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

Genetic markers of cardiac autonomic neuropathy in the Kazakh population

BACKGROUND

Cardiac autonomic neuropathy (CAN) is a complication of diabetes mellitus (DM) that increases the risk of morbidity and mortality by disrupting cardiac innervation. Recent evidence suggests that CAN may manifest even before the onset of DM, with prediabetes and metabolic syndrome potentially serving as precursors. This study aims to identify genetic markers associated with CAN development in the Kazakh population by investigating the SNPs of specific genes.

MATERIALS AND METHODS

A case-control study involved 82 patients with CAN (cases) and 100 patients without CAN (controls). A total of 182 individuals of Kazakh nationality were enrolled from a hospital affiliated with the RSE "Medical Center Hospital of the President's Affairs Administration of the Republic of Kazakhstan". 7 SNPs of genes FTO, PPARG, SNCA, XRCC1, FLACC1/CASP8 were studied. Statistical analysis was performed using Chi-square methods, calculation of odds ratios (OR) with 95% confidence intervals (CI), and logistic regression in SPSS 26.0.

RESULTS

Among the SNCA gene polymorphisms, rs2737029 was significantly associated with CAN, almost doubling the risk of CAN (OR 2.03(1.09-3.77), p = 0.03). However, no statistically significant association with CAN was detected with the rs2736990 of the SNCA gene (OR 1.00 CI (0.63-1.59), p = 0.99). rs12149832 of the FTO gene increased the risk of CAN threefold (OR 3.22(1.04-9.95), p = 0.04), while rs1801282 of the PPARG gene and rs13016963 of the FLACC1 gene increased the risk twofold (OR 2.56(1.19-5.49), p = 0.02) and (OR 2.34(1.00-5.46), p = 0.05) respectively. rs1108775 and rs1799782 of the XRCC1 gene were associated with reduced chances of developing CAN both before and after adjustment (OR 0.24, CI (0.09-0.68), p = 0.007, and OR 0.43, CI (0.22-0.84), p = 0.02, respectively).

CONCLUSION

The study suggests that rs2737029 (SNCA gene), rs12149832 (FTO gene), rs1801282 (PPARG gene), and rs13016963 (FLACC1 gene) may be predisposing factors for CAN development. Additionally, SNPs rs1108775 and rs1799782 (XRCC1 gene) may confer resistance to CAN. Only one polymorphism rs2736990 of the SNCA gene was not associated with CAN.

Combining Celiac and Hepatic Vagus Nerve Neuromodulation Reverses Glucose Intolerance and Improves Glycemic Control in Pre- and Overt-Type 2 Diabetes Mellitus

Neurological disorders and type 2 diabetes mellitus (T2DM) are deeply intertwined. For example, autonomic neuropathy contributes to the development of T2DM and continued unmanaged T2DM causes further progression of nerve damage. Increasing glycemic control has been shown to prevent the onset and progression of diabetic autonomic neuropathies. Neuromodulation consisting of combined stimulation of celiac vagal fibers innervating the pancreas with concurrent electrical blockade of neuronal hepatic vagal fibers innervating the liver has been shown to increase glycemic control in animal models of T2DM. The present study demonstrated that the neuromodulation reversed glucose intolerance in alloxan-treated swine in both pre- and overt stages of T2DM. This was demonstrated by improved performance on oral glucose tolerance tests (OGTTs), as assessed by area under the curve (AUC). In prediabetic swine (fasting plasma glucose (FPG) range: 101-119 mg/dL) the median AUC decreased from 31.9 AUs (IQR = 28.6, 35.5) to 15.9 AUs (IQR = 15.1, 18.3) p = 0.004. In diabetic swine (FPG range: 133-207 mg/dL) the median AUC decreased from 54.2 AUs (IQR = 41.5, 56.6) to 16.0 AUs (IQR = 15.4, 21.5) p = 0.003. This neuromodulation technique may offer a new treatment for T2DM and reverse glycemic dysregulation at multiple states of T2DM involved in diabetic neuropathy including at its development and during progression.

Brain Dopamine-Clock Interactions Regulate Cardiometabolic Physiology: Mechanisms of the Observed Cardioprotective Effects of Circadian-Timed Bromocriptine-QR Therapy in Type 2 Diabetes Subjects

