HIGH GLUCOSE INCREASES SUSCEPTIBILITY TO OXIDATIVE-STRESS-INDUCED APOPTOSIS AND DNA DAMAGE IN K-562 CELLS

High Glucose Increases DNA Damage and Elevates the Expression of Multiple DDR Genes

The DNA Damage Response (DDR) pathways sense DNA damage and coordinate robust DNA repair and bypass mechanisms. A series of repair proteins are recruited depending on the type of breaks and lesions to ensure overall survival. An increase in glucose levels was shown to induce genome instability, yet the links between DDR and glucose are still not well investigated. In this study, we aimed to identify dysregulation in the transcriptome of normal and cancerous breast cell lines upon changing glucose levels. We first performed bioinformatics analysis using a microarray dataset containing the triple-negative breast cancer (TNBC) MDA-MB-231 and the normal human mammary epithelium MCF10A cell lines grown in high glucose (HG) or in the presence of the glycolysis inhibitor 2-deoxyglucose (2DG). Interestingly, multiple DDR genes were significantly upregulated in both cell lines grown in HG. In the wet lab, we remarkably found that HG results in severe DNA damage to TNBC cells as observed using the comet assay. In addition, several DDR genes were confirmed to be upregulated using qPCR analysis in the same cell line. Our results propose a strong need for DDR pathways in the presence of HG to oppose the severe DNA damage induced in cells.

Cardiorenal Metabolic Consequences of Nighttime Snacking: Is it an Innocent Eating Behavior?

PURPOSE OF REVIEW

Health consequences of nighttime eating, as a publicly discussed eating behavior type, have been speculated lately. Nighttime eating has been linked to various metabolic outcomes including hyperlipidemia, hypertriglyceridemia, hyperglycemia, weight gain, elevated blood pressure, obesity, and metabolic syndrome, and cardiorenal outcomes such as atherosclerosis, a decline in eGFR, and proteinuria.

RECENT FINDINGS

Although the exact underlying pathophysiological mechanism is not yet clear, multiple hypotheses including disrupted circadian rhythm, altered hormonal levels, and decline in cellular regeneration have been proposed. In this review, we aim to evaluate the growing literature on nighttime eating behavior in terms of metabolic and cardiorenal outcomes, pathophysiological basis, and potential therapeutic alternatives.

Imbalance in the antioxidant defence system and pro-genotoxic status induced by high glucose concentrations: In vitro testing in human liver cells

It has been hypothesized that high glucose concentrations might contribute to the overall intracellular oxidative stress either by the direct generation of reactive oxygen species (ROS) or by altering the redox balance. Moreover, it has also been suggested that high glucose concentration can increase the susceptibility of DNA to genotoxic effects of xenobiotics. The aim of this approach was to test high glucose concentrations for pro-genotoxicity in human liver cells by setting up an in vitro model for hyperglycaemia. The experimental design included performing of tests on both human HepG2 tumour cells and HepaRG immortalized cells. Increased cell susceptibility to genotoxic xenobiotics was tested by challenging cell cultures with 4-nitroquinoline-N-oxide (4NQO) and evaluating the extent of primary DNA damage by comet assay. Moreover, we evaluated the relationship between glucose concentration and intracellular ROS, as well as the effects of glucose concentration on the induction of Nrf2-dependent genes such as Glutathione S-transferases, Heme‑oxygenase-1, and Glutathione peroxidase-4. To investigate the involvement of ROS in the induced pro-genotoxic activity, parallel experimental sets were set up by considering co-treatment of cells with the model mutagen 4NQO and the antioxidant, glutathione precursor N-acetyl-L-cysteine. High glucose concentrations caused a significant increase in the levels of primary DNA damage, with a pro-genotoxic condition closely related to the concentration of glucose in the culture medium when cells were exposed to 4NQO. High glucose concentrations also stimulated the production of ROS and down-regulated genes involved in contrasting of the effects of oxidative stress. In conclusion, in the presence of high concentrations of glucose, the cells are in unfavourable conditions for the maintenance of genome integrity.

High Glucose Affects the Cytotoxic Potential of Rapamycin, Metformin and Hydrogen Peroxide in Cultured Human Mesenchymal Stem Cells

BACKGROUND

Oxidative stress and chronic hyperglycemia are two major side effects of type 2 diabetes affecting all cell types including mesenchymal stem cells (MSCs). As a cell therapy choice, understanding the behavior of MSCs will provide crucial information for efficient treatment.

