Nutrient overload, lipid peroxidation and pancreatic beta cell function

Lipidomics Reveals Myocardial Lipid Composition in a Murine Model of Insulin Resistance Induced by a High-Fat Diet

Ectopic fat accumulation in non-adipose tissues is closely related to diabetes-related myocardial dysfunction. Nevertheless, the complete picture of the lipid metabolites involved in the metabolic-related myocardial alterations is not fully characterized. The aim of this study was to characterize the specific lipid profile in hearts in an animal model of obesity/insulin resistance induced by a high-fat diet (HFD). The cardiac lipidome profiles were assessed via liquid chromatography-mass spectrometry (LC-MS)/MS-MS and laser desorption/ionization-mass spectrometry (LDI-MS) tissue imaging in hearts from C57BL/6J mice fed with an HFD or standard-diet (STD) for 12 weeks. Targeted lipidome analysis identified a total of 63 lipids (i.e., 48 triacylglycerols (TG), 5 diacylglycerols (DG), 1 sphingomyelin (SM), 3 phosphatidylcholines (PC), 1 DihydroPC, and 5 carnitines) modified in hearts from HFD-fed mice compared to animals fed with STD. Whereas most of the TG were up-regulated in hearts from animals fed with an HFD, most of the carnitines were down-regulated, thereby suggesting a reduction in the mitochondrial β-oxidation. Roughly 30% of the identified metabolites were oxidated, pointing to an increase in lipid peroxidation. Cardiac lipidome was associated with a specific biochemical profile and a specific liver TG pattern. Overall, our study reveals a specific cardiac lipid fingerprint associated with metabolic alterations induced by HFD.

Impaired Detoxification of Trans, Trans-2,4-Decadienal, an Oxidation Product from Omega-6 Fatty Acids, Alters Insulin Signaling, Gluconeogenesis and Promotes Microvascular Disease

Omega-6 fatty acids are the primary polyunsaturated fatty acids in most Western diets, while their role in diabetes remains controversial. Exposure of omega-6 fatty acids to an oxidative environment results in the generation of a highly reactive carbonyl species known as trans, trans-2,4-decadienal (tt-DDE). The timely and efficient detoxification of this metabolite, which has actions comparable to other reactive carbonyl species, such as 4-hydroxynonenal, acrolein, acetaldehyde, and methylglyoxal, is essential for disease prevention. However, the detoxification mechanism for tt-DDE remains elusive. In this study, the enzyme Aldh9a1b is identified as having a key role in the detoxification of tt-DDE. Loss of Aldh9a1b increased tt-DDE levels and resulted in an abnormal retinal vasculature and glucose intolerance in aldh9a1b-/- zebrafish. Transcriptomic and metabolomic analyses revealed that tt-DDE and aldh9a1b deficiency in larval and adult zebrafish induced insulin resistance and impaired glucose homeostasis. Moreover, alterations in hyaloid vasculature is induced by aldh9a1b knockout or by tt-DDE treatment can be rescued by the insulin receptor sensitizers metformin and rosiglitazone. Collectively, these results demonstrated that tt-DDE is the substrate of Aldh9a1b which causes microvascular damage and impaired glucose metabolism through insulin resistance.

Predictive performance of triglyceride glucose index (TyG index) to identify glucose status conversion: a 5-year longitudinal cohort study in Chinese pre-diabetes people

OBJECTIVE

Triglyceride glucose index (TyG index) has been recommended as an alternative indicator of insulin resistance. However, the association between TyG and regression from prediabetes to normoglycemia remains to be elucidated.

METHODS

This retrospective cohort study involved 25,248 subjects with prediabetes at baseline conducted from 2010 to 2016. A Cox proportional hazard regression model was designed to evaluate the role of TyG in identifying people at converting from prediabetes to normoglycemia. Cox proportional hazards regression with cubic spline functions and smooth curve fitting was used to dig out the nonlinear relationship between them. Detailed evaluations for TyG were also performed using sensitivity and subgroup analyse.

RESULTS

Among the included prediabetes subjects (n = 25,248), the mean age was 49.27 ± 13.84 years old, and 16,701 (66.15%) were male. The mean TyG was 8.83 ± 0.60. The median follow-up time was 2.96 ± 0.90 years. 11,499 (45.54%) individuals had a final diagnosis of normoglycemia. After adjusting for covariates, TyG was negatively affecting the results of glucose status conversion in prediabetes people (HR 0.895, 95% CI 0.863, 0.928). There was a nonlinear connection between TyG and normoglycemia in prediabetes people, and the inflection point was 8.88. The effect sizes (HR) on the left and right sides of the inflection point were 0.99 (0.93, 1.05) and 0.79 (0.74, 0.85), respectively. Sensitivity analysis confirmed the robustness of these results. Subgroup analysis showed that TyG was more strongly associated with incident glucose status conversion in male, BMI ≥ 25. In contrast, there was a weaker relationship in those with female, BMI < 25.

