Avocado Oil Delays Kidney Injury by Improving Serum Adiponectin Levels and Renal Mitochondrial Dysfunction in Type 2 Diabetic Rats

Abstract

Background: Type 2 diabetes mellitus decreases blood adiponectin levels, which leads to mitochondrial dysfunction in the kidney and diabetic nephropathy. Strategies for enhancing blood adiponectin levels have been proposed as therapeutic approaches for the treatment of diabetic nephropathy. As oleic acid increases serum adiponectin levels, we determined whether avocado oil, a source of oleic acid, improves diabetic nephropathy by enhancing blood adiponectin levels and mitochondrial function in type 2 diabetic Goto-Kakizaki rats during a one-year follow up. Methods: Normoglycemic rats were fed standard rodent chow control (CTRL) group or standard rodent chow plus avocado oil (AVO) group for 3, 6, and 12 months while Goto-Kakizaki rats were fed standard rodent chow diabetic (DB) group or standard rodent chow plus avocado oil (DB + AVO group). The levels of 24 h-proteinuria, serum adiponectin, and insulin were assessed using enzyme-linked immunosorbent assay (ELISA) kits. The kidneys of rats were collected for histological analysis and mitochondrial isolation. Oxidative phosphorylation coupling in the isolated mitochondria was assessed using a polarographic method. Statistical differences between means were analyzed using analysis of variance (ANOVA) and Bonferronis post hoc test. Results: Throughout the study period, adiponectin levels were lower in the DB group than in the CTRL group (p < 0.05). Adiponectin levels improved in the DB + AVO group compared to that in the DB group at months 3 and 6 of the study (p < 0.05). Insulin levels gradually decreased in a parallel manner in the DB and DB + AVO groups (p < 0.05). Proteinuria and glomerular degeneration progressively increased in the DB group during the study period. Proteinuria and glomerular degeneration decreased in the DB + AVO group compared to that in the DB group at months 3 and 6 of treatment. Mitochondrial function was impaired in the DB group at all stages of the study based on a notable decrease in respiration in the phosphorylated state (p < 0.05). This reduction was prevented in the DB + AVO group throughout the study (p < 0.05). Conclusions: Avocado oil could delay glomerular injury in the kidney and improve adiponectin levels and mitochondrial function in diabetic rats, independent of insulin levels. This finding suggests that avocado oil intake may be a nutritional strategy for attenuating diabetic nephropathy.