The effects of short-term vitamin D supplementation on glucose metabolism in dialysis patients: a systematic review and meta-analysis

Effect of vitamin D supplementation on type 2 diabetes biomarkers: an umbrella of interventional meta-analyses

BACKGROUND

Vitamin D supplementation exerts several supporting effects on improving glycemic status, however, results are inconclusive. Thus, in the present study, we aimed to conduct an umbrella of meta-analysis regarding the impact of vitamin D on type 2 diabetes (T2DM) biomarkers.

METHODS

The Scopus, PubMed, Web of Science, Embase, and Google Scholar online databases were searched up to March 2022. All meta-analyses evaluating the impact of vitamin D supplementation on T2DM biomarkers were considered eligible. Overall, 37 meta-analyses were included in this umbrella meta-analysis.

RESULTS

Our findings indicated that vitamin D supplementation significantly decreased fasting blood sugar (FBS) (WMD =  - 3.08; 95% CI: - 3.97, - 2.19, p < 0.001, and SMD =  - 0.26; 95% CI: - 0.38, - 0.14, p < 0.001), hemoglobin A1c (HbA1c) (WMD =  - 0.05; 95% CI: - 0.10, - 0.01, p = 0.016, and SMD =  - 0.16; 95% CI: - 0.27, - 0.05, p = 0.004), insulin concentrations (WMD =  - 2.62; 95% CI: - 4.11, - 1.13; p < 0.001, and SMD =  - 0.33; 95% CI: - 0.56, - 0.11, p = 0.004), and homeostatic model assessment for insulin resistance (HOMA-IR) (WMD =  - 0.67; 95% CI: - 1.01, - 0.32, p < 0.001, and SMD =  - 0.31; 95% CI: - 0.46, - 0.16, p < 0.001).

CONCLUSION

This umbrella meta-analysis proposed that vitamin D supplementation may improve T2DM biomarkers.

The Effects of Vitamin D Supplementation on Anthropometric and Biochemical Indices in Patients With Non-alcoholic Fatty Liver Disease: A Systematic Review and Meta-analysis

Background: Vitamin D was reported to be associated with non-alcoholic fatty liver disease (NAFLD). This systematic review and meta-analysis aimed to investigate the effects of the vitamin D supplementation on anthropometric and biochemical indices in patient with NAFLD. Methods: PubMed, Web of science, Scopus, and Embase databases were explored to identify all randomized controlled trial (RCT) investigating the effects of vitamin D supplementation on anthropometric and biochemical indices in patients with NAFLD. A random-effects model was used to pool weighted mean difference (WMD) and corresponding 95% confidence intervals (CIs). The statistical heterogeneity among the studies was assessed using I2 statistic (high ≥ 50%, low < 50%) and Cochran's Q-test. Results: Sixteen RCTs were included in this meta-analysis. The results identified that high-density lipoprotein-cholesterol (HDL-C) level significantly increased following vitamin D supplementation (P = 0.008). Vitamin D reduced body weight (P = 0.007), body mass index (P = 0.002), waist circumstance (WC) (P = 0.02), serum alanine transaminase (ALT) (P = 0.01), fasting blood sugar (FBS) (P = 0.01), homeostatic model assessment for insulin resistance (HOMA-IR) (P = 0.004), and calcium (P = 0.01). No significant changes were found on body fat, triglyceride (TG), total cholesterol, low-density lipoprotein-cholesterol (LDL-C), aspartate transaminase, alkaline phosphatase, gamma-glutamyl transferase, and adiponectin following vitamin D supplementation. Conclusion: Vitamin D had significant effects on anthropometric and biochemical indices including HDL-C, body weight, BMI, WC, serum ALT, serum FBS, HOMA-IR, and calcium. Vitamin D supplementation can be considered as an effective strategy in management of patients with NAFLD. Systematic Review Registration: [website], identifier [registration number].

