Continuous subcutaneous glucose monitoring in diabetic patients: a multicenter analysis

Clinical Performance Evaluation of Continuous Glucose Monitoring Systems: A Scoping Review and Recommendations for Reporting

The use of different approaches for design and results presentation of studies for the clinical performance evaluation of continuous glucose monitoring (CGM) systems has long been recognized as a major challenge in comparing their results. However, a comprehensive characterization of the variability in study designs is currently unavailable. This article presents a scoping review of clinical CGM performance evaluations published between 2002 and 2022. Specifically, this review quantifies the prevalence of numerous options associated with various aspects of study design, including subject population, comparator (reference) method selection, testing procedures, and statistical accuracy evaluation. We found that there is a large variability in nearly all of those aspects and, in particular, in the characteristics of the comparator measurements. Furthermore, these characteristics as well as other crucial aspects of study design are often not reported in sufficient detail to allow an informed interpretation of study results. We therefore provide recommendations for reporting the general study design, CGM system use, comparator measurement approach, testing procedures, and data analysis/statistical performance evaluation. Additionally, this review aims to serve as a foundation for the development of a standardized CGM performance evaluation procedure, thereby supporting the goals and objectives of the Working Group on CGM established by the Scientific Division of the International Federation of Clinical Chemistry and Laboratory Medicine.

Continuous Glucose Monitoring Enabled by Fluorescent Nanodiamond Boronic Hydrogel

Continuous monitoring of glucose allows diabetic patients to better maintain blood glucose level by altering insulin dosage or diet according to prevailing glucose values and thus to prevent potential hyperglycemia and hypoglycemia. However, current continuous glucose monitoring (CGM) relies mostly on enzyme electrodes or micro-dialysis probes, which suffer from insufficient stability, susceptibility to corrosion of electrodes, weak or inconsistent correlation, and inevitable interference. A fluorescence-based glucose sensor in the skin will likely be more stable, have improved sensitivity, and can resolve the issues of electrochemical interference from the tissue. This study develops a fluorescent nanodiamond boronic hydrogel system in porous microneedles for CGM. Fluorescent nanodiamond is one of the most photostable fluorophores with superior biocompatibility. When surface functionalized, the fluorescent nanodiamond can integrate with boronic polymer and form a hydrogel, which can produce fluorescent signals in response to environmental glucose concentration. In this proof-of-concept study, the strategy for building a miniatured device with fluorescent nanodiamond hydrogel is developed. The device demonstrates remarkable long-term photo and signal stability in vivo with both small and large animal models. This study presents a new strategy of fluorescence based CGM toward treatment and control of diabetes.

Mesoporous Silica-Based Metal Oxide Electrode for a Nonenzymatic Glucose Sensor at a Physiological pH

To construct an electrochemical biosensing platform, we propose a glucose sensor whose electrode interface was modified by mesoporous silica (MPSi) as an electronic signal transmission interface between a biomarker and an electrochemical device. We develop an enzyme-free glucose sensor using an MPSi-coated Ta₂O₅ electrode in an actual biological fluid such as blood serum. MPSi includes a phenylboronic acid (PBA) molecule, in which glucose binds to a synthesized PBA-silane compound in an ca. 150 nm thick MPSi nanolayer, which changes the density of molecular charges of the PBA/glucose complex on the surface of MPSi. The charge changes derived from the equilibrium reaction of PBA with glucose lead to changes in surface potential of the Ta₂O₅ electrode, and the surface potential changes depending on glucose concentration were measured by a potentiometric detector. As a result, a remarkable surface potential response was observed in the vicinity of neutral pH. K_d = 6.0 mM and V_max = 194 mV were obtained from the fitting curve of the Langmuir adsorption isotherm. Finally, we confirmed the glucose response of the PBA-MPSi-coated Ta₂O₅ substrate in human serum by considering the influence of various contaminants. Although the surface potential change was suppressed by approximately one-third of that in the buffer system, it was suggested that it could be applied to measurements in the blood glucose concentration range. From the results of this study, it was clarified that blood-level glucose response could be monitored using a PBA-MPSi-coated Ta₂O₅ substrate, which suggests the possibility of using a nonenzymatic glucose sensor as an alternative to the existing enzyme sensor.

Three-Dimensional Paper-Based Microfluidic Analysis Device for Simultaneous Detection of Multiple Biomarkers with a Smartphone

Paper-based microfluidic analysis devices (μPADs) have attracted attention as a cost-effective platform for point-of-care testing (POCT), food safety, and environmental monitoring. Recently, three-dimensional (3D)-μPADs have been developed to improve the performance of μPADs. For accurate diagnosis of diseases, however, 3D-μPADs need to be developed to simultaneously detect multiple biomarkers. Here, we report a 3D-μPADs platform for the detection of multiple biomarkers that can be analyzed and diagnosed with a smartphone. The 3D-μPADs were fabricated using a 3D digital light processing printer and consisted of a sample reservoir (300 µL) connected to 24 detection zones (of 4 mm in diameter) through eight microchannels (of 2 mm in width). With the smartphone application, eight different biomarkers related to various diseases were detectable in concentrations ranging from normal to abnormal conditions: glucose (0–20 mmol/L), cholesterol (0–10 mmol/L), albumin (0–7 g/dL), alkaline phosphatase (0–800 U/L), creatinine (0–500 µmol/L), aspartate aminotransferase (0–800 U/L), alanine aminotransferase (0–1000 U/L), and urea nitrogen (0–7.2 mmol/L). These results suggest that 3D-µPADs can be used as a POCT platform for simultaneous detection of multiple biomarkers.

A new microdialysis probe for continuous lactate measurement during fetal monitoring: Proof of concept in an animal model

INTRODUCTION

Cardiotocography (CTG) is currently the most commonly used method for intrapartum fetal monitoring during labor. However, a high false-positive rate of fetal acidosis indicated by CTG leads to an increase in obstetric interventions. We developed a microdialysis probe that is integrated into a fetal scalp electrode allowing continuous measurement of lactate subcutaneously, thus giving instant information about the oxygenation status of the fetus. Our aim was to establish proof of concept in an animal model using a microdialysis probe to monitor lactate subcutaneously.

