Cardiovascular autonomic neuropathy: A silent killer with long reach

Cardiovascular Autonomic Neuropathy and Risk of Kidney Function Decline in Type 1 and Type 2 Diabetes: Findings From the PERL and ACCORD Cohorts

Results of previous studies have suggested that cardiovascular autonomic neuropathy (CAN) may predict rapid kidney function decline among people with diabetes. We analyzed the association between baseline CAN and subsequent glomerular filtration rate (GFR) decline among individuals with type 1 diabetes (T1D) from the Preventing Early Renal Loss in Diabetes (PERL) study (N = 469) and with type 2 diabetes (T2D) from Action to Control Cardiovascular Risk in Diabetes (ACCORD) (N = 7,973). Baseline CAN was ascertained with electrocardiogram-derived heart rate variability indices. Its association with GFR slopes, rapid kidney function decline (GFR loss of ≥5 mL/min/1.73 m2/year), and ≥40% GFR loss was evaluated by linear mixed-effects, logistic, and Cox regression, respectively. Participants with CAN experienced more rapid GFR decline, by an excess 1.15 mL/min/1.73 m2/year (95% CI -1.93 to -0.37; P = 4.0 × 10-3) in PERL and 0.34 mL/min/1.73 m2/year (95% CI -0.49 to -0.19; P = 6.3 × 10-6) in ACCORD. This translated to 2.11 (95% CI 1.23-3.63; P = 6.9 × 10-3) and 1.39 (95% CI 1.20-1.61; P = 1.1 × 10-5) odds ratios of rapid kidney function decline in PERL and ACCORD, respectively. Baseline CAN was also associated with a greater risk of ≥40% GFR loss events during follow-up (hazard ratio 2.60 [95% CI 1.15-5.45], P = 0.02, in PERL and hazard ratio 1.54 [95% CI 1.28-1.84], P = 3.8 × 10-6, in ACCORD). These associations remained significant after adjustment for potential confounders, including baseline GFR and albuminuria. Our findings indicate that CAN is a strong, independent predictor of rapid kidney function decline in both T1D and T2D. Further studies of the link between these two complications may help with development of new therapies to prevent kidney function decline in patients with diabetes.

ARTICLE HIGHLIGHTS

Spectrum of Diabetic Neuropathy: New Insights in Diagnosis and Treatment

Diabetic neuropathy is a highly prevalent complication of diabetes. It consists of a broad range of neuropathic conditions, such as distal symmetric polyneuropathy and various forms of autonomic neuropathies involving the cardiovascular, gastrointestinal, and urogenital systems. Prevention or diagnosis in early stages of disease is crucial to prevent symptomatic onset and progression, particularly in the absence of current disease-modifying therapies. In this review, we describe the four main types of diabetic neuropathy. We review current understanding with respect to diagnosis and treatment while highlighting knowledge gaps and future directions.

Evaluation of association between time in range, a continuous glucose monitoring metric, and cardiac autonomic neuropathy in type 2 diabetes patients

Introduction

Time in range (TIR), a metric of continuous glucose monitoring (CGM) provides better information regarding the individual's glycemic variability than a static measure like glycated hemoglobin (HbA1c). TIR is emerging as an independent risk factor for diabetic complications, both microvascular and macrovascular complications independent of HbA1c. Hence, this study evaluates the association between TIR and cardiac autonomic neuropathy (CAN) in type 2 diabetic patients.

Materials and Methods

A total of 42 patients with type 2 diabetes mellitus were enrolled in this study and underwent a 3-day CGM using the "FreeStyle Libre Pro Flash Glucose Monitoring System Sensor" along with tests for CAN within the 3 days of attaching the CGM.

Results

Out of 42 patients, 36 patients (85.7%) were diagnosed with CAN (early CAN 57.1% and definite CAN 28.6%) and the mean TIR was 64.4% ±23.5%. Out of those with TIR <70%, 42.9% were affected with definite CAN compared to only 14.3% among those with TIR >70%. Patients with more severe CAN were found to have a lower TIR (P = 0.115).

