Journal
PEERJ
Volume 6, Issue -, Pages -Publisher
PEERJ INC
DOI: 10.7717/peerj.5936
Keywords
Glucocorticoid; IGF-1; Stress response; Panurus biarmicus; HPS axis; Life-history trade offs
Categories
Funding
- Hungarian Scientific Research Fund [OTKA K113108]
- National Development, Research and Innovation Fund [TET 15-1-2016-0044]
- European Union
- European Social Fund [EFOP-3.6.1-16-2016-00022]
- Hungarian Ministry of National Resources-National Talent Program [NTP-EFO-P-15-041]
- NSF [OIA-1738594]
- Romanian Ministry of Education [PN-III-P4-ID-PCE-2016-0572]
- NIH [P20 GM103650]
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Background. Physiological regulators of life history trade-offs need to be responsive to sudden changes of resource availability. When homeostasis is challenged by unpredictable stressors, vertebrates respond through a set of physiological reactions, which can promote organismal survival. Glucocorticoids have been traditionally recognized as one of the main regulators of the physiological stress response, but the role of an evolutionarily more conserved pathway, the hypothalamic-pituitary-somatotropic (HPS) axis producing insulin-like growth factor-1 (IGF-1) has received much less attention. Although IGF-1 is known to affect several life history traits, little is known about its role in the physiological stress response and it has never been studied directly in adult wild animals. Methods. In this study, we combined field observations with a controlled experiment to investigate how circulating levels of IGF-1 change in response to stress and whether this change is due to concomitant change in glucocorticoids in a free-living songbird, the bearded reedling Panurus biarmicus. We used a standard capture-restraint protocol in field observation, in which we took first and second (stress induced: 15 minutes later) samples. In a follow-up experiment, we used a minimally invasive oral corticosterone manipulation. Results. We showed that corticosterone levels significantly increased while IGF-1 levels significantly decreased during capture and handling stress. However, change in corticosterone levels were not related to change in IGF-1 levels. We found that experimentally elevated corticosterone levels did not affect IGF-1 levels. Discussion. Our results are the first to highlight that circulating IGF-1 levels are responsive to stress independently from glucocorticoids and suggest that the HPS axis is an autonomous physiological pathway that may play an important role as regulator of life-history decisions.
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