Perturbed autonomic nervous system function in metabolic syndrome

An increase in adenosine-5'-triphosphate (ATP) content in rostral ventrolateral medulla is engaged in the high fructose diet-induced hypertension

Background

The increase in fructose ingestion has been linked to overdrive of sympathetic activity and hypertension associated with the metabolic syndrome. The premotor neurons for generation of sympathetic vasomotor activity reside in the rostral ventrolateral medulla (RVLM). Activation of RVLM results in sympathoexcitation and hypertension. Neurons in the central nervous system are able to utilize fructose as a carbon source of ATP production. We examined in this study whether fructose affects ATP content in RVLM and its significance in the increase in central sympathetic outflow and hypertension induced by the high fructose diet (HFD).

Results

In normotensive rats fed with high fructose diet (HFD) for 12 weeks, there was a significant increase in tissue ATP content in RVLM, accompanied by the increases in the sympathetic vasomotor activity and blood pressure. These changes were blunted by intracisternal infusion of an ATP synthase inhibitor, oligomycin, to the HFD-fed animals. In the catecholaminergic-containing N2a cells, fructose dose-dependently upregulated the expressions of glucose transporter 2 and 5 (GluT2, 5) and the rate-limiting enzyme of fructolysis, ketohexokinase (KHK), leading to the increases in pyruvate and ATP production, as well as the release of the neurotransmitter, dopamine. These cellular events were significantly prevented after the gene knocking down by lentiviral transfection of small hairpin RNA against KHK.

Conclusion

These results suggest that increases in ATP content in RVLM may be engaged in the augmented sympathetic vasomotor activity and hypertension associated with the metabolic syndrome induced by the HFD. At cellular level, the increase in pyruvate levels via fructolysis is involved in the fructose-induced ATP production and the release of neurotransmitter.

Type 2 diabetes elicits lower nitric oxide, bradykinin concentration and kallikrein activity together with higher DesArg(9)-BK and reduced post-exercise hypotension compared to non-diabetic condition

This study compared the plasma kallikrein activity (PKA), bradykinin concentration (BK), DesArg(9)-BK production, nitric oxide release (NO) and blood pressure (BP) response after moderate-intensity aerobic exercise performed by individuals with and without type 2 diabetes. Ten subjects with type 2 diabetes (T2D) and 10 without type 2 diabetes (ND) underwent three sessions: 1) maximal incremental test on cycle ergometer to determine lactate threshold (LT); 2) 20-min of constant-load exercise on cycle ergometer, at 90% LT and; 3) control session. BP and oxygen uptake were measured at rest and at 15, 30 and 45 min post-exercise. Venous blood samples were collected at 15 and 45 minutes of the recovery period for further analysis of PKA, BK and DesArg(9)-BK. Nitrite plus nitrate (NOx) was analyzed at 15 minutes post exercise. The ND group presented post-exercise hypotension (PEH) of systolic blood pressure and mean arterial pressure on the 90% LT session but T2D group did not. Plasma NOx increased ~24.4% for ND and ~13.8% for T2D group 15 min after the exercise session. Additionally, only ND individuals showed increases in PKA and BK in response to exercise and only T2D group showed increased DesArg(9)-BK production. It was concluded that T2D individuals presented lower PKA, BK and NOx release as well as higher DesArg(9)-BK production and reduced PEH in relation to ND participants after a single exercise session.

Elevated depressive symptoms in metabolic syndrome in a general population of Japanese men: a cross-sectional study

BACKGROUND

Uncertainty still surrounds the association between metabolic syndrome (MetS) and depression. We aimed to evaluate the association between MetS and elevated depressive symptoms in a general Japanese population.

METHODS

This is a cross-sectional survey of 3,113 community-dwelling individuals aged 40 years or over. MetS was defined according to the joint interim statement. MetS was diagnosed when a subject had three or more of the following components: 1) central obesity (waist circumference ≥ 90 cm for men, ≥ 80 cm in for women); 2) elevated blood pressure (≥ 130/85 mmHg or current use of antihypertensive medication); 3) hypertriglyceridemia (≥ 1.7 mmol/L); 4) low HDL cholesterol (< 1.0 mmol/L for men, < 1.3 mmol/L for women); and 5) elevated fasting plasma glucose (≥ 5.55 mmol/L or current use of antidiabetic medication). Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale (CES-D). The age- and multivariable-adjusted odds ratio (OR) and 95% confidence interval (CI) were estimated using a logistic regression model.

RESULTS

Elevated depressive symptoms were observed in 4.3% of male and 6.3% of female participants. In men, the age-adjusted prevalence of elevated depressive symptoms was significantly higher in subjects with MetS than in those without (7.1% versus 3.6%, p = 0.04). The prevalence of elevated depressive symptoms rose progressively as the number of MetS components increased (3.5%, 3.6%, 5.8%, and 9.2% in male subjects with 0-1, 2, 3, and ≥ 4 components, respectively; p = 0.02 for trend). This association remained significant even after adjustment for age, marital status, history of cardiovascular disease, smoking habit, alcohol intake, and regular exercise. In women, on the other hand, there was no clear association between MetS and depressive symptoms.

CONCLUSIONS

MetS was associated with elevated depressive symptoms in a general population of Japanese men.

