Pinitol from soybeans reduces postprandial blood glucose in patients with type 2 diabetes mellitus.

The effect of 3-O-methyl-D-chiro-inositol (D-pinitol), purified from soybean, on the postprandial blood glucose response in patients with type 2 diabetes mellitus was examined. Fifteen Korean subjects with type 2 diabetes mellitus (seven men, eight women; 60.3 +/- 3.1 years old) ingested cooked white rice containing 50 g of available carbohydrate with or without prior ingestion of soy pinitol. Pinitol was given either as a 1.2 g dose at 0, 60, 120, or 180 minutes prior to rice ingestion, or as a 0.6 g dose at 60 minutes prior to rice ingestion. Capillary blood glucose levels were monitored for 4 hours after rice consumption. The ingestion of 1.2 g of pinitol 60 minutes prior to rice consumption controlled postprandial capillary blood glucose most effectively, significantly diminishing the postprandial increase in plasma glucose levels measured at 90 and 120 minutes after rice consumption (P < .05). The incremental area under the plasma glucose response curve for subjects who consumed both pinitol and rice was significantly lower than that for subjects who consumed only rice (P < .05), but pinitol had no apparent effect on postprandial insulin levels. Therefore, soybean-derived pinitol may be useful in controlling postprandial increases in blood glucose in patients with type 2 diabetes.

Porcine pancreatic alpha-amylase hydrolysis of native starch granules as a function of granule surface area.

Porcine pancreatic alpha-amylase activity on native starch granules is more accurately described as a function of surface area of the granules rather than of substrate concentration. The apparent K(m) of alpha-amylolysis of native starch from potato, maize, and rice expressed as a function of substrate concentration was largest for potato with a single value of V(max). However, the ratio of the slope of a Lineweaver-Burk plot to that of rice for enzymatic hydrolysis of native potato and maize starch were 7.78 and 2.58, respectively, which were very close to the ratio of surface area per mass of the two starch granules to that of rice. Therefore, the reciprocal of initial velocity was a linear function of the reciprocal of surface area for each starch granule. Surface area was calculated assuming the starch granules were spherical. The values obtained by this calculation were in good agreement with the value obtained by the photomicrographic method. By comparing enzymatic digestion of native maize granules to that of rice granules, it was concluded that the presence of pores in maize granules appeared to significantly affect overall rate of digestion after sufficient reaction time, but not at the very initial stage of hydrolysis.