Smoking is associated with impaired glucose regulation and a decrease in insulin sensitivity and the disposition index in first-degree relatives of type 2 diabetes subjects independently of the presence of metabolic syndrome.

The aim of this study was to investigate glucose tolerance, insulin secretion and insulin resistance according to smoking habits in first-degree relatives of type 2 diabetes patients, a population at high risk for developing diabetes. One thousand three hundred (646 females and 654 males) subjects underwent an oral glucose tolerance test (OGTT) to investigate their glucose metabolism and answered questionnaires about their lifestyle habits. Smoker subjects showed significant impairment compared with non-smoker subjects in 2-h post-oral glucose tolerance test (2hOGTT, 129.3 ± 40.2 vs. 117.7 ± 37.6 mg/dl, p < 0.001), the OGTT insulin sensitivity (386.3 ± 54.9 vs. 400.5 ± 53.4 ml min(-1) m(2), p < 0.01) method and the insulin sensitivity and secretion index-2 (ISSI-2, 1.7 ± 0.8 vs. 2.0 ± 1.0, p < 0.005). Metabolic syndrome (MS) was higher in the smoker than in the non-smoker group (46.5 vs. 29.7 %, p < 0001), and smokers were more sedentary than non-smokers (3.94 ± 3.77 vs. 4.86 ± 4.41 h/week, p < 0.001). Smokers showed an increased risk of impaired glucose regulation (IGR: impaired glucose tolerance or diabetes mellitus) with a hazard ratio (HR) adjusted by gender, metabolic syndrome and physical activity of 1.78, 95 % CI 1.27-2.47 (p < 0.001). The association between smoking and MS conferred a risk of IGR that was five times higher (HR 5.495, 95 % CI 4.07-7.41, p < 0.001). Smoking habit was a significant explanatory variable in a multiple forward stepwise regression analysis performed using 2hOGTT and ISSI-2 as dependent variables (p < 0.0001, R = 0.313 and p < 0.0001, R = 0.347, respectively). In conclusions, our results show that tobacco smoking is tightly associated with impairments in glucose metabolism and insulin sensitivity and insulin secretion.

A novel truncated form of eNOS associates with altered vascular function.

AIMS: Nitric oxide (NO) plays a key role in vascular homeostasis and is produced by endothelial NO synthase (eNOS), encoded by NOS3 gene. We previously reported the genetic association between NOS3 rs753482-A>C polymorphism on intron 19 and coronary artery disease (CAD). In the attempt of conferring functional implication to the rs753482-A>C polymorphism, we investigated its influence on transcript maturation. METHODS AND RESULTS: A transcript variant skipping exons 20-21 is prevalent in carriers of the rs753482-C allele and is translated in a novel truncated form of eNOS. The truncated eNOS displays increased basal NO production, is insensitive to calcium stimulation, and, upon heterodimerization with the full-length eNOS protein, exerts a dominant-negative effect on NO production. CAD patients and healthy subjects' carriers of the rs753482-C genotype are characterized by increased NO basal levels in peripheral blood and platelets, and negatively respond to oral glucose load by failing to increase NO synthesis following insulin wave. Furthermore, forearm vasodilation after reactive hyperaemia is dramatically impaired in rs753482-C carriers. CONCLUSIONS: We demonstrated that subjects carrying the rs753482-C genotype express a novel stable truncated form of eNOS with altered enzymatic activity that influences NO production and endothelial function. These findings open to new intriguing perspectives to several diseases involving vascular response to NO.

L-arginine enriched biscuits improve endothelial function and glucose metabolism: a pilot study in healthy subjects and a cross-over study in subjects with impaired glucose tolerance and metabolic syndrome.

