We investigated whether various carotenoids present in foodstuffs were potentially involved in cancer-preventing action on human prostate cancer. The effects of 15 kinds of carotenoids on the viability of three lines of human prostate cancer cells, PC-3, DU 145 and LNCaP, were evaluated. When the prostate cancer cells were cultured in a carotenoid-supplemented medium for 72 h at 20 micromol/L, 5,6-monoepoxy carotenoids, namely, neoxanthin from spinach and fucoxanthin from brown algae, significantly reduced cell viability to 10.9 and 14.9% for PC-3, 15.0 and 5.0% for DU 145, and nearly zero and 9.8% for LNCaP, respectively. Acyclic carotenoids such as phytofluene, zeta-carotene and lycopene, all of which are present in tomato, also significantly reduced cell viability. On the other hand, phytoene, canthaxanthin, beta-cryptoxanthin and zeaxanthin did not affect the growth of the prostate cancer cells. DNA fragmentation of nuclei in neoxanthin- and fucoxanthin-treated cells was detected by in situ TdT-mediated dUTP nick end labeling (TUNEL) assay. Neoxanthin and fucoxanthin were found to reduce cell viability through apoptosis induction in the human prostate cancer cells. These results suggest that ingestion of leafy green vegetables and edible brown algae rich in neoxanthin and fucoxanthin might have the potential to reduce the risk of prostate cancer.

Gut microbiota mediates the effects of diet, thereby modifying host metabolism and the incidence of metabolic disorders. Increased consumption of omega-6 polyunsaturated fatty acid (PUFA) that is abundant in Western diet contributes to obesity and related diseases. Although gut-microbiota-related metabolic pathways of dietary PUFAs were recently elucidated, the effects on host physiological function remain unclear. Here, we demonstrate that gut microbiota confers host resistance to high-fat diet (HFD)-induced obesity by modulating dietary PUFAs metabolism. Supplementation of 10-hydroxy- cis -12-octadecenoic acid (HYA), an initial linoleic acid-related gut-microbial metabolite, attenuates HFD-induced obesity in mice without eliciting arachidonic acid-mediated adipose inflammation and by improving metabolic condition via free fatty acid receptors. Moreover, Lactobacillus -colonized mice show similar effects with elevated HYA levels. Our findings illustrate the interplay between gut microbiota and host energy metabolism via the metabolites of dietary omega-6-FAs thereby shedding light on the prevention and treatment of metabolic disorders by targeting gut microbial metabolites.

Glycolipids from edible plant sources were accurately quantified by silica-based, normal-phase high-performance liquid chromatography using an evaporative light-scattering detector. Five major glycolipid classes (acylated steryl glucoside, steryl glucoside, ceramide monohexoside, monogalactosyldiacylglycerol, and digalactosyldiacylglycerol) were separated and determined with a binary gradient system consisting of chloroform and methanol/water (95:5, vol/vol) without any interference from other lipid classes and pigments. The described method was applied to 48 edible plants available in Japan including cereals, legumes, vegetables, and fruits. Examined plant species contained glycolipids in wide concentration ranges, such as 5-645 mg/100 g tissue.

Despite the interest in the beneficial roles of dietary carotenoids in human health, little is known about their solubilization from foods to mixed bile micelles during digestion and the intestinal uptake from the micelles. We investigated the absorption of carotenoids solubilized in mixed micelles by differentiated Caco-2 human intestinal cells, which is a useful model for studying the absorption of dietary compounds by intestinal cells. The micelles were composed of 1 micromol/L carotenoids, 2 mmol/L sodium taurocholate, 100 micromol/L monoacylglycerol, 33.3 micromol/L fatty acid and phospholipid (0-200 micromol/L). The phospholipid content of micelles had profound effects on the cellular uptake of carotenoids. Uptake of micellar beta-carotene and lutein was greatly suppressed by phosphatidylcholine (PC) in a dose-dependent manner, whereas lysophosphatidylcholine (lysoPC), the lipolysis product of PC by phospholipase A2 (PLA2), markedly enhanced both beta-carotene and lutein uptake. The addition of PLA2 from porcine pancreas to the medium also enhanced the uptake of carotenoids from micelles containing PC. Caco-2 cells could take up 15 dietary carotenoids, including epoxy carotenoids, such as violaxanthin, neoxanthin and fucoxanthin, from micellar carotenoids, and the uptakes showed a linear correlation with their lipophilicity, defined as the distribution coefficient in 1-octanol/water (log P(ow)). These results suggest that pancreatic PLA2 and lysoPC are important in regulating the absorption of carotenoids in the digestive tract and support a simple diffusion mechanism for carotenoid absorption by the intestinal epithelium.

