Elevated plasma free fatty acid (FFA) levels are responsible for much of the insulin resistance in obese patients with type 2 diabetes. To lower plasma FFA levels effectively and long term, we have treated eight obese patients with type 2 diabetes for 2 months with placebo followed by 2 months of treatment with a combination of rosiglitazone (RGZ) (8 mg/day) and fenofibrate (FFB) (160 mg/day) in a single-blind placebo-controlled study design. Compared with placebo, RGZ/FFB lowered mean 24-h plasma FFA levels 30% (P < 0.03) and mean 24-h glucose levels 23% (P < 0.03) and increased insulin-stimulated glucose uptake (glucose rate of disappearance [G(R)(d)], determined using euglycemic-hyperinsulinemic clamp) 442% (P < 0.01), oral glucose tolerance (area under the curve for 3-h oral glucose tolerance test) 28% (P < 0.05), and plasma adiponectin levels 218% (P < 0.01). These RGZ/FFB results were compared with results obtained in five patients treated with RGZ alone. RGZ/FFB prevented the fluid retention usually associated with RGZ (-1.6 vs. 5.6%, P < 0.05), lowered fasting plasma FFA more effectively than RGZ alone (-22 vs. 5%, P < 0.05), and tended to be more effective than RGZ alone in lowering A1C (-0.9 vs. -0.4%) and triglyceride levels (-38 vs. -5%) and increasing G(Rd) (442 vs. 330%). We conclude that RGZ/FFB is a promising new therapy for type 2 diabetes that lowers plasma FFA more than RGZ alone and in contrast to RGZ does not cause water retention and weight gain.

The long-term impact of dietary carbohydrate type, in particular sucrose, on insulin resistance and the development of diabetes and atherosclerosis is not established. Current guidelines for the healthy population advise restriction of sucrose intake. We investigated the effect of high- versus low-sucrose diet (25 vs. 10%, respectively, of total energy intake) in 13 healthy subjects aged 33 +/- 3 years (mean +/- SE), BMI 26.6 +/- 0.9 kg/m(2), in a randomized crossover design with sequential 6-week dietary interventions separated by a 4-week washout. Weight maintenance, eucaloric diets with identical macronutrient profiles and fiber content were designed. All food was weighed and distributed. Insulin action was assessed using a two-step euglycemic clamp; glycemic profiles were assessed by the continuous glucose monitoring system and vascular compliance by pulse-wave analysis. There was no change in weight across the study. Peripheral glucose uptake and suppression of endogenous glucose production were similar after each diet. Glycemic profiles and measures of vascular compliance did not change. A rise in total and LDL cholesterol was observed. In this study, a high-sucrose intake as part of an eucaloric, weight-maintaining diet had no detrimental effect on insulin sensitivity, glycemic profiles, or measures of vascular compliance in healthy nondiabetic subjects.

The Epidemiology of Diabetes Interventions and Complications (EDIC) study, an observational follow-up of the Diabetes Control and Complications Trial (DCCT) type 1 diabetes cohort, measured coronary artery calcification (CAC), an index of atherosclerosis, with computed tomography (CT) in 1,205 EDIC patients at approximately 7-9 years after the end of the DCCT. We examined the influence of the 6.5 years of prior conventional versus intensive diabetes treatment during the DCCT, as well as the effects of cardiovascular disease risk factors, on CAC. The prevalences of CAC >0 and >200 Agatston units were 31.0 and 8.5%, respectively. Compared with the conventional treatment group, the intensive group had significantly lower geometric mean CAC scores and a lower prevalence of CAC >0 in the primary retinopathy prevention cohort, but not in the secondary intervention cohort, and a lower prevalence of CAC >200 in the combined cohorts. Waist-to-hip ratio, smoking, hypertension, and hypercholesterolemia, before or at the time of CT, were significantly associated with CAC in univariate and multivariate analyses. CAC was associated with mean HbA(1c) (A1C) levels before enrollment, during the DCCT, and during the EDIC study. Prior intensive diabetes treatment during the DCCT was associated with less atherosclerosis, largely because of reduced levels of A1C during the DCCT.

