Low 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 levels are independently associated with macroalbuminuria, but not with retinopathy and macrovascular disease in type 1 diabetes: the EURODIAB prospective complications study

Association between serum 25- hydroxyvitamin D and albuminuiria in middle-aged and older Chinese patients with type 2 diabetes

OBJECTIVE

The objective was to analyze the relationship between serum 25-hydroxy-vitamin D (25(OH)D) level and albuminuiria in middle-aged and older patients with type 2 diabetes of Gansu Province.

METHODS

Data pertaining to 380 in-patients with type 2 diabetes were collected. Subjects were classified groups based on gender,age,25(OH)D,BMI and UACR.Serum 25(OH)D and other clinical characteristics among various UACR groups were compared.The relationship between albuminuiria and 25(OH)D was analyzed.

RESULTS

Out of the 380 subjects, 83.4%were classified as vitamin D deficiency, 14.5%were classified as vitamin D insufficiency, while 2.1% were classified as vitamin D sufficiency. Among the participants,41% had albuminuria (microalbuminuria,28.7%;macroalbuminuria,12.3%).The prevalence of 25(OH)D deficiency in the albuminuria group(84.6%) was significantly higher than that in the normoalbuminuria group(82.6%)(Mann-Whitney U test:Z = -3.86,P = 0.000); patients with macroalbuminuria had the highest prevalence of 25(OH)D deficiency (91.5%; P < 0.01 versus normoalbuminuria).A binary logistic analysis demonstrated that 25(OH)D were protective factors for albuminuria.

CONCLUSIONS

The prevalence of vitamin D deficiency in patients with albuminuria was overtly higher than that in patients without albuminuria among middle-aged and older adults with type 2 diabetes.

Micronutrients and Diabetic Retinopathy: Evidence From The National Health and Nutrition Examination Survey and a Meta-analysis

PURPOSE

To investigate the associations between circulating micronutrients (vitamins A, C, D, E, and carotenoids) and risk of diabetic retinopathy (DR).

DESIGN

Cross-sectional study and meta-analysis.

METHODS

The cross-sectional study included 517 diabetic participants aged ≥40 years in the 2005-2006 National Health and Nutrition Examination Survey. Serum vitamin D was converted to liquid chromatography-tandem mass spectrometry-equivalent results, while other micronutrients were measured using high-performance liquid chromatography. Presence of DR was determined based on non-mydriatic fundus photographs. A meta-analysis was subsequently performed, which included relevant studies published from January 01, 1990 to December 31, 2020.

RESULTS

Of the 517 included participants, DR was identified in 159 participants (25.17%). After adjusting for multiple confounders, only serum vitamin C was associated with a lower risk of DR (odds ratio [OR]: 0.60; 95% confidence interval [CI]: 0.38-0.95). A total of 35 studies were included in the subsequent meta-analysis. Comparing 1056 participants with DR to 920 controls, the pooled weighted mean difference (WMD) of vitamin C was -11.01 (95% CI: -19.35 to -2.67). Regarding vitamins D and E, the pooled WMD was -3.06 (95% CI: -5.15 to -0.96) and -3.03 (95% CI: -4.24 to -1.82), respectively. No associations were identified between DR and circulating vitamin A or carotenoids.

CONCLUSIONS

Lower levels of circulating vitamins C, D, and E were found in DR patients than those without. More high-quality studies are required to assess the real effects of micronutrients on DR.

Vitamin D and Ocular Diseases: A Systematic Review

The contributory roles of vitamin D in ocular and visual health have long been discussed, with numerous studies pointing to the adverse effects of vitamin D deficiency. In this paper, we provide a systematic review of recent findings on the association between vitamin D and different ocular diseases, including myopia, age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), dry eye syndrome (DES), thyroid eye disease (TED), uveitis, retinoblastoma (RB), cataract, and others, from epidemiological, clinical and basic studies, and briefly discuss vitamin D metabolism in the eye. We searched two research databases for articles examining the association between vitamin D deficiency and different ocular diseases. One hundred and sixty-two studies were found. There is evidence on the association between vitamin D and myopia, AMD, DR, and DES. Overall, 17 out of 27 studies reported an association between vitamin D and AMD, while 48 out of 54 studies reported that vitamin D was associated with DR, and 25 out of 27 studies reported an association between vitamin D and DES. However, the available evidence for the association with other ocular diseases, such as glaucoma, TED, and RB, remains limited.

Correlation Between Serum 25-Hydroxyvitamin D Levels in Albuminuria Progression of Diabetic Kidney Disease and Underlying Mechanisms By Bioinformatics Analysis

AIM

This study aimed to assess the correlation between serum concentration of 25-hydroxyvitamin D and albuminuria progression of diabetic kidney disease (DKD) and to use bioinformatics methods to determine the potential mechanism in the pathological process of advanced DKD.

METHODS

A total of 178 type 1 diabetes mellitus (T1DM) patients with microalbuminuria complications who were hospitalized at least twice (with an interval > 24 months) in the Department of Endocrinology of The First Affiliated Hospital of USTC were included in this study. According to the urinary albumin creatinine ratio (UACR), we classified DKD stages as follows: microalbuminuria (UACR, 30-300 mg/g), and macroalbuminuria (UACR, >300 mg/g). We divided the patients into DKD progression (N=44) and stable group (N=134) on account of urinary albumin-to-creatinine ratio (UACR) by at least two randomized measurements. Stable group was defined as UACR between 30 and 300 mg/g, whereas progression group was defined as UACR >300 mg/g at the end of follow-up. Data were obtained from participants' medical records, and the 25-hydroxyvitamin D level was categorized into three groups as follows: G1 (N=45), <10 ng/mL; G2 (N=80), 10-20 ng/ml; and G3 (N=53), ≥20 ng/mL. The Nephroseq database (http://v5.nephroseq.org) was used to identify VDR expression in diabetic nephropathy. The dataset GSE142025 from GEO (http://www.ncbi.nlm.nih.gov/geo) was downloaded. After stratification by the median-centered log2 VDR expression value, the 21 advanced DKD samples were divided into two groups (low VDR expression group and high VDR expression group). Gene set enrichment analysis (GSEA) (http://software.broadinstitute.org/gsea/index.jsp). Differentially expressed genes (DEGs) were screened by the limma package (adjusted p < 0.05, |logFC| > 1). The Gene Ontology (GO; http://www.geneontology.org/) database and pathway analysis within the Kyoto Encyclopedia of Genes and Genomes (KEGG; https://www.kegg.jp/) were performed using the R package ClusterProfile. The CIBERSORT (Cell type Identification By Estimating Relative Subsets Of known RNA Transcripts) algorithm was utilized for calculating the infiltrated immune cells in advanced kidney tissues.

