Chronic stress and Rosiglitazone increase indices of vascular stiffness in male rats

FGF21 Induces Skeletal Muscle Atrophy and Increases Amino Acids in Female Mice: A Potential Role for Glucocorticoids

Fibroblast growth factor-21 (FGF21) is an intercellular signaling molecule secreted by metabolic organs, including skeletal muscle, in response to intracellular stress. FGF21 crosses the blood-brain barrier and acts via the nervous system to coordinate aspects of the adaptive starvation response, including increased lipolysis, gluconeogenesis, fatty acid oxidation, and activation of the hypothalamic-pituitary-adrenocortical (HPA) axis. Given its beneficial effects for hepatic lipid metabolism, pharmaceutical FGF21 analogues are used in clinical trials treatment of fatty liver disease. We predicted pharmacologic treatment with FGF21 increases HPA axis activity and skeletal muscle glucocorticoid signaling and induces skeletal muscle atrophy in mice. Here we found a short course of systemic FGF21 treatment decreased muscle protein synthesis and reduced tibialis anterior weight; this was driven primarily by its effect in female mice. Similarly, intracerebroventricular FGF21 reduced tibialis anterior muscle fiber cross-sectional area; this was more apparent among female mice than male littermates. In agreement with the reduced muscle mass, the topmost enriched metabolic pathways in plasma collected from FGF21-treated females were related to amino acid metabolism, and the relative abundance of plasma proteinogenic amino acids was increased up to 3-fold. FGF21 treatment increased hypothalamic Crh mRNA, plasma corticosterone, and adrenal weight, and increased expression of glucocorticoid receptor target genes known to reduce muscle protein synthesis and/or promote degradation. Given the proposed use of FGF21 analogues for the treatment of metabolic disease, the study is both physiologically relevant and may have important clinical implications.

The Effects of Rosiglitazone on Task Specific Anxiety-Like Behavior and Novelty Seeking in a Model of Chronic Adolescent Unpredictable Stress

Adolescence is characterized as a period of increased social behavior, risk taking, and novelty seeking, partly due to ongoing maturation in critical brain areas and the hypothalamic-pituitary-adrenal (HPA) negative-feedback system. During this period there is heightened vulnerability to stress that can drive neuro-immune-endocrine remodeling, resulting in the emergence of maladaptive behaviors that increase susceptibility to alcohol and substance abuse. Here we used a rat model to investigate the impact of chronic adolescent unpredictable stress on a battery of behavioral measures to assess anxiety, novelty seeking, risk taking, depression, and voluntary ethanol consumption while determining whether the PPARγ agonist rosiglitazone can attenuate these effects. Adolescent female rats that experienced stress showed increased risk taking behavior and novelty seeking behavior with no change in ethanol consumption. The administration of rosiglitazone during stress induction attenuated stress-induced cortisol elevation, normalized risk taking behavior in a model anxiety, and attenuated novelty seeking in a task-specific manner. Depressive-like behavior was not impacted by adolescent unpredictable stress or the administration of rosiglitazone. The results from this study demonstrate that exposure to unpredictable stress during adolescence increases the prevalence of maladaptive behaviors that are known to increase susceptibility to alcohol and substance abuse, and that rosiglitazone may be an effective therapeutic to attenuate the emergence of select risk taking and novelty seeking behaviors in females.

