The plasma retinol levels as pro-oxidant/oxidant agents in haemodialysis patients

Associations between serum retinol and all-cause mortality among adults with prediabetes and diabetes: A cohort study

We aimed to explore the associations between serum retinol and all-cause mortality among people with prediabetes and diabetes. The study included 2582 participants with prediabetes and 1654 with diabetes aged ≥40 years from the National Health and Nutrition Examination Survey 2001-2006. Serum retinol was collected from laboratory tests and categorized into five groups, including <50, 50-60, 60-70, 70-80, and ≥80 μg/dL. Deaths were obtained by linkage to National Death Index up to December 31, 2019. Cox proportional hazards models were used to estimate the associations between serum retinol and all-cause mortality. During the follow-up, 993 participants with prediabetes died and 874 participants with diabetes died. There were U-shaped associations between serum retinol and mortality among participants with prediabetes and diabetes, separately. Among participants with prediabetes, compared to serum retinol levels of 50-60 μg/dL, the hazard ratio (HR) (95% confidence interval [CI]) of mortality was 1.40 (95% CI 1.11 to 1.76) and 1.26 (95% CI 1.00 to 1.57) for serum retinol <50 or ≥80 μg/dL, respectively. Among participants with diabetes, compared to serum retinol levels of 50-60 μg/dL, the hazard ratio (HR) (95% confidence interval [CI]) of mortality was 1.25 (95% CI 0.96 to 1.62) and 1.21 (95% CI 0.91 to 1.62) for serum retinol <50 or ≥80 μg/dL, respectively. The U-shaped associations between serum retinol and mortality still existed among participants aged ≥60 years with prediabetes or diabetes but were not statistically significant among those aged 40-59 years with prediabetes or diabetes. In conclusion, both low and excessive serum retinol tended to be with higher mortality risk among people with abnormal blood glucose.

Association between plasma retinol levels and the risk of all-cause mortality in general hypertensive patients: A nested case-control study

To evaluate the association between plasma retinol levels with all-cause mortality and investigate the possible effect modifiers in general hypertensive patients with no previous cardiovascular disease (CVD). This case-control study was nested in the China Stroke Primary Prevention Trial (CSPPT), a randomized, double-blind, controlled trial conducted in 32 communities in Anhui and Jiangsu provinces in China. The current study included 617 cases of all-cause mortality and 617 controls matched on age (≤1 year), sex, treatment group, and study site. All-cause mortality was the main outcome in this analysis, which included death due to any reason. The median follow-up duration was 4.5 years. Overall, there was a U-shaped relation of plasma retinol with all-cause mortality. In the threshold effect analysis, the risk of all-cause mortality significantly decreased with the increase in plasma retinol (per 10 μg/dL increments: OR, 0.73; 95% CI: 0.61-0.87) in participants with plasma retinol <58.3 μg/dL and increased with the increase in plasma retinol (per 10 μg/dL increments: OR, 1.08; 95% CI: 1.01-1.16) in those with plasma retinol ≥58.3 μg/L. In participants with plasma retinol <58.3 μg/dL, a stronger inverse association was observed in those with higher time-averaged SBP (≥140 vs <140 mm Hg; P-interaction = .034), or higher vitamin E levels (≥11.5 [quartile 4]; vs <11.5 μg/mL; P-interaction = .013). The present study demonstrated that there was a U-shaped relationship of plasma retinol levels with the risk of all-cause mortality in general hypertensive patients, with a turning point around 58.3 μg/dL.

Plasma Retinol Concentration Is Mainly Driven by Transthyretin in Hemodialysis Patients

OBJECTIVE

Micronutrients deficiencies in hemodialysis patients are due to low dietary intakes and intradialytic losses for hydrophilic micronutrients. Conversely, lipophilic nondialyzable compounds might accumulate because of a lack of elimination through renal metabolism or dialysis. Other compounds have complex metabolism: their concentration is not explained by these phenomenons. The aim of this study was to report plasma concentrations of lipophilic micronutrients in hemodialysis patients and to analyze if these concentrations were predictive of mortality.

