Darrell V. Pavitt

Effects of Xanthine Oxidase Inhibition With Allopurinol on Endothelial Function and Peripheral Blood Flow in Hyperuricemic Patients With Chronic Heart Failure: Results From 2 Placebo-Controlled Studies

Background—In patients with chronic heart failure (CHF), hyperuricemia is a common finding and is associated with reduced vasodilator capacity and impaired peripheral blood flow. It has been suggested that the causal link of this association is increased xanthine oxidase (XO)–derived oxygen free radical production and endothelial dysfunction. We therefore studied the effects of XO inhibition with allopurinol on endothelial function and peripheral blood flow in CHF patients after intra-arterial infusion and after oral administration in 2 independent placebo-controlled studies. Methods and Results—In 10 CHF patients with normal serum uric acid (UA) levels (315±42 &mgr;mol/L) and 9 patients with elevated UA (535±54 &mgr;mol/L), endothelium-dependent (acetylcholine infusion) and endothelium-independent (nitroglycerin infusion) vasodilation of the radial artery was determined. Coinfusion of allopurinol (600 &mgr;g/min) improved endothelium-dependent but not endothelium-independent vasodilation in hyperuricemic patients (P <0.05). In a double-blind, crossover design, hyperuricemic CHF patients were randomly allocated to allopurinol 300 mg/d or placebo for 1 week. In 14 patients (UA 558±21 &mgr;mol/L, range 455 to 743 &mgr;mol/L), treatment reduced UA by >120 &mgr;mol/L in all patients (mean reduction 217±15 &mgr;mol/L, P <0.0001). Compared with placebo, allopurinol improved peak blood flow (venous occlusion plethysmography) in arms (+24%, P =0.027) and legs (+23%, P =0.029). Flow-dependent flow improved by 58% in arms (P =0.011). Allantoin, a marker of oxygen free radical generation, decreased by 20% after allopurinol treatment (P <0.001). There was a direct relation between change of UA and improvement of flow-dependent flow after allopurinol treatment (r =0.63, P <0.05). Conclusions—In hyperuricemic CHF patients, XO inhibition with allopurinol improves peripheral vasodilator capacity and blood flow both locally and systemically.

Type 2 Diabetes Is Associated with Reduced ATP-Binding Cassette Transporter A1 Gene Expression, Protein and Function

Objective Increasing plasma glucose levels are associated with increasing risk of vascular disease. We tested the hypothesis that there is a glycaemia-mediated impairment of reverse cholesterol transport (RCT). We studied the influence of plasma glucose on expression and function of a key mediator in RCT, the ATP binding cassette transporter-A1 (ABCA1) and expression of its regulators, liver X receptor-α (LXRα) and peroxisome proliferator-activated receptor–γ (PPARγ). Methods and Results Leukocyte ABCA1, LXRα and PPARγ expression was measured by polymerase chain reaction in 63 men with varying degrees of glucose homeostasis. ABCA1 protein concentrations were measured in leukocytes. In a sub-group of 25 men, ABCA1 function was quantified as apolipoprotein-A1-mediated cholesterol efflux from 2–3 week cultured skin fibroblasts. Leukocyte ABCA1 expression correlated negatively with circulating HbA1c and glucose (rho = −0.41, p<0.001; rho = −0.34, p = 0.006 respectively) and was reduced in Type 2 diabetes (T2DM) (p = 0.03). Leukocyte ABCA1 protein was lower in T2DM (p = 0.03) and positively associated with plasma HDL cholesterol (HDL-C) (rho = 0.34, p = 0.02). Apolipoprotein-A1-mediated cholesterol efflux correlated negatively with fasting glucose (rho = −0.50, p = 0.01) and positively with HDL-C (rho = 0.41, p = 0.02). It was reduced in T2DM compared with controls (p = 0.04). These relationships were independent of LXRα and PPARγ expression. Conclusions ABCA1 expression and protein concentrations in leukocytes, as well as function in cultured skin fibroblasts, are reduced in T2DM. ABCA1 protein concentration and function are associated with HDL-C levels. These findings indicate a glycaemia- related, persistent disruption of a key component of RCT.

