Adverse effects of noise stress on glucose homeostasis and insulin resistance in Sprague-Dawley rats

Short-term aircraft noise stress induces a fundamental metabolic shift in heart proteome and metabolome that bears the hallmarks of cardiovascular disease

Environmental stressors in the modern world can fundamentally affect human physiology and health. Exposure to stressors like air pollution, heat, and traffic noise has been linked to a pronounced increase in non-communicable diseases. Specifically, aircraft noise has been identified as a risk factor for cardiovascular and metabolic diseases, such as arteriosclerosis, heart failure, stroke, and diabetes. Noise stress leads to neuronal activation with subsequent stress hormone release that ultimately activates the renin-angiotensin-aldosterone system, increases inflammation and oxidative stress thus substantially affecting the cardiovascular system. However, despite the epidemiological evidence of a link between noise stress and metabolic dysfunction, the consequences of exposure at the molecular, metabolic level of the cardiovascular system are largely unknown. Here, we use a murine model system of short-term aircraft noise exposure to show that noise stress profoundly alters heart metabolism. Within 4 days of noise exposure, the heart proteome and metabolome bear the hallmarks of reduced potential for generating ATP from fatty-acid beta-oxidation, the tricarboxylic acid cycle, and the electron transport chain. This is accompanied by the increased expression of glycolytic metabolites, including the end-product, lactate, suggesting a compensatory shift of energy production towards anaerobic glycolysis. Intriguingly, the metabolic shift is reminiscent of what is observed in failing and ischaemic hearts. Mechanistically, we further show that the metabolic rewiring is likely driven by reactive oxygen species (ROS), as we can rescue the phenotype by knocking out NOX-2/gp91phox, a ROS inducer, in mice. Our results suggest that within a short exposure time, the cardiovascular system undergoes a fundamental metabolic shift that bears the hallmarks of cardiovascular disease. These findings underscore the urgent need to comprehend the molecular consequences of environmental stressors, paving the way for targeted interventions to mitigate health risks associated with chronic noise exposure in modern, environments heavily disturbed by noise pollution.

Road traffic noise exposure and its impact on health: evidence from animal and human studies-chronic stress, inflammation, and oxidative stress as key components of the complex downstream pathway underlying noise-induced non-auditory health effects

In heavily urbanized world saturated with environmental pollutants, road traffic noise stands out as a significant factor contributing to widespread public health issues. It contributes in the development of a diverse range of non-communicable diseases, such as cardiovascular diseases, metabolic dysregulation, cognitive impairment, and neurodegenerative disorders. Although the exact mechanisms behind these non-auditory health effects remain unclear, the noise reaction model centres on the stress response to noise. When exposed to noise, the body activates the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system, leading to the secretion of stress hormones like catecholamines and cortisol. Prolonged exposure to noise-induced stress results in chronic inflammation and oxidative stress. This review underscores the role of inflammation and oxidative stress in the progression of noise-induced vascular dysfunction, disruption of the circadian rhythm, accelerated aging, neuroinflammation, and changes in microbiome. Additionally, our focus is on understanding the interconnected nature of these health outcomes: These interconnected factors create a cascade effect, contributing to the accumulation of multiple risk factors that ultimately lead to severe adverse health effects.

Short-term impact of air pollution, noise and temperature on emergency hospital admissions in Madrid (Spain) due to liver and gallbladder diseases

BACKGROUND

Very few epidemiological studies have explored the environmental and meteorological risk factors that influence liver diseases and gallbladder disorders, and no studies have addressed the specific case of Spain.

METHODS

This is a retrospective ecological study conducted during 2013-2018. We analysed emergency admissions in the central area of the Region of Madrid for the following causes: Liver and gallbladder diseases (L&GB) (ICD-10: K70-K81); disorders of gallbladder (DGB) (ICD 10: K80-K81); liver disease (LD) (ICD 10: K70-K77); alcoholic liver disease (ALD) (ICD-10: K70); viral hepatitis (VH) (ICD10:B15-B19); and hepatic failure, not elsewhere classified (HFNS) (ICD-10: K72). Independent variables used: meteorological (maximum daily temperature (Tmax in ⁰C), minimum daily temperature (Tmin in ⁰C), and relative humidity (RH in %)); chemical air pollution (8-hO3, NO2, PM10, PM2.5 in μg/m3); and noise pollution (equivalent level of daily noise (Ld in dB(A)). Transformed variables: extreme heat in degrees (Theat); wet cold (WC); and high ozone. We fitted Poisson models, negative binomials and zero-inflated Poisson controlled for seasonality, day of the week, holidays, trend, and autoregressive trend. Based on these models, the percentage of cases attributable to statistically significant risk factors was then estimated.

