Blood–Brain Barrier Permeability to Sodium. Modification by Glucose or Insulin?

In order to explore the pathogenetic mechanism underlying the changes in blood-brain barrier sodium transport in experimental diabetes, the effects of hyperglycemia and of hypoinsulinemia were studied in nondiabetic rats. In untreated diabetes, the neocortical blood-brain barrier permeability for sodium decreased by 20% (5.6 +/- 0.7 versus 7.0 +/- 0.8 X 10(5) ml/g/s) as compared to controls. Intravenous infusion of 50% glucose for 2 h was associated with a decrease in the blood-brain barrier permeability to sodium (5.4 +/- 1.2 X 10(5) ml/g/s), whereas rats treated with an inhibitor of insulin-secretion (SMS 201-995, a somatostatin-analogue) had normal sodium permeability (7.3 +/- 2.0 X 10(5) ml/g/s). Acute insulin treatment of diabetic rats normalized the sodium permeability within a few hours as compared to a separate control group (7.7 +/- 1.1 versus 6.9 +/- 1.4 X 10(5) ml/g/s). To elucidate whether the abnormal blood-brain barrier passage is caused by a metabolic effect of glucose or by the concomitant hyperosmolality, rats were made hyperosmolar by intravenous injection of 50% mannitol. Although not statistically significant, blood-brain barrier sodium permeability increased in hyperosmolar rats as compared to the control rats (8.3 +/- 1.0 and 7.0 +/- 1.9 X 10(5) ml/g/s, respectively). It is concluded that either hyperglycemia per se or a glucose metabolite is responsible for the blood-brain barrier abnormality which occurs in diabetes. Further, we suggest that the specific decrease of sodium permeability could be the result of glucose-mediated inhibition of the Na+K+-ATPase localized at the blood-brain barrier.     

How Much Do I Give? Reevaluation of Insulin Dosing Estimation Formulas Using Continuous Glucose Monitoring

ObjectiveTo reevaluate current formulas for determining the total basal insulin dosage (TBD), insulin to carbohydrate ratio (ICR), and correction factor (CF) from weight or total daily dosage (TDD) in pump-treated patients with type 1 diabetes mellitus.MethodsFrom a post hoc analysis of data from 4 previously published studies, subjects who met the inclusion criteria were selected. No subject was duplicated. For all studies, the basal glucose target was to have fewer than 20% of glucose readings greater than 170 mg/dL and to have 10% or fewer glucose readings less than 70 mg/dL. Bolus insulin was adjusted to achieve a 2to 4-hour postbolus glucose value within 20% of the premeal glucose (ICR) or 80 to 120 mg/dL from premeal hyperglycemia (CF). In the first 2 studies, dosing titration by CGM was performed from 72-hour CGM tracings every week to every 6 weeks. In the other 2 studies, 24to 72-hour CGM downloads and insulin adjustments were done each weekday.ResultsOf 101 participants, 61 (59% women) met the inclusion criteria. Estimation formulas could be rounded to the following: TBD = 0.2 × weight (kg) or 0.4 × TDD; ICR = 300 ÷ TDD; and CF = 1500 ÷ TDD. In particular the relationship between all 3 dosing factors could be represented as 100 ÷ TBD = ICR = CF ÷ 4.5.ConclusionsThese results suggest that current formulas give a higher estimate for TBD and a lower estimate for the bolus dose. (Endocr Pract. 2010;16:428-432)     

Aging-related Correlation of Insulin-degrading Enzyme with γ-Secretase-generated Products Involving Insulin and Glucose Levels in Transgenic Mice

Insulin-degrading enzyme (IDE) is a 110-kDa thiol zinc-methalloendopeptidase that can cleave small Aβ peptides and the APP intracellular domain (AICD). The aim of this study was to examine aging-related correlation of IDE with γ-secretase-generated products involving insulin and glucose levels in transgenic brains expressing neuron-specific enolase (NSE)-controlled human mutant presenilin-2 (hPS2m). Herein, we concluded that the levels of IDE expression in transgenic brains were decreased relative to those of control mice at 15 months of age. In parallel, inhibition in the IDE expression at this age underlies to the levels-up of Aβ-42, AICD, γ-secretase, and glucose with a level-down of insulin. Thus, IDE expression is critical target for the therapeutic trials.     

