Alterations in serum levels of 1 alpha,25(OH)2 D3 and osteocalcin in patients with early diabetic nephropathy

Alleviation of Diabetic Retinopathy by Glucose-Triggered Delivery of Vitamin D via Dextran-Gated Functionalized Mesoporous Silica Nanoparticles

Diabetic retinopathy (DR) is the most common retinal disorder, developed in 35% of patients with diabetes mellitus. Lower serum levels of 25-hydroxyvitamin D are associated with the increased risk of developing DR. High doses of the active form of vitamin D (VD), on the contrary, for a long period of time may lead to hypercalcemia and an imbalance in the regulation of bone metabolism. Herein, we studied the efficacy of dextran-gated carboxyphenylboronic acid (CPBA)-functionalized mesoporous silica nanoparticles (MSNs) for glucose-sensitive delivery of 1,25-dihydroxyvitamin D3 to modulate cellular oxidative stress and inflammation for managing DR. The physical adsorption technique was employed to load VD onto nanoparticles (263.63 μg/mg (w/w)). In the presence of glucose, the dextran molecules detach from pores, allowing VD to release since glucose has 1,2-cis diol groups which have very high affinity to CPBA. Approximately 75% of VD was released upon exposure to 25 mM glucose at a time point of 10 h, demonstrating glucose-responsive delivery. Furthermore, MSN-CPBA was able to deliver VD in a glucose-dependent manner and improve the bioavailability of VD. In high-glucose-supplemented human retinal cells, MSN-CPBA increased the bioavailability of VD and reduced cellular oxidative stress and inflammation. The results suggested that the VD-loaded nanocarrier exerted remarkable therapeutic capacity in reducing the risk of developing DR. By using MSN-CPBA as a delivery platform with dextran gating, the research proposes an effective treatment approach for improving the bioavailability and effectiveness of a hydrophobic molecule in the treatment of DR.

Fracture patterns in adult onset type 1 diabetes and associated risk factors - A nationwide cohort study

OBJECTIVE

This study aimed to determine the hazard ratios (HR) for various fracture sites and identify associated risk factors in a cohort of relatively healthy adult people with newly diagnosed type 1 diabetes (T1D).

METHODS

The study utilized data from the UK Clinical Practice Research Datalink GOLD (1987-2017). Participants included people aged 20 and above with a T1D diagnosis code (n = 3281) and a new prescription for insulin. Controls without diabetes were matched based on sex, year of birth, and practice. Cox regression analysis was conducted to estimate HRs for any fracture, major osteoporotic fractures (MOFs), and peripheral fractures (lower-arm and lower-leg) in people with T1D compared to controls. Risk factors for T1D were examined and included sex, age, diabetic complications, medication usage, Charlson comorbidity index (CCI), hypoglycemia, previous fractures, falls, and alcohol consumption. Furthermore, T1D was stratified by duration of disease and presence of microvascular complications.

RESULTS

The proportion of any fracture was higher in T1D (10.8 %) than controls (7.3). Fully adjusted HRs for any fracture (HR: 1.43, CI95%: 1.17-1.74), MOFs (HR: 1.46, CI95%: 1.04-2.05), and lower-leg fractures (HR: 1.37, CI95%: 1.01-1.85) were statistically significantly increased in people with T1D compared to controls. The primary risk factor across all fracture sites in T1D was a previous fracture. Additional risk factors at different sites included previous falls (HR: 1.64, CI95%: 1.17-2.31), antidepressant use (HR: 1.34, CI95%: 1.02-1.76), and anxiolytic use (HR: 1.54, CI95%: 1.08-2.29) for any fracture; being female (HR: 1.65, CI95%: 1.14-2.38) for MOFs; the presence of retinopathy (HR: 1.47, CI95%: 1.02-2.11) and previous falls (HR: 2.04, CI95%: 1.16-3.59) for lower-arm and lower-leg fractures, respectively. Lipid-lowering medication use decreased the risk of MOFs (HR: 0.66, CI95%: 0.44-0.99). Stratification of T1D by disease duration showed that the relative risk of any fracture in T1D did not increase with longer diabetes duration (0-4 years: HR: 1.52, CI95%: 1.23-1.87; 5-9 years: HR: 1.30, CI95%: 0.99-1.71; <10 years: HR: 1.07, CI95%: 0.74-1.55). Similar patterns were observed for other fracture sites. Moreover, the occurrence of microvascular complications in T1D was linked to a heightened risk of fractures in comparison to controls. However, when considering the T1D cohort independently, the association was not statistically significant.