Obesity-related cardiorenal disease: the benefits of bariatric surgery

The inexorable increase in the prevalence of obesity is a global health concern, which will result in a concomitant escalation in health-care costs. Obesity-related metabolic syndrome affects approximately 25% of adults and is associated with cardiovascular and renal disease. The heart and kidneys are physiologically interdependent, and the pathological effects of obesity can lead to cardiorenal syndrome and, ultimately, kidney and heart failure. Weight loss can prevent or ameliorate obesity-related cardiorenal syndrome, but long-term maintenance of a healthy weight has been difficult to achieve through lifestyle changes or pharmacotherapy. Bariatric surgery offers both sustained weight loss and favourable metabolic changes, including dramatic improvements in glycaemic control and symptoms of type 2 diabetes mellitus. Procedures such as Roux-en-Y gastric bypass offer immediate multisystemic benefits, including bile flow alteration, reduced gastric size, anatomical gut rearrangement and altered flow of nutrients, vagal manipulation and enteric hormone modulation. In patients with cardiorenal syndrome, bariatric surgery also offers renoprotection and cardioprotection, and attenuates both kidney and heart failure by improving organ perfusion and reversing metabolic dysfunction. However, further research is required to understand how bariatric surgery acts on the cardiorenal axis, and its pioneering role in novel treatments and interventions for cardiorenal disease.

Dysregulation of the autonomic nervous system predicts the development of the metabolic syndrome

CONTEXT

Stress is suggested to lead to metabolic dysregulations as clustered in the metabolic syndrome. Although dysregulation of the autonomic nervous system is found to associate with the metabolic syndrome and its dysregulations, no longitudinal study has been performed to date to examine the predictive value of this stress system in the development of the metabolic syndrome.

OBJECTIVE

We examined whether autonomic nervous system functioning predicts 2-year development of metabolic abnormalities that constitute the metabolic syndrome.

DESIGN

Data of the baseline and 2-year follow-up assessment of a prospective cohort: the Netherlands Study of Depression and Anxiety was used.

SETTING

Participants were recruited in the general community, primary care, and specialized mental health care organizations.

PARTICIPANTS

A group of 1933 participants aged 18-65 years.

MAIN OUTCOME MEASURES

The autonomic nervous system measures included heart rate (HR), respiratory sinus arrhythmia (RSA; high RSA reflecting high parasympathetic activity), pre-ejection period (PEP; high PEP reflecting low sympathetic activity), cardiac autonomic balance (CAB), and cardiac autonomic regulation (CAR). Metabolic syndrome was based on the updated Adult Treatment Panel III criteria and included high waist circumference, serum triglycerides, blood pressure, serum glucose, and low high-density lipoprotein (HDL) cholesterol.

RESULTS

Baseline short PEP, low CAB, high HR, and CAR were predictors of an increase in the number of components of the metabolic syndrome during follow-up. High HR and low CAB were predictors of a 2-year decrease in HDL cholesterol, and 2-year increase in diastolic and systolic blood pressure. Short PEP and high CAR also predicted a 2-year increase in systolic blood pressure, and short PEP additionally predicted 2-year increase in diastolic blood pressure. Finally, a low baseline RSA was predictive for subsequent decreases in HDL cholesterol.

CONCLUSION

Increased sympathetic activity predicts an increase in metabolic abnormalities over time. These findings suggest that a dysregulation of the autonomic nervous system is an important predictor of cardiovascular diseases and diabetes through dysregulating lipid metabolism and blood pressure over time.

Understanding the somatic consequences of depression: biological mechanisms and the role of depression symptom profile

Depression is the most common psychiatric disorder worldwide. The burden of disease for depression goes beyond functioning and quality of life and extends to somatic health. Depression has been shown to subsequently increase the risk of, for example, cardiovascular, stroke, diabetes and obesity morbidity. These somatic consequences could partly be due to metabolic, immuno-inflammatory, autonomic and hypothalamic-pituitary-adrenal (HPA)-axis dysregulations which have been suggested to be more often present among depressed patients. Evidence linking depression to metabolic syndrome abnormalities indicates that depression is especially associated with its obesity-related components (for example, abdominal obesity and dyslipidemia). In addition, systemic inflammation and hyperactivity of the HPA-axis have been consistently observed among depressed patients. Slightly less consistent observations are for autonomic dysregulation among depressed patients. The heterogeneity of the depression concept seems to play a differentiating role: metabolic syndrome and inflammation up-regulations appear more specific to the atypical depression subtype, whereas hypercortisolemia appears more specific for melancholic depression. This review finishes with potential treatment implications for the downward spiral in which different depressive symptom profiles and biological dysregulations may impact on each other and interact with somatic health decline.

Autonomic cardiac innervation: development and adult plasticity

Autonomic cardiac neurons have a common origin in the neural crest but undergo distinct developmental differentiation as they mature toward their adult phenotype. Progenitor cells respond to repulsive cues during migration, followed by differentiation cues from paracrine sources that promote neurochemistry and differentiation. When autonomic axons start to innervate cardiac tissue, neurotrophic factors from vascular tissue are essential for maintenance of neurons before they reach their targets, upon which target-derived trophic factors take over final maturation, synaptic strength and postnatal survival. Although target-derived neurotrophins have a central role to play in development, alternative sources of neurotrophins may also modulate innervation. Both developing and adult sympathetic neurons express proNGF, and adult parasympathetic cardiac ganglion neurons also synthesize and release NGF. The physiological function of these “non-classical” cardiac sources of neurotrophins remains to be determined, especially in relation to autocrine/paracrine sustenance during development.

