[Analysis and Health Risk Assessment of Cadmium and Arsenic in Japanese, Vietnamese, and Indonesian Rice]

Herein, we quantified the concentrations of cadmium (Cd) and arsenic (As) in 63 milled rice (Oryza sativa L.) cultivated in Japan, Vietnam, and Indonesia. We estimated the daily intake of Cd and As by adults and children consuming this rice by inductively coupled plasma-mass spectrometer (ICP-MS). Cd and As were detected in all milled rice samples. No significant differences were observed in Cd concentrations between Japanese (50th percentile concentration: 0.036 mg/kg), Vietnamese (0.035 mg/kg), and Indonesian rice (0.022 mg/kg). However, As concentrations in Vietnamese rice (50th percentile concentration: 0.142 mg/kg) were significantly higher than those in Japanese (0.101 mg/kg, p<0.001) and Indonesian rice (0.038 mg/kg, p<0.0001). Target hazard quotients (THQs) were then calculated to evaluate the non-carcinogenic health risk from ingestion of individual heavy metals (Cd and As) by rice consumption. Results revealed that THQs of individual heavy metals for Japanese, Vietnamese, and Indonesian adults and children consuming this rice were all less than one, suggesting that no health risk is associated with the intake of a single heavy metal via rice consumption.

Ezetimibe inhibits lymphatic transport of esterified cholesterol but not free cholesterol in thoracic lymph duct-cannulated rats

PURPOSE

Ezetimibe has been shown to inhibit dietary cholesterol absorption in animal models and humans, but studies on lymphatic lipid transport have not yet been performed. Rats subjected to permanent lymph duct cannulation were used to investigate the effects of ezetimibe on lipid transport.

METHODS

Rats were fed diets with and without ezetimibe (5.0 mg/kg), and their lymph was collected after feeding to quantify lymphatic lipid levels. Total cholesterol content in the intestinal mucosa was also measured.

RESULTS

Rats that consumed ezetimibe had significantly lower lymphatic total cholesterol transport with the reduction of esterified cholesterol transport. According to the calculation based on cholesterol consumption, ezetimibe reduced the total cholesterol lymphatic recovery rate by 54 %. We also determined that ezetimibe significantly reduced the total cholesterol content in the intestinal mucosa.

CONCLUSION

This is the first direct evidence that ezetimibe inhibits esterified but not free cholesterol lymphatic transport in thoracic duct-cannulated rats. The results also indicate that ezetimibe is not involved in the lymphatic transport of triacylglycerols, phospholipids, or α-tocopherol.

Dietary kakrol (Momordica dioica Roxb.) flesh inhibits triacylglycerol absorption and lowers the risk for development of fatty liver in rats

Kakrol ( Momordica dioica Roxb.) is a cucurbitaceous vegetable native to India and Bangladesh. Bitter gourd ( Momordica charantia Linn.), a species related to kakrol, has been shown to have pharmacological properties including antidiabetic and antisteatotic effects. In this study, we investigated the effect of dietary kakrol on lipid metabolism in rats. Sprague-Dawley rats were fed AIN-76 formula diets containing 3% freeze-dried powders of whole kakrol or bitter gourd for two weeks. Results showed significantly lowered liver cholesterol and triacylglycerol levels in rats fed on both diets. Fecal lipid excretion increased in rats fed the kakrol diet, and lymphatic transport of triacylglycerol and phospholipids decreased in rats fed the kakrol diet after permanent lymph cannulation. Furthermore, n-butanol extract from kakrol caused a significant concentration-dependent decrease in the pancreatic lipase activity in vitro. These results indicate that the mechanisms of action on lipid metabolism in kakrol and bitter gourd are different and that dietary kakrol reduces liver lipids by inhibiting lipid absorption.

Dietary guar gum reduces lymph flow and diminishes lipid transport in thoracic duct-cannulated rats

Guar gum has a well-recognized hypolipidemic effect. This effect is thought to be due to the physicochemical properties of guar gum, which may cause changes in adsorption of lipids or the viscosity of the intestinal contents. Guar gum is a non-specific absorption inhibitor of any type of lipid-soluble compound. Permanent lymph duct cannulation was performed on rats to investigate the effects of dietary guar gum on lymph flow and lipid transport. Rats fed a 5% guar gum diet were compared with those fed a 5% cellulose diet, and lymph was collected after feeding. The water-holding capacity (WHC), settling volume in water (SV), and viscosity of guar gum were compared with those of cellulose. Rats fed with the guar gum diet had significantly lower lymph flow and lymphatic lipid transport than did rats fed with the cellulose diet. The WHC, SV, and viscosity of guar gum were significantly higher than those of cellulose. We propose that dietary guar gum reduces lymph flow and thereby diminishes lipid transport by means of its physicochemical properties related to water behavior in the intestine.

