The Contribution of Singlet Oxygen to Insulin Resistance

The Other Side of the Perfect Cup: Coffee-Derived Non-Polyphenols and Their Roles in Mitigating Factors Affecting the Pathogenesis of Type 2 Diabetes

The global prevalence of type 2 diabetes (T2D) is 10.5% among adults in the age range of 20-79 years. The primary marker of T2D is persistent fasting hyperglycemia, resulting from insulin resistance and β-cell dysfunction. Multiple factors can promote the development of T2D, including obesity, inflammation, and oxidative stress. In contrast, dietary choices have been shown to prevent the onset of T2D. Oatmeal, lean proteins, fruits, and non-starchy vegetables have all been reported to decrease the likelihood of T2D onset. One of the most widely consumed beverages in the world, coffee, has also demonstrated an impressive ability to reduce T2D risk. Coffee contains a diverse array of bioactive molecules. The antidiabetic effects of coffee-derived polyphenols have been thoroughly described and recently reviewed; however, several non-polyphenolic molecules are less prominent but still elicit potent physiological actions. This review summarizes the effects of select coffee-derived non-polyphenols on various aspects of T2D pathogenesis.

Updates on Molecular Targets and Epigenetic-Based Therapies for PCOS

Polycystic ovarian syndrome (PCOS) can cause infertility in females due to hyperandrogenism and neuroendocrine abnormalities. The aim of this study is to decipher the impact of endocrine variables, hyperandogenism, insulin resistance, oxidative stress, and dietary conditions in PCOS conditions, subsequently to depict the role of epigenetic factors relative to phenotypic manifestations in PCOS conditions. We have reviewed several metabolic milieus pertinent to PCOS conditions. Comparative efficacies of various PCOS therapies, and recent clinical recommendations for the effective management of PCOS and role of metabolic/endocrine variables in PCOS conditions were described. Comparative therapeutic effects were vividly delineated according to the variable pathophysiology and internal variables during PCOS syndrome on the female body through the formation of cascade of endocrine pathology, which affects working capacity and fosters redox stress-induced cardiovascular, neural, and liver abnormalities. GLP-1 agonists, insulin sensitizers (metformin), and diet and exercise regimens efficacy were explained in enhancing the fertility outcomes among the overweight or obese females with PCOS. Comprehensive appraisal of DNA methylation as epigenetic changes and the manifestations of methylated genes in PCOS conditions were discussed particularly to screen novel molecular targets for developing efficient diagnostic indicators for predicting PCOS risk or its progression. Due to the reversible nature of epigenetic modifications, it is possible to screen the "druggable" regions to target or to correct abnormalities in the gene expression subsequently to develop chromatin-modifying therapies against PCOS.

Significance of Singlet Oxygen Molecule in Pathologies

Reactive oxygen species, including singlet oxygen, play an important role in the onset and progression of disease, as well as in aging. Singlet oxygen can be formed non-enzymatically by chemical, photochemical, and electron transfer reactions, or as a byproduct of endogenous enzymatic reactions in phagocytosis during inflammation. The imbalance of antioxidant enzymes and antioxidant networks with the generation of singlet oxygen increases oxidative stress, resulting in the undesirable oxidation and modification of biomolecules, such as proteins, DNA, and lipids. This review describes the molecular mechanisms of singlet oxygen production in vivo and methods for the evaluation of damage induced by singlet oxygen. The involvement of singlet oxygen in the pathogenesis of skin and eye diseases is also discussed from the biomolecular perspective. We also present our findings on lipid oxidation products derived from singlet oxygen-mediated oxidation in glaucoma, early diabetes patients, and a mouse model of bronchial asthma. Even in these diseases, oxidation products due to singlet oxygen have not been measured clinically. This review discusses their potential as biomarkers for diagnosis. Recent developments in singlet oxygen scavengers such as carotenoids, which can be utilized to prevent the onset and progression of disease, are also described.

Spectroscopy of Laser-Induced Dielectric Breakdown Plasma in Mixtures of Air with Inert Gases Ar, He, Kr, and Xe

The generation of ozone and nitrogen oxides by laser-induced dielectric breakdown (LIDB) in mixtures of air with noble gases Ar, He, Kr, and Xe is investigated using OES and IR spectroscopy, mass spectrometry, and absorption spectrophotometry. It is shown that the formation of NO and NO₂ noticeably depends on the type of inert gas; the more complex electronic configuration and the lower ionization potential of the inert gas led to increased production of NO and NO₂. The formation of ozone occurs mainly due to the photolytic reaction outside the gas discharge zone. Equilibrium thermodynamic analysis showed that the formation of NO in mixtures of air with inert gases does not depend on the choice of an inert gas, while the equilibrium concentration of the NO+ ion decreases with increasing complexity of the electronic configuration of an inert gas.