MATERIAL AND METHODS

We performed an in vivo study in adult male wild-type Wistar rats. We modified electrodes used for CTG monitoring in human fetuses to incorporate a microdialysis membrane. Optimum flow rates for microdialysis were determined in vitro. For the in vivo experiment, a microdialysis probe was inserted into the skin on the back of the animal. De-oxygenation and acidosis were induced by lowering the inspiratory oxygen pressure. Oxygenation and heart rate were monitored. A jugular vein cannula was inserted to draw blood samples for analysis of lactate, pH, pco2 , and saturation. Lactate levels in dialysate were compared with plasma lactate levels.

RESULTS

Baseline blood lactate levels were around 1 mmol/L. Upon de-oxygenation, oxygen saturation fell to below 40% for 1 h and blood lactate levels increased 2.5-fold. Correlation of dialysate lactate levels with plasma lactate levels was 0.89 resulting in an R2 of .78 in the corresponding linear regression.

CONCLUSIONS

In this animal model, lactate levels in subcutaneous fluid collected by microdialysis closely reflected blood lactate levels upon transient de-oxygenation, indicating that our device is suitable for subcutaneous measurement of lactate. Microdialysis probe technology allows the measurement of multiple compounds in the dialysate, such as glucose, albumin, or inflammatory mediators, so this technique may offer the unique possibility to shed light on fetal physiology during the intrapartum period.

Modulating the mixed potential for developing biosensors: Direct potentiometric determination of glucose in whole, undiluted blood

The growing demand for tools to generate chemical information in decentralized settings is creating a vast range of opportunities for potentiometric sensors, since their combination of robustness, simplicity of operation and cost can hardly be rivalled by any other technique. In previous works, we have shown that the mixed potential of a Pt electrode can be controlled with analytical purposes using a coating of Nafion, thus providing a way to develop a potentiometric biosensor for glucose. Unfortunately, the linear range of this device did not match the relevant clinical range for glucose in blood. This work presents a novel strategy to control the mixed potential that allows the development of a potentiometric biosensor for the direct detection of glucose in whole, undiluted blood without any sample pretreatment. By changing the ionomer, the analytical response can be tuned, shifting the linear range while keeping the sensitivity. Aquivion, a polyelectrolyte from the same family as Nafion, is used to stabilize the mixed potential of a platinized paper-based electrode, to entrap the enzyme and to reduce the interference from negatively charged species. Factors affecting the generation of the signal and the principle of detection are discussed. Optimization of the biosensor composition was achieved with particular focus on the characterization of the linear range and sensitivity. The accurate measurement of blood sugar levels in a single drop of whole blood with excellent recovery is presented.

Effect of Lupin-Enriched Biscuits as Substitute Mid-Meal Snacks on Post-Prandial Interstitial Glucose Excursions in Post-Surgical Hospital Patients with Type 2 Diabetes

Hospital biscuit snacks offered to Type 2 Diabetes Mellitus (T2DM) patients may adversely affect glycaemic control. This study investigated the effect of lupin mid-meal biscuit snacks, compared to spelt or standard hospital biscuits, on interstitial glucose levels in post-operative T2DM inpatients. In a pilot cross-over pragmatic study, 20 patients (74 ± 12 years) consumed, in order, lupin biscuits (20% lupin), wholemeal spelt and standard plain sweet biscuits as mid-meal snacks (2 biscuits each for morning and afternoon tea) on three consecutive days. Continuous glucose monitoring, appetite perceptions and bowel motions were recorded. Glucose levels were not significantly different in the first 90 min after mid-meal biscuit consumption at morning and afternoon tea, irrespective of type. However, after consuming the lupin biscuits only, glucose levels were significantly (p < 0.001) reduced 90 min postprandially after dinner, indicating a potential second-meal effect. Patients also reported improved satiety after lupin biscuit consumption on day 1, compared to days 2 and 3 (p = 0.018). These findings suggest that lupin-enriched biscuits may improve both glycaemic control and satiety in hospitalised T2DM patients, potentially contributing to reduced length of stay. Larger controlled studies are warranted to confirm these findings and inform potential revision of hospital menu standards for T2DM patients.

Reliability of real-time continuous glucose monitoring in infants

BACKGROUND

Neonatal hypoglycemia is a common and treatable risk factor for neurological impairment. Real-time continuous glucose monitoring (RT-CGM) can show glucose concentration in real time. Using an RT-CGM alarm, physicians can be alerted and intervene in hypoglycemia. No reports, however, have evaluated the reliability of RT-CGM at low glucose levels in infants. This study therefore investigated the difference between blood glucose (BG) and RT-CGM sensor data at low glucose levels and assessed the optimum method of using a hypoglycemic alarm in infants.

METHODS

We enrolled infants whose glycemic management was difficult. We calculated the mean absolute difference (MAD) and mean absolute relative difference (MARD) between BG and RT-CGM sensor data. We compared the MAD and MARD between the low BG fluctuation and high BG fluctuation groups.

RESULTS

We used RT-CGM for 12 patients (29 times) and investigated 448 pairs of BG and RT-CGM sensor data. The MAD between these pairs was 9.3 ± 8.9 mg/dL, and the MARD was 11.5%. The MAD at low glucose was 7.7 ± 6.0 mg/dL, and the MARD was 16.2%. The MAD and MARD were 6.8 ± 5.4 mg/dL and 7.8% in the low fluctuation group and 10.1 ± 9.5 mg/dL and 12.7% in the high fluctuation group, respectively.

CONCLUSIONS

The difference between BG and RT-CGM sensor data changes with the degree of fluctuation in BG. When physicians set the hypoglycemic alarm, consideration of this difference and a change in the alarm setting according to the degree of fluctuation in BG may be useful.

Incorporating Unannounced Meals and Exercise in Adaptive Learning of Personalized Models for Multivariable Artificial Pancreas Systems

BACKGROUND

Despite the recent advancements in the modeling of glycemic dynamics for type 1 diabetes mellitus, automatically considering unannounced meals and exercise without manual user inputs remains challenging.

METHOD

An adaptive model identification technique that incorporates exercise information and estimates of the effects of unannounced meals obtained automatically without user input is proposed in this work. The effects of the unknown consumed carbohydrates are estimated using an individualized unscented Kalman filtering algorithm employing an augmented glucose-insulin dynamic model, and exercise information is acquired from noninvasive physiological measurements. The additional information on meals and exercise is incorporated with personalized estimates of plasma insulin concentration and glucose measurement data in an adaptive model identification algorithm.

