QT prolongation caused by insulin-induced hypoglycaemia - An interventional study in 119 individuals

An overview of the controversies of adult growth hormone deficiency diagnosis

INTRODUCTION

Growth hormone (GH) not only drives growth but also has significant metabolic, structural, and quality-of-life impacts. While GH deficiency (GHD) in childhood impairs growth, in adulthood, it leads to metabolic syndrome and multisystem functional abnormalities, collectively termed adult GHD syndrome. Despite being recognized for decades, adult GHD syndrome continues to pose diagnostic and therapeutic challenge.

AREAS COVERED

The aim of this review is to analyze the main controversies that persist in diagnosing adult GHD more than 30 years after the initial studies demonstrating the existence of GHD syndrome in adulthood.

EXPERT OPINION

The only reliable method for diagnosing adult GHD is demonstrating the failure of GH levels to rise above a specific threshold following pharmacological stimulation tests. Various tests are available, and the choice of the most appropriate one depends on the clinical context, the presence of potential contraindications, and the availability of specific pharmacological agents. It is also important to note that the reproducibility of some stimulation tests for diagnosing adult GHD has been questioned. The GH cutoff values considered diagnostic for GHD differ depending on the test used, are significantly influenced by the individual's body composition and age as well as by assay method employed.

Unmasking Long QT Syndrome in a Serviceman: Effects of Hypoglycemia and a Flight Duty Medical Examination

We report the case of a 29-year-old male soldier with a time in service above 10 years, found to have asymptomatic long QT syndrome (LQTS), a condition associated with increased risk of potentially fatal ventricular arrhythmias, during a flight physical. A review of his past medical history revealed a transient QT prolongation during an episode of hypoglycemia due to endogenous hyperinsulinism caused by an insulinoma, as an infantryman 7 years earlier; the resolution of the QT prolongation was spontaneous. He was evaluated and considered fit for duty by cardiology. Before returning to duty, he underwent a Whipple procedure for the resection of the insulinoma; there was no sequela or recurrence. Seven years later, he was noted to have QT prolongation on a resting electrocardiogram during a routine evaluation to obtain clearance for advanced schooling to become a helicopter pilot. Consequently, he underwent additional workup including genetic testing and was found to be heterozygous for a well-known pathogenic variant KCNQ1: c.1031C > T (p.Ala344Val), LQT1 locus, and additionally for a rare variant in the SNTA1 gene, SNTA1: c.1003_1021dup (p.Ala341Glufs*103), LQT12 locus. The clinical implication, management, and the medical retention determination are presented. We conclude that the stringent requirement for an electrocardiogram as part of medical evaluation for fitness for flight duties in the U.S. Military setting facilitated the detection of an otherwise occult LQTS in this asymptomatic young serviceman. Retrospectively, the LQTS was transiently unmasked during an episode of hypoglycemia. Hypoglycemia deserves more recognition as a potential cause of QT prolongation.

Cardiovascular autonomic neuropathy in diabetes: an update with a focus on management

Cardiovascular autonomic neuropathy (CAN) is an under-recognised yet highly prevalent microvascular complication of diabetes. CAN affects approximately 20% of people with diabetes, with recent studies highlighting the presence of CAN in prediabetes (impaired glucose tolerance and/or impaired fasting glucose), indicating early involvement of the autonomic nervous system. Understanding of the pathophysiology of CAN continues to evolve, with emerging evidence supporting a potential link between lipid metabolites, mitochondrial dysfunction and genetics. Recent advancements, such as streamlining CAN detection through wearable devices and monitoring of heart rate variability, present simplified and cost-effective approaches for early CAN detection. Further research on the optimal use of the extensive data provided by such devices is required. Despite the lack of specific pharmacological interventions targeting the underlying pathophysiology of autonomic neuropathy, several studies have suggested a favourable impact of newer glucose-lowering agents, such as sodium-glucose cotransporter 2 inhibitors and glucagon-like peptide-1 receptor agonists, where there is a wealth of clinical trial data on the prevention of cardiovascular events. This review delves into recent developments in the area of CAN, with emphasis on practical guidance to recognise and manage this underdiagnosed condition, which significantly increases the risk of cardiovascular events and mortality in diabetes.

Factors Influencing Hypoglycemia in Type 2 Diabetes Mellitus Outpatients with State Health Insurance at Regional General Hospitals in Jakarta, Indonesia

BACKGROUND

Hypoglycemia is an acute episode that can lead to death in patients with diabetes mellitus (DM). This condition is preventable with patient education, and identifying factors influencing their occurrence is essential to creating effective and efficient education. It also leads to prevention and control by re-organizing the service system and diabetes policies. This study aimed to determine factors contributing to hypoglycemic episodes in type 2 DM outpatients covered by the state-provided Jaminan Kesehatan Nasional (JKN) health insurance.

