Effects of an enriched environment on metabolic markers and ultrastructural morphology of optic nerve in an experimental model of diabetes

Abstract

Abstract: 

Type 2 diabetes (DBT2) affects the central nervous system (CNS) and vision. Environmental enrichment (EA), allows to develop greater physical activity and neurocognitive stimulation, being able to help in experimental animals in the treatment of CNS pathologies. Objective: To study the effect of exposure to EA on the ultrastructure of the optic nerve and metabolic markers in diabetic animals.

We used 24 12-month-old male Wistar rats, divided into 6 groups, 4 with a diet with 30% saturated fat (HFD) and / or moderate consumption (0.42 g / kg weight / day) of alcohol (Alc). The 2 non-diabetic control groups (C), consumed a standard chow diet. The EA groups were housed in large cages, with treadmills and ramps, the other groups in standard animal cages. The trial lasted 16 months. Metabolic markers (lipidemia, glycemia and weight) were measured. At the end of the test, the optic nerves were extracted, fixed and processed for electron microscopy. The data obtained were analyzed by ANOVA, p≤0.05.

The animals presented DBT2 at 7 months of the test, in groups HFD, Alc, HFD + Alc, hypertriglyceridemia and hypercholesterolemia and obesity were observed. Animals with EA at the end of the trial decreased their glycemic values ​​(118 ± 5 mg / dl) and had a normal weight. In the optic nerves, signs of atrophy, alteration of the shape of mitochondria and their crests were observed in the animals on the HFD and / or Alcohol diet, compared with the control groups (C and C + AE). The HFD, Alc, HFD + Alc and HFD + Alc + AE groups showed thickening of the myelin sheaths (between 39 and 233%, p = 0.01). In the animals with the HFD diet, more intracytoplasmic electrodense deposits were found, in HFD + Alc and HFD + Alc + AE the myelin sheath was observed with a greater separation of the axon (75 and 50% more, p = 0.05) than in the group C. In the Alc group, larger mitochondria were observed (119 vs 107 nm, p = 0.05) than in C.

Diet and lack of physical activity led the animals to develop DBT2. This condition affected the ultrastructure of the optic nerve. Exposure to an enriched environment partially improved metabolic and ultrastructural alterations.