Different tocopherol isoforms vary in capacity to scavenge free radicals, prevent inflammatory response, and induce apoptosis in both adult- and fetal-derived intestinal epithelial cells

Butyrate and tributyrin reduce LPS-induced inflammatory cytokine production from human visceral fat

INTRODUCTION

The current obesity crisis has resulted in many people with excess adipose tissue suffering from chronic inflammation. This inflammation is largely due to the release of cytokines and chemokines from visceral fat. The aim of this study was to identify potential anti-inflammatory agents that might alleviate obesity-induced chronic inflammation.

METHODS

To identify agents that might alleviate this obesity-induced chronic inflammation we have developed a simple protocol for incubating intact pieces of human visceral adipose tissue in 35 mm tissue culture plates, in the presence of low-dose lipopolysaccharide (LPS) and co-incubating these samples with potential anti-inflammatory agents. RNA-Seq analysis was performed to identify enriched gene expression signatures among the most significantly differentially expressed genes.

RESULTS

From this screen, we have identified the short-chain fatty acid (SCFA) sodium butyrate and its triacylglyceride form, tributyrin, as effective agents, significantly reducing the production of LPS-induced inflammatory cytokines and chemokines from all adipose tissue samples tested. As well, these agents appear to be non-toxic at the concentrations tested. RNA-Seq analysis has revealed that IL36γ is one of the most upregulated genes in response to LPS and one of the most downregulated when sodium butyrate is added to human fat samples stimulated with LPS. IL-36γ ELISAs confirmed this holds true at the protein level as well.

CONCLUSIONS

These studies suggest that the short-chain fatty acid, sodium butyrate, and its triacylglyceride form, tributyrin, might alleviate the chronic inflammation that is associated with many individuals with obesity.

Vitamin E research: Past, now and future

The early history of vitamin E from its discovery by Herbert M. Evans and Katharine J. S. Bishop in 1922 up to its chemical synthesis by Paul Karrer and coworkers in 1938 and the development of the concept that vitamin E acts as an antioxidant in vivo are recalled. Some more recent results shedding doubt on this hypothesis are reviewed. They comprise influence of vitamin E on enzyme activities, signaling cascades, gene expression and bio-membrane structure. The overall conclusion is that our knowledge of the vitamin's mechanism of action still remains fragmentary. The metabolism of tocopherols and tocotrienols is presented and discussed in respect to bioactivity of the metabolites, interference with drug metabolism and the future design of clinical trials. Some strategies are recommended how to reach the final goal: the identification of the primary vitamin E target(s) and the analysis of the downstream events up to the physiological phenomena.

Vitamin E beyond Its Antioxidant Label

Vitamin E, comprising tocopherols and tocotrienols, is mainly known as an antioxidant. The aim of this review is to summarize the molecular mechanisms and signaling pathways linked to inflammation and malignancy modulated by its vitamers. Preclinical reports highlighted a myriad of cellular effects like modulating the synthesis of pro-inflammatory molecules and oxidative stress response, inhibiting the NF-κB pathway, regulating cell cycle, and apoptosis. Furthermore, animal-based models have shown that these molecules affect the activity of various enzymes and signaling pathways, such as MAPK, PI3K/Akt/mTOR, JAK/STAT, and NF-κB, acting as the underlying mechanisms of their reported anti-inflammatory, neuroprotective, and anti-cancer effects. In clinical settings, not all of these were proven, with reports varying considerably. Nonetheless, vitamin E was shown to improve redox and inflammatory status in healthy, diabetic, and metabolic syndrome subjects. The anti-cancer effects were inconsistent, with both pro- and anti-malignant being reported. Regarding its neuroprotective properties, several studies have shown protective effects suggesting vitamin E as a potential prevention and therapeutic (as adjuvant) tool. However, source and dosage greatly influence the observed effects, with bioavailability seemingly a key factor in obtaining the preferred outcome. We conclude that this group of molecules presents exciting potential for the prevention and treatment of diseases with an inflammatory, redox, or malignant component.

