Daniel T O'Connor

University of California, San Diego, San Diego, California, United States

Are you Daniel T O'Connor?

Claim your profile

Publications (347)2010.2 Total impact

  • Source
    [Show abstract] [Hide abstract]
    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.
    Endocrinology 07/2014; · 4.72 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Diabetes 07/2014; · 7.90 Impact Factor
  • [Show abstract] [Hide abstract]
    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 3 common trait-determining variants (top hit rs1611115, p=7.2 x 10(-51)). We confirmed their effects on transcription and showed that the 3 variants each acted additively on gene expression. Results were replicated in a population sample of Native American descent (top hit rs1611115, p=4.1 x 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 x 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=1.31x10(-14)) on chromosome 9q. We conclude that 3 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 (MR) approaches to test causal effects of this intermediate trait on disease.
    Human Molecular Genetics 06/2014; · 7.69 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Psychosomatic Medicine 05/2014; · 4.08 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    American Journal of Hypertension 02/2014; · 3.67 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    PLoS ONE 01/2014; 9(1):e84132. · 3.73 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    EB Meeting; 01/2014
  • [Show abstract] [Hide abstract]
    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.
    Journal of the American College of Cardiology 01/2014; · 14.09 Impact Factor
  • [Show abstract] [Hide abstract]
    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 ~ 48% fewer secretory granules on electron microscopy, diminished capacity for catecholamine uptake (by ~ 79%), and a ~ 73% decline in stores available for nicotinic cholinergic-stimulated secretion. In vivo, loss of Chgb in knockout mice resulted in a ~ 35% decline in chromaffin granule abundance and ~ 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 ~ 127% elevation in CHGB protein, with ~ 122% greater abundance of secretory granules, but only ~ 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 ~ 72%. One conserved-region CHGB peptide inhibited nicotinic-triggered secretion by up 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. Here, we show reciprocal actions of Chromogranin B (CHGB) on catecholamine storage (stimulation) and release (inhibition). The figure synthesizes consequences of experimental results. Within chromaffin cells, CHGB participates in assembly of catecholamine secretory vesicles, and governs their secretory capacity under nicotinic stimulation. After cleavage and release into the extracellular space, CHGB [and its peptide hCHGB[60-67](KFEVRLLR)] exerts negative feedback effects to inhibit the secretory response to acetylcholine (ACh).
    Journal of Neurochemistry 11/2013; · 3.97 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Journal of the American College of Cardiology 10/2013; · 14.09 Impact Factor
  • Yuqing Chen, Daniel T O'Connor
    Kidney International 08/2013; 84(2):411-3. · 8.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Bioorganic & medicinal chemistry 07/2013; · 2.82 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Journal of Neurochemistry 06/2013; · 3.97 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Psychoneuroendocrinology 06/2013; · 5.14 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Hypertension is a common hereditary syndrome with unclear pathogenesis. Chromogranin A (Chga), which catalyzes formation and cargo storage of regulated secretory granules in neuroendocrine cells, contributes to blood pressure homeostasis centrally and peripherally. Elevated Chga occurs in Spontaneously Hypertensive Rat (SHR) adrenal glands and plasma, but central expression is unexplored. In this report, we measured SHR and WKY (control) Chga expression in central and peripheral nervous systems, and found Chga protein to be decreased in SHR brainstem yet increased in adrenal and plasma. By re-sequencing, we systematically identified 5 promoter, 2 coding, and one 3'-untranslated-region (3'-UTR) polymorphism at the SHR (versus WKY or BN) Chga locus. Using HXB/BXH recombinant inbred (RI) strain linkage and correlations, we demonstrated genetic determination of Chga expression in SHR, including a cis-QTL (i.e., at the Chga locus), and such expression influenced biochemical determinants of blood pressure, including a cascade of catecholamine biosynthetic enzymes, catecholamines themselves, and steroids. Luciferase reporter assays demonstrated that the 3'-UTR polymorphism (which disrupts microRNA miR-22 motif) and promoter polymorphisms altered gene expression consistent with the decline in SHR central Chga expression. Coding region polymorphisms did not account for changes in Chga expression or function. Thus we hypothesized that the 3'-UTR and promoter mutations lead to dysregulation (diminution) of Chga in brainstem cardiovascular control nuclei, ultimately contributing to the pathogenesis of hypertension in SHR. Accordingly, we demonstrated that in vivo administration of miR-22 antagomir to SHR causes substantial (∼18&emsp14;mmHg) reductions in blood pressure, opening a novel therapeutic avenue for hypertension.
    Human Molecular Genetics 05/2013; · 7.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: Kallikrein-1 (KLK1) is a highly conserved serine protease that is expressed in the kidney and involved in blood pressure regulation. The activity of this enzyme is diminished in acute kidney injury (AKI). Methods: We first evaluated the potential role of functional multiallelic KLK1 promoter gene polymorphisms in a case-control study of 481 subjects (214 hospitalized patients with AKI of mixed causes and 267 healthy subjects). The complex, multiallelic G/C-rich repeat region of the proximal KLK1 promoter was determined by direct Sanger/capillary resequencing. Results: 16 alleles were identified in a complex, polymorphic G/C-rich region of the KLK1 proximal promoter; 5 of these alleles (F, G, H, I, and K) were associated with development of AKI. Alleles I and G were classified as risk-alleles (unadjusted OR 1.86; 95% CI 1.23, 2.81; p = 0.003), whereas alleles F, H, and K were classified as protective-alleles (unadjusted OR 0.32; 95% CI 0.22, 0.46; p < 0.001) according to their directional association with development of AKI. After adjustment for sex, race, preexisting chronic kidney disease and APACHE II score, the KLK1 risk-allele (I or G) carrier state was associated with the composite of ≥2-fold increase in serum creatinine, oliguria, or dialysis requirement (adjusted OR 2.71; 95% CI 1.14, 6.44; p = 0.02). The KLK1 risk-allele carrier state was also marginally associated with the composite of ≥2-fold increase in serum creatinine, oliguria, dialysis requirement, or in-hospital death (adjusted OR 2.33; 95% CI 0.98, 5.52; p = 0.06). Conclusions: KLK1 promoter polymorphisms are associated with development of AKI and adverse outcomes. Further studies are needed to validate these findings.
    Nephron Clinical Practice 04/2013; 122(3-4):107-113. · 1.65 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Uromodulin (UMOD) genetic variants cause familial juvenile hyperuricemic nephropathy, characterized by hyperuricemia with decreased renal excretion of UMOD and uric acid, suggesting a role for UMOD in the regulation of plasma uric acid. To determine this, we screened common variants across the UMOD locus in one community-based Chinese population of 1000 individuals and the other population from 642 American twins and siblings of European and Hispanic ancestry. Transcriptional activity of promoter variants was estimated in luciferase reporter plasmids transfected into HEK-293 cells and mIMCD3 cells. In the primary Chinese population, we found that carriers of the GCC haplotype had higher plasma uric acid, and three promoter variants were associated with plasma uric acid. UMOD promoter variants displayed reciprocal effects on urine uric acid excretion and plasma uric acid concentration, suggesting a primary effect on renal tubular handling of urate. These UMOD genetic marker-on-trait associations for uric acid were replicated in the independent American cohort. Site-directed mutagenesis at trait-associated UMOD promoter variants altered promoter activity in transfected luciferase reporter plasmids. Thus, UMOD promoter variants seem to initiate a cascade of transcriptional and biochemical changes influencing UMOD secretion, leading to altered plasma uric acid levels.Kidney International advance online publication, 23 January 2013; doi:10.1038/ki.2012.449.
    Kidney International 01/2013; · 8.52 Impact Factor
  • Source
  • Source
    [Show abstract] [Hide abstract]
    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.
    PLoS ONE 01/2013; 8(12):e82956. · 3.73 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Advances in pharmacology (San Diego, Calif.) 01/2013; 68:93-113.

