Large Cohort Of Healthy Subjects Research Articles

The Voxel-Wise Functional Connectome Can Be Efficiently Derived from Co-activations in a Sparse Spatio-Temporal Point-Process

Large efforts are currently under way to systematically map functional connectivity between all pairs of millimeter-scale brain regions based on large neuroimaging databases. The exploratory unraveling of this “functional connectome” based on functional Magnetic Resonance Imaging (fMRI) can benefit from a better understanding of the contributors to resting state functional connectivity. In this work, we introduce a sparse representation of fMRI data in the form of a discrete point-process encoding high-amplitude events in the blood oxygenation level-dependent (BOLD) signal and we show it contains sufficient information for the estimation of functional connectivity between all pairs of voxels. We validate this method by replicating results obtained with standard whole-brain voxel-wise linear correlation matrices in two datasets. In the first one (n = 71), we study the changes in node strength (a measure of network centrality) during deep sleep. The second is a large database (n = 1147) of subjects in which we look at the age-related reorganization of the voxel-wise network of functional connections. In both cases it is shown that the proposed method compares well with standard techniques, despite requiring only data on the order of 1% of the original BOLD signal time series. Furthermore, we establish that the point-process approach does not reduce (and in one case increases) classification accuracy compared to standard linear correlations. Our results show how large fMRI datasets can be drastically simplified to include only the timings of large-amplitude events, while still allowing the recovery of all pair-wise interactions between voxels. The practical importance of this dimensionality reduction is manifest in the increasing number of collaborative efforts aiming to study large cohorts of healthy subjects as well as patients suffering from brain disease. Our method also suggests that the electrophysiological signals underlying the dynamics of fMRI time series consist of all-or-none temporally localized events, analogous to the avalanches of neural activity observed in recordings of local field potentials (LFP), an observation of potentially high neurobiological relevance.

Physiologic correlates of tricuspid annular plane systolic excursion in 1168 healthy subjects

BackgroundTAPSE provides a simple, reproducible estimate of the longitudinal function of the right ventricle (RV). However, the normal limits and physiologic correlates of tricuspid annular plane systolic excursion (TAPSE) are not exactly known. The aim of this study was to explore the full spectrum of TAPSE values and determine the physiologic correlates of TAPSE. Methods and resultsFrom June 2007 to December 2013, 1168 healthy subjects [mean age 45.1±16years, range 16 to 92; 555 (47.5%) men] underwent comprehensive transthoracic echocardiography (TTE) as recommended by current guidelines. TAPSE values were higher in men than women (24.0±3.5 vs 23.2±3.0mm, p value<0.0001) but did not vary according to age. On multivariable linear regression analysis, cardiac output, RV basal and longitudinal dimensions were the only variables independently associated with TAPSE (β coefficient=0.161, 0.116 and 0.115 respectively). On the other hand echocardiographically-derived systolic pulmonary artery pressure (SPAP), pulmonary vascular resistance and mitral E/e′ ratio were significantly higher in older subjects. Therefore a significant decrease of TAPSE/SPAP was detected in >60years old cohort (p=0.0001). ConclusionsOur large cohort of healthy subjects provides sex and age-based TAPSE and TAPSE/SPAP normal cut-offs. TAPSE was found to be higher in men but not influenced by age. It was mainly correlated with echo-Doppler indices reflecting pre-load as opposed to afterload. On the other hand a significant decrease of TAPSE/SPAP with older age was registered as a direct consequence of increased SPAP with aging.

Optimizing Blood Sampling Protocols in Patients With Acromegaly for the Estimation of Growth Hormone Secretion.

Optimal blood sampling schemas of GH for the estimation of the 24-hour secretion rate have not been established in acromegalic patients. By censoring available 24-hour GH serum profiles, we investigated the reliability of such simplified schemas. Design, Subjects, and Methods: We used 24-hour serum GH concentration profiles obtained with 10-minute sampling in a large cohort of healthy subjects (n = 130; mean age, 42; range, 18-77 years) and acromegalic patients (n = 87; mean age, 48; range 18-72 years). Patient categories were active disease, surgically cured, and somatostatin analog-treated individuals. The regression coefficients of determination (R(2)) and the linear slopes (β) between 24-hour secretion rates or mean concentrations (144 samples) on the one hand and mean values with less frequent sampling on the other, decreased in controls and in patients a short (1-2 weeks) or long (2-5 years) time after successful surgery. By contrast, the regression parameters remained essentially unchanged in patients with active acromegaly and those under GH suppressive treatment. Excellent correlations (R(2) ≥ 0.90) without GH underestimation existed between mean GH of daytime profiles and mean GH of 24-hour profiles and GH secretion rates estimated by deconvolution in patients with active acromegaly and patients treated with somatostatin analogs. Simplified sampling schemes, particularly a day profile, can be used for the estimation of GH secretion in patients with active acromegaly and under medical treatment. However, in healthy controls and patients after successful surgery, prolonged and frequent sampling schemes, at least at 2-hour intervals, reliably reflect 24-hour secretion.