 

Cardiac autonomic nerves are closely spatially associated in cardiac plexuses, ganglia and pacemaker regions and so are sensitive to release of neurotransmitter, neuropeptides and trophic factors from adjacent nerves. As such, in many cardiac pathologies, it is an imbalance within the two arms of the autonomic system that is critical for disease progression. Although this crosstalk between sympathetic and parasympathetic nerves has been well established for adult nerves, it is unclear whether a degree of paracrine regulation occurs across the autonomic limbs during development. Aberrant nerve remodeling is a common occurrence in many adult cardiovascular pathologies, and the mechanisms regulating outgrowth or denervation are disparate. However, autonomic neurons display considerable plasticity in this regard with neurotrophins and inflammatory cytokines having a central regulatory function, including in possible neurotransmitter changes. Certainly, neurotrophins and cytokines regulate transcriptional factors in adult autonomic neurons that have vital differentiation roles in development. Particularly for parasympathetic cardiac ganglion neurons, additional examinations of developmental regulatory mechanisms will potentially aid in understanding attenuated parasympathetic function in a number of conditions, including heart failure.

Autonomic nervous system in the control of energy balance and body weight: personal contributions

The prevalence of obesity is increasing in the industrialized world, so that the World Health Organization considers obesity as a "pandemia" in rich populations. The autonomic nervous system plays a crucial role in the control of energy balance and body weight. This review summarizes our own data and perspectives, emphasizing the influence exerted by autonomic nervous system on energy expenditure and food intake, which are able to determine the body weight. Activation of the sympathetic discharge causes an increase in energy expenditure and a decrease in food intake, while reduction of food intake and body weight loss determines a reduction of the sympathetic activity. On the other hand, pathophysiological mechanisms of the obesity involve alterations of the sympathetic nervous system in accordance with the "Mona Lisa Hypothesis," an acronym for "most obesities known are low in sympathetic activity." Furthermore, the parasympathetic influences on the energy expenditure are analyzed in this review, showing that an increase in parasympathetic activity can induce a paradoxical enhancement of energy consumption.

Evaluating the risk of type 2 diabetes mellitus using artificial neural network: an effective classification approach

AIM

To develop and evaluate an effective classification approach without biochemical parameters to identify those at high risk of T2DM in rural adults.

METHODS

A cross-sectional survey was conducted. Of 8640 subjects who met inclusion criteria, 75% (N1=6480) were randomly selected to provide training set for constructing artificial neural network (ANN) and multivariate logistic regression (MLR) models. The remaining 25% (N2=2160) were assigned to validation set for performance comparisons of the ANN and MLR models. Predictive performance of different models was analyzed by the receiver operating characteristic (ROC) curve using the validation set.

RESULTS

The prevalence rates of T2DM were 8.66% (n=561) and 9.21% (n=199) in training and validation sets, respectively. For ANN model, the sensitivity, specificity, positive and negative predictive value for identifying T2DM were 86.93%, 79.14%, 31.86%, and 98.18%, respectively, while MLR model were only 60.80%, 75.48%, 21.78%, and 94.52%, respectively. Area under the ROC curve (AUC) value for identifying T2DM when using the ANN model was 0.891, showing more accurate predictive performance than the MLR model (AUC=0.744) (P=0.0001).

CONCLUSION

The ANN model is an effective classification approach for identifying those at high risk of T2DM based on demographic, lifestyle and anthropometric data.

Diabetes and technology for increased activity study: the effects of exercise and technology on heart rate variability and metabolic syndrome risk factors

This study tested the hypothesis that an 8-week exercise intervention supported by mobile health (mHealth) technology would improve metabolic syndrome (MetS) risk factors and heart rate variability (HRV) in a population with MetS risk factors. Participants (n = 12; three male; aged 56.9 ± 7.0 years) reported to the laboratory for assessment of MetS risk factors and fitness (VO2max) at baseline (V 0) and after 8-weeks (V 2) of intervention. Participants received an individualized exercise prescription and a mHealth technology kit for remote monitoring of blood pressure (BP), blood glucose, physical activity, and body weight via smartphone. Participants underwent 24-h ambulatory monitoring of R-R intervals following V 0 and V 2. Low and high frequency powers of HRV were assessed from the recording and the ratio of low-to-high frequency powers and low and high frequency powers in normalized units were calculated. One-way repeated measures analysis of variance showed that waist circumference (V 0: 113.1 ± 11.0 cm, V 2: 108.1 ± 14.7 cm; p = 0.004) and diastolic BP (V 0: 81 ± 6 mmHg, V 2: 76 ± 11 mmHg; p = 0.04) were reduced and VO2max increased (V 0: 31.3 ml/kg/min, V 2: 34.8 ml/kg/min; p = 0.02) with no changes in other MetS risk factors. Low and high frequency powers in normalized units were reduced (V 0: 75.5 ± 12.0, V 2: 72.0 ± 12.1; p = 0.03) and increased (V 0: 24.5 ± 12.0, V 2: 28.0 ± 12.1; p = 0.03), respectively, with no other changes in HRV. Over the intervention period, changes in systolic BP were correlated negatively with the changes in R-R interval (r = -0.600; p = 0.04) and positively with the changes in heart rate (r = 0.611; p = 0.03), with no other associations between MetS risk factors and HRV parameters. Thus, this 8-week mHealth supported exercise intervention improved MetS risk factors and HRV parameters, but only changes in systolic BP were associated with improved autonomic function.

The impact of metabolic syndrome and endothelial dysfunction on exercise-induced cardiovascular changes

OBJECTIVE

There is limited information regarding the synergistic or additive effects of metabolic syndrome (MS) and endothelial dysfunction (ED) on cardiovascular disease (CVD). Altered cardiovascular responses to exercise have been shown to predict future cardiovascular events as well as assess autonomic function. The present study evaluated the impact of MS and brachial artery reactivity (a proxy of ED) on peak exercise-induced cardiovascular changes.

