Age-Independent Hypocholesterolemic Effects of Rice Protein via FXR-Mediated Stimulation of Cholesterol Elimination

The present study investigated the effect of rice protein (RP) on plasma cholesterol clearance by administering diets containing either casein or RP to growing and adult male Wistar rats over a two-week period. RP intake markedly upregulated the gene and protein expression of key regulators involved in cholesterol transport and metabolism, including ATP-binding cassette transporter G1 (ABCG1), scavenger receptor class B type I (SR-BI), ABCG5, bile salt export pump (BSEP), coactivator-associated arginine methyltransferase 1 (CARM1), and farnesoid X receptor (FXR), in both age groups. These findings indicate that RP effectively promotes cholesterol and bile acid excretion. Consequently, RP significantly reduced cholesterol concentrations in both plasma and liver (p < 0.05), while fecal excretion of cholesterol and bile acids was significantly increased (p < 0.05). Overall, the results reveal a clear association between the cholesterol-lowering effects of RP and its regulatory role in cholesterol elimination, irrespective of age. Notably, the ability of RP to stimulate the expression of ABCG1, low-density lipoprotein receptor (LDLR), SR-BI, ABCG5, BSEP, CARM1, and FXR remains unaffected by aging, suggesting a consistent hypocholesterolemic effect across different life stages.