Neurobiological origin of spurious brain morphological changes: A quantitative MRI study.

The high gray‐white matter contrast and spatial resolution provided by T1‐weighted magnetic resonance imaging (MRI) has made it a widely used imaging protocol for computational anatomy studies of the brain. While the image intensity in T1‐weighted images is predominantly driven by T1, other MRI parameters affect the image contrast, and hence brain morphological measures derived from the data. Because MRI parameters are correlates of different histological properties of brain tissue, this mixed contribution hampers the neurobiological interpretation of morphometry findings, an issue which remains largely ignored in the community. We acquired quantitative maps of the MRI parameters that determine signal intensities in T1‐weighted images (R 1 (=1/T1), R 2*, and PD) in a large cohort of healthy subjects (n = 120, aged 18–87 years). Synthetic T1‐weighted images were calculated from these quantitative maps and used to extract morphometry features—gray matter volume and cortical thickness. We observed significant variations in morphometry measures obtained from synthetic images derived from different subsets of MRI parameters. We also detected a modulation of these variations by age. Our findings highlight the impact of microstructural properties of brain tissue—myelination, iron, and water content—on automated measures of brain morphology and show that microstructural tissue changes might lead to the detection of spurious morphological changes in computational anatomy studies. They motivate a review of previous morphological results obtained from standard anatomical MRI images and highlight the value of quantitative MRI data for the inference of microscopic tissue changes in the healthy and diseased brain. Hum Brain Mapp 37:1801–1815, 2016. © 2016 The Authors. Human Brain Mapping Published by Wiley Periodicals, Inc.

Prevalence of ultrasound synovial inflammatory findings in healthy subjects.

To evaluate the prevalence of joint inflammatory abnormalities and erosions detected by grey-scale and Doppler ultrasound (US) in the small joints of hands and feet in healthy subjects. US of the dorsal surface of 32 joints (10 metacarpophalangeal, 10 proximal interphalangeal, 10 metatarsophalangeal (MTP) and 2 wrists) was performed in 207 healthy subjects without joint symptom. Synovial effusion (SE), synovial hypertrophy (SH) and power Doppler (PD) signal were scored using a semiquantitative grading scale (0-3) and erosion binary. One-hundred and eighty-two subjects had at least one US abnormality: 52% of the subjects had SE alone, 13% SH alone (5% with and 8% without PD) and 35% both SH and SE. US findings were detected in 9% of the total joints examined, mostly in the feet, and in particular in the MTP1 (33% of the positive joints). SE was the most frequently detected finding (68% of the positive joints), followed by SH (31%). Severity was mild (grade 1 in average) whatever the finding recorded (SH, SE or PD). Four erosions were detected (MTP1). This study describes for the first time, in a large cohort of healthy subjects, the prevalence and location of US signs of joint inflammation and of structural damage in small joints of hands and feet. US abnormalities were quite common, and mostly located in the feet. Further studies are needed to define which US components may allow to discriminate between pathological and physiological findings in the joints commonly affected by inflammatory arthritis conditions.

