High-dose Insulin Treatment Research Articles

Treatment-Induced Neuropathy in Diabetes (TIND)-Developing a Disease Model in Type 1 Diabetic Rats.

Treatment-induced neuropathy in diabetes (TIND) is defined by the occurrence of an acute neuropathy within 8 weeks of an abrupt decrease in glycated hemoglobin-A1c (HbA1c). The underlying pathogenic mechanisms are still incompletely understood with only one mouse model being explored to date. The aim of this study was to further explore the hypothesis that an abrupt insulin-induced fall in HbA1c may be the prime causal factor of developing TIND. BB/OKL (bio breeding/OKL, Ottawa Karlsburg Leipzig) diabetic rats were randomized in three groups, receiving insulin treatment by implanted subcutaneous osmotic insulin pumps for 3 months, as follows: Group one received 2 units per day; group two 1 unit per day: and group three 1 unit per day in the first month, followed by 2 units per day in the last two months. We serially examined blood glucose and HbA1c levels, motor- and sensory/mixed afferent conduction velocities (mNCV and csNCV) and peripheral nerve morphology, including intraepidermal nerve fiber density and numbers of Iba-1 (ionized calcium binding adaptor molecule 1) positive macrophages in the sciatic nerve. Only in BB/OKL rats of group three, with a rapid decrease in HbA1c of more than 2%, did we find a significant decrease in mNCV in sciatic nerves (81% of initial values) after three months of treatment as compared to those group three rats with a less marked decrease in HbA1c <2% (mNCV 106% of initial values, p ≤ 0.01). A similar trend was observed for sensory/mixed afferent nerve conduction velocities: csNCV were reduced in BB/OKL rats with a rapid decrease in HbA1c >2% (csNCV 90% of initial values), compared to those rats with a mild decrease <2% (csNCV 112% of initial values, p ≤ 0.01). Moreover, BB/OKL rats of group three with a decrease in HbA1c >2% showed significantly greater infiltration of macrophages by about 50% (p ≤ 0.01) and a decreased amount of calcitonin gene related peptide (CGRP) positive nerve fibers as compared to the animals with a milder decrease in HbA1c. We conclude that a mild acute neuropathy with inflammatory components was induced in BB/OKL rats as a consequence of an abrupt decrease in HbA1c caused by high-dose insulin treatment. This experimentally induced neuropathy shares some features with TIND in humans and may be further explored in studies into the pathogenesis and treatment of TIND.

Insulin Treatment Attenuates Small Nerve Fiber Damage in Rat Model of Type 2 Diabetes.

Introduction Current clinical guidelines for management of diabetic peripheral neuropathy (DPN) emphasize good glycemic control. However, this has limited effect on prevention of DPN in type 2 diabetic (T2D) patients. This study investigates the effect of insulin treatment on development of DPN in a rat model of T2D to assess the underlying causes leading to DPN. Methods Twelve-week-old male Sprague-Dawley rats were allocated to a normal chow diet or a 45% kcal high-fat diet. After eight weeks, the high-fat fed animals received a mild dose of streptozotocin to induce hyperglycemia. Four weeks after diabetes induction, the diabetic animals were allocated into three treatment groups receiving either no insulin or insulin-releasing implants in a high or low dose. During the 12-week treatment period, blood glucose and body weight were monitored weekly, whereas Hargreaves' test was performed four, eight, and 12 weeks after treatment initiation. At study termination, several blood parameters, body composition, and neuropathy endpoints were assessed. Results Insulin treatment lowered blood glucose in a dose-dependent manner. In addition, both doses of insulin lowered lipids and increased body fat percentage. High-dose insulin treatment attenuated small nerve fiber damage assessed by Hargreaves' test and intraepidermal nerve fiber density compared to untreated diabetes and low-dose insulin; however, neuropathy was not completely prevented by tight glycemic control. Linear regression analysis revealed that glycemic status, circulating lipids, and sciatic nerve sorbitol level were all negatively associated with the small nerve fiber damage observed. Conclusion In summary, our data suggest that high-dose insulin treatment attenuates small nerve fiber damage. Furthermore, data also indicate that both poor glycemic control and dyslipidemia are associated with disease progression. Consequently, this rat model of T2D seems to fit well with progression of DPN in humans and could be a relevant preclinical model to use in relation to research investigating treatment opportunities for DPN.

