Enhanced rice bran extracts attenuate STZ-induced β-cell injury and diabetes-related metabolic disturbances

초록

Diabetes mellitus is a metabolic disease characterized by impaired glucose homeostasis resulting from defective insulin secretion and/or action. Current therapeutic strategies remain limited by adverse effects and incomplete glycemic control. Rice bran is a by-product generated during rice milling rich in bioactive components, including γ-oryzanol, phenolic compounds, and tocopherols/tocotrienols, and has attracted attention as a potential antidiabetic agent. This study investigated whether rice bran extracts obtained using various processing techniques protect pancreatic β-cells against streptozotocin (STZ)-induced injury in vitro and ameliorate STZ-induced diabetes in vivo . In vitro , STZ treatment of hamster-derived HIT-T15 and mouse-derived NIT-1 β-cell lines induced a diabetic-like phenotype characterized by reduced cell viability, increased reactive oxygen species (ROS) production, disrupted cytosolic calcium homeostasis, and altered expression of key β-cell regulatory proteins such as Glut1, Glut4, and Pdx1, with the magnitude of these changes differing between the two cell lines. Treatment with rice bran extracts partially reversed these alterations in a cell line–dependent manner, with selected preparations improving viability and significantly attenuating ROS accumulation and calcium/protein abnormalities in NIT-1 cells, while most treatments produced only modest or non-significant changes in HIT-T15 cells, thereby indicating a limited yet selective protective influence on β-cell integrity. In an STZ-induced diabetic mouse model, dietary supplementation with rice bran extracts attenuated weight loss and polydipsia and partially improved fasting hyperglycemia and glucose tolerance, mirroring the protective effects observed in vitro . Histological examination further revealed reduced hepatic lipid accumulation and attenuation of exocrine pancreatic injury in rice bran extract–supplemented groups. Additionally, rice bran extract administration modulated plasma glucagon-like peptide-1 (GLP-1) levels and partially restored epididymal white adipose tissue (eWAT) mass, supporting partial restoration of systemic metabolic homeostasis. Collectively, these findings demonstrate that rice bran extracts produced through enzyme-based processing and fermentation protect pancreatic β-cells against STZ-induced oxidative stress and cell death in vitro and improve dysregulated glycemic control, hepatic lipid metabolism, and adipose tissue morphology in vivo , supporting their potential as antidiabetic functional ingredients. © 2026 The Authors.

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