Metformin reduces mitochondrial ROS levels and improves mitochondrial mass, membrane potential and respiratory complexes in leukocytes of type 2 diabetic subjects

Anesthetic Preconditioning (APC) protects the myocardium from ischemia/reperfusion injury. The cardioprotective effects of APC is diminished or even eliminated in individuals with diabetes mellitus and/or hyperglycemia. The development of patient-specific induced pluripotent stem cells and their differentiation capability has provided us with an in vitro model to study the inefficiency of APC in these individuals.To investigate the underlying mechanisms involved in the attenuation of APC in both diabetic individuals and in hyperglycemia we utilized cardiomyocytes derived from Type 2 diabetic patient and healthy individual iPSCs, (T2DM-iPSCs and N-iPSCs, respectively). Contracting cardiomyocytes were dissociated and selected by the expression of green fluorescent protein under the transcriptional control of myosin light chain-2v. Cardiomyocytes were exposed to varying glucose concentrations (5, 11, and 25 mM). Lactate dehydrogenase (LDH) release was measured using a colorimetric cytotoxicity assay kit and read spectrophotometrically. Mitochondrial membrane potential and reactive oxygen species (ROS) generation were measured with confocal microscopy. APC reduced oxidative stress-induced lactate dehydrogenase (LDH) release in cardiomyocytes derived from both N-iPSCs- and T2DM-iPSCs in 5 and 11 mM glucose concentrations, but not in 25 mM glucose. Baseline membrane potential was similar between non-diabetic- and Type 2 diabetic-derived cardiomyocytes; however 25 mM glucose hyperpolarized the mitochondrial membrane potential. T2DM-iPSC-derived cardiomyocytes had an increase in ROS baseline levels compared to N-iPSC-derived cardiomyocytes. Additionally, high glucose concentrations increased oxidative stress-induced ROS production compared to lower glucose conditions in both cell lines. Our preliminary data shows that high glucose generates excessive ROS and hyperpolarizes the mitochondrial membrane and may contribute to the inefficiency of diabetic and/or hyperglycemic individuals to be anesthetically preconditioned. By utilizing human iPSC-derived cardiomyocytes we can begin to understand the inability of hyperglycemic and diabetic individuals to be anesthetically preconditioned.

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Bioenergetic Analysis of Single Pancreatic β-Cells Indicates an Impaired Metabolic Signature in Type 2 Diabetic Subjects

Endocrinology ◽

10.1210/en.2015-1552 ◽

2015 ◽

Vol 156 (10) ◽

pp. 3496-3503 ◽

Cited By ~ 8

Author(s):

Akos A. Gerencser

Keyword(s):

Insulin Secretion ◽

Membrane Potential ◽

Energy Metabolism ◽

Tricarboxylic Acid Cycle ◽

Atp Synthesis ◽

Tricarboxylic Acid ◽

Β Cells ◽

Acid Cycle ◽

Type 2 Diabetic

Impaired activation of mitochondrial energy metabolism by glucose has been demonstrated in type 2 diabetic β-cells. The cause of this dysfunction is unknown. The aim of this study was to identify segments of energy metabolism with normal or with altered function in human type 2 diabetes mellitus. The mitochondrial membrane potential (ΔψM), and its response to glucose, is the main driver of mitochondrial ATP synthesis and is hence a central mediator of glucose-induced insulin secretion, but its quantitative determination in β-cells from human donors has not been attempted, due to limitations in assay technology. Here, novel fluorescence microscopic assays are exploited to quantify ΔψM and its response to glucose and other secretagogues in β-cells of dispersed pancreatic islet cells from 4 normal and 3 type 2 diabetic organ donors. Mitochondrial volume densities and the magnitude of ΔψM in low glucose were not consistently altered in diabetic β-cells. However, ΔψM was consistently less responsive to elevation of glucose concentration, whereas the decreased response was not observed with metabolizable secretagogue mixtures that feed directly into the tricarboxylic acid cycle. Single-cell analysis of the heterogeneous responses to metabolizable secretagogues indicated no dysfunction in relaying ΔψM hyperpolarization to plasma membrane potential depolarization in diabetic β-cells. ΔψM of diabetic β-cells was distinctly responsive to acute inhibition of ATP synthesis during glucose stimulation. It is concluded that the mechanistic deficit in glucose-induced insulin secretion and mitochondrial hyperpolarization of diabetic human β-cells is located upstream of the tricarboxylic acid cycle and manifests in dampening the control of ΔψM by glucose metabolism.

