Yasuo Nagata

D-psicose, an epimer of D-fructose, favorably alters lipid metabolism in Sprague-Dawley rats.

D-Psicose, a C3 epimer of D-fructose, is known to lower body weight and adipose tissue weight and affect lipid metabolism. The precise mechanism remains unknown. It has been reported that D-psicose has a short half-life and is not metabolized in the body. To determine how D-psicose modifies lipid metabolism, rats were fed diets with or without 3% D-psicose for 4 weeks. Rats were decapitated without fasting every 6 h over a period of 24 h. Changes in serum and liver lipid levels, liver enzyme activity, and gene expression were quantified in experiment 1. Rats fed D-psicose had significantly lower serum insulin and leptin levels. Liver enzyme activities involved in lipogenesis were significantly lowered by the D-psicose diet, whereas gene expression of a transcriptional modulator of fatty acid oxidation was enhanced. In experiment 2, feeding the D-psicose diet gave significantly lower body weight (389 ± 3 vs 426 ± 6 g, p < 0.05) and food intake (23.8 ± 0.2 vs 25.7 ± 0.4 g/day, p < 0.05) compared to the control diet. Rats fed the D-psicose diet gave significantly higher energy expenditure in the light period and fat oxidation in the dark period compared to rats fed the control diet, whereas carbohydrate oxidation was lower. In summary, these results indicate that the D-psicose diet decreases lipogenesis, increases fatty acid oxidation, and enhances 24 h energy expenditure, leading to d-psicoses potential for weight management.

Theflavins and theasinensin A derived from fermented tea have antihyperglycemic and hypotriacylglycerolemic effects in KK-Ay mice and Sprague-Dawley rats

Although tea polyphenols are reported to improve serum glucose and lipid levels by inhibiting amylase activity and reducing lipid absorption, in vivo data are lacking. We evaluated in vivo the antihyperglycemic and hypotriacylglycerolemic effects of theaflavins (TFs) and theasinensin A (TSA) refined from fermented tea to purities of 12 and 59%, respectively. Feeding male KK-A(y) mice diets with 0.1% TFs or TSA for 6 weeks reduced serum glucose levels by >30% compared to a control diet. Rats fed diets containing 0.2% TFs or TSA for 4 weeks had higher fecal fat excretion and 33% lower hepatic triacylglycerol; hepatic fatty acid synthase activity was not affected. Oral administration of TFs or TSA reduced the increase in serum triacylglycerol after an oral bolus of a fat emulsion. These results indicate TFs and TSA induce antihyperglycemic responses in diabetic mice and are hypotriacylglycerolemic in rats by suppressing intestinal fat absorption.

Hypotriglyceridemic potential of fermented mixed tea made with third-crop green tea leaves and camellia (Camellia japonica) leaves in Sprague-Dawley rats.

Fermented mixed tea made with third-crop green tea leaves and camellia leaves by a tea-rolling process has been developed. The objective of this study was to investigate hypotriglyceridemic potential of the mixed tea in rats. The mixed tea contained theasinensins and theaflavins. Rats fed the mixed tea extract at the level of 1% exerted significantly lower body weight and adipose tissue weight compared to animals fed third-crop green tea or camellia tea extract alone for 4 weeks. Serum and hepatic triglyceride was significantly and dose-dependently decreased by the mixed tea. This decrease was associated with lowered lipogenic enzyme activities in the liver. Furthermore, an oral administration of 4 or 8% of the mixed tea extract followed by fat emulsion suppressed the increment of serum triglyceride level. These results suggest that the mixed tea has hypotriglyceridemic action, partially via delaying triglyceride absorption in the small intestine and repressing hepatic lipogenic enzymes.

Rare Sugar Syrup Containing d-Allulose but Not High-Fructose Corn Syrup Maintains Glucose Tolerance and Insulin Sensitivity Partly via Hepatic Glucokinase Translocation in Wistar Rats

Ingestion of high-fructose corn syrup (HFCS) is associated with the risk of both diabetes and obesity. Rare sugar syrup (RSS) has been developed by alkaline isomerization of HFCS and has anti-obesity and anti-diabetic effects. However, the influence of RSS on glucose metabolism has not been explored. We investigated whether long-term administration of RSS maintains glucose tolerance and whether the underlying mechanism involves hepatic glucokinase translocation. Wistar rats were administered water, RSS, or HFCS in drinking water for 10 weeks and then evaluated for glucose tolerance, insulin tolerance, liver glycogen content, and subcellular distribution of liver glucokinase. RSS significantly suppressed body weight gain and abdominal fat mass (p < 0.05). The glucose tolerance test revealed significantly higher blood glucose levels in the HFCS group compared to the water group, whereas the RSS group had significantly lower blood glucose levels from 90 to 180 min (p < 0.05). At 30, 60, and 90 min, the levels of insulin in the RSS group were significantly lower than those in the water group (p < 0.05). The amount of hepatic glycogen was more than 3 times higher in the RSS group than that in the other groups. After glucose loading, the nuclear export of glucokinase was significantly increased in the RSS group compared to the water group. These results imply that RSS maintains glucose tolerance and insulin sensitivity, at least partly, by enhancing nuclear export of hepatic glucokinase.

Okara, a By-Product of Tofu Manufacturing, Modifies Triglyceride Metabolism at the Intestinal and Hepatic Levels.

