Does the autonomic nervous system play a role in the development of insulin resistance? A study on heart rate variability in first-degree relatives of Type 2 diabetes patients and control subjects

Comparison of cardiac autonomic function across complete glycaemic spectrum

OBJECTIVES

Autonomic imbalance is attributed as key mechanism altering metabolic regulation in diabetes mellitus. In view of controversial reports on autonomic function in FDRD and prediabetes, we aimed to assess and compare the autonomic function across the complete glycaemic spectrum in Indian population.

METHODS

Short term heart rate variability and cardiac autonomic reactivity tests - blood pressure and heart rate response to orthostatic tolerance and deep breathing exercise, and diastolic response to isometric handgrip exercise were recorded in normoglycemic apparently healthy individual, normoglycemic first degree relatives of diabetes, prediabetes and diabetes individuals.

RESULTS

Resting heart rate is significantly higher in FDRD, prediabetes and diabetes as compared to controls (control < FDRD = prediabetes = diabetes). Total power, LF power (control < FDRD < prediabetes = diabetes) and HF power (control < FDRD < prediabetes < diabetes) decreased along the glycaemic spectrum. Time-domain variables of HRV (SDNN, RMSSD, NN50, pNN50) were reduced as we move along the glycaemic spectrum (control < FDRD < prediabetes = diabetes). Cardiac autonomic function reactivity parameters such as 30:15 ratio and E:I ratio are decreased in prediabetes and diabetes group as compared to control and FDRD group (control = FDRD < prediabetes = diabetes). Diastolic response to isometric hand grip increases along the glycaemic spectrum starting from FDRD (control < FDRD < prediabetes = diabetes).

CONCLUSIONS

Autonomic dysfunction is observed even in first degree relatives of diabetes. Autonomic dysfunction increases as we move along the glycaemic spectrum (control < FDRD < prediabetes < diabetes).

Altered glucose-dependent secretion of glucagon and ACTH is associated with insulin resistance, assessed by population analysis

This study aimed to characterize how the dysregulation of counter-regulatory hormones can contribute to insulin resistance and potentially to diabetes. Therefore, we investigated the association between insulin sensitivity and the glucose- and insulin-dependent secretion of glucagon, adrenocorticotropic hormone (ACTH), and cortisol in non-diabetic individuals using a population model analysis. Data, from hyperinsulinemic-hypoglycemic clamps, were pooled for analysis, including 52 individuals with a wide range of insulin resistance (reflected by glucose infusion rate 20-60 min; GIR20-60min). Glucagon secretion was suppressed by glucose and, to a lesser extent, insulin. The GIR20-60min and BMI were identified as predictors of the insulin effect on glucagon. At normoglycemia (5 mmol/L), a 90% suppression of glucagon was achieved at insulin concentrations of 16.3 and 43.4 µU/mL in individuals belonging to the highest and lowest quantiles of insulin sensitivity, respectively. Insulin resistance of glucagon secretion explained the elevated fasting glucagon for individuals with a low GIR20-60min. ACTH secretion was suppressed by glucose and not affected by insulin. The GIR20-60min was superior to other measures as a predictor of glucose-dependent ACTH secretion, with 90% suppression of ACTH secretion by glucose at 3.1 and 3.5 mmol/L for insulin-sensitive and insulin-resistant individuals, respectively. This difference may appear small but shifts the suppression range into normoglycemia for individuals with insulin resistance, thus, leading to earlier and greater ACTH/cortisol response when the glucose falls. Based on modeling of pooled glucose-clamp data, insulin resistance was associated with generally elevated glucagon and a potentiated cortisol-axis response to hypoglycemia, and over time both hormonal pathways may therefore contribute to dysglycemia and possibly type 2 diabetes.

Low heart rate variability from 10-s electrocardiograms is associated with development of non-alcoholic fatty liver disease

Reduced heart rate variability (HRV) is reflective of autonomic imbalance. However, its impact on non-alcoholic fatty liver disease (NAFLD) is unknown. We investigated the association between 10-s HRV and incident NAFLD. A cohort of 154,286 Korean adults with no NAFLD at baseline were followed up. 10-s electrocardiograms were used to estimate two time-domain HRV, the standard deviation of normal-to-normal intervals (SDNN) and the root mean square of successive differences in RR intervals (RMSSD). Hepatic steatosis (HS) and liver fibrosis were assessed using ultrasonography and the fibrosis-4 index (FIB-4). A total of 27,279 incident HS (median follow up of 4.2 years) and 1250 incident HS plus high FIB-4 (median follow up of 4.2 years) cases were identified at follow-up. The multivariable adjusted hazard ratios (aHRs) (95% confidence intervals [CIs]) in a model with time-dependent variables for incident HS, comparing the lowest quintile to the highest and reference quintile of the RMSSD, was 1.43 (1.37-1.49), and the corresponding HR for incident HS plus intermediate/high FIB-4 was 1.70 (1.35-2.15). Similarly, SDNN was inversely associated with incident HS and HS plus intermediate/high FIB-4. The results were similar using the NAFLD fibrosis score. Autonomic imbalance assessed by HRV may help to identify individuals at a high risk of HS and its progression and warrant further studies.

Slow deep breathing modulates cardiac vagal activity but does not affect peripheral glucose metabolism in healthy men

Parasympathetic nervous system innervates peripheral organs including pancreas, hepatic portal system, and gastrointestinal tract. It thereby contributes to the regulation of whole-body glucose metabolism especially in the postprandial state when it promotes secretion of insulin and enhances its action in major target organs. We now aimed to evaluate the effect of parasympathetic modulation on human glucose metabolism. We used slow deep breathing maneuvers to activate the parasympathetic nervous system and tested for effects on metabolism during an oral glucose tolerance test in a randomized, controlled, cross-over trial in 15 healthy young men. We used projections towards the heart as a readout for parasympathetic activity. When analyzing heart rate variability, there was a significant increase of RMSSD (root mean square of successive differences) when participants performed slow deep breathing compared to the control condition, indicating a modulation of parasympathetic activity. However, no statistically significant effects on peripheral glucose metabolism or energy expenditure after the glucose tolerance test were detected. Of note, we detected a significant association between mean heart rate and serum insulin and C-peptide concentrations. While we did not find major effects of slow deep breathing on glucose metabolism, our correlational results suggest a link between the autonomic nervous system and insulin secretion after oral glucose intake. Future studies need to unravel involved mechanisms and develop potential novel treatment approaches for impaired insulin secretion in diabetes.

Acute ingestion of a high-fructose drink impairs vascular autonomic modulation and reflex control of blood pressure in first-degree relatives of diabetic patients

First-degree relatives of diabetes patients, despite being euglycemic, presented impaired BRS and exacerbation of sympathetic modulation after ingestion of a high fructose drink when challenged to orthostatic stress. This finding alerts the importance of early autonomic dysfunction even in clinically healthy people, especially in face of a stressful situation.

Longitudinal associations between ambient air pollution and insulin sensitivity: results from the KORA cohort study

BACKGROUND

Impaired insulin sensitivity could be an intermediate step that links exposure to air pollution to the development of type 2 diabetes. However, longitudinal associations of air pollution with insulin sensitivity remain unclear. Our study investigated the associations of long-term air pollution exposure with the degree and rate of change of insulin sensitivity.

METHODS

In this longitudinal study, we analysed data from the Cooperative Health Research in the Region of Augsburg (KORA) cohort from Augsburg, Germany, which recruited participants aged 25-74 years in the survey between 1999 and 2001 (KORA S4), with two follow-up examinations in 2006-08 (KORA F4) and 2013-14 (KORA FF4). Serum concentrations of fasting insulin and glucose, and homoeostasis model assessment of insulin resistance (HOMA-IR, a surrogate measure of insulin sensitivity) and β-cell function (HOMA-B, a surrogate marker for fasting insulin secretion) were assessed at up to three visits between 1999 and 2014. Annual average air pollutant concentrations at the residence were estimated by land-use regression models. We examined the associations of air pollution with repeatedly assessed biomarker levels using mixed-effects models, and we assessed the associations with the annual rate of change in biomarkers using quantile regression models.

