Investigation of the effects of L-theanine on pancreas and liver tissue damages in diabetic rats

Diabetes mellitus (DM), characterized by hyperglycemia, is a common chronic disease associated with disorders in carbohydrate, protein and lipid metabolism. Signaling pathways triggered by hyperglycemia in diabetes play an important role in the development of diabetic complications by increasing oxidative stress, inflammation and cellular death. L-Theanine (LT) is a special amino acid found in Camellia Sinensis teas, with beneficial effects on health such as antioxidant, antiinflammatory, and antidepressant. In this study, the effects of 200 mg/kg LT supplementation by gavage for 28 days on oxidative stress, inflammation and apoptosis in pancreatic and liver tissues of streptozotocin (STZ, 60 mg/kg, intraperitoneal (i.p.), single dose) / nicotinamide (NA, 120 mg/kg, i.p., single dose) induced diabetic rats were investigated. For this purpose, 28 Wistar male rats (150-250 g, 2-3 months) were divided into 4 groups with 7 animals in each group: Control, LT, DM and DM+LT. In tissues, total and oxidized glutathione levels (TGSH and GSSG, respectively) as an indicator of oxidative stress by enzymatic colorimetric method; the gene expressions and protein levels of inducible nitric oxide synthase 2 (NOS2) and tumor necrosis factor-α (TNF-α) as the indicators of inflammation, and caspase-3 as an indicator of apoptosis by Real Time PCR and ELISA methods, respectively, were determined. Tissues were also evaluated histopathologically. When the DM+LT group was compared with the DM group; the gene expressions of TNF-α, NOS2 and the levels of caspase-3 protein in pancreatic tissue, and the levels of GSSG and GSSG/TGSH in liver tissue were found to be significantly lower (p<0.05). It was also observed that histopathological degeneration decreased in tissues. In conclusion, LT supplementation especially affected inflammation and apoptosis in pancreatic tissue and oxidative stress in liver tissue in DM. However, these needs to be supported by detailed studies on its effect on diabetes pathology in humans. Keywords: Apoptosis, Diabetes Mellitus, Inflammation, Oxidative Stress, L-Theanine