Leptin Signaling in the Arcuate Nucleus Reduces Insulin’s Capacity to Suppress Hepatic Glucose Production in Obese Mice

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The Apoptotic Effect of HIF-1α Inhibition Combined with Glucose plus Insulin Treatment on Gastric Cancer under Hypoxic Conditions

Gastric cancer grows under a hypoxic environment. HIF-1α is known to play an important role in controlling the production of reactive oxygen species (ROS) in the mitochondria under hypoxic conditions. We previously established HIF-1α knockdown (KD) cells and control (SC) cells in the 58As9 gastric cancer cell line. In this study, we revealed that KD cells, but not SC cells, induced apoptosis under conditions of hypoxia (1% O₂) due to excessive production of ROS. A quantitative RT-PCR analysis demonstrated that the expressions of ten genes, which are involved in the control mechanisms of ROS (including the Warburg effect, mitophagy, electron transport chain [ETC] modification and ROS scavenging), were regulated by HIF-1α. Moreover, the promotion of glucose uptake by glucose plus insulin (GI) treatment enhanced the apoptotic effect, which was accompanied by further ROS production in hypoxic KD cells. A Western blot analysis showed that the membranous expression of GLUT1 in KD cells was elevated by glucose and/or insulin treatments, indicating that the GI-induced glucose uptake is mediated by the increased translocation of GLUT1 on the cell membrane. Finally, the anti-tumor effect of HIF-1α knockdown (KD) plus GI was evaluated using a tumor xenograft model, where a hypoxic environment naturally exists. As a result, the GI treatment strongly inhibited the growth of the KD tumors whereby cell apoptosis was highly induced in comparison to the control treatment. In contrast, the growth of the SC tumors expressing HIF-1α was not affected by the GI treatment. Taken together, the results suggest that HIF-1α inhibition plus GI may be an ideal therapy, because the apoptosis due to the destruction of ROS homeostasis is specifically induced in gastric cancer that grows under a hypoxic environment, but not in the normal tissue under the aerobic conditions.     

Effects of Glucose, Insulin, and Supernatant from Pancreatic β-cells on Brain–Pancreas Relative Protein in Rat Hippocampus

Brain–pancreas relative protein (BPRP) is a novel protein that mainly expresses in brain and pancreas. In our previous study, we found that various stressors significantly decreased the expression of BPRP in pancreas in vivo, accompanied by changes in insulin and glucose levels, and that expression of BPRP in pancreas also decreased significantly in diabetic rats induced by Streptozocin (STZ). All these findings suggest that BPRP may be a glucose or insulin-sensitive protein. However, how the changes in insulin or glucose levels influence the expression of BPRP in hippocampus requires further study. Here, we investigated the effects of insulin or glucose on the expression of BPRP in primary cultured hippocampal neurons. We supplied hippocampal neurons with glucose, insulin, or supernatant from pancreatic β-cells, which secrete insulin into the supernatant. Our data showed that insulin had beneficial effect on the viability while no significant effect on the expression of BPRP in hippocampal neurons. On the contrary, 40 mM glucose or free glucose culture significantly decreased the expression of BPRP, while had no significant effect on the viability and apoptosis of hippocampal neurons. Further study showed that levels of insulin in the supernatant collected from pancreatic β-cells medium changed over days, and that supernatant increased the viability of hippocampal neurons, while it had no obvious effect on the expression of BPRP in hippocampal neurons. These results suggest that BPRP may be a glucose-sensitive protein.     

