High day-to-day and diurnal variability of oxidative stress and inflammation biomarkers in people with type 2 diabetes mellitus and healthy individuals

Figures & data

Table 1. Participant characteristics.

	CON (n = 10)	T2D (n = 10)
Diabetes duration (years)	–	3.1 ± 1.8*
Female (n, %)	3 (30%)	3 (30%)
Age (years)	52.8 ± 10.1	53.4 ± 8.1
Height (cm)	1.79 ± 0.09	1.76 ± 0.09
Weight (m)	92.9 ± 19.1	87.7 ± 15.2
BMI (kg/m^2)	28.5 ± 4.2	28.3 ± 3.8
Waist girth (cm)	104.4 ± 13.8	107.1 ± 27.5
HbA1c (%)	5.46 ± 0.22	6.35 ± 0.97*
Glucose (mmol/L)	5.26 ± 0.47	7.28 ± 1.84*
HOMA-IR	1.7 ± 0.7	2.2 ± 0.7
Cholesterol (mmol/L)	5.04 ± 0.53	5.04 ± 1.08
Triglycerides (mmol/L)	1.25 ± 0.57	1.90 ± 1.12
HDL (mmol/L)	1.40 ± 0.48	1.24 ± 0.36
LDL (mmol/L)	3.08 ± 0.42	2.95 ± 1.04
Hb (g/dl)	14.5 ± 0.9	14.7 ± 1.3
hs-CRP	1.28 ± 0.90	2.51 ± 2.70

NB. * denotes difference between T2D and CON (p < 0.05). BMI – body mass index, HbA1c – glycated haemoglobin, HOMA-IR – homeostatic model assessment – insulin resistance, HDL – high density lipoprotein cholesterol, LDL – low density lipoprotein cholesterol, Hb – haemoglobin, hs-CRP – high sensitivity C-reactive protein.

Figure 1. Concentration of plasma inflammatory biomarkers in participants with type 2 diabetes and healthy control (mean ± SD). N.B. TNF-α – Tumour necrosis factor alpha.

Figure 2. Concentration of plasma oxidative stress biomarkers in participants with type 2 diabetes and healthy control (mean ± SD).

Table 2. Median (IQR) and intraclass correlation coefficient (90% CI) for inflammatory and oxidative stress biomarkers.

	Median (IQR)		Intraclass correlation coefficient (90% CI)
	T2D	CON	T2D	CON
Inflammation
Interleukin-10 (pg/mL)	14.78 (24.24)	8.96 (9.04)	0.53 (0.29–0.78)	0.20 (0.00–0.52)
Interleukin-8 (pg/mL)	2.04 (2.05)	1.45 (1.15)	0.41 (0.18–0.70)	0.53 (0.29–0.78)
Interleukin-6 (pg/mL)	2.93 (6.67)	1.88 (1.65)	0.46 (0.22–0.73)	0.64 (0.42–0.85)
Tumour necrosis factor-α (pg/mL)	3.03 (3.27)	1.96 (2.24)	0.39 (0.16–0.69)	0.32 (0.09–0.63)
Oxidative stress
F2-isoprostane (pg/mL)	171.34 (71.22)	173.15 (96.94)	0.19 (0.00–0.52)	0.40 (0.17–0.69)
Glutathione peroxidase activity (U/L)	106.65 (10.01)	105.20 (9.37)	0.47 (0.22–0.75)	–
Total antioxidant capacity (mmol/L)	1.50 (0.25)	1.46 (0.26)	0.19 (0.00–0.51)	0.01 (−0.12–0.28)
Protein carbonyls (U/mg protein)	0.61 (0.28)	0.66 (0.23)	–	–

Table 3. Average intra-individual coefficients of variation (CV) for inflammatory and oxidative stress biomarkers (%).

	Combined (average of 6 timepoints)		Afternoon (average of 3 timepoints)		Morning (average of 3 timepoints)
	T2D	CON	T2D	CON	T2D	CON
Interleukin-10	77.7	64.0	79.7	52.3	84.1	63.7
Interleukin-6	92.1	66.9	93.4*	60.1*	79.9	59.9
Interleukin-8	62.8	55.3	64.4	50.0	67.8	53.6
Tumour necrosis factor-α	79.6	78.4	82.8	63.1	76.2	73.6
F2-isoprostanes	31.2	29.7	28.0	24.9	32.8	29.9
Glutathione peroxidase activity	10.9	9.3	9.7	8.5	6.6	8.6
Total antioxidant capacity	7.4	8.7	7.1	6.4	7.4	8.3
Protein carbonyls	27.4	28.5	30.3	34.2†	27.8	23.7†

N.B. * denotes a difference between groups, † denotes a diurnal difference.

Table 4. Average inter-individual coefficients of variation (CV) for inflammatory and oxidative stress biomarkers (%).

	Combined (average of 6 timepoints)		Afternoon (average of 3 timepoints)		Morning (average of 3 timepoints)
	T2D	CON	T2D	CON	T2D	CON
Interleukin-10	190.4	195.1	167.7	186.3	161.5	114.1
Interleukin-6	259.0	194.4	164.6	154.5	186.0	167.1
Interleukin-8	100.9	143.7	97.2	134.6	98.0	102.0
Tumour necrosis factor-α	162.7	187.8	121.4	123.8	136.4	135.8
F2-isoprostanes	41.1	43.0	34.7	38.0	46.7	45.7
Glutathione peroxidase activity	17.1	10.2	16.6	10.4	7.8	8.9
Total antioxidant capacity	8.8	8.6	8.8	7.2	8.9	8.1
Protein carbonyls	29.1	29.1	29.5	29.5	27.3	27.4

Table 5. Number of participants (n) needed per group to obtain a low (d = 0.2) effect size for a randomized control trial or crossover trial design in people with T2D.

	Randomized control design	Crossover design
Interleukin-10 (pg/mL)	104	26
Interleukin-8 (pg/mL)	131	33
Interleukin-6 (pg/mL)	120	30
Tumour necrosis factor-α (pg/mL)	136	34
F2-isoprostane (pg/mL)	180	45
Glutathione peroxidase activity (U/L)	118	30
Total antioxidant capacity (mmol/L)	180	45

N.B. Sample size is calculated using the following assumptions: α = 0.05, power = 0.8, allocation ratio of 1:1, two-tailed difference between means, effect size d = 0.2.