Relation between insulin resistance and plasma concentrations of lipid hydroperoxides, carotenoids, and tocopherols. (33/470)

BACKGROUND: It is not known whether total circulating lipid hydroperoxides are increased in insulin-resistant individuals and whether this correlates with depletion of liposoluble antioxidant vitamins that are consumed during lipid peroxidation. OBJECTIVE: The goal of this study was to define the relation between resistance to insulin-mediated glucose disposal and plasma concentrations of lipid hydroperoxides and liposoluble antioxidant vitamins in healthy volunteers. DESIGN: Insulin-mediated glucose disposal was determined in 36 healthy, nondiabetic volunteers by measuring their steady-state plasma insulin (SSPI) and glucose (SSPG) concentrations in response to a 180-min constant infusion of octreotide, insulin, and glucose. In addition, fasting plasma concentrations of lipid hydroperoxides and liposoluble antioxidant vitamins were determined by using the FOX 2 assay and liquid chromatography. RESULTS: Statistically significant direct relations were observed between SSPG and mean arterial blood pressure (r = 0.44, P: = 0.008) and plasma lipid hydroperoxide concentrations (r = 0.42, P: = 0.01), whereas significant inverse correlations were found between SSPG and alpha-carotene (r = -0.58, P: = 0.0002), beta-carotene (r = -0.49, P: = 0.004), lutein (r = -0.35, P: = 0.04), alpha-tocopherol (r = -0. 36, P: = 0.04), and delta-tocopherol (r = -0.45, P: = 0.007). CONCLUSIONS: Variations in insulin-mediated glucose disposal in healthy individuals are significantly related to plasma concentrations of lipid hydroperoxides and liposoluble antioxidant vitamins. These findings suggest that total plasma lipid peroxidation is increased in insulin-resistant individuals at an early, preclinical stage, ie, well before the development of glucose intolerance and type 2 diabetes.  (+info)

Photodamage of the photosynthetic apparatus and its dependence on the leaf developmental stage in the npq1 Arabidopsis mutant deficient in the xanthophyll cycle enzyme violaxanthin de-epoxidase. (34/470)

The npq1 Arabidopsis mutant is deficient in the violaxanthin de-epoxidase enzyme that converts violaxanthin to zeaxanthin in excess light (xanthophyll cycle). We have compared the behavior of mature leaves (ML) and developing leaves of the mutant and the wild type in various light environments. Thermoluminescence measurements indicated that high photon flux densities (>500 micromol m(-2) s(-1)) promoted oxidative stress in the chloroplasts of npq1 ML, which was associated with a loss of chlorophyll and an inhibition of the photochemical activity. Illuminating leaf discs in the presence of eosin, a generator of singlet oxygen, brought about pronounced lipid peroxidation in npq1 ML but not in wild-type leaves. No such effects were seen in young leaves (YL) of npq1, which were quite tolerant to strong light and eosin-induced singlet oxygen. Non-photochemical energy quenching was strongly inhibited in npq1 YL and ML and was not improved with high-light acclimation. Our results confirm that the xanthophyll cycle protects chloroplasts from photooxidation by a mechanism distinct from non-photochemical energy quenching and they reveal that the absence of xanthophyll cycle can be compensated by other protective mechanisms. npq1 YL were observed to accumulate considerable amounts of vitamin E during photoacclimation, suggesting that this lipophilic antioxidant could be involved in the high phototolerance of those leaves.  (+info)

Influence of lutein supplementation on macular pigment, assessed with two objective techniques. (35/470)

PURPOSE: Macular pigment (MP) may protect against age-related macular degeneration. This study was conducted to determine the extent of changes in the macular pigment density as a consequence of oral supplementation with lutein. A second purpose was to compare two objective measurement techniques. METHODS: In the first technique, reflectance maps were made with a scanning laser ophthalmoscope. Digital subtraction of log reflectance maps and comparison between the foveal area and a 14 degrees temporal site provided MP density estimates. In the second technique, spectral fundus reflectance of the fovea was measured with a fundus reflectometer and analyzed with a detailed optical model, to arrive at MP density values. Eight subjects participated in this study. They took 10 mg lutein per day for 12 weeks. Plasma lutein concentration was measured at 4-week intervals. RESULTS: After 4 weeks, mean blood level of lutein had increased from 0.18 to 0.90 microM. It stayed at this level throughout the intake period and declined to 0.28 microM 4 weeks after termination. Measurement of the density of MP showed a within-subject variation of 10% with MP maps and 17% with spectral reflectance analysis. MP density showed a mean linear 4-week increase of 5.3% (P: < 0.001) and 4.1% (P: = 0. 022), respectively. CONCLUSIONS: Supplementation with lutein significantly increased the density of the MP. Analyzing reflectance maps with a scanning laser ophthalmoscope provided very reliable estimates of MP.  (+info)

