Genome-wide scan for adiposity-related phenotypes in adults from American Samoa

OBJECTIVE

To detect quantitative trait loci influencing adiposity-related phenotypes assessed by body mass index (BMI), abdominal circumference (ABDCIR), percent body fat (%BFAT) and fasting serum leptin and adiponectin using a whole genome linkage scan of families from American Samoa.

DESIGN

Family-based linkage analysis, the probands and family members were unselected for obesity.

SUBJECTS

A total of 583 phenotyped American Samoan adults, of which 578 were genotyped in 34 pedigrees.

MEASUREMENTS

A total of 377 autosomal and 18 X chromosome microsatellite markers were typed at an approximate average spacing of 10 cM spanning the genome. Multipoint LOD (logarithm of the odds) scores were calculated using variance-components approaches and SOLAR/LOKI software. The covariates simultaneously evaluated were age, sex, education, farm work and cigarette smoking, with a significance level of 0.1. Due to the stochastic nature of LOKI, we report the average of maximum LOD scores from 10 runs.

RESULTS

Significant linkage to leptin was found at 6q32.2 with LOD of 3.83. Suggestive linkage to leptin was found at 16q21:LOD=2.98, 1q42.2:LOD=1.97, 5q11.2:LOD=2.08, 12q24.23:LOD=2.00, 19p13.3:LOD=2.05; adiponectin was linked to 13q33.1-q22.1:LOD=2.41; %BFAT was linked to 16q12.2-q21, LOD=2.24; ABDCIR was linked to 16q23.1:LOD=1.95; %BFAT-adjusted leptin to 14q12, LOD=2.01; %BFAT-adjusted ABDCIR to 1q31.1, LOD=2.36, to 3q27.3-q28, LOD=2.10 and to 12p12.3, LOD=2.04.

CONCLUSION

We found strong evidence for a major locus on 6q23.2 influencing serum leptin levels in American Samoans. The 16q21 region appears to harbor a susceptibility locus that has significant pleiotrophic effects on phenotypes BMI, %BFAT, leptin and ABDCIR as shown by bivariate linkage analyses. Several other loci of varying significance were detected across the genome.

In vitro metabolism of indiplon and an assessment of its drug interaction potential

This study was designed to study the in vitro metabolism of indiplon, a novel hypnotic agent, and to assess its potential to cause drug interactions. In incubations with pooled human liver microsomes, indiplon was converted to two major, pharmacologically inactive metabolites, N-desmethyl-indiplon and N-desacetyl-indiplon. The N-deacetylation reaction did not require NADPH, and appeared to be catalyzed by organophosphate-sensitive microsomal carboxylesterases. The N-demethylation of indiplon was catalyzed by CYP3A4/5 based on the following observations: (1) the sample-to-sample variation in N-demethylation of indiplon ([S] = 100 microM) in a bank of human liver microsomes was strongly correlated with testosterone 6beta-hydroxylase (CYP3A4/5) activity (r(2) = 0.98), but not with any other CYP enzyme; (2) recombinant CYP1A1, CYP1A2, CYP3A4, CYP3A5 and CYP3A7 had the ability to catalyze this reaction; (3) the N-demethylation of indiplon was inhibited by CYP3A4/5 inhibitors (ketoconazole and troleandomycin), but not by a CYP1A2 inhibitor (furafylline). In pooled human liver microsomes, indiplon exhibited a weak capacity to inhibit CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2D6, CYP2E1, CYP3A4/5 and carboxylesterase (p-nitrophenylacetate hydrolysis) activities (IC50 >/= 20 microM). Clinical data available on indiplon support the conclusions of this paper that the in vitro metabolism of indiplon is catalyzed by multiple enzymes, and indiplon is a weak inhibitor of human CYP enzymes.