The impact of irbesartan treatment on biomarkers of low-grade inflammation, endothelial dysfunction, growth factors, and advanced glycation end products (AGEs) during the Irbesartan in Patients with Type 2 Diabetes and Microalbuminuria (IRMA 2) study was evaluated. IRMA 2 was a 2-year multicenter, randomized, double-blind trial in patients comparing irbesartan (150 or 300 mg once daily) versus placebo. The primary end point was onset of overt nephropathy. A subgroup (n = 269, 68%) was analyzed for biomarkers at baseline and after 1 and 2 years. High-sensitivity C-reactive protein (hs-CRP), interleukin (IL)-6, fibrinogen, adhesion molecules, transforming growth factor-beta, and AGE peptides were assessed. Irbesartan treatment yielded significant changes in hs-CRP (based on generalized estimating equation regression coefficient) with a 5.4% decrease per year versus a 10% increase per year in the placebo group (P < 0.001). Fibrinogen decreased 0.059 g/l per year from baseline versus placebo's 0.059 g/l increase per year (P = 0.027). IL-6 showed a 1.8% increase per year compared with placebo's 6.5% increase per year (P = 0.005). Changes in IL-6 were associated with changes in albumin excretion (P = 0.04). There was no treatment effect on the other biomarkers. Irbesartan (300 mg once daily) reduces low-grade inflammation in this high-risk population, and this may reduce the risk of micro- and macrovascular disease.

An automated closed-loop insulin delivery system based on subcutaneous glucose sensing and subcutaneous insulin delivery was evaluated in 10 subjects with type 1 diabetes (2 men, 8 women, mean [+/-SD] age 43.4 +/- 11.4 years, duration of diabetes 18.2 +/- 13.5 years). Closed-loop control was assessed over approximately 30 h and compared with open-loop control assessed over 3 days. Closed-loop insulin delivery was calculated using a model of the beta-cell's multiphasic insulin response to glucose. Plasma glucose was 160 +/- 66 mg/dl at the start of closed loop and was thereafter reduced to 71 +/- 19 by 1:00 p.m. (preprandial lunch). Fasting glucose the subsequent morning on closed loop was not different from target (124 +/- 25 vs. 120 mg/dl, respectively; P > 0.05). Mean glucose levels were not different between the open and closed loop (133 +/- 63 vs. 133 +/- 52 mg/dl, respectively; P > 0.65). However, glucose was within the range 70-180 mg/dl 75% of the time under closed loop versus 63% for open loop. Incidence of biochemical hypoglycemia (blood glucose <60 mg/dl) was similar under the two treatments. There were no episodes of severe hypoglycemia. The data provide proof of concept that glycemic control can be achieved by a completely automated external closed-loop insulin delivery system.

Glucosamine is a popular nutritional supplement used to treat osteoarthritis. Intravenous administration of glucosamine causes insulin resistance and endothelial dysfunction. However, rigorous clinical studies evaluating the safety of oral glucosamine with respect to metabolic and cardiovascular pathophysiology are lacking. Therefore, we conducted a randomized, placebo-controlled, double-blind, crossover trial of oral glucosamine at standard doses (500 mg p.o. t.i.d.) in lean (n = 20) and obese (n = 20) subjects. Glucosamine or placebo treatment for 6 weeks was followed by a 1-week washout and crossover to the other arm. At baseline, and after each treatment period, insulin sensitivity was assessed by hyperinsulinemic-isoglycemic glucose clamp (SI(Clamp)) and endothelial function evaluated by brachial artery blood flow (BAF; Doppler ultrasound) and forearm skeletal muscle microvascular recruitment (ultrasound with microbubble contrast) before and during steady-state hyperinsulinemia. Plasma glucosamine pharmacokinetics after oral dosing were determined in each subject using a high-performance liquid chromatography method. As expected, at baseline, obese subjects had insulin resistance and endothelial dysfunction when compared with lean subjects (SI(Clamp) [median {25th-75th percentile}] = 4.3 [2.9-5.3] vs. 7.3 [5.7-11.3], P < 0.0001; insulin-stimulated changes in BAF [% over basal] = 12 [-6 to 84] vs. 39 [2-108], P < 0.04). When compared with placebo, glucosamine did not cause insulin resistance or endothelial dysfunction in lean subjects or significantly worsen these findings in obese subjects. The half-life of plasma glucosamine after oral dosing was approximately 150 min, with no significant changes in steady-state glucosamine levels detectable after 6 weeks of therapy. We conclude that oral glucosamine at standard doses for 6 weeks does not cause or significantly worsen insulin resistance or endothelial dysfunction in lean or obese subjects.

