Effect of glycemic control and disease duration on cardiac autonomic function and oxidative stress in type 2 diabetes mellitus

Remodeling of the Intracardiac Ganglia During the Development of Cardiovascular Autonomic Dysfunction in Type 2 Diabetes: Molecular Mechanisms and Therapeutics

Type 2 diabetes mellitus (T2DM) is one of the most significant health issues worldwide, with associated healthcare costs estimated to surpass USD 1054 billion by 2045. The leading cause of death in T2DM patients is the development of cardiovascular disease (CVD). In the early stages of T2DM, patients develop cardiovascular autonomic dysfunction due to the withdrawal of cardiac parasympathetic activity. Diminished cardiac parasympathetic tone can lead to cardiac arrhythmia-related sudden cardiac death, which accounts for 50% of CVD-related deaths in T2DM patients. Regulation of cardiovascular parasympathetic activity is integrated by neural circuitry at multiple levels including afferent, central, and efferent components. Efferent control of cardiac parasympathetic autonomic tone is mediated through the activity of preganglionic parasympathetic neurons located in the cardiac extensions of the vagus nerve that signals to postganglionic parasympathetic neurons located in the intracardiac ganglia (ICG) on the heart. Postganglionic parasympathetic neurons exert local control on the heart, independent of higher brain centers, through the release of neurotransmitters, such as acetylcholine. Structural and functional alterations in cardiac parasympathetic postganglionic neurons contribute to the withdrawal of cardiac parasympathetic tone, resulting in arrhythmogenesis and sudden cardiac death. This review provides an overview of the remodeling of parasympathetic postganglionic neurons in the ICG, and potential mechanisms contributing to the withdrawal of cardiac parasympathetic tone, ventricular arrhythmogenesis, and sudden cardiac death in T2DM. Improving cardiac parasympathetic tone could be a therapeutic avenue to reduce malignant ventricular arrhythmia and sudden cardiac death, increasing both the lifespan and improving quality of life of T2DM patients.

Effect of Heart Rate Variability Biofeedback on Cardiac Autonomic Activation and Diabetes Self-Care in Patients with Type II Diabetes Mellitus

In type 2 diabetes mellitus (T2DM), decreased autonomic activation and heightened negative emotions may worsen glycemic control. This study investigated the effects of heart rate variability biofeedback (HRVB) on autonomic activation, negative emotions, diabetes self-care, and glycemic control in patients with T2DM. A total of 61 participants with T2DM were assigned to either the HRVB group (n = 30; 62.67 ± 7.28 years; 14 females) or the control group (n = 31; 63.39 ± 6.96 years; 14 females). Both groups received the treatment as usual, and the HRVB group received 60 min of HRVB sessions weekly for 6 weeks. Participants completed psychological questionnaires, a resting electrocardiogram (ECG), and breathing rate assessments at pre- and post-tests. Heart rate variability (HRV) indices were derived from ECG data, and glycated hemoglobin (HbA1c) levels were collected from the electronic medical records. The analysis revealed significant Group × Time interaction effects on HRV indices, breathing rate, depression symptoms, and diabetes self-care behavior. The HRVB group demonstrated higher HRV indices, lower breathing rate, and improved diabetes self-care behavior compared to the control group. Moreover, the HRVB group showed enhanced HRV indices and diabetes self-care behavior, as well as reduced breathing rate and depression in the post-test compared to the pre-test. However, there was no significant interaction effect on HbA1c levels. Six sessions of HRVB proved effective as a complementary therapy for T2DM, enhancing HRV indices, alleviating depressive symptoms, and promoting better diabetes self-care behaviors.

Effect of SGLT-2 inhibitors on cardiac autonomic function in type 2 diabetes mellitus: a meta-analysis of randomized controlled trials

BACKGROUND

Cardiac autonomic neuropathy (CAN) is a common complication of type 2 diabetes mellitus (T2DM). We sought to determine whether sodium-glucose co-transporter-2 (SGLT-2) inhibitors affect indices of CAN in patients with T2DM.

METHODS

We searched for parallel group or cross-over randomized controlled trials (RCTs) enrolling adult subjects with T2DM, assigned to a SGLT-2 inhibitor versus placebo or active comparator and addressing their effect on CAN. PubMed, Cochrane Library and gray literature sources were searched. We set as primary efficacy outcome the change in the low-frequency-to-high-frequency (LF/HF) ratio. We set as secondary efficacy outcomes: first, the change in the standard deviation of all 5 min mean normal RR intervals and second, the change in the square root of the mean of the sum of the squares of differences between adjacent RR intervals (r-MSSD). Protocol has not been registered at a publicly available repository.