Lymphatic absorption and deposition of various plant sterols in stroke-prone spontaneously hypertensive rats, a strain having a mutation in ATP binding cassette transporter G5

ATP binding cassette transporter G5 (ABCG5) and ATP binding cassette transporter G8 (ABCG8) have been suggested to transport absorbed plant sterols and cholesterol from enterocytes to the intestinal lumen and from hepatocytes to bile. It has been thought that mutations of ABCG5 or ABCG8 cause the deposition of plant sterols in the body. In the present study, lymphatic absorption of various plant sterols and their deposition in various tissues was investigated in stroke-prone spontaneously hypertensive rats (SHRSP), having a mutation in Abcg5 and depositing plant sterols in the body. The order of lymphatic 24-h recovery of plant sterols was as follows: campesterol > sitosterol > brassicasterol > stigmasterol = sitostanol. When SHRSP were fed a diet containing one of the plant sterols, the depositions of campesterol and sitosterol were comparatively higher than those of brassicasterol, stigmasterol and sitostanol. Highly positive correlations were obtained between lymphatic recovery of plant sterols and their levels in plasma, liver, adipose tissue and heart. The tendency of differential absorption of plant sterols to the lymph in SHRSP was similar to that in normal Wistar rats previously reported by us (Hamada et al. Lipids 41:551-556, 2006). These observations suggest that differential absorption of various plant sterols is kept in SHRSP in spite of a mutation in Abcg5.

Campest-5-en-3-one, an oxidized derivative of campesterol, activates PPARα, promotes energy consumption and reduces visceral fat deposition in rats

Dietary campest-5-en-3-one (campestenone), an oxidized derivative of campesterol, significantly reduced visceral fat weight and the concentration of triacylglycerol in serum and liver of rats. Dietary campestenone dramatically increased the activities and the mRNA expressions of mitochondrial and peroxisomal enzymes involved in beta-oxidation in the liver. Campestenone activated human peroxisome proliferator-activated receptor (PPAR) alpha as determined using the novel GAL4 ligand-binding domain chimera assay system with coactivator coexpression. In contrast, dietary campestenone reduced the activities and the mRNA expressions of enzymes involved in fatty acid synthesis, except for the malic enzyme. Dietary campestenone decreased the sterol regulatory element binding protein-1 (SREBP-1) mRNA level. Energy expenditure was significantly higher in the feeding of campestenone in rats. Dietary campestenone reduced hepatic cholesterol concentration and increased fecal excretion of neutral steroids originated from cholesterol. Lymphatic absorption of cholesterol was reduced by the coadministration of campestenone in rats cannulated in the thoracic duct. These observations suggest a possibility that campestenone has an ability to prevent coronary heart disease by improving obesity and abnormality of lipid metabolism.

Oxysterol regulation of estrogen receptor alpha-mediated gene expression in a transcriptional activation assay system using HeLa cells

In order to test the estrogenic activity of sterol oxidation products from cholesterol and phytosterols, an estrogen-dependent gene expression assay was performed in estrogen receptor alpha-stably transformed HeLa cells. The ranking of the estrogenic potency of these compounds was different: 17beta-estradiol >> genistein >> beta-epoxycholesterol = daidzein = cholestanetriol = 22(R)-hydroxycholesterol = 20(S)-hydroxycholesterol = sitostanetriol > campestanetriol = beta-epoxysitosterol = 7beta-hydroxycholesterol. These compounds were not estrogenic in estrogen receptor-negative HeLa cells.