Despite enormous global efforts within clinical research and medical practice to reduce cardiovascular disease(s) (CVD), it still remains the leading cause of death worldwide. While genetic factors clearly contribute to CVD etiology, the preponderance of epidemiological data indicate that a major common denominator among diverse ethnic populations from around the world contributing to CVD is the composite of Western lifestyle cofactors, particularly Western diets (high saturated fat/simple sugar [particularly high fructose and sucrose and to a lesser extent glucose] diets), psychosocial stress, depression, and altered sleep/wake architecture. Such Western lifestyle cofactors are potent drivers for the increased risk of metabolic syndrome and its attendant downstream CVD. The central nervous system (CNS) evolved to respond to and anticipate changes in the external (and internal) environment to adapt survival mechanisms to perceived stresses (challenges to normal biological function), including the aforementioned Western lifestyle cofactors. Within the CNS of vertebrates in the wild, the biological clock circuitry surveils the environment and has evolved mechanisms for the induction of the obese, insulin-resistant state as a survival mechanism against an anticipated ensuing season of low/no food availability. The peripheral tissues utilize fat as an energy source under muscle insulin resistance, while increased hepatic insulin resistance more readily supplies glucose to the brain. This neural clock function also orchestrates the reversal of the obese, insulin-resistant condition when the low food availability season ends. The circadian neural network that produces these seasonal shifts in metabolism is also responsive to Western lifestyle stressors that drive the CNS clock into survival mode. A major component of this natural or Western lifestyle stressor-induced CNS clock neurophysiological shift potentiating the obese, insulin-resistant state is a diminution of the circadian peak of dopaminergic input activity to the pacemaker clock center, suprachiasmatic nucleus. Pharmacologically preventing this loss of circadian peak dopaminergic activity both prevents and reverses existing metabolic syndrome in a wide variety of animal models of the disorder, including high fat-fed animals. Clinically, across a variety of different study designs, circadian-timed bromocriptine-QR (quick release) (a unique formulation of micronized bromocriptine-a dopamine D2 receptor agonist) therapy of type 2 diabetes subjects improved hyperglycemia, hyperlipidemia, hypertension, immune sterile inflammation, and/or adverse cardiovascular event rate. The present review details the seminal circadian science investigations delineating important roles for CNS circadian peak dopaminergic activity in the regulation of peripheral fuel metabolism and cardiovascular biology and also summarizes the clinical study findings of bromocriptine-QR therapy on cardiometabolic outcomes in type 2 diabetes subjects.

Effect of trehalose on heart functions in rats model after myocardial infarction: assessment of novel intraventricular pressure and heart rate variability

Background

Myocardial infarctions remain a leading cause of global deaths. Developing novel drugs to target cardiac remodeling after myocardial injury is challenging. There is an increasing interest in exploring natural cardioprotective agents and non-invasive tools like intraventricular pressure gradients (IVPG) and heart rate variability (HRV) analysis in myocardial infarctions. Trehalose (TRE), a natural disaccharide, shows promise in treating atherosclerosis, myocardial infarction, and neurodegenerative disorders.

Objectives

The objective of this study was to investigate the effectiveness of TRE in improving cardiac functions measured by IVPG and HRV and reducing myocardial remodeling following myocardial infarction in rat model.

Methods

Rats were divided into three groups: sham, myocardial infarction (MI), and trehalose-treated MI (TRE) groups. The animals in the MI and TRE groups underwent permanent ligation of the left anterior descending artery. The TRE group received 2% trehalose in their drinking water for four weeks after the surgery. At the end of the experiment, heart function was assessed using conventional echocardiography, novel color M-mode echocardiography for IVPG evaluation, and HRV analysis. After euthanasia, gross image scoring, histopathology, immunohistochemistry, and quantitative real-time PCR were performed to evaluate inflammatory reactions, oxidative stress, and apoptosis.

Results

The MI group exhibited significantly lower values in multiple IVPG parameters. In contrast, TRE administration showed an ameliorative effect on IVPG changes, with results comparable to the sham group. Additionally, TRE improved HRV parameters, mitigated morphological changes induced by myocardial infarction, reduced histological alterations in wall mass, and suppressed inflammatory reactions within the infarcted heart tissues. Furthermore, TRE demonstrated antioxidant, anti-apoptotic and anti-fibrotic properties.

Conclusion

The investigation into the effect of trehalose on a myocardial infarction rat model has yielded promising outcomes, as evidenced by improvements observed through conventional echocardiography, histological analysis, and immunohistochemical analysis. While minor trends were noticed in IVPG and HRV measurements. However, our findings offer valuable insights and demonstrate a correlation between IVPG, HRV, and other traditional markers of echo assessment in the myocardial infarction vs. sham groups. This alignment suggests the potential of IVPG and HRV as additional indicators for future research in this field.

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.

Hepatalin: the missing link in prediabetes, obesity, and type 2 diabetes

Hepatalin is a hormone secreted by the liver in response to pulses of insulin after a mixed nutrient meal, but only if the liver receives two permissive synergistic feeding signals from the stomach. Hepatalin stimulates glucose uptake and storage as glycogen in skeletal muscle, heart, and kidney but not liver, intestines, or adipocytes. Insulin acts primarily on liver and fat. Reduced hepatalin action results in postprandial hyperglycemia, compensatory elevation of insulin secretion, and a resultant shift in partitioning of nutrient energy storage from glycogen in muscle, to fat. Chronic hepatalin suppression leads to a predictable chronology of dysfunctions, first diagnosable as Absence of Meal-induced Insulin Sensitization (AMIS) which progresses to prediabetes, adiposity, and type 2 diabetes. The focus on nutrient partitioning and the role of hepatalin allows AMIS to be diagnosed, prevented, and treated, including through the use of lifestyle interventions.

The Association of Measures of Cardiovascular Autonomic Function, Heart Rate, and Orthostatic Hypotension With Incident Glucose Disorders: The Cardiovascular Health Study

OBJECTIVE

The autonomic nervous system (ANS) innervates pancreatic endocrine cells, muscle, and liver, all of which participate in glucose metabolism. We tested whether measures of cardiovascular ANS function are independently associated with incident diabetes and annual change in fasting glucose (FG) levels as well as with insulin secretion and insulin sensitivity in older adults without diabetes.