CONCLUSION

Based on sample of subjects evaluated between 2010 and 2016, TyG index appears to be a promising marker for predicting normoglycemic conversion among prediabetes people in China. This study demonstrates a negative and non-linear association between TyG and glucose status conversion from prediabetes to normoglycemia. TyG is strongly related to glucose status conversion when TyG is above 8.88. From a therapeutic point of view, it is meaningful to maintain TyG levels within the inflection point to 8.88.

A Novel Drug Delivery System: Hyodeoxycholic Acid-Modified Metformin Liposomes for Type 2 Diabetes Treatment

Metformin is a first-line drug for the clinical treatment of type 2 diabetes; however, it always leads to gastrointestinal tolerance, low bioavailability, short half-life, etc. Liposome acts as an excellent delivery system that could reduce drug side effects and promote bioavailability. Hyodeoxycholic acid, a cholesterol-like structure, can regulate glucose homeostasis and reduce the blood glucose levels. As an anti-diabetic active ingredient, hyodeoxycholic acid modifies liposomes to make it overcome the disadvantages of metformin as well as enhance the hypoglycemic effect. By adapting the thin-film dispersion method, three types of liposomes with different proportions of hyodeoxycholic acid and metformin were prepared (HDCA:ME-(0.5:1)-Lips, HDCA:ME-(1:1)-Lips, and HDCA:ME-(2:1)-Lips). Further, the liposomes were characterized, and the anti-type 2 diabetes activity of liposomes was evaluated. The results from this study indicated that three types of liposomes exhibited different characteristics—Excessive hyodeoxycholic acid decreased encapsulation efficiency and drug loading. In the in vivo experiments, liposomes could reduce the fasting blood glucose levels, improve glucose tolerance, regulate oxidative stress markers and protect liver tissue in type 2 diabetic mice. These results indicated that HDCA:ME-(1:1)-Lips was the most effective among the three types of liposomes prepared and showed better effects than metformin. Hyodeoxycholic acid can enhance the hypoglycemic effect of metformin and play a suitable role as an excipient in the liposome.

Biomarkers of oxidative stress and reproductive complications

Oxidative stress is the result of an imbalance between the formation of reactive oxygen species (ROS) and the levels of enzymatic and non-enzymatic antioxidants. The assessment of biological redox status is performed by the use of oxidative stress biomarkers. An oxidative stress biomarker is defined as any physical structure or process or chemical compound that can be assessed in a living being (in vivo) or in solid or fluid parts thereof (in vitro), the determination of which is a reproducible and reliable indicator of oxidative stress. The use of oxidative stress biomarkers allows early identification of the risk of developing diseases associated with this process and also opens up possibilities for new treatments. At the end of the last century, interest in oxidative stress biomarkers began to grow, due to evidence of the association between the generation of free radicals and various pathologies. Up to now, a significant number of studies have been carried out to identify and apply different oxidative stress biomarkers in clinical practice. Among the most important oxidative stress biomarkers, it can be mentioned the products of oxidative modifications of lipids, proteins, nucleic acids, and uric acid as well as the measurement of the total antioxidant capacity of fluids in the human body. In this review, we aim to present recent advances and current knowledge on the main biomarkers of oxidative stress, including the discovery of new biomarkers, with emphasis on the various reproductive complications associated with variations in oxidative stress levels.

Lipid hydroperoxide-derived insulin resistance and its inhibition by pyridoxamine in skeletal muscle cells

Oxidative stress is strongly associated with the onset and/or progression of diabetes. Under conditions of oxidative stress, lipid hydroperoxides are decomposed to reactive aldehydes that have been reported to induce insulin resistance by modifying proteins involved in insulin signaling. Pyridoxamine (PM) can inhibit the formation of advanced glycation/lipoxidation end products by scavenging reactive carbonyl species. Thus, PM has emerged as a promising drug candidate for various chronic conditions, including diabetic complications. In this study, L6 skeletal muscle cells were treated with 4-oxo-2(E)-nonenal (ONE), one of the most abundant and reactive lipid-derived aldehydes. Cellular insulin resistance was assessed by measuring insulin-stimulated glucose uptake using 2-deoxyglucose. ONE induced a time- and dose-dependent decrease in glucose uptake. Liquid chromatography/electrospray ionization-mass spectrometry analysis of the reaction between ONE and insulin receptor substrate 1 (IRS1) lysate identified multiple modifications that could disturb the interaction between IRS1 and activated IR, leading to insulin resistance. Pretreatment of the cells with PM restored the ONE-induced decrease in glucose uptake. Concomitantly, the formation of PM-ONE adducts in cell culture medium was increased in a PM-dose dependent manner. PM can therefore prevent lipid hydroperoxide-derived insulin resistance by quenching ONE.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-022-00155-z.

