beta-Carotene and canthaxanthin alter the pro-oxidation and antioxidation balance in rats fed a high-cholesterol and high-fat diet

Associations of serum carotenoids with all-cause and cardiovascular mortality in adults with MAFLD

BACKGROUND AND AIMS

The associations between serum carotenoids and mortality are contradictory in various metabolic-associated diseases. This study aimed to examine the associations of five major serum carotenoids with mortality among adults with metabolic dysfunction-associated fatty liver disease (MAFLD).

METHODS AND RESULTS

This analysis included 3040 individuals with MAFLD from the Third National Health and Nutrition Examination Survey (NHANES III). All-cause and cardiovascular mortality were ascertained by linkage to the National Death Index through December 31, 2019. Cox proportional hazards regression models were employed to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), and restricted cubic spline (RCS) analyses were performed to assess the linearity of the associations. During a follow-up period of 826,547 person-years, 1325 all-cause and 429 cardiovascular deaths occurred. For all-cause mortality, compared with those in the lowest quartiles, the multivariable-adjusted HRs (95% CIs) in the highest quartiles were 0.63 (0.49-0.81) for α-carotene; 0.65 (0.52-0.80) for β-carotene; 0.64 (0.51-0.81) for β-cryptoxanthin; 0.73 (0.56-0.95) for lycopene; and 0.69 (0.52-0.91) for lutein/zeaxanthin. For cardiovascular mortality, the multivariable-adjusted HRs (95% CIs) in the highest quartiles were 0.51 (0.33-0.78) for α-carotene; 0.54 (0.35-0.82) for β-carotene; 0.52 (0.34-0.80) for β-cryptoxanthin; 0.63 (0.44-0.90) for lycopene; and 0.62 (0.39-0.99) for lutein/zeaxanthin. Besides, serum α-carotene, β-cryptoxanthin, and lycopene exhibited linear correlations with all-cause mortality in MAFLD adults, and four serum carotenoids, except β-carotene, were linearly correlated with cardiovascular mortality.

CONCLUSIONS

Lower serum α-carotene, β-carotene, β-cryptoxanthin, lycopene, and lutein/zeaxanthin concentrations were associated with higher risk of all-cause and cardiovascular mortality in US adults with MAFLD.

Function and Regulation of the Calcium-Activated Chloride Channel Anoctamin 1 (TMEM16A)

Various human tissues express the calcium-activated chloride channel Anoctamin 1 (ANO1), also known as TMEM16A. ANO1 allows the passive chloride flux that controls different physiological functions ranging from muscle contraction, fluid and hormone secretion, gastrointestinal motility, and electrical excitability. Overexpression of ANO1 is associated with pathological conditions such as hypertension and cancer. The molecular cloning of ANO1 has led to a surge in structural, functional, and physiological studies of the channel in several tissues. ANO1 is a homodimer channel harboring two pores - one in each monomer - that work independently. Each pore is activated by voltage-dependent binding of two intracellular calcium ions to a high-affinity-binding site. In addition, the binding of phosphatidylinositol 4,5-bisphosphate to sites scattered throughout the cytosolic side of the protein aids the calcium activation process. Furthermore, many pharmacological studies have established ANO1 as a target of promising compounds that could treat several illnesses. This chapter describes our current understanding of the physiological roles of ANO1 and its regulation under physiological conditions as well as new pharmacological compounds with potential therapeutic applications.

