Kazuki Shiga

Reducing Effect of Ingesting Tannic Acid on the Absorption of Iron, but Not of Zinc, Copper and Manganese by Rats

Interest in the beneficial effects of polyphenols, including tannic acid (TA), is increasing, although, these compounds also have adverse effects; for example, on the absorption of iron (Fe), and possibly other trace minerals. We examined the effect of a graded dose of TA on the absorption of Fe and compared with that of zinc (Zn), copper (Cu) and manganese (Mn) in rats. We also investigated the effect of TA on cecal fermentation which plays a role in absorption. In Experiment 1, to set the optimum dose of Fe, male Sprague-Dawley rats (weighing 70–90 g) after acclimatization were fed with different levels of dietary Fe (5, 10, 20, 30 and 35 mg/kg). We observed that the hematocrit (Ht), serum Fe concentration and transferrin saturation (%) were each reduced in those rats fed less than 20 mg/kg Fe in a dose-dependant manner. In Experiment 2, the rats were fed with test diets containing the minimum required level of Fe, 30 mg/kg diet, with (5, 10, 15 and 20 g/kg diet) or without TA for a period of three weeks. Feeding a diet containing more than 10 g TA/kg diet, but not 5 g TA/kg diet, reduced the hemoglobin concentration (Hb), Ht and serum Fe concentration due to decreased Fe absorption. In contrast, the Zn, Cu and Mn absorption was not affected by TA feeding. It is also demonstrated that liver Fe, but not the Zn, Cu and Mn contents, were lower in the TA groups than in the TA-free control group. Feeding TA slightly decreased the pH value of the cecal contents with an increase in the major short-chain fatty acid pool. About 15% of the ingested TA were recovered in the feces of each TA-fed group. Our results demonstrate that more than 10 g TA/kg diet induced anemia by reducing the Fe absorption, although there was no effect on the absorption of other important trace minerals. Our findings suggest that the usual intake of polyphenols is relatively safe, but that a high intake by supplementation or by dietary habit of tannin affects only the Fe level.

Ingestion of water-soluble soybean fiber improves gastrectomy-induced calcium malabsorption and osteopenia in rats

OBJECTIVE Total gastrectomy produces calcium malabsorption and osteopenia. We examined the effects of feeding water-soluble soybean fiber (WSSF), a highly fermentable dietary fiber with low viscosity, on calcium absorption and bone characteristics in totally gastrectomized rats. METHODS Male Sprague-Dawley rats were assigned to two groups: sham operation and gastrectomy. After the postoperative recovery period, rats of each group were fed diets with or without WSSF (50 g/kg diet) for 4 wk. RESULTS Net calcium absorption and femoral dry weight and calcium content and maximum breaking force were lower in the gastrectomy groups than in the sham groups. In the gastrectomy groups, calcium absorption and these femoral parameters were higher in rats fed the WSSF diet than in rats fed the WSSF-free diet. Feeding WSSF increased the concentrations of short-chain fatty acids and soluble calcium and decreased the pH in cecal contents. Net calcium absorption in gastrectomized rats correlated positively with the concentration of total short-chain fatty acids (the sum of acetic, propionic, and butyric acids) in cecal contents (r = 0.545, P < 0.05) and negatively with cecal pH (r = -0.628, P < 0.05). CONCLUSIONS These findings indicate that ingestion of WSSF partly prevents the diminished calcium absorption after total gastrectomy in rats, resulting in the improvement of postgastrectomy osteopenia. The increase of calcium absorption may be associated with cecal fermentation of WSSF.

Massive large bowel resection decreases bone strength and magnesium content but not calcium content of the femur in rats

We examined the effects of massive large bowel resection (cecocolonectomy) on calcium and magnesium absorption and bone characteristics in rats. Male Sprague-Dawley rats were divided into two groups: sham-operated and cecocolonectomized rats. The rats were fed a sucrose-based diet containing casein at 250 g/kg diet for 10 d after a 9- to 10-d postoperative recovery period. Apparent magnesium absorption but not calcium absorption was lower in the resection group than in the sham group. There was a tendency of lower serum magnesium concentration (P = 0.070) but not calcium concentration (P = 0.418) in the resection group compared with the sham group. The maximum breaking force and magnesium content but not the calcium content of the femur were lower in the resection group than in the sham group. These results suggest that massive large bowel resection influences magnesium kinetics and decreases bone strength through reduction of the magnesium content of the femur in rats. Femoral breaking force was positively correlated (r = 0.617, P = 0.011) with only the magnesium content. We conclude that the changes in magnesium kinetics caused by cecocolonectomy could contribute to the fragility of bone.

Ingestion of difructose anhydride III, a non-digestible disaccharide, improves postgastrectomy osteopenia in rats

Objective. Total gastrectomy produces osteopenia with calcium malabsorption. We previously demonstrated that difructose anhydride III (DFAIII), a non-digestible disaccharide, stimulates intestinal calcium absorption in normal and ovariectomized rats. In the present study, we examined the effects of feeding DFAIII on gastrectomy-induced calcium malabsorption and osteopenia in rats. The potential of DFAIII to promote large intestinal calcium absorption was also evaluated through comparison with that of fructooligosaccharides (FOS). Material and methods. Male Sprague-Dawley rats were divided into two groups: totally gastrectomized and sham-operated rats. After a postoperative recovery period, rats from each group were divided into three subgroups and fed the control, DFAIII (30 g/kg), or FOS (30 g/kg) diet for 28 days. Results. Total gastrectomy severely reduced net calcium absorption, femoral calcium content and bone mineral density, resulting in fragility of the femur. DFAIII or FOS feeding partly and similarly restored the lowered calcium absorption and femoral variables, with an increase in the total short-chain fatty acid pool in the cecum. In gastrectomized rats, net calcium absorption was correlated with several cecal parameters, suggesting that cecal fermentation of DFAIII is associated with the improvement in gastrectomy-induced calcium malabsorption. Urinary excretion of deoxypyridinoline (D-Pyr) as a marker of bone resorption was increased by gastrectomy, and the elevated D-Pyr excretion was suppressed by feeding DFAIII. Conclusions. Supplemental feeding of DFAIII partly prevents postgastrectomy osteopenia as a result of an improvement in calcium absorption. Our results suggest that the promotive effects of DFAIII on calcium absorption in the large intestine are comparable to those of FOS.