OBJECTIVE: The aim of this study was to evaluate the effects of a new L-arginine-enriched biscuit on endothelial function, insulin sensitivity/secretion and body composition. MATERIALS/METHODS: The project was composed of two studies. The first study was an acute pilot postprandial study in 7 healthy subjects that evaluated bio-availability and vascular effects of L-arginine-enriched biscuits that contained 6.6 gL-arginine, 21.9 g carbohydrates, 3.6 g protein, 7.5 g fat and 4.3 g dietary fiber compared with placebo biscuits and 6.6 g powdered L-arginine. Subjects underwent the tests in random order, in at least 14-day intervals. The second study was a double-blind crossover study in 15 obese subjects with IGT and MS. These subjects consumed 6.6 g of L-arginine-enriched biscuits or placebo biscuits in a 1600 kcal diet. Each study period lasted 2 weeks with a 2-week washout in between. Endothelial function, glucose tolerance, insulin sensitivity and insulin secretion were evaluated at the end of each intervention period. RESULTS: In the first study, the groups that received the L-arginine-enriched biscuits and the powdered L-arginine had similarly increased L-arginine, NOx and cGMP levels and post-ischemic blood flow (PI-BF). In both cases, these levels were significantly higher than those in the placebo biscuit recipient group. In the second study, the L-arginine-enriched biscuit recipient group displayed increased L-arginine, NOx, cGMP, PI-BF, and Matsuda index levels, whereas their circulating glucose, proinsulin/insulin ratio and fat mass were decreased compared with the placebo biscuit recipient group. CONCLUSIONS: L-Arginine-enriched biscuits with low sugar and protein content enhance endothelial function and improve glucose metabolism, insulin sensitivity and insulin secretion in subjects with IGT and MS.

Effect of normalization of fasting glucose by intensified insulin therapy and influence of eNOS polymorphisms on the incidence of restenosis after peripheral angioplasty in patients with type 2 diabetes: a randomized, open-label clinical trial.

Primary objective was to evaluate whether an intensified insulin therapy (IIT) incorporating the target of normal fasting glucose and HbA1c levels could halve the incidence of restenosis/amputation/SCA/death at 6 months after peripheral angioplasty compared with standard care (SC) in patients with type 2 diabetes (DMT2) affected by critical limb ischemia (CLI). Forty-six consecutive patients with DMT2 and CLI were randomly assigned to a parallel, open-label study with IIT (basal-bolus glulisine + glargine administrations) or SC (glargine administration + oral antidiabetic drugs). A SNP of eNOS (rs753482-A>C) and circulating CD34(+) and CD34(+)KDR(+) progenitor cells were determined. At the end of the study, although HbA1c levels were lower in IIT than in SC (6.9 ± 1.3 % vs. 7.6 ± 1.2 %, p < 0.05), IIT did not reduce the cumulative incidence of restenosis/amputation/SCA/death (52 and 65 %, respectively, odd ratio 0.59; CI 95 %: 0.21-1.62, p = 0.59). rs753482AC+CC as compared with rs753482AA increased the cumulative incidence of restenosis/amputation/SCA/death (79 and 42 %; odd ratio 5.3; CI 95 %: 1.41-19.5, p < 0.02). Baseline CD34(+)KDR(+) were higher in rs753482AA (166.2 ± 154.0 × 10(6) events) than in rs753482AC+CC (63.1 ± 26.9 × 10(6) events, p < 0.01). At the end of the study, the highest circulating CD34(+)KDR(+) were found in IIT rs753482AA (246.9 ± 194.0 × 10(6) events) while the lowest levels were found in SC rs753482AC+CC (70.9 ± 45.0 × 10(6) events). IIT did not decrease the cumulative incidence of restenosis/amputation/SCA/death in DMT2 and CLI patients. These patients correspond to a class of fragile subjects at high risk of cardiovascular events, and new predictors of restenosis should be contemplated, such as of eNOS polymorphism, (rs753482-A>C SNP) and circulating endothelial progenitor cells.

Aerobic and resistance training effects compared to aerobic training alone in obese type 2 diabetic patients on diet treatment.

AIMS: The study was designed to compare a combined aerobic and resistance training (ART) with an aerobic training (AT) over hemodynamic, glucose metabolism and endothelial factors, adipokines and pro-inflammatory marker release in a population of obese type 2 diabetic patients. METHODS: Forty-seven patients were randomly assigned to aerobic (27 patients) or aerobic plus resistance (20 patients) exercise trainings, on the top of a diet regime. Anthropometric, metabolic, hormonal and inflammatory variables were measured at hospitalization and discharge. RESULTS: Both exercise programs equally improved body weight and fructosamine levels however ART only partially decreased HOMA index compared with AT (ART: -25% vs AT: -54%, p<0.01). Mean blood pressure (AT: -3.6 mmHg vs ART: +0.6 mmHg, p<0.05) and endothelin-1 (ET-1) incremental areas during walking test (AT: -11% vs ART: +30%, p<0.001) decreased after AT while increased after ART. Adiponectin levels increased by 54% after AT while decreased by 13% after ART (p<0.0001) and matrix metalloproteinase-2 (MMP-2), tumor necrosis factor-alpha (TNF-alpha) and monocyte chemoattractan protein-1 (MCP-1) levels significantly decreased in AT while increased in ART group. CONCLUSIONS: Compared with AT, ART similarly enhanced body weight loss but exerted less positive effects on insulin sensitivity and endothelial factors, adipokines and pro-inflammatory marker release.

