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16-06-2022 | Diet | Adis Journal Club | Article

Diabetes Therapy

A Pilot Study to Assess Glucose, Insulin, and Incretin Responses Following Novel High Resistant Starch Rice Ingestion in Healthy Men

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Authors: Kazuyuki Takahashi, Hiroki Fujita, Naoko Fujita, Yuya Takahashi, Shunsuke Kato, Tatsunori Shimizu, Yumi Suganuma, Takehiro Sato, Hironori Waki & Yuichiro Yamada

Abstract 

Introduction

A newly developed resistant starch (RS) rice line with double mutation of starch synthase IIIa and branching enzyme IIb (ss3a/be2b) exhibits a tenfold greater percentage RS value than the wild-type rice line. Currently, the effects of cooked rice with such high RS content on secretion and action of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are unclear. Therefore, we conducted a pilot study to assess postprandial responses of GLP-1 and GIP along with glucose and insulin and also gastric emptying after ingestion of the high-RS cooked rice with ss3a/be2b in healthy subjects.

Methods

In a non-randomized crossover design, five healthy men ingested two test foods, control (low-RS) and high-RS cooked rice, with at least 1-week washout period between testing days. Plasma glucose, serum insulin, plasma total GLP-1, plasma total GIP, and also gastric emptying rate were measured after ingestion of each test food, and the incremental area under the curves (iAUC) was calculated for each biochemical parameter using the values from 0 to 180 min after ingestion.

Results

The high-RS cooked rice ingestion tended to reduce iAUC-glucose (p = 0.06) and significantly reduced iAUC-insulin (p < 0.01) and iAUC-GLP-1 (p < 0.05) but not iAUC-GIP (p = 0.21) relative to control cooked rice ingestion. In addition, the high-RS cooked rice ingestion did not affect gastric emptying.

Conclusions

The present results indicate that the suppressive effects of the high-RS cooked rice ingestion on postprandial responses of glucose and insulin may be provided through attenuation in GLP-1 secretion along with its low digestibility into glucose. We suggest that the high-RS rice with ss3a/be2b may serve as a better carbohydrate source and also as a novel functional food for dietary interventions to improve postprandial hyperglycemia and hyperinsulinemia without both enhancing GLP-1 secretion and affecting gastric emptying in patients with diabetes.

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Key Summary Points

Why carry out this study?

The effects of ingestion of novel high resistant starch (RS) rice with double mutation of starch synthase IIIa and branching enzyme IIb (ss3a/be2b) on secretion and action of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are unclear.

In a non-randomized crossover design, five healthy men ingested two test foods, control (low-RS) and high-RS cooked rice, with at least 1-week washout period between testing days, and biochemical parameters including plasma glucose, serum insulin, plasma total GLP-1, and plasma total GIP and also gastric emptying rate were measured after ingestion of each test food.

What was learned from this study?

High-RS cooked rice ingestion tended to attenuate postprandial plasma glucose elevation and significantly suppressed postprandial elevations of serum insulin and plasma total GLP-1 but not plasma total GIP relative to ingestion of control cooked rice, and it did not affect gastric emptying.

High-RS rice with ss3a/be2b may serve as a novel functional food for dietary interventions to ameliorate postprandial hyperglycemia and hyperinsulinemia without both enhancing GLP-1 release and affecting gastrointestinal motility in patients with diabetes.