Peter D Reaven

Phoenix VA Health Care System, Phoenix, Arizona, United States

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Publications (113)789.47 Total impact

  • Aramesh Saremi · Gideon D Bahn · Peter D Reaven
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    ABSTRACT: Objective: To determine whether a link exists between serious hypoglycemia and progression of atherosclerosis in a substudy of the Veterans Affairs Diabetes Trial (VADT) and to examine whether glycemic control during the VADT modified the association between serious hypoglycemia and coronary artery calcium (CAC) progression. Research design and methods: Serious hypoglycemia was defined as severe episodes with loss of consciousness or requiring assistance or documented glucose <50 mg/dL. Progression of CAC was determined in 197 participants with baseline and follow-up computed tomography scans. Results: During an average follow-up of 4.5 years between scans, 97 participants reported severe hypoglycemia (n = 23) or glucose <50 mg/dL (n = 74). Serious hypoglycemia occurred more frequently in the intensive therapy group than in the standard treatment group (74% vs. 21%, P < 0.01). Serious hypoglycemia was not associated with progression of CAC in the entire cohort, but the interaction between serious hypoglycemia and treatment was significant (P < 0.01). Participants with serious hypoglycemia in the standard therapy group, but not in the intensive therapy group, had ∼50% greater progression of CAC than those without serious hypoglycemia (median 11.15 vs. 5.4 mm(3), P = 0.02). Adjustment for all baseline differences, including CAC, or time varying risk factors during the trial, did not change the results. Examining the effect of serious hypoglycemia by on-trial HbA1c levels (cutoff 7.5%) yielded similar results. In addition, a dose-response relationship was found between serious hypoglycemia and CAC progression in the standard therapy group only. Conclusions: Despite a higher frequency of serious hypoglycemia in the intensive therapy group, serious hypoglycemia was associated with progression of CAC in only the standard therapy group.
    No preview · Article · Jan 2016 · Diabetes care
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    ABSTRACT: Introduction: Apolipoprotein C-III (apoC-III) regulates triglyceride (TG) metabolism. In plasma, apoC-III exists in non-sialylated (apoC-III0a without glycosylation and apoC-III0b with glycosylation), monosialylated (apoC-III1) or disialylated (apoC-III2) proteoforms. Our aim was to clarify the relationship between apoC-III sialylation proteoforms with fasting plasma TG concentrations. Methods: In 204 non-diabetic adolescent participants, the relative abundance of apoC-III plasma proteoforms was measured using mass spectrometric immunoassay. Results: Compared with the healthy weight subgroup (n = 16), the ratios of apoC-III0a, apoC-III0b, and apoC-III1 to apoC-III2 were significantly greater in overweight (n = 33) and obese participants (n = 155). These ratios were positively correlated with BMI z-scores and negatively correlated with measures of insulin sensitivity (Si). The relationship of apoC-III1 / apoC-III2 with Si persisted after adjusting for BMI (p = 0.02). Fasting TG was correlated with the ratio of apoC-III0a / apoC-III2 (r = 0.47, p<0.001), apoC-III0b / apoC-III2 (r = 0.41, p<0.001), apoC-III1 / apoC-III2 (r = 0.43, p<0.001). By examining apoC-III concentrations, the association of apoC-III proteoforms with TG was driven by apoC-III0a (r = 0.57, p<0.001), apoC-III0b (r = 0.56. p<0.001) and apoC-III1 (r = 0.67, p<0.001), but not apoC-III2 (r = 0.006, p = 0.9) concentrations, indicating that apoC-III relationship with plasma TG differed in apoC-III2 compared with the other proteoforms. Conclusion: We conclude that apoC-III0a, apoC-III0b, and apoC-III1, but not apoC- III2 appear to be under metabolic control and associate with fasting plasma TG. Measurement of apoC-III proteoforms can offer insights into the biology of TG metabolism in obesity.
