Published Online
on November 24, 2008

A more recent version of this article appeared on February 1, 2009

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Submitted on October 6, 2008
Revised on October 11, 2008

Diabetic Hypertensive Leptin Receptor–Deficient db/db Mice Develop Cardioregulatory Autonomic Dysfunction

Andrey C. da Costa Goncalves; Jens Tank; André Diedrich; Aline Hilzendeger; Ralph Plehm; Michael Bader; Friedrich C. Luft; Jens Jordan; and Volkmar Gross^*

From the Max Delbrück Center for Molecular Medicine (A.C.d.C.G., A.H., R.P., M.B., F.C.L., V.G.), Berlin, Germany; Institute of Clinical Pharmacology (J.T., J.J.), Hannover Medical School, Hannover, Germany; Division of Clinical Pharmacology (A.D.), Department of Medicine, Autonomic Dysfunction Service, Vanderbilt University School of Medicine, Nashville, Tenn; Department of Biophysics (A.H.), Escola Paulista de Medicina, Federal University of São Paulo, São Paulo, Brazil; and the Medical Faculty of the Charité (F.C.L.), Franz Volhard Clinic, HELIOS Klinikum, Berlin, Germany

^* To whom correspondence should be addressed. E-mail: vgross{at}mdc-berlin.de.

Abstract—Leptin receptor–deficient db/db mice develop human type 2 diabetes mellitus, hypertension, and obesity with disrupted circadian blood pressure (BP) rhythm. Whether leptin is the sole mechanism mediating autonomic imbalance and hypertension is unclear. To explore this notion further, we measured BP by radiotelemetry combined with fast Fourier transformation and assessed autonomic function pharmacologically before and after renin-angiotensin system blockade with enalapril. The resting period BP (117±3 versus 108±1.0 mm Hg) and heart rate (HR; 488±12 versus 436±8 bpm) were higher in db/db mice compared with db/+ mice. BP and HR amplitudes were lower in db/db mice compared with db/+ mice. BP response to trimetaphan (-43±5 versus -27±3 mm Hg) and HR response to metoprolol (-59±12 versus -5±4 bpm) were greater in db/db mice than in db/+ mice. The HR response to atropine was blunted in db/db mice (59±17 versus 144±24 bpm), as were baroreflex sensitivity and HR variability. Enalapril improved autonomic regulation in db/db mice. Stimulation of central -2 adrenoreceptors enhanced both parasympathetic HR control and baroreflex sensitivity in db/db mice. We suggest that functional, rather than structural, -2 adrenoceptor changes and the renin-angiotensin system are involved in the increased sympathetic and decreased parasympathetic tones in db/db mice. Our data suggest that db/db mice exhibit features found in humans with type 2 diabetic autonomic neuropathy and could serve as a model for this complication.

Key words: type 2 diabetes mellitus • obesity • hypertension • ACE inhibition • -2 adrenoceptors • autonomic dysfunction

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