Effect of oxidation and in vitro intestinal hydrolysis on phospholipid toxicity towards HT29 cell line serving as a model of human intestinal epithelium

Oxidation of food-derived phospholipids (PLs) can influence nutrient digestion and induce oxidative stress in gastrointestinal epithelium. In this study, hen egg yolk PL fraction was used to evaluate the effect of lipoxygenase (LOX)-induced PL oxidation on the rate of PL hydrolysis catalyzed by pancreatic phospholipase A₂ (PLA₂) in the presence of bile salts (BSs). Then, PL/BS solutions containing native or oxidized PLs were used in in vitro intestinal digestion to assess the effect of PL oxidation and hydrolysis on the toxicity towards HT29 cell line. Based on the obtained results, we suggest that hexanal and (E)-2-nonenal, formed by the decomposition of PL hydroperoxides, inhibited PLA₂ activity. The cell exposure to simulated intestinal fluid (SIF) containing BSs decreased HT29 cell viability and significantly damaged cellular DNA. However, the genotoxic effect was reversed in the presence of all tested PL samples, while the protective effect against the BS-induced cytotoxicity was observed for native non-hydrolyzed PLs, but was not clearly visible for other samples. This can result from an overlap of other toxic effects such as lipotoxicity or disturbance of cellular redox homeostasis. Taking into account the data obtained, it was proposed that the PLA₂ activity decline in the presence of PL oxidation products may be a kind of protective mechanism against rapid release of oxidized FAs characterized by high cytotoxic effect towards intestinal epithelium cells.

Glucose-lowering effects of orally administered superoxide dismutase in type 2 diabetic model rats

Superoxide dismutase (SOD) is an enzyme found in most food sources, might be a candidate to reduce oxidative damage to intestinal barrier, thereby ameliorating the vicious circle between hyperglycemia and the oxidative damage. Here we report the oral administration of SOD, liposome-embedded SOD (L-SOD), and SOD hydrolysate to type 2 diabetic model rats to confirm this hypothesis. Oxidative damage severity in model rat intestine was indicated by malondialdehyde level, GSSG/GSH ratio, and antioxidant enzyme activity. The damage was significantly repaired by L-SOD. Furthermore, blood glucose and related indexes correlated well not only with oxidative damage results but also with indexes indicating physical intestinal damage such as colon density, H&E staining, immunohistochemical analysis of the tight junction proteins occludin and ZO-1 in the colon, as well as lipopolysaccharide and related inflammatory cytokine levels. The order of the magnitude of the effects of these SOD preparations was L-SOD > SOD > SOD hydrolysate. These data indicate that orally administered SOD can exhibit glucose-lowering effect via targeting the intestine of diabetic rats and systemic lipopolysaccharide influx.

Oral fat tolerance testing identifies abnormal pancreatic β-cell function and insulin resistance in individuals with normal glucose tolerance

AIMS/INTRODUCTION

Insulin sensitivity and β-cell function are affected by lipid metabolism disorders, even before the onset of type 2 diabetes. People are in the postprandial state most of the time. Therefore, identifying postprandial hyperlipemia is important. This study aimed to assess patients with abnormalities in lipid metabolism, but with normal glucose tolerance, using oral fat tolerance testing (OFTT) to identify defects in insulin sensitivity and β-cell function.

MATERIALS AND METHODS

We included 248 volunteers with normal glucose tolerance who underwent OFTT. They were divided into three groups in accordance with their fasting and 4-h postprandial triglyceride (TG) concentrations. Their lipid concentrations during OFTT were compared. The disposition index (DI) was applied to estimate β-cell function, and the Matsuda insulin sensitivity index (ISI_M ) was used to assess insulin sensitivity. We used multiple linear regression analysis to estimate the relationships of fasting and postprandial TG concentrations with β-cell function and insulin sensitivity .

RESULTS

The changes in TG concentrations during OFTT were more marked than those in low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol or total cholesterol concentrations. As lipid metabolism deteriorated, the ISI_M and the DI gradually decreased. Multiple linear regression analysis showed that fasting and 4-h postprandial TG concentrations affected LnISI_M and LnDI.

CONCLUSIONS

In individuals with normal glucose tolerance, β-cell function and insulin sensitivity gradually decrease with a deterioration in the lipid profile. Not only fasting TG, but also postprandial TG concentrations are independent risk factors for impaired β-cell function and insulin resistance.

Associations of propylene oxide exposure with fasting plasma glucose and diabetes: Roles of oxidative DNA damage and lipid peroxidation

Whether propylene oxide (PO) exposure is associated with hyperglycemia were rarely explored. We aimed to determine the relationship between PO exposure and glucose metabolism, and potential role of oxidative stress. Among 3294 Chinese urban adults, urinary PO metabolite (N-Acetyl-S-(2-hydroxypropyl)-L-cysteine, 2HPMA), biomarkers of oxidative DNA damage (8-oxo-7,8-dihydro-20-deoxyguanosine, 8-OHdG) and lipid peroxidation (8-isoprostane, 8-iso-PGF_2α) in urine were determined. The associations of 2HPMA with 8-OHdG, 8-iso-PGF_2α, fasting plasma glucose (FPG), and risk of diabetes were explored. The roles of 8-OHdG and 8-iso-PGF_2α on association of 2HPMA with FPG and risk of diabetes were detected. After adjusted for potential confounders, each 1-unit increase in log-transformed concentration of 2HPMA was associated with a 0.15-mmol/L increase in FPG level, and the adjusted OR (95% CI) of diabetes by the associations of log-transformed urinary 2HPMA concentrations was 1.47 (95% CI: 1.03-2.11). Combination effects of 2HPMA with 8-OHdG or 8-iso-PGF_2α on risk of diabetes were detected, and elevated 8-iso-PGF_2α significantly mediated 34.5% of the urinary 2HPMA-associated FPG elevation. PO exposure was positively associated with FPG levels and risk of diabetes. PO exposure combined with DNA oxidative damage or lipid peroxidation may increase the risk of diabetes, and lipid peroxidation may partially mediate the PO exposure-induced FPG elevation.