This article is available online at http://dmd.aspetjournals.org ABSTRACT:Fucoxanthin, a major carotenoid in edible brown algae, potentially inhibits the proliferation of human prostate cancer cells via apoptosis induction. However, it has been postulated that dietary fucoxanthin is hydrolyzed into fucoxanthinol in the gastrointestinal tract before absorption in the intestine. In the present study, we investigated the further biotransformation of orally administered fucoxanthin and estimated the cytotoxicity of fucoxanthin metabolites on PC-3 human prostate cancer cells. After the oral administration of fucoxanthin in mice, two metabolites, fucoxanthinol and an unknown metabolite, were found in the plasma and liver. The unknown metabolite was isolated from the incubation mixture of fucoxanthinol and mouse liver preparation (10,000g supernatant of homogenates), and a series of instrumental analyses identified it as amarouciaxanthin A [(3S,5R,6S)-3,5,6-trihydroxy-6,7-didehydro-5,6,7,8-tetrahydro-␤,⑀-carotene-3,8-dione]. The conversion of fucoxanthinol into amarouciaxanthin A was predominantly shown in liver microsomes. This dehydrogenation/isomerization of the 5,6-epoxy-3-hydroxy-5,6-dihydro-␤ end group of fucoxanthinol into the 6-hydroxy-3-oxo-⑀ end group of amarouciaxanthin A required NAD(P)؉ as a cofactor, and the optimal pH for the conversion was 9.5 to 10.0. Fucoxanthinol supplemented to culture medium via HepG2 cells was also converted into amarouciaxanthin A. The 50% inhibitory concentrations on the proliferation of PC-3 human prostate cancer cells were 3.0, 2.0, and 4.6 M for fucoxanthin, fucoxanthinol, and amarouciaxanthin A, respectively. To our knowledge, this is the first report on the enzymatic dehydrogenation of a 3-hydroxyl end group of xanthophylls in mammals.

The metabolic fate in mammals of dietary fucoxanthin, a major carotenoid in brown algae, is not known. We investigated the absorption and metabolism of fucoxanthin in differentiated Caco-2 human intestinal cells, a useful model for studying the absorption of dietary compounds by intestinal cells. Fucoxanthin was taken up by Caco-2 cells incubated with micellar fucoxanthin composed of 1 micromol/L fucoxanthin, 2 mmol/L sodium taurocholate, 100 micromol/L monoacylglycerol, 33.3 micromol/L fatty acids and 50 micromol/L lysophosphatidylcholine. Fucoxanthinol, the deacetylated product of fucoxanthin, was also found in both medium and cells, with its level increasing significantly in a time-dependent manner. No conjugated forms of fucoxanthin and fucoxanthinol were found in either medium or cells. In the animal study, fucoxanthinol (10.4 +/- 5.3 nmol/L plasma, n = 4) was detected in plasma of mice 1 h after intubation of 40 nmol fucoxanthin. These results indicate that dietary fucoxanthin is incorporated as fucoxanthinol, the deacetylated form, from the digestive tract into the blood circulation system in mammals.

