Protective actions of taurine against streptozotocin-induced hyperglycemia

Abstract

The effect of continuous administration of taurine (2-aminoethanesulfonic acid) on streptozotocin (STZ)-induced hyperglycemia was examined. Acute administration of STZ (250 mg/kg, i.v.) to ddy strain mice induced transient but significant increase in the serum level of glucose and decrease in the pancreatic immunoreactive insulin (IRI) content at 24 hr after the administration. These changes induced by acute STZ administration were suppressed significantly by the oral pretreatment of animals with taurine (7–9 g/kg/day, for 5–7 days). Similar preventive effects were also observed when methionine or cysteine was orally administered for 7 days prior to the sacrifice of STZ administered animals, whereas isoleucine and valine had not such preventive properties. Since the administration of these three amino acids, which have a suppressive effect on STZ-induced hyperglycemia, significantly increased taurine content in the pancreas, it is suggested that the increase in pancreatic taurine may be intimately related to the protective effect against the pancreato-toxic action of STZ. In CD-1 strain mice, one of the STZ-sensitive strains, the continuous administration of taurine not only exhibited significant preventive effects on hyperglycemia and decrease in serum and pancreatic contents of IRI induced by acute administration of STZ (150 mg/kg, i.v.), but also suppressed the continuous hyperglycemia and fall in pancreatic IRI content caused by the repeated administration of STZ (50 mg/kg, i.p., for 5 days). In addition, it was also found that morphological alterations in the islets of Langerhans induced by STZ were considerably less in taurine-treated animals than those found in animals treated with STZ alone. These results suggest that pancreatic taurine may play important physiological roles in maintaining the function and/or integrity of β cells in the islets of Langerhans and protecting these structures from pancreato-toxic substances such as STZ.