Lower levels of 25-hydroxyvitamin D3 are associated with a higher prevalence of microvascular complications in patients with type 2 diabetes.
OBJECTIVE
Low levels of serum 25-hydroxyvitamin D [25(OH)D] are commonly found in type 2 diabetes. We examined whether there is an association between circulating 25(OH)D concentrations and the presence of microvascular complications in people with type 2 diabetes.


METHODS
We studied 715 outpatients with type 2 diabetes who regularly attended our clinic. Participants were evaluated for the presence of microvascular complications (namely retinopathy and/or nephropathy) by clinical evaluation, fundus examination, urine examination and biochemical tests. Serum 25(OH)D levels were also measured for each participant.


RESULTS
Hypovitaminosis D (ie, a serum 25(OH)D level <30 ng/mL) was found in 75.4%, while deficiency (ie, a 25(OH)D level <20 ng/mL) was found in 36.6% of these patients. Serum 25(OH)D levels decreased significantly in relation to the severity of either retinopathy or nephropathy or both. In multivariate logistic regression analysis, lower 25(OH)D levels were independently associated with the presence of microvascular complications (considered as a composite end point; OR 0.758; 95% CI 0.607 to 0.947, p=0.015). Notably, this association remained significant even after excluding those with an estimated glomerular filtration rate <60 mL/min/1.73 m(2).


CONCLUSIONS
We found an inverse and independent relationship between circulating 25(OH)D levels and the prevalence of microvascular complications in patients with type 2 diabetes. However, vitamin D may be simply a marker and causality cannot be implied from our cross-sectional study. Whether vitamin D supplementation in patients with type 2 diabetes may have beneficial effects on the risk of microvascular complications remains to be investigated.
Department of Medicine, Section of Endocrinology, Diabetes and Metabolism , Azienda Ospedaliera Universitaria Integrata, University of Verona , Verona , Italy.
Giacomo
G
Zoppini
Department of Medicine, Section of Endocrinology, Diabetes and Metabolism , Azienda Ospedaliera Universitaria Integrata, University of Verona , Verona , Italy.
Anna
A
Galletti
Department of Medicine, Section of Endocrinology, Diabetes and Metabolism , Azienda Ospedaliera Universitaria Integrata, University of Verona , Verona , Italy.
Giovanni
G
Targher
Department of Medicine, Section of Endocrinology, Diabetes and Metabolism , Azienda Ospedaliera Universitaria Integrata, University of Verona , Verona , Italy.
Corinna
C
Brangani
Department of Medicine, Section of Endocrinology, Diabetes and Metabolism , Azienda Ospedaliera Universitaria Integrata, University of Verona , Verona , Italy.
Isabella
I
Pichiri
Department of Medicine, Section of Endocrinology, Diabetes and Metabolism , Azienda Ospedaliera Universitaria Integrata, University of Verona , Verona , Italy.
Maddalena
M
Trombetta
Department of Medicine, Section of Endocrinology, Diabetes and Metabolism , Azienda Ospedaliera Universitaria Integrata, University of Verona , Verona , Italy.
Carlo
C
Negri
Department of Medicine, Section of Endocrinology, Diabetes and Metabolism , Azienda Ospedaliera Universitaria Integrata, University of Verona , Verona , Italy.
Francesca
F
De Santi
Department of Medicine, Section of Endocrinology, Diabetes and Metabolism , Azienda Ospedaliera Universitaria Integrata, University of Verona , Verona , Italy.
Vincenzo
V
Stoico
Department of Medicine, Section of Endocrinology, Diabetes and Metabolism , Azienda Ospedaliera Universitaria Integrata, University of Verona , Verona , Italy.
Vittorio
V
Cacciatori
Department of Medicine, Section of Endocrinology, Diabetes and Metabolism , Azienda Ospedaliera Universitaria Integrata, University of Verona , Verona , Italy.
Enzo
E
Bonora
Microangiopathy; Microvascular Complications; Vitamin D