Jeffrey I. Joseph

Clinical review: Consensus recommendations on measurement of blood glucose and reporting glycemic control in critically ill adults

The management reporting and assessment of glycemic control lacks standardization. The use of different methods to measure the blood glucose concentration and to report the performance of insulin treatment yields major disparities and complicates the interpretation and comparison of clinical trials. We convened a meeting of 16 experts plus invited observers from industry to discuss and where possible reach consensus on the most appropriate methods to measure and monitor blood glucose in critically ill patients and on how glycemic control should be assessed and reported. Where consensus could not be reached, recommendations on further research and data needed to reach consensus in the future were suggested. Recognizing their clear conflict of interest, industry observers played no role in developing the consensus or recommendations from the meeting. Consensus recommendations were agreed for the measurement and reporting of glycemic control in clinical trials and for the measurement of blood glucose in clinical practice. Recommendations covered the following areas: How should we measure and report glucose control when intermittent blood glucose measurements are used? What are the appropriate performance standards for intermittent blood glucose monitors in the ICU? Continuous or automated intermittent glucose monitoring - methods and technology: can we use the same measures for assessment of glucose control with continuous and intermittent monitoring? What is acceptable performance for continuous glucose monitoring systems? If implemented, these recommendations have the potential to minimize the discrepancies in the conduct and reporting of clinical trials and to improve glucose control in clinical practice. Furthermore, to be fit for use, glucose meters and continuous monitoring systems must match their performance to fit the needs of patients and clinicians in the intensive care setting.See related commentary by Soto-Rivera and Agus, http://ccforum.com/content/17/3/155

Diurnal variation of the human adipose transcriptome and the link to metabolic disease

BackgroundCircadian (diurnal) rhythm is an integral part of the physiology of the body; specifically, sleep, feeding behavior and metabolism are tightly linked to the light-dark cycle dictated by earths rotation.MethodsThe present study examines the effect of diurnal rhythm on gene expression in the subcutaneous adipose tissue of overweight to mildly obese, healthy individuals. In this well-controlled clinical study, adipose biopsies were taken in the morning, afternoon and evening from individuals in three study arms: treatment with the weight loss drug sibutramine/fasted, placebo/fed and placebo/fasted.ResultsThe results indicated that diurnal rhythm was the most significant driver of gene expression variation in the human adipose tissue, with at least 25% of the genes having had significant changes in their expression levels during the course of the day. The mRNA expression levels of core clock genes at a specific time of day were consistent across multiple subjects on different days in all three arms, indicating robust diurnal regulation irrespective of potential confounding factors. The genes essential for energy metabolism and tissue physiology were part of the diurnal signature. We hypothesize that the diurnal transition of the expression of energy metabolism genes reflects the shift in the adipose tissue from an energy-expending state in the morning to an energy-storing state in the evening. Consistent with this hypothesis, the diurnal transition was delayed by fasting and treatment with sibutramine. Finally, an in silico comparison of the diurnal signature with data from the publicly-available Connectivity Map demonstrated a significant association with transcripts that were repressed by mTOR inhibitors, suggesting a possible link between mTOR signaling, diurnal gene expression and metabolic regulation.ConclusionDiurnal rhythm plays an important role in the physiology and regulation of energy metabolism in the adipose tissue and should be considered in the selection of novel targets for the treatment of obesity and other metabolic disorders.

Continuous glucose control in the ICU: report of a 2013 round table meeting

Achieving adequate glucose control in critically ill patients is a complex but important part of optimal patient management. Until relatively recently, intermittent measurements of blood glucose have been the only means of monitoring blood glucose levels. With growing interest in the possible beneficial effects of continuous over intermittent monitoring and the development of several continuous glucose monitoring (CGM) systems, a round table conference was convened to discuss and, where possible, reach consensus on the various aspects related to glucose monitoring and management using these systems. In this report, we discuss the advantages and limitations of the different types of devices available, the potential advantages of continuous over intermittent testing, the relative importance of trend and point accuracy, the standards necessary for reporting results in clinical trials and for recognition by official bodies, and the changes that may be needed in current glucose management protocols as a result of a move towards increased use of CGM. We close with a list of the research priorities in this field, which will be necessary if CGM is to become a routine part of daily practice in the management of critically ill patients.