No effect of vitamin D supplementation on metabolic parameters but on lipids in patients with type 2 diabetes and chronic kidney disease

Background/Aims: Trials on the effects of cholecalciferol supplementation in type 2 diabetes with chronic kidney disease patients were underexplored. Therefore, the aim of this study was to investigate the effects of two different doses of vitamin D supplementation on serum 25-hydroxyvitamin D [25(OH)D] concentrations and metabolic parameters in vitamin D-deficient Korean diabetes patients with chronic kidney disease. Methods: 92 patients completed this study: the placebo group (A, n = 33), the oral cholecalciferol 1,000 IU/day group (B, n = 34), or the single 200,000 IU injection group (C, n = 25, equivalent to 2,000 IU/day). 52% of the patients had less than 60 mL/min/1.73m² of glomerular filtration rates. Laboratory test and pulse wave velocity were performed before and after supplementation. Results: After 12 weeks, serum 25(OH)D concentrations of the patients who received vitamin D supplementation were significantly increased (A, -2.4 ± 1.2 ng/mL vs. B, 10.7 ± 1.2 ng/mL vs. C, 14.6 ± 1.7 ng/mL; p < 0.001). In addition, the lipid profiles in the vitamin D injection group (C) showed a significant decrease in triglyceride and a rise in HDL cholesterol. However, the other parameters showed no differences. Conclusions: Our data indicated that two different doses and routes of vitamin D administration significantly and safely increased serum 25(OH)D concentrations in vitamin D-deficient diabetes patients with comorbid chronic kidney disease. In the group that received the higher vitamin D dose, the lipid profiles showed significant improvement, but there were no beneficial effects on other metabolic parameters.

The Effects of Dairy Intake on Insulin Resistance: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

The incidence of type 2 diabetes mellitus (DM) has increased in the US over the last several years. The consumption of low-fat dairy foods has been linked with decreasing the risk of DM but studies have yet to show a clear correlation. We conducted a systematic review and meta-analysis of randomized clinical trials (RCTs) evaluating the effects of dairy intake on homeostatic model assessment of insulin resistance (HOMA-IR), waist circumference, and body weight. In MEDLINE and Embase, we identified and reviewed 49 relevant RCTs: 30 had appropriate data format for inclusion in the meta-analysis. Using the Review Manager 5 software, we calculated the pooled standardized mean differences comparing dairy dietary interventions to control for our outcomes of interest. For HOMA-IR (794 individuals), we found a mean difference of −1.21 (95% CI −1.74 to −0.67; p-value < 0.00001; I² = 92%). For waist circumference (1348 individuals), the mean difference was −1.09 cm (95% CI 1.68 to −0.58; p-value < 0.00001; I² = 94%). For body weight (2362 individuals), the dairy intake intervention group weighed 0.42 kg less than control (p-value < 0.00001; I² = 92%). Our findings suggest that dairy intake, especially low-fat dairy products, has a beneficial effect on HOMA-IR, waist circumference, and body weight. This could impact dietary recommendations to reduce DM risk.

Insights into the Association of Vitamin D Deficiency with Parathyroid Hormone Levels with Relevance to Renal Function and Insulin Resistance

Objective:

The rationale of the current study was to investigate whether this inverse association is agedependent and whether it has any role in modulating renal function and insulin resistance.

Methods:

To test this hypothesis, we have carried out a hospital based study enrolling 848 subjects (558 men and 290 women) with the mean age of 50.9 ± 15.9 y. Chemiluminometric competitive immune assays were performed using commercial kits to determine 25-OH vitamin D and Parathyroid Hormone (PTH) levels. Fasting glucose levels and serum creatinine were used to evaluate diabetes and renal function.