RESULTS

1) A multivariate Cox regression analysis revealed that DR (diabetic retinopathy), eGFR (estimated glomerular filtration rate), and 25-hydroxyvitamin D were significant independent predictors of DKD progression (HR: 2.57, 95% CI: 1.44.4.24, p=0.007; HR: 2.13, 95% CI: 1.58.3.79, p = 0.011; HR: 0.732, 95% CI: 0.232-0.816, p = 0.023, respectively). 2) Kaplan-Meier survival curves of DKD progression by serum 25-hydroxyvitamin D stratification showed that the G2 and G3 groups were significantly different when compared with the G1 group (log-rank χ2 = 14.69, p <0.001; χ2 = 28.26, p <0.001, respectively). 3) There was a weak negative correlation between 25-hydroxyvitamin D level and UACR at baseline,and the overall mean rate of change in eGFR was 1.121 ± 0.19 ml/min/1.73 m2/year. Neither crude nor adjusted rate of decline in eGFR was significantly different among patients classified according to baseline serum 25-hydroxyvitamin D levels (all p<0.05). 4) The high expression of VDR group was most positively correlated with enriched gene sets like reactome innate immune system and reactome G alpha I signaling events when compared with the low expression of VDR group. 5) The CIBERSORT algorithm showed decreased M2 macrophage infiltration in advanced kidneys in comparison to low VDR expression and high VDR expression.

CONCLUSION

This study concluded that low 25-hydroxyvitamin D levels can predict an increased risk of DKD albuminuria progression and eGFR decline. Decreased M2 macrophage infiltration may be a potential mechanism involved in this pathogenesis.

Vitamin D Deficiency Is Significantly Associated with Retinopathy in Type 2 Diabetes Mellitus: A Case-Control Study

AIM

Results from meta-analyses point to an association between vitamin D deficiency and the onset of diabetic retinopathy (DR). The objectives of the present study were to evaluate the association of vitamin D for the development of DR and to determine the levels of vitamin D associated with a greater risk of DR.

METHODS

Between November 2013 and February 2015, we performed a case-control study based on a sample of patients with diabetes in Spain. The study population comprised all patients who had at least one evaluable electroretinogram and recorded levels of 25(OH)D. We collected a series of analytical data: 25(OH)D, 1,25(OH)2D, iPTH, calcium, albumin, and HbA1c. Glycemic control was evaluated on the basis of the mean HbA1c values for the period 2009-2014. A logistic regression analysis was performed to identify the variables associated with DR.

RESULTS

The final study sample comprised 385 patients, of which 30 (7.8%) had DR. Significant differences were found between patients with and without DR for age (69.54 vs. 73.43), HbA1c (6.68% vs. 7.29%), years since diagnosis of diabetes (10.9 vs. 14.17), level of 25(OH)D (20.80 vs. 15.50 ng/mL), level of 1,25(OH)2D (35.0 vs. 24.5 pg/mL), treatment with insulin (14.9% vs. 56.7%), hypertension (77.7% vs. 100%), cardiovascular events (33.2% vs. 53.3%), and kidney failure (22.0% vs. 43.3%). In the multivariate analysis, the factors identified as independent risk factors for DR were treatment of diabetes (p = 0.001) and 25(OH)D (p = 0.025). The high risk of DR in patients receiving insulin (OR 17.01) was also noteworthy.

CONCLUSIONS

Levels of 25(OH)D and treatment of diabetes were significantly associated with DR after adjusting for other risk factors. Combined levels of 25(OH)D < 16 ng/mL and levels of 1,25(OH)2D < 29 pg/mL are the variables that best predict the risk of having DR with respect to vitamin D deficiency. The risk factor with the strongest association was the treatment of type 2 diabetes mellitus. This was particularly true for patients receiving insulin, who had a greater risk of DR than those receiving insulin analogues. However, further studies are necessary before a causal relationship can be established.

Vitamin D Deficiency in Patients with Diabetes in French Guiana: Epidemiology and Relation with Microvascular and Macrovascular Complications

Vitamin D (VD) insufficiency is common among patients with diabetes in French Guiana. The study aimed to evaluate the prevalence of VD deficiency in the different type of diabetes encountered and to analyze the relationship between VD deficiency and diabetes complications. Methods: An observational study was conducted between May 2019 and May 2020 in French Guiana, based on data from the CODIAM study (Diabetes Cohort in French Amazonia), describing the characteristics of patients with diabetes mellitus. Among 600 patients enrolled with diabetes, 361 had an available VD assay. Results: The mean 25(OH)VD (hydroxycalciferol) level was 27.9 ng/mL. The level of VD was inversely proportional to the HbA1c (glycated hemoglobin) level. Patients with angina pectoris had a greater proportion of deficiencies VD < 20 ng/mL than those without angina. By contrast, patients with retinopathy had higher vitamin D concentrations than those without retinopathy. There was no association between vitamin D and arteriopathy, stroke, nephropathy and polyneuropathy. VD deficiency was more frequent in women, and in patients with a high school education. Conclusion: The prevalence of VD deficiency was high in patients with diabetes in French Guiana, emphasizing the importance of VD supplementation.

Relationship of serum vitamin D levels with diabetic microvascular complications in patients with type 2 diabetes mellitus

Background:

Vitamin D deficiency has been reported to be associated with diabetic microvascular complications, but previous studies have only focused on the relationship between vitamin D and specific complications. Therefore, we aimed to explore the relationship between vitamin D level and diabetic microvascular complications in general, including diabetic retinopathy (DR), diabetic nephropathy (DN), and diabetic peripheral neuropathy (DPN).

Methods:

This was a cross-sectional study of 815 patients with type 2 diabetes mellitus (T2DM). Clinical information and laboratory results were collected from the medical records. The relationship between vitamin D and the three diabetic microvascular complications was investigated.