FINDINGS

Among 9620 observations from 4261 participants in the KORA cohort, we included 6008 (62·5%) observations from 3297 (77·4%) participants in our analyses. Per IQR increment in annual average air pollutant concentrations, HOMA-IR significantly increased by 2·5% (95% CI 0·3 to 4·7) for coarse particulate matter, by 3·1% (0·9 to 5·3) for PM_2·5, by 3·6% (1·0 to 6·3) for PM_{2·5absorbance}, and by 3·2% (0·6 to 5·8) for nitrogen dioxide, and borderline significantly increased by 2·2% (-0·1 to 4·5) for ozone, whereas it did not significantly increase for the whole range of ultrafine particles. Similar positive associations in slightly smaller magnitude were observed for HOMA-B and fasting insulin levels. In addition, air pollutant concentrations were positively associated with the annual rate of change in HOMA-IR, HOMA-B, and fasting insulin. Neither the level nor the rate of change of fasting glucose were associated with air pollution exposure.

INTERPRETATION

Our study indicates that long-term air pollution exposure could contribute to the development of insulin resistance, which is one of the key factors in the pathogenesis of type 2 diabetes.

FUNDING

German Federal Ministry of Education and Research.

No modulation of postprandial metabolism by transcutaneous auricular vagus nerve stimulation: a cross-over study in 15 healthy men

Experimental evidence suggests a crucial role of the autonomic nervous system in whole body metabolism with major regulatory effects of the parasympathetic branch in postprandial adaptation. However, the relative contribution of this mechanism is still not fully clear in humans. We therefore compared the effects of transcutaneous auricular vagus nerve stimulation (taVNS, Cerbomed Nemos) with sham stimulation during an oral glucose tolerance test in a randomized, single-blind, cross-over design in 15 healthy lean men. Stimulation was performed for 150 min, 30 min before and during the entire oral glucose tolerance test with stimulation cycles of 30 s of on-phase and 30 s of off-phase and a 25 Hz impulse. Heart rate variability and plasma catecholamine levels were assessed as proxies of autonomic tone in the periphery. Neither analyzed heart rate variability parameters nor plasma catecholamine levels were significantly different between the two conditions. Plasma glucose, insulin sensitivity and insulin secretion were also comparable between conditions. Thus, the applied taVNS device or protocol was unable to achieve significant effects on autonomic innervation in peripheral organs. Accordingly, glucose metabolism remained unaltered. Therefore, alternative approaches are necessary to investigate the importance of the autonomic nervous system in postprandial human metabolism.

A review of the molecular pathways mediating the improvement in diabetes mellitus following caloric restriction

Lifestyle modification is the cornerstone of diabetes prevention and treatment. Weight loss through caloric restriction (CR) is effective in improving glycemic control, though it is difficult for patients to follow in practice, and remains critical to achieve optimal glucose homeostasis. In this review, we look at what is known about the molecular pathways involved in CR-induced insulin sensitivity and improved insulin resistance.

Early commitment of cardiovascular autonomic modulation in Brazilian patients with congenital generalized lipodystrophy

BACKGROUND

Metabolic abnormalities in congenital generalized lipodystrophy (CGL) are associated with microvascular complications. However, the evaluation of different types of neuropathy in these patients, including the commitment of cardiovascular autonomic modulation, is scarce. The objective of the present study was to determine the prevalence of cardiovascular autonomic neuropathy (CAN) in patients with CGL compared with individuals with type 1 diabetes and healthy subjects.

METHODS

Ten patients with CGL, 20 patients with type 1 diabetes and 20 healthy subjects were included in the study. Controls were paired 1:2 for age, gender, BMI and pubertal stage. Heart rate variability (HRV) was analyzed using cardiovascular autonomic reflex tests, including postural hypotension test, Valsalva (VAL), respiratory (E/I) and orthostatic (30/15) coefficients, and spectral analysis of the HRV, determining very low (VLF), low (LF) and high (HF) frequencies components. The diagnosis of CAN was defined as the presence of at least two altered tests.

RESULTS

CAN was detected in 40% of the CGL patients, 5% in type 1 diabetes patients and was absent in healthy individuals (p < 0.05). We observed a significant reduction in the E/I, VLF, LF and HF in CGL cases vs. type 1 diabetes and healthy individuals and lower levels of 30/15 and VAL in CGL vs. healthy individuals. A significant positive correlation was observed between leptin and 30/15 coefficient (r = 0.396; p = 0.036) after adjusting for insulin resistance and triglycerides. Autonomic cardiovascular tests were associated with HbA1c, HOMA-IR, triglycerides and albumin/creatinine ratio in CGL cases.

CONCLUSIONS

We observed a high prevalence of CAN in young patients with CGL, suggesting that insulin resistance, hypertriglyceridemia and hypoleptinemia, may have been involved in early CAN development. Additional studies are needed to evaluate the role of leptinemia in the physiopathogenesis of the condition.

Association between Exposure to Ambient Air Particulates and Metabolic Syndrome Components in a Saudi Arabian Population

Recent epidemiological evidence suggests that exposure to particulates may be a factor in the etiology of metabolic syndrome (MetS). In this novel study, we investigated the relationship between particulate levels and prevalence of MetS component abnormalities (hypertension, hyperglycemia, obesity) in a recruited cohort (N = 2025) in Jeddah, Saudi Arabia. We observed significant associations between a 10 μg/m³ increase in PM_2.5 and increased risks for MetS (Risk Ratio (RR): 1.12; 95% Confidence Interval (CI): 1.06-1.19), hyperglycemia (RR: 1.08; 95% CI: 1.03-1.14), and hypertension (RR: 1.09; 95% CI: 1.04-1.14). PM_2.5 from soil/road dust was found to be associated with hyperglycemia (RR: 1.12; 95% CI: 1.06-1.19) and hypertension (RR: 1.11; 95% CI: 1.05-1.18), while PM_2.5 from traffic was associated with hyperglycemia (RR: 1.33; 95% CI: 1.05-1.71). We did not observe any health associations with source-specific mass exposures. Our findings suggest that exposure to specific elemental components of PM_2.5, especially Ni, may contribute to the development of cardiometabolic disorders.

Diurnal Variation and Twenty-Four Hour Sleep Deprivation Do Not Alter Supine Heart Rate Variability in Healthy Male Young Adults

Heart rate variability (HRV) has become an increasingly popular index of cardiac autonomic control in the biobehavioral sciences due to its relationship with mental illness and cognitive traits. However, the intraindividual stability of HRV in response to sleep and diurnal disturbances, which are commonly reported in mental illness, and its relationship with executive function are not well understood. Here, in 40 healthy adult males we calculated high frequency HRV—an index of parasympathetic nervous system (PNS) activity—using pulse oximetry during brain imaging, and assessed attentional and executive function performance in a subsequent behavioral test session at three time points: morning, evening, and the following morning. Twenty participants were randomly selected for total sleep deprivation whereas the other 20 participants slept as normal. Sleep deprivation and morning-to-night variation did not influence high frequency HRV at either a group or individual level; however, sleep deprivation abolished the relationship between orienting attention performance and HRV. We conclude that a day of wake and a night of laboratory-induced sleep deprivation do not alter supine high frequency HRV in young healthy male adults.

Prolonged job strain reduces time-domain heart rate variability on both working and resting days among cardiovascular-susceptible nurses

INTRODUCTION

Modifications of hearth rate variability (HRV) constitute a marker of the autonomic nervous system (ANS) deregulation, a promising pathway linking job strain (JS) and cardiovascular diseases (CVD). The study objective is to assess whether exposures to recent and prolonged JS reduce time-domain HRV parameters on working days (WD) among CVD-susceptible nurses and whether the association also persists on resting days (RD).

MATERIAL AND METHODS

313 healthy nurses were investigated twice with one year interval to assess JS based on the demand-control and the effort-reward models. 36, 9 and 16 CVD-susceptible nurses were classified as low JS in both surveys (stable low strain - SLS), recent high JS (high JS at the second screening only-RHS) and prolonged high JS (high strain in both surveys-PHS), respectively. In 9, 7 and 10 of them, free from comorbidities/treatments interfering with HRV, two 24-h ECG recordings were performed on WD and RD. Differences in the time domain HRV metrics among JS categories were assessed using ANCOVA, adjusted for age and smoking.