Results:

Vitamin D deficiency was predominant irrespective of age group (p = 0.21) and gender (p = 0.12). An inverse association between vitamin D and PTH was observed (r = -0.24) in middle age subjects (p = 0.02). The data segregation based on plasma vitamin D levels which were <20 ng/ml, 20.1- 30 ng/ml and >30 ng/ml confirmed the inverse association between vitamin D and PTH levels (ptrend: 0.007). Subjects with low plasma vitamin D and increased PTH exhibited elevated blood urea, serum creatinine and blood glucose. Subjects with 25-OHD deficiency showed a 3.03-folds (95% CI: 2.26- 4.07) and 2.09-fold (1.41-3.10) increased risk for diabetes and renal disease, respectively.

Conclusion:

Based on the results of the present study, it is suggested that those with vitamin D deficiency need to be evaluated for possible presence of renal dysfunction, diabetes/insulin resistance in addition to assessing their PTH status.

Pre, peri and posttransplant diabetes mellitus

PURPOSE OF REVIEW

The leading cause of death in both chronic kidney disease (CKD) and renal transplant patients is cardiovascular events. Post-transplant diabetes mellitus (PTx-DM), which is a major cardiovascular risk factor, is a metabolic disorder that affects 5.5-60.2% of renal allograft recipients by 1-year posttransplant (PTx). PTx-DM has been associated with a negative impact on patient and graft outcomes and survival.

RECENT FINDINGS

Individuals who develop PTx-DM are usually prone to this condition prior to and/or after developing CKD. Genetic factors, obesity, inflammation, medications and CKD all are risk factors for PTx-diabetes mellitus. The path to development of disease continues PTx frequently augmented by the use of diabetogenic maintenance immunosuppressive and some nonimmunosuppressive medications. These risk factors are usually associated with an increase in insulin resistance, a decrease in insulin gene expression and/or β-cell dysfunction and apoptosis.

SUMMARY

Some new anti-diabetes mellitus medications may help to improve the overall outcome; however, there is a real need for developing a preventive strategy. Identifying and targeting PTx-DM risk factors may help to guide the development of an effective programme. This could include the adoption of nondiabetogenic immunosuppressive protocols for high-risk patients.

Treating endothelial dysfunction with vitamin D in chronic kidney disease: a meta-analysis

Background

Vitamin D deficiency is common in patients with chronic kidney disease (CKD), and is associated with endothelial dysfunction and cardiovascular disease. We performed a meta-analysis to assess the effect of vitamin D treatment on flow mediated vasodilation (FMD) in CKD patients.

Methods

PubMed/Medline, Web of Science, Embase and Cochrane trials and reviews were searched systematically for randomized controlled trials (RCT:s) using any vitamin D compound, at any stage of CKD, with FMD as outcome. Fixed and random effects models were performed using the standardized mean difference effect size post treatment for each trial. Heterogeneity was assessed by I² statistics.

Results

4 trials were included, comprising 305 patients. One used both 1 and 2 μg for two intervention groups and was therefore split in two during the analysis. Patients in the included trials had a mean age of 44–65 years and were all in CKD 3 to 4. One study used cholecalciferol, the others all used paricalcitol as treatment. Study duration was 12–16 weeks. Intervention with vitamin D was associated with ameliorated FMD (STANDmean ES 0.78, 95% CI 0.55–1.01) in a fixed model. Heterogeneity was substantial (I² = 84%). Secondary analysis with random model analysis also showed significant results.

Conclusions

Short term intervention with vitamin D is associated with improvements in endothelial function, as measured by FMD. This indicates positive effects of vitamin D on vascular disease in CKD. Limitations of this meta-analysis are the small number of studies performed, and the short duration of intervention.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1042-y) contains supplementary material, which is available to authorized users.

Vitamin D receptor activation by paricalcitol and insulin resistance in CKD

BACKGROUND AND AIMS

The nature of the link (causal vs non-causal) between low 1,25-OH vitamin D and insulin resistance (IR) in patients with chronic kidney disease (CKD) remains elusive. We have now made a post hoc analysis of the effect of vitamin D receptor activation by paricalcitol on IR in the complete dataset of a double-blind, randomized, placebo controlled trial, the Paricalcitol and ENdothelial fuNction in chronic kidneY disease (PENNY).