Homocysteine induces endothelial dysfunction via inhibition of arginine transport

Hyperhomocysteinemia is an independent risk factor for cardiovascular diseases. High levels of plasma homocysteine (HCY) increase oxidative stress and reduce endothelial-dependent relaxation. We determined whether hyperhomocysteinemia-induced endothelial dysfunction is mediated through inhibition of cellular transport of L-arginine. In endothelial cells, HCY had a biphasic effect on arginine transport. HCY treatment for 6 hr increased L-arginine uptake by 34%; however, uptake was decreased by 25% after 24 h. HCY caused membrane hyperpolarization during both 6 and 24 h incubation periods, indicating that the negative charge facilitating arginine uptake was maintained. HCY significantly reduced expression of cellular arginine transporter protein (CAT-1) after 24 h treatment; whereas endothelial nitric oxide synthase (eNOS) protein levels and basal eNOS activity were not altered. Nevertheless, nitric oxide (NO) formation was significantly decreased. The antioxidant ascorbic acid prevented the effect of HCY on arginine transport. HCY induced formation of the peroxynitrite biomarker nitrotyrosine, which was blocked by supplemental L-arginine. HCY treatment of aortic rings caused decreased vasorelaxation to acetylcholine, which was prevented by supplemental arginine. In conclusion, HCY decreased NO formation and induced endothelial dysfunction without altering protein level or basal activity of eNOS, but through decreases in function and protein expression of the CAT-1 transporter. Reduced arginine supply may lead to eNOS uncoupling and generation of superoxide, contributing to HCY-induced oxidative stress.

Investigation of optimal beam margins for stereotactic radiotherapy of lung-cancer using Monte Carlo dose calculations

This work investigated the selection of beam margins in lung-cancer stereotactic body radiotherapy (SBRT) with 6 MV photon beams. Monte Carlo dose calculations were used to systematically and quantitatively study the dosimetric effects of beam margins for different lung densities (0.1, 0.15, 0.25, 0.35 and 0.5 g cm(-3)), planning target volumes (PTVs) (14.4, 22.1 and 55.3 cm3) and numbers of beam angles (three, six and seven) in lung-cancer SBRT in order to search for optimal beam margins for various clinical situations. First, a large number of treatment plans were generated in a commercial treatment planning system, and then recalculated using Monte Carlo simulations. All the plans were normalized to ensure that 95% of the PTV at least receives the prescription dose and compared quantitatively. Based on these plans, the relationships between the beam margin and quantities such as the lung toxicity (quantified by V20, the percentage volume of the two lungs receiving at least 20 Gy) and the maximum target (PTV) dose were established for different PTVs and lung densities. The impact of the number of beam angles on the relationship between V20 and the beam margin was assessed. Quantitative information about optimal beam margins for lung-cancer SBRT was obtained for clinical applications.

Novel role of HDAC inhibitors in AML1/ETO AML cells: activation of apoptosis and phagocytosis through induction of annexin A1

The chimeric fusion protein AML1-ETO, created by the t(8;21) translocation, recruits histone deacetylase (HDAC) to AML1-dependent promoters, resulting in transcriptional repression of the target genes. We analyzed the transcriptional changes in t(8;21) Kasumi-1 AML cells in response to the HDAC inhibitors, depsipeptide (FK228) and suberoylanilide hydroxamic acid (SAHA), which induced marked growth inhibition and apoptosis. Using cDNA array, annexin A1 (ANXA1) was identified as one of the FK228-induced genes. Induction of ANXA1 mRNA was associated with histone acetylation in ANXA1 promoter and reversal of the HDAC-dependent suppression of C/EBPalpha by AML1-ETO with direct recruitment of C/EBPalpha to ANXA1 promoter. This led to increase in the N-terminal cleaved isoform of ANXA1 protein and accumulation of ANXA1 on cell membrane. Neutralization with anti-ANXA1 antibody or gene silencing with ANXA1 siRNA inhibited FK228-induced apoptosis, suggesting that the upregulation of endogenous ANXA1 promotes cell death. FK228-induced ANXA1 expression was associated with massive increase in cell attachment and engulfment of Kasumi-1 cells by human THP-1-derived macrophages, which was completely abrogated with ANXA1 knockdown via siRNA transfection or ANXA1 neutralization. These findings identify a novel mechanism of action of HDAC inhibitors, which induce the expression and externalization of ANXA1 in leukemic cells, which in turn mediates the phagocytic clearance of apoptotic cells by macrophages.