RESULTS

The efficacy of the proposed personalized and adaptive modeling algorithm is demonstrated using clinical data involving closed-loop experiments of the artificial pancreas system, and the results demonstrate accurate glycemic modeling with the average root-mean-square error (mean absolute error) of 25.50 mg/dL (18.18 mg/dL) for six-step (30 minutes ahead) predictions.

CONCLUSIONS

The approach presented is able to identify reliable time-varying individualized glucose-insulin models.

Computerized Generation of Circadian Sensor Modal Days with Continuous Glucose Monitoring for Comparison of Various Insulin Regimens Based on Insulin Glargine in Type 1 Diabetes

Aim

Our aims were (1) to design and standardize a statistical approach for data reduction in continuous glucose monitoring, allowing comparison of circadian glycemic patterns in therapeutic subcohorts of patients with type 1 diabetes, and (2) to investigate the applicability of this approach for CGMS® assessment in clinical study of basal insulin replacement quality with various timings of basal injections (pre-breakfast, dinner, bedtime) of a new insulin analog.

Methods

Prospective randomized three-arm parallel study with switch over after 6 months for another 3 months of free choice injection time point (options pre-breakfast, pre-dinner and bedtime) of the new insulin analog in 16 type 1 diabetic subjects on functional insulin treatment (FIT: basal, prandial and correctional dosages). CGMS® was used at the end of each follow up period of a clinical study. Representative daily profiles were off-line computed as “circadian sensor modal days” for each insulin regimen consisting of consecutive means of hourly glucose values.

Results

Although the overall quality of glycemic control (HbAIC) for different regimens did not reach statistical differences, CGMS® displayed slightly divergent maximal swings in the course of glycemia (p=0.04–0.08) and allowed – with delineated data reduction procedure – a reliable between treatment comparison.

Conclusion

Off-line computation of “hourly circadian sensor modal days” for data reduction can be effectively used with CGMS® for description of circadian glycemic patterns in type 1 diabetes. (Int J Artif Organs 2003; 26: 728–34)

Moving Toward a Unified Platform for Insulin Delivery and Sensing of Inputs Relevant to an Artificial Pancreas

Advances in insulin pump and continuous glucose monitoring technology have primarily focused on optimizing glycemic control for people with type 1 diabetes. There remains a need to identify ways to minimize the physical burden of this technology. A unified platform with closely positioned or colocalized interstitial fluid glucose sensing and hormone delivery components is a potential solution. Present challenges to combining these components are interference of glucose sensing from proximate insulin delivery and the large discrepancy between the life span of current insulin infusion sets and glucose sensors. Addressing these concerns is of importance given that the future physical burden of this technology is likely to be even greater with the ongoing development of the artificial pancreas, potentially incorporating multiple hormone delivery, glucose sensing redundancy, and sensing of other clinically relevant nonglucose biochemical inputs.

An Overview of Insulin Pumps and Glucose Sensors for the Generalist

Continuous subcutaneous insulin, or the insulin pump, has gained popularity and sophistication as a near-physiologic programmable method of insulin delivery that is flexible and lifestyle-friendly. The introduction of continuous monitoring with glucose sensors provides unprecedented access to, and prediction of, a patient’s blood glucose levels. Efforts are underway to integrate the two technologies, from “sensor-augmented” and “sensor-driven” pumps to a fully-automated and independent sensing-and-delivery system. Implantable pumps and an early-phase “bionic pancreas” are also in active development. Fine-tuned “pancreas replacement” promises to be one of the many avenues that offers hope for individuals suffering from diabetes. Although endocrinologists and diabetes specialists will continue to maintain expertise in this field, it behooves the primary care physician to have a working knowledge of insulin pumps and sensors to ensure optimal clinical care and decision-making for their patients.

Basement Membrane-Based Glucose Sensor Coatings Enhance Continuous Glucose Monitoring in Vivo

BACKGROUND

Implantable glucose sensors demonstrate a rapid decline in function that is likely due to biofouling of the sensor. Previous efforts directed at overcoming this issue has generally focused on the use of synthetic polymer coatings, with little apparent effect in vivo, clearly a novel approach is required. We believe that the key to extending sensor life span in vivo is the development of biocompatible basement membrane (BM) based bio-hydrogels as coatings for glucose sensors.

METHOD

BM based bio-hydrogel sensor coatings were developed using purified BM preparations (ie, Cultrex from Trevigen Inc). Modified Abbott sensors were coated with Cultrex BM extracts. Sensor performance was evaluated for the impact of these coatings in vitro and in vivo in a continuous glucose monitoring (CGM) mouse model. In vivo sensor function was assessed over a 28-day time period expressed as mean absolute relative difference (MARD) values. Tissue reactivity of both Cultrex coated and uncoated glucose sensors was evaluated at 7, 14, 21 and 28 days post-sensor implantation with standard histological techniques.

RESULTS

The data demonstrate that Cultrex-based sensor coatings had no effect on glucose sensor function in vitro. In vivo glucose sensor performance was enhanced following BM coating as determined by MARD analysis, particularly in weeks 2 and 3. In vivo studies also demonstrated that Cultrex coatings significantly decreased sensor-induced tissue reactions at the sensor implantation sites.

CONCLUSION

Basement-membrane-based sensor coatings enhance glucose sensor function in vivo, by minimizing or preventing sensor-induced tissues reactions.

Current status and future of implantable insulin pumps for the treatment of diabetes

The data from the Diabetes Control and Complications Trial show that control of blood glucose with intensive insulin therapy significantly delays complications of diabetes when compared with conventional therapy consisting of one or two insulin injections per day. However, the subcutaneous intensive insulin therapy, including insulin infusion by external pumps, required to achieve the glycemic goals defined by the Diabetes Control and Complications Trial, led to an increased frequency of severe hypoglycemia. Improvements in parenteral insulin therapy are possible by either modifying subcutaneous insulin kinetics (insulin analogs) or developing better routes of administration. Intraperitoneal insulin infusion offers a more physiologic route of insulin delivery. The ultimate goal for the treatment of diabetes remains the development of a fully automated glucose-controlled device.