Irrespective of a well-known hypocholesterolemic action, a few studies have shown a hypotriglyceridemic potential of okara, a by-product of tofu manufacturing. Okara was fed to rats at the level of 2.5 and 5.0% as dietary protein for 4 wk, and serum and hepatic lipid levels were determined. In addition, soy flour, which has a well-known hypolipidemic action, was used to compare effects on lipid metabolism. Mechanisms of action were further evaluated by measuring hepatic enzyme activity, gene expression of lipid metabolism-related proteins and fecal excretion of lipids. Feeding the okara diets resulted in a significantly lower weight of the liver and adipose tissue in a dose-dependent manner. Serum triglyceride levels were more than 50% lower in rats fed the okara diets compared to those fed the control diet. Enzyme activities of fatty acid synthesis were significantly lowered by the okara diet. Fecal weight was significantly higher in the okara group than in the control group, and fecal excretion of steroids tended to be higher. Therefore, a relatively low amount of okara may exert hypotriglyceridemic action in rats in part through decreased hepatic triglyceride synthesis. The present study also suggests an involvement of intestinal events in altered lipid metabolism in rats fed the okara diets.

Dietary Soybean Peptides Containing a Low-Molecular Fraction Can Lower Serum and Liver Triglyceride Levels in Rats

We investigated the effects of dietary soybean peptides, particularly low-molecular-weight peptides, on serum and hepatic concentrations of lipids in rats. Soybean protein isolate (SPI) was digested with protease to produce low-molecular-weight peptides (LD) or a mixture of high- and low-molecular-weight peptides (HLD). Rats were fed diets containing 20% casein, SPI, LD or HLD as a nitrogen source, with or without 0.5% cholesterol, for 2 wk. Next, rats were fed cholesterol-free diets containing 0%, 5%, 10%, or 20% LD at the expense of casein for 2 wk. Serum triglyceride levels were the lowest in the LD group, and liver triglyceride levels were significantly lower in rats fed SPI and LD/HLD diets than in those fed casein diets, both in the presence and absence of dietary cholesterol. In addition, dietary LD significantly lowered serum and liver triglyceride levels in a dose-dependent manner. These results suggest that low-molecular-weight soybean peptides have a potent hypotriglyceridemic effect and may be beneficial for improving lipid metabolism.

Rare sugars, d-allulose, d-tagatose and d-sorbose, differently modulate lipid metabolism in rats

BACKGROUND Rare sugars including d-allulose, d-tagatose, and d-sorbose are present in limited quantities in nature; some of these rare sugars are now commercially produced using microbial enzymes. Apart from the anti-obesity and anti-hyperglycaemic activities of d-allulose, effects of these sugars on lipid metabolism have not been investigated. Therefore, we aimed to determine if and how d-tagatose and d-sorbose modulate lipid metabolism in rats. After feeding these rare sugars to rats, parameters on lipid metabolism were determined. RESULTS No diet-related effects were observed on body weight and food intake. Hepatic lipogenic enzyme activity was lowered by d-allulose and d-sorbose but increased by d-tagatose. Faecal fatty acid excretion was non-significantly decreased by d-allulose, but significantly increased by d-sorbose without affecting faecal steroid excretion. A trend toward reduced adipose tissue weight was observed in groups fed rare sugars. Serum adiponectin levels were decreased by d-sorbose relative to the control. Gene expression of cholesterol metabolism-related liver proteins tended to be down-regulated by d-allulose and d-sorbose but not by d-tagatose. In the small intestine, SR-B1 mRNA expression was suppressed by d-sorbose. CONCLUSION Lipid metabolism in rats varies with rare sugars. Application of rare sugars to functional foods for healthy body weight maintenance requires further studies.

Effects of Pantethine on the Levels of Apolipoproteins in Serum and Intestinal Lymph of Rats Fed Soybean Protein or Casein

肪食 で は, 大 豆 た ん 白質食 で カゼ イ ン食 に比 べ て, 血清apo A-I濃 度 はi著 し く 低 く, 逆 にapo Bは 増 加 した. PaSSを 大 豆 た ん 白質 食 に添 加 す る と, カゼインのレベルまでapo A-Iは 上昇 し, apo B は減少 した. なお, このPaSS効 果は添加量依存 性であった. Tocの 添加は血清apo A-Iに は影響i しなかったが, apo Bを 有意に増加 させた. 食餌 たん白質, PaSSお よびTocは 血清apo E濃 度に 一定の影響を与えなかった. 5%脂 肪食ではPaSS の血清apo A-I上 昇効果は明確ではなかった. カゼインに比べて, 大豆たん白質は糞量および 糞へのステロイ ド排泄を増加させたが, 2種 のビ タミンの添加はステロイ ドの排泄にはほとんど影 響 しなかった. 食餌たん白質の質的差 異 お よびTocの 添加は 脂肪組織のCHOL濃 度に影響 を与 え ない が, PaSSは 有意に増加させ, 体内のCHOL分 布 を変 動 させる可能性 を示唆した. 低脂肪 レベルではリンパの流量およびapo A-I 濃度は大豆たん白質群でカゼイン群より有意に低 いが, PaSSは これ らをカゼイ ンのレベルまで増 加 させた. 大豆たん白質群での低値は各 リポたん 白画分で認められ, またPaSSの 上昇効果はいず れの画分でも観察された. しかしながら, 5%脂 肪食ではPaSSの 効果は明確でなかった. 以上の結果から, PaSSは 無CHOL食 ラットの 血清CHOL濃 度には影響 しないが, 小腸機能へ の影響, すなわち脂質の吸収あるいはアポリポた ん白質産生能の変化を介 して, 血清apo A-I濃 度 の上昇に関与すると思われる. *1981年5月 , 第13回 日本動脈硬化学会 において発表 **九 州大学農学部栄養化学教室