RESULTS

In L&GB emergency admissions daily noise is related to 4.4% (CI95%: 0.8 7.9) of admissions; NO2 to 2.9% (CI95%: 0.1 5.7) and wet cold to 0.2% (CI95%: 0.8 7.9). Heat wave temperature was only related to ALD. In addition, the wet cold association with L&GB is also related to HFNS attributing 1.0% (CI95%: 0.3 1.8) of admissions for this cause.

CONCLUSIONS

Daily noise and NO2 are associated with more than 7% of urgent L&GB admissions. Both pollutants, are mainly emitted by road traffic. A reduction of traffic in cities would result in a reduction of emergency admissions due to this cause.

Effects of Aqueous Saffron Extract on Glucoregulation as Well as Hepatic Agt and TNF-α Gene Expression in Rats Subjected to Sub-Chronic Stress

Background

Stress and saffron seem to affect glucoregulation mechanisms and insulin resistance in different ways. Impacts of the aqueous saffron extract were investigated on serum glucose levels, serum insulin levels, the homeostatic model assessment of β-cell function (HOMA-B), the homeostatic model assessment of insulin resistance (HOMA-IR), adrenal weight, and hepatic gene expression of angiotensinogen (Agt) and tumor necrosis factor-α (TNF-α) in rats under sub-chronic stress.

Materials and Methods

Forty-two male rats were divided into six groups: control, restraint stress (6h/day for seven days), saffron (30 and 60 mg/kg) treatments for seven days, and post-stress saffron (30 and 60 mg/kg) treatments for seven days. The serum glucose and insulin levels, hepatic gene expressions of Agt and TNF-α, HOMA-IR, HOMA-B, and adrenal gland weight were measured.

Results

One-week recovery following sub-chronic stress led to non-significant hyperglycemia, hyperinsulinemia, and insulin resistance. The hepatic Agt and TNF-α mRNA levels increased significantly in this group. Saffron administration led to enhanced hepatic Agt mRNA in the non-stressed subjects. In addition, serum glucose levels, insulin resistance, and hepatic Agt gene expression significantly increased in stress-saffron groups. The hepatic TNF-α gene expression was reduced only in the stress-saffron 60 group.

Conclusion

Saffron treatment after sub-chronic stress not only did not improve glucose tolerance but also enhanced insulin resistance. It indicated the interaction of saffron and sub-chronic stress to promote renin-angiotensin system activity. In addition, the saffron treatment decreased TNF-α gene expression after sub-chronic stress. The synergistic stimulating effect of saffron and sub-chronic stress on gene expression of hepatic Agt led to insulin resistance and hyperglycemia.

Biomarkers of growth and carbohydrate metabolism in neonatal rats supplemented with fish oil and/or antioxidants during intermittent hypoxia

OBJECTIVE

Extremely low gestational age neonates (ELGANs) experience frequent intermittent hypoxia (IH) episodes during therapeutic oxygen. ELGANs exhibit poor postnatal growth requiring lipid supplementation. Lipids are targets of reactive oxygen species resulting in lipid peroxidation and cell death, particularly in preterm infants with compromised antioxidant systems. We tested the hypothesis that early supplementation with lipids and/or antioxidants promotes growth and influences biomarkers of carbohydrate metabolism in neonatal rats exposed to IH.

DESIGN

Newborn rats (n = 18/group) were exposed to brief hypoxia (12% O₂) during hyperoxia (50% O₂), or room air (RA), from birth (P0) to P14 during which they received daily oral supplementation with: 1) fish oil; 2) Coenzyme Q10 (CoQ10) in olive oil; 3) glutathione nanoparticles (nGSH); 4) fish oil+CoQ10; or 5) olive oil. At P21, plasma samples were assessed for glucose, insulin, glucokinase (GCK), glucagon, glucagon-like peptide (GLP)-1, growth hormone (GH), corticosterone, and ghrelin. Liver was assessed for histopathology, apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling, TUNEL stain), and GH, insulin-like growth factor (IGF)-I, GH binding protein (GHBP), and IGF binding protein (IGFBP)-3.

RESULTS

Neonatal IH resulted in decreased liver weight and liver/body weight ratios, as well as hepatocyte swelling, steatosis, and apoptosis, which were attenuated with fish oil, nGSH, and combined fish oil+CoQ10. IH also decreased plasma glucose, insulin, GCK, and ghrelin, but increased GLP-1. All treatments improved plasma glucose in IH, but insulin was higher with CoQ10 and nGSH only. Glucagon was increased with CoQ10, fish oil, and CoQ10 + fish oil, while corticosterone was higher with nGSH and CoQ10 + fish oil. IGF-I and IGFBP-3 were significantly higher in the liver with CoQ10 in IH, while deficits in GH were noted with CoQ10 and fish oil in RA and IH. Treatment with nGSH and combined CoQ10 + fish oil reduced IGF-I in RA and IH but increased IGFBP-3.

