Degradation rates influence the ability of composite samples to represent 24-hourly means of SARS-CoV-2 and other microbiological target measures in wastewater.

The utility of using severe-acute respiratory syndrome coronavirus-2 (SARS-CoV-2) RNA for assessing the prevalence of COVID-19 within communities begins with the design of the sample collection program. The objective of this study was to assess the utility of 24-hour composites as representative samples for measuring multiple microbiological targets in wastewater, and whether normalization of SARS-CoV-2 by endogenous targets can be used to decrease hour to hour variability at different watershed scales. Two sets of experiments were conducted, in tandem with the same wastewater, with samples collected at the building, cluster, and community sewershed scales. The first set of experiments focused on evaluating degradation of microbiological targets: SARS-CoV-2, Simian Immunodeficiency Virus (SIV) - a surrogate spiked into the wastewater, plus human waste indicators of Pepper Mild Mottle Virus (PMMoV), Beta-2 microglobulin (B2M), and fecal coliform bacteria (FC). The second focused on the variability of these targets from samples, collected each hour on the hour. Results show that SARS-CoV-2, PMMoV, and B2M were relatively stable, with minimal degradation over 24-h. SIV, which was spiked-in prior to analysis, degraded significantly and FC increased significantly over the course of 24 h, emphasizing the possibility for decay and growth within wastewater. Hour-to-hour variability of the source wastewater was large between each hour of sampling relative to the variability of the SARS-CoV-2 levels calculated between sewershed scales; thus, differences in SARS-CoV-2 hourly variability were not statistically significant between sewershed scales. Results further provided that the quantified representativeness of 24-h composite samples (i.e., statistical equivalency compared against hourly collected grabs) was dependent upon the molecular target measured. Overall, improvements made by normalization were minimal within this study. Degradation and multiplication for other targets should be evaluated when deciding upon whether to collect composite or grab samples in future studies.

Sex differences in the association of vital exhaustion with regional fat deposition and subclinical cardiovascular disease risk.

OBJECTIVE: Vital exhaustion (VE) is more strongly associated with cardiovascular disease (CVD) risk for women than men. This study examined whether sex differences in associations of VE with CVD risk markers are accounted for by unique associations of VE with regional adiposity. METHODS: The study enrolled 143 persons (18-55 years) without diagnosed conditions. VE was assessed by the Maastricht questionnaire. CVD indices were measured using the euglycemic-hyperinsulinemia clamp, resting blood pressure, and blood draws. Regional adiposity was measured using computed tomography and 2-D echocardiography. This cross-sectional study employed a path analysis approach, including relevant covariates. RESULTS: Of the cohort, aged 38.7 ± 8.4 years, 65% were men, and 41% were obese. The final model had excellent fit (χ2(36) = 36.5, p = .45; RMSEA = 0.009, CFI = 0.999). For women, but not men, the model indicated paths from VE to: 1) lower insulin sensitivity (B = -0.10, p = .04), and higher total cholesterol to HDL ratio (B = 0.12, p = .09), triglycerides (B = 0.10, p = .08), and C-reactive protein (B = 0.08, p = .09) through visceral adiposity; 2) higher mean arterial pressure (B = 0.14, p = .04), lower insulin sensitivity (B = -0.09, p = .08), and higher C-reactive protein (B = 0.12, p = .07) through subcutaneous adiposity; 3) lower insulin sensitivity (B = -0.07, p = .08) and higher total cholesterol to HDL ratio (B = 0.16, p = .03) through liver adiposity; and 4) higher C-reactive protein (B = 0.08, p = .09) through epicardial adiposity. CONCLUSION: Results extend prior evidence by showing that the association of VE with CVD risk in women is linked with specific regional adiposity elevation. Further study of adiposity-related mechanisms in women who experience early decline in vitality may inform clinical targets for CVD prevention.

Positive Psychosocial Factors and Oxytocin in the Ovarian Tumor Microenvironment.