Assay of serum allantoin in humans by gas chromatography-mass spectrometry.

BACKGROUND The small amount of allantoin present in human serum results from free radical (FR) action on urate and may provide a stable marker of free radical activity in vivo. We describe a gas chromatography-mass spectrometry (GC-MS) assay for serum allantoin and report a reference range in healthy individuals. METHODS Fasting blood samples were obtained from 134 healthy middle-aged volunteers (56 men, mean age 55, range 45-72; 78 women, mean age 55, range 50-72) Allantoin was assayed using 15N(2) allantoin as an internal standard. After isolation from aqueous standards or serum by extraction onto an anion exchange column (AG-MP1), allantoin was derivatised with N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA). Derivatives were injected onto an HP-1 column and analysed using a Mass Selective Detector with Single Ion Monitoring at 398 and 400 m/z. RESULTS The distribution of serum allantoin concentrations in men and women was non-Gaussian and log transformation was used for the analysis of data. Women (10.8 +/- 1.7 micromol/l (mean +/- S.D.)) had significantly lower serum allantoin levels than men (13.4 +/- 1.6 micromol/l, p=0.015). Reference ranges (95% CI) for middle-aged healthy subjects were 7.4-46.8 micromol/l (men) and 3.7-31.2 micromol/l (women). CONCLUSION Gas chromatography-mass spectrometry provides a reliable and accurate method for the determination of serum allantoin.

Lipoprotein separation in a novel iodixanol density gradient, for composition, density, and phenotype analysis

Separation of lipoproteins by traditional sequential salt density floatation is a prolonged process (∼72 h) with variable recovery, whereas iodixanol-based, self-generating density gradients provide a rapid (∼4 h) alternative. A novel, three-layered iodixanol gradient was evaluated for its ability to separate lipoprotein fractions in 63 subjects with varying degrees of dyslipidemia. Lipoprotein cholesterol, triglycerides, and apolipoproteins were measured in 21 successive iodixanol density fractions. Iodixanol fractionation was compared with sequential floatation ultracentrifugation. Iodixanol gradient formation showed a coefficient of variation of 0.29% and total lipid recovery from the gradient of 95.4% for cholesterol and 84.7% for triglyceride. Recoveries for VLDL-, LDL-, and HDL-cholesterol, triglycerides, and apolipoproteins were approximately 10% higher with iodixanol compared with sequential floatation. The iodixanol gradient effectively discriminated classic lipoproteins and their subfractions, and there was evidence for improved resolution of lipoproteins with the iodixanol gradient. LDL particles subfractionated by the gradient showed good correlation between density and particle size with small, dense LDL (<25.5 nm) separated in fractions with density >1.028 g/dl. The new iodixanol density gradient enabled rapid separation with improved resolution and recovery of all lipoproteins and their subfractions, providing important information with regard to LDL phenotype from a single centrifugation step with minimal in-vitro modification of lipoproteins.

Intrahepatic Insulin Exposure, Intrahepatocellular Lipid and Regional Body Fat in Nonalcoholic Fatty Liver Disease