METHODS AND RESULTS

Eighty-eight patients with stage 3-4 CKD were randomized (1:1) to receive 2 μg/day paricalcitol or matching placebo for 12 weeks. IR was measured by five IR indices: the homeostasis model assessment of insulin resistance (HOMA-IR), the quantitative insulin sensitivity check index (QUICKI), the McAuley index, the HOMA corrected for adiponectin (HOMA-AD) and the Leptin-adiponectin ratio (LAR). As compared to placebo, paricalcitol produced the expected small rise in serum calcium (+0.07 mmol/L, P = 0.01) and phosphate (+0.08 mmol/L, P = 0.034) and the expected parathyroid hormone suppression (-96 pg/ml, P < 0.001). However, the drug largely failed to affect the five indices of IR which remained unchanged both in the active and the placebo arm (paricalcitol vs placebo, P ranging from 0.25 to 0.62) and no effect modification of paricalcitol on IR by vitamin D or other parameters was registered.

CONCLUSION

Paricalcitol treatment for 12 weeks does not improve IR in patients with stage 3-4 CKD. Low vitamin D receptor activation is not a causal factor for IR in the CKD population.

Association between serum 25-hydroxyvitamin D and glycated hemoglobin levels in type 2 diabetes patients with chronic kidney disease

AIMS/INTRODUCTION

Vitamin D is suggested to influence glucose homeostasis. An inverse relationship between serum 25-hydroxyvitamin D (25[OH]D) and glycemic control in non-chronic kidney disease (CKD) patients with type 2 diabetes was reported. We aimed to examine this association among type 2 diabetes patients with CKD.

MATERIALS AND METHODS

A total of 100 type 2 diabetes participants with stage 3-4 CKD were recruited. Blood for glycated hemoglobin (HbA1c ), serum 25(OH)D, renal and lipid profiles were drawn at enrollment. Correlation and regression analyses were carried out to assess the relationship of serum 25(OH)D, HbA1c and other metabolic traits.

RESULTS

A total of 30, 42, and 28% of participants were in CKD stage 3a, 3b and 4, respectively. The proportions of participants based on ethnicity were 51% Malay, 24% Chinese and 25% Indian. The mean (±SD) age and body mass index were 60.5 ± 9.0 years and 28.3 ± 5.9 kg/m2 , whereas mean HbA1c and serum 25(OH)D were 7.9 ± 1.6% and 37.1 ± 22.2 nmol/L. HbA1c was negatively correlated with serum 25(OH)D (rs = -0.314, P = 0.002), but positively correlated with body mass index (rs = 0.272, P = 0.006) and serum low-density lipoprotein cholesterol (P = 0.006). There was a significant negative correlation between serum 25(OH)D and total daily dose of insulin prescribed (rs = -0.257, P = 0.042). Regression analyses showed that every 10-nmol/L decline in serum 25(OH)D was associated with a 0.2% increase in HbA1c .

CONCLUSIONS

Lower serum 25(OH)D was associated with poorer glycemic control and higher insulin use among multi-ethnic Asians with type 2 diabetes and stage 3-4 CKD.

Effects of Vitamin D Supplementation on Glucose and Insulin Homeostasis and Incident Diabetes among Nondiabetic Adults: A Meta-Analysis of Randomized Controlled Trials

AIMS

Emerging evidence has suggested a mechanistic link from vitamin D metabolism to glucose and insulin homeostasis. This study is aimed at specifically quantifying the direct effects of vitamin D supplementation on indexes of glucose and insulin homeostasis as well as incidence of type 2 diabetes (T2D) among nondiabetic adults.

METHODS

We systematically searched randomized controlled trials (RCTs) of vitamin D supplementation in nondiabetic adults in PubMed, EMBASE, and CENTRAL. Random-effects meta-analysis was conducted to pool the estimates.