Conclusion

The study found a high prevalence of cardiac autonomic neuropathy (CAN) of around 85.7% in type 2 diabetes patients. Lower TIR values were associated with a higher incidence of definite CAN (42.9% vs. 14.3% in TIR <70% vs. >70% groups). The findings suggest TIR is inversely associated with the presence and severity of cardiac autonomic neuropathy in type 2 diabetic patients and also a potential link between TIR and CAN severity.

Urinary epidermal growth factor levels correlate with cardiovascular autonomic neuropathy indices in adults with type 1 diabetes

The relationship between urinary endothelial growth factor (uEGF) and cardiovascular autonomic neuropathy (CAN) in adults with type 1 diabetes was evaluated. uEGF levels at baseline and standardized CAN measures were collected at baseline and annually for 3 years for type 1 diabetes adults. Linear regression analysis and linear mixed effects model were used for analysis. In this cohort (n = 44, 59% women, mean ± standard deviation age 34 ± 13 years and diabetes duration 14 ± 6 years), lower baseline uEGF levels correlated with lower baseline expiration : inspiration ratios (P = 0.03) and greater annual declines in Valsalva ratios (P = 0.02) in the unadjusted model, and correlated with lower low-frequency power : high-frequency power ratios (P = 0.01) and greater annual changes in low-frequency power : high-frequency power ratios (P = 0.01) after adjustment for age, sex, body mass index, and hemoglobin A1C. In conclusion, baseline uEGF levels correlate to baseline and longitudinal changes in CAN indices. A large-scale, long-term study is needed to validate uEGF as a reliable CAN biomarker.

Diabetes-Induced Cardiac Autonomic Neuropathy: Impact on Heart Function and Prognosis

Cardiovascular autonomic neuropathy (CAN) is a severe complication of the advance stage of diabetes. More than 50% of diabetic patients diagnosed with peripheral neuropathy will have CAN, with clinical manifestations including tachycardia, severe orthostatic hypotension, syncope, and physical exercise intolerance. Since the prevalence of diabetes is increasing, a concomitant increase in CAN is expected and will reduce quality of life and increase mortality. Autonomic dysfunction is associated with reduced baroreflex sensitivity and impairment of sympathetic and parasympathetic modulation. Various autonomic function tests are used to diagnose CAN, a condition without adequate treatment. It is important to consider the control of glucose level and blood pressure as key factors for preventing CAN progression. However, altered biomarkers of inflammatory and endothelial function, increased purinergic receptor expression, and exacerbated oxidative stress lead to possible targets for the treatment of CAN. The present review describes the molecular alterations seen in CAN, diagnosis, and possible alternative treatments.

Higher frequency of cardiovascular autonomic neuropathy in youth with type 2 compared to type 1 diabetes: Role of cardiometabolic risk factors

OBJECTIVE

Cardiovascular autonomic neuropathy (CAN) is an overlooked but common and serious diabetes complication. We examined CAN in youth with diabetes and associations with cardiovascular risk factors.

RESEARCH DESIGN AND METHODS

This was a prospective cohort of youth aged <20 years with type 2 or type 1 diabetes (n = 66/1153, median age 15.4/16.5 years, duration 1.7/8.0 years), assessed between 2009 and 2020. CAN was defined as ≥2 abnormal heart rate variability measures across time, geometric, and frequency domains. Obesity was defined as BMI ≥ 95th percentile and severe obesity as ≥120% of 95th percentile. Multivariable generalized estimating equations (GEE) were used to examine putative risk factors for CAN, including diabetes type, obesity, and HbA_1c .

RESULTS

At most recent assessment, youth with type 2 versus type 1 diabetes had median: HbA₁ c 7.1% (54 mmol/mol) versus 8.7% (72 mmol/mol) and BMI SDS (2.0 vs. 0.7); frequency of CAN (47% vs. 27%), peripheral nerve abnormality (47% vs. 25%), hypertension (29% vs. 12%), albuminuria (21% vs. 3%), and severe obesity (35% vs. 2%). In multivariable GEE, CAN was associated with type 2 diabetes: Odds Ratio 2.53, 95% CI 1.46, 4.38, p = 0.001, higher BMI SDS: 1.49, 95% CI 1.29, 1.73, p < 0.0001, and obesity: 2.09, 95% CI 1.57, 2.78, p < 0.0001.