RESEARCH DESIGN AND METHODS

Heart rate (HR) and measures of HR variability (HRV) were derived from 24-h electrocardiographic monitoring. Blood pressure, seated and standing, was measured. Cox proportional hazards models and linear mixed models were used to analyze the associations between HRV, HR, and orthostatic hypotension (SBP >20 mmHg decline) and incident diabetes or longitudinal FG change.

RESULTS

The mean annual unadjusted FG change was 1 mg/dL. Higher detrended fluctuation analyses (DFA) values, averaged over 4-11 (DFA1) or 12-20 beats (DFA2)-reflecting greater versus less organization of beat-to-beat intervals-were associated with less FG increase over time (per 1-SD increment: DFA1: -0.49 mg/dL/year [-0.96, -0.03]; DFA2: -0.55 mg/dL/year [-1.02, -0.09]). In mutually adjusted analyses, higher SD of the N-N interval (SDNN) was associated with less FG increase over time (per 1-SD increment: SDNN: -0.62 mg/dL/year [-1.22, -0.03]). Higher values of DFA1, DFA2, and SDNN were each associated with greater insulin secretion and insulin sensitivity but not with incident diabetes. We observed no association of HR or orthostatic hypotension with diabetes or FG change.

CONCLUSIONS

Specific measures of cardiac autonomic function are prospectively related to FG level changes and insulin secretion and action.

Cardiac Autonomic Neuropathy in Patients with Newly Diagnosed Carbohydrate Disturbances

Cardiac autonomic neuropathy (CAN) is a serious complication of diabetes mellitus that can predispose patients to higher risk for cardiovascular death. The aim of the present study was to evaluate the presence of cardiac autonomic neuropathy and sudomotor dysfunction in patients with newly diagnosed carbohydrate disturbances (prediabetes or diabetes) and to assess their relationship to metabolic disturbances and cardiovascular risk. In the present study, we included 160 patients -78 with obesity without carbohydrate disturbances, 52 with prediabetes, and 30 with newly diagnosed diabetes. CAN was diagnosed using cardiovascular reflex tests and sudomotor function was evaluated by SUDOSCAN. Cardiovascular risk was calculated using SCORE and FRMINGHAM risk scores. The prevalence of cardiac autonomic neuropathy was significantly higher in patients with newly diagnosed diabetes. Independently of their glycemic status, the patients who had blood glucose on the 60th-minute of OGTT>8.5 mmol/l had significantly higher prevalence of cardiac autonomic neuropathy (30.2% vs 15.6%, р=0.044). Patients with high cardiovascular risk according to FRAMINGHAM and SCORE had worse heart rate variability scores. Autonomic neuropathy risk assessed by SUDOSCAN was a good predictor for the presence of CAN. In conclusion, CAN has a higher prevalence on patients with newly diagnosed diabetes compared to prediabetic and normoglycemic subjects, while the patients with blood glucose>8.5 mmol/l on the 60th-minute of OGTT have higher prevalence of CAN independently of their glycemic status. SUDOSCAN testing can be used to assess the risk of CAN and to select patients that should undergo further testing.

Nicotinamide attenuates streptozotocin-induced diabetes complications and increases survival rate in rats: role of autonomic nervous system

BACKGROUND

To evaluate the effect of nicotinamide prior to streptozotocin-induced (STZ) diabetes in baroreflex sensitivity and cardiovascular autonomic modulation, and its association with hemodynamics and metabolic parameters.

METHODS

Methods: Male Wistar rats were divided into control (Cont) and STZ-induced diabetes (Diab). Half of the rats from each group received a single dose of nicotinamide (100 mg/Kg) before STZ injection (Cont+NicA and Diab+NicA). All groups were followed-up for 5 weeks.

RESULTS

Body weight loss of more than 40% was observed in Diab throughout the period (Diab: 271.00 ± 12.74 g; Diab+NicA: 344.62 ± 17.82). Increased glycemia was seen in Diab rats (541.28 ± 18.68 mg/dl) while Diab+NicA group had a slight decrease (440.87 ± 20.96 mg/dl). However, insulin resistance was observed only in Diab. In relation to Cont, heart rate, mean blood pressure and diastolic function were reduced when compared to Diab, together with parasympathetic modulation and baroreflex sensitivity. All of these parameters were improved in Diab+NicA when compared to Diab. Improved baroreflex sensitivity and parasympathetic modulation were correlated with glycemia, insulin resistance, and body weight mass. Additionally, Diab+NicA group increased survival rate.

CONCLUSIONS

Results suggest that the association of nicotinamide in STZ-induced diabetic rats prevents most of the expected derangements mainly by preserving parasympathetic and baroreflex parameters.

Altered hormonal and autonomic nerve responses to hypo- and hyperglycaemia are found in overweight and insulin-resistant individuals and may contribute to the development of type 2 diabetes

AIMS/HYPOTHESIS

Results from animal models and some clinical work suggest a role for the central nervous system (CNS) in glucose regulation and type 2 diabetes pathogenesis by modulation of glucoregulatory hormones and the autonomic nervous system (ANS). The aim of this study was to characterise the neuroendocrine response to various glucose concentrations in overweight and insulin-resistant individuals compared with lean individuals.

METHODS

Overweight/obese (HI, n = 15, BMI ≥27.0 kg/m²) and lean (LO, n = 15, BMI <27.0 kg/m²) individuals without diabetes underwent hyperinsulinaemic euglycaemic-hypoglycaemic clamps and hyperglycaemic clamps on two separate occasions with measurements of hormones, Edinburgh Hypoglycaemic Symptom Scale (ESS) score and heart rate variability (HRV). Statistical methods included groupwise comparisons with Mann-Whitney U tests, multilinear regressions and linear mixed models between neuroendocrine responses and continuous metabolic variables.