OBJECTIVE: Clinical ovarian cancer research shows relationships between psychosocial factors and disease-promoting aspects of the stress response (e.g., norepinephrine and cortisol). However, little is known about how psychosocial factors might relate to beneficial hormones in the ovarian tumor microenvironment. Here we examine relationships between psychosocial factors and tumor-associated oxytocin, a hormone linked to survival and antitumor processes in ovarian cancer. METHODS: Patients with ovarian cancer (n = 96) completed assessments of positive psychosocial factors (social support, positive affect, and purpose in life) and distress (perceived stress and depression) at the time of surgery. Levels of oxytocin and interleukin (IL) 6 in ascites fluid were obtained during surgery and analyzed by enzyme-linked immunosorbent assay. Multiple regression analyses adjusting a priori for patient age and disease stage examined associations between psychosocial factors and ascites oxytocin. IL-6 was used as a covariate in secondary analyses to examine the potentially confounding effects of inflammation in these relationships. RESULTS: Higher levels of positive affect (ß = 0.22, p = .034), purpose in life (ß = 0.31, p = .021), and social nurturance (ß = 0.24, p = .024) were all related to higher levels of tumor-associated oxytocin at the time of surgery. In contrast, we found no effects for distress or social attachment. Relationships between oxytocin, purpose in life, and social nurturance were independent of IL-6, whereas positive affect was no longer significant with IL-6 in the model. CONCLUSIONS: Tumor-associated oxytocin may be a previously uninvestigated link in the relationship between psychosocial factors and health in ovarian cancer. Future studies should examine causal mechanisms of relationships observed in this study.

Oxytocin reduces adipose tissue inflammation in obese mice.

BACKGROUND: Obesity and adipose tissue expansion is characterized by a chronic state of systemic inflammation that contributes to disease. The neuropeptide, oxytocin, working through its receptor has been shown to attenuate inflammation in sepsis, wound healing, and cardiovascular disease. The current study examined the effects of chronic oxytocin infusions on adipose tissue inflammation in a murine model of obesity, the leptin receptor-deficient (db/db) mouse. METHODS: The effect of obesity on oxytocin receptor protein and mRNA expression in adipose tissue was evaluated by Western blotting and real-time polymerase chain reaction. Mice were implanted with osmotic minipumps filled with oxytocin or vehicle for 8 weeks. At study endpoint adipose tissue inflammation was assessed by measurement of cytokine and adipokine mRNA tissue levels, adipocyte size and macrophage infiltration via histopathology, and plasma levels of adiponectin and serum amyloid A as markers of systemic inflammation. RESULTS: The expression of adipose tissue oxytocin receptor was increased in obese db/db mice compared to lean controls. In adipose tissue oxytocin infusion reduced adipocyte size, macrophage infiltration, IL-6 and TNFα mRNA expression, and increased the expression of the anti-inflammatory adipokine, adiponectin. In plasma, oxytocin infusion reduced the level of serum amyloid A, a marker of systemic inflammation, and increased circulating adiponectin. CONCLUSIONS: In an animal model of obesity and diabetes chronic oxytocin treatment led to a reduction in visceral adipose tissue inflammation and plasma markers of systemic inflammation, which may play a role in disease progression.

Oxytocin in the tumor microenvironment is associated with lower inflammation and longer survival in advanced epithelial ovarian cancer patients.

BACKGROUND: Prior research demonstrates a protective role for oxytocin in ovarian cancer based on its anti-proliferative, anti-migratory, and anti-invasive effects in vitro and in vivo. However, the role of endogenous oxytocin has not been examined in ovarian cancer patients. Oxytocin also has anti-inflammatory properties that have not been examined in cancer. The purpose of this investigation was to examine relationships between endogenous oxytocin, tumor-associated inflammation (interleukin-6), and survival in advanced epithelial ovarian cancer patients. METHODS: Tumor microenvironment (ascites) and plasma oxytocin levels were analyzed via ELISA on extracted samples obtained from 79 patients. In vitro models were used to characterize oxytocin and oxytocin receptor expression in four ovarian cancer cell lines and to investigate direct anti-inflammatory effects of oxytocin on tumor cell secretion of interleukin-6. High and variable levels of oxytocin were observed in ascites, up to 200 times greater than in plasma. Higher levels of ascites oxytocin were associated with lower levels of systemic and tumor-associated interleukin-6, an inflammatory cytokine implicated in ovarian tumor progression. Oxytocin also attenuated interleukin-6 secretion from multiple ovarian tumor cell lines in vitro. Higher levels of ascites oxytocin were associated with a significant survival advantage and statistical mediation analyses suggested this effect was partially mediated by interleukin-6. CONCLUSIONS: These data identify a previously unacknowledged hormone in the ovarian tumor microenvironment and provide initial evidence that oxytocin has protective effects in ovarian cancer via anti-inflammatory mechanisms. Future studies should examine the therapeutic utility of oxytocin.

