Etlingera elatior Flower Aqueous Extract Protects against Oxidative Stress-Induced Nephropathy in a Rat Model of Type 2 Diabetes.

Diabetes mellitus (DM) is a known systemic disease with increasing global prevalence and multi-organ complications including diabetic nephropathy (DN). The trend of using medicinal plants in the management of DM is increasing exponentially. Etlingera elatior is a medicinal plant that contains chemicals and antioxidants that delay the oxidation process. However, available data focusing on its use on DN are inconsistent and scarce. This study aims to investigate the antidiabetic and nephroprotective effects of E. elatior flower aqueous extract (EEAE) in a type 2 DM rat (T2DR) model. The T2DR model was developed using a combination of a high-fat diet (HFD) and a low dose of streptozotocin (STZ) at 35 mg/kg. Thirty-two Sprague Dawley male rats were randomly divided into four groups ( n  = 8): (1) control (normal rat), (2) T2DR (untreated-type 2 diabetic rat), (3) Met (250 mg/kg metformin-treated T2DR), and (4) EEAE (1000 mg/kg EEAE-treated T2DR). All treatments were administered orally for 6 weeks. EEAE significantly reduced fasting blood glucose (FBG), microalbuminuria, serum creatinine, and serum blood urea nitrogen. EEAE also reduced malondialdehyde (MDA) and enhanced the levels of antioxidant markers-superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and total antioxidant capacity (T-AOC). The inflammatory marker (interleukin (IL)-6) and fibrosis markers (transforming growth factor-beta (TGF- β ), and connective tissue growth factor (CTGF)) were significantly decreased in the EEAE-treated group. The T2DR group developed DN, which was characterized by segmental sclerosis of the glomeruli associated with focal tubular atrophy and interstitial fibrosis. Interestingly, the histology of kidney tissue in the EEAE group was preserved. This effect was similar to that of the control drug metformin. In summary, the antidiabetic and nephroprotective effects might be related to the antioxidant properties and anti-inflammatory effects of the EEAE. The antidiabetic activity could be due to the presence of the active compound cyanidin-3-O-glycosides, which is an anthocyanin antioxidant, that is present in the EEAE. E. elatior has the potential to be developed as a natural source of antioxidants that can be used for the prevention or even the treatment of DM. These findings could lead to future research into the therapeutic use of E. elatior in alleviating the progression of DM and thus preventing nephropathy.