RESULTS

We pooled data from four RCTs in a total of 247 subjects with T2DM. SGLT-2 inhibitor treatment did not have a significant effect on LF/HF ratio (MD = - 0.11, 95% CI - 0.35 to 0.12, I² = 0%, p = 0.36). SGLT-2 inhibitor treatment did not have a significant impact either on SDNN (MD = - 2.83, 95% CI - 7.41 to 1.75, I² = 31%, p = 0.23), or on r-MSSD (MD = - 0.14, 95% CI - 3.52 to 3.25, I² = 46%, p = 0.94). Overall risk of bias was graded as low across the selected RCTs.

CONCLUSION

SGLT-2 inhibitor treatment in patients with T2DM does not seem to provide any significant beneficial effect on CAN indices.

Cardiac autonomic dysfunctions in type 2 diabetes mellitus: an investigative study with heart rate variability measures

Cardiac autonomic neuropathy (CAN) is a common yet underdiagnosed complication of Type 2 diabetes mellitus (T2DM). Heart rate variability (HRV), a sensitive diagnostic marker of cardiovascular risk, could help detect CAN at its earliest stage. However, the progression of CAN based on age and disease duration in T2DM is lacking. In this study, we propose to explore the occurrence of CAN in patients with varying stages and duration of T2DM. This cross-sectional study involves participants with T2DM (n = 160) and healthy volunteers (n = 40) with an age range of 30-60 years of both genders. Patients in the T2DM group were further subdivided into four subgroups based on their disease duration [Prediabetes, disease duration <5 yrs (D1), 5-10 yrs (D2), and >10 yrs (D3)]. All participants underwent short-term HRV recording for 20 minutes and analyzed for both time and frequency domain measures. The study results showed a significant increase in Heart Rate (HR) in D1 (P = 0.031) and D3 (P = 0.001) groups compared to healthy controls. The time-domain measures of HRV were significantly reduced in the T2DM group compared to the healthy controls. Furthermore, this reduction is more intense in the D3 group than in D2 and D1. Correspondingly, in frequency domain parameters: total power, high-frequency power, and low-frequency power were significantly reduced in all the T2DM groups compared to healthy controls. The study concludes that the overall HRV (as determined by total power), sympathetic activity (low frequency power) and parasympathetic activity (time domain measures and high frequency power) were significantly reduced in all the diabetic subgroups except prediabetes as compared to the healthy controls, implying that both sympathetic and parasympathetic limbs are symmetrically affected in T2DM patients even in the earliest stages (<5 yrs) implying subclinical cardiac autonomic dysfunction in the earliest stages.

Association of depression and parasympathetic activation with glycemic control in type 2 diabetes mellitus

AIM

Patients with type 2 diabetes mellitus exhibited autonomic nervous system (ANS) dysfunction and comorbidities with depressive or anxiety symptoms were related to poor glycemic control. Heart rate variability (HRV) converted from electrocardiogram (ECG) has been used as the ANS index. The study aimed to explore the associations between depression, anxiety, HRV, and glycemic control in patients with type 2 diabetes mellitus.

METHODS

The Patient Health Questionnaire-9 (PHQ-9) and Generalized Anxiety Disorder-7 (GAD-7) questionnaires were used to assess depressive and anxiety symptoms in 647 patients with type 2 diabetes mellitus (mean age was 63 ± 10 years, 56 % males). The ECG raw signals were collected from a 5-min sitting and resting baseline and then transformed to HRV indices referring ANS activation. Blood glucose and lipid profiles including glycated hemoglobin (HbA1c), high-density lipoprotein (HDL), low-density lipoprotein (LDL), and triglyceride were obtained from the electronic medical records.

RESULTS

Ninety-nine (15 %) participants had depressive symptoms and 59 (9 %) had anxiety symptoms. Depression and HbA1c were negatively correlated with parasympathetic activation. Depression and anxiety were positively correlated with sympathetic activation. After controlling for demographic data and lipid profiles, depression was a significant positive predictor for HbA1c levels; and HRV indices (lnLF and lnHF) were the significant negative predictors for HbA1c levels. Mediation effect analysis showed that depression was a mediator between parasympathetic activation and glycemic control.