METHODS

The study used a cross-sectional design and collected data from five regional general hospitals in Jakarta, Indonesia. The outpatients were sampled consecutively from two hospitals in September-November 2021, one in January-March 2022, and two others in April-June 2023. Interviews produced primary data related to experienced hypoglycemic episodes, and medical records provided secondary data on patients' clinical characteristics and treatments. Binary logistic regression analysis was employed to process the contributing factors statistically.

RESULTS

From 501 patients who met the inclusion and exclusion criteria, it was found that the prevalence of hypoglycemia was 53.3%. Factors that significantly increased hypoglycemic risk (p < 0.05) were high HbA1c levels (OR 1.9; 95% CI 1.2-2.9), comorbidities (OR 1.6; 95% CI 1.1-2.4), insulin/sulfonylurea therapy (OR 2; 95% CI 1-4), non-smoking habit (OR 2.2; 95% CI 1.3-3.6) and physically active lifestyle (OR 1.8; 95% CI 1.2-2.6).

CONCLUSION

The prevalence of hypoglycemia in type 2 diabetes mellitus (DM) outpatients with the state-provided health insurance Jaminan Kesehatan Nasional (JKN) at general hospitals in Jakarta is high. The diabetes self-management education (DSME) services provided by health professionals for these outpatients must be further improved.

Dysglycemia and arrhythmias

Disorders in glucose metabolism can be divided into three separate but interrelated domains, namely hyperglycemia, hypoglycemia, and glycemic variability. Intensive glycemic control in patients with diabetes might increase the risk of hypoglycemic incidents and glucose fluctuations. These three dysglycemic states occur not only amongst patients with diabetes, but are frequently present in other clinical settings, such as during critically ill. A growing body of evidence has focused on the relationships between these dysglycemic domains with cardiac arrhythmias, including supraventricular arrhythmias (primarily atrial fibrillation), ventricular arrhythmias (malignant ventricular arrhythmias and QT interval prolongation), and bradyarrhythmias (bradycardia and heart block). Different mechanisms by which these dysglycemic states might provoke cardiac arr-hythmias have been identified in experimental studies. A customized glycemic control strategy to minimize the risk of hyperglycemia, hypoglycemia and glucose variability is of the utmost importance in order to mitigate the risk of cardiac arrhythmias.

Prevalence of QT prolongation and its risk factors in patients with type 2 diabetes

BACKGROUND

QT prolongation increases cardiovascular mortality in diabetes. The risk factors for QT prolongation vary across different studies. There is no data on the QT prolongation in patients with diabetes from the Arab region, where diabetes is highly prevalent. Here we aimed to assess the prevalence of QT prolongation and its associated risk factors in patients with type 2 diabetes from Saudi Arabia.

METHOD

This was a retrospective, cross-sectional, hospital-based file review study. Data were collected from the medical records of patients with type 2 diabetes aged above 14 years and underwent ECG examination, and laboratory investigations were done within one month of ECG.

RESULTS

The study included 782 patients with a prevalence of QTc prolongation of 13%. Patients with prolonged QTc interval were characterized by older age, higher BMI, longer diabetes duration, lower total cholesterol and LDL-C, and more diabetic nephropathy, hypertension, and CVD cases. They were also more in insulin treatment, antihypertensive medications, loop diuretics, and potassium-sparring diuretics. Logistic regression analysis revealed the odds of prolonged QTc interval increased significantly with CVD (OR = 1.761, 95% CI:1.021-3.036, p = 0.042), and usage of loop diuretics (OR = 2.245, 95% CI:1.023-4.923, p = 0.044) after adjusting for age, gender, and duration of diabetes.

CONCLUSION

The risk factors associated with QTc prolongation in patients with type 2 diabetes are CVD, and loop diuretics. Age, BMI, and diabetes duration were more in people with QTc prolongation, whereas total cholesterol and LDL-C levels were lower. More patients had diabetic nephropathy, hypertension, and CVD with prolonged QTc.

Impact of hypoglycemia at the time of hospitalization for heart failure from emergency department on major adverse cardiovascular events in patients with and without type 2 diabetes

Background

Few studies have examined the association between hypoglycemic episodes among people with type 2 diabetes (T2DM) at the time of hospitalization for heart failure (HF) and cardiovascular outcomes.

