Impact of glycemic and blood pressure variability on surrogate measures of cardiovascular outcomes in type 2 diabetic patients

Glycemic Variability Assessed by Continuous Glucose Monitoring and Short-Term Outcome in Diabetic Patients Undergoing Percutaneous Coronary Intervention: An Observational Pilot Study

Poor glycemic control is associated with unfavorable outcome in patients undergoing percutaneous coronary intervention (PCI), irrespective of diabetes mellitus. However a complete assessment of glycemic status may not be fully described by glycated hemoglobin or fasting blood glucose levels, whereas daily glycemic fluctuations may influence cardiovascular risk and have even more deleterious effects than sustained hyperglycemia. Thus, this paper investigated the effectiveness of a continuous glucose monitoring (CGM), registering the mean level of glycemic values but also the extent of glucose excursions during coronary revascularization, in detecting periprocedural outcome such as renal or myocardial damage, assessed by serum creatinine, neutrophil gelatinase-associated lipocalin (NGAL), and troponin I levels. High glycemic variability (GV) has been associated with worse postprocedural creatinine and NGAL variations. Moreover, GV, and predominantly hypoglycemic variations, has been observed to increase in patients with periprocedural myocardial infarction. Thus, our study investigated the usefulness of CGM in the setting of PCI where an optimal glycemic control should be achieved in order to prevent complications and improve outcome.

Effects of vildagliptin compared with glibenclamide on glucose variability after a submaximal exercise test in patients with type 2 diabetes: study protocol for a randomized controlled trial, DIABEX VILDA

BACKGROUND

Cardiovascular disease, endothelial dysfunction, and oxidative stress are common complications among patients with type 2 diabetes (T2DM). In addition to the average blood glucose concentration, glycemic variability may be an important factor for the development of chronic diabetes complications. Patients with T2DM are treated with various types of oral glucose-lowering drugs. Exercise is considered to benefit the health of both healthy and unhealthy individuals, which has been confirmed by a number of scientific research studies in which the participants' health improved. Our general aim in this study will be to evaluate glucose variability after submaximal exercise test in patients receiving treatment with either vildagliptin or glibenclamide. The specific aims of this study are to evaluate the oxidative stress, endothelial function, and metabolic and cardiovascular responses to exercise under treatment with vildagliptin or glibenclamide. All these responses are important in patients with T2DM.

METHODS/DESIGN

This study is a PROBE (Prospective, Randomized, Open-label, Blinded-Endpoint) design clinical trial. The estimated sample needed is 20 patients with T2DM. In addition to the routine treatment (metformin), patients will receive a second drug orally for 12 weeks: the METV group will receive metformin plus vildagliptin (50 mg twice daily), and the METG group will receive metformin plus glibenclamide (5 to 10 mg twice daily.). Before and after intervention, evaluation of glycemic variability, endothelial function, oxidative stress, and metabolic and cardiovascular response will be performed at rest, during and after a submaximal exercise test (30 minutes, with an intensity based at 10% under the heart rate at the second threshold).

DISCUSSION

In addition to drug treatment, exercise is recommended for treatment of glycemic control in patients with T2DM, especially for its beneficial effects on blood glucose and HbA1c. Few studies have determined the effects of the association between exercise and oral glucose-lowering drugs. The study will be conducted to assess the metabolic and cardiovascular responses at rest, and during and after submaximal exercise in patients receiving one of two oral glucose-lowering drugs (vildagliptin or glibenclamide).

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01867502 study release date: May-17-2013.

A very low-carbohydrate, low-saturated fat diet for type 2 diabetes management: a randomized trial

OBJECTIVE

To comprehensively compare the effects of a very low-carbohydrate, high-unsaturated/low-saturated fat diet (LC) with those of a high-unrefined carbohydrate, low-fat diet (HC) on glycemic control and cardiovascular disease (CVD) risk factors in type 2 diabetes (T2DM).

RESEARCH DESIGN AND METHODS

Obese adults (n = 115, BMI 34.4 ± 4.2 kg/m(2), age 58 ± 7 years) with T2DM were randomized to a hypocaloric LC diet (14% carbohydrate [<50 g/day], 28% protein, and 58% fat [<10% saturated fat]) or an energy-matched HC diet (53% carbohydrate, 17% protein, and 30% fat [<10% saturated fat]) combined with structured exercise for 24 weeks. The outcomes measured were as follows: glycosylated hemoglobin (HbA1c), glycemic variability (GV; assessed by 48-h continuous glucose monitoring), antiglycemic medication changes (antiglycemic medication effects score [MES]), and blood lipids and pressure.

RESULTS

A total of 93 participants completed 24 weeks. Both groups achieved similar completion rates (LC 79%, HC 82%) and weight loss (LC -12.0 ± 6.3 kg, HC -11.5 ± 5.5 kg); P ≥ 0.50. Blood pressure (-9.8/-7.3 ± 11.6/6.8 mmHg), fasting blood glucose (-1.4 ± 2.3 mmol/L), and LDL cholesterol (-0.3 ± 0.6 mmol/L) decreased, with no diet effect (P ≥ 0.10). LC achieved greater reductions in triglycerides (-0.5 ± 0.5 vs. -0.1 ± 0.5 mmol/L), MES (-0.5 ± 0.5 vs. -0.2 ± 0.5), and GV indices; P ≤ 0.03. LC induced greater HbA1c reductions (-2.6 ± 1.0% [-28.4 ± 10.9 mmol/mol] vs. -1.9 ± 1.2% [-20.8 ± 13.1 mmol/mol]; P = 0.002) and HDL cholesterol (HDL-C) increases (0.2 ± 0.3 vs. 0.05 ± 0.2 mmol/L; P = 0.007) in participants with the respective baseline values HbA1c >7.8% (62 mmol/mol) and HDL-C <1.29 mmol/L.