DESIGN

The design was monocentric observational longitudinal study.

SUBJECTS

A total of 123 hemodialysis patients included in this observational study.

MAIN OUTCOME MEASURE

Plasma concentration of lipophilic micronutrients retinol and its two co-transporters transthyretin and retinol-binding protein 4, tocopherol, and carotenoids (α-carotene and β-carotene, β-cryptoxanthin, lycopene, lutein, and zeaxanthin), and all factors associated with 1-year mortality.

RESULTS

Within the 123 patients of the study, median age (interquartile range) was 77.5 (69.5-84.5) years and 58.5% were male. Median retinol plasma concentration was 4.07 (2.65-5.51) μmol/L, and 91.9% of patient had high plasma retinol concentrations. In monovariate analysis, retinol levels were inversely correlated with mortality (hazard ratio = 0.57 [0.45-0.72]; P < .001). This effect remained significant after adjustment with several parameters. Nevertheless, the correlation between retinol and mortality disappeared as soon as transthyretin was added in the statistical model, suggesting an effect of transthyretin as confusing bias. Median tocopherol plasma concentration was 34.8 (28.3-42.9) μmol/L and 72.4% of patients had high plasma tocopherol concentration. Neither tocopherol plasma levels nor carotenoids concentrations were correlated with death in multivariate analysis.

CONCLUSIONS

In hemodialysis patients, the correlation between retinol plasma concentration and mortality represents the nutritional status but not a direct biological effect of retinol. Retinol is only a surrogate predictor of mortality. It might not represent vitamin A levels, but likely the transthyretin level. Plasma retinol levels should be interpreted cautiously in hemodialysis patients.

Retinoids have therapeutic action in type 2 diabetes

OBJECTIVE

Uncontrolled diabetes is associated with a compromised antioxidant state of the body. Consequentially, the reactive oxygen species generated lead to oxidative insult and associated complications. Based on this paradigm, exogenous antioxidant supplementation is thought to exert a therapeutic role in type 2 diabetes (T2-D) biology.

METHODS

In the present study, the effect of vitamin A supplementation was assessed on disease progression in T2-D BALB/c mice. Animals were divided into three groups. With the exception of control, the mice in remaining groups were induced with experimental T2-D. After a 15-day treatment protocol, the mice were sacrificed and various parameters were analyzed.

RESULTS

The treated group evidenced a considerable improvement in total antioxidant potential and glycemic control. A therapeutic effect on beta cell degeneration as compared to the diabetic group was also found.

CONCLUSIONS

The study illustrates the antihyperglycemic and antioxidant potential of vitamin A in vivo, which has potential to serve as a dietary intervention in T2-D.

Liver δ-aminolevulinate dehydratase activity is inhibited by neonicotinoids and restored by antioxidant agents

Neonicotinoids represent the most used class of insecticides worldwide, and their precursor, imidacloprid, is the most widely marketed. The aim of this study was to evaluate the effect of imidacloprid on the activity of hepatic δ-aminolevulinate dehydratase (δ-ALA-D), protective effect of potential antioxidants against this potential effect and presence of chemical elements in the constitution of this pesticide. We observed that δ-ALA-D activity was significantly inhibited by imidacloprid at all concentrations tested in a dose-dependent manner. The IC₅₀ value was obtained and used to evaluate the restoration of the enzymatic activity. δ-ALA-D inhibition was completely restored by addition of dithiotreitol (DTT) and partly by ZnCl_2, demonstrating that the inhibition occurs by oxidation of thiol groups and by displacement of the Zn (II), which can be explained by the presence of chemical elements found in the constitution of pesticides. Reduced glutathione (GSH) had the best antioxidant effect against to δ-ALA-D inhibition caused by imidacloprid, followed by curcumin and resveratrol. It is well known that inhibition of the enzyme δ-ALA-D may result in accumulation of its neurotoxic substrate (δ-ALA), in this line, our results suggest that further studies are needed to investigate the possible neurotoxicity induced by neonicotinoids and the involvement of antioxidants in cases of poisoning by neonicotinoids.

