Non-diabetic State Research Articles

Alterations in Insulin-Signaling and Coagulation Pathways in Platelets During Hyperglycemia-Hyperinsulinemia

AbstractAbstract 633Type 2 diabetes mellitus (T2DM) patients have increased incidence of acute vascular events, due in part to a prothrombotic/proinflammatory state with elevated plasma coagulation factors and enhanced platelet responsiveness. The hallmarks of T2DM, hyperglycemia (HG) and hyperinsulinemia (HI), are independent risk factors for mortality but their contributions to the prothrombotic mechanisms are unclear. Our prior studies in healthy non-diabetic subjects using infusion clamps showed that selective HI and HG, and more so the combination of HI+HG, increased circulating membrane-bound tissue factor-procoagulant activity (TF-PCA), plasma coagulation factor (F) VIII, and markers of thrombin generation. In addition, HI+HG induced platelet and monocyte activation and upregulated monocyte TF. In T2DM and type 1 DM patients, TF-PCA and FVII were elevated under basal conditions. To understand mechanisms underlying these prothrombotic changes in platelets and monocytes, we performed expression profiling of leukocyte-depleted platelets and monocytes before and after 24 h of HG+HI clamping in a healthy non-diabetic subject using U133 Plus 2.0 GeneChips (Affymetrix, Santa Clara, CA). Glucose was maintained ∼200 mg/dl by glucose infusion, which elevates endogenous insulin levels to induce HI. Profiling data was analyzed in Genomics Suite™ (Partek Inc.) to detect differentially expressed mRNAs. We generated a list of time-dependent differential mRNA expression (24 h fold change ≥2) common to both platelets and monocytes. Identification of biological pathways in which these genes may be critical players was determined in Ingenuity Pathways Analysis software. In particular, the insulin receptor signaling and coagulation canonical pathways were highly altered for both platelets and monocytes. A preliminary group of up or downregulated genes was selected from these for qRT-PCR confirmation (Table). For additional validity, the 24 h platelet sample was compared to the 0 h sample and 4 normal controls. Notably, 8 out of the 9 selected transcripts were confirmed in platelets and/or monocytes (Table, asterisks). In platelets, these include ↑GSK3B, ↓STXBP4 (Synip), ↑PTPN11 (platelet phosphatase SHP2) in insulin signaling, and ↑F3 (tissue-factor) and ↑TFPI on the coagulation side. In monocytes, there was downregulation of STXBP4, PIK3C3, PTPN11 and TFPI. The upregulation of platelet TF is a potentially important finding and is associated with possible compensatory up-regulation of TFPI, the principal TF inhibitor present in platelets and megakaryocytes, and GSK3B, a negative regulator of TF synthesis. To confirm this, we studied TF protein from the same subject. In isolated platelets and monocytes TF antigen (ELISA) increased 2-fold (8 to 16 pg/mg protein) and 5-fold (0.6 to 2.9 pg/mg), respectively. In addition, TF-PCA in whole blood increased (7.9 to 69.7 u/mL) over 24 h. Because of limited protein available, we were only able to immunoblot for GSKb3 (↑∼34%) and PTPN11 (↑∼42%). Taken together, these studies support the hypothesis that HG+HI, even in the non-diabetic state, induces demonstrable changes in platelets including alterations in insulin-signaling and coagulation pathways. Further studies in healthy subjects and DM patients will validate and better define these alterations and their cumulative prothrombotic effects.Table 1Expression Profile and qRT-PCR Fold Changes for Selected Insulin Receptor Signaling and Coagulation TranscriptsGene SymbolGene TitlePlateletsMonocytesFold Change Expression (24 vs. 0 hrs)Fold Change qRT-PCR (24hrs vs. 0 hours and 4) NormalsFold Change Expression (24 vs. 0 hrs)Fold Change qRT-PCR (24 vs. 0 hrs)IRS1Insulin receptor substrate 10.142.451 (2.27, 2.64)0.730.88 (0.72, 1.08)INSRInsulin receptor0.231.00 (0.83, 1.21)0.890.88* (0.86, 0.91)GSK3BGlycogen synthase kinase 3 beta5.511.62* (1.52, 1.74)1.050.87 (0.83, 0.91)F3Tissue factor3.747.08* (1.08, 46.32)0.401.12 (1.01, 1.23)TFPITissue factor pathway inhibitor4.481.30* (1.26, 1.35)0.790.66* (0.56, 0.79)VAMP2Vesicle-associated membrane protein 214.290.82 (0.75, 0.89)0.860.85* (0.83, 0.86)STXBP4Syntaxin binding protein 40.130.87* (0.87, 0.88)0.970.91* (0.83, 0.99)PIK3C3Phosphoinositide-3-kinase class 30.311.37 (1.31, 1.44)0.160.81* (0.75, 0.87)PTPN11Protein tyrosine phosphatase, non-receptor type II13.001.97* (1.56, 2.49)0.600.65* (0.65, 0.65) Disclosures:No relevant conflicts of interest to declare.

