Postgrad Corner: Yun Wang

Published in the July 2016 issue

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Yun Melinda Wang low resYun (Melinda) Wang has long been fascinated by the body’s complex and finely-tuned internal systems. Trained as a medical doctor in China, Melinda spent the first five years of her career working in the respiratory, neurological, gastrointestinal, cardiac, renal and endocrinology departments of the Wu Han No1 hospital before becoming a specialist physician in the endocrinology department. Melinda has also mentored junior medical staff. The Wu Han No 1 hospital is affiliated with the Tong Ji Medical University (also a teaching hospital) where she practised clinical work, took charge of clinical instruction for junior doctors and the interns, and taught clinical classes to medical students.

In 2009 Melinda moved to Australia to study the Master of Public Health at Southern Cross University. After graduation, she returned to China briefly before again relocating to Australia in 2012 to undertake PhD research at SCU.

Melinda’s thesis is ‘Effects and molecular mechanisms of acute and intermittent exposure to hypoxia environment and endurance exercise on glucose homeostasis and insulin resistance in obese mice with Type 2 diabetes’.  She delivered a presentation at a Sports Medicine Australia conference in 2014 about the effects of four weeks’ intermittent exposure to hypoxia environment and/or endurance exercise on glucose homeostasis and body weight in obese mice with Type-2 diabetes.

Her supervisors at SCU are Professor Shi Zhou, Associate Professor Allan Davie and Dr Suzanne Broadbent, all in the School of Health and Human Sciences.

 

PhD thesis: ‘Effects and molecular mechanisms of acute and intermittent exposure to hypoxia environment and endurance exercise on glucose homeostasis and insulin resistance in obese mice with Type 2 diabetes’

Type 2 diabetes (T2D) has become one of the main threats to human health in the 21st century. T2D is the most popular form of diabetes mellitus, accounting for approximately 90 to 95 per cent of diagnosed diabetes in the world. There were 382 million people (aged 20–79 years) with diabetes in 2013, and the prevalence is expected to increase to 592 million by 2035. It is well known that individuals with T2D can gain benefits from regular exercise and weight loss in improving glycaemia control. However, to motivate people to participate in regular exercise is a real challenge. In addition, there is a need for suitable types of interventions for individuals who have limitations in participating in physical activity, such as disability, arthritis or extreme obesity. Therefore, to seek new interventions with better acceptability and minimal side-effects for the prevention and treatment of T2D is still on the agenda of researchers and practitioners. ‘Intermittent hypoxia’ (IH) refers to repeated exposure to hypoxia conditions (air with lower oxygen levels), from minutes to hours, separated by normoxia conditions. During last decade, IH intervention has been explored as a means of therapy for some health conditions, for example, it showed better control of blood pressure in patients with arterial hypertension and beneficial effects on weight control, fasting blood glucose (FBG) and insulin levels in both human and rodents. However, there is a paucity of research on the underlying mechanisms of IH intervention for T2D. We conducted the research that was the first study on acute effects of hypoxia and a long term of repeated IH on T2D mice. The study using animal models provided experimental evidence that is difficult to obtain from human patients in vivo.

The outcomes of the research advanced our knowledge on understanding of the efficacy and mechanisms of IH intervention for T2D. Particularly, the research filled the gaps in the current knowledge on acute effects of hypoxia and long term repeated IH on glucose homeostasis and insulin sensitivity, insulin signalling pathway indicated by GLUT4 translocation, insulin receptor phosphorylation, GSK3 phosphorylation and Akt activity in skeletal muscle, and β-cell function indicated by GLUT2 expression and glucose-stimulated insulin secretion (GSIS) in pancreatic islets in T2D.  Furthermore, it produced new evidence that 1) both a single bout and a long term hypoxia intervention can improve glycaemia control and insulin sensitivity in mice with diet-induced T2D; 2) a single bout of one hour hypoxia intervention can relieve diabetic skeletal muscle insulin resistance via an insulin-independent way and the repeated IH for four weeks can improve skeletal muscle insulin sensitivity by the Akt signalling pathway via insulin-dependent way; and 3) a single bout of one hour hypoxia intervention did not affect islets β-cell function, whereas the repeated IH for four weeks enhanced GSIS. The outcomes of the research may also contribute to the development of effective, alternative and complementary interventions for management of hyperglycaemia and T2D.

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