Insulin therapy for hyperglycemia in neonatal sepsis using a preterm mouse model.

Stress-induced hyperglycemia is a frequent complication of neonatal sepsis. Hyperglycemia induces oxidative stress and immunosuppression. We investigated the glucose kinetics and effect of insulin administration during stress-induced hyperglycemia in a neonatal sepsis mouse model. A stock cecal slurry (CS) solution was prepared from adult cecums and 3.0mg of CS/g (LD40 ) was administered intraperitoneally to 4-day-old FVB mouse pups. Blood glucose levels were measured at 1.5, 3, 6, and 9h post-sepsis induction and compared with basal levels. Two different doses of ultrafast-acting insulin were administered subcutaneously, and blood glucose levels and survival rates were monitored. Blood glucose levels were significantly higher than those of baseline levels with a peak at 3h, which progressively decreased from 6 to 9h post-sepsis induction. Insulin treatment reduced post-sepsis-induced hyperglycemia at 1.5 and 3h. The mortality rate of CS-only pups (39%) was similar to that of CS+1 U/kg insulin pups (60%). However, the mortality rate of CS+5 U/kg insulin pups (82%) was significantly higher than that of CS-only pups. Marked hyperglycemia was induced immediately after post-sepsis induction, and the high-dose insulin treatment increased mortality post-induction. Stress-induced hyperglycemia could therefore be a physiological and protective response for preterm sepsis, and aggressive treatment of this hyperglycemia might be contraindicated.

The Trend of High-Dose Insulin Usage Among Patients with Diabetes in the UK: A Retrospective Study.

IntroductionMany patients with diabetes may require high-dose insulin treatment to achieve target HbA1c level, but the prevalence, disease burden, and patient characteristics of the population remain unclear. We therefore investigated people with insulin-treated diabetes in the UK from 2009 to 2013, who were prescribed high daily doses (> 200 units/day).MethodsA retrospective analysis was conducted using the UK primary care electronic dataset from the Clinical Practice Research Datalink (CPRD). Trends of demographics, insulin dose, clinical characteristics, and annualized incidence rate of the insulin initiators were analyzed. Patients with type 1 (T1D) or type 2 diabetes (T2D) and who were prescribed insulin between 2009 and 2013 were categorized into either a low- or high-dose insulin user group. Two-sample t test and chi-square test were used for comparison of continuous variables and categorical variables, respectively. A multivariable negative binomial regression analysis with (log) person time as an offset was used to assess the impact of different covariates on incidence of high-dose insulin initiation.ResultsBetween 2009 and 2013, 19,631 patients with diabetes were treated with insulin (T1DM, 7620; T2DM, 12,011). In 2013, 415 high-dose insulin initiators were identified (T1DM, N = 170; T2DM, N = 245). More than half were male (T1DM/T2DM, 62.4%/56.3%) and 94.1%/83.7% of T1DM/T2DM patients were prescribed an insulin analogue at high-dose insulin initiation. At 6 months, 43.6% of T1DM and 42.6% of T2DM remained to have suboptimal HbA1c level of ≥ 8% (64 mmol/mol). Overall, 15.9%/63.3% of high-dose insulin initiators (HDII) with T1DM/T2DM took oral antidiabetics. From 2009 to 2013, the estimated glomerular filtration rate worsened in both T1DM and T2DM HDII.ConclusionDespite a number of patients requiring high doses of insulin in the UK, achievement of optimal HbA1c levels remains poor. Early identification of HDII is important in order to plan for alternative/adjuvant antidiabetic and lifestyle strategies to achieve optimal glycemic targets in this patient group.FundingEli Lilly and Company.

The effect of baseline characteristics on clinical efficacy of liraglutide in patients treated with high-dose insulin.