CONCLUSIONS

Youth with type 2 diabetes have a higher frequency of CAN, peripheral nerve abnormality, hypertension, albuminuria and severe obesity despite shorter diabetes duration and younger age. Our findings highlight the importance of targeting modifiable risk factors to prevent cardiovascular disease in youth with diabetes.

The conundrum of diabetic neuropathies-Past, present, and future

Diabetic neuropathy (DN) remains arguably the most prevalent chronic complication in people with both type 1 and type 2 diabetes, including in youth, despite changes in the current standards of clinical care. Additionally, emerging evidence demonstrates that neuropathy affects a large proportion of people with undiagnosed diabetes and/or prediabetes, as well as those with obesity. Here we summarize the latest epidemiology of DN, recent findings regarding the pathophysiology of the disease, as well as current outcome measures for screening and diagnosis, in research and clinical settings. The authors discuss novel perspectives on the impact of social determinants of health in DN development and management, and the latest evidence on effective therapies, including pharmacological and nonpharmacological therapies for neuropathic pain. Throughout the publication, we identify knowledge gaps and the need for future funding to address these gaps, as well as needs to advocate for a personalized care approach to reduce the burden of DN and optimize quality of life for all affected individuals.

American Association of Clinical Endocrinology Clinical Practice Guideline: Developing a Diabetes Mellitus Comprehensive Care Plan-2022 Update

OBJECTIVE

The objective of this clinical practice guideline is to provide updated and new evidence-based recommendations for the comprehensive care of persons with diabetes mellitus to clinicians, diabetes-care teams, other health care professionals and stakeholders, and individuals with diabetes and their caregivers.

METHODS

The American Association of Clinical Endocrinology selected a task force of medical experts and staff who updated and assessed clinical questions and recommendations from the prior 2015 version of this guideline and conducted literature searches for relevant scientific papers published from January 1, 2015, through May 15, 2022. Selected studies from results of literature searches composed the evidence base to update 2015 recommendations as well as to develop new recommendations based on review of clinical evidence, current practice, expertise, and consensus, according to established American Association of Clinical Endocrinology protocol for guideline development.

RESULTS

This guideline includes 170 updated and new evidence-based clinical practice recommendations for the comprehensive care of persons with diabetes. Recommendations are divided into four sections: (1) screening, diagnosis, glycemic targets, and glycemic monitoring; (2) comorbidities and complications, including obesity and management with lifestyle, nutrition, and bariatric surgery, hypertension, dyslipidemia, retinopathy, neuropathy, diabetic kidney disease, and cardiovascular disease; (3) management of prediabetes, type 2 diabetes with antihyperglycemic pharmacotherapy and glycemic targets, type 1 diabetes with insulin therapy, hypoglycemia, hospitalized persons, and women with diabetes in pregnancy; (4) education and new topics regarding diabetes and infertility, nutritional supplements, secondary diabetes, social determinants of health, and virtual care, as well as updated recommendations on cancer risk, nonpharmacologic components of pediatric care plans, depression, education and team approach, occupational risk, role of sleep medicine, and vaccinations in persons with diabetes.

CONCLUSIONS

This updated clinical practice guideline provides evidence-based recommendations to assist with person-centered, team-based clinical decision-making to improve the care of persons with diabetes mellitus.