Dietary Canthaxanthin Supplementation Promotes the Laying Rate and Follicular Development of Huaixiang Hens

Canthaxanthin(CX) is a ketocarotenoid, which is widely used in poultry production as a lipophilic antioxidant. Huaixiang chickens are a local breed in China famous for their excellent meat quality; improving their laying rate via nutritional regulation has attracted extensive attention. The aim of this study was to evaluate the effects of dietary CX on the laying rate and follicular development in Huaixiang hens. A total of 180 Huaixiang hens were randomly divided into five groups with six replicates, and six chickens per replication. The control group (CON) were fed a basal diet, and the treatment group (NT) were fed a basal diet supplemented with 4, 6, 8 and 10 mg/kg CX. All chickens were 26 weeks old, living at an average environmental temperature of 25 ± 2 °C with a relative humidity of 65-75%. The results showed that supplementing the CX improved the laying rate and large white follicles (LWF) number (p < 0.05) and increased the concentration of reproductive hormones (LH, FSH, E2 and Prog) (p < 0.05), and the basal diet supplemented with 6 mg/kg CX worked best. Moreover, CX could increase the activities of antioxidant enzymes SOD and GSH-Px (p < 0.05) and reduce the content of the lipid peroxidation product MDA in Huaixiang chickens (p < 0.05); again, 6 mg/kg CX was best. In conclusion, dietary CX had positive effects on the laying rate, ovarian structure, reproductive hormone secretion, follicle development, and the antioxidant capacity of Huaixiang hens, and 6 mg/kg CX was recommended to be added to the diet of Huaixiang chickens.

Astaxanthin Attenuates D-Galactosamine-Induced Pancreatic Injury by Activating Antioxidant Enzymes and Inhibiting VEGF-C Gene Expression

&lt;b&gt;Background and Objective:&lt;/b&gt; Astaxanthin (3,3'-dihydroxy-β-β-carotene-4,4'-dione) is a carotenoid, commonly found in marine environments has been reported to possess versatile biological properties including anti-inflammatory and antioxidant. In this study, the pancreatic protective effect of astaxanthin was investigated in D-Galactosamine-induced pancreas injury in rats. &lt;b&gt;Materials and Methods:&lt;/b&gt; In this experimental study, MTT assay was used to determine cytotoxic effects of the Astaxanthin on pnc1 cells. A total of 30 adult albino rats divided into 5 groups, six rats in each. Group I was given an equal amount of distilled water, group II was received 400 mg kg&lt;sup&gt;1&lt;/sup&gt; b.wt. D-galactosamine on 15th day, groups III-V were treated with astaxanthin (50 and 100 mg kg&lt;sup&gt;1&lt;/sup&gt;) and/or silymarin (50 mg kg&lt;sup&gt;1&lt;/sup&gt;) for 14 days + 400 mg kg&lt;sup&gt;1&lt;/sup&gt; b.wt. D-galactosamine on the 15th day, respectively. &lt;b&gt;Results:&lt;/b&gt; IC&lt;sub&gt;50 &lt;/sub&gt;of Astaxanthin against the pnc1 cell line was 92.9 μg mL&lt;sup&gt;1&lt;/sup&gt;. The daily oral administration of astaxanthin (50 and 100 mg kg&lt;sup&gt;1&lt;/sup&gt;) as well as silymarin (50 mg kg&lt;sup&gt;1&lt;/sup&gt;) for 14 days to rats treated with D-galactosamine resulted in a significant improvement in plasma AST, ALT, ALP as well as pancreatic TNF-α, IL-1β, IL-10, NO and VEGF-C gene expression. On the other hand, inducible oral administration of astaxanthin increased the activity of pancreatic GSH, SOD, GPx, GR, CAT and the level of TBARs in D-galactosamine-treated pancreatic of rats. Furthermore, Astaxanthin almost normalized these effects in pancreatic tissue histoarchitecture and MRI examination. &lt;b&gt;Conclusion:&lt;/b&gt; The obtained results showed that Astaxanthin protected experimental animals against D-galactosamine-induced pancreatic injury through activation of antioxidant enzymes and IL-10 and inhibition of VEGF-C activation.