CONCLUSION

In a cohort of relatively healthy and newly diagnosed people with T1D HRs for any fracture, MOFs, and lower-leg fractures compared to controls were increased. A previous fracture was the most consistent risk factor for a subsequent fracture, whereas retinopathy was the only diabetes related one. We postulate a potential initial fracture risk, succeeded by a subsequent risk reduction, which might potentially increase in later years due to the accumulation of complications and other factors.

Bone-kidney axis: A potential therapeutic target for diabetic nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease (ESRD). However, its pathogenesis remains unclear, and effective prevention and treatment strategies are lacking. Recently, organ-to-organ communication has become a new focus of studies on pathogenesis. Various organs or tissues (the liver, muscle and adipose tissue) secrete a series of proteins or peptides to regulate the homeostasis of distal organs in an endocrine manner. Bone, an important part of the body, can also secrete bone-derived proteins or peptides that act on distal organs. As an organ with high metabolism, the kidney is responsible for signal and material exchange with other organs at any time through circulation. In this review, we briefly discussed bone composition and changes in bone structure and function in DN and summarized the current status of bone-derived proteins and their role in the progression of DN. We speculated that the "bone-kidney axis" is a potential target for early diagnosis and treatment of DN.

Vitamin D receptor rs7975232, rs731236 and rs1544410 single nucleotide polymorphisms, and 25-hydroxyvitamin D levels in Egyptian children with type 1 diabetes mellitus: effect of vitamin D co-therapy

Purpose: We aimed to examine the possible association role of vitamin D and vitamin D receptor (VDR) single nucleotide polymorphisms (SNPs) in type 1 diabetes mellitus (T1DM) development, glycemic control and complications among a cohort of Egyptian children. Subjects and methods: A prospective case-control study has been conducted on 50 Egyptian children with T1DM who were comparable with 50 controls. Vitamin D and HbA1c were measured. VDR-SNPs [ApaI (rs7975232), TaqI (rs731236) and BsmI (rs1544410)] detection was done by polymerase chain reaction through restriction fragment length polymorphism (PCR-RFLP) technique. Vitamin D supplements were given to the included T1DM children with low vitamin D and reassessments of both HbA1c% and 25(OH)D serum levels were performed in those children three months later. Results: Eighty percent of the included diabetic patients have poor glycemic control. Vitamin D was deficient in 68% and insufficient in 16% of diabetic patients. Significant improvements in both vitamin D and glycemic status among T1DM children, who have low vitamin D and received vitamin D supplementations. There were significantly negative correlations between serum levels of vitamin D with both HbA1c % (r= -0.358, P˂0.05) and daily insulin dose (r=-0.473, P˂0.05). Compared with controls, T1DM children presented more commonly with ApaI a allele (OR: 2.87; 95%CI: 1.39-5.91, P˂0.05) and BsmI b allele (OR: 4.38; 95%CI: 2.30-8.33, P˂0.05). TaqI t allele wasn't significantly differing among patients and controls (P˃0.05). Aa+aa and Bb+bb genotypes were significantly higher among T1DM vs the controls (OR: 3.08;, 95%CI: 1.33-7.15, P˂0.05 and OR: 9.33; 95%CI: 3.61-24.17, P˂0.05respectively). Conclusion: ApaI and BsmI were associated with risk of T1DM development among Egyptian children. Low vitamin D status was frequently occurring among T1DM with significant improvement in the glycemic control of such children when adding vitamin D supplements to the standard insulin therapy.