DESIGN AND METHODS

Individuals (n = 303) undergoing a standard nuclear medicine exercise stress test were assessed for MS. Participants underwent a Forearm Hyperaemic Reactivity test and were considered to have dysfunctional reactivity if their rate of uptake ratio (RUR) was <3.55. Resting and peak blood pressure (BP) and heart rate (HR) were measured. Reactivity was calculated as the difference between peak and resting measures.

RESULTS

Analyses, adjusting for age, sex, resting HR, total metabolic equivalents (METs), and a history of major CVD, revealed a main effect of MS (F = 5.51, η(2) = 0.02, P = 0.02) and RUR (F = 6.69, η(2) = 0.02, P = 0.01) on HR reactivity, such that patients with MS and/or poor RUR had reduced HR reactivity. There were no interactive effects of RUR and MS. There were no effects of RUR or MS on systolic BP (SBP) or diastolic BP (DBP) reactivity or rate pressure product (RPP) reactivity.

CONCLUSIONS

The presence of decreased HR reactivity among participants with MS or poor brachial artery reactivity, combined with the lack of difference in other exercise-induced cardiovascular changes, indicates that these patients may have some degree of parasympathetic dysregulation. Further longitudinal studies are needed to understand the long-term implications of MS and endothelial abnormalities in this context.

Immune sculpting of norepinephrine on MHC-I, B7-1, IDO and B7-H1 expression and regulation of proliferation and invasion in pancreatic carcinoma cells

BACKGROUND

The sympathetic neurotransmitter Norepinephrine (NE) contributes to tumorigenesis and cancer progression. This study aims to investigate the role of NE in modulating the immune phenotype and allowing pancreatic carcinoma (PC) cells to escape the immune response.

METHODS

Varied concentrations of NE and interferon-gamma (IFN-γ) were administrated to MIA PaCa-2 and BxPC-3 cell lines for 48 hours. Proliferation and invasion were then investigated using an MTT assay and a membrane invasion culture system respectively. MHC-I, B7-1, IDO and B7-H1 expression were measured using real-time quantitative RT-PCR, western blotting and immunocytochemistry. The synergistic and time-dependent effects of NE/IFN-γ were also investigated. Adrenergic antagonists were used to identify the relevant target receptor of NE.

RESULTS

The results showed that NE had dose-dependent and time-dependent effects on cell biological processes as well as on the expression of MHC-I, B7-1, IDO and B7-H1. These effects occurred mainly via the β(2)-adrenergic receptor. Long-term NE treatment was able to antagonize some of the effects of IFN-γ (after 2 weeks of treatment), but NE and IFN-γ had significant synergistic stimulatory effects on IDO and B7-H1 expression. The residual effects on biological activities lasted for 2 weeks, while the immunophenotypic changes decreased at early time points after treatment.

CONCLUSIONS

NE plays important roles in modulating PC cell biological activities and affecting MHC-I, B7-1, IDO and B7-H1 expression in vitro, mainly via the β2-adrenergic receptor (β2-AR) in a time- and dose-dependent fashion. Only at extended treatment durations could NE affect PC cell progression and immune evasion.

Associations of the lower urinary tract symptoms with the lifestyle, prostate volume, and metabolic syndrome in the elderly males

This study aimed to evaluate the influence of the lifestyle, prostate volume (PV), and metabolic syndrome (MS) on lower urinary tract symptoms (LUTS) in the elderly males. A total of 764 men aged greater than 40 years were enrolled. Their severities of LUTS were assessed by the International Prostate Symptom Score questionnaire, while their MS was diagnosed according to the criteria developed by the National Cholesterol Education Program Adult Treatment Panel III. Lifestyle factors, PV, and components of MS were compared between no/mild and moderate/severe LUTS groups. In univariate analysis, age, cigarette smoking, alcohol consumption, physical activity, and PV significantly correlated with the severity of LUTS, but the presence or any components of MS did not. Results of multivariate analysis showed that aging, cigarette smoking, lack of regular exercise, and larger PV were independent predictors for moderate/severe LUTS. Notably, the risk factors for LUTS was influenced by the presence of MS. PV may play a role in determining the severity of LUTS for men without MS, while physical activity was the critical factor for men with MS. It was suggested that healthy lifestyle would be beneficial to lessen the severity of LUTS in the elderly males.

Decreased adrenergic tone in acromegaly: evidence from direct recording of muscle sympathetic nerve activity

OBJECTIVE

Sympathovagal imbalance has been shown in acromegaly by indirect measurements of adrenergic tone. Data regarding direct measurement of sympathetic activity are lacking as yet. Aim of this study was to assess the adrenergic tone through direct recording of muscle sympathetic nerve activity (MSNA) in acromegalic patients.

DESIGN

Fifteen patients (age 26-66 years, eight women) with newly diagnosed active acromegaly without hyperprolactinaemia, pituitary hormone deficiencies, obstructive sleep apnoea and cardiac hypertrophy, and 15 healthy subjects matched for age, sex and body mass index were recruited. After evaluating anthropometric and echocardiographic parameters, anterior pituitary function, glucose and lipid metabolism, and measuring plasma leptin, direct recording of sympathetic outflow via the microneurographic technique was performed.