CONCLUSIONS

Both diets achieved substantial improvements for several clinical glycemic control and CVD risk markers. These improvements and reductions in GV and antiglycemic medication requirements were greatest with the LC compared with HC. This suggests an LC diet with low saturated fat may be an effective dietary approach for T2DM management if effects are sustained beyond 24 weeks.

Glycemic variability and oxidative stress: a link between diabetes and cardiovascular disease?

Diabetes is associated with a two to three-fold increase in risk of cardiovascular disease. However, intensive glucose-lowering therapy aiming at reducing HbA1c to a near-normal level failed to suppress cardiovascular events in recent randomized controlled trials. HbA1c reflects average glucose level rather than glycemic variability. In in vivo and in vitro studies, glycemic variability has been shown to be associated with greater reactive oxygen species production and vascular damage, compared to chronic hyperglycemia. These findings suggest that management of glycemic variability may reduce cardiovascular disease in patients with diabetes; however, clinical studies have shown conflicting results. This review summarizes the current knowledge on glycemic variability and oxidative stress, and discusses the clinical implications.

Lower blood glucose and variability are associated with earlier recovery from renal injury caused by episodic urinary tract infection in advanced type 2 diabetic chronic kidney disease

PURPOSE

In our previous study, type 2 diabetic chronic kidney disease (CKD) patients with glomerular filtration rates of <30 mL/min upon hospitalization for urinary tract infection (UTI) were at a risk for acute kidney injury. This study aimed to clarify the effect of glucose and its variability on renal outcomes during admission for the treatment of UTI.

MATERIALS AND METHODS

Based on the date of renal recovery (RIFLE criteria: acute kidney injury occurred within 1-7 days and was sustained over 1 day), we divided these patients into early- (≤9 days, Group A) and late-recovery (>9 days, Group B) groups. The differences in the continuous and categorical variables of the two groups were assessed separately. The mean glucose levels and their variability (using the standard deviation and the coefficient of standard deviation) were compared at the fasting, midday pre-meal, evening pre-meal, and evening post-meal time points during hospitalization. We have organized the manuscript in a manner compliant with the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) statement.

RESULTS

Acute kidney injury occurred within the two groups (p = 0.007 and p = 0.001, respectively). The early-morning blood glucose levels (149.7±44.0 mg/dL) and average blood glucose levels (185.6±52.0 mg/dL) were better in Group A (p = 0.01, p = 0.02). Group A patients also had lower glucose variability than Group B at the different time points (p<0.05). Group A also had earlier renal recovery. More relevant pathogens were identified from blood in Group B (p = 0.038).

CONCLUSIONS

Early-morning fasting and mean blood glucose levels and their variability can be good indicators of severe infection and predictors of renal outcome in type 2 diabetic patients with CKD and UTI.

Association between impaired cardiovascular autonomic function and hypoglycemia in patients with type 1 diabetes

OBJECTIVE

We studied the association between glycemic variability (GV) reflecting hypoglycemic stress and cardiovascular autonomic function in subjects with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Forty-four type 1 diabetic patients (mean age 34 ± 13 years, 40% male, 86% Caucasian, mean diabetes duration 13 ± 6 years, mean hemoglobin A1c [HbA1c] 8.0 ± 1.2% [64 ± 5 mmol/mol]) without cardiovascular disease, dyslipidemia, or hypertension participated in this pilot study. Indices of GV reflective of hypoglycemic stress (low blood glucose index [LBGI] and area under the curve [AUC] for hypoglycemia) were computed using data obtained during 5-day continuous glucose monitoring. Cardiovascular autonomic neuropathy (CAN) was assessed using standardized cardiovascular reflex testing and measures of heart rate variability (HRV), which were analyzed as time and frequency domain measures.

RESULTS

Both LBGI and AUC hypoglycemia had a significant negative association with the low-frequency power of HRV (r = -0.47, P = 0.002; r = -0.43, P = 0.005, respectively) and with the high-frequency power of HRV (r = -0.37, P = 0.018; r = -0.38, P = 0.015, respectively). These inverse associations persisted after adjusting for HbA1c, although they were attenuated in multivariable analysis after adjustment for age, diabetes duration, and several other covariates.

CONCLUSIONS

Increased GV promoting hypoglycemic stress was associated with reduced HRV independent of glycemic control as assessed by HbA1c. These pilot data suggest that glucose variability may contribute to cardiovascular autonomic dysfunction among adults with type 1 diabetes.