Dutch Lipid Clinic Network low-density lipoprotein cholesterol criteria are associated with long-term mortality in the general population

Heterozygous familial hypercholesterolaemia (HeFH) is a severe autosomal dominant disease that is underdiagnosed, inadequately treated and has a severe long-term cardiovascular risk. Few studies have evaluated the long-term risk of high low-density lipoprotein cholesterol (LDL-C) concentrations. To evaluate long-term mortality in a large cohort of healthy subjects, according to LDL-C concentrations. Based on a sample of 6956 subjects visiting a preventive cardiology department, we selected adult subjects without a personal history of cardiovascular disease. From 1995 to 2011, 4930 healthy subjects were examined and followed up until 31 December 2011. All-cause deaths were collected exhaustively. A Cox-based multivariable analysis evaluated long-term total mortality risk according to Dutch Lipid Clinic Network (DLCN) LDL-C concentrations. After a mean follow-up of 8.6 years, 123 all-cause deaths were recorded (cumulative mortality rate, 2.5%). In the final multivariable model, major risk factors such as age, sex, tobacco use and diabetes were significantly associated with mortality. After adjustment for age, sex, tobacco use, hypertension, diabetes and statin therapy, and in comparison with subjects with LDL-C<4 mmol/L (<155 mg/dL), subjects with LDL-C between 4 and <5 mmol/L (155 to <190 mg/dL) had a hazard ratio (HR) of 1.99 (95% confidence interval [CI] 1.31-3.02; P=0.001), subjects with LDL-C between 5 and <6.5 mmol/L (190 to <250 mg/dL) had an HR of 1.81 (95% CI, 1.06-3.02; P=0.030), subjects with LDL-C between 6.5 and<8.5 mmol/L (250 to <330 mg/dL) had an HR of 2.69 (95% CI, 1.06-6.88; P=0.038) and subjects with LDL-C ≥ 8.5 mmol/L (≥330 mg/dL) had an HR of 6.27 (95% CI, 0.84-46.57; P=0.073). After excluding patients on statins at baseline, subjects with LDL-C ≥ 8.5 mmol/L (≥330 mg/dL) had an HR of 8.17 (95% CI, 1.08-62.73; P=0.042). The severity of LDL-C elevation is associated with a higher risk of death in healthy subjects. DLCN LDL-C concentrations may be used in daily practice to identify patients with HeFH who warrant aggressive treatment.

Glucagon cell hyperplasia and neoplasia with and without glucagon receptor mutations.

Glucagon cell adenomatosis (GCA) was recently recognized as a multifocal hyperplastic and neoplastic disease of the glucagon cells unrelated to multiple endocrine neoplasia type 1 and von-Hippel-Lindau disease. The study focused on the molecular analysis of the glucagon receptor (GCGR) gene in GCA and a description of the clinicopathological features of GCA with and without GCGR mutations. Pancreatic tissues from patients showing multiple glucagon cell tumors were morphologically characterized and macro- or microdissected. All exons of the GCGR gene were analyzed for mutations by Sanger and next-generation sequencing. Genotyping for all detected GCGR variants was performed in 2560 healthy individuals. Six patients with GCA, and the parents of one patient were included in the study. The main outcome measures were the correlations between the patients' GCGR mutation status and the respective clinicopathological data. GCGR germline mutations were found in three of six patients. Patient 1 harbored a homozygous stop mutation. This patient's parents showed an identical but heterozygous GCGR mutation. Patient 2 had two different heterozygous point mutations leading each to premature stop codons. Patient 3 exhibited two homozygous missense mutations. No GCGR mutations were identified in the three other patients and in a large cohort of healthy subjects. The patients harboring GCGR mutations exhibited a greater number of tumors and larger tumors than patients with wild-type GCGR. One of the patients with wild-type GCGR showed lymph node micrometastases. GCA with GCGR germline mutations seems to follow an autosomal-recessive trait. By interrupting the GCGR signaling pathways GCGR mutations probably cause GCA via glucagon cell hyperplasia. GCA also occurs in patients without GCGR mutations, but seems to be associated with fewer and smaller tumors.

Normal values and clinical relevance of left atrial myocardial function analysed by speckle-tracking echocardiography: multicentre study.

The aim of this multicentre study was to determine the normal range and the clinical relevance of the myocardial function of the left atrium (LA) analysed by 2D speckle-tracking echocardiography (2DSTE). We analysed 329 healthy adult subjects prospectively included in 10 centres and a validation group of 377 patients with left ventricular diastolic dysfunction (LVDD). LA myocardial function was analysed by LA strain rate peak during LA contraction (LA-SRa) and LA strain peak during LA relaxation (LA-Strain). The range of values of LA myocardial function in healthy subjects was LA-SRa -2.11 ± 0.61 s(-1) and LA-Strain 45.5 ± 11.4%, and the lowest expected values of these LA analyses (calculated as -1.96 SD from the mean of healthy subjects) were LA-SRa -0.91 s(-1) and LA-Strain 23.1%. Concerning the clinical relevance of these LA myocardial analyses, LA-SRa and LA-Strain detected subtle LA dysfunction in patients with LVDD, even though LA volumetric measurements were normal. In addition, in these patients we found that the functional class (dyspnoea-NYHA classification) was inversely related to both LA-Strain and LA-SRa. In the present multicentre study analysing a large cohort of healthy subjects and patients with LVDD, the normal range and the clinical relevance of the myocardial function of the LA using 2DSTE have been determined.