Carotenoids and fatty liver disease: Current knowledge and research gaps

Carotenoids form an important part of the human diet, consumption of which has been associated with many health benefits. With the growing global burden of liver disease, increasing attention has been paid on the possible beneficial role that carotenoids may play in the liver. This review focuses on carotenoid actions in non-alcoholic fatty liver disease (NAFLD), and alcoholic liver disease (ALD). Indeed, many human studies have suggested an association between decreased circulating levels of carotenoids and increased incidence of NAFLD and ALD. The literature describing supplementation of individual carotenoids in rodent models of NAFLD and ALD is reviewed, with particular attention paid to β-carotene and lycopene, but also including β-cryptoxanthin, lutein, zeaxanthin, and astaxanthin. The effect of beta-carotene oxygenase 1 and 2 knock-out mice on hepatic lipid metabolism is also discussed. In general, there is evidence to suggest that carotenoids have beneficial effects in animal models of both NAFLD and ALD. Mechanistically, these benefits may occur via three possible modes of action: 1) improved hepatic antioxidative status broadly attributed to carotenoids in general, 2) the generation of vitamin A from β-carotene and β-cryptoxanthin, leading to improved hepatic retinoid signaling, and 3) the generation of apocarotenoid metabolites from β-carotene and lycopene, that may regulate hepatic signaling pathways. Gaps in our knowledge regarding carotenoid mechanisms of action in the liver are highlighted throughout, and the review ends by emphasizing the importance of dose effects, mode of delivery, and mechanism of action as important areas for further study. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Effects of astaxanthin and canthaxanthin on oxidative stress biomarkers in rainbow trout

Farmed trout are commonly fed carotenoid-enriched diets during the finishing period to acquire typical red-to-pink flesh color in salmonid muscle. The aim of this study was to examine the effects of two xanthophylls, astaxanthin (Ax) or canthaxanthin (Cx), administered individually or in combination, on oxidative stress biomarkers in kidney and liver of rainbow trout. Specimens were fed Ax (75 mg/kg) or Cx (25 mg/kg) individually or in combination in the diets for 8 weeks. Changes in concentration of oxidative stress biomarkers, including total glutathione, superoxide dismutase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase, were recorded in Ax- and Cx-dosed trout. These two carotenoids, predominantly Cx, initiated enzymatic responses in rainbow trout. It is noteworthy that lipid peroxidation processes were not apparent in all Ax or Cx-dosed trout. Further, both combined xanthophylls did not exert significant synergistic effects in liver and kidney. Biomarker responses were generally altered in both tissues through the 4 and 8 weeks suggesting that different time-dependent mechanisms led to enhanced antioxidant defense in Ax and/or Cx-fed trout. Data demonstrated that these two xanthophylls did not exert detrimental effects on rainbow trout.

Varied effects of dietary carotenoid supplementation on oxidative damage in tissues of two waterfowl species

Carotenoids are regarded as a cornerstone of avian vitality and coloration. Currently, the antioxidant potential of dietary carotenoids is debated for birds. Although some studies support a protective role, others report either no effect or pro-oxidant effects. However, the majority of research on this topic has not analyzed the oxidative status of a series of tissues in animals nor considered a range of carotenoid dosages. We investigated the effects of three levels of carotenoid supplementation on plasma, liver, adipose, heart and breast muscle oxidative damage in two congeneric species of waterfowl that exhibit marked differences in carotenoid coloration. After a 6-week depletion period, captive adult northern pintail (Anas acuta) and mallard (A. platyrhynchos) ducks of both sexes were fed either a carotenoid-depleted diet (<3 μg/g xanthophylls, lutein and zeaxanthin), a carotenoid-supplemented diet (50 μg/g) within physiological range, or a carotenoid-rich diet (100 μg/g) within pharmacological range for 22 to 32 weeks. We hypothesized that these dosages of dietary carotenoids would differentially affect oxidative damage between species and sexes and among the tissues examined. We found that dietary xanthophyll supplementation had no significant effect on tissue pro-oxidation in males and females from both species. Moreover, sex or species differences in oxidative stress were only observed in two tissues (plasma and heart). Significant correlations in the levels of oxidative damage were not observed among the tissues examined. In conclusion, the current study does not support a consistent antioxidant role for dietary carotenoids in the tissues of these two waterfowl species. Instead, our results align with the notion that carotenoids play complex, tissue- and species-specific roles in oxidative status in birds.