Results:

The serum 25-hydroxyvitamin D (25 [OH] D) level of patients with DPN and/or DN was significantly lower than that of T2DM patients without any microvascular complications (P < 0.01). Univariate analysis showed that the 25 (OH) D level was related to DPN and DN, but not DR. After adjustment, the 25 (OH) D level was confirmed to be an independent protective factor for DPN (odds ratio [OR]: 0.968, P = 0.004]) and DN (OR: 0.962, P = 0.006). The prevalence of DPN and DN increased significantly as the serum 25 (OH) D levels decreased. Furthermore, patients with both DPN and DN had the lowest concentration of serum 25 (OH) D (P < 0.001), and the prevalence of macroalbuminuria increased more abruptly than that of microalbuminuria across the 25 (OH) D tertiles. Among the patients with vitamin D insufficiency, those with DPN presented more comorbid macroalbuminuria than those without DPN (15.32% vs. 4.91%; P = 0.001).

Conclusions:

Vitamin D deficiency is independently associated with higher risk of DPN and DN, but not DR, in T2DM patients. Further, it may be a potential predictor for both the occurrence and severity of DPN and DN.

Association Between 25(OH)Vitamin D, HbA1c and Albuminuria in Diabetes Mellitus: Data From a Population-Based Study (VIDAMAZON)

BACKGROUND

The effect of glycemic control on diabetic kidney disease (DKD) is well known. Recent evidence has suggested that Vitamin D (VD) may have a nephroprotective effect in diabetes, but the relationship between VD, glycemic control, and albuminuria has yet to be clarified.

OBJECTIVE

Evaluate the relationship between 25-hydroxy-vitamin D [25(OH)D], HbA1c, and albuminuria in Diabetes Mellitus (DM).

PATIENTS AND METHODS

Cross-sectional study with 1576 individuals with DM who had 25(OH)D, HbA1c, and albuminuria levels measured. Patients with abnormal creatinine levels were excluded, in order to avoid interference on VD levels by impaired kidney function.

RESULTS

Patients with HbA1c ≥7% had lower 25(OH)D when compared to patients with HbA1c <7% (29.7 ± 10.2 vs 28.1 ± 9.9 ng/ml, p = 0.003) and 25(OH)D levels seems to predict 1.5% of HbA1c behavior. The 25(OH)D concentrations in patients with normoalbuminuria were higher than the levels observed in those with micro or macroalbuminuria (29.8 ± 9.0 vs 26.8 ± 8.6 and 25.1 ± 7.6, respectively, p = 0.001), patients who had 25(OH)D <20 ng/ml and 25(OH)D <30 ng/ml were at a higher risk of presenting albuminuria [OR = 2.8 (95% CI = 1.6 - 4.9), p<0.001, and OR = 2.1 (95% CI = 1.3 - 4.6), p<0.001, respectively]. In our regression model, albuminuria was influenced by HbA1c (r² = 0.076, p<0.00001) and 25(OH)D (r² = 0.018, p = 0.002) independently.

CONCLUSION

Our study found an association between vitamin D levels, HbA1c and DKD. Additionally, our data suggest that the association between urinary albumin excretion and vitamin D levels is independent of glycemic control in patients with diabetes. Even though our patients presented normal creatinine levels, it is necessary further prospective studies to confirm if this association precedes or not the loss of renal function.

Vitamin D status in Israeli pediatric type 1 diabetes patients: the AWeSoMe Study Group experience and literature review

Background The prevalence of both vitamin D (VitD) deficiency and type 1 diabetes mellitus (T1DM) has increased worldwide over the last few decades. The objectives of this study were: (1) to evaluate the prevalence of VitD deficiency and insufficiency among Israeli youth with T1DM and (2) to assess the association between VitD status, seasonality and T1D glycemic control characteristics. Methods This was a multi-centered, cross-sectional study. VitD levels were routinely tested during the years 2008-2011 in T1DM patients aged up to 21 years. Medical records were reviewed for demographic, clinical and laboratory characteristics. Results The study population consisted of 199 participants (53% males), mean age 12.24±4.11 years, mean T1DM duration 3.77±3.43 years. VitD levels were within the normal range in 19.6%, insufficient (15-29 ng/mL, 37-72 nmol/L) in 62.3% and deficient (<15 ng/mL, <37 nmol/L) in 18.1%. Mean VitD level was higher during the summer than during spring, autumn and winter (28.65 ng/mL, 23.16 ng/mL, 21.65 ng/mL, 17.55 ng/mL, respectively, p<0.001). Mean VitD level was higher among secular patients compared to the religious (whole-year heavily dressed) population (23.57 ng/mL, 15.54 ng/mL, respectively, p<0.001). VitD level was negatively associated with body mass index calculation of standard deviation scores (BMI-SDS), high-density lipoprotein (HDL) and age at diagnosis (r=-0.171, p=0.016; r=-0.149, p=0.043; r=-0.150, p=0.037, respectively). No association was demonstrated with disease duration and glycemic control indices and metabolic parameters. Conclusions VitD insufficiency is largely prevalent among Israeli youth with T1DM, as is in Israeli youth in general. The VitD level is associated with seasonality, clothing habits and BMI.

Determinants of Vitamin D Supplementation among Individuals with Type 1 Diabetes

Half of the individuals with type 1 diabetes (T1DM) may present Vitamin D (VD) deficiency. There is little known about factors determining a decision on VD supplementation. The study aimed to determine the factors affecting vitamin D supplementation in people with T1DM. A cross-sectional survey study using the authors’ questionnaire paper and its digital version was performed. The questions involved data on the basic characteristics of the respondent, medical history, VD supplementation status, influence of the social environment, self-education, and the most important personal motivator for VD supplement use. Multivariate logistic regression analysis was performed. We collected a total of n = 184 papers and n = 550 digital complete surveys. From 734 total respondents, 62.0% declared VD supplementation. The main personal rationale for VD supplementation were recommendation of medical specialist 172 (37.8%) and self-education 135 (29.7%). The main reasons for non-supplementation of VD were lack of knowledge about VD 159 (57.0%) and lack of motivation 77 (27.6%). VD supplementation was independently associated with a family doctor (odds ratio (OR), 95% confidence interval (CI): 4.67, 2.32–9.40) or medical specialist recommendation (16.20, 9.57–27.43), and self-education (5.97, 3.90–9.13). Most Polish individuals with T1DM use VD supplements, and the decision is related to physicians’ recommendations and self-education.

