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Levay E, Nasser H, Zelko M, Penman J, Johns T. Lemming and Vole Cycles: A New Intrinsic Model. Ecol Evol 2024; 14:e70440. [PMID: 39440212 PMCID: PMC11493491 DOI: 10.1002/ece3.70440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Accepted: 09/27/2024] [Indexed: 10/25/2024] Open
Abstract
It is 100 years since the first paper described the multiannual cycles in Arctic rodents and lagomorphs. The mechanisms driving population cycles in animals like lemmings and voles are complex, often attributed to extrinsic factors, such as food availability and quality, pathogens, parasites and/or predators. While extrinsic factors provide insights into population cycles, none fully explain the phenomenon. We propose an underlying innate, intrinsic mechanism, based on epigenetic regulation, that drives population cycles under harsh arctic conditions. We propose that epigenetically driven phenotypic changes associated with sexual development, growth and behaviour accumulate over time in offspring, eventually producing a phase change from rising population density to eventual population collapse. Under this hypothesis, and unlike previous hypotheses, extrinsic factors modify population cycles but would not be primary drivers. The interaction between our intrinsic cycle and extrinsic factors explains established phenomena like delayed-density dependence, whereby population growth is controlled by time-dependent negative feedback. We advocate integrating a century of field research with the latest epigenetic analysis to better understand the drivers of population cycles.
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Affiliation(s)
- Elizabeth A. Levay
- School of Psychology and Public HealthLa Trobe UniversityMelbourneVictoriaAustralia
- Epigenes Australia Pty LtdMelbourneVictoriaAustralia
| | - Helen Nasser
- School of Psychology and Public HealthLa Trobe UniversityMelbourneVictoriaAustralia
- Epigenes Australia Pty LtdMelbourneVictoriaAustralia
| | | | - Jim Penman
- Epigenes Australia Pty LtdMelbourneVictoriaAustralia
| | - Terrance G. Johns
- School of Psychology and Public HealthLa Trobe UniversityMelbourneVictoriaAustralia
- Epigenes Australia Pty LtdMelbourneVictoriaAustralia
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Marshall CJ, Blake A, Stewart C, Liddle TA, Denizli I, Cuthill F, Evans NP, Stevenson TJ. Prolactin Mediates Long-Term, Seasonal Rheostatic Regulation of Body Mass in Female Mammals. Endocrinology 2024; 165:bqae020. [PMID: 38417844 PMCID: PMC10904104 DOI: 10.1210/endocr/bqae020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 01/31/2024] [Accepted: 02/27/2024] [Indexed: 03/01/2024]
Abstract
A series of well-described anabolic and catabolic neuropeptides are known to provide short-term, homeostatic control of energy balance. The mechanisms that govern long-term, rheostatic control of regulated changes in energy balance are less well characterized. Using the robust and repeatable seasonal changes in body mass observed in Siberian hamsters, this report examined the role of prolactin in providing long-term rheostatic control of body mass and photoinduced changes in organ mass (ie, kidney, brown adipose tissue, uterine, and spleen). Endogenous circannual interval timing was observed after 4 months in a short photoperiod, indicated by a significant increase in body mass and prolactin mRNA expression in the pituitary gland. There was an inverse relationship between body mass and the expression of somatostatin (Sst) and cocaine- and amphetamine-regulated transcript (Cart). Pharmacological inhibition of prolactin release (via bromocriptine injection), reduced body mass of animals maintained in long photoperiods to winter-short photoperiod levels and was associated with a significant increase in hypothalamic Cart expression. Administration of ovine prolactin significantly increased body mass 24 hours after a single injection and the effect persisted after 3 consecutive daily injections. The data indicate that prolactin has pleiotropic effects on homeostatic sensors of energy balance (ie, Cart) and physiological effectors (ie, kidney, BAT). We propose that prolactin release from the pituitary gland acts as an output signal of the hypothalamic rheostat controller to regulate adaptive changes in body mass.
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Affiliation(s)
- Christopher J Marshall
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol BS8 1TD, UK
| | - Alexandra Blake
- Institute of Molecular Biology, University of Mainz, Mainz 55122, Germany
| | - Calum Stewart
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - T Adam Liddle
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - Irem Denizli
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - Fallon Cuthill
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - Neil P Evans
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - Tyler J Stevenson
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
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Bodelon C, Gierach GL, Hatch EE, Riseberg E, Hutchinson A, Yeager M, Sandler DP, Taylor JA, Hoover RN, Xu Z, Titus L, Palmer JR, Troisi R. In utero exposure to diethylstilbestrol and blood DNA methylation in adult women: Results from a meta-analysis of two cohort studies. ENVIRONMENTAL RESEARCH 2023; 231:115990. [PMID: 37149030 PMCID: PMC10442904 DOI: 10.1016/j.envres.2023.115990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/10/2023] [Accepted: 04/24/2023] [Indexed: 05/08/2023]
Abstract
BACKGROUND Prenatal exposure to diethylstilbestrol (DES) is associated with several adverse health outcomes. Animal studies have shown associations between prenatal DES exposure and DNA methylation. OBJECTIVE The aim of this study was to explore blood DNA methylation in women exposed and unexposed to DES in utero. METHODS Sixty women (40 exposed and 20 unexposed) in the National Cancer Institute's Combined DES Cohort Study and 199 women (99 exposed and 100 unexposed women) in the Sister Study Cohort were included in this analysis. Within each study, robust linear regression models were used to assess associations between DES exposure and blood DNA methylation. Study-specific associations were combined using fixed-effect meta-analysis with inverse variance weights. Our analysis focused on CpG sites located within nine candidate genes identified in animal models. We further explored whether in utero DES exposure was associated with age acceleration. RESULTS Blood DNA methylation levels at 10 CpG sites in six of the nine candidate genes were statistically significantly associated with prenatal DES exposure (P < 0.05) in this meta-analysis. Genes included EGF, EMB, EGFR, WNT11, FOS, and TGFB1, which are related to cell proliferation and differentiation. The most statistically significant CpG site was cg19830739 in gene EGF, and it was associated with lower methylation levels in women prenatally exposed to DES compared with those not exposed (P < 0.0001; false discovery rate<0.05). The association between prenatal DES exposure in utero and age acceleration was not statistically significant (P = 0.07 for meta-analyzed results). CONCLUSIONS There are few opportunities to investigate the effects of prenatal DES exposure. These findings suggest that in utero DES exposure may be associated with differential blood DNA methylation levels, which could mediate the increased risk of several adverse health outcomes observed in exposed women. Our findings need further evaluation using larger data sets.