B22 Glu Des-B30 Insulin： A Novel Monomeric Insulin

Studies on monomeric insulin with reduced self-association are important in the development of insulin pharmaceutical preparations with rapid hypoglycemic action on patients with diabetes. Here we report a novel monomeric insulin, B22 Glu des-B30 insulin, prepared from a single chain insulin precursor with B22 Arg mutated to Glu, which was expressed in Pichia pastoris and converted to B22 Glu des-B30 insulin by tryptic digestion. It still retains 50% of the in vivo biological activity of porcine insulin and does not form a dimer even at a concentration of 10 mg/ml, showing that B22 Glu plays a key role in reducing the self- association of the insulin molecule without greatly reducing its biological activity. This novel monomeric insulin might have potential applications in the clinic.     

High-dose Insulin Therapy: is it Time for U-500 Insulin?

ObjectiveTo provide an overview of U-500 regular insulin action, review published clinical studies with U- 500 regular insulin, and offer guidance to practicing endocrinologists for identifying patients for whom U-500 regular insulin may be appropriate.MethodsThis review has been produced through a synthesis of relevant published literature compiled via a literature search (MEDLINE search of the English-language literature published between January 1969, and July 2008, related to U-500, insulin resistance, concentrated insulin, high-dose insulin, insulin pharmacokinetics, and diabetes management) and the authors’ collective clinical experience.ResultsThe obesity epidemic is contributing to an increase in the prevalence of type 2 diabetes, as well as to increasing insulin requirements in insulin-treated patients. Many of these patients exhibit severe insulin resistance, manifested by daily insulin requirements of 200 units or greater or more than 2 units/kg. Delivering an appropriate insulin volume to these patients can be difficult and inconvenient and may be best accomplished with U-500 regular insulin by multiple daily injections or with continuous subcutaneous insulin infusion, rather than with standard U-100 insulin. Implementation of U-500 regular insulin in patients previously on other insulin formulations is described with a treatment algorithm covering dosage requirements ranging from 150 to more than 600 units per day on the basis of the authors’ experience.ConclusionRegimen conversion of appropriately selected patients from high-dose, U-100 insulin to U-500 regular insulin therapy on the basis of the recommendations presented in this article may potentially result in improved glycemic control and lower cost. (Endocr Pract. 2009;15:71-79)     

Inhibition of Pancreatic β-Cell Ca2+/Calmodulin-dependent Protein Kinase II Reduces Glucose-stimulated Calcium Influx and Insulin Secretion,Impairing Glucose Tolerance

Glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells is caused by Ca²⁺ entry via voltage-dependent Ca²⁺ channels. CaMKII is a key mediator and feedback regulator of Ca²⁺ signaling in many tissues, but its role in β-cells is poorly understood, especially in vivo. Here, we report that mice with conditional inhibition of CaMKII in β-cells show significantly impaired glucose tolerance due to decreased GSIS. Moreover, β-cell CaMKII inhibition dramatically exacerbates glucose intolerance following exposure to a high fat diet. The impairment of islet GSIS by β-cell CaMKII inhibition is not accompanied by changes in either glucose metabolism or the activities of K_ATP and voltage-gated potassium channels. However, glucose-stimulated Ca²⁺ entry via voltage-dependent Ca²⁺ channels is reduced in islet β-cells with CaMKII inhibition, as well as in primary wild-type β-cells treated with a peptide inhibitor of CaMKII. The levels of basal β-cell cytoplasmic Ca²⁺ and of endoplasmic reticulum Ca²⁺ stores are also decreased by CaMKII inhibition. In addition, CaMKII inhibition suppresses glucose-stimulated action potential firing frequency. These results reveal that CaMKII is a Ca²⁺ sensor with a key role as a feed-forward stimulator of β-cell Ca²⁺ signals that enhance GSIS under physiological and pathological conditions.     

