Hydrolea zeylanica improves cognitive impairment in high-fat diet fed-streptozotocin-induced diabetic encephalopathy in rats via regulating oxidative stress, neuroinflammation, and neurotransmission in brain

Type2 diabetes mellitus is a progressive metabolic disorder characterized by β-cell dysfunction with the increase in hepatic glucose synthesis and insulin resistance which leads to microvascular complications like diabetic encephalopathy that impairs cognitive dysfunctions, and dementia. The green and leafy vegetables of Hydrolea zeylanica are used in diet as rich source of nutrition, dietary fibers in reducing malnutrition and keeps in control the blood sugar level to treat diabetes related vascular complications. This study investigated the effect of hydroalcohol extracted fraction of leaves of H. zeylanica (HHZ) on high-fat diet fed-streptozotocin (HFD/STZ)-induced diabetes encephalopathy in experimental rats, and quantified the flavonoids, nutrients contents by HPLC analysis. HHZ demonstrated potential cellular antioxidant protection in ORAC, CAP-e tests. HHZ showed mixed competitive inhibition towards acetylcholinesterase (AChE), and butyrylcholineserase (BChE) activities, and exhibited dose dependent inhibition to both neurotransmitter activities. After 4 weeks administration of HHZ (oral, 300, and 400 mg/kg b.w.) in HFD/STZ-induced diabetic rats, HHZ-400 significantly (p < 0.001) improved the learning and memory impairment with the reduction in serum glucose and elevation in insulin level in encephalopathy rats. It also significantly (p < 0.001) improved oxidative (MDA, SOD, CAT, and GSH), and proinflammatory markers (TNF-α, IL-6, and hs-CRP) with the reduction in cholinesterase (AChE, BChE) and β-secretase (BACE1, BACE2) activities as evidenced by histological architecture of cortex in diabetic encephalopathy rats. Diet rich source of flavonoids e.g., quercetin, caffeic acid, rutin, gallic acid, and ferulic acid, nutrients, and vitamins in H. zeylanica enhanced the cellular antioxidant protection by reducing oxidative stress, neuroinflammation and neurotransmission in the brain of diabetic encephalopathy rats.