Regulation of the macrophage oxytocin receptor in response to inflammation.

It has been demonstrated that the neuropeptide oxytocin (OT) attenuates oxidative stress and inflammation in macrophages. In the current study, we examined the role of inflammation on the expression of the oxytocin receptor (OXTR). We hypothesized that OXTR expression is increased during the inflammation through a nuclear factor-κB (NF-κB)-mediated pathway, thus responding as an acute-phase protein. Inflammation was induced by treating macrophages (human primary, THP-1, and murine) with lipopolysaccharide (LPS) and monitored by expression of IL-6. Expression of OXTR and vasopressin receptors was assessed by qPCR, and OXTR expression was confirmed by immunoblotting. Inflammation upregulated OXTR transcription 10- to 250-fold relative to control in THP-1 and human primary macrophages and increased OXTR protein expression. In contrast, vasopressin receptor-2 mRNA expression was reduced following LPS treatment. Blocking NF-κB activation prevented the increase in OXTR transcription. OT treatment of control cells and LPS-treated cells increased ERK1/2 phosphorylation, demonstrating activation of the OXTR/Gαq/11 signaling pathway. OT activation of OXTR reduced secretion of IL-6 in LPS-activated macrophages. Collectively, these findings suggest that OXTR is an acute-phase protein and that its increased expression is regulated by NF-κB and functions to attenuate cellular inflammatory responses in macrophages.

Structural Remodeling of Sympathetic Innervation in Atherosclerotic Blood Vessels: Role of Atherosclerotic Disease Progression and Chronic Social Stress.

OBJECTIVE: The sympathetic nervous system (SNS) can undergo dramatic structural plasticity in response to behavioral factors and/or the presence of disease, leading to SNS hyperinnervation of peripheral tissues. The SNS has been proposed as an important mediator between stressful behavior and the progression of atherosclerosis in the vasculature. The present study examined whether structural remodeling of the SNS occurs in the vasculature in a genetically hyperlipidemic animal model of atherosclerosis, the Watanabe heritable hyperlipidemic rabbit (WHHL; relative to normolipidemic New Zealand white rabbits [NZW]), and whether SNS plasticity is driven by the progression of disease and/or by stressful social behavior. METHODS: WHHL and NZW rabbits were assigned to an unstable or stable social environment for 4 months. Aortic atherosclerosis was assessed and SNS aortic innervation quantified using immunofluorescent microscopy. RESULTS: Numerous SNS varicosities were observed throughout the aorta in WHHLs and NZWs, extending into the vascular media and intima, an innervation pattern not previously reported. WHHLs exhibited significantly greater innervation than NZWs (F(1,41) = 55.3, p < .001), with extensive innervation of the atherosclerotic neointima. The innervation density was highly correlated with the extent of disease in the WHHLs (r(21) = 0.855, p < .001). Social environment did not influence innervation in NZWs (aortic arch: p = .078, thoracic aorta: p = .34) or WHHLs (arch: p = .97, thoracic: p = .61). CONCLUSIONS: The findings suggest that hyperinnervation is driven largely by the progression of disease rather than social environment. SNS innervation patterns observed in atherosclerotic human and mouse aortas were consistent with the rabbit, suggesting that SNS hyperinnervation of the diseased vessel wall is a general feature across mammalian species.

A Practical Approach to Quantitative Processing and Analysis of Small Biological Structures by Fluorescent Imaging.