The Artificial Pancreas

The discovery of insulin was lifesaving. However, it converted type 1 diabetes, which had been an acute and lethal disease, into a chronic disease, with its attendant complications. It had long been considered—and was clearly demonstrated in the Diabetes Control and Complications Trial (1)—that microvascular complications such as retinopathy, nephropathy, and neuropathy (as well as micro- and macrovascular legacy effects) were improved with intensive glucose control—that is, when circulating glucose levels were closer to those seen in the nondiabetic state. This entailed increased involvement on the part of a person with diabetes in their management: glucose monitoring, frequent insulin injections, or continuous subcutaneous insulin infusion (CSII). It also increased the risk of hypoglycemia. The mitigation of this trade-off, as well as controlling “brittle” diabetes, improving the quality of life of the person with diabetes, and the availability of the necessary technology, has motivated the evolution of self-managed intensive control into automated control. Indeed, the artificial pancreas has been a major goal of research in type 1 diabetes since exogenous insulin became available. Articles on the automated control of glycemia in the absence of endogenous insulin (2,3) were published on (almost) the 50th anniversary of the discovery of insulin. This early version of the artificial pancreas depended on very frequent, automated measurements of blood glucose and an intravenous delivery of insulin. It was also bulky. Nevertheless, over the short term, it could maintain near normoglycemia. Initial versions operated using versions of a proportional (P) controller (4):![Graphic][1] where uP is the insulin infusion rate, g(t) the blood glucose concentration, gtarget the target concentration, and K 1 the proportionality constant. Subsequent versions incorporated derivative (D) control:![Graphic][2] Essentially, this allows improved projections of glucose values into the future and thus better control of these future values. Albisser et al. … [1]: /embed/inline-graphic-1.gif [2]: /embed/inline-graphic-2.gif

Abstract P282: Increased Nuclear Localization of Fyn May Limit the Cardioprotective Effects of Hydrogen Sulfide by Interfering with Nrf2 Signaling

Background: Hydrogen sulfide (H2S) therapy reduces myocardial infarct size by up to 56% in non-diabetic mice. Here, we sought to examine if H2S could provide cardioprotection in the setting of diabetes. Methods and Results: Diabetic mice (db/db) were subjected to 30 min of left coronary artery occlusion (LCA) followed by reperfusion for 24 hours at which time the extent of myocardial infarction was evaluated. Sodium sulfide (Na2S, 100 μ g/kg) administered at the time of reperfusion decreased infarct size relative the area-at-risk by 18% compared to vehicle treated animals (p<0.001). Previously, Na2S has been shown to increase the nuclear localization of Nrf-2 and upregulates its downstream target, heme oxygenase (HO)-1, in non-diabetic mice. To investigate if this cascade contributed to the observed cardioprotection, Na2S was administered (tail vein) to non-diabetic and diabetic mice and heart tissue was excised 1 hr and 24 hrs later. One hr following the administration of Na2S, the nuclear expression of Nrf2 was increased in both groups. In contrast, Na2S only increased the expression of HO-1 (24 hrs) in the non-diabetic heart. Further studies investigating Fyn, a tyrosine kinase known to inhibit Nrf2 signaling, revealed an upregulation of nuclear Fyn expression in the diabetic heart compared to the non-diabetic heart. Conclusion: This data demonstrates the complexity of therapeutic intervention for diabetics following myocardial ischemia, as the robust cardioprotective effects of H2S in the non-diabetic state were found to be diminished in the diabetic state. This data also suggests that interference of Nrf2 signaling by Fyn may be responsible for the loss of protection.