RESULTS

During hypoglycaemic clamps, there was an elevated cortisol response in HI vs LO (median ΔAUC 12,383 vs 4793 nmol/l × min; p = 0.050) and a significantly elevated adrenocorticotropic hormone (ACTH) response in HI vs LO (median ΔAUC 437.3 vs 162.0 nmol/l × min; p = 0.021). When adjusting for clamp glucose levels, obesity (p = 0.033) and insulin resistance (p = 0.009) were associated with elevated glucagon levels. By contrast, parasympathetic activity was less suppressed in overweight individuals at the last stage of hypoglycaemia compared with euglycaemia (high-frequency power of HRV, p = 0.024). M value was the strongest predictor for the ACTH and P_HF responses, independent of BMI and other variables. There was a BMI-independent association between the cortisol response and ESS score response (p = 0.024). During hyperglycaemic clamps, overweight individuals displayed less suppression of glucagon levels (median ΔAUC -63.4% vs -73.0%; p = 0.010) and more suppression of sympathetic relative to parasympathetic activity (low-frequency/high-frequency power, p = 0.011).

CONCLUSIONS/INTERPRETATION

This study supports the hypothesis that altered responses of insulin-antagonistic hormones and the ANS to glucose fluctuations occur in overweight and insulin-resistant individuals, and that these responses are probably partly mediated by the CNS. Their potential role in development of type 2 diabetes needs to be addressed in future research. Graphical abstract.

Association between Objective Activity Intensity and Heart Rate Variability: Cardiovascular Disease Risk Factor Mediation (CARDIA)

PURPOSE

We evaluated the associations between accelerometer-estimated physical activity (PA) intensity and heart rate variability (HRV) and examined mediation of these associations by glycemic control indices and other cardiovascular disease risk factors.

METHODS

Data were from 1668 participants (X[Combining Overline]age = 45.9 ± 3.5 yr, 58.0% female, 39.9% black) who participated in year 20 (2005-2006) of the Coronary Artery Risk Development in Young Adults Fitness Study. The ActiGraph 7164 estimated participants' mean minutes per day of vigorous-intensity PA (VPA), moderate-intensity PA (MPA), and light-intensity PA (LPA) over 7 d. Three sequential 10-s 12-lead ECG strips were used to derive standard deviation of all normal RR intervals (SDNN) and root mean square of all successive RR intervals (rMSSD) HRV. Mediators representing glycemic control indices included fasting glucose, fasting insulin, and 2-h oral glucose tolerance, with other mediators being traditional cardiovascular disease risk factors. Multiple linear regression assessed independent associations of PA intensity with HRV per 1-SD. Mediation analyses computed the proportion of the PA-HRV association attributable to physiological mediators.

RESULTS

Participants averaged 2.7 ± 6.2 min·d, 33.0 ± 22.0 min·d, and 360.2 ± 83.8 min·d of VPA, MPA, and LPA, respectively, with mean values for SDNN (32.6 ± 22.4 ms) and rMSSD (34.0 ± 24.8 ms) similar. After adjustment for demographic and lifestyle behaviors, VPA was associated with both HRV metrics (SDNN: std beta = 0.06 [0.03, 0.10]; rMSSD: std beta = 0.08 [0.05, 0.12]) and LPA with rMSSD only (std beta = 0.05 [0.01, 0.08]). Fasting insulin and glucose mediated 11.6% to 20.7% of the association of VPA and LPA with HRV, with triglycerides also potentially mediating these associations (range, 9.6%-13.4%).

CONCLUSIONS

Accelerometer-estimated VPA was associated with higher (i.e., improved) HRV. Light-intensity PA also demonstrated a positive association. Mediation analyses suggested these associations may be most attributable to glucose-insulin dynamics.

The Impact of Remote Ischaemic Conditioning on Beat-to-Beat Heart Rate Variability Circadian Rhythm in Healthy Adults

BACKGROUND

Remote ischaemic conditioning (RIC) is an intervention that may exert a protective effect over multiple tissues or organs by regulating neuronal signal transduction. Heart rate variability (HRV) can assess the state of the autonomic nervous system. However, whether RIC can also regulate HRV in humans remains unknown.

METHOD

This was a self-controlled interventional study in which serial beat-to-beat monitoring was performed at the same seven time points (7, 9, and 11 AM; 2, 5, and 8 PM; and 8 AM on the next day) with or without RIC in 50 healthy adults. The seven time points on the RIC day were defined as baseline, 1 hour, 3 hours, 6 hours, 9 hours, 12 hours, and 24 hours after RIC. The RIC protocol consisted of 4×5-minute inflation/deflation in one arm and one thigh cuff at 200 mmHg pressure from 7:20 to 8 AM. This study is registered on ClinicalTrials.gov (NCT02965547).