Are delta-aminolevulinate dehydratase inhibition and metal concentrations additional factors for the age-related cognitive decline?

Aging is often accompanied by cognitive impairments and influenced by oxidative status and chemical imbalances. Thus, this study was conducted to examine whether age-related cognitive deficit is associated with oxidative damage, especially with inhibition of the enzyme delta-aminolevulinate dehydratase (ALA-D), as well as to verify the influence of some metals in the enzyme activity and cognitive performance. Blood ALA-D activity, essential (Fe, Zn, Cu, Se) and non-essential metals (Pb, Cd, Hg, As, Cr, Ni, V) were measured in 50 elderly and 20 healthy young subjects. Cognitive function was assessed by tests from Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) battery and other. The elderly group presented decreased ALA-D activity compared to the young group. The index of ALA-D reactivation was similar to both study groups, but negatively associated with metals. The mean levels of essential metals were within the reference values, while the most toxic metals were above them in both groups. Cognitive function impairments were observed in elderly group and were associated with decreased ALA-D activity, with lower levels of Se and higher levels of toxic metals (Hg and V). Results suggest that the reduced ALA-D activity in elderly can be an additional factor involved in cognitive decline, since its inhibition throughout life could lead to accumulation of the neurotoxic compound ALA. Toxic metals were found to contribute to cognitive decline and also to influence ALA-D reactivation.

Alterations to oxidative stress markers in dogs after a short-term stress during transport

While methods to evaluate antioxidant capacity in animals exist, one problem with the models is induction of oxidative stress. It is necessary to promote a great enough challenge to induce measurable alterations to oxidative parameters while ensuring the protocol is compatible with animal welfare. The aim of the present study was to evaluate caged transport as a viable short-term stress that would significantly affect oxidative parameters. Twenty adult Beagle dogs, maintained on the same diet for 60 d prior to the transport, were included in the study. To simulate the stress, the dogs were housed in pairs in transport cages (1·0 m × 1·0 m × 1·5 m), placed on a truck coupled to a trailer and transported for a period of 15 min. Blood collection was performed immediately before and again 3 h after the transportation to evaluate oxidative parameters in blood serum, including thiobarbituric acid reactive substances (TBARS), total antioxidant capacity (TAC), sequestration activity of the radical 2,2-diphenyl-1-picryl-hydrazyl (DPPH•), protein carbonylation (PC), total sulfhydryl groups (SH), alpha-tocopherol (αToc) and retinol (Ret). PC, SH and αToc were not significantly changed in the study; however, TBARS, TAC and DPPH increased, whereas Ret decreased after the transport. Although the lack of a control group of dogs not submitted to transport is a limitation to be considered, we conclude that the transport model is effective in inducing an antioxidant response in dogs and relevant blood parameters show sensitivity to this proposed model.

Preparation, drug releasing property and pharmacodynamics of soy isoflavone-loaded chitosan microspheres

Soybean isoflavone (SIF) has anti-aging properties and many other biological functions; however, SIF is difficult to reach higher blood concentration due to its rapid metabolism. Therefore, it is of great value to design and produce a sustained-release formulation that is able to maintain a stable level of plasma concentrations. In this paper, soybean isoflavone sustained-release microsphere from chitosan and sodium alginate was prepared successfully. The important factors that determined the quality of the microspheres were the sodium alginate concentration in solution B, the ratio of soybean isoflavone to chitosan and the mixing speed. The relative yield, encapsulation efficiency and drug loading capability of SIF were much higher than the existing commercial formulations. In real gastrointestinal conditions, compared with the non-sustained release group, the release rate of SIF slowed down and the reaction time was prolonged. Animal experiments showed that sustained-release microspheres intensified the anti-aging potentials of SIF. Compared with the Non-sustained release (NSR) group mice, oral SIF/CHI microsphere treated mice were better in the Morris Water Maze Test (MWMT), the MDA level in the both plasma and brain of the sustained release (SR) group mice decreased, and SOD content was remarkably improved.

