Vitamin E metabolite 13′-carboxychromanols inhibit pro-inflammatory enzymes, induce apoptosis and autophagy in human cancer cells by modulating sphingolipids and suppress colon tumor development in mice.

Jang Y, Park NY, Rostgaard-Hansen AL, Huang J, Jiang Q.

Free Radic Biol Med. 2016 Jun;95:190-9. doi: 10.1016/j.freeradbiomed.2016.03.018.

Abstract

Vitamin E forms are substantially metabolized to various carboxychromanols including 13′-carboxychromanols (13′-COOHs) that are found at high levels in feces. However, there is limited knowledge about functions of these metabolites. Here we studied δT-13′-COOH and δTE-13′-COOH, which are metabolites of δ-tocopherol and δ-tocotrienol, respectively. δTE-13′-COOH is also a natural constituent of a traditional medicine Garcinia Kola. Both 13′-COOHs are much stronger than tocopherols in inhibition of pro-inflammatory and cancer promoting cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX), and in induction of apoptosis and autophagy in colon cancer cells. The anticancer effects by 13′-COOHs appeared to be partially independent of inhibition of COX-2/5-LOX. Using liquid chromatography tandem mass spectrometry, we found that 13′-COOHs increased intracellular dihydrosphingosine and dihydroceramides after short-time incubation in HCT-116 cells, and enhanced ceramides while decreased sphingomyelins during prolonged treatment. Modulation of sphingolipids by 13′-COOHs was observed prior to or coinciding with biochemical manifestation of cell death. Pharmaceutically blocking the increase of these sphingolipids partially counteracted 13′-COOH-induced cell death. Further, 13′-COOH inhibited dihydroceramide desaturase without affecting the protein expression. In agreement with these mechanistic findings, δTE-13′-COOH significantly suppressed the growth and multiplicity of colon tumor in mice. Our study demonstrates that 13′-COOHs have anti-inflammatory and anticancer activities, may contribute to in vivo anticancer effect of vitamin E forms and are promising novel cancer prevention agents.

Gagic Z, Ivkovic B, Srdic-Rajic T, Vucicevic J, Nikolic K, Agbaba D.

Eur J Pharm Sci. 2016 Jun 10;88:59-69. doi: 10.1016/j.ejps.2016.04.008.

Abstract

Tocopherols and tocotrienols belong to the family of vitamin E (VE) with the well-known antioxidant properties. For certain α-tocopherol and γ-tocotrienol derivatives used as the lead compounds in this study, antitumor activities against various cancer cell types have been reported. In the course of the last decade, structural analogs of VE (esters, ethers and amides) with an enhanced antiproliferative and proapoptotic activity against various cancer cells were synthesized. Within the framework of this study, seven amino acid esters of α-tocopherol (4a-d) and γ-tocotrienol (6a-c) were prepared using the EDC/DMAP reaction conditions and their ability to inhibit proliferation of the MCF-7 and MDA-MB-231 breast cancer cells and the A549 lung cancer cells was evaluated. Compound 6a showed an activity against all three cell lines (IC50: 20.6μM, 28.6μM and 19μM for the MCF-7, MDA-MB-231 and A549 cells, respectively), while compound 4a inhibited proliferation of the MCF-7 (IC50=8.6μM) and A549 cells (IC50=8.6μM). Ester 4d exerted strong antiproliferative activity against the estrogen-unresponsive, multi-drug resistant MDA-MB-231 breast cancer cell line, with IC50 value of 9.2μM. Compared with the strong activity of compounds 4a, 4d and 6a, commercial α-tocopheryl succinate and γ-tocotrienol showed only a limited activity against all three cell lines, with IC50 values >50μM. Investigation of the cell cycle phase distribution and the cell death induction confirmed an apoptosis of the MDA-MB-231 cells treated with 4d, as well as a synergistic effect of 4d with the known anticancer drug doxorubicin. This result suggests a possibility of a combined therapy of breast cancer in order to improve the therapeutic response and to lower the toxicity associated with a high dose of doxorubicin. The stability study of 4d in human plasma showed that ca. 83% initial concentration of this compound remains in plasma in the course of six hours incubation. The ligand based virtual screening of the ChEMBL database identified new compounds with a potential antiproliferative activity on MCF-7 and on multi-drug resistant MDA-MB 231 breast cancer cells.