RESULTS

For similar anthropometric and metabolic parameters in patients and controls, HOMA index was significantly increased in the former (4·2 ± 2·39 vs 1·6 ± 0·19, P < 0·001). Surprisingly, this finding of insulin resistance was accompanied by a marked sympathetic inhibition (MSNA 18·3 ± 8·10 vs 37·3 ± 6·48 bursts/min, P < 0·0001, respectively in patients and controls). A reduction in plasma leptin (1·6 ± 1·04 vs 6·5 ± 2·01 μg/l, P < 0·0001) was also recorded in the patients. MSNA was positively correlated with leptin (P < 0·0001).

CONCLUSIONS

Newly diagnosed acromegalic patients without cardiac hypertrophy display a decreased sympathetic outflow in spite of insulin resistance. This finding might be related to hypoleptinaemia.

Impaired sympathoadrenal axis function contributes to enhanced insulin secretion in prediabetic obese rats

The involvement of sympathoadrenal axis activity in obesity onset was investigated using the experimental model of treating neonatal rats with monosodium L-glutamate. To access general sympathetic nervous system activity, we recorded the firing rates of sympathetic superior cervical ganglion nerves in animals. Catecholamine content and secretion from isolated adrenal medulla were measured. Intravenous glucose tolerance test was performed, and isolated pancreatic islets were stimulated with glucose and adrenergic agonists. The nerve firing rate of obese rats was decreased compared to the rate for lean rats. Basal catecholamine secretion decreased whereas catecholamine secretion induced by carbachol, elevated extracellular potassium, and caffeine in the isolated adrenal medulla were all increased in obese rats compared to control. Both glucose intolerance and hyperinsulinaemia were observed in obese rats. Adrenaline strongly inhibited glucose-induced insulin secretion in obese animals. These findings suggest that low sympathoadrenal activity contributes to impaired glycaemic control in prediabetic obese rats.

Maternal perinatal undernutrition has long-term consequences on morphology, function and gene expression of the adrenal medulla in the adult male rat

Epidemiological studies suggest that maternal undernutrition sensitises to the development of chronic adult diseases, such as type 2 diabetes, hypertension and obesity. Although the physiological mechanisms involved in this 'perinatal programming' remain largely unknown, alterations of stress neuroendocrine systems such as the hypothalamic-pituitary-adrenal (HPA) and sympathoadrenal axes might play a crucial role. Despite recent reports showing that maternal perinatal undernutrition disturbs chromaffin cells organisation and activity in male rats at weaning, its long-term effects on adrenal medulla in adult animals are unknown. Using a rat model of maternal perinatal 50% food restriction (FR50) from the second week of gestation until weaning, histochemistry approaches revealed alterations in noradrenergic chromaffin cells aggregation and in cholinergic innervation in the adrenal medulla of 8-month-old FR50 rats. Electron microscopy showed that chromaffin cell granules exhibited ultrastructural changes in FR50 rats. These morphological changes were associated with reduced circulating levels and excretion of catecholamines. By contrast, catecholamine plasma levels were significantly increased after a 16 or 72 h of fasting, indicating that the responsiveness of the sympathoadrenal system to food deprivation was accentuated in FR50 adult rats. Among 384 pituitary adenylate cyclase-activating polypeptide-sensitive genes, we identified 129 genes (33.6%) that were under expressed (ratio < 0.7) in FR50 animals. A large number of these genes are involved in cytoskeleton remodelling and vesicle trafficking. Taken together, our results show that maternal perinatal undernutrition programmes adrenomedullary function and gene expression in adult male rats. Because catecholamines contribute to metabolic homeostasis, as well as arterial blood pressure regulation, the alterations observed in the adrenal medulla of adult male FR50 rats may participate in the programming of chronic adult diseases.

Metabolic depression: a chronic depressive subtype? Findings from the InCHIANTI study of older persons

OBJECTIVE

Several studies report a cross-sectional association between metabolic syndrome and depression. Possibly, metabolic syndrome promotes onset or chronicity of depression. However, such a longitudinal link has not yet been confirmed. This study examines whether metabolic syndrome or its components are associated with onset and chronicity of depression.

METHOD

Secondary analyses were performed on data from 823 participants (≥ 65 years of age) in the InCHIANTI study, a prospective, population-based cohort study of older persons. From 1998 to 2000, the study sample was randomly selected from the population registry of 2 sites in Italy using a multistage stratified sampling method. Baseline data collection consisted of a home interview and a medical evaluation at the study clinic. Follow-up for each participant occurred after 3 years and 6 years. Metabolic syndrome at baseline was defined as ≥ 3 of the following: abdominal obesity, high triglycerides, low high-density lipoprotein cholesterol, high blood pressure, and high fasting glucose. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression scale (CES-D) at baseline and after 3 and 6 years. Sample characteristics were compared between persons with and without depression at baseline using χ² and t statistics. Logistic regression analyses were conducted separately in persons with and without depression at baseline to test whether metabolic syndrome at baseline could predict onset and chronicity of depression at follow-up.

RESULTS

At baseline, 235 persons had metabolic syndrome, and 168 were depressed (CES-D score ≥ 20). Among persons not depressed at baseline, 26.0% developed depression. Higher waist circumference increased the odds of depression onset (adjusted OR per SD increase = 1.28; 95% CI, 1.05-1.56), but there was no association between other metabolic syndrome components and onset of depression. Among persons depressed at baseline, depression had a chronic character in 69.0% of persons without and 88.5% of persons with metabolic syndrome. Metabolic syndrome was associated with an almost 3-fold increase in the odds of chronicity of depression (adjusted OR = 2.66; 95% CI, 1.01-7.00), with almost every metabolic syndrome component contributing to this association.