Changes in salivary biomarkers associated with periodontitis and diabetic neuropathy in individuals with type 1 diabetes

The objective of this pilot clinical study was to identify salivary biomarkers that are associated with periodontal disease and measures of diabetic autonomic dysfunction. Saliva samples from 32 participants were obtained from 3 groups: healthy (H), type 1 diabetes mellitus (DM), and type 1 diabetes mellitus with neuropathy (DMN). Based on the periodontal examination, individuals’ mean Periodontal Screening and Recording scores were categorized into two groups (periodontally healthy and gingivitis), and correlated to specific salivary inflammatory biomarkers assessed by a customized protein array and enzyme assay. The mean salivary IgA level in DM was 9211.5 ± 4776.4 pg/ml, which was significantly lower than H (17,182.2 ± 8899.3 pg/ml). IgA in DMN with healthy periodontium was significantly lower (5905.5 ± 3124.8 pg/ml) compared to H, although IgA levels in DMN patients with gingivitis (16,894. 6 ± 7084.3) were not. According to the result of a logistic regression model, IgA and periodontal condition were the indicators of the binary response given by H versus DM, and H versus DMN, respectively. These data suggest that selected salivary biomarkers, such as IgA, combined with a periodontal examination prior to obtaining salivary samples can offer a non-invasive method to assess risk for developing diabetic neuropathy.

Diagnostic Tools, Biomarkers, and Treatments in Diabetic polyneuropathy and Cardiovascular Autonomic Neuropathy

The various manifestations of diabetic neuropathy, including distal symmetric sensorimotor polyneuropathy (DSPN) and cardiovascular autonomic neuropathy (CAN), are among the most prevalent chronic complications of diabetes. Major clinical complications of diabetic neuropathies, such as neuropathic pain, chronic foot ulcers, and orthostatic hypotension, are associated with considerable morbidity, increased mortality, and diminished quality of life. Despite the substantial individual and socioeconomic burden, the strategies to diagnose and treat diabetic neuropathies remain insufficient. This review provides an overview of the current clinical aspects and recent advances in exploring local and systemic biomarkers of both DSPN and CAN assessed in human studies (such as biomarkers of inflammation and oxidative stress) for better understanding of the underlying pathophysiology and for improving early detection. Current therapeutic options for DSPN are (I) causal treatment, including lifestyle modification, optimal glycemic control, and multifactorial risk intervention, (II) pharmacotherapy derived from pathogenetic concepts, and (III) analgesic treatment against neuropathic pain. Recent advances in each category are discussed, including non-pharmacological approaches, such as electrical stimulation. Finally, the current therapeutic options for cardiovascular autonomic complications are provided. These insights should contribute to a broader understanding of the various manifestations of diabetic neuropathies from both the research and clinical perspectives.

Efficacy of high-intensity interval training on cardiac autonomic modulation in cardiovascular diseases and lifestyle disorders: a systematic review and meta-analysis

The study aims to investigate the literature on the effect of high-intensity interval training (HIIT) on cardiac autonomic function in individuals with cardiovascular disease (CVD) and lifestyle disorders. We performed electronic database search from CENTRAL, WoS, Scopus, Pubmed, and PEDro up to 25th February 2021. Randomised control trials/quasi-experimental trials/cross-over trials that assessed the effects of HIIT with control/alternative treatment on cardiac autonomic control were included in this review. A total of 11 studies were included for qualitative analysis and among them, 8 were quantitatively analysed. A random-effect model of standardised mean difference (SMD) and mean difference of the respective outcome measures for cardiac autonomic control was determined. The findings of the qualitative analysis revealed the beneficial effects of HIIT on cardiac autonomic modulation. However, the majority of the studies had an unclear or high risk of bias for randomisation, concealment methods, and blinding of participants to the intervention that could have influenced the interpretation of the findings. The SMD revealed a significant effect of HIIT on standard deviation of N-N intervals (SDNN) (ms) [SMD: 0.40, 95% confidence interval (CI): -0.001 to 0.80, P=0.05], high frequency power (HF) (ms2) [0.46, 95% CI: 0.17 to 0.76, P=0.002], and ratio of low and high frequency power, (LF/HF) [-0.80, 95% CI: -1.27 to -0.33, P=0.0008]. In conclusion, HIIT may effectively modulate cardiac autonomic function by increasing parasympathetic dominance, sympathetic withdrawal, and sympathovagal balance in individuals with CVD and lifestyle disorders. The study has a PROSPERO registration number: CRD42021231225

Quantitative sensory testing can effectively predict cardiovascular autonomic neuropathy in patients with type 2 diabetes mellitus

AIMS

Cardiovascular autonomic neuropathy (CAN) is one of the most serious types of diabetic autonomic neuropathy and is a class of small fibre neuropathy. Among many inspection methods, quantitative sensory testing is an effective and convenient method for diagnosing diabetic small fibre neuropathy. This cross-sectional study aimed to identify the correlation between the development of cardiovascular autonomic neuropathy and quantitative sensory testing parameters in patients with type 2 diabetes mellitus.