RESULTS

We included 50 healthy adult volunteers (aged 34.54±12.01 years, 22 men [44%], all Asian). The variables analysed in frequency-domain measures performed as power of low-frequency in normalised units (0.04-0.15 Hz), high-frequency in normalised units (0.15-0.40 Hz), and ratio of low frequency to high frequency. The time-domain parameters standard deviation (SD) of all normal to normal (NN) intervals (SDNN), mean of the 5-minute SD of the NN intervals, SD of the consecutive 5-minute averages of NN intervals, and the root mean square of successive differences of NN intervals, and time-domain parameters calculated from Poincaré plots, SD of the short diagonal axis in Poincaré plot (SD1), SD of the long diagonal axis in Poincaré plot (SD2), and SD1/SD2 were also obtained. The SDNN and SD2 significantly increased 1 hour after RIC (p=0.029 and p=0.045, respectively). Additionally, the SD2 increased a second time 12 hours after RIC (p=0.041), which represented inhibited sympathetic activity.

CONCLUSIONS

Heart rate variability increase and sympathetic inhibition induced by RIC appeared both on the early and delayed protective window of RIC, which may indicate some of the underlying mechanisms by which RIC may offer protection.

Dysregulated Neurovascular Control Underlies Declining Microvascular Functionality in People With Non-alcoholic Fatty Liver Disease (NAFLD) at Risk of Liver Fibrosis

Background/Aims

Increasing evidence shows that non-alcoholic fatty liver disease (NAFLD) is associated with dysregulation of microvascular perfusion independently of established cardio-metabolic risk factors. We investigated whether hepatic manifestations of NAFLD such as liver fibrosis and liver fat are associated with microvascular hemodynamics through dysregulation of neurovascular control.

Methods

Microvascular dilator (post-occlusive reactive hyperemia) and sympathetically mediated constrictor (deep inspiratory breath-hold) responses were measured at the forearm and finger, respectively, using laser Doppler fluximetry. Non-linear complexity-based analysis was used to assess the information content and variability of the resting blood flux (BF) signals, attributable to oscillatory flow-motion activity, and over multiple sampling frequencies.

Results

Measurements were made in 189 adults (113 men) with NAFLD, with (n = 65) and without (n = 124) type 2 diabetes mellitus (T2DM), age = 50.9 ± 11.7 years (mean ± SD). Microvascular dilator and constrictor capacity were both negatively associated with age (r = −0.178, p = 0.014, and r = −0.201, p = 0.007, respectively) and enhanced liver fibrosis (ELF) score (r = −0.155, p = 0.038 and r = −0.418, p < 0.0001, respectively). There was no association with measures of liver fat, obesity or T2DM. Lempel-Ziv complexity (LZC) and sample entropy (SE) of the BF signal measured at the two skin sites were associated negatively with age (p < 0.01 and p < 0.001) and positively with ELF score (p < 0.05 and p < 0.0001). In individuals with an ELF score ≥7.8 the influence of both neurogenic and respiratory flow-motion activity on LZC was up-rated (p < 0.0001).

Conclusion

Altered microvascular network functionality occurs in adults with NAFLD suggesting a mechanistic role for dysregulated neurovascular control in individuals at risk of severe liver fibrosis.

Decreased Vagal Activity and Deviation in Sympathetic Activity Precedes Development of Diabetes

OBJECTIVE

The objective of this study was to examine whether altered heart rate variability (HRV) could predict the risk of diabetes in Asians.

RESEARCH DESIGN AND METHODS

A cohort study was conducted in 54,075 adults without diabetes who underwent 3-min HRV measurement during health checkups between 2011 and 2014 at Kangbuk Samsung Hospital. We analyzed the time domain (SD of the normal-to-normal interval [SDNN] and root mean square differences of successive normal-to-normal intervals [RMSSD]) and the frequency domain (total power, normalized low-frequency power [LF], and normalized high-frequency power [HF] and LF/HF ratio). We compared the risk of diabetes until 2017 according to tertiles of heart rate and HRV variables, with tertile 1 serving as the reference group.

RESULTS

During 243,758.2 person-years, 1,369 subjects were diagnosed with diabetes. Both time and frequency domain variables were lower in the group with diabetes, with the exception of those with normalized LF and LF/HF ratio. In Cox analysis, as SDNN, RMSSD, and normalized HF tertiles increased, the risk of diabetes decreased (hazard ratios [95% CIs] of tertile 3: 0.81 [0.70-0.95], 0.76 [0.65-0.90], and 0.78 [0.67-0.91], respectively), whereas the risk of diabetes increased in the case of heart rate, normalized LF, and LF/HF ratio (hazard ratios [95% CIs] of tertile 3: 1.41 [1.21-1.65], 1.32 [1.13-1.53], and 1.31 [1.13-1.53), respectively) after adjusting for age, sex, BMI, smoking, drinking, systolic blood pressure, lipid level, CRP, and HOMA of insulin resistance.

CONCLUSIONS

Abnormal HRV, especially decreased vagal activity and deviation in sympathovagal imbalance to sympathetic activity, might precede incident diabetes.