VLED and formula LED in the management of type 2 diabetes: defining the clinical need and research requirements.

It has been known for many years that substantial weight loss, achieved by bariatric surgery or non-surgical means can mean normalize glucose tolerance. Recent randomized controlled trial evidence indicates that >15 kg weight loss is necessary, to this and it may lead to near normalization (doubling) of life expectancy. Less than 5% of patients achieve this through even the best, evidence-based medical weight management programme (Counterweight http://www.counterweight.org). A weight loss of >15 kg is easily achievable by 8 weeks very low-energy diet (VLED)/LELD (Low energy Liquid-formula Diet) in compliant patients, with little difference between 400 and 800 kcal day(-1) , but weight maintenance after VLED has until recently been so poor that VLED is not, at present, recommended in clinical guidelines. However, mean weight loss close to >15 kg can be maintained 18-24 months using a variety of maintenance strategies. These include a structured reintroduction of foods linked to an education programme with behavioural strategies, intermittent VLED use and prescribable anti-obesity drugs (dexfenfluramine, orlistat, sibutramine). Most of these studies have been in non-diabetic subjects. A new 'curative' paradigm in type 2 diabetes mellitus management, aiming to normalize glucose tolerance and health risks by achieving and maintaining >15 kg loss, as soon as possible after diagnosis, should be highly acceptable to patients, generating many additional Quality Adjusted Life Years (QALYs). It is likely to be highly cost-effective by avoiding the current recommended, mainly palliative, model, using polypharmacy which provides an overall risk reduction of only 5-10%. Clinical trials are on-going to establish the feasibility of delivering formula (LELD) and a maintenance programme to large numbers of patients within routine primary care. There is urgent need, to run similar studies in diabetic patients. New approaches to long-term (lifelong) maintenance of weight loss and a non-diabetic state may include anti-obesity drugs.

Assessing the association of the HNF1A G319S variant with C-reactive protein in Aboriginal Canadians: a population-based epidemiological study

BackgroundC-reactive protein (CRP), a biomarker of inflammation, has been associated with increased risk of developing cardiovascular disease. Common variants of the hepatocyte nuclear factor 1A (HNF1A) gene encoding HNF-1α have been associated with plasma CRP in predominantly European Caucasian samples. HNF1A might therefore have an impact on vascular disease and diabetes risk that is mediated by CRP. In an Aboriginal Canadian population, a private polymorphism, HNF1A G319S, was associated with increased prevalence of type 2 diabetes. However, it has not been investigated whether this association is mediated by CRP. We aimed to investigate whether CRP was mediating the association between HNF1A G319S and type 2 diabetes in an Aboriginal Canadian population with a high prevalence of diabetes.MethodsA total of 718 individuals who participated in a diabetes prevalence and risk factor survey were included in the current analysis. Participants were genotyped for HNF1A G319S. Fasting plasma samples were analyzed for CRP. Fasting plasma glucose and a 75-g oral glucose tolerance test were obtained to determine type 2 diabetes.ResultsThe prevalence rate of type 2 diabetes was 17.4% (125/718) using the 1999 World Health Organization definition and was higher among S319 allele carriers compared to G/G homozygotes (p < 0.0001). Among participants without type 2 diabetes, CRP levels were higher among G/G homozygotes (1.64 [95% confidence interval 1.35-2.00] mg/l) than in S319 carriers (1.26 [1.04-1.54] mg/l) (p = 0.009) after adjustment for age, sex, 2-h post-load glucose, waist circumference, and serum amyloid A. CRP levels were elevated among those with diabetes after similar adjustment (4.39 [95% confidence interval 3.09-6.23] and 4.44 [3.13-6.30] mg/L, respectively), and no significant difference in CRP was observed between S319 carriers and non-carriers (p = 0.95).ConclusionsCRP levels were lower in S319 allele carriers of the HNF1A gene compared to non-carriers among individuals without diabetes, but this difference was not present among those with diabetes, who uniformly had elevated CRP levels. Therefore, while HNF1A appears to influence CRP concentrations in the non-diabetic state, chronic elevation of CRP is unlikely mediating the association between the HNF1A polymorphism and the high prevalence of type 2 diabetes in this Aboriginal population.

