The serum concentration and activity of DPP4 is positively related with the severity of hyperthyroidism in patients with Graves’ disease

Figures & data

Table 1. The baseline characteristics of the control, LT4 and GD groups.

Parameters	Control group (n = 122)	LT4 group (n = 20)	GD group (n = 82)	p
Age, years	41.4 ± 11.7	40.4 ± 11.1	39.6 ± 13.0	.293
Gender, M/F, n	28/94	4/16	19/63	.486
BMI, kg/m^2	24.17 ± 4.03	22.95 ± 3.47	21.75 ± 3.42**	.000
FT3, pmol/L	4.98 ± 0.55	11.56 ± 6.06**	23.11 ± 7.72**^##	.000
FT4, pmol/L	16.34 ± 2.07	36.43 ± 20.27**	68.49 ± 31.50**^##	.000
TSH, μIU/mL	1.87 (1.22–2.25)	0.001 (0.01–0.03)**	0.01 (0.00–0.01)**	.000
TRAb, IU/L	0.60 (0.00–1.30)	0.80 (0.80–1.07)	9.41 (5.75–20.98)**^##	.000
TPOAb, IU/mL	31.00 (28.00–49.62)	34.40 (28.00–50.20)	954.85(58.67–2937.20)**^##	.000
TgAb, IU/mL	16.20 (15.00–22.25)	25.50 (15.00–49.00)	104.25 (30.02–250.75)**^##	.000
WBC, 10^9 /L	6.20 ± 1.72	6.06 ± 1.99	5.79 ± 1.54	.297
Neutrophil, 10^9 /L	3.65 ± 1.32	3.81 ± 1.80	2.98 ± 1.13**^##	.002
Lymphocyte, 10^9 /L	2.01 ± 0.58	1.73 ± 0.37	2.20 ± 0.73^##	.021
ALT, U/L	19.0 (14.0–27.0)	21.0 (11.0–39.0)	37.0 (22.5–48.5)**^#	.000
AST, U/L	20.0 (17.0–24.0)	20.0 (15.0–28.0)	38.0 (21.5–44.0)**^##	.000
FBG, mmol/L	5.10 ± 0.87	5.12 ± 0.74	5.24 ± 0.66	.225
FINS, mIU/L	9.30 (6.40–13.40)	8.35 (6.00–13.07)	12.10 (7.65–16.05)*^#	.044
HOMA-IR	1.98 (1.38–2.99)	2.01 (1.31–3.26)	2.91 (1.81–3.64)**	.034
HbA1c, %	5.47 ± 0.39	5.48 ± 0.36	5.50 ± 0.42	.710
DPP4 concentration, ng/mL	576.73 ± 147.18	504.51 ± 134.79	739.28 ± 202.77**^##	.000
DPP4 activity, microunits/mL	1217.64 ± 549.70	1357.78 ± 513.05	1775.08 ± 632.28**^##	.000

Notes: Data are means ± SD unless indicated otherwise. TSH, TRAb, TPOAb, TgAb, ALT, AST, FINS and HOMA-IR are shown as median, upper and lower quartiles. M: males; F: females; BMI: body mass index; FT3: free triiodothyronine; FT4: free thyroxine; TRAb: anti-thyrotropin receptor antibodies; TPOAb: antithyroid peroxidase antibodies; TgAb: antithyroglobulin antibodies; WBC: white blood cell; ALT: alanine aminotransferase; AST: aspartate aminotransferase; FBG: fasting plasma glucose; FINS: fasting insulin; HOMA-IR: homeostasis model assessment of insulin resistance; HbA1c: haemoglobin A1c; DPP-4: dipeptidyl peptidase-4; LT4: levothyroxine; GD: Graves’ disease. Compared with the control group, *p < .05, **p < .01. Compared with the LT4 group, ^#p < .05, ^##p < .01.

Figure 1. The DPP4 concentration (a)/activity (B) of the control, LT4 and GD groups. LT4: levothyroxine; GD: Graves’ disease; NS: no significance.

Table 2. Correlation analysis between serum concentration/activity of DPP4 and clinical parameters in the GD patients.