Glucose Fluctuations during Gestation: An Additional Tool for Monitoring Pregnancy Complicated by Diabetes

Continuous glucose monitoring (CGM) gives a unique insight into magnitude and duration of daily glucose fluctuations. Limited data are available on glucose variability (GV) in pregnancy. We aimed to assess GV in healthy pregnant women and cases of type 1 diabetes mellitus or gestational diabetes (GDM) and its possible association with HbA1c. CGM was performed in 50 pregnant women (20 type 1, 20 GDM, and 10 healthy controls) in all three trimesters of pregnancy. We calculated mean amplitude of glycemic excursions (MAGE), standard deviation (SD), interquartile range (IQR), and continuous overlapping net glycemic action (CONGA), as parameters of GV. The high blood glycemic index (HBGI) and low blood glycemic index (LBGI) were also measured as indicators of hyperhypoglycemic risk. Women with type 1 diabetes showed higher GV, with a 2-fold higher risk of hyperglycemic spikes during the day, than healthy pregnant women or GDM ones. GDM women had only slightly higher GV parameters than healthy controls. HbA1c did not correlate with GV indicators in type 1 diabetes or GDM pregnancies. We provided new evidence of the importance of certain GV indicators in pregnant women with GDM or type 1 diabetes and recommended the use of CGM specifically in these populations.

Near-infrared fluorescence glucose sensing based on glucose/galactose-binding protein coupled to 651-Blue Oxazine

Near-infrared (NIR) fluorescent dyes that are environmentally sensitive or solvatochromic are useful tools for protein labelling in in vivo biosensor applications such as glucose monitoring in diabetes since their spectral properties are mostly independent of tissue autofluorescence and light scattering, and they offer potential for non-invasive analyte sensing. We showed that the fluorophore 651-Blue Oxazine is polarity-sensitive, with a marked reduction in NIR fluorescence on increasing solvent polarity. Mutants of glucose/galactose-binding protein (GBP) used as the glucose receptor were site-specifically and covalently labelled with Blue Oxazine using click chemistry. Mutants H152C/A213R and H152C/A213R/L238S showed fluorescence increases of 15% and 21% on addition of saturating glucose concentrations and binding constants of 6 and 25mM respectively. Fluorescence responses to glucose were preserved when GBP-Blue Oxazine was immobilised to agarose beads, and the beads were excited by NIR light through a mouse skin preparation studied in vitro. We conclude GBP-Blue Oxazine shows proof-of-concept as a non-invasive continuous glucose sensing system.

A comparative effectiveness analysis of three continuous glucose monitors

OBJECTIVE

To compare three continuous glucose monitoring (CGM) devices in subjects with type 1 diabetes under closed-loop blood glucose (BG) control.

RESEARCH DESIGN AND METHODS

Six subjects with type 1 diabetes (age 52 ± 14 years, diabetes duration 32 ± 14 years) each participated in two 51-h closed-loop BG control experiments in the hospital. Venous plasma glucose (PG) measurements (GlucoScout, International Biomedical) obtained every 15 min (2,360 values) were paired in time with corresponding CGM glucose (CGMG) measurements obtained from three CGM devices, the Navigator (Abbott Diabetes Care), the Seven Plus (DexCom), and the Guardian (Medtronic), worn simultaneously by each subject. Errors in paired PG-CGMG measurements and data reporting percentages were obtained for each CGM device.

RESULTS

The Navigator had the best overall accuracy, with an aggregate mean absolute relative difference (MARD) of all paired points of 11.8 ± 11.1% and an average MARD across all 12 experiments of 11.8 ± 3.8%. The Seven Plus and Guardian produced aggregate MARDs of all paired points of 16.5 ± 17.8% and 20.3 ± 18.0%, respectively, and average MARDs across all 12 experiments of 16.5 ± 6.7% and 20.2 ± 6.8%, respectively. Data reporting percentages, a measure of reliability, were 76% for the Seven Plus and nearly 100% for the Navigator and Guardian.

CONCLUSIONS

A comprehensive head-to-head-to-head comparison of three CGM devices for BG values from 36 to 563 mg/dL revealed marked differences in performance characteristics that include accuracy, precision, and reliability. The Navigator outperformed the other two in these areas.

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.

Intraindividual differences between two simultaneous glucose measurement systems in type 2 diabetic patients

AIMS

Continuous glucose measurement systems are an established tool to support diabetes therapy. Because of different technical solutions one can propose different potential limitations in daily practice. So we tried to identify the accuracy of two different devices head to head in daily routine to point out individual characteristics.

METHODS

We included 24 patients with type 2 diabetes mellitus to wear the GlucoDay and the MiniMed continuous glucose measurement system at the same time for 48 h. We examined the mean differences in simultaneous glucose measurements, the confidence intervals were calculated by standard methods based on the t-distribution.

RESULTS

Comparison of glucose levels of both continuous glucose measurement systems showed that there was a tendency for higher glucose levels measured by the GlucoDay device. These differences were dependent on the time of the day. The absolute difference between two consecutive glucose measurements was higher for the GlucoDay system what means a somehow higher fluctuation of the GlucoDay measurements.

CONCLUSIONS

The differences in intraindividual comparison of the GlucoDay and the MiniMed continuous glucose measurement systems in type 2 diabetic patients may be taken into account when using different systems for detection of nocturnal hypoglycemia and the observation of trends used for therapeutic decisions.

A human pilot study of the fluorescence affinity sensor for continuous glucose monitoring in diabetes

OBJECTIVE

We report results of a pilot clinical study of a subcutaneous fluorescence affinity sensor (FAS) for continuous glucose monitoring conducted in people with type 1 and type 2 diabetes. The device was assessed based on performance, safety, and comfort level under acute conditions (4 h).

RESEARCH DESIGN AND METHODS

A second-generation FAS (BioTex Inc., Houston, TX) was subcutaneously implanted in the abdomens of 12 people with diabetes, and its acute performance to excursions in blood glucose was monitored over 4 h. After 30-60 min the subjects, who all had fasting blood glucose levels of less than 200 mg/dl, received a glucose bolus of 75 g/liter dextrose by oral administration. Capillary blood glucose samples were obtained from the finger tip. The FAS data were retrospectively evaluated by linear least squares regression analysis and by the Clarke error grid method. Comfort levels during insertion, operation, and sensor removal were scored by the subjects using an analog pain scale.

RESULTS

After retrospective calibration of 17 sensors implanted in 12 subjects, error grid analysis showed 97% of the paired values in zones A and B and 1.5% in zones C and D, respectively. The mean absolute relative error between sensor signal and capillary blood glucose was 13% [±15% standard deviation (SD), 100-350 mg/dl] with an average correlation coefficient of 0.84 (±0.24 SD). The actual average "warm-up" time for the FAS readings, at which highest correlation with glucose readings was determined, was 65 (±32 SD) min. Mean time lag was 4 (±5 SD) min during the initial operational hours. Pain levels during insertion and operation were modest.

