ASSESSMENT OF AMELIORATIVE POTENTIALS OF UNRIPE PLANTAIN (MUSA PARADISIACA) PEELS AGAINST HEPATO-PANCREATIC REDOX IMBALANCE AND INFLAMMATION IN TYPE-2 DIABETIC RATS

Abstract

Diabetes mellitus (DM) is a multifactorial disease affecting 10% of the adult population worldwide, with a huge economic and social burden. Type-2 diabetes mellitus (T2DM) accounts for over 90% of all cases of DM and remains a leading cause of death and morbidity globally. Medicinal plants could provide effective and affordable bioactive agents for the management of T2DM. This study therefore evaluated the in vitro antidiabetic potential and effects of unripe plantain (Musa paradisiaca L.) fruit peel in a rodent model of T2DM. Ethanol extract of the unripe Musa paradisiaca L. peel (MPE) was prepared by maceration, qualitatively and quantitatively screened for phytoconstituents and tested for in vitro antioxidant propereties. In vitro anti-diabetic potential of MPE was determined by evaluating its α-amylase and α- glucosidase inhibitory activities and its active constituents were docked against proteins relevant to the diabetic phenotype to ascertain possible mechanisms of interaction. Acute toxicity profiling of extract was carried out in male Wistar rats orally administered MPE at various doses 0, 100, 200, and 400 mg/kg and serum lipid and antioxidant profiles as well as biochemical indices of tissue toxicity were evaluated. T2DM was induced in rats by a combination of high-fat diet regimen for 12 weeks and single low-dose streptozotocin (35 mg/kg i.p) administration. Animals with blood glucose levels ≥220 mg/dL were considered diabetic and randomized into groups (n=6). The diabetic animals were post-treated (orally) with MPE (200 and 400 mg/kg) or standard drug, metformin (150 mg/kg) for 30 days. After the period of treatment, biochemical indices, antioxidant profiles, and levels of inflammatory mediators {tumor necrosis factor- α (TNF-α) and interleukin 1β, (Il-1β)} were evaluated in the serum, and the hepatic/pancreatic tissue homogenates. Also, levels of redox signaling proteins/factors (NADH, NAD +, NF-KB, C- reactive protein, 4-hydroxynonenal, protein carbonyl) were quantified. In addition, mRNA quantification of insulin signaling proteins and inflammatory cytokines (insulin receptor substrate 1, IRS-1; glycogen synthase kinase 3 beta, GSK3-β; TNF-α and Il-1β) were carried out followed by histopathological examination of the liver and pancreas. Phytochemical screening revealed the presence of tannins, polyphenols, terpenoids and cardiac glycosides. GC-FID fingerprinting also revealed large concentrations of antioxidant phytochemicals including quercetin, luteolin, myricetin, apigenin, kaempferol. These phytochemicals showed significant docking interactions with peroxisome proliferator-activated receptor gamma, PPAR-γ. MPE exhibited appreciable antioxidant activity and inhibition of carbohydrate-metabolizing enzymes in vitro, while causing no toxic effects to rats at the evaluated dosages. MPE (200 and 400 mg/kg) reversed diabetes-induced hyperglycaemia (respectively by 67% and 60%), impaired glucose tolerance, dyslipidemia and oxidoinflammatory imbalances typified by alterations in NADH/NAD + ratio (p<0.001), elevation in the levels of C-reactive protein, 4-hydroxynonenal, malondialdehyde, TNF-α and Il-1β, and reduction in endogenous antioxidant enzymes including superoxide dismutase and glutathione peroxidase. Gene expression analysis revealed downregulation of pro-inflammatory genes (TNF-α, Il-1β and GSK3-β) and upregulation of insulin receptor substrate (IRS-1) gene (up to 50% in hepatic and pancreatic tissues). The results revealed that the anti-diabetic potential of MPE proceeded through inhibition of glucose- metabolizing enzymes, antioxidant and hypolipidemic activities, and modulation of redox and inflammatory signaling events in hepatic and pancreatic tissues.