Translational studies on mitochondrial function and hypoxia in complications of diabetes mellitus

Abstract

Diabetes Mellitus (DM) is a major concern for societies and healthcare systems globally. DM-associated morbidity and mortality is mediated by diabetic complications. Hypoxia and oxidative stress have emerged as key players in the pathogenesis of various macro- and microvascular complications of DM. This work aimed to investigate different aspects of the relationship between hypoxia, regulation of hypoxia inducible factor-1 (HIF-1), mitochondrial function and the development of common DM complications from a translational perspective.

Paper I investigates the endogenous antioxidant Coenzyme Q10 in a Swedish cohort of DM patients. We explored the association between markers of oxidative stress and the prevalence of vascular complications of DM. Our results showed hyperlipidemia, hyperglycemia, and inflammation to be associated with markers of oxidative stress, which in turn was correlated to the prevalence of diabetes complications such as peripheral neuropathy. In Paper II, we investigated a novel epoxidated Tocotrienol derivative exhibiting antioxidative properties affecting mitochondrial function. Mono-epoxy-tocotrienol-alpha was seen to stimulate pro-wound healing processes such as fibroblast migration rates and endothelial tube formation in vitro. The compound was also shown to increase wound closure rates in diabetic mice. This paper demonstrated experimentally that modulating mitochondrial function can improve factors underlying deficient wound healing in DM. The association between hypoxia regulation, wound healing and cellular bioenergetics in DM was studied in Paper III. HypoxamiR-210 (miR-210) is induced by HIF-1 in response to hypoxia. We found that hyperglycaemia reduced hypoxia-dependent miR-210 induction. miR- 210 increased the rate of wound healing in diabetic mice. The same treatment reduced oxygen consumption rate and ROS production in wound tissue. We thus showed that the hypoxia associated dysregulation in wound healing can be reversed through miR-210-mediated improvement of cellular metabolism. Finally, Paper IV explored the relationship between HIF-1 repression by hyperglycemia and overproduction of ROS in DM. Using a translational approach employing cell cultures, mice and human subjects exposed to hypoxic conditions, we showed that HIF-1-deficient induction of ROS production is specific feature in DM. Reversing this process was shown to be a protective factor against diabetic nephropathy. Hence, reversing impaired HIF-1 function is a potential therapeutic target in the treatment of DM complications.