Ulnar nerve at the elbow – normative nerve conduction study

IntroductionA goal of our work was to perform nerve conduction studies (NCSs) of the ulnar nerve focused on the nerve conduction across the elbow on a sufficiently large cohort of healthy subjects in order to generate reliable reference data.MethodsWe examined the ulnar nerve in a position with the elbow flexion of 90o from horizontal. Motor response was recorded from the abductor digiti minimi muscle (ADM) and the first dorsal interosseous muscle (FDI).ResultsIn our sample of 227 healthy volunteers we have examined 380 upper arms with the following results: amplitude (Amp)-CMAP(wrist) for ADM 9.6 ± 2.3 mV, MNCV at the forearm 60.4 ± 5.2 m/s, MNCV across the elbow 57.1 ± 5.9 m/s.DiscussionOur study showed that motor NCSs of the ulnar nerve above elbow (AE) and below elbow (BE) in a sufficiently large cohort using methodology recommended by AANEM gave results well comparable for registration from FDI and ADM.

Association of central serotonin transporter availability and body mass index in healthy Europeans

Serotonin-mediated mechanisms, in particular via the serotonin transporter (SERT), are thought to have an effect on food intake and play an important role in the pathophysiology of obesity. However, imaging studies that examined the correlation between body mass index (BMI) and SERT are sparse and provided contradictory results. The aim of this study was to further test the association between SERT and BMI in a large cohort of healthy subjects. Methods: 127 subjects of the ENC DAT database (58 females, age 52±18 years, range 20–83, BMI 25.2±3.8kg/m2, range 18.2–41.1) were analysed using region-of-interest (ROI) and voxel-based approaches to calculate [123I]FP-CIT specific-to-nonspecific binding ratios (SBR) in the hypothalamus/thalamus and midbrain/brainstem as SERT-specific target regions. Results: In the voxel-based analysis, SERT availability and BMI were positively associated in the thalamus, but not in the midbrain. In the ROI-analysis, the interaction between gender and BMI showed a trend with higher correlation coefficient for men in the midbrain albeit not significant (0.033SBRm2/kg, p=0.1). Conclusions: The data are in agreement with previous PET findings of an altered central serotonergic tone depending on BMI, as a probable pathophysiologic mechanism in obesity, and should encourage further clinical studies in obesity targeting the serotonergic system.

Multidirectional Global Left Ventricular Systolic Function in Normal Subjects and Patients with Hypertension: Multicenter Evaluation

The aim of this multicenter study was to determine the normal ranges and the clinical relevance of multidirectional systolic parameters to evaluate global left ventricular (LV) systolic function. Three hundred twenty-three healthy adult subjects prospectively included at 10 centers and a cohort of 310 patients with hypertension were analyzed. Multidirectional global LV systolic function was analyzed using two-dimensional speckle-tracking echocardiography by means of two indices: longitudinal-circumferential systolic index (the average of longitudinal and circumferential global systolic strain) and global systolic index (the average of longitudinal, circumferential, and radial global systolic strain). The ranges of values of the multidirectional systolic parameters in healthy subjects were -21.22 ± 2.22% for longitudinal-circumferential systolic index and 29.71 ± 5.28% for global systolic index. In addition, the lowest expected values of these multidirectional indices were determined in this population (calculated as -1.96 SDs from the mean): -16.86% for longitudinal-circumferential systolic index and 19.36% for global systolic index. Concerning the clinical relevance of these measurements, these indices indicated the presence of subtle LV global systolic dysfunction in patients with hypertension, even though LV global longitudinal systolic strain and LV ejection fraction were normal. Moreover, in these patients, functional class (dyspnea [New York Heart Association classification]) was inversely related to both the longitudinal-circumferential index and the global systolic index. In the present multicenter study analyzing a large cohort of healthy subjects and patients with hypertension, the normal range and the clinical relevance of multidirectional systolic parameters to evaluate global LV systolic function have been determined.