Torquato P, Ripa O, Giusepponi D, Galarini R, Bartolini D, Wallert M, Pellegrino R, Cruciani G, Lorkowski S, Birringer M, Mazzini F, Galli F.

J Pharm Biomed Anal. 2016 May 30;124:399-412. doi: 10.1016/j.jpba.2016.01.056. Review.

Abstract

After more than 90 years from its discovery and thousands of papers published, the physiological roles of vitamin E (tocopherols and tocotrienols) are still not fully clarified. In the last few decades, the enzymatic metabolism of this vitamin has represented a stimulating subject of research. Its elucidation has opened up new horizons to the interpretation of the biological function of that class of molecules. The identification of specific properties for some of the physiological metabolites and the definition of advanced analytical techniques to assess the human metabolome of this vitamin in vivo, have paved the way to a series of hypotheses on the functional implications that this metabolism may have far beyond its catabolic role. The present review collects the available information on the most relevant analytical strategies employed to assess the status and metabolism of vitamin E in humans as well as in other model systems. A particular focus is dedicated to the analytical methods used to measure vitamin E metabolites, and particularly long-chain metabolites, in biological fluids and tissues. Preliminary information on a new LC-APCI-MS/MS method to measure these metabolites in human serum is reported.

Abubakar IB, Lim KH, Kam TS, Loh HS.

J Ethnopharmacol. 2016 May 26;184:107-18. doi: 10.1016/j.jep.2016.03.004.

Abstract

The genus Tabernaemontana has widespread distribution throughout tropical and subtropical parts of the world, i.e. Africa, Asia and America which has long been used for treatments of different disease conditions including tumours, wounds, syphilis, stomach ache and headache. Some Tabernaemontana species are used for treatment of piles, spleen and abdominal tumours in India. In particular, the leaf of Tabernaemontana corymbosa is used for treatment of tumours in Bangladesh. Parts of the plant or whole plants are used as decoctions, steam bath, powder and ointments. The present study was undertaken to study the mechanism of apoptosis induction in human glioblastoma (U87MG) and colorectal adenocarcinoma (HT-29) cancer cells by a novel indole alkaloid, jerantinine B isolated from T. corymbosa, δ-tocotrienoland the combined low-dose treatments of δ-tocotrienol with IC20 dose of jerantinine B. In summary, this study demonstrated the mechanism for cytotoxic potency of δ-tocotrienol and jerantinine B against U87MG and HT-29 cells. Furthermore, combined low-dose treatments induced concurrent synergistic inhibition of cancer cell growth with concomitant dose reduction thus minimizing toxicity to normal cells and improving potency of δ-tocotrienol and jerantinine B.

Xu H, Xiong Z, Ärnlöv J, Qureshi AR, Cederholm T, Sjögren P, Lindholm B, Risérus U, Carrero JJ.

J Ren Nutr. 2016 May;26(3):177-82. doi: 10.1053/j.jrn.2015.11.005.

Abstract

Insulin resistance is common in individuals with chronic kidney disease (CKD) and may be partly explained by modifiable risk factors. In the general population, vitamin E supplementation has been suggested to improve both insulin sensitivity and secretion. We here explore the potential role of vitamin E as a modifiable risk factor for insulin resistance among individuals with CKD. A total of 273 nondiabetic men aged 70 to 71 years with CKD defined as either cystatin C estimated glomerular filtration rate < 60 mL/minute/1.73 m(2) or urinary albumin excretion rate ≥ 20 μg/minute were included in this study. Serum α-, β-, and γ-tocopherol concentrations were measured by high-performance liquid chromatography and expressed as μmol/total serum cholesterol and triglycerides (in mmol). Dietary vitamin E intake was estimated from 7-day food records. Insulin sensitivity index (M/I ratio) was measured by hyperinsulinemic-euglycemic glucose clamps. Univariate and multivariate regression models were fitted to assess the association between M/I and circulating concentrations of tocopherols. Conclusion, serum α-tocopherol concentration associates with insulin sensitivity in nondiabetic older men with CKD.

Farzollahi M, Tayefi-Nasrabadi H, Mohammadnejad D, Abedelahi A.

J Obstet Gynaecol Res. 2016 May;42(5):526-35. doi: 10.1111/jog.12933.