In patients requiring high-dose insulin treatment, a randomized, double-blind, placebo-controlled study showed that liraglutide improved glycaemic control and treatment satisfaction while promoting weight loss. We performed a post hoc analysis to evaluate if patients' baseline characteristics impact the efficacy of liraglutide, and which outcomes correlate with treatment satisfaction. We used regression analysis to model the change in HbA1c and weight, with treatment assignment and baseline characteristics [HbA1c, age, body mass index (BMI), total daily dose (TDD) of insulin, duration of insulin treatment, and type of insulin regimen] as independent variables. Improvement in HbA1c was best predicted by treatment with liraglutide, followed by higher baseline HbA1c, BMI and age. Changes in weight were only associated with liraglutide treatment, independent of all baseline characteristics. Improvement in HbA1c was the only significant predictor of improvement in treatment satisfaction, while weight loss, change in TDD of insulin and rate of hypoglycaemia did not influence treatment satisfaction. In patients treated with high-dose insulin, liraglutide significantly improved glycaemic control and led to weight loss regardless of patients' baseline characteristics. Improvement in HbA1c was the most important predictor of patients' treatment satisfaction.

Mechanisms of Action of Liraglutide in Patients With Type 2 Diabetes Treated With High-Dose Insulin.

The mechanisms of action of incretin mimetics in patients with long-standing type 2 diabetes (T2D) and high insulin requirements have not been studied. To evaluate changes in β-cell function, glucagon secretion, and fat distribution after addition of liraglutide to high-dose insulin. A single-center, randomized, double-blind, placebo-controlled trial. University of Texas Southwestern and Parkland Memorial Hospital clinics. Seventy-one patients with long-standing (median, 17 years) T2D requiring high-dose insulin treatment (>1.5 U/kg/d; average, 2.2 ± 0.9 U/kg/d). Patients were randomized to liraglutide 1.8 mg/d or matching placebo for 6 months. We measured changes in insulin and glucagon secretion using a 4-hour mixed-meal challenge test. Magnetic resonance-based techniques were used to estimate sc and visceral fat in the abdomen and ectopic fat in the liver and pancreas. Glycosylated hemoglobin improved significantly with liraglutide treatment, with an end-of-trial estimated treatment difference between groups of −0.9% (95% confidence interval, −1.5, −0.4%) (P = .002). Insulin secretion improved in the liraglutide group vs placebo, as measured by the area under the curve of C-peptide (P = .002) and the area under the curves ratio of C-peptide to glucose (P = .003). Insulin sensitivity (Matsuda index) and glucagon secretion did not change significantly between groups. Liver fat and sc fat decreased in the liraglutide group vs placebo (P = .0006 and P = .01, respectively), whereas neither visceral nor pancreatic fat changed significantly. Treatment with liraglutide significantly improved insulin secretion, even in patients with long-standing T2D requiring high-dose insulin treatment. Liraglutide also decreased liver and sc fat, but it did not alter glucagon secretion.

The effect of short-term continuous intravenous insulin infusion on long-term metabolic control in patients with type 2 diabetes

Background and aims. In a large group of obese patients with type 2 diabetes achieving good metabolic control is extremely difficult, despite using all treatment options available in the outpatient setting (i.e. intensive education, intensive high-dose insulin treatment combined with oral antidiabetic agents administration). These patients may be treated with continuous intravenous insulin infusion (CIVII) in hospital as this mode of treatment improves blood glucose level rapidly and is believed to counteract glucose toxicity. However, the long-term effect of this procedure on metabolic control in diabetes is unknown. We conducted the study to assess the effect of short term CIVII on long term glucose control in obese subjects with type 2 diabetes. Material and methods. The experimental group comprised of 36 type 2 diabetes patients treated with insulin [23 women and 13 men, mean age (± SD) 59.9 ± ± 7.7 years, diabetes duration 6.3 ± 3.0 years, body weight 92.9 ± 19.1 kg, BMI 33.5 ± 5.8 kg/m 2 , HbA 1 c 9.7 ± 1.8%]. In all subjects body weight, BMI, waist-to-hip ratio (WHR), blood pressure, fasting plasma triglycerides, total cholesterol, LDL and HDL cholesterol, and HbA1c levels were measured before and 6 months after CIVII. CIVII was applied for at least 72 hours; it consisted of basal insulin infusion and three 90-min insulin boluses per day administered at the meal time. Capillary blood glucose level was measured every 90–120 min throughout the day and night. During the study period the subjects who used oral antidiabetic medication maintained it at stable doses. In the control group of 24 type 2 diabetes patients (mean age 61.3 ± 7.2 years, BMI 32.8 ± 5.1 kg/m 2 , HbA 1c 9.4 ± 1.6%), who were subjects of a standard outpatient care, the same parameters as in the experimental group were examined at baseline and after 6-months. Results. In obese type 2 patients 6 months after CIVII treatment HbA 1c decreased significantly to 8.8 ± 1.6% (p &lt; 0.05); however, no improvement in body weight, WHR, blood pressure or plasma lipid parameters was noted. Shortly after CIVII, daily insulin dose was significantly reduced (from 64.5 ± 24.6 at baseline to 50.7 ± 10.8 IU/day on discharge from the hospital, p &lt; 0.05); yet 6 months later it was similar to the baseline insulin requirement. In the control group no statistically significant changes in analysed parameters were found during the study period. Conclusion. In patients with type 2 diabetes with poor metabolic control CIVII results in significant improvement of long-term glucose control, with no effect on other metabolic parameters.