Standards in quantitative fluorescent imaging are vaguely recognized and receive insufficient discussion. A common best practice is to acquire images at Nyquist rate, where highest signal frequency is assumed to be the highest obtainable resolution of the imaging system. However, this particular standard is set to insure that all obtainable information is being collected. The objective of the current study was to demonstrate that for quantification purposes, these correctly set acquisition rates can be redundant; instead, linear size of the objects of interest can be used to calculate sufficient information density in the image. We describe optimized image acquisition parameters and unbiased methods for processing and quantification of medium-size cellular structures. Sections of rabbit aortas were immunohistochemically stained to identify and quantify sympathetic varicosities, >2 µm in diameter. Images were processed to reduce background noise and segment objects using free, open-access software. Calculations of the optimal sampling rate for the experiment were based on the size of the objects of interest. The effect of differing sampling rates and processing techniques on object quantification was demonstrated. Oversampling led to a substantial increase in file size, whereas undersampling hindered reliable quantification. Quantification of raw and incorrectly processed images generated false structures, misrepresenting the underlying data. The current study emphasizes the importance of defining image-acquisition parameters based on the structure(s) of interest. The proposed postacquisition processing steps effectively removed background and noise, allowed for reliable quantification, and eliminated user bias. This customizable, reliable method for background subtraction and structure quantification provides a reproducible tool for researchers across biologic disciplines.

Oxytocin administration attenuates atherosclerosis and inflammation in Watanabe Heritable Hyperlipidemic rabbits.

Oxytocin (OT) is a neurohypophyseal peptide traditionally associated with female reproductive functioning, and more recently with prosocial behavior. OT and its receptor are also expressed in the heart and vascular tissue and play a role in cardiovascular homeostasis. In vitro, it has been demonstrated that OT decreases NADPH-dependent superoxide production and pro-inflammatory cytokine release from vascular endothelial cells and macrophages, suggesting that OT may attenuate pathophysiological processes involved with atherosclerotic lesion formation. The present study sought to determine the effect of chronic exogenous OT administration on inflammation and atherosclerosis in an animal model of dyslipidemia and atherosclerosis, the Watanabe Heritable Hyperlipidemic (WHHL) rabbit. Twenty-two, 3-month-old WHHLs were surgically implanted with osmotic mini-pumps containing OT (n=11) or vehicle (n=11), and then were individually housed for the entire study. Blood and 24-h urine samples were taken at baseline and after 8 (midpoint) and 16 (endpoint) weeks of treatment. At endpoint, the aortas and visceral fat samples were dissected and stored for analyses. There were no group differences in body weight, serum lipids, plasma/urinary measures of oxidative stress, plasma cortisol or urinary catecholamines over the 16-week treatment. OT-treated animals exhibited significantly lower plasma C-reactive protein levels at midpoint and endpoint and developed significantly less atherosclerosis in the thoracic aorta relative to vehicle control animals at endpoint (p<0.05). Cytokine gene expression from visceral adipose tissue samples suggested that there was a decrease in adipose tissue inflammation in the OT-treated group compared to the vehicle control group, however these differences were not statistically significant. These results suggest that chronic peripheral OT administration can inhibit inflammation and atherosclerotic lesion development.

The influence of social environment on endocrine, cardiovascular and tissue responses in the rabbit.

Previous work from our lab demonstrated that social environment influences the progression of atherosclerosis in genetically hyperlipidemic rabbits. The purpose of the current study was to examine behavioral and physiological responses associated with these distinct chronic social conditions. Normolipidemic rabbits were exposed to one of three social environments for 4 hours/day over 20 weeks: 1) an Unstable Group in which animals were paired weekly with a different unfamiliar rabbit, 2) a Stable Group in which rabbits were paired with the same littermate for the entire study, and 3) an Individually Caged Group in which animals were socially isolated. It was found that the Unstable Group, characterized by increased agonistic behavior and relatively less affiliative behavior, exhibited physiological responses indicative of chronic stress (increased urinary norepinephrine, plasma cortisol, splenic weight, and decreased visceral fat and body weight compared to the other groups). These animals also had increased acute plasma oxytocin responses relative to the other groups 10 minutes into the social pairing. In contrast, the Stable Group exhibited more affiliative behavior and less stressful physiological and tissue responses. The Individually Caged Group had elevated urinary norepinephrine relative to the Stable Group, and they exhibited higher heart rates at the end of the study compared to the other groups, suggesting that this social environment is also associated with chronic sympathetic arousal. It was concluded that distinct social contexts lead to different patterns of behavioral and physiological responses, and these responses are relevant to the pathophysiology of atherosclerosis and cardiovascular disease.