RESULTS

In the entire sample (mean age: 39 years, 83% females) the prevalence of high job strain was 38.7% in the second survey. SDNN (standard deviation of all normal RR intervals) on WD significantly declined among JS categories (p = 0.02), with geometric mean values of 169.1, 145.3 and 128.9 ms in SLS, RHS, PHS, respectively. In the PHS group, SDNN remained lower on RD as compared to the low strain subjects (142.4 vs. 171.1 ms, p = 0.02). Similar findings were found for the SDNN_Index, while SDANN (standard deviation of average RR intervals in all 5 min segments of registration) mean values reduced in the PHS group during WD only.

CONCLUSIONS

Our findings suggest that persistent JS lowers HRV time-domain parameters, supporting the hypothesis that the ANS disorders may play an intermediate role in the relationship between work stress and CVD.

Physiological characteristics of patients with schizophrenia prematurely dying from circulatory diseases

INTRODUCTION

Patients with schizophrenia before reaching geriatric age are at high risk of circulatory mortality. However, investigations are lacking on the characteristics of physiological measurement among these at-risk patients.

METHODS

In this study, we followed acutely inpatients with schizophrenia disorder for cause of death through record linkage to the Death Certification System in Taiwan. Cases of patients who died because of circulatory morbidity (ICD-9 401-443) before turning 65 years old were used. Each schizophrenia case was then matched with two mentally healthy controls for the age and sex, and date of laboratory examination. Clinical data of all subjects were obtained by reviewing medical records.

RESULTS

Totally, 81 patients with schizophrenia who died from circulatory diseases at mean ages of 48.0 ± 10.7 years were investigated. The mean age at the final acute psychiatric hospitalization was 43.0 ± 10.9 years. Multivariate analysis showed that elevated fasting serum glucose levels (95% confidence interval [CI] for odds ratio (OR) = 1.00-1.03), blood leukocyte counts (95% CI for odds ratio (OR) = 1.07-1.55), and heart rates on electrocardiogram (95% CI for OR = 1.04-1.10) in the final psychiatric hospitalization collectively provided the predictive validity for premature circulatory death.

CONCLUSION

Systemic inflammatory activation and autonomic nervous system dysfunction along with dysregulation of glucose metabolism rather than lipids could be the physiological characteristics of schizophrenia patients at risk of premature circulatory mortality.

Gastric Bypass Reduces Symptoms and Hormonal Responses in Hypoglycemia

Gastric bypass (GBP) surgery, one of the most common bariatric procedures, induces weight loss and metabolic effects. The mechanisms are not fully understood, but reduced food intake and effects on gastrointestinal hormones are thought to contribute. We recently observed that GBP patients have lowered glucose levels and frequent asymptomatic hypoglycemic episodes. Here, we subjected patients before and after undergoing GBP surgery to hypoglycemia and examined symptoms and hormonal and autonomic nerve responses. Twelve obese patients without diabetes (8 women, mean age 43.1 years [SD 10.8] and BMI 40.6 kg/m(2) [SD 3.1]) were examined before and 23 weeks (range 19-25) after GBP surgery with hyperinsulinemic-hypoglycemic clamp (stepwise to plasma glucose 2.7 mmol/L). The mean change in Edinburgh Hypoglycemia Score during clamp was attenuated from 10.7 (6.4) before surgery to 5.2 (4.9) after surgery. There were also marked postsurgery reductions in levels of glucagon, cortisol, and catecholamine and the sympathetic nerve responses to hypoglycemia. In addition, growth hormone displayed a delayed response but to a higher peak level. Levels of glucagon-like peptide 1 and gastric inhibitory polypeptide rose during hypoglycemia but rose less postsurgery compared with presurgery. Thus, GBP surgery causes a resetting of glucose homeostasis, which reduces symptoms and neurohormonal responses to hypoglycemia. Further studies should address the underlying mechanisms as well as their impact on the overall metabolic effects of GBP surgery.

Alterations in heart rate variability during everyday life are linked to insulin resistance. A role of dominating sympathetic over parasympathetic nerve activity?

Aims

To evaluate the role of the autonomic nervous system (ANS) in the development of insulin resistance (IR) and assess the relationship between IR and activity of ANS using power spectrum analysis of heart rate variability (HRV).

Subjects and methods

Twenty-three healthy first-degree relatives of patients with type 2 diabetes (R) and 24 control subjects without family history of diabetes (C) group-matched for age, BMI and sex were included. Insulin sensitivity (M value) was assessed by hyperinsulinemic (56 mU/m²/min) euglycemic clamp. Activity of the ANS was assessed using power spectrum analysis of HRV in long-term recordings, i.e., 24-h ECG monitoring, and in short-term recordings during manoeuvres activating the ANS. Computed tomography was performed to estimate the amount and distribution of abdominal adipose tissue.

Results

Insulin sensitivity (M value, mg/kg lbm/min) did not differ significantly between the R and C groups. Total spectral power (P_tot) and very low-frequency (P_VLF) power was lower in R than C during 24 h ECG-recordings (p = 0.02 and p = 0.03). The best fit multiple variable linear regression model (r² = 0.37, p < 0.001 for model) indicated that body composition (BMI) and long-term low to high frequency (LF/HF) power ratio (std β = −0.46, p = 0.001 and std β = −0.28, p = 0.003, respectively) were significantly and independently associated with the M value.

Conclusion

Altered heart rate variability, assessed by power spectrum analysis, during everyday life is linked to insulin resistance. The data suggest that an increased ratio of sympathetic to parasympathetic nerve activity, occurring via both inherited and acquired mechanisms, could potentially contribute to the development of type 2 diabetes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0411-8) contains supplementary material, which is available to authorized users.

HEART RATE VARIABILITY IN METABOLICALLY HEALTHY AND METABOLICALLY UNHEALTHY OBESE PREMENOPAUSAL WOMEN

Content

Metabolically healthy obese (MHO) individuals are characterized by absence of metabolic syndrome. The role of autonomic nervous system in metabolic profile of obese subjects has not been sufficiently investigated.

Objective

We analyzed heart rate variability (HRV) in MHO and metabolically unhealthy obese (MUO) premenopausal women.

Design

In 42 women metabolic profile was defined as MHO and MUO.

Subjects and Methods

For metabolic profile Wildman, IDF and HOMA-IR criteria were used. Autonomic nervous system activity was assessed by analysis of heart rate variability.

Results

There was no significant difference in HRV between MHO and MUO premenopausal women. In Wildman division, after adjustment for systolic blood pressure, RRNN and LF/HF were statistically different between groups (p=0.0001; p=0.029). In IDF division, adjusting for waist circumference, LF was significantly different between groups (p=0.004). In HOMA division, adjusting for HOMA, groups were different in SDNN (p=0.009), RMSSD (p=0.002), pNN50 (p=0.003), HF(p=0.002) and TP (p=0.005).

Conclusions

Autonomic nervous system does not share the leading role in premenopausal women metabolic profile. The differences in HRV between MHO and MUO women depend on the metabolic health criteria. Systolic blood pressure, HOMA and waist circumference have significant effect on HRV differences between MHO and MUO premenopausal women.

Postprandial insulin action relies on meal composition and hepatic parasympathetics: dependency on glucose and amino acids: Meal, parasympathetics & insulin action

Insulin sensitivity (IS) increases following a meal. Meal composition affects postprandial glucose disposal but still remains unclear which nutrients and mechanisms are involved. We hypothesized that gut-absorbed glucose and amino acids stimulate hepatic parasympathetic nerves, potentiating insulin action. Male Sprague-Dawley rats were 24 h fasted and anesthetized. Two series of experiments were performed. (A) IS was assessed before and after liquid test meal administration (10 ml.kg(-1), intraenteric): glucose + amino acids + lipids (GAL, n=6); glucose (n=5); amino acids (n=5); lipids (n=3); glucose + amino acids (GA, n=9); amino acids + lipids (n=3); and glucose + lipids (n=4). (B) Separately, fasted animals were submitted to hepatic parasympathetic denervation (DEN); IS was assessed before and after GAL (n=4) or GA administration (n=4). (A) Both GAL and GA induced significant insulin sensitization. GAL increased IS from 97.9±6.2 mg glucose/kg bw (fasting) to 225.4±18.3 mg glucose/kg bw (P<0.001; 143.6±26.0% potentiation of IS); GA increased IS from 109.0±6.6 to 240.4±18.0 mg glucose/kg bw (P<0.001; 123.1±13.4% potentiation). None of the other meals potentiated IS. (B) GAL and GA did not induce a significant insulin sensitization in DEN animal. To achieve maximal insulin sensitization following a meal, it is required that gut-absorbed glucose and amino acids trigger a vagal reflex that involves hepatic parasympathetic nerves.

