Daniel T O'Connor

University of Washington Seattle, Seattle, Washington, United States

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Publications (378)2233.34 Total impact

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    ABSTRACT: To determine whether biomarkers of oxidized lipoproteins are genetically determined. Lipoprotein(a) (Lp[a]) is a heritable risk factor and carrier of oxidized phospholipids (OxPL). We measured oxidized phospholipids on apolipoprotein B-containing lipoprotein (OxPL-apoB), Lp(a), IgG, and IgM autoantibodies to malondialdehyde-modified low-density lipoprotein, copper oxidized low-density lipoprotein, and apoB-immune complexes in 386 monozygotic and dizygotic twins to estimate trait heritability (h(2)) and determine specific genetic effects among traits. A genome-wide linkage study followed by genetic association was performed. The h(2) (scale: 0-1) for Lp(a) was 0.91±0.01 and for OxPL-apoB 0.87±0.02, which were higher than physiological, inflammatory, or lipid traits. h(2) of IgM malondialdehyde-modified low-density lipoprotein, copper oxidized low-density lipoprotein, and apoB-immune complexes were 0.69±0.04, 0.67±0.05, and 0.80±0.03, respectively, and for IgG malondialdehyde-modified low-density lipoprotein, copper oxidized low-density lipoprotein, and apoB-immune complexes 0.62±0.05, 0.52±0.06, and 0.53±0.06, respectively. There was an inverse correlation between the major apo(a) isoform and OxPL-apoB (R=-0.49; P<0.001) and Lp(a) (R=-0.48; P<0.001) and OxPL-apoB was modestly correlated with Lp(a) (ρ=0.57; P<0.0001). The correlation in major apo(a) isoform size was concordant (R=1.0; P<0.001) among monozygotic twins but not dizygotic twins (R=0.40; P=0.055). Lp(a) and OxPL-apoB shared genetic codetermination (genetic covariance, ρG=0.774±0.032; P=1.09×10(-38)), although not environmental determination (environmental covariance, ρE=0.081±0.15; P=0.15). In contrast, Lp(a) shared environmental but not genetic codetermination with autoantibodies to malondialdehyde-modified low-density lipoprotein and copper oxidized low-density lipoprotein, and apoB-immune complexes. Sib-pair genetic linkage of the Lp(a) trait revealed that single nucleotide polymorphism rs10455872 was significantly associated with OxPL-apoB after adjusting for Lp(a). OxPL-apoB and other biomarkers of oxidized lipoproteins are highly heritable cardiovascular risk factors that suggest novel genetic origins of atherothrombosis. © 2015 American Heart Association, Inc.
    No preview · Article · May 2015 · Arteriosclerosis Thrombosis and Vascular Biology
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    ABSTRACT: The molecular factors involved in the development of Post-Traumatic Stress Disorder (PTSD) remain poorly understood. Previous transcriptomic studies investigating the mechanisms of PTSD apply targeted approaches to identify individual genes under a cross-sectional framework lack a holistic view of the behaviours and properties of these genes at the system-level. Here we sought to apply an unsupervised gene-network based approach to a prospective experimental design using whole-transcriptome RNA-Seq gene expression from peripheral blood leukocytes of U.S. Marines (N=188), obtained both pre- and post-deployment to conflict zones. We identified discrete groups of co-regulated genes (i.e., co-expression modules) and tested them for association to PTSD. We identified one module at both pre- and post-deployment containing putative causal signatures for PTSD development displaying an over-expression of genes enriched for functions of innate-immune response and interferon signalling (Type-I and Type-II). Importantly, these results were replicated in a second non-overlapping independent dataset of U.S. Marines (N=96), further outlining the role of innate immune and interferon signalling genes within co-expression modules to explain at least part of the causal pathophysiology for PTSD development. A second module, consequential of trauma exposure, contained PTSD resiliency signatures and an over-expression of genes involved in hemostasis and wound responsiveness suggesting that chronic levels of stress impair proper wound healing during/after exposure to the battlefield while highlighting the role of the hemostatic system as a clinical indicator of chronic-based stress. These findings provide novel insights for early preventative measures and advanced PTSD detection, which may lead to interventions that delay or perhaps abrogate the development of PTSD.Molecular Psychiatry advance online publication, 10 March 2015; doi:10.1038/mp.2015.9.