Omentin-1: A newly discovered warrior against metabolic related diseases

INTRODUCTION

: Chronic metabolism-related diseases are challenging clinical problems. Omentin-1 is mainly expressed in stromal vascular cells of adipose tissue and can also be expressed in airway goblet cells, mesothelial cells, and vascular cells. Omentin-1 has been found to exert important anti-inflammatory, antioxidative and anti-apoptotic roles and to regulate endothelial dysfunction. Moreover, omentin-1 also has protective effects against cancer, atherosclerosis, type 2 diabetes mellitus, and bone metabolic diseases. The current review will discuss the therapeutic potential of omentin-1.

AREAS COVERED

: This review summarizes the biological actions of omentin-1 and provides an overview of omentin-1 in metabolic-related diseases. The relevant literature was derived from a PubMed search spanning 1998-2021 using these search terms: omentin-1, atherosclerosis, diabetes mellitus, bone, cancer, inflammation, and oxidative stress.

EXPERT OPINION

: As a novel adipocytokine, omentin-1 is a promising therapeutic target in metabolic-related diseases. Preclinical animal studies have shown encouraging results. Moreover, circulating omentin-1 has excellent potential as a noninvasive biomarker. In the future, strategies for regulating omentin-1 need to be investigated further in clinical trials in a large cohort.

Astaxanthin, a Marine Carotenoid, Maintains the Tolerance and Integrity of Adipose Tissue and Contributes to Its Healthy Functions

Recently, obesity-induced insulin resistance, type 2 diabetes, and cardiovascular disease have become major social problems. We have previously shown that Astaxanthin (AX), which is a natural antioxidant, significantly ameliorates obesity-induced glucose intolerance and insulin resistance. It is well known that AX is a strong lipophilic antioxidant and has been shown to be beneficial for acute inflammation. However, the actual effects of AX on chronic inflammation in adipose tissue (AT) remain unclear. To observe the effects of AX on AT functions in obese mice, we fed six-week-old male C57BL/6J on high-fat-diet (HFD) supplemented with or without 0.02% of AX for 24 weeks. We determined the effect of AX at 10 and 24 weeks of HFD with or without AX on various parameters including insulin sensitivity, glucose tolerance, inflammation, and mitochondrial function in AT. We found that AX significantly reduced oxidative stress and macrophage infiltration into AT, as well as maintaining healthy AT function. Furthermore, AX prevented pathological AT remodeling probably caused by hypoxia in AT. Collectively, AX treatment exerted anti-inflammatory effects via its antioxidant activity in AT, maintained the vascular structure of AT and preserved the stem cells and progenitor's niche, and enhanced anti-inflammatory hypoxia induction factor-2α-dominant hypoxic response. Through these mechanisms of action, it prevented the pathological remodeling of AT and maintained its integrity.

ROS systems are a new integrated network for sensing homeostasis and alarming stresses in organelle metabolic processes

Reactive oxygen species (ROS) are critical for the progression of cardiovascular diseases, inflammations and tumors. However, the mechanisms of how ROS sense metabolic stress, regulate metabolic pathways and initiate proliferation, inflammation and cell death responses remain poorly characterized. In this analytic review, we concluded that: 1) Based on different features and functions, eleven types of ROS can be classified into seven functional groups: metabolic stress-sensing, chemical connecting, organelle communication, stress branch-out, inflammasome-activating, dual functions and triple functions ROS. 2) Among the ROS generation systems, mitochondria consume the most amount of oxygen; and nine types of ROS are generated; thus, mitochondrial ROS systems serve as the central hub for connecting ROS with inflammasome activation, trained immunity and immunometabolic pathways. 3) Increased nuclear ROS production significantly promotes cell death in comparison to that in other organelles. Nuclear ROS systems serve as a convergent hub and decision-makers to connect unbearable and alarming metabolic stresses to inflammation and cell death. 4) Balanced ROS levels indicate physiological homeostasis of various metabolic processes in subcellular organelles and cytosol, while imbalanced ROS levels present alarms for pathological organelle stresses in metabolic processes. Based on these analyses, we propose a working model that ROS systems are a new integrated network for sensing homeostasis and alarming stress in metabolic processes in various subcellular organelles. Our model provides novel insights on the roles of the ROS systems in bridging metabolic stress to inflammation, cell death and tumorigenesis; and provide novel therapeutic targets for treating those diseases. (Word count: 246).

