Clinical characteristic of patients
The characteristic of the elderly (EA) and non-elderly asthmatics (nEA) is presented in the Table 2. EA showed a more severe airway obstruction both in the large airways (as assessed by spirometry) and in the small airways (as assessed by IOS). Both groups demonstrated a similar level of asthma control and comparable severity according to the GINA criteria. However, EA more frequently reported exacerbation in the last 12 months and received a higher mMRC score.
Table 2
Comparison between elderly and non-elderly asthmatic patients.
|
elderly asthma, n = 28
|
non-elderly asthma, n = 31
|
p
|
women, n/N (%)
|
17/28 (60.71%)
|
19/31 (61.29%)
|
ns
|
age yrs, mean ± SD
|
71 ± 5.4
|
39.5 ± 5.8
|
< 0.001
|
age at asthma diagnosis, yrs, mean ± SD
|
52.3 ± 15.9
|
21.1 ± 13.4
|
< 0.001
|
current smokers, n/N (%)
|
1/28 (3.57%)
|
3/31 (9.68%)
|
ns
|
atopy, n/N (%)
|
13/27 (48.15%)
|
22/25 (88%)
|
0.002
|
BMI, mean ± SD
|
29.3 ± 4.7
|
26.5 ± 6.3
|
0.02
|
FEV1%pred. val., mean ± SD
|
88.4 ± 20.9
|
94.8 ± 15.1
|
ns
|
FEV1%/FVC, mean ± SD
|
64.5 ± 8.9
|
74.1 ± 7.2
|
0.001
|
MEF75/25%pred. val., mean ± SD
|
36.6 ± 17.9
|
64.5 ± 22.5
|
< 0.001
|
R5Hz %pred. value, mean ± SD
|
142.6 ± 59.5
|
125.9 ± 37.7
|
ns
|
abnormal X5 Hz, n/N (%)
|
7/27 (25.93%)
|
9/31 (29.03%)
|
ns
|
δR5-R20% pred., mean ± SD
|
35.2 ± 22.2
|
22.6 ± 19.3
|
0.02
|
δR5-R20 > 20%, n/N (%)
|
20/27 (74.07%)
|
16/31 (51.61%)
|
ns
|
FeNO, ppb, mean ± SD
|
27.2 ± 20.3
|
29.2 ± 25.9
|
ns
|
Asthma control
|
ACT, mean ± SD
|
19.5 ± 5.8
|
21.4 ± 3.7
|
ns
|
ACT < 20 score, n/N (%)
|
11/27 (40.74%)
|
9/31 (29.03%)
|
ns
|
mMRC, mean ± SD
|
1.6 ± 1.2
|
0.9 ± 1
|
0.01
|
Asthma control according to GINA 2017
|
controlled, n/N (%)
|
10/27 (37.04%)
|
17/31 (54.84%)
|
ns
|
partially controlled, n/N (%)
|
9/27 (33.33%)
|
10/31 (32.26%)
|
ns
|
Uncontrolled, n/N (%)
|
8/27 (29.63%)
|
4/31 (12.9%)
|
ns
|
Severity of asthma according to GINA 2017
|
Mild, n/N (%)
|
6/28 (21.43%)
|
2/31 (6.45%)
|
ns
|
Moderate, n/N (%)
|
6/28 (21.43%)
|
9/31 (29.03%)
|
ns
|
Severe, n/N (%)
|
15/28 (53.57%)
|
16/31 (51.61%)
|
ns
|
Exacerbations in the last 12 months
|
Patients with exacerbation/last year, n/N (%)
|
19/28 (67.9%)
|
11/31 (35.5%)
|
0.012
|
Number of comorbidities, mean ± SD
|
6.68 ± 2.57
|
3.58 ± 1.96
|
< 0.001
|
Circulating miRNA expression in non-elderly asthmatics correlated with asthma control and airway inflammation
There was no difference in the serum miRNA expression between the asthmatics and non-asthmatics. However, when the age-stratified groups were compared, the EA subjects had lower expression of miRNA − 19b and miRNA-146a, while the nEA patients had a higher expression of miRNA − 146a than the age-matched controls. The elderly asthmatics had a higher serum expression of miRNA − 106a and miRNA-126a than nEA (Fig. 1). In all asthmatics, the serum miRNA − 106a and miRNA-126a expression levels were correlated with age (r = 0.29, p < 0.0 and r = 0.38, p < 0.05, respectively). In EA, we found a positive correlation between the number of comorbidities and miRNA − 106 and − 126a (r = 0.42, p < 0.0 and r = 0.6, p < 0.05, respectively) (Fig. 2).