    No preview · Article · Mar 2015 · Molecular Psychiatry
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    ABSTRACT: Chromogranin A (CHGA) is coreleased with catecholamines from secretory vesicles in adrenal medulla and sympathetic axons. Genetic variation in the CHGA 3'-region has been associated with autonomic control of circulation, hypertension, and hypertensive nephropathy, and the CHGA 3'-untranslated region (3'-UTR) variant C+87T (rs7610) displayed peak associations with these traits in humans. Here, we explored the molecular mechanisms underlying these associations. C+87T occurred in a microRNA-107 (miR-107) motif (match: T>C), and CHGA mRNA expression varied inversely with miR-107 abundance. In cells transfected with chimeric luciferase/CHGA 3'-UTR reporters encoding either the T allele or the C allele, changes in miR-107 expression levels had much greater effects on expression of the T allele. Cotransfection experiments with hsa-miR-107 oligonucleotides and eukaryotic CHGA plasmids produced similar results. Notably, an in vitro CHGA transcription/translation experiment revealed that changes in hsa-miR-107 expression altered expression of the T allele variant only. Mice with targeted ablation of Chga exhibited greater eGFR. Using BAC transgenesis, we created a mouse model with a humanized CHGA locus (T/T genotype at C+87T), in which treatment with a hsa-miR-107 inhibitor yielded prolonged falls in SBP/DBP compared with wild-type mice. We conclude that the CHGA 3'-UTR C+87T disrupts an miR-107 motif, with differential effects on CHGA expression, and that a cis:trans (mRNA:miR) interaction regulates the association of CHGA with BP and hypertensive nephropathy. These results indicate new strategies for probing autonomic circulatory control and ultimately, susceptibility to hypertensive renal sequelae.
    Full-text · Article · Nov 2014 · Journal of the American Society of Nephrology
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    ABSTRACT: Background: Research on the etiology of post-traumatic stress disorder (PTSD) has rapidly matured, moving from candidate gene studies to interrogation of the entire human genome in genome-wide association studies (GWAS). Here we present the results of a GWAS performed on samples from combat-exposed U.S. Marines and Sailors from the Marine Resiliency Study (MRS) scheduled for deployment to Iraq and/or Afghanistan. The MRS is a large, prospective study with longitudinal follow-up designed to identify risk and resiliency factors for combat-induced stress-related symptoms. Previously implicated PTSD risk loci from the literature and polygenic risk scores across psychiatric disorders were also evaluated in the MRS cohort. Methods: Participants (N=3494) were assessed using the Clinician-Administered PTSD Scale and diagnosed using the DSM-IV diagnostic criterion. Subjects with partial and/or full PTSD diagnosis were called cases, all other subjects were designated controls, and study-wide maximum CAPS scores were used for longitudinal assessments. Genomic DNA was genotyped on the Illumina HumanOmniExpressExome array. Individual genetic ancestry was determined by supervised cluster analysis for subjects of European, African, Hispanic/Native American, and other descent. To test for association of SNPs with PTSD, logistic regressions were performed within each ancestry group and results were combined in meta-analyses. Measures of childhood and adult trauma were included to test for gene-by-environment (GxE) interactions. Polygenic risk scores from the Psychiatric Genomic Consortium were used for major depressive disorder (MDD), bipolar disorder (BPD), and schizophrenia (SCZ). Results: The array produced >800K directly genotyped and >21M imputed markers in 3494 unrelated, trauma-exposed males, of which 940 were diagnosed with partial or full PTSD. The GWAS meta-analysis identified the phosphoribosyl transferase domain containing 1 gene (PRTFDC1) as a genome-wide significant PTSD locus (rs6482463; OR=1.47, SE=0.06, p=2.04×10(-9)), with a similar effect across ancestry groups. Association of PRTFDC1 with PTSD in an independent military cohort showed some evidence for replication. Loci with suggestive evidence of association (n=25 genes, p<5×10(-6)) further implicated genes related to immune response and the ubiquitin system, but these findings remain to be replicated in larger GWASs. A replication analysis of 25 putative PTSD genes from the literature found nominally significant SNPs for the majority of these genes, but associations did not remain significant after correction for multiple comparison. A cross-disorder analysis of polygenic risk scores from GWASs of BPD, MDD, and SCZ found that PTSD diagnosis was associated with risk sores of BPD, but not with MDD or SCZ. Conclusions: This first multi-ethnic/racial GWAS of PTSD highlights the potential to increase power through meta-analyses across ancestry groups. We found evidence for PRTFDC1 as a potential novel PTSD gene, a finding that awaits further replication. Our findings indicate that the genetic architecture of PTSD may be determined by many SNPs with small effects, and overlap with other neuropsychiatric disorders, consistent with current findings from large GWAS of other psychiatric disorders.