Chronic Stress A Potential Suspect Zero of Atherosclerosis: A Systematic Review

Atherosclerosis (AS) is a chronic vascular inflammatory disease, in which the lipid accumulation in the intima of the arteries shows yellow atheromatous appearance, which is the pathological basis of many diseases, such as coronary artery disease, peripheral artery disease and cerebrovascular disease. In recent years, it has become the main cause of death in the global aging society, which seriously endangers human health. As a result, research on AS is increasing. Lesions of atherosclerosis contain macrophages, T cells and other cells of the immune response, together with cholesterol that infiltrates from the blood. Recent studies have shown that chronic stress plays an important role in the occurrence and development of AS. From the etiology of disease, social, environmental and genetic factors jointly determine the occurrence of disease. Atherosclerotic cardio-cerebrovascular disease (ASCVD) is often caused by chronic stress (CS). If it cannot be effectively prevented, there will be biological changes in the body environment successively, and then the morphological changes of the corresponding organs. If the patient has a genetic predisposition and a combination of environmental factors triggers the pathogenesis, then chronic stress can eventually lead to AS. Therefore, this paper discusses the influence of chronic stress on AS in the aspects of inflammation, lipid metabolism, endothelial dysfunction, hemodynamics and blood pressure, plaque stability, autophagy, ferroptosis, and cholesterol efflux.

Sexually divergent cortical control of affective-autonomic integration

Depression and cardiovascular disease reduce quality of life and increase mortality risk. These conditions commonly co-occur with sex-based differences in incidence and severity. However, the biological mechanisms linking the disorders are poorly understood. In the current study, we hypothesized that the infralimbic (IL) prefrontal cortex integrates mood-related behaviors with the cardiovascular burden of chronic stress. In a rodent model, we utilized optogenetics during behavior and in vivo physiological monitoring to examine how the IL regulates affect, social motivation, neuroendocrine-autonomic stress reactivity, and the cardiac consequences of chronic stress. Our results indicate that IL glutamate neurons increase socio-motivational behaviors specifically in males. IL activation also reduced endocrine and cardiovascular stress responses in males, while increasing reactivity in females. Moreover, prior IL stimulation protected males from subsequent chronic stress-induced sympatho-vagal imbalance and cardiac hypertrophy. Our findings suggest that cortical regulation of behavior, physiological stress responses, and cardiovascular outcomes fundamentally differ between sexes.

Prefrontal Cortex Regulates Chronic Stress-Induced Cardiovascular Susceptibility

Background The medial prefrontal cortex is necessary for appropriate appraisal of stressful information, as well as coordinating visceral and behavioral processes. However, prolonged stress impairs medial prefrontal cortex function and prefrontal-dependent behaviors. Additionally, chronic stress induces sympathetic predominance, contributing to health detriments associated with autonomic imbalance. Previous studies identified a subregion of rodent prefrontal cortex, infralimbic cortex (IL), as a key regulator of neuroendocrine-autonomic integration after chronic stress, suggesting that IL output may prevent chronic stress-induced autonomic imbalance. In the current study, we tested the hypothesis that the IL regulates hemodynamic, vascular, and cardiac responses to chronic stress. Methods and Results A viral-packaged small interfering RNA construct was used to knockdown vesicular glutamate transporter 1 (vGluT1) and reduce glutamate packaging and release from IL projection neurons. Male rats were injected with a vGluT1 small interfering RNA-expressing construct or GFP (green fluorescent protein) control into the IL and then remained as unstressed controls or were exposed to chronic variable stress. IL vGluT1 knockdown increased heart rate and mean arterial pressure reactivity, while chronic variable stress increased chronic mean arterial pressure only in small interfering RNA-treated rats. In another cohort, chronic variable stress and vGluT1 knockdown interacted to impair both endothelial-dependent and endothelial-independent vasoreactivity ex vivo. Furthermore, vGluT1 knockdown and chronic variable stress increased histological markers of fibrosis and hypertrophy. Conclusions Knockdown of glutamate release from IL projection neurons indicates that these cells are necessary to prevent the enhanced physiological responses to stress that promote susceptibility to cardiovascular pathophysiology. Ultimately, these findings provide evidence for a neurobiological mechanism mediating the relationship between stress and poor cardiovascular health outcomes.

