Tumor necrosis factor receptor 2 as a possible marker of COPD in smokers and ex-smokers

Figures & data

Figure 1 Flowchart of study patient disposition.

Table 1 General characteristics of individuals in the study

Variables	Never smokers (n=32)	Smokers (n=32)	COPD I/II (n=32)	P-value
Age (years)	49.5 (46.0–58.5)a	53.0 (51.0–55.0)a,b	64.5 (58.0–74.5)b	<0.001
Sex (M/F)	9/23	7/25	12/20	0.75
BMI (kg/m^2)	26.8±4.5	25.8±3.6	24.4±4.2	0.07
FFM (kg)	47.6±8.4a	46.8±8.9a,b	41.5±10.7b	0.02
FFMI (kg/m^2)	23.3 (20.3–29.8)a	19.8 (17.4–24.3)a,b	18.4 (16.7–22.5)b	0.008
Current smokers (n/%)	0/0	32/100	14/44	<0.001
Smoking history (pack-years)	0a	38.0 (21.5–50.7)b	55.5 (39.5–77.5)c	<0.001
CO (ppm)	0a	10.0 (8.2–15.7)b	0.0 (0–12.0)c	<0.001
FVC (L)	3.6 (3.1–4.0)a	3.0 (2.6–3.4)b,c	2.7 (2.3–3.4)c	<0.001
FVC (% predicted)	102.0 (93.0–110.0)	97.0 (90.0–103.0)	93 (79.5–103.0)	0.06
FEV1 (L)	2.9±0.4a	2.3±0.5b	1.8±0.5c	<0.001
FEV1 (% predicted)	100.8±12.9a	91.1±14.5b	77.4±17.0c	<0.001
FEV1/FVC	0.81 (0.79–0.85)a	0.78 (0.73–0.83)b	0.63 (0.59–0.67)c	<0.001
SpO2 (%)	96.0 (95.0–97.5)	96.0 (95.0–97.0)	95.0 (93.0–97.0)	0.16
Borg Dyspnoea Scale score	0 (0–0)	0 (0–0)	0 (0–0)	1.00

Notes: Values expressed as mean ± standard deviation or median (quartile 1 – quartile 3);

a,b,c Different letters and bold values indicate statistically significant difference. P<0.05. χ², ANOVA and Tukey or Kruskal–Wallis and Dunn’s tests.

Abbreviations: COPD I/II, mild/moderate; GOLD, Global Initiative for Chronic Obstructive Lung Disease; kg, kilogram; m, meter; BMI, body mass index; FFM, fat-free mass; FFMI, fat-free mass index; CO, carbon monoxide; FEV₁, forced expiratory volume in 1 second; FVC, forced volume capacity; SpO₂, pulse oximetry; M, male; F, female; ANOVA, analysis of variance.

Figure 2 AGEs concentrations in never smokers, smokers, and patients with mild/moderate COPD; P<0.05 (Kruskal–Wallis and Dunn’s tests).

Abbreviations: AGEs, advanced glycation end products; NS, no significance.

Figure 3 TNFR2 concentrations in never smokers, smokers, and patients with mild/moderate COPD; P<0.05 (Kruskal–Wallis and Dunn’s tests).

Abbreviations: NS, no significance; TNFR2, tumor necrosis factor alpha receptor 2.

Figure 4 CRP concentrations in never smokers, smokers, and patients with mild/moderate COPD; P<0.05 (Kruskal–Wallis and Dunn’s tests).

Abbreviations: CRP, C-reactive protein; NS, no significance.

Table 2 Predictors of oxidative stress and systemic inflammatory status

Dependent variable	Variables	Coefficient (95% CI)	P-value
AGEs (R^2=0.13)	Age, years	0.031 (0.000–0.000)	0.80
	Male	−0.090 (−0.001–0.001)	0.40
	Smoking (presence)	0.214 (0.000–0.002)	0.04
	COPD (presence)	0.086 (−0.001–0.002)	0.47
	CRP, mg/L	0.217 (0.000–0.000)	0.03
TNFR2 (R^2=0.29)	Age, years	0.23 (0.36–45.15)	0.04
	Male	−0.07 (−629.09–263.45)	0.41
	Smoking (presence)	0.03 (−331.97–479.01)	0.72
	COPD (presence)	0.24 (64.99–1,040.66)	0.02
	CRP, mg/L	0.32 (29.40–104.70)	0.001
CRP (R^2=0.13)	Age, years	0.01 (−0.11–0.13)	0.92
	Male	0.07 (−1.51–3.22)	0.47
	Smoking (presence)	0.22 (0.14–4.40)	0.03
	COPD (presence)	−0.01 (−2.75–2.50)	0.92
	TNFR1, pg/mL	0.31 (0.00–0.05)	0.006
IL-6 (R^2=0.13)	Age, years	0.13 (−0.06–0.20)	0.29
	Male	−0.05 (−3.35–1.90)	0.58
	Smoking (presence)	0.14 (−0.80–4.11)	0.18
	COPD (presence)	0.10 (−1.74–4.17)	0.41
	AGEs, μg/L	0.22 (47.37–1,097.43)	0.03
IL-6 (R^2=0.17)	Age, years	0.239 (−0.017–0.260)	0.08
	Male	−0.019 (−2.856–2.396)	0.86
	Smoking (presence)	0.008 (−2.753–2.929)	0.95
	COPD (presence)	−0.169 (−6.278–2.219)	0.34
	AGEs, μg/L	0.270 (154.986–1,206.115)	0.01
	Interaction (smoking × COPD)	0.335 (0.242–10.989)	0.04
TNFR2 (R^2=0.22)	Age, years	0.33 (12.94–52.24)	0.001
	Male	−0.09 (−704.87–277.05)	0.38
	Interaction (smoking × COPD)	0.10 (−313.46–948.31)	0.32
	FEV1 (% predicted)	−0.22 (−27.20–−0.76)	0.03

Note: Bold represents significant values (P<0.05).

Abbreviations: AGEs, advanced glycation end products; TNFR1, tumor necrosis factor alpha receptor 1; TNFR2, tumor necrosis factor alpha receptor 2; CRP, C-reactive protein; IL-6, interleukin 6; FEV₁, forced expiratory volume in 1 second.