    Full-text · Article · Oct 2014 · Psychoneuroendocrinology
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    ABSTRACT: Cigarette smoking causes insulin resistance. However, nicotine induces anti-inflammation and improves glucose tolerance in insulin resistant animal models. Here, we determined the effects of nicotine on glucose metabolism in insulin sensitive C57BL/J6 mice. Acute nicotine administration (30 min) caused fasting hyperglycemia and lowered insulin sensitivity acutely, which depended on the activation of nicotinic-cholinergic receptors (nAChRs) and correlated with increased catecholamine secretion, nitric oxide (NO) production, and glycogenolysis. Chlorisondamine (CSM), an inhibitor of nAChRs, reduced acute nicotine-induced hyperglycemia. Quantitative RT-PCR analysis revealed that the liver and muscle express predominantly β4>α10>α3>α7 and β4>α10>β1>α1 mRNA for nAChR subunits respectively, whereas the adrenal gland expresses β4>α3>α7>α10 mRNA. Chronic nicotine treatment significantly suppressed expression of α3-nAChR (predominant peripheral α-subunit) in liver. While acute nicotine treatment raised plasma norepinephrine (NE) and epinephrine (Epi) levels, chronic nicotine exposure raised only Epi. Acute nicotine treatment raised both basal and glucose-stimulated insulin secretion (GSIS). After chronic nicotine treatment, basal insulin level was elevated, but GSIS after acute saline or nicotine treatment was blunted. Chronic nicotine exposure caused an increased buildup of NO in plasma and liver, leading to decreased glycogen storage, along with a concomitant suppression of Pepck and G6Pase mRNA, thus preventing hyperglycemia. The insulin sensitizing effect of chronic nicotine was independent of weight loss. Chronic nicotine treatment enhanced PI-3K activities and increased Akt and GSK-3β phosphorylation in a nAChR-dependent manner coupled with decreased CREB phosphorylation. The latter effects caused suppression of Pepck and G6Pase gene expression. Thus, nicotine causes both insulin resistance and insulin sensitivity depending on the duration of the treatment.
    Full-text · Article · Jul 2014 · Endocrinology
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    ABSTRACT: Chromogranin A knockout (Chga-KO) mice exhibit enhanced insulin sensitivity despite obesity. Here we probed the role of the Chromogranin A-derived peptide pancreastatin (PST: CHGA273-301), by investigating the effect of diet-induced obesity (DIO) on insulin sensitivity of these mice. We found that on a high fat diet (HFD), Chga-KO mice (KO-DIO) remain more insulin sensitive than wild-type DIO (WT-DIO) mice. Concomitant with this phenotype is enhanced Akt and AMPK signaling in muscle and white adipose tissue (WAT) as well as increased FoxO1 phosphorylation and expression of mature Srebp-1c in liver and downregulation of the hepatic gluconeogenic genes, Pepck and G6pase. KO-DIO mice also exhibited downregulation of cytokines and pro-inflammatory genes and upregulation of anti-inflammatory genes in WAT, and peritoneal macrophages from KO mice displayed similarly reduced pro-inflammatory gene expression. The insulin-sensitive, anti-inflammatory phenotype of KO-DIO mice is masked by supplementing PST. Conversely, a PST variant peptide PSTv1 (PST-NΔ3: CHGA276-301), lacking PST activity, simulated the KO phenotype by sensitizing WT-DIO mice to insulin. In summary, the reduced inflammation due to PST deficiency prevented the development of insulin resistance in KO-DIO mice. Thus, obesity manifests insulin resistance only in the presence of PST, and in its absence obesity is dissociated from insulin resistance.
    Full-text · Article · Jul 2014 · Diabetes
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    ABSTRACT: Dopamine beta-hydroxylase (DBH) is the biosynthetic enzyme catalyzing formation of norepinephrine. Changes in DBH expression or activity have been implicated in the pathogenesis of cardiovascular and neuropsychiatric disorders. Genetic determination of DBH enzymatic activity and its secretion are only incompletely understood. We began with a genome-wide association search for loci contributing to DBH activity in human plasma. Initially, in a population sample of European ancestry, we identified the proximal DBH promoter as a region harboring three common trait-determining variants (top hit rs1611115, P = 7.2 × 10−51). We confirmed their effects on transcription and showed that the three variants each acted additively on gene expression. Results were replicated in a population sample of Native American descent (top hit rs1611115, P = 4.1 × 10−15). Jointly, DBH variants accounted for 57% of DBH trait variation. We further identified a genome-wide significant SNP at the LOC338797 locus on chromosome 12 as trans-quantitative trait locus (QTL) (rs4255618, P = 4.62 × 10−8). Conditional analyses on DBH identified a third genomic region contributing to DBH variation: a likely cis-QTL adjacent to DBH in SARDH (rs7040170, P = 1.31 × 10−14) on chromosome 9q. We conclude that three common SNPs in the DBH promoter act additively to control phenotypic variation in DBH levels, and that two additional novel loci (SARDH and LOC338797) may also contribute to the expression of this catecholamine biosynthetic trait. Identification of DBH variants with strong effects makes it possible to take advantage of Mendelian randomization approaches to test causal effects of this intermediate trait on disease.