Methods

From March 2016 to June 2018, we conducted a retrospective cohort study to investigate hypoglycemia during HF hospitalization in the emergency department, three-point major adverse cardiovascular events (3P-MACE), and all-cause mortality; these were followed up through June 2021. HF hospitalization was defined according to American Heart Association criteria. Hypoglycemia was defined as a glucose level < 3.9 mmol/L at the time of HF hospitalization. We classified the enrolled patients into three groups (reference group, those without T2DM or hypoglycemia; those diagnosed with T2DM without hypoglycemia; and those with hypoglycemia and T2DM). We used Cox proportional hazard regression analysis to investigate the association between the three groups and the development of the first occurrence of 3P-MACE and all-cause mortality.

Results

During a median of 25 months of follow-up, a total of 783 patients admitted due to HF were analyzed. In total, 159 (20.3%) cases of 3P-MACE were identified, and the mortality rate was 20.2% (n = 158). The median age of patients was 76.0 (65.0–82.0) years, and 49.0% were men. Patients with 3P-MACE had a lower body mass index (22.6 [20.4–25.1] vs. 23.8 [21.3–26.7]), higher frequency of previous history of HF (24.5% vs. 15.7%), T2DM (64.2% vs. 47.3%), higher rates of hypoglycemia at the time of HF hospitalization (19.5% vs. 7.7%), and lower eGFR levels (61.1 [36.0–80.7] mL/min/1.73 m² vs. 69.2 [45.8–89.5] mL/min/1.73 m²) than those without 3P-MACE. The multivariable adjusted HR of 3P-MACE was as follows: group with hypoglycemia and T2DM: HR, 2.29; 95% CI: 1.04–5.06; group with T2DM without hypoglycemia: HR: 1.42; 95% CI: 0.86–2.33; and all-cause mortality group with hypoglycemia and T2DM: HR: 2.58; 95% CI: 1.26–5.31, group with T2DM without hypoglycemia: HR: 1.32; 95% CI: 0.81–2.16; compared to the reference group (group without T2DM or hypoglycemia).

Conclusions

T2DM and hypoglycemia are independent risk factors for 3P-MACE and all-cause mortality compared to those without hypoglycemia during HF hospitalization.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01651-0.

Severe hypoglycemia and risk of hospitalization for heart failure in adults with diabetes treated with oral medications with or without insulin: A population-based study

AIMS

We aimed to determine if severe hypoglycemia (SH) independently increases the risk of hospitalization for heart failure (hHF) in type 2 diabetes, regardless of the prevalent or incident cardiovascular disease (CVD).

METHODS

This was a nationwide population-based propensity score-matched study using Korean National Health Insurance Service data (2002-2018). The hazards of hHF were compared in individuals who experienced SH (n = 8,965) and 1:3 matched controls, among adults with diabetes using oral anti-diabetes medications (OADs) with or without insulin and without previous hHF at baseline.

RESULTS

During 236,417 person-years, 1,189 cases of hHF occurred. The hazard of hHF was higher in individuals with SH compared to matched controls (adjusted hazard ratio [aHR] 1.503, 95 % confidence interval [CI] 1.324-1.707). The increase in aHR remained significant when excluding participants with prevalent or incident major adverse cardiovascular events (MACE; aHR 1.352, 95 % CI 1.228-1.622) and any CVD (aHR 1.342, 95 % CI 1.025-1.756). Two or more SH events were associated with further increase in hHF risk.

CONCLUSION

SH was associated with increased risks of hHF among adults with diabetes using OAD with or without insulin. The increased risk was attenuated but remained significant in those without prevalent or incident MACE or CVDs.

The Challenges of Predicting Drug-Induced QTc Prolongation in Humans

The content of this article derives from a Health and Environmental Sciences Institute (HESI) consortium with a focus to improve cardiac safety during drug development. A detailed literature review was conducted to evaluate the concordance between nonclinical repolarization assays and the clinical thorough QT (TQT) study. Food and Drug Administration and HESI developed a joint database of nonclinical and clinical data, and a retrospective analysis of 150 anonymized drug candidates was reviewed to compare the performance of 3 standard nonclinical assays with clinical TQT study findings as well as investigate mechanism(s) potentially responsible for apparent discrepancies identified. The nonclinical assays were functional (IKr) current block (Human ether-a-go-go related gene), action potential duration, and corrected QT interval in animals (in vivo corrected QT). Although these nonclinical assays demonstrated good specificity for predicting negative clinical QT prolongation, they had relatively poor sensitivity for predicting positive clinical QT prolongation. After review, 28 discordant TQT-positive drugs were identified. This article provides an overview of direct and indirect mechanisms responsible for QT prolongation and theoretical reasons for lack of concordance between clinical TQT studies and nonclinical assays. We examine 6 specific and discordant TQT-positive drugs as case examples. These were derived from the unique HESI/Food and Drug Administration database. We would like to emphasize some reasons for discordant data including, insufficient or inadequate nonclinical data, effects of the drug on other cardiac ion channels, and indirect and/or nonelectrophysiological effects of drugs, including altered heart rate. We also outline best practices that were developed based upon our evaluation.