Conditioned medium of adipose derived Mesenchymal Stem Cells reverse insulin resistance through downregulation of stress induced serine kinases

Insulin resistance (IR) is a constituent part of Type 2 Diabetes Mellitus (T2DM). Conditioned medium from Adipose derived Mesenchymal Stem Cells (ADMSCs-CM) has been shown to reverse IR. However, its effect on cellular stress is not well established. The objective of this study was to explore the effect of ADMSCs-CM on reactive oxygen species, mitochondrial membrane potential (ΔΨm), endoplasmic reticulum (ER) stress and expression of oxidative and inflammatory stress induced serine kinases (SISK) which are pathophysiologically linked to IR. In insulin resistant, 3T3-L1 adipocytes and C2C12 myoblast cell culture models, glucose uptake was assayed by 2-NBDG uptake. Immunomodulatory cytokines, intracellular reactive oxygen species generation, ΔΨm and protein expression of JNK1, IKKβ and phospho-IRS1 (307) were analyzed using FACS. mRNA expression of ER stress markers (CHOP1 and IRE1) and SISK (JNK1, IKKβ, ERK1 and S6K1) were analyzed using RT-PCR. ADMSCs-CM effectively improve glucose uptake as evidenced by 2-NBDG uptake assay. FACS analysis showed that ADMSCs-CM possessed significantly higher levels of IL-6 and IL-10. ADMSCs-CM decreased intracellular generation of reactive oxygen species where it restored ΔΨm in C2C12 cells. ADMSCs-CM mediated reduction in ER stress was confirmed by down-regulation in CHOP1 and IRE1 mRNA expression. ADMSCs-CM treatment showed significant down-regulation of SISK mRNA expression including IKKβ, JNK, ERK and S6K1. Our results unequivocally demonstrate for the first time the mechanism of action of ADMSCs-CM in amelioration IR by reducing oxidative and inflammatory cellular stress. This study identifies SISK as potential therapeutic targets for T2DM therapy.

Lysine Reacts with Cholesterol Hydroperoxide to Form Secosterol Aldehydes and Lysine-Secosterol Aldehyde Adducts

Two cholesterol secosterol aldehydes, namely, 3β-hydroxy-5-oxo-5,6-secocholestan-6-al (secosterol A) and its aldolization product 3β-hydroxy-5β-hydroxy-B-norcholestane-6β-carboxyaldehyde (secosterol B), are highly bioactive compounds which have been detected in human tissues and potentially contribute to the development of physiological dysfunctions such as atherosclerosis, Alzheimer’s disease, diabetes, and cancer. They were originally considered to be exclusive products of cholesterol ozonolysis and thus to be evidence for endogenous ozone formation. However, it was recently postulated that primary amines such as lysine may catalyse their formation from cholesterol-5α-hydroperoxide (Ch-5α-OOH), the main product of the oxidation of cholesterol with singlet oxygen. This involves cyclization of Ch-5α-OOH to an unstable dioxetane intermediate, which decomposes to form secosterol aldehydes with triplet carbonyl groups, whose return to the singlet state is at least partly coupled to the conversion of triplet molecular oxygen to singlet oxygen. Here, we subjected cholesterol to photosensitized oxidation, which predominantly produces Ch-5α-OOH and minor amounts of the 6α- and 6β-hydroperoxides, exposed the hydroperoxide mixture to lysine in the presence of the antioxidant 2,6-ditertiary-butyl-4-hydroxytoluene (BHT), and analysed the reaction mixture by liquid chromatography-electrospray ionization-mass spectrometry. Consistent with the postulated lysine-catalysed formation of secosterol aldehydes, we detected formation of the latter and several types of their lysine adducts, including carbinolamines, Schiff’s bases, and amide-type adducts. We propose that the amide type adducts, which are major biomarkers of lipid oxidation, are mainly formed by singlet oxygen-mediated oxidation of the carbinolamine adducts.