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Coronary endothelial dysfunction and mitochondrial reactive oxygen species in type 2 diabetic mice

AJP Cell Physiology ◽

10.1152/ajpcell.00234.2013 ◽

2013 ◽

Vol 305 (10) ◽

pp. C1033-C1040 ◽

Cited By ~ 34

Author(s):

Young-Eun Cho ◽

Aninda Basu ◽

Anzhi Dai ◽

Michael Heldak ◽

Ayako Makino

Keyword(s):

Reactive Oxygen Species ◽

Blood Flow ◽

Endothelial Dysfunction ◽

Reactive Oxygen ◽

Oxygen Species ◽

Vascular Relaxation ◽

Mitochondrial Ros ◽

Coronary Endothelial Dysfunction ◽

Type 2 Diabetic

Endothelial cell (EC) dysfunction is implicated in cardiovascular diseases, including diabetes. The decrease in nitric oxide (NO) bioavailability is the hallmark of endothelial dysfunction, and it leads to attenuated vascular relaxation and atherosclerosis followed by a decrease in blood flow. In the heart, decreased coronary blood flow is responsible for insufficient oxygen supply to cardiomyocytes and, subsequently, increases the incidence of cardiac ischemia. In this study we investigate whether and how reactive oxygen species (ROS) in mitochondria contribute to coronary endothelial dysfunction in type 2 diabetic (T2D) mice. T2D was induced in mice by a high-fat diet combined with a single injection of low-dose streptozotocin. ACh-induced vascular relaxation was significantly attenuated in coronary arteries (CAs) from T2D mice compared with controls. The pharmacological approach reveals that NO-dependent, but not hyperpolarization- or prostacyclin-dependent, relaxation was decreased in CAs from T2D mice. Attenuated ACh-induced relaxation in CAs from T2D mice was restored toward control level by treatment with mitoTempol (a mitochondria-specific O2− scavenger). Coronary ECs isolated from T2D mice exhibited a significant increase in mitochondrial ROS concentration and decrease in SOD2 protein expression compared with coronary ECs isolated from control mice. Furthermore, protein ubiquitination of SOD2 was significantly increased in coronary ECs isolated from T2D mice. These results suggest that augmented SOD2 ubiquitination leads to the increase in mitochondrial ROS concentration in coronary ECs from T2D mice and attenuates coronary vascular relaxation in T2D mice.

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Platelets of type 2 diabetic patients are characterized by high ATP content and low mitochondrial membrane potential

Platelets ◽

10.3109/09537100903288422 ◽

2009 ◽

Vol 20 (8) ◽

pp. 588-593 ◽

Cited By ~ 32

Author(s):

Jianmin Ran ◽

Xinmin Guo ◽

Qingmei Li ◽

Guangzhong Mei ◽

Gancheng Lao

Keyword(s):

Membrane Potential ◽

Mitochondrial Membrane Potential ◽

Mitochondrial Membrane ◽

Diabetic Patients ◽

Atp Content ◽

Type 2 Diabetic Patients ◽

Type 2 Diabetic

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Effects of water stably-enriched with oxygen as a novel method of tissue oxygenation on mitochondrial function, and as adjuvant therapy for type 2 diabetes in a randomized placebo-controlled trial

PLoS ONE ◽

10.1371/journal.pone.0254619 ◽

2021 ◽

Vol 16 (7) ◽

pp. e0254619

Author(s):

Joan Khoo ◽

Christoph E. Hagemeyer ◽

Darren C. Henstridge ◽

Sumukh Kumble ◽

Ting-Yi Wang ◽

...

Keyword(s):

Type 2 Diabetes ◽

Membrane Potential ◽

High Glucose ◽

Blood Oxygen ◽

Mitochondrial Mass ◽

Arterial Blood ◽

Arterial Blood Oxygen ◽

Cells Cultured ◽

In Cells

Background Diabetes mellitus is associated with inadequate delivery of oxygen to tissues. Cellular hypoxia is associated with mitochondrial dysfunction which increases oxidative stress and hyperglycaemia. Hyperbaric oxygenation therapy, which was shown to improve insulin sensitivity, is impractical for regular use. We evaluated the effects of water which is stably-enriched with oxygen (ELO water) to increase arterial blood oxygen levels, on mitochondrial function in the presence of normal- or high-glucose environments, and as glucose-lowering therapy in humans. Methods We compared arterial blood oxygen levels in Sprague-Dawley rats after 7 days of ad libitum ELO or tap water consumption. Mitochondrial stress testing, and flow cytometry analysis of mitochondrial mass and membrane potential, were performed on human HepG2 cells cultured in four Dulbecco’s Modified Eagle Medium media, made with ELO water or regular (control) water, at normal (5.5 mM) or high (25 mM) glucose concentrations. We also randomized 150 adults with type 2 diabetes (mean age 53 years, glycated haemoglobin HbA1c 8.9% [74 mmol/mol], average duration of diabetes 12 years) to drink 1.5 litres daily of bottled ELO water or drinking water. Results ELO water raised arterial oxygen tension pO2 significantly (335 ± 26 vs. 188 ± 18 mmHg, p = 0.006) compared with tap water. In cells cultured in control water, mitochondrial mass and membrane potential were both significantly lower at 25 mM glucose compared with 5.5 mM glucose; in contrast, mitochondrial mass and membrane potential did not differ significantly at normal or high glucose concentrations in cells cultured in ELO water. The high-glucose environment induced a greater mitochondrial proton leak in cells cultured in ELO water compared to cells cultured in control medium at similar glucose concentration. In type 2 diabetic adults, HbA1c decreased significantly (p = 0.002) by 0.3 ± 0.7% (4 ± 8 mmol/mol), with ELO water after 12 weeks of treatment but was unchanged with placebo. Conclusions ELO water raises arterial blood oxygen levels, appears to have a protective effect on hyperglycaemia-induced reduction in mitochondrial mass and mitochondrial dysfunction, and may be effective adjuvant therapy for type 2 diabetes.

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