CONCLUSIONS

Lower parasympathetic activation and higher depressive symptoms may affect glycemic control in patients with type 2 diabetes mellitus. Intervention programs targeting to increase parasympathetic activities and reducing depression could be further tested for their effects on glycemic outcomes for potential clinical use.

High Fasting Glycemia Predicts Impairment of Cardiac Autonomic Control in Adults With Type 2 Diabetes: A Case-Control Study

INTRODUCTION

Type 2 diabetes (T2D) is characterized by a metabolic disorder that elevates blood glucose concentration. Chronic hyperglycemia has been associated with several complications in patients with T2D, one of which is cardiac autonomic dysfunction that can be assessed from heart rate variability (HRV) and heart rate recovery (HRR) response, both associated with many aspects of health and fitness, including severe cardiovascular outcomes.

OBJECTIVE

To evaluate the effects of T2D on cardiac autonomic modulation by means of HRV and HRR measurements.

MATERIALS AND METHODS

This study has an observational with case-control characteristic and involved ninety-three middle-aged adults stratified into two groups (control group - CG, n = 34; diabetes group - DG, n = 59). After signing the free and informed consent form, the patients were submitted to the evaluation protocols, performed biochemical tests to confirm the diagnosis of T2D, collection of R-R intervals for HRV analysis and cardiopulmonary effort test to quantify HRR.

RESULTS

At rest, the DG showed a reduction in global HRV (SDNN= 19.31 ± 11.72 vs CG 43.09 ± 12.74, p < 0.0001), lower parasympathetic modulation (RMSSD= 20.49 ± 14.68 vs 52.41 ± 19.50, PNN50 = 4.76 ± 10.53 vs 31.24 ± 19.24, 2VD%= 19.97 ± 10.30 vs 28.81 ± 9.77, p < 0.0001 for both indices) and higher HRrest when compared to CG. After interruption of physical exercise, a slowed heart rate response was observed in the DG when compared to the CG. Finally, a simple linear regression showed that fasting glycemia was able to predict cardiac autonomic involvement in volunteers with T2D.

CONCLUSION

Patients with T2D presented lower parasympathetic modulation at rest and slowed HRR after physical exercise, which may be associated with higher cardiovascular risks. The findings show the glycemic profile as an important predictor of impaired cardiac autonomic modulation.

Association of leukocyte telomere length with metabolic syndrome in type 2 diabetes mellitus

Background:

Leukocyte telomere length (LTL) has been revealed to be associated with aging-related diseases such as metabolic syndrome (MetS) and Type 2 diabetes mellitus (T2DM). We aimed to investigate the correlation of LTL with MetS and its components in T2DM patients in this cross-sectional study.

Materials and Methods:

A total of 344 T2DM patients were enrolled into this study. LTL was measured by Southern blot-based terminal restriction fragment length analysis. MetS was clinically defined by 2007 Chinese Guidelines on Prevention and Treatment of Dyslipidemia in Adults.

Results:

Of 344 T2DM patients, 53% had MetS. T2DM patients with MetS had significantly longer LTL than those without MetS (6451.95 ± 51.10 base pairs vs. 6076.13 ± 55.13 base pairs, P < 0.001), especially when T2DM patients had poor glycemic control (hemoglobin A1c ≥7%). Meanwhile, the trend of longer LTL was associated with the increased components of MetS in T2DM patient. Finally, LTL had a significant association with MetS (odds ratio [OR]: 2.096, 95% confidence interval [CI] 1.337–3.285, P = 0.001), low levels of high-density lipoprotein-cholesterol (HDL-C) (OR: 2.412, 95% CI 1.350–4.308, P = 0.003) in T2DM patients.

Conclusion:

T2DM patients with MetS had a significantly longer LTL than those without MetS. The longer LTL was especially evident in T2DM patients with poor glycemic control. Longer LTL was positively associated with MetS, particularly low levels of HDL-C in T2DM patients.