Genetic Variants in Group-Specific Component (GC) Gene Are Associated with Breast Cancer Risk among Chinese Women

The group-specific component (GC) gene, one of the vitamin D pathway genes, seems to play an important role in cancer development. A population-based breast cancer study including 818 cases and 935 controls in a Chinese population was carried out to evaluate the potential associations of four polymorphisms (rs16847024, rs17467825, rs2298850, and rs3755967) in the GC gene with risk of breast cancer. We detected three SNPs with statistically significant effects on breast cancer development after adjusting for age, menopausal status, body mass index (BMI), family history of breast cancer, income, waist circumference, and education (rs17467825: adjusted OR = 0.80, 95% CI = 0.65–0.99; rs2298850: adjusted OR = 0.80, 95% CI = 0.65–0.98; rs3755967: adjusted OR = 0.80, 95% CI = 0.65–0.98). Stratified analysis found that when an individual had a waist circumference <80 cm, rs17467825, rs2298850, and rs3755967 could markedly reduce the risk of breast cancer. Significant interactions between polymorphisms of rs2298850 and rs3755967 and waist circumference were also observed for breast cancer risk. Combined analysis revealed a significant association among the allele numbers of protective effects with decreased breast cancer risk (P_trend=0.043). These results indicated that, in the GC gene, genetic mutations might be related to breast cancer susceptibility in Chinese women.

Insulin Resistance in Adults with Type 1 Diabetes is Associated with Lower Vitamin D Serum Concentration

AIM

Type 1 diabetes mellitus (T1DM) is a disease characterized by an absolute deficiency of endogenous insulin secretion. Insulin resistance (IR) may develop among patients with T1DM. Vitamin D deficiency was reported to be a risk factor in the development of IR. The aim of the study was to assess the relationship between serum concentrations of 25-hydroxyvitamin D (25(OH)D) and IR among patients with T1DM.

METHODS

The test group consisted of 110 adult patients [males=65 (59%)] with T1DM. Participants were recruited in Poland between 1^st October and 30^th April in 2015/2016 and 2016/2017. VD serum level was assessed by ELISA array. IR was assessed by estimated Glucose Disposal Rate (eGDR).

RESULTS

In the study group 21 (19%) patients were recognized as IR according to eGDR cut-offs (<7.5 mg/kg/min), 52 (47.3%) patients had VD deficiency (25(OH)D<20 ng/ml), 16 (14.5%) patients had 25(OH)D<10 ng/ml. Only 6 (5%) participants reported VD supplementation. Patients with IR, according to eGDR cut-off revealed significantly lower 25(OH)D serum level 15.7 (9.2-28.4) vs. 22.1 (13.0-38.4) ng/ml; p=0.04 as compared to patients without IR. R Spearman analysis found a positive relationship between VD and eGDR (Rs=0.27; p<0.01). Logistic regression analysis revealed significant relationship between the presence of IR and VD serum level/presence of 25(OH)D serum level below 10 ng/ml, both models adjusted to sex, age, BMI, LDL and triglycerides, accordingly (OR=0.95, CI: 0.90-0.99; p=0.04) and (OR=4.19, CI: 1.04-16.93; p=0.04).

CONCLUSION

The serum concentration of Vitamin D is negatively associated with insulin resistance in patients with T1DM and may have clinical implications.

ASSOCIATIONS BETWEEN VITAMIN D AND MICROVASCULAR COMPLICATIONS IN MIDDLE-AGED AND ELDERLY DIABETIC PATIENTS

Objective: The objective of this cross-sectional study was to investigate the association of serum 25-hydroxyvitamin D (25[OH]D) levels with estimated glomerular filtration rate (eGFR), albumin/creatinine ratio (ACR), and the prevalence of diabetic retinopathy (DR) in Chinese diabetic adults. Methods: A total of 4,767 diabetic participants were enrolled from seven communities in Shanghai, China, in 2018. Participants underwent several examinations, which included the measurement of anthropometric parameters, blood pressure, glucose, lipid profiles, 25(OH)D, and ACR. DR was detected based on high-quality fundus photographs and remotely read by ophthalmologists. Results: Compared with the first 25(OH)D quartile, participants in the fourth quartile had a lower prevalence of high ACR (odds ratio [OR], 0.77; 95% confidence interval [CI], 0.61 to 0.96) (P for trend <.01). No association was found between 25(OH)D levels and eGFR. For DR, the OR (95% CI) for DR ranging from 0 to 4 in ordinal logistic regression associated with 25(OH)D was 0.62 (0.47 to 0.82) for the fourth 25(OH)D quartile (P for trend <.01) compared with the first quartile. These associations were all fully adjusted for confounding factors. Conclusion: Lower serum 25(OH)D concentration is significantly associated with increased ACR and higher prevalence of DR in middle-aged and elderly diabetic adults. However, the possibility of a causal relationship between 25(OH)D deficiency and diabetic microvascular complications remains to be demonstrated. Abbreviations: 25(OH)D = 25-hydroxyvitamin D; ACR = albumin/creatinine ratio; BMI = body mass index; CI = confidence interval; DKD = diabetic kidney disease; DR = diabetic retinopathy; eGFR = estimated glomerular filtration rate; HbA1c = glycated hemoglobin; HDL = high-density lipoprotein; LDL = low-density lipoprotein; OR = odds ratio; T2DM = type 2 diabetes mellitus.

The role of vitamin D in the pathogenesis and treatment of diabetes mellitus: a narrative review

Diabetes mellitus, a metabolic disorder associated with chronic complications, is traditionally classified into two main subtypes. Type 1 diabetes mellitus (T1DM) results from gradual pancreatic islet β cell autoimmune destruction, extending over months or years. Type 2 diabetes mellitus (T2DM) is a heterogeneous disorder, with both insulin resistance and impairment in insulin secretion contributing to its pathogenesis. Vitamin D is a fat-soluble vitamin with an established role in calcium metabolism. Recently, several studies have provided evidence suggesting a role for it in various non-skeletal metabolic conditions, including both types of diabetes mellitus. Preclinical studies of vitamin D action on insulin secretion, insulin action, inflammatory processes, and immune regulation, along with evidence of an increase of hypovitaminosis D worldwide, have prompted several epidemiological, observational, and supplementation clinical studies investigating a potential biological interaction between hypovitaminosis D and diabetes. This narrative review aims to summarize current knowledge on the effect of vitamin D on T1DM and T2DM pathogenesis, prevention, and treatment, as well as on micro- and macrovascular complications of the disease. Furthermore, on the basis of current existing evidence, we aim to highlight areas for potential future research.

