DNA (blue) staining of oocytes obtained from animals in each of the acute dietary treatment groups. Meiotic spindles appeared normal in 4/5 (80%) mature oocytes from animals in the DHA group as compared with 2/3 (66%) and 0/5 (0%) mature oocytes from animals in the CHOW and SOY groups, respectively (P = 0.03). All bars indicate mean ± SD.

Fig. 4

Evaluation of safety of the omega-3-rich diet with fatty acid profiles and growth. (A–D) Serum fatty acid profiles over multiple generations (N = 4, 5, 5, 5, 4, 15 for F1 HCO, F1 SOY, F2 SOY, F1 DHA, F2 DHA, and F5 DHA groups, respectively). (A) Serum triene/tetraene ratios demonstrate that no animals on the SOY or DHA diet had evidence of biochemical essential fatty acid deficiency (triene/tetraene ratio > 0.2, horizontal dashed line). (B) Serum omega-6/omega-3 fatty acid ratios and the total percent of fatty acid attributable to (C) omega-6 and (D) omega-3 fatty acids differed significantly between groups. (E–H) Growth data. Weekly average body weight of representative F1 generation (E) males and (F) females from week 3 (wean) to week 8 of life. Weekly body weights did not differ between animals on the CHOW, SOY, and DHA diets but were consistently lower for animals on the HCO diet (N = 5, 11, 7, 5 male and N = 5, 6, 9, 5 female animals for CHOW, HCO, SOY, and DHA diet groups, respectively). Weekly average body weight of representative F1, F2, and F5 generation (G) males and (H) females from week 3 (wean) to week 8 of life. Animals on the DHA diet continued to demonstrate normal growth despite lifelong treatment with this diet over multiple generations (N = 5, 8, 6 male and N = 5, 5, 6 female animals for F1, F2, and F5 DHA groups, respectively). All data represented as mean ± SD.