The viscosity of gut contents may affect the rate of digestion and absorption by reducing the diffusion rate of food components, digestive enzymes and nutrients. Our previous study showed that the content of large solid particles in digesta was positively correlated with the viscosity of pig cecal contents in vitro. The purpose of the present study was to examine the contribution of dietary solid particles such as cellulose to the viscosity of gut contents and to intestinal tissue weight in vivo. Using an E-type viscometer, we estimated the coefficient of viscosity of gastric, small-intestinal and cecal contents with solid particles in rats fed a purified polymeric diet containing 0, 11 or 13% cellulose. We also assessed the effect of cellulose ingestion on the weight of the mucosa, submucosa, and muscularis externa in the intestinal tissue of rats by morphometry. Ingestion of cellulose increased the coefficient of viscosity of small-intestinal and cecal contents (p<0.05), and the weight of colonic mucosa (p<0.05). These findings indicate that ingestion of solid particles increases the viscosity of gut contents in vivo.

View full abstract

The inhibitory effect of an extract of guava leaves (GvEx) on the activities of sugar-degrading enzymes such as α-amylase and sucrase, in combination with acarbose or voglibose, was studied. Acarbose and voglibose were used at concentrations that inhibited the activity of α-amylase and sucrase by approximately 50%, respectively. Addition of GvEx to the reaction system in combination with the respective enzymes-sugars increased the degree of inhibition of each enzyme activity. To confirm these in vitro effects, an in vivo study was undertaken using normal ICR mice loaded with either cooked starch (1g/kg) and sucrose (2g/kg). The GvEx (250mg/kg) was administrated together with acarbose or voglibose at a dose that prevented the increase in the postprandial blood glucose level. The GvEx had no effect on the blood glucose-lowering effect of the drugs. However, when GvEx was administered to mice loaded with a high concentration cooked starch (without sucrose) together with acarbose or voglibose at a dose that failed to prevent the increase of the postprandial blood glucose level, there was a significant reduction in the rise of the blood glucose level. These results suggest that GvEx is useful for preventing the increase in the blood glucose level in combination with both acarbose and voglibose without having to increase the dose of these drugs. Furthermore it is emphasized that the use of GvEx jointly with acarbose and voglibose has no adverse toxic effects.

View full abstract

The aim of this study was to determine the effect of dietary intake on LDL-cholesterol and visceral fat in pre-and postmenopausal obese women during a weight reduction program and a one-year follow-up period. The subjects were 117 middle-aged obese women (78 pre-and 29 postmenopausal) who participated in a weight reduction program for three months. Before the program, the visceral fat area and level of LDL-cholesterol were significantly higher in postmenopausal than in premenopausal women. After three months, the caloric intake decreased significantly and both the body weight and visceral fat area decreased in both the pre-and postmenopausal women. The changes in the LDL-cholesterol level correlated significantly with the changes in the visceral fat area. In addition, multiple regression analysis revealed a significant positive association between the change in the LDL-cholesterol level and both the change in the sugar intake and the percentage of energy as fat in postmenopausal women. One year after the end of the weight reduction program, 20 subjects (11 pre- and 9 postmenopausal) participated in a follow-up study. The caloric intake per standard weight had increased significantly in both groups. In addition, both the body weight and visceral fat area had increased, but the increases were not significant in either group. The change in abdominal total fat area and visceral fat area showed a significant positive correlation with the change in the sugar intake only in postmenopausal women. In conclusion, these data suggest that both the LDL-cholesterol level and visceral fat area are higher in obese postmenopausal women than in premenopausal women. In addition, the change in the LDL-cholesterol level is correlated with both the change in the visceral fat area and the intake of sugar during weight reduction, while the change in the area of visceral fat is more closely associated with the change in sugar intake than with the change in caloric intake during both the weight reduction period and the subsequent follow-up period.

View full abstract

The effects of vitamin C (L-ascorbic acid), L-cysteine and vitamin E (d-α-tocopherol succinate) on skin pigmentation were studied using brownish guinea pigs. While exposure of the depilated backs of brownish guinea pigs to mid-ultraviolet (UV-B) radiation decreased the luminosity score and increased the number of DOPA-positive melanocytes, oral administration of vitamin C with L-cysteine significantly inhibited the decrease of luminosity score and also decreased the number of DOPA-positive melanocytes. When vitamin C, L-cysteine and vitamin E were simultaneously administered to the guinea pigs, the inhibitory effect was stronger than when vitamin E was omitted. Single administration of vitamin C produced no significant inhibition. These results show that oral administration of vitamin C, L-cysteine and vitamin E is effective for inhibiting the melanogenesis induced by UV-B exposure.