Vitamin D Deficiency in Chronic Kidney Disease: Recent Evidence and Controversies

Vitamin D (VD) is a pro-hormone essential for life in higher animals. It is present in few types of foods and is produced endogenously in the skin by a photochemical reaction. The final step of VD activation occurs in the kidneys involving a second hydroxylation reaction to generate the biologically active metabolite 1,25(OH)₂-VD. Extrarenal 1α-hydroxylation has also been described to have an important role in autocrine and paracrine signaling. Vitamin D deficiency (VDD) has been in the spotlight as a major public healthcare issue with an estimated prevalence of more than a billion people worldwide. Among individuals with chronic kidney disease (CKD), VDD prevalence has been reported to be as high as 80%. Classically, VD plays a pivotal role in calcium and phosphorus homeostasis. Nevertheless, there is a growing body of evidence supporting the importance of VD in many vital non-skeletal biological processes such as endothelial function, renin-angiotensin-aldosterone system modulation, redox balance and innate and adaptive immunity. In individuals with CKD, VDD has been associated with albuminuria, faster progression of kidney disease and increased all-cause mortality. Recent guidelines support VD supplementation in CKD based on extrapolation from cohorts conducted in the general population. In this review, we discuss new insights on the multifactorial pathophysiology of VDD in CKD as well as how it may negatively modulate different organs and systems. We also critically review the latest evidence and controversies of VD monitoring and supplementation in CKD patients.

Bone disease in diabetes: another manifestation of microvascular disease?

Type 1 and type 2 diabetes are generally accepted to be associated with increased bone fracture risk. However, the pathophysiological mechanisms of diabetic bone disease are poorly understood, and whether the associated increased skeletal fragility is a comorbidity or a complication of diabetes remains under debate. Although there is some indication of a direct deleterious effect of microangiopathy on bone, the evidence is open to question, and whether diabetic osteopathy can be classified as a chronic, microvascular complication of diabetes remains uncertain. Here, we review the current knowledge of potential contributory factors to diabetic bone disease, particularly the association between diabetic microangiopathy and bone mineral density, bone structure, and bone turnover. Additionally, we discuss and propose a pathophysiological model of the effects of diabetic microvascular disease on bone, and examine the progression of bone disease alongside the evolution of diabetes.

Vitamin D and Albuminuria in Youth with and without Type 1 Diabetes

BACKGROUND/AIMS

In adults, lower vitamin D has been associated with increased albuminuria. This association has not been extensively studied in youth with or without type 1 diabetes.

METHODS

We examined the cross-sectional association between vitamin D and albuminuria (urine albumin to creatinine ratio ≥30 mg/g) in 8,789 participants of the National Health and Nutrition Survey 2001-2006 (NHANES), who were 6-19 years old. Further, we examined the association between vitamin D and albuminuria in 938 participants from the SEARCH Nutritional Ancillary Study (SNAS), a longitudinal cohort of youth with type 1 diabetes.

RESULTS

Of the NHANES participants, 5.3, 19.5, and 53.7% had vitamin D levels <30, 50 and 80 nmol/L, respectively. Albuminuria was present in 12.8% and was more common in younger children, females, non-Hispanic whites, non-obese children, and children with hypertension. After adjustments, there was no association between vitamin D and albuminuria. Among the SNAS participants with type 1 diabetes, we also found no association between baseline vitamin D and subsequent albuminuria in unadjusted or adjusted analyses.

CONCLUSION

We did not find an association between serum vitamin D and albuminuria in either non-diabetic youth or those with type 1 diabetes. Further research is needed to more fully understand this relationship.

The Association between Vitamin D Deficiency and Diabetic Retinopathy in Type 2 Diabetes: A Meta-Analysis of Observational Studies

Emerging evidence from in vivo and in vitro studies have shown that vitamin D may play an important role in the development of diabetic retinopathy (DR), but individually published studies showed inconclusive results. The aim of this study was to quantitatively summarize the association between vitamin D and the risk of diabetic retinopathy. We conducted a systematic literature search of Pubmed, Medline, and EMBASE updated in September 2016 with the following keywords: "vitamin D" or "cholecalciferol" or "25-hydroxyvitamin D" or "25(OH)D" in combination with "diabetic retinopathy" or "DR". Fifteen observational studies involving 17,664 subjects were included. In this meta-analysis, type 2 diabetes patients with vitamin D deficiency (serum 25(OH)D levels <20 ng/mL) experienced a significantly increased risk of DR (odds ratio (OR) = 2.03, 95% confidence intervals (CI): 1.07, 3.86), and an obvious decrease of 1.7 ng/mL (95% CI: -2.72, -0.66) in serum vitamin D was demonstrated in the patients with diabetic retinopathy. Sensitivity analysis showed that exclusion of any single study did not materially alter the overall combined effect. In conclusion, the evidence from this meta-analysis indicates an association between vitamin D deficiency and an increased risk of diabetic retinopathy in type 2 diabetes patients.