Low-dose Insulin Treatment Ameliorate Glucose Metabolism in Type 1 Diabetic Rats

Study background: Type 1 diabetes is an insulin-dependent diabetes mellitus (IDDM) because the body does not produce sufficient insulin for daily need. Persistent high glucose level in the blood circulation can stimulate the advanced glycation end products/receptor for AGEs (AGE/RAGE) pathway leading to diabetic complications. Currently, there is no preventive measure for IDMM with only treatment focusing on delaying the onset of diabetic complications. This study aimed to investigate how the different insulin regimens given affect the glycemic control and glucose metabolism in type 1 diabetes. The effects on the AGE/RAGE axis were determined as well. Methods: Twenty-one male Sprague-Dawley rats were randomly assigned into three groups (Group A: streptozotocin-induced diabetic rats given high-dose insulin [5-7U per day], Group B: streptozotocin-induced diabetic rats given low-dose insulin [0-3U per day], Group C: non-diabetic control). Throughout the eight-week treatment, the body weight, systolic blood pressure and non-fasting blood glucose concentration were monitored. After eight weeks of treatment, fasting blood glucose concentration, glycated haemoglobin (HbA1c), nuclear factor kappa B (NF-κB), AGE level and RAGE expression were measured. Results: High-dose insulin treatment impaired glucose metabolism. On the contrary, diabetic rats receiving lowdose insulin showed reduced glucose level and improved insulin sensitivity towards the end of experiment. HbA1c level was significantly lower in low-dose insulin treated rats while NF-κB level was significantly lower in high-dose insulin treated rats (p ≤ 0.05). There was no significant difference in AGE levels in all the groups (p>0.05) and only the heart tissues from the low-dose insulin treated group showed significant down regulation of the RAGE gene expression (p ≤ 0.05). Conclusion: Low-dose insulin treatment was shown to be a better therapeutic intervention for type 1 diabetes.

Myricetin attenuates hyperinsulinemia-induced insulin resistance in skeletal muscle cells

Previous studies have shown that hyperinsulinemia is not only a marker of insulin resistance, but also the causative factor of peripheral tissue insulin resistance. It also has been suggested that prolonged high-dose insulin treatment can mimic the effects of hyperinsulinemia and exacerbate insulin resistance in skeletal muscle cells. However, how to prevent or reverse insulin resistance induced by hyperinsulinemia remains largely unclear. In the past few decades, the use of myricetin as an anti-diabetic agent has gained much attention, but little information is available regarding the effects of myricetin on glucose uptake and hyperinsulinemia-induced insulin resistance in skeletal muscle cells. The present study focuses on the effect of myricetin on insulin signaling in skeletal muscle cell line C2C12 myotubes. Initially, the effect of myricetin under normal condition was determined. We found that myricetin’s enhancement in glucose uptake coincided with both protein kinase B (Akt) and AMP-activated protein kinase (AMPK) activities. After that, the role of hyperinsulinemia was investigated. It was showed that prolonged high-dose insulin treatment inhibited both Akt and AMPK activities. As the results, the low-dose insulin stimulation of glucose uptake was inhibited by hyperinsulinemia. However, the treatment of myricetin improved low-dose insulin-stimulated glucose uptake in the hyperinsulinemic state, and this effect essentially depended on the AMPK signal pathway. Together, our data suggest a putative link between hyperinsulinemia and insulin resistance in C2C12 myotubes, and the myricetin treatment stimulates glucose uptake and attenuates insulin resistance.