CONTEXT Insulin is pivotal in regulating hepatic lipid synthesis, metabolism, and export. OBJECTIVE We tested the hypothesis that intrahepatic insulin exposure is an important determinant of intrahepatocellular lipid (IHCL), taking into account regional adiposity and both glucoregulatory and antilipolytic insulin sensitivity. RESEARCH DESIGN AND METHODS We compared 21 European males with known nonalcoholic fatty liver disease (NAFLD) with 19 healthy male controls. Insulin sensitivity, secretion, and percentage hepatic extraction were derived from iv glucose tolerance test (IVGTT) glucose, insulin, and C-peptide concentrations. Intrahepatic insulin exposure was calculated as percentage hepatic insulin extraction multiplied by basal or IVGTT insulin secretion. IHCL was quantified by proton magnetic resonance spectroscopy. Total and regional adipose tissue was measured using whole body magnetic resonance imaging. RESULTS Percentage hepatic extraction of newly secreted insulin differed between cases with NAFLD and controls at borderline significance (median, 76 vs. 83%; P = 0.07). Cases had higher intrahepatic insulin exposure than controls, both in the basal (34 vs. 18 pmol; P = 0.0002) and glucose-stimulated states (58 vs. 24 pmol; P = 0.01). IHCL was significantly related to both basal (r(s) = 0.62; P < 0.0001) and IVGTT intrahepatic insulin exposure (r(s) = 0.47; P = 0.002). As predictors of IHCL, both basal and IVGTT intrahepatic insulin exposure were dependent on the waist-to-hip ratio and homeostasis model assessment insulin resistance, but not on magnetic resonance imaging fat measures or IVGTT insulin sensitivity. CONCLUSIONS Men with NAFLD have higher intrahepatic insulin exposure than controls. This correlates with IHCL, but the principal determinants of IHCL were fat distribution and hepatic rather than peripheral insulin resistance.

Feasibility Study of a Bio-inspired Artificial Pancreas in Adults with Type 1 Diabetes

BACKGROUND This study assesses proof of concept and safety of a novel bio-inspired artificial pancreas (BiAP) system in adults with type 1 diabetes during fasting, overnight, and postprandial conditions. In contrast to existing glucose controllers in artificial pancreas systems, the BiAP uses a control algorithm based on a mathematical model of β-cell physiology. The algorithm is implemented on a miniature silicon microchip within a portable hand-held device that interfaces the components of the artificial pancreas. MATERIALS AND METHODS In this nonrandomized open-label study each subject attended for a 6-h fasting study followed by a 13-h overnight and post-breakfast study on a separate occasion. During both study sessions the BiAP system was used, and microboluses of insulin were recommended every 5 min by the control algorithm according to subcutaneous sensor glucose levels. The primary outcome was percentage time spent in the glucose target range (3.9-10.0 mmol/L). RESULTS Twenty subjects (55% male; mean [SD] age, 44 [10] years; duration of diabetes, 22 [12] years; glycosylated hemoglobin, 7.4% [0.7%] [57 (7) mmol/mol]; body mass index, 25 [4] kg/m(2)) participated in the fasting study, and the median (interquartile range) percentage time in target range was 98.0% (90.8-100.0%). Seventeen of these subjects then participated in the overnight/postprandial study, where 70.7% (63.9-77.4%) of time was spent in the target range and, reassuringly, 0.0% (0.0-2.3%) of time was spent in hypoglycemia (<3.9 mmol/L). CONCLUSIONS The BiAP achieves safe glycemic control during fasting, overnight, and postprandial conditions.

Metabolic Control With the Bio-inspired Artificial Pancreas in Adults With Type 1 Diabetes: A 24-Hour Randomized Controlled Crossover Study.