Endothelial dysfunction is a characteristic finding in both patients with type 1 diabetes and in regular smokers and is an important precursor to atherosclerosis. The urate molecule has antioxidant properties, which could influence endothelial function. The impact of acutely raising uric acid concentrations on endothelial function was studied in eight men with type 1 diabetes, eight healthy regular smokers, and eight age-matched healthy control subjects in a randomized, four-way, double-blind, placebo-controlled study. Subjects received 1,000 mg uric acid i.v. in vehicle, 1,000 mg vitamin C as a control antioxidant, vehicle alone, or 0.9% saline on separate occasions over 1 h. Forearm blood flow responses to intrabrachial acetylcholine and sodium nitroprusside were assessed using venous occlusion plethysmography. Responses to acetylcholine, but not sodium nitroprusside, were impaired in patients with diabetes (P < 0.001) and in smokers (P < 0.005) compared with control subjects. Administration of uric acid and vitamin C selectively improved acetylcholine responses in patients with type 1 diabetes (P < 0.01) and in regular smokers (P < 0.05). Uric acid administration improved endothelial function in the forearm vascular bed of patients with type 1 diabetes and smokers, suggesting that high uric acid concentrations in vivo might serve a protective role in these and other conditions associated with increased cardiovascular risk.

We directly assessed the efficacy of vitamin E supplements for primary prevention of type 2 diabetes among apparently healthy women in the Women's Health Study randomized trial. Between 1992 and 2004, 38,716 apparently healthy U.S. women aged >or=45 years and free of diabetes, cancer, and cardiovascular disease were in two randomly assigned intervention groups and received 600 IU of vitamin E (alpha-tocopherol, n = 19,347) or placebo (n = 19,369) on alternate days. During a median 10-year follow-up, there were 827 cases of incident type 2 diabetes in the vitamin E group and 869 in the placebo group, a nonsignificant 5% risk reduction (relative risk [RR] 0.95 [95% CI 0.87-1.05], P = 0.31). There was no evidence that diabetes risk factors including age, BMI, postmenopausal hormone use, multivitamin use, physical activity, alcohol intake, and smoking status modified the effect of vitamin E on the risk of type 2 diabetes. In a sensitivity analysis taking compliance into account, women in the vitamin E group had an RR of 0.93 (95% CI 0.83-1.04) (P = 0.21) compared with those randomized to placebo. In this large trial with 10-year follow-up, alternate-day doses of 600 IU vitamin E provided no significant benefit for type 2 diabetes in initially healthy women.

Type 1 diabetes is a chronic autoimmune disease mediated by autoreactive T-cells. Several experimental therapies targeting T-cells are in clinical trials. To understand how these therapies affect T-cell responses in vivo, assays that directly measure human T-cell function are needed. In a blinded, multicenter, case-controlled study conducted by the Immune Tolerance Network, we tested responses in an immunoblot and T-cell proliferative assay to distinguish type 1 diabetic patients from healthy control subjects. Peripheral blood cells from 39 healthy control subjects selected for DR4 and 23 subjects with recently diagnosed type 1 diabetes were studied. Autoantibody responses were measured in serum samples. Positive responses in both assays were more common in peripheral blood mononuclear cells from new-onset type 1 diabetic patients compared with control subjects. The proliferative, immunoblot, and autoantibody assays had sensitivities of 58, 91, and 78% with specificities of 94, 83, and 85%, respectively. When cellular assays were combined with autoantibody measurements, the sensitivity of the measurements was 75% with 100% specificity. We conclude that cellular assays performed on peripheral blood have a high degree of accuracy in discriminating responses in subjects with type 1 diabetes from healthy control subjects. They may be useful for assessment of cellular autoimmune responses involved in type 1 diabetes.

