NON-INSULIN-DEPENDENT DIABETES-MELLITUS IN PSAMMOMYS-OBESUS IS INDEPENDENT OF CHANGES IN TISSUE FATTY-ACID COMPOSITION

Recently it has been postulated that membrane fatty acid composition m ay be involved in the pathogenesis of insulin resistance and non-insul in dependent diabetes mellitus (NIDDM). The aim of this study was to d etermine whether alterations in tissue phospholipid (PL) fatty acids a re present in hyperglycemic and hyperinsulinemic Psammomys obesus. On a native diet of salt bush, P. obesus (Israeli sand rat) remains lean and free of diabetes; however, when placed on a normal laboratory chow , a significant proportion of these animals develops a number of metab olic disorders associated with NIDDM, providing an ideal animal model of obesity and NIDDM. Four groups of mature P. obesus were studied: gr oup A: normoglycemic and normoinsulinemic; group B: normoglycemic and hyperinsulinemic; group C: hyperglycemic and hyperinsulinemic; and gro up D: hyperglycemic and hypoinsulinemic. In liver and red gastrocnemiu s muscle, there were no significant differences between groups A, B, a nd C in fatty acid composition of FL. Minor differences in individual fatty acids were demonstrated in group D animals (increased liver 20:4 n-6 and increased muscle 22:5n-3); however, the unsaturation indices i n liver and muscle were not significantly different between any of the groups. In considering that the minor changes in group D animals were not demonstrated in hyperinsulinemic group B animals or hyperglycemic hyperinsulinemic group C animals, it is likely that the differences i n group D animals were secondary to the more severe disturbances in gl ucose homeostasis and hypoinsulinemia present in these animals. The re sults of this study suggest that in this rodent diabetic model signifi cant disturbances in glucose homeostasis and hyperinsulinemia may deve lop independently of changes in tissue fatty acid composition.