Evaluation of lipid damage related to pathological and physiological conditions

Several diseases and xenobiotics are known to generate reactive species that may trigger oxidative stress when not properly scavenged by the antioxidant defenses and result in tissue damage. We investigated lipid peroxidation (LPO) as a possible mechanism for tissue damage in some pathologies, in the normal aging process, and in subjects exposed to organic solvents. Plasmatic malondialdehyde (MDA) was quantified by high-performance liquid chromatography with visible wavelength detection in 239 subjects and divided into the following: acute myocardium infarction (AMI), diabetes without complications (D) and hemodialysis (HD) patients; into healthy children, adults, and elderly, all nonexposed to xenobiotics; and into painters occupationally exposed to organic solvents (P). Troponin, glycated hemoglobin, and transminases [aspartate aminotransferase (AST) and alanine aminotransferase] were analyzed. An increase in LPO was observed in AMI, D, HD, and P groups, when compared to healthy adults. No correlation between MDA and age was found. Further, we found positive correlations between MDA versus troponin (r = 0.47), MDA versus HbA1c (r = 0.56), and MDA versus AST (r = 0.41) in AMI, diabetics, and painters, respectively. This work has demonstrated increased lipid and protein damages in myocardium and blood, along with an alteration of hepatic transaminase activities and induction of LPO, suggesting that MDA levels are important to evaluate the extent of tissue alterations and development of acute and chronic conditions.

The relationships between exogenous and endogenous antioxidants with the lipid profile and oxidative damage in hemodialysis patients

Background

We sought to investigate the relationships among the plasma levels of carotenoids, tocopherols, endogenous antioxidants, oxidative damage and lipid profiles and their possible effects on the cardiovascular risk associated with hemodialysis (HD) patients.

Methods

The study groups were divided into HD and healthy subjects. Plasma carotenoid, tocopherol and malondialdehyde (MDA) levels, as well as erythrocyte reduced glutathione (GSH), were measured by HPLC. Blood antioxidant enzymes, kidney function biomarkers and the lipid profiles were analyzed by spectrophotometric methods.

Results

Plasma lycopene levels and blood glutathione peroxidase (GPx) activity were significantly decreased in HD patients compared with healthy subjects. Total cholesterol, low-density lipoprotein cholesterol (LDL-c), creatinine, urea, MDA, GSH, superoxide dismutase (SOD) and catalase (CAT) were significantly increased in HD (p < 0.05). Lycopene levels were correlated with MDA (r = -0.50; p < 0.01), LDL-c (r = -0.38; p = 0.01) levels, the LDL-c/HDL-c index (r = -0.33; p = 0.03) and GPx activity (r = 0.30; p = 0.03). Regression models showed that lycopene levels were correlated with LDL-c (β estimated = -31.59; p = 0.04), while gender was correlated with the TC/HDL-c index and triglycerides. Age did not present a correlation with the parameters evaluated. GPx activity was negatively correlated with MDA levels and with the LDL-c/HDL-c and CT/HDL-c indexes.

Conclusions

Lycopene may represent an additional factor that contributes to reduced lipid peroxidation and atherogenesis in hemodialysis patients.

Vitamin A and retinoid derivatives for lung cancer: a systematic review and meta analysis

BACKGROUND

Despite reported antiproliferative activity of vitamin A and its common use for cancer, there is no comprehensive synthesis of its safety and efficacy in lung cancers. To address this issue we conducted a systematic review of the safety and efficacy of vitamin A for the treatment and prevention of lung cancers.

