Reduced systemic levels of IL-10 are associated with the severity of obstructive sleep apnea and insulin resistance in morbidly obese humans

Abstract

Obstructive sleep apnea (OSA) has been related to elevation of inflammatory cytokines and development of insulin resistance in morbidly obese (MO) subjects. However, it is still unclear whether the systemic concentration of anti-inflammatory mediators is also affected in MO subjects directly related to the severity of OSA and level of insulin resistance. Normal weight and MO subjects were subjected to overnight polysomnography in order to establish the severity of OSA, according to the apnea-hypopnea index (AHI). Blood samples were obtained for estimation of total cholesterol and triglycerides, insulin, glucose, insulin resistance, tumor necrosis factor alpha (TNF-α), interleukin 12 (IL12), and interleukin 10 (IL-10). Serum levels of IL-10 were significantly lower in MO subjects with OSA than in MO and control individuals without OSA. Besides being inversely associated with serum TNF-α and IL-12, decreased IL-10 levels were significantly related to increased AHI, hyperinsulinemia, and insulin resistance. Serum IL-10 is significantly reduced in morbidly obese subjects with severe OSA while also showing a clear relationship with a state of hyperinsulinemia and insulin resistance probably regardless of obesity in the present sample. It may be of potential clinical interest to identify the stimulatory mechanisms of IL-10 in obese individuals with OSA.

Figure 1

(a) Box plot of circulating IL-10 levels for control, MO, and MO+OSA subjects. Data are expressed as the median and interquartile range in a box plot analysis. (b) Correlation between AHI and IL-10 circulating levels. AHI was negatively correlated with IL-10 levels. Coefficient r and P values were calculated by the Spearman's correlation model. The correlation level was considered significant when P < 0.05. ^∗ P < 0.05 and ^∗∗ P < 0.001.

Figure 2

Circulating levels of IL-10 showed a negative significant association with (a) insulin levels and (b) HOMA-IR index. In contrast, AHI values were positively associated with (c) Insulin levels and (d) HOMA-IR index. Coefficient r and P values were calculated using Spearman's correlation model. The correlation level was considered significant when P < 0.05.