Transcriptional control in the mammalian liver: liver development, perinatal repression, and zonal gene regulation

Liver function is crucial for maintaining metabolic homeostasis in mammals. Numerous genes must be properly regulated for the liver to develop and perform a variety of activities. Several recent gene-knockout studies in mice have clarified the roles of GATA6, HNF4alpha, and Foxa1/Foxa2 in early stages of liver formation. After the liver forms, transcriptional changes continue to occur; during the perinatal period, certain genes such as alpha-fetoprotein and H19 are silenced, others are activated, and position-dependent (or zonal) regulation is established. Zhx2 was recently identified as one factor involved in postnatal repression of alpha-fetoprotein and other genes. Furthermore, several studies indicate that negative regulation is involved in the zonal control of glutamine synthetase. Finally, exciting new evidence indicates that signaling through the Wnt/beta-catenin pathway is also involved in zonal regulation in the adult liver.

Variation in proton affinity of the guanidino group between free and blocked arginine

In this paper, the analog of arginine residues in peptides was synthesized and characterized by ESI-MS/MS (electrospray ionization with tandem mass spectrometry), (31)P NMR, (1)H NMR, IR and high-resolution mass spectrometry. When the Todd reaction activity of the guanidino group in free arginine and the arginine peptide analog were compared, it was found that the proton affinity of the guanidino group was decreased when both the N- and the C-terminal were blocked. As a result, the guanidino group of arginine residues in peptides could be phosphorylated under the Todd reaction condition, but not the free arginine. This result was further proved by the theoretical calculation of their proton affinity.

Acrylamide, an in vivo thyroid carcinogenic agent, induces DNA damage in rat thyroid cell lines and primary cultures

Chronic treatment of rats with acrylamide induces various tumors among which thyroid tumors are the most frequent. The aim of the present study was to develop an in vitro model of acrylamide action on thyroid cells to allow the investigation of the mechanism of this tumorigenic action. The first part of the study considered as targets, characteristics of thyroid metabolism, which could explain the thyroid specificity of acrylamide action: the cAMP mitogenic effect and the important H2O2 generation by thyroid cells. However, acrylamide did not modulate H2O2 or cAMP generation in the thyroid cell models studied. No effect on thyroid cell proliferation was observed in the rat thyroid cell line FRTL5. On the other hand, as shown by the comet assay, acrylamide induced DNA damage, as the positive control H2O2 in the PC Cl3 and FRTL5 rat thyroid cell lines, as well as in thyroid cell primary cultures. The absence of effect of acrylamide on H2AX histone phosphorylation suggests that this effect does not reflect the induction of DNA double strand breaks. DNA damage leads to the generation of mutations. It is proposed that such mutations could play a role in the carcinogenic effect of acrylamide. The mechanism of this effect can now be studied in this in vitro model.

Increased reactive oxygen species contributes to kidney injury in mineralocorticoid hypertensive rats

Hypertension is associated with increased reactive oxygen species (ROS). Renal ROS production and their effects on renal function have never been investigated in mineralocorticoid hypertensive rats. In this study we hypothesized that increased ROS production in kidneys from deoxycorticosterone (DOCA)-salt rats contributes to adverse renal morphological changes and impaired renal function in DOCA-salt hypertensive rats. We also determined whether ROS-induced renal injury was dependent on blood pressure. DOCA-salt hypertensive rats exhibited a marked increase in blood pressure, renal ROS production, glomerular and tubular lesions, and microalbuminuria compared to sham rats. Treatment of DOCA-salt hypertensive rats with apocynin for 28 days resulted in attenuation of systolic blood pressure and improvement of renal morphology. Renal superoxide level in DOCA-salt rats was 215% of sham-operated rats and it was significantly decreased to 140% with apocynin treatment. Urinary protein level was decreased from 27 +/- 3 mg/day in DOCA-salt hypertensive rats to 9 +/- 2 mg/day. 28 days of Vitamin E treatment also reduced renal injury in regard to urinary protein level and renal morphology but had no effect on blood pressure in DOCA-salt rats. Increased urinary 8-isoprostane, a marker for oxidative stress, in DOCA-salt hypertensive rats (55 +/- 8 ng/day) was diminished by vitamin E treatment (24 +/- 6 ng/day). These data suggest that renal injury characteristic of mineralocorticoid hypertension is associated with oxidative stress and is partly independent of blood pressure.