The association between 25-hydroxy vitamin D deficiency and diabetic complications in patients with type 2 diabetes mellitus

AIMS

To evaluation the relationship between serum 25-hydroxy vitamin D [25-(OH)D] deficiency and diabetic complications in patients with type 2 diabetes (T2DM).

METHODS

One hundred and sixty three patients with T2DM [DM + uncomplicated (n = 36), DM + nephropathy (n = 31), DM + neuropathy (n = 30), DM + retinopathy (n = 30), DM + cardiovascular disease (CAD) (n = 36)], 35 CAD and 40 healthy volunteers were included.

RESULTS

Serum 25-(OH)D levels were found as significantly lower in all patients compared to the control group (p < 0.05). 25-(OH)D in patients with DM + retinopathy (p < 0.006), DM + nephropathy (p < 0.001) and DM + neuropathy (p < 0.001) was significantly lower than that of the control group. 25-(OH)D in patients with DM + nephropathy (p < 0.001), DM + neuropathy (p < 0.01) and DM + retinopathy (p < 0.001) was significantly lower than in the DM + uncomplicated group. 25-(OH)D levels were found as significantly lower in DM + CAD compared to the CAD group (p < 0.01). Serum 25-(OH)D and HbA1c and parathyroid hormone (PTH) were found to be negatively correlated with each other in DM + all complications.

CONCLUSIONS

Low serum 25-OHD levels were found to be associated with the development of diabetes and complications. Low serum 25-OHD levels may be a consequence of even worse metabolic control of diabetes.

Long-term treatment with metformin in type 2 diabetes and vitamin D levels: A post-hoc analysis of a randomized placebo-controlled trial

AIMS

To study the effects of metformin, as compared to placebo, on serum levels of vitamin D (25-hydroxyvitamin D [25(OH)D]) in patients with advanced type 2 diabetes.

MATERIALS AND METHODS

In the HOME trial, a randomized placebo-controlled trial, 390 insulin-treated patients with type 2 diabetes were treated with 850 mg metformin or placebo thrice daily for 52 months. In a post-hoc analysis, we examined changes in the combined levels of 25(OH)D₂ and 25(OH)D₃ at 4 and 16 months during the study.

RESULTS

Mean combined 25(OH)D at baseline was 68.2 nmoL/L (95% confidence interval [CI]: 65.5-71.1). In mixed model analysis, metformin, as compared to placebo, had no effect on 25(OH)D levels during 16 months (coefficient: 1.002 per month, multiplicative model; 95% CI: 0.998-1.006, P = .30). Metformin was associated with a small increase of 25(OH)D₂ (coefficient: 1.012 per month; 95% CI: 1.003-1.021, P = .008). However, 25(OH)D₂ is only a very small fraction (3%) of 25(OH)D. Seasonal variation had the biggest impact on 25(OH)D levels. Vitamin B12 levels were not associated with the levels of 25(OH)D.

CONCLUSION

Metformin had no effect on serum 25(OH)D during 16 months in the setting of a clinical randomized controlled trial in patients with type 2 diabetes. Our results show that metformin doesn't lead to vitamin D deficiency.

Association of serum vitamin D levels and diabetic retinopathy in Asian Indians with type 2 diabetes

BACKGROUND

Vitamin D deficiency (VDD) is a condition that has been associated with diabetic retinopathy (DR) in various populations, but has not been studied in Asian Indians.

AIMS

To evaluate the association of serum 25-hydroxyvitamin D (25(OH)D) levels with presence and severity of DR among Asian Indians with type 2 diabetes.

METHODS

We collected information on individuals with type 2 diabetes that received care at a tertiary diabetes centre in India, between 2012 and 2015. Patients were 18 years of age or older, underwent retinal examinations with DR severity grading and had serum 25(OH)D measurements.

RESULTS

Serum 25(OH)D levels were lower in patients with retinopathy compared to those without (11.9 ± 2.2 ng/ml vs. 13.7 ± 2.1 ng/ml, p < 0.001). Stratifying patients by DR grade, reduced geometric means of 25(OH)D levels were associated with increased retinopathy severity. After adjusting for six key covariates, VDD was associated with increased rates of proliferative DR (OR 2.05; 95% CI 1.35-3.11; p = 0.001).

CONCLUSIONS

In Asian Indians with type 2 diabetes, lower serum 25(OH)D was associated with increased severity of DR and the presence of VDD was associated with a two-fold increased risk for proliferative DR.

Effect of Treating Vitamin D Deficiency in Uncontrolled Type 2 Diabetes: A Randomized, Placebo-Controlled Study

BACKGROUND

Literature increasingly supports the inverse relationship of vitamin D (VitD) level and type 2 diabetes (T2DM). Proposed protective mechanisms of VitD include its anti-inflammatory effects, increased insulin secretion via pancreatic β-cell stimulation, and downregulation of parathyroid hormone levels. Interventional studies show mixed results of VitD therapy in prediabetic patients with VitD deficiency or diabetic patients with normal VitD levels.

STUDY QUESTION

Does high-dose VitD replacement improve glycemic control and microalbuminuria (MAU) in uncontrolled T2DM and concurrent VitD deficiency?

STUDY DESIGN

This placebo-controlled, double-blinded study randomized 30 subjects aged 30-65 years with an elevated HbA1c level of 7.5%-10% and a low total 25-hydroxyvitamin-D value of <20 ng/mL to either placebo (n = 16) or ergocalciferol 50,000 IU (n = 14) once weekly for 8 weeks then once monthly for 4 months.

MEASURES AND OUTCOMES

Primary outcome was difference in HbA1c from baseline to month 6 between the VitD-intervention group and the placebo-controlled group. Secondary end points were differences in total 25-hydroxyvitamin-D and MAU. Paired t tests and linear mixed-effects models were used for statistical analysis.