The association between bone turnover markers and microvascular complications of type 2 diabetes

Background

Global epidemic of diabetes is a serious health care concern because of its complications and consequently reduced life expectancy and increased morbidity. However, the bone turnover and thus bone health may be affected or even compromised by diabetes and its complications. The aim of this study was to assess whether bone turnover markers are associated with diabetes micro-vascular complications.

Methods

A total of 204 type 2 diabetes patients (104 patients with diabetic micro-vascular complications (retinopathy and/or nephropathy) as a case group and 100 patients without retinopathy and/or nephropathy) as a control group were recruited in this case–control study. The biochemical and metabolic parameters and bone turnover markers were assessed in all patients.

Results

Our findings showed serum levels of osteocalcin (OC) (p = 0.0001) and, carboxy-terminal collagen crosslinks (CTX) (p = 0.006) were higher in diabetic patients with both diabetic retinopathy and nephropathy compared with control group. However, there was no significant difference in serum levels of procollagen I aminoterminal propeptide (P1NP) between diabetic patients with diabetic retinopathy (DR) and/or diabetic nephropathy (DN) compared with control.

In diabetes patients with complications, there were significant negative correlation between OC and CTX with estimated-glomerular filtration rate (e-GFR) and also positive correlation between each bone marker (OC and CTX) and PTH levels (p = 0.0001) and BUN (p = 0.0001).

In a general linear model, after adjusting for age, sex and BMI, and microvascular complications, there was not any significant association between three bone turnover markers and metabolic markers including fasting glucose, insulin, and lipid profile. Among kidney markers, there were significant positive associations between serum levels of CTX and OC with BUN (p < 0.05) as well as PTH (p < 0.0001).

Conclusions

Our data suggest the possible role of PTH and BUN levels in modulating bone turnover markers in diabetic patients.

Vitamin D and diabetic nephropathy: A systematic review and meta-analysis

OBJECTIVE

There has been a long history documenting the use of different vitamin D derivatives as therapy for renal diseases. However, to our knowledge, there is no comprehensive assessment of the relation between vitamin D deficiency and risk for diabetic nephropathy (DN). Additionally, the effect of vitamin D supplementation on DN is still unclear. The aim of this meta-analysis was to assess these issues by pooling together the results from cross-sectional studies and clinical trials.

METHODS

A systematic literature search of PubMed, Scopus, and Google Scholar was conducted, ending in September 2014. For cross-sectional studies, odds ratio was used as a measure of the association between vitamin D status and risk for DN; for clinical trials, mean and SD of the main outcome (urine albumin-to-creatinine ratio [UACR]) in intervention and placebo groups were considered for analysis.

RESULTS

The final selected articles were published between 2009 and 2014. In all, 3700 and 219 patients were enrolled in observational and interventional studies, respectively. The pooled odds ratio from six cross-sectional studies was 1.80 (95% confidence interval [CI], 1.25-2.59; P = 0.002), indicating a significant inverse association between serum vitamin D status and risk for nephropathy in patients with diabetes. However, the pooled data of UACR levels in clinical trials suggested no significant change following vitamin D supplementation (17.98; 95% CI, -35.35 to 71.32; P = 0.51).

CONCLUSION

This meta-analysis showed the higher risk for nephropathy in vitamin D-deficient patients with diabetes. Pooling the results of available clinical trials after vitamin D supplementation did not support causality in this association.

Non-linear association of serum 25-hydroxyvitamin D with urinary albumin excretion rate in normoalbuminuric subjects

Background

Vitamin D deficiencies and increases in urinary albumin excretion (UAE) are both important and potentially related health problems; however, the nature of their relationship has not been established in normoalbuminuric subjects.

Methods

We obtained data from 14,594 normoalbuminuric Korean adults who underwent voluntary health screenings. We used a generalized additive model to examine the threshold level for relationship between serum 25-hydroxyvitamin D [25(OH)D] and urinary-albumin creatinine ratio (UACR) levels. We conducted multivariate logistic regression for high-normal UAE (UACR, 10–29 mg/g), according to various categories of vitamin D status.