Testosterone induces apoptosis via Fas/FasL-dependent pathway in bone marrow-derived macrophages

The detailed mechanisms behind the apoptosis of macrophages induced by testosterone are not clear. In the present study, we tried to delineate the effect of testosterone on the apoptosis of bone marrow-derived macrophages (BMMs) and the function of Fas/FasL (Fas ligand) pathway in this course. BMMs were stimulated with testosterone in the presence of macrophage colony stimulating factor (M-CSF) or without. Flow cytometry was used to quantify the apoptosis of BMMs. Real-time RT-PCR and Western blot were performed to analyze the expression of caspase-8, caspase-3, and poly(ADP-ribose) polymerase (PARP) during the Fas/FasL pathway. Our data showed that testosterone could induce the apoptosis of BMMs, similar to removing growth factor M-CSF from the culture medium. They were both associated with the enhanced expression of caspase-8, caspase-3, and PARP. And the phosphorothioate antisense oligodeoxynucleotides to fas-associated death domain protein (FADD) could block the expression of FADD, which is an upstream factor of caspase-8 in the Fas/FasL pathway. It led to the reduced obvious expression of caspase-8 and decreasing apoptosis of BMMs. These results suggest that the Fas/FasL pathway may play an important role in the testosterone-induced apoptosis of macrophages.

Value of B-type natriuretic peptide in diagnosing left ventricular dysfunction in dialysis-dependent patients

BACKGROUND

B-type natriuretic peptide (BNP) is elevated in patients with end-stage renal failure. The reported accuracy of BNP in diagnosing left ventricular dysfunction in these patients has been inconsistent.

AIM

To investigate the diagnostic values of BNP for left ventricular dysfunction in patients undergoing haemodialysis for chronic renal failure.

METHODS

We measured plasma BNP before and at 10 min and 3, 6 and 24 h after haemodialysis in 56 patients.

RESULTS

The average plasma BNP before haemodialysis was 284 +/- 369 pg/mL, which was higher than that of healthy subjects (37 +/- 37 pg/mL; n = 32, P < 0.01). The average plasma BNP in patients with left ventricular dysfunction (n = 21) was substantially higher than that in those with normal ventricular function before and at 10 min and 3, 6 and 24 h after haemodialysis (P < 0.001). The area under the receiver operating characteristic curves was greater than 0.895 before and at the four time points after haemodialysis (P < 0.01). Using 152 pg/mL as a cut-off value, predialysis BNP has 81% sensitivity and 83% specificity in diagnosing left ventricular dysfunction in these patients.

CONCLUSION

We concluded that plasma BNP offers a good sensitivity and specificity in diagnosing left ventricular dysfunction in patients with dialysis-dependent renal failure.

Measles viral load may reflect SSPE disease progression

Subacute sclerosing panencephalitis (SSPE) is a rare, slowly progressive neurological disorder caused by the persistent infection with measles virus (MV). Despite much research into SSPE, its pathology remains obscure. We examined autopsy tissues of eight SSPE patients by real time quantitative PCR, immunohistochemistry and immunoblotting to determine viral load. MV N, M and H gene RNA could be detected in the central nervous system (CNS) of all patients and in two non-CNS tissues of one patient. The viral burden between patients differed up to four-fold by quantitative PCR and corresponded with detection of MV protein. The level of both viral RNA and antigen in the brain may correlate with disease progression.

Measles-associated encephalopathy in children with renal transplants

Two children, boys of 8 and 13 years, presented with measles-associated encephalopathy several years after kidney transplantation for congenital nephrotic syndrome. In the absence of prior clinical measles, the neurological symptoms initially eluded diagnosis, but retrospective analysis of stored samples facilitated the diagnosis of measles-associated encephalopathy without recourse to biopsy of deep cerebral lesions. Each had received a single dose of measles mumps and rubella vaccine before 12 months of age. Prior vaccination, reduction of immunosuppression and treatment with intravenous immunoglobulin and ribavirin may have contributed to their survival. Persistent measles virus RNA shedding, present in one child, was not controlled by treatment with i.v. ribavirin. Two years later, both patients continue to have functioning allografts with only minimal immunosuppression. These cases illustrate the difficulty in diagnosing measles-associated encephalopathy in the immunocompromised host, even in the era of molecular diagnostics, and highlight the renewed threat of neurological disease in communities with incomplete herd immunity.