D-Chiro-Inositol – Its Functional Role in Insulin Action and its Deficit in Insulin Resistance

In this review we discuss the biological significance of D-chiro-inositol, originally discovered as a component of a putative mediator of intracellular insulin action, where as a putative mediator, it accelerates the dephosphorylation of glycogen synthase and pyruvate dehydrogenase, rate limiting enzymes of non-oxidative and oxidative glucose disposal.Early studies demonstrated a linear relationship between its decreased urinary excretion and the degree of insulin resistance present. When tissue contents, including muscle, of type 2 diabetic subjects were assayed, they demonstrated a more general body deficiency. Administration of D-chiro-inositol to diabetic rats, Rhesus monkeys and now to humans accelerated glucose disposal and sensitized insulin action.A defect in vivo in the epimerization of myoinositol to chiro-inositol in insulin sensitive tissues of the GK type 2 diabetic rat has been elucidated. Thus, administered D-chiro-inositol may act to bypass a defective normal epimerization of myo-inositol to D-chiro-inositol associated with insulin resistance and act to at least partially restore insulin sensitivity and glucose disposal.     

Circulating Betatrophin Correlates with Triglycerides and Postprandial Glucose among Different Glucose Tolerance Statuses—A Case-Control Study

Purpose

Previous researches of betatrophin on glucose and lipids metabolism under insulin-resistant condition have reached controversial conclusions. To further identify the possible impact of betatrophin, we measured the circulating betatrophin levels in newly diagnosed type 2 diabetes (T2DM) patients, and in subjects with both impaired glucose tolerance (IGT) and normal glucose tolerance (NGT) and investigated the relationship between serum betatrophin and other clinical parameters in these patients with different glucose tolerance statuses.

Methods

A total of 460 permanent residents of the Fengxian District, aged 40–60 years, were enrolled. Based on the results of a 75 g oral glucose tolerance test, we selected newly diagnosed T2DM (n = 50) patients and subjects with IGT (n = 51) and NGT (n = 50) according to their age, gender and body mass index (18–28 kg/m²). Anthropometric parameters, glycosylated haemoglobin, blood lipids and fasting insulin were measured. Serum betatrophin concentrations were determined via ELISA.

Results

Serum betatrophin levels in T2DM patients were increased significantly compared with IGT and NGT groups, and decreased in subjects with better islet beta cell function. Serum betatrophin was positively correlated with triglyceride, 2-hour postprandial glucose, alanine aminotransferase and aspartate transaminase after adjusting for age, sex and body mass index in all subjects. Multiple regression analysis showed that 2-hour postprandial glucose was independently associated with serum betatrophin significantly.

Conclusions

Circulating betatrophin is increased in newly-diagnosed T2DM patients and positively correlated with the triglycerides and postprandial glucose levels. The results suggest that betatrophin may participate in glucose and triglycerides metabolism.     

Glucose—a sweet way to die

TRAIL, a putative anticancer cytokine, induces extrinsic cell death by activating the caspase cascade directly (Type I cells) via the death-inducing signaling complex (DISC) or indirectly (Type II cells) by caspase-8 cleavage of Bid and activation of the mitochondrial cell death pathway. Cancer cells are characterized by their dependence on aerobic glycolysis, which, although inefficient in terms of ATP production, facilitates tumor metabolism. Our studies show that TRAIL-induced cell death is significantly affected by the metabolic status of the cell. Inhibiting glycolysis with 2-deoxyglucose potentiates TRAIL-induced cell death, whereas glucose deprivation can paradoxically inhibit apoptosis. These conflicting responses to glycolysis inhibition are modulated by the balance between the Akt and AMPK pathways and their subsequent downstream regulation of mTORC1. This results in marked changes in protein translation, in which the equilibrium between anti- and pro-apoptotic Bcl-2 family member proteins is decided by their individual degradation rates. This regulates the mitochondrial cell death pathway and alters its sensitivity not only to TRAIL, but to ABT-737, a Bcl-2 inhibitor. Taken together, our studies show that the sensitivity of cancer cells to apoptosis can be modulated by targeting their unique metabolism in order to enhance sensitivity to apoptotic agents.     