Recombinant human IGF-I (rhIGF-I) complexed with its natural binding protein IGF-binding protein (IGFBP)-3 (rhIGF-I/IGFBP-3) is a novel formulation that has been shown to improve insulin sensitivity in type 1 diabetes, yet the mechanisms are not clear. We used stable isotopes to investigate the effects of rhIGF-I/IGFBP-3 on glucose and glycerol metabolism in type 1 diabetes. Fifteen subjects (age 13-24 years; 10 males) were studied on three occasions in random order. Each study period lasted for two days, and an injection of either placebo or rhIGF-I/IGFBP-3 (0.1-0.8 mg x kg(-1) x day (-1)) was given subcutaneously at 6:00 p.m. on days 1 and 2. Following the second injection, the subjects were kept euglycemic overnight by a variable rate insulin infusion, followed by a 4-h, two-step (insulin 0.6 and 1.5 mU x kg(-1) x min (-1)) hyperinsulinemic-euglycemic clamp. During the overnight basal steady state, rhIGF-I/IGFBP-3 dose-dependently reduced endogenous glucose production rate (R(a)) (P = 0.004), while peripheral glucose uptake (R(d)) was not different from placebo. The increase in glucose R(d) during hyperinsulinemic clamp was greater following rhIGF-I/IGFBP-3 than placebo, both during the first (P = 0.008) and second step (P = 0.008) of the clamp. No significant differences were found in glycerol R(a), a measure of lipolysis, between rhIGF-I/IGFBP-3 and placebo. In conclusion, rhIGF-I/IGFBP-3 enhances glucose metabolism by controlling both endogenous glucose output and peripheral glucose uptake.

The Finnish DPS (Diabetes Prevention Study) demonstrated that lifestyle intervention, aimed at increasing physical activity, improving diet, and decreasing body weight, reduced the incidence of type 2 diabetes in individuals with overweight and impaired glucose tolerance by 58%. Here, we studied which immunological markers at baseline predicted subsequent type 2 diabetes and whether there are immunologically defined subsets of subjects who are more or less responsive to the protective effects of lifestyle intervention. We randomly assigned 522 participants to a control group (n = 257) or a lifestyle intervention group (n = 265). Immunological parameters at baseline included high-sensitivity C-reactive protein (CRP), serum amyloid A, interleukin-6, regulated on activation normal T-cell expressed and secreted (RANTES), macrophage migration inhibitory factor (MIF), and soluble intercellular adhesion molecule. In the control group, CRP was the best immunological predictor for progression to overt type 2 diabetes. In the intervention group, progression to type 2 diabetes was significantly higher in subjects with the highest RANTES concentrations and was lower in subjects with the highest MIF levels. Ratios of RANTES to MIF in the upper tertile were highly predictive of incident type 2 diabetes in the intervention group (P = 0.006), whereas the association was less pronounced in the control group (P = 0.088). Thus, systemic concentrations of immune mediators appear to be associated with the progression to type 2 diabetes and the prevention of type 2 diabetes by lifestyle changes.

Skeletal muscle contraction stimulates multiple signaling cascades that govern a variety of metabolic and transcriptional events. Akt/protein kinase B regulates metabolism and growth/muscle hypertrophy, but contraction effects on this target and its substrates are varied and may depend on the mode of the contractile stimulus. Accordingly, we determined the effects of endurance or resistance exercise on phosphorylation of Akt and downstream substrates in six trained cyclists who performed a single bout of endurance or resistance exercise separated by approximately 7 days. Muscle biopsies were taken from the vastus lateralis at rest and immediately after exercise. Akt Ser(473) phosphorylation was increased (1.8-fold; P=0.011) after endurance but was unchanged after resistance exercise. Conversely, Akt Thr(308) phosphorylation was unaltered after either bout of exercise. Several exercise-responsive phosphoproteins were detected by immunoblot analysis with a phospho-Akt substrate antibody. pp160 and pp300 were identified as AS160 and filamin A, respectively, with increased phosphorylation (2.0- and 4.9-fold, respectively; P<0.05) after endurance but not resistance exercise. In conclusion, AS160 and filamin A may provide an important link to mediate endurance exercise-induced bioeffects in skeletal muscle.