METHODS

A total of 266 participants with type 2 diabetes mellitus from Nanjing Drum Tower Hospital were enrolled in this study, and each of them received cardiovascular reflex tests (CARTs) and quantitative sensory testing, including testing of cold, warm, cold pain, and heat pain detection thresholds (CDT, WDT, CPT, and HPT, respectively). The results of CARTs were compared with the thermal detection thresholds in quantitative sensory testing by using SPSS 26.0.

RESULTS

A total of 266 participants were divided into the CAN group, early CAN (ECAN) group, and without CAN (NCAN) group. There were significant differences in quantitative sensory testing parameters among three groups, and CARTs presented a positive correlation with the WDT and HPT and a negative correlation with the CDT. Moreover, after adjusting for age, sex, diabetes duration, and other influencing factors, WDT, HPT, and CDT were independent risk factors for cardiovascular autonomic neuropathy.

CONCLUSIONS

The thermal detection thresholds, including cold, warm, and heat pain detection thresholds, in quantitative sensory testing were found to be significantly related to the results of CARTs. Some thermal detection thresholds were independent risk factors for cardiovascular autonomic neuropathy. Therefore, this study showed that quantitative sensory testing has a reliable predictive ability for the occurrence and development of cardiovascular autonomic neuropathy.

Cardiovascular autonomic nervous system function and hip fracture risk: the Cardiovascular Health Study

Among 1299 older adults with 24-h Holter monitoring data at baseline, followed for approximately 15 years, 190 incident hip fractures occurred. Increased heart rate variability was independently associated with reduced risk of hip fracture among female participants.

PURPOSE

Autonomic nervous system function modulates bone remodeling in rodent osteoporosis models. We tested whether cardiovascular autonomic function is associated with hip fracture risk in humans.

METHODS

Participants were 1299 subjects from the Cardiovascular Health Study (mean age 72.8 years). Eight heart rate variability (HRV) measures (time and frequency domains, detrended fluctuation analysis variables, and heart rate turbulence) were derived from 24-h Holter monitor scans in sinus rhythm. Median follow-up for incident hip fracture was 14.7 years [IQR 9.1, 20.2]. Cox proportional hazards models were used to calculate hazard ratios (95% confidence intervals, CI).

RESULTS

There were 144 hip fractures among 714 women (1.31 [1.06, 1.61] per 100-person years) and 46 among 585 men (0.62 [0.43, 0.90] per 100 person-years). From among HRV variables examined, a one standard deviation (SD) higher variation between normal heart beats over 24 h (the SD of NN intervals [SDNN]) was associated with a multivariable-adjusted lower hip fracture risk (HR [Formula: see text] 0.80; 95% CI 0.65-0.99; p = 0.04) in women. The adjusted association between very low frequency power, and hip fracture was borderline statistically significant in women (HR [Formula: see text] 0.82; 95% CI, 0.66-1.00; p = 0.06). When the 8 HRV variables were considered conjointly and adjusted for each other's association with hip fracture risk, a 1 SD higher SDNN value was significantly associated with reduced hip fracture risk in women (HR 0.74; 95% CI, 0.50-0.99; p = 0.05). No HRV variables were associated with hip fracture in men.

CONCLUSIONS

In older women, increased heart rate variation is associated with hip fracture risk.

Validation and Reliability of a Novel Vagus Nerve Neurodynamic Test and Its Effects on Heart Rate in Healthy Subjects: Little Differences Between Sexes

Background

The vagus nerve (VN), also called the pneumogastric nerve, connects the brainstem to organs contained in the chest and abdomen. Physiologically, VN stimulation can rapidly affect cardiac activity and heart rate (HR). VN neuropathy can increase the risk of arrhythmias and sudden death. Therefore, a selective test of VN function may be very useful. Since peripheral neurodynamic tests (NDT) are reliable for the assessment of neuropathies in somatic nerves, we aimed to validate a novel NDT to assess VN activity, namely, the VN-NTD.

