The effects of early life stress on factors associated with food intake and body weight changes in sprague dawley rats
Date
2016-03-10
Authors
Masemola, Maphoko Adelade
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Abstract
The early years of life are critical for neuroendocrine development. Early life adverse events during this developmental period can alter the Hypothalamic-Pituitary-Adrenal (HPA) axis with consequences on physical and mental health. These consequences may persist into adulthood and result in the dysregulation of the HPA axis and immune system, increased susceptibility to developing obesity, metabolic syndrome and cardiovascular complications. The present study determined the long term effects of early life stress (maternal separation), adolescent social isolation and foot-shock stress on food intake, body mass gain, visceral fat mass, glucose concentrations, insulin concentrations and HOMA-IR (Homeostatic model of insulin resistance), the innate immune response and corticosterone concentrations in male and female Sprague Dawley rats. Our findings show that whilst maternal separation in male rats resulted in significantly (p<0.05) increased visceral adiposity, hyperinsulinemia and increased corticosterone; foot-shock stress resulted in decreased body mass gain, visceral fat mass and plasma glucose concentrations and activation of the innate immune response in male rats. Social isolation in female rats resulted in significantly (p<0.05) increased feed conversion ratio, body mass gain, visceral adiposity and hyperinsulinaemia. The findings of the current study indicate that social isolation increases the parameters that contribute to the development of metabolic syndrome in female rats. However, in male rats maternal separation increases markers (visceral obesity and hyperinsulinaemia) of metabolic syndrome. This draws attention to the fact that male and female rats respond differently to specific stressors. The mechanisms underlying these variations in gender related stress responses remain unclear.
Description
A dissertation submitted to the Faculty of Health Sciences, University of Witwatersrand, School of Physiology in fulfilment of the requirements for the degree of Master of Science in Medicine