Intake of specific carotenoids and risk of lung cancer in 2 prospective US cohorts. (36/470)

BACKGROUND: Carotenoids may reduce lung carcinogenesis because of their antioxidant properties; however, few studies have examined the relation between intakes of individual carotenoids and lung cancer risk. OBJECTIVE: The aim of this study was to examine the relation between lung cancer risk and intakes of alpha-carotene, beta-carotene, lutein, lycopene, and beta-cryptoxanthin in 2 large cohorts. DESIGN: During a 10-y follow-up period, 275 new cases of lung cancer were diagnosed in 46924 men; during a 12-y follow-up period, 519 new cases were diagnosed in 77283 women. Carotenoid intakes were derived from the reported consumption of fruit and vegetables on food-frequency questionnaires administered at baseline and during follow-up. The data were analyzed separately for each cohort and the results were pooled to compute overall relative risks (RRs). RESULTS: In the pooled analyses, alpha-carotene and lycopene intakes were significantly associated with a lower risk of lung cancer; the association with beta-carotene, lutein, and beta-cryptoxanthin intakes were inverse but not significant. Lung cancer risk was significantly lower in subjects who consumed a diet high in a variety of carotenoids (RR: 0.68; 95% CI: 0.49, 0.94 for highest compared with lowest total carotenoid score category). Inverse associations were strongest after a 4-8-y lag between dietary assessment and date of diagnosis. In subjects who never smoked, a 63% lower incidence of lung cancer was observed for the top compared with the bottom quintile of alpha-carotene intake (RR: 0.37; 95% CI: 0.18, 0.77). CONCLUSION: Data from 2 cohort studies suggest that several carotenoids may reduce the risk of lung cancer.  (+info)

Carotenoids in the spermatophores of bushcrickets (Orthoptera: Ephippigerinae). (37/470)

During mating male bushcrickets transfer large spermatophores, which have been demonstrated to play an important role in female nutrition and egg production. Until now only relatively unspecific substances such as water and proteins were known to be present within these spermatophores. We found that in the bushcricket Ephippiger zelleri the spermatophores contain substantial amounts of carotenoids (mainly lutein and zeaxanthin) that are also found in the eggs of this species. Carotenoids are well known for their positive effects on survival and reproduction in animals. This is the first example, to our knowledge, where such specific vitamin-like substances were found to be transferred from male to female during mating.  (+info)

Influence of increased fruit and vegetable intake on plasma and lipoprotein carotenoids and LDL oxidation in smokers and nonsmokers. (38/470)

BACKGROUND: Epidemiological studies suggest a cardioprotective role for carotenoid-rich foods. Smokers have a high risk of cardiovascular disease and low dietary intake and plasma concentrations of carotenoids. The aim of this study was to determine the carotenoid response of smokers and nonsmokers to increased intake of 300-400 g of vegetables and its effect on LDL oxidation. METHODS: After a depletion period of 8 days, 34 healthy females (18 nonsmokers, 16 smokers) were supplemented with beta-carotene- and lutein-rich (green) and lycopene-rich (red) vegetable foods, each for 7 days. RESULTS: Baseline concentrations (mean +/- SD) of plasma beta-carotene (0.203+/-0.28 micromol/L vs. 0.412+/-0.34 micromol/L; P <0.005) and lutein (0.180 +/-0.10 vs. 0.242+/-0.11 micromol/L; P<0.05) but not lycopene (0.296+/-0.10 vs. 0.319+/-0.33 micromol/L) were significantly lower in smokers compared with nonsmokers. After supplementation, the change (supplementation minus depletion) in plasma beta-carotene (0.152+/- 0.43 vs. 0.363+/-0.29 micromol/L in smokers vs. nonsmokers; P = 0.002) and LDL lutein (0.015+/-0.03 vs. 0.029+/-0.03 micromol/mmol cholesterol; P = 0.01) was significantly lower in smokers than nonsmokers. Green-vegetable supplementation had no effect on the resistance of LDL to oxidation (lag-phase) in either group. After red-vegetable supplementation, plasma and LDL lycopene concentrations were increased in both groups, but only nonsmokers showed a significant increase in the lag-phase (44.9+/-9.5 min at baseline, 41.4+/-6.5 min after depletion, and 49.0+/-8.9 min after supplementation; P<0.01) compared with depletion. CONCLUSIONS: In this short-term intervention study, a dietary intake of >40 mg/day of lycopene by a group of nonsmoking individuals significantly reduced the susceptibility of LDL to oxidation, whereas an equivalent increase in lycopene by a group of smokers showed no such effect.  (+info)