    Full-text · Article · Dec 2015 · PLoS ONE
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    Rodney A Hayward · Peter D Reaven · Nicholas V Emanuele

    Preview · Article · Sep 2015 · New England Journal of Medicine
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    ABSTRACT: The Veterans Affairs Diabetes Trial previously showed that intensive glucose lowering, as compared with standard therapy, did not significantly reduce the rate of major cardiovascular events among 1791 military veterans (median follow-up, 5.6 years). We report the extended follow-up of the study participants. After the conclusion of the clinical trial, we followed participants, using central databases to identify procedures, hospitalizations, and deaths (complete cohort, with follow-up data for 92.4% of participants). Most participants agreed to additional data collection by means of annual surveys and periodic chart reviews (survey cohort, with 77.7% follow-up). The primary outcome was the time to the first major cardiovascular event (heart attack, stroke, new or worsening congestive heart failure, amputation for ischemic gangrene, or cardiovascular-related death). Secondary outcomes were cardiovascular mortality and all-cause mortality. The difference in glycated hemoglobin levels between the intensive-therapy group and the standard-therapy group averaged 1.5 percentage points during the trial (median level, 6.9% vs. 8.4%) and declined to 0.2 to 0.3 percentage points by 3 years after the trial ended. Over a median follow-up of 9.8 years, the intensive-therapy group had a significantly lower risk of the primary outcome than did the standard-therapy group (hazard ratio, 0.83; 95% confidence interval [CI], 0.70 to 0.99; P=0.04), with an absolute reduction in risk of 8.6 major cardiovascular events per 1000 person-years, but did not have reduced cardiovascular mortality (hazard ratio, 0.88; 95% CI, 0.64 to 1.20; P=0.42). No reduction in total mortality was evident (hazard ratio in the intensive-therapy group, 1.05; 95% CI, 0.89 to 1.25; P=0.54; median follow-up, 11.8 years). After nearly 10 years of follow-up, patients with type 2 diabetes who had been randomly assigned to intensive glucose control for 5.6 years had 8.6 fewer major cardiovascular events per 1000 person-years than those assigned to standard therapy, but no improvement was seen in the rate of overall survival. (Funded by the VA Cooperative Studies Program and others; VADT number, NCT00032487.).
    No preview · Article · Jun 2015 · New England Journal of Medicine
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    ABSTRACT: Rosiglitazone may be associated with increased risk of cardiovascular (CV) disease in patients with type 2 diabetes (T2D). We evaluated the relationship between patterns of rosiglitazone use and CV outcomes in the Veterans Affairs Diabetes Trial (VADT). Time-dependent survival analyses, case-control and 1:1 propensity matching approaches were used to examine this relationship in the VADT, a randomized controlled study that assessed the effect of intensive glycemic control on CV outcomes in 1791 T2D patients (mean age of 60.4 ± 9 years). Participants were recruited from December 1, 2000, through May 31, 2003, and were followed for 5 to 7.5 years (median 5.6) with the final visit by May 31, 2008. Rosiglitazone (4 mg and 8 mg daily) was initiated per protocol in both intensive-therapy and standard-therapy groups. Main outcomes include a composite CV outcome, CV death, and myocardial infarction (MI). Both daily doses of rosiglitazone were associated with lower risk for the primary composite CV outcome (HR 0.63; 95% CI 0.49-0.81 and HR 0.60; 95% CI 0.49-0.75, respectively) after adjusting for demographic and clinical covariates. A reduction of CV death was also observed (HR 0.25, p < 0.001, for both 4 and 8 mg/day rosiglitazone), however the effect on MI was less evident for 8 mg/day and not significant for 4 mg/day. In older patients with T2D the use of rosiglitazone was associated with decreased risk of the primary CV composite outcome and CV death. Rosiglitazone use did not lead to higher risk of MI. This article is protected by copyright. All rights reserved.
    No preview · Article · May 2015 · Diabetes Obesity and Metabolism
  • Juraj Koska · Michelle Sands · Camelia Burciu · Peter Reaven
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    ABSTRACT: Cardiovascular (CV) disease is the leading cause of mortality and morbidity in patients with type 2 diabetes mellitus (T2DM). However, improving glycaemic control alone has not decreased CV events. Therapies that improve glycaemic control, CV disease risk factors and CV function are more likely to be successful. Dipeptidyl peptidase-4 (DPP-4) inhibitors prevent breakdown of incretin hormones glucagon-like peptide-1(GLP-1) and glucose-dependent insulinotropic peptide and improve glycaemic control in patients with T2DM. DPP-4 acts on other substrates, many associated with cardioprotection. Thus, inhibition of DPP-4 may lead to elevations in these potentially beneficial substrates. Data from animal studies and small observational studies in humans suggest that DPP-4 inhibitors may potentially reduce CV risk. However, recently completed CV outcome trials in patients with T2DM and CV disease or at high risk of adverse CV events have shown that the DPP-4 inhibitors saxagliptin and alogliptin neither increased nor decreased major adverse CV events. © The Author(s) 2015.