Short- and long-term glucocorticoid treatment enhances insulin signalling in human subcutaneous adipose tissue

Background:Endogenous or exogenous glucocorticoid (GC) excess (Cushing's syndrome) is characterized by increased adiposity and insulin resistance. Although GCs cause global insulin resistance in vivo, we have previously shown that GCs are able to augment insulin action in human adipose tissue, contrasting with their action in skeletal muscle. Cushing's syndrome develops following chronic GC exposure and, in addition, is a state of hyperinsulinemia.Objectives:We have therefore compared the impact of short- (24 h) and long-term (7 days) GC administration on insulin signalling in differentiated human adipocytes in the presence of low or high concentrations of insulin.Results:Both short- (24 h) and long-term (7 days) treatment of chub-s7 cells with dexamethasone (Dex) (0.5 μ) increased insulin-stimulated pTyr612IRS1 and pSer473akt/PKB, consistent with insulin sensitization. Chronic high-dose insulin treatment induced insulin resistance in chub-s7 cells. However, treatment with both high-dose insulin and Dex in combination still caused insulin sensitization.Conclusions:In this human subcutaneous adipocyte cell line, prolonged GC exposure, even in the presence of high insulin concentrations, is able to cause insulin sensitization. We suggest that this is an important mechanism driving adipogenesis and contributes to the obese phenotype of patients with Cushing's syndrome.

Cardiovascular and Metabolic Effects of High-dose Insulin in a Porcine Septic Shock Model

High-dose insulin (HDI) has inotropic and vasodilatory properties in various clinical conditions associated with myocardial depression. The authors hypothesized that HDI will improve the myocardial depression produced by severe septic shock and have beneficial effects on metabolic parameters. In an animal model of severe septic shock, this study compared the effects of HDI treatment to normal saline (NS) resuscitation alone. Ten pigs were randomized to an insulin (HDI) or NS group. All were anesthetized and instrumented to monitor cardiovascular function. In both arms, Escherichia coli endotoxin lipopolysaccharide (LPS) and NS infusions were begun. LPS was titrated to 20 mug/kg/hour over 30 minutes and continued for 5 hours, and saline was infused at 20 mL/kg/hour throughout the protocol. Dextrose (50%) was infused to maintain glucose in the 60-150 mg/dL range, and potassium was infused to maintain a level greater than 2.8 mmol/L. At 60 minutes, the HDI group received an insulin infusion titrated from 2 to 10 units/kg/hour over 40 minutes and continued at that rate throughout the protocol. Survival, heart rate (HR), mean arterial pressure (MAP), pulmonary artery and central venous pressure, cardiac output, central venous oxygen saturation (SVO(2)), and lactate were monitored for 5 hours (three pigs each arm) or 7 hours (two pigs each arm) or until death. Cardiac index, systemic vascular resistance (SVR), pulmonary vascular resistance (PVR), O(2) delivery, and O(2) consumption were derived from measured data. Outcomes from the repeated-measures analysis were modeled using a mixed-effects linear model that assumed normally distributed errors and a random effect at the subject level. No significant baseline differences existed between arms at time 0 or 60 minutes. Survival was 100% in the HDI arm and 60% in the NS arm. Cardiovascular variables were significantly better in the HDI arm: cardiac index (p < 0.001), SVR (p < 0.003), and PVR (p < 0.01). The metabolic parameters were also significantly better in the HDI arm: SVO(2) (p < 0.01), O(2) delivery (p < 0.001), and O(2) consumption (p < 0.001). No differences in MAP, HR, or lactate were found. In this animal model of endotoxemic-induced septic shock that results in severe myocardial depression, HDI is associated with improved cardiac function compared to NS resuscitation alone. HDI also demonstrated favorable metabolic, pulmonary, and peripheral vascular effects. Further studies may define a potential role for the use of HDI in the resuscitation of septic shock.