Fasting hyperinsulinemia associates with increased sub-clinical inflammation in first-degree relatives normal glucose tolerant women independently of the metabolic syndrome.

BACKGROUND: To evaluate the influence of gender on the relationship between inflammation and hyperinsulinemia in first-degree relatives of type 2 diabetic patients independently of metabolic syndrome. METHODS: Study group consisted in 217 first-degree relatives with normal glucose tolerance after an oral glucose tolerance test. A logistic analysis, adjusted for age, sex and all the components of the metabolic syndrome, was used to determine the relationship between interleukin-6 (IL-6) and leptin and tertiles of fasting insulin, and to take into account the influence of gender. RESULTS: In the whole cohort, IL-6 and leptin were significantly higher and adiponectin significantly lower in the III tertile when corrected for age, body mass index (BMI) and metabolic syndrome components. In women, but not in men, IL-6 and leptin remained significantly higher when corrected for metabolic syndrome. In the whole cohort and in women, univariate correlations between IL-6 concentrations and the parameters under evaluation showed that IL-6 and leptin were positively correlated with age, BMI, waist, systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting glucose, fasting insulin, Delta AUC insulin area, triglyceride (TG), free fatty acids (FFA) and monocyte chemoattractant protein-1 (MCP-1) and inversely correlated with HDL cholesterol (HDL-C) and adiponectin. In women a forward stepwise linear regression analysis in a model including age, BMI, features of metabolic syndrome, fasting insulin, Delta AUC insulin and insulin sensitivity index (ISI) index revealed that only IL-6 and leptin were independently associated with fasting insulin levels. CONCLUSIONS: In first-degree relatives normal glucose tolerant women, fasting hyperinsulinemia, independently of the presence of metabolic syndrome, is associated with elevated IL-6 and leptin levels, suggesting an increased cardiovascular risk.

Oral L-arginine supplementation improves endothelial function and ameliorates insulin sensitivity and inflammation in cardiopathic nondiabetic patients after an aortocoronary bypass.

It is known that L-arginine treatment can ameliorate endothelial dysfunction and insulin sensitivity in type 2 diabetes mellitus patients, but little is known on L-arginine effects on these variables in nondiabetic patients with stable cardiovascular disease (coronary artery disease). We evaluated the effects of long-term oral L-arginine treatment on endothelial dysfunction, inflammation, adipokine levels, glucose tolerance, and insulin sensitivity in these patients. Sixty-four patients with cardiovascular disease previously submitted to an aortocoronary bypass and not known for type 2 diabetes mellitus had an oral glucose load to define their glucose tolerance. Thirty-two patients with nondiabetic response were eligible to receive, in a double-blind randomized parallel order, L-arginine (6.4 g/d) or placebo for 6 months. An evaluation of insulin sensitivity index during the oral glucose load, markers of systemic nitric oxide bioavailability and inflammation, and blood flow was performed before and at the end of the treatment in both groups. Compared with placebo, L-arginine decreased asymmetric dimethylarginine levels (P < .01), indices of endothelial dysfunction, and increased cyclic guanosine monophosphate (P < .01), L-arginine to asymmetric dimethylarginine ratio (P < .0001), and reactive hyperemia (P < .05). Finally, L-arginine increased insulin sensitivity index (P < .05) and adiponectin (P < .01) and decreased interleukin-6 and monocyte chemoattractant protein-1 levels. In conclusion, insulin resistance, endothelial dysfunction, and inflammation are important cardiovascular risk factors in coronary artery disease patients; and L-arginine seems to have anti-inflammatory and metabolic advantages in these patients.