Impaired effectiveness of glucose to suppress endogenous glucose production (EGP) is an important cause of worsening hyperglycemia in type 2 diabetes. Elevated free fatty acids (FFAs) may impair glucose effectiveness via several mechanisms, including rapid changes in metabolic fluxes and/or more gradual changes in gene expression of key enzymes or other proteins. Thus, we examined the magnitude and time course of effects of FFAs on glucose effectiveness in type 2 diabetes and whether glucose effectiveness can be restored by lowering FFAs. Glucose fluxes ([3-(3)H]-glucose) were measured during 6-h pancreatic clamp studies, at euglycemia (5 mmol/l glucose, t=0-240 min), and hyperglycemia (10 mmol/l, t=240-360 min). We studied 19 poorly controlled subjects with type 2 diabetes (HbA(1c) 10.9 +/- 0.4%, age 50 +/- 3 years, BMI 30 +/- 2 kg/m(2)) on at least two occasions with saline (NA- group) or nicotinic acid (NA group) infusions for 3, 6, or 16 h (NA3h, NA6h, and NA16h groups, respectively) to lower FFAs to nondiabetic levels. As a reference group, glucose effectiveness was also assessed in 15 nondiabetic subjects. There was rapid improvement in hepatic glucose effectiveness following only 3 h of NA infusion (NA3h = 31 +/- 6% suppression of EGP with hyperglycemia vs. NA- = 8 +/- 7%; P<0.01) and complete restoration of glucose effectiveness after 6 h of NA (NA6h = 41 +/- 8% suppression of EGP; P = NS vs. nondiabetic subjects). Importantly, the loss of hepatic glucose effectiveness in type 2 diabetes is completely reversible upon correcting the increased FFA concentrations. A longer duration of FFA lowering may be required to overcome the chronic effects of increased FFAs on hepatic glucose effectiveness.

Plasma phospholipid transfer protein (PLTP) plays an important role in lipoprotein metabolism. PLTP activity is elevated in patients with diabetes, a condition with strongly elevated risk for coronary heart disease. The aim of this study was to test the hypothesis that statins reduce PLTP activity and to examine the potential role of apolipoprotein E (apoE). PLTP activity and apoE were measured in patients with type 2 diabetes from the DALI (Diabetes Atorvastatin Lipid Intervention) Study, a 30-week randomized double-blind placebo-controlled trial with atorvastatin (10 and 80 mg daily). At baseline, PLTP activity was positively correlated with waist circumference, HbA(1c), glucose, and apoE (all P < 0.05). Atorvastatin treatment resulted in decreased PLTP activity (10 mg atorvastatin: -8.3%, P < 0.05; 80 mg atorvastatin: -12.1%, P < 0.002). Plasma apoE decreased by 28 and 36%, respectively (P < 0.001). The decrease in apoE was strongly related to the decrease in PLTP activity (r = 0.565, P < 0.001). The change in apoE remained the sole determinant of the change in PLTP activity in a multivariate model. The activity of PLTP in type 2 diabetes is decreased by atorvastatin. The association between the decrease in PLTP activity and apoE during statin treatment supports the hypothesis that apoE may prevent PLTP inactivation.

The splanchnic bed produces cortisol at rates approximating extraadrenal tissues by converting cortisone to cortisol via the 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 1 pathway. It is not known whether splanchnic cortisol production is regulated by nutrient ingestion and/or by the accompanying changes in hormone secretion. To address this question, 18 healthy humans were randomized to ingest either a mixed meal or to receive an intravenous saline infusion while total-body, splanchnic, and D3 cortisol production (an index of 11beta-HSD type 1 activity) were measured using the combined hepatic catheterization and D4 cortisol infusion methods. Fasting glucose and insulin concentrations did not differ on the meal and saline study days. Glucose and insulin concentrations increased after meal ingestion, peaking at 11.0 +/- 1.0 mmol/l and 451 +/- 64 pmol/l, respectively, at 45 min, then fell to baseline thereafter. In contrast, glucose and insulin concentrations slowly fell to 5.1 +/- 0.1 mmol/l and 27 +/- 6 pmol/l during the 6 h of observation on the saline study day. Fasting cortisol concentration did not differ on the meal and saline study days. Cortisol increased (P < 0.05) to a peak of 353 +/- 55 nmol/l after meal ingestion but did not change after saline infusion. The increase in cortisol after meal ingestion was associated with an increase in both total body cortisol (from 748 +/- 63 to 1,620 +/- 235 nmol/min; P < 0.01) and total body D3 cortisol (from 99 +/- 11 to 143 +/- 11 nmol/min; P < 0.01) production, whereas there was no change in either on the saline study day. The increase in total-body cortisol and D3 cortisol production after meal ingestion originated in extrasplanchnic tissues since splanchnic cortisol production (mean 0-360 min: 254 +/- 83 vs. 262 +/- 36 nmol/min) and splanchnic D3 cortisol production (mean 0-360 min: 72 +/- 22 vs. 77 +/- 14 nmol/min) did not differ on the meal and saline study days. We conclude that ingestion of a mixed meal does not alter either splanchnic cortisol production or the conversion of D4 cortisol to D3 cortisol or, therefore by implication, flux via the splanchnic 11beta-HSD type 1 pathway.