Insulin activates the PI3K-Akt survival pathway in vulnerable neurons following global brain ischemia

Insulin is neuroprotective following transient global brain ischemia; however, the mechanisms by which insulin exerts its salutary effects remain unclear.Objective: We assessed insulin's effect on the PI3K-Akt survival system and consequent modulation of the pro-apoptotic proteins Bim, Bad and FoxO3a.Methods: We utilized rats subjected to 10 minutes of global brain ischemia, with or without insulin administered at the onset of reperfusion.Results: In sham-operated animals, minimal pAkt immunofluorescence was detected in the CA1. Moreover, at 30 minute reperfusion, there was no change in pAkt in CA1 neurons. Single bolus high-dose insulin treatment resulted in an early increase in pAkt after 30 minutes, preservation of CA1 neurons to 14 days of reperfusion and preservation of spatial learning ability. Insulin treatment increased cytoplasmic and nuclear staining for pAkt in both CA1 and cortex. Insulin-induced Akt phosphorylation was suppressed by the PI3K inhibitor wortmannin. Neither reperfusion nor insulin induced any change in the phosphorylation or subcellular localization of FoxO3a, Bim or Bad. A single bolus of high-dose insulin reduced CA1 neuronal cell death and thus represents a potential therapeutic intervention for global brain ischemia.Discussion: These results reveal that proximal elements of a known cell-survival pathway are triggered by high-dose insulin during early reperfusion. Insulin induces robust PI3K-dependent phosphorylation of Akt by 30 minute reperfusion and results in improvement of hippocampal structure and function. However, the Akt substrates FoxO3a, Bim and Bad do not undergo corresponding changes in phosphorylation or subcellular localization in this model of global brain ischemia. The downstream components of insulin-induced Akt survival signaling after transient global brain ischemia remain to be identified.

Anti‐inflammatory effect of high‐dose insulin treatment after urgent coronary revascularization surgery

The administration of insulin has been shown to exert cardioprotective and immunomodulatory properties. Ischemia and inflammation are typical features of acute coronary syndrome, thus it was hypothesized that high-dose glucose-insulin-potassium (GIK) treatment could suppress the systemic inflammatory reaction and attenuate myocardial ischemia-reperfusion injury in patients with unstable angina pectoris after urgent coronary artery bypass surgery. Forty patients with unstable angina pectoris scheduled for urgent coronary artery bypass surgery and cardiopulmonary bypass were randomly assigned to receive either high-dose insulin treatment (short-acting insulin 1 IU/kg/h with 30% glucose 1.5 ml/kg/h administered separately) or control treatment (saline). Blood glucose levels were targeted to 6.0-8.0 mmol/l in both groups by adjusting the rate of glucose infusion in the GIK group and by additional insulin in the control group as needed. High-dose insulin treatment was associated with significantly lower average C-reactive protein (23.8 vs. 40.1 mg/l, P= 0.008) and free fatty acid levels (0.22 vs. 0.41 mmol/l, P= < 0.001) post-operatively. Average blood glucose levels were comparable during the intensive care unit (ICU) stay (7.1 vs. 6.9 mmol/l, P= 0.5) and 95% of the control patients received supplemental insulin. The pro-inflammatory cytokine response [interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-alpha)] did not differ between the groups and beneficial effects on myocardial injury were not detected. High-dose insulin treatment has potential anti-inflammatory properties independent of its ability to lower blood glucose levels. Even profound suppression of free fatty acid levels, the attenuation of myocardial ischemia-reperfusion injury was not detected.

Cerebral ischemia-induced apoptosis and necrosis in normal and diabetic rats: Effects of insulin and C-peptide

Neuronal apoptosis has been demonstrated to be a significant factor in neurological deficiencies associated with diabetes, and these deficiencies are exaggerated following ischemia. Diabetic rats have an increased basal level of apoptosis compared to non-diabetics and it has been previously demonstrated that infarct volumes were greater in diabetic animals following middle cerebral artery occlusion (MCAO) when compared to non-diabetics. In this study, we evaluated both the acute and chronic effects of insulin and/or C-peptide on CNS necrosis and apoptosis in non-diabetic and streptozotocin-induced diabetic rats following MCAO with reperfusion. Two brain areas, the sensori-motor cortex (layers-5 and 6) and the CA1 and CA3 sectors (pyramidal cell layers) of the hippocampus, were analyzed for apoptosis using TUNEL and Caspase-3 immunoreactivity. The chronic administration of a low maintenance concentration of insulin (2 U/kg), or the acute administration of insulin (2 U/kg) with or without C-peptide, did not alter the lesion volume or basal levels of apoptosis or the apoptotic levels in animals subjected to 2-h MCAO followed by 24-h reperfusion. However, both the acute or chronic administration of a high concentration of insulin (12 U/kg) significantly decreased lesion volume and apoptosis subsequent to 2-h MCAO followed by 24-h reperfusion. High dose insulin treatment also decreased the basal level of apoptosis. We conclude that in diabetic rats subjected to ischemia and reperfusion chronic insulin treatment decreased the basal apoptotic level, and both acute and chronic insulin decreased the MCAO-induced lesion volume and apoptosis. Maintenance insulin concentrations with or without C-peptide were without effect.