Incretin-based therapies in type 2 diabetes: a review of clinical results.

GLP-1 analogues (incretin mimetics) and DPP-4 inhibitors (incretin enhancers) represent new classes of anti-diabetic agents for the treatment of type 2 diabetes. The efficacy and safety of the incretin mimetic exenatide and of the DPP-4 inhibitors, sitagliptin and vildagliptin, have been clearly demonstrated by a very large number of clinical trials. Efficacy was demonstrated in terms of reduction of HbA1c, fasting and postprandial glucose. Moreover, exenatide showed a favourable effect on weight, while DPP-4 inhibitors were neutral with respect to this outcome. The low rate of hypoglycemic events seen in all studies confirms the glucose dependent action of incretins.

Effects of growth hormone treatment on arginine to asymmetric dimethylarginine ratio and endothelial function in patients with growth hormone deficiency.

Patients with growth hormone deficiency (GHD) are known to have reduced life expectancy due to increased cardiovascular and cerebrovascular events. An increase in asymmetric dimethylarginine (ADMA) levels previously found in GHD patients could promote premature atherosclerosis. The aim of this study was to determine whether 6-month growth hormone (GH) replacement therapy was able to decrease ADMA levels and ameliorate endothelial dysfunction. Thirty-one GHD patients were studied before and after 6 months of GH (4 microg/[kg d], daily) replacement therapy. Reduced pretreatment levels of serum insulin-like growth factor (IGF) 1 were normalized during GH treatment (88.2 +/- 62.5 to 191.7 +/- 80.3 ng/mL, P < .0001). After 6 months of GH replacement, plasma cyclic guanosine monophosphate levels significantly increased (2.14 +/- 0.52 to 3.54 +/- 1.2 ng/mL, P < .0001), serum ADMA levels were significantly decreased (0.65 +/- 0.1 vs 0.59 +/- 0.11 mumol/L, P < .05), and arganine (Arg) to ADMA ratio was significantly higher (155 +/- 53 vs 193 +/- 61, P < .01). No changes were observed for plasma nitric oxide end products (nitrite and nitrate) levels after GH treatment (21.9 +/- 14.9 vs 24.1 +/- 19.0 mumol/L, not significant). Basal forearm blood flow remained unchanged, whereas reactive hyperemia increased from 7.30 +/- 5.31 mL/100 mL forearm per minute before GH therapy to 13.18 +/- 7.30 mL/100 mL forearm per minute after 6 months of therapy (P < .001). There was a positive correlation between IGF-1 and cyclic guanosine monophosphate (r = 0.73, P < .0001), IGF-1 and reactive hyperemia (r = 0.63, P < .0001), and IGF-1 and Arg/ADMA ratio (r = 0.44, P < .01). Conversely, a negative correlation was found between IGF-1 and ADMA levels (r = -0.41, P < .02). At the end of the study period, fat-free mass, plasma glucose, and hemoglobin A(1c) levels significantly increased, even if they were still in the reference range, suggesting moderate alteration of glucose metabolism. In conclusion, in GHD patients, GH replacement contributes to decreased, to some extent, cardiovascular risk, reducing ADMA levels and improving Arg/ADMA ratio and endothelial dysfunction.

Hyperinsulinemia and impaired leptin-adiponectin ratio associate with endothelial nitric oxide synthase polymorphisms in subjects with in-stent restenosis.

Little is known about the association of endothelial nitric oxide synthase (NOS3) gene polymorphisms and the presence of insulin resistance and the early evolution of atherosclerosis in nondiabetic subjects with cardiovascular disease (CAD) and stent implantation. The present study was performed in an attempt to better understand whether metabolic, endothelial, and angiographic findings characteristic of subjects with cardiovascular disease and in-stent restenosis are related to NOS3 variants. This is a case-control study performed from 2002 to 2006. All subjects admitted to the study were recruited in the Nord-Centre of Italy, most from Milan and its surrounding towns. Measures of glucose tolerance, insulin sensitivity, markers of endothelial dysfunction, forearm vasodilation, and adipokine levels were determined and associated to the frequency of two single-nucleotide polymorphisms of NOS3, i.e., Glu298Asp (rs1799983, G/T) and rs753482 (intron 18 A/C). A total of 747 subjects, not known to have diabetes, were evaluated: 333 subjects had asymptomatic CAD, 106 subjects had unstable angina and were evaluated for in-stent restenosis 6 mo after stent placement, and 308 were control subjects. The presence of TT and CC minor alleles was significantly greater in case groups compared with control subjects. At phenotypic level, subjects with the polymorphisms were characterized by hyperinsulinemia and reduced reactive hyperemia, whereas increased leptin and decreased adiponectin levels were present in subjects with restenosis in the presence of reduced minimal lumen diameter and length of stenosis almost doubled. Hyperinsulinemia, endothelial dysfunction, and a more atherogenic profile seem to be peculiar features of subjects with asymptomatic CAD and restenosis carrying NOS3 gene variants.