The role of ubiquitin-proteasome system in the accelerated atherosclerotic progression of diabetic patients is unclear. We evaluated ubiquitin-proteasome activity in carotid plaques of asymptomatic diabetic and nondiabetic patients, as well as the effect of rosiglitazone, a peroxisome proliferator-activated receptor (PPAR)-gamma activator, in diabetic plaques. Plaques were obtained from 46 type 2 diabetic and 30 nondiabetic patients undergoing carotid endarterectomy. Diabetic patients received 8 mg rosiglitazone (n = 23) or placebo (n = 23) for 4 months before scheduled endarterectomy. Plaques were analyzed for macrophages (CD68), T-cells (CD3), inflammatory cells (HLA-DR), ubiquitin, proteasome 20S activity, nuclear factor (NF)-kappaB, inhibitor of kappaB (IkappaB)-beta, tumor necrosis factor (TNF)-alpha, nitrotyrosine, matrix metalloproteinase (MMP)-9, and collagen content (immunohistochemistry and enzyme-linked immunosorbent assay). Compared with nondiabetic plaques, diabetic plaques had more macrophages, T-cells, and HLA-DR+ cells (P < 0.001); more ubiquitin, proteasome 20S activity (TNF-alpha), and NF-kappaB (P < 0.001); and more markers of oxidative stress (nitrotyrosine and O2(-) production) and MMP-9 (P < 0.01), along with a lesser collagen content and IkappaB-beta levels (P < 0.001). Compared with placebo-treated plaques, rosiglitazone-treated diabetic plaques presented less inflammatory cells (P < 0.01); less ubiquitin, proteasome 20S, TNF-alpha, and NF-kappaB (P < 0.01); less nitrotyrosine and superoxide anion production (P < 0.01); and greater collagen content (P < 0.01), indicating a more stable plaque phenotype. Similar findings were obtained in circulating monocytes obtained from the two groups of diabetic patients and cultured in the presence or absence of rosiglitazone (7.0 micromol/l). Ubiquitin-proteasome over-activity is associated with enhanced inflammatory reaction and NF-kappaB expression in diabetic plaques. The inhibition of ubiquitin-proteasome activity in atherosclerotic lesions of diabetic patients by rosiglitazone is associated with morphological and compositional characteristics of a potential stable plaque phenotype, possibly by downregulating NF-kappaB-mediated inflammatory pathways.

The Pioglitazone In Prevention Of Diabetes (PIPOD) study was conducted to evaluate beta-cell function, insulin resistance, and the incidence of diabetes during treatment with pioglitazone in Hispanic women with prior gestational diabetes who had completed participation in the Troglitazone In Prevention Of Diabetes (TRIPOD) study. Women who completed the TRIPOD study were offered participation in the PIPOD study for a planned 3 years of drug treatment and 6 months of postdrug washout. Oral glucose tolerance tests were performed annually on pioglitazone and at the end of the postdrug washout. Intravenous glucose tolerance tests (IVGTTs) for assessment of insulin sensitivity and beta-cell function were conducted at baseline, after 1 year on pioglitazone, and at the end of the postdrug washout. Of 95 women who were not diabetic at the end of the TRIPOD study, 89 enrolled in the PIPOD study, 86 completed at least one follow-up visit, and 65 completed all study visits, including the postdrug tests. Comparison of changes in beta-cell compensation for insulin resistance across the TRIPOD and PIPOD studies revealed that pioglitazone stopped the decline in beta-cell function that occurred during placebo treatment in the TRIPOD study and maintained the stability of beta-cell function that had occurred during troglitazone treatment in the TRIPOD study. The risk of diabetes, which occurred at an average rate of 4.6% per year, was lowest in women with the largest reduction in total IVGTT insulin area after 1 year of treatment. The similarity of findings between the PIPOD and TRIPOD studies support a class effect of thiazolidinedione drugs to enhance insulin sensitivity, reduce insulin secretory demands, and preserve pancreatic beta-cell function, all in association with a relatively low rate of type 2 diabetes, in Hispanic women with prior gestational diabetes.

