Browsing by Author "Pagano, Gennaro"

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    Calcium release channel RyR2 regulates insulin release and glucose homeostasis
    (2015-04) Santulli, Gaetano; Pagano, Gennaro; Sardu, Celestino; Xie, Wenjun; Reiken, Steven; D'Ascia, Salvatore Luca; Cannone, Michele; Marziliano, Nicola; Trimarco, Bruno; Guise, Theresa A.; Lacampagne, Alain; Marks, Andrew R.; Department of Medicine, IU School of Medicine
    The type 2 ryanodine receptor (RyR2) is a Ca2+ release channel on the endoplasmic reticulum (ER) of several types of cells, including cardiomyocytes and pancreatic β cells. In cardiomyocytes, RyR2-dependent Ca2+ release is critical for excitation-contraction coupling; however, a functional role for RyR2 in β cell insulin secretion and diabetes mellitus remains controversial. Here, we took advantage of rare RyR2 mutations that were identified in patients with a genetic form of exercise-induced sudden death (catecholaminergic polymorphic ventricular tachycardia [CPVT]). As these mutations result in a “leaky” RyR2 channel, we exploited them to assess RyR2 channel function in β cell dynamics. We discovered that CPVT patients with mutant leaky RyR2 present with glucose intolerance, which was heretofore unappreciated. In mice, transgenic expression of CPVT-associated RyR2 resulted in impaired glucose homeostasis, and an in-depth evaluation of pancreatic islets and β cells from these animals revealed intracellular Ca2+ leak via oxidized and nitrosylated RyR2 channels, activated ER stress response, mitochondrial dysfunction, and decreased fuel-stimulated insulin release. Additionally, we verified the effects of the pharmacological inhibition of intracellular Ca2+ leak in CPVT-associated RyR2-expressing mice, in human islets from diabetic patients, and in an established murine model of type 2 diabetes mellitus. Taken together, our data indicate that RyR2 channels play a crucial role in the regulation of insulin secretion and glucose homeostasis.
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    Longitudinal Analysis of Multiple Neurotransmitter Metabolites in Cerebrospinal Fluid in Early Parkinson's Disease
    (Wiley, 2021-08) Kremer, Thomas; Taylor, Kirsten I.; Siebourg-Polster, Juliane; Gerken, Thomas; Staempfli, Andreas; Czech, Christian; Dukart, Juergen; Galasko, Douglas; Foroud, Tatiana; Chahine, Lana M.; Coffey, Christopher S.; Simuni, Tanya; Weintraub, Daniel; Seibyl, John; Poston, Kathleen L.; Toga, Arthur W.; Tanner, Caroline M.; Marek, Kenneth; Hutten, Samantha J.; Dziadek, Sebastian; Trenkwalder, Claudia; Pagano, Gennaro; Mollenhauer, Brit; Medical and Molecular Genetics, School of Medicine
    Background: Cerebrospinal fluid (CSF) levels of monoamine metabolites may represent biomarkers of Parkinson's disease (PD). Objective: The aim of this study was quantification of multiple metabolites in CSF from PD versus healthy control subjects (HCs), including longitudinal analysis. Methods: Absolute levels of multiple monoamine metabolites in CSF were quantified by liquid chromatography coupled with tandem mass spectrometry from 161 individuals with early PD and 115 HCs from the Parkinson's Progression Marker Initiative and de novo PD (DeNoPA) studies. Results: Baseline levels of homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were lower in individuals with PD compared with HCs. HVA levels correlated with Movement Disorder Society Unified Parkinson's Disease Rating Scale total scores (P < 0.01). Both HVA/dopamine and DOPAC/dopamine levels correlated with caudate nucleus and raw DOPAC with putamen dopamine transporter single-photon emission computed tomography uptake ratios (P < 0.01). No metabolite changed over 2 years in drug-naive individuals, but some changed on starting levodopa treatment. Conclusions: HVA and DOPAC CSF levels mirrored nigrostriatal pathway damage, confirming the central role of dopaminergic degeneration in early PD.