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Affiliation(s)
- Clara Bodelon
- Integrative Tumor Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
| | - Gretchen L Gierach
- Integrative Tumor Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Elizabeth E Hatch
- Department of Epidemiology, Boston University School of Public Health, Boston University, Boston, MA, USA
| | - Emily Riseberg
- Department of Nutrition, Harvard T. H. Chan School of Public Health, Harvard University, Boston, MA, USA
| | - Amy Hutchinson
- Cancer Genomics Research Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Meredith Yeager
- Cancer Genomics Research Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Dale P Sandler
- Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Jack A Taylor
- Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA; Epigenetic and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Robert N Hoover
- Trans-Divisional Research Program, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Zongli Xu
- Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Linda Titus
- Public Health, Muskie School of Public Service, University of Southern Maine, Portland, ME, USA
| | - Julie R Palmer
- Slone Epidemiology Center and Department of Medicine, Boston University School of Medicine, Boston University, Boston, MA, USA
| | - Rebecca Troisi
- Trans-Divisional Research Program, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
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Tolla E, Stevenson TJ. Photoperiod-induced changes in hypothalamic de novo DNA methyltransferase expression are independent of triiodothyronine in female Siberian hamsters (Phodopus sungorus). Gen Comp Endocrinol 2020; 299:113604. [PMID: 32866475 DOI: 10.1016/j.ygcen.2020.113604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 08/17/2020] [Accepted: 08/24/2020] [Indexed: 11/27/2022]
Abstract
Many temperate zone animals engage in seasonal reproductive physiology and behavior as a strategy to maximise the propagation of the species. The hypothalamus integrates environmental cues and hormonal signalling to optimize the timing of reproduction. Recent work has revealed that epigenetic modifications, such as DNA methylation, vary across seasonal reproductive states. Multiple hormones act in the hypothalamus to permit or inhibit reproductive physiology, and the increase in thyroid hormone triiodothyronine (T3) has been implicated in the initiation of breeding in many species. The objective of this study was to examine the effect of T3 on the photoperiod-dependent regulation of reproductive physiology and hypothalamic DNA methyltransferase enzyme expression in female Siberian hamsters (Phodopus sungorus). We tested the hypothesis that T3 in short days (SD) would stimulate hypothalamic Rfrp3 and de novo DNA methyltransferase (Dnmt) expression in female Siberian hamsters. 10 weeks of SD lengths induced a decrease in body and uterine mass. Hamsters maintained in SD were found to express lower levels of GnRH, Rfrp3, Dnmt3a and Dnmt3b. Two weeks of daily T3 injections did not affect body mass, uterine mass, Gnrh, Rfrp3, Dnmt3a or Dnmt3b expression in neuroendocrine tissues. SD significantly lowered Tshβ mRNA expression and T3 reduced Tshβ in LD hamsters. Our data indicate sex-dependent effects of T3 for the neuroendocrine regulation of seasonal reproduction in hamsters.
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Affiliation(s)
- E Tolla
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK.
| | - T J Stevenson
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK
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Tolla E, Stevenson TJ. Sex Differences and the Neuroendocrine Regulation of Seasonal Reproduction by Supplementary Environmental Cues. Integr Comp Biol 2020; 60:1506-1516. [PMID: 32869105 DOI: 10.1093/icb/icaa096] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Seasonal rhythms in reproduction are conserved across nature and optimize the timing of breeding to environmental conditions favorable for offspring and parent survival. The primary predictive cue for timing seasonal breeding is photoperiod. Supplementary cues, such as food availability, social signals, and temperature, fine-tune the timing of reproduction. Male and female animals show differences in the sensory detection, neural integration, and physiological responses to the same supplementary cue. The neuroendocrine regulation of sex-specific integration of predictive and supplementary cues is not well characterized. Recent findings indicate that epigenetic modifications underlie the organization of sex differences in the brain. It has also become apparent that deoxyribonucleic acid methylation and chromatin modifications play an important role in the regulation and timing of seasonal rhythms. This article will highlight evidence for sex-specific responses to supplementary cues using data collected from birds and mammals. We will then emphasize that supplementary cues are integrated in a sex-dependent manner due to the neuroendocrine differences established and maintained by the organizational and activational effects of reproductive sex hormones. We will then discuss how epigenetic processes involved in reproduction provide a novel link between early-life organizational effects in the brain and sex differences in the response to supplementary cues.
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Affiliation(s)
- Elisabetta Tolla
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Tyler J Stevenson
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK
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