Elevated triglyceride-glucose (TyG) index predicts impaired islet β-cell function: A hospital-based cross-sectional study

OBJECTIVE

To explore the relationship between the TyG index and the insulin secretion function of pancreatic β-cells, and to determine the possibility of the TyG index in predicting β-cell dysfunction and the development of diabetes.

METHODS

A cross-sectional study was performed among 914 participants who took their annual health checkups at the Third Xiangya Hospital. The early- and late-phase pancreatic β-cell secretion was assessed based on the results of the oral glucose tolerance test (OGTT). In addition to anthropometric parameters and laboratory parameters, information about health-related habits and disease histories was obtained from the National Physical Examination Questionnaire. Partial correlation analysis was used to study the relationship between the TyG index and pancreatic β-cell function. The receiver operating characteristic (ROC) curve was used to calculate the cut-off points of the TyG index in predicting β-cell dysfunction. According to the OGTT results and medical history, the participants were categorized into three groups: the normal glucose tolerance group (NGT, n=276), the impaired glucose regulation group (IGT, n=323), and the diabetes group (DM, n=315). The correlation between the TyG index and β-cell function among the three groups and the association between the TyG index and glucose metabolic conditions were further explored.

RESULTS

The TyG index was negatively correlated with the indexes that reflect the early and late secretory function of β-cells, not only in the NGT group but also in the IGT and DM group. The minimum cut-off values for the TyG index to identify the risk of early- and late-phase β-cell dysfunction are 9.08 and 9.2 respectively. The TyG indexes of the IGT and DM group were higher than that of the NGT group, and with the growth of the TyG index, the risk of prediabetes and diabetes increased significantly.

CONCLUSION

Increased TyG index is associated with impaired β-cell function regardless of the glucose metabolic conditions. The TyG index is an alternative indicator for predicting β-cell dysfunction.

Elevated 4-hydroxynonenal induces hyperglycaemia via Aldh3a1 loss in zebrafish and associates with diabetes progression in humans

Increased methylglyoxal (MG) formation is associated with diabetes and its complications. In zebrafish, knockout of the main MG detoxifying system Glyoxalase 1, led to limited MG elevation but significantly elevated aldehyde dehydrogenases (ALDH) activity and aldh3a1 expression, suggesting the compensatory role of Aldh3a1 in diabetes. To evaluate the function of Aldh3a1 in glucose homeostasis and diabetes, aldh3a1^−/− zebrafish mutants were generated using CRISPR-Cas9. Vasculature and pancreas morphology were analysed by zebrafish transgenic reporter lines. Corresponding reactive carbonyl species (RCS), glucose, transcriptome and metabolomics screenings were performed and ALDH activity was measured for further verification. Aldh3a1^−/− zebrafish larvae displayed retinal vasodilatory alterations, impaired glucose homeostasis, which can be aggravated via pdx1 silencing induced hyperglycaemia. Unexpectedly, MG was not altered, but 4-hydroxynonenal (4-HNE), another prominent lipid peroxidation RCS exhibited high affinity with Aldh3a1, was increased in aldh3a1 mutants. 4-HNE was responsible for the retinal phenotype via pancreas disruption induced hyperglycaemia and can be rescued via l-Carnosine treatment. Furthermore, in type 2 diabetic patients, serum 4-HNE was increased and correlated with disease progression. Thus, our data suggest impaired 4-HNE detoxification and elevated 4-HNE concentration as biomarkers but also the possible inducers for diabetes, from genetic susceptibility to the pathological progression.

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Aldh3a1 mutant was generated using CRISPR/Cas9 and displayed impaired glucose homeostasis.

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Elevated 4-Hydroxynonenal (4-HNE) was responsible for hyperglycaemia in aldh3a1 mutants and was rescued by Carnosine.

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Patient serum 4-HNE level was correlated with HbA1c and fasting glucose.

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Impaired 4-HNE detoxification acts as possible inducers for diabetes, from genetic susceptibility to pathological progress.

U-Shaped Associations Between Urinary Iodine Concentration and the Prevalence of Metabolic Disorders: A Cross-Sectional Study