CONCLUSIONS

The in vivo performance of the FAS demonstrates feasibility of the fluorescence affinity technology to determine blood glucose excursions accurately and safely under acute dynamic conditions in humans with type 1 and type 2 diabetes. Specific engineering challenges to sensor and instrumentation robustness remain. Further studies will be required to validate its promising performance over longer implantation duration (5-7 days) in people with diabetes.

Exenatide improves glycemic variability assessed by continuous glucose monitoring in subjects with type 2 diabetes

BACKGROUND

Daily glycemic fluctuation leads to development of long-term complications. The aim of our pilot study was to determine if exenatide reduces glycemic variability, assessed with a continuous glucose monitoring (CGM) system, compared with glimepiride.

METHODS

We enrolled six consecutive subjects with type 2 diabetes, for whom exenatide was suggested as second-line treatment, and six control subjects, for whom glimepiride was suggested as second-line treatment. CGM was performed at baseline and after 16 weeks of treatment. As measures of glycemic variability we calculated the total daily mean glucose (MG), SD, and mean amplitude of glycemic excursions (MAGE).

RESULTS

Exenatide significantly reduced MG, SD, and MAGE, whereas glimepiride did not. Fasting glucose and glycated hemoglobin were lowered in both groups, even if the reduction was not significant.

CONCLUSION

Exenatide can reduce glycemic variability compared with glimepiride, providing additional beneficial effects in controlling glucose homeostasis.

Production of rapidly reversible antibody and its performance characterization as binder for continuous glucose monitoring

To effectively control diabetes, a method to reliably measure glucose fluctuations in the body over given time periods needs to be developed. Current glucose monitoring systems depend on the substrate decomposition by an enzyme to detect the product; however, the enzyme activity significantly decays over time, which complicates analysis. In this study, we investigated an alternative method of glucose analysis based on antigen-antibody binding, which may be active over an extended period of time. To produce monoclonal antibodies, mice were immunized with molecular weight (M(W)) 10K dextran chemically conjugated with keyhole limpet hemocyanin. Since dextran contains glucose molecules polymerized via a 1,6-linkage, the produced antibodies had a binding selectivity that could discriminate biological glucose compounds with a 1,4-linkage. Three antibody clones with different affinities were screened using the M(W) 1K dextran-bovine serum albumin conjugates as the capture ligand. Among the antibodies tested, the antibody clone Glu 26 had the lowest affinity (K(A) = 3.56 × 10(6) M(-1)) and the most rapid dissociation (k(d) = 1.17 × 10(-2) s(-1)) with the polysaccharide immobilized on the solid surfaces. When glucose was added to the medium, the sensor signal was inversely proportional to the glucose concentration in a range between 10 and 1000 mg dL(-1), which covered the clinical range. Under the optimal conditions, the response time was about 3 min for association and 8 min for dissociation based on a 95% recovery of the final equilibrium.

Continuous blood glucose monitoring in diabetes treatment

Continuous glucose monitoring system (CGMS) is a developing technology in the field of diabetes treatment since it enables patients to effectively control and adjust their insulin therapy. Clinical trials have shown its efficacy in lowering HbAlc significantly especially in adults with type 1 diabetes and those with HbAlc >8%. Improvement is sustained for at least one year. Conflicting data exist for children. Most recent studies agree that the nearly daily use of CGMS is accompanied by significant lowering of HbA1c independent of age. However, the randomized clinical trials have shown that the use of CGMS does not reduce significantly the number of severe hypoglycemic episodes as it is expected, but recent data indicate that it reduces the time spent in hypoglycemia. Accuracy remains a key issue for CGMS, particularly in children and adolescents who may have increased variability of blood glucose. CGMS cost is another barrier to the everyday use since reimbursement of CGM is limited to a few countries only. This review will focus on the present status of the use of CGMS in type 1 diabetes (T1D) patients.

Long-term in vivo glucose monitoring using fluorescent hydrogel fibers

The use of fluorescence-based sensors holds great promise for continuous glucose monitoring (CGM) in vivo, allowing wireless transdermal transmission and long-lasting functionality in vivo. The ability to monitor glucose concentrations in vivo over the long term enables the sensors to be implanted and replaced less often, thereby bringing CGM closer to practical implementation. However, the full potential of long-term in vivo glucose monitoring has yet to be realized because current fluorescence-based sensors cannot remain at an implantation site and respond to blood glucose concentrations over an extended period. Here, we present a long-term in vivo glucose monitoring method using glucose-responsive fluorescent hydrogel fibers. We fabricated glucose-responsive fluorescent hydrogels in a fibrous structure because this structure enables the sensors to remain at the implantation site for a long period. Moreover, these fibers allow easy control of the amount of fluorescent sensors implanted, simply by cutting the fibers to the desired length, and facilitate sensor removal from the implantation site after use. We found that the polyethylene glycol (PEG)-bonded polyacrylamide (PAM) hydrogel fibers reduced inflammation compared with PAM hydrogel fibers, transdermally glowed, and continuously responded to blood glucose concentration changes for up to 140 days, showing their potential application for long-term in vivo continuous glucose monitoring.

Glucose variability in diabetic pregnancy

BACKGROUND

Fetal overgrowth is the most important complication of gestational (GDM) and pregestational diabetes mellitus.

METHODS

We correlated maternal glucose profiles, as detected by continuous glucose monitoring (CGM), with fetal growth parameters for 80 pregnant women (32 with type 1 diabetes, 31 with GDM, and 17 healthy controls). Glucose profiles were monitored in the first, second, and third trimesters of pregnancy for type 1 diabetes women and in the second and third trimesters for GDM women and controls. To analyze glycemic variability, we considered the mean amplitude of glycemic excursion, mean glycemia, the continuous overlapping net glycemic action (CONGA), the SD, the High Blood Glucose Index (HBGI), the Low Blood Glucose Index, and the interquartile range (IQR).

RESULTS

Mean age was the same for the three groups. Prepregnancy body mass index was higher for the women with diabetes (GDM and type 1) than for controls. The newborn's mean birth weight and ponderal index were higher, although not significantly so, for the women with diabetes than for controls. For the type 1 diabetes patients, ponderal index correlated with the HBGI in the first trimester, CONGA1 and IQR in the second, and mean glycemia and SD in the third. For GDM patients, ponderal index correlated with mean glycemia and the HBGI in the second trimester.

