Social defeat and footshock increase body mass and adiposity in male Syrian hamsters

Department of Biology, Georgia State University, Atlanta, Georgia, United States
AJP Regulatory Integrative and Comparative Physiology (Impact Factor: 3.11). 02/2007; 292(1):R283-90. DOI: 10.1152/ajpregu.00330.2006
Source: PubMed


Obesity is a world-wide epidemic, and many factors, including stress, have been linked to this growing trend. After social stress (i.e., defeat), subordinate laboratory rats and most laboratory mice become hypophagic and, subsequently, lose body mass; the opposite is true of subordinate Syrian hamsters. After social defeat, Syrian hamsters become hyperphagic and gain body mass compared with nonstressed controls. It is unknown whether this increase in body mass and food intake is limited to subordinate hamsters. In experiment 1, we asked, do dominant hamsters increase food intake, body mass, and adiposity after an agonistic encounter? Subordinate hamsters increased food intake and body mass compared with nonstressed controls. Although there was no difference in food intake or absolute body mass between dominant and nonstressed control animals, cumulative body mass gain was significantly higher in dominant than in nonstressed control animals. Total carcass lipid and white adipose tissue (WAT) (i.e., retroperitoneal and epididymal WAT) masses were significantly increased in subordinate, but not dominant, hamsters compared with nonstressed controls. In experiment 2, we asked, does footshock stress increase food intake, body mass, and adiposity. Hamsters exposed to defeat, but not footshock stress, increased food intake relative to nonstressed controls. In animals exposed to defeat or footshock stress, body mass, as well as mesenteric WAT mass, increased compared with nonstressed controls. Collectively, these data demonstrate that social and nonsocial stressors increase body and lipid mass in male hamsters, suggesting that this species may prove useful for studying the physiology of stress-induced obesity in some humans.

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    • "In animal models, the types of stressors used commonly include psychological and pathophysiological insults, such as immobilization stress, restraint stress, handling, social defeat, or lipopolysaccharide injection (Haleem et al., 1988, 2013; Martí et al., 1994; Rybkin et al., 1997; Vallès et al., 2000; Solomon et al., 2007; Calvez et al., 2011). All these stressors are reported to reduce food intake, but immobilization stress has a greater impact in suppressing food intake and body weight relative to other stressors. "
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    ABSTRACT: Stress is defined as a state that can threaten homeostasis in an organism to initiate the adaptive process. Stress mediators, which include the classic neuroendocrine hormones and a number of neurotransmitters, cytokines, and growth factors, regulate both basal and threatened homeostasis to help control the stress. Severity of stress, as well as malfunctioning of stress pathways, may impair its controllability, leading to the pathogenesis of psychiatric illnesses including depression. Leptin was initially identified as an antiobesity hormone, acting as a negative feedback adiposity signal to control energy homeostasis by binding to its receptors in the hypothalamus. Accumulating evidence has expanded the function of leptin from the control of energy balance to the regulation of other physiological and psychological processes. The aim of this paper is to evaluate the potential role of leptin in stress controllability. To this end, studies on the role of leptin in stress-induced activation of the hypothalamus-pituitary-adrenocortical axis, feeding behavior, learned helplessness, and other depression models have been accumulated. The knowledge accumulated in this article may facilitate the development of alternative treatment strategies, beyond serotonin and noradrenaline reuptake inhibition, for psychiatric care and stress-related disorders.
    Full-text · Article · Jul 2014 · Behavioural Pharmacology
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    • "Despite the anorectic hormonal profile in response to repeated foot shock, animals show no change in food intake but still maintain a positive energy balance and show greater cumulative weight gain relative to nonstressed controls (Solomon et al., 2007). The changes in body mass and body composition following repeated foot shocks are said to be reminiscent of the metabolic consequences of subordinate animals in the intruder resident paradigm, albeit occurred at a much faster rate (Solomon et al., 2007). "
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    ABSTRACT: Stress is defined as the behavioral and physiological responses generated in the face of, or in anticipation of, a perceived threat. The stress response involves activation of the sympathetic nervous system and recruitment of the hypothalamic-pituitary-adrenal (HPA) axis. When an organism encounters a stressor (social, physical, etc.), these endogenous stress systems are stimulated in order to generate a fight-or-flight response, and manage the stressful situation. As such, an organism is forced to liberate energy resources in attempt to meet the energetic demands posed by the stressor. A change in the energy homeostatic balance is thus required to exploit an appropriate resource and deliver useable energy to the target muscles and tissues involved in the stress response. Acutely, this change in energy homeostasis and the liberation of energy is considered advantageous, as it is required for the survival of the organism. However, when an organism is subjected to a prolonged stressor, as is the case during chronic stress, a continuous irregularity in energy homeostasis is considered detrimental and may lead to the development of metabolic disturbances such as cardiovascular disease, type II diabetes mellitus and obesity. This concept has been studied extensively using animal models, and the neurobiological underpinnings of stress induced metabolic disorders are beginning to surface. However, different animal models of stress continue to produce divergent metabolic phenotypes wherein some animals become anorexic and loose body mass while others increase food intake and body mass and become vulnerable to the development of metabolic disturbances. It remains unclear exactly what factors associated with stress models can be used to predict the metabolic outcome of the organism. This review will explore a variety of rodent stress models and discuss the elements that influence the metabolic outcome in order to further our understanding of stress-induced obesity.
    Full-text · Article · Jul 2013 · Frontiers in Neuroscience
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    • "This clear-cut effect is not present in the human literature and the DSM-IV defines weight gain or loss as a diagnostic criterion for major depression [25]. Recently, our and other laboratories described animal models for chronic stress-induced increase in body weight and adiposity [26]–[29] and vulnerability to diet induced obesity [28], [30], [31]. In addition, recent studies have showed neuroendocrine evidences of metabolic syndrome in defeated rats fed high fat diet but not a standard diet [32]. "
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    ABSTRACT: Social and psychological factors interact with genetic predisposition and dietary habit in determining obesity. However, relatively few pre-clinical studies address the role of psychosocial factors in metabolic disorders. Previous studies from our laboratory demonstrated in male mice: 1) opposite status-dependent effect on body weight gain under chronic psychosocial stress; 2) a reduction in body weight in individually housed (Ind) male mice. In the present study these observations were extended to provide a comprehensive characterization of the metabolic consequences of chronic psychosocial stress and individual housing in adult CD-1 male mice. Results confirmed that in mice fed standard diet, dominant (Dom) and Ind had a negative energy balance while subordinate (Sub) had a positive energy balance. Locomotor activity was depressed in Sub and enhanced in Dom. Hyperphagia emerged for Dom and Sub and hypophagia for Ind. Dom also showed a consistent decrease of visceral fat pads weight as well as increased norepinephrine concentration and smaller adipocytes diameter in the perigonadal fat pad. On the contrary, under high fat diet Sub and, surprisingly, Ind showed higher while Dom showed lower vulnerability to obesity associated with hyperphagia. In conclusion, we demonstrated that social status under chronic stress and individual housing deeply affect mice metabolic functions in different, sometime opposite, directions. Food intake, the hedonic response to palatable food as well as the locomotor activity and the sympathetic activation within the adipose fat pads all represent causal factors explaining the different metabolic alterations observed. Overall this study demonstrates that pre-clinical animal models offer a suitable tool for the investigation of the metabolic consequences of chronic stress exposure and associated psychopathologies.
    Full-text · Article · Feb 2009 · PLoS ONE
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