Background: Iodine is important in both thyroid function and human metabolism. Studies have explored the effect of iodine on metabolic disorders through thyroid function. This study aimed to investigate the relationship between iodine status and metabolic disorders, such as metabolic syndrome (MetS), hypertension, impaired glucose metabolism, central obesity, and dyslipidemia. Methods: A total of 51,795 subjects aged ≥18 years from the TIDE (Thyroid Disorders, Iodine Status and Diabetes, a national epidemiological cross-sectional study) program were included. The prevalence of metabolic disorders and its related diseases was calculated based on the level of urinary iodine concentrations (UICs) using the chi-square method. To further explore whether the prevalence was associated with UIC, quadratic and UIC-stratified logistic regression models were used. Results: The prevalence of metabolic disorders as a function of UIC was found to be U-shaped with a lower prevalence of 76.0% at an UIC of 300-499 μg/L. Participants with an UIC of 300-499 μg/L showed an association with metabolic disorders (odds ratio [OR] = 0.857, 95% confidence interval [CI 0.796-0.922]) and hypertension (OR = 0.873 [CI 0.814-0.936]). An UIC of 300-799 μg/L was found to be associated with the occurrence of MetS and impaired glucose tolerance. An UIC of 500-799 μg/L was associated with the occurrence of prediabetes (OR = 0.883 [CI 0.797-0.978]). An UIC of ≥300 μg/L was associated with the occurrence of hypertriglyceridemia, hypercholesterolemia, and high levels of low-density lipoprotein cholesterol. Furthermore, an UIC of <100 μg/L showed an association with hypertension (OR = 1.097 [CI 1.035-1.162]) and hypercholesterolemia (OR = 1.178 [CI 1.117-1.242]). Conclusions: The association between UICs in adults and metabolic disorders and its related diseases is U-shaped. The association between UIC and metabolic disorders disappears in cases of iodine deficiency (<100 μg/L) or excess (≥500 μg/L).

Acrylamide Exposure and Oxidative DNA Damage, Lipid Peroxidation, and Fasting Plasma Glucose Alteration: Association and Mediation Analyses in Chinese Urban Adults

OBJECTIVE

Acrylamide exposure from daily-consumed food has raised global concern. We aimed to assess the exposure-response relationships of internal acrylamide exposure with oxidative DNA damage, lipid peroxidation, and fasting plasma glucose (FPG) alteration and investigate the mediating role of oxidative DNA damage and lipid peroxidation in the association of internal acrylamide exposure with FPG.

RESEARCH DESIGN AND METHODS

FPG and urinary biomarkers of oxidative DNA damage (8-hydroxy-deoxyguanosine [8-OHdG]), lipid peroxidation (8-iso-prostaglandin-F2α [8-iso-PGF2α]), and acrylamide exposure (N-acetyl-S-[2-carbamoylethyl]-l-cysteine [AAMA], N-acetyl-S-[2-carbamoyl-2-hydroxyethyl]-l-cysteine [GAMA]) were measured for 3,270 general adults from the Wuhan-Zhuhai cohort. The associations of urinary acrylamide metabolites with 8-OHdG, 8-iso-PGF2α, and FPG were assessed by linear mixed models. The mediating roles of 8-OHdG and 8-iso-PGF2α were evaluated by mediation analysis.

RESULTS

We found significant linear positive dose-response relationships of urinary acrylamide metabolites with 8-OHdG, 8-iso-PGF2α, and FPG (except GAMA with FPG) and 8-iso-PGF2α with FPG. Each 1-unit increase in log-transformed level of AAMA, AAMA + GAMA (ΣUAAM), or 8-iso-PGF2α was associated with a 0.17, 0.15, or 0.23 mmol/L increase in FPG, respectively (P and/or P trend < 0.05). Each 1% increase in AAMA, GAMA, or ΣUAAM was associated with a 0.19%, 0.27%, or 0.22% increase in 8-OHdG, respectively, and a 0.40%, 0.48%, or 0.44% increase in 8-iso-PGF2α, respectively (P and P trend < 0.05). Increased 8-iso-PGF2α rather than 8-OHdG significantly mediated 64.29% and 76.92% of the AAMA- and ΣUAAM-associated FPG increases, respectively.

CONCLUSIONS

Exposure of the general adult population to acrylamide was associated with FPG elevation, oxidative DNA damage, and lipid peroxidation, which in turn partly mediated acrylamide-associated FPG elevation.

Acrocomia aculeata (Jacq.) Lodd. ex Mart. Leaves Increase SIRT1 Levels and Improve Stress Resistance

Oxidative stress is a metabolic disorder linked with several chronic diseases, and this condition can be improved by natural antioxidants. The fruit pulp of the palm Acrocomia aculeata (Jacq.) Lodd. ex Mart. is widely used in the treatment of various illnesses, but as far as we know, there are no reports regarding the properties of its leaves. Thus, we aimed to evaluate the antioxidant activity of A. aculeata leaf extracts obtained with water (EA-Aa), ethanol (EE-Aa), and methanol (EM-Aa) solvents. The extracts were chemically characterized, and their antioxidant activity was assessed through the scavenging of the free radicals DPPH and ABTS. EE-Aa and EM-Aa showed the highest amounts of phenolic compounds and free radical scavenging activity. However, EA-Aa was more efficient to protect human erythrocytes against AAPH-induced hemolysis and lipid peroxidation. Thus, we further show the antioxidant effect of EA-Aa in preventing AAPH-induced protein oxidation, H₂O₂-induced DNA fragmentation, and ROS generation in Cos-7 cells. Increased levels of Sirt1, catalase, and activation of ERK and Nrf2 were observed in Cos-7 treated with EA-Aa. We also verify increased survival in nematodes C. elegans, when induced to the oxidative condition by Juglone. Therefore, our results showed a typical chemical composition of plants for all extracts, but the diversity of compounds presented in EA-Aa is involved in the lower toxicity and antioxidant properties provided to the macromolecules tested, proteins, DNA, and lipids. This protective effect also proven in Cos-7 and in C. elegans was probably due to the activation of the Sirt1/Nrf2 pathway. Altogether, the low toxicity and the antioxidant properties of EA-Aa showed in all the experimental models support its further use in the treatment of oxidative stress-related diseases.