Glycemic variability in nondiabetic morbidly obese persons: results of an observational study and review of the literature

Glycemic variability (GV) is correlated with oxidative stress which may lead to increased cardiovascular risk and poor clinical outcomes in people with prediabetes and diabetes. We sought to understand whether morbidly obese persons without diabetes by standard criteria have dysglycemia as measured by GV. We performed an observational study of GV metrics and carotid intima media thickness (CIMT) in 21 morbidly obese normoglycemic and 15 morbidly obese prediabetic applicants to The Biggest Loser television show. The results were compared to previously published studies in normoglycemic nonobese and obese individuals. Glucose was measured with a masked continuous glucose monitor (CGM) over 3 to 8 days and carotid intima media thickness (CIMT) was determined by ultrasound. CGM-derived GV metrics for GV were coefficient of variation (CV), standard deviation (SD), mean amplitude of glycemic excursions (MAGE), continuous overall net glycemic action-1 hour (CONGA1), and mean of daily differences (MODD). We found that morbidly obese subjects (n = 21) who were normoglycemic by standard criteria had higher GV (CV = 22%, SD = 24.2 mg/dl and MAGE = 48.6 mg/dl) than previous reports of normoglycemic, nonobese individuals (CV = 12-18%, SD = 11.5-15.0 mg/dl, and MAGE = 26.3-28.3 mg/dl). Morbidly obese prediabetic subjects (n = 15) had GV metrics indistinguishable from those morbidly obese subjects who were normoglycemic. CIMT was higher in both morbidly obese groups compared with historical age- and sex-matched controls. Normoglycemic and prediabetic morbidly obese individuals have higher GV compared with normal weight, nondiabetic individuals. We speculate that this may increase the risk for macrovascular disease through excessive oxidative stress.

Relationship of hypoglycemia and glucose variability with autonomic dysfunction in children and adolescents with type 1 diabetes

Aim. Glucose variability (GV) and hypoglycaemia frequency and duration, depending on cardiovascular autonomic dysfunction, in children and adolescents with type 1 diabetes mellitus (T1DM) were evaluated. Materials and methods. One hundred and thirty T1DM patients, aged 6?18 years, were included in this study. The study included 3 tests:. continuous glucose monitoring (CGM) with GV evaluation, frequency and duration of hypoglycaemia;24-h ECG monitoring with automatic calculation of QTc interval and heart rate variability (HRV) parameters;cardiovascular autonomic tests.Results. The estimated prevalence of cardiovascular autonomic neuropathy (CAN) was 19.2%. CAN positive (CAN+) patients had lower values from cardiovascular autonomic tests and HRV and longer QTc intervals compared with CAN negative (CAN-) patients (p 

Acute hyperglycemia reduces cerebrovascular reactivity: the role of glycemic variability

CONTEXT

Cerebral vasomotor reactivity (CVR) is reduced in patients with diabetes mellitus (DM), and glucose variability (GV) might be responsible for cerebrovascular damage.

OBJECTIVE

Studying patients with insulin resistance without DM, we explored the role of GV in impairing CVR.

PATIENTS

We studied 18 metabolic syndrome (MS) patients without DM, 9 controls (C), and 26 patients with DM.

MAIN OUTCOME MEASURES

Groups were compared in terms of CVR, GV, and 24-hour blood pressure. To evaluate the impact of acute hyperglycemia on CVR, a hyperglycemic clamp was performed in MS patients and controls.

RESULTS

Baseline CVR was reduced in DM vs C and MS (C vs DM = 20.2, 95% CI = 3.5-36.9, P = .014; and MS vs DM = 22.2, 95% CI = 8.6-35.8, P = .001), but similar between MS and C (MS vs C = 2.0, 95% CI = -14.7 to 18.7, P = .643). During acute hyperglycemia, CVR fell in MS and C to values comparable to DM. GV progressively increased from C to MS to DM. In MS, CVR at 120 minutes and GV displayed a negative correlation (r = -0.48, P = .043), which did not change after controlling for mean 24-hour systolic and diastolic blood pressure. In MS, the CVR reduction was significantly correlated to GV (r = 0.55, P = .02).

CONCLUSIONS

GV is increased in patients with MS but without DM and is the major predictor of CVR reduction induced by acute hyperglycemia, possibly representing the earliest cause of cerebrovascular damage in DM.

Effects of subtracting sitting versus adding exercise on glycemic control and variability in sedentary office workers

Recent evidence suggests that, like adding exercise, reducing sitting time may improve cardiometabolic health. There has not been a direct comparison of the 2 strategies with energy expenditure held constant. The purpose of this study was to compare fasting and postmeal glucose and insulin concentrations in response to a day with frequent breaks from sitting but no exercise versus considerable sitting plus moderate exercise. Ten sedentary overweight/obese office workers were tested in 3 conditions: (i) walking per activity guidelines (AGW): sitting for majority of workday with a 30 min pre-lunch walk; (ii) frequent long breaks (FLB): no structured exercise but frequent breaks from sitting during workday with energy expenditure matched to AGW; and (iii) frequent short breaks (FSB): number of breaks matched to FLB, but duration of breaks were shorter. Plasma glucose and insulin areas under the curve were measured in response to a meal tolerance test (MTT) at the end of the workday and interstitial glucose was evaluated throughout the day and overnight using continuous glucose monitoring. Using repeated-measures linear mixed models, area under the curve of plasma glucose or insulin after the MTT was not different between conditions. Glycemic variability was lower in FLB compared with AGW (p < 0.05), and nocturnal duration of elevated glucose (>7.8 mmol/L) was shorter after FLB (2.5 ± 2.5 min) than AGW (32.7 ± 16.4 min) or FSB (45.6 ± 29.6 min, p = 0.05). When energy expenditure was matched, breaks from sitting approximated the effects of moderate-intensity exercise on postmeal glucose and insulin responses and more effectively constrained glycemic variability.

Glycemic variability and outcome in critically ill

Background:

Acute hyperglycemia, hypoglycemia and glycemic variability (GV) have been found to be the three principal domains of glycemic control, which can adversely affect patient outcome. GV may be the confounding factor in tight glycemic control trials in surgical and medical patient.

