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Postnatal development of the circadian adrenocortical rhythm in rats with different neonatal nutrition
Insights
Neonatal overfeeding in rats disrupts the development of corticosterone diurnal rhythms, leading to altered hormone levels in adulthood. Early nutrition significantly impacts stress hormone regulation and circadian patterns.
Area of Science:
- Endocrinology
- Chronobiology
- Developmental Biology
Background:
- Early life nutrition profoundly influences physiological development and stress responses.
- Circadian rhythms, including hormone secretion patterns, are established during postnatal development.
- Corticosterone is a key stress hormone regulated by the hypothalamic-pituitary-adrenal (HPA) axis.
Purpose of the Study:
- To investigate the impact of neonatal nutritional status (overfeeding, standard feeding, underfeeding) on the development of diurnal rhythms of plasma and adrenal corticosterone.
- To determine the age of onset and characteristics of circadian corticosterone rhythms in rats subjected to different early-life feeding regimens.
- To assess the long-term effects of neonatal nutrition on corticosterone rhythmicity and levels in adult rats.
Main Methods:
- Rats were subjected to overfeeding (4 pups/litter), standard feeding (8 pups/litter), or underfeeding (14 pups/litter) during the suckling period.
- Plasma and adrenal corticosterone levels were measured across different postnatal ages to track the development of diurnal rhythms.
- Circadian rhythm parameters, including presence, timing of peak concentration, amplitude, and mesor, were analyzed.
Main Results:
- The circadian rhythm of plasma corticosterone emerged by postnatal day 18 in overfed and standard-fed rats, with a slight delay in underfed rats (day 21).
- A distinct circadian rhythm was evident in 23- to 30-day-old rats.
- Adult overfed rats showed a blunted diurnal rhythm of corticosterone, unlike standard-fed and underfed rats. Peak corticosterone shifted from the dark period in young rats to the end of the light period in adults.
- Mesor values were higher in underfed compared to overfed weaned and adult rats.
Conclusions:
- Neonatal overfeeding significantly impairs the development and maintenance of diurnal corticosterone rhythms in rats, suggesting long-term HPA axis dysregulation.
- Early nutritional interventions can alter the timing and robustness of circadian hormone patterns, with implications for stress responsiveness.
- The findings highlight the critical role of early-life nutrition in programming endocrine and circadian systems, influencing health outcomes later in life.
Abstract:
The development of diurnal rhythm of plasma and adrenal corticosterone levels was examined in rats overfed, standardfed and underfed during the suckling period (realised by adjustment of the number of suckling pups per litter to 4, 8, and 14). The first presence of circadian rhythm of plasma corticosterone was observed in 18-day-old overfed and standardfed rats, and slight delay in the manifestation of rhythm was noted in neonatally underfed animals (rhythm present in 21-day-old rats). The distinct circadian rhythm was present in 23- to 30-day-old rats. However in adult animals a significant diurnal rhythm of plasma and adrenal corticosterone content was noted in standardfed and underfed rats, whereas the variation of hormone levels was not significant in the neonatally overfed group. In young animals the peak of plasma corticosterone concentration occurred during the dark period while in adult animals it was shifted to the end of the light period. The values of amplitude of plasma corticosterone variation are increasing during the postnatal period. In weaned and adult rats the mesor values were found to be higher in neonatally underfed rats in comparison to the neonatally overfed group.