Insulin treatment prevents diabetes-induced alterations in astrocyte glutamate uptake and GFAP content in rats at 4 and 8 weeks of diabetes duration

Rat astrocyte function is changed by diabetes mellitus relative to the nondiabetic state and we believe that altered function contributes to the central nervous system symptoms manifested by individuals with diabetes. We report here a comparison of astrocyte glutamate uptake and GFAP expression in streptozotocin-induced type 1 diabetic rats and insulin-treated diabetic rats at 4 and 8 weeks following diabetes onset. In glial plasmalemmal vesicle (GPV) preparations from treated rats, insulin prevented the increase observed in untreated, diabetic rats of both sodium-dependent and sodium-independent glutamate uptake. We determined by immunoblotting and immunohistochemistry that insulin treatment prevented the decrease of GFAP expression detected in the cerebral cortex, hippocampus, and cerebellum of untreated, diabetic rats. These observations indicate that insulin effects on astrocyte function are significant in managing diabetes-induced central nervous system pathology.

RAGE: a novel biological and genetic marker for vascular disease

RAGE [receptor for AGEs (advanced glycation end-products)] plays an important role in the development and progression of vascular disease. Studies in cultured cells and small animal models of disease have clearly demonstrated that RAGE is central to the pathogenesis of vascular disease of the macro- and micro-vessels in both the diabetic and non-diabetic state. Emerging results from human clinical studies have revealed that levels of circulating soluble RAGE in the plasma may reflect the presence and/or extent of vascular disease state. Additionally, genetic variants of the RAGE gene (AGER in HUGO nomenclature) have been associated with vascular disease risk. Combining RAGE circulating protein levels and the presence of particular RAGE polymorphisms may be a useful clinical tool for the prediction of individuals at risk for vascular disease. Therapeutic intervention targeted at the RAGE gene may therefore be a useful means of treating pathologies of the vasculature.

The Parodox of Glycemic Control and Cardiovascular Complications: Sorting Out the Data

The results of three recent trials, the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial, the Action in Diabetes and Vascular Disease (ADVANCE) trial, and the Veterans Affairs Diabetes Trial (VADT), indicate that lower blood glucose levels are not always better. The major aim of all three randomized controlled trials was to determine whether lowering the blood glucose (hemoglobin A [A1C]) to normal or near-normal would 1c reduce the occurrence of cardiovascular events. In the ACCORD trial, unexpected deaths in the intensive therapy (IT) group, over and above the number of deaths in the conventional therapy (CT) group, resulted in the early discontinuation of the trial.1 There were no findings of increased mortality related to IT in the ADVANCE trial; however, preliminary analyses have found no reduction in rates of macrovascular events in the IT group.2 The VADT also found no difference in macrovascular event rates between IT and CT groups.3 Taken together, data from all three of these trials suggest there is no benefit of aggressive glycemic control on macrovascular complications in diabetic patients. These outcomes leave many of us questioning what we thought we knew. Glycemic control as close to the normal range as possible purportedly simulates the nondiabetic state. It is well established that tight glycemic control reduces rates of microvascular complications in diabetic patients; why wouldn't the same hold true for macrovascular events and cardiovascular mortality? A closer look at these important clinical trials may clarify some points but may also leave us with further questions. All three trials shared the aim of determining the relationship between glycemic control and macrovascular events (myocardial infarction and stroke); however, the study designs, populations, and outcomes were somewhat different. ACCORD randomized 10,251 patients with type 2 diabetes (mean age 62 years) and a baseline median …

