Association between a protein polymorphism in the start codon of the vitamin D receptor gene and severe diabetic retinopathy in C-peptide-negative type 1 diabetes.
BACKGROUND
The vitamin D (VD) receptor (VDR) is extensively expressed in retina. The plasma concentration of 1,25-dihydroxyvitamin D3 has been inversely correlated with the severity of diabetic retinopathy (DR), which raises the possibility that VD, through its antiinflammatory, antioxidant, antiproliferative, and antiangiogenic properties, may protect diabetic retina. The TaqI VDR polymorphism has been associated with severe DR. The FokI VDR polymorphism is a T-to-C substitution in the first codon (f allele), abolishing the first translation initiation site and resulting in a peptide lacking three amino acids (F allele), which increases the transcriptional activity of VDR.


OBJECTIVE
To examine whether FokI polymorphism is involved in severe DR, 254 Caucasians with longstanding C-peptide-negative type 1 diabetes, 128 patients with absent/mild DR (control group), and 126 patients with preproliferative/proliferative DR (study group) were genotyped using PCR-restriction fragment length polymorphism analysis.


RESULTS
The genotype distribution was in Hardy-Weinberg equilibrium and was different between groups (P = 0.046). The frequency of F allele was significantly higher in the control (66.4%) than in the study group (56%, odds ratio = 0.64, 95% confidence interval 0.44-0.92, P = 0.016). In subjects with fewer than 25 yr of diabetes duration (median value, n = 134), this association was strongly increased (P = 0.0008).


CONCLUSIONS
In conclusion, we observed, in a cohort of Caucasians with C-peptide-negative type 1 diabetes, a novel association between the functional FokI VDR polymorphism and severe DR, especially among subjects with fewer than 25 yr of diabetes duration.
Taverna
Mariano J
MJ
Institut National de la Santé et de la Recherche Médicale U. 341, Department of Diabetology, Hôtel-Dieu Hospital (Paris), 1 place du Parvis de Notre-Dame 5ème A1, 75181 Paris Cedex 04, France. taverna1@yahoo.fr
Selam
Jean-Louis
JL
Slama
Gérard
G
D000328:Adult; D002096:C-Peptide / Q000097:blood; D016022:Case-Control Studies; D018387:Codon, Initiator; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000453:epidemiology / Q000235:genetics*; D003928:Diabetic Nephropathies / Q000097:blood / Q000453:epidemiology / Q000235:genetics; D003930:Diabetic Retinopathy / Q000097:blood / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic; D018167:Receptors, Calcitriol / Q000235:genetics*; D012307:Risk Factors; D012720:Severity of Illness Index; D044465:White People / Q000235:genetics
D002096:C-Peptide; D018387:Codon, Initiator; D006442:Glycated Hemoglobin; D018167:Receptors, Calcitriol