RESULTS

Our meta-analysis included 47 RCTs involving 44,161 nondiabetic individuals with a median trial duration of 4 months and a median dose of 4000 IU/d. Vitamin D supplementation significantly reduced fasting glucose by 0.11 mmol/L, fasting insulin by 1.47 mIU/L, and HOMA-IR by 0.32 while increasing total 25 (OH) D levels by 40.14 nmol/L. We found no significant effects of vitamin D supplementation on insulin secretion or beta cell function indexes. Based on the data from six trials involving 39,633 participants and 2533 incident T2D cases, vitamin D supplementation was not associated with the risk of incident diabetes compared to placebo (pooled relative risk: 1.01, 95% confidence interval: 0.93 to 1.08).

CONCLUSIONS

Our meta-analysis found that vitamin D supplementation might improve glucose and insulin metabolism without affecting the risk of T2D among nondiabetic adults.

Clinical Trial on the Effects of Vitamin D Supplementation on Metabolic Profiles in Diabetic Hemodialysis

The current study was conducted to assess the effects of vitamin D supplementation on insulin metabolism, lipid fractions, biomarkers of inflammation, and oxidative stress in diabetic hemodialysis (HD) patients. This randomized double-blind placebo-controlled clinical trial was carried out among 60 diabetic HD patients. Subjects were randomly allocated into two groups to intake either oral vitamin D3 supplements at a dosage of 50 000 IU (n=30) or placebo (n=30) every 2 weeks for 12 weeks. After 12 weeks of intervention, subjects who received vitamin D supplements compared with the placebo had significantly decreased serum insulin concentrations (-3.4±3.7 vs. +2.0±4.2 μIU/ml, p<0.001), homeostasis model of assessment-estimated insulin resistance (HOMA-IR) (-1.2±1.8 vs. +0.9±2.3, p<0.001), and improved quantitative insulin sensitivity check index (QUICKI) (+0.02±0.03 vs. -0.01±0.02, p<0.001). In addition, compared with the placebo, vitamin D supplementation led to significant reductions in serum high-sensitivity C-reactive protein (hs-CRP) (-1.4±2.5 vs. +1.4±4.8 mg/l, p=0.007), plasma malondialdehyde (MDA) (-0.1±0.2 vs. +0.1±0.2 μmol/l, p=0.009) and a significant increase in plasma total antioxidant capacity (TAC) concentrations (+33.8±56.7 vs. -2.0±74.5 mmol/l, p=0.04). We did not see any significant effect of vitamin D supplementation on lipid profiles and other biomarkers of inflammation and oxidative stress compared with the placebo. Overall, we found that vitamin D supplementation had beneficial effects on serum insulin, HOMA-IR, QUICKI, serum hs-CRP, plasma MDA, and TAC levels among diabetic HD patients for 12 weeks. CLINICAL REGISTRATION:: http://www.irct.ir: IRCT201611155623N92.

The effects of vitamin D supplementation on metabolic profiles and liver function in patients with non-alcoholic fatty liver disease: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to summarize the evidence on the effect of vitamin D supplementation on metabolic profiles in patients with non-alcoholic fatty liver disease (NAFLD).

METHODS

We systematically searched PubMed, EMBASE and five other databases to identify all RCTs investigating the association between vitamin D and NAFLD up until 5 October 2016. Seven RCTs with 452 participants (227 patients and 225 controls) were included in the meta-analysis.

RESULTS

The results showed that vitamin D administration had no beneficial effect on fasting plasma glucose (FPG) (standardized mean difference [SMD]-0.23; 95% confidence interval [CI], -0.88, 0.42), insulin (SMD -1.09; 95% CI, -2.70,0.52) and homeostasis model assessment of insulin resistance (HOMA-IR) (SMD -1.89; 95% CI, -3.88,0.09). Vitamin D supplementation also had no effect on lipid profiles including triglycerides (SMD -0.36; 95% CI, -1.77, 1.04), and total-cholesterol (SMD -0.46; 95% CI: -1.3, 0.39), as well as on aspartate transaminase (AST) (SMD -0.53; 95% CI, -1.11, 0.05), alanine aminotransferase (ALT) (SMD -0.66; 95% CI, -1.43,0.11), and body mass index (BMI) (SMD -0.25; 95% CI, -0.76,0.27).