Metabolic and Hemodynamic Effects of High-Dose Insulin Treatment in Aortic Valve and Coronary Surgery

Glucose and insulin have been used as an adjuvant therapy in cardiac surgery because of their potentially beneficial effects on myocardial metabolism and contractile function. This study evaluated the effects of high-dose insulin on systemic metabolism and hemodynamics after combined heart surgery. Forty elective patients scheduled for combined aortic valve replacement and coronary artery bypass surgery were randomly assigned to receive either high-dose insulin treatment (short-acting insulin 1 IU.kg(-1).h(-1) with 30% glucose 1.5 mL.kg(-1).h(-1) administered separately) or control treatment (saline). The blood glucose levels were maintained within a targeted range by adjusting the rate of glucose infusion in the treatment group and by short-acting insulin bolus doses in the control group. The lactate clearance was faster (p = 0.046), and the lactate levels (p = 0.016), blood glucose levels (p < 0.001), and free fatty acid levels (p < 0.001) were lower in the insulin group postoperatively. Besides, there was lesser need for dobutamine support (p = 0.013) and a trend toward better cardiac indices. Insulin treatment increased the respiratory quotient (p < 0.001), but there were no differences between the groups with regard to systemic oxygen consumption or energy expenditure measured by indirect calorimetry. The average glucose uptake in the insulin group was 7.1 g/kg in 24 hours (28 kcal.kg(-1).day(-1)). The high-dose insulin treatment was associated with lower blood glucose levels, better preserved myocardial contractile function, and less need for inotropic support, and hence led to lower lactate levels postoperatively. The protocol is safe, but requires strict control of blood glucose level.

Changes in aortic endothelial gene expressions and relaxation responses following chronic short-term insulin treatment in diabetic rats

The purpose of the present study was to examine the relationship between the changes in the expressions of several mRNAs and changes in endothelial function in streptozotocin-induced diabetic and chronic short-term insulin-treated rats. Aortas from later-stage (10 week) diabetics, but not those from their insulin-treated counterparts, showed an impaired endothelial function. We found that the mRNA expressions for 30 genes were significantly upregulated, while those for 13 other genes were downregulated in aortic endothelial cells from diabetis. In later-stage diabetes, chronic insulin treatment ameliorated the endothelial dysfunction and normalized the expressions for 20 out of the 43 genes altered in diabetes. Further, 12 of the remaining 23 genes were altered by high-dose insulin treatment in the controls. In early-stage (1 week) diabetic aortas, which did not show impaired endothelial function, expression changes were shown by only 12/30 and 5/13 of the genes up- or downregulated, respectively, in later-stage diabetes. Thus, in the diabetic aortasndothelial gene expressions and function exhibited time-related changes, and several gene expressions and endothelial function were normalized by insulin treatment. The hyperinsulinemia caused by this treatment may oppose the alterations in some gene expressions and the endothelial proliferation (cell growth-related gene expressions) that occur in established diabetes.

Failure of high-dose insulin treatment to increase β-cell insulin content in diabetic non obese diabetic (NOD) mice

High-dose insulin treatment in the first period after clinical onset of insulin-dependent diabetes mellitus (IDDM) has been found to reduce diabetic manifestations in humans. The aim of the present study was to examine whether high-dose insulin treatment of newly diagnosed diabetic non obese diabetic (NOD) mice would increase β-cell insulin content after termination of treatment in this experimental IDDM animal model. Newly diagnosed diabetic female NOD mice were randomized into three groups composed of a low-dose insulin treated group ( n=10) injected subcutaneously with 15 IU/kg per day of NPH for 14 days followed by 5 days without insulin, a high-dose insulin treated group ( n=8) injected subcutaneously with 150 IU/kg per day of Actrapid for 14 days followed by 5 days without insulin and an untreated group sacrificed 3 days after diagnosis ( n=11). A reference group of age matched non-diabetic untreated female NOD mice ( n=11) was included in the study and sacrificed at the same time as the untreated diabetic mice. No significant difference in the amount of insulin extracted from the total pancreas was found by comparison of the three diabetic groups, consisting of the newly diagnosed untreated mice, the low-dose insulin treated mice and the high-dose insulin treated mice, respectively. The level was about 100-fold less than in the non-diabetic group. Blood glucose values in the two treated diabetic groups were at a high level (median>18 mM) throughout the study. We conclude that no increase in β-cell insulin content could be demonstrated in newly diagnosed diabetic NOD mice after early high-dose insulin treatment, at least not in the presence of high blood glucose values.

