Key words alginate; toxic metal; binding mechanism; affinity Metal ions absorbed via the intestinal tract, respiratory system or skin can cause serious damage to various internal organs, depending on their type and amount. For example, lead (Pb) causes acute damage to the central nervous system, and chronic damage to the kidney and hematopoetic and nervous systems.1,2) Long-term, low-dose exposure to cadmium (Cd) damages the lung (chronic bronchitis, fibrosis, emphysema), kidney (renal tubular degeneration, interstitial inflammation, fibrosis, diabetes, proteinuria), and bone (fake fracture, osteomalacia).3) Cadmium is well known to induce itai-itai disease (kidney tubular damage and osteomalacia), 4) and moreover, it is carcinogenic. 3,5) In addition, aluminum (Al) causes encephalopathy and osteodystrophy, 6,7) and copper (Cu) causes hemolytic anemia and gastroenteritis. 8) In the case of acute oral exposure, damage can be reduced by immediate treatments such as induction of vomiting and/or the use of a laxative to promote excretion of the metal. In addition, chelating agents can be administered; for example, ethylenediaminetetraacetic acid and dimercaptopropionylsulfonate are used as antidotes for Pb poisoning, 9-11) and dimercaprol is used for detoxification of Pb and Cu.11,12) However, in the case of chronic exposure, it is essential to use intrinsically safe absorption inhibitors and/or excretion accelerators that are suitable for long-term administration.Alginate (Alg), an intercellular polysaccharide found in brown algae, is used as a health food and food additive to reduce cholesterol in the blood and to inhibit weight gain. [13][14][15] It also protects the gastric mucous membrane.16) Moreover, it was reported that accumulation of strontium (Sr) in the human body decreased when sodium alginate (Na-Alg) was ingested before exposure to Sr. 17) Further, when rats pre-fed with NaAlg for ten days were administered Sr, the cumulative amount of Sr in the body was markedly reduced, compared with the control group.18) Consequently, it has been suggested that daily intake of Na-Alg would offer protection against radiation damage from radioactive fall-out by decreasing the absorption of radioactive Sr. Accordingly, the International Atomic Energy Agency (IAEA) has recommended Na-Alg intake for persons exposed to large amounts of radioactive Sr. 19)We have compared the effects of Na-Alg and Ca-Alg in promoting excretion and decreasing absorption of Sr and cesium (Cs) in rats. 20) Both additives increased the excretion of Sr, though Cs concentration was significantly reduced only in the Ca-Alg group. There have been some reports describing the capacity of Alg for metal binding and the order of affinity between Alg and metals. 21,22) However, there is little information about the relationship between the physical parameters of various metal ions and the binding affinity of these metal ions for Alg. Therefore we performed range and limitation tests of the adapting metals by evaluating the binding constants and the b...

We examined whether calcium alginate (Ca-Alg) reduces blood cholesterol levels in rats fed a highcholesterol diet. First, we examined taurocholate adsorption in vitro by various types of sodium alginate (NaAlg). High molecular-weight, guluronic acid-rich Na-Alg showed the greatest adsorption of taurocholate, and therefore the corresponding Ca-Alg was chosen for the in vivo study. Rats were fed a high-cholesterol diet or a Ca-Alg-containing diet for 2 weeks. Body weight and diet intake were measured, and the general condition of the animals was monitored during this period. After 14 d, the plasma concentration of cholesterol, portal plasma concentration of bile acid, and bile acid in feces were measured. The plasma concentration of cholesterol was significantly reduced in rats fed a 2% Ca-Alg-containing diet. Furthermore, the portal concentration of bile acid was significantly lowered in the 2% Ca-Alg group. A tendency for a Ca-Alg concentrationdependent increase in fecal excretion of bile acid was also seen, although it was not statistically significant. While several changes in biochemical parameters and histopathological findings were observed, all the values remained within the physiological range. These results indicate that Ca-Alg is effective in reducing plasma cholesterol. A possible mechanism would be enhanced fecal excretion of bile acid due to reduced intestinal reabsorption, which in turn might stimulate bile acid synthesis from cholesterol in the liver, leading to a decrease in plasma cholesterol.Key words alginate; cholesterol; bile acid Heart disease and cerebrovascular disease account for about one-quarter of all deaths in Japan, 1) and a major factor in their etiology is considered to be dyslipidemia.2-4) Indeed, dyslipidemia can be considered predominantly a modern lifestylerelated disease.5,6) Therefore, there is considerable interest in food additives or health foods that decrease cholesterol absorption or promote cholesterol excretion. Possible candidates include alginate (Alg), a cationic intercellular polysaccharide derived from brown seaweed. 7,8) We have compared the effects of sodium alginate (Na-Alg) and calcium alginate (Ca-Alg) in promoting excretion and decreasing absorption of Sr and cesium (Cs) in rats.9) Both additives increased the excretion of Sr, though Cs concentration was significantly reduced only in the Ca-Alg group. We also measured the plasma concentration of cholesterol in that study, and interestingly found that Ca-Alg has a greater cholesterol-lowering effect than Na-Alg. 9)At present, Na-Alg is widely used as a food additive (thickening agent) and as a health food to decrease blood cholesterol and inhibit weight gain. [10][11][12] However, sodium intake is associated with hypertension, 13) and Ca-Alg may be preferable to Na-Alg, if it has an equivalent pharmaceutical effect. Therefore, in this study we first examined various types of Na-Alg to evaluate their bile acid-absorbing ability in vitro. Based on the results, we selected high-molecular-weight, guluronic acidri...