Enzymatic antioxidant system in vascular inflammation and coronary artery disease

In biological systems there is a balance between the production and neutralization of reactive oxygen species (ROS). This balance is maintained by the presence of natural antioxidants and antioxidant enzymes such as superoxide dismutase (SOD), catalase and glutathione peroxidase. The enhancement of lipid peroxidation or the decrease of antioxidant protection present in metabolic diseases or bad lifestyle can induce endothelial dysfunction and atherosclerosis. Clinical studies have shown that oxidative stress can increase ROS reducing the formation of antioxidant defences, especially in subjects with coronary artery disease (CAD). Some observation indicated that in the early stages of the disease there is a homeostatic up-regulation of the antioxidant enzyme system in response to increased free radicals to prevent vascular damage. As soon as free radicals get to chronically elevated levels, this compensation ceases. Therefore, SOD and the other enzymes may represent a good therapeutic target against ROS, but they are not useful markers for the diagnosis of CAD. In conclusion antioxidant enzymes are reduced in presence of metabolic disease and CAD. However the existence of genes that promote their enzymatic activity could contribute to create new drugs for the treatment of damage caused by metabolic diseases or lifestyle that increases the plasma ROS levels.

In Vivo Effects of Free Form Astaxanthin Powder on Anti-Oxidation and Lipid Metabolism with High-Cholesterol Diet

Astaxanthin extracted from Pomacea canaliculata eggs was made into free-form astaxanthin powder (FFAP) and its effects on lipid metabolism, liver function, antioxidants activities and astaxanthin absorption rate were investigated. 45 hamsters were split into 5 groups and fed with normal diet, high-cholesterol control (0.2% cholesterol), 1.6FFAP (control+1.6% FFAP), 3.2FFAP (control+3.2% FFAP) and 8.0FFAP (control+8.0% FFAP), respectively, for 6 weeks. FFAP diets significantly decreased the liver total cholesterol, triglyceride levels and increased liver fatty acids (C20:5n3; C22:6n3) compositions. It decreased plasma alanine aminotransferase and aspartate aminotransferase. In terms of anti-oxidative activities, we found 8.0 FFAP diet significantly decreased plasma and liver malonaldehyde (4.96±1.96 μg TEP eq./mL and 1.56±0.38 μg TEP eq./g liver) and liver 8-isoprostane levels (41.48±13.69 μg 8-ISOP/g liver). On the other hand, it significantly increased liver catalase activity (149.10±10.76 μmol/min/g liver), Vitamin C (2082.97±142.23 μg/g liver), Vitamin E (411.32±81.67 μg/g liver) contents, and glutathione levels (2.13±0.42 mg GSH eq./g liver). Furthermore, 80% of astaxanthin absorption rates in all FFAP diet groups suggest FFAP is an effective form in astaxanthin absorption. Finally, astaxanthin was found to re-distribute to the liver and eyes in a dose dependent manner. Taken together, our results suggested that the appropriate addition of FFAP into high cholesterol diets increases liver anti-oxidative activity and reduces the concentration of lipid peroxidase and therefore, it may be beneficial as a material in developing healthy food.

Dietary β-carotene regulates interleukin-1β-induced expression of apolipoprotein E in astrocytes isolated from stroke-prone spontaneously hypertensive rats