Metabolic Syndrome - Risk Factors for Atherosclerosis and Diabetes

To evaluate the lipoprotein profiles, triglycerides and glycemia along with the abdominal fat to explore the risk factors associated with non-diabetic state to IGF, IGT and Type-2 diabetes in Canadian population. We examined 780 subjects using the ADA and WHO criteria to classify them into groups based on (1) normal glucose tolerance with FBS <6.0 and 2hBS <7.0 mmol/l), (2) IFG; FPG > or =6.1 mmol/l but 2hBS >7.8-11.1 mmol/l; (3) combined IFG/IGT (FPG > or =7.0 mmol/l and 2hBS >11.1 mmol/l). We compared the three groups for glycemia, insulin secretion and insulin sensitivity based on their WHR, abdominal and visceral fat measurements. The subjects with higher 2 hrs glucose levels 5.2 for NGT vs. 9.1 for IGT and 13.4 mmol/l for NIDDM, p<0.001, apo C-III level (12.8 (DM) vs. 8.9 mg/dl (normal), p<0.001), waist to hip ratio (0.91 (IGT) vs. 0.89 (Normal), p<0.01) and abdominal fat and were found to be highly insulin resistant. The higher apolipoproteins levels, BMI and abdominal and visceral fat accompanied by poor glycemia were shown to be associated strongly with the metabolic abnormalities. These factors led to the worsening of insulin secretory dysfunction and insulin resistance and were strong predictors of diabetes.

Antihypertensive effect of total flavones extracted from seed residues of Hippophae rhamnoides L. in sucrose-fed rats

The study was designed to investigate the antihypertensive effect of total flavones extracted from seed residues of Hippophae rhamnoides L. (TFH-SR) and its underlying mechanism in chronic sucrose-fed rats by evaluating its ability to regulate insulin and angiotensin ∥ levels. Feeding of high-sucrose diet (HS: 77% of kcal from carbohydrate, 16% from protein and 6% from lipid, respectively) for 6 weeks resulted in significant rise in systolic blood pressure (SBP) by 25.60%, plasma insulin by 114.24%, triglycerides by 85.14% and activated angiotensin ∥ contents in heart and kidney. However, TFH-SR treatment significantly suppressed the elevated hypertension, hyperinsulinemia and dyslipidemia. Furthermore, TFH-SR (especially at the dose of 150 mg/kg/day) increased the circulatory blood angiotensin ∥ level as effective as angiotensin ∥ receptor blocker. These results indicated that TFH-SR exerted its antihypertensive effects at least in part by improving insulin sensitivity and blocking angiotensin ∥ signal pathway. Findings of the present study suggested that TFH-SR might prove to be of potential use in the management of hyperinsulinemia in non-diabetic state with cardiovascular diseases.

Plasma visfatin levels are positively associated with circulating interleukin-6 in apparently healthy Korean women

Even though visfatin has been suggested as a proinflammatory adipokine, there are few studies of the relationship between plasma visfatin concentrations and proinflammatory markers in the nondiabetic population. We showed that plasma visfatin concentrations were positively associated with circulating interleukin-6 levels and diastolic blood pressure independent of obesity in nondiabetic healthy Korean women. These results suggest that circulating visfatin may be related with some proinflammatory condition even in a nondiabetic state.

