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This Article Full Text Full Text (PDF) All Versions of this Article: JOE-09-0043v1 JOE-09-0043v2 201/3/377    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Klieverik, L. P Articles by Kalsbeek, A. PubMed PubMed Citation Articles by Klieverik, L. P Articles by Kalsbeek, A.

Laboratory of Endocrinology, Departments of¹ , Endocrinology and Metabolism² Clinical Chemistry, Academic Medical Center, University of Amsterdam, F5-162, 1105 AZ Amsterdam, The Netherlands³ Netherlands Institute for Neuroscience, 1105 AZ Amsterdam, The Netherlands⁴ Department of Physiology and Pharmacology, School of Medicine, Oregon Health and Science University, Portland, Oregon 97239-3098, USA

(Correspondence should be addressed to L P Klieverik; Email: l.p.klieverik{at}amc.nl)

^* (E Fliers and A Kalsbeek are joint senior authors)

Thyronamines are naturally occurring, chemical relatives of thyroid hormone. Systemic administration of synthetic 3-iodothyronamine (T₁AM) and – to a lesser extent – thyronamine (T₀AM), leads to acute bradycardia, hypothermia, decreased metabolic rate, and hyperglycemia. This profile led us to hypothesize that the central nervous system is among the principal targets of thyronamines. We investigated whether a low dose i.c.v. infusion of synthetic thyronamines recapitulates the changes in glucose metabolism that occur following i.p. thyronamine administration. Plasma glucose, glucoregulatory hormones, and endogenous glucose production (EGP) using stable isotope dilution were monitored in rats before and 120 min after an i.p. (50 mg/kg) or i.c.v. (0.5 mg/kg) bolus infusion of T₁AM, T₀AM, or vehicle. To identify the peripheral effects of centrally administered thyronamines, drug-naive rats were also infused intravenously with low dose (0.5 mg/kg) thyronamines. Systemic T₁AM rapidly increased EGP and plasma glucose, increased plasma glucagon, and corticosterone, but failed to change plasma insulin. Compared with i.p.-administered T₁AM, a 100-fold lower dose administered centrally induced a more pronounced acute EGP increase and hyperglucagonemia while plasma insulin tended to decrease. Both systemic and central infusions of T₀AM caused smaller increases in EGP, plasma glucose, and glucagon compared with T₁AM. Neither T₁AM nor T₀AM influenced any of these parameters upon low dose i.v. administration. We conclude that central administration of low-dose thyronamines suffices to induce the acute alterations in glucoregulatory hormones and glucose metabolism following systemic thyronamine infusion. Our data indicate that thyronamines can act centrally to modulate glucose metabolism.