Potential Therapeutic Use of Neurosteroids for Hypertension

The sympathetic nervous system (SNS) contribution to long-term setting of blood pressure (BP) and hence hypertension has been a continuing controversy over many decades. However, the contribution of increased sympathetic vasomotor tone to the heart, kidney, and blood vessels has been suggested as a major influence on the development of high BP which affects 30-40% of the population. This is relevant to hypertension associated with chronic stress, being overweight or obese as well to chronic kidney disease. Treatments that have attempted to block the peripheral aspects of the SNS contribution have included surgery to cut the sympathetic nerves as well as agents to block α- and β-adrenoceptors. Other treatments, such as centrally acting drugs like clonidine, rilmenidine, or moxonidine, activate receptors within the ventrolateral medulla to reduce the vasomotor tone overall but have side effects that limit their use. None of these treatments target the cause of the enhanced sympathetic tone. Recently we have identified an antihypertensive action of the neurosteroid allopregnanolone in a mouse model of neurogenic hypertension. Allopregnanolone is known to facilitate high-affinity extra-synaptic γ-aminobutyric acid A receptors (GABA_AR) through allosteric modulation and transcriptional upregulation. The antihypertensive effect was specific for increased expression of δ subunits in the amygdala and hypothalamus. This focused review examines the possibility that neurosteroids may be a novel therapeutic approach to address the neurogenic contribution to hypertension. We discuss the causes and prevalence of neurogenic hypertension, current therapeutic approaches, and the applicability of using neurosteroids as antihypertensive therapy.

Sex-dependent effects of MC4R genotype on HPA axis tone: implications for stress-associated cardiometabolic disease

The melanocortin-4 receptor (MC4R) facilitates hypothalamic-pituitary-adrenocortical (HPA) axis responses to acute stress in male rodents and is a well known to regulator of energy balance. Mutations in the MC4R is the most common monogenic cause of obesity in humans and has been associated with sex-specific effects, but whether stress regulation by the MC4R is sex-dependent, and whether the MC4R facilitates HPA responses to chronic stress, is unknown. We hypothesized that MC4R-signaling contributes to HPA axis dysregulation and metabolic pathophysiology following chronic stress exposure. We measured changes in energy balance, HPA axis tone, and vascular remodeling during chronic variable stress (CVS) in male and female rats with MC4R loss-of-function. Rats were placed into three groups (n = 9-18/genotype/sex) and half of each group was subjected to CVS for 30 days or were non-stressed littermate controls. All rats underwent an acute restraint stress challenge on Day 30. Rats were euthanized on Day 31, adrenals collected for weight, and descending aortas fixed for morphological indices of vascular pathophysiology. We observed a marked interaction between Mc4r genotype and sex for basal HPA axis tone and acute stress responsivity. MC4R loss-of-function blunted both endpoints in males but exaggerated them in females. Contrary to our hypothesis, Mc4r genotype had no effect on either HPA axis responses or metabolic responses to chronic stress. Heightened stress reactivity of females with MC4R mutations suggests a possible mechanism for the sex-dependent effects associated with this mutation in humans and highlights how stress may differentially regulate metabolism in males and females. Lay summary The hypothalamic melanocortin system is an important regulator of energy balance and stress responses. Here, we report a sex-difference in the stress reactivity of rats with a mutation in this system. Our findings highlight how stress may regulate metabolism differently in males and females and may provide insight into sex-differences associated with this mutation in humans.

Late-life time-restricted feeding and exercise differentially alter healthspan in obesity

Aging and obesity increase multimorbidity and disability risk, and determining interventions for reversing healthspan decline is a critical public health priority. Exercise and time‐restricted feeding (TRF) benefit multiple health parameters when initiated in early life, but their efficacy and safety when initiated at older ages are uncertain. Here, we tested the effects of exercise versus TRF in diet‐induced obese, aged mice from 20 to 24 months of age. We characterized healthspan across key domains: body composition, physical, metabolic, and cardiovascular function, activity of daily living (ADL) behavior, and pathology. We demonstrate that both exercise and TRF improved aspects of body composition. Exercise uniquely benefited physical function, and TRF uniquely benefited metabolism, ADL behavior, and circulating indicators of liver pathology. No adverse outcomes were observed in exercised mice, but in contrast, lean mass and cardiovascular maladaptations were observed following TRF. Through a composite index of benefits and risks, we conclude the net healthspan benefits afforded by exercise are more favorable than those of TRF. Extrapolating to obese older adults, exercise is a safe and effective option for healthspan improvement, but additional comprehensive studies are warranted before recommending TRF.