Serum leptin and its relation to anthropometric measures of obesity in pre-diabetic Saudis

BackgroundLittle information is available on leptin concentrations in individuals with IGT. This study aims to determine and correlate leptin levels to anthropometric measures of obesity in pre-diabetic, (IFG and IGT), type 2 diabetic and normoglycaemic Saudis.Methods308 adult Saudis (healthy controls n = 80; pre-diabetes n = 86; Type 2 diabetes n = 142) participated. Anthropometric parameters were measured and fasting blood samples taken. Serum insulin was analysed, using a solid phase enzyme amplified sensitivity immunoassay and also leptin concentrations, using radio-immunoassay. The remaining blood parameters were determined using standard laboratory procedures.ResultsLeptin levels of diabetic and pre-diabetic men were higher than in normoglycaemic men (12.4 [3.2–72] vs 3.9 [0.8–20.0] ng/mL, (median [interquartile range], p = 0.0001). In females, leptin levels were significantly higher in pre-diabetic subjects (14.09 [2.8–44.4] ng/mL) than in normoglycaemic subjects (10.2 [0.25–34.8] ng/mL) (p = 0.046). After adjustment for BMI and gender, hip circumference was associated with log leptin (p = 0.006 with R2 = 0.086) among all subjects.ConclusionLeptin is associated with measures of adiposity, hip circumference in particular, in the non-diabetic state among Saudi subjects. The higher leptin level among diabetics and pre-diabetics is not related to differences in anthropometric measures of obesity.

Cost effectiveness of rimonabant use in patients at increased cardiometabolic risk: estimates from a Markov model

SummaryRimonabant, the first selective CB-1 receptor blocker, is expected to reduce cardiometabolic risk substantially. This study assesses the economics of such treatment in patients at elevated cardiometabolic risk.A Markov model was developed using data from the Rimonabant in Obesity (RIO) trial, published risk equations, and UK cost and utility data. Patients begin either in a diabetic or a non-diabetic state and can transition to cardiovascular disease or to death (based on UK life tables). Transitions to diabetes and subsequent cardiovascular events are also counted. Resource use due to events and long-term management were translated to UK costs (2005 GBP). Tariffs for events and states were applied to age-dependent utilities. Extensive univariate and multivariate probabilistic sensitivity analyses were carried out.Over 10 years, 8% will suffer a cardiovascular event with a loss of more than 1,000 quality-adjusted life years (QALYs) and a cost of more than £500,000 per 1,000 patients. Projecting risk for a lifetime, 1 year of rimonabant use is estimated to gain >65 QALYs at £8,574/QALY. In probabilistic sensitivity analysis, incremental cost-effectiveness ratios varied from £2,657 to £22,141/QALY.Based on the metabolic effects seen in clinical trials, rimonabant should reduce cardiovascular risk in obese or overweight people at reasonable cost.

Contribution of postprandial glucose to chronic hyperglycaemia: from the “glucose triad” to the trilogy of “sevens”

Even though fasting and postprandial glucose are both contributors to the overall hyperglycaemia as observed in patients with type 2 diabetes, their respective contributions are varying with the degree of diabetic control. The contribution of postprandial glucose is predominant in patients with satisfactory control of diabetes (HbAlc < 7.3%) whereas the contribution of fasting glucose increases progressively with worsening diabetes. As a consequence an overall picture of the diabetic control should normally be based on the assessment of the "glucose triad" with its three components: HbAlc which integrates the diabetic control over a 3-month period, fasting and postprandial glucose. The two later are good indicators of the glycaemic regulation over the two main physiological periods of daytime: the fasting and postprandial states. Postprandial glucose concentrations should be more particularly tested at mid-morning time since in most patients this period corresponds to the highest glucose concentrations of daytime. However postprandial measurements at 2-h after lunch provide an evaluation of the overall diabetic control since we have demonstrated that glucose concentrations < 7 mmol/L at this time point are excellent predictors of HbAlc levels < 7% (specificity 2 90%). Therefore, in order to simplify the work of health care providers the "glucose triad" concept can be translated into the trilogy of "sevens": HbA1c goals < 7% and postprandial glucose targets < 7 mmol/L 2-h after lunch, both for assessing a satisfactory diabetic control, and fasting glucose < 7 mmol/L for defining the non-diabetic state.

