Disruption of energy homeostasis by food restriction or high ambient temperature exposure affects gonadal function in ma
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ORIGINAL PAPER
Disruption of energy homeostasis by food restriction or high ambient temperature exposure affects gonadal function in male house finches (Haemorhous mexicanus) Shelley Valle1,2 · Daphne Eagleman1,3 · Natalie Kieffer1 · Pierre Deviche1 Received: 16 December 2019 / Revised: 18 June 2020 / Accepted: 10 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Reproductive success requires that individuals acquire sufficient energy resources. Restricting food availability or increasing energy expenditure (e.g., thermoregulation) inhibits reproductive development in multiple avian species, but the nature of the energy-related signal mediating this effect is unclear. To investigate this question, we examined reproductive and metabolic physiology in male house finches that either underwent moderate food restriction (FR) or were exposed to high temperature (HT), in which birds were held at a high, but not locally atypical, ambient temperature cycle (37.8 °C day, 29.4 °C night) compared to a control group (CT; 29.4 °C day, 21.1 °C night). We hypothesized that FR and HT inhibit reproductive development by lowering available metabolic fuel, in particular plasma glucose (GLU) and free fatty acids (FFA). Following FR for 4 weeks, finches lost body mass, had marginally higher plasma FFA, and experienced a 90% reduction in testis mass compared to CT birds. Four weeks of HT exposure resulted in reduced voluntary food consumption and muscle mass, as well as an 80% reduction in testis mass relative to CT birds. Both FR and HT birds expressed less testicular 17β-hydroxysteroid dehydrogenase (17β-HSD) mRNA than controls but the expression of other testicular genes measured was unaffected by either treatment. Neither treatment significantly influenced plasma GLU. This study is among the first to demonstrate a negative effect of HT on reproductive development in a wild bird. Further studies are needed to clarify the role of metabolic mediators and their involvement under various conditions of energy availability and demand. Keywords Energy homeostasis · Reproduction · Gonads · Metabolite · Food restriction · High temperature Abbreviations 17β-HSD 17β-Hydroxysteroid dehydrogenase ANOVA Analysis of variance AL Ad libitum CP Cloacal protuberance CORT Corticosterone FR Food-restricted FFA Free fatty acids Communicated by K. H. Dausmann. * Shelley Valle [email protected] 1
School of Life Sciences, Arizona State University, Tempe, AZ, USA
2
Present Address: Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
3
Present Address: Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
FSHR Follicle-stimulating hormone receptor GLU Glucose GnIH Gonadotropin-inhibitory hormone GR Glucocorticoid receptor GSI Gonadosomatic index HPG Hypothalamic-pituitary–gonadal HSP60 Heat shock protein 60 HSP70 Heat shock protein 70 HT High temperature LHR Luteinizing hormone receptor MR Mineralocorticoid receptor StAR Steroi
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