Autonomic cardiac regulation during spontaneous nocturnal hypoglycemia in children with type 1 diabetes

BACKGROUND

Hypoglycemia is the most common complication in insulin treated diabetes. Though mostly mild, it can be fatal in rare cases: It is hypothesized that hypoglycemia related QTc prolongation contributes to cardiac arrhythmia.

OBJECTIVE

To evaluate influence of nocturnal hypoglycemia on QTc and heart rate variability (HRV) in children with T1D.

METHODS

Children and adolescents with T1D for at least 6 months participated in an observational study using continuous glucose monitoring (CGM) and Holter electrocardiogram for five consecutive nights. Mean QTc was calculated for episodes of nocturnal hypoglycemia (<3.7 mmol/L) and compared to periods of the same duration preceding hypoglycemia. HRV (RMSSD, low and high frequency power LF and HF) was analyzed for different 15 min intervals: before hypoglycemia, onset of hypoglycemia, before/after nadir, end of hypoglycemia and after hypoglycemia.

RESULTS

Mean QTc during hypoglycemia was significantly longer compared to euglycemia (412 ± 15 vs. 405 ± 18 ms, p = 0.005). HRV changed significantly: RMSSD (from 88 ± 57 to 73 ± 43 ms) and HF (from 54 ± 17 to 47 ± 17nu) decreased from before hypoglycemia to after nadir, while heart rate (from 69 ± 9 to 72 ± 12 bpm) and LF (from 44 ± 17 to 52 ± 21 nu) increased (p = 0.04).

CONCLUSION

A QTc lengthening effect of nocturnal hypoglycemia in children with T1D was documented. HRV changes occurred even before detection of nocturnal hypoglycemia by CGM, which may be useful for hypoglycemia prediction.

Hypoglycaemia and Cardiovascular Disease Risk in Patients with Diabetes

Hypoglycaemia represents an important side effect of insulin therapy and insulin secretagogues. It can occur in both type 1 and type 2 diabetes mellitus patients. Also, some associations between hypoglycaemia and cardiovascular (CV) risk have been reported. Several mechanisms may be involved, including the sympathoadrenal system, hypokalaemia, endothelial dysfunction, coagulation, platelets, inflammation, atherothrombosis and impaired autonomic cardiac reflexes. This narrative review discusses the associations of hypoglycaemia with CV diseases, including coronary heart disease (CHD), cardiac arrhythmias, stroke, carotid disease and peripheral artery disease (PAD), as well as with dementia. Severe hypoglycaemia has been related to CHD, CV and all-cause mortality. Furthermore, there is evidence supporting an association between hypoglycaemia and cardiac arrhythmias, potentially predisposing to sudden death. The data linking hypoglycaemia with stroke, carotid disease and PAD is limited. Several factors may affect the hypoglycaemia-CV relationships, such as the definition of hypoglycaemia, patient characteristics, co-morbidities (including chronic kidney disease) and antidiabetic drug therapy. However, the association between hypoglycaemia and dementia is bilateral. Both the disorders are more common in the elderly; thus, glycaemic goals should be carefully selected in older patients. Further research is needed to elucidate the impact of hypoglycaemia on CV disease.

Multiple daily insulin injections ameliorate QT interval by lowering blood glucose levels in patients with type 2 diabetes

BACKGROUND

A prolonged QT interval plays a causal role in fatal arrhythmia and is known to be a risk factor for sudden cardiac death. Although diabetic patients with microvascular complications tend to have a longer QT interval, the therapeutic effect of diabetes on the QT interval remains unclear. Here, we assessed the changes in QT interval in patients with type 2 diabetes (T2D) who received multiple daily insulin injections.

MATERIALS AND METHODS

Patients with T2D (n = 34) who were admitted to our hospital and initiated multiple daily insulin injections for glycemic control were enrolled in this study. Clinical measurements, including electrocardiogram, were taken on admission and discharge. The QT interval was measured manually in lead II on the electrocardiogram, and corrected QT interval (QTc) was calculated using Bazett's formula. The change in QTc (ΔQTc) during hospitalization (median, 15 days) and clinical parameters affecting ΔQTc were investigated.

RESULTS

QTc was shortened from 439 ± 24 to 427 ± 26 ms during hospitalization (p < 0.0001). ΔQTc was positively correlated with the changes in fasting plasma glucose (ΔFPG, r = 0.55, p = 0.0008) and glycated albumin (r = 0.38, p = 0.026) following insulin therapy, but not with the final dose of insulin (r = -0.20, p = 0.26). The multiple regression analyses revealed that ΔFPG was independently associated with ΔQTc.