A Clinical Trial of the Accuracy and Treatment Experience of the Dexcom G4 Sensor (Dexcom G4 System) and Enlite Sensor (Guardian REAL-Time System) Tested Simultaneously in Ambulatory Patients with Type 1 Diabetes

BACKGROUND Continuous glucose monitoring (CGM) is a tool widely used in the treatment of patients with type 1 diabetes. The purpose of the current study was to evaluate whether accuracy and patient treatment satisfaction differ between the Enlite™ (Medtronic MiniMed, Inc., Northridge, CA) and Dexcom(®) (San Diego, CA) G4 PLATINUM CGM sensors. SUBJECTS AND METHODS Thirty-eight ambulatory patients with type 1 diabetes used the Dexcom G4 and Enlite sensors simultaneously for a minimum of 4 and maximum of 6 days. Patients measured capillary glucose levels with a HemoCue(®) (Ängelholm, Sweden) system six to 10 times a day. In addition, two inpatient studies were performed between Days 1-3 and 4-6. RESULTS The mean absolute relative difference (MARD) in blood glucose for the Dexcom G4 was significantly lower (13.9%) than for the Enlite sensor (17.8%) (P<0.0001). The corresponding MARDs for Days 1-3 were 15.0% versus 19.4% (P=0.0027) and 13.6% versus 15.9% (P=0.026) for Days 4-6. For glucose levels in the hypoglycemic range (<4.0 mmol/L), the MARD for the Dexcom G4 was 20.0% compared with 34.7% for the Enlite (P=0.0041). On a visual analog scale (VAS) (0-100), patients rated the Dexcom G4 more favorably than the Enlite in 12 out of the 13 user experience questions. For example, more patients rated their experience with the Dexcom G4 as positive (VAS, 79.7 vs. 46.6; P<0.0001) and preferred to use it in their daily lives (VAS, 79.1 vs. 42.1; P<0.0001). CONCLUSIONS The Dexcom G4 sensor was associated with greater overall accuracy than the Enlite sensor during initial (Days 1-3) and later (Days 4-6) use and for glucose levels in the hypoglycemic range. Patients reported a significantly more positive experience using the Dexcom G4 than the Enlite.

Clinical need for continuous glucose monitoring in the hospital.

Automation and standardization of the glucose measurement process have the potential to greatly improve glycemic control, clinical outcome, and safety while reducing cost. The resources required to monitor glycemia in hospitalized patients have thus far limited the implementation of intensive glucose management to patients in critical care units. Numerous available and up-and-coming technologies are targeted for the hospital patient population. Advantages and limitations of these devices are discussed herewith in.

Evaluation of the VIA Blood Chemistry Monitor for Glucose in Healthy and Diabetic Volunteers.

