Effects of low-dose VOSO4 on age-related changes in glucose homeostasis inrats

The effects of low doses of vanadyl sulfate (0.2 mg/ml in the drinking wate r) on the age-related impairment of glucose homeostasis in Sprague-Dawley r ats were investigated. VOSO4 administration was initiated in 5-month-old an imals and lasted 3 months. Thus, in 8-month-old rats, we investigated gluco se metabolism in vive and insulin secretory function in vitro. Results show ed that VOSO4 allowed the disposal of an oral glucose load at lower insulin levels than in age-matched controls. No significant changes were found in muscle glucose transporter (GLUT-4) levels or in glycogen content upon VOSO 4 treatment. Islets isolated from VOSO4-treated rats released less insulin than control islets, but showed a better preserved sensitivity to secretago gues, in terms of incremental release over basal release, secretory efficie ncy, and maintenance of the priming effect of glucose. In conclusion, chron ic low-dose VOSO4 treatment facilitates insulin action by a mechanism indep endent of muscle GLUT-4 levels and helps preserve the appropriate sensitivi ty of beta cells to stimuli, thereby preventing age-dependent functional al terations. (C) 2000 Elsevier Science B.V. All rights reserved.