Digesta flow-behavior types in the intestinal lumen, such as turbulent and laminar flow, should define modes of digestion and absorption. This review presents a simulation of flow behavior in the intestinal lumen and discusses the behavior of nutrients and enzymes in the intestinal lumen under laminar-flow conditions. The significance of digesta viscosity for glucose and water absorption and digestion and fermentation in the intestine is also discussed.
Alkaline phosphatase (ALP) hydrolyzes a variety of monophosphate esters into inorganic acid and alcohol at a high optimum pH (pH 8-10). Previously, we identified a significant increase of intestinal ALP (IAP) activity in the rat intestine on long-term dietary vitamin K supplementation. However, it was unclear whether the induction of ALP gene expression was caused by vitamin K intake. In the present study, we examined the effects of vitamin K on IAP gene expression. A total of 21 male ICR strain mice (7 wk old) were divided into three groups: control, PK, and MK groups. Mice were orally administered a 0.1-mL solution of physiological saline in the control group, phylloquinone (3 mg/kg mouse) in the PK group, and menaquinone-4 (3 mg/kg mouse) in the MK group. Four hours after administration, we determined the ALP activity of the intestinal mucosa in three areas (duodenum, jejunum, and ileum). In the MK groups, the levels of ALP activity in the jejunum increased significantly compared with the control. Moreover, reverse transcription-polymerase chain reaction (RT-PCR) analysis using specific primers revealed that IAP mRNA expression was significantly enhanced in the jejunum in both PK and MK groups. Interestingly, vitamin K administration also increased the expression of pregnane X receptor mRNA. This is the first report concerning IAP mRNA expression induced by oral administration of vitamin K. The results support the possible involvement of vitamin K in the regulation of IAP mRNA expression as a novel pharmacological effect of vitamin K.
It has been reported that supplementation with high-dose vitamin B6 (B6) exerts antitumor effects in rodent models of cancer. However, the mechanism of these effects remains poorly understood. High-dose B6 also suppresses cell proliferation and induces apoptosis of human breast adenocarcinoma MCF-7 cells. Based on preliminary experiments using DNA microarray analyses, we hypothesized that high-dose pyridoxine (PN) might induce IGF-binding protein-3 (IGFBP-3) expression in MCF-7 cells. In this study, we investigated IGFBP-3 induction by 3 or 10 mM PN using a quantitative real-time PCR method. We found that the induction reached a maximum of 24-fold with 10 mM PN for 72 h compared with non-treated cells. The induction of IGFBP-3 by PN was inhibited by a p53-specific inhibitor, pifithrin-α, in a dose-dependent manner, but was not affected by PD169316 (MAPK inhibitor), AS601245 (c-Jun N-terminal kinase inhibitor) or SL327 (MEK1/2 inhibitor). High-dose PN did not induce p53 mRNA expression. The IGFBP-3 induction by PN seemed to be related to p53 activation.
The purpose of this study was to determine whether the regulation of brain protein synthesis was mediated through changes in the plasma concentration of growth hormone (GH) when dietary γ-aminobutyric acid (GABA) treatment was manipulated in hypophysectomized or sham-operated aged rats. Experiments were done on four groups of hypophysectomized and sham-operated (24-wk-old) male rats given 0% or 0.5% GABA added to a 20% casein diet. The concentrations of plasma GH and fractional rates of protein synthesis in the brains increased significantly with the 20% casein+0.5% GABA compared with the 20% casein diet alone in the sham-operated rats. However GABA treatment to the basal diet did not affect the rates of protein synthesis in the hypophysectomized rats. In the cerebral cortex and cerebellum, the RNA activity [g protein synthesized/(g RNA·d)] significantly correlated with the fractional rate of protein synthesis. The RNA concentration (mg RNA/g protein) was also related to the fractional rate of protein synthesis in these organs. The results suggest that treatment with GABA is likely to increase the concentrations of GH and the rate of brain protein synthesis in sham-operated rats only, not in hypophysectomized rats, and that the GABA-induced increase in the concentration of GH may be primarily responsible for changes in the brain protein synthesis. The RNA activity is at least partly related to the fractional rate of brain protein synthesis.
Iron deficiency anemia (IDA) is one of the most serious forms of malnutrition. This experiment was conducted to investigate whether acidic xylooligosaccharide (U-XOS), expected to have a high iron bioavailability, was useful in the prevention of iron deficiency. Experiment 1: Nineteen female Sprague-Dawley rats (20 wk old) were fed three different diets for 28 d; a U-XOS-supplemented low-iron diet (LI-X, n=7), a low-iron diet (LI, n=6), and a control diet (C, n=6). On day 28, the LI-X and LI groups showed iron deficiency without anemia. A significant difference in the total and unsaturated iron binding capacity, and serum transferrin saturation level was shown in the LI-X and LI groups, compared with the C group. However, the decrease of hepatic iron content of the LI-X group was suppressed compared with the LI group. Experiment 2: Eleven male Sprague-Dawley rats (7 wk old) were fed a U-XOS-supplemented diet (X, n=5) or a control diet (C, n=6) for 7 d. No significant difference in body weight gain or food intake was demonstrated between the two groups; the apparent iron absorption rate of the X group increased clearly compared with that of the C group. These results suggested that a U-XOS diet could preserve storage of hepatic iron in adult female rats fed a low-iron diet and could prevent IDA by promotion of dietary iron absorption, inhibition of iron excretion, and/or improvement of iron bioavailability.
Selenocysteine lyase (SCL) catalyzes the decomposition of L-selenocysteine to yield L-alanine and selenium by acting exclusively on l-selenocysteine. The X-ray structural analysis of rat SCL has demonstrated how SCL discriminates L-selenocysteine from L-cysteine on the molecular basis. SCL has been proposed to function in the recycling of the micronutrient selenium from degraded selenoproteins containing selenocysteine residues, but the role of SCL in selenium metabolism in vivo remains unclear. We here demonstrate that the 75Se-labeling efficiency of selenoproteins with 75Se-labeled selenoprotein P (Sepp1) as a selenium source was decreased in HeLa cells transfected with SCL siRNA as compared to the cells transfected with control siRNA. Immunocytochemical analyses showed high SCL expression in kidney and liver cells, where selenocysteine is recovered from selenoproteins. Mature testes of mice exhibited a specific staining pattern of SCL in spermatids that actively produce selenoproteins. However, SCL was weakly expressed in Sertoli cells, which receive Sepp1 and supply selenium to germ cells. These demonstrate that SCL occurs in the cells requiring selenoproteins, probably to recycle selenium derived from selenoproteins such as Sepp1.
Water spinach (Ipomoea aquatica Forsk; I. aquatica) of the green-stemmed type (green type) is widely consumed, but there also exists a red-stemmed variety (red type). In the present study, the antioxidant capacity of the red type was compared to that of the green type in carbon tetrachloride (CCl4)-treated mice. CCl4-induced thiobarbituric acid reactive substrate (TBARS) formation in the liver was significantly suppressed in mice fed 5% red-type I. aquatica, while the green type showed no effect. Hydrophobic oxygen radical absorbance capacity (H-ORACFL) in the red type showed a lower level than that in the green type; however, lipophilic ORAC (L-ORACFL) and total-ORACFL levels were significantly higher in the red type than in the green type. α-Tocopherol, anthocyanidin/proanthocyanidin, and β-carotene contents were all significantly higher in the red type than in the green type. These results suggest that the wild red-type I. aquatica contains certain lipophilic components that exert antioxidant capacities not only in vitro but also in vivo. Such effective components in the red type would be beneficial phytochemicals for suppressing several diseases related to oxidative stress.