Unsaponifiable Matter from Rice Bran Attenuates High Glucose-Induced Lipid Accumulation by Activating AMPK in HepG2 Cells

Rice bran, a major by-product of rice milling, has a variety of health benefits, including antioxidant, anti-inflammatory, and cholesterol-lowering effects. However, the effects of rice bran unsaponifiable matter (USM) on hepatic lipid metabolism remain unclear. In this study, the effects of rice bran USM in the prevention of high glucose-induced lipid accumulation and its putative mechanism in HepG2 cells were investigated. USM significantly inhibited high glucose-induced lipid accumulation and suppressed fatty acid synthase and sterol regulatory element-binding protein-1c expression in HepG2 cells. It also increased the phosphorylation of AMP-activated protein kinase (AMPK) and acetyl coenzyme A carboxylase. Moreover, a specific inhibitor of AMPK attenuated the effects of USM on lipid accumulation. These results demonstrate that rice bran USM prevents hepatic lipid accumulation via an AMPK-dependent signaling pathway and provides a promising approach for novel lipid-lowering therapies. Practical Application: Rice bran is known to be rich in phytosterols, tocopherols, tocotrienols, and γ-oryzanol, all of which have health benefits. In recent years, the recognition of the health benefits of rice bran has resulted in its increased use in a range of food products, which far exceeds its usage as a dietary supplement. This study provides biological evidence that supports the use of rice bran unsaponifiable matter in the prevention of hepatic lipid accumulation.