Cardiac Autonomic Neuropathy in Obesity, the Metabolic Syndrome and Prediabetes: A Narrative Review

Cardiac autonomic neuropathy (CAN) is a major complication of type 1 and type 2 diabetes mellitus (T1DM and T2DM). The increased morbidity, cardiovascular and all-cause mortality associated with CAN is established from numerous epidemiological studies. However, CAN is increasingly recognised in people with prediabetes (pre-DM) and the metabolic syndrome (MetS) with a reported prevalence up to 11% and 24% respectively. CAN is associated with components of MetS including hypertension and obesity, predating hyperglycaemia. The aetiology of CAN is multifactorial and there is a reciprocal relationship with insulin resistance and MetS. Obstructive sleep apnoea (OSA) is also associated with CAN possibly through MetS and an independent mechanism. An estimated global prevalence of the impaired glucose tolerance (IGT) form of pre-DM of 587 million people by 2045 means CAN will become a major clinical problem. CAN is independently associated with silent myocardial ischaemia, major cardiovascular events, myocardial dysfunction and cardiovascular mortality. Screening for CAN in pre-DM using risk scores with analysis of heart rate variability (HRV) or Sudoscan is important to allow earlier treatment at a reversible stage. The link between obesity and CAN highlights the therapeutic potential of lifestyle interventions including diet and physical activity to reverse MetS and prevent CAN. Weight loss achieved using these dietary and exercise lifestyle interventions improves the sympathetic and parasympathetic HRV indices of cardiac autonomic function. Further research is needed to identify high-risk populations of people with pre-DM or obesity that might benefit from targeted pharmacotherapy including metformin, sodium/glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 (GLP-1) analogues. Bariatric surgery also improves HRV through weight loss which might also prevent CAN in severe obesity. This article reviews the literature on CAN in obesity, pre-DM and MetS, to help determine a rationale for screening, early intervention treatment and formulate future research questions in this highly prevalent condition.

Heart Rate, Autonomic Function, and Future Changes in Glucose Metabolism in Individuals Without Diabetes: The Whitehall II Cohort Study

OBJECTIVE

Autonomic nervous system dysfunction is associated with impaired glucose metabolism, but the temporality of this association remains unclear in individuals without diabetes. We investigated the association of autonomic function with 5-year changes in glucose metabolism in individuals without diabetes.

RESEARCH DESIGN AND METHODS

Analyses were based on 9,000 person-examinations for 3,631 participants without diabetes in the Whitehall II cohort. Measures of autonomic function included 5-min resting heart rate and six heart rate variability (HRV) indices. Associations between baseline autonomic function measures and 5-year changes in fasting and 2-h plasma glucose, serum insulin concentrations, insulin sensitivity (insulin sensitivity index [ISI0-120] and HOMA of insulin sensitivity), and β-cell function (HOMA of β-cell function) were estimated in models adjusting for age, sex, ethnicity, metabolic factors, and medication.

RESULTS

A 10-bpm higher resting heart rate was associated with 5-year changes in fasting and 2-h insulin and ISI0-120 of 3.3% change (95% CI 1.8; 4.8), P < 0.001; 3.3% change (1.3; 5.3), P = 0.001; and -1.4% change (-2.4; -0.3), P = 0.009, respectively. In models adjusted for age, sex, and ethnicity, higher baseline values of several HRV indices were associated with a 5-year decrease in fasting and 2-h insulin and ISI0-120. However, significance was lost by full adjustment. A majority of HRV indices exhibited a trend toward higher values being associated with lower insulin levels and higher insulin sensitivity.

CONCLUSIONS

Higher resting heart rate in individuals without diabetes is associated with future unfavorable changes in insulin levels and insulin sensitivity. Associations may be mediated via autonomic function; however, results are inconclusive. Resting heart rate may be a risk marker for future pathophysiological changes in glucose metabolism.

Is the Brain a Key Player in Glucose Regulation and Development of Type 2 Diabetes?

Ever since Claude Bernards discovery in the mid 19th-century that a lesion in the floor of the third ventricle in dogs led to altered systemic glucose levels, a role of the CNS in whole-body glucose regulation has been acknowledged. However, this finding was later overshadowed by the isolation of pancreatic hormones in the 20th century. Since then, the understanding of glucose homeostasis and pathology has primarily evolved around peripheral mechanism. Due to scientific advances over these last few decades, however, increasing attention has been given to the possibility of the brain as a key player in glucose regulation and the pathogenesis of metabolic disorders such as type 2 diabetes. Studies of animals have enabled detailed neuroanatomical mapping of CNS structures involved in glucose regulation and key neuronal circuits and intracellular pathways have been identified. Furthermore, the development of neuroimaging techniques has provided methods to measure changes of activity in specific CNS regions upon diverse metabolic challenges in humans. In this narrative review, we discuss the available evidence on the topic. We conclude that there is much evidence in favor of active CNS involvement in glucose homeostasis but the relative importance of central vs. peripheral mechanisms remains to be elucidated. An increased understanding of this field may lead to new CNS-focusing pharmacologic strategies in the treatment of type 2 diabetes.

Good decision-making is associated with an adaptive cardiovascular response to social competitive stress

Competition elicits different psychological and cardiovascular responses depending on a person's skills. Decision-making has been considered a distal factor that influences competition, but there are no studies analyzing this relationship. Our objective was to analyze whether decision-making affects the response to competition. Specifically, we aimed to test whether good performers on a decision-making test, the Iowa Gambling Task (IGT), showed an adaptive cardiovascular response to competition. In all, 116 participants (44 women) performed the IGT and were classified into Good or Poor decision-makers. Subsequently, they were exposed to a stress task in two different conditions: a face-to-face competition (winners/losers) or a control condition, while an electrocardiogram was recorded. In the competition group, good decision-makers increased their high-frequency respect to the total heart rate variability (HF/HRV) levels during the task, compared to Poor decision-makers. Again, competition group good decision-makers, showed lower LF and higher HF/HRV reactivity than the control group, which represents lower HRV stress pattern. Moreover, in the group of losers, good decision-makers had a decline in low frequency (LF) during the task and faster recovery than poor decision-makers. In conclusion, good decision-makers have a more adaptive stress response and higher levels of mental effort, based on total HRV interpretation. Decision-making skills could be a factor in a more adaptive cardiovascular response to competition.

