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Background and Aims: A link between increased blood viscosity and type 2 diabetes has been previously reported. Herein, we investigated the association of blood viscosity with prediabetes, identified by glycated hemoglobin A1c (HbA1c) according to the new American Diabetes Association criteria, and subclinical atherosclerosis., Methods and Results: The study cohort includes 1136 non-diabetic adults submitted to anthropometrical evaluation, an oral glucose tolerance test and ultrasound measurement of carotid intima-media thickness (IMT). Whole blood viscosity was estimated using a validated formula based on hematocrit and total plasma proteins. After adjusting for age, and gender, individuals with HbA1c-defined prediabetes (HbA1c 5.7-6.4% [39-47 mmol/mol]) exhibited significantly higher values of hematocrit, and predicted blood viscosity as compared with controls. Increased levels of IMT were observed in subjects with HbA1c-defined prediabetes in comparison to controls. Predicted blood viscosity was positively correlated with age, waist circumference, blood pressure, cholesterol, triglycerides, fibrinogen, white blood cell, HbA1c, fasting and 2-h post-load glucose levels, fasting insulin, IMT and inversely correlated with HDL and Matsuda index of insulin sensitivity. Of the three glycemic parameters, i.e. HbA1c, fasting and 2-h post-load glucose, only HbA1c showed a significant correlation with predicted blood viscosity (β = 0.054, P = 0.04) in a multivariate regression analysis model including multiple atherosclerosis risk factors., Conclusion: The study shows that individuals with HbA1c-defined prediabetes have increased predicted blood viscosity and IMT. The HbA1c criterion may be helpful to capture individuals with an increased risk of diabetes and cardiovascular disease who may benefit from an intensive lifestyle intervention., (Copyright © 2017 The Italian Society of Diabetology, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition, and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.)

Background and Aims: Low insulin-like growth factor-1 (IGF-1) levels and high uric acid concentrations are associated with cardio-metabolic disorders. Acute IGF-1 infusion decreases uric acid concentration in healthy individuals. In this study, we aimed to examine the relationship between IGF-1 and uric acid levels., Methods and Results: 1430 adult non diabetic subjects were stratified into quartiles according to their circulating IGF-1 values. Significant differences in uric acid concentration, measured by the URICASE/POD method were observed between low (quartile 1), intermediate (quartile 2 and 3), and high (quartile 4) IGF-1 levels groups after adjusting for age, gender, and body mass index (P = 0.02). These differences remained significant after adjustment for blood pressure, total cholesterol, high density lipoprotein, triglycerides, fasting and 2 h post-load glucose levels, HOMA-IR index (P = 0.005), liver enzymes (P = 0.03), glucose tolerance status (P = 0.02), growth hormone levels (GH) (P = 0.05), anti-hypertensive treatments (P = 0.04) or diuretics use (P = 0.04)). To clarify the molecular links between IGF-1 and uric acid, we performed an in vitro study, incubating human hepatoma cells with uric acid for 24 or 48 h in the presence of GH and observed a 21% and 26% decrease, respectively, in GH-stimulated IGF-1 mRNA expression (P = 0.02 and P = 0.012, respectively). This effect appears to be mediated by uric acid ability to down regulate GH intracellular signaling; in fact we observed a significant decrease of GH activated JAK2 and Stat5 phosphorylation., Conclusions: These data demonstrate an inverse relationship between IGF-1 and uric acid levels in adults and suggest that uric acid might affect hepatic IGF-1 synthesis., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background and Aims: The A1C diagnostic criterion for identifying individuals at increased risk for diabetes, introduced by the American Diabetes Association in 2010, was not defined on the basis of the principal pathophysiological abnormalities responsible for the development and progression of type 2 diabetes; we therefore wished to gain a deeper insight into the metabolic abnormalities characterizing the group of at risk individuals with an A1C value of 5.7-6.4%., Methods and Results: As many as 338 non-diabetic offspring of type 2 diabetic patients were consecutively recruited. Insulin secretion was assessed using both indexes derived from oral glucose tolerance test (OGTT), and intravenous glucose tolerance test (IVGTT). Insulin sensitivity was measured by hyperinsulinemic euglycemic clamp. As compared with subjects with A1C <5.7%, individuals with A1C of 5.7-6.4% exhibited lower insulin sensitivity after adjusting for age, gender and body mass index (BMI). Insulin secretion estimated from the OGTT, did not differ between the two groups. By contrast, as compared with subjects with A1C <5.7%, the acute insulin response (AIR) during an IVGTT and both IVGTT-derived and OGTT-derived disposition indexes were reduced in individuals with A1C of 5.7-6.4% after adjusting for age, gender and BMI. As A1C increased to ≥ 5.7%, a sharp decrease in insulin sensitivity and β-cell function, measured as disposition index, was observed., Conclusions: Caucasian individuals with A1C ≥ 5.7% exhibit both core pathophysiological defects of type 2 diabetes i.e. insulin resistance and β-cell dysfunction., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Background and Aims: The American Diabetes Association (ADA) has revised