Objective:

This study was conducted to establish if there was any relationship between GV and intensive care unit (ICU) mortality in the Indian context.

Study Design:

A retrospective review of a large cohort of prospectively collected database.

Setting:

Adult Medical/Surgical/Trauma/Neuro ICU of a tertiary care hospital.

Patient Population:

All patients who had four or more blood glucose measured during the ICU stay.

Outcome:

ICU mortality.

Result:

2208 patients with a total of 11,335 blood glucose values were analyzed. GV measured by the standard deviation (SD) of mean blood glucose and glycemic lability index (GLI), both were significantly (P < 0.001) associated with ICU mortality. This relationship was maintained (odds ratio (OR): 2.023, 95% confidence interval (CI): 1.483-2.758) even after excluding patients with hypoglycemia (<60 mg/dl). Patients with blood glucose values in the euglycemic range but highest SD had higher mortality (54%) compared to mortality (24%) in patients above the euglycemic range. Similarly patients with blood sugar values below the average for study cohort and high GLI, another marker of GV had higher mortality (OR: 5.62, CI: 3.865-8.198) than compared to patients in the hyperglycemic range, reflecting the importance of GV as a prognostic marker in patients with blood sugar in the euglycemic range.

Conclusion:

This study demonstrated that high glucose variability is associated with increased ICU mortality in a large heterogeneous cohort of ICU patients. This effect was particularly evident among patients in the euglycemic range.

Glycaemic variability in diabetes: a tool for assessing the quality of glycaemic control and the risk of complications

The routine approach to evaluating the effectiveness of diabetes treatment based on the level of glycated haemoglobin (HbA. 1c) accounts for the average glucose level but does not consider the scope and frequency of its fluctuations. The development of computational methods to analyse glycaemic oscillations has made it possible to propose the concept of glycaemic variability (GV). The interest in research focused on GV increased dramatically after continuous glucose monitoring (CGM) technology was introduced, which provided the opportunity to study in detail the temporal structure of blood glucose curves. Numerous methods for assessing GV proposed over the past five decades characterize glycaemic fluctuations as functions of concentration and time and estimate the risks of hypoglycaemia and hyperglycaemia. Accumulating evidence indicates that GV may serve as a significant predictor of diabetic complications. Prospective studies demonstrate that certain GV parameters have independent significance for predicting diabetic retinopathy, nephropathy and cardiovascular diseases. There is evidence that GV correlates with the severity of atherosclerotic vascular lesions and cardiovascular outcomes in diabetic patients. The mechanisms underlying the relationship between GV and vascular complications are being intensively studied, and recent data show that the effect of GV on vascular walls may be mediated by oxidative stress, chronic inflammation and endothelial dysfunction. Average blood glucose levels and GV are considered independent predictors of hypoglycaemia. Increased GV is associated with impaired hormonal response to hypoglycaemia and is a long-term predictor of hypoglycaemia unawareness. These data allow us to conclude that computational methods for analysing GV in patients with diabetes may serve as a promising tool for personalized assessment of glycaemic control and the risk of vascular complications and hypoglycaemia. Thus, the reduction of GV can be regarded as one of the therapeutic targets to treat diabetes.

Potential anti-atherosclerotic effects of dipeptidyl peptidase-4 inhibitors in type 2 diabetes mellitus

Cardiovascular disease (CVD) is the leading cause of mortality in patients with diabetes. Pharmacotherapy that can reduce hyperglycemia and also exhibit pleiotropic effects that can result in a reduction in cardiovascular disease will be a major advance. Recently, the dipeptidyl-peptidase-4 inhibitors were introduced as ant-hyperglycemic therapy. Studies from numerous groups have reported effects that could potentially result in a reduction in CVD. Some of the drugs in this class, especially vildagliptin and sitagliptin, have been shown to reduce postprandial hyperlipidemia following a fat load, improve endothelial function as evidenced by increased forearm blood flow, and also display anti-inflammatory effects. Their effects on platelet function, blood pressure, and oxidative stress are very preliminary and need to be confirmed. Finally, they have been shown to reduce subclinical atherosclerosis by reducing carotid intimal-medial thickness. However, the final arbiter with respect to a reduction in CVD will be the ongoing clinical trials.

Relationship between autonomic nervous system function and continuous interstitial glucose measurement in patients with type 2 diabetes

AIMS

The Aim of the present study was to examine whether there is a relationship between autonomic nervous system function and glycemic variability (GV) in patients with type 2 diabetes (T2D).

METHODS

A total of 50 (29 males) patients with T2D (mean age 58.4 ± 9.9 years, median diabetes duration 5.5 [IQR 2.0-9.25] years), on oral antidiabetic agents, underwent ECG recording and subcutaneous glucose monitoring, simultaneously and continuously, for 24 hours.

RESULTS

After adjustment for HbA1c and diabetes duration, total power of heart rate variability (HRV) was inversely associated with the standard deviation of the mean interstitial tissue glucose (MITG) and with the M-value during the entire recording (r: -0.29, P = 0.052; r: -0.30, P = 0.047, resp.) and during the night (r: -0.29, P = 0.047; r: -0.31, P = 0.03, resp.). Most of the HRV time-domain indices were significantly correlated with standard deviation of the MITG and the M-value. These correlations were stronger for the HRV recordings during the night. No significant association was found between HRV parameters and MAGE.