    No preview · Article · May 2015 · Diabetes & Vascular Disease Research
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    ABSTRACT: GLP-1 receptor (GLP-1R) agonists may improve endothelial function (EF) via metabolic improvement and direct vascular action. The present study determined the effect of GLP-1R agonist exenatide on postprandial EF in type 2 diabetes and the mechanisms underlying GLP-1R agonists-mediated vasodilation.Two crossover studies were conducted: 36 participants with type 2 diabetes received subcutaneous exenatide or placebo for 11 days and EF, glucose and lipid responses to breakfast and lunch were determined; 32 participants with impaired glucose tolerance (IGT) or diet-controlled type 2 diabetes had EF measured before and after intravenous exenatide, with or without the GLP-1R antagonist exendin-9. Mechanisms of GLP-1R agonist action were studied ex vivo on human subcutaneous adipose tissue arterioles and endothelial cells.Subcutaneous exenatide increased postprandial EF independent of reductions in plasma glucose and triglycerides. Intravenous exenatide increased fasting EF and exendin-9 abolished this effect. Ex vivo, exenatide elicited a dose-dependent vasorelaxation and reduced high-glucose or lipid-induced endothelial dysfunction in arterioles, and eNOS activation and NO production in endothelial cells. These effects were reduced with AMP-kinase inhibition.Exenatide augmented postprandial EF in subjects with diabetes and prevented high-glucose and lipid-induced endothelial dysfunction in human arterioles. These effects were largely direct, via GLP-1R and AMP-kinase activation. © 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.
    No preview · Article · Feb 2015 · Diabetes
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    ABSTRACT: Using mass spectrometric immunoassay, the abundance of SAA truncations relative to the native variants was examined in plasma of 91 participants with type 2 diabetes and chronic kidney disease and 69 participants without diabetes. The ratio of SAA 1.1 (missing N-terminal arginine) to native SAA 1.1 was lower in diabetics compared to non-diabetics (p = 0.004), and in males compared to females (p<0.001). This ratio was negatively correlated with glycated hemoglobin (r = -0.32, p<0.001) and triglyceride concentrations (r = -0.37, p<0.001), and positively correlated with HDL cholesterol concentrations (r = 0.32, p<0.001). The relative abundance of the N-terminal arginine truncation of SAA1.1 is significantly decreased in diabetes and negatively correlates with measures of glycemic and lipid control.
    Full-text · Article · Jan 2015 · PLoS ONE
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    ABSTRACT: Objective: The objective was to test the clinical utility of Quantose M(Q) to monitor changes in insulin sensitivity after pioglitazone therapy in prediabetic subjects. Quantose M(Q) is derived from fasting measurements of insulin, α-hydroxybutyrate, linoleoyl-glycerophosphocholine, and oleate, three nonglucose metabolites shown to correlate with insulin-stimulated glucose disposal. Research design and methods: Participants were 428 of the total of 602 ACT NOW impaired glucose tolerance (IGT) subjects randomized to pioglitazone (45 mg/d) or placebo and followed for 2.4 years. At baseline and study end, fasting plasma metabolites required for determination of Quantose, glycated hemoglobin, and oral glucose tolerance test with frequent plasma insulin and glucose measurements to calculate the Matsuda index of insulin sensitivity were obtained. Results: Pioglitazone treatment lowered IGT conversion to diabetes (hazard ratio = 0.25; 95% confidence interval = 0.13-0.50; P < .0001). Although glycated hemoglobin did not track with insulin sensitivity, Quantose M(Q) increased in pioglitazone-treated subjects (by 1.45 [3.45] mg·min(-1)·kgwbm(-1)) (median [interquartile range]) (P < .001 vs placebo), as did the Matsuda index (by 3.05 [4.77] units; P < .0001). Quantose M(Q) correlated with the Matsuda index at baseline and change in the Matsuda index from baseline (rho, 0.85 and 0.79, respectively; P < .0001) and was progressively higher across closeout glucose tolerance status (diabetes, IGT, normal glucose tolerance). In logistic models including only anthropometric and fasting measurements, Quantose M(Q) outperformed both Matsuda and fasting insulin in predicting incident diabetes. Conclusions: In IGT subjects, Quantose M(Q) parallels changes in insulin sensitivity and glucose tolerance with pioglitazone therapy. Due to its strong correlation with improved insulin sensitivity and its ease of use, Quantose M(Q) may serve as a useful clinical test to identify and monitor therapy in insulin-resistant patients.
