Effects of fermented red bean extract on nephropathy in streptozocin-induced diabetic rats

Kung-Chi Chan; Kar-Eng Kok; Keh-Feng Huang; Yao-Lin Weng; Yun-Chin Chung

doi:10.29219/fnr.v64.4272

Effects of fermented red bean extract on nephropathy in streptozocin-induced diabetic rats

Food Nutr Res. 2020 Dec 22:64. doi: 10.29219/fnr.v64.4272. eCollection 2020.

Authors

Kung-Chi Chan¹, Kar-Eng Kok¹, Keh-Feng Huang², Yao-Lin Weng¹, Yun-Chin Chung¹

Affiliations

¹ Department of Food and Nutrition, Providence University, Taichung, Republic of China (Taiwan).
² Department of Applied Chemistry, Providence University, Taichung, Republic of China (Taiwan).

Abstract

Background: The antioxidant effects of Bacillus subtilis-fermented red bean (natto-red bean) extract (NRBE) in young (6 weeks old) Sprague-Dawley rats and aged (12 months old) mice had been reported previously.

Objective: To evaluate the antioxidant and anti-inflammatory effects of NRBE in the kidneys of streptozocin-induced diabetic rats.

Design: Normal control rats and diabetic rats were orally gavaged with saline and low-dose NRBE (100 mg/kg body weight [BW]), medium-dose NRBE (200 mg/kg BW), and high-dose NRBE (500 mg/kg BW), for 12 weeks and then sacrificed. Concentration of fasting glucose, adiponectin, renal function markers, antioxidative markers, and pro-inflammatory markers were measured.

Results: Oral administration of 50% ethanolic extract of NRBE with a dosage of 100 mg/kg BW, 200 mg/kg BW, or 500 mg/kg BW could improve the symptoms of kidney enlargement and renal function. Supplementation of NRBE can effectively inhibit the formation of renal reactive oxygen species and advanced-glycation end-products and increase renal glutathione content and serum adiponectin. A low dose of NRBE (100 mg/kg BW) decreased fasting blood sugar and renal interleukin (IL)-6 expression. Serum C-reactive protein, renal tumor necrosis factor-α, and monocyte chemoattractant protein-1 concentrations were decreased, and renal superoxide dismutase activity was increased in the medium-dose NRBE group. Twenty-four hour creatinine clearance and urinary albumin excretion also improved by medium-dose NRBE supplementation. In NRBE, total phenols and flavonoids were 6.3 mg gallic acid equivalent/g and 12.02 mg rutin equivalent/g, respectively, and kampherol was the major active antioxidant compound.

Conclusion: This study demonstrated that appropriate amount of NRBE, 200 mg/kg BW in rats, could prevent diabetic nephropathy by improving antioxidant status and inhibiting inflammation in renal tissue.

Keywords: 24-hour creatinine clearance; C-reactive protein; advanced-glycation end-products; diabetic rats; natto-red bean extract.