Yukiko Yamamoto

In vitro digestibility and fermentability of levan and its hypocholesterolemic effects in rats

This study describes the in vitro digestibility and fermentability of high molecular weight (ca. 2,000,000) levan and its effect on the metabolism of lipids in growing rats fed cholesterol-free diets. Levan was synthesized from sucrose using bacterial levansucrase immobilized on a honeycomb-shaped ceramic support. Although body weight gain, weight of visceral organs, morphologic changes in the digestive tract, and the serum triacylglycerol and glucose concentrations were not affected by feeding levan diets for 4 weeks, a significant hypocholesterolemic effect was observed. Serum cholesterol level was decreased to 83% or 59% by feeding a 1% or 5% levan diet, respectively. The hypocholesterolemic effect was accompanied by a significant increase in fecal excretion of sterols and lipids. High molecular weight levan, though not hydrolyzed by the salivary amylases, was hydrolyzed by artificial gastric juice and was changed to a low molecular weight (ca. 4,000) levan with a small amount of fructose, but did not produce any fructooligosaccharides. Low molecular weight (ca. 6,000) levan was not hydrolyzed by either pancreatic juice or small intestinal enzymes. This suggests that, in vivo, low molecular weight levan derived from the high molecular weight material is not further digested and reaches the colon intact. The fermentation of low molecular weight levan (ca. 6,000) by several strains of bifidobacteria was not observed. These results showed that the hypocholesterolemic effect of levan may result from the prevention of intestinal sterol absorption, and not from the action of the fermentation products of levan.

Antihypertensive Effect of Quercetin in Rats Fed with a High-Fat High-Sucrose Diet

The effects of different levels of quercetin on the blood pressure were studied in 6-week-old male Sprague-Dawley rats. The rats were fed with a control diet or a high-fat high-sucrose (HFS) diet containing 0, 0.02, 0.07, 0.2, or 0.5% quercetin for 4 weeks. The systolic blood pressure and the lipid peroxides in the plasma were both higher in the rats fed with the HFS diet without quercetin than in the rats fed with the control diet. The nitric oxide synthase (NOS) activity in the vascular tissues and nitric oxide (NO) metabolites in the plasma and urine were both lower in these rats. A distinct depression of the increase in blood pressure was found in the rats fed with the HFS diets containing quercetin. Each level of quercetin examined was effective, the 0.5% level being much more effective than other levels. Dietary quercetin decreased lipid peroxidation in the plasma of the rats fed with the HFS diets. Quercetin also suppressed the decrease in NO metabolites in the plasma and urine, and the NOS activity in the vascular tissues of these rats. These results suggest that the increased NO availability caused by the elevated NOS activity, and the antioxidative activity in these rats fed with quercetin may be sources of the antihypertensive effect of quercetin.

Antioxidative and Antihypertensive Effects of Welsh Onion on Rats Fed with a High-Fat High-Sucrose Diet

The effects of Welsh onion on the development of hypertension and autoxidation were studied in 6-week-old male Sprague-Dawley rats. The rats were fed with a control diet or a high-fat high-sucrose (HFS) diet with or without 5% Welsh onion (green-leafy type or white-sheath type) for 4 weeks. The systolic blood pressure was elevated and the thiobarbituric acid reactive substances (TBARS) in plasma were increased in the rats fed with the HFS diet without Welsh onion. The rats fed with the HFS diet containing Welsh onion, especially the green-leafy type, had lower blood pressure. They also had a higher level of nitric oxide (NO) metabolites in both the urine and plasma, lower activity of NADH/NADPH oxidase in the aorta, and suppressed angiotensin II production. The effect of white Welsh onion on decreasing the blood pressure was not significant, although the effects on increasing NO metabolites in the urine and decreasing NADH oxidase activity in the aorta were significant. The TBARS value in the plasma was lowered in the rats fed with either green or white Welsh onion, but the in vitro radical scavenging and ferric reducing antioxidative activities were much higher with green Welsh onion than with the white type. These results suggest that the green-leafy Welsh onion, but not the white type, reduced superoxide generation by suppressing the angiotensine II production and then the NADH/NADPH oxidase activity, increasing the NO availability in the aorta, and consequently lowering the blood pressure in the rats fed with the HFS diet. The radical scavenging and reducing antioxidative activities of green Welsh onion may also be effective in decreasing superoxide.

Antihypertensive effects of onion on NO synthase inhibitor-induced hypertensive rats and spontaneously hypertensive rats

This study was designed to show the effects of onion on blood pressure in N G-nitro-L-arginine methyl ester (L-NAME) induced-hypertensive rats and stroke prone spontaneously hypertensive rats (SHRSP) using dried onion at 5% in their diets. For the experiment with L-NAME induced-hypertensive rats, male 6-weeks-old Sprague-Dawley rats were given tap water containing L-NAME to deliver 50 mg/kg BW/day. In this experiment, we found distinct antihypertensive effects of onion on the L-NAME induced-hypertensive rats and the SHRSP. Dietary onion decreased the thiobarbituric acid reactive substances (TBARS) in plasma in these hypertensive rats. Also, onion increased the nitrate/nitrite (products of nitric oxide (NO)) excreted in urine and the NO synthase (NOS) activity in the kidneys in SHRSP. These results suggested that the increased NO caused by the greater NOS activity, and additionally by the increased saving of NO by the antioxidative activity of onion, was one of the cause of the antihypertensive effect of onion in SHRSP. In the L-NAME induced hypertensive rats, onion did not significantly block the inhibition of NOS activity by L-NAME, and decreased nitrate/nitrite excretion in urine was not restored. The mechanism of the antihypertensive effect of onion probably involves increased saving of NO by antioxidative activity of onion in L-NAME induced-hypertensive rats.