CONCLUSIONS

Multiple daily insulin injections can ameliorate QT interval by lowering the blood glucose levels in T2D, suggesting that glycemic control is important for preventing patients with T2D from sudden cardiac death.

In vivo cardiopulmonary impact of skeletal M3Dq DREADD expression: a pilot study

The muscarinic M₃ receptor (M₃R) is implicated in cardiopulmonary control and many other peripheral physiologic functions. Previous observations report mortality in mice expressing a Gq-linked designer G-protein coupled receptor (Dq) selectively in striated muscle, while M₃Dq DREADD (Designer Receptor Exclusively Activated by Designer Drug), selectively expressed in skeletal muscle (SKM) impacts glucose metabolism. We investigated whether activation of SKM M₃Dq impacts cardiopulmonary function. Heart rate (HR), body temperature (Tb) and locomotor activity (ACT) were measured in 4 conscious, chronically instrumented M₃Dq DREADD mice and 4 wildtype controls. Circadian values of HR, BT and ACT were not different between genotypes (p > 0.05). Activation of the M₃Dq DREADD by clozapine N-oxide (CNO; 0.1 mg/kg) resulted in: a significant drop in heart rate, 2 h after injection, compared with a time-matched baseline control period from the same animals (460 ± 28 vs. 532 ± 6, p < 0.05), significantly lower ACT compared to the baseline control (p < 0.05) and reduced pulmonary minute ventilation compared to pre-CNO control (p < 0.05). M₃Dq DREADD activation did not cause bronchoconstriction (separate protocol), however, there was a concomitant reduction in HR, Tb and ventilation, accompanied by cardiac arrhythmias. We speculate that reductions in Tb, HR and ventilation reflect a mechanistic link between SKM Gq signaling and the metabolic responses associated with the initiation of torpor. Supported by the Canadian Institutes of Health Research (CIHR MOP-81211).

Clinical Outcomes in Patients With Isolated or Combined Diabetic Ketoacidosis and Hyperosmolar Hyperglycemic State: A Retrospective, Hospital-Based Cohort Study

OBJECTIVE

Many patients with hyperglycemic crises present with combined features of diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS). The implications of concomitant acidosis and hyperosmolality are not well known. We investigated hospital outcomes in patients with isolated or combined hyperglycemic crises.

RESEARCH DESIGN AND METHODS

We analyzed admissions data listing DKA or HHS at two academic hospitals. We determined 1) the frequency distributions of HHS, DKA, and combined DKA-HHS (DKA criteria plus elevated effective osmolality); 2) the relationship of markers of severity of illness and clinical comorbidities with 30-day all-cause mortality; and 3) the relationship of hospital complications associated with insulin therapy (hypoglycemia and hypokalemia) with mortality.

RESULTS

There were 1,211 patients who had a first admission with confirmed hyperglycemic crises criteria, 465 (38%) who had isolated DKA, 421 (35%) who had isolated HHS, and 325 (27%) who had combined features of DKA-HHS. After adjustment for age, sex, BMI, race, and Charlson Comorbidity Index score, subjects with combined DKA-HHS had higher in-hospital mortality compared with subjects with isolated hyperglycemic crises (adjusted odds ratio [aOR] 2.7; 95% CI 1.4, 4.9; P = 0.0019). In all groups, hypoglycemia (<40 mg/dL) during treatment was associated with a 4.8-fold increase in mortality (aOR 4.8; 95% CI 1.4, 16.8). Hypokalemia ≤3.5 mEq/L was frequent (55%). Severe hypokalemia (≤2.5 mEq/L) was associated with increased inpatient mortality (aOR 4.9; 95% CI 1.3, 18.8; P = 0.02).

CONCLUSIONS

Combined DKA-HHS is associated with higher mortality compared with isolated DKA or HHS. Severe hypokalemia and severe hypoglycemia are associated with higher hospital mortality in patients with hyperglycemic crises.

Complex Arrhythmias Due to Reversible Causes

Abnormalities in cardiac rhythm are caused by disorders of impulse generation, conduction, or a combination of the 2, and may be life-threatening because of a reduction in cardiac output or myocardial oxygenation. Cardiac arrhythmias are commonly classified as tachycardias (supraventricular or ventricular) or bradycardias. Bradycardias are uncommon in the critically ill patient and often are caused by an underlying reversible disorder (eg, hyperkalemia, drug toxicity). Supraventricular and ventricular tachycardias are more often encountered in the critically ill patient and often have underlying treatable disorders that precipitate their development (eg, hypokalemia, hypomagnesemia, antiarrhythmic proarrhythmia, myocardial ischemia).