Alginate (ALA), which is an intercellular polysaccharide associated with brown algae, is used as a food additive, a health food and a medicine. Here, we first examined the adsorption of strontium (Sr) and cesium (Cs) by ALA in vitro, and then evaluated the effects of ALA on absorption and excretion of Sr and Cs in rats, in order to evaluate its potential usefulness for minimizing radiation damage from materials released after a nuclear accident. Both Sr and Cs were concentration-dependently adsorbed by sodium alginate (ALA-Na) in vitro. In rats given diet containing either ALA-Na or calcium alginate (ALA-Ca) for two weeks, the plasma concentration of Sr gradually decreased compared with the controls (normal diet); however, in the case of Cs, the plasma concentration was decreased only in the ALA-Ca group, but not the ALA-Na group. Moreover, we examined the effect of preadministration of diet containing either ALA-Na or ALA-Ca on absorption of Sr and Cs administered orally as the chloride salts to rats. Absorption of both Sr and Cs was reduced in the ALA-Ca group, while absorption of only Sr was reduced in the ALA-Na group. Safety assessments indicated that ALA-Ca is safer than ALA-Na. These results indicate that ALA-Ca reduces absorption and promotes excretion of both Sr and Cs, while ALA-Na does so only for Sr.

In this study, rats were fed a high-fat diet containing calcium alginate (Ca-Alg) for 5 weeks to examine the effects of Ca-Alg on lipid metabolism including triglyceride (TG) levels in the blood. We also investigated the mechanism of the TG-reducing effect of Alg in vitro. Rats were randomized into 5 groups: high-fat diet group (14% (w/w) lard, HF); three Ca-Alg-containing diet groups (2.5, 5 or 10% (w/w) Ca-Alg) and a resistant maltodextrin (RMD) diet group as a positive control (with 5% (w/w) RMD). The 10% Ca-Alg group showed a significant reduction of body weight increase from the 7th day. In addition, the increase of TG in blood was significantly suppressed, and the amount of TG excreted in feces was increased. Increase of body fat mass was in the order HF > RMD > Ca-Alg 2.5% > Ca-Alg 5% > Ca-Alg 10%, while the total weight of the extracted fat tissues was significantly reduced in the RMD, 5% and 10% Ca-Alg groups. Hepatic pathology showed clear circular vacuoles apparently representing TG accumulation in the HF group, while fewer vacuoles were seen in the Ca-Alg groups. The results of in vitro experiments indicated that Ca-Alg does not directly inhibit lipase activity, but may suppress absorption of TG by forming non-absorbable macromolecular micelles containing TG. These results suggest that Ca-Alg promotes excretion and suppresses absorption of TG, leading to reduced blood TG levels, and decreased hepatic and total body accumulation of fat. The findings should be helpful for designing future clinical trials.

(1996) studied the influence of alginate on starch retrogradation by analyzing the possible interactions between hydrocolloids and starch or gluten. Rosell et al. (2001b) showed that the addition of sodium alginate improved wheat dough stability during proofing.The reasons why alginates are effective in bread making are currently unknown; thus, in order to expand seaweed usage in the future, it is necessary to determine the mechanism by which alginates function in bread making. In this study, bread making tests were performed with various kinds of alginic acid-related materials (alginic acid, alginates, and PGA), and enhanced bread making properties were obtained using PGA and sodium alginate.PGA and sodium alginate are generally used as bakery materials, however the detailed mechanism of their improving effects on bread is unknown. Therefore, bread dough temperature, gas production by yeast, baking absorption, exuded liquid, oven spring, and shrinkage of bread dough were examined in PGA or sodium alginate/wheat flour dough, and the mechanism by which PGA and sodium alginate affect bread making properties was investigated.