    Full-text · Article · Jun 2014 · Human Molecular Genetics
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    ABSTRACT: Heart rate variability (HRV), thought to reflect autonomic nervous system function, is lowered under conditions such as posttraumatic stress disorder (PTSD). The potential confounding effects of traumatic brain injury (TBI) and depression in the relationship between HRV and PTSD have not been elucidated in a large cohort of military service members. Here we describe HRV associations with stress disorder symptoms in a large study of Marines while accounting for well-known covariates of HRV and PTSD including TBI and depression. Four battalions of male active-duty Marines (n = 2430) were assessed 1 to 2 months before a combat deployment. HRV was measured during a 5-minute rest. Depression and PTSD were assessed using the Beck Depression Inventory and Clinician-Administered PTSD Scale, respectively. When adjusting for covariates, including TBI, regression analyses showed that lower levels of high-frequency HRV were associated with a diagnosis of PTSD (β = -0.20, p = .035). Depression and PTSD severity were correlated (r = 0.49, p < .001); however, participants with PTSD but relatively low depression scores exhibited reduced high frequency compared with controls (p = .012). Marines with deployment experience (n = 1254) had lower HRV than did those with no experience (p = .033). This cross-sectional analysis of a large cohort supports associations between PTSD and reduced HRV when accounting for TBI and depression symptoms. Future postdeployment assessments will be used to determine whether predeployment HRV can predict vulnerability and resilience to the serious psychological and physiological consequences of combat exposure.
    No preview · Article · May 2014 · Psychosomatic Medicine
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    ABSTRACT: Objectives We coupled two strategies – trait extremes and genome-wide pooling – to discover a novel BP locus that encodes a previously uncharacterized thiamine transporter. Background Hypertension is a heritable trait that remains the most potent and widespread cardiovascular risk factor, though details of its genetic determination are poorly understood. Methods. Representative genomic DNA pools were created from male and female subjects in the highest and lowest 5th %iles of BP in a primary care population of >50,000 individuals. The peak associated SNPs were typed in individual DNA samples, as well as twins/siblings phenotyped for cardiovascular and autonomic traits. Biochemical properties of the associated transporter were evaluated in cellular assays. Results After chip hybridization and calculation of relative allele scores, the peak associations were typed in individual samples, revealing association of hypertension, SBP, and DBP to the previously uncharacterized solute carrier SLC35F3. The BP genetic association at SLC35F3 was validated by meta-analysis in an independent sample from the original source population, as well as the ICBP (across North America and Western Europe). Sequence homology to a putative yeast thiamine (vitamin B1) transporter prompted us to express human SLC35F3 in E. coli, which catalyzed [3H]-thiamine uptake. SLC35F3 risk allele (T/T) homozygotes displayed decreased erythrocyte thiamine content on microbiological assay. In twin pairs, the SLC35F3 risk allele predicted heritable cardiovascular traits previously associated with thiamine deficiency, including elevated cardiac stroke volume with decreased vascular resistance, and elevated pressor responses to environmental (cold) stress. Allelic expression imbalance (AEI) confirmed that cis-variation at the human SLC35F3 locus influenced expression of that gene, and the AEI peak coincided with the hypertension peak. Conclusions Novel strategies were coupled to position a new hypertension susceptibility locus, uncovering a previously unsuspected thiamine transporter whose genetic variants predicted several disturbances in cardiac and autonomic function. The results have implications for the pathogenesis and treatment of systemic hypertension.
    Full-text · Article · Apr 2014 · Journal of the American College of Cardiology
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    ABSTRACT: Elevated blood pressure (BP), a heritable risk factor for many age-related disorders, is commonly investigated in population and genetic studies, but antihypertensive use can confound study results. Routine methods to adjust for antihypertensives may not sufficiently account for newer treatment protocols (i.e., combination or multiple drug therapy) found in contemporary cohorts. We refined an existing method to impute unmedicated BP in individuals on antihypertensives by incorporating new treatment trends. We assessed BP and antihypertensive use in male twins (n = 1,237) from the Vietnam Era Twin Study of Aging: 36% reported antihypertensive use; 52% of those treated were on multiple drugs. Estimated heritability was 0.43 (95% confidence interval (CI) = 0.20-0.50) and 0.44 (95% CI = 0.22-0.61) for measured systolic BP (SBP) and diastolic BP (DBP), respectively. We imputed BP for antihypertensives by 3 approaches: (i) addition of a fixed value of 10/5mm Hg to measured SBP/DBP; (ii) incremented addition of mm Hg to BP based on number of medications; and (iii) a refined approach adding mm Hg based on antihypertensive drug class and ethnicity. The imputations did not significantly affect estimated heritability of BP. However, use of our most refined imputation method and other methods resulted in significantly increased phenotypic correlations between BP and body mass index, a trait known to be correlated with BP. This study highlights the potential usefulness of applying a representative adjustment for medication use, such as by considering drug class, ethnicity, and the combination of drugs when assessing the relationship between BP and risk factors.