Results

The generalized additive model confirmed a non-linear relationship between serum 25(OH)D and UACR levels, and the threshold concentration of 25(OH)D was 8.0 ng/mL after multivariate adjustment. Comparing subjects who fell into the lowest category of serum 25(OH)D levels with subjects who were in the reference range (the highest category), we observed that the multivariate adjusted odds ratio (OR) for high-normal UAE was significantly increased, regardless of the criteria used to categorize vitamin D levels: OR of the 1^st quartile over the 4^th quartile, 1.20 (95% CI, 1.04-1.39); OR of the 1.0-4.9^th percentile over the 50-100^th percentile, 1.56 (95% CI, 1.25-1.93); and OR of vitamin D deficiency group over vitamin D sufficiency group, 1.28 (95% CI, 1.08-1.52).

Conclusions

We demonstrated that there was an inverse relationship between serum 25(OH)D less than 8.0 ng/mL and UACR in normoalbuminuric subjects, suggesting that severe vitamin D deficiency could cause an increase in UAE in subjects with normoalbuminuria.

Hypovitaminosis d in patients with type 2 diabetes mellitus: a relation to disease control and complications

Aims. This study aims at assessing the relationship between 25 (OH) vitamin D (25-OHD) levels and microvascular complications in patients with type 2 diabetes mellitus (DM2). Methods. 136 patients (59 ± 11 years) with DM2 (disease duration 8.6 ± 7 years) participated in this cross-sectional study. Anthropometric data, HbA1c, 25-OHD levels, serum creatinine, and urine microalbumin/creatinine ratio were collected. Dilated retinal exam was performed, and diabetic neuropathy was assessed using the United Kingdom Screening Score. Results. Serum 25-OHD correlated negatively with HbA1c (r = -0.20,  P = 0.049). Mean 25-OHD levels were lower in subjects with diabetic retinopathy compared to those without retinopathy (12.3 ± 5.5 versus 21.8 ± 13.7, P < 0.001) and lower in subjects with diabetic neuropathy compared to those without neuropathy (16.4 ± 10.4 versus 23.5 ± 14.5, P = 0.004). After adjustment for BMI, diabetes duration, and smoking, 25-OHD was an independent predictor of HbA1c ( β   -0.14; P = 0.03). After adjustment for HbA1c, age, smoking, BMI and disease duration, 25-OHD were independent predictors for diabetic retinopathy: OR 2.8 [95% CI 2.1-8.0] and neuropathy: OR 4.5 [95% CI 1.6-12] for vitamin D < 20 versus vitamin D ≥ 20 ng/mL. Conclusion. Low serum 25-OHD level was an independent predictor of HbA1c, diabetic neuropathy, and diabetic retinopathy in patients with DM2.

Associations of plasma 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D concentrations with death and progression to maintenance dialysis in patients with advanced kidney disease

BACKGROUND

Low vitamin D concentrations are prevalent in patients with chronic kidney disease (CKD). We investigated the relationship between plasma 25-hydroxyvitamin D (25[OH]D) or 1,25-dihydroxyvitamin D (1,25[OH](2)D) concentrations with death, cardiovascular events, and dialysis therapy initiation in patients with advanced CKD.

STUDY DESIGN

The HOST (Homocysteinemia in Kidney and End Stage Renal Disease) Study was a randomized double-blind trial evaluating the effects of high doses of folic acid on death and long-term dialysis therapy initiation in patients with advanced CKD (stages 4 and 5 not yet on dialysis therapy). 25(OH)D and 1,25(OH)(2)D were measured in stored plasma samples obtained 3 months after trial initiation and evaluated at clinically defined cutoffs (<10, 10-30, and >30 ng/mL) and tertiles (<15, 15-22, and >22 pg/mL), respectively. Cox proportional hazard models were used to examine the association between vitamin D concentrations and clinical outcomes.

SETTING & PARTICIPANTS

1,099 patients with advanced CKD from 36 Veteran Affairs Medical Centers.

PREDICTORS

25(OH)D and 1,25(OH)(2)D concentrations.

OUTCOMES

Death, cardiovascular events, and time to initiation of long-term dialysis therapy.