Cardiac Autonomic Neuropathy: A Progressive Consequence of Chronic Low-Grade Inflammation in Type 2 Diabetes and Related Metabolic Disorders

Cardiac autonomic neuropathy (CAN) is one of the earliest complications of type 2 diabetes (T2D), presenting a silent cause of cardiovascular morbidity and mortality. Recent research relates the pathogenesis of cardiovascular disease in T2D to an ensuing chronic, low-grade proinflammatory and pro-oxidative environment, being the hallmark of the metabolic syndrome. Metabolic inflammation emerges as adipose tissue inflammatory changes extending systemically, on the advent of hyperglycemia, to reach central regions of the brain. In light of changes in glucose and insulin homeostasis, dysbiosis or alteration of the gut microbiome (GM) emerges, further contributing to inflammatory processes through increased gut and blood-brain barrier permeability. Interestingly, studies reveal that the determinants of oxidative stress and inflammation progression exist at the crossroad of CAN manifestations, dictating their evolution along the natural course of T2D development. Indeed, sympathetic and parasympathetic deterioration was shown to correlate with markers of adipose, vascular, and systemic inflammation. Additionally, evidence points out that dysbiosis could promote a sympatho-excitatory state through differentially affecting the secretion of hormones and neuromodulators, such as norepinephrine, serotonin, and γ-aminobutyric acid, and acting along the renin-angiotensin-aldosterone axis. Emerging neuronal inflammation and concomitant autophagic defects in brainstem nuclei were described as possible underlying mechanisms of CAN in experimental models of metabolic syndrome and T2D. Drugs with anti-inflammatory characteristics provide potential avenues for targeting pathways involved in CAN initiation and progression. The aim of this review is to delineate the etiology of CAN in the context of a metabolic disorder characterized by elevated oxidative and inflammatory load.

Aspartic acid supplementation ameliorates symptoms of diabetic kidney disease in mice

Diabetic kidney disease (DKD) is among the most common and serious complications of both type 1 and type 2 diabetes. In this study, we used KK/Ta‐Ins2^Akita (KK‐Akita) mice as a model of DKD and KK/Ta (KK) mice as controls to identify novel factors related to the development/progression of DKD. Capillary electrophoresis coupled with mass spectrometry analysis revealed that circulating Asp (l‐aspartic acid) levels in diabetic KK‐Akita mice tend to be lower than those in control KK mice. Therefore, we evaluated the effect of Asp supplementation to prevent the progression of DKD in KK‐Akita mice. Mice were divided into three groups: (a) untreated KK mice (Control group), (b) untreated KK‐Akita mice (DKD group), and (c) treated (double‐volume Asp diet) KK‐Akita mice (Tx group). Kidney sections were stained with fluorescein isothiocyanate‐labeled lectins, wheat germ agglutinin (WGA), and anti‐endothelial nitric oxide synthase (eNOS) antibody for evaluation of endothelial surface layer (ESL) and NO synthesis. The mesangial area and glomerular size in the DKD group were significantly larger than those in the Control group; however, there was no significant difference in those between the DKD and Tx groups. Albuminuria, the ratio of foot process effacement, and thickness of glomerular basement membrane in the Tx group were significantly lower than those in the DKD group. Furthermore, the expression levels of glomerular WGA and microvascular eNOS in the Tx group improved significantly and approached the level in the Control group. In conclusion, the improvement of albuminuria in the Tx group may be caused by the reduction of oxidative stress in the kidneys, which may lead to the subsequent improvement of glomerular ESL.

A novel mechanism of vitamin D anti-inflammatory/antioxidative potential in type 2 diabetic patients on metformin therapy

INTRODUCTION

The performed study focused on determining the effect of vitamin D supplementation on enzymes involved in both inflammation and reactive oxygen species (ROS) production and ROS degradation in patients with type 2 diabetes mellitus (T2DM).

MATERIAL AND METHODS

The 6-month follow-up, randomized, controlled study included 140 patients with T2DM, ≥ 30 years old, with good metabolic control, treated with metformin and lifestyle advice only. All patients were randomly assigned to two groups (70 each). Patients from the first group (Intervention group) were assigned to receive vitamin D3 50 000 IU or 14 000 IU regarding their vitamin D baseline levels. Patients from the second (Metformin) group continued to receive only metformin during the 6-month study period.

RESULTS

After 6 months, the myeloperoxidase activity was significantly lower and gradually decreased in the Intervention group by about 40%, compared to the baseline measurement (p = 0.015) and compared to the Metformin group (p = 0.001). After 6 months, the xanthine oxidase (XO) activity decreased significantly in the Intervention group compared to the baseline and 3^rd month levels (p < 0.001). In the Metformin group there was also a significant decrease in XO after 6 months compared to baseline (p < 0.001) and the 3^rd month (p = 0.003). The catalase activity significantly increased within the Intervention group only when comparing the 3^rd and 6^th month (p = 0.027).