    Full-text · Article · Feb 2014 · American Journal of Hypertension
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    ABSTRACT: The chromogranin A-derived peptide pancreastatin (PST) is a dysglycemic, counter-regulatory peptide for insulin action, especially in liver. Although previous evidence for a PST binding protein has been reported, such a receptor has not been identified or sequenced. We used ligand affinity to purify the PST target, with biotinylated human PST (hCHGA273-301-amide) as "bait" and mouse liver homogenate as "prey", and identified GRP78 (a.k.a. "78 kDa Glucose Regulated Protein", HSPA5, BIP) as a major interacting partner of PST. GRP78 belongs to the family of heat shock proteins (chaperones), involved in several cellular processes including protein folding and glucose metabolism. We analyzed expression of GRP78 in the absence of PST in a mouse knockout model lacking its precursor CHGA: hepatic transcriptome data revealed global over-expression of not only GRP78 but also other heat shock transcripts (of the "adaptive UPR") in CHGA(-/-) mice compared to wild-type (+/+). By contrast, we found a global decline in expression of hepatic pro-apoptotic transcripts in CHGA(-/-) mice. GRP78's ATPase enzymatic activity was dose-dependently inhibited by PST (IC50∼5.2 µM). PST also inhibited the up-regulation of GRP78 expression during UPR activation (by tunicamycin) in hepatocytes. PST inhibited insulin-stimulated glucose uptake in adipocytes, and increased hepatic expression of G6Pase (the final step in gluconeogenesis/glycogenolysis). In hepatocytes not only PST but also other GRP78-ATPase inhibitors (VER-155008 or ADP) increased G6Pase expression. GRP78 over-expression inhibited G6Pase expression in hepatocytes, with partial restoration by GRP78-ATPase inhibitors PST, VER-155008, or ADP. Our results indicate that an unexpected major hepatic target of PST is the adaptive UPR chaperone GRP78. PST not only binds to GRP78 (in pH-dependent fashion), but also inhibits GRP78's ATPase enzymatic activity, and impairs its biosynthetic response to UPR activation. PST decreases insulin-stimulated cellular glucose uptake, and PST as well as other chaperone ATPase activity inhibitors augment expression of G6Pase; GRP78 over-expression antagonizes this PST action. Analysis of the novel PST/GRP78 interaction may provide a new avenue of investigation into cellular glycemic control as well as dysglycemia.
    Full-text · Article · Jan 2014 · PLoS ONE
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    ABSTRACT: Chromogranin A (CHGA) is a major protein in secretory vesicles of neuroendocrine cells, co-released with catecholamines. Genetic variation in the CHGA 3’-UTR region is associated with hypertensive nephropathy. This study documents the biological mechanism underlying the genetic association of marker and trait. Methods and Results: An African-American population case/control study showed that individuals carrying the CHGA 3’-UTR variant C+87T (rs7610) haplotype are likely to develop end stage renal disease. Computational analysis showed that the variant is in a micro-RNA (hsa-miR-107) recognition motif, with a superior match for the risk (T) allele. In vitro expression studies revealed that CHGA mRNA expression is inversely dependent on miR-107 abundance in cells and tissues. The effects of miR-107 were seen with transfected chimeric luciferase/CHGA 3’-UTR (C+87 versus +87T) reporters in cell lines and corroborated in studies of coupled in vitro transcription/translation of each 3’-UTR/C+87T allele in CHGA cDNA. In vivo, we exploited mice with a “humanized”CHGA locus (T/T homozygotes) generated by BAC transgenesis. These mice treated with miR-107 antagomir yielded prolonged, significant falls in SBP/DBP compared to the wild-type mice. Conclusion: The 3’-UTRmRNA:miRNA-107 (cis:trans) interaction plays a role in the clinical manifestations of the CHGA 3’-UTR associations with BP and nephropathy.
