The effect of dietary proteins and vitamin A status on the gene expression of cellular retinol-binding protein I (CRBP I) was studied in the rat liver. The gene expression was estimated as amounts of transcript (mRNA) by Northern blot analysis using rat CRBP I cDNA. Though vitamin A status is known to positively regulate the gene expres-sion of CRBP I in the extrahepatic tissues, in the present study we observed that the amount of the CRBP I transcript in liver was neither reduced by vitamin A-deficiency, nor affected by replenishment with an excess dose of all-trans retinoic acid. These results indicate that in the liver, different from the extrahepatic tissues, the gene expression of CRBP I may not be controlled by vitamin A. However, when the rats were fed on the diets that differed in dietary proteins, the gene expression of CRBP I in liver was enhanced by higher quality and quantity of dietary proteins, though no effect of dietary proteins was observed upon the hepatic contents of retinol. The concentrations of serum retinol were almost proportional to the mRNA levels of CRBP I. In contrast, the hepatic gene expression of another retinol-binding protein, RBP, and one subtype of retinoic acid receptor, RARa was not influenced in the nutritional condition tested here. Our findings suggest that the gene expression of CRBP I in liver may be under control of the intake of dietary proteins. Thus, it is likely that in the light of the function of CRBP I on cellular transport and metabolism of retinol, dietary proteins may affect the actions of vitamin A in the extrahepatic tissues through changing the amounts of CRBP I in liver.
A simple and sensitive assay method for a pharmacokinetic study of Menaquinone-4 in dogs was established using HPLC with fluorescence detection following extraction with organic solvent. The quantification limit of this method was 1 ng/ml of plasma. A new oily solution formulation of Menaquinone-4 was administered orally to non-fasted dogs at doses of 0.4, 4 and 40 mg/kg. The plasma concentrations reached maximum levels at 1 to 1.5 h after dosing, and then decreased slowly. AUC values up to 24 h after administration were almost dose-proportional. Menaquinone-4 was also administered to dogs in soft-capsules, for comparison with a conventional hard-capsule oral formula-tion and an intravenous lecithin formulation. The mean AUC for oral dosing in the soft-capsule formulation was 13.5% of that for intravenous dosing in lecithin, and was 4.6 times higher than that for oral dosing in hard-capsules. Additional dosing in fasted dogs indicated that the AUC in pre-fed dogs was about 4 times higher, suggesting that feeding before giving Menaquinone-4 raises the bioavailability. Overall Menaquinone-4 was absorbed rapidly after administration in non-fasted dogs and dose-proportional bioavailability was obtained among the doses of 0.4 to 40 mg/kg. Higher plasma concentrations were observed after administration in the soft-capsule formulation rather than in the hard-capsule formula-tion. These findings suggest that the soft-capsule formulation would show a good pharmacokinetic profile for elderly patients with osteoporosis.
Streptozotocin-induced diabetic and control rats were placed in one of two dietary groups and fed diets with a P/S ratio of 2.2-2.3 for 4 weeks. The n-3/n-6 ratios in the dietary groups were 0.01 (SAF group) and 2.92 (PER group). A decrease in the 20: 4n-6 level, and an increase in the 18 :2n-6 level were observed in the erythrocyte lipids of diabetic rats of both dietary groups, as compared with the levels in control rats. The cholesterol/lipid-P ratio in erythrocyte lipids was significantly higher in diabetic rats than in control rats in both dietary groups, while the ratio in livers was significantly lower in diabetic rats. In liver phospholipids, the differences between the polyunsaturated fatty acid contents of control and diabetic rats in the SAF group, were almost identical to those in erythrocyte lipids. However, in the PER group, a small increase in the 20:4n-6 level, besides an obvious increase in the 18:2n-6 level, was observed in diabetic rats, and n-3 fatty acid levels, especially that of 20:5n-3, were lower significantly in diabetic rats than in control rats. Plasma triglyceride and cholesterol levels in diabetic rats were higher than those in control rats in both dietary groups. The two dietary groups showed significant different triglyceride levels, but similar cholesterol levels. It is suggested that the physiological effect of 18:3n-3 is impaired in diabetes in the same manner as that of 18:2n-6 is.
Rats with atrophic intestinal mucosa due to enteral nutri-tion supplied by an elemental diet (ED) for 4 weeks or more, received a fat-enriched ED containing 10% long chain triglycerides (10% FED) orally. The atrophic ileal mucosa became trophic 4 weeks after adminis-tration of the 10% FED. Ornithine decarboxylase activity in the ileal mucosa increased 3 days after the administration of 10% FED. Rats with atrophic intestinal mucosa that had undergone a 70% proximal jejunoile-ectomy, received an oral ED containing 4% long chain triglycerides (4% FED). In the jejunoileectomized rats, marked proliferation of the re-maining ileum was observed irrespective of diet, when compared with the transected control group. In the transected group, the 4% FED had trophic efects on the ileum, but in the jejunoileectomized group, the 4% FED had no siginificant trophic effect on the remaining ileum. In conclusion, long chain triglycerides had mild trophic effects on ileal mucosa and were effective in the treatment of atrophic intestinal mucosa. However, the trophic effects of fat were apparently masked by the marked proliferation of the ileal mucosa following jejunoileectomy.