criteria for diagnosis of type 2 diabetes recommending an A1C cut point of ≥6.5% in addition to criteria based on glucose levels. We compared A1C, fasting plasma glucose (FPG) or 2-h post-challenge glucose (2-hPG) criteria for the diagnosis of diabetes in a cohort of Italian Caucasians., Methods and Results: A total of 1019 individuals without known diabetes completed an oral glucose tolerance test (OGTT) and had A1C measured. Moderate agreement existed for A1C and FPG criteria for diagnosis of type 2 diabetes (κ coefficient = 0.522), with 85.5% of individuals classified as not having diabetes by both A1C and FPG criteria, and 5.8% classified as having diabetes by both A1C and FPG criteria. Discordant classifications occurred for 5.5% of individuals who had an A1C ≥ 6.5% and FPG <126 mg dl(-1), and for 3.2% who had an A1C <6.5% and FPG ≥126 mg dl(-1). Modest agreement existed for A1C and 2-hPG criteria for diagnosis of type 2 diabetes (κ coefficient = 0.427), with 81.8% of individuals classified as not having diabetes by both A1C and 2-hPG criteria, and 6.0% classified as having diabetes by both A1C and 2-hPG criteria. The area under the receiver operating characteristic curve of A1C for identifying subjects with diabetes according to FPG or 2-hPG criteria was 0.856 and 0.794, respectively. Modest agreement existed for A1C and FPG and/or 2-hPG criteria for diagnosis of type 2 diabetes (κ coefficient = 0.446)., Conclusions: A1C ≥ 6.5% demonstrates a moderate agreement with fasting glucose and 2-hPG for diagnosing diabetes among adult Italian Caucasians subjects., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Background and Aim: Weight gain is associated with a decline in insulin sensitivity and a compensatory increase in insulin secretion. IGF-1 is a plausible candidate to explain these divergent phenomena. In this cross-sectional study, we analyzed the relationship between IGF-1 levels, insulin sensitivity and secretion in 110 nondiabetic subjects with a wide range of BMI to verify this hypothesis., Methods and Results: Subjects underwent OGTT, IVGTT and euglycemic-hyperinsulinemic clamp. HOMA-beta, IVGTT-derived and OGTT-derived indexes for first-phase and second-phase insulin secretion were higher in obese as compared with overweight and normal-weight groups, while glucose disposal was lower. IGF-1 levels were negatively correlated with IVGTT-derived and OGTT-derived indexes first-phase and second-phase insulin secretion, and positively correlated with glucose disposal. These correlations were no longer significant after adjustment for BMI. In a multivariate analysis, the variables associated with glucose disposal were IGF-1, age, triglycerides, and 2-h post-load glucose accounting for 23.4% of its variation. When BMI was entered into the model, the variables associated with glucose disposal were triglycerides, 2-h post-load glucose and BMI accounting for 27.2% of variation. In a multivariate analysis, the only variable associated with IVGTT-derived first-phase and second-phase insulin secretion was IGF-1 accounting for 10.4% and 15.1% of variation, respectively. When BMI was entered into the model, it became the only variable associated with both first-phase and second-phase insulin secretion accounting for 25.7% and 37.6% of variation, respectively., Conclusion: These data suggest that progressive reduction in IGF-1 levels may be involved in obesity-related changes in both insulin sensitivity and secretion.

Background and Aims: We evaluated whether hyperinsulinemia and/or insulin resistance are independently associated with plasma lipids, uric acid and blood pressure in non-diabetic subjects., Methods and Results: A database of non-diabetic Italian subjects has recently been set up using data from hyperinsulinemic euglycemic clamp studies carried out using the standard technique (40 mU per min per square meter of body surface area). In this database we evaluated the relationships between fasting plasma insulin (FPI), glucose metabolized during clamp (M) and plasma levels of triglycerides (TG), high density lipoprotein cholesterol (HDL-C), uric acid (UA) as well as blood pressure (BP) in non-diabetic subjects with fasting plasma glucose <6.1 mmol/l. Parallel analyses were conducted in all subjects in the database (n=1093) and in those with all variables available (n=309). In the univariate analysis both FPI and M were significantly correlated with TG, HDL-C, UA and BP (systolic, diastolic and mean). Multivariate regression analyses including center, sex, age, body mass index (BMI), FPI and M as independent variables showed that: (1) TG and UA were positively correlated with FPI and negatively correlated with M; (2) HDL-C was negatively correlated with FPI and positively correlated with M; and (3) BP was negatively correlated with both FPI and M. Analyses of covariance showed that, after adjusting for center, sex, age and BMI, subjects with isolated hyperinsulinemia or isolated insulin resistance had higher TG and UA and lower HDL-C. Subjects with isolated insulin resistance had also higher BP whereas subjects with isolated hyperinsulinemia had lower BP. Subjects with both defects had a worse profile., Conclusions: Hyperinsulinemia and insulin resistance might contribute with distinct and independent mechanisms to the development of several metabolic and hemodynamic disorders often clustering in the same individual. In particular, hypertriglyceridemia, low HDL-cholesterol and hyperuricemia seem to be related to both hyperinsulinemia and insulin resistance, whereas hypertension seems to be related only to insulin resistance.