Cardiac coherence, self-regulation, autonomic stability, and psychosocial well-being

The ability to alter one’s emotional responses is central to overall well-being and to effectively meeting the demands of life. One of the chief symptoms of events such as trauma, that overwhelm our capacities to successfully handle and adapt to them, is a shift in our internal baseline reference such that there ensues a repetitive activation of the traumatic event. This can result in high vigilance and over-sensitivity to environmental signals which are reflected in inappropriate emotional responses and autonomic nervous system dynamics. In this article we discuss the perspective that one’s ability to self-regulate the quality of feeling and emotion of one’s moment-to-moment experience is intimately tied to our physiology, and the reciprocal interactions among physiological, cognitive, and emotional systems. These interactions form the basis of information processing networks in which communication between systems occurs through the generation and transmission of rhythms and patterns of activity. Our discussion emphasizes the communication pathways between the heart and brain, as well as how these are related to cognitive and emotional function and self-regulatory capacity. We discuss the hypothesis that self-induced positive emotions increase the coherence in bodily processes, which is reflected in the pattern of the heart’s rhythm. This shift in the heart rhythm in turn plays an important role in facilitating higher cognitive functions, creating emotional stability and facilitating states of calm. Over time, this establishes a new inner-baseline reference, a type of implicit memory that organizes perception, feelings, and behavior. Without establishing a new baseline reference, people are at risk of getting “stuck” in familiar, yet unhealthy emotional and behavioral patterns and living their lives through the automatic filters of past familiar or traumatic experience.

Nonreassuring fetal heart rate decreases heart rate variability in newborn infants

BACKGROUND

Nonreassuring fetal status (NRFS) refers to a compromised fetal condition which implies hypoxia. The influence of intrapartum hypoxia on autonomic nervous system function in early postnatal life is unknown. This study explored the influence of NRFS on the heart rate variability (HRV) of newborn infants.

METHODS

Singleton newborn infants delivered through Cesarean delivery (CD) with indications of elective purpose (n = 32), dystocia (n = 29), or NRFS (n = 22), and through vaginal birth (VB) (n = 80) were consecutively collected. HRV parameters including standard deviation of average NN intervals (SDANN), low frequency (LF), high frequency (HF), LF%, HF%, and total power (TP), were obtained for analysis in 3 days postpartum. An independent t-test or one-way ANOVA was used to compare differences in numeric data.

RESULTS

SDANN, HF, HF%, and TP of newborn infants in the VB group were significantly higher than those in the CD group. The NRFS group had significantly lower SDANN, HF, and TP than those of the elective group, and significantly lower HF, HF%, and TP than those of the dystocia group.

CONCLUSIONS

Newborn infants delivered through Cesarean section had lower HRV, especially those who experienced NRFS during labor. The long-term effects of changes of HRV in neonates require further evaluation.

Variability in HOMA-IR, lipoprotein profile and selected hormones in young active men

Resistance to insulin actions is contributing to many metabolic disturbances. Such factors as age, sex, nutrition, body fat, and physical activity determine body insulin resistance. Present study attempted to asses insulin resistance and its metabolic effects with respect to energy intake in young, lean, and active men. A total of 87 men aged 18-23 participated in the study. Plasma levels of glucose, insulin, lipoproteins, cortisol, and TSH were determined. Insulin resistance was expressed as Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) and calculated using homeostatic model. The median value of HOMA-IR (1.344) was used to divide subjects into two groups. Men did not differ in anthropometric parameters, daily physical activity, and plasma TSH and cortisol levels. However, in men with higher HOMA-IR significantly lower daily energy intake was observed concomitantly with higher TG, TC, and HDL-C concentrations in plasma versus their counterparts with lower HOMA-IR. Exclusively in subjects with higher HOMA-IR significant and positive correlation was noted between HOMA-IR and TC and LDL-C. We concluded that despite a normal body weight and physical activity, a subset of young men displayed unfavorable changes in insulin sensitivity and lipid profile, probably due to insufficient energy intake.

Food-intake dysregulation in type 2 diabetic Goto-Kakizaki rats: hypothesized role of dysfunctional brainstem thyrotropin-releasing hormone and impaired vagal output

Thyrotropin-releasing hormone (TRH), a neuropeptide contained in neural terminals innervating brainstem vagal motor neurons, enhances vagal outflow to modify multisystemic visceral functions and food intake. Type 2 diabetes (T2D) and obesity are accompanied by impaired vagal functioning. We examined the possibility that impaired brainstem TRH action may contribute to the vagal dysregulation of food intake in Goto-Kakizaki (GK) rats, a T2D model with hyperglycemia and impaired central vagal activation by TRH. Food intake induced by intracisternal injection of TRH analog was reduced significantly by 50% in GK rats, compared to Wistar rats. Similarly, natural food intake in the dark phase or food intake after an overnight fast was reduced by 56-81% in GK rats. Fasting (48h) and refeeding (2h)-associated changes in serum ghrelin, insulin, peptide YY, pancreatic polypeptide and leptin, and the concomitant changes in orexigenic or anorexigenic peptide expression in the brainstem and hypothalamus, all apparent in Wistar rats, were absent or markedly reduced in GK rats, with hormone release stimulated by vagal activation, such as ghrelin and pancreatic polypeptide, decreased substantially. Fasting-induced Fos expression accompanying endogenous brainstem TRH action decreased by 66% and 91%, respectively, in the nucleus tractus solitarius (NTS) and the dorsal motor nucleus of the vagus (DMV) in GK rats, compared to Wistar rats. Refeeding abolished fasting-induced Fos-expression in the NTS, while that in the DMV remained in Wistar but not GK rats. These findings indicate that dysfunctional brainstem TRH-elicited vagal impairment contributes to the disturbed food intake in T2D GK rats, and may provide a pathophysiological mechanism which prevents further weight gain in T2D and obesity.

Adiposity, muscle, and physical activity: predictors of perturbations in heart rate variability

OBJECTIVES

This study examines cross-sectional associations of indices of adiposity, lean body mass, and physical activity, with heart rate variability (HRV), a marker for parasympathetic cardiac vagal control.

METHODS

The study population consists of 360 officers from the Buffalo New York Police Department. Indices of adiposity include body mass index, waist circumference, and a fat-mass index taken from dual-energy X-ray absorptiometry (DEXA) measurements. Lean body mass indices were derived from DEXA measurements of trunk mass and extremity lean mass. Physical activity was measured using a 7-day self-report questionnaire. HRV was obtained from 5-min electrocardiogram measurements by means of parametric spectral analysis resulting in estimates for high-frequency (HF) and low-frequency (LF) HRV.

RESULTS

Both HF and LF HRV were significantly associated with markers for adiposity, two components of lean mass and physical activity with all associations being in the expected direction except that for trunk lean mass. This unexpected result is explained by the possibility that trunk mass is a marker for visceral adiposity rather than lean mass. Body mass index did not explain any additional variance in HRV above and beyond waist circumference and the DEXA indices.

CONCLUSIONS

Higher levels of physical activity, lower levels of markers for central adiposity and higher lean mass in the extremities predict higher levels of HRV in this population of police officers. This association between modifiable risk factors and markers for autonomic function suggest possible interventions that may improve health and performance.

Correlation between glycemic trends assessed by 24 h continuous monitoring and autonomic activity in patients with recent onset type 2 diabetes

We observe, in patients with type 2 diabetes of recent onset, the activity of the autonomic nervous system and glucose metabolic impairment. The data indicate the hyperactivity of the sympathetic and minimal changes in glucose values. The role played by glycemia appeared to be less important than that represented by insulin resistance.