Evaluation of enzyme immunoassay and radioimmunoassay methods for the measurement of plasma oxytocin.

OBJECTIVE: There is increased interest in measuring peripheral oxytocin levels to better understand the role of this peptide in mammalian behavior, physiology, and disease. The purpose of this study was to compare methods for plasma oxytocin measurement using a commercially available enzyme immunoassay (EIA) and radioimmunoassay (RIA), to evaluate the need for sample extraction, and to assess the immunospecificity of the assays. METHODS: Oxytocin was measured in extracted and unextracted human plasma samples (n = 39). Oxytocin and its degradation products were separated by high-performance liquid chromatography and gel filtration chromatography and then assayed by EIA or RIA to identify oxytocin immunoreactive peaks. RESULTS: Without extraction, plasma measured by EIA was more than 100-fold higher than in extracted plasma, and the correlation between oxytocin levels in extracted and unextracted plasma was minimal (Spearman ρ = -0.10, p = .54). Using the RIA, most samples (>90%) were below the level of detection with or without extraction. After chromatographic fractionation of sample extracts, multiple immunoreactive products were found to be present in addition to oxytocin, which casts doubts on the specificity of the assays. CONCLUSIONS: Changes in oxytocin levels have been reported in social and behavioral challenge studies. This study indicates that sample extraction is necessary to obtain valid assay results. Changes in oxytocin degradation products are likely to contribute to the previously observed responses in circulating oxytocin levels to behavioral and social challenge. There is a critical need for valid and reliable methods to measure oxytocin in biologic samples.

Oxytocin indexes relational distress following interpersonal harms in women.

The hypothalamic neuropeptide oxytocin, known for its involvement in social affiliation and bonding in animals, has recently been associated with a host of prosocial behaviors that are beneficial for maintaining positive social relationships in humans. Paradoxically, however, people with high endogenous levels of oxytocin also tend to report relational distress and interpersonal difficulties in their everyday lives. To address these contradictory findings, oxytocin reactivity was measured in response to a well-defined laboratory task in young adult women following recent interpersonal harms. Elevated mean peripheral oxytocin reactivity (but not baseline levels of oxytocin or cortisol reactivity) was associated with increased post-conflict anxiety and decreased levels of forgiveness. These results corroborate previous research implicating oxytocin as a neuroendocrine marker of relational distress, but not general stress, and demonstrate the utility of studying oxytocin in response to naturally occurring relational events.

Oxytocin attenuates atherosclerosis and adipose tissue inflammation in socially isolated ApoE-/- mice.

OBJECTIVE: To determine the effect of exogenous oxytocin (OT) administration on inflammation and atherosclerosis in socially isolated apoE(-/-) mice. Hyperlipidemic animals housed in isolated or stressful social environments display more extensive atherosclerosis than those in an affiliative social environment. The neurohypophyseal peptide OT may be involved in both affiliative social behavior and cardiovascular homeostasis, suggesting a role in mediating the benefits of positive social interactions on atherosclerosis. METHODS: A total of 43, 12-week-old, apoE(-/-) mice were surgically implanted with osmotic minipumps containing OT (n = 23) or vehicle (n = 20). Blood samples were taken at baseline and after 6 weeks and 12 weeks of treatment. After 12 weeks of treatment, animals were killed, and samples of adipose tissue were dissected from a subset of OT-treated (n = 12) and vehicle-treated (n = 12) animals and incubated in culture media for 6 hours. Media samples were analyzed for interleukin (IL)-6 concentration corrected by sample dry weight. Aortas were dissected, formalin-fixed, and stained with oil-red O for en face quantification of lesion area. t tests were used to compare group means on measures of percent lesion area and IL-6 concentrations. RESULTS: There were no group differences in plasma lipids. Adipose tissue samples taken from OT-treated animals secreted significantly less IL-6 over 6 hours (p < .01). OT-treated animals displayed significantly less atherosclerosis in the thoracic aorta (p < .05). CONCLUSIONS: These results indicate that peripheral OT administration can inhibit atherosclerotic lesion development and adipose tissue inflammation, suggesting a potential role for this neuropeptide in mediating the benefits of stable group housing on atherosclerosis.