Tea catechins with a galloyl moiety suppress postprandial hypertriacylglycerolemia by delaying lymphatic transport of dietary fat in rats

Tea catechins, (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epigallocatechin gallate (EGCG), have been shown to be epimerized to (-)-catechin (C), (-)-gallocatechin (GC), (-)-catechin gallate (CG), and (-)-gallocatechin gallate (GCG), respectively, during heat treatment. In this study, we examined the effect of tea catechins rich in ECG and EGCG and heat-treated tea catechins rich in CG and GCG on postprandial hypertriacylglycerolemia in rats. Both tea catechins and heat-treated tea catechins suppressed postprandial hypertriacylglycerolemia. Lymphatic recovery of (14)C-trioleoylglycerol in rats cannulated in the thoracic duct was delayed by the administration of tea catechins and heat-treated tea catechins. Tea catechins and heat-treated tea catechins had the same effect on all variables tested. These catechin preparations dose-dependently inhibited the activity of pancreatic lipase in vitro. When purified catechins were used, only those with a galloyl moiety inhibited the activity of pancreatic lipase. These results suggest that catechins with a galloyl moiety suppress postprandial hypertriacylglycerolemia by slowing down triacylglycerol absorption through the inhibition of pancreatic lipase. Because postprandial hypertriacylglycerolemia is a risk factor for coronary heart disease, our results suggest that catechins with a galloyl moiety may prevent this disease.

Phytosterol oxidation products are absorbed in the intestinal lymphatics in rats but do not accelerate atherosclerosis in apolipoprotein E-deficient mice

Phytosterol oxidation products (oxyphytosterols) are formed during the processing and storage of foods. However, it is unknown whether oxyphytosterols affect human health. To address these issues, we prepared beta-sitosterol and campesterol oxides, evaluated their lymphatic absorption in rats, and examined the effect of an oxyphytosterol diet on atherosclerosis in apolipoprotein (apo) E-deficient mice. The lymphatic absorption of cholesterol and 6 oxyphytosterols (7alpha-hydroxy, 7beta-hydroxy, beta-epoxy, alpha-epoxy, dihydroxy, and 7-keto) of beta-sitosterol or campesterol was assessed in thoracic duct-cannulated rats fed an AIN-93G-based diet containing 2.5 g of cholesterol, oxyphytosterols, or intact phytosterols per kg. Lymphatic recoveries (on a mass basis) of oxycampesterols (15.9 +/- 2.8%, n = 10) and oxysitosterols (9.12 +/- 1.77%, n = 10) were higher than for campesterol (5.47 +/- 1.02%, n = 12, P < 0.05) and beta-sitosterol (2.16 +/- 0.37%, n = 12, P < 0.05), but lower than for cholesterol (37.3 +/- 8.3%, n = 6, P < 0.05). Apo E-deficient mice were fed an AIN-93G-based diet containing 0.2 g oxyphytosterols or intact phytosterols per kg for 9 wk. Diet-derived oxyphytosterols accumulated in the serum, liver, and aorta. Furthermore, the oxyphytosterol diet increased oxycholesterol in the serum compared to the phytosterol diet. However, there was no significant difference between the 2 groups in the serum and aortic cholesterol concentration, the lesion area in the aortic root, or 8-iso-prostaglandin F2alpha concentration in the urine. These results indicate that exogenous oxyphytosterols are well-absorbed and accumulate in the body, but do not promote the development of atherosclerosis in apo E-deficient mice.

Low-density lipoprotein receptor-related protein 5 (LRP5) is essential for normal cholesterol metabolism and glucose-induced insulin secretion

A Wnt coreceptor low-density lipoprotein receptor-related protein 5 (LRP5) plays an essential role in bone accrual and eye development. Here, we show that LRP5 is also required for normal cholesterol and glucose metabolism. The production of mice lacking LRP5 revealed that LRP5 deficiency led to increased plasma cholesterol levels in mice fed a high-fat diet, because of the decreased hepatic clearance of chylomicron remnants. In addition, when fed a normal diet, LRP5-deficient mice showed a markedly impaired glucose tolerance. The LRP5-deficient islets had a marked reduction in the levels of intracellular ATP and Ca(2+) in response to glucose, and thereby glucose-induced insulin secretion was decreased. The intracellular inositol 1,4,5-trisphosphate (IP3) production in response to glucose was also reduced in LRP5-- islets. Real-time PCR analysis revealed a marked reduction of various transcripts for genes involved in glucose sensing in LRP5-- islets. Furthermore, exposure of LRP5++ islets to Wnt-3a and Wnt-5a stimulates glucose-induced insulin secretion and this stimulation was blocked by the addition of a soluble form of Wnt receptor, secreted Frizzled-related protein-1. In contrast, LRP5-deficient islets lacked the Wnt-3a-stimulated insulin secretion. These data suggest that WntLRP5 signaling contributes to the glucose-induced insulin secretion in the islets.