Silicon dioxide nanoparticles induce insulin resistance through endoplasmic reticulum stress and generation of reactive oxygen species

Background

Silicon dioxide nanoparticles (SiO₂ NPs) are one of the most widely utilized NPs in various food sectors. However, the potential endocrine toxicity of SiO₂ NPs has not been characterized.

Results

In the present study, mice were orally administered a series of doses of SiO₂ NPs. All doses of SiO₂ NPs were absorbed into the blood, liver, and pancreas of the mice. Administration of 100 mg/kg bw (body weight) of SiO₂ NPs significantly increased blood glucose levels in mice. However, the same dose of SiO₂ fine-particles (FPs) did not result in altered blood glucose. Whole-genome analysis showed that SiO₂ NPs affected the expression of genes associated with reactive oxygen species (ROS) production and endoplasmic reticulum (ER) stress. In addition, we showed that SiO₂ NPs activated xenobiotic metabolism, resulting in ER stress. Endoplasmic reticulum stress resulted in increased ROS production, which activated the NF-κB pathway leading to expression of inflammatory cytokines. Increased inflammatory cytokine expression resulted in serine phosphorylation of IRS1, which induced insulin resistance (IR). Furthermore these inflammatory cytokines activated the MAPK pathway, which further promoted the serine phosphorylation of IRS1. Insulin resistance resulted in elevated blood glucose. The ER stress inhibitor 4-phenylbutyric acid (4-PBA) inhibited SiO₂ NP-induced ROS production. The ROS scavenger N-acetylcysteine (NAC) did not affect SiO₂ NP-induced ER stress, but inhibited SiO₂ NP-induced activation of the NF-κB and MAPK pathways, expression of inflammatory cytokines, SiO₂ NP-induced serine phosphorylation of IRS1, and SiO2 NP-induced elevations of blood glucose.

Conclusion

Silicon dioxide NPs induced IR through ER stress and generation of ROS, but SiO₂ FPs did not. Therefore, lifelong exposure of humans to SiO₂ NPs may result in detrimental effects on blood glucose. The results of this study strongly suggested that non-nanoformed SiO₂ should be used as food additives.

Mechanisms of titanium dioxide nanoparticle-induced oxidative stress and modulation of plasma glucose in mice

Titanium dioxide nanoparticles (TiO₂ NPs) are reported to increase plasma glucose levels in mice at specific doses. The production and accumulation of reactive oxygen species (ROS) is potentially the most important factor underlying the biological toxicity of TiO₂ NPs but the underlying mechanisms are unclear at present. Data from genome-wide analyses showed that TiO₂ NPs induce endoplasmic reticulum (ER) stress and ROS generation, leading to the inference that TiO₂ NP-induced ER stress contributes to enhancement of ROS in mice. Resveratrol (Res) effectively relieved TiO₂ NP-induced ER stress and ROS generation by ameliorating expression of a common set of activated genes for both processes, signifying that ER stress and ROS are closely related. TiO₂ NP-induced ER stress occurred earlier than ROS generation. Upon treatment with 4-phenylbutyric acid to relieve ER stress, plasma glucose levels tended toward normal and TiO₂ NP increased ROS production was inhibited. These results suggest that TiO2 NP-induced ER stress promotes the generation of ROS, in turn, triggering increased plasma glucose levels in mice. In addition, Res that displays the ability to reduce ER stress presents a dietary polyphenol antioxidant that can effectively prevent the toxicological effects of TiO₂ NPs on plasma glucose metabolism.

Molecular mechanisms underlying zinc oxide nanoparticle induced insulin resistance in mice

Zinc oxide nanoparticles (ZnO NPs) represent an important class of commercially applied materials. Recently, adverse effects of ZnO NPs were found in humans and animals following ingestion, although the effects on endocrine system disease remain unclear. In this study, ZnO NPs were orally administered to mice, and at doses of 25 mg/kg bw (body weight) ZnO NPs and above, plasma glucose increased significantly. The genome-wide effects of ZnO NPs were then investigated using RNA-sequencing technology. In the cluster analysis, the most significantly enriched Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways concerned membranes and their close association with endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) generation. Biochemical and gene and protein expression analyses revealed that ZnO NPs activated a xenobiotic biodegradation response and increased the expression of cytochrome P450 (CYP) enzymes in mice livers, leading to ER stress. The ER stress increased ROS generation. The high levels of ROS activated the MAPK and NF-κB pathways and induced an inflammation response, resulting in the phosphorylation of insulin receptor substrate 1. Thus, the insulin resistance that developed was the primary mechanism for the increase in the plasma glucose of mice treated orally with ZnO NPs.

