Development of a novel transgenic rice with hypocholesterolemic activity via high-level accumulation of the alpha' subunit of soybean beta-conglycinin

摘要

Soybean 7S globulin, known as beta-conglycinin, has been shown to regulate human plasma cholesterol and triglyceride levels. Furthermore, the alpha' subunit of beta-conglycinin has specifically been shown to possess low-density lipoprotein (LDL)-cholesterol-lowering activity. Therefore, accumulation of the alpha' subunit of beta-conglycinin in rice seeds could lead to the production of new functional rice that could promote human health. Herein, we used the low-glutelin rice mutant 'Koshihikari' (var. a123) and suppressed its glutelins and prolamins, the major seed storage proteins of rice, by RNA interference. The accumulation levels of the alpha' subunit in the lines with suppressed glutelin and prolamin levels were > 20 mg in 1 g of rice seeds, which is considerably higher than those in previous studies. Oral administration of the transgenic rice containing the alpha' subunit exhibited a hypocholesterolemic activity in rats; the serum total cholesterol and LDL cholesterol levels were significantly reduced when compared to those of the control rice (var. a123). The cholesterol-lowering action by transgenic rice accumulating the alpha' subunit induces a significant increase in fecal bile acid excretion and a tendency to increase in fecal cholesterol excretion. This is the first report that transgenic rice exhibits a hypocholesterolemic activity in rats in vivo by using the beta-conglycinin alpha' subunit.