CONCLUSIONS

HRV is inversely associated with GV in patients with T2D, which might be a sign of causation between GV and autonomic dysfunction. Prospective studies are needed to further investigate the importance of GV in the pathogenesis of long-term complications of diabetes.

Cerebral hemodynamics and systemic endothelial function are already impaired in well-controlled type 2 diabetic patients, with short-term disease

Objective

Impaired cerebral vasomotor reactivity (VMR) and flow-mediated dilation (FMD) were found in selected subgroups of type 2 diabetes mellitus (T2DM) patients with long-term disease. Our study aimed to evaluate cerebral hemodynamics, systemic endothelial function and sympatho-vagal balance in a selected population of well-controlled T2DM patients with short-term disease and without cardiac autonomic neuropathy (CAN).

Research Design and Methods

Twenty-six T2DM patients with short-term (4.40±4.80 years) and well-controlled (HbA1C = 6.71±1.29%) disease, without any complications, treated with diet and/or metformin, were consecutively recruited. Eighteen controls, comparable by sex and age, were enrolled also.

Results

FMD and shear rate FMD were found to be reduced in T2DM subjects with short-term disease (8.5% SD 3.5 and 2.5 SD 1.3, respectively) compared to controls (15.4% SD 4.1 and 3.5 SD 1.4; p<.001 and p<.05). T2DM patients also displayed reduced VMR values than controls (39.4% SD 12.4 vs 51.7%, SD 15.5; p<.05). Sympatho-vagal balance was not different in T2DM patients compared to healthy subjects. FMD and shear rate FMD did not correlate with VMR in T2DM patients or in controls (p>.05).

Conclusions

In well-controlled T2DM patients with short-term disease cerebral hemodynamics and systemic endothelial function are altered while autonomic balance appeared to be preserved.

Effect of eating vegetables before carbohydrates on glucose excursions in patients with type 2 diabetes

The aim of this review was to evaluate whether eating vegetables before carbohydrates could reduce the postprandial glucose, insulin, and improve long-term glycemic control in Japanese patients with type 2 diabetes. We studied the effect of eating vegetables before carbohydrates on postprandial plasma glucose, insulin, and glycemic control for 2.5 y in patients with type 2 diabetes. The postprandial glucose and insulin levels decreased significantly when the patients ate vegetables before carbohydrates compared to the reverse regimen, and the improvement of glycemic control was observed for 2.5 y. We also compared the postprandial glucose and glucose fluctuations assessed by continuous glucose monitoring system for 72-h in patients with type 2 diabetes and subjects with normal glucose tolerance when subjects ate vegetables before carbohydrates and carbohydrates before vegetables in a randomized crossover design. The glycemic excursions and incremental glucose peak were significantly lower when the subjects ate vegetables before carbohydrates compared to the reverse regimen. This evidence supports the effectiveness of eating vegetables before carbohydrates on glucose excursions in the short-term and glycemic control in the long-term in patients with type 2 diabetes.

Glucose variability: An emerging target for the treatment of diabetes mellitus

Alterations in glucose metabolism in individuals with diabetes have been considered for many years, as they appear at first glance, i.e., simply as hyperglycemia, and its surrogate marker, glycated hemoglobin (HbA1c), used both to estimate the risk of developing diabetic complications and to define the targets and measure the efficacy of diabetes treatments. However, over time diabetes-related glycemic alterations have been considered in more complex terms, by attempting to identify the role of fasting glycemia, postprandial glycemia and hypoglycemia in the overall assessment of the disease. This set of evaluations has led to the concept of glucose variability. Although intuitively easy to understand, it cannot be equally simply translated into terms of definition, measuring, prognostic and therapeutic impact. The literature available on glucose variability is extensive yet confused, with the only common element being the need to find out more on the subject. The purpose of this manuscript is not only to review the most recent evidence on glucose variability, but also to help the reader to better understand the available measurement options, and how the various definitions can differently be related with the development of diabetic complications. Finally, we provide how new and old drugs can impact on glucose variability.

Parental history of type 2 diabetes, TCF7L2 variant and lower insulin secretion are associated with incident hypertension. Data from the DESIR and RISC cohorts

AIMS/HYPOTHESIS

The relationship between insulin secretion and the incidence of hypertension has not been well characterised. We hypothesised that both a parental history of diabetes and TCF7L2 rs7903146 polymorphism, which increases susceptibility to diabetes because of impaired beta cell function, are associated with incident hypertension. In a separate cohort, we assessed whether low insulin secretion is related to incident hypertension.

METHODS

Nine year incident hypertension was studied in 2,391 normotensive participants from the Data from an Epidemiological Study on the Insulin Resistance Syndrome (DESIR) cohort. The relationship between insulin secretion and 3 year incident hypertension was investigated in 1,047 non-diabetic, normotensive individuals from the Relationship between Insulin Sensitivity and Cardiovascular Disease (RISC) cohort. Insulin secretion during OGTT was expressed in relation to the degree of insulin resistance, as assessed by a hyperinsulinaemic-euglycaemic clamp.

RESULTS

In the DESIR cohort, a parental history of diabetes and the TCF7L2 at-risk variant were both associated with hypertension incidence at year 9, independently of waist circumference, BP, fasting glucose, insulin levels and HOMA-IR at inclusion (p = 0.02 for parental history, p = 0.006 for TCF7L2). In the RISC cohort, a lower insulin secretion rate during the OGTT at baseline was associated with both higher BP and a greater risk of hypertension at year 3. This inverse correlation between the insulin secretion rate and incident hypertension persisted after controlling for baseline insulin resistance, glycaemia and BP (p = 0.007).