RESULTS

No significant differences were seen in HbA1c or MAU between baseline versus postintervention visits within the placebo group (HbA1c: 8.4% ± 0.2 vs. 8.1% ± 0.3, P = 0.088; MAU: 94.1 mg/g ± 43.9 vs. 45.9 mg/g ± 20.2, P = 0.152) and the intervention group (HbA1c: 8.8% ± 0.3 vs. 8.7% ± 0.4, P = 0.692; MAU: 167.8 mg/g ± 70.1 vs. 108.5 mg/g ± 39.9, P = 0.356). The difference between placebo-slope and intervention-slope was nonsignificant for MAU (β = -0.1 mg/g ± 0.4, P = 0.835) but was significant for total 25-hydroxyvitamin-D (β = 11.7 ng/mL ± 2.5, P ≤ 0.001). Greater HbA1c reduction occurred unexpectedly in the placebo group ((Equation is included in full-text article.)= -0.4% ± 0.2) than in the intervention group ((Equation is included in full-text article.)= -0.2% ± 0.4), although the difference in slopes was not significant (β = 0.2% ± 0.4, P = 0.640).

CONCLUSIONS

Our proof-of-concept study found no benefit of high-dose VitD therapy in glycemic control and MAU in uncontrolled T2DM and VitD deficiency. Post hoc analyses raise concerns for high-dose VitD therapy to delay glycemic improvement. Large-scale interventional trials are much needed in this patient population to substantiate our findings and elucidate VitD's mechanisms on glucose metabolism.

Glycated hemoglobin A1C and vitamin D and their association with diabetic retinopathy severity

OBJECTIVES

This retrospective, population-based, cross-sectional study evaluated the association between vitamin D deficiency and retinopathy severity in diabetic patients with poorly or well controlled glycaemia. Other potential risk factors for diabetic retinopathy severity were also assessed.

METHODS

The National Health and Nutrition Examination Survey (NHANES) 2005-2008 data were used for the study. Outcomes assessed included retinopathy severity, HbA1c levels, socioeconomic, behavioral, and biological factors. Univariate and multivariate regression analysis was used to evaluate association of different parameters with retinopathy severity. The interaction among HbA1c control, vitamin D deficiency, and retinopathy severity were also explored.

RESULTS

The population included 842 adults (52.8% women) with mean age of 61.2 years. Retinopathy was detected in 301 subjects (35.7%). Mild non-proliferative retinopathy (NPR) was present in 195 subjects (23.2%), severe non-proliferative and proliferative retinopathy in 106 subjects (12.6%). Multivariate ordinal regression analysis found being male (odds ratio (OR): 1.602, P=0.001), increased duration of diabetes (OR: 1.072, P=3.77E-7) and poorly controlled HbA1c (OR: 3.522, P=2.00E-5) were associated with greater retinopathy severity. The association between vitamin D deficiency and retinopathy severity only found in diabetic patients with well controlled glycaemia.

CONCLUSIONS

The findings of this study indicate that vitamin D deficiency associated with severe diabetic retinopathy in patients with well controlled diabetes. The findings provide possible relationship for the previous conflict results, and highlight the need for controlling modifiable risk factors to reduce the development of sever diabetic retinopathy.

Vitamin D and diabetes mellitus: Causal or casual association?

The incidence of both type 2 and type 1 diabetes mellitus has been increasing worldwide. Vitamin D deficiency, or the awareness of its prevalence, has also been increasing. Vitamin D may have a role in the pathogenic mechanisms predisposing to type 2 diabetes by modulating insulin resistance and/or pancreatic β-cell function. Vitamin D status or elements involved in its activation or transport may also be involved in the development of type 1 diabetes mellitus through immunomodulatory role . Based on these observations a potential association between vitamin D and diabetes has been hypothesized. In this review we discuss up to date evidence linking vitamin D with the development of diabetes. Moreover, the role of vitamin D supplementation in the prevention of both types of diabetes is analysed together with its role in improving glycemic control in diabetic patients. We also address the potential role of vitamin D deficiency in the development of macro- and microvascular complications in diabetes. Finally, we provide recommendation for Vitamin D therapy in diabetes in view of current evidence and highlight areas for potential future research in this area.

A pilot interventional study to evaluate the impact of cholecalciferol treatment on HbA1c in type 1 diabetes (T1D)

BACKGROUND

Higher 25(OH)D3 levels are associated with lower HbA1c, but there are limited UK interventional trials assessing the effect of cholecalciferol on HbA1c.

AIMS

(1) To assess the baseline 25(OH)D3 status in a Manchester cohort of children with type 1 diabetes (T1D). (2) To determine the effect of cholecalciferol administration on HbA1c.

METHODS

Children with T1D attending routine clinic appointments over three months in late winter/early spring had blood samples taken with consent. Participants with a 25(OH)D3 level <50 nmol/L were treated with a one-off cholecalciferol dose of 100,000 (2-10 years) or 160,000 (>10 years) units. HbA1c levels before and after treatment were recorded.

RESULTS

Vitamin D levels were obtained from 51 children. 35 were Caucasian, 11 South Asian and 5 from other ethnic groups. 42 were vitamin D deficient, but 2 were excluded from the analysis. All South Asian children were vitamin D deficient, with mean 25(OH)D3 of 28 nmol/L. In Caucasians, there was a negative relationship between baseline 25(OH)D3 level and HbA1c (r = -0.484, P < 0.01). In treated participants, there was no significant difference in mean HbA1c at 3 months (t = 1.010, P = 0.328) or at 1 year (t = -1.173, P = 0.248) before and after treatment. One-way ANCOVA, controlling for age, gender, ethnicity, BMI and diabetes duration showed no difference in Δ HbA1c level.

CONCLUSION

We report important findings at baseline, but in children treated with a stat dose of cholecalciferol, there was no effect on HbA1c. Further studies with larger sample sizes and using maintenance therapy are required.

Vitamin D (25(OH)D) in patients with chronic kidney disease stages 2-5

OBJECTIVE

To establish the impact the chronic kidney disease stage has in the native vitamin D levels in patients not undergoing dialysis treatment.

METHODS

A study performed in Manizales, Colombia, a city located 2,200 meters above sea level, without important stational variations. Patients with 18 years of age or more, with chronic kidney disease stages 2 to 5 and not undergoing dialysis treatment were recruited for this study. Demographic and anthropometric variations were evaluated as well as solar exposure, CKD etiology and laboratory variables related to bone and mineral diseases. For each CKD clinical stage, correlations were evaluated for vitamin D levels, laboratory results for bone and mineral diseases, solar exposure and ethnicity.

RESULTS

Three hundred thirty-three patients were evaluated with a median age of 71 years, most of them mestizo (71%), 173 were women. The main CKD etiology was hypertensive nephropathy (32.2%). 21.1% of patients had normal vitamin D levels, 70.1% were within insufficient range and 8.8% were in deficit. A negative correlation was found between the levels of vitamin 25 (OH) D and the values for: creatinine, phosphorous, calcium x phosphorous product, PTH, 24 hours urine protein and BMI. A positive relationship was found for calcium and albumin. Positive significant statistical correlation was found for vitamin 25(OH) D levels and solar exposure for stages 3b and 4 of CKD.

