The transcriptional basis of seasonal life-history transitions in the Siberian hamster

Stewart, Calum (2024) The transcriptional basis of seasonal life-history transitions in the Siberian hamster. PhD thesis, University of Glasgow.

Abstract

Seasonal changes in physiology and behaviour are widespread in plants and animals. Changes in external photoperiod provide an initial predictive cue which animals used to drives changes in physiology. These long-term regulated changes in physiological stability are referred to as programmed rheostasis. Rheostasis controls changes in the set-point of homeostatically defended physiological variables. The aim of this thesis was to investigate the neuroendocrine mechanisms which regulate programmed regulation of energy rheostasis in the Siberian hamsters (Phodopus sungorus). Next-generation sequencing was used to examine the expression of transcripts within the hypothalamus during the photoperiod-induced involution and regrowth in body mass. Despite large changes in body mass and food intake, neuroendocrine markers showed limited changes in expression with only somatostatin (sst) showing large seasonal changes. Expression of many transcripts is upregulated exclusively when the set-point in body mass is decreasing. One such transcript Myocyte enhancer factor 2c (mef2c), is a transcription factor which may be involved in effecting transciption changes to control the set-point. Then, two separate studies using common manipulations of negative and positive energy balance were conducted to identify molecular markers associated with rheostatic and homeostatic regulation of energy balance. Short term food restriction was shown to increase neuropeptide-y (npy) expression. Conversely, Sst expression increased significantly in short photoperiod hamsters but remained stable despite food restriction. Next, by a manipulation of positive energy balance using a high-fat diet paradigm it was found that neither homeostatic, nor rheostatic programs in energy balance were impacted. Overall, the studies describe here provide evidence for two separate neuroendocrine systems that independently regulate short-term homeostatic, versus long-term rheostatic changes in energy balance.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QP Physiology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Supervisor's Name: Stevenson, Professor Tyler
• Date of Award: 2024
• Depositing User: Theses Team
• Unique ID: glathesis:2024-84136
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Mar 2024 16:30
• Last Modified: 22 Mar 2024 15:22
• Thesis DOI: 10.5525/gla.thesis.84136
• URI: https://theses.gla.ac.uk/id/eprint/84136