We investigated the digestion of cerebrosides of plant origin prepared from maize, focusing especially on the digestive fates of trans-4, cis-8- and trans-4, trans-8-sphingadienine, which are common in higher plants. In the small intestinal mucosa and cecal contents of rats, the cerebrosidase activity at pH 5.2 toward the glucosyl linkage in maize cerebrosides (glucosylceramides) was similar to that in cerebrosides of mammalian origin. Similarly, the ceramidase activity toward the amide linkage in ceramides prepared from maize cerebrosides at pH 7.0 was the same as that toward ceramides of mammalian origin. In addition, maize cerebrosides were hydrolyzed to ceramide and free sphingoid bases in the digestive tract of rats after oral administration. To further evaluate the uptake by enterocytes of 4,8-sphingadienine, we used differentiated Caco-2 cells, derived from human colonic carcinoma, as a model of intestinal epithelial cells. The accumulation of sphingoid bases in Caco-2 cells incubated with each isomer of sphingadienine was lower than that after incubation with sphingosine (P < 0.05). Verapamil, a P-glycoprotein inhibitor, increased the accumulation of each sphingadienine but not of sphingosine, suggesting that the efflux of sphingadienine of plant origin, but not sphingosine of mammalian origin, was affected by P-glycoprotein. The digestibility of maize cerebrosides appears similar to that of cerebrosides of mammalian origin, but the metabolic fate of sphingoid bases of plant origin within enterocytes differs from that of sphingosine. Isomers of 4,8-sphingadienine degraded from dietary plant cerebrosides appear to be poorly absorbed from the digestive tract.

mammalian sphingolipids is sphingosine ( trans -4-sphingenine, d18:1 4t ). Smaller amounts of other sphingoid bases, such as sphinganine (dihydrosphingosine, d18:0) and phytosphingosine (4-hydroxysphinganine, t18:0), are encountered frequently. In higher plants, the structures of sphingoid bases are more complicated than in mammals, because they can be desaturated at the C8-position by a ⌬ 8-sphingolipid desaturase, yielding cis -and trans -isomers of ⌬ 8-unsaturated sphingoid bases (d18:2 4t,8c(t) ) ( 3, 4 ). 9-Methyl-trans -4, trans -8-sphingadienine (d19:2 4t,8t ) is a typical structure found in yeasts ( 5 ). Sphingolipids of marine invertebrates have unique triene types of sphingoid bases with a conjugated diene such as 2-amino-4,8,10-octatriene-1, 3-diol (d18:3 4,8,10 ) and 2-amino-9-methyl-4,8,10-octatriene-1, 3-diol (d19:3 4,8,10 ) ( 6 ). Therefore, sphingolipids having various structures of sphingoid bases are ingested daily from foodstuffs ( 7-9 ).Dietary sphingolipids have gained attention for their potential to protect against infl ammation and cancers in the gut ( 10-13 ). One plausible mechanism for these effects may be via the hydrolysis of complex sphingolipids to bioactive ceramides and sphingosine, because those breakdown products are known to play important roles as intracellular mediators ( 14, 15 ). We previously demonstrated that dietary maize and yeast sphingolipids with sphingoid bases distinct from those of mammals are able to prevent the formation of aberrant crypt foci in 1,2-dimethylhydrazine-treated mice ( 16,17 ). We further showed that sphingoid bases prepared from various dietary sources can induce apoptosis in cancer cells (18)(19)(20).In early studies, Nilsson ( 21-23 ) investigated the digestion and intestinal absorption of sphingolipids containing sphingosine and sphinganine. Dietary sphingolipids can be hydrolyzed to their components, such as sphingoid bases, fatty acids, and the polar head group, by intestinal enzymes and are then taken up by mucosal cells ( 24,25 ). A large portion of sphingosine absorbed Sphingolipids are ubiquitous in all eukaryotic organisms and constitute a family of compounds that have a sphingoid base (long-chain base) with an amide-linked fatty acid and a polar head group. It is well known that there are diverse structures of sphingoid bases in nature ( Fig. 1 ) ( 1, 2 ). The most common sphingoid base of