Organisation of xanthophyll pigments lutein and zeaxanthin in lipid membranes formed with dipalmitoylphosphatidylcholine. (39/470)

Carotenoid pigments and in particular xanthophylls play several physiological functions in plant and animal membranes. Xanthophylls are present in biological membranes in the form of pigment-protein complexes but also as direct components of lipid phase. The biological activity of carotenoids in membranes depends on a molecular organisation of pigments in lipid bilayers, in particular the localisation, orientation and aggregational state. In the present work the organisation of lutein- and zeaxanthin-containing lipid membranes was analysed with the application of electronic absorption spectroscopy. Both xanthophyll pigments incorporated to the dipalmitoylphosphatidylcholine (DPPC) unilamellar liposomes form H-type molecular aggregates, manifested by the hypsochromic shift of the main absorption band of carotenoids. The aggregation of lutein and zeaxanthin in DPPC membranes was observed even at relatively low concentrations of a pigment in the lipid phase (1-5 mol%). Gaussian analysis of the absorption spectra of lutein and zeaxanthin in DPPC membranes in terms of the exciton splitting theory revealed the formation of different molecular structures of pigments interpreted as dimers, trimers, tetramers and large aggregates. The fraction of lutein and zeaxanthin in the monomeric form was found to depend on the physical state of the lipid phase. Pronounced monomerisation of lutein and zeaxanthin was observed as accompanying the transition from the P(beta)' phase to the L(alpha) phase of DPPC, mostly at the expense of the trimeric and tetrameric forms. The fraction of monomers of lutein is always lower by 10-30% than that of zeaxanthin under the same experimental conditions. Different organisational forms of lutein and zeaxanthin in the model system studied are discussed in terms of possible physiological functions of these pigments in the membranes of the retina: zeaxanthin in the protection of the lipid phase against oxidative damage and lutein in absorbing short wavelength radiation penetrating retina membranes.  (+info)

Global spectral-kinetic analysis of room temperature chlorophyll a fluorescence from light-harvesting antenna mutants of barley. (40/470)

This study presents a novel measurement, and simulation, of the time-resolved room temperature chlorophyll a fluorescence emission spectra from leaves of the barley wild-type and chlorophyll-b-deficient chlorina (clo) f2 and f104 mutants. The primary data were collected with a streak-camera-based picosecond-pulsed fluorometer that simultaneously records the spectral distribution and time dependence of the fluorescence decay. A new global spectral-kinetic analysis programme method, termed the double convolution integral (DCI) method, was developed to convolve the exciting laser pulse shape with a multimodal-distributed decay profile function that is again convolved with the spectral emission band amplitude functions. We report several key results obtained by the simultaneous spectral-kinetic acquisition and DCI methods. First, under conditions of dark-level fluorescence, when photosystem II (PS II) photochemistry is at a maximum at room temperature, both the clo f2 and clo f104 mutants exhibit very similar PS II spectral-decay contours as the wild-type (wt), with the main band centred around 685 nm. Second, dark-level fluorescence is strongly influenced beyond 700 nm by broad emission bands from PS I, and its associated antennae proteins, which exhibit much more rapid decay kinetics and strong integrated amplitudes. In particular a 705-720 nm band is present in all three samples, with a 710 nm band predominating in the clo f2 leaves. When the PS II photochemistry becomes inhibited, maximizing the fluorescence yield, both the clo f104 mutant and the wt exhibit lifetime increases for their major distribution modes from the minimal 205-500 ps range to the maximal 1500-2500 ps range for both the 685 nm and 740 nm bands. The clo f2 mutant, however, exhibits several unique spectral-kinetic properties, attributed to its unique PS I antennae and thylakoid structure, indicating changes in both PS II fluorescence reabsorption and PS II to PS I energy transfer pathways compared to the wt and clo f104. Photoprotective energy dissipation mediated by the xanthophyll cycle pigments and the PsbS protein was uninhibited in the clo f104 mutant but, as commonly reported in the literature, significantly inhibited in the clo f2; the inhibited energy dissipation is partly attributed to its thylakoid structure and PS II to PS I energy transfer properties. It is concluded that it is imperative with steady-state fluorometers, especially for in vivo studies of PS II efficiency or photoprotective energy dissipation, to quantify the influence of the PS I spectral emission.  (+info)