Increased insulin-stimulated endothelin-1 release is a distinct vascular phenotype distinguishing Cushing's disease from metabolic syndrome.

OBJECTIVE: Although much is known about the anti-inflammatory effects of an acute corticosteroid therapy, little is known about the effects on chronic hypercortisolism on endothelial dysfunction and proinflammatory alterations in patients with Cushing's disease (CD). PATIENTS AND METHODS: We studied 9 patients with CD, 10 patients with metabolic syndrome and 27 normal controls. The tests consisted of an intravenous bolus of 0.1 U/kg insulin combined with a euglycaemic clamp technique with an arterialized forearm and assessment of the training parameters deep-venous balance of forearm glucose uptake (as an index of insulin sensitivity); NO(x) (nitric oxide end-products), c-GMP (second messenger of nitric oxide) and endothelin-1 release, as indices of endothelial function and proinflammatory systemic markers. RESULTS: Forearm glucose uptake incremental area was significantly lower in Cushing's disease and in the metabolic syndrome than in controls, suggesting a state of severe insulin resistance. Compared to controls and to the metabolic syndrome, basal and insulin-stimulated NO(x) release incremental areas were significantly reduced in Cushing's disease, while forearm c-GMP release was similarly decreased in CD and metabolic syndrome. By contrast, endothelin-1 incremental areas after insulin bolus were significantly higher in CD than in controls and the metabolic syndrome, in the presence of increased TNF-alpha, IL-6 and CRP levels. Forearm glucose uptake incremental area significantly correlated with NO(x) incremental area, forearm c-GMP release incremental area, TNF-alpha levels and ET-1 incremental area. CONCLUSIONS: In patients with CD, supraphysiological insulin levels are not able to overcome the insulin resistance due to chronic hypercortisolism. Furthermore, an increased proatherogenic risk profile is characterized by decreased nitric oxide synthesis and activity, enhanced endothelin-1 levels and increased proinflammatory markers.

Beneficial effects of a long-term oral L-arginine treatment added to a hypocaloric diet and exercise training program in obese, insulin-resistant type 2 diabetic patients.

Because chronic L-arginine supplementation improves insulin sensitivity and endothelial function in nonobese type 2 diabetic patients, the aim of this study was to evaluate the effects of a long-term oral L-arginine therapy on adipose fat mass (FM) and muscle free-fat mass (FFM) distribution, daily glucose levels, insulin sensitivity, endothelial function, oxidative stress, and adipokine release in obese type 2 diabetic patients with insulin resistance who were treated with a combined period of hypocaloric diet and exercise training. Thirty-three type 2 diabetic patients participated in a hypocaloric diet plus an exercise training program for 21 days. Furthermore, they were divided into two groups in randomized order: the first group was also treated with L-arginine (8.3 g/day), and the second group was treated with placebo. Although in the placebo group body weight, waist circumference, daily glucose profiles, fructosamine, insulin, and homeostasis model assessment index significantly decreased, L-arginine supplementation further decreased FM (P < 0.05) and waist circumference (P < 0.0001), preserving FFM (P < 0.03), and improved mean daily glucose profiles (P < 0.0001) and fructosamine (P < 0.03). Moreover, change in area under the curve of cGMP (second messenger of nitric oxide; P < 0.001), superoxide dismutase (index of antioxidant capacity; P < 0.01), and adiponectin levels (P < 0.02) increased, whereas basal endothelin-1 levels (P < 0.01) and leptin-to-adiponectin ratio (P < 0.05) decreased in the L-arginine group. Long-term oral L-arginine treatment resulted in an additive effect compared with a diet and exercise training program alone on glucose metabolism and insulin sensitivity. Furthermore, it improved endothelial function, oxidative stress, and adipokine release in obese type 2 diabetic patients with insulin resistance.