Macimorelin as a Diagnostic Test for Adult GH Deficiency

PURPOSE

The diagnosis of adult GH deficiency (AGHD) is challenging and often requires confirmation with a GH stimulation test (GHST). The insulin tolerance test (ITT) is considered the reference standard GHST but is labor intensive, can cause severe hypoglycemia, and is contraindicated for certain patients. Macimorelin, an orally active GH secretagogue, could be used to diagnose AGHD by measuring stimulated GH levels after an oral dose.

MATERIALS AND METHODS

The present multicenter, open-label, randomized, two-way crossover trial was designed to validate the efficacy and safety of single-dose oral macimorelin for AGHD diagnosis compared with the ITT. Subjects with high (n = 38), intermediate (n = 37), and low (n = 39) likelihood for AGHD and healthy, matched controls (n = 25) were included in the efficacy analysis.

RESULTS

After the first test, 99% of macimorelin tests and 82% of ITTs were evaluable. Using GH cutoff levels of 2.8 ng/mL for macimorelin and 5.1 ng/mL for ITTs, the negative agreement was 95.38% (95% CI, 87% to 99%), the positive agreement was 74.32% (95% CI, 63% to 84%), sensitivity was 87%, and specificity was 96%. On retesting, the reproducibility was 97% for macimorelin (n = 33). In post hoc analyses, a GH cutoff of 5.1 ng/mL for both tests resulted in 94% (95% CI, 85% to 98%) negative agreement, 82% (95% CI, 72% to 90%) positive agreement, 92% sensitivity, and 96% specificity. No serious adverse events were reported for macimorelin.

CONCLUSIONS

Oral macimorelin is a simple, well-tolerated, reproducible, and safe diagnostic test for AGHD with accuracy comparable to that of the ITT. A GH cutoff of 5.1 ng/mL for the macimorelin test provides an excellent balance between sensitivity and specificity.

Metabolic syndrome and its components as risk factors for prolonged corrected QT interval in apparently healthy Korean men and women

BACKGROUND

Metabolic syndrome (MetS) is clinically important because of its association with increased risk of sudden cardiac death, as well as cardiovascular disease-related mortality. Data between MetS and prolonged corrected QT (QTc) intervals, a useful predictor of sudden cardiac death, are limited in apparently healthy adults.

OBJECTIVE

This study determined the association between MetS and QTc interval in apparently healthy Korean men and women.

METHODS

We examined the association between MetS and QTc interval in 2157 Korean adults (1317 men and 840 women) in a health examination program but excluded participants with a history of ischemic heart disease, stroke, cardiac arrhythmia, cancer, thyroid, respiratory, renal, hepatobiliary, or rheumatologic disease. The QTc interval was calculated using Bazett's formula (QTc = QT/√RR). Multivariate-adjusted mean QTc values by the number of MetS components were calculated after sex stratification and compared using analysis of covariance test.

RESULTS

The overall prevalence of MetS was 30.5% in men and 19.8% in women. The QTc interval positively correlated with age, body mass index, blood pressure, fasting plasma glucose, triglycerides, and potassium level in both men and women and negatively correlated with calcium and potassium levels and smoking status in men. The multivariate-adjusted mean QTc value increased proportionally with increasing number of MetS components (P values < 0.001 for both men and women).

CONCLUSION

We confirmed the arrhythmogenic potential of MetS in apparently healthy Korean men and women. These findings suggest that careful monitoring of electrocardiography is necessary to evaluate possible arrhythmic risk in individuals with MetS.

The somatostatin-secreting pancreatic δ-cell in health and disease

The somatostatin-secreting δ-cells comprise ~5% of the cells of the pancreatic islets. The δ-cells have complex morphology and might interact with many more islet cells than suggested by their low numbers. δ-Cells contain ATP-sensitive potassium channels, which open at low levels of glucose but close when glucose is elevated. This closure initiates membrane depolarization and electrical activity and increased somatostatin secretion. Factors released by neighbouring α-cells or β-cells amplify the glucose-induced effects on somatostatin secretion from δ-cells, which act locally within the islets as paracrine or autocrine inhibitors of insulin, glucagon and somatostatin secretion. The effects of somatostatin are mediated by activation of somatostatin receptors coupled to the inhibitory G protein, which culminates in suppression of the electrical activity and exocytosis in α-cells and β-cells. Somatostatin secretion is perturbed in animal models of diabetes mellitus, which might explain the loss of appropriate hypoglycaemia-induced glucagon secretion, a defect that could be mitigated by somatostatin receptor 2 antagonists. Somatostatin antagonists or agents that suppress somatostatin secretion have been proposed as an adjunct to insulin therapy. In this Review, we summarize the cell physiology of somatostatin secretion, what might go wrong in diabetes mellitus and the therapeutic potential of agents targeting somatostatin secretion or action.