CONCLUSIONS

Neonatal IH impairs liver growth with significant hepatocyte damage. Of all supplements in IH, nGSH and combined fish oil+CoQ10 were most effective for preserving liver growth and carbohydrate metabolism. Data suggest that these supplements may improve poor postnatal organ and body growth; and metabolic dysfunction associated with neonatal IH.

Phenotypically Determined Liver Dysfunction in a Wistar Rat Model of Post-Traumatic Stress Disorder

The extraordinary situation of the 2019–2022 pandemic caused a dramatic jump in the incidence of post-traumatic stress disorder (PTSD). PTSD is currently regarded not only as a neuropsychiatric disorder, but also as a comorbidity accompanied by cardiovascular diseases, circulatory disorders, liver dysfunction, etc. The relationship between behavioral disorders and the degree of morphofunctional changes in the liver remains obscure. In this study, PTSD was modeled in sexually mature male Wistar rats using predatory stress induced by a prey’s fear for a predator. Testing in an elevated plus maze allowed the rat population to be divided into animals with low-anxiety (LAP) and high-anxiety (HAP) phenotypes. It was found that morphofunctional analysis of the liver, in contrast to its biochemical profiling, provides a clearer evidence that predatory stress induces liver dysfunction in rats of both phenotypes. This may indicate a decrease in the range of compensatory adaptive reactions in stressed animals. However, in HAP rats, the level of morphofunctional abnormalities in the mechanisms responsible for carbohydrate-fat, water-electrolyte and protein metabolism in the liver testified the prenosological state of the organ, while further functional loading and resulting tension of the regulatory systems could lead to homeostatic downregulation. Meanwhile, the liver of LAP animals was only characterized by insignificant diffuse changes. Thus, we demonstrate here a link between behavioral changes and the degree of morphofunctional transformation of the liver.

Cerebral consequences of environmental noise exposure

The importance of noise exposure as a major environmental determinant of public health is being increasingly recognized. While in recent years a large body evidence has emerged linking environmental noise exposure mainly to cardiovascular disease, much less is known concerning the adverse health effects of noise on the brain and associated neuropsychiatric outcomes. Despite being a relatively new area of investigation, indeed, mounting research and conclusive evidence demonstrate that exposure to noise, primarily from traffic sources, may affect the central nervous system and brain, thereby contributing to an increased risk of neuropsychiatric disorders such as stroke, dementia and cognitive decline, neurodevelopmental disorders, depression, and anxiety disorder. On a mechanistic level, a significant number of studies suggest the involvement of reactive oxygen species/oxidative stress and inflammatory pathways, among others, to fundamentally drive the adverse brain health effects of noise exposure. This in-depth review on the cerebral consequences of environmental noise exposure aims to contribute to the associated research needs by evaluating current findings from human and animal studies. From a public health perspective, these findings may also help to reinforce efforts promoting adequate mitigation strategies and preventive measures to lower the societal consequences of unhealthy environments.

Glucocorticoid Receptor Antagonist Alters Corticosterone and Receptor-sensitive mRNAs in the Hypoxic Neonatal Rat

Hypoxia, a common stressor with preterm birth, increases morbidity and mortality associated with prematurity. Glucocorticoids (GCs) are administered to the preterm infant to improve oxygenation; prolonged use of GCs remains controversial. We evaluated a selective glucocorticoid receptor (GR) antagonist (CORT113176) in our neonatal rat model of human prematurity to assess how fasting and hypoxia-induced increases in neonatal corticosterone affects endogenous hormones and endocrine pancreas function. Neonatal rat pups at postnatal day (PD) 2, PD8, and PD15 were pretreated with CORT113176 and, after 60 minutes of separation and fasting, exposed to hypoxia (8% O2) or control (normoxia) for 30 or 60 minutes while fasting was continued. Plasma corticosterone, ACTH, glucose, and insulin were measured and fasting Homeostatic Model Assessment of Insulin Resistance was calculated. Glucocorticoid and insulin receptor-sensitive gene mRNAs were analyzed in liver, muscle, and adipose to evaluate target tissue biomarkers. CORT113176 pretreatment augmented baseline and hypoxia-induced increases in corticosterone and attenuated hypoxia-induced increases in insulin resistance at PD2. Normoxic and hypoxic stress increased the hepatic GR-sensitive gene mRNAs, Gilz and Per1; this was eliminated by pretreatment with CORT113176. CORT113176 pretreatment decreased baseline insulin receptor-sensitive gene mRNAs Akt2, Irs1, Pik3r1, and Srebp1c at PD2. We show that CORT113176 variably augments the stress-induced increases in corticosterone concentrations (attenuation of negative feedback) and that GR is critical for hepatic responses to stress in the hypoxic neonate. We also propose that measurement of Gilz and Per1 mRNA expression may be useful to evaluate the effectiveness of GR antagonism.