Background: The Bio-inspired Artificial Pancreas (BiAP) is a closed-loop insulin delivery system based on a mathematical model of beta-cell physiology and implemented in a microchip within a low-powered handheld device. We aimed to evaluate the safety and efficacy of the BiAP over 24 hours, followed by a substudy assessing the safety of the algorithm without and with partial meal announcement. Changes in lactate and 3-hydroxybutyrate concentrations were investigated for the first time during closed-loop. Methods: This is a prospective randomized controlled open-label crossover study. Participants were randomly assigned to attend either a 24-hour closed-loop visit connected to the BiAP system or a 24-hour open-loop visit (standard insulin pump therapy). The primary outcome was percentage time spent in target range (3.9-10 mmol/l) measured by sensor glucose. Secondary outcomes included percentage time in hypoglycemia (<3.9 mmol/l) and hyperglycemia (>10 mmol/l). Participants were invited to attend for an additional visit to assess the BiAP without and with partial meal announcements. Results: A total of 12 adults with type 1 diabetes completed the study (58% female, mean [SD] age 45 [10] years, BMI 25 [4] kg/m2, duration of diabetes 22 [12] years and HbA1c 7.4 [0.7]% [58 (8) mmol/mol]). The median (IQR) percentage time in target did not differ between closed-loop and open-loop (71% vs 66.9%, P = .9). Closed-loop reduced time spent in hypoglycemia from 17.9% to 3.0% (P < .01), but increased time was spent in hyperglycemia (10% vs 28.9%, P = .01). The percentage time in target was higher when all meals were announced during closed-loop compared to no or partial meal announcement (65.7% [53.6-80.5] vs 45.5% [38.2-68.3], P = .12). Conclusions: The BiAP is safe and achieved equivalent time in target as measured by sensor glucose, with improvement in hypoglycemia, when compared to standard pump therapy.

Changes in lipoprotein profile and urinary albumin excretion in familial LCAT deficiency with lipid lowering therapy.

Familial lecithin:cholesterol acyltransferase deficiency (FLD) is a monogenic autosomal recessive condition, affecting cholesterol esterification and leads to progressive renal impairment and end-stage renal failure, probably due to the abnormal lipoprotein (X) (Lp(X)). We report a case of FLD, whom we treated with a combination of nicotinic acid 1.5g nocte and fenofibrate M/R 160mg od and report changes in lipid profile and Lp(X), after six weeks and serum creatinine and urine albumin/creatinine ratio after 12 months. We assessed the cardiovascular risk using electron beam computed tomography. At baseline total cholesterol was 6.61mmol/L; HDL cholesterol 0.57mmol/L; Lp(X) cholesterol 3.24mmol/L; triglyceride 4.13mmol/L; apolipoprotein A1 46mg/dL; and apolipoprotein B 53mg/dL. After six weeks of treatment his total cholesterol was 4.16; HDL cholesterol 0.52; Lp(X) cholesterol 1.73mmol/L; triglyceride 1.80mmol/L; apolipoprotein A1 36mg/dL; and apolipoprotein B 50mg/dL. Baseline serum creatinine was 106micromol/L and urine albumin/creatinine ratio was 127.3mg/mmol and after 12 months was 101micromol/L and 31.5mg/mmol respectively. His coronary artery calcification score was zero. We have shown, we believe for the first time, that combination lipid modifying therapy in FLD leads to a reduction in Lp(X) concentration and an associated reduction in urine albumin excretion at 12 months.

The effects of rosiglitazone on atherosclerotic progression in patients with Type 2 diabetes at high cardiovascular risk

Diabet. Med. 27, 1392–1400 (2010)

Can protein biomarkers provide an index of coronary artery calcification in patients with Type 2 diabetes

OBJECTIVES By exploring differences between patients with high and low coronary artery calcification score (CACS), a plasma protein biomarker might be identified as an alternative to CACS screening. METHODS We selected stored samples (12 per group) from a cohort study of patients with Type 2 diabetes and CACS >1000 or <100 Agatston units, with matching for age, BMI, blood pressure, lipids and lipoproteins and fibrinogen. Multiplex, immunobead-based assay or ELISA measured 18 cardiovascular-related protein biomarkers. SELDI-TOF mass spectrometry (MS) screened for proteins differing significantly between high and low CACS. RESULTS Only monocyte chemotactic protein-1 was higher in the high compared with the low CACS group but concentrations overlapped appreciably. On SELDI-TOF MS, several mass/charge ratio peak intensities significantly discriminated high and low CACS but these differences were not confirmed in larger samples from the cohort. CONCLUSIONS Plasma protein biomarkers are unlikely to provide an effective alternative to measurement of CACS.