To gain an insight into a mechanism whereby maltitol increases intestinal absorption of calcium, we evaluated transepithelial calcium transport of everted segments of rat small intestine by comparing the values in the presence of maltitol with the values in the presence of maltose. In jejunal segments, no significant difference in the rate of calcium transport was seen between the incubations in the medium containing 100 mM maltitol and in the medium containing 100 mM malt-ose, regardless of the calcium concentrations in the mucosal-side medium. By contrast, the everted ileal segments incubated in the presence of maltitol exhibited two-fold greater transepithelial calcium transport than did the segments incubated in the presence of maltose at a high (10 mM) concentration of calcium, whereas at a low (0.5 mM) concentration of calcium, maltitol did not produce a significant effect. With the conditions in which intesinal a-glucosidases were inhibited using the medium con-taining Tris or acarbose, a slight (40%) but significant increase of calcium transport was again observed in the segments incubated in the medium containing maltitol as compared with the medium containing maltose. The results suggest that maltitol enhances the rate of transepithelial calcium transport in the lower part of small intestine by modulating the passive diffusion of calcium, and that not only the nature of low digestibil-ity, but also some other nature(s) of maltitol might be responsible for the maltitol-induced increase of ileal calcium transport.
We prepared the antibody specific against plant xyloglucan and applied it to enzyme-linked immunosorbent assay in order to estimate xyloglucan contents in several vegetables. In this experiment, xyloglucan was detected in the 24% aqueous potassium hydroxide-soluble fractions of tomato, cabbage, lettuce, and eggplant. The xyloglucan contents of these vegetables were estimated to be 1.4 mg, 54μg, 14μg, and 4μg per one hundred grams of their edible portions, respectively, using tamarind xyloglucan as a standard xyloglucan.
Large unilamellar liposomes comprising of egg yolk phos-phatidylcholine (PC) was exposed to photoirradiation in the presence of methylene blue (water-soluble photosensitizes) or 12-(1-pyrene)dodecan-oic acid (P-12, lipid-soluble photosensitizer) to estimate the inhibitory effect of β-carotene and astaxanthin on photosensitized oxidation of phospholipid bilayers. Without sensitizers, astaxanthin decreased much slower than β-carotene and other hydrocarbon carotenoids (lycopene, a-carotene). Astaxanthin lasted longer than β-carotene even in the presence of methylene blue or P-12. Decrease of astaxanthin was also much slower than that of β-carotene when egg yolk PC was replaced by dimyristoyl PC. However, inhibitory effect of astaxanthin was lower than β-carotene in the case of P-12 sensitized photooxidation. These results suggest that effectiveness of carotenoids as antioxidants on photosensi-tized oxidation (Type II) in phospholipid bilayers depends on the site of singlet oxygen to be generated, as well as their stability on photoirradia-tlon.
To examine the effect of bile acids on the activity of intestinal aminopeptidase in vivo, we measured the activity of aminopeptidase in the intestinal mucosa from rats fed the diet containing cholestyramine which sequesters luminal bile acids (experiment 1) and from bile diverted rats (experiment 2). After 32 h fasting, rats were refed for 16 h either of a standard diet (25% casein diets), the same diet containing cholestyramine, or the fat-free diet in experiment 1. In the intestinal washing, the content of total bile acids was markedly decreased with feeding cholestyramine and activities of trypsin and chymotrypsin were also lowered with cholestyramine. Cholestyramine feeding decreased the specific activity of aminopeptidase in the homogenate of intestinal mucosa but increased the specific activities of sucrase and alkaline phosphatase. All these parameters were not modified by the fat-free diet. In experiment 2, bile diverted and sham operated rats were refed the standard diet for 16 h with prior 32 h fasting. Bile diversion, like cholestyramine feeding, lowered the content of total bile acids, the activities of pancreatic hydrolases in the intestinal washings, and the specific activity of aminopeptidase in the intestinal mucosa. The specific activity of sucrase in the intestinal mucosa was higher in bile diverted rats but the activity of alkaline phosphatase was not changed. These data indicate that the decreased abundance of intraluminal bile acid affects the activity of intestinal aminopeptidase not through the decreased absorption of dietary lipid. We propose that the intraluminal bile acids may be important for maintaining the activity of aminopeptidase while the degradation of sucrase by the pancreatic proteinases may be accelerated by the bile acids.
Radish and spinach leaf protein isolates (RLP and SLP, respectively) were prepared from chilled aqueous 0.2% sodium hydroxide extract of their leaves. The RLP and SLP, and those supplemented with methionine (RLP + Met and SLP + Met, respectively) to become equal to casein in methionine content, were compared with casein for their effects on serum cholesterol level in rats fed with a cholesterol-enriched diet for 14 days. Each protein isolate was incorporated into the cholesterol-enriched diet to provide a 15% protein level. RLP was extremely inferior to SLP and casein for body weight gain of rats, but that of rats fed with RLP + Met diet was almost equal to that of casein and SLP groups. The serum cholesterol level in rats fed with SLP and SLP + Met diets was significantly lower as compared with that of the casein-fed rats. Both the amounts of excreted cholesterol and bile acids were significantly higher in rats fed with the SLP and SLP + Met diets than that of the casein-fed rats. These results suggest that the hypocholesterolemic action of SLP may in part have been due to the inhibition of intestinal absorption of both cholesterol and bile acids. RLP + Met diet tended to decrease the serum cholesterol level as compared to casein diet, but the difference was not significant.
The effects of galactooligosaccharides intake on fecal mic-roflora and their metabolism were investigated in twelve healthy volun-teers, in whom the numbers of indigenous bifidobacteria are comparative-ly low. The galactooligosaccharides ingestion increased the number of bifidobacteria, but remarkable changes of other organisms were not observed. This sugar also lowered fecal nitroreductase activity, the concentrations of indole and isovaleric acid.