Right atrial size and function assessed with three-dimensional and speckle-tracking echocardiography in 200 healthy volunteers

Right atrial (RA) size predicts the outcome in some pathological conditions but reference values for RA volumes and myocardial function remain to be defined. Thus, we used two-dimensional speckle-tracking echocardiography (2D-STE) and three-dimensional echocardiography (3DE) to define normative reference values of RA volumes and function. Two hundreds healthy volunteers (43 ± 15 years, range 18-75; 44% men) underwent two-dimensional echocardiography (2DE) to obtain RA volumes and longitudinal strain (LS) of RA wall using 2D-STE, and 3DE to measure maximal (Vmax), minimal, and preA volumes to calculate total, passive, and active emptying volumes (TotEV, PassEV, and ActEV) and emptying fractions (TotEF, PassEF, and ActEF). Three-dimensional echocardiography volumes (Vmax, 52 ± 15 mL vs. 41 ± 14 mL), EVs (TotEV, 33 ± 10 mL vs. 24 ± 9 mL), and EFs (TotEF, 63 ± 9 vs. 58 ± 9%) were larger than 2DE ones (all P < 0.0001). Indexed 3D volumes were significantly larger in men than in women. RA TotEF correlated with total LS (r = 0.24, P = 0.025) and PassEF with positive LS (LSpos; r = 0.34, P < 0.0001). Ageing was associated with a decrease in passive (LSpos, r = -041; PassEV, r = -0.26; PassEF, r = -0.38; all P < 0.0001) and an increase in active RA function (negative LS, r = 0.34; ActEV, r = 0.25; all P < 0.0001; and ActEF, r = 0.15; P = 0.035) in order to maintain TotEV (r = -0.14, P = 0.05). Our study provides normative values for RA volumes and function measured by 3DE and 2D-STE in a relatively large cohort of healthy subjects with a wide age range. These data will help clinicians to identify RA remodelling and dysfunction.

Effects of Aging and Gender on Brain Intrinsic Functional Connectivity: A Resting State Study in a Large Cohort of Healthy Subjects (IN8-2.002)

Effects of Aging and Gender on Brain Intrinsic Functional Connectivity: A Resting State Study in a Large Cohort of Healthy Subjects (IN8-2.002)

Effects of Aging and Gender on Brain Intrinsic Functional Connectivity: A Resting State Study in a Large Cohort of Healthy Subjects (P06.023)

Effects of Aging and Gender on Brain Intrinsic Functional Connectivity: A Resting State Study in a Large Cohort of Healthy Subjects (P06.023)

Transcranial Doppler Velocities in a Large, Healthy Population

Transcranial Doppler (TCD) ultrasonography has been extensively used in the evaluation and management of patients with cerebrovascular disease since the clinical application was first described in 1982 by Aaslid and colleagues TCD is a painless, safe, and noninvasive diagnostic technique that measures blood flow velocity in various cerebral arteries. Numerous commercially available TCD devices are currently approved for use worldwide, and TCD is recognized to have an established clinical value for a variety of clinical indications and settings. Although many studies have reported normal values, there have been few recently, and none to include a large cohort of healthy subjects across age, race, and gender. As more objective, automated processes are being developed to assist with the performance and interpretation of TCD studies, and with the potential to easily compare results against a reference population, it is important to define stable normal values and variances across age, race, and gender, with clear understanding of variability of the measurements, as well as the yield from various anatomic segments. To define normal TCD values in a healthy population, we enrolled 364 healthy subjects, ages 18-80 years, to have a complete, nonimaging TCD examination. Subjects with known or suspected cerebrovascular disorders, systemic disorders with cerebrovascular effects, as well as those with known hypertension, diabetes, stroke, coronary artery disease, or myocardial infarction, were excluded. Self-reported ethnicity, handedness, BP, and BMI were recorded. A complete TCD examination was performed by a single experienced sonographer, using a single gate nonimaging TCD device, and a standardized protocol to interrogate up to 23 arterial segments. Individual Doppler spectra were saved for each segment, with velocity and pulsatility index (PI) values calculated using the instrument's automated waveform tracking function. Descriptive analysis was done to determine the mean velocities and PI, and all data were analyzed for changes by decade of age, sex race, handedness, BMI, and BP. Among the key intracranial segments, mean blood flow velocities (MBFV) were highest in the MCA and lowest in the PCA across all ages, sexes, and ethnic groups. There was no difference in the MBFVs between left and right side segments of the Circle of Willis, with the exception of the distal M1 (P = .022) and the C1 (P < .0001), both slightly higher on the left. MBFV were higher among women than men in all segments except for the OA. MBFV decreased with advancing age in both men and women, but this was specific to Caucasian subjects. There were lower velocities in the OA for non-Caucasians. The PI was lower in the left VA (P < .0001), and for most segments was lower in women than men. The PI increased with age in all segments for women, but only in some segments for men, and this finding was also specific to Caucasian subjects. The yield of usable data ranged from 99.7% for the VA and BA, to 88.2% for C2. Our study provides normal, reference TCD values for a large cohort of healthy subjects across a wide range of age, sex, and race groups. We observed decreased MBFV and increased PI with aging, and higher MBFV in women. There were few differences in MBFV related to side or ethnicity, but the MFBV and PI changes with age were specific to Caucasians. We provide means and standard deviations of MBFVs across various demographic groups in key intracranial arteries. Such normal TCD values across age, gender, and ethnic groups in healthy subjects represent a useful reference tool for detecting individuals with TCD values outside normal limits and at increased vascular risk. TCD studies in large multiethnic populations are still required to determine differences in brain hemodynamics across various ethnic groups.

