Antidiabetic and Liver Histological and Ultrastructural Effects of Cynara scolymus Leaf and Flower Head Hydroethanolic Extracts in Nicotinamide/Streptozotocin-Induced Diabetic Rats

This study aims to investigate the effect of hydroethanolic extracts of Cynara scolymus (C. scolymus) leaf (CLHE) and C. scolymus flower (CFHE) on the hepatic histopathological lesions and functional biochemical changes induced by type 2 diabetes mellitus (T2DM). The rat model of T2DM was induced by intraperitoneal injection of streptozotocin (STZ) in a dose of 60 mg/kg for 15 minutes following nicotinamide (NA) (60 mg/kg). The rats were allocated into four groups: group 1 (negative control), group 2 (diabetic control), group 3 (diabetic rats supplemented with 100 mg/kg/day CLHE), and group 4 (diabetic rats supplemented with 100 mg/kg/day CFHE). Treatment with CLHE and CFHE, for the study duration of 28 days, significantly improved the deteriorated hepatic glycogen content, glycogen phosphorylase, glucose-6-phosphatase activities, serum fructosamine levels, lipid profile, aspartate transaminase activities, and alanine transaminase activities as well as serum insulin and C-peptide levels. The elevated liver lipid peroxidation and the decreased activities of superoxide dismutase and glutathione peroxidase were significantly alleviated. The elevated expression of the proinflammatory cytokine tumor necrosis factor-α in the liver of diabetic rats was significantly reduced by treatments with CLHE and CFHE. NA/STZ-induced T2DM exhibited hepatic histopathological changes in the form of disordered hepatocytes, cytoplasm dissolution, and mononuclear leukocytic infiltration. The electron microscopic ultrastructure study revealed damaged mitochondria with ill-defined cristae and fragmentation of the rough endoplasmic reticulum. Treatments with CLHE and CFHE remarkably amended these histopathological and EM ultrastructural changes. In conclusion, both CLHE and CFHE may have antidiabetic and improvement effects on the liver function and structural integrity, which may be mediated, at least in part, via suppression of inflammation and oxidative stress and enhancement of the antioxidant defence system.