Oxytocin attenuates NADPH-dependent superoxide activity and IL-6 secretion in macrophages and vascular cells.

Oxytocin is synthesized and released in the heart and vasculature, tissues that also express oxytocin receptors. Although it has been established this intrinsic cardiovascular oxytocin system is important in normal homeostatic cardiac and vascular regulation, a role for this system in cardiovascular pathophysiology has not been investigated. The current study examined the influence of oxytocin on mechanisms in atherogenesis, oxidative stress, and inflammation in cultured human vascular cells, THP-1 monocytes, and macrophages. Oxytocin receptor protein and mRNA expression, NADPH-dependent superoxide activity, and interleukin-6 secretion were measured. Results demonstrated oxytocin receptor protein and mRNA in THP-1 monocytes and macrophages. Incubation of cells at physiological levels of oxytocin significantly decreased basal and stimulated NADPH-dependent superoxide activity in vascular cells, monocytes, and macrophages by 24-48%. Oxytocin also attenuated interleukin-6 secretion from stimulated THP-1 macrophages and endothelial cells by 56 and 26%, respectively. These findings suggest that oxytocin attenuates vascular oxidative stress and inflammation, two important pathophysiological processes in atherosclerosis. The fact that oxytocin receptors are found in monocytes and macrophages, and oxytocin decreases both superoxide production and release of a proinflammatory cytokine from these cells, suggests a potentially larger role for oxytocin in the attenuation of disease.

The effect of social environment on markers of vascular oxidative stress and inflammation in the Watanabe heritable hyperlipidemic rabbit.

OBJECTIVE: Previous research demonstrated that social environment can influence progression of atherosclerosis in the Watanabe Heritable Hyperlipidemic (WHHL) rabbit. This study examined the effect of social environment on markers of oxidative stress and inflammation to clarify the physiological pathways potentially responsible for the influence of social environment on disease. METHODS AND RESULTS: WHHL rabbits were assigned to 1 of 3 social groups: an unstable group, in which unfamiliar rabbits were paired daily, with the pairing switched each week; a stable group, in which littermates were paired daily; and an individually-caged group. The stable group engaged in more affiliative social behavior than the unstable group. The unstable group showed more agonistic behavior compared with the stable group and higher C-reactive protein levels than the individually caged group. The individually caged group was behaviorally sedentary, had higher 24-hour urinary catecholamine levels than the other groups, and exhibited higher NAD(P)H-oxidase activity in the aortic arch relative to the stable group. CONCLUSIONS: The results suggest that social environment creates distinct behavioral contexts that can affect markers of inflammation and oxidative stress early in the development of atherosclerosis. Specifically, physical inactivity associated with individual caging affects indices of oxidative stress and inflammation. These pathophysiological markers may help to explain behaviorally related differences in the extent of atherosclerosis observed in prior studies.

Social experience influences hypothalamic oxytocin in the WHHL rabbit.