BDNF Val66Met genotype modulates the effect of childhood adversity on subgenual anterior cingulate cortex volume in healthy subjects

According to the neurotrophic hypothesis of depression, stress can lead to brain atrophy by modifying brain-derived neurotrophic factor (BDNF) levels. Given that BDNF secretion is affected by a common polymorphism (rs6265, Val66Met), which also is associated with depression, we investigated whether this polymorphism modifies the effect of childhood adversity (CA) on local gray matter (GM) volume in depression-relevant brain regions, using data from two large cohorts of healthy subjects. We included 568 healthy volunteers (aged 18-50 years, 63% female) in our study, for whom complete data were available, with magnetic resonance imaging data at 1.5 Tesla (N=275) or 3 Tesla (N=293). We used a whole brain optimized voxel-based morphometry (VBM) approach assessing genotype-dependent GM differences, with focus on the amygdala, hippocampus and medial prefrontal cortex (PFC; including anterior cingulate cortex (ACC) and orbitomedial PFC). CA was assessed using a validated questionnaire. In both cohorts, we found that BDNF methionine (Met)-allele carriers with a history of CA had significantly less GM in subgenual ACC (P<0.05) compared with Met-allele carriers without CA and Val/Val homozygotes with CA. No differences were found in hippocampus, amygdala and orbitomedial PFC. On the basis of our findings, we conclude that BDNF Met-allele carriers are particularly sensitive to CA. Given the key role of the subgenual ACC in emotion regulation, this finding provides an important mechanistic link between stress and BDNF on one hand and mood impairments on the other hand.

Genetic determinants of plasma von Willebrand factor antigen levels: a target gene SNP and haplotype analysis of ARIC cohort

Abstractvon Willebrand factor (VWF) is an essential component of hemostasis and has been implicated in thrombosis. Multimer size and the amount of circulating VWF are known to impact hemostatic function. We associated 78 VWF single nucleotide polymorphisms (SNPs) and haplotypes constructed from those SNPs with VWF antigen level in 7856 subjects of European descent. Among the nongenomic factors, age and body mass index contributed 4.8% and 1.6% of VWF variation, respectively. The SNP rs514659 (tags O blood type) contributed 15.4% of the variance. Among the VWF SNPs, we identified 18 SNPs that are associated with levels of VWF. The correlative SNPs are either intronic (89%) or silent exonic (11%). Although SNPs examined are distributed throughout the entire VWF gene without apparent cluster, all the positive SNPs are located in a 50-kb region. Exons in this region encode for VWF D2, D′, and D3 domains that are known to regulate VWF multimerization and storage. Mutations in the D3 domain are also associated with von Willebrand disease. Fifteen of these 18 correlative SNPs are in 2 distinct haplotype blocks. In summary, we identified a cluster of intronic VWF SNPs that associate with plasma levels of VWF, individually or additively, in a large cohort of healthy subjects.