Chronic stress: a critical risk factor for atherosclerosis

Chronic stress refers to the non-specific systemic reaction that occurs when the body is stimulated by various internal and external negative factors over a long time. The physiological response to chronic stress exposure has long been recognized as a potent modulator in the occurrence of atherosclerosis. Furthermore, research has confirmed the correlation between atherosclerosis and cardiovascular events. Chronic stress is pervasive during negative life events and may lead to the formation of plaque. Several epidemiological studies have shown that chronic stress is an independent risk factor for the development of vascular disease and for increased morbidity and mortality in patients with pre-existing coronary artery disease. One possible mechanism for this process is that chronic stress causes endothelial injury, directly activating macrophages, promoting foam cell formation and generating the formation of atherosclerotic plaque. This mechanism involves numerous variables, including inflammation, signal pathways, lipid metabolism and endothelial function. The mechanism of chronic stress in atherosclerosis should be further investigated to provide a theoretical basis for efforts to eliminate the effect of chronic stress on the cardiocerebral vascular system.

Dietary Manipulations That Induce Ketosis Activate the HPA Axis in Male Rats and Mice: A Potential Role for Fibroblast Growth Factor-21

In response to an acute threat to homeostasis or well-being, the hypothalamic-pituitary-adrenocortical (HPA) axis is engaged. A major outcome of this HPA axis activation is the mobilization of stored energy, to fuel an appropriate behavioral and/or physiological response to the perceived threat. Importantly, the extent of HPA axis activity is thought to be modulated by an individual's nutritional environment. In this study, we report that nutritional manipulations signaling a relative depletion of dietary carbohydrates, thereby inducing nutritional ketosis, acutely and chronically activate the HPA axis. Male rats and mice maintained on a low-carbohydrate high-fat ketogenic diet (KD) exhibited canonical markers of chronic stress, including increased basal and stress-evoked plasma corticosterone, increased adrenal sensitivity to adrenocorticotropin hormone, increased stress-evoked c-Fos immunolabeling in the paraventricular nucleus of the hypothalamus, and thymic atrophy, an indicator of chronic glucocorticoid exposure. Moreover, acutely feeding medium-chain triglycerides (MCTs) to rapidly induce ketosis among chow-fed male rats and mice also acutely increased HPA axis activity. Lastly, and consistent with a growing literature that characterizes the hepatokine fibroblast growth factor-21 (FGF21) as both a marker of the ketotic state and as a key metabolic stress hormone, the HPA response to both KD and MCTs was significantly blunted among mice lacking FGF21. We conclude that dietary manipulations that induce ketosis lead to increased HPA axis tone, and that the hepatokine FGF21 may play an important role to facilitate this effect.

Emotional Stress and Cardiovascular Complications in Animal Models: A Review of the Influence of Stress Type

Emotional stress has been recognized as a modifiable risk factor for cardiovascular diseases. The impact of stress on physiological and psychological processes is determined by characteristics of the stress stimulus. For example, distinct responses are induced by acute vs. chronic aversive stimuli. Additionally, the magnitude of stress responses has been reported to be inversely related to the degree of predictability of the aversive stimulus. Therefore, the purpose of the present review was to discuss experimental research in animal models describing the influence of stressor stimulus characteristics, such as chronicity and predictability, in cardiovascular dysfunctions induced by emotional stress. Regarding chronicity, the importance of cardiovascular and autonomic adjustments during acute stress sessions and cardiovascular consequences of frequent stress response activation during repeated exposure to aversive threats (i.e., chronic stress) is discussed. Evidence of the cardiovascular and autonomic changes induced by chronic stressors involving daily exposure to the same stressor (predictable) vs. different stressors (unpredictable) is reviewed and discussed in terms of the impact of predictability in cardiovascular dysfunctions induced by stress.