CONCLUSIONS

Our study showed that vitamin D may improve endothelial dysfunction in patients with T2DM on metformin therapy by influencing two important factors implicated in the pathogenesis of diabetic complications - ROS production and inflammation, which can additionally contribute to a stable metabolic control during metformin therapy.

Short term optimization of glycaemic control using insulin improves sympatho-vagal tone activities in patients with type 2 diabetes

INTRODUCTION

Diabetic cardiac autonomic neuropathy (CAN) is potentially life threatening and its severity might further be aggravated by poor glycaemic control. A decrease in Heart rate variability (HRV) is the earliest finding of CAN even at the sub clinical stage. While intensive glycaemic control prevents the development of CAN in patients with type 1 diabetes, it is not known whether the intensification of glycaemic control using insulin would improve cardiovascular autonomic functions in type 2 diabetes patients. This study aimed to determine the short term effects of optimizing glycaemic control using insulin on the HRV in type 2 diabetes patients.

METHODS

We conducted a single arm open label clinical trial. Participants were poorly controlled non-insulin treated type 2 diabetes mellitus patients (HbA1c ≥ 7%). The intervention lasted 60 days and consisted in the intensification of glycaemic control through the initiation of a basal plus insulin regimen with titration of insulin to protocol defined glycaemic targets which were; fasting glycaemia: 0.70-1.30 g/L and post prandial glycaemia <1.80 g/L. Long term HRV measurement was done using a 24-h ambulatory electrocardiographic (ECG) recording on day 0 and day 60. Wilcoxon signed rank test was used to compare differences in HRV parameters before and after the intervention.

RESULTS

A total of 29 (14 males and 15 females) consenting type 2 diabetes mellitus patients without clinical signs of CAN were enrolled and allocated to intervention (14 males and 15 females). The median age was 52 [43-59] years, and duration of diabetes 3.0 [0.6-6.7] years. The intervention induced a reduction in HbA1c from 10.1 [9.1-11.9]% to 6.7 [5.9-6.9]% (p < 0.001) without severe hypoglycaemic events. Concerning HRV parameters, there was a significant improvement in markers of the parasympathetic tone (PNN50: 5.7 [3.6-10.3]% to 8.1 [3.1-16.9]%, p = 0.008) and sympathetic tone (SDNN: 102.01 [90.45-111.05] ms to 122.40 [91.70-135.95] ms, p = 0.01).

CONCLUSION

The optimization of glycaemic control using a basal plus insulin regimen while inducing a significant reduction in glycated hemoglobin, significantly improves 24-h ambulatory ECG derived sympathetic and parasympathetic activities. This suggests that tight glycaemic control using insulin may revert cardiac autonomic neuropathy in type 2 diabetes mellitus patients.

Association between heart rate recovery after exercise and renal function in patients referred for treadmill exercise test

Introduction

Heart rate recovery (HRR) is a marker of parasympathetic activity recovery after exercise, and it is associated with cardiovascular mortality and total mortality. Impaired renal function is also associated with cardiac mortality. The aim of this study was to investigate the association between HRR after exercise and renal function in patients referred for a treadmill exercise test.

Patients and methods

This cross-sectional study was conducted at a regional hospital in southern Taiwan. Patients who completed a symptom-limited treadmill exercise test from January 2015 to February 2018 were recruited. Before the treadmill exercise test, patients were asked to complete a questionnaire on the past disease history and lifestyle factors. Serum creatinine measurement within two years prior to or after the date of the treadmill exercise test of the patients was also obtained from the medical records for these patients. Estimated glomerular filtration rate (eGFR) was calculated. Simple and multiple linear regression analyses were performed to investigate the association between one-minute HRR and eGFR.

Results

A total of 2,825 patients completed the treadmill exercise test, and serum creatinine measurement was identified from medical records for 2,153 patients (76.2%). Multiple linear regression analysis revealed that a lower eGFR was significantly associated with lower one-minute HRR (P< 0.001), adjusting for other significant independent factors, including age, waist circumference, type 2 diabetes mellitus, and smoking.

Conclusions

In this cross-sectional observational study, a lower eGFR was significantly and independently associated with decreased one-minute HRR, suggesting that parasympathetic activity recovery after exercise could be impaired by a decrease in renal function.