Abstract

The aim of this study was to evaluate the effects of preventive vitamin E (α-tocopherol) on antral follicle development and embryogenesis of oocytes obtained after vitrification of mouse ovarian tissue. Female Balb/c mice were killed by cervical dislocation after the injection of pregnant mare’s serum gonadotrophin (10 IU) and their ovaries were randomly divided into three groups: control or non-vitrified (n = 10), vitrification 1 (5, 10% ethylene glycol + 5, 10% dimethylsulfoxide) (n = 15), and vitrification 2 (10, 15% ethylene glycol + 10, 15% dimethylsulfoxide) (n = 15) with ascending concentration of cryoprotectants. After toxicity tests and vitrification-warming, mechanically isolated antral follicles were cultured in α-minimum essential medium, which was supplemented with or without α-tocopherol (100 μM). The follicular maturation rates and embryo development were collected and assessed. Also, the viability, morphology and ultrastructure of derived antral follicles from vitrified ovaries were analyzed. Results showed the morphology and ultrastructure of follicles were well preserved in the vitrified groups and α-tocopherol supplementation of culture media significantly increased the proportion of oocytes that reached metaphase II blastocyst rates compared to non-α-tocopherol supplemented media (P < 0.01). In conclusion, Vitamin E improves in vitro maturation rates and blastocyst rates of oocytes that are isolated from vitrified ovarian tissue.

Cheng K, Niu Y, Zheng XC, Zhang H, Chen YP, Zhang M, Huang XX, Zhang LL, Zhou YM, Wang T.

Asian-Australas J Anim Sci. 2016 May;29(5):681-8. doi: 10.5713/ajas.15.0819.

Abstract

The present study was conducted to compare the supplementation of natural (D-α-tocopherol) and synthetic (DL-α-tocopherolacetate) vitamin E on the growth performance, meat quality, muscular antioxidant capacity and genes expression related to oxidative status of broilers. A total of 144 1 day-old Arbor Acres broiler chicks were randomly allocated into 3 groups with 6 replicates of 8 birds each. Birds were given a basal diet (control group), and basal diet supplemented with either 20 IU D-α-tocopherol or DL-α-tocopherolacetate for 42 days, respectively. The results indicated that treatments did not alter growth performance of broilers (p>0.05). Compared with the control group, concentration of α-tocopherol in the breast muscle was increased by the supplementation of vitamin E (p<0.05). In the thigh, α-tocopherol content was also enhanced by vitamin E inclusion, and this effect was more pronounced in the natural vitamin E group (p<0.05). Vitamin E supplementation increased the redness of breast (p<0.05). In the contrast, the inclusion of synthetic vitamin E decreased lightness of thigh (p<0.05). Dietary vitamin E inclusion reduced drip loss at 24 h of thigh muscle (p<0.05), and this effect was maintained for drip loss at 48 h in the natural vitamin E group (p<0.05). Broilers given diet supplemented with vitamin E showed decreased malondialdehyde (MDA) content in the breast (p<0.05). Additionally, natural rather than synthetic vitamin E reduced MDA accumulation in the thigh (p<0.05). Neither natural nor synthetic vitamin E supplementation altered muscular mRNA abundance of genes related to oxidative stress (p>0.05). It was concluded that vitamin E supplementation, especially the natural vitamin E, can enhance the retention of muscular α-tocopherol, improve meat quality and muscular antioxidant capacity of broilers.

Parthasarathi S, Muthukumar SP, Anandharamakrishnan C.

Food Funct. 2016 May 18;7(5):2294-302. doi: 10.1039/c5fo01517k.

Abstract

Vitamin E (α-tocopherol) is a nutraceutical compound, which has been shown to possess potent antioxidant and anticancer activity. However, its biological activity may be limited by its poor bioavailability. Colloidal delivery systems have shown wide applications in the food and pharmaceutical industries to deliver lipophilic bioactive compounds. In this study, we have developed conventional and nanoemulsions of vitamin E from food grade ingredients (sunflower oil, saponin, and water) and showed the nanoemulsion formulation increased the oral bioavailability when compared to the conventional emulsion. The mean droplet diameters in the nano and conventional emulsions were 0.277 and 1.285 μm, respectively. The stability of the emulsion formulation after thermal processing, long-term storage at different temperatures, mechanical stress and in plasma was determined. The results showed that the saponin coated nanoemulsion was stable to droplet coalescence during thermal processing (30-90 °C), long-term storage and mechanical stress when compared to the conventional emulsion. The biological fate of the emulsion formulations were studied using male Wistar rats as an animal model. The emulsion droplet stability during passage through the gastrointestinal tract was evaluated by their introduction into rat stomachs. Microscopy was used to investigate the structural changes that occurred during digestion. Both the conventional emulsion and nanoemulsion formulations showed strong evidence of droplet flocculation and coalescence during in vivo digestion. The in vivo oral bioavailability study revealed that vitamin E in a nanoemulsion form showed a 3-fold increase in the AUC when compared to the conventional emulsion. The information reported in this study will facilitate the design of colloidal delivery systems using nanoemulsion formulations.