CONCLUSIONS

Fetal exposure to glycemic variability and hyperglycemia seems to be important in determining fetal overgrowth in pregnant women with diabetes. Optimal glucose control and less glucose variability are needed as early as possible in both type 1 diabetes and GDM patients to ensure normal fetal growth.

Postprandial hyperglycemia is highly prevalent throughout the day in type 2 diabetes patients

AIM

Although postprandial hyperglycemia is recognized as an important target in type 2 diabetes treatment, information on the prevalence of postprandial hyperglycemia throughout the day is limited. Therefore, we assessed the prevalence of hyperglycemia throughout the day in type 2 diabetes patients and healthy controls under standardized dietary, but otherwise free-living conditions.

METHODS

60 male type 2 diabetes patients (HbA(1c) 7.5±0.1% [58±1 mmol/mol]) and 24 age- and BMI-matched normal glucose tolerant controls were recruited to participate in a comparative study of daily glycemic control. During a 3-day experimental period, blood glucose concentrations throughout the day were assessed by continuous glucose monitoring.

RESULTS

Type 2 diabetes patients experienced hyperglycemia (glucose concentrations >10 mmol/L) 38±4% of the day. Even diabetes patients with an HbA(1c) level below 7.0% (53 mmol/mol) experienced hyperglycemia for as much as 24±5% throughout the day. Hyperglycemia was negligible in the control group (3±1%).

CONCLUSION

Hyperglycemia is highly prevalent throughout the day in type 2 diabetes patients, even in those patients with a HbA(1c) level well below 7.0% (53 mmol/mol). Standard medical care with prescription of oral blood glucose lowering medication does not provide ample protection against postprandial hyperglycemia.

Metabolic biofouling of glucose sensors in vivo: role of tissue microhemorrhages

OBJECTIVE

Based on our in vitro study that demonstrated the adverse effects of blood clots on glucose sensor function, we hypothesized that in vivo local tissue hemorrhages, induced as a consequence of sensor implantation or sensor movement post-implantation, are responsible for unreliable readings or an unexplained loss of functionality shortly after implantation.

RESEARCH DESIGN AND METHODS

To investigate this issue, we utilized real-time continuous monitoring of blood glucose levels in a mouse model. Direct injection of blood at the tissue site of sensor implantation was utilized to mimic sensor-induced local tissue hemorrhages.

RESULTS

It was found that blood injections, proximal to the sensor, consistently caused lowered sensor glucose readings, designated temporary signal reduction, in vivo in our mouse model, while injections of plasma or saline did not have this effect.

CONCLUSION

These results support our hypothesis that tissue hemorrhage and resulting blood clots near the sensor can result in lowered local blood glucose concentrations due to metabolism of glucose by the clot. The lowered local blood glucose concentration led to low glucose readings from the still functioning sensor that did not reflect the systemic glucose level.

A new index to optimally design and compare continuous glucose monitoring glucose prediction algorithms

BACKGROUND

Continuous glucose monitoring (CGM) data can be exploited to prevent hypo-/hyperglycemic events in real time by forecasting future glucose levels. In the last few years, several glucose prediction algorithms have been proposed, but how to compare them (e.g., methods based on polynomial rather than autoregressive time-series models) and even how to determine the optimal parameter set for a given method (e.g., prediction horizon and forgetting) are open problems.

METHODS

A new index, J, is proposed to optimally design a prediction algorithm by taking into account two key components: the regularity of the predicted profile and the time gained thanks to prediction. Effectiveness of J is compared with previously proposed criteria such as the root mean square error (RMSE) and continuous glucose-error grid analysis (CG-EGA) on 20 Menarini (Florence, Italy) Glucoday® CGM data sets.

RESULTS

For a given prediction algorithm, the new index J is able to suggest a more consistent and better parameter set (e.g., prediction horizon and forgetting factor of choice) than RMSE and CG-EGA. In addition, the minimization of J can reliably be used as a selection criterion in comparing different prediction methods.

CONCLUSIONS

The new index can be used to compare different prediction strategies and to optimally design their parameters.

Patients' evaluation of nocturnal hypoglycaemia with GlucoDay continuous glucose monitoring in paediatric patients

A study was conducted to evaluate the accuracy of GlucoDay (A. Menarini Diagnostics) during 48 h of continuous glucose monitoring (CGMS) in type 1 diabetic adolescents and use this novel approach to assess otherwise ignored nocturnal hypoglycaemias, in relationship to intermediate-acting insulin administration timing. Twenty type 1 diabetic adolescents with poor metabolic control were selected from our out-patient department. Equal doses of intermediate insulin were administered at 19:00 and at 22:00 of the first and second night of the study, respectively. Correlation coefficient between GlucoDay and standard glucometer was 0.94; 98.3% of data fall in the A + B area of Error Grid Analysis and 1.7% in the D area. The mean error was 13.9% overall and 16.4% with blood glucose values (BGV) <75 mg/dl. The accuracy, ±15 mg/dl, was 82% for BGV <75 mg/dl and 74% for BGV >75 mg/dl. The CGMS discovered nocturnal hypoglycaemia (NH) in 12/18 patients, but no severe hypoglycaemia. During the first night, 8 asymptomatic NH episodes were found with BGV <60 mg/dl and 12 with BGV <80. During the second night, 4 asymptomatic NH episodes with BGV <60 mg/dl and 5 with BGV <80 were found. Furthermore, during the second night, the mean duration of BGV <126 mg/dl was lower than in the first night. GlucoDay is a reliable device for CGMS in paediatric patients and able to determine asymptomatic NH. Bedtime insulin injections provided safer glycaemic profiles and a lower percentage of hypoglycaemic events, representing a safer insulin administration scheme.

Continuous glucose monitoring reveals delayed nocturnal hypoglycemia after intermittent high-intensity exercise in nontrained patients with type 1 diabetes

OBJECTIVE

Exercise is a cornerstone of diabetes therapy in type 1 diabetes mellitus (DMT1) patients. The type of exercise is important in determining the propensity to hypoglycemia. We assessed, by continuous glucose monitoring (CGM), the glucose profiles during and in the following 20h after a session of two different types of exercise.

RESEARCH DESIGN AND METHODS

Eight male volunteers with well-controlled DMT1 were studied. They underwent 30min of both intermittent high-intensity exercise (IHE) and moderate-intensity exercise (MOD) in random order. Expired air was recorded during exercise, while metabolic and hormonal determinations were performed before and for 120 min after exercises. The CGM system and activity monitor were applied for the subsequent 20h.