Hyperglycaemia is responsible for the inhibited gastrointestinal transit in the early diabetic rat.

The effect of plasma glucose levels on the gastrointestinal motility of the rat was studied. Chronic hyperglycaemia was induced by i.v. injection of streptozotocin 1 week before the motility experiment. Some rats received additional daily insulin therapy (1.25, 2.5 or 10 IU kg-1) after induction of diabetes mellitus. Acute hyperglycaemia was induced by the continuous i.v. infusion of glucose solution (11, 22, 44 or 88 mg kg-1 min-1) 10 min before the motility experiments. The rats were killed 15 min after successful orogastric feeding of a charcoal-contained suspension. Gastrointestinal transit was calculated as the percentage of the overall length of the small intestine to which the charcoal moved during this time period. The diabetic rats were found to have delayed transit compared with controls (mean +/- SEM: 32.2 +/- 2.1% vs. 42.9 +/- 4.2%, P < 0.05). Correction of hyperglycaemia with moderate doses of insulin therapy failed to inhibit transit, whereas hypoglycaemia induced by high-dose insulin treatment enhanced transit. High doses of glucose elicited acute hyperglycaemia and delayed transit when compared with saline infused non-diabetic rats. In early diabetes, hyperglycaemia probably mediates the inhibited gastrointestinal transit, since correction of hyperglycaemia usually restores the delayed transit.

Glucagon Binding and Adenylate Cyclase Activity in Liver Membranes from Untreated and Insulin-Treated Diabetic Rats

To investigate the role of hepatic glucagon receptors in the hypersensitivity to glucagon observed in insulin-deprived diabetics, liver plasma membranes were prepared from control rats and from streptozotocin-induced diabetic rats some of whom were treated with high-dose and low-dose insulin. The untreated diabetic animals exhibited hyperglycemia, weight loss, hypoinsulinemia, and hyperglucagonemia. High-dose insulin treatment (2 U Protamine-zinc-insulin/100 g per day) resulted in normoglycemia, normal weight gain, mild hyperinsulinemia, and return of glucagon levels toward base line. The low-dose (1 U protamine-zinc-insulin/100 g per day) insulin-treated diabetic group demonstrated chemical changes intermediate between the untreated and the high-dose insulin-treated animals. In liver plasma membranes from the untreated diabetic rats, specific binding of (125)I-glucagon was increased by 95%. Analysis of binding data suggested that the changes in glucagon binding were a consequence of alterations in binding capacity rather than changes in binding affinity. Furthermore, in the untreated diabetic rats, both basal and glucagon (2 muM)-stimulated adenylate cyclase activity were twofold higher than in controls. In the high-dose insulin-treated diabetic rats, glucagon binding and basal and glucagon-stimulated adenylate cyclase activity were normalized to control values, whereas low-dose insulin treatment resulted in changes intermediate between control and untreated diabetic rats. In contrast to glucagon-stimulated adenylate cyclase activity, fluoride-stimulated adenylate cyclase activity was similar in all groups of rats. Liver plasma membranes from untreated and insulin-treated diabetic animals degraded (125)I-glucagon to the same extent as control rats. The specific binding of (125)I-insulin in the untreated diabetic animals was 40% higher than in control rats. In low-dose insulin-treated diabetic rats, insulin binding was not significantly different from that of control rats, whereas in the high-dose insulin-treated group in whom plasma insulin was 70% above control levels, insulin binding was 30% lower than in control rats. These findings suggest that alterations in glucagon receptors may contribute to the augmented glycemic and ketonemic response to glucagon observed in insulin-deprived diabetics.