Publication Stats

7k Citations
2,010.20 Total Impact Points

Institutions

  • 1982–2014
    • University of California, San Diego
      • • Department of Medicine
      • • Skaggs School of Pharmacy and Pharmaceutical Sciences
      • • Department of Family and Preventive Medicine
      • • Department of Bioengineering
      San Diego, California, United States
  • 2013
    • The Scripps Research Institute
      • Department of Molecular and Experimental Medicine
      La Jolla, California, United States
  • 2011–2013
    • St. Elizabeth's Medical Center
      Boston, Massachusetts, United States
    • Queensland Institute of Medical Research
      • Genetic Epidemiology Laboratory
      Brisbane, Queensland, Australia
    • Inje University
      Kŭmhae, South Gyeongsang, South Korea
  • 2010–2013
    • Beijing Medical University
      • Department of Medicine
      Peping, Beijing, China
    • Tufts Medical Center
      • Division of Nephrology
      Boston, Massachusetts, United States
  • 2000–2013
    • VA San Diego Healthcare System
      San Diego, California, United States
  • 2012
    • Shanghai Jiao Tong University
      Shanghai, Shanghai Shi, China
    • Tufts University
      • Department of Medicine
      Medford, MA, United States
  • 1987–2010
    • National University (California)
      San Diego, California, United States
  • 2006
    • Uppsala University Hospital
      Uppsala, Uppsala, Sweden
  • 2005
    • CSU Mentor
      Long Beach, California, United States
    • California College San Diego
      San Diego, California, United States
  • 2004
    • Université de Rennes 2
      Roazhon, Brittany, France
  • 2002
    • St Andrew’s Hospital
      Tarndarnya, South Australia, Australia
  • 1995
    • Central University of Venezuela
      Caracas, Distrito Federal, Venezuela