Postprandial glycemia is a key determinant of overall glycemic control. One mechanism by which dietary strategies can reduce postprandial glycemic excursions is by slowing gastric emptying. This study aimed to evaluate the acute effect of ingesting riceberry rice (RR) compared to that of ingesting white rice (WR) on gastric emptying rate (GER), plasma glucose, and glucose-regulating hormones, including insulin, glucose-dependent insulinotropic polypeptide (GIP), and glucagon-like peptide 1 (GLP-1), in healthy subjects. A randomized, open-label, within-subject, crossover study was performed in 6 healthy men. GER was measured by scintigraphy over 240 minutes, and plasma concentrations of glucose, insulin, GLP-1 and GIP were measured at multiple time points over 180 minutes. This study revealed that RR slows GER with a reduction in postprandial plasma glucose concentrations compared to WR. Plasma insulin and GLP-1 concentrations did not differ between RR and WR. However, plasma GIP concentrations were markedly increased after WR ingesting versus after RR ingestion. We conclude that RR attenuates postprandial glycemia by slowing GER without altering plasma insulin or GLP-1. Plasma GIP concentrations are likely related to differences in GER and carbohydrate absorption. We propose that dietary fiber-enriched foods, including RR, could contribute to improvement in postprandial glycemia via delayed gastric emptying.

Gastric motility disturbance is commonly found in long-standing hyperglycemia. Both delayed and rapid gastric emptying has been reported in diabetes. However, very few studies have followed the changes in gastric emptying during disease progression in diabetes because of technical limitations.13 C-Acetic acid breath test is a validated method which is non-invasive and can be used repeatedly or serially to evaluate gastric emptying changes in animal. We investigated the gastric emptying changes in different stages of diabetes using 13 C-acetic acid breath test, as well as its related mechanisms involving interstitial cells of Cajal (ICCs), and stem cell factor (SCF) in streptozotocin-induced diabetic rats. The results showed that gastric emptying was accelerated at the early stage (12 weeks of diabetes) whereas intramuscular ICCs (ICC-IM) networks were not different from normal group. At long-term stage (28 weeks of diabetes), gastric emptying had returned to normal pattern with no delayed. ICC-IM networks were decreased in the diabetic group compared to 12th weeks, and were lower than in the normal group at the same time point. SCF levels were constantly high in the diabetic group than in the normal group. This result indicated that 13 C-acetic acid breath test is useful to track the alteration in gastric emptying during disease progression. The change of gastric emptying was not found to be significantly associated with ICC-IM. Elevated SCF may help to preserve ICC-IM, especially in the early phase of diabetes.

Long-term exposure to high glucose levels causes glucotoxicity in pancreatic β-cells associated with diabetes mellitus. The presence of natural antioxidant phenolic compounds, including the compounds from Syzygium samarangense, may help mitigate this metabolic disorder. This study aimed to optimize microwave-assisted extraction (MAE) for maximum phenolic recovery and assess the protective properties of Syzygium samarangense extract (SSE) against pancreatic β-cell mortality caused by glucotoxicity. We demonstrated that the MAE-based response surface methodology provided higher concentrations of total phenolics than the conventional reflux method (10.21 ± 0.22 mg GAE/g and 6.44 ± 0.13 mg GAE/g, respectively). According to in vitro studies, the percentage of viable rat insulinoma cell lines (INS-1 cells) was significantly lower when cultured in high glucose (HG) medium (40 mM) than in normal glucose medium (11.1 mM). Upon treatment of INS-1 cells with SSE (10, 50, and 100 µg/ml) in combination with HG, SSE exhibited a protective effect on the cell viability and inhibited cell apoptosis. In addition, SSE reduced intracellular superoxide ion concentrations in a dose-dependent manner. We conclude that the phenolics of SSE could function as antioxidants, thereby protecting pancreatic β-cells against glucotoxicity-induced apoptosis.

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