CONCLUSIONS

It is common to find low levels of vitamin 25(OH) D in patients with CKD; these can contribute to the appearance of secondary hyperparathyroidism.

OBJETIVO

Establecer el impacto del estadio clínico en los niveles de vitamina D nativa en pacientes con enfermedad renal crónica (ERC) sin diálisis.

MÉTODOS

Estudio realizado en Manizales, Colombia, una ciudad tropical ubicada a 2,200 metros de altura sobre el nivel del mar, sin variaciones estacionales importantes a lo largo del año. Se incluyeron pacientes mayores de 18 años, con enfermedad renal crónica estadio 2 a 5 sin tratamiento dialítico. En ellos se evaluaron variables demográficas, antropométricas, grado de exposición solar, etiología de la enfermedad, y variables de laboratorio relacionadas con desórdenes óseos y minerales. Para cada estadío clínico se evaluó la correlación entre los niveles de vitamina D y los resultados de las pruebas de laboratorio relacionadas con desordenes óseos y minerales, exposición solar y etnia.

RESULTADOS

Se evaluaron 331 pacientes, con una edad media de 71 años, la mayoría mestizos (71%), 173 mujeres. La principal etiología de ERC fue nefropatía hipertensiva (33.2%). El 21.1% de los pacientes tenían niveles normales de vitamina D, fueron insuficientes en 70.1% y 8.8% en déficit. Se detectó correlación negativa, entre los niveles de vitamina 25(OH)D y los valores de creatinina, fósforo, producto calcio x fósforo, PTH, proteínas en orina de 24 horas e IMC. Correlación positiva para el calcio y la albumina. Se encontró significancia estadística positiva entre los niveles de vitamina 25(OH)D y la exposición solar para los estadios 3b y 4.

CONCLUSIONES

En pacientes con ERC es comun detectar bajos niveles de 25(OH)D, los cuales pueden contribuir a la generación de hiperparatiroidismo secundario.

Adequate vitamin D status is associated with the reduced odds of prevalent diabetic retinopathy in African Americans and Caucasians

BACKGROUND

Vitamin D status has been hypothesized to protect against development of diabetic retinopathy via its anti-inflammatory and anti-angiogenic properties. Additionally, in vitro and in vivo studies suggest vitamin D favorably influences blood pressure and blood glucose control, strong risk factors for diabetic retinopathy. We examined the association between vitamin D status and prevalent diabetic retinopathy in participants with diabetes from a population-based cohort.

METHODS

Among participants in the Atherosclerosis Risk in Communities (ARIC) study with diabetes at visit 3 (1993-1995), 1339 (906 Caucasians, 433 African Americans) had serum 25-hydroxyvitamin (25[OH]D) concentrations assessed at visit 2 (1989-1992) and nonmydriatic retinal photographs taken at visit 3. Dietary intake of vitamin D was assessed at visit 1 (1987-1989). Logistic regression was used to estimate odds ratios (ORs) and 95 % confidence intervals (CIs) for diabetic retinopathy by categories of season-adjusted 25(OH)D (<30 [referent], 30-<50, 50-<75 and ≥75 nmol/L), by quartile of vitamin D intake (IU/day), and use of vitamin D or fish oil supplements (yes/no). P for trend was estimated using continuous 25(OH)D or vitamin D intake. ORs were adjusted for race, and duration of diabetes. We further adjusted for HBA1c and hypertension to examine if 25(OH)D influenced diabetic retinopathy via its effects on either glycemic control or blood pressure.

RESULTS

ORs (95 % CIs) for retinopathy, adjusted for race and duration, were 0.77 (0.45-1.32), 0.64 (0.37-1.10), and 0.39 (0.20-0.75), p for trend = 0.001, for participants with 25(OH)D of 30-<50, 50-<75, and ≥75 nmol/L, respectively. Further adjustment for hypertension minimally influenced results (data not show), but adjustment for HBA1c attenuated the OR among those with 25(OH)D ≥75 (0.47 [0.23-0.96], p for trend = 0.030). No statistically significant association was observed between vitamin D intake from foods or supplements and retinopathy.

CONCLUSIONS

25(OH)D concentrations ≥75 nmol/L were associated with lower odds of any retinopathy assessed 3 years later. We speculate this may be due in part to vitamin D's influence on blood glucose control.

High levels of serum vitamin D are associated with a decreased risk of metabolic diseases in both men and women, but an increased risk for coronary artery calcification in Korean men

Background

There are conflicting results for relationships between serum vitamin D levels and metabolic diseases. The aim of this study was to investigate whether serum vitamin D levels were associated with various metabolic diseases including insulin resistance (IR), metabolic syndrome (MS), fatty liver (FL), and coronary artery calcification (CAC), along with assessing gender differences for these relationships in Korean adults.

Methods

A total of 180,918 subjects (98,412 men and 82,506 women) who participated in a comprehensive health examination in the 2012–2013 period at Kangbuk Samsung Hospital, College of Medicine, Sungkyunkwan University were included. Serum vitamin D and metabolic markers were analyzed and CAC was estimated. Subjects were divided according to quartile groups of serum vitamin D. To examine the relationships of serum vitamin D to metabolic diseases and metabolic factors, multivariate logistic analysis was conducted.

Results

High levels of serum vitamin D was associated with lower ORs for MS, IR and FL both in men and women (all p < 0.05). For men, ORs for CAC were significantly higher in third and the highest quartile groups for serum vitamin D in all the analyzed models (all p < 0.05). However, women showed no significant results between serum vitamin D and CAC.

Conclusions

High levels of serum vitamin D were associated with lower risk of MS, IR and FL in both Korean men and women, but were associated with higher risk of CAC only in men, and not in women.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0432-3) contains supplementary material, which is available to authorized users.

