Effects of Maternal Stress on the Development of the Somatotropic Axis During the Larval and Juvenile Stages in Zebrafish (Danio rerio)

Stress is recognized as an adaptive response to potentially harmful environmental stimuli. The primary physiological adaptation to stress is an increase in circulating cortisol levels, which, in excess, can be transferred and incorporated into the oocytes of maturing females, affecting the embryonic developmental program. Additionally, maternal energy availability is an essential environmental factor that modulates this program. Based on this background, we investigated the effects of maternal cortisol on the development of the somatotropic axis in zebrafish offspring and juveniles. Zebrafish mothers were divided into two groups based on diet: Group 1 received a cortisol-enriched diet, to mimic maternal stress, while Group 2 (control) received a standard diet, for five days. On the third day after treatment, the control and treated females were bred with untreated males. Offspring were assessed at 0, 24, 48, 72, 96, 120, and 144 h post-fertilization (hpf). Morphological analyses were performed during embryonic development, including survival rate, body length, the presence of pericardial edema, and heartbeat. We examined the gene expression of key somatotropic axis components, including mtor, foxo3a, mafbx, murf1, mstna, gh, igf1, igf2a, igf2b, 11hsdb2, and fkbp5. The study demonstrated that cortisol-treated females significantly influenced offspring development, resulting in higher mortality rates and increased morphological abnormalities, particularly pericardial edema. Gene expression analysis revealed alterations in transcripts related to the somatotropic axis, especially genes involved in protein synthesis, with signs of accelerated growth in the first hour post-fertilization. At 30 days post-fertilization, juveniles from cortisol-treated females displayed a marked increase in muscle bundle size and cross-sectional diameter compared to the control group. Our findings provide valuable insights into the intricate interaction between maternal factors and the development of the somatotropic axis in offspring.