RESULTS

Blood glucose level declined during both type of exercise. At 150 min following the start of exercise, plasma glucose content was slightly higher after IHE. No changes were observed in plasma insulin concentration. A significant increase of norepinephrine concentration was noticed during IHE. Between midnight and 6:00 a.m. the glucose levels were significantly lower after IHE than those observed after MOD (area under the curve, 23.3 ± 3 vs. 16 ± 3 mg/dL/420 min [P = 0.04]; mean glycemia at 3 a.m., 225 ± 31 vs. 147 ± 17 mg/dL [P<0.05]). The number of hypoglycemic episodes after IHE was higher than that observed after MOD (seven vs. two [P<0.05]).

CONCLUSIONS

We demonstrate that (1) CGM is a useful approach in DMT1 patients who undergo an exercise program and (2) IHE is associated with delayed nocturnal hypoglycemia.

Use of sensors in the treatment and follow-up of patients with diabetes mellitus

Glucose control is the cornerstone of Diabetes Mellitus (DM) treatment. Although self-regulation using capillary glycemia (SRCG) still remains the best procedure in clinical practice, continuous glucose monitoring systems (CGM) offer the possibility of continuous and dynamic assessment of interstitial glucose concentration. CGM systems have the potential to improve glycemic control while decreasing the incidence of hypoglycemia but the efficiency, compared with SRCG, is still debated. CGM systems have the greatest potential value in patients with hypoglycemic unawareness and in controlling daily fluctuations in blood glucose. The implementation of continuous monitoring in the standard clinical setting has not yet been established but a new generation of open and close loop subcutaneous insulin infusion devices are emerging making insulin treatment and glycemic control more reliable.

"Smart" continuous glucose monitoring sensors: on-line signal processing issues

The availability of continuous glucose monitoring (CGM) sensors allows development of new strategies for the treatment of diabetes. In particular, from an on-line perspective, CGM sensors can become “smart” by providing them with algorithms able to generate alerts when glucose concentration is predicted to exceed the normal range thresholds. To do so, at least four important aspects have to be considered and dealt with on-line. First, the CGM data must be accurately calibrated. Then, CGM data need to be filtered in order to enhance their signal-to-noise ratio (SNR). Thirdly, predictions of future glucose concentration should be generated with suitable modeling methodologies. Finally, generation of alerts should be done by minimizing the risk of detecting false and missing true events. For these four challenges, several techniques, with various degrees of sophistication, have been proposed in the literature and are critically reviewed in this paper.

Glucose levels at the site of subcutaneous insulin administration and their relationship to plasma levels

OBJECTIVE

To examine insulin's effect on the tissue glucose concentration at the site of subcutaneous insulin administration.

RESEARCH DESIGN AND METHODS

A CMA-60 microdialysis (MD) catheter and a 24-gauge microperfusion (MP) catheter were inserted into the subcutaneous adipose tissue of fasting, healthy subjects (n = 5). Both catheters were perfused with regular human insulin (100 units/ml) over a 6-h period and used for glucose sampling and simultaneous administration of insulin at sequential rates of 0.33, 0.66, and 1.00 units/h (each rate was used for 2 h). Before and after the insulin delivery period, both catheters were perfused with an insulin-free solution (5% mannitol) for 2 h and used for glucose sampling only. Blood plasma glucose was clamped at euglycemic levels during insulin delivery.

RESULTS

Start of insulin delivery with MD and MP catheters resulted in a decline of the tissue glucose concentration and the tissue-to-plasma glucose ratio (TPR) for approximately 60 min (P < 0.05). However, during the rest of the 6-h period of variable insulin delivery, tissue glucose concentration paralleled the plasma glucose concentration, and the TPR for MD and MP catheters remained unchanged at 83.2 +/- 3.1 and 77.1 +/- 4.8%, respectively. After subsequent switch to insulin-free perfusate, tissue glucose concentration and TPR increased slowly and reattained preinsulin delivery levels by the end of the experiments.

CONCLUSIONS

The results show the attainment of a stable TPR value at the site of insulin administration, thus indicating that insulin delivery and glucose sensing may be performed simultaneously at the same adipose tissue site.

Use of the site of subcutaneous insulin administration for the measurement of glucose in patients with type 1 diabetes

OBJECTIVE To simplify and improve the treatment of patients with type 1 diabetes, we ascertained whether the site of subcutaneous insulin infusion can be used for the measurement of glucose. RESEARCH DESIGN AND METHODS Three special indwelling catheters (24-gauge microperfusion [MP] catheters) were inserted into the subcutaneous adipose tissue of subjects with type 1 diabetes (n = 10; all C-peptide negative). One MP catheter was perfused with short-acting insulin (100 units/ml, Aspart) and used for insulin delivery and simultaneous glucose sampling during an overnight fast and after ingestion of a standard glucose load (75 g). As controls, the further two MP catheters were perfused with an insulin-free solution (5% mannitol) and used for glucose sampling only. Plasma glucose was measured frequently at the bedside. RESULTS Insulin delivery with the MP catheter was adequate to achieve and maintain normoglycemia during fasting and after glucose ingestion. Tissue glucose concentrations derived with the insulin-perfused catheter agreed well with plasma glucose levels. Median correlation coefficient and median absolute relative difference values were found to be 0.93 (interquartile range 0.91-0.97) and 10.9%, respectively. Error grid analysis indicated that the percentage number of tissue values falling in the clinically acceptable range is 99.6%. Comparable analysis results were obtained for the two mannitol-perfused catheters. CONCLUSIONS Our data suggest that estimation of plasma glucose concentrations from the glucose levels directly observed at the site of subcutaneous insulin infusion is feasible and its quality is comparable to that of estimating plasma glucose concentrations from glucose levels measured in insulin-unexposed subcutaneous tissue.

Assessment of different techniques for subcutaneous glucose monitoring in Type 1 diabetic patients during 'real-life' glucose excursions

AIMS

To compare the accuracy of two marketed subcutaneous glucose monitoring devices (Guardian RT, GRT; GlucoDay S, GDS) and standard microdialysis (CMA60; MD) in Type 1 diabetic patients.