Calcitriol regulates angiotensin-converting enzyme and angiotensin converting-enzyme 2 in diabetic kidney disease

To investigate the effects of calcitriol on angiotensin-converting enzyme (ACE) and ACE2 in diabetic nephropathy. Streptozotocin (STZ) induced diabetic rats were treated with calcitriol for 16 weeks. ACE/ACE2 and mitogen activated protein kinase (MAPK) enzymes were measured in the kidneys of diabetic rats and rat renal tubular epithelial cells exposed to high glucose. Calcitriol reduced proteinuria in diabetic rats without affecting calcium-phosphorus metabolism. ACE and ACE2 levels were significantly elevated in diabetic rats compared to those in control rats. The increase in ACE levels was greater than that of ACE2, leading to an elevated ACE/ACE2 ratio. Calcitriol reduced ACE levels and ACE/ACE2 ratio and increased ACE2 levels in diabetic rats. Similarly, high glucose up-regulated ACE expression in NRK-52E cells, which was blocked by the p38 MAPK inhibitor SB203580, but not the extracellular signal-regulated kinase (ERK) inhibitor FR180204 or the c-Jun N-terminal kinase (JNK) inhibitor SP600125. High glucose down-regulated ACE2 expression, which was blocked by FR180204, but not SB203580 or SP600125. Incubation of cells with calcitriol significantly inhibited p38 MAPK and ERK phosphorylation, but not JNK phosphorylation, and effectively attenuated ACE up-regulation and ACE2 down-regulation in high glucose conditions. The renoprotective effects of calcitriol in diabetic nephropathy were related to the regulation of tubular levels of ACE and ACE2, possibly by p38 MAPK or ERK, but not JNK pathways.

Vitamin D and Diabetic Complications: True or False Prophet?

Vitamin D deficiency is now recognized as a condition of increasing prevalence worldwide. Vitamin D has an established role in calcium and bone metabolism; however, more recently associations with vitamin D deficiency and risk of developing diabetes, diabetes complications, and cardiovascular disease have all been acknowledged. The vitamin D receptor is ubiquitously expressed, and experimental, in vitro, and in vivo studies strongly suggest a role in regulating the transcription of multiple genes beyond calcium homeostasis. These include antiproliferative, immunomodulatory, angiogenic, inhibition of the renin-angiotensin-aldosterone system, and neurotrophic factor expression. Observational studies report a strong association between vitamin D deficiency and cardiovascular and metabolic disorders; however, there remains a paucity of large long-term randomized clinical trials showing a benefit with treatment. An increasing body of literature suggests a possible pathogenetic role of vitamin D in the long-term complications of diabetes and vitamin D deficiency may also exacerbate symptoms of painful diabetic peripheral neuropathy. It remains unknown if supplementation of vitamin D to normal or non-deficient levels alters pathogenetic processes related to diabetic microvascular complications. With the high prevalence of vitamin D deficiency in patients with diabetes and putative mechanisms linking vitamin D deficiency to diabetic complications, there is a compelling argument for undertaking large well-designed randomized controlled trials of vitamin D supplementation.

Early changes in cardiovascular structure and function in adolescents with type 1 diabetes

Background

Children with type 1 diabetes (T1D) are at higher risk of early adult-onset cardiovascular disease. We assessed cardiovascular structure and function in adolescents with T1D compared with healthy controls and the relationships between peripheral vascular function and myocardial parameters.

Methods and results

199 T1D [14.4 ± 1.6 years, diabetes duration 6.2 (2.0–12.8) years] and 178 controls (14.4 ± 2.1 years) completed endothelial function by flow mediated vasodilatation (FMD), arterial stiffness using pulse wave velocity (PWV) along with M-mode, pulse wave and tissue Doppler, and myocardial deformation echocardiographic imaging. Systolic (113 ± 10 vs. 110 ± 9 mmHg; p = 0.0005) and diastolic (62 ± 7 vs. 58 ± 7 mmHg; p < 0.0001) blood pressures, carotid femoral PWV and endothelial dysfunction measurements were increased in T1D compared with controls. Systolic and diastolic left ventricular dimensions and function by M-mode and pulse wave Doppler assessment were not significantly different. Mitral valve lateral e’ (17.6 ± 2.6 vs. 18.6 ± 2.6 cm/s; p < 0.001) and a’ (5.4 ± 1.1 vs. 5.9 ± 1.1 cm/s; p < 0.001) myocardial velocities were decreased and E/e’ (7.3 ± 1.2 vs. 6.7 ± 1.3; p = 0.0003) increased in T1D. Left ventricular mid circumferential strain (−20.4 ± 2.3 vs. −19.5 ± 1.7 %; p < 0.001) was higher, whereas global longitudinal strain was lower (−19.0 ± 1.9 vs. −19.8 ± 1.5 % p < 0.001) in T1D.

Conclusions

Adolescents with T1D exhibit early changes in blood pressure, peripheral vascular function and left ventricular myocardial deformation indices with a shift from longitudinal to circumferential shortening. Longitudinal follow-up of these changes in ongoing prospective trials may allow detection of those most at risk for cardiovascular abnormalities including hypertension that could preferentially benefit from early therapeutic interventions.

Vitamin D Deficiency Is Not Associated with Diabetic Retinopathy or Maculopathy

BACKGROUND

Experimental and clinical studies suggest a possible association between vitamin D deficiency and both diabetic retinopathy and maculopathy.

METHODS

We have performed a cross-sectional study in adults with types 1 and 2 diabetes mellitus. The relationship between the presence and severity of diabetic retinopathy and maculopathy with serum 25-hydroxyvitamin D concentration was evaluated using logistic regression analyses in the presence of demographic and clinical covariates.

RESULTS

657 adults with diabetes were stratified based on retinopathy grading: No Diabetic Retinopathy (39%), Background Diabetic Retinopathy (37%), Preproliferative Diabetic Retinopathy (21%), and Proliferative Diabetic Retinopathy (3%), respectively. There were no differences in serum 25-hydroxyvitamin D concentrations (25(OH)D) between the groups (15.3 ± 9.0 versus 16.4 ± 10.5 versus 15.9 ± 10.4 versus 15.7 ± 8.5 ng/mL, P = NS). Logistic regression analysis demonstrated no statistically significant relationship between the severity of retinopathy and serum 25(OH)D. Furthermore, there was no difference in serum 25(OH)D between those with (n = 94, 14%) and those without (n = 563, 86%) Diabetic Maculopathy (16.2 ± 10.0 versus 15.8 ± 9.8, P = NS) and no relationship was demonstrated by logistic regression analyses between the two variables.

CONCLUSIONS

This study has found no association between serum 25(OH)D and the presence and severity of diabetic retinopathy or maculopathy.