RESULTS

After a median follow-up of 2.9 years, 41% (n = 453) died, whereas 56% (n = 615) initiated dialysis therapy. Mean 25(OH)D and 1,25(OH)(2)D concentrations were 21 ± 10 ng/mL and 20 ± 11 pg/mL, respectively. After adjustment for potential confounders, the lowest tertile of 1,25(OH)(2)D was associated with death (HR, 1.33; 95% CI, 1.01-1.74) and initiation of long-term dialysis therapy (HR, 1.78; 95% CI, 1.40-2.26) compared with the highest tertile. The association with death and initiation of dialysis therapy was moderately attenuated after adjustment for plasma fibroblast growth factor 23 (FGF-23) concentrations (HRs of lower tertiles of 1.20 [95% CI, 0.91-1.58] and 1.56 [95% CI, 1.23-1.99], respectively, compared with highest tertile). There was no association between 25(OH)D concentrations and outcomes.

LIMITATIONS

Participants were mostly men.

CONCLUSIONS

Low plasma 1,25(OH)(2)D concentrations are associated with death and initiation of long-term dialysis therapy in patients with advanced CKD. FGF-23 level may attentuate this relationship.

Serum undercarboxylated osteocalcin levels are inversely associated with glycemic status and insulin resistance in an elderly Japanese male population: Fujiwara-kyo Osteoporosis Risk in Men (FORMEN) Study

SUMMARY

Recent animal studies have demonstrated that undercarboxylated osteocalcin upregulates insulin secretion via osteoblast-insulin signaling. However, it remains unclear whether such a pathway exists in humans. This study showed that serum undercarboxylated osteocalcin levels were inversely associated with fasting plasma glucose, hemoglobin A(1c), and homeostasis model assessment of insulin resistance (HOMA-IR) levels in community-dwelling elderly Japanese men.

INTRODUCTION

Undercarboxylated osteocalcin (ucOC) was reported to increase insulin secretion and improve glucose tolerance via osteoblast-insulin signaling in animal-based studies. Whether this pathway also exists in humans is unknown. We aimed to clarify whether serum ucOC levels are associated with glycemic status and insulin resistance in the general Japanese population.

METHODS

We included 2,174 Japanese men (≥65 years) who were able to walk without aid from others and lived at home in four cities of Nara Prefecture. We excluded participants with a history of diseases or medications that affect bone metabolism, other than type 2 diabetes mellitus (T2DM). Fasting plasma glucose, glycated hemoglobin A(1c), and HOMA-IR levels were determined as outcome measures.

RESULTS

Of the 1,597 participants included in the analysis, both intact OC (iOC) and ucOC levels showed significant inverse correlations with all outcome measures, even after adjusting for potential confounders. Mean values of outcome measures showed a significant decreasing trend with higher quintiles of iOC or ucOC after adjusting for confounders. This trend remained significant for ucOC quintiles after further adjustment for iOC levels, but was not significant for iOC quintiles after adjusting for ucOC levels. These results were attenuated, but still apparent, after excluding participants receiving drug therapy for T2DM.

CONCLUSIONS

Levels of ucOC, but not iOC, were inversely associated with glycemic index and insulin resistance in a population of Japanese men. These findings will need to be confirmed with longitudinal studies.

Optimal vitamin D, calcitriol, and vitamin D analog replacement in chronic kidney disease: to D or not to D: that is the question

PURPOSE OF REVIEW

Patients with chronic kidney disease (CKD) are often insufficient in 25(OH) vitamin D and are almost uniformly deficient in 1,25(OH)2 vitamin D, because of decreased renal hydroxylation resulting from hyperphosphatemia and elevated fibroblast growth factor-23 (FGF-23) levels. These same abnormalities lead to secondary hyperparathyroidism for which the administration of calcitriol or vitamin D analogs has been the mainstay of therapy for decades. This review summarizes new trials of vitamin D, calcitriol, and its analogs over the last 2 years.

RECENT FINDINGS

In addition to the endocrine effects of the vitamin D axis on bone and mineral metabolism, studies have demonstrated there is also extrarenal conversion of 25(OH) vitamin D to 1,25(OH)2 vitamin D in multiple cells leading to autocrine effects. This advance has led to the speculation that CKD patients may also need to be supplemented with ergocalciferol or cholecalciferol. Unfortunately, to date, the majority of interventional studies have focused on biochemical end points. There are no randomized controlled trials demonstrating that therapy with any formulation of vitamin D results in improved patient level outcomes.

