Inhibition by natural dietary substances of gastrointestinal absorption of starch and sucrose in rats 2. Subchronic studies

Abstract

Acute oral consumption of various natural inhibitors of amylase (bean and hibiscus extracts) and sucrase (L-arabinose) reduce absorption of starch and sucrose respectively in rats and pigs measured by lessened appearance of circulating glucose levels. The present subchronic study was designed to determine whether these selected inhibitors of gastrointestinal starch and sucrose absorption (so-called "carb blockers") remain effective with continued use and to assess their metabolic influences after prolonged intake. Sprague-Dawley rats were gavaged twice daily over nine weeks with either water or an equal volume of water containing a formula that included bean and hibiscus extracts and L-arabinose. To estimate CHO absorption, control and treated Sprague-Dawley rats were gavaged with either water alone or an equal volume of water containing glucose, rice starch, sucrose, or combined rice starch and sucrose. Circulating glucose was measured at timed intervals over four hours. The ability to decrease starch and sucrose absorption use. No toxic effects (hepatic, renal, hematologic) were evident. Blood chemistries revealed significantly lower circulating glucose levels and a trend toward decreased HbA1C in the nondiabetic rats receiving the natural formulation compared to control. Subchronic administration of enzyme inhibitors was also associated with many metabolic changes including lowered systolic blood pressure and altered fluid-electrolyte balance. We postulate that proper intake of natural amylase and sucrase inhibitors may be useful in the prevention and treatment of many chronic disorders associated with perturbations in glucose-insulin homeostasis secondary to the rapid absorption of refined CHO.

Keywords: L-arabinose; bean and hibiscus extracts; hibiscus extract; starch blockers; sucrose blockers.

Fig 1

The changes in body weight after daily challenges with water or two grams of the novel formulation dissolved in a similar volume of water is depicted. Mean ± SEM shown for eight rats in each group. All rats drank a solution of 10% w/v sucrose in place of water from week 5 on

Fig 2

The changes in systolic blood pressure (SBP) after daily challenges with water or two grams of the novel formulation dissolved in water is depicted. Mean ± SEM shown for eight rats in each group. Rats drank a solution of 10% w/v sucrose in place of water from week 5 on. * Significantly different at that time point when compared to control.

Fig 3

Both groups of eight rats that had received water (control) or water plus two grams of the formulation (test) daily for six-nine weeks underwent a similar regimen as described in reference 26. On the day of study, instead of the usual daily gavage, they were gavaged acutely with two grams of rice starch. One-half hour prior to the CHO challenges and at the time of challenges a total of four ml of water was given to control, or two gram of formulation in four ml water was given to the test group. The change in circulating glucose at timed intervals after various challenges is depicted. Mean ± SEM shown for eight rats in each group. * Significantly different at that time point when compared to control.

Fig 4

Both groups of eight rats received a sucrose challenge. For details, see legend for Fig 3.

Fig 5

Both groups of eight rats received a glucose challenge. For details, see legend for Fig 3.

Fig 6

Both groups of 8 rats received a combined rice starch (2 grams)-sucrose (2 grams) challenge. For details, see figure legend for Fig 3.

Fig 7

Twenty-four hour intake of food and water during the ninth week of the subchronic study. * Significantly different at that time point when compared to control. N=8 in the control [C] and test [T] groups.