Evidence for the Formation of Ozone (or Ozone-Like Oxidants) by the Reaction of Singlet Oxygen with Amino Acids

Antibodies or some amino acids, namely, cysteine, methionine, histidine, and tryptophan, were previously reported to catalyse the conversion of singlet oxygen (1O2) to ozone (O3). The originally proposed mechanism for such biological ozone formation was that antibodies or amino acids catalyse the oxidation of water molecules by singlet oxygen to yield dihydrogen trioxide (HOOOH) as a precursor of ozone and hydrogen peroxide (H2O2). However, because HOOOH readily decomposes to form water and singlet oxygen rather than ozone and hydrogen peroxide, an alternative hypothesis has been proposed; ozone is formed due to the reaction of singlet oxygen with amino acids to form polyoxidic amino acid derivatives as ozone precursors. Evidence in support of the latter hypothesis is presented in this article, in that in the presence of singlet oxygen, methionine sulfoxide (RS(O)CH3), an oxidation product of methionine (RSCH3), was found to promote reactions that can best be attributed to the trioxidic anionic derivative RS+(OOO−)CH3 or ozone.

Cellular Stresses and Stress Responses in the Pathogenesis of Insulin Resistance

Insulin resistance (IR), a key component of the metabolic syndrome, precedes the development of diabetes, cardiovascular disease, and Alzheimer's disease. Its etiological pathways are not well defined, although many contributory mechanisms have been established. This article summarizes such mechanisms into the hypothesis that factors like nutrient overload, physical inactivity, hypoxia, psychological stress, and environmental pollutants induce a network of cellular stresses, stress responses, and stress response dysregulations that jointly inhibit insulin signaling in insulin target cells including endothelial cells, hepatocytes, myocytes, hypothalamic neurons, and adipocytes. The insulin resistance-inducing cellular stresses include oxidative, nitrosative, carbonyl/electrophilic, genotoxic, and endoplasmic reticulum stresses; the stress responses include the ubiquitin-proteasome pathway, the DNA damage response, the unfolded protein response, apoptosis, inflammasome activation, and pyroptosis, while the dysregulated responses include the heat shock response, autophagy, and nuclear factor erythroid-2-related factor 2 signaling. Insulin target cells also produce metabolites that exacerbate cellular stress generation both locally and systemically, partly through recruitment and activation of myeloid cells which sustain a state of chronic inflammation. Thus, insulin resistance may be prevented or attenuated by multiple approaches targeting the different cellular stresses and stress responses.

Role of disturbed fatty acids metabolism in the pathophysiology of diabetic erectile dysfunction

BACKGROUND

Vasculogenic erectile dysfunction (VED) is considered as a common complication among people with type 2 diabetes (T2D). We tested whether changes in fatty acid (FAs) classes measured in erythrocytes are associated with increased risk of diabetic VED along with related risk factors.

METHODS

We assessed erythrocyte FAs composition, lipid peroxidation parameters and inflammatory cytokines among 72 T2D men with VED, 78 T2D men without VED and 88 healthy volunteers with similar age. Biochemical, hepatic, lipid and hormonal profiles were measured.

RESULTS

T2D people with VED had significant decrease in the indexes of Δ6-desaturase and elongase activities compared to the other studied groups. The same group of participants displayed lower erythrocytes levels of dihomo-γ-linolenic acid (C20:3n-6) (P < .001), precursor of the messenger molecule PGE1 mainly involved in promoting erection. Moreover, absolute SFAs concentration and HOMA IR levels were higher in T2D people with VED when compared to controls and associated with impaired NO concentration (1.43 vs 3.30 ng/L, P < .001). Our results showed that IL-6 and TNF-α were significantly increased and positively correlated with MDA levels only in T2D people with VED (r = 0.884, P = .016 and r = 0.753, P = .035; respectively) suggesting a decrease in the relative availability of vasodilator mediators and an activation of vasoconstrictors release.

CONCLUSION

Our findings show that the deranged FAs metabolism represents a potential marker of VED in progress, or at least an indicator of increased risk within men with T2D.