SUMMARY

Despite the physiologic importance of vitamin D in health and disease, more research is required to determine which vitamin D derivative is required for optimal health in CKD patients.

A randomized trial of cholecalciferol versus doxercalciferol for lowering parathyroid hormone in chronic kidney disease

BACKGROUND AND OBJECTIVES

The optimal treatment of secondary hyperparathyroidism in chronic kidney disease (CKD) is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a randomized, blinded, 3-month trial in vitamin D-deficient CKD stage 3 and 4 patients with parathyroid hormone (PTH) values above the Kidney Disease Outcomes Quality Initiative target, comparing cholecalciferol (4000 IU/d x 1 month, then 2000 IU/d; n = 22) to doxercalciferol (1 microg/d; n = 25).

RESULTS

There was no difference in baseline demographics or lab tests, except a slightly higher estimated GFR (eGFR) in the doxercalciferol group. There was a significant increase in vitamin D level in the cholecalciferol group (14 +/- 6 to 37 +/- 10 ng/ml; P < 0.001) but no change in the doxercalciferol group. The PTH decreased by 27% +/- 34% in the doxercalciferol group (P = 0.002) and decreased by 10% +/- 31% in the cholecalciferol group (P = 0.16), but the difference between treatments was NS (P = 0.11). Similar results were found when absolute PTH change from baseline to end point was analyzed in a repeated-measures ANOVA model. The serum calcium and urine calcium excretions were not different. Additional non-mineral-related end points, albuminuria, and BP were evaluated, and although trends were present, this did not reach significance.

CONCLUSIONS

This prospective, randomized trial demonstrated a within-group reduction in PTH in the doxercalciferol-treated patients but no significant difference between the doxercalciferol and cholecalciferol patients. Larger, long-term studies are needed to demonstrate efficacy of mineral-related and non-mineral-related end points and safety.

25-Hydroxyvitamin D levels and albuminuria in the Third National Health and Nutrition Examination Survey (NHANES III)

BACKGROUND

Albuminuria is a risk factor for chronic kidney disease progression, end-stage renal disease, cardiovascular events, and mortality. Animal studies suggested that vitamin D insufficiency may contribute to the pathogenesis of albuminuria.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

15,068 adults participating in the Third National Health and Nutrition Examination Survey.

PREDICTOR

Serum 25-hydroxyvitamin D concentration, examined in quartiles.

OUTCOMES & MEASUREMENTS

Albuminuria, defined using established sex-specific cutoff values for urine albumin-creatinine ratio (25 to 2,999 mg/g for women, 17 to 2,999 mg/g for men).

RESULTS

A stepwise increase in the prevalence of albuminuria was observed with decreasing quartiles of vitamin D concentration: 8.9%, 11.5%, 13.7%, and 15.8% (P < 0.001). Adjusting for age, sex, race/ethnicity, region and season of measurement, smoking status, body mass index, and estimated glomerular filtration rate, relative risks for albuminuria by decreasing quartile of vitamin D concentration were 1.00 (reference group), 1.14 (95% confidence interval, 0.95 to 1.37), 1.22 (95% confidence interval, 1.03 to 1.45), and 1.37 (95% confidence interval, 1.10 to 1.71; P = 0.006). Additionally adjusting for blood pressure and diabetes mellitus, these risks were somewhat attenuated and retained statistical significance.

LIMITATIONS

The cross-sectional design of this study does not allow demonstration of temporal or causal relationships between vitamin D and albuminuria.

CONCLUSIONS

Additional studies are needed to clarify the relationship of vitamin D with albuminuria and determine whether vitamin D therapy prevents or improves markers of kidney and cardiovascular disease.