Dietary cholesterol-oxidation products accumulate in serum and liver in apolipoprotein E-deficient mice, but do not accelerate atherosclerosis

There are conflicting reports regarding the effect of dietary cholesterol-oxidation products (oxysterols) on the development of atherosclerosis in experimental animals. To address this issue, apolipoprotein (Apo) E-deficient mice were fed a purified diet (AIN-93) or the same purified diet containing 0.2 g cholesterol or 0.2 g oxysterols/kg. The dietary oxysterols had no significant effect on the serum lipid levels. Although all of the diet-derived oxysterols (cholest-5-en-3beta,7alpha-diol, cholest-5-en-3beta,7beta-diol, cholestan-5alpha,6alpha-epoxy-3beta-ol, cholestan-5beta,6beta-epoxy-3beta-ol, cholestan-3beta, 5alpha, 6beta-triol, cholest-5-en-3beta-ol-7-one and cholest-5-en-3beta, 25-diol) accumulated in the serum and liver, only cholest-5-en-3beta-ol-7-one and cholestan-3beta, 5alpha, 6beta-triol accumulated significantly (P<0.05) in the aorta. The oxysterol diet did not result in elevation of the aortic cholesterol level or the lesion volume in the aortic valve. These present results indicate that exogenous oxysterols do not promote the development of atherosclerosis in ApoE-deficient mice.

Lymphatic transport of dietary cholesterol oxidation products, cholesterol and triacylglycerols in rats

Rats were fed on a diet containing 0.5% cholesterol oxidation products (oxysterols) or 0.5% cholesterol for 30 min, and their lymph was collected for 7 h. The amount of each of the individual oxysterols absorbed in the lymph depended on the ingested amounts, but the recovery was the highest for 5alpha,6alpha-epoxycholesterol (10.5%), this being followed by 7-ketocholesterol (5.8%), cholestanetriol (5.2%), 7beta-hydroxycholesterol (4.8%), 7alpha-hydroxycholesterol (3.4%), 5beta,6beta-epoxycholesterol (2.2%), and 25-hydroxycholesterol (1.8%). A diet enriched with oxysterol, but not cholesterol, resulted in increased transport of triacylglycerols in the lymph. These results suggest that the absorption rate of oxysterols depends on the type, and indicate that the effect of dietary oxysterols on the lymphatic transport of triacylglycerols differs from that of dietary cholesterol. It therefore remains to be determined which oxysterol was responsible for the triacyglycerol transport.

Differential effect of walnut oil and safflower oil on the serum cholesterol level and lesion area in the aortic root of apolipoprotein E-deficient mice

Walnut oil (WO) is a good source of alpha-linolenic acid. We compared the effects of WO and high-linoleic safflower oil (HLSO) on the serum lipid level and atherosclerosis development in male and female apolipoprotein (apo) E-deficient mice. The WO diet resulted in a higher level of serum cholesterol than with HLSO. Female mice fed on the WO diet had a greater lesion area in the aortic root than did those on the HLSO diet. There was no diet-dependent difference in the level of cholesterol and its oxidation products in the abdominal and thoracic aorta. These results suggest that the unpleasant effects of the WO diet on apo E-deficient mice may be attributable to alpha-linolenic acid.

[Light and electron microscopic study of orbital cavernous hemangioma]

We examined the specimens of tumors from three patients with orbital cavernous hemangioma by light and electron microscopy. The tumors mostly consisted of many vessels of various sizes. A part of the tumor tissues showed irregular vascular inner spaces like sinusoids. Apart from the sinusoid-like vessels, we divided the other vessels into 10 groups at every 100 microns-interval based on the difference of the inner diameter and measured the maximum and minimum width of the media. The average maximum width increased until the inner diameter reached 300-400 microns, while the average minimum width increased until it reached 200-300 microns. In groups with greater inner diameter, the average maximum and average minimum widths were approximately constant. There were three kinds of vessels: vessels of cuboid endothelia, of flat endothelia, and of both cuboid and flat endothelia. The width of media of the vessels having cuboid and flat endothelia was greater than that of the other types of vessels. The lamina densa of endothelia was broken or stratified. Myofibroblast-like cells proliferated among the vessels and could not be distinguished from tumor cells of hemangiopericytoma. These results indicate that smooth muscle cells proliferate by an unknown mechanism and proliferation is associated with changes of endothelia in cavernous hemangioma, and strongly suggest that this tumor is hamartoma.