Background: Manual methods of blood glucose monitoring are labor-intensive, costly, prone to error, and expose the caregiver to blood. The VIA® blood chemistry monitor for glucose can automatically measure plasma glucose (PG) every 5 minutes for 72 hours using blood sampled from a peripheral vein/artery or a central vein. Methods: VIA performance was evaluated in eight normal and five type 1 diabetic (T1DM) subjects in 15 separate experiments. The VIA device was connected to a peripheral vein and reported a PG value every 5 minutes during each 510-minute experiment. Blood samples were collected manually every 10 minutes and assayed using a HemoCue® β-glucose analyzer (HC). Whole blood HC measurements were corrected to PG values. Paired HC/VIA measurements (n = 717) were analyzed. Results: Mean PG was 90 ± 14 and 96 ± 12 mg/dl in normal subjects and 194 ± 64 and 173 ± 48 mg/dl in T1DM subject as measured by the HC and VIA, respectively. Clark error grid analysis revealed 86% points in zone A, 11% points in zone B, and 2% points in zone D. Linear regression analysis yielded the following equation: VIA = 0.732 × HC + 30.5 (r 2 = 0.954). Residual analysis revealed a glucose-dependent bias between the HC and the VIA. VIA data were transformed using the linear regression equation to correct for bias. After the correction, the mean absolute relative difference between the VIA and the HC was less than 10%, and 99.6% of data were in zones A and B. The VIA was able to sample blood automatically every 5 minutes for more than 8 hours in the laboratory setting. On average, the VIA reported glucose values for 94% of the samples it attempted to obtain. Conclusions: This study demonstrated that the VIA blood chemistry monitor for glucose can reliably sample blood frequently for a prolonged period of time safely and effectively in diabetic and nondiabetic volunteers. Agreement between the two devices was the closest at normal glucose concentrations. After correcting for a glucose-dependent bias between the devices, the MARD was consistently less than 10% for all glucose ranges.

Protein-tyrosine phosphatase activity in human adipocytes is strongly correlated with insulin-stimulated glucose uptake and is a target of insulin-induced oxidative inhibition.

Protein-tyrosine phosphatases (PTPases), in particular PTP1B, have been shown to modulate insulin signal transduction in liver and skeletal muscle in animal models; however, their role in human adipose tissue remains unclear. The uptake of (14)C-D-glucose in response to 10 or 100 nmol/L insulin was measured in isolated subcutaneous adipocytes from subjects with a mean age of 44 years (range, 26 to 58) and mean body mass index (BMI) of 35.6 (range, 29.7 to 45.5). The endogenous activity of total PTPases and specifically of PTP1B in immunoprecipitates was measured in cell lysates under an inert atmosphere with and without added reducing agents. Using nonlinear regression analysis, higher BMI was significantly correlated with lower adipocyte glucose uptake (r = 0.73, P =.01) and with increased endogenous total PTPase activity (r = 0.64, P =.04). Correlation with waist circumference gave similar results. The endogenous total PTPase activity also strongly correlated with insulin-stimulated glucose uptake (R =.89, P <.0001); however, the activity of PTP1B was unrelated to the level of glucose uptake. Consistent with the insulin-stimulated oxidative inhibition of thiol-dependent PTPases reported for 3T3-L1 adipocytes and hepatoma cells, treatment of human adipocytes with 100 nmol/L insulin for 5 minutes lowered endogenous PTPase activity to 37% of control (P <.001), which was increased 25% by subsequent treatment with dithiothreitol in vitro. Cellular treatment with diphenyleneiodonium (DPI), an NADPH oxidase inhibitor that blocks the cellular generation of H(2)O(2) and reduces the insulin-induced reduction of cellular PTPase activity, also diminished insulin-stimulated glucose uptake by 82% (P =.001). These data suggest that total cellular PTPase activity, but not the activity of PTP1B, is higher in more obese subjects and is negatively associated with insulin-stimulated glucose transport. The insulin-stimulated oxidative inhibition of PTPases may also have an important permissive role in the transmission of the insulin signal to glucose transport in human adipocytes.

Constitutive overexpression of phosphomimetic phospholemman S68E mutant results in arrhythmias, early mortality, and heart failure: potential involvement of Na+/Ca2+ exchanger