CONCLUSIONS

Vitamin D supplementation had no effect on FPG, insulin, HOMA-IR, triglycerides, total-, LDL-cholesterol, AST, ALT, and BMI.

Clinical trial of the effects of vitamin D supplementation on psychological symptoms and metabolic profiles in maintenance methadone treatment patients

BACKGROUND

Vitamin D deficiency may be associated with some complications including nonspecific musculoskeletal pain and periodontal disease in maintenance methadone treatment (MMT) patients. This study was designed to determine the effect of vitamin D supplementation on psychological symptoms and metabolic profiles in MMT patients.

METHODS

This randomized, double-blind, placebo-controlled, clinical trial was carried out among 68 MMT patients. Participants were randomly allocated to receive either 50,000IU vitamin D supplements (n=34) or placebo (n=34) every 2weeks for 12weeks. Fasting blood samples were taken at baseline and post-intervention to evaluate relevant variables.

RESULTS

After the 12-week intervention, serum 25(OH) vitamin D levels significantly increased in the intervention group compared with the placebo group (+8.1±4.9 vs. -0.4±3.0, P<0.001). In addition, vitamin D supplementation significantly improved Pittsburgh Sleep Quality Index (-1.5±2.2 vs. -0.2±2.3, P=0.02) and Beck Depression Inventory (-4.8±7.3 vs. -1.5±6.1, P=0.04) compared with the placebo. Patients who received vitamin D supplements had significantly decreased fasting plasma glucose (-7.5±10.6 vs. +0.3±10.7mg/dL, P=0.004), serum insulin levels (-3.6±5.3 vs. -0.9±3.5 μIU/mL, P=0.01), homeostasis model of assessment-insulin resistance (-1.0±1.3 vs. -0.2±0.7, P=0.003), serum triglycerides (-9.6±30.8 vs. +15.6±30.2mg/dL, P=0.001), total- (-8.7±20.9 vs. +11.0±27.4mg/dL, P=0.001) and LDL-cholesterol (-11.1±17.9 vs. +5.9±27.5mg/dL, P=0.004) compared with the placebo. Additionally, vitamin D intake resulted in a significant decrease in serum high sensitivity C-reactive protein (-2.2±4.2 vs. +2.0±3.7mg/L, P<0.001), and significant increases plasma total antioxidant capacity (+26.2±99.8 vs. -86.3±127.5mmol/L, P<0.001) and glutathione levels (+292.3±172.4 vs. +48.9±208.9μmol/L, P<0.001) compared with the placebo. There was no significant effect of vitamin D supplementation on serum HDL-cholesterol, and other markers of insulin metabolism, inflammation and oxidative stress.

CONCLUSIONS

Totally, taking 50,000IU vitamin D supplement every 2weeks for 12weeks in MMT patients had beneficial effects on psychological symptoms and few metabolic profiles.