    No preview · Article · Jan 2015 · Journal of Clinical Endocrinology & Metabolism
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    ABSTRACT: The chemokine RANTES plays a key role in inflammation, cell recruitment and T cell activation. RANTES is heterogenic and exists as multiple variants in vivo. Herein we describe the development and characterization of a fully quantitative mass spectrometric immunoassay (MSIA) for analysis of intact RANTES and its proteoforms in human serum and plasma samples. The assay exhibits linearity over a wide concentration range (1.56 - 200ng/mL), intra- and inter-assay precision with CVs <10%, and good linearity and recovery correlations. The assay was tested in different biological matrices, and it was benchmarked against an existing RANTES ELISA. The new RANTES MSIA was used to analyze RANTES and its proteoforms in a small clinical cohort, revealing the quantitative distribution and frequency of the native and truncated RANTES proteoforms. In the last two decades, RANTES has been studied extensively due to its association with numerous clinical conditions, including kidney-related, autoimmune, cardiovascular, viral and metabolic pathologies. Although a single gene product, RANTES is expressed in a range of cells and tissues presenting with different endogenously produced variants and PTMs. The structural variety and population diversity that has been identified for RANTES necessitate developing advanced methodologies that can provide insight into the protein heterogeneity and its function and regulation in disease. In this work we present a simple, efficient and high-throughput mass spectrometric immunoassay (MSIA) method for analysis of RANTES proteoforms. RANTES MSIA can detect and analyze RANTES proteoforms and provide an insight into the endogenous protein modifications. Copyright © 2014. Published by Elsevier B.V.
    No preview · Article · Dec 2014 · Journal of Proteomics
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    ABSTRACT: The oxidative modification of apolipoprotein A-I’s methionine148 (M148) is associated with defective HDL function in vitro. Multiple reaction monitoring (MRM) is a mass spectrometric technique that can be used to quantitate post-translational modifications. In this study, we developed an MRM assay to monitor the abundance ratio of the peptide containing oxidized M148 to the native peptide in ApoA-I. Measurement of the oxidized-to-unoxidized-M148 ratio was reproducible (CV < 5%). The extent of methionine M148 oxidation in the HDL of healthy controls, and type 2 diabetic participants with and without prior cardiovascular events (CVD) were then examined. The results suggest a significant increase in the relative ratio of the peptide containing oxidized M148 to the unmodified peptide in the HDL of participants with diabetes and CVD (p < 0.001), compared to participants without CVD. Monitoring the abundance ratio of the peptides containing oxidized and unoxidized M148 by MRM provides a means of examining the relationship between M148 oxidation and vascular complications in CVD.
    Full-text · Article · Dec 2014 · Translational Proteomics
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    ABSTRACT: Objective To examine the effect of intensive glycemic control on cardiovascular disease events (CVD) among the major race/ethnic groups in a post-hoc analysis of the VADT. Materials and Methods Participants included 1111 non-Hispanic Whites, 307 Hispanics and 306 non-Hispanic Blacks randomized to intensive or standard glucose treatment in VADT. Multivariable Cox proportional hazards models were constructed to assess the effect of intensive glucose treatment on CVD events among race/ethnic groups. Results Mean age was 60.4 years and median follow-up was 5.6 years. By design, modifiable risk factors were managed equally well in both treatment arms and only differed modestly between race/ethnic groups. HbA1c decreased significantly from baseline with intensive glucose treatment in each race/ethnic group, with a trend for a greater response in Hispanics (P = 0.01 for overall comparison between groups). Intensive glucose treatment was associated with reduced risk of CVD events for Hispanics but not for others (hazard ratios ranged from 0.54 to 0.75 for Hispanics whereas they were consistently close to 1 for others). Sensitivity analyses with different definitions of race/ethnicity or limited to individuals free of previous known CVD yielded similar results. Conclusions The results of these analyses support the hypothesis that race/ethnicity is worthy of consideration when tailoring intensive treatment for individuals with long-standing type 2 diabetes. However, additional studies are needed to confirm the findings of this post-hoc analysis.