	DPP4 concentration		DPP4 activity
	r	p	R	p
Age	−.250	.028	−.109	.296
BMI	−.025	.827	−.178	.087
FT3	.469	.000	.343	.001
FT4	.486	.000	.398	.000
TSH	−.229	.027	−.297	.004
TRAb	.402	.000	.432	.000
TPOAb	−.101	.385	.012	.909
TgAb	−.080	.491	.089	.401
WBC	−.067	.532	−.010	.926
Neutrophil	−.087	.417	−.198	.061
Lymphocyte	.231	.029	.252	.017
ALT	.052	.618	.115	.269
AST	.185	.076	.173	.095
FBG	−.104	.373	−.093	.387
FINS	.034	.768	−.048	.679
HOMA-IR	−.007	.955	−.048	.687
HbA1c	.168	.225	.143	.153

Note: BMI: body mass index; FT3: free triiodothyronine; FT4: free thyroxine; TRAb: anti-thyrotropin receptor antibodies; TPOAb: antithyroid peroxidase antibodies; TgAb: antithyroglobulin antibodies; WBC: white blood cell; ALT: alanine aminotransferase; AST: aspartate aminotransferase; FBG: fasting plasma glucose; FINS: fasting insulin; HOMA-IR: homeostasis model assessment of insulin resistance; HbA1c: haemoglobin A1c; DPP-4: dipeptidyl peptidase-4; GD: Graves’ disease.

Table 3. Multivariate linear regression for the association of serum DPP4 concentration with thyroid function and TRAb in the GD group.

	Model 1		Model 2		Model 3
Variables	Standardized β (95% CI)	p	Standardized β (95% CI)	p	Standardized β (95% CI)	P
FT3	0.451 (0.266, 0.636)	<.001	0.436 (0.243, 0.629)	.001	_	_
FT4	0.475 (0.293, 0.658)	<.001	0.467 (0.273, 0.660)	<.001	_	_
TSH	−0.229 (−0.430, −0.027)	.026	−0.217 (−0.423, −0.012)	.038	_	_
TRAb	0.524 (0.348, 0.700)	<.001	0.436 (0.246, 0.625)	<.001	0.265 (0.026, 0.504)	.030

Note: Model 1 unadjusted; Model 2 adjusted for age, sex and BMI; Model 3 adjusted for age, gender, BMI, FT3, lymphocyte count, AST and HOMA-IR. BMI: body mass index; FT3: free triiodothyronine; FT4: free thyroxine; TRAb: anti-thyrotropin receptor antibodies; AST: aspartate aminotransferase; HOMA-IR: homeostasis model assessment of insulin resistance; DPP-4: dipeptidyl peptidase-4; GD: Graves’ disease.

Table 4. Multivariate linear regression for the association of DPP4 activity with thyroid function and TRAb in the GD group.

	Model 1		Model 2		Model 3
Variables	Standardized β (95% CI)	p	Standardized β (95% CI)	p	Standardized β (95% CI)	P
FT3	0.365 (0.172, 0.558)	<.001	0.356 (0.158, 0.554)	.001	_	_
FT4	0.433 (0.247, 0.620)	<.001	0.421 (0.225, 0.617)	<.001	_	_
TSH	−0.218 (−0.420, −0.016)	.035	−0.195 (-14.841, −0.351)	.061	_	_
TRAb	0.433 (0.262, 0.632)	<.001	0.428 (0.239, 0.616)	<.001	0.325 (0.086, 0.564)	.008

Note: Model 1 unadjusted; Model 2 adjusted for age, sex and BMI; Model 3 adjusted for age, gender, BMI, FT3, lymphocyte count, AST and HOMA-IR. BMI: body mass index; FT3: free triiodothyronine; FT4: free thyroxine; TRAb: anti-thyrotropin receptor antibodies; AST: aspartate aminotransferase; HOMA-IR: homeostasis model assessment of insulin resistance; DPP-4: dipeptidyl peptidase-4; GD: Graves’ disease.

Data availability statement

All data of this study are available from the corresponding author Jia Liu for reasonable request.