A rooster (left) and a hen (right). Image from http://en.wikipedia.org/wiki/File:Female_pair.jpg
It’s hard to make babies when you’re stressed, even if you are a chicken. In a recent paper in the Journal of Lipid Research, a group of Chinese investigators looked into how stress can disrupt lipid metabolism, a source of reproductive energy, in egg-laying hens.
“Stress is a common problem that disrupts breeding in either birds or mammals,” explains Hai Lin at Shandong Agricultural University in China, who led the team of investigators. “Glucocorticoids participate in the arousal of stress responses and trigger physiological adjustments that shift energy away from reproduction toward survival.”
Glucocorticoids work to control whole-body homeostasis and trigger stress responses. Lin says the group’s previous work on immature chickens showed that glucocorticoids enhanced hepatic lipogenesis and fat deposition in adipose tissues, indicating the redistribution of energy stores.
To see how energy sources got redistributed from reproduction to survival, Lin and colleagues tested the effects of corticosterone, a type of glucocorticoid, on egg-laying hens. They did two different experiments to see how corticosterone affected the development of ovarian follicles in hens. These follicles supply yolk precursors, which are very low-density lipoproteins, for eggs. In the first experiment, the investigators looked into how fasting and feeding affected ovarian follicular development and lipid production in the liver with or without corticosterone. In the second experiment, the investigators tested the effects of corticosterone on two groups of hens, each fed a diet with a different calorie count.
Lin says their results demonstrated that corticosterone “mimicked the endogenous glucocorticoids under stress to shift the energy expenditure away from reproduction to survival by suppressing ovarian follicular development, laying rate and egg production via multiple actions.” The investigators concluded that stress’ effects to suppress reproduction were energy-dependent.
The group will next look into the effects of stress on estrogen release. (Estrogen plays a role in triglyceride synthesis). Lin explains that the investigators are interested in this direction of research because in their current study “the circulating concentration of estrogen was decreased by corticosterone, suggesting that the suppressive effect of corticosterone on ovarian follicular development is associated with a reduced estrogen release.” They also would like to see if isoflavones, a class of plant-derived compounds with estrogenic activity, such as those found in soy, has any potential to regulate the effects on stress-induced perturbation in reproduction.