Resilience Training Program Reduces Physiological and Psychological Stress in Police Officers

Research suggests that police work is among the most stressful occupations in the world and officers typically suffer a variety of physiological, psychological, and behavioral effects and symptoms. Officers operating under severe or chronic stress are likely to be at greater risk of error, accidents, and overreactions that can compromise their performance, jeopardize public safety, and pose significant liability costs to the organization. Therefore, this study explored the nature and degree of physiological activation typically experienced of officers on the job and the impact of the Coherence Advantage resilience and performance enhancement training on a group of police officers from Santa Clara County, California. Areas assessed included vitality, emotional well-being, stress coping and interpersonal skills, work performance, workplace effectiveness and climate, family relationships, and physiological recalibration following acute stressors. Physiological measurements were obtained to determine the real-time cardiovascular impact of acutely stressful situations encountered in highly realistic simulated police calls used in police training and to identify officers at increased risk of future health challenges. The resilience-building training improved officers' capacity to recognize and self-regulate their responses to stressors in both work and personal contexts. Officers experienced reductions in stress, negative emotions, depression, and increased peacefulness and vitality as compared to a control group. Improvements in family relationships, more effective communication and cooperation within work teams, and enhanced work performance also were noted. Heart rate and blood pressure measurements taken during simulated police call scenarios showed that acutely stressful circumstances typically encountered on the job result in a tremendous degree of physiological activation, from which it takes a considerable amount of time to recover. Autonomic nervous system assessment based on heart rate variability (HRV) analysis of 24-hour electrocardiogram (ECG) recordings revealed that 11% of the officers were at higher risk for sudden cardiac death and other serious health challenges. This is more than twice the percentage typically found in the general population and is consistent with epidemiological data indicating that police officers have more than twice the average incidence of cardiovascular-related disease. The data suggest that training in resilience building and self-regulation skills could significantly benefit police organizations by improving judgment and decision making and decreasing the frequency of onthe-job driving accidents and the use of excessive force in high-stress situations. Potential outcomes include fewer citizens' complaints, fewer lawsuits, decreased organizational liabilities, and increased community safety. Finally, this study highlights the value of 24-hour HRV analysis as a useful screening tool to identify officers who are at increased risk, so that efforts can be made to reverse or prevent the onset of disease in these individuals.

Dysregulation of the Autonomic Nervous System Can Be a Link between Visceral Adiposity and Insulin Resistance

OBJECTIVE

To evaluate the interplay among abdominal adipose tissue distribution, the cortisol axis, the autonomic nervous system, and insulin resistance.

RESEARCH METHODS AND PROCEDURES

Two age-, sex-, and BMI-matched groups were studied. Fifteen subjects were first-degree relatives of patients with type 2 diabetes (R), and 15 had no family history of diabetes (controls, C). A hyperinsulinemic euglycemic clamp, cortisol measurements, and analysis of heart rate variability (HRV) were performed. Computed tomography was performed in a subgroup (n = 9 + 9) to determine abdominal adipose tissue distribution.

RESULTS

R tended to be less insulin-sensitive than C (M value 9.2 +/- 1.0 vs 10.3 +/- 0.7 mg/kg per minute, not significant). Stimulation with tetracosactin or corticotropin releasing hormone yielded lower peak serum cortisol levels in R (p = 0.03 and p = 0.06, respectively). The amount of visceral abdominal fat (VAT) tended to be greater in R. In all subjects, VAT was negatively correlated to insulin sensitivity (r = -0.93, p < 0.001). There was a positive association between VAT and resting heart rate (r = 0.70, p = 0.003) and sympathetic/parasympathetic ratio in HRV assessment after tilt (r = 0.53, p = 0.03). Subcutaneous abdominal tissue was not associated with insulin sensitivity or any of the hormonal or HRV assessments.

DISCUSSION

Subjects genetically predisposed for type 2 diabetes had a tendency toward a larger amount of VAT and to lower insulin sensitivity compared with control subjects. The amount of visceral fat was strongly associated with insulin resistance and signs of a high ratio of sympathetic vs. parasympathetic reactivity. A large amount of visceral fat may act in concert with sympathetic/parasympathetic imbalance to promote the development of insulin resistance, and this may be partly independent of genetic background.

Measurement fidelity of heart rate variability signal processing: the devil is in the details

Heart rate variability (HRV) is a particularly valuable quantitative marker of the flexibility and balance of the autonomic nervous system. Significant advances in software programs to automatically derive HRV have led to its extensive use in psychophysiological research. However, there is a lack of systematic comparisons across software programs used to derive HRV indices. Further, researchers report meager details on important signal processing decisions making synthesis across studies challenging. The aim of the present study was to evaluate the measurement fidelity of time- and frequency-domain HRV indices derived from three predominant signal processing software programs commonly used in clinical and research settings. Triplicate ECG recordings were derived from 20 participants using identical data acquisition hardware. Among the time-domain indices, there was strong to excellent correspondence (ICC(avg)=0.93) for SDNN, SDANN, SDNNi, rMSSD, and pNN50. The frequency-domain indices yielded excellent correspondence (ICC(avg)=0.91) for LF, HF, and LF/HF ratio, except for VLF which exhibited poor correspondence (ICC(avg)=0.19). Stringent user-decisions and technical specifications for nuanced HRV processing details are essential to ensure measurement fidelity across signal processing software programs.

Cardiac vagal control as a prospective predictor of anxiety in women diagnosed with breast cancer

Low cardiac vagal control (CVC) has been associated with state and trait anxiety and anxiety spectrum disorders. Studies indicate that diagnosis and treatments for breast cancer may be associated with anxiety. The current study examined whether CVC prospectively predicted a trajectory of change in anxiety following breast cancer diagnosis. Forty-three women diagnosed with non-metastatic breast cancer completed the Taylor Manifest Anxiety Scale and the Perceived Stress Scale, and a 5-min resting electrocardiographic (ECG) segment was recorded. Self-report measures were completed approximately every 3 months for a year. Respiratory sinus arrhythmia (RSA) significantly predicted the trajectory of change in anxiety over the follow-up period: participants with higher baseline RSA evidenced decreasing anxiety, whereas those with lower baseline RSA had increasing anxiety. These results are consistent with the hypothesis that CVC facilitates the modulation of anxiety in women coping with significant stressors of breast cancer diagnosis and treatment.

Air pollution and incidence of hypertension and diabetes mellitus in black women living in Los Angeles

BACKGROUND

Evidence suggests that longer-term exposure to air pollutants over years confers higher risks of cardiovascular morbidity and mortality than shorter-term exposure. One explanation is that the cumulative adverse effects that develop over longer durations lead to the genesis of chronic disease. Preliminary epidemiological and clinical evidence suggests that air pollution may contribute to the development of hypertension and type 2 diabetes mellitus.

METHODS AND RESULTS

We used Cox proportional hazards models to assess incidence rate ratios (IRRs) and 95% confidence intervals (CIs) for incident hypertension and diabetes mellitus associated with exposure to fine particulate matter (PM(2.5)) and nitrogen oxides in a cohort of black women living in Los Angeles. Pollutant levels were estimated at participants' residential addresses with land use regression models (nitrogen oxides) and interpolation from monitoring station measurements (PM(2.5)). Over follow-up from 1995 to 2005, 531 incident cases of hypertension and 183 incident cases of diabetes mellitus occurred. When pollutants were analyzed separately, the IRR for hypertension for a 10-μg/m(3) increase in PM(2.5) was 1.48 (95% CI, 0.95-2.31), and the IRR for the interquartile range (12.4 parts per billion) of nitrogen oxides was 1.14 (95% CI, 1.03-1.25). The corresponding IRRs for diabetes mellitus were 1.63 (95% CI, 0.78-3.44) and 1.25 (95% CI, 1.07-1.46). When both pollutants were included in the same model, the IRRs for PM(2.5) were attenuated and the IRRs for nitrogen oxides were essentially unchanged for both outcomes.

CONCLUSION

Our results suggest that exposure to air pollutants, especially traffic-related pollutants, may increase the risk of type 2 diabetes mellitus and possibly of hypertension.

