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The mechanism of the suppressive effect of rice albumin (RA) on postprandial hyperglycemia after glucose loading was investigated. In order to examine if small peptides derived from RA are responsible for prevention of postprandial hyperglycemia, RA was hydrolysed to indigestible high-molecular-weight peptides (HMP) and low-molecular-weight peptides (LMP) by trypsin, HMP and LMP being fractionated by gel-filtration chromatography. In oral glucose tolerance test (OGTT), both HMP and LMP suppressed the increase in blood glucose levels. In vitro diffusion test results showed that HMP adsorbed glucose and retarded its diffusion rate like dietary fibers. On the other hand, LMP suppressed the expression of sodium-dependent glucose transporter-1 (SGLT1) in STC-1 cells. Therefore, the suppressive effect of RA on postprandial hyperglycemia would be due to the dual actions of HMP and LMP. Our results demonstrated the potential use of RA as a functional food material to prevent diabetes.

Abstract Empagliflozin, a sodium-glucose co-transporter (SGLT) inhibitor, reduces heart failure and sudden cardiac death but the underlying mechanisms remain elusive. In cardiomyocytes, SGLT1 and SGLT2 expression is upregulated in diabetes mellitus, heart failure, and myocardial infarction. We hypothesise that empagliflozin exerts direct effects on cardiomyocytes that attenuate diabetic cardiomyopathy. To test this hypothesis, cardiomyocytes derived from human induced pluripotent stem cells (hiPSCs) were used to test the potential effects of empagliflozin on neutralization of cardiac dysfunction induced by diabetic-like cultures. Our results indicated that insulin-free high glucose culture significantly increased the size of and NPPB, SGLT1 and SGLT2 expression of hiPSC-derived cardiomyocytes. In addition, high glucose-treated hiPSC-derived cardiomyocytes exhibited reduced contractility regardless of the increased calcium transient capacity. Interestingly, application of empagliflozin before or after high glucose treatment effectively reduced the high glucose-induced cardiac abnormalities. Since application of empagliflozin did not significantly alter viability or glycolytic capacity of the hiPSC-derived cardiomyocytes, it is plausible that empagliflozin exerts its effects via the down-regulation of SGLT1, SGLT2 and GLUT1 expression. These observations provide supportive evidence that may help explain its unexpected benefit observed in the EMPA-REG trial.

• Rice albumin was digested to indigestible HMP (14 kDa) and LMP (<2 kDa) by trypsin. • HMP and LMP suppressed the blood glucose and insulin elevation in rats (OGTT). • HMP adsorbed glucose and retarded its diffusion rate like dietary fibers. • LMP suppressed the expression of sodium-dependent glucose transporter-1 (SGLT1). The mechanism of the suppressive effect of rice albumin (RA) on postprandial hyperglycemia after glucose loading was investigated. In order to examine if small peptides derived from RA are responsible for prevention of postprandial hyperglycemia, RA was hydrolysed to indigestible high-molecular-weight peptides (HMP) and low-molecular-weight peptides (LMP) by trypsin, HMP and LMP being fractionated by gel-filtration chromatography. In oral glucose tolerance test (OGTT), both HMP and LMP suppressed the increase in blood glucose levels. In vitro diffusion test results showed that HMP adsorbed glucose and retarded its diffusion rate like dietary fibers. On the other hand, LMP suppressed the expression of sodium-dependent glucose transporter-1 (SGLT1) in STC-1 cells. Therefore, the suppressive effect of RA on postprandial hyperglycemia would be due to the dual actions of HMP and LMP. Our results demonstrated the potential use of RA as a functional food material to prevent diabetes. [ABSTRACT FROM AUTHOR]