Enhancement of glucose toxicity by hyperbaric oxygen exposure in diabetic rats

The side effects of hyperbaric oxygen (HBO) treatment, such as oxidative stress and oxygen toxicity, have long been of interest. However, there are no comprehensive studies evaluating such toxic effects in diabetes mellitus (DM). The purpose of this study was to determine the effects of HBO on glucose homeostasis and histological changes in pancreatic beta-cells of experimentally induced diabetic rats. A total of 24 male Wistar rats were randomly divided into 4 groups: 1) Control group, no diabetic induction without HBO treatment; 2) HBO group, exposed to 100% oxygen at 2.8 ATA (atmosphere absolute) for 2 h once daily, for 7 days; 3) DM group, diabetes induced by streptozotocin (STZ) injection; and 4) DM + HBO group, received both STZ injection and HBO exposure. HBO treatment, with clinically recommended pressures and duration of therapy, was started on day 5 after STZ injection, when the blood glucose levels were significantly increased. After the last HBO treatment, the pancreatic tissues were immunostained to measure the areas of insulin immunoreactive beta-cells in the islets of Langerhans. The blood glucose increased significantly following exposure to HBO, with the highest levels achieved in rats, which had been treated with both HBO and diabetic induction. The area populated with insulin immunoreactive beta-cells decreased significantly following diabetic induction and/or HBO exposure, with the smallest area in DM + HBO group. Thus, HBO exposure enhanced the cytotoxic effect of STZ in the beta-cells of the pancreas. HBO should be cautiously employed in diabetic patients.