Antioxidants help favorably regulate the kinetics of lipid peroxidation, polyunsaturated fatty acids degradation and acidic cannabinoids decarboxylation in hempseed oil

The seed of the hemp plant (Cannabis sativa L.) has been revered as a nutritional resource in Old World Cultures. This has been confirmed by contemporary science wherein hempseed oil (HSO) was found to exhibit a desirable ratio of omega-6 and omega-3 polyunsaturated fatty acids (PUFAs) considered optimal for human nutrition. HSO also contains gamma-linoleic acid (GLA) and non-psychoactive cannabinoids, which further contribute to its’ potential bioactive properties. Herein, we present the kinetics of the thermal stability of these nutraceutical compounds in HSO, in the presence of various antioxidants (e.g. butylated hydroxytoluene, alpha-tocopherol, and ascorbyl palmitate). We focussed on oxidative changes in fatty acid profile and acidic cannabinoid stability when HSO was heated at different temperatures (25 °C to 85 °C) for upto 24 h. The fatty acid composition was evaluated using both GC/MS and ¹H-NMR, and the cannabinoids profile of HSO was obtained using both HPLC-UV and HPLC/MS methods. The predicted half-life (DT50) for omega-6 and omega-3 PUFAs in HSO at 25 °C was about 3 and 5 days, respectively; while that at 85 °C was about 7 and 5 hours respectively, with respective activation energies (E_a) being 54.78 ± 2.36 and 45.02 ± 2.87 kJ/mol. Analysis of the conjugated diene hydroperoxides (CDH) and p-Anisidine value (p-AV) revealed that the addition of antioxidants significantly (p < 0.05) limited lipid peroxidation of HSO in samples incubated at 25–85 °C for 24 h. Antioxidants reduced the degradation constant (k) of PUFAs in HSO by upto 79%. This corresponded to a significant (p < 0.05) increase in color stability and pigment retention (chlorophyll a, chlorophyll b and carotenoids) of heated HSO. Regarding the decarboxylation kinetics of cannabidiolic acid (CBDA) in HSO, at both 70 °C and 85 °C, CBDA decarboxylation led to predominantly cannabidiol (CBD) production. The half-life of CBDA decarboxylation (originally 4 days) could be increased to about 17 days using tocopherol as an antioxidant. We propose that determining acidic cannabinoids decarboxylation kinetics is a useful marker to measure the shelf-life of HSO. The results from the study will be useful for researchers looking into the thermal treatment of hempseed oil as a functional food product, and those interested in the decarboxylation kinetics of the acidic cannabinoids.

Potential Protective Effect of Dietary Intake of Non-α-Tocopherols on Cellular Aging Markers Mediated by Tumor Necrosis Factor-α in Prediabetes: A Cross-Sectional Study of Chinese Adults

It remains unknown how different glucose tolerance status affects the relationships between dietary intake of different tocopherol isoforms (α-, β-, γ-, and δ-tocopherol) and cellular aging, oxidative stress, and inflammatory markers. The authors conducted a cross-sectional study among 582 Chinese adults with different glucose tolerance status to explore the association between dietary intake of different tocopherol isoforms and cellular aging, oxidative stress, and inflammatory markers. The inverse correlations between non-α-tocopherols and tumor necrosis factor-alpha (TNF-α) varied substantially across different glucose tolerance status, with the strongest observed in prediabetes (r = −0.33 for β-/γ-tocopherol, r = −0.37 for δ-tocopherol, p < 0.01), followed by normal glucose tolerance (NGT). While such correlations were abolished in established diabetes. Furthermore, within prediabetes, the strongest inverse correlations between non-α-tocopherols and TNF-α were observed in impaired fasting glucose (IFG) (r = −0.42 for β-/γ-tocopherol, r = −0.55 for δ-tocopherol, p < 0.01), while such correlations were significantly attenuated in individuals with impaired glucose tolerance (IGT) and IFG+IGT. And mediation model analysis displayed that TNF-α mediated the protective effect of non-α-tocopherols on leukocyte telomere length and mitochondrial DNA copy number, which was uniquely observed in prediabetes, while such mediation effect was statistically nonsignificant in NGT and established diabetes. In conclusion, our findings indicate that dietary intake of non-α-tocopherols might protect against cellular aging markers mediated by TNF-α in prediabetes. Individuals with prediabetes, especially for IFG, might benefit from increasing dietary intake of non-α-tocopherol in alleviating inflammation and cellular aging, which might provide a new dietary avenue for delaying diabetes onset.