Sympathetic overactivity precedes metabolic dysfunction in a fructose model of glucose intolerance in mice

Consumption of high levels of fructose in humans and animals leads to metabolic and cardiovascular dysfunction. There are questions as to the role of the autonomic changes in the time course of fructose-induced dysfunction. C57/BL male mice were given tap water or fructose water (100 g/l) to drink for up to 2 mo. Groups were control (C), 15-day fructose (F15), and 60-day fructose (F60). Light-dark patterns of arterial pressure (AP) and heart rate (HR), and their respective variabilities were measured. Plasma glucose, lipids, insulin, leptin, resistin, adiponectin, and glucose tolerance were quantified. Fructose increased systolic AP (SAP) at 15 and 60 days during both light (F15: 123 ± 2 and F60: 118 ± 2 mmHg) and dark periods (F15: 136 ± 4 and F60: 136 ± 5 mmHg) compared with controls (light: 111 ± 2 and dark: 117 ± 2 mmHg). SAP variance (VAR) and the low-frequency component (LF) were increased in F15 (>60% and >80%) and F60 (>170% and >140%) compared with C. Cardiac sympatho-vagal balance was enhanced, while baroreflex function was attenuated in fructose groups. Metabolic parameters were unchanged in F15. However, F60 showed significant increases in plasma glucose (26%), cholesterol (44%), triglycerides (22%), insulin (95%), and leptin (63%), as well as glucose intolerance. LF of SAP was positively correlated with SAP. Plasma leptin was correlated with triglycerides, insulin, and glucose tolerance. Results show that increased sympathetic modulation of vessels and heart preceded metabolic dysfunction in fructose-consuming mice. Data suggest that changes in autonomic modulation may be an initiating mechanism underlying the cluster of symptoms associated with cardiometabolic disease.

Effects of adrenaline on whole-body glucose metabolism and insulin-mediated regulation of glycogen synthase and PKB phosphorylation in human skeletal muscle

In the present study, we investigated the effect of adrenaline on insulin-mediated regulation of glucose and fat metabolism with focus on regulation of skeletal muscle PKB, GSK-3, and glycogen synthase (GS) phosphorylation. Ten healthy subjects (5 men and 5 women) received a 240-minute intravenous infusion of adrenaline (0.05 μg/[kg min]) or saline; after 120 minutes, a hyperinsulinemic-euglycemic clamp was added. Adrenaline infusion increased blood glucose concentration by approximately 50%, but the hyperinsulinemic clamp normalized blood glucose within 30 minutes. Glucose infusion rate during the last hour was approximately 60% lower during adrenaline infusion compared with saline (4.3 ± 0.5 vs 11.2 ± 0.6 mg/kg lean body mass per minute). Insulin increased PKB Ser⁴⁷³, PKB Thr³⁰⁸, and GSK-3β Ser⁹ phosphorylation in skeletal muscles; coinfusion of adrenaline did not influence insulin-stimulated PKB and GSK-3 phosphorylation. Adrenaline alone did not influence phosphorylation of PKB and GSK-3β. Insulin increased GS fractional activity and decreased GS Ser⁶⁴¹ and Ser⁶⁴⁵,⁶⁴⁹,⁶⁵³,⁶⁵⁷ phosphorylation. In the presence of adrenaline, insulin did neither activate GS nor dephosphorylate GS Ser⁶⁴¹. Surprisingly, GS Ser⁷ phosphorylation was not influenced by adrenaline. Adrenaline increased plasma lactate concentration; and muscle glycogen content was reduced in skeletal muscle the day after adrenaline infusion, supporting that insulin does not stimulate glycogen synthesis in skeletal muscles when adrenaline is present. In conclusion, adrenaline did not influence basal or insulin-stimulated PKB and GSK-3β phosphorylation in muscles, but completely blocked insulin-mediated GS activation and Ser⁶⁴¹ dephosphorylation. Still, insulin normalized adrenaline-mediated hyperglycemia.

Gender Differences in Glucose Variability after Severe Trauma

Gender differences in the physiological response to trauma can affect outcome. Both hyperglycemia and blood glucose (BG) variability predict a poor outcome after trauma. This study examined the hypothesis that both BG levels and the degree of BG variability after trauma are gender-specific and correlate with mortality and morbidity. A retrospective observational cohort study of 1915 trauma patients requiring critical care was performed. Admission BG as well as all BG values obtained during the first week while in the intensive care unit were analyzed. In each patient, the mean BG and the degree of BG variability were calculated. A total of 1560 males and 355 females were studied with an overall mortality rate of 12 per cent. Seventy-six per cent of deaths had a BG greater than 125 mg/dL on admission and as BG variability worsened, the mortality rate also increased. There was a significant difference in male BG variability when comparing survivors with nonsurvivors. Female BG variability did not predict mortality. Failed glucose homeostasis is an important marker of endocrine dysfunction after severe injury. Increased BG variability in males is associated with a higher mortality rate. In females, mortality cannot be predicted based on BG levels or BG variability. These data have significant implications for gender-related differences in postinjury management.

The relationship of autonomic imbalance, heart rate variability and cardiovascular disease risk factors

Cardiovascular disease (CVD) is the leading cause of death and disability worldwide. The understanding of the risk factors for CVD may yield important insights into the prevention, etiology, course, and treatment of this major public health concern. Autonomic imbalance, characterized by a hyperactive sympathetic system and a hypoactive parasympathetic system, is associated with various pathological conditions. Over time, excessive energy demands on the system can lead to premature aging and diseases. Therefore, autonomic imbalance may be a final common pathway to increased morbidity and mortality from a host of conditions and diseases, including cardiovascular disease. Heart rate variability (HRV) may be used to assess autonomic imbalances, diseases and mortality. Parasympathetic activity and HRV have been associated with a wide range of conditions including CVD. Here we review the evidence linking HRV to established and emerging modifiable and non-modifiable CVD risk factors such as hypertension, obesity, family history and work stress. Substantial evidence exists to support the notion that decreased HRV precedes the development of a number of risk factors and that lowering risk profiles is associated with increased HRV. We close with a suggestion that a model of autonomic imbalance may provide a unifying framework within which to investigate the impact of risk factors, including psychosocial factors and work stress, on cardiovascular disease.

Cytisine induces autonomic cardiovascular responses via activations of different nicotinic receptors

Nicotinic cholinergic receptors mediate autonomic transmission at ganglia. However, whether different subtypes of nicotinic cholinergic receptors expressed in autonomic ganglia elicit distinct roles in mediating sympathetic and parasympathetic regulations remain to be defined. In this study, we observed that different subtypes of nicotinic receptors were responsible for the sympathetic and parasympathetic cardiovascular responses. In urethane anesthetized mice, intravenous injection with cytisine, a non-selective nicotinic agonist, induced a brief but pronounced decrease in heart rate, followed by increases in heart rate and arterial blood pressure. The bradycardic response was blocked by atropine, and the pressor response was blocked by prazosin, confirming that these responses were parasympathetic and sympathetic activities, respectively. Hexamethonium, a ganglionic blocker, blocked both sympathetic and parasympathetic responses. Pretreatment with methyllycaconitine citrate, a selective alpha7 nicotinic receptor antagonist, significantly attenuated cytisine-induced sympathetic response with little effect on the parasympathetic response. In contrast, pretreatment with dihydro-beta-erythroidine hydrobromide, a selective alpha4beta2 nicotinic receptor antagonist, blocked cytisine-induced parasympathetic response but not the sympathetic response. Pretreatment with dihydro-beta-erythroidine hydrobromide also blocked baroreflex associated parasympathetic bradycardic response. Moreover, treatment with nicotine induced a bradycardic response without a significant pressor response, which was also attenuated by dihydro-beta-erythroidine hydrobromide. Collectively, these data suggest that different nicotinic receptors play distinct roles in sympathetic and parasympathetic ganglia. Specifically, activations of alpha7 and alpha4beta2 nicotinic receptors are involved in cytisine-induced cardiovascular sympathetic and parasympathetic responses, respectively.

Association of serum amyloid A levels with adipocyte size and serum levels of adipokines: differences between men and women

The aim of this study was to characterize the association between adipocyte enlargement and circulating levels of serum amyloid A (SAA). Furthermore, we wanted to search for possible associations with measures of glycemic control and levels of circulating adipokines and/or inflammatory markers in men and women with a large range in body mass index. The study cohort consisted of 167 subjects, 114 non-diabetic and 53 with Type 2 diabetes. Adipocyte diameter as well as circulating levels of SAA, C-reactive protein (CRP), adiponectin, leptin, interleukin-6, tumor necrosis factor alpha, glucose and insulin were measured. Women had higher serum levels of SAA than men (p=0.044). SAA levels were weakly but positively correlated with BMI (p=0.043) and % body fat (p=0.027) in all subjects as well as subcutaneous adipocyte diameter (p=0.034) in women. Furthermore, in all subjects we found correlations between SAA levels and levels of CRP (p<0.001), interleukin-6 (p<0.001), leptin (p=0.003), insulin (p=0.006), HbA1c (p=0.02) and HOMA-IR (p=0.002). A majority of the correlations were strongest in women. In conclusion, serum levels of SAA are strongly correlated with serum levels of inflammatory markers as well as measures of glycemic control. There seems to be large sex differences in these associations suggesting that sex-specific factors need to be considered when analyzing SAA levels in relation to metabolic disease.