CONCLUSIONS/INTERPRETATION

Parental history of diabetes, TCF7L2 rs7903146 polymorphism and a reduced insulin secretion rate were consistently associated with incident hypertension. A low insulin secretion rate might be a new risk factor for incident hypertension, beyond insulin resistance.

High-density lipoprotein cholesterol and the risk of nephropathy in type 2 diabetic patients

BACKGROUND AND AIMS

To date, few studies have demonstrated the impact of variations in blood pressure, blood glucose and lipid levels on the progression of diabetic nephropathy (DN) in type 2 diabetic patients. This study aimed to assess the associations of mean values and variability in metabolic parameters with the development of DN in type 2 diabetic patients.

METHODS AND RESULTS

A total of 864 patients who had participated in a comprehensive diabetic care program for at least for 3 years were studied. Patients were stratified into progressor (n = 180) and non-progressor groups (n = 684) according to the status of progression of DN during the follow-up period. By Cox regression analysis, a higher mean HDL-C level was observed to be a protective factor against the progression of DN [hazard ratio (95% CI): 0.971(0.953-0.989), P = 0.002] and a higher HDL-C variation was found to be associated with a higher risk [hazard ratio (95% CI): 1.177(1.032-1.341), P = 0.015] of DN progression. By the Kaplan-Meier survival curve, patients with a higher HDL-C level and lower HDL-C variability were found to have the lowest risk of development of nephropathy.

CONCLUSIONS

Our study demonstrated for the first time that type 2 diabetic patients under a standard disease management program who have a stable and a higher mean HDL-C level were associated with a lower risk of development of DN.

Ambulant 24-h glucose rhythms mark calendar and biological age in apparently healthy individuals

Glucose metabolism marks health and disease and is causally inferred in the aging process. Ambulant continuous glucose monitoring provides 24-h glucose rhythms under daily life conditions. We aimed to describe ambulant 24-h glucose rhythms measured under daily life condition in relation to calendar and biological age in apparently healthy individuals. In the general population and families with propensity for longevity, we studied parameters from 24-h glucose rhythms; glucose levels; and its variability, obtained by continuous glucose monitoring. Participants were 21 young (aged 22-37 years), 37 middle-aged (aged 44-72 years) individuals from the general population, and 26 middle-aged (aged 52-74 years) individuals with propensity for longevity. All were free of diabetes. Compared with young individuals, middle-aged individuals from the general population had higher mean glucose levels (5.3 vs. 4.7 mmol L(-1) , P < 0.001), both diurnally (P < 0.001) and nocturnally (P = 0.002). Glucose variability was higher in the middle-aged compared with the young (standard deviation 0.70 vs. 0.57 mmol L(-1) , P = 0.025). Compared with middle-aged individuals from the general population, middle-aged individuals with propensity for longevity had lower overall mean glucose levels (5.2 vs. 5.4 mmol L(-1) , P = 0.047), which were more different nocturnally (4.8 vs. 5.2 mmol L(-1) , P = 0.003) than diurnally (5.3 vs. 5.5 mmol L(-1) , P = 0.14). There were no differences in glucose variability between these groups. Results were independent of body mass index. Among individuals without diabetes, we observed significantly different 24-h glucose rhythms depending on calendar and biological age.

Blood Pressure Variability and Cognitive Function in the Elderly

With the increase in the aging population, it is important to understand the individual diseases and their interactions which are prevalent and have a great impact on the health status of the elderly. Hypertension is one of the most common diseases in older age and may impact the health status because it is the main risk factor for cardiovascular and cerebrovascular diseases such as heart failure and stroke. Recently, much evidence has been accumulated showing that hypertension plays an important role in the development and progression of cognitive impairment and dementia. Cerebral hypoperfusion secondary to severe atherosclerosis resulting from long-standing hypertension may be a major biological pathway linking high blood pressure (BP) to cognitive decline and dementia. Furthermore, increased BP variability has also been reported to be significantly associated with white matter hyperintensities and brain atrophy, which are predisposing conditions of dementia, depression, and falls in the elderly even after adjusting for BP levels and other confounding variables. Several mechanisms have been shown to be involved in the association between BP variability and cognitive impairment in elderly individuals. In addition to an increased cerebral blood flow fluctuation, neurohumoral activation, endothelial dysfunction, inflammation, and oxidative stress have been suggested to be the underlying mechanisms. However, clinical trials provide limited evidence for a protective effect of antihypertensive therapy against dementia and stroke-related cognitive decline. In this article, we aimed to review the existing evidence of the connection between BP variability and cognitive impairment in elderly people.

Aerobic and combined exercise sessions reduce glucose variability in type 2 diabetes: crossover randomized trial

Purpose

To evaluate the effects of aerobic (AER) or aerobic plus resistance exercise (COMB) sessions on glucose levels and glucose variability in patients with type 2 diabetes. Additionally, we assessed conventional and non-conventional methods to analyze glucose variability derived from multiple measurements performed with continuous glucose monitoring system (CGMS).

Methods

Fourteen patients with type 2 diabetes (56±2 years) wore a CGMS during 3 days. Participants randomly performed AER and COMB sessions, both in the morning (24 h after CGMS placement), and at least 7 days apart. Glucose variability was evaluated by glucose standard deviation, glucose variance, mean amplitude of glycemic excursions (MAGE), and glucose coefficient of variation (conventional methods) as well as by spectral and symbolic analysis (non-conventional methods).