Metabolic and endothelial effects of trimetazidine on forearm skeletal muscle in patients with type 2 diabetes and ischemic cardiomyopathy.

The aim of the present study was to evaluate the effect of prolonged inhibition of beta-oxidation on glucose and lipid muscle forearm metabolism and cGMP and endothelin-1 forearm release in patients with type 2 diabetes mellitus and ischemic cardiomyopathy. Fifteen patients were randomly allocated in a double-blind cross-over parallel study with trimetazidine (20 mg tid) or placebo lasting 15 days. At the end of each period, all patients underwent euglycemic hyperinsulinemic clamps with forearm indirect calorimetry and endothelial balance of vasodilator and vasoconstricor factors. Compared with placebo, trimetazidine induced 1) an increase in insulin-induced forearm glucose uptake and glucose oxidation accompanied by a reduction in forearm lipid oxidation and citrate release and 2) a decrease of endothelin-1 release paralleled by a significant increase in forearm cGMP release. Forearm glucose oxidation significantly correlated with cGMP release (r=0.37, P<0.04), whereas forearm lipid oxidation positively correlated with endothelin-1 release (r=0.40, P<0.03). In conclusion, for the first time, we demonstrated that insulin-induced forearm glucose oxidation and forearm cGMP release were increased whereas forearm endothelin-1 release was decreased during trimetazidine treatment. Muscle's metabolic and vascular effects of trimetazidine add new interest in the use of trimetazidine in type 2 diabetic patients with cardiovascular disease.

Nitric-oxide mediated effects of transdermal capsaicin patches on the ischemic threshold in patients with stable coronary disease.

BACKGROUND: Capsaicin has been shown to exert direct vasodilating effects through increased calcitonin gene-related peptide (CGRP) release. However, no data exist on its effect following systemic administration in humans. METHODS: Twelve male patients with stable coronary disease and a persistently positive exercise were selected for study. According to a double blind, placebo-controlled, cross-over study, patients were randomized to placebo or 3 g oleic capsaicin-containing patches, on 2 different days and with a 2-day interval between treatments. Patients performed treadmill exercise testing according to the Bruce protocol. Time to 1 mm ST segment depression and to peak exercise, maximal ST segment depression, and the number of ECG leads showing diagnostic changes were also measured. Blood samples for nitric oxide (NO) and CGRP were drawn at baseline, 2, 6, and 24 hours after exercise. RESULTS: On placebo, all patients had a positive ECG during exercise test. Only 1 patient experienced angina, on both treatments. With capsaicin, 1 patient had a negative exercise, while 8 patients significantly increased time to 1 mm ST depression from 328 +/- 167 to 401 +/- 174 seconds (P = 0.01). Of the remaining patients, 1 did not show any changes and 2 showed a worse ischemic threshold when on capsaicin. CGRP levels were not significantly different between placebo and capsaicin treatment. Conversely, when on capsaicin, NO significantly increased at 6 hours. CONCLUSIONS: Transdermal capsaicin may improve ischemic threshold in patients with stable coronary disease, probably through arteriolar vasodilation. Increased capsaicin-induced NO availability could represent the principal mechanism of action.

Insulin resistance and endothelial function are improved after folate and vitamin B12 therapy in patients with metabolic syndrome: relationship between homocysteine levels and hyperinsulinemia.

