Calbindin-D(28k) controls [Ca(2+)](i) and insulin release. Evidence obtained from calbindin-d(28k) knockout mice and beta cell lines

Optimal vitamin D supplement dosage for improving insulin resistance in children and adolescents with overweight/obesity: a systematic review and network meta-analysis

PURPOSE

We conducted a network meta-analysis which aims to evaluate the comparative efficacy of different supplementation dosages of vitamin D on cardiometabolic and bone-metabolic indicators as well as insulin resistance in children and adolescents with overweight/obesity.

METHODS

Eligible studies published before December 10, 2022 were retrieved from PubMed, EMBASE, Cochrane Library, and Web of Science. Mean difference and 95% confidence interval (CI) were used to express pooled estimates. Network meta-analysis of multiple doses, including low (< 1000 IU/day, LDS), medium (1000-2000 IU/day, MDS), high (2000-4000 IU/day, HDS), and extremely high (> 4000 IU/day, EHDS) dosage strategy, was conducted using STATA/MP 14.0.

RESULTS

Our network meta-analysis of 15 RCTs suggested that, compared with placebo and LDS, EHDS was increased 25-(OH)-D, with a pooled MD of 8.65 (95% CI 4.72-12.58) and 7.66 (95% CI 0.91-14.41), respectively. Meanwhile, EHDS also decreased ho meostasis model assessment-insulin resistance (HOMA-IR) (MD: - 0.74; 95% CI: - 1.45 to - 0.04) and C-reactive protein (CRP) (MD: - 18.99; 95% CI - 21.60 to - 16.38), and EHDS was also better than LDS (MD: - 18.47; 95% CI - 20.66 to - 16.28) and MDS (MD: - 19.69; 95% CI - 22.17 to - 17.21) in decreasing CRP. Ranking probability suggested that EHDS ranked best for increasing 25-(OH)-D, and decreasing HOMA-IR and CRP, with a probability of 86.1%, 83.1%, and 76.6%, respectively.

CONCLUSIONS

The results of our network meta-analysis suggest that EHDS may be the best strategy for vitamin D supplementation to reduce inflammatory responses as well as improve insulin resistance in children and adolescents with overweight/obesity.

PROSPERO REGISTRATION NUMBER

CRD42023387775.

Proteomic Profiling Identifies Distinct Regulation of Proteins in Obese Diabetic Patients Treated with Metformin

Background: Obesity and type 2 diabetes mellitus (T2DM) are characterized by underlying low-grade chronic inflammation. Metformin has been used as the first line of therapy in T2DM as it decreases hepatic glucose production and glucose intestinal absorption, enhances insulin sensitivity and weight loss, and is known to ameliorate inflammation. The mechanisms through which metformin exerts its effect remain unclear. Proteomics has emerged as a unique approach to explore the biological changes associated with diseases, including T2DM. It provides insight into the circulating biomarkers/mediators which could be utilized for disease screening, diagnosis, and prognosis. Methods: This study evaluated the proteomic changes in obese (Ob), obese diabetics (OD), and obese diabetic patients on metformin (ODM) using a 2D DIGE MALDI-TOF mass spectrometric approach. Results: Significant changes in sixteen plasma proteins (15 up and 1 down, ANOVA, p ≤ 0.05; fold change ≥ 1.5) were observed in the ODM group when compared to the Ob and OD groups. Bioinformatic network pathway analysis revealed that the majority of these altered plasma proteins are involved in distinct pathways involving acute-phase response, inflammation, and oxidative response and were centered around HNF4A, ERK, JNK, and insulin signaling pathways. Conclusions: Our study provides important information about the possible biomarkers altered by metformin treatment in obese patients with and without T2DM. These altered plasma proteins are involved in distinct pathways involving acute-phase response, inflammation, and oxidative response and were centered around HNF4A, ERK, JNK, and insulin signaling pathways. The presented proteomic profiling approach may help in identifying potential biomarkers/mediators affected by metformin treatment in T2DM and inform the understanding of metformin's mechanisms of action.

Efficacy of vitamin D supplementation on child and adolescent overweight/obesity: a systematic review and meta-analysis of randomized controlled trials