Results

Baseline fasting glycemia was 139±05 mg/dL and HbA1c 7.9±0.7%. Glucose levels decreased immediately after AER and COMB protocols by ∼16%, which was sustained for approximately 3 hours. Comparing the two exercise modalities, responses over a 24-h period after the sessions were similar for glucose levels, glucose variance and glucose coefficient of variation. In the symbolic analysis, increases in 0 V pattern (COMB, 67.0±7.1 vs. 76.0±6.3, P = 0.003) and decreases in 1 V pattern (COMB, 29.1±5.3 vs. 21.5±5.1, P = 0.004) were observed only after the COMB session.

Conclusions

Both AER and COMB exercise modalities reduce glucose levels similarly for a short period of time. The use of non-conventional analysis indicates reduction of glucose variability after a single session of combined exercises.

Trial Registration

Aerobic training, aerobic-resistance training and glucose profile (CGMS) in type 2 diabetes (CGMS exercise). ClinicalTrials.gov ID: NCT00887094.

Relationship between fluctuations in glucose levels measured by continuous glucose monitoring and vascular endothelial dysfunction in type 2 diabetes mellitus

Background

Fluctuations in blood glucose level cause endothelial dysfunction and play a critical role in onset and/or progression of atherosclerosis. We hypothesized that fluctuation in blood glucose levels correlate with vascular endothelial dysfunction and that this relationship can be assessed using common bedside medical devices.

Methods

Fluctuations in blood glucose levels were measured over 24 hours by continuous glucose monitoring (CGM) on admission day 2 in 57 patients with type 2 diabetes mellitus. The reactive hyperemia index (RHI), an index of vascular endothelial function, was measured using peripheral arterial tonometry (EndoPAT) on admission day 3.

Results

The natural logarithmic-scaled RHI (L_RHI) correlated with SD (r=−0.504; P<0.001), the mean amplitude of glycemic excursions (MAGE) (r=−0.571; P<0.001), mean postprandial glucose excursion (MPPGE) (r=−0.411; P=0.001) and percentage of time ≥200 mg/dl (r=−0.292; P=0.028). In 12 patients with hypoglycemia, L_RHI also correlated with the percentage of time at hypoglycemia (r=−0.589; P=0.044). L_RHI did not correlate with HbA1c or fasting plasma glucose levels. Furthermore, L_RHI did not correlate with LDL cholesterol, HDL cholesterol, and triglyceride levels or with systolic and diastolic blood pressures. Finally, multivariate analysis identified MAGE as the only significant determinant of L_RHI.

Conclusions

Fluctuations in blood glucose levels play a significant role in vascular endothelial dysfunction in type 2 diabetes.

Trial registration

UMIN000007581

Italian contributions to the development of continuous glucose monitoring sensors for diabetes management

Monitoring glucose concentration in the blood is essential in the therapy of diabetes, a pathology which affects about 350 million people around the World (three million in Italy), causes more than four million deaths per year and consumes a significant portion of the budget of national health systems (10% in Italy). In the last 15 years, several sensors with different degree of invasiveness have been proposed to monitor glycemia in a quasi-continuous way (up to 1 sample/min rate) for relatively long intervals (up to 7 consecutive days). These continuous glucose monitoring (CGM) sensors have opened new scenarios to assess, off-line, the effectiveness of individual patient therapeutic plans from the retrospective analysis of glucose time-series, but have also stimulated the development of innovative on-line applications, such as hypo/hyper-glycemia alert systems and artificial pancreas closed-loop control algorithms. In this review, we illustrate some significant Italian contributions, both from industry and academia, to the growth of the CGM sensors research area. In particular, technological, algorithmic and clinical developments performed in Italy will be discussed and put in relation with the advances obtained in the field in the wider international research community.

Diabetic autonomic imbalance and glycemic variability

Diabetic autonomic neural imbalance is a severe complication of long-term diabetes patients and may progress to diabetic autonomic neuropathy (DAN). The prevalence of DAN is reported to be between 20 and 70%, depending on the studies. The pathogenesis of DAN remains unresolved. However, emerging evidence suggests that glycemic variability (GV) may be associated with autonomic imbalance in patients with both type 1 and type 2 diabetes. As symptoms are initially weak and uncharacteristic, the condition often remains undiagnosed until late manifestations present themselves. Predominant symptoms may include nausea, vomiting, gastroparesis, involuntary diarrhea, postural hypotension, voiding difficulties, and sexual dysfunction. Analyzing the patterns of heart rate variability carries the potential for detection of autonomic imbalance in the subclinical and asymptomatic stages. In this context, GV may affect the sympathovagal balance by increasing oxidative stress and proinflammatory cytokines. Establishing a GV risk profile could therefore be important in determining risk factors in diabetes patients. This review addresses the issues above and in particular the possible association between diabetic autonomic imbalance and GV.

Impact of glycemic variability on cardiovascular outcomes beyond glycated hemoglobin. Evidence and clinical perspectives

AIMS

The aim of this review is to focus on intra-day glucose variability (GV), specifically reviewing its correlation with HbA1c, the methods currently available to measure it, and finally the relationship between GV and cardiovascular outcomes, in type 1 and type 2 diabetic patients, and in the non-diabetic population.