Redox Switches in Noise-Induced Cardiovascular and Neuronal Dysregulation

Environmental exposures represent a significant health hazard, which cumulatively may be responsible for up to 2/3 of all chronic non-communicable disease and associated mortality (Global Burden of Disease Study and The Lancet Commission on Pollution and Health), which has given rise to a new concept of the exposome: the sum of environmental factors in every individual’s experience. Noise is part of the exposome and is increasingly being investigated as a health risk factor impacting neurological, cardiometabolic, endocrine, and immune health. Beyond the well-characterized effects of high-intensity noise on cochlear damage, noise is relatively well-studied in the cardiovascular field, where evidence is emerging from both human and translational experiments that noise from traffic-related sources could represent a risk factor for hypertension, ischemic heart disease, diabetes, and atherosclerosis. In the present review, we comprehensively discuss the current state of knowledge in the field of noise research. We give a brief survey of the literature documenting experiments in noise exposure in both humans and animals with a focus on cardiovascular disease. We also discuss the mechanisms that have been uncovered in recent years that describe how exposure to noise affects physiological homeostasis, leading to aberrant redox signaling resulting in metabolic and immune consequences, both of which have considerable impact on cardiovascular health. Additionally, we discuss the molecular pathways of redox involvement in the stress responses to noise and how they manifest in disruptions of the circadian rhythm, inflammatory signaling, gut microbiome composition, epigenetic landscape and vessel function.

High-intensity infrasound effects on glucose metabolism in rats

Recent focus has been given on the effects of high-intensity infrasound (HII) exposure, and whether it induces changes in pancreatic morphology and glucose metabolism is still unknown. As such, we have studied the impact of HII exposure on glucose tolerance, insulin sensitivity, pancreatic islet morphology, muscle GLUT4 and plasma insulin and corticosterone levels. Normal and glucose intolerant wild-type Wistar rats were randomly divided in two groups: one group not exposed to HII and the other continuously exposed to HII. Animals were sacrificed at three timepoints of exposure (1, 6 or 12 weeks). An intraperitoneal glucose tolerance test was performed, blood samples were collected and the pancreas and the quadriceps femoris muscle were excised. Circulating insulin and corticosterone levels were determined and pancreatic and muscular tissue were routinely processed for histochemistry and immunohistochemistry with an anti-GLUT4 antibody. Animals exposed to HII had higher corticosterone levels than animals not exposed. No differences were found on insulin concerning HII exposure or glucose intolerance. Glucose intolerant animals had pancreatic islet fibrosis and no differences were found in GLUT4 ratio concerning HII exposure. In conclusion, we found that continuous exposure to HII increases stress hormone levels without inducing glucose intolerance in rats.

Insulin and glucose responses to hypoxia in male and female neonatal rats: Effects of the androgen receptor antagonist flutamide

Hypoxia is common with preterm birth and may lead to long-term effects on adult pancreatic endocrine function and insulin sensitivity. This phenomenon may be sexually dimorphic due to the hypoxia-induced augmentation of the neonatal androgen surge in male newborns. We evaluated this phenomenon by pretreating neonatal rats on postnatal days (PD) 1, 6, 13, or 20 with flutamide (a nonsteroidal androgen receptor antagonist) at a standard or a high dose (10 or 50 mg/kg) compared to vehicle control. One day later, neonatal rats were exposed to either acute normoxic or hypoxic separation (fasting) for 90 min, and blood was sampled for the measurement of insulin and glucose and the calculation of HOMA-IR as an index of insulin resistance. During normoxic and hypoxic separation (fasting), flutamide increased insulin secretion in PD2, PD7, and PD14 pups, high dose flutamide attenuated insulin secretion, and high dose flutamide attenuated the increase in HOMA-IR due to hypoxia. Our studies suggest a unique role of the androgen receptor in the control of neonatal pancreatic function, possibly by blocking a direct effect of neonatal testosterone or in response to indirect regulatory effects of androgens on insulin sensitivity.