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1 Servizio Diabetologia, Dipartimento Struttura Clinica Medica e Patologia Speciale Medica, and 2 Dipartimento Scienze Biomediche Sezione di Fisiologia Umana, Universita' di Sassari, 07100 Sassari, Italy
The main aim of this study was to set up a
new animal model to study insulin resistance. Wistar rats (6 or 7 per
group) received the following for 4 wk in experiment 1:
1) vehicle, 2) 2 µg/day subcutaneous
dexamethasone, 3) metformin (400 mg · kg
1 · day
1 os), and
4) dexamethasone plus metformin. In experiment 2 the rats received the following: 1) vehicle, 2)
dexamethasone, 3) dexamethasone plus arginine (2%; as
substrate of the nitric oxide synthase for nitric oxide production) in
tap water, and 4) dexamethasone plus isosorbide dinitrate
(70 mg/kg; as direct nitric oxide donor) in tap water. Insulin
sensitivity was significantly reduced by dexamethasone already at
week 1, before the increase in blood pressure (day
15) and without significant changes in body weight compared with
vehicle. Dexamethasone-treated rats had significantly higher
triglycerides, hematocrit, and insulin, whereas serum total nitrates/ nitrites were lower compared with vehicle. The
concomitant treatment with metformin minimized all the described
effects of dexamethasone. In experiment 2, only
isosorbide dinitrate was able to prevent the observed
dexamethasone-induced metabolic, hemodynamic, and insulin
sensitivity changes. Chronic low-dose subcutaneous dexamethasone
(2 µg/day) is a useful model to study the relationships between
insulin resistance and blood pressure in the rat, and dexamethasone
might decrease insulin sensitivity and increase blood pressure through
an endothelium-mediated mechanism.
glucocorticoids; metabolic syndrome; metformin; hypertension
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