Vitamin D, vitamin D receptor FokI polymorphism, and diabetic retinopathy: A case-control study in Kunming, China

Table 1 Anthropometric and biochemical data of the study subjects, n (%)/mean ± SD

Observational index	Healthy control group (n = 58)	Type 2 diabetes mellitus group (n = 130)	Diabetic retinopathy group (n = 115)	P value
Male	33 (57.90)	81 (62.31)	76 (66.09)	0.479
Age (years)	50.43 ± 12.53	51.57 ± 11.24	53.52 ± 10.87	0.191
Body mass index (kg/m2)	22.29 ± 4.18	22.98 ± 3.25	23.12 ± 3.38	0.319
Diabetes duration (years)	-	8.00 (2.00, 14.25)	12.00 (6.00, 18.00)	< 0.001a
Family history of diabetes	-	25 (19.23)	24 (20.87)	0.749
History of diabetic retinopathy	-	5 (3.85)	21 (18.26)	< 0.001a
Systolic blood pressure (mmHg)	113.30 ± 18.89	120.79 ± 19.93	128.11 ± 23.21	< 0.001a
Diastolic blood pressure (mmHg)	70.88 ± 4.52	77.81 ± 9.14	78.89 ± 10.57	< 0.001a
Serum uric acid (μmol/L)	335.92 ± 97.22	351.10 ± 89.81	353.00 ± 94.05	0.490
Total cholesterol (mmol/L)	4.97 ± 0.87	4.58 ± 0.93	4.56 ± 1.33	0.045a
Triglycerides (mmol/L)	1.36 ± 0.64	2.42 ± 1.98	2.46 ± 2.48	0.001a
Low-density lipoprotein cholesterol (mmol/L)	2.93 ± 0.78	2.79 ± 0.82	2.68 ± 1.18	0.277
High-density lipoprotein cholesterol (mmol/L)	1.53 ± 0.43	1.04 ± 0.29	1.02 ± 0.33	< 0.001a
Serum 25-hydroxy vitamin D, nmol/L	65.56 ± 12.78	57.89 ± 18.84	51.53 ± 21.81	< 0.001a
Fasting plasma glucose (mmol/L)	-	7.85 ± 3.14	7.90 ± 2.96	0.898
Neutrophil-to-lymphocyte ratio	1.52 ± 0.54	1.71 ± 0.73	1.93 ± 0.85	0.002a
Platelet-to-lymphocyte ratio	107.35 ± 43.04	112.84 ± 42.98	127.26 ± 45.22	0.016a
Systemic immune-inflammation index	331.91 ± 151.42	376.17 ±194.71	422.72 ± 263.50	0.029a

^aP < 0.05.

Table 2 Association between diabetic retinopathy and vitamin D deficiency, n (%)

Vitamin D status	Diabetic retinopathy (n = 115)	Type 2 diabetes mellitus (n = 130)	Healthy control (n = 58)	Odds ratio (95%CI)	P value
VDD	63 (54.78)	41 (31.54)	12 (20.69)	3.09 (1.90-5.01)	< 0.001a
Non VDD	52 (45.22)	89 (68.46)	46 (79.31)	Reference	-

^aP < 0.05.

VDD: Vitamin D deficiency.

Table 3 Distribution of FokI genotypes and allele frequencies of the study participants, n (%)

Genotype	Diabetic retinopathy (n = 115)	Type 2 diabetes mellitus (n = 130)	Control (n = 58)	Odds ratio (95%CI)	P value
ff	59 (51.30)	48 (36.92)	11 (18.97)	2.36 (1.27-4.39)	0.007a
Ff	32 (27.83)	51 (39.23)	25 (43.10)	1.09 (0.57-2.08)	0.792
FF	24 (20.87)	31 (23.85)	22 (37.93)	Reference
Allele frequency
f	150 (65.22)	147 (56.54)	47 (40.52)	1.67 (1.18-2.36)	0.004a
F	80 (34.78)	113 (43.46)	69 (59.48)	Reference

^aP < 0.05.

Table 4 Association of FokI genotype with clinical characteristic, n (%)/mean ± SD

Variables	FF (n = 77)	Ff (n = 108)	ff (n = 118)	P value
Male	48 (62.34)	70 (64.81)	72 (61.02)	0.838
Age (years)	52.62 ± 11.98	54.56 ± 12.34	52.19 ± 11.91	0.318
Body mass index (kg/m2)	22.32 ± 3.25	22.68 ± 3.58	23.16 ± 3.20	0.218
Systolic blood pressure (mmHg)	116.85 ± 6.22	115.95 ± 5.37	117.05 ± 5.01	0.290
Diastolic blood pressure (mmHg)	76.12 ± 4.39	76.28 ± 4.50	76.84 ± 4.70	0.492
Serum uric acid (μmol/L)	340.98 ± 81.86	346.95 ± 91.15	356.91 ± 100.89	0.473
Total cholesterol (mmol/L)	4.68 ± 1.02	4.70 ± 1.04	4.58 ± 1.19	0.702
Triglycerides (mmol/L)	2.07 ± 2.13	2.17 ± 1.81	2.41 ± 2.24	0.471
Low-density lipoprotein cholesterol (mmol/L)	2.80 ± 0.82	2.82 ± 0.93	2.72 ± 1.10	0.742
High-density lipoprotein cholesterol (mmol/L)	1.19 ± 0.42	1.13 ± 0.39	1.07 ± 0.36	0.100a
Serum 25-hydroxy vitamin D (nmol/L)	59.08 ± 24.46	57.89 ± 18.87	54.61 ± 16.56	0.244
Fasting plasma glucose (mmol/L)	7.16 ± 3.15	7.06 ± 3.01	7.57 ± 2.64	0.382
Neutrophil-to-lymphocyte ratio	1.60 ± 0.53	1.72 ± 0.81	1.84 ± 0.81	0.073
Platelet-to-lymphocyte ratio	110.61 ± 40.27	113.48 ± 42.82	113.26 ± 44.36	0.885
Systemic immune-inflammation index	351.10 ± 156.80	392.70 ± 234.59	397.65 ± 234.66	0.291

^aP < 0.05.