In an effort to better understand the relationship of insulin resistance to oxidative stress caused by insufficient levels of oxygen, scientists from the University of Southampton and University College London (UCL) performed experiments at the top of Mt. Everest to study how low oxygen levels are associated with the development of type II diabetes. The scientists who performed the experimentation hope to improve care of critically ill patients who are suffering from hypoxia.
Diabetes is a comprehensively studied metabolic disease whose victims suffer from high blood sugar. Type II diabetes is a condition where the patients’ cells are no longer able to respond to insulin, which normally functions to allow cells to take up glucose from the blood.
To perform the experiment, 24 healthy subjects were selected, all of whom were sea-level natives, all of whom were free of respiratory or cardiovascular disease, and who took no medication. Baseline testing was performed in London, after which they flew to Kathmandu to begin their trek. At Mt. Everest, they were separated into two groups of 12. One of the groups stayed at Everest Base Camp at 5,300 meters, while the other went up the mountain to 8,848 meters. To assess the possible effect of the low oxygen levels atop Mount Everest on physiological indicators of type II diabetes, measurements of glucose control, body weight changes, and biomarkers of inflammation were taken of both groups at six weeks and again at eight weeks.
During the trek, the team became the first to measure blood oxygen level at 8400 meters, on Everest’s balcony. Blood samples were taken from the subjects, and plasma was separated from the blood by centrifugation (spinning the tubes really fast – the blood cells pellet at the bottom of the tube with the liquid plasma above). The samples were then quickly stored in liquid nitrogen and taken back to the UK on dry ice for analysis. The team looked at a number of parameters in the samples: osmolality (the body’s electrolyte-to-water balance), levels of lactate, and creatinine; also hormones involved in regulation of glucose metabolism. Measurements of glucose, insulin and C-peptide levels were taken (C-peptides hold two parts of the insulin molecule together). Peripheral oxygen saturation was assessed the same morning of the day the blood was analyzed, by a pulse oximeter after 10 minutes of rest. To eliminate observational bias, the measurements were taken by different individuals; the subject was not permitted to see the data, and so could not alter the results with biofeedback. Oxidative stress markers (such as might arise from the over-production of reactive oxygen species) and markers of inflammation were also studied.
Mike Grocott, Professor of Anaesthesia and Critical Care at the University of Southampton, and co-founder of UCL CASE Medicine, explained why the study of factors affecting Type II diabetes had to be done on top of Everest. It is supposed by scientists that the fat tissue in obese people is mildly hypoxic. The study was undertaken at the top of Everest to allow a comparison between the mildly hypoxic state in healthy people at high altitudes, with measurements which are normally only seen in obese people at sea level. The results obtained suggest that reducing oxidative stress and inflammation in people with type II diabetes may be useful strategies to slow down the progression of the disease.
By Laura Prendergast