The role of nitric oxide in obstructive sleep apnea-induced insulin resistance

Background: Insulin resistance (IR) is a characteristic feature in patients who are developing Type 2 diabetes in the prediabetic stage. Obstructive sleep apnea (OSA) is a breathing disorder characterized by frequent episodes of reduced airflow due to obstruction in the upper airway while sleeping. OSA is associated with intermittent hypoxia and predisposition to increased IR. Aims and Objectives: This study investigates the extent of IR in prediabetics and OSA patients and also compares serum nitric oxide (NO) levels in the three study groups. Materials and Methods: Three groups each comprising of 50 people were selected: Group I - control group; Group II - prediabetic patients; and Group III - OSA patients. Fasting blood glucose, insulin, and NO levels were measured in these subjects and IR calculated. Results: Insulin levels and IR were significantly higher in OSA and prediabetic patients when compared to control subjects. There was no significant difference in insulin levels (P > 0.05) between OSA and prediabetic groups. OSA group had significantly lower level of NO compared to both control and prediabetic groups. Conclusion: High insulin levels and IR in prediabetics indicate that they are prone to develop Type 2 diabetes. The same findings in OSA patients could mean that they are also prone to develop Type 2 diabetes. NO levels are significantly low in OSA patients. Low NO level has been associated with hypoxia; this molecule with its wide array of actions may be involved in glucose homeostasis.