Intermittent streptozotocin administration induces behavioral and pathological features relevant to Alzheimer's disease and vascular dementia

RATIONALE

Diabetes mellitus (DM) is a major risk factor for Alzheimer's disease and vascular dementia. Few animal models exist that focus on the metabolic contributions to dementia onset and progression. Thus, there is strong scientific rationale to explore the effects of streptozotocin (STZ), a diabetogenic compound, on vascular and inflammatory changes within the brain.

OBJECTIVE AND METHODS

The present study was designed to evaluate the effect of staggered, low-dose administration of STZ on behavioral and cognitive deficits, neuroinflammation, tau pathology, and histopathological alterations related to dementia.

RESULTS

Staggered administration (Days 1, 2, 3, 14, 15) of streptozotocin (40 mg/kg/mL) induced a diabetic-like state in mice, resulting in sustained hyperglycemia. STZ-treated animals displayed memory deficits in the novel object recognition task as well as increased tau phosphorylation and increased neuroinflammation. Additionally, STZ led to altered insulin signaling, exhibited by decreased plasma insulin and decreased levels of insulin degrading enzyme and pAKT within the hippocampus.

CONCLUSIONS

STZ-treated animals exhibit cognitive deficits and histopathological changes seen in dementia. This model of dementia warrants continued investigation to better understand the role that DM plays in dementia-related alterations.

Protection of tauroursodeoxycholic acid on high glucose-induced human retinal microvascular endothelial cells dysfunction and streptozotocin-induced diabetic retinopathy rats

ETHNOPHARMACOLOGICAL RELEVANCE

Tauroursodeoxycholic acid (TUDCA), one of the main ingredients from bear gall which hold "Clearing heat and detoxification, Removing liver fire for improving eyesight" functions, is formed by the conjugation of ursodeoxycholic acid (UDCA) with taurine. However, the limited information of TUDCA on protecting diabetic retinopathy (DR) has been known. The present study was conducted to evaluate the protection of TUDCA on high glucose-induced human retinal microvascular endothelial cells (HRMECs) dysfunction and streptozotocin (STZ)-induced diabetic retinopathy (DR) rats and the possible mechanism underlying was also explored.

MATERIALS AND METHODS

The proliferation of high glucose-induced HRMECs was determined by MTT assay. DR rats' model was established by an administration of high-glucose-fat diet and an intraperitoneal injection of STZ (30mg/kg). The cell supernatant and rats' serum were collected for the assays of NO content by ELISA kits. Retinas were stained with hematoxylin and eosin (HE) to observe pathological changes. Immunohistochemical assay was applied to examine the protein expression of ICAM-1, NOS, NF-κB p65 and VEGF in rat retinas. Furthermore, western blot analysis was carried out to examine the protein expression of ICAM-1, NOS, NF-κB p65 and VEGF in high glucose-induced HRMECs.

RESULTS

After treating with TUDCA, high glucose-induced HRMECs proliferation could be significantly inhibited. TUDCA (5.0μM, 25.0μM and 125.0μM) could decrease NO content in high glucose-induced HRMECs. Furthermore, TUDCA (500mg/kg/d and 250mg/kg/d) also decrease NO content in serum of DR rats. Additionally, both immunocytochemistry analysis and western blot analysis showed that the over-expression of ICAM-1, NOS, NF-κB p65 and VEGF were significantly decreased by TUDCA.

CONCLUSION

The data indicated that TUDCA could ameliorate DR by decreasing NO content and down-regulating the protein expression of ICAM-1, NOS, NF-κB p65 and VEGF. Thus, our experimental results suggested that TUDCA might be a potential drug for the prevention and treatment of DR.