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

Abstract

Background: It has been reported that intermittent exercise in hypoxia environments results inbetterweight loss effect thanexercise in normoxia conditions in individuals with obesity. There has also been a recent report that 1h of exercise in a hypoxic environment resulted in acute improvement of insulin sensitivity and short term glycaemia control in patients with Type 2 diabetes (T2DM). The aim of this study was to examine the effects of 4 weeks exposure to ahypoxic environment,withorwithout exercise, onglucose homeostasis and body weight in obese mice with T2DM. Methods: Eight-week old male C57BL/6 J mice were fed with a high-fat diet (14% protein, 21% carbohydrates and 55% fat) for approximately 12weeks to induce T2DM. Themicewere then allocated into three experimental groupswithn=7 in each: (1) hypoxia at 15%O2, no exercise, (2) hypoxia at 15%O2 and submaximal treadmill exercise and (3) normoxia and submaximal treadmill exercise. These groups were given the corresponding intervention with 1h per session, 6 sessions per week, for 4 weeks. There were also two control groups: (4) normal diet (14% protein, 72% carbohydrates and 4% fat) control group, and (5) diabetes control group (fed by the high-fat diet), both were not exposed to exercise and hypoxia. Before and after the 4 weeks intervention, mice were assessed for fasting blood glucose level (FBS) and weight change. Results: The 4 weeks intervention resulted in a significant reduction of FBS in the three intervention groups (from14.17, 13.74 and 13.87mmol/l to 9.43, 8.83 and 8.86mmol/l, respectively), but no significant difference between pre-FBS and post-FBS in control groups (9.1 vs 9.07mmol/l in the normal control group, and 13.56 vs 13.03mmol/l in the diabetes control group). The body weight of all groups increased during the intervention (an average of 20.8% of increase in the intervention groups, and 56.8% of increase in the control groups); however significant differences between preweight and post-weightwere only found in the two control groups. Discussion: The 4 weeks of intermittent hypoxia intervention reduced the FBS of the obese mice with T2DM to normal level, and sloweddown the trendof theirweight increase. The studyprovided new evidence that intermittent exposure to hypoxia environment for 4 weeks, with or without exercise, can be beneficial in management of blood glucose and body weight in mice with T2DM.