Improved hypolipidemic effects of xanthan gum-galactomannan mixtures in rats.

This study describes the effects of mixtures of xanthan gum and galactomannan, guar gum, or locust bean gum, on the lipids in plasma and liver in non-diabetic and diabetic rats. Non-diabetic rats were fed cholesterol-free diets with 3% guar gum, locust bean gum, or xanthan gum (3G, 3L, and 3X), or a mixture of xanthan gum and guar gum or locust bean gum (1:2, w/w) (2G1X, 2L1X) for 2 weeks. Rats fed diets not containing these polysaccharides were used as controls. The total cholesterol in plasma and the triacylglycerol in liver were significantly lowered in rats fed the 2G1X diet. The 3G, 3X, 3L, and 2L1X diets showed no significant effect on the total cholesterol and triacylglycerol in plasma and liver. In the streptozotocin-induced (STZ) diabetic rats, the total cholesterol in plasma was lowered in rats fed the 3G, 3X or 2G1X diet for 4 weeks, and the 2G1X diet was more effective than the 3G and 3X diets. The triacylglycerol in plasma in STZ diabetic rats was also significantly lowered by the 2G1X diet. These results showed that a mixture of xanthan gum and guar gum has an improved hypolipidemic effect on non-diabetic and STZ diabetic rats. The effects of the 2G1X diet on the diabetic symptoms in STZ diabetic rats, suppression of food and water intakes, decrease in glucose in urine, and lowering of plasma glucose, were also observed.

Welsh onion attenuates hyperlipidemia in rats fed on high-fat high-sucrose diet.

The effects of two types of Welsh onion, green-leafy and white-sheath types, on hyperlipidemia in rats fed on diets high in fat and sucrose were studied. A significant lowering effect on cholesterol in the plasma and on total lipids, triacylglycerol, and cholesterol in the liver was observed in rats fed on the green, but not white, Welsh onion. These Welsh onions had no significant effect on the hepatic enzyme activities responsible for fatty acid synthesis and degradation. The results suggest that the green Welsh onion might be effective in attenuating hyperlipidemia in a manner other than affecting fatty acid metabolism in the liver. Kaempferol seemed to be one of the components in green Welsh onion acting to lower lipid deposition.

Enhancing Effect of β-Lactoglobulin on the Antioxidative Activity of α-Tocopherol in an Emulsion of Linoleic Acid

The antioxidative activity of α-tocopherol and Trolox, a water-soluble carboxylic acid derivative of α-tocopherol, in an emulsion stabilized with the hydrophilic emulsifier, polyoxyethylene (20) sorbitan monolaurate, was evaluated by measuring the changes in linoleic acid content, peroxide value, and thiobarbituric acid value. The activity of α-tocopherol and Trolox to depress the autoxidation of linoleic acid was stronger when they were added in the aqueous phase than when added in the oil phase, and Trolox in the aqueous phase was the most effective. The results of interfacial-tension measurements support the idea that the affinity of phenolic antioxidants to the surface layer of oil droplets might be related to their antioxidative activity. The antioxidative activity of α-tocopherol and Trolox added in the oil phase was markedly enhanced by using β-lactoglobulin together with Tween 20 to stabilize a linoleic acid emulsion. The results of a linoleic acid determination with cold and radioactive linoleic acid indicate that linoleic acid in a complex with the β-lactoglobulin molecule would be effectively protected by the phenolic antioxidants, α-tocopherol and Trolox, against autoxidation.

Effects of Physical Properties and Eating Habits on Bone Mass in Female Students

1) 女子学生50人の右踵骨骨量を超音波骨評価装置により測定し, 音響的骨評価値 (OSI) で表した. 対象者のOSIの平均値は2.619±0.241で, 老人保健法によるスクリーニングのための判定基準の97.1%であった.2) 対象者をOSI値で3群に区分して主要食品の摂取頻度, 嗜好度を比較した結果, 現在ならびに過去の牛乳の摂取頻度, 嗜好度に有意差がみられ, 牛乳摂取と骨量の関連性が示唆された. また, 小魚の過去の摂取頻度にも3群間に有意差が見られた.3) 食品の嗜好度および摂取頻度について, 現在の学生と親の相関を調べた結果, 大豆・大豆製品, スナック菓子, インスタント食品およびファーストフードの嗜好度, 牛乳・乳製品, 野菜, 海藻, きのこ類, スナック菓子及びファーストフードの摂取頻度に相関が認められた. しかし, 牛乳・乳製品に対する嗜好度, 小魚の嗜好度, 摂取頻度には相関が見られなかった.4) OSI値で区分した3群間について現在の栄養素等摂取量, 年齢, 身長, 体重, BMI, 初経年齢, 初経後の経過期間, 運動量を比較したが, いずれも有意な差が見られなかった.

Self-selection of glycine and tyrosine in rats.

非必須アミノ酸 (non-EAA) であるGlyとL-Tyrの選択摂取実験を離乳直後のラットを用いて行いこれまでの必須アミノ酸 (EAA) の結果と比較した。その結果Glyの選択摂取時には7%添加食を忌避したがそれ以下ではGly含量の多い飼料を好んで摂取し, L-Tyrの選択摂取時には3%以上添加した飼料を忌避したがそれ以下ではL-Tyr含量の多い飼料を好んで摂取した。このような結果から, ラットはGly, L-Tyrのようなnon-EAAについても過剰摂取による害作用を防止する機構により最大摂取量を調節する能力を有していることが明らかになった。