View full abstract

The accuracy and precision of energy expenditure (EE) measured using the whole-body indirect human calorimeter (IHC) at the National Institute of Health and Nutrition in Japan were evaluated. A total of 40 six-hour ethanol combustion experiments were performed. V_O2 and V_CO2 computed by the currently used real time algorithm were compared with the expected values from the weight of ethanol consumed. The mean±SD of the ratio between the computed and expected values (computed value/expected value) of V_O2, V_CO2 and ∑EE were 101.0±2.1, 100.6±1.7 and 100.9±1.9%, respectively. The mean values and SDs indicated that the accuracy and precision of our IHC are acceptable. However, increases of SDs were observed for short combustion periods corresponding to small amounts of ethanol combustion (e.g., less than 20g of ethanol).

View full abstract

We have previously reported (J Jpn Soc Nutr Food Sci 55:149 (2002)) that food restriction causes symptoms of osteoporosis in rats. In the present study, we examined the effects of exercise in preventing such diet-induced osteopenia. Six-week-old female Wistar rats were maintained on a standard diet prepared according to AIN-93G for 10 days before the start of the experiment. The rats were then separated into four groups. First two groups were fed the standard diet ad libitum, while the last two groups were fed an experimental diet consisting of double concentrations of protein, minerals and vitamins, but in an amount that was 50% less than in the ad libitum standard diet groups. In order to check the effects of exercise on diet-induced osteoporosis, one diet-restricted group and one ad libitum group were each made to run 10min per day at 0.7km/h. The results obtained were as follows: (1) Body weight of rats in Group 1 fed the standard diet ad libitum increased by 35g during 3 weeks. Body weights of rats in Group 3 subjected to restricted food intake and Group 4 subjected to restricted food intake with exercise finally showed a decrease of 49 and 44g, respectively, compared with Group 1. (2) Group 3 subjected to restricted food intake exhibited osteopenia with low values of bone mineral density and bone breaking energy and a high X-ray density. (3) Group 4 subjected to food restriction with exercise did not develop osteopenia. (4) As restricted food intake involving reduction of carbohydrate and lipid causes osteopenia, it seems reasonable to avoid dieting and to take a sufficient amount of carbohydrate and lipid. (5) When reducing the intake of carbohydrate and lipid with the aim of losing weight, it is important to take sufficient amounts of protein, vitamins and minerals and take reasonable amounts of exercise such as running to prevent osteopenia.

View full abstract

The effect of Ukogi (Acanthopanax siebldianus) leaves on blood glucose level and glucose tolerance was investigated in rats with neonatally induced streptozotocin (type 2) diabetes (n-STZ rats). Neonatal rats were made diabetic by injection of 80mg/kg STZ. From the age of 8 weeks, n-STZ rats were given a diet containing ukogi (DM-U group) or cellulose (DM-C group), or a control diet (DM group), for 10 weeks. Normal rats were given the control diet (Normal group). Impairment of glucose tolerance in rats of the DM group increased with age. In the DM-U group, however, glucose tolerance was better than in the DM group (p<0.05). At the end of the experiments, the blood glucose level in the DM group was higher than that in the Normal group, although that in the DM-U group was significantly lower than in the DM group (p<0.05). The serum triglyceride level was also decreased by intake of ukogi leaves (p<0.05). These results suggest that ukogi leaves improve the blood glucose level, glucose tolerance and serum triglyceride in n-STZ rats.

View full abstract

Preferences for food and drink were analyzed using laboratory animals. There were no preferences for particular diets common to both humans and animals. However, our animal studies demonstrated that some nutritional requirements under specific physiological conditions and some fundamental mechanisms of food selection, i.e., positive reinforcing effects, would be applicable for understanding the basis of human diet preference. In the present communication, I focus on animal studies on preference for beer and addiction to dietary fat as examples.

View full abstract

Regulating the intestinal absorption of nutrients is effective for prevention of certain diseases, including lifestyle-related diseases. However, the mechanisms of intestinal absorption are too complicated to analyze only by in vivo or in situ experiments. Studies using cultured cells are essential for revealing the characteristics and regulatory mechanisms of functional molecules such as transporters and tight junctions, which are involved in intestinal absorption. Caco-2, an intestinal epithelial cell line established from human colon adenocarcinoma tissues, expresses a variety of functions observed in small-intestinal epithelial cells. Although some of the properties of this cell line differ from those of small-intestinal cells, the transport functions of Caco-2 for hydrophobic drugs and cholesterol, for example, are well correlated with the results obtained in in vivo experiments. We have recently developed a model system for evaluating the intestinal absorption of dioxins using Caco-2 cell monolayers and dioxin-responsive HepG2 cells. This approach may be useful for searching for food substances that suppress the intestinal absorption of dioxins. As Caco-2 expresses MDR1, an efflux pump for xenobiotics, this cell line is useful for analyzing the intestinal absorption of xenobiotics and its regulation. The utility of cultured cells for analysis of molecular mechanisms and for screening experiments should be recognized.

View full abstract