Background: Obstructive sleep apnea (OSA) is often associated with multisystem damage. The gut is a pivotal organ that initiates the pathophysiological processes of multisystem diseases. Intermittent hypoxia resulting from OSA may impair the intestinal barrier prior to the induction of systemic inflammation. We hypothesize that the intestinal barrier markers D-lactic acid (D-LA) and intestinal fatty acid-binding protein (I-FABP) levels would be higher in patients with OSA.
Methods: Consecutive snoring and nonsnoring adults were included in this study and were grouped based on their apnea-hypopnea index (AHI) scores: the control group (AHI < 5) and the OSA group (AHI ≥ 5). Plasma D-LA and I-FABP levels were measured using colorimetry and ELISA, respectively. Other parameters, such as fasting levels of lipids, routine blood tests, and glucose were also assessed.
Results: Of 76 participants, patients in the OSA group accounted for 73% (55/76). Plasma D-LA and I-FABP levels were significantly higher in patients with OSA [7.90 (7.42) (IQR) vs. 0.88 (2.79) (IQR) mmol/L, p < 0.001 and 1851.99 ± 754.23 (SD) vs. 1131.98 ± 383.38 pg/mL, p < 0.001, respectively]. Increased glucose, triglycerides (TGs), leukocytes, neutrophils, and monocytes but decreased high density lipoprotein (HDL) were also found in patients with OSA. It was also observed that the increase in D-LA and I-FABP exhibited the strongest positive association with AHI (r = 0.443, p < 0.001; r = 0.645, p < 0.001), followed by the lowest SaO2 (p ≤ 0.001), BMI (p ≤ 0.017), glucose (p ≤ 0.011), and TGs (p ≤ 0.025). Moreover, multivariate regression analysis showed that D-LA (B = 0.823, p < 0.001) and I-FABP (B = 0.002, p = 0.017) were independently associated with OSA.
Conclusions: The systemic expression of D-LA and I-FABP is dramatically higher in OSA patients, suggesting that hypoxia resulting from OSA might have the capacity to impair the intestinal barrier prior to the induction of multisystem dysfunction.
Keywords: D-lactic acid (D-LA); Intestinal barrier; Intestinal fatty acid; Obstructive sleep apnea; binding protein (I-FABP).