Methods

In this cross-sectional double-blind, sex-balanced study, 30 participants (15 females) completed a checklist of autonomic dysfunction symptoms. During the VN-NDT administration, HR and symptoms (i.e., mechanical allodynia) were monitored in parallel to a real-time ultrasonography imaging (USI) and motion capture analysis of the neck. The VN-NDT impact on HR and its accuracy for autonomic symptoms reported in the last 7 days were tested.

Results

The VN-NDT induced a significant HR reduction of about 12 and 8 bpm in males and females [t(1, 119) = 2.425; p < 0.017; η_p² = 0.047, 95% confidence interval (CI): 0.93–9.18], respectively. No adverse events were observed during VN-NDT. A substantial interexaminer agreement between the evaluators in symptoms induction by VN-NDT was detected [F(1, 119) = 0.540; p = 0.464; η_p² = 0.005, low effect]. Notably, mechanical allodynia accuracy for gastrointestinal dysfunctions was excellent (p < 0.05; 95% CI: 0.52–0.73; p < 0.001; 95% CI: 0.81–0.96).

Conclusions

The novel VN-NDT is a valid and accurate test capable of detecting VN activation with high sensitivity. Data provided are suitable for both sexes as a hallmark of HR variation due to VN normal response. The proposed VN-NDT may be reliable as daily routine neurological examination tests for the evaluation of neuropathic signs related to neuroinflammation of the VN.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT04192877.

Dapagliflozin and measures of cardiovascular autonomic function in patients with type 2 diabetes (T2D)

AIMS

Sodium-glucose cotransporter-2 (SGLT-2) inhibitors reduce blood pressure without compensatory heart rate elevation, possibly by modulating sympathetic/parasympathetic activity. This may contribute to their cardiovascular benefits in type 2 diabetes (T2D). We evaluated the effects of dapagliflozin (DAPA) on measures of cardiovascular autonomic neuropathy (CAN), cardiac function, and glucose variability (GV) in T2D.

METHODS

Pilot, randomized, two-period crossover trial comparing 12-week DAPA versus 12-week glimepiride treatment on CAN measures (cardiovascular autonomic reflex tests and heart rate variability), B-type natriuretic peptide (BNP), and GV (Abbott's Libre Pro devices) using signed rank tests and mixed models from baseline to 12 weeks within and between each period.

RESULTS

Forty-five T2D participants on metformin monotherapy (mean age 57 ± 8 years, duration 7 ± 6 years, HbA1c 7.8 ± 1.3%) were enrolled with 41 completing the trial. There were no differences in CAN indices or BNP with each drug compared to baseline and each other. Participants on DAPA demonstrated greater weight loss, reduced time in hypoglycemia, and improved GV compared to glimepiride.

CONCLUSIONS

Short term treatment with DAPA did not affect CAN measures or BNP in uncomplicated and relatively healthy T2D participants. Longer prospective studies in patients with advanced disease are needed to better understand relationships between SGLT-2 inhibitors and CAN.

CLINICAL TRIAL REGISTRATION

NCT02973477.

Associations of Microvascular Complications With the Risk of Cardiovascular Disease in Type 1 Diabetes

OBJECTIVE

We examined whether the presence of microvascular complications was associated with increased subsequent risk of cardiovascular disease (CVD) among participants with type 1 diabetes in the Diabetes Control and Complications Trial and Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study followed for >35 years.

RESEARCH DESIGN AND METHODS

Standardized longitudinal data collection included: 1) stereoscopic seven-field retinal fundus photography centrally graded for retinopathy stage and clinically significant macular edema; 2) urinary albumin excretion rate (AER) and estimated glomerular filtration rate (eGFR); 3) cardiovascular autonomic neuropathy (CAN) reflex testing; and 4) adjudicated CVD events, including death from CVD, nonfatal myocardial infarction, stroke, subclinical myocardial infarction on electrocardiogram, confirmed angina, or coronary artery revascularization. Cox proportional hazards models assessed the association of microvascular complications with subsequent risk of CVD.