Regional and global pancreatic T*2 MRI for iron overload assessment in a large cohort of healthy subjects: Normal values and correlation with age and gender

Multiecho gradient-echo T*2 magnetic resonance imaging is a well-established technique for iron overload assessment but there are few reports concerning the pancreas. The aim of this work was to assess the feasibility and reproducibility of the magnetic resonance imaging for measuring pancreatic regional and global T*2 values, to establish the lower limit of normal in a large cohort of healthy subjects and to correlate the measured values with age and gender. One hundred and twenty healthy subjects (61 males, 51±17 years) underwent magnetic resonance imaging (1.5T) using a multiecho gradient-echo T*2 sequence. T*2 measurements were performed in pancreatic head, body, and tail. The global value was calculated as the mean. Measurement of pancreatic T*2 values was feasible in all subjects. For the T*2 global value the coefficient of variation for intraoperator and interoperator reproducibility were 7.7% and 13%, respectively. The global T*2 values ranged from 24 to 52 ms with the lower limit of normal of 26 ms. There were no significant differences among the regional pancreatic T*2 values. No significant correlation was found between T*2 and patient age or gender. In conclusion, pancreatic T*2 measurements appear to be feasible, reproducible, nontime-consuming and reliable. Gender- and age-related differences concerning pancreatic T*2 were not found.

Regulation of PTH secretion by 25-hydroxyvitamin D and ionized calcium depends on vitamin D status: A study in a large cohort of healthy subjects

Introduction Previous papers investigating vitamin D status have often outlined the significant relationships between serum parathyroid hormone (PTH) and 25-hydroxyvitamin D (25OHD), but the influence of ionized calcium levels has not been concomitantly considered. Design Cross-sectional. Materials and methods In 1050 healthy men (547) and women (503), serum ionized calcium (iCa), creatinine (Cr), albumin, 25OHD, and PTH were measured. After conventional analysis, a regression tree was fitted on the data set. Results 25OHD and PTH values showed significant opposite seasonal changes. 25OHD levels negatively correlated with PTH, which in turn negatively correlated with iCa. A regression tree was fitted to the whole data set using PTH as the response variable and 25OHD and iCa as covariates. PTH concentration depended on that of iCa only in subjects with 25OHD levels > 16.35 ng/mL, while for 25OHD <16.35 ng/mL it depended on 25OHD values. Conclusions Our results indicated that PTH levels were highly conditioned by those of 25OHD in subjects with 25OHD values lower than 16.35 ng/mL and by those of iCa only for higher 25OHD concentration.

Influence of the ACE Gene Insertion/Deletion Polymorphism on Insulin Sensitivity and Impaired Glucose Tolerance in Healthy Subjects

Recent studies suggested that the blockade of the renin-angiotensin system (RAS) may be associated with metabolic benefits. However, data about the potential influence of the ACE insertion/deletion (I/D) genotype on insulin resistance have been contradictory with studies of limited sample sizes. The purpose of this study was to investigate the relationship between the ACE gene I/D polymorphism and both insulin sensitivity and glucose intolerance in a large cohort of healthy subjects. A total of 1,286 participants in the Relationship Between Insulin Sensitivity and Cardiovascular Disease Risk Study had a 75-g oral glucose tolerance test and a hyperinsulinemic-euglycemic clamp to assess whole-body insulin sensitivity. Age, BMI, waist, fat-free mass (ffm), and physical activity did not differ by ACE genotype. Fasting glucose and insulin were similar among genotypes, but 2-h glucose levels were higher in DD than in ID and II subjects (DD: 5.9 +/- 1.7; ID: 5.7 +/- 1.5; II: 5.6 +/- 1.5 mmol/l) (P = 0.004). Participants with the DD genotype were more likely to have impaired glucose tolerance than those with the ID and II genotypes (13.1 vs. 8.7%; P = 0.02). Insulin sensitivity was lower in participants with the DD genotype than in those with the II genotype (136 +/- 63 vs. 147 +/- 65 micromol x min(-1)x kg ffm(-1) x mmol(-1) x l(-1); P = 0.02). The presence of the D allele was associated with a trend, albeit not significant, for reduced insulin secretion during the oral glucose tolerance test (P = 0.07). The ACE I/D polymorphism is associated with whole-body insulin sensitivity and with impaired glucose tolerance in our healthy population. These findings confirm potential interactions between the RAS and glucose metabolism.