METHODS AND FINDINGS

Two independent reviewers searched six electronic databases from inception to July 2009 for clinical, observational, and preclinical evidence pertaining to the safety and efficacy of vitamin A and related retinoids for lung cancers. 248 studies were included for full review and analysis. Five RCTs assessed treatment of lung cancers, three assessed primary prevention, and three looked at secondary prevention of lung cancers. Five surrogate studies, 26 phase I/II, 32 observational, and 67 preclinical studies were also included. 107 studies were included for interactions between vitamin A and chemo- or radiation-therapy. Although some studies demonstrated benefits, there was insufficient evidence overall to support the use of vitamin A or related retinoids for the treatment or prevention of lung cancers. Retinyl palmitate combined with beta carotene increased risk of lung cancer in smokers in the large CARET trial. Pooling of three studies pertaining to treatment and three studies on secondary prevention revealed no significant effects on response rate, second primary tumor, recurrence, 5-year survival, and mortality. There was a small improvement in event free survival associated with vitamin A compared to controls, RR 1.24 (95% CI 1.13-1.35). The synthetic rexinoid bexarotene increased survival significantly among a subset of patients in two RCTs (p<0.014, <0.087).

CONCLUSIONS

There is a lack of evidence to support the use of naturally occurring retinoids for the treatment and prevention of lung cancers. The rexinoid bexarotene may hold promise for use among a subset of patients, and deserves further study.

Dietary intake in hemodialysis patients does not reflect a heart healthy diet

OBJECTIVE

Cardiovascular disease is highly prevalent and has a major effect on morbidity and mortality in patients undergoing maintenance hemodialysis (MHD). Dietary factors that may contribute to cardiovascular disease have not been well studied in this population. We hypothesize that dietary intake in this population does not meet the guidelines for cardiovascular risk reduction.

DESIGN

A cross-sectional study was completed using the validated "Block Dialysis 1 Food Frequency Questionnaire" to assess dietary intake of MHD patients.

SETTING AND PATIENTS

A total of 70 patients undergoing MHD at our outpatient dialysis center completed the questionnaire under the supervision of a trained dietitian. The population consisted of 38 men and 32 women.

MAIN OUTCOME MEASURE

Dietary intake was the main outcome measure, with a focus on calories, soluble fiber, saturated fatty acid (SFA), unsaturated fatty acid intake (UFA), and protein.

RESULTS

The mean fiber intake was 10.77 (±5.87) g/day, and only 2 of 71 (2.9%) were in compliance with the recommended daily intake of >25 g/day. As percentage of total calories, of the 70 patients, 5 (7.1%) had a fat intake of <30%, 22 (31.4%) had SFA intake of <10%, 64 (91.4%) had a UFA of ≤30%, 22 (31.4%) had a protein-based diet of ≥15%, and 66 (94.3%) had a carbohydrate diet of <60%.

CONCLUSIONS

Most patients did not meet the dietary guidelines for reducing the risk of cardiovascular disease. Substituting UFA or soluble fiber for SFA improves low density lipoprotein (LDL) cholesterol levels without negative effects on other lipid parameters.

Effects of low-level exposure to xenobiotics present in paints on oxidative stress in workers

Paints are composed of an extensive variety of hazardous substances, such as organic solvents and heavy metals. Biomonitoring is an essential tool for assessing the risk to occupational health. Thus, this study analyzed the levels of biomarkers of exposure for toluene, xylene, styrene, ethylbenzene, and lead, as well as the oxidative stress biomarker alterations in painters of an industry. Lipid peroxidation biomarker (MDA), delta-aminolevulinate dehydratase (ALA-D), nonprotein thyol groups, superoxide dismutase and catalase (CAT) were analyzed in exposed and nonexposed subjects. We estimated which of the paint constituents have the greatest influence on the changes in the biomarkers of oxidative stress in this case of co-exposure. The results demonstrated that despite the fact that all the biomarkers of exposure were below the biological exposure limits, the MDA levels and antioxidant enzyme activities were increased, while nonprotein thyol groups and ALA-D levels were decreased in painters when compared with nonexposed subjects. After statistic test, toluene could be suggested as the principal factor responsible for increased lipid peroxidation and inhibition of ALA-D enzyme; however, further studies on the inhibition of ALA-D enzyme by toluene are necessary.