Stroke-prone spontaneously hypertensive rats (SHRSP) have an abnormality in cholesterol synthesis, but the pathological relevance of this to stroke and related neuronal disorders is not yet clear. The induction of astrocyte-derived cholesterol transportation to neurons by apolipoprotein E (apoE) promotes neuronal repair after brain injuries such as stroke. Such repair is reduced by interleukin-1 beta (IL-1β) and stroke conditions. Furthermore, fibroblast growth factor 1 (FGF1) regulates the production of apoE-cholesterol-rich high density lipoproteins (HDL) and induces gliosis of astrocytes. On the other hand, high levels of plasma carotenoids reduce the risk of ischemic stroke. Thus, we investigated the expression of apoE in primary astrocytes that had been treated with IL-1β or β-carotene. In addition, we compared the expression levels of Apoe genes in astrocytes from SHRSP/Izm and normal control rats, Wistar-Kyoto rats (WKY/Izm) following hypoxia/reoxygenation (H/R). The expression levels of genes and proteins were investigated by RT-PCR, Western blotting (WB), and immunofluorescence analysis. IL-1β decreased the expression levels of the Apoe gene. Conversely, β-carotene significantly enhanced the expression levels of genes related to cholesterol regulation, including Abca1, Abcg1, Hmgcr as well as Apoe. During H/R, the gene expression levels of Apoe were decreased in the SHRSP/Izm rats in comparison with the WKY/Izm rats. These results suggest that IL-1β decreases Apoe expression levels, whereas β-carotene strongly elevates Apoe levels and inhibits FGF1-mediated gliosis of astrocytes. Furthermore, under hypoxic stress, astrocytes isolated from SHRSP/Izm rats displayed altered regulation of Apoe compared with those from WKY/Izm rats.

Developing an emulsion model system containing canthaxanthin biosynthesized by Dietzia natronolimnaea HS-1

An acceptable strategy to incorporate canthaxanthin (CX) as a natural colorant into products is by means of oil-in-water emulsions. The used CX in this study was produced by bacterium Dietzia natronolimnaea HS-1 using a batch bioreactor system. A central composite rotatable design-response surface methodology (CCRD-RSM) consisting of three-factored factorial design with five levels was applied for analysis of the results to obtain the optimal formulation of emulsions. Three independent variables including fenugreek gum (FG, 0.2-0.5%, w/w), coconut oil (CO, 6-10%, w/w), and CO/CX ratio (10:1-50:1) were transformed to coded values and second-order polynomial models was developed to predict the responses (p<0.0001). The studied independent variables were the stability, viscosity and droplet size properties such as volume-weighted mean diameter (D₄₃), specific surface area (S(v)) and polydispersity index (PDI) of emulsions. The 3-D response surface plot derived from the mathematical models was used to determine the optimal conditions. Main emulsion components under the optimum conditions ascertained presently by RSM: 50:1 CO/CX ratio, 0.49% (w/w) FG content and 6.28% (w/w) CO concentration. At this optimum point, stability, viscosity, D₄₃, S(v) and PDI were 90.6%, 0.0118 Pas, 0.595 μm, 12.03 m²/ml and 1.380, respectively.

Target molecules of food phytochemicals: food science bound for the next dimension

Phytochemicals are generally defined as secondary metabolites in plants that play crucial roles in their adaptation to a variety of environmental stressors. There is a great body of compelling evidence showing that these metabolites have pronounced potentials for regulating and modulating human health and disease onset, as shown by both experimental and epidemiological approaches. Concurrently, enormous efforts have been made to elucidate the mechanism of actions underlying their biological and physiological functions. For example, the pioneering work of Tachibana et al. uncovered the receptor for (-)-epigallocatechin-3-gallate (EGCg) as the 67 kDa laminin receptor, which was shown to partially mediate the functions of EGCg, such as anti-inflammatory, anti-allergic, and anti-proliferative activities. Thereafter, several protein kinases were identified as binding proteins of flavonoids, including myricetin, quercetin, and kaempferol. Isothiocyanates, sulfur-containing phytochemicals present in cruciferous plants, are well known to target Keap1 for activating the transcription factor Nrf2 for inducing self-defensive and anti-oxidative gene expression. In addition, we recently identified CD36 as a cell surface receptor for ursolic acid, a triterpenoid ubiquitously occurring in plants. Importantly, the above mentioned target proteins are indispensable for phytochemicals to exhibit, at least in part, their bioactivities. Nevertheless, it is reasonable to assume that some of the activities and potential toxicities of metabolites are exerted via their interactions with unidentified, off-target proteins. This notion may be supported by the fact that even rationally designed drugs occasionally display off-target effects and induce unexpected outcomes, including toxicity. Here we update the current status and future directions of research related to target molecules of food phytochemicals.