OBJECTIVE: The purpose of this study was (a) to study whether a folate and vitamin B12 treatment, aimed at decreasing homocysteine levels, might ameliorate insulin resistance and endothelial dysfunction in patients with metabolic syndrome according to the National Cholesterol Education Program-Adult Treatment Panel-III criteria and (b) to evaluate whether, under these metabolic conditions, there is a relationship between hyperhomocysteinemia and insulin resistance. DESIGN AND METHODS: A double-blind, parallel, identical placebo-drug, randomized study was performed for 2 months in 50 patients. Patients were randomly allocated to two groups. In group 1, patients were treated with diet plus placebo for 2 months. In group 2, patients were treated with diet plus placebo for 1 month, followed by diet plus folic acid (5 mg/day) plus vitamin B12 (500 microg/day) for another month. RESULTS: In group 2, folate treatment significantly decreased homocysteine levels by 27.8% (12.2+/-1.2 vs 8.8+/-0.7 micromol/l; P<0.01). A significant decrement was observed for insulin levels (19.9+/-1.7 vs 14.8+/-1.6 microU/ml; P<0.01) accompanied by a 27% reduction in the homeostasis model assessment levels. A positive relationship was found between the decrement of homocysteine and insulin levels (r=0.60; P<0.002). In parallel, endothelial dysfunction significantly improved in the treated group, since post-ischemic maximal hyperemic vasodilation increased by 29.8% and cGMP by 13.6% while asymmetrical dimethylarginine levels decreased by 21.7%. On the contrary, in group 1 patients, treated with placebo, no changes were shown in any of the variables. CONCLUSIONS: Folate and vitamin B12 treatment improved insulin resistance and endothelial dysfunction, along with decreasing homocysteine levels, in patients with metabolic syndrome, suggesting that folic acid has several beneficial effects on cardiovascular disease risk factors.

Myocardial insulin resistance associated with chronic hypertriglyceridemia and increased FFA levels in Type 2 diabetic patients.

We evaluated the influence of chronic hypertriglyceridemia and endothelial dysfunction on myocardial glucose uptake (MGU) in Type 2 diabetic patients without coronary heart disease. Patients were divided into two groups according to fasting triglyceride (TG) levels: 5.4 +/- 1.1 and 1.5 +/- 0.3 mmol/l for high- and normal-TG groups, respectively. Five subjects were assigned to the high-TG group and 11 to the normal-TG group. Age, gender, body mass index, systolic and diastolic blood pressure, glucose, insulin, HbA1c, cholesterol, and HDL cholesterol were similar in the two groups, whereas free fatty acid (FFA) levels were higher in the high-TG group basally and at the end of the clamp. Furthermore, five healthy subjects were subjected to the same protocol and used as the control group. MGU was assessed by using 18F-labeled 2-fluoro-2-deoxy-D-glucose under hyperglycemic-hyperinsulinemic conditions. Basal endothelin-1 and nitric oxide levels were significantly higher in the high-TG group than in the normal-TG and control groups, and cGMP and maximal postischemic vasodilation were significantly decreased in the high-TG group compared with the normal-TG and control groups. However, significant alterations were found in the same parameters in the normal-TG group compared with the control group. By the end of the hyperglycemic clamp, in the high-TG group, MGU was approximately 40 and 65% of that in the normal-TG and control groups. MGU negatively correlated with TG, FFA, and endothelin-1, whereas a positive correlation was found with cGMP and maximal postischemic vasodilation. In conclusion, increased TG and FFA levels are risks, in addition to Type 2 diabetes mellitus, for myocardial insulin resistance, endothelial dysfunction, and alteration of nitric oxide/cGMP levels.

Effect of oral L-arginine on blood pressure and symptoms and endothelial function in patients with systemic hypertension, positive exercise tests, and normal coronary arteries.

Thirteen hypertensive patients with microvascular angina were studied before and after receiving oral L-arginine (4 weeks, 2 g, 3 times daily). L-arginine significantly improved angina class, systolic blood pressure at rest, and quality of life. Maximal forearm blood flow, plasma L-arginine, L-arginine:asymmetric dimethyl arginine ratio, and cyclic guanylate monophosphate increased significantly after treatment. In medically treated hypertensive patients with micro-vascular angina, oral L-arginine may represent a useful therapeutic option.

Association of insulin resistance, hyperleptinemia, and impaired nitric oxide release with in-stent restenosis in patients undergoing coronary stenting.

