SUN-LB121 Nifedipine Worsens Glucose Tolerance in C57BL/6J Mice Exposed to Intermittent Hypoxia

Background: Intermittent hypoxemia (IH), a pathognomonic component of obstructive sleep apnea (OSA), has been independently associated with development of glucose intolerance, insulin resistance, and type 2 diabetes. L-type calcium channel blockers (CCB) influence glucose homeostasis including insulin sensitivity and secretion. To date, the potential impact of the combined effects of L-type CCB and IH on fasting glycemia and glucose tolerance have not been examined. The objective of this study was to determine whether CCB alters glucose metabolism in a murine model of IH. Methods: Adult male C57BL6/J mice (age 19-week-old) were exposed to IH using an automated system with specially-modified cages that oscillated FiO(2)from 21% to 5.5% at a target rate of 60 events/h during a 12 h (7am – 7pm) light cycle to simulate severe OSA for 5 days. The L-type CCB, nifedipine, or vehicle (polyethleneglycol-400) were administered at a dose of 20mg/kg/day via subcutaneous osmotic pumps (Alzet model 2001). Mice were exposed to IH or intermittent air (IA) with four resulting groups: IA-vehicle (n=12), IH-vehicle (n=16), IA–nifedipine (n=10), and IH–nifedipine (n=13). Fasting glucose, intraperitoneal glucose tolerance test, and insulin levels were obtained after exposures. Results: In the absence of a L-type CCB, IH increased fasting (105.1 vs. 71.2 mg/dL; p<0.001) and 2-hour glucose levels (104.8 vs. 82.0 mg/dL; p=0.003). The area under the glucose tolerance curve (AUC) was also higher with IH than IA in mice treated with vehicle (17896.3 vs.13965.8 mg-min/dL; p<0.001). Although the effects of IH on fasting glucose levels were comparable with and without L-type CCB treatment, the 2-hour glucose levels and the AUCs were substantially different. A statistically significant interaction was noted for the 2-hr glucose levels between IH and treatment with a L-type CCB (IH-CCB: 193.7; IH-V: 122.6; IA-CCB: 103.5; and IA-V: 82.0 mg/dL; p<0.05 for interaction between IH and CCB). Finally, the AUC for IH-CCB treated mice was significantly higher than the AUC for IH-V treated mice (IH-CCB: 30223.1; IH-V: 17896.3. mg-min/dL; p=0.0001) Conclusions: In a murine model of IH, treatment with an L-type CCB exacerbates the deleterious effects of IH on glucose tolerance. Thus, use of CCB in patients with OSA should take into consideration these unfavorable effects particularly in those who are metabolically compromised.