Identification and validation of serum amino acids as diagnostic biomarkers for diabetic peripheral neuropathy

Table 1 Clinical characteristics of the participants in the two cohorts, n (%)

Variable	Training cohort			Validation cohort
	DPN	T2DM	Normal	DPN	T2DM	Normal
n	84	82	50	112	93	58
Age (years)	63.74 ± 11.51	61.28 ± 14.68	61.96 ± 15.68	64.38 ± 11.34	62.98 ± 11.53	66.59 ± 15.82
Male	50 (59.52)	41 (50)	23 (46)	61 (54.46)	49 (52.69)	25 (43.10)
Diabetes duration (years)	11.87 ± 6.92a	9.33 ± 6.86		12.35 ± 7.14a	9.68 ± 6.78
BMI (kg/m²)	24.49 ± 4.16	24.72 ± 3.64	23.97 ± 3.78	24.83 ± 3.67	24.54 ± 3.29	24.02 ± 3.34
Hypertension	47 (55.95)	44 (53.66)	20 (40)	64 (57.14)	51 (54.84)	29 (50)
SBP (mmHg)	133.20 ± 12.61	133.46 ± 14.33	130.52 ± 10.80	133.31 ± 12.02	134.67 ± 12.40	131.22 ± 10.11
DBP (mmHg)	75.17 ± 9.92	75.38 ± 10.85	73.92 ± 10.07	75.08 ± 9.56	75.68 ± 8.99	75.84 ± 9.75
FT3 (pmol/L)	4.78 ± 0.65	4.80 ± 0.61	4.77 ± 0.91	4.68 ± 0.74	4.72 ± 0.73	4.60 ± 0.79
FT4 (pmol/L)	16.53 ± 2.18	16.48 ± 1.68	16.65 ± 2.52	16.49 ± 2.48	16.51 ± 2.46	16.70 ± 2.52
TSH (mIU/L)	1.94 ± 0.99	1.86 ± 0.92	2.08 ± 1.17	2.01 ± 1.04	2.10 ± 2.25	2.17 ± 1.00
ALB (g/L)	38.95 ± 3.41b	39.54 ± 3.53c	41.52 ± 4.17	38.74 ± 3.88b	39.40 ± 3.53	41.04 ± 5.17
ALT (U/L)	20.63 ± 7.91	21.42 ± 8.52	20.89 ± 6.99	21.98 ± 9.33	21.06 ± 8.54	20.36 ± 8.05
AST (U/L)	20.79 ± 5.02	20.20 ± 5.15	21.26 ± 4.30	20.87 ± 5.43	20.65 ± 4.96	20.75 ± 4.81
Scr (μmol/L)	68.92 ± 14.28	66.17 ± 12.16	65.00 ± 12.99	67.46 ± 13.78	67.47 ± 12.05	64.90 ± 13.46
GFR (mL/minute/1.73 m²)	99.36 ± 9.20	101.17 ± 9.80	101.72 ± 10.83	99.06 ± 9.24	100.10 ± 9.40	100.82 ± 9.44
UA (mmol/L)	326.96 ± 92.50	322.86 ± 107.13	330.95 ± 94.19	332.44 ± 96.06	338.70 ± 98.43	329.08 ± 102.57
FBG (mmol/L)	8.24 ± 3.19b	7.59 ± 2.77c	6.08 ± 2.03	8.23 ± 3.93b	7.67 ± 2.93c	5.78 ± 1.69
TG (mmol/L)	1.65 ± 1.36	1.86 ± 1.25	1.62 ± 0.58	1.62 ± 1.32	1.58 ± 0.97	1.67 ± 0.47
HDL (mmol/L)	1.03 ± 0.22b	1.01 ± 0.21c	1.14 ± 0.20	1.07 ± 0.25	1.03 ± 0.26	1.11 ± 0.23
LDL (mmol/L)	2.75 ± 1.16	2.57 ± 0.87	2.45 ± 0.92	2.64 ± 1.01	2.77 ± 0.91	2.70 ± 0.94
HbA1c (%)	9.31 ± 2.43b	8.68 ± 1.92c	5.49 ± 0.46	9.23 ± 2.25b	8.92 ± 2.42c	5.37 ± 0.41
BNP (pg/mL)	34.55 ± 17.83	32.42 ± 14.29	35.72 ± 17.14	34.50 ± 20.54	35.09 ± 15.46	37.14 ± 21.84

^aP < 0.05, comparison of diabetic peripheral neuropathy (DPN) patients with type 2 diabetes mellitus (T2DM) patients were significantly different.

^bP < 0.05, comparison of DPN patients with normal controls were significantly different.

^cP < 0.05, comparison of T2DM patients with normal controls were significantly different.

AUC: Area under the curve; T2DM: Type 2 diabetes mellitus; DPN: Diabetic peripheral neuropathy; TC: Training cohort; VC: Validation cohort; BMI: Body mass index; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; FT3: Free triiodothyronine; FT4: Free thyroxine; TSH: Thyroid stimulating hormone; ALB: Albumin; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; Scr: Serum creatinine; GFR: Glomerular filtration rate; UA: Uric acid; FBG: Fasting blood glucose; TG: Triglyceride; HDL: High-density lipoprotein; LDL: Low-density lipoprotein; HbA1c: Glycated hemoglobin A1c; BNP: Brain natriuretic peptide.