The somatostatin-secreting pancreatic δ-cell in health and disease

The somatostatin-secreting δ-cells comprise ~5% of the cells of the pancreatic islets. The δ-cells have complex morphology and might interact with many more islet cells than suggested by their low numbers. δ-Cells contain ATP-sensitive potassium channels, which open at low levels of glucose but close when glucose is elevated. This closure initiates membrane depolarization and electrical activity and increased somatostatin secretion. Factors released by neighbouring α-cells or β-cells amplify the glucose-induced effects on somatostatin secretion from δ-cells, which act locally within the islets as paracrine or autocrine inhibitors of insulin, glucagon and somatostatin secretion. The effects of somatostatin are mediated by activation of somatostatin receptors coupled to the inhibitory G protein, which culminates in suppression of the electrical activity and exocytosis in α-cells and β-cells. Somatostatin secretion is perturbed in animal models of diabetes mellitus, which might explain the loss of appropriate hypoglycaemia-induced glucagon secretion, a defect that could be mitigated by somatostatin receptor 2 antagonists. Somatostatin antagonists or agents that suppress somatostatin secretion have been proposed as an adjunct to insulin therapy. In this Review, we summarize the cell physiology of somatostatin secretion, what might go wrong in diabetes mellitus and the therapeutic potential of agents targeting somatostatin secretion or action.

Theoretical overview of clinical and pharmacological aspects of the use of etelcalcetide in diabetic patients undergoing hemodialysis

Etelcalcetide is the first intravenous calcimimetic agent authorized for the treatment of secondary hyperparathyroidism (sHPT) in patients undergoing hemodialysis in Europe, the US, and Japan. The relationship between sHPT and diabetes resides on complex, bidirectional effects and largely unknown homeostatic mechanisms. Although 30% or more patients with end-stage renal disease are diabetics and about the same percentage of those patients suffer from sHPT associated with hemodialysis, no data on the specificities of the use of etelcalcetide in such patients are available yet. Regarding pharmacokinetic interactions, etelcalcetide may compete with oral hypoglycemics recommended for use in patients undergoing hemodialysis and insulins detemir and degludec, causing unexpected hypocalcemia or hypoglycemia. More importantly, hypocalcemia, a common side effect of etelcalcetide, may cause decompensation of preexisting cardiac insufficiency in diabetic patients or worsen dialysis-related hypotension and lead to hypotension-related cardiac events, such as myocardial ischemia. In diabetic patients, hypocalcemia may lead to dangerous ventricular arrhythmias, as both insulin-related hypoglycemia and hemodialysis prolong QT interval. Patients with diabetes, therefore, should be strictly monitored for hypocalcemia and associated effects. Due to an altered parathormone activity in this patient group, plasma calcium should be the preferred indicator of etelcalcetide effects. Until more clinical experience with etelcalcetide is available, the clinicians should be cautious when using this calcimimetic in patients with diabetes.

Usefulness of simultaneous and sequential monitoring of glucose level and electrocardiogram in monkeys treated with gatifloxacin under conscious and nonrestricted conditions

Drug-induced cardiac electrophysiological abnormalities accompanied by hypoglycemia or hyperglycemia increase the risk for life-threatening arrhythmia. To assess the drug-induced cardiotoxic potential associated with extraordinary blood glucose (GLU) levels, the effect of gatifloxacin (GFLX) which was frequently associated with GLU abnormality and QT/QTc prolongations in the clinic on blood GLU and electrocardiogram (ECG) parameters was investigated in cynomolgus monkeys (n=4) given GFLX orally in an ascending dose regimen (10, 30, 60 and 100 mg/kg). Simultaneous and sequential GLU and ECG monitoring with a continuous GLU monitoring system and Holter ECG, respectively, were conducted for 24 h under free-moving conditions. Consequently, GFLX at 30 and 60 mg/kg dose-dependently induced a transient decrease in GLU without any ECG abnormality 2–4 h postdose. Highest dose of 100 mg/kg caused severe hypoglycemia with a mean GLU of <30 mg/dL, accompanied by remarkable QT/QTc prolongations by 20–30% in all animals. In contrast, hyperglycemia without QT/QTc prolongations was noted 24 h after dosing in one animal. A close correlation between GLU and QTc values was observed in animals treated with 100 mg/kg, suggesting that GFLX-induced hypoglycemia enhanced QT/QTc prolongations. Furthermore, the 24-h sequential GLU monitoring data clearly distinguished between GFLX-induced GLU abnormality and physiological GLU changes influenced by feeding throughout the day. In conclusion, the combined assessment of continuous GLU and ECG monitoring is valuable in predicting the drug-induced cardio-electrophysiological risk associated with both GLU and ECG abnormalities.