RESULTS

A total of 239 participants developed CVD, including 120 participants who suffered major adverse cardiovascular events (MACE) defined as nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death. The presence of microvascular disease (diabetic retinopathy, kidney disease, or CAN) was associated with increased risk of subsequent CVD and MACE (hazard ratios 1.86 to 3.18 and 2.09 to 3.63, respectively), associations that remained significant after adjusting for age and HbA_1c. After adjustment for traditional CVD risk factors, however, only sustained AER ≥30 mg/24 h occurring alone and/or with eGFR <60 mL/min/1.73 m² and the presence of both retinal and kidney disease remained associated with CVD.

CONCLUSIONS

Advanced microvascular disease, especially moderate to severe albuminuria or eGFR <60 mL/min/1.73 m², conveyed an increased risk of subsequent cardiovascular disease in the DCCT/EDIC cohort.

The Association Between Continuous Glucose Monitoring-Derived Metrics and Cardiovascular Autonomic Neuropathy in Outpatients with Type 2 Diabetes

Background: Continuous glucose monitoring (CGM)-derived metrics, including time in range (TIR), are attracting attention as new indicators, beyond hemoglobin A1c, of glycemic control and diabetes complications. This study investigated the associations between CGM-derived TIR, hyperglycemia, and hypoglycemia metrics and cardiovascular autonomic neuropathy (CAN) in patients with type 2 diabetes. Methods: A total of 284 patients with type 2 diabetes who underwent CGM using GOLD™ (Medtronic MiniMed) for 3 days or iPro™2 (Medtronic MiniMed) for 6 days and autonomic function tests within 3 months based on outpatient data were recruited. The definition of CGM-derived metrics was subject to the most recent international consensus. CAN was defined as an abnormal result in two or more parasympathetic test, and the severity of CAN was estimated as the sum of the scores of the five cardiovascular autonomic function tests. Results: A total of 84 patients (29.6%) were diagnosed with CAN, and the mean TIR was 57.0% ± 7.0%. A multiple logistic regression analysis revealed that the odds ratio (OR) of presence of CAN was 0.876 [95% confidence interval (CI): 0.79-0.98] per 10% increase in the TIR 70-180 mg/dL, after adjusting for age, sex, diabetes duration, any medications, and glycemic variability. A 10% increase in the TIR was significantly inversely associated with the severity of CAN (OR: 0.89, 95% CI: 0.81-0.98). Among the metrics of hyperglycemia, each 10% increase in a time above range (TAR) >180 mg/dL was also independently correlated with the presence of CAN (OR: 1.141, 97.5% CI: 1.01-1.29) and the severity of CAN (OR: 1.13, 97.5% CI: 1.01-1.26). Conclusion: A TIR 70-180 mg/dL and a TAR >180 mg/dL were significantly associated with CAN in outpatients with type 2 diabetes.

Diabetic neuropathy in children and youth: New and emerging risk factors

Pediatric neuropathy attributed to metabolic dysfunction is a well-known complication in children and youth with type 1 diabetes. Moreover, the rise of obesity and in particular of type 2 diabetes may cause an uptick in pediatric neuropathy incidence. However, despite the anticipated increase in neuropathy incidence, pathogenic insights and strategies to prevent or manage neuropathy in the setting of diabetes and obesity in children and youth remain unknown. Data from adult studies and available youth cohort studies are providing an initial understanding of potential diagnostic, management, and preventative measures in early life. This review discusses the current state of knowledge emanating from these efforts, with particular emphasis on the prevalence, clinical presentation, diagnostic approaches and considerations, and risk factors of neuropathy in type 1 and type 2 diabetes in children and youth. Also highlighted are current management strategies and recommendations for neuropathy in children and youth with diabetes. This knowledge, along with continued and sustained emphasis on identifying and eliminating modifiable risk factors, completing randomized controlled trials to assess effectiveness of strategies like weight loss and exercise, and enhancing awareness to support early detection and prevention, are pertinent to addressing the rising incidence of neuropathy associated with diabetes and obesity in children and youth.

