Modification of circulating and cardiac expressions of adiponectin and CINC-1 by intermittent hypoxia in vivo

Abstract

RATIONALE: Adiponectin is an adipokine that exerts anti-inflammatory and cardiovascular protective properties. Obstructive sleep apnea (OSA), characterized by recurrent intermittent hypoxia (IH), is highly associated with cardiovascular diseases. This study aimed to explore the effects of IH on circulating and cardiac expressions of adiponectin and cytokine induced neutrophil chemoattractant (CINC)-1 in the rat model in vivo, thus identifying possible links between OSA and cardiovascular risks. METHODS: Male Sprague-Dawley rats were randomly divided into two groups: control and IH exposed. The IH exposure was performed using OxyCycler A84 System (BioSpherix, Redfield, NY, USA) daily, and composed of cycles of 4 min hypoxia (10% O2) followed by 2 min normoxia (21% O2) for 6 hours. After 14 or 28 days, sera and heart tissues were collected. Circulating and heart tissue levels of adiponectin and CINC-1 were measured by ELISA. RESULTS: IH caused a decrease in serum adiponectin level at 28 days (6.09 ± 0.37 vs 8.24 ± 0.82 μg/ml for IH and control groups respectively; p < 0.05) but not at 14 days, and significant increases in serum CINC-1 level at both 14 days (1.4-fold) and 28 days (1.7-fold). However, cardiac adiponectin level showed a trend of decrease at 14 days but a significant increase at 28 days (0.60 ± 0.048 vs 0.45 ± 0.04 μg/mg protein for IH and control groups respectively; p < 0.05). Cardiac CINC-1 level showed no significant differences at both time points. CONCLUSION: This study suggests that IH-induced reduction in adiponectin and elevation in CINC-1 in serum levels may serve as the possible underlying mechanisms of OSA-related cardiovascular diseases.