CONCLUSION

In late life, waist circumference, but not metabolic syndrome, predicted onset of depression. Depressed persons with metabolic syndrome were more likely to have persistent or recurrent depression. The latter may suggest that depression with metabolic abnormalities, which could be labeled metabolic depression, identifies a chronic subtype of depression.

Relationship between muscle sympathetic nerve activity and aortic wave reflection characteristics in young men and women

Increased arterial stiffness is associated with higher levels of aortic wave reflection and aortic blood pressure. Recent evidence suggests a link between muscle sympathetic nerve activity and indices of arterial stiffness. Therefore, the aims of this study were to examine the relationship between resting muscle sympathetic nerve activity and characteristics of aortic pressure wave reflection and the influence of sex on these relationships. In 44 subjects (23 females and 21 males; 25 ± 1 years of age), we measured muscle sympathetic nerve activity via peroneal microneurography. In addition, noninvasive aortic pressure waveforms were synthesized from radial pressure waveforms obtained from applanation tonometry. Aortic blood pressure, augmentation index, wave reflection amplitude, and wasted left ventricular energy were calculated. Resting sympathetic activity (bursts/100 heart beats) was not associated with any of the aortic pressure wave reflection characteristics for all patients. However, there was a positive relationship between sympathetic activity and augmentation index (r = 0.46; P = 0.05) in men. Further, sympathetic activity in men was related to wave reflection amplitude (r = 0.53; P<0.05) and wasted left ventricular energy (r = 0.57; P<0.01). In contrast to men, women demonstrated strong inverse relationships between sympathetic activity and augmentation index (r = -0.63), wave reflection amplitude ( r = -0.59), and wasted left ventricular energy (r = -0.58; P<0.01 for all). Our results suggest another possible mechanism by which young women are protected against the development of cardiovascular disease.

Noninvasive method to estimate anaerobic threshold in individuals with type 2 diabetes

BACKGROUND

While several studies have identified the anaerobic threshold (AT) through the responses of blood lactate, ventilation and blood glucose others have suggested the response of the heart rate variability (HRV) as a method to identify the AT in young healthy individuals. However, the validity of HRV in estimating the lactate threshold (LT) and ventilatory threshold (VT) for individuals with type 2 diabetes (T2D) has not been investigated yet.

AIM

To analyze the possibility of identifying the heart rate variability threshold (HRVT) by considering the responses of parasympathetic indicators during incremental exercise test in type 2 diabetics subjects (T2D) and non diabetics individuals (ND).

METHODS

Nine T2D (55.6 ± 5.7 years, 83.4 ± 26.6 kg, 30.9 ± 5.2 kg.m2(-1)) and ten ND (50.8 ± 5.1 years, 76.2 ± 14.3 kg, 26.5 ± 3.8 kg.m2(-1)) underwent to an incremental exercise test (IT) on a cycle ergometer. Heart rate (HR), rate of perceived exertion (RPE), blood lactate and expired gas concentrations were measured at the end of each stage. HRVT was identified through the responses of root mean square successive difference between adjacent R-R intervals (RMSSD) and standard deviation of instantaneous beat-to-beat R-R interval variability (SD1) by considering the last 60 s of each incremental stage, and were known as HRVT by RMSSD and SD1 (HRVT-RMSSD and HRVT-SD1), respectively.

RESULTS

No differences were observed within groups for the exercise intensities corresponding to LT, VT, HRVT-RMSSD and HHVT-SD1. Furthermore, a strong relationship were verified among the studied parameters both for T2D (r = 0.68 to 0.87) and ND (r = 0.91 to 0.98) and the Bland & Altman technique confirmed the agreement among them.

CONCLUSION

The HRVT identification by the proposed autonomic indicators (SD1 and RMSSD) were demonstrated to be valid to estimate the LT and VT for both T2D and ND.

Particulate air pollution, metabolic syndrome, and heart rate variability: the multi-ethnic study of atherosclerosis (MESA)

BACKGROUND

Cardiac autonomic dysfunction has been suggested as a possible biologic pathway for the association between fine particulate matter ≤ 2.5 µm in diameter (PM2.5) and cardiovascular disease (CVD). We examined the associations of PM2.5 with heart rate variability, a marker of autonomic function, and whether metabolic syndrome (MetS) modified these associations.

METHODS

We used data from the Multi-Ethnic Study of Atherosclerosis to measure the standard deviation of normal-to-normal intervals (SDNN) and the root mean square of successive differences (rMSSD) of 5,465 participants 45-84 years old who were free of CVD at the baseline examination (2000-2002). Data from the U.S. regulatory monitor network were used to estimate ambient PM2.5 concentrations at the participants' residences. MetS was defined as having three or more of the following criteria: abdominal obesity, hypertriglyceridemia, low high-density lipoprotein cholesterol, high blood pressure, and high fasting glucose.

RESULTS

After controlling for confounders, we found that an interquartile range (IQR) increase in 2-day average PM2.5 (10.2 µg/m3) was associated with a 2.1% decrease in rMSSD [95% confidence interval (CI), -4.2 to 0.0] and nonsignificantly associated with a 1.8% decrease in SDNN (95% CI, -3.7 to 0.1). Associations were stronger among individuals with MetS than among those without MetS: an IQR elevation in 2-day PM2.5 was associated with a 6.2% decrease in rMSSD (95% CI, -9.4 to -2.9) among participants with MetS, whereas almost no change was found among participants without MetS (p-interaction = 0.005). Similar effect modification was observed in SDNN (p-interaction = 0.011).

CONCLUSION

These findings suggest that autonomic dysfunction may be a mechanism through which PM exposure affects cardiovascular risk, especially among persons with MetS.

