Renal hemodynamics in Otsuka Long-Evans Tokushima fatty rat, a model rat of spontaneous non-insulin-dependent diabetes mellitus with obesity

Renal hemodynamic features in obese non-insulin-dependent diabetic rats remain unknown. We investigated renal hemodynamic and morphologic changes in Otsuka Long-Evans Tokushima Fatty (OLETF) rats at the age of 5 and 10 months compared with age-matched lean nondiabetic control rats (LETO). OLETF rats showed obesity compared with age-matched LETO rats. Hyperglycemia was mild in 5-month-old OLETF rats and moderate in 10-month-old OLETF rats. The absolute value for glomerular filtration rate (GFR) was significantly higher in OLETF rats than in age-matched LETO rats at the age of 5 and 10 months. Ten-month-old OLETF rats had significantly higher absolute values for renal plasma flow (RPF) than age-matched LETO rats but not 5-month-old OLETF rats. Stepwise multiple regression analysis revealed that body weight was a powerful determinant of GFR and RPF. When factored for body weight, no difference in GFR was demonstrated between 5-month-old OLETF and LETO rats, whereas 10-month-old OLETF rats still had significantly higher GFR and RPF than age-matched LETO rats. Renal hypertrophy was demonstrated in both 5- and 10-month-old OLETF rats even when factored for body weight. Glomerular volume was significantly increased in 10-month-old OLETF rats, but the ratio of glomerular volume to body weight was not different among the groups. Both absolute value for glomerular capillary length free from mesangial area and the value factored for glomerular area were significantly longer in OLETF rats than in age-matched LETO rats. Mesangial matrix expansion was remarkable in 10-month-old OLETF rats, and the glomerular sclerosis index was significantly higher in 10-month-old OLETF rats than in age-matched LETO rats. Stepwise multiple regression analysis revealed that body weight, hemoglobin A1c, and hypertriglyceridemia were powerful determinants for kidney weight and glomerular volume. These data suggest that renal hyperfiltration and hypertrophy observed in 10-month-old OLETF rats are related to diabetic metabolic disorders and that obesity-related conditions may be involved in the renal hemodynamic and morphologic features in OLETF rats.