    No preview · Conference Paper · Jan 2014
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    ABSTRACT: Elevated sympathetic activity is associated with kidney dysfunction. Here we used twin pairs to probe heritability of GFR and its genetic covariance with other traits. We evaluated renal and adrenergic phenotypes in twins. GFR was estimated by CKD-EPI algorithm. Heritability and genetic covariance of eGFR and associated risk traits were estimated by variance-components. Meta-analysis probed reproducibility of DBH genetic effects. Effect of DBH genetic variation on renal disease was tested in the NIDDK-AASK cohort. Norepinephrine secretion rose across eGFR tertiles while eGFR fell (p<0.0001). eGFR was heritable, at h(2) = 67.3±4.7% (p = 3.0E-18), as were secretion of norepinephrine (h(2) = 66.5±5.0%, p = 3.2E-16) and dopamine (h(2) = 56.5±5.6%, p = 1.8E-13), and eGFR displayed genetic co-determination (covariance) with norepinephrine (ρG = -0.557±0.088, p = 1.11E-08) as well as dopamine (ρG = -0.223±0.101, p = 2.3E-02). Since dopamine β-hydroxylase (DBH) catalyzes conversion of dopamine to norepinephrine, we studied functional variation at DBH; DBH promoter haplotypes predicted transcriptional activity (p<0.001), plasma DBH (p<0.0001) and norepinephrine (p = 0.0297) secretion; transcriptional activity was inversely (p<0.0001) associated with basal eGFR. Meta-analysis validated DBH haplotype effects on eGFR across 3 samples. In NIDDK-AASK, we established a role for DBH promoter variation in long-term renal decline rate (GFR slope, p = 0.003). The heritable GFR trait shares genetic determination with catecholamines, suggesting new pathophysiologic, diagnostic and therapeutic approaches towards disorders of GFR as well as CKD. Adrenergic activity may play a role in progressive renal decline, and genetic variation at DBH may assist in profiling subjects for rational preventive treatment.
    Full-text · Article · Dec 2013 · PLoS ONE
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    ABSTRACT: Chromogranin B (CHGB) is the major matrix protein in human catecholamine storage vesicles. CHGB genetic variation alters catecholamine secretion and blood pressure. Here, effective Chgb protein under-expression was achieved by siRNA in PC12 cells, resulting in similar to 48% fewer secretory granules on electron microscopy, diminished capacity for catecholamine uptake (by similar to 79%), and a similar to 73% decline in stores available for nicotinic cholinergic-stimulated secretion. In vivo, loss of Chgb in knockout mice resulted in a similar to 35% decline in chromaffin granule abundance and similar to 44% decline in granule diameter, accompanied by unregulated catecholamine release into plasma. Over-expression of CHGB was achieved by transduction of a CHGB-expressing lentivirus, resulting in similar to 127% elevation in CHGB protein, with similar to 122% greater abundance of secretory granules, but only similar to 14% increased uptake of catecholamines, and no effect on nicotinic-triggered secretion. Human CHGB protein and its proteolytic fragments inhibited nicotinic-stimulated catecholamine release by similar to 72%. One conserved-region CHGB peptide inhibited nicotinic-triggered secretion by up to similar to 41%, with partial blockade of cationic signal transduction. We conclude that bi-directional quantitative derangements in CHGB abundance result in profound changes in vesicular storage and release of catecholamines. When processed and released extra-cellularly, CHGB proteolytic fragments exert a feedback effect to inhibit catecholamine secretion, especially during nicotinic cholinergic stimulation.
    Full-text · Article · Nov 2013 · Journal of Neurochemistry
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    ABSTRACT: To understand the role of genetic variation in the catecholamine biosynthetic pathway for control of human heart rate (HR) BACKGROUND: Human HR is an integrated cardiovascular trait predictive of morbidity and survival. Since the autonomic pathway exerts rapid control over the heart, we probed the role of heredity in control of HR, focusing on a component of the autonomic sympathetic pathway already predictive of outflow responses: Cytochrome b561 (CYB561), the electron shuttle in catecholamine vesicle membranes for transmitter biosynthesis METHODS: We studied hereditary control of HR with the twin pair design, at rest and during environmental (cold) stress. SNP disruption of a micro-RNA recognition motif in the human CYB561 3'-UTR was identified computationally, and its differential effect on gene expression was demonstrated in a transfected luciferase reporter / 3'-UTR variant. We exposed of stem-cell-derived human embryoid bodies to the micro-RNA mimic or antagomir oligonucleotides, and observed effects on contraction rate in proto-hearts RESULTS: Substantial heritability (h2) was demonstrated, by twin pair variance components, for both basal/resting HR (h2=50.9±6.4% of trait variation, p=2.47E-10) and stress-augmented HR (h2=55.1±5.9%, p=8.79E-13), and the two HR traits shared genetic determination (genetic covariance ρG=0.747±0.058, p=2.85E-09). CYB561 displayed one common genetic variant in the transcript region: A+1485G (rs3087776), in the 3'-UTR, 1485 bp downstream of the termination codon, in a conserved region, with the A-allele ancestral in primates. In a twin/sibling sample (n=576), A+1485G influenced HR, both at rest (p=0.010) and after environmental stress (p=0.002), with the minor (A) allele displaying a recessive effect with lower HR. The effect of A+1485G on HR was extended by meta-analysis into two additional population samples (total n=2579), and the influence remained directionally consistent and significant (p=0.007). A+1485G disrupted a micro-RNA (hsa-miR-1294) recognition motif in the 3'-UTR (with AG) was demonstrated in a transfected luciferase reporter / human 3'-UTR variant system in two different neuronal/neuroendocrine cell types, and the micro-RNA effect was further documented by co-transfection of a hsa-miR-1294 mimic, yielding an exaggerated decline in expression of the A-allele (better match) reporter (p=4.3E-05). Similar findings of differential 3'-UTR allelic susceptibility to miR-1294 were noted during expression of the full-length human CYB561 mRNA with its cognate 3'-UTR. Finally, exposure of stem-cell-derived human embryoid bodies to miR-1294 mimic or antagomir oligonucleotides yielded directionally opposite effects on contraction rate in proto-hearts CONCLUSIONS: HR is a substantially heritable trait, with genetic influence by variation in the adrenergic pathway, here shown for mRNA translational control at the CYB561 step of transmitter formation. The results have implications for potentially modifiable autonomic pathways that influence this risk trait in the population.