Biological Redox Impact of Tocopherol Isomers Is Mediated by Fast Cytosolic Calcium Increases in Living Caco-2 Cells

Most of the biological impacts of Vitamin E, including the redox effects, have been raised from studies with α-tocopherol only, despite the fact that tocopherol-containing foods carry mixed tocopherol isomers. Here, we investigated the cellular mechanisms involved in the immediate antioxidant responses evoked by α-, γ- and δ-tocopherol in Caco-2 cells. In order to track the cytosolic redox impact, we performed imaging on cells expressing HyPer, a fluorescent redox biosensor, while cytosolic calcium fluctuations were monitored by means of Fura-2 dye and imaging. With this approach, we could observe fast cellular responses evoked by the addition of α-, γ- and δ-tocopherol at concentrations as low as 2.5 μM. Each isomer induced rapid and consistent increases in cytosolic calcium with fast kinetics, which were affected by chelation of extracellular Ca²⁺, suggesting that tocopherols promoted a calcium entry upon the contact with the plasma membrane. In terms of redox effects, δ-tocopherol was the only isomer that evoked a significant change in the HyPer signal at 5 μM. By mimicking Ca²⁺ entry with ionomycin and monensin, a decline in the HyPer signal was induced as well. Finally, by silencing calcium with 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA), an intracellular Ca²⁺ chelator, none of the isomers were able to induce redox changes. Altogether, our data indicate that an elevation in cytoplasmic Ca²⁺ is necessary for the development of a tocopherol-induced antioxidant impact on the cytoplasm of Caco-2 cells reported by HyPer biosensor.

Dietary antioxidants remodel DNA methylation patterns in chronic disease

Chronic diseases account for over 60% of all deaths worldwide according to the World Health Organization reports. Majority of cases are triggered by environmental exposures that lead to aberrant changes in the epigenome, specifically, the DNA methylation patterns. These changes result in altered expression of gene networks and activity of signalling pathways. Dietary antioxidants, including catechins, flavonoids, anthocyanins, stilbenes and carotenoids, demonstrate benefits in the prevention and/or support of therapy in chronic diseases. This review provides a comprehensive discussion of potential epigenetic mechanisms of antioxidant compounds in reversing altered patterns of DNA methylation in chronic disease. Antioxidants remodel the DNA methylation patterns through multiple mechanisms, including regulation of epigenetic enzymes and chromatin remodelling complexes. These effects can further contribute to antioxidant properties of the compounds. On the other hand, decrease in oxidative stress itself can impact DNA methylation delivering additional link between antioxidant mechanisms and epigenetic effects of the compounds. LINKED ARTICLES: This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc.

Vitamin E status and associations in maternal-infant Dyads in the Midwestern United States

BACKGROUND

Oxidative stress has been associated with adverse neonatal outcomes, and vitamin E has powerful anti-oxidant properties. Vitamin E occurs in several different isoforms which differ in their ability to modulate inflammation and oxidative stress. Therefore, the purpose of this study was to evaluate the status of α-, γ- and δ-tocopherol in maternal-infant pairs, and the impact on maternal-newborn outcomes.

METHODS

Vitamin E status was evaluated in 189 mother-infant pairs. Concentrations of α-, γ- and δ-tocopherol were measured using HPLC. Descriptive statistics were calculated and Spearman coefficients were used to assess correlations between maternal and cord measurements. Linear and logistic regression models were used to adjust for relevant confounders. A p < 0.05 was considered statistically significant.

RESULTS

Maternal and cord serum tocopherol concentrations were positively correlated for γ-tocopherol (r = 0.32, p ˂ 0.001) and δ-tocopherol (r = 0.46, p ˂ 0.001) but not for α-tocopherol. After adjustment for confounders, maternal concentrations of tocopherols were positively associated with Apgar scores (p = 0.02) and infant growth parameters at birth. Conversely, cord tocopherol levels were inversely associated with Apgar scores (p = 0.02) and infant growth. Cord concentrations of α-tocopherol were higher in infants born to mothers with a diagnosis of pre-eclampsia (p = 0.04).

CONCLUSION

Maternal-fetal transfer of γ- and δ-tocopherols is higher than α-tocopherol and may be mediated by either different or more efficient methods, conversely tissue uptake of α-tocopherol by the developing fetus may be higher. As serum levels of maternal tocopherols are positively associated with outcomes while higher cord levels show a negative impact, uptake and tissue deposition of vitamin E by the fetus may be crucial in growth and development. More research into the role of maternal diet, placental regulation, and fetal uptake of vitamin E tocopherols in relation to clinical outcomes is warranted.

