Objective. The present study was conducted to evaluate the relationship between plasma oxidative stress markers such as malondialdehyde (MDA) and glutathione (GSH), inflammatory marker pentraxin-3 (PTX3), and cerebellar accumulation of alpha-synuclein in streptozotocin-(STZ-) induced diabetes model in rats. Methods. Twelve rats were included in the study. Diabetes (p = 6) was induced with a single intraperitoneal injection of streptozotocin (STZ, 60 mg/kg). Diabetes was verified after 48 h by measuring blood glucose levels. Six rats served as controls. Following 8 weeks, rats were sacrificed for biochemical and immunohistochemical evaluation. Results. Plasma MDA levels were significantly higher in diabetic rats when compared with the control rats (p < 0.01), while plasma GSH levels were lower in the diabetic group than in the control group (p < 0.01). Also, plasma pentraxin-3 levels were statistically higher in diabetic rats than in the control rats (p < 0.01). The analysis of cerebellar alpha-synuclein immunohistochemistry showed a significant increase in alpha-synuclein immunoexpression in the diabetic group compared to the control group (p < 0.01). Conclusion. Due to increased inflammation and oxidative stress in the chronic period of hyperglycemia linked to diabetes, there may be alpha-synuclein accumulation in the cerebellum and the plasma PTX3 levels may be assessed as an important biomarker of this situation.