Differential influence of increased polyol pathway on protein kinase C expressions between endoneurial and epineurial tissues in diabetic mice.

To explore the relationship between polyol pathway and protein kinase C (PKC), we examined PKC activities and expressions of PKC isoforms separately in endoneurial and vessel-rich epineurial tissues in diabetic mice transgenic for human aldose reductase (Tg). Tg and littermate control mice (Lm) were made diabetic by streptozotocin at 8 weeks of age and treated orally with aldose reductase inhibitor (ARI) (fidarestat 3-5 mg/kg/day) or placebo for 12 weeks. At the end, compared with non-diabetic state, sorbitol contents were increased 6.4-fold in endoneurium and 5.1-fold in epineurium in diabetic Tg, whereas the increase was detected only in endoneurium in diabetic Lm. Endoneurial PKC activity was significantly reduced in diabetic Tg. By contrast, epineurial PKC activity was increased in both diabetic Lm and diabetic Tg and there was no significant difference between the two groups. These changes were all corrected by ARI treatment. Consistent with the changes of PKC activities, diabetic Tg showed decreased expression of PKC alpha in endoneurium, whereas there was an increased expression of PKC beta II in epineurium in both diabetic Tg and diabetic Lm. These findings suggest the presence of dichotomous metabolic pathway between neural and vascular tissues in the polyol-PKC-related pathogenesis of diabetic neuropathy.

Apoptosis of autoreactive CD8 lymphocytes as a potential mechanism for the abrogation of type 1 diabetes by islet-specific TNF-alpha expression at a time when the autoimmune process is already ongoing.

The role of TNF-alpha in type 1 diabetes pathogenesis is controversial. Using double transgenic mice expressing (i) the glycoprotein (GP) of lymphocytic choriomeningitis virus (LCMV) as an islet self-antigen and (ii) TNF-alpha under control of a tetracycline-regulated promotor system (tTA) in the pancreatic beta cells, we could previously demonstrate a differential effect of TNF-alpha on the incidence of type 1 diabetes. Most interestingly, late expression of TNF-alpha resulted in a reversion of mice that were already diabetic to a nondiabetic state. Here we provide a model of how experienced autoaggressive CD8 lymphocytes are dying by apoptosis as a result of beta cell-specific TNF-alpha expression at a time when the autoimmune process is already ongoing.

The insulinotropic effect of acute exendin-4 administered to humans: comparison of nondiabetic state to type 2 diabetes.

Exendin-4 is a potent and long-acting agonist of the glucagon-like peptide-1 (GLP-1) receptor. GLP-1 is an insulinotropic gut peptide and is being evaluated for the regulation of plasma glucose in type 2 diabetes. The purpose of the present study was to ascertain whether exendin-4 is insulinotropic and whether it has long-lived biological effects in nondiabetic and type 2 diabetic subjects. Because incretins are glucose dependent with respect to their insulin-releasing capacity, we used the hyperglycemic glucose clamp technique to begin to address these issues in two separate protocols. In one protocol, we infused exendin-4 (0.15 pmol x kg(-1) x min(-1)) in seven nondiabetic and seven type 2 diabetic subjects during the second hour of a 5-h hyperglycemic clamp in which fasting plasma glucose was raised by 5.4 mmol/liter. The second protocol was identical to the first except that plasma glucose was allowed to fall to the fasting levels during the fourth hour and again raised by 5.4 mmol/liter during the fifth hour in four nondiabetic and four diabetic subjects. With the initiation of exendin-4 infusion at 60 min, plasma insulin response was potentiated 4- to 5-fold in both groups. Despite termination of exendin-4 at the end of the second hour, the insulin levels remained elevated for several hours and hyperglycemia was maintained. All volunteers ate a meal 5.5 h after inducing hyperglycemia. Postprandial plasma glucose, insulin, and GLP-1 did not rise in any subject, possibly because of delayed gastric emptying by exendin-4 even though its infusion had been terminated 4 h previously. We concluded that exendin-4 is a potent and long-lasting insulinotropic agent in nondiabetic and diabetic subjects.

