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

Abstract

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 to drink 1.5 litres daily of bottled ELO water or drinking water.

Results

ELO water raised arterial oxygen tension pO2 significantly 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 by 0.3 ± 0.7% 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.

Introduction

Oxygen is essential for maintenance of life and normal metabolic function in humans but is often overlooked in the management of diseases related to disturbances of metabolism. Numerous disease processes are associated with cellular hypoxia, in particular diabetes mellitus, for which postulated mechanisms include impaired release of oxygen from haemoglobin, slowed haemoglobin oxygen saturation, defective mitochondrial oxidative phosphorylation and impaired insulin signalling. Hyperglycaemia also exacerbates hypoxia which worsens insulin resistance, induces pancreatic beta-cell dysfunction through oxidative stress, and beta-cell de-differentiation which decreases functional beta-cell mass, resulting in a vicious circle of hypoxia and hyperglycaemia.

The challenge of using water as a vehicle for oxygen delivery is the naturally low solubility of oxygen in water in the absence of hyperbaric pressure. If oxygen can be dissolved in water at higher than usual concentrations and its concentration of dissolved oxygen stably maintained in solution in a normobaric environment, it would be possible to use drinking water to deliver oxygen. We identified a commercially available oxygen-enriched bottled drinking water (ELO water) that could stably maintain a higher dissolved oxygen concentration and utilised it to test our hypothesis that gastrointestinal absorption of oxygen in drinking water could raise arterial oxygen level.

Discussion & Key Findings

We demonstrated that drinking ELO oxygen-enriched water was able to raise arterial oxygen levels. It is likely that the oxygen in ELO water was transported through the gut into the bloodstream through aquaporins which transport both water and oxygen. We also found that mitochondrial respiration rates were elevated in cells cultured in ELO water as evidenced by higher oxygen-consumption rates associated with basal respiration and ATP-linked respiration, possibly facilitated by the oxygen-enriched environment.

At high glucose concentrations, we demonstrated that mitochondrial mass and dysfunction decreased in control-water media, consistent with hyperglycaemia causing fragmentation and apoptosis of mitochondria. We additionally found that at high-glucose concentrations, incubation with ELO water preserved mitochondrial mass, and prevented the reduction in mitochondrial membrane potential, a sign of hyperglycaemia-induced mitochondrial dysfunction. Taken together, our findings suggest that ELO water is protective against hyperglycaemia-induced mitochondrial dysfunction and attrition.

ELO water improved glycaemic control within 12 weeks as an adjuvant to standard therapy for type 2 diabetes in our human subjects. The reduction in HbA1c of ~0.3% in the ELO water group occurred without hypoglycaemia or other adverse effects. ELO water was thus associated with a significant improvement in glycaemic control. Placebo water did not significantly improve HbA1c, suggesting that effects of ELO water are related to oxygenation rather than solely from improved hydration.

In conclusion, we found that ELO water raised arterial oxygen levels in animal models, improved cellular oxygenation and altered markers of mitochondrial function, and is an effective adjuvant therapy even in people with longstanding diabetes already on insulin.