Expression and activity of cardiac Na(+)/Ca(2+) exchanger (NCX1) are altered in many disease states. We engineered mice in which the phosphomimetic phospholemman S68E mutant (inhibits NCX1 but not Na(+)-K(+)-ATPase) was constitutively overexpressed in a cardiac-specific manner (conS68E). At 4-6 wk, conS68E mice exhibited severe bradycardia, ventricular arrhythmias, increased left ventricular (LV) mass, decreased cardiac output (CO), and ∼50% mortality compared with wild-type (WT) littermates. Protein levels of NCX1, calsequestrin, ryanodine receptor, and α(1)- and α(2)-subunits of Na(+)-K(+)-ATPase were similar, but sarco(endo)plasmic reticulum Ca(2+)-ATPase was lower, whereas L-type Ca(2+) channels were higher in conS68E hearts. Resting membrane potential and action potential amplitude were similar, but action potential duration was dramatically prolonged in conS68E myocytes. Diastolic intracellular Ca(2+) ([Ca(2+)](i)) was higher, [Ca(2+)](i) transient and maximal contraction amplitudes were lower, and half-time of [Ca(2+)](i) transient decline was longer in conS68E myocytes. Intracellular Na(+) reached maximum within 3 min after isoproterenol addition, followed by decline in WT but not in conS68E myocytes. Na(+)/Ca(2+) exchange, L-type Ca(2+), Na(+)-K(+)-ATPase, and depolarization-activated K(+) currents were decreased in conS68E myocytes. At 22 wk, bradycardia and increased LV mass persisted in conS68E survivors. Despite comparable baseline CO, conS68E survivors at 22 wk exhibited decreased chronotropic, inotropic, and lusitropic responses to isoproterenol. We conclude that constitutive overexpression of S68E mutant was detrimental, both in terms of depressed cardiac function and increased arrhythmogenesis.

Use of an anaerobic environment to preserve the endogenous activity of protein-tyrosine phosphatases isolated from intact cells

Protein‐tyrosine phosphatases (PTPases) have a common cysteine residue whose reduced state is integral to their phosphocysteine‐mediated reaction mechanism. The catalytic cysteine thiol can be oxidized or conjugated during cellular redox reactions, which provides an important means of PTPase regulation in vivo. Because exposure to air can artifactually oxidize this reactive thiol, PTPase assays have typically used potent reducing agents such as dithiothreitol to reactivate the enzymes present. However, this approach does not allow for the measurement of endogenous PTPase activity as directly isolated from the in vivo cellular environment. Here we show that sample processing and assay in an anaerobic chamber by using deoxygenated buffers can preserve the overall activity of PTPases in subcellular fractions of 3T3‐L1 adipocytes, HepG2 hepatoma cells, and human adipose tissue, as well as with PTP1B, specifically isolated by immunoprecipitation. Cell lysis into air reduced the PTPase activity to as low as 20% of the level observed with sample handling in the anaerobic environment, which was variably restored towards the activity in the anaerobic samples by treatment with dithiothreitol. The approach reported here provides a new framework for characterizing the activity of PTPases as isolated from the intracellular milieu, which more closely reflects the endogenous reactivity and potential impact of these PTPases on signal transduction pathways involving reversible protein‐tyrosine phosphorylation.

Synthesis, Characterization and In Vivo Efficacy of PEGylated Insulin for Oral Delivery with Complexation Hydrogels

PurposeThis work evaluated the feasibility of combining insulin PEGylation with pH responsive hydrogels for oral insulin delivery.MethodsA mono-substituted PEG–insulin conjugate was synthesized and purified. The site of conjugation was determined by MALDI-TOF MS. Uptake and release of PEGylated insulin was performed in complexation hydrogels to simulate oral dosing. The bioactivity of the conjugate and PK/PD profile was measured in vivo in rats.ResultsPEGylation was confirmed to be specifically located at the amino terminus of the B-chain of insulin. Higher loading efficiency was achieved with PEGylated insulin than regular human insulin in pH responsive hydrogels. The release of PEGylated insulin was lower than that of human insulin at all pH levels considered. Full retention of bioactivity of the PEG–insulin conjugate was confirmed by intravenous dosing while subcutaneous dosing exhibited a relative hypoglycemic effect 127.8% that of human insulin.ConclusionsPolyethylene glycol conjugated specifically to the amino terminus of the B-chain of insulin maintained the bioactivity of the protein and significantly extended the duration of the hypoglycemic effect. Used in combination with pH responsive hydrogels, PEGylated insulin has significant potential for oral delivery.