The Insulinotropic Effect of Acute Exendin-4 Administered to Humans: Comparison of Nondiabetic State to Type 2 Diabetes

Exendin-4 is a potent and long-acting agonist of the glucagon-like peptide-1 (GLP-1) receptor. GLP-1 is an insulinotropic gut peptide and is being evaluated for the regulation of plasma glucose in type 2 diabetes. The purpose of the present study was to ascertain whether exendin-4 is insulinotropic and whether it has long-lived biological effects in nondiabetic and type 2 diabetic subjects. Because incretins are glucose dependent with respect to their insulin-releasing capacity, we used the hyperglycemic glucose clamp technique to begin to address these issues in two separate protocols. In one protocol, we infused exendin-4 (0.15 pmol·kg−1·min−1) in seven nondiabetic and seven type 2 diabetic subjects during the second hour of a 5-h hyperglycemic clamp in which fasting plasma glucose was raised by 5.4 mmol/liter. The second protocol was identical to the first except that plasma glucose was allowed to fall to the fasting levels during the fourth hour and again raised by 5.4 mmol/liter during the fifth hour in four nondiabetic and four diabetic subjects. With the initiation of exendin-4 infusion at 60 min, plasma insulin response was potentiated 4- to 5-fold in both groups. Despite termination of exendin-4 at the end of the second hour, the insulin levels remained elevated for several hours and hyperglycemia was maintained. All volunteers ate a meal 5.5 h after inducing hyperglycemia. Postprandial plasma glucose, insulin, and GLP-1 did not rise in any subject, possibly because of delayed gastric emptying by exendin-4 even though its infusion had been terminated 4 h previously. We concluded that exendin-4 is a potent and long-lasting insulinotropic agent in nondiabetic and diabetic subjects.

Simultaneous pancreas-kidney and pancreas transplantation.

The discovery of insulin in 1922 changed the treatment of type 1 diabetes mellitus (DM) forever. Insulin was the first effective therapy for type 1 DM; however, its success engendered a terrible paradox for patients with this disease. The use of insulin transformed type 1 DM from a rapidly fatal

Splanchnic glucagon kinetics in exercising alloxan-diabetic dogs.

The purpose of this study was to define the relationship between arterial immunoreactive glucagon (IRG) and IRG that perfuses the liver via the portal vein during exercise in the diabetic state. Dogs underwent surgery >16 days before the experiment, at which time flow probes were implanted in the portal vein and the hepatic artery, and Silastic catheters were inserted in the carotid artery, portal vein, and hepatic vein for sampling. Dogs were made diabetic with alloxan injected intravenously approximately 3 wk before study (AD) or were studied in the nondiabetic state (ND). Each study consisted of a 30-min basal period and a 150-min moderate-exercise period on a treadmill. The findings from these studies indicate that the exercise-induced increment in portal vein IRG can be substantially greater in AD compared with ND, even when arterial and hepatic vein increments are not different. The larger IRG gradient from the portal vein to the systemic circulation in AD dogs is a function of a twofold greater increase in nonhepatic splanchnic IRG release and a fivefold greater hepatic fractional IRG extraction during exercise. In conclusion, during exercise, arterial IRG concentrations greatly underestimate the IRG levels to which the liver is exposed in ND, and this underestimation is considerably greater in dogs with poorly controlled diabetes.