The Role of Lipoxidation in the Pathogenesis of Diabetic Retinopathy

Lipids can undergo modification as a result of interaction with reactive oxygen species (ROS). For example, lipid peroxidation results in the production of a wide variety of highly reactive aldehyde species which can drive a range of disease-relevant responses in cells and tissues. Such lipid aldehydes react with nucleophilic groups on macromolecules including phospholipids, nucleic acids, and proteins which, in turn, leads to the formation of reversible or irreversible adducts known as advanced lipoxidation end products (ALEs). In the setting of diabetes, lipid peroxidation and ALE formation has been implicated in the pathogenesis of macro- and microvascular complications. As the most common diabetic complication, retinopathy is one of the leading causes of vision loss and blindness worldwide. Herein, we discuss diabetic retinopathy (DR) as a disease entity and review the current knowledge and experimental data supporting a role for lipid peroxidation and ALE formation in the onset and development of this condition. Potential therapeutic approaches to prevent lipid peroxidation and lipoxidation reactions in the diabetic retina are also considered, including the use of antioxidants, lipid aldehyde scavenging agents and pharmacological and gene therapy approaches for boosting endogenous aldehyde detoxification systems. It is concluded that further research in this area could lead to new strategies to halt the progression of DR before irreversible retinal damage and sight-threatening complications occur.

Protective effect of hydrogen sulfide on oxidative stress-induced neurodegenerative diseases

Hydrogen sulfide is an antioxidant molecule that has a wide range of biological effects against oxidative stress. Balanced oxidative stress is also vital for maintaining cellular function in biological system, where reactive oxygen species are the main source of oxidative stress. When the normal redox balance is disturbed, deoxyribonucleic acid, lipid, and protein molecules are oxidized under pathological conditions, like diabetes mellitus that leads to diabetic peripheral neuropathy. In diabetes mellitus-induced diabetic peripheral neuropathy, due to hyperglycemia, pancreatic beta cell (β cell) shows resistance to insulin secretion. As a consequence, glucose metabolism is disturbed in neuronal cells which are distracted from providing proper cell signaling pathway. Not only diabetic peripheral neuropathy but also other central damages occur in brain neuropathy. Neurological studies regarding type 1 diabetes mellitus patients with Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis have shown changes in the central nervous system because high blood glucose levels (HbA1c) appeared with poor cognitive function. Oxidative stress plays a role in inhibiting insulin signaling that is necessary for brain function. Hydrogen sulfide exhibits antioxidant effects against oxidative stress, where cystathionine β synthase, cystathionine γ lyase, and 3-mercaptopyruvate sulfurtransferase are the endogenous sources of hydrogen sulfide. This review is to explore the pathogenesis of diabetes mellitus-induced diabetic peripheral neuropathy and other neurological comorbid disorders under the oxidative stress condition and the anti-oxidative effects of hydrogen sulfide.

The Combination of Whole Cell Lipidomics Analysis and Single Cell Confocal Imaging of Fluidity and Micropolarity Provides Insight into Stress-Induced Lipid Turnover in Subcellular Organelles of Pancreatic Beta Cells

Modern omics techniques reveal molecular structures and cellular networks of tissues and cells in unprecedented detail. Recent advances in single cell analysis have further revolutionized all disciplines in cellular and molecular biology. These methods have also been employed in current investigations on the structure and function of insulin secreting beta cells under normal and pathological conditions that lead to an impaired glucose tolerance and type 2 diabetes. Proteomic and transcriptomic analyses have pointed to significant alterations in protein expression and function in beta cells exposed to diabetes like conditions (e.g., high glucose and/or saturated fatty acids levels). These nutritional overload stressful conditions are often defined as glucolipotoxic due to the progressive damage they cause to the cells. Our recent studies on the rat insulinoma-derived INS-1E beta cell line point to differential effects of such conditions in the phospholipid bilayers in beta cells. This review focuses on confocal microscopy-based detection of these profound alterations in the plasma membrane and membranes of insulin granules and lipid droplets in single beta cells under such nutritional load conditions.