Social experience influences behavior and the progression of atherosclerosis in the Watanabe Heritable Hyperlipidemic (WHHL) rabbit, such that WHHL rabbits exposed to a consistent, stable social experience exhibited more affiliative social behavior and less aortic atherosclerosis compared to other social groups. Oxytocin (OT) has been implicated in the expression of social behavior, stress responses, and may provide a mechanism by which social experience influences atherogenesis in WHHL rabbits. The current study examined acute and chronic changes in central and peripheral OT before and after WHHL rabbits were exposed to one of three social conditions. Cannula implanted adjacent to the hypothalamic paraventricular nucleus (PVN) allowed chronic sampling of extracellular OT concentration via microdialysis. Rabbits were exposed to one of three social conditions: an Unstable group, with initially unfamiliar rabbits paired daily for 4h during the initial week and similarly paired with a different, unfamiliar rabbit each week; a Stable group; with the same 2 littermates paired daily for 4h the entire study; and an Individually Caged group. Dialysates from the PVN and blood from the marginal ear vein were collected twice, 20 days apart, from rabbits before and after 2h of exposure to their respective social condition. Dialysates were assayed for OT and plasma was assayed for OT, catecholamines and glucocorticoids. There were no changes in PVN OT in any group following the initial social experience. In contrast, after 20 consecutive days of exposure to their respective social condition, PVN OT increased significantly in the Unstable group, but was relatively unchanged in the Stable group following the social experience on day 22. Peripheral OT was not altered in any group following the 2h social experience on day 1 or 22. The concentration of peripheral OT was the highest in the Stable group at all times. The Stable group also exhibited significantly less aortic atherosclerosis, consistent with earlier findings from our laboratory. Data from the present study suggest that the type of social experience WHHL rabbits are exposed influences PVN OT, social behavior and the progression of atherosclerosis in the WHHL rabbit model of disease.

Effect of behavioral interventions on insulin sensitivity and atherosclerosis in the Watanabe heritable hyperlipidemic rabbit.

OBJECTIVE: A previous study suggested that insulin metabolic variables play a role in the progression of atherosclerosis in Watanabe heritable hyperlipidemic (WHHL) rabbits. The present study sought to determine: 1) if young, individually caged WHHLs are insulin-resistant relative to New Zealand white (NZW) rabbits and 2) whether dietary or exercise interventions can improve insulin sensitivity and slow the development of atherosclerosis in these animals. METHODS: Forty-two WHHLs were assigned to a dietary, exercise, or control condition, and 12 NZWs were used as a comparison control group. The intervention ran from 3 to 7 months of age, and all animals received an intravenous glucose tolerance test at the beginning and end of the intervention. RESULTS: WHHLs were insulin-resistant relative to NZWs at 3 months of age. Whereas the dietary intervention was effective in controlling insulin resistance, WHHLs in the exercise group without dietary restriction and the control group exhibited significant increases in insulin resistance. No intervention significantly influenced the progression of atherosclerosis. CONCLUSIONS: Young WHHLs are insulin-resistant during an early period when atherosclerosis is developing rapidly. Dietary restriction, but not exercise without weight control, is effective in controlling insulin metabolic variables in the WHHL model. Although dietary intervention can reduce cardiovascular risk factors such as insulin resistance, it is not effective in slowing the development of atherosclerosis in these genetically dyslipidemic animals. Similarly, exercise training, without dietary control, does not influence the progression of disease in WHHLs.

Social environment influences the progression of atherosclerosis in the watanabe heritable hyperlipidemic rabbit.

BACKGROUND: Although there is evidence that emotionally stressful behavior can accelerate the progression of atherosclerosis, there is less data to support the notion that affiliative social behavior can slow disease progression. The present study examines the influence of social environment on the progression of atherosclerosis in the Watanabe Heritable Hyperlipidemic (WHHL) rabbit, a model that spontaneously develops lesions because of a genetic defect in lipoprotein clearance. METHODS AND RESULTS: WHHL rabbits were assigned to 1 of 3 social or behavioral groups: an unstable group, in which unfamiliar rabbits were paired daily, with the pairing switched each week; a stable group, in which littermates were paired daily for the entire study; and an individually caged group. The stable group exhibited more affiliative social behavior and less agonistic behavior than the unstable group and significantly less aortic atherosclerosis than each of the other 2 groups. Although the unstable and individually caged groups had comparable aortic lesion areas, the severity of the disease progressed faster in the unstable group, as indexed by a larger area of calcification and increased fibrous cap thickness in complex lesions. The unstable group showed increased agonistic behavior and signs of chronic adrenocortical and gonadal activation, whereas the individually caged group was relatively sedentary, had low glucocorticoid levels, and was hyperinsulinemic compared with the other groups. CONCLUSIONS: The present study demonstrates that social environment can slow, as well as accelerate, the progression of atherosclerosis. It also emphasizes the importance of behavioral factors in atherogenesis, even in a model of disease with strong genetic determinants.