BACKGROUND: Previously undiagnosed diabetes, impaired glucose tolerance, and insulin resistance are common in patients with acute myocardial infarction and coronary heart disease (CHD) and might be involved in early restenosis after stent implantation. To evaluate whether markers of insulin resistance syndrome, including leptin, and endothelial dysfunction are related to increased rate of early restenosis, we studied nondiabetic patients with CHD after successful coronary stenting. METHODS AND RESULTS: Both patients with CHD undergoing coronary stenting (120 patients) and control subjects (58 patients) were submitted to an oral glucose tolerance test (OGTT). Fasting leptin levels and fasting and postglucose load insulin sensitivity were assessed. Endothelial function was measured by nitrite and nitrate release (NOx) during OGTT. More than 50% of patients treated with stent implantation presented impaired glucose tolerance or type 2 diabetes, which was previously undiagnosed. These patients also had higher glucose, insulin, and leptin levels than control subjects. Among the stented patients, insulin and leptin levels were higher in patients with restenosis than in patients without restenosis. A significant increase in NOx levels was found during OGTT both in patients without restenosis and in control subjects. On the contrary, NOx profiles were blunted in patients with restenosis. At multiple regression analysis, only DeltaAUC-NOx areas and insulin sensitivity index showed an independent correlation with the minimal lumen diameter at follow-up. CONCLUSIONS: We demonstrated that insulin resistance and endothelial dysfunction are independent predictors of early restenosis after coronary stenting.

Endothelial nitric oxide synthase polymorphisms are associated with type 2 diabetes and the insulin resistance syndrome.

Endothelial nitric oxide synthase (eNOS) variants were previously demonstrated in cardiovascular disease. To evaluate whether eNOS gene variants are associated with insulin resistance and type 2 diabetes, we evaluated polymorphisms in Exon7 (E298D), intron 18 (IVS18 + 27A-->C), and intron 23 (IVS23 + 10G-->T) in 159 type 2 diabetic patients without macrovascular complications and in 207 healthy control subjects. Samples for all hormonal and metabolic variables were obtained after an overnight fast. The D298 and IVS18 + 27C alleles, but not the IVS23 + 10G-->T variant, were significantly more frequent in type 2 diabetic patients than in control subjects. The two- and three-loci haplotype analysis showed that there is a statistically significant association between the eNOS variants and type 2 diabetes. No significant differences were observed in the clinical characteristics of type 2 diabetic patients according to genotypes (except for visceral obesity [waist-to-hip ratio], which was significantly more present in D298 homozygotes). Healthy control subjects homozygous for both D298 and IVS18 + 27C presented higher insulin, C-peptide, and nitric oxide levels, as well as higher HOMA (homeostasis model assessment) values than the double wild-type homozygotes, with values superimposable on those found in type 2 diabetic patients. In conclusion, we described a significant association between eNOS gene polymorphisms and type 2 diabetes, suggesting a new genetic susceptibility factor for hyperinsulinemia, insulin resistance, and type 2 diabetes.

Acute intravenous L-arginine infusion decreases endothelin-1 levels and improves endothelial function in patients with angina pectoris and normal coronary arteriograms: correlation with asymmetric dimethylarginine levels.

BACKGROUND: We tested the hypothesis that asymmetric dimethylarginine (ADMA) levels could be elevated and influence endothelin-1 and nitric oxide release and action in patients with cardiac syndrome X (CSX). In addition, we evaluated whether an intravenous infusion of L-arginine would improve endothelial function in these subjects. METHODS AND RESULTS: Nine patients with CSX and 14 control subjects underwent a continuous infusion of L-arginine (0.125 g/min) or saline for 120 minutes. Sixty minutes after L-arginine or saline infusions, an intravenous insulin bolus (0.1 U/kg) combined with a euglycemic clamp was performed. Basal ADMA and endothelin-1 levels were higher in patients with CSX than in controls. At the end of the first hour of infusion, compared with saline, L-arginine infusion increased basal forearm blood flow, nitrite and nitrate (NOx), and forearm cGMP release and decreased endothelin-1. After insulin bolus, during saline, insulin-induced NOx, endothelin-1, and forearm cGMP release was almost abolished. Conversely, L-arginine restored a physiological profile of all endothelial variables compared with control subjects. In control subjects, compared with saline infusion, L-arginine infusion did not modify any parameter. ADMA levels were positively correlated with basal endothelin-1 levels and negatively correlated with insulin-induced incremental levels of NOx and forearm cGMP release. CONCLUSIONS: Plasma ADMA levels are increased in patients with CSX, and they are correlated with increases in endothelin-1 and reductions in insulin-induced increments in plasma NOx and cGMP, effects that are reversed by intravenous L-arginine. These data suggest that increased ADMA levels play a role in the abnormal vascular reactivity that is observed in patients with CSX.