Differential associations of lower cardiac vagal tone with insulin resistance and insulin secretion in recently diagnosed type 1 and type 2 diabetes

OBJECTIVE

It is unclear to which extent altered insulin sensitivity/secretion contribute to the development of diabetic cardiovascular autonomic neuropathy (CAN) characterized by diminished heart rate variability (HRV). We hypothesised that lower HRV is differentially associated with measures of insulin resistance and insulin secretion in recent-onset type 1 and type 2 diabetes.

MATERIALS/METHODS

This cross-sectional study included participants from the German Diabetes Study with type 1 (n=275) or type 2 diabetes (n=450) with known diabetes duration ≤1year and glucose-tolerant controls (n=81). Four time domain and frequency domain HRV measures each, reflecting vagal and/or sympathetic modulation were determined over 3h during a hyperinsulinaemic-euglycaemic clamp. Insulin sensitivity was calculated as the M-value, while insulin secretion was determined by glucagon-stimulated incremental C-peptide (ΔC-peptide).

RESULTS

After adjustment for sex, age, BMI, smoking, and HbA1c, both M-value and ΔC-peptide were lower in the diabetes groups compared to controls (P<0.05). In multiple linear regression analyses after Bonferroni correction, vagus-mediated HRV indices were positively associated with M-value in both diabetes types (P<0.05) and inversely associated with ΔC-peptide only in participants with type 1 diabetes (P<0.05). In type 2 diabetes, the low-frequency/high-frequency (LF/HF) power as an indicator of sympathovagal balance was weakly inversely associated with M-value.

CONCLUSIONS

Insulin resistance may contribute to the development of early cardiovagal suppression rather than sympathetic predominance in both diabetes types, while in type 1 diabetes a lower glucagon-stimulated insulin secretion is linked to a possibly compensatory higher parasympathetic tone. Whether interventions aimed at reducing insulin resistance could also reduce the risk of CAN remains to be established.

Diminution of Heart Rate Variability in Bipolar Depression

Autonomic nervous system (ANS) dysregulation in depression is associated with symptoms associated with the ANS. The beat-to-beat pattern of heart rate defined as heart rate variability (HRV) provides a noninvasive portal to ANS function and has been proposed to represent a means of quantifying resting vagal tone. We quantified HRV in bipolar depressed (BDD) patients as a measure of ANS dysregulation seeking to establish HRV as a potential diagnostic and prognostic biomarker for treatment outcome. Forty-seven BDD patients were enrolled. They were randomized to receive either escitalopram-celecoxib or escitalopram-placebo over 8 weeks in a double-blind study design. Thirty-five patients completed the HRV studies. Thirty-six healthy subjects served as controls. HRV was assessed at pretreatment and end of study and compared with that of controls. HRV was quantified and corrected for artifacts using an algorithm that incorporates time and frequency domains to address non-stationarity of the beat-to-beat heart rate pattern. Baseline high frequency-HRV (i.e., respiratory sinus arrhythmia) was lower in BDD patients than controls, although the difference did not reach significance. Baseline low-frequency HRV was significantly lower in BDD patients (ln4.20) than controls (ln = 5.50) (p < 0.01). Baseline heart period was significantly shorter (i.e., faster heart rate) in BDD patients than controls. No significant change in HRV parameters were detected over the course of the study with either treatment. These findings suggest that components of HRV may be diminished in BDD patients.

Adiponectin, biomarkers of inflammation and changes in cardiac autonomic function: Whitehall II study

BACKGROUND

Biomarkers of inflammation and adiponectin are associated with cardiovascular autonomic neuropathy (CAN) in cross-sectional studies, but prospective data are scarce. This study aimed to assess the associations of biomarkers of subclinical inflammation and adiponectin with subsequent changes in heart rate (HR) and heart rate variability (HRV) in non-diabetic and diabetic individuals.

METHODS

Data are based on up to 25,050 person-examinations for 8469 study participants of the Whitehall II cohort study. Measures of CAN included HR and several HRV indices. Associations between baseline serum levels of high-sensitivity C-reactive protein (hsCRP), interleukin (IL)-6, IL-1 receptor antagonist (IL-1Ra) and adiponectin and 5-year changes in HR and six HRV indices were estimated using mixed-effects models adjusting for age, sex, ethnicity, body mass index (BMI), metabolic covariates and medication. A modifying effect of diabetes was tested.

RESULTS

Higher levels of IL-1Ra were associated with higher increases in HR. Additional associations with measures of HRV were observed for hsCRP, IL-6 and IL-1Ra, but these associations were explained by BMI and other confounders. Associations between adiponectin, HR and HRV differed depending on diabetes status. Higher adiponectin levels were associated with more pronounced decreases in HR and increases in three measures of HRV reflecting both sympathetic and vagal activity, but these findings were limited to individuals with type 2 diabetes.