Fructo-oligosaccharide systemically diminishedd-galactose-induced oxidative molecule damages in BALB/cJ mice

Subcutaneous (s.c.)d-galactose (DG) treatment has been shown to facilitate the development of biomarkers for Alzheimer's disease in C57BL/6J mice. The aim of the present study was to determine whether this treatment in young BALB/cJ mice, another mouse strain, enhanced oxidative stress to similar extents shown in older mice, and to further determine the effects of fructo-oligosaccharide (FO), a prebiotic fibre and vitamin E (antioxidant control) on the DG-induced oxidative damage of lipids, proteins and mitochondrial DNA, and erythrocyte antioxidant enzyme activities. Mice (12 weeks of age,n40) were divided into four groups: vehicle (s.c. saline)+control (modified rodent chow); DG (s.c. 1·2 g/kg body weight)+control; DG+FO (5 %, w/w); DG+vitamin E (α-tocopherol, 0·2 %). Then, the animals were killed after 52 d of treatment. Another natural ageing (NA) group without any injection was killed at 47 weeks of age, which served as an aged control. The results indicated that the DG treatment enhanced malonaldehyde dimethyl acetal (MDA) levels in the plasma, liver and cerebral cortex, and protein carbonyl levels in the liver and hippocampus to similar levels shown in the NA group. FO, similar to α-tocopherol, systemically normalised DG-induced elevations in the levels of MDA in the plasma, liver and cerebral cortex, protein carbonyls in the liver and hippocampus, hepatic mitochondrial 8-oxo-deoxyguanosine and erythrocyte superoxide dismutase activity. In conclusion, the s.c. DG treatment in younger BALB/cJ mice resembled the oxidative status in older mice. FO supplementation systemically prevented DG-induced oxidative stress, probably through its fermentation products and prebiotic effect.

Food grade lingonberry extract: polyphenolic composition and in vivo protective effect against oxidative stress

Fractionation of the polyphenols constituting a food grade lingonberry extract (Vaccinium vitis-idaea) highlighted a composition more complex than described until now in the berry. Procyanidins B1, B2, and A2 were identified by UPLC/ESI-MS(2) along with the presence of other flavanol oligomers. Processing induced the release of large amounts of aglycones for ferulic acid, p-coumaric acid, and quercetin. The described anthocyanic composition of lingonberry was completed with hexoside derivatives of peonidin, petunidin, malvidin, and delphinidin. Besides confirmation of in vitro antioxidant activity, in vivo study was performed on rats fed a diet inducing oxidative stress. Supplementation with lingonberry extract significantly decreased the total oxidant status and favorably affected antioxidant defense enzymes in red blood cells and liver. A drop in the serum reduced glutathione level was also prevented, and uric acid was maintained at low level, confirming the antioxidant activity of the extract (5% proanthocyanidins) from a dosage of 23 mg/kg of body weight.

Antioxidative and hepatoprotective effects of fructo-oligosaccharide ind-galactose-treated Balb/cJ mice