CD36 single nucleotide polymorphism is associated with variation in low-density lipoprotein-cholesterol in young Japanese men

Macrophages uptake oxidized low-density lipoprotein (LDL) via a scavenger receptor such as CD36 from plasma, and then become foam cells. We examined the association of CD36 gene single nucleotide polymorphisms (SNPs) with certain metabolic characteristics in a young male Japanese population (n = 494). The G allele in a SNP located at +30215 on the 3'-untranslated region (UTR) was significantly correlated with the plasma LDL-cholesterol concentrations (r = 0.13, p <0.01). The difference in LDL-cholesterol concentrations was 10 mg dl(-1) between GG- and AA-genotype carriers (p <0.05). The CD36 gene SNP is a novel maker of the variation in the LDL-cholesterol levels in young Japanese men.

Risk of type 2 diabetes among individuals with high and low glomerular filtration rates

AIMS/HYPOTHESIS

Metabolic abnormalities frequently develop prior to the diagnosis of type 2 diabetes and chronic kidney disease. However, it is not known whether GFR predicts the onset of type 2 diabetes.

METHODS

Incident diabetes was ascertained in the Insulin Resistance Atherosclerosis Study (IRAS) (n = 864; age 40-69 years; median follow-up 5.2 years [4.5-6.6 years]; 141 incident cases of diabetes). GFR was estimated by the Modification of Diet in Renal Disease equation. We assessed the relationship between GFR and incident diabetes by logistic regression analysis. Results were adjusted for age, sex, ethnicity, clinic location, BMI, systolic blood pressure, antihypertensive treatment, family history of diabetes, insulin sensitivity and secretion, albumin to creatinine ratio, and levels of triacylglycerols, HDL-cholesterol, plasminogen activator inhibitor-1, and fasting and 2 h glucose.

RESULTS

The relationship between GFR and incident diabetes was not linear. This relationship was statistically significant (p = 0.039) using a restricted cubic polynomial spline for GFR as a regression modelling strategy. Participants were stratified by GFR quintiles. Mean values for GFR from the first to the fifth quintile were 60.8, 71.6, 79.8, 88.2 and 109.0 ml min(-1) 1.73 m(-2). Relative to the fourth quintile, the odds ratios of incident diabetes for the first, second, third and fifth quintiles were 2.32 (95% CI 1.06-5.05), 1.76 (95% CI 0.80-3.88), 1.26 (95% CI 0.56-2.84) and 2.59 (95% CI 1.18-5.65), respectively.

CONCLUSIONS/INTERPRETATION

Individuals in the upper and lower ranges of GFR are at increased risk of future diabetes. GFR and type 2 diabetes may share common pathogenic mechanisms.

Specific subtypes of nicotinic cholinergic receptors involved in sympathetic and parasympathetic cardiovascular responses

Various subtypes of nicotinic cholinergic receptors are expressed in autonomic ganglia. The distinct functional roles of these receptors in autonomic ganglionic transmission to different target organs remain to be elucidated. In this study, we tested the sympathetic and parasympathetic cardiovascular responses to nicotinic agonist and antagonists in urethane-anesthetized mice. Intravenous injection with a nicotinic agonist, 1,1-dimethyl-4-phenylpiperazinium iodide, induced a brief but pronounced decrease in heart rate, followed by significant increases in heart rate and arterial blood pressure. The bradycardic response was blocked by atropine whereas the pressor response was blocked by prazosine, confirming those responses were parasympathetic and sympathetic activities, respectively. The sympathetic response was blocked by methyllycaconitine citrate, a selective alpha 7 nicotinic cholinergic receptor (nAchR) antagonist. The parasympathetic response was blocked by a selective alpha 4 beta 2 nAchR antagonist, dihydro-beta-erythroidine hydrobromide. Moreover, injection with a selective alpha 4 beta 2 nAchR agonist, RJR2403 oxalate, induced a pronounced parasympathetic response with a smaller sympathetic response. Collectively, these data show that activations of alpha 4 beta 2 nAchRs elicits a parasympathetic cardiovascular response and activation of alpha 7 nAchRs elicits a sympathetic cardiovascular response. These data suggest that specific subtypes of nicotinic receptors at the level of the ganglia may play distinct roles in mediating sympathetic or parasympathetic activation.

Urinary incontinence and overactive bladder in patients with heart failure

PURPOSE

We explored the nature of the relationship between heart failure and urinary symptoms, specifically urinary incontinence and overactive bladder.

MATERIALS AND METHODS

An 81-item written survey about urinary incontinence, urgency, frequency, nocturia and other symptoms was administered to hospitalized and clinic patients with heart failure. A medical records review was also conducted to determine types of medications, body mass index and documentation of the New York Heart Association Classification of heart failure.

RESULTS

Of 408 respondents 296 (average age 62.2 years) had information about heart failure stage and urinary symptoms. Of these respondents 45% and 57% reported urinary incontinence and overactive bladder, respectively. Adjusted odds ratio for having overactive bladder over no symptoms for respondents with New York Heart Association Class III or Class IV heart failure was 2.9 (95% CI 1.344-6.250) and for higher fatigue-depression composite was 2.155 (95% CI 1.206-3.860). Adjusted odds ratio for having overactive bladder over frequency/nocturia for respondents with higher body mass index was 1.458 (95% CI 1.087-1.953) and for higher fatigue-depression composite was 1.629 (95% CI 1.038-2.550).

CONCLUSIONS

Urinary incontinence and overactive bladder are prevalent in patients with heart failure. Evidence of late stage heart failure, higher fatigue-depression composite and higher body mass index were associated with overactive bladder. Sex, age and diuretic use were not associated with urinary incontinence and overactive bladder.

Preserved heart rate variability in first-degree relatives of subjects with Type 2 diabetes mellitus without metabolic disorders

AIMS

To investigate the influence of a family history of Type 2 diabetes mellitus (T2DM) on resting heart rate variability in the absence of concomitant metabolic disorders.

METHODS

We studied 55 first-degree relatives (FDRs) of subjects with T2DM and 36 control subjects without any known family history of diabetes. FDRs were recruited from a University Hospital out-patient diabetes clinic. The protocol included: oral glucose tolerance test (30, 60, 90 and 120 min after ingestion of 75 g glucose) blood glucose, plasma insulin, cholesterol and subfractions, triglycerides, leptin and C-reactive protein. Heart rate variability (HRV) at rest was determined by spectral analysis of interbeat intervals recorded during 10 min in the supine position.

RESULTS

HRV was lower in FDRs compared with control subjects (P < 0.05). Multiple regression analysis identified cholesterol (P = 0.014) and triglycerides (P = 0.014) as significant independent predictors (model r = 0.40; P < 0.001) of HRV. Since FDRs had higher values for anthropometric and metabolic variables known to alter HRV, we performed an ancova adjusted for cholesterol and triglycerides and also another analysis in which the groups were comparable for anthropometric and metabolic characteristics. Comparison of FDRs and comparable control subjects revealed no significant difference in HRV (P > 0.05).

CONCLUSIONS

A family history of T2DM, in the absence of concomitant metabolic disorders, does not impair heart rate variability.

The effect of rosiglitazone on orthostatic tolerance during heat exposure in individuals with type II diabetes

BACKGROUND AND METHODS

Twenty-two subjects with type II diabetes and 30 control subjects participated in a 1-year study to examine the effect of rosiglitazone on heart rate variability at rest and the blood pressure, heart rate, and blood flow changes during a change in body position from horizontal to the 45 degrees head up position. To assess nerve damage, latency was measured for sensory nerves in the foot.

RESULTS

The results of the experiments showed that subjects with diabetes had an approximate 50% impairment in sural, medial, and lateral plantar nerve latency. After 1 year of administration of rosiglitazone, there was improvement by about 50% in sural, medial, and lateral nerve plantar latency. The changes in blood flow in the subject with diabetes was less than half that of control subjects, during tilting from the horizontal to the vertical position. Heart rate variability was less during tilt, and the blood pressure change was significantly greater in subjects with diabetes than control subjects (P < 0.01). After administration of rosiglitazone for 1 year, the changes in blood flow, blood pressure, and heart rate, while improving by about half, were not equal to those of age matched controls (P < 0.01).

