Plasma melatonin levels in patients with diabetic retinopathy secondary to type 2 diabetes

Table 1 Baseline characteristics, disease information and laboratory data of the healthy controls, without diabetic retinopathy, non-proliferative diabetic retinopathy and proliferative diabetic retinopathy groups

	Healthy controls (n = 118)	DM			P value
		NDR (n = 57)	NPDR (n = 64)	PDR (n = 61)
Baseline characteristics
Gender (male, %)	56 (48.70)	27 (47.37)	26 (40.63)	29 (47.54)	0.947
Age (yr)	59.84 ± 9.60	58.21 ± 7.75	60.89 ± 9.93	65.72 ± 8.36	< 0.001
BMI (kg/m2)	26.11 ± 3.18	27.39 ± 3.71	26.86 ± 2.76	25.93 ± 3.89	0.047
SBP (mmHg)	123.53 ± 14.47	126.82 ± 17.62	131.66 ± 10.63	136.34 ± 11.87	< 0.001
DBP (mmHg)	73.97 ± 12.08	73.54 ± 12.69	81.14 ± 15.42	77.52 ± 13.09	0.0019
MAP (mmHg)	90.49 ± 9.41	91.30 ± 10.86	97.98 ± 10.78	97.13 ± 10.04	< 0.001
Disease information
Diabetes duration (yr)	-	5.72 ± 2.64	10.92 ± 6.01	12.52 ± 4.96	< 0.001
Fasting blood glucose (mg/dL)	84.73 ± 23.85	133.81 ± 24.98	143.28 ± 36.25	167.86 ± 40.42	< 0.001
HbA1C (%)	5.87 ± 1.32	7.85 ± 1.69	8.61 ± 2.11	9.27 ± 1.80	< 0.001
Use of oral hypoglycemic agents	-	38 (66.67)	50 (78.13)	44 (72.13)	0.369
Use of insulin	-	15 (26.31)	24 (37.50)	21 (34.43)	0.408
Hypertension (n, %)	52 (44.07)	25 (43.86)	38 (59.38)	41 (67.21)	0.009
Smoking (n, %)	37 (31.36)	14 (24.56)	18 (28.13)	19 (31.15)	0.801
Drinking (n, %)	41 (34.75)	20 (30.09)	19 (29.69)	24 (39.34)	0.730
Laboratory data
Triglycerides (mmol/L)	4.70 ± 1.50	4.79 ± 1.28	4.55 ± 1.28	4.88 ± 1.20	0.567
Total cholesterol (mmol/L)	4.57 ± 1.54	5.01 ± 1.64	4.25 ± 1.77	4.77 ± 1.79	0.077
LDL cholesterol (mmol/L)	3.12 ± 1.12	2.96 ± 1.20	2.98 ± 1.09	2.87 ± 0.94	0.504
HDL cholesterol (mmol/L)	1.18 ± 0.27	1.14 ± 0.26	1.19 ± 0.29	1.16 ± 0.28	0.740
Total bilirubin (mmol/L)	12.79 ± 3.34	13.44 ± 3.89	11.55 ± 4.04	11.21 ± 3.89	0.002
AST (U/L)	21.76 ± 9.08	22.62 ± 9.15	22.38 ± 8.78	22.40 ± 9.60	0.930
ALT (U/L)	21.16 ± 8.66	22.78 ± 9.35	23.16 ± 8.92	22.61 ± 8.33	0.4251

SBP: Systolic blood pressure; DBP: Diastolic blood pressure; MAP: Mean arterial pressure; FBG: Fasting blood glucose; HbA1C: Hemoglobin A1C; BMI: Body mass index; LDL: Low-density lipoprotein; HDL: High-density lipoprotein; AST: Aspartate transaminase; ALT: Alanine aminotransferase; DM: Diabetes mellitus.

Table 2 Multiple logistic regression analysis of the association between clinical characteristics and diabetic retinopathy/proliferative diabetic retinopathy risk

	DR		PDR
	Multivariate OR (95%CI)	P value	Multivariate OR (95%CI)	P value
Age (10 yr)	0.03 (0.008 to 0.063)	0.134	0.939 (0.003 to 0.011)	0.005
Diabetes duration(1 yr)	0.032 (0.025 to 0.039)	< 0.001	0.007 (0.007 to 0.023)	0.002
Hypertension	-0.023 (-0.105 to 0.059)	0.577	0.015 (-0.129 to 0.022)	< 0.001
BMI	-0.008 (-0.019 to 0.001)	0.090	-0.053 (-0.023 to -0.001)	0.166
Smoking	-0.033 (-0.109 to 0.044)	0.402	-0.012 (-0.098 to 0.075)	0.032
Drinking	-0.023 (-0.096 to 0.050)	0.532	-0.012 (-0.143 to 0.021)	0.791
FBG (mg/dL)	0.002 (0.001 to 0.003)	< 0.001	-0.061 (0.001 to 0.004)	0.143
HbA1C (%)	0.017 (-0.002 to 0.036)	0.084	0.002 (-0.006 to 0.037)	< 0.001
Total bilirubin (mmol/L)	0.004 (-0.006 to 0.014)	0.428	0.015 (-0.016 to 0.006)	0.158
Melatonin (pg/mL)	-0.008 (-0.010 to -0.005)	< 0.001	-0.005 (-0.004 to 0.002)	0.412

FBG: Fasting blood glucose; BMI: body mass index; HbA1C: Hemoglobin A1C.

Table 3 Correlations between baseline information and laboratory data and plasma melatonin concentrations

Baseline information and laboratory data	Plasma melatonin concentrations
	r	P value
Age	-0.1018	0.078
Gender	-0.1428	0.013
Diabetes duration	-0.5623	< 0.001
SBP	-0.2224	< 0.001
DBP	-0.1326	0.022
MAP	-0.2146	< 0.001
Hypertension	0.1429	0.013
BMI	-0.09046	0.118
Smoking	-0.0543	0.349
Drinking	-0.06159	0.288
FBG (mg/dL)	-0.464	< 0.001
HbA1C (%)	-0.481	< 0.001
Triglycerides (mmol/L)	0.04224	0.466
Total cholesterol (mmol/L)	0.01544	0.790
LDL cholesterol (mmol/L)	0.02813	0.628
HDL cholesterol (mmol/L	-0.01587	0.784
Total bilirubin (mmol/L)	0.4386	< 0.001
AST (U/L)	-0.06536	0.259
ALT (U/L)	-0.06815	0.239

SBP: Systolic blood pressure; DBP: Diastolic blood pressure; MAP: Mean arterial pressure; FBG: Fasting blood glucose; HbA1C: Hemoglobin A1C; BMI: Body mass index; LDL: Low-density lipoprotein; HDL: High-density lipoprotein; AST: Aspartate transaminase; ALT: Alanine aminotransferase.