Integrated Insulin Pump and Continuous Glucose Monitoring Technology in Diabetes Care Today: A Perspective of Real-Life Experience With the Minimed™ 670G Hybrid Closed-Loop System

Objective: Intensive glucose management with insulin pump and continuous glucose monitoring therapy in insulin-treated patients with diabetes poses many challenges in all aspects of daily life. Automated insulin delivery (AID) is the ultimate goal of insulin replacement therapy to reduce the burden of managing this condition. Many systems are being tested in the clinical research setting, and one hybrid closed-loop (HCL) system has received Food and Drug Administration (FDA) approval for use in type 1 diabetes patients above the age of 14 years.Methods: Literature review and clinical practice experience from the Diabetes and Technology Program at an academic medical center.Results: This review outlines recent advances in AID systems, focusing on the FDA-approved MiniMed™ 670G HCL system and the real-life experience 1-year post-release in an academic medical center with over 60 patients on this system. The unique challenges of adapting to this new system outside the clinical trial setting are highlighted, and a training protocol designed specifically for the onboarding of first-time users is described.Conclusion: HCL insulin therapy offers several advantages, at the same time posing unique challenges to the user. Systematic training of patients with diabetes transitioning to this system is essential for retention and success of use.Abbreviations: AID = automated insulin delivery; CGM = continuous glucose monitoring; FDA = Food and Drug Administration; HbA1c = glycated hemoglobin; HCL = hybrid closed-loop; ICR = insulin to carbohydrate ratio; SAP = sensor augmented pump; T1DM = type 1 diabetes     

Spectral Changes of the γ-Irradiated Glucose Solution

β-1,3-Xylanase was purified to gel electrophoretic homogeneity and 83-fold from a cell-free culture fluid of Vibrio sp. XY-214 by ammonium sulfate precipitation and successive chromatographies. The enzyme had a pl of 3.6 and a molecular mass of 52 kDa. The enzyme had the highest level of activity at pH 7.0 and 37°C. The enzyme activity was completely inhibited by Cu²⁺, Hg²⁺, and N-bromosuccinimide. The enzyme hydrolyzed β-1,3-xylan to produce mainly xylotriose and xylobiose but did not act on xylobiose, p-nitrophenyl-β-D-xyloside, β-1,4-xylan, β-1,3-glucan, or carboxymethyl cellulose.     

Clinical and Cost-Effectiveness of Insulin Delivery with V-GO® Disposable Insulin Delivery Device Versus Multiple Daily Injections in Patients with Type 2 Diabetes Inadequately Controlled on Basal Insulin

Objective: To compare two methods of delivering intensified insulin therapy (IIT) in patients with type 2 diabetes inadequately controlled on basal insulin ± concomitant antihyperglycemic agents in a real-world clinical setting.Methods: Data for this retrospective study were obtained using electronic medical records from a large multicenter diabetes system. Records were queried to identify patients transitioned to V-Go® disposable insulin delivery device (V-Go) or multiple daily injections (MDI) using an insulin pen to add prandial insulin when A1C was >7% on basal insulin therapy. The primary endpoint was the difference in A1C change using follow-up A1C results.Results: A total of 116 patients were evaluated (56 V-Go, 60 MDI). Both groups experienced significant glycemic improvement from similar mean baselines. By 27 weeks, A1C least squares mean change from baseline was -1.98% (-21.6 mmol/mol) with V-Go and -1.34% (-14.6 mmol/mol) with MDI, for a treatment difference of -0.64% (-7.0 mmol/mol; P = .020). Patients using V-Go administered less mean ± SD insulin compared to patients using MDI, 56 ± 17 units/day versus 78 ± 40 units/day (P<.001), respectively. Diabetes-related direct pharmacy costs were lower with V-Go, and the cost inferential from baseline per 1% reduction in A1C was significantly less with V-Go ($118.84 ± $158.55 per patient/month compared to $217.16 ± $251.66 per patient/month with MDI; P = .013).Conclusion: Progression to IIT resulted in significant glycemic improvement. Insulin delivery with V-Go was associated with a greater reduction in A1C, required less insulin, and proved more cost-effective than administering IIT with MDI.Abbreviations:A1C = glycated hemoglobinANCOVA = analysis of covarianceCI = confidence intervalCSII = continuous subcutaneous insulin infusionFPG = fasting plasma glucoseIIT = intensified insulin therapyLSM = least squares meanMDI = multiple daily injectionsT2DM = type 2 diabetes mellitusTDD = total daily dose