DATA SYNTHESIS

The term GV has been used in the literature to express many different concepts; in the present review, we focus our attention on intra-day GV. In particular, we try to assess whether GV provides additional information on glycemic control beyond HbA1c, since GV seems to be incompletely expressed by HbA1c, particularly in patients with good metabolic control. Many different indexes have been proposed to measure GV, however at the moment no "gold standard" procedure is available. Evidence in vitro, in experimental settings and in animal studies, shows that fluctuating glucose levels display a more deleterious effect than constantly high glucose exposure. However, these findings are not completely reproducible in human settings. Moreover, the relationship between GV and cardiovascular events is still controversial.

CONCLUSIONS

The term GV should be reserved to indicate intra-day variability and different indexes of GV should be used, depending on the metabolic profile of the population studied and the specific issue to be investigated. Self glucose monitoring or continuous glucose monitoring should be used for assessing glucose variability.

Glycemic variability and glycemic control in the acutely ill cardiac patient

The mechanisms for hyperglycemia-mediated harm in the hospitalized cardiac patient are poorly understood. Potential obstacles in the inpatient management of hyperglycemia in cardiac patients include rapidly changing clinical status, frequent procedures and interruptions in carbohydrate exposure, and short hospital length of stay. A patient's preadmission regimen is rarely suitable for inpatient glycemic control. Instead, an approach to a flexible, physiologic insulin regimen is described, which is intended to minimize glycemic excursions. When diabetes or hyperglycemia is addressed early and consistently, the hospital stay can serve as a potential window of opportunity for reinforcing self-care behaviors that reduce long-term complications.

Visit-to-visit variability in systolic blood pressure is correlated with diabetic nephropathy and atherosclerosis in patients with type 2 diabetes

OBJECTIVE

Recent studies make remarks on the effect of variability in systolic blood pressure (SBP) on the development of cardiovascular disease. The aim of this study was to investigate the relationship between the variability in SBP and the degree of diabetic nephropathy and atherosclerosis in patients with type 2 diabetes.

METHODS

We measured SBP in 422 consecutive patients with type 2 diabetes at every visit during a year, and we calculated the coefficient of variation (CV) of SBP. Then, we evaluated relationships of variability of SBP to degree of urinary albumin excretion (UAE), which is a useful marker for cardiovascular disease as well as diabetic nephropathy, ankle-brachial index (ABI) and pulse wave velocity (PWV).

RESULTS

CV of SBP positively correlated with logUAE (r=0.210, P<0.0001) or PWV (r=0.409, P<0.0001), whereas CV of SBP inversely correlated with ABI (r=-0.098, P=0.0463). Multiple regression analysis demonstrated that CV of SBP independently correlated with logUAE (β=0.149, P=0.0072), PWV (β=0.337, P<0.0001) or ABI (β=-0.162, P=0.0101).

CONCLUSIONS

Not only average SBP but also variability in SBP is correlated with diabetic nephropathy and atherosclerosis in patients with type 2 diabetes.

Blood pressure regulation in diabetic patients with and without peripheral neuropathy

Cardiac and vascular dysfunctions resulting from autonomic neuropathy (AN) are complications of diabetes, often undiagnosed. Our objectives were to: 1) determine sympathetic and parasympathetic components of compromised blood pressure (BP) regulation in patients with peripheral neuropathy and 2) rank noninvasive indexes for their sensitivity in diagnosing AN. We continuously measured electrocardiogram, arterial BP, and respiration during supine rest and 70° head-up tilt in 12 able-bodied subjects, 7 diabetics without, 7 diabetics with possible, and 8 diabetics with definite, sensory, and/or motor neuropathy (D2). During the first 3 min of tilt, systolic BP (SBP) of D2 decreased [-10.9 ± 4.5 (SE) mmHg] but increased in able-bodied (+4.8 ± 5.4 mmHg). Compared with able-bodied, D2 had smaller low-frequency (0.04-0.15 Hz) spectral power of diastolic BP, lower baroreflex effectiveness index (BEI), and more SBP ramps. Except for low-frequency power of SBP, D2 had greater SBP and smaller RR interval harmonic and nonharmonic components at rest across the 0.003- to 0.45-Hz region. In addition, our results support previous findings of smaller HF RR interval power, smaller numbers of baroreflex sequences, and lower baroreflex sensitivity in D2. We conclude that diabetic peripheral neuropathy is accompanied by diminished parasympathetic and sympathetic control of heart rate and peripheral vasomotion and diminished baroreflex regulation. A novel finding of this study lies in the sensitivity of BEI to detect AN, presumably because of its combination of parameters that measure reductions in both sympathetic control of vasomotion and parasympathetic control of heart rate.

International Forum for the Advancement of Diabetes Research and Care, April 29-30, 2011, Athens, Greece

The International Forum for the Advancement of Diabetes Research and Care brought together distinguished international experts in diabetes to discuss diverse trends and emerging issues in diabetes therapy and management. The plenary sessions on the first day focused on trends in insulin therapy, the role of glucagon-like peptide-1 receptor agonists in diabetes treatment, the relationship between diabetes and cardiovascular risk, and the challenges associated with the development of clinically relevant treatment guidelines. Interactive breakout sessions addressed the following topics: microvascular complications of diabetes; the need for a team approach to patient education; optimal management of Asian people with diabetes; the role of continuous glucose monitoring in assessing glucose variability; and lessons learned from biosimilar drugs. The plenary sessions on the second day covered self-monitoring of blood glucose, treatment and prevention of type 1 diabetes, and future directions for diabetes therapy. The meeting represented an excellent forum for the presentation of new research and the exchange of ideas aimed at improving outcomes for people with diabetes.