    Full-text · Article · Oct 2014 · Metabolism
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    James Deer · Juraj Koska · Marlies Ozias · Peter Reaven
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    ABSTRACT: Insulin resistance is a significant factor in the development of type 2 diabetes mellitus, however the connection between the Western diet and the development of insulin resistance has not been fully explained. Dietary macronutrient composition has been examined in a number of articles, and diets enriched in saturated fatty acids, and possibly in fructose, appear to be most consistently associated with the development of insulin resistance. However, mechanistic insights into the metabolic effects of such diets are lacking, and merit further study.
    Full-text · Article · Sep 2014 · Metabolism
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    ABSTRACT: Background: Evidence point to vascular dysfunction and hypoperfusion as early abnormalities in Alzheimer's disease (AD); probing their mechanistic bases can lead to new therapeutic approaches. We tested the hypotheses that β-amyloid peptide induces endothelial dysfunction and oxidative stress in human microvasculature and that response will be similar between peripheral adipose and brain leptomeningeal arterioles. New method: Abdominal subcutaneous arterioles from living human subjects ( n= 17) and cadaver leptomeningeal arterioles ( n= 6) from rapid autopsy were exposed to Aβ1-42 (Aβ) for 1-h and dilation response to acetylcholine/papaverine were measured and compared to baseline response. Adipose arteriole reactive oxygen species (ROS) production and nitrotyrosine content were measured. Comparison with existing methods: Methods described allow direct investigation of human microvessel functional response that cannot be replicated by human noninvasive imaging or post-mortem histology. Results: Adipose arterioles exposed to 2. μM Aβ showed impaired dilation to acetylcholine that was reversed by antioxidant polyethylene glycol superoxide dismutase (PEG-SOD) (Aβ-60.9. ±. 6%, control-93.2. ±. 1.8%, Aβ+PEGSOD-84.7. ±. 3.9%, both p<. 0.05 vs. Aβ). Aβ caused reduced dilation to papaverine. Aβ increased adipose arteriole ROS production and increased arteriole nitrotyrosine content. Leptomeningeal arterioles showed similar impaired response to acetylcholine when exposed to Aβ (43.0. ±. 6.2% versus 81.1. ±. 5.7% control, p<. 0.05). Conclusion: Aβ exposure induced adipose arteriole endothelial and non-endothelial dysfunction and oxidative stress that were reversed by antioxidant treatment. Aβ-induced endothelial dysfunction was similar between peripheral adipose and leptomeningeal arterioles. Ex vivo living adipose and cadaver leptomeningeal arterioles are viable, novel and practical human tissue models to study Alzheimer's vascular pathophysiology.
    No preview · Article · Jul 2014 · Journal of Neuroscience Methods
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    ABSTRACT: Rationale: The mechanisms underlying lipotoxic/diabetic cardiomyopathy remain poorly understood. Saturated fatty acid (SFA) levels, elevated in obesity and type 2 diabetes, induce apoptosis in many cell types including cardiomyocytes. Signaling pathways, including the p38α mitogen-activated kinase (MAPK)-dependent pathway, have been implicated in apoptosis due to a diverse range of insults. Objective: We tested the hypothesis that SFA-induced cardiomyocyte apoptosis is dependent on p38α activation. Methods and results: Human adult ventricular cardiomyocytes (AC16 cells) were exposed to high physiological levels of palmitate (PA), a SFA. The apoptotic response was measured using annexin-V by flow cytometry, and the p38α-dependent pathway was evaluated using a p38 inhibitor PD169316, and by p38α small interfering RNA (siRNA) knockdown. PA exposure for 16 h dose-dependently increased apoptosis in AC16 cardiomyocytes (control: 2.6±0.6%, 150 μM PA: 3.5±0.9%, 300 μM PA: 11.5±1.6%, n=4, p<0.01). PA did not change total p38α protein levels, but increased p38α phosphorylation dose-dependently (n=5, p<0.01). PD169316 tended to reduce PA-induced apoptosis (n=4, p=0.05). Specific p38α siRNA markedly reduced the expression of p38α but not p38β (n=3, p<0.0001), and dose-dependently attenuated PA-induced apoptosis (control siRNA: 7.7±1.0%, 300 μM PA: 34.4±5.0%, 300 μM PA+30 pmol siRNA: 23.7±4.4%, 300 μM PA+60 pmol siRNA: 19.7±2.6%, 300 μM PA+120 pmol siRNA: 17.3±2.8%, n=4, p<0.0001). Conclusions: These results demonstrate that PA induces p38α activation, and reducing p38α expression attenuates PA-induced cardiomyocyte apoptosis. Our results support a potential mechanism by which high plasma SFA levels through p38α activation may lead to the development of lipotoxic/diabetic cardiomyopathy.
