MedicalResearch.com Interview with:
Eric Ravussin, Ph.D., Boyd Professor
Director Nutrition Obesity Research Center
Douglas L. Gordon Chair in Diabetes and Metabolism
Associate Executive Director for Clinical Science
Baton Rouge LA
Medical Research: What is the background of this study?
Dr. Ravussin: It has long been postulated that hypoxia is bad for metabolic health.
Hypoxia of adipose tissue has been thought to cause oxidative stress, resulting in the recruitment of macrophages with resultant secretion of cytokines and inflammation. However, repeated bouts of hypoxia induced during vigorous exercise results in increased glucose uptake and vascularization of muscle tissue. In addition, living at high altitude is associated with a lower prevalence of impaired fasting glucose and type 2 diabetes compared with living at low altitude.
Therefore, we asked the question, “What is the balance between the beneficial effects of hypoxia in muscle tissue and ‘bad’ effects in adipose tissue”? We devised a study in eight healthy men of different ethnicities, put into a hypoxic environment for 10 consecutive nights for 10 hours. The subjects slept in a hypoxic tent, using nitrogen dilution.
Medical Research: What are the main findings of the study?
Dr. Ravussin: The main findings of this study included:
- Adipose tissue hypoxia was confirmed;
- Subjects lost an average of 1.2 kg;
- This study reports for the first time a reduced fasting glucose level and improved whole-body (skeletal muscle) and hepatic insulin sensitivity after nightly exposure to moderate hypoxia.
Medical Research: Were any of the findings unexpected?
Dr. Ravussin: Insulin sensitivity increased a surprising 23%, with a significant improvement in the glucose disposal rate (measured using a hyper-insulinemic euglycemic clamp)
Medical Research: What should clinicians and patients take away from your report?
Dr. Ravussin: Our study suggests that while hypoxia may be bad for adipose tissue, it may not be bad overall in terms of metabolic health. The impact on appetite in particular is interesting, as it is known that individuals often lose weight when exposed to high altitudes. At this point, we can speculate that occasional hypoxia may be somewhat protective against diabetes.
Medical Research: What recommendations do you have for future research as a result of this study?
- First, we have applied for a grant to do a similar study in diabetics, using an oral glucose tolerance test instead of a clamp.
- Second, we would like to examine alternatives to a hypoxic tent, perhaps using a CPAP type mask.
- Third, we would like to study whether less frequent hypoxic exposure, perhaps 1-2 nights per week, would have a beneficial effect on insulin sensitivity and fasting glucose.
Virgile Lecoultre, Courtney M. Peterson, Jeffrey D. Covington, Philip J. Ebenezer, Elizabeth A. Frost, Jean-Marc Schwarz, and Eric Ravussin
Diabetes Care December 2013 36:12 e197-e198; doi:10.2337/dc13-1350 1935-5548