Chronic subcutaneous (s.c.) administration ofd-galactose (DG) to BL/6J mice has been shown to induce oxidative stress and is considered a model to mimic accelerated ageing. Fructo-oligosaccharide (FO) is a well-defined prebiotic and its fermentation by lactic acid bacteria has been shown to exert antioxidative capacity. The present study was aimed to determine whether FO attenuated DG-induced oxidative stress and hepatopathy in Balb/cJ mice. Mice (12 weeks of age,n40) were divided into control (s.c. saline), DG (s.c. 1·2 g/kg body weight), DG+FO (5 %, w/w) and DG+vitamin E (0·2 %, w/w) groups and were killed after 52 d of treatment. Results indicated that DG significantly decreased the hepatic superoxide dismutase and glutathione peroxidase activities. These alterations were ameliorated both by FO and vitamin E. DG increased the hepatic TAG content approximately by 7·2 % compared with the vehicle control, which was in agreement with the histological alteration. FO, similar to vitamin E, almost normalised the hepatic TAG content and ameliorated the histological characteristics of fatty liver. Similarly, the increased plasma alanine aminotransferase activity induced by DG was normalised by FO and vitamin E, respectively. Faecal bifidobacteria counts were greater in the DG+FO and DG+vitamin E groups compared with the DG group, respectively. In conclusion, the present study indicated that FO diminished the altered hepatic antioxidative enzyme activities and morphology caused by chronic DG administration in Balb/cJ mice, partially associated with its prebiotic role in the colon.

Artichoke leaf extract reduces oxidative stress and lipoprotein dyshomeostasis in rats fed on high cholesterol diet

Hypercholesterolemia and lipid peroxidation play complementary role in atherosclerosis. Artichoke leaf extract (ALE) is rich in natural antioxidants and has a cholesterol-reducing effect. However, there is no study investigating the effect of ALE on lipid levels and lipid peroxidation in experimental hypercholesterolemic conditions. Rats were fed on 4% (w/w) cholesterol and 1% (w/w) cholic acid supplemented diet for 1 month. ALE (1.5 g/kg/day) was given by gavage during the last 2 weeks. Serum lipid composition, malondialdehyde (MDA) and diene conjugate (DC) levels and plasma antioxidant activity (AOA) were measured. In addition, endogenous DC and copper-induced MDA levels were determined in apo B-containing lipoproteins (LDL+VLDL fraction). Serum cholesterol and triglyceride levels and the ratio of cholesterol to HDL-cholesterol decreased due to ALE treatment in rats fed on HC diet. Significant decreases in serum MDA and DC levels and increases in plasma AOA were detected in serum in ALE-treated hypercholesterolemic rats. Endogenous DC and copper-induced MDA levels were also lower in LDL+VLDL fraction due to ALE-treatment in hypercholesterolemic rats. Our results indicate that ALE may be useful for the prevention of hypercholesterolemia-induced pro-oxidant state in LDL+VLDL fraction and the reduction of increased serum cholesterol and triglyceride levels.

Effect of chitosan on hepatic drug-metabolizing enzymes and oxidative stress in rats fed low- and high-fat diets

Chitosan is sold worldwide as a lipid-lowering functional food and may be taken with certain medications. To investigate the effect of chitosan on drug-metabolizing enzymes and oxidative stress in the liver, male Wistar rats were fed a low- or high-fat diet with cellulose or chitosan for 4 weeks. A significant decrease in cytochrome P450 (CYP) 3A-catalyzed testosterone 6beta-hydroxylation in liver microsomes was observed in rats fed the chitosan with low- and high-fat diets. The expression of CYP 3A1 and 3A2, however, was suppressed by chitosan in rats fed the low-fat diet only. Furthermore, rats fed the low-fat diet with chitosan had lower hepatic glutathione S-transferase (GST) activity and superoxide dismutase activity and higher total tissue and microsomal lipid hydroperoxides. Hepatic alpha-tocopherol was lower in rats fed the chitosan-containing diet. The results suggest that chitosan is likely to modulate CYP 3A activity and protein expression and GST activity partially in a dietary fat-dependent manner. This change may cause a decrease in the metabolism of drugs catalyzed by these enzymes in liver tissues. Moreover, decrease of alpha-tocopherol level and SOD activity by chitosan partly accounts for the increase of hepatic lipid peroxidation.