    Full-text · Article · Jun 2014 · Biochemical and Biophysical Research Communications
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    ABSTRACT: Objective Our objective was to examine the role of hypertriglyceridemia on the capacity of HDL to facilitate ABCA-1 mediated cholesterol efflux in type 2 diabetes (T2DM). Methods HDL mediated cholesterol efflux through the ABCA-1 transporter was measured using BHK cell lines in samples of 71 participants with T2DM in presence or absence of high triglyceride levels (TG). Additionally, HDL mediated efflux was measured in 13 diabetic and non-diabetic participants fasting and four hours after a high-fat test challenge. Results HDL mediated cholesterol efflux function was increased in participants with T2DM with hypertriglyceridemia when compared to participants with T2DM without hypertriglyceridemia (efflux ratio mean ± standard deviation (SD), T2DM + TG: 1.17 ± 0.25 vs. T2DM – TG: 1.03 ± 0.19, p = 0.0098). In the fat challenge study, we observed a significant increase in ABCA-1 mediated cholesterol efflux capacity following an ingestion of high-fat test meal by participants in both groups of T2DM (n = 6, efflux ratio, mean ± SD, pre: 0.86 ± 0.4 vs. post: 1.34 ± 0.6, p = 0.01) and non-diabetic participants (n = 7, efflux ratio mean ± SD pre : 1.24 ± 0.31 vs. post: 1.39 ± 0.42, p = 0.04) that was partly explained by the difference in CETP activity (r = 0.6, p = 0.03). Conclusion Our study suggests that high triglyceride levels facilitate ABCA-1 mediated efflux function of HDL in part by activating CETP.
    No preview · Article · May 2014 · Metabolism: clinical and experimental
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    ABSTRACT: OBJECTIVE Plasma adiponectin levels are reduced in type 2 diabetes mellitus (T2DM) and other insulin-resistant states. We examined whether plasma adiponectin levels at baseline and after pioglitazone treatment in impaired glucose tolerance (IGT) subjects were associated with improved insulin sensitivity (SI) and glucose tolerance status.RESEARCH DESIGN AND METHODSA total of 602 high-risk IGT subjects in ACT NOW were randomized to receive pioglitazone or placebo with a median follow-up of 2.4 years.RESULTSPioglitazone reduced IGT conversion to diabetes by 72% in association with improved β-cell function by 64% (insulin secretion/insulin resistance index) and increased tissue sensitivity by 88% (Matsuda index). In pioglitazone-treated subjects, plasma adiponectin concentration increased threefold from 13 ± 0.5 to 38 ± 2.5 μg/mL (P < 0.001) and was strongly correlated with the improvement in SI (r = 0.436, P < 0.001) and modestly correlated with glucose area under the curve during oral glucose tolerance test (r = 0.238, P < 0.005) and insulin secretion/insulin resistance index (r = 0.306, P < 0.005). The increase in adiponectin was a strong predictor of reversion to normal glucose tolerance and prevention of T2DM. In the placebo group, plasma adiponectin did not change and was not correlated with changes in glucose levels. There was an inverse association between baseline plasma adiponectin concentration and progression to diabetes in the placebo group but not in the pioglitazone group.CONCLUSIONS Baseline adiponectin does not predict the response to pioglitazone. The increase in plasma adiponectin concentration after pioglitazone therapy in IGT subjects is strongly related to improved glucose tolerance status and enhanced tissue sensitivity to insulin.