Insulin resistance in chronic kidney disease: a systematic review

Insulin resistance (IR) is an early metabolic alteration in chronic kidney disease (CKD) patients, being apparent when the glomerular filtration rate is still within the normal range and becoming almost universal in those who reach the end stage of kidney failure. The skeletal muscle represents the primary site of IR in CKD, and alterations at sites beyond the insulin receptor are recognized as the main defect underlying IR in this condition. Estimates of IR based on fasting insulin concentration are easier and faster but may not be adequate in patients with CKD because renal insufficiency reduces insulin catabolism. The hyperinsulinemic euglycemic clamp is the gold standard for the assessment of insulin sensitivity because this technique allows a direct measure of skeletal muscle sensitivity to insulin. The etiology of IR in CKD is multifactorial in nature and may be secondary to disturbances that are prominent in renal diseases, including physical inactivity, chronic inflammation, oxidative stress, vitamin D deficiency, metabolic acidosis, anemia, adipokine derangement, and altered gut microbiome. IR contributes to the progression of renal disease by worsening renal hemodynamics by various mechanisms, including activation of the sympathetic nervous system, sodium retention, and downregulation of the natriuretic peptide system. IR has been solidly associated with intermediate mechanisms leading to cardiovascular (CV) disease in CKD including left ventricular hypertrophy, vascular dysfunction, and atherosclerosis. However, it remains unclear whether IR is an independent predictor of mortality and CV complications in CKD. Because IR is a modifiable risk factor and its reduction may lower CV morbidity and mortality, unveiling the molecular mechanisms responsible for the pathogenesis of CKD-related insulin resistance is of importance for the identification of novel therapeutic targets aimed at reducing the high CV risk of this condition.

Study of the effect of vitamin D supplementation on glycemic control in type 2 diabetic prevalent hemodialysis patients

Vitamin D is claimed to have an adjuvant effect on glycemic control by dual action on pancreatic β-cells and insulin resistance. The aim of this study was to assess the possible effect of short-term alfacalcidol supply on glycemic control in type 2 diabetic hemodialysis (HD) patients. Twenty type 2 diabetic HD patients (using diet and oral drugs but not insulin) were randomly selected from our dialysis unit as well as 20 non-diabetic HD patients as control. A third group of 12 healthy subjects were studied as well. All three groups were similar in age, sex, and body mass index. Oral alfacalcidol therapy was administrated daily as recommended by Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines for 12 weeks guided by monthly serum phosphorus and Cax PO4 product. Corrected total calcium, phosphorus, intact parathyroid hormone, 25-hydroxy vitamin D (25[OH]D), and glucoparameters (fasting blood glucose, glycated hemoglobin [HbA1c%], insulin resistance by homeostatic model assessment, and β-cell function by HOMA-β%) were measured under basal conditions and after 3 months of therapy. 25(OH)D was non-significantly lower in diabetic than non-diabetic HD patients, but significantly lower than healthy subjects at the start of the study. However, vitamin D level increased significantly after 3 months of trial, although the levels did not reach normal values. This vitamin D rise was associated with highly significant improvement in concentrations of fasting blood sugar (FBS), fasting insulin, HbA1c%, and HOMA-β-cell function in diabetic and non-diabetic controls. However, there was a significant rise in insulin resistance after treatment. The percentage of change was evident more in diabetics regarding FBS and 25(OH)D concentration. Adjustment of 25(OH)D level in type 2 diabetic prevalent HD patients may improve, at least with short-term therapy, glycemic control mainly through improving β-cell function.

Ocular Surface Disorders in a Group of Egyptian Children with End Stage Renal Failure on Dialysis: A Cross-Sectional Study

Purpose. To investigate tear function, ocular manifestations, and squamous metaplasia of the conjunctival epithelium (SMCE) in children with end stage renal failure (ESRF) on dialysis. Methods. Thirty children with ESRF and 20 age and sex matched controls during the period from January 2014 to May 2015 underwent full ophthalmologic examination and the tear function was investigated by the Schirmer and tear film break-up time (TBUT) tests. SMCE was evaluated by impression cytology and immunocytochemistry. The correlations of tear function status with ESRF-related clinical and biochemical variables were measured statistically. Results. Dry eye symptoms were detected in 26% of children with ESRF, compared with none of the controls (P = 0.05) and SMCE was almost absent. Values of the Schirmer and TBUT tests were significantly lower in children with ESRF for right eye (t = 24.63, P = 0.01, and t = 11.9, P = 0.002, resp.) and left eye (t = 24.7, P = 0.02, and t = 11.4, P = 0.0004, resp.). TBUT and the Schirmer test values were correlated inversely with the duration of ESRF (R = -0.45, P = 0.01, and R = -0.46, P = 0.01, resp.) and with the duration of dialysis (R = -0.39, P = 0.03, and R = -0.45, P = 0.01, resp.). None of the following parameters was associated with distorted tear function including serum creatinine, electrolytes, parathyroid hormone, total protein, albumin, CBC parameters, and systolic or diastolic blood pressure. Conclusion. The basal tear secretion and tear film stability were lower while the dry eye symptoms such as itching and redness were more common among children with ESRF. The duration of ESRF and dialysis duration seem to be related to the disturbances in tear secretion and tear film stability. However, SMCE is very rare.