CONCLUSIONS

The results of the experiments indicate that the insulin sensitizer rosiglitazone cannot reverse all of the damage associated with diabetes to the autonomic nervous system, but much can be reversed.

Metabolic stress in insulin's target cells leads to ROS accumulation - A hypothetical common pathway causing insulin resistance

The metabolic syndrome is a cluster of cardiovascular risk factors, and visceral adiposity is a central component that is also strongly associated with insulin resistance. Both visceral obesity and insulin resistance are important risk factors for the development of type 2 diabetes. It is likely that adipose tissue, particularly in the intra-abdominal depot, is part of a complex interplay involving several tissues and that dysregulated hormonal, metabolic and neural signalling within and between organs can trigger development of metabolic disease. One attractive hypothesis is that many factors leading to insulin resistance are mediated via the generation of abnormal amounts of reactive oxygen species (ROS). There is much evidence supporting that detrimental effects of glucose, fatty acids, hormones and cytokines leading to insulin resistance can be exerted via such a common pathway. This review paper mainly focuses on metabolic and other 'stress' factors that affect insulin's target cells, in particular adipocytes, and it will highlight oxidative stress as a potential unifying mechanism by which these stress factors promote insulin resistance and the development and progression of type 2 diabetes.

Metabolic syndrome: psychosocial, neuroendocrine, and classical risk factors in type 2 diabetes

This article summarizes some aspects of stress in the metabolic syndrome at the psychosocial, tissue, and cellular levels. The metabolic syndrome is a valuable research concept for studying population health and social-biological translation. The cluster of cardiovascular risk factors labeled the metabolic syndrome is linked with low socioeconomic status. Systematic differences in diet and physical activity contribute to social patterning of the syndrome. In addition, psychosocial factors including chronic work stress are linked with its development. Psychosocial factors could lead to metabolic perturbations and increase cardiovascular risk via activation of neuroendocrine responses, for example, in the autonomic nervous system and in several hormonal pathways. High glucocorticoid levels will promote lipid storage in visceral rather than subcutaneous adipose tissue. Adipocytes secrete several proinflammatory cytokines, which considered major contributors to increase in oxidants and cell injury. Upregulation of heme oxygenase 1 (HO-1) and peroxidase in the early development of diabetes produces a decrease in oxidative-mediated injury. Increased HO activity is associated with a significant decrease in superoxide, endothelial cell shedding and blood pressure. Finally, it is proposed that overexpression of glutathione peroxidase in beta cells may protect beta cell deterioration from oxidative stress during development of diabetes and hyperglycemia and this may result in attenuation of beta cell failure. If this proves to be the case, then the scene will be set to develop glutathione peroxidase mimetics for use in preclinical and clinical trials.

Adrenal insufficiency, heart rate variability, and complex biologic systems: a study of 1,871 critically ill trauma patients

BACKGROUND

Reduction in integer heart rate variability (HRVi), one potential measurement of complex biologic systems, is common in ICU patients and is strongly associated with hospital mortality. Adrenal insufficiency (AI) and reduced HRVi are associated with autonomic dysfunction. Failure of the autonomic nervous system can be associated with loss of biologic complexity. We hypothesize decreased HRVi is associated with AI, and HRVi improves after treatment of AI, suggesting "recomplexification" (resumption of normal stress response to injury).

STUDY DESIGN

Of 4,116 trauma ICU admissions from December 2000 to November 2005, 1,871 patients had sufficient physiologic, laboratory, pharmacy, and demographic data for analysis. Seventy-five patients failing cosyntropin-stimulation testing were defined as AI; the remaining 1,796 were defined as no AI. HRVi was calculated as integer heart rate standard deviation over 5-minute intervals. HRVi 10th, 50th (median), and 90th percentiles were calculated over the 72 hours pre-, or poststeroid, or both administration (AI). HRVi percentiles in non-AI patients were evaluated at the same interval and compared with AI using Wilcoxon's rank-sum test. In patients with AI, daily HRVi was computed 3 days before and after steroid administration, and compared between survivors and nonsurvivors.

RESULTS

There were 2.9 million heart-rate intervals measured. HRVi stratified patients with AI (cosyntropin failure), and without AI. HRVi was similar in AI survivors and nonsurvivors before steroid treatment, but differed after treatment. HRVi increased substantially in survivors after steroid administration, yet did not change in nonsurvivors. HRVi does not increase in patients who are unresponsive to steroids and die.

CONCLUSIONS

Reduced heart-rate variability, a potential measurement of complex biologic systems, is associated with cosyntropin-confirmed AI; improved in patients responding to steroid therapy; and is a noninvasive, real-time biomarker suggesting AI.

Fat cell enlargement is an independent marker of insulin resistance and 'hyperleptinaemia'

AIMS/HYPOTHESIS

The aim of this study was to explore whether fat cell size in human subcutaneous and omental adipose tissue is independently related to insulin action and adipokine levels.

MATERIALS AND METHODS

Fat cells were prepared from abdominal subcutaneous biopsies obtained from 49 type 2 diabetic and 83 non-diabetic subjects and from omental biopsies obtained from 37 non-diabetic subjects. Cell size and insulin action on glucose uptake capacity in vitro were assessed in isolated fat cells. Insulin sensitivity in vivo was assessed with euglycaemic-hyperinsulinaemic clamps. Fasting blood samples were collected and adipokines and NEFA were measured.

RESULTS

Negative correlations were found between subcutaneous fat cell size and insulin sensitivity assessed as M-value during clamp and as insulin action on glucose uptake in fat cells in vitro. This was seen in non-diabetic subjects after including age, sex and BMI in the analyses. No such relationship was found in type 2 diabetic subjects. In both groups, subcutaneous fat cell size correlated positively and independently with plasma levels of leptin but not to any of the other assessed adipokines. In non-diabetic subjects, omental fat cell size was independently and negatively correlated with insulin action in subcutaneous, but not omental, fat cells in vitro.

CONCLUSIONS/INTERPRETATION

Fat cell enlargement is associated with insulin resistance in non-diabetic individuals independently of BMI. This was not seen in type 2 diabetic subjects, suggesting that after development of type 2 diabetes other factors, not related to fat cell size, become more important for the modulation of insulin resistance.

Impaired cardiac autonomic function in women with prior gestational diabetes mellitus

BACKGROUND

Cardiac autonomic neuropathy is a common dysfunction in manifest diabetes mellitus and is associated with duration of diabetes and/or an inadequate glycaemic control. Heart rate variability (HRV) reflects autonomic heart function. The aim of the present study was to investigate whether in women with prior gestational diabetes (GD; pre-type 2 diabetes) alterations of cardiac autonomic function can be observed after delivery in relation to insulin sensitivity and glycaemic control.

MATERIALS AND METHODS

Forty-eight healthy women with prior GD were consecutively admitted to the study. HRV was analysed by both time, as well as frequency, domain methods using 24-h Holter monitoring. In addition, 20 women with normal glucose tolerance during and after pregnancy were investigated as control subjects. All women underwent a frequently sampled intravenous glucose tolerance test (FSIGT) for measurement of insulin sensitivity.

RESULTS

Time domain analysis (standard deviation of normal RR intervals; SDNN) showed a reduced HRV in 25 out of the 48 (52%) women with prior GD. Frequency domain analysis revealed that in these 25 subjects both low and high frequency components of power spectral density (reflecting mainly sympathetic respectively parasympathetic activity) were reduced, indicating that sympathetic as well as parasympathetic functional impairment may be assumed. However, a relative predominance of the sympathetic over parasympathetic cardiac function was observed. The impairment of cardiac autonomic function (reduced SDNN) was correlated with HbA1c values and the 2-h blood glucose concentration (oral glucose tolerance test) but not with insulin sensitivity.

CONCLUSION

The present results demonstrate that in 52% of the women examined who had prior GD, an impairment of cardiac sympathetic as well as parasympathetic function was present, which related to glycaemic control, but not to insulin sensitivity. This infers that functional autonomic changes could be an early prognostic indicator in pre-type 2 diabetes.