CONCLUSIONS

Higher IL-1Ra levels appeared as novel risk marker for increases in HR. Higher adiponectin levels were associated with a more favourable development of cardiovascular autonomic function in individuals with type 2 diabetes independently of multiple confounders.

Resting heart rate and impaired glucose regulation in middle-aged and elderly Chinese people: a cross-sectional analysis

Background

Elevated resting heart rate (RHR) has been reported to be associated with metabolic syndrome and type 2 diabetes. The aim of this study was to explore whether a positive relationship exists between RHR and impaired glucose regulation (IGR) among middle-aged and older Chinese individuals.

Methods

We conducted a cross-sectional analysis that included a total of 9898 subjects (3194 men and 6704 women) in a Chinese population. The RHRs were derived from ECG recordings, and the subjects were stratified based on RHR quartiles.

Results

RHR levels were significantly higher in the subjects with isolated impaired fasting glucose (i-IFG), isolated impaired glucose tolerance (i-IGT), IFG + IGT and diabetes than in those with normal glucose regulation. When multivariate logistic regression analyses were performed, the odds ratios were substantially higher for the subjects with IGR (odds ratio 2.19, 95% confidence interval 1.85–2.58) in the fourth RHR quartile compared with those in the first quartile after adjustment for potential confounding covariates, and the corresponding OR for the combined IGR and type 2 diabetes group was 2.56 (95% CI 2.20–2.98, p < 0.001). Multiple regression analyses demonstrated that RHR was significantly associated with fasting plasma glucose, 2-h OGTT plasma glucose and A1c.

Conclusions

Our cross-sectional findings provide evidence that high RHR is associated with existing IGR among middle-aged and older Chinese individuals.

α-Glucosidase inhibitor miglitol attenuates glucose fluctuation, heart rate variability and sympathetic activity in patients with type 2 diabetes and acute coronary syndrome: a multicenter randomized controlled (MACS) study

Background

Little is known about clinical associations between glucose fluctuations including hypoglycemia, heart rate variability (HRV), and the activity of the sympathetic nervous system (SNS) in patients with acute phase of acute coronary syndrome (ACS). This pilot study aimed to evaluate the short-term effects of glucose fluctuations on HRV and SNS activity in type 2 diabetes mellitus (T2DM) patients with recent ACS. We also examined the effect of suppressing glucose fluctuations with miglitol on these variables.

Methods

This prospective, randomized, open-label, blinded-endpoint, multicenter, parallel-group comparative study included 39 T2DM patients with recent ACS, who were randomly assigned to either a miglitol group (n = 19) or a control group (n = 20). After initial 24-h Holter electrocardiogram (ECG) (Day 1), miglitol was commenced and another 24-h Holter ECG (Day 2) was recorded. In addition, continuous glucose monitoring (CGM) was performed throughout the Holter ECG.

Results

Although frequent episodes of subclinical hypoglycemia (≤4.44 mmo/L) during CGM were observed on Day 1 in the both groups (35% of patients in the control group and 31% in the miglitol group), glucose fluctuations were decreased and the minimum glucose level was increased with substantial reduction in the episodes of subclinical hypoglycemia to 7.7% in the miglitol group on Day 2. Holter ECG showed that the mean and maximum heart rate and mean LF/HF were increased on Day 2 in the control group, and these increases were attenuated by miglitol. When divided 24-h time periods into day-time (0700–1800 h), night-time (1800–0000 h), and bed-time (0000–0700 h), we found increased SNS activity during day-time, increased maximum heart rate during night-time, and glucose fluctuations during bed-time, which were attenuated by miglitol treatment.

Conclusions

In T2DM patients with recent ACS, glucose fluctuations with subclinical hypoglycemia were associated with alterations of HRV and SNS activity, which were mitigated by miglitol, suggesting that these pathological relationships may be a residual therapeutic target in such patients.

Trial registration Unique Trial Number, UMIN000005874 (https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000006929)

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-017-0571-1) contains supplementary material, which is available to authorized users.

The relationship between right ventricular deformation and heart rate variability in asymptomatic diabetic patients

OBJECTIVE

To investigate heart rate variability (HRV) and right ventricular (RV) remodeling in asymptomatic diabetic patients, as well as the relationship between HRV indices and RV structure, function and deformation.

METHOD

This cross-sectional study included 59 asymptomatic patients with type 2 diabetes and 45 healthy controls without cardiovascular risk factors. All study subjects underwent 24-h Holter monitoring, laboratory analyses and complete two-dimensional echocardiography examination (2DE).

RESULTS

RV diastolic function and longitudinal deformation were significantly impaired in diabetic individuals comparing with controls. RV global longitudinal strain and layer-specific longitudinal strains were significantly decreased in diabetic group. The same trend of changes in RV deformation was observed for global RV and lateral wall. All parameters of time and frequency domain of HRV were reduced in diabetic subjects. RV endocardial longitudinal strain together with LV mass index, mitral E/e' ratio and HbA1c correlated with HRV parameters. However, multivariate linear regression analysis showed that only RV endocardial longitudinal strain and LV mass index are associated with HRV parameters independently of age, BMI, HbA1c, RV free wall thickness and pulmonary artery pressure.

CONCLUSIONS

RV subendocardial strain is independently associated with HRV parameters in the whole study population. This reveals potentially important role of determination of layer-specific RV longitudinal function as important marker of preclinical cardiac damage, but also indirectly show the impairment of cardiac autonomic function in diabetic patients.