METHODS

Seven male Type diabetic patients were investigated over a period of 26 h simulating real-life meal glucose excursions. Catheters of the three systems were inserted into subcutaneous adipose tissue of the abdominal region. For MD, interstitial fluid was sampled at 30- to 60-min intervals for offline glucose determination. Reference samples were taken at 15- to 60-min intervals. All three systems were prospectively calibrated to reference. Median differences, median absolute relative differences (MARD), median absolute differences (MAD), Bland-Altman plot and Clark Error Grid were used to determine accuracy.

RESULTS

Bland-Altman analysis indicated a mean glucose difference (2 standard deviations) between reference and interstitial glucose of -10.5 (41.8) % for GRT, 20.2 (55.9) % for GDS and 6.5 (35.2) % for MD, respectively. Overall MAD (interquartile range) was 1.07 (0.39; 2.04) mmol/l for GRT, 1.59 (0.54; 3.08) mmol/l for GDS and 0.76 (0.26; 1.58) mmol/l for MD. Overall MARD was 15.0 (5.6; 23.4) % (GRT), 19.7 (6.1; 37.6) % (GDS) and 8.7 (4.1; 18.3) % (MD), respectively. Total sensor failure occurred in two subjects using GRT and one subject using GDS.

CONCLUSIONS

The three investigated technologies had comparable performance. Whereas GRT underestimated actual blood glucose, GDS and MD overestimated blood glucose. Considerable deviations during daily life meal glucose excursions from reference glucose were observed for all three investigated technologies. Present technologies may require further improvement until individual data can lead to direct and automated generation of therapeutic advice in diabetes management.

Glycemic control in critically ill patients before and after institution of an intensive insulin infusion protocol: circadian rhythm and the quality duration calculator

INTRODUCTION

A circadian rhythm of blood glucose values has been recently reported in critically ill patients, but there are no reports of how this rhythm is altered by a continuous intensive insulin infusion therapy protocol (IIT). We wished to examine the effect of IIT on this rhythm as well as to describe the use of the quality duration calculator (QDC) for the evaluation of glycemic control before and after IIT.

METHODS

This was a retrospective multihospital observational study that took place in the medical and surgical intensive care units (ICUs) of 2 tertiary care hospitals. Cohorts of consecutively admitted critically ill patients from 2-year periods before and after institution of an IIT protocol were examined. Laboratory, demographic, and outcome data were extracted from hospital databases.

RESULTS

We studied 167,645 blood glucose measurements from 8,327 patients. We observed a circadian rhythm of blood glucose control in the pre-IIT cohort that was greatly attenuated in the post-IIT cohort. The difference between the morning and the average daily blood glucose in the pre-IIT cohort was 3.53 mg/dL (P < .001), and the difference between these values in the post-IIT cohort was 1.10 mg/dL (P = .031). In addition, the circadian nature of hyperglycemia incidence observed in the pre-IIT cohort was not seen in the post-IIT cohort. The amount of time spent in goal glycemic range increased from 23.69% (95% CI 23.01-24.38) in the pre-IIT cohort to 29.67% (95% CI 29.04-30.31) in the post-IIT cohort as estimated by the QDC. The amount of time spent in the hyperglycemic decreased from 20.17% (95% CI 19.33-20.99) in the pre-IIT cohort to 14.80% (95% CI 14.15-15.39) in the post-IIT cohort.

CONCLUSIONS

The circadian rhythm of blood glucose control confirmed in our pre-IIT cohort was lost after institution of IIT. The morning blood glucose value appears to be a reasonable surrogate of overall glycemic control in a critically ill population on IIT, although this may vary based on the degree of control achieved. The QDC method is useful for analyzing glycemic control in patients on IIT.

An online self-tunable method to denoise CGM sensor data

Continuous glucose monitoring (CGM) devices can be very useful in diabetes management. Unfortunately, their use in online applications, e.g., for hypo/hyperalert generation, is made difficult by random noise measurement. Remarkably, the SNR of CGM data varies with the sensor and with the individual. As a consequence, approaches in which filter parameters are not allowed to adapt to the current SNR are likely to be suboptimal. In this paper, we present a new online methodology to reduce noise in CGM signals by a Kalman filter (KF), whose unknown parameters are adjusted in a given individual by a stochastically based smoothing criterion exploiting data of a burn-in interval. The performance of the new KF approach is quantitatively assessed on Monte Carlo simulations and 24 real CGM datasets. Our results are compared with those obtained by a moving-average (MA) filtering approach with fixed parameters currently in use in likely all commercial CGM devices. Results show that the new KF approach performs much better than MA. For instance, on real data, for comparable signal denoising, the delay introduced by KF is about 35% less than that obtained by MA.

Prevalence of daily hyperglycemia in obese type 2 diabetic men compared with that in lean and obese normoglycemic men: effect of consumption of a sucrose-containing beverage

BACKGROUND

Hyperglycemia forms a direct and independent risk factor for the development of cardiovascular comorbidities in type 2 diabetes. Consumption of sucrose-sweetened soft drinks might further increase the prevalence of hyperglycemic episodes.

OBJECTIVE

The objective was to assess glycemic control in type 2 diabetic subjects and healthy lean and obese control subjects under strict dietary standardization but otherwise free-living conditions, with and without the consumption of soft drinks.

DESIGN

Obese type 2 diabetic men (n = 11) and lean (n = 10) and obese (n = 10) normoglycemic male control subjects participated in a randomized crossover study. The subjects were provided with a standardized diet in 2 periods, during which they consumed 250 mL water with or without (control) sucrose (37.5 g) 2 h after breakfast and lunch. Blood glucose concentrations were assessed by continuous glucose monitoring.

RESULTS

In the type 2 diabetic subjects, the mean 24-h glucose concentrations were significantly elevated (9.1 +/- 0.6 mmol/L), and hyperglycemia (glucose >10 mmol/L) was evident over 33 +/- 8% (8 +/- 2 h) of a 24-h period (P < 0.01). Hyperglycemia was rarely present in the normoglycemic lean and obese control subjects (5 +/- 2%/24 h for both). Consumption of 75 g sucrose, equivalent to 2 cans of a soft drink, did not further augment the prevalence of hyperglycemia throughout the day in any group.

CONCLUSIONS

Type 2 diabetic subjects taking oral blood glucose-lowering medication experience hyperglycemia during most of the daytime. Moderate consumption of sucrose-sweetened beverages does not further increase the prevalence of hyperglycemia in type 2 diabetic subjects or in normoglycemic lean or obese men.