Pathogenesis and Molecular Treatment Strategies of Diabetic Neuropathy Collateral Glucose-Utilizing Pathways in Diabetic Polyneuropathy

Diabetic polyneuropathy (DPN) is the most common neuropathy manifested in diabetes. Symptoms include allodynia, pain, paralysis, and ulcer formation. There is currently no established radical treatment, although new mechanisms of DPN are being vigorously explored. A pathophysiological feature of DPN is abnormal glucose metabolism induced by chronic hyperglycemia in the peripheral nerves. Particularly, activation of collateral glucose-utilizing pathways such as the polyol pathway, protein kinase C, advanced glycation end-product formation, hexosamine biosynthetic pathway, pentose phosphate pathway, and anaerobic glycolytic pathway are reported to contribute to the onset and progression of DPN. Inhibitors of aldose reductase, a rate-limiting enzyme involved in the polyol pathway, are the only compounds clinically permitted for DPN treatment in Japan, although their efficacies are limited. This may indicate that multiple pathways can contribute to the pathophysiology of DPN. Comprehensive metabolic analysis may help to elucidate global changes in the collateral glucose-utilizing pathways during the development of DPN, and highlight therapeutic targets in these pathways.

Baroreflex sensitivity with different lags and random forests for staging cardiovascular autonomic neuropathy in subjects with diabetes

Impaired baroreflex sensitivity (BRS) may indicate cardiovascular autonomic neuropathy (CAN), which often remains undiagnosed during the initial course of diabetes mellitus. The baroreflex mechanism can be considered negative feedback because of baroreflex delay, the time delay between a change in blood pressure and the counteracting heart rate response. This work sought to analyze BRS considering lags from 1 to 10 RR intervals. We hypothesized that diabetic patients with subclinical CAN (SCAN) have a detectable delay in autonomic nervous system activity and that this would differ from patients without CAN (NCAN) and with established CAN (ECAN). In the first stage, 30 patients were included in an exploratory analysis using the Principal Component Analysis. Six indexes related to the BRS delay were proposed and considered significant for staging diabetic patients. Three indexes allowed for the differentiating of patients with and without CAN, and three indexes distinguished subjects with SCAN from subjects with NCAN or ECAN. Then, in the second stage, a random forest model was developed with 72 subjects, using the variables selected in the first stage. It was possible to detect SCAN, and to point out those subjects with the potential to change the CAN stage, allowing for the tracking of CAN progression. The model achieved a sensitivity of 96% and specificity of 100% to detect SCAN. Thus, the BRS analysis considering delayed reaction in the dynamics of heart rate variability may contribute to an accurate screening tool to staging CAN, in addition to indicating patients with most insidious disease progress.

Hypoglycemia unawareness and autonomic dysfunction in diabetes: Lessons learned and roles of diabetes technologies

Impaired awareness of hypoglycemia (IAH) is a reduction in the ability to recognize low blood glucose levels that would otherwise prompt an appropriate corrective therapy. Identified in approximately 25% of patients with type 1 diabetes, IAH has complex pathophysiology, and might lead to serious and potentially lethal consequences in patients with diabetes, particularly in those with more advanced disease and comorbidities. Continuous glucose monitoring systems can provide real-time glucose information and generate timely alerts on rapidly falling or low blood glucose levels. Given their improvements in accuracy, affordability and integration with insulin pump technology, continuous glucose monitoring systems are emerging as critical tools to help prevent serious hypoglycemia and mitigate its consequences in patients with diabetes. This review discusses the current knowledge on IAH and effective diagnostic methods, the relationship between hypoglycemia and cardiovascular autonomic neuropathy, a practical approach to evaluating cardiovascular autonomic neuropathy for clinicians, and recent evidence from clinical trials assessing the effects of the use of CGM technologies in patients with type 1 diabetes with IAH.