engleski

Effects of anti-diabetic agent troglitazone on insulin resistance induced with oleic acid in cultured rat hepatocytes

Aim. The aim of this study was to elucidate mechanism of oleic acid induced post-binding changes and effects of new orally anti-diabetic drug troglitazone on insulin resistance in cultured rat hepatocytes. Methods. Hepatocytes were isolated by a modified collagenase perfusion technique of Berry and Friend and cultured for 24 h in M199 serum-free medium. To assess amino acid transport hepatocytes were incubated in Hanks-Hepes medium containing ?-amino14C-isobutyric acid (AIB) to the final concentration of 1 mmol/L. One hour later the medium was removed and hepatocytes were quickly frozen in liquid nitrogen after three washes with cold saline. The cells were digested in 0.2 mol/L NaOH and a aliquot were taken for determination of protein and radioactivity. Results. In hepatocytes obtained from rats on standard diet insulin almost two fold increased AIB transport (5.76ą0.21 vs. 11.05ą0.41 ; p<0.01). Oleic acid did not change basal AIB transport but reduced insulin effect to less than a half value (5.26ą0.17 vs. 6.57ą0.29 ; p<0.01). Pretreatment with phorbol 12- myristate 13-acetate (TPA) significantly stimulate basal AIB transport, but insulin effect did not change. Polymyxin B partially antagonizes the oleic acid induced reduction of AIB transport (5.01ą0.1 vs. 7.11ą0.13 ; p<0.01). Troglitazone did not produce any increase of basal and insulin stimulated AIB transport in normal hepatocytes, but normalized insulin-stimulated transport in oleic acid-induced (5.73ą0.19 vs. 9.05ą0.21 ; p<0.01). Conclusion. Troglitazone is able to prevent and reverse insulin resistance induced by oleic acid. Insulin resistance was probably result of changes in receptor-kinase activity involving of protein kinase C.

amino acid transport; anti-diabetic; insulin; insulin resistance; oleic acid; protein kinase C; Troglitazone

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