Only in the non-elderly asthmatics, the expression of selected miRNAs was associated with the level of asthma control and airway inflammation. The patients with uncontrolled disease according to GINA demonstrated lower serum miRNA-106a and miRNA-126 expression ([Dct]: -0.53 ± 0.3 vs. 0.06 ± 0.42; p = 0.01, and − 2.01 ± 0.54 vs.-1.2 ± 0.86; p = 0.047, respectively). Similarly, the patients with ACT < 19 points had lower miRNA-126a and − 106a expression ([Dct]: -0.47 ± 0.2 vs. 0.17 ± 0.38; p < 0.001 and − 2.08 ± 0.52 vs.-1.03 ± 0.79; p = 0.001, respectively). The non-elderly asthmatics with a history of asthma exacerbation in the past 12 months had a significantly lower expression of miRNA-106a ([Dct]: -0.19 ± 0.53 vs. 0.08 ± 0.37; p = 0.04). ACT was positively correlated with miRNA-106a (r = 0.45, p < 0.05) and with miRNA-126a (r = 0.44, p < 0.05). The FeNO level in the non-elderly asthmatics was negatively correlated with miRNA-106a (r=-062, p < 0.05), -126a (r=-0.6, p < 0.05) and − 146a (r=-0.41, p < 0.05) (Fig. 3).
Elevated levels of systemic inflammation markers were associated with worsened asthma control and the impaired respiratory function as related to age
In all asthmatics (n = 59), the mean TNFα and sTNF RI levels were elevated as compared to the control group (Fig. 4A). The sTNF RI level was correlated with the large airways (FEV1% pred., FVC%pred., PEF%pred, FEV1%FVC, R5Hz% pred.) and the small airways (MEF75-25%pred.; δR5-20Hz) function (Table 3.) as well as positively correlated with mMRC (r = 0.56, p < 0.05).
Table 3
Correlations between respiratory parameters assessed by spirometry and impulse oscillometry and selected serum cytokines concentrations in asthmatic patients (n = 59). For all p < 0.05
|
sTNF RI serum levels
|
IL-6 serum levels
|
Spirometric parameters
|
FEV1% pred.
|
-0.34
|
-0.26
|
MEF75/25% pred
|
-0.37
|
ns
|
FEV1%/FVC
|
-0.31
|
-0.28
|
Oscillometric parametrs
|
R5Hz
|
0.43
|
0.33
|
fres
|
0.44
|
0.32
|
AX
|
0.45
|
0.3
|
δ R5-R20 Hz
|
0.4
|
ns
|
In the EA group, serum levels of TNFα and sTNF RI were higher than in the nEA subjects, and higher as compared to age-matched controls (Fig. 4B.). In the elderly asthmatics, sTNF RI negatively correlated with ACT (r=-0.5; p < 0.05, with the large airway function (FEV1% pred. (r=-0.49, p < 0.05), and positively - with mMRC (r = 0.62, p < 0.05). In the nEA participants, the sTNF RI level was positively correlated with R5 Hz %pred. (r = 0.4, p < 0.05).
IL-6 serum levels in all asthmatic patients positively correlated with mMRC (r = 0.36, p < 0.05) and were associated with a worse respiratory function assessed by both spirometry and IOS (Table 3). In the EA subjects, the IL-6 serum level negatively correlated with ACT (r=-0.42, p < 0.05). In the nEA patients, IL-6 was positively correlated with mMRC (r = 0.43, p < 0.05).
The serum level of IL-8 was significantly lower in the nEA participants than in the age-matched control group (7.1 ± 9.72 pg/ml vs. 8.9 ± 6,57 pg/ml; p = 0.047) and in the EA individuals, the serum level of IL-8 was negatively correlated with FEV1%/FVC (r=-0.62, p < 0.05).
The level of proinflammatory cytokines was increased among asthmatics with small airway obstruction
Some of the asthmatics demonstrated small airways obstruction (SAO) defined as presence of concurrently abnormal R5 Hz %pred., X5 Hz and δ R5-R20 Hz.; the prevalence of SAO was similar in the EA and nEA groups (5/27 (18.52% vs. 6/31 (19.35%), ns). SAO was not present in the healthy controls. Patients with SAO suffered from uncontrolled asthma more frequently (5/11 (45.5%) vs. 6/47 (12.8%), p = 0.02), had a higher number of frequent exacerbations (three and more) in the last 12 months (6/11 (54.5%) vs. 5/47 (10.6%), p = 0.002), more often received extra courses of oCS in the last year (6/11 (54.5%) vs 6/47 (12.8%), p = 0.004) and received a higher mMRC score (1.91 ± 1.22 vs 1.02 ± 1.06, p = 0.04). The level of proinflammatory cytokines was higher in the asthmatics with SAO than in the patients without SAO - sTNF R (1476.04 ± 302.51 pg/ml vs.1231.42 ± 301.23 pg/ml; p = 0.008) and IL-6 (1.64 ± 1.07 pg/ml vs. 1.2 ± 0.9 pg/ml; p = 0.02).
Serum markers of systemic inflammation corelated with miRNA expression
Serum sTNF RI levels in all the asthmatics correlated with miRNA-106a (0.44, p<0.05) and miRNA -126a (r=0.41, p<0.05), while in EA, miRNA -126a was positively correlated with TNF α (r=0.5, p<0.05) and miRNA -146a was negatively correlated with IL-8 (r=-0.41, p<0.05). In the nEA group, there was a positive correlation between the level of sTNF RI and miRNA -106a (r=0.38, p<0.05), -126a (r=0.37, p<0.05) and -146a (r=0.38, p<0.05).