METHODS

Placental mesenchymal stem cells were treated with various concentrations of glucose, metformin, rapamycin, and hydrogen peroxide to monitor their viability and cell cycle distribution. Cellular viability was examined via the MTT assay. Cell cycle distribution was studied by propidium iodide staining and apoptosis was determined using Annexin Vpropidium iodide staining and flow cytometry. Involvement of potential signaling pathways was evaluated by Western blotting for activation of Akt, P70S6K, and AMPK.

RESULTS

The results indicated that high glucose augmented cell viability and reduced metformin toxic potential. However, the hydrogen peroxide and rapamycin toxicities were exacerbated.

CONCLUSION

Our findings suggest that high glucose concentration has a major effect on placental mesenchymal stem cell viability in the presence of rapamycin, metformin and hydrogen peroxide in culture.

Attenuation of oxidative stress and cardioprotective effects of zinc supplementation in experimental diabetic rats

Oxidative stress plays a major role in the pathogenesis of diabetes mellitus, which further exacerbates damage of cardiac, hepatic and other tissues. We have recently reported that Zn supplementation beneficially modulates hyperglycaemia and hypoinsulinaemia, with attendant reduction of associated metabolic abnormalities in diabetic rats. The present study assessed the potential of Zn supplementation in modulating oxidative stress and cardioprotective effects in diabetic rats. Diabetes was induced in Wistar rats with streptozotocin, and groups of diabetic rats were treated with 5- and 10-fold dietary Zn interventions (0·19 and 0·38 g Zn/kg diet) for 6 weeks. The markers of oxidative stress, antioxidant enzyme activities and concentrations of antioxidant molecules, lipid profile, and expressions of fibrosis and pro-apoptotic factors in the cardiac tissue were particularly assessed. Supplemental Zn showed significant attenuation of diabetes-induced oxidative stress in terms of altered antioxidant enzyme activities and increased the concentrations of antioxidant molecules. Hypercholesterolaemia and hyperlipidaemia were also significantly countered by Zn supplementation. Along with attenuated oxidative stress, Zn supplementation also showed significant cardioprotective effects by altering the mRNA expressions of fibrosis and pro-apoptotic factors (by >50 %). The expression of lipid oxidative marker 4-hydroxy-2-nonenal (4-HNE) protein in cardiac tissue of diabetic animals was rectified (68 %) by Zn supplementation. Elevated cardiac and hepatic markers in circulation and pathological abnormalities in cardiac and hepatic tissue architecture of diabetic animals were ameliorated by dietary Zn intervention. The present study indicates that Zn supplementation can attenuate diabetes-induced oxidative stress in circulation as well as in cardiac and hepatic tissues.

Fructose protects baker's yeast against peroxide stress: potential role of catalase and superoxide dismutase

The negative effects of fructose due to its chronic consumption are well documented, while short-term application of fructose is found to protect different types of cells against oxidative stress. Reactive oxygen species (ROS) are suggested to mediate both the cytotoxic and defensive effects. Here, we compare the influence of glucose and fructose on yeast under H(2)O(2)-induced stress. Under control conditions, fructose-grown comparing with glucose-grown yeast demonstrated higher metabolic activity and ROS level. Therefore, fructose was suggested to provoke a mild stress that resulted in the acquisition of cellular resistance to lethal challenges, which explained the higher survival of fructose-grown yeast under H(2)O(2)-induced shock. Exposure to H(2)O(2) increased ROS level in glucose-grown cells, whereas it decreased the ROS level in fructose-grown cells. Hydrogen peroxide activated superoxide dismutase (SOD) and catalase in both the cell types studied, but glucose-grown cells demonstrated a sharp rise of the activities, while cells grown on fructose showed a broad peak of activation. Thus, fructose is likely to protect the antioxidant enzymes against their inactivation by H(2)O(2). Despite a different type of the enzyme activation in both the studied cell types (glucose- and fructose-grown), a strong positive correlation between SOD and catalase was found. The physiological meaning of this relationship and possible mechanisms of the fructose protective effect are discussed.