    Full-text · Article · Oct 2013 · Journal of the American College of Cardiology
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    ABSTRACT: Catecholamines (CAs) and granin peptides are costored in dense-core vesicles within the chromaffin cells of the adrenal medulla and in other endocrine organs and neurons. Granins play a major functional and structural role in chromaffin cells but are ubiquitous proteins, which are present also in secretory cells of the nervous, endocrine, and immune systems, where they regulate a number of cellular functions. Furthermore, recent studies also demonstrate that granin-derived peptides can functionally interact with CA to modulate key physiological functions such as lipolysis and blood pressure. In this chapter, we will provide a brief update on the interaction between CA and granins at the cellular and organ levels. We will first discuss recent data on the regulation of exocytosis of CA and peptides from the chromaffin cells by the sympathetic nervous system with a specific reference to the prominent role played by splanchnic nerve-derived pituitary adenylate cyclase-activating peptide (PACAP). Secondly, we will discuss the role of granins in the storage and regulation of exocytosis in large dense-core vesicles. Finally, we will provide an up-to-date review of the roles played by two granin-derived peptides, the chromogranin A-derived peptide catestatin and the VGF-derived peptide TLQP-21, on lipolysis and obesity. In conclusion, the knowledge gathered from recent findings on the role played by proteins/peptides in the sympathetic/target cell synapses, discussed in this chapter, would contribute to and provide novel mechanistic support for an increased appreciation of the physiological role of CA in human pathophysiology.
    Full-text · Article · Sep 2013 · Advances in pharmacology (San Diego, Calif.)
  • Yuqing Chen · Daniel T O'Connor
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    ABSTRACT: Kidney International aims to inform the renal researcher and practicing nephrologists on all aspects of renal research. Clinical and basic renal research, commentaries, The Renal Consult, Nephrology sans Frontieres, minireviews, reviews, Nephrology Images, Journal Club. Published weekly online and twice a month in print.
    No preview · Article · Aug 2013 · Kidney International
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    ABSTRACT: The endogenous catecholamine release-inhibitory peptide catestatin (CST) regulates events leading to hypertension and cardiovascular disease. Earlier we studied the structure of CST by NMR, molecular modeling, and amino acid scanning mutagenesis. That structure has now been exploited for elucidation of interface pharmacophores that mediate binding of CST to its target, with consequent secretory inhibition. Designed pharmacophore models allowed screening of 3D structural domains. Selected compounds were tested on both cultured catecholaminergic cells and an in vivo model of hypertension; in each case, the candidates showed substantial mimicry of native CST actions, with preserved or enhanced potency and specificity. The approach and compounds have thus enabled rational design of novel drug candidates for treatment of hypertension or autonomic dysfunction.