Imbalance of the autonomic nervous system at night in women with gestational diabetes

AIMS

Autonomic nervous system dysfunction is observed in Type 2 diabetes. As gestational diabetes is a potent risk factor of later Type 2 diabetes, we set out to determine whether autonomic nervous system imbalance could already be observed in women with this condition. Because activity of the sympathetic nervous system tends to be relatively stable in the nocturnal hours, we performed the study at night.

RESEARCH DESIGN AND METHODS

We studied 41 women with gestational diabetes, 22 healthy pregnant controls and 14 non-pregnant controls. We assayed plasma noradrenaline at 24.00, 04.00 and 07.00 h and performed an overnight Holter recording for heart rate variability analysis. In addition, we assayed plasma adrenomedullin, a cardiovascular protective hormone.

RESULTS

Compared with non-pregnant controls, plasma noradrenaline levels were increased at 04.00 and 07.00 h in the gestational diabetic (P = 0.003) and pregnant control (P = 0.002) groups, with no difference between them. Heart rate variability, very-low-frequency and low-frequency power were lower in pregnant groups compared to the non-pregnant controls. Heart rate variability remained unchanged between specified sampling times in the gestational diabetic group, in contrast to fluctuation seen in the control groups.

CONCLUSIONS

Gestational diabetes, compared with normal pregnancy, seems not to be a state of overall sympathetic nervous system activation. At the heart level, however, an inhibitory effect on autonomic nervous system modulation was seen. Plasma noradrenaline and heart rate variability correlated well, supporting the use of this function in future studies of overall sympathetic activity during pregnancy.

Clinical significance of B7-H1 and B7-1 expressions in pancreatic carcinoma

BACKGROUND

Cancer cells develop mechanisms to evade immune cells and achieve progression. Aberrant B7-H1 and B7-1 expressions may help pancreatic carcinoma (PC) cells escape immune attack; these molecules can be considered as prognostic markers for patients with PC who have undergone radical resection.

METHODS

We recruited 81 patients who had undergone radical surgical resection for PC between 1999 and 2007. To investigate the prognostic factors, we evaluated the B7-H1 and B7-1 protein expressions in the tissue specimens of these 81 patients by immunohistochemistry and analyzed the clinical and pathological features of these specimens.

RESULTS

B7-H1 was expressed mainly in pancreatic islets, and no B7-1 expression was detected in normal pancreatic tissues. B7-H1 and B7-1 expressions were higher in pancreatic carcinoma tissues than in normal pancreatic tissues (P < 0.05). B7-H1 and B7-1 significantly correlated with the pathological grade and tumor-node-metastasis (TNM) stage, respectively (P < 0.05). Furthermore, B7-1-negative or B7-H1-positive statuses were prognostic indicators of poor disease-specific survival (P < 0.05), but only combined B7-1/B7-H1 expression retained the prognostic potential after adjusting by Cox proportional hazards regression models (P < 0.05).

CONCLUSIONS

Both B7-H1 and B7-1 are expressed in PC; these molecules are important markers for PC progression. Furthermore, combined B7-1/B7-H1 expression can serve as an independent prognostic marker for PC.

Increased sympathetic and decreased parasympathetic activity rather than changes in hypothalamic-pituitary-adrenal axis activity is associated with metabolic abnormalities

CONTEXT

Stress is suggested to lead to metabolic dysregulations as clustered in the metabolic syndrome, but the underlying biological mechanisms are not yet well understood.

OBJECTIVE

We examined the relationship between two main str systems, the autonomic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis, with the metabolic syndrome and its components.

DESIGN

The design was baseline data (yr 2004-2007) of a prospective cohort: the Netherlands Study of Depression and Anxiety (NESDA).

SETTING

The study comprised general community, primary care, and specialized mental health care.

PARTICIPANTS

This study included 1883 participants aged 18-65 yr.

MAIN OUTCOME MEASURES

Autonomic nervous system measures included heart rate, respiratory sinus arrhythmia (RSA; high RSA reflecting high parasympathetic activity), and preejection period (PEP; high PEP reflecting low sympathetic activity). HPA axis measures included the cortisol awakening response, evening cortisol, and a 0.5 mg dexamethasone suppression test as measured in saliva. Metabolic syndrome was based on the updated Adult Treatment Panel III criteria and included high waist circumference, serum triglycerides, blood pressure, serum glucose, and low high-density lipoprotein cholesterol.

RESULTS

RSA and PEP were both independently negatively associated with the presence of the metabolic syndrome, the number of metabolic dysregulations as well as all individual components except high-density lipoprotein cholesterol (all P < 0.02). Heart rate was positively related to the metabolic syndrome, the number of metabolic dysregulations, and all individual components (all P < 0.001). HPA axis measures were not related to metabolic syndrome or its components.

CONCLUSION

Our findings suggest that increased sympathetic and decreased parasympathetic nervous system activity is associated with metabolic syndrome, whereas HPA axis activity is not.

The interactive effects of metabolic syndrome, blood pressure, and mental health in worksite employees

BACKGROUND

Cardiovascular disease (CVD), CVD-related conditions, and mental health disorders are prevalent in the US workforce. We examined associations between metabolic syndrome (METS), blood pressure (BP), and mental health indicators in 1813 employees (25.4% women; 74.6% men) from a large manufacturing firm.

METHODS

Employees participated in a health screen. Biometric measures were body mass index, waist circumference, BP, and fingerstick determinations of blood lipid-lipoproteins and glucose. Mental health was assessed with 5 self-reported questions regarding anger, depression, anxiety, and family and work stress. Multivariate analysis of covariance tested for differences in BP and mental health indicators in employees (370 employees with METS, and 1443 employees without).