    Preview · Article · Apr 2014 · Diabetes care

  • No preview · Article · Apr 2014 · The FASEB Journal
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    ABSTRACT: Insulin-like growth factor 1 (IGF1) is an important biomarker for the management of growth hormone disorders. Recently there has been rising interest in deploying mass spectrometric (MS) methods of detection for measuring IGF1. However, widespread clinical adoption of any MS-based IGF1 assay will require increased throughput and speed to justify the costs of analyses, and robust industrial platforms that are reproducible across laboratories. Presented here is an MS-based quantitative IGF1 assay with performance rating of >1,000 samples/day, and a capability of quantifying IGF1 point mutations and posttranslational modifications. The throughput of the IGF1 mass spectrometric immunoassay (MSIA) benefited from a simplified sample preparation step, IGF1 immunocapture in a tip format, and high-throughput MALDI-TOF MS analysis. The Limit of Detection and Limit of Quantification of the resulting assay were 1.5 μg/L and 5 μg/L, respectively, with intra- and inter-assay precision CVs of less than 10%, and good linearity and recovery characteristics. The IGF1 MSIA was benchmarked against commercially available IGF1 ELISA via Bland-Altman method comparison test, resulting in a slight positive bias of 16%. The IGF1 MSIA was employed in an optimized parallel workflow utilizing two pipetting robots and MALDI-TOF-MS instruments synced into one-hour phases of sample preparation, extraction and MSIA pipette tip elution, MS data collection, and data processing. Using this workflow, high-throughput IGF1 quantification of 1,054 human samples was achieved in approximately 9 hours. This rate of assaying is a significant improvement over existing MS-based IGF1 assays, and is on par with that of the enzyme-based immunoassays. Furthermore, a mutation was detected in ∼1% of the samples (SNP: rs17884626, creating an A→T substitution at position 67 of the IGF1), demonstrating the capability of IGF1 MSIA to detect point mutations and posttranslational modifications.
    Full-text · Article · Mar 2014 · PLoS ONE
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    ABSTRACT: The aim of this study was to test the hypothesis that intensive glycaemic control (INT) and higher plasma C-peptide levels in patients with poorly controlled diabetes would be associated with better eye outcomes. The incidence and progression of diabetic retinopathy (DR) was assessed by grading seven-field stereoscopic fundus photographs at baseline and 5 years later in 858 of 1,791 participants in the Veterans Affairs Diabetes Trial (VADT). After adjustment for all covariates, risk of progression (but not incidence) of DR increased by 30% for each 1% increase in baseline HbA1c (OR 1.3; 95% CI 1.123, 1.503; p = 0.0004). Neither assignment to INT nor age was independently associated with DR in the entire cohort. However, INT showed a biphasic interaction with age. The incidence of DR was decreased in INT participants ≤55 years of age (OR 0.49; 95% CI 0.24, 1.0) but increased in those ≥70 years old (OR 2.88; 95% CI 1.0, 8.24) (p = 0.0043). The incidence of DR was reduced by 67.2% with each 1 pmol/ml increment in baseline C-peptide (OR 0.328; 95% CI 0.155, 0.7; p = 0.0037). Baseline C-peptide was also an independent inverse risk factor for the progression of DR, with a reduction of 47% with each 1 pmol/ml increase in C-peptide (OR 0.53; 95% CI 0.305, 0.921; p = 0.0244). Poor glucose control at baseline was associated with an increased risk of progression of DR. INT was associated with a decreased incidence of DR in younger patients but with an increased risk of DR in older patients. Higher C-peptide at baseline was associated with reduced incidence and progression of DR.
    No preview · Article · Mar 2014 · Diabetologia

Publication Stats

8k Citations
789.47 Total Impact Points


  • 2008-2015
    • Phoenix VA Health Care System
      Phoenix, Arizona, United States
  • 2010-2014
    • The University of Arizona
      Tucson, Arizona, United States
  • 2013
    • University of Texas Health Science Center at San Antonio
      San Antonio, Texas, United States
  • 2012
    • Good Samaritan Hospital
      Cincinnati, Ohio, United States
  • 2009-2011
    • Arizona State University
      Tempe, Arizona, United States
  • 2006-2007
    • United States Department of Veterans Affairs
      Бедфорд, Massachusetts, United States
  • 2004-2006
    • Stanford University
      • Department of Medicine
      Palo Alto, California, United States
    • U.S. Department of Veterans Affairs
      Washington, Washington, D.C., United States
  • 2002
    • University of Southern California
      • School of Pharmacy
      Los Angeles, California, United States
  • 1991-2002
    • University of California, San Diego
      • • Division of Endocrinology & Metabolism
      • • Department of Medicine
      San Diego, California, United States