Severity and multiplicity of microvascular complications are associated with QT interval prolongation in patients with type 2 diabetes

Aims/Introduction

A prolonged QT interval plays a causal role in life‐threatening arrhythmia, and becomes a risk factor for sudden cardiac death. Here, we assessed the association between microvascular complications and the QT interval in patients with type 2 diabetes.

Materials and Methods

Patients with type 2 diabetes (n = 219) admitted to Nippon Medical School Hospital (Tokyo, Japan) for glycemic control were enrolled. QT interval was measured manually in lead II on the electrocardiogram, and corrected for heart rate using Bazett's formula (QTc). Diabetic neuropathy, retinopathy and nephropathy were assessed by neuropathic symptoms or Achilles tendon reflex, ophthalmoscopy and urinary albumin excretion, respectively.

Results

In univariate analyses, female sex (P = 0.025), duration of type 2 diabetes (P = 0.041), body mass index (P = 0.0008), systolic blood pressure (P = 0.0011) and receiving insulin therapy (P < 0.0001) were positively associated with QTc. Patients with each of the three microvascular complications had longer QTc than those without: neuropathy (P = 0.0005), retinopathy (P = 0.0019) and nephropathy (P = 0.0001). As retinopathy or nephropathy progressed, QTc became longer (P < 0.001 and P < 0.001 for trend in retinopathy and nephropathy, respectively). Furthermore, QTc was prolonged with the multiplicity of the microvascular complications (P < 0.001 for trend). Multiple regression analyses showed that neuropathy, nephropathy and the multiplicity of the microvascular complications were independently associated with QTc.

Conclusions

Patients with type 2 diabetes with severe microvascular complications might be at high risk for life‐threatening arrhythmia associated with QT interval prolongation.

Patients With Long-QT Syndrome Caused by Impaired hERG-Encoded Kv11.1 Potassium Channel Have Exaggerated Endocrine Pancreatic and Incretin Function Associated With Reactive Hypoglycemia

Supplemental Digital Content is available in the text.

Background:

Loss-of-function mutations in hERG (encoding the K_v11.1 voltage-gated potassium channel) cause long-QT syndrome type 2 (LQT2) because of prolonged cardiac repolarization. However, K_v11.1 is also present in pancreatic α and β cells and intestinal L and K cells, secreting glucagon, insulin, and the incretins glucagon-like peptide-1 (GLP-1) and GIP (glucose-dependent insulinotropic polypeptide), respectively. These hormones are crucial for glucose regulation, and long-QT syndrome may cause disturbed glucose regulation. We measured secretion of these hormones and cardiac repolarization in response to glucose ingestion in LQT2 patients with functional mutations in hERG and matched healthy participants, testing the hypothesis that LQT2 patients have increased incretin and β-cell function and decreased α-cell function, and thus lower glucose levels.

Methods:

Eleven patients with LQT2 and 22 sex-, age-, and body mass index–matched control participants underwent a 6-hour 75-g oral glucose tolerance test with ECG recording and blood sampling for measurements of glucose, insulin, C-peptide, glucagon, GLP-1, and GIP.

Results:

In comparison with matched control participants, LQT2 patients had 56% to 78% increased serum insulin, serum C-peptide, plasma GLP-1, and plasma GIP responses (P=0.03–0.001) and decreased plasma glucose levels after glucose ingestion (P=0.02) with more symptoms of hypoglycemia (P=0.04). Sixty-three percent of LQT2 patients developed hypoglycemic plasma glucose levels (<70 mg/dL) versus 36% control participants (P=0.16), and 18% patients developed serious hypoglycemia (<50 mg/dL) versus none of the controls. LQT2 patients had defective glucagon responses to low glucose, P=0.008. β-Cell function (Insulin Secretion Sensitivity Index-2) was 2-fold higher in LQT2 patients than in controls (4398 [95% confidence interval, 2259–8562] versus 2156 [1961–3201], P=0.03). Pharmacological K_v11.1 blockade (dofetilide) in rats had similar effect, and small interfering RNA inhibition of hERG in β and L cells increased insulin and GLP-1 secretion up to 50%. Glucose ingestion caused cardiac repolarization disturbances with increased QTc intervals in both patients and controls, but with a 122% greater increase in QTcF interval in LQT2 patients (P=0.004).

Conclusions:

Besides a prolonged cardiac repolarization phase, LQT2 patients display increased GLP-1, GIP, and insulin secretion and defective glucagon secretion, causing decreased plasma glucose and thus increased risk of hypoglycemia. Furthermore, glucose ingestion increased QT interval and aggravated the cardiac repolarization disturbances in LQT2 patients.

Clinical Trial Registration:

URL: http://clinicaltrials.gov. Unique identifier: NCT02775513.