RESULTS

Participants were primarily middle-aged (44.8 +/- 0.3 years), overweight (27.9 +/- 0.1 kg/m(2)) men (n = 1352) and women (n = 461) with a resting BP of 122.5 +/- 0.3 mm Hg and 79.8 +/- 0.2 mm Hg, respectively. Diastolic BP (DBP) was found to be 5 mm Hg higher in men with METS compared with men who did not have METS. When questioned, men with higher DBP stated that they often experienced anxiety (n = 39; 91.0 +/- 2 mm Hg) compared with men who reported they rarely experienced anxiety (n = 112; 86.2 +/- 1.9 mm Hg) (P = 0.020). Similarly, systolic BP (SBP) tended to be 4 mm Hg higher in men with METS who stated they often experienced anxiety (n = 39; 138.9 +/- 2 mm Hg) compared with men who reported they rarely experienced anxiety (n = 112; 134.5 +/- 1.2 mm Hg) (P = 0.119). Diastolic BP tended to be 2 mm Hg higher among men with METS who stated they often experienced anger (n = 117; 89.4 +/- 0.9 mm Hg) compared with those who indicated they rarely experienced anger (n = 157; 87.3 +/- 0.8 mm Hg) (P = 0.086), and DBP was 3 mm Hg higher in men with METS who reported overwhelming work stress (n = 83; 89.7 +/- 1.1 mm Hg) compared with those reporting little work stress (n = 79; 86.6 +/- 1.2 mm Hg) (P = 0.176). In contrast, no associations were found between BP and mental health in men without METS, and in women, regardless of the presence or absence of METS (P > 0.05).

CONCLUSIONS

Men with METS who reported higher levels of anxiety, anger, and work stress had higher BP than men without METS, who also reported lower levels of these mental health indicators. The METS appeared to adversely interact with BP and mental health in men at this worksite. Our findings suggest worksite health promotion programs can improve the cardiometabolic and mental health profile of US employees.

beta-cell function in obese-hyperglycemic mice [ob/ob Mice]

This review summarizes key aspects of what has been learned about the physiology of pancreatic islets and leptin deficiency from studies in obese ob/ob mice. ob/ob Mice lack functional leptin. They are grossly overweight and hyperphagic particularly at young ages and develop severe insulin resistance with hyperglycemia and hyperinsulinemia. ob/ob Mice have large pancreatic islets. The beta-cells respond adequately to most stimuli, and ob/ob mice have been used as a rich source of pancreatic islets with high insulin release capacity. ob/ob Mice can perhaps be described as a model for the prediabetic state. The large capacity for islet growth and insulin release makes ob/ob mice a good model for studies on how beta-cells can cope with prolonged functional stress.

Mitochondrial dysfunction and metabolic syndrome-looking for environmental factors

The centerpiece of the pathophysiologic mechanism of metabolic syndrome is insulin resistance. Recently, it is becoming evident that mitochondrial dysfunction is closely related to insulin resistance and metabolic syndrome. The underlying mechanism of mitochondrial dysfunction is very complex, which includes genetic factors from both nuclear and mitochondrial genome and numerous environmental factors. Several mitochondrial DNA polymorphisms are associated with the components of metabolic syndrome. Numerous chemicals and drugs may cause mitochondrial dysfunction and insulin resistance. Notably, it was recently reported that serum levels of several mitochondrial toxins, such as persistent organic pollutants are associated with metabolic syndrome, which necessitates further investigation to reveal its precise mechanism. Given that the health impact of metabolic syndrome is tremendous, it is necessary to develop therapeutic modalities to correct mitochondrial dysfunction or at least to halt its aggravation. In this regard, exercise can improve both mitochondrial function and insulin sensitivity, and some pharmaceutical agents were reported to improve mitochondrial function. However, further studies are warranted to find more effective therapeutic strategies to treat mitochondrial dysfunction. By doing so, we can also shed light on the path of research for other diseases related to mitochondrial dysfunction.

Reversal of high pancreatic islet and white adipose tissue blood flow in type 2 diabetic GK rats by administration of the beta3-adrenoceptor inhibitor SR-59230A

Previous studies have shown that the Goto-Kakizaki (GK) rat, a nonobese type 2 diabetes model, has an increased white adipose tissue (WAT) and islet blood flow when compared with control rats. The aim of the study was to examine if these increased blood flow values in GK rats could be affected by the beta(3)-adrenoceptor antagonist SR-59230A. We measured organ blood flow with a microsphere technique 10 min after administration of SR-59230A (1 mg/kg body wt), or the corresponding volume of 0.9% NaCl solution (1 ml/kg body wt) in rats anaesthetized with thiobutabarbital. The GK rat had an increased blood flow in all intra-abdominal adipose tissue depots except for the sternal fat pad compared with Wistar-Furth (WF) rats. However, no differences were seen in the blood perfusion of subcutaneous white or brown adipose tissue. The blood flow was also increased in both the pancreas and in the islets in the GK rat compared with WF rats. SR-59230A treatment affected neither WAT nor pancreatic blood flow in WF rats. In GK rats, on the other hand, SR-59230A decreased both WAT and islet blood flow values to values similar to those seen in control WF rats. The whole pancreatic blood flow was not affected by SR-59230A administration in GK rats. Interestingly, the brown adipose tissue blood flow in GK rats increased after SR-59230A administration. These results suggest that beta(3)-adrenoceptors are involved in regulation of blood flow both in islet and in adipose tissue.