Alpha-Tocopherol prevents esophageal squamous cell carcinoma by modulating PPARγ-Akt signaling pathway at the early stage of carcinogenesis

The poor prognosis of esophageal squamous cell carcinoma (ESCC) emphasizes the urgent need to better understand the carcinogenesis and develop prevention strategies. Previous studies have highlighted the potential of using Vitamin E (tocopherols) for cancer chemoprevention, but the preventive activity of α-Tocopherol against ESCC remains to be elucidated. Our data showed that early-stage supplementation with α-Tocopherol significantly prevented esophageal carcinogenesis induced by N-nitrosomethylbenzylamine (NMBA) in ESCC rat model. In the Het-1A cell model, α-Tocopherol markedly suppressed cell proliferation, promoted cell cycle G2-phase arrest and increased apoptosis. Gene microarray and proteins array analysis indicated that Akt signaling was a potential target for α-Tocopherol. We further demonstrated that α-Tocopherol increased the expression of PPARγ and its downstream tumor suppressor PTEN. Knockdown of PPARγ activated Akt signaling transduction, whereas this process was attenuated by the presence of α-Tocopherol and PPARγ agonist Rosiglitazone. In contrast, the effect of α-Tocopherol on Akt inhibition was not observed in established tumors, neither in cancerous cell lines which constitutively expressed higher levels of PPARγ. These results were closely correlated with the ineffectiveness of α-Tocopherol in the late stage of ESCC carcinogenesis. Taken together, our study suggested that α-Tocopherol may serve as a PPARγ agonist for the chemoprevention of esophageal cancer.

Tocopherol isoforms (α-, γ-, and δ-) show distinct capacities to control Nrf-2 and NfκB signaling pathways that modulate inflammatory response in Caco-2 intestinal cells

We recently showed that α-, γ-, and δ-tocopherols (Toc) were isoform dependent in modulating an inflammatory response in differentiated human Caco-2 intestinal cells. Here, we aim to investigate the relative capacity of Toc isoforms to modify the stress-activated NfκB and Nrf-2 signaling pathways that regulate the expression of pro-inflammatory cytokines and antioxidant enzymes, respectively, in this well-established in vitro model of the small intestine The modulation of IFNγ/phorbol myristate acetate (PMA)-induced inflammatory responses, determined by the expression of IL8 mRNA and protein, corresponded to the extent by which different Toc isoforms altered intracellular oxidative status in Caco-2 cells. α Toc was more effective at suppressing IFNγ/PMA-induced NfκB activation than γ-Toc, while δ-Toc was ineffective. On the other hand, only δ-Toc and to a lesser extent γ-Toc promoted IFNγ/PMA-induced Nrf-2 activation. Up-regulation of Nrf-2 by δ-Toc coincided with a decrease in GSH/GSSG ratio, thus pointing to pro-oxidant activity of δ-Toc isoform in IFNγ/PMA-stimulated Caco-2 cells. The induction of oxidative stress in IFNγ/PMA-treated cells by δ-Toc was lowered (P < 0.05) in the presence of ascorbic acid. Ascorbic acid also enabled a greater suppression of IL8 secretion than when cells were treated with δ-Toc isoform alone. Our findings show that δ-Toc uniquely promoted oxidative stress which translated to Toc isoform-specific modulation of the stress-activated Nrf-2 and NfκB signaling pathway and an influence on IL8 expression.

Modulation of NF-κB and Nrf2 control of inflammatory responses in FHs 74 Int cell line is tocopherol isoform-specific

The present study investigates the relative ability of α-, γ-, and δ-tocopherol (Toc) to modulate cell signaling events that are associated with inflammatory responses in fetal-derived intestinal (FHs 74 Int) cells. Secretion of the proinflammatory cytokine IL-8 in FHs 74 Int cells was stimulated in the following order: α-Toc<γ-Toc<δ-Toc. A similar proinflammatory response was observed when inflammation was induced in FHs 74 Int cells. Modulation of IL-8 expression by Toc corresponded to an isoform-specific modulation of NF-κB and nuclear factor-erythroid 2-related factor 2 (Nrf2) cell signaling pathways involved in expression of proinflammatory cytokines and antioxidant enzymes, respectively. δ-Toc and, to a lesser extent, γ-Toc activated NF-κB and Nrf2 signaling, as indicated by the greater nuclear translocation of transcription factors. Activation of NF-κB signaling by γ- and δ-Toc was accompanied by upregulation of NF-κB target genes, such as IL-8 and prostaglandin-endoperoxide synthase 2, with and without a prior IFNγ-PMA challenge. Nevertheless, γ- and δ-Toc, particularly δ-Toc, concurrently downregulated glutamate-cysteine ligase, a Nrf2 target gene that encodes for glutathione biosynthesis. This observation was substantiated by confirmation that γ- and δ-Toc were effective at decreasing glutamate-cysteine ligase protein expression and cellular glutathione content. Downregulation of glutathione content in fetal intestinal cells corresponded to induction of apoptosis-mediated cytotoxicity. In conclusion, γ- and δ-Toc are biologically active isoforms of vitamin E and show superior bioactivity to α-Toc in modulating cell signaling events that contribute to a proinflammatory response in fetal-derived intestinal cells.