Serum levels of carboxy-terminal propeptide of human type I procollagen are an indicator for the progression of diabetic nephropathy in patients with type 2 diabetes mellitus

The finding that glomerular mesangial cells produce human type I collagen suggests that the serum levels of carboxy-terminal propeptide of human type I procollagen (P1CP) may reflect the severity of diabetic nephropathy. We therefore investigated the relationship between serum P1CP levels and the extent of diabetic complications in 100 patients (46 males and 54 females) with Type 2 diabetes and in 64 healthy subjects. Serum P1CP was determined by radioimmunoassay. In diabetes, we defined P1CP levels less than 142 ng/ml as a normal P1CP group (group A), whereas we defined them as equal to or greater than 142 ng/ml as a high P1CP group (group B). The diabetic patients had significantly elevated serum P1CP levels compared with the controls. The prevalence of hypertension, proliferative diabetic retinopathy or macroalbuminuria was significantly higher in group B than in group A. Serum P1CP levels showed a significant positive correlation with urinary albumin excretion, but not with fasting blood glucose, glycosylated hemoglobin A(1c) or serum osteocalcin. Macroalbuminuric patients showed significantly higher P1CP levels than the normoalbuminuric patients. In patients in the absence of diabetic nephropathy, no significant differences of P1CP levels were found among the severity of diabetic retinopathy. The present results suggest that serum P1CP levels reflect the progression of diabetic nephropathy in patients with Type 2 diabetes.

Serum 1,25 dihydroxy vitamin D (1,25(OH)2D3), 25 hydroxy vitamin D (25(OH)D) and parathormone levels in diabetic retinopathy

OBJECTIVES

To investigate whether there is a relationship between serum 1,25 dihydroxy vitamin D3 [1,25(OH)2D3], which is an inhibitor of angiogenesis, concentrations and severity of diabetic retinopathy (DR).

DESIGN AND METHODS

Serum 1,25(OH)2D3, 25 hydroxy vitamin D [25(OH)D] and parathormone (PTH) concentrations were measured in diabetic patients (n = 66) and nondiabetic healthy subjects (n = 20).

RESULTS

The mean serum 1,25(OH)2D3 concentration in diabetic patients was lower than that in nondiabetics (57.3+/-21.44 vs. 89.4+/-18.01 pmol/L, p<0.001); mean 1,25(OH)2D3 concentrations fell with increasing severity of DR [being 63.4+/-17.26 pmol/L for background DR (BDR), 47.7+/-13.27 pmol/L for preproliferative DR (pre-PDR), and 43.1+/-19.45 pmol/L for proliferative DR (PDR)]. Compared with the control group, serum 25(OH)D concentrations were found to be decreased in diabetic patients (p<0.001). There were negative correlations between 1,25(OH)2D3 and age (r = -0.331, p<0.01) and duration of diabetes (r = -0.255, p<0.05).

CONCLUSION

From these findings, it was found that there was an inverse relationship between the severity of the retinopathy, i.e., neovascularization, and serum 1,25(OH)2D3 concentrations, being the lowest in PDR and the highest in diabetic patients without retinopathy (NDR) patients. The measurement of serum 1,25(OH)2D3 concentrations might be helpful to predict severity of DR in patients with diabetes mellitus.

Calcium metabolism in adolescents and young adults with type 1 diabetes mellitus without and with persistent microalbuminuria

Alterations in calcium metabolism can be demonstrated in the course of insulin-dependent diabetes mellitus. In order to clarify if the presence of persistent microalbuminuria (MA) can affect the main parameters of calcium metabolism, we studied 22 diabetic adolescents and young adults with persistent MA and compared them with 24 patients without MA and 24 healthy controls. Mean values of serum calcium, phosphorus and magnesium were similar in diabetic children and young adults without persistent MA and in controls. In addition, the mean values of PTH and 25-OHD, 1,25 (OH)2D3 and OC did not differ between these diabetics and controls. Diabetics with persistent MA showed no significant difference from the values of either controls or the group of diabetics without persistent MA for the mean values of serum calcium, phosphorus and magnesium and PTH. In contrast, diabetics with persistent MA had significantly (p<0.01) lower 25-OHD (26.5+/-5.2 ng/ml) and 1,25 (OH)2D3 (24.7+/-5.6 pg/ml) as well as OC levels (9.8+/-2.5 ng/ml; p<0.001) than controls (38.1+/-4.9 ng/ml, 40.7+/-6.4 pg/ml and 16.5+/-5.8 ng/ml, respectively) and subjects with normoalbuminuria (36.0+/-4.5 ng/ml, 38.8+/-8.9 pg/ml and 14.5+/-3.2 ng/ml). In conclusion, our study suggests that abnormalities in 25-OHD, 1,25(OH)2D3 and OC can be present in diabetic adolescents and young adults with incipient nephropathy.