    Full-text · Article · Jul 2013 · Bioorganic & medicinal chemistry
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    ABSTRACT: The Syrian Cardiomyopathic Hamster (BIO-14.6/53.58 strains) model of cardiac failure, resulting from naturally occurring deletion at the SGCD (delta-sarcoglycan) locus, displays widespread disturbances in catecholamine metabolism. Rare Mendelian myopathy disorders of human SGCD occur, though common naturally occurring SGCD genetic variation has not been evaluated for effects on human norepinephrine (NE) secretion. This study investigated the effect of SGCD genetic variation on control of NE secretion in healthy twin pairs. Genetic associations profiled SNPs across the SGCD locus. Trait heritability (h(2) ) and genetic covariance (pleiotropy; shared h(2) ) were evaluated. Sympathochromaffin exocytosis in vivo was probed in plasma by both catecholamines and CHGB. Plasma NE is substantially heritable (P=3.19E-16, at 65.2±5.0% of trait variance), sharing significant (P<0.05) genetic determination with circulating and urinary catecholamines, CHGB, eGFR and several cardio-metabolic traits. Participants with higher pNE showed significant (P<0.05) differences in several traits, including increased BP and hypertension risk factors. Peak SGCD variant rs1835919 predicted elevated systemic vascular compliance, without changes in specifically myocardial traits. We used a chimeric regulated secretory pathway photoprotein (CHGA-EAP) to evaluate the effect of SGCD on the exocytotic pathway in transfected PC12 cells; in transfected cells, expression of SGCD augmented CHGA trafficking into the exocytotic regulated secretory pathway. Thus our investigation determined human NE secretion to be a highly heritable trait, influenced by common genetic variation within the SGCD locus. Circulating NE aggregates with BP and hypertension risk factors. Additionally, coordinate NE and CHGB elevation by rs1835919 implicates exocytosis as the mechanism of release. This article is protected by copyright. All rights reserved.
    Full-text · Article · Jun 2013 · Journal of Neurochemistry
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    ABSTRACT: Neuropeptide Y (NPY) is abundant in mammals, where it contributes to diverse behavioral and physiological functions, centrally and peripherally, but little information is available in regard to NPY cerebrospinal fluid (CSF)/plasma concentration relationships and dynamics. Since plasma NPY levels are commonly used as proxy "biomarkers" for central NPY activity in stress and mental health research in humans this study aims to better characterize the CSF/plasma NPY relationships. Subjects were eleven healthy male volunteers, admitted to the clinical research center for placement of an indwelling CSF catheter, as well as venous catheter, for 24-h collection of CSF NPY (cNPY) and plasma NPY (pNPY) samples. As observed in prior studies, group mean (SE) cNPY concentrations [792.1 (7.80) pg/mL] were higher than pNPY concentrations [220.0 (3.63) pg/mL]. For the eleven normal volunteers who had sufficient common (hourly) pNPY and cNPY data points, analysis of pNPY/cNPY concentration ratios and lagged cross-correlation analysis was completed. Average pNPY/cNPY concentration ratios ranged from .20 to .40 across study subjects, with a mean of .29. pNPY/cNPY cross correlation analyses, computed at varying time lags, were non-significant. An attempt was made to analyze the circadian rhythmicity of NPY secretion, but circadian components were not detectable. Using 24-h data collection, we characterized CSF/plasma NPY relationships, including presentation of evidence of weak CSF and plasma correlations, an important consideration for study design of NPY in stress or mental health.
    No preview · Article · Jun 2013 · Psychoneuroendocrinology

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  • 2015
    • University of Washington Seattle
      Seattle, Washington, United States
  • 1998-2014
    • VA San Diego Healthcare System
      San Diego, California, United States
    • Robarts Research Institute
      London, Ontario, Canada
  • 1979-2014
    • University of California, San Diego
      • • Department of Medicine
      • • Department of Bioengineering
      • • Division of Nephrology
      San Diego, California, United States
  • 2013
    • Beijing Medical University
      • Department of Medicine
      Peping, Beijing, China
  • 2007-2009
    • Uppsala University
      • Department of Medical Sciences
      Uppsala, Uppsala, Sweden
    • University of Dallas
      Irving, Texas, United States
  • 2006
    • Uppsala University Hospital
      Uppsala, Uppsala, Sweden
    • Leiden University
      Leyden, South Holland, Netherlands
    • San Diego State University
      • Department of Biology
      San Diego, California, United States
  • 1978-2006
    • National University (California)
      San Diego, California, United States
  • 2005
    • Hospital Universitario Virgen Macarena
      Hispalis, Andalusia, Spain
    • California College San Diego
      San Diego, California, United States
  • 1999-2005
    • Queensland Institute of Medical Research
      • Genetic Epidemiology Laboratory
      Brisbane, Queensland, Australia
  • 2004
    • Indiana University-Purdue University Indianapolis
      Indianapolis, Indiana, United States
  • 2002
    • St Andrew’s Hospital
      Tarndarnya, South Australia, Australia
  • 2001
    • Vanderbilt University
      • Department of Neurology
      Нашвилл, Michigan, United States
    • Case Western Reserve University
      Cleveland, Ohio, United States
  • 1993
    • University of Gothenburg
      Goeteborg, Västra Götaland, Sweden
  • 1978-1981
    • Naval Medical Center San Diego
      San Diego, California, United States