Chen JX, Liu A, Lee MJ, Wang H, Yu S, Chi E, Reuhl K, Suh N, Yang CS.

Mol Carcinog. 2016 May 13. doi: 10.1002/mc.22481. [Epub ahead of print]

Abstract

Tocopherols, the major forms of vitamin E, are a family of fat-soluble compounds that exist in alpha (α-T), beta (β-T), gamma (γ-T), and delta (δ-T) variants. A cancer preventive effect of vitamin E is suggested by epidemiological studies. However, past animal studies and human intervention trials with α-T, the most active vitamin E form, have yielded disappointing results. A possible explanation is that the cancer preventive activity of α-T is weak compared to other tocopherol forms. In the present study, we investigated the effects of δ-T, γ-T, and α-T (0.2% in diet) in a novel colon cancer model induced by the meat-derived dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and promoted by dextran sodium sulfate (DSS)-induced colitis in CYP1A-humanized (hCYP1A) mice. PhIP/DSS treatments induced multiple polypoid tumors, mainly tubular adenocarcinomas, in the middle to distal colon of the hCYP1A mice after 10 wk. Dietary supplementation with δ-T and γ-T significantly reduced colon tumor formation and suppressed markers of oxidative and nitrosative stress (i.e., 8-oxo-dG and nitrotyrosine) as well as pro-inflammatory mediators (i.e., NF-κB p65 and p-STAT3) in tumors and adjacent tissues. By administering δ-T at different time periods, we obtained results suggesting that the inhibitory effect of δ-T against colon carcinogenesis is mainly due to protection against early cellular and DNA damages caused by PhIP. α-T was found to be ineffective in inhibiting colon tumors and less effective in attenuating the molecular changes. Altogether, we demonstrated strong cancer preventive effects of δ-T and γ-T in a physiologically relevant model of human colon cancer.

Miyazaki H, Takitani K, Koh M, Inoue A, Tamai H.

J Clin Biochem Nutr. 2016 May;58(3):223-31. doi: 10.3164/jcbn.15-133.

Abstract

In humans, dehydroepiandrosterone and its sulfate ester metabolite DHEA-S are secreted predominantly from the adrenal cortex, and dehydroepiandrosterone is converted to steroid hormones, including androgens and estrogens, and neurosteroid. Dehydroepiandrosterone exerts protective effects against several pathological conditions. Although there are reports on the association between dehydroepiandrosterone and vitamins, the exact relationship between dehydroepiandrosterone and vitamin Eremains to be determined. Therefore, we attempted to elucidate the effect of dehydroepiandrosterone on vitamin E status and the expression of various vitamin E-related proteins, including binding proteins, transporters, and cytochrome P450, in vitamin E-deficient rats. Plasma α-tocopherol levels in vitamin E-deficient rats increased in response to dehydroepiandrosterone administration. The expression of hepatic α-tocopherol transfer protein was repressed in vitamin E-deficient rats compared to that in control rats; however, dehydroepiandrosterone administration significantly upregulated this expression. Hepatic expression of CYP4F2, an α-tocopherolmetabolizing enzyme, in vitamin E-deficient rats was decreased by dehydroepiandrosterone administration, whereas hepatic expression of ATP-binding cassette transporter A1, an α-tocopherol transporter, was not altered following dehydroepiandrosterone administration. Dehydroepiandrosterone repressed lipid peroxidation in the liver of vitamin E-deficient rats. Therefore, adequate dehydroepiandrosterone supplementation may improve lipid peroxidation under several pathological conditions, and dehydroepiandrosterone may modulate α-tocopherol levels through altered expression of vitamin E-related proteins.