Beta-carotene affects oxidative stress-related DNA damage in lung epithelial cells and in ferret lung

Beta-carotene (BC) was found to enhance lung cancer risk in smokers. This adverse effect was unexpected because BC was thought to act as an anti-oxidant against cigarette smoke-derived radicals. These radicals can directly or indirectly damage DNA, leading to the formation of pro-mutagenic DNA lesions such as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) and 3-(2-deoxy-beta-D-erythro-pentafuranosyl)pyrimido[1,2-alpha]purin-10(3H)-one deoxyguanosine (M(1)dG). Later, it was suggested that high concentrations of BC could also result in pro-oxidant effects. Therefore, we investigated whether high but physiologically feasible concentrations of BC were able to alter (i) the formation of radicals in vitro assessed by electron spin resonance spectroscopy, (ii) the levels of 8-oxo-dG and M(1)dG in vitro in lung epithelial cells after incubation with hydrogen peroxide (H(2)O(2)) and the smoke-derived carcinogen benzo[a]pyrene (B[a]P) and (iii) the levels of 8-oxo-dG and M(1)dG in vivo in ferrets' lung after chronic exposure to B[a]P. BC increased in vitro hydroxyl radical formation in the Fenton reaction but inhibited the formation of carbon-centered radicals. Similarly, BC was able to enhance 8-oxo-dG in vitro in lung epithelial cells. On the other hand, BC significantly inhibited M(1)dG formation in lung epithelial cells, especially after induction of M(1)dG by H(2)O(2) or B[a]P. Finally, BC supplementation of ferrets also resulted in a significant decrease in M(1)dG, but in contrast to the in vitro experiments, no effect was observed on 8-oxo-dG levels, probably because of increased base excision repair capacities as assessed by a modified comet assay. These data indicate that the fate of BC being a pro- or anti-oxidant strongly depends on the type of radical involved.

Influence of dietary lipids on the erythrocyte antioxidant status of hypercholesterolaemic children

The aim of this work was to examine the effect of dietary lipid intakes on the biomarkers of red cell antioxidant status in hypercholesterolaemic children. The study population included 34 children (18 boys and 16 girls) with cholesterol levels > or =5.2 mmol/l and 16 normolipidaemic children (9 boys and 7 girls) between 6 and 12 years of age. The status of the erythrocyte antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and reduced glutathione (GSH) were estimated spectrophotometrically. Dietary intake was assessed by 24-h recall and seven-day records. The hypercholesterolaemic children showed a decreased activity of antioxidant enzymes in relation to the control group. There was a negative correlation between energy intake and the activity of antioxidant enzymes (SOD and CAT) and GSH levels. Cholesterol intake was inversely correlated with CAT and GPx activity and GSH levels. The intake of polyunsaturated fat was positively correlated with the GPx activity. A decrease in the fat content of the diet for 6 months was proposed and 15 children followed the diet strictly. The activities of antioxidant enzymes in these children were significantly higher after the low-fat diet; the greatest increment was noted in the activity of GPx (91% with respect to the initial values), SOD was increased by 44% and CAT by 70%. We conclude that the intake of dietary lipids can modulate the antioxidant defence system, and an excess of energy and cholesterol has a negative influence on the antioxidant enzymes.

Dietary antioxidants and glucose metabolism

PURPOSE OF REVIEW

Oxidative stress seems to play a pathogenic role in the vicious circle linking obesity, insulin resistance and type 2 diabetes. Hypothetically, dietary antioxidants should decrease oxidative stress and therefore improve glucose metabolism. However, many interventional trials evaluating the effect of antioxidant supplementation on insulin resistance, plasma glucose levels and risk of type 2 diabetes gave inconsistent results.

RECENT FINDINGS

Many studies have recently demonstrated a positive effect of vitamin supplementation and of food enriched in antioxidant (seafood, whole nut, etc.) on markers of oxidative stress, insulin resistance, fasting plasma glucose and incidence of diabetes. The present paper critically reviews the consolidated notions on dietary antioxidant in view of the recent evidences.

SUMMARY

Although a definitive estimation of the impact of dietary antioxidants on glucose metabolism is still lacking, food with high antioxidant concentrations seems to have a protective effect, improving oxidative stress-mediated detrimental effects on the vicious circle among obesity, insulin resistance and redox imbalance.