Contribution of Oxidative Stress and Impaired Biogenesis of Pancreatic β-Cells to Type 2 Diabetes

Significance: Type 2 diabetes development involves multiple changes in β-cells, related to the oxidative stress and impaired redox signaling, beginning frequently by sustained overfeeding due to the resulting lipotoxicity and glucotoxicity. Uncovering relationships among the dysregulated metabolism, impaired β-cell "well-being," biogenesis, or cross talk with peripheral insulin resistance is required for elucidation of type 2 diabetes etiology. Recent Advances: It has been recognized that the oxidative stress, lipotoxicity, and glucotoxicity cannot be separated from numerous other cell pathology events, such as the attempted compensation of β-cell for the increased insulin demand and dynamics of β-cell biogenesis and its "reversal" at dedifferentiation, that is, from the concomitantly decreasing islet β-cell mass (also due to transdifferentiation) and low-grade islet or systemic inflammation. Critical Issues: At prediabetes, the compensation responses of β-cells, attempting to delay the pathology progression-when exaggerated-set a new state, in which a self-checking redox signaling related to the expression of Ins gene expression is impaired. The resulting altered redox signaling, diminished insulin secretion responses to various secretagogues including glucose, may lead to excretion of cytokines or chemokines by β-cells or excretion of endosomes. They could substantiate putative stress signals to the periphery. Subsequent changes and lasting glucolipotoxicity promote islet inflammatory responses and further pathology spiral. Future Directions: Should bring an understanding of the β-cell self-checking and related redox signaling, including the putative stress signal to periphery. Strategies to cure or prevent type 2 diabetes could be based on the substitution of the "wrong" signal by the "correct" self-checking signal.

Antioxidant and Anti-Diabetic Activities of Polysaccharides from Guava Leaves

Guava (Psidium guajava L., Myrtaceae) leaves have been used as a folk herbal tea to treat diabetes for a long time in Asia and North America. In this study, we isolated polysaccharides from guava leaves (GLP), and evaluated its antioxidant activity in vitro and anti-diabetic effects on diabetic mice induced by streptozotocin combined with high-fat diet. The results indicated that GLP exhibited good DPPH, OH, and ABTS free-radical scavenging abilities, and significantly lowered fasting blood sugar, total cholesterol, total triglycerides, glycated serum protein, creatinine, and malonaldehyde. Meanwhile, it significantly increased the total antioxidant activity and superoxide dismutase (SOD) enzyme activity in diabetic mice, as well as ameliorated the damage of liver, kidney, and pancreas. Thus, polysaccharides from guava leaves could be explored as a potential antioxidant or anti-diabetic agents for functional foods or complementary medicine.

Connecting pancreatic islet lipid metabolism with insulin secretion and the development of type 2 diabetes

Obesity is the major contributing factor for the increased prevalence of type 2 diabetes (T2D) in recent years. Sustained positive influx of lipids is considered to be a precipitating factor for beta cell dysfunction and serves as a connection between obesity and T2D. Importantly, fatty acids (FA), a key building block of lipids, are a double-edged sword for beta cells. FA acutely increase glucose-stimulated insulin secretion through cell-surface receptor and intracellular pathways. However, chronic exposure to FA, combined with elevated glucose, impair the viability and function of beta cells in vitro and in animal models of obesity (glucolipotoxicity), providing an experimental basis for the propensity of beta cell demise under obesity in humans. To better understand the two-sided relationship between lipids and beta cells, we present a current view of acute and chronic handling of lipids by beta cells and implications for beta cell function and health. We also discuss an emerging role for lipid droplets (LD) in the dynamic regulation of lipid metabolism in beta cells and insulin secretion, along with a potential role for LD under nutritional stress in beta cells, and incorporate recent advancement in the field of lipid droplet biology.

Advanced lipoxidation end products (ALEs) as RAGE binders: Mass spectrometric and computational studies to explain the reasons why

Advanced Lipoxidation End-products (ALEs) are modified proteins that can act as pathogenic factors in several chronic diseases. Several molecular mechanisms have so far been considered to explain the damaging action of ALEs and among these a pathway involving the receptor for advanced glycation end products (RAGE) should be considered. The aim of the present work is to understand if ALEs formed from lipid peroxidation derived reactive carbonyl species (RCS) are able to act as RAGE binders and also to gain a deeper insight into the molecular mechanisms involved in the protein-protein engagement. ALEs were produced in vitro, by incubating human serum albumin (HSA) with 4-hydroxy-trans− 2-nonenal (HNE), acrolein (ACR) and malondialdehyde (MDA). The identification of ALEs was performed by MS. ALEs were then subjected to the VC1 Pull-Down assay (VC1 is the ligand binding domain of RAGE) and the enrichment factor (the difference between the relative abundance in the enriched sample minus the amount in the untreated one) as an index of affinity, was determined. Computation studies were then carried out to explain the factors governing the affinity of the adducted moieties and the site of interaction on adducted HSA for VC1-binding. The in silico analyses revealed the key role played by those adducts which strongly reduce the basicity of the modified residues and thus occur at their neutral state at physiological conditions (e.g. the MDA adducts, dihydropyridine-Lysine (DHPK) and N-2-pyrimidyl-ornithine (NPO), and acrolein derivatives, N-(3-formyl-3,4-dehydro-piperidinyl) lysine, FDPK). These neutral adducts become unable to stabilize ion-pairs with the surrounding negative residues which thus can contact the RAGE positive residues.

In conclusion, ALEs derived from lipid peroxidation-RCS are binders of RAGE and this affinity depends on the effect of the adduct moiety to reduce the basicity of the target amino acid and on the acid moieties surrounding the aminoacidic target.

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A wide set of ALEs-HSA was obtained by in vitro incubation of HSA with different RCS.