Vitamin D and Clinical Outcomes in Dialysis

Most dialysis patients are vitamin D deficient, including deficiencies in both activated vitamin D (1, 25-dihydroxyvitamin D) and the less active 25-hydroxyvitamin D. These and other abnormalities associated with chronic kidney disease (CKD), if they remain untreated, lead to secondary hyperparathyroidism and bone changes, such as osteitis fibrosa cystica. Activated vitamin D has been proven to decrease parathyroid hormone (PTH) levels in dialysis patients and is currently used for this indication. There are multiple other potential "pleotrophic" effects associated with vitamin D therapy. These include associations with lower all-cause and cardiovascular mortality, lower rates of infections and improved glycemic indexes. Meta-analyses of multiple observational studies have shown activated vitamin D therapy to be associated with improved survival. Observational data also suggest fewer infections and better glucose control. There have been no randomized clinical trials powered to evaluate mortality or other clinical outcomes. Small trials of nutritional vitamin D (ergocalciferol and cholecalciferol) showed increases in 25-hydroxyvitamin D levels without hypercalcemia or hyperphosphatemia, even when given in addition to activated vitamin D therapy. While activated vitamin D therapy is associated with improved outcomes, it also leads to higher fibroblast growth factor 23 (FGF-23) levels, which may be detrimental in dialysis patients. Further research is needed to evaluate whether activated or nutritional vitamin D therapy are beneficial in dialysis patients for outcomes other than secondary hyperparathyroidism.

Serum 25-hydroxyvitamin D level and diabetic nephropathy in patients with type 2 diabetes mellitus

OBJECTIVE

Patients with chronic kidney disease have a very high prevalence of deficiency of 25-hydroxyvitamin D [25(OH)D]. We evaluate the association between 25(OH)D and diabetic nephropathy (DN) in a Chinese sample with type 2 diabetes mellitus.

METHOD

The subjects were patients with diabetes mellitus who were hospitalized at our hospital during the period from June 2012 to July 2014. Serum levels of 25(OH)D were tested at admission. DN was defined as a urinary albumin-to-creatinine ratio ≥30 mg/g in a random spot urine sample. Multivariate analyses were performed using logistic regression models.

RESULTS

We found that serum 25(OH)D levels were significantly lower in diabetes with DN as compared to without DN [8.5 (IQR 6.8-11.3) vs. 13.9 (IQR 11.2-18.2) ng/ml, P < 0.0001]. Based on the ROC curve, the optimal cutoff value of serum 25(OH)D levels as an indicator for diagnosis of DN was projected to be 10.5 ng/ml, which yielded a sensitivity of 82.6 % and a specificity of 72.7 %, with the area under the curve at 0.807 [95 % confidence interval (CI) 0.764-0.849]. Multivariate logistic regression analysis adjusted for common risk factors showed that with serum 25(OH)D level ≤10.5 ng/ml was an independent indicator of DN [odds ratio (OR) = 6.559; 95 % CI 2.864-11.368].

CONCLUSIONS

Our findings suggested that diabetes with DN had lower serum 25(OH)D levels and that determination of 25(OH)D statuses might be used to identify patients at increased risk of developing nephropathy complications.