Insulin infusion improves myocardial blood flow (MBF) in healthy subjects. Until now, the effect of insulin on myocardial perfusion in type 2 diabetic subjects with coronary artery disease (CAD) has been unknown. We studied the effects of insulin on MBF in ischemic regions evaluated by single-photon emission-computed tomography and coronary angiography and in nonischemic regions in 43 subjects (ages 63 +/- 7 years) with type 2 diabetes (HbA(1c) 7.1 +/- 0.9%). MBF was measured at fasting and during a euglycemic-hyperinsulinemic clamp at rest (n = 43) and during adenosine-induced (140 mug . kg(-1) . min(-1) for 7 min) hyperemia (n = 26) using positron emission tomography and (15)O-labeled water. MBF was significantly attenuated in ischemic regions as compared with in nonischemic regions (P < 0.0001) and was increased by insulin as compared with in the fasting state (P < 0.0001). At rest, insulin infusion increased MBF by 13% in ischemic regions (P = 0.043) and 22% in nonischemic regions (P = 0.003). During adenosine infusion, insulin enhanced MBF by 20% (P = 0.018) in ischemic regions and 18% (P = 0.045) in nonischemic regions. In conclusion, insulin infusion improved MBF similarly in ischemic and nonischemic regions in type 2 diabetic subjects with CAD. Consequently, in addition to its metabolic effects, insulin infusion may improve endothelial function and thus increase the threshold for ischemia and partly contribute to the beneficial effects found in clinical trials in these subjects.

Hyperglycemia is associated with increased susceptibility to atherothrombotic stimuli. The glycocalyx, a layer of proteoglycans covering the endothelium, is involved in the protective capacity of the vessel wall. We therefore evaluated whether hyperglycemia affects the glycocalyx, thereby increasing vascular vulnerability. The systemic glycocalyx volume was estimated by comparing the distribution volume of a glycocalyx permeable tracer (dextran 40) with that of a glycocalyx impermeable tracer (labeled erythrocytes) in 10 healthy male subjects. Measurements were performed in random order on five occasions: two control measurements, two measurements during normoinsulinemic hyperglycemia with or without N-acetylcysteine (NAC) infusion, and one during mannitol infusion. Glycocalyx measurements were reproducible (1.7 +/- 0.2 vs. 1.7 +/- 0.3 l). Hyperglycemia reduced glycocalyx volume (to 0.8 +/- 0.2 l; P < 0.05), and NAC was able to prevent the reduction (1.4 +/- 0.2 l). Mannitol infusion had no effect on glycocalyx volume (1.6 +/- 0.1 l). Hyperglycemia resulted in endothelial dysfunction, increased plasma hyaluronan levels (from 70 +/- 6 to 112 +/- 16 ng/ml; P < 0.05) and coagulation activation (prothrombin activation fragment 1 + 2: from 0.4 +/- 0.1 to 1.1 +/- 0.2 nmol/l; d-dimer: from 0.27 +/- 0.1 to 0.55 +/- 0.2 g/l; P < 0.05). Taken together, these data indicate a potential role for glycocalyx perturbation in mediating vascular dysfunction during hyperglycemia.

Heterozygous mutations in the transcription factors hepatocyte nuclear factor (HNF)-1alpha and -1beta result in MODY (maturity-onset diabetes of the young). Despite structural similarity between HNF-1alpha and -1beta, HNF-1beta mutation carriers have hyperinsulinemia, whereas HNF-1alpha mutation carriers have normal or reduced insulin concentrations. We examined whether HNF-1beta mutation carriers are insulin resistant. The endogenous glucose production rate and rate of glucose uptake were measured with a two-step, low-dose (0.3 mU . kg(-1) . min(-1)) and high-dose (1.5 mU . kg(-1) . min(-1)) hyperinsulinemic-euglycemic clamp, with an infusion of [6,6-(2)H(2)]glucose, in six subjects with HNF-1alpha mutations, six subjects with HNF-1beta mutations, and six control subjects, matched for age, sex, and BMI. Endogenous glucose production rate was not suppressed by low-dose insulin in HNF-1beta subjects but was suppressed by 89% in HNF-1alpha subjects (P = 0.004) and 80% in control subjects (P < 0.001). Insulin-stimulated glucose uptake and suppression of lipolysis were similar in all groups at low- and high-dose insulin. Subjects with HNF-1beta mutations have reduced insulin sensitivity of endogenous glucose production but normal peripheral insulin sensitivity. This is likely to reflect reduced action of HNF-1beta in the liver and possibly the kidney. This may be mediated through regulation by HNF-1beta of the key gluconeogenic enzymes glucose-6-phosphatase or PEPCK.