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ALEs-HSA before and after VC1 enrichment were fully characterized by MS.

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Retention efficiency of the identified ALEs-HSA by VC1 was determined.

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Elucidation of structural requirements making an ALE a RAGE binder was obtained by computational studies.

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The mechanism here proposed for ALEs can be considered as a general mechanism of protein-protein interaction.

Lipoproteins as targets and markers of lipoxidation

Lipoproteins are essential systemic lipid transport particles, composed of apolipoproteins embedded in a phospholipid and cholesterol monolayer surrounding a cargo of diverse lipid species. Many of the lipids present are susceptible to oxidative damage by lipid peroxidation, giving rise to the formation of reactive lipid peroxidation products (rLPPs). In view of the close proximity of the protein and lipid moieties within lipoproteins, the probability of adduct formation between rLPPs and amino acid residues of the proteins, a process called lipoxidation, is high. There has been interest for many years in the biological effects of such modifications, but the field has been limited to some extent by the availability of methods to determine the sites and exact nature of such modification. More recently, the availability of a wide range of antibodies to lipoxidation products, as well as advances in analytical techniques such as liquid chromatography tandem mass spectrometry (LC-MSMS), have increased our knowledge substantially. While most work has focused on LDL, oxidation of which has long been associated with pro-inflammatory responses and atherosclerosis, some studies on HDL, VLDL and Lipoprotein(a) have also been reported. As the broader topic of LDL oxidation has been reviewed previously, this review focuses on lipoxidative modifications of lipoproteins, from the historical background through to recent advances in the field. We consider the main methods of analysis for detecting rLPP adducts on apolipoproteins, including their advantages and disadvantages, as well as the biological effects of lipoxidized lipoproteins and their potential roles in diseases.

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Lipoproteins can be modified by reactive Lipid Peroxidation Products (rLPPs).

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Lipoprotein lipoxidation is known to occur in several inflammatory diseases.

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Biochemical, immunochemical and mass spectrometry methods can detect rLPP adducts.

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Due to higher information output, MS can facilitate localization of modifications.

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Antibodies against some rLPPs have been used to identify lipoxidation in vivo.

Cyanidin and delphinidin modulate inflammation and altered redox signaling improving insulin resistance in high fat-fed mice

Consumption of diets high in fat and/or fructose content promotes tissue inflammation, oxidative stress, and insulin resistance, activating signals (e.g. NF-κB/JNK) that downregulate the insulin cascade. Current evidence supports the concept that select flavonoids can mitigate obesity and type 2 diabetes (T2D). This work investigated if supplementation with the anthocyanidins (AC) cyanidin and delphinidin could attenuate the adverse consequences of consuming a high fat diet (HFD) in mice. Consumption of an AC-rich blend mitigated HFD-induced obesity, dyslipidemia and insulin resistance (impaired responses to insulin and glucose). HFD-fed mice were characterized by increased liver lipid deposition and inflammation, which were also attenuated upon AC supplementation. HFD caused liver oxidative stress showing an increased expression of NADPH oxidases, generators of superoxide and H2O2, and high levels of oxidized lipid-protein adducts. This was associated with the activation of the redox sensitive signals IKK/NF-κB and JNK1/2, and increased expression of the NF-κB-regulated PTP1B phosphatase, all known inhibitors of the insulin pathway. In agreement with an improved insulin sensitivity, AC supplementation inhibited oxidative stress, NF-κB and JNK activation, and PTP1B overexpression. Thus, cyanidin and delphinidin consumption either through diet or by supplementation could be a positive strategy to control the adverse effects of Western style diets, including overweight, obesity, and T2D. Modulation of inflammation, oxidative stress, and NF-κB/JNK activation emerge as relevant targets of AC beneficial actions.

Melatonin Supplementation Lowers Oxidative Stress and Regulates Adipokines in Obese Patients on a Calorie-Restricted Diet

Obesity is one of the major global health problems. Melatonin deficiency has been demonstrated to correlate with obesity. The aim of the study was to estimate the effect of melatonin on oxidative stress and adipokine levels in obese patients on a calorie-restricted diet. Thirty obese patients were supplemented with a daily dose of 10 mg of melatonin (n = 15) or placebo (n = 15) for 30 days with a calorie-restricted diet. Serum levels of melatonin, 4-hydroxynonenal (HNE), adiponectin, omentin-1, leptin, and resistin, as well as erythrocytic malondialdehyde (MDA) concentration and Zn/Cu-superoxide dismutase, catalase, and glutathione peroxidase (GPx) activities, were measured at baseline and after supplementation. Significant body weight reduction was observed only in the melatonin group. After melatonin supplementation, the adiponectin and omentin-1 levels and GPx activities statistically increased, whereas the MDA concentrations were reduced. In the placebo group, a significant rise in the HNE and a drop in the melatonin concentrations were found. The results show evidence of increased oxidative stress accompanying calorie restriction. Melatonin supplementation facilitated body weight reduction, improved the antioxidant defense, and regulated adipokine secretion. The findings strongly suggest that melatonin should be considered in obesity management. This trial is registered with CTRI/2017/07/009093.