The global prevalence of overweight and obesity in children and adolescents has been increasing. Child and adolescent overweight/obesity has been demonstrated to be partially associated with vitamin D deficiency. This systematic review and meta-analysis aims to assess the efficacy of vitamin D supplementation on child and adolescent overweight/obesity. PubMed, Embase, Cochrane Library, and Web of science were searched from inception to June 20th, 2022. Randomized controlled trials (RCTs) assessing the efficacy of vitamin D on child and adolescent overweight/obesity were included. The Cochrane bias risk assessment tool was used to assess the bias risk of included studies, and subgroup analysis was conducted based on different administration dosages. All data-analyses were performed using R 4.2.1. There were 1502 articles retrieved, and 10 eligible studies were finally included, with a total of 595 participants. Meta-analysis showed no differences in LDL, TC, TG, BMI, ALP, Ca, and PTH between vitamin-D (Vit-D) group and placebo, while Vit-D group resulted in improved HOMA-IR[WMD =  - 0.348, 95%CI (- 0.477, - 0.219), p = 0.26]. Subgroup-analysis showed no significant difference in the increase of 25-(OH)-D between subgroups (p = 0.39), whereas the serum 25-(OH)-D level was increased under different Vit-D doses [WMD = 6.973, 95%CI (3.072, 10.873)]. High daily dose (≥ 4000 IU/d) of Vit-D might decrease CRP and increase HDL levels.   Conclusion: High dose of Vit-D supplementation (over 4000 IU/d) would reduce several cardiometabolic risk indicators and improve insulin resistance. More high-quality and large-scale RCTs are needed to provide more robust evidence. What is Known: • Vit-D deficiency is common in overweight/obesity (OW/OB) children and adolescents. • Previous randomized studies on the benefit of Vit-D supplementation to OW/OB children and adolescents are inconsistent. What is New: • This is the first meta-analysis conducted to assess the efficacy of Vit-D supplementation on child and adolescent OW/OB. • High dose of Vit-D supplementation is beneficial to cardiovascular metabolism, and improve insulin resistance on child and adolescent OW/OB.

The Association between Vitamin D Hypovitaminosis and Cardiovascular Disease Risk in Saudi Diabetic Patients Type II

We evaluated the prevalence and association of Vitamin D deficiency with glycemic control and CVD risk in T2DM patients. Serum 25 (OH)D₃, lipid profile, glucose panel, HbA1c, serum insulin, and HOMA-IR were assessed in 93 T2DM patients and 69 controls. 10 years and lifetime ASCVD risk scores were calculated. The levels of 25(OH)D₃ were significantly low in T2DM patients compared to the control. T2DM patients with hypovitaminosis D displayed significantly increased FBG, insulin, and HOMA-IR compared to normovitaminosis. Their lifetime and 10-year ASCVD risk scores were significantly higher regardless of vitamin D deficiency levels (P=0.006; P=0.023) in comparison to patients with sufficient levels of vitamin D. Among patients, the lifetime and 10 years of ASCVD risk showed a significant negative correlation with serum 25(OH)D₃ and HDLc (P=0.037; 0.018) (P=0.0001), respectively, and significant positive correlation with T2DM duration, serum insulin, and HOMA-IR (P=0.018; 0.0001) (P=0.002; 0.001) (P=0.005; 0.001), respectively. The 10-year ASCVD risk exhibited a significant positive correlation with FBG (P=0.003) and HbA1c (P=0.009). T2DM duration was a predictor of vitamin D deficiency among T2DM patients (β = 0.22; CI = 0.002–0.04). There is a considerable association between lifetime and 10 years of ASCVD risk with hypovitaminosis D in T2DM, regardless of the deficiency levels which could be predicted by the diabetes duration.

The importance of kidney calcium handling in the homeostasis of extracellular fluid calcium

Extracellular fluid calcium concentration must be maintained within a narrow range in order to sustain many biological functions, encompassing muscle contraction, blood coagulation, and bone and tooth mineralization. Blood calcium value is critically dependent on the ability of the renal tubule to reabsorb the adequate amount of filtered calcium. Tubular calcium reabsorption is carried out by various and complex mechanisms in 3 distinct segments: the proximal tubule, the cortical thick ascending limb of the loop of Henle, and the late distal convoluted/connecting tubule. In addition, calcium reabsorption is tightly controlled by many endocrine, paracrine, and autocrine factors, as well as by non-hormonal factors, in order to adapt the tubular handling of calcium to the metabolic requirements. The present review summarizes the current knowledge of the mechanisms and factors involved in calcium handling by the kidney and, ultimately, in extracellular calcium homeostasis. The review also highlights some of our gaps in understanding that need to be addressed in the future.

The correlation between vitamin D, glucose homeostasis and androgen level among polycystic ovary syndrome patients: a cross-sectional study

MATERIAL AND METHODS

A total of 290 women with PCOS participated in this cross-sectional study. Glucose homeostasis was assessed by a 75-g oral glucose tolerance test and the concentration of serum 25-hydroxy vitamin D was determined among all subjects. The homeostasis model assessment of insulin resistance (HOMA-IR) was taken as the indicator of insulin resistance. Beta cell function was estimated using the insulinogenic index and the disposition index. Free androgen index (FAI) was used to represent the androgen level.

RESULTS

In our study, 7.2% of the patients had Vit D severe deficiency, 75.2% had Vit D deficiency and 15.5% had vit D insufficiency. The level of serum 25(OH)D showed a significant positive association with insulinogenic index (r = 0.147, p < .05), disposition index (r = 0.280, p < .05), and SHBG (r = 0.178, p < .05) but exhibited a negative association with HOMA-IR (r = -0.198, p < .05), FAI (r = -0.178, p < .05). Adjusted age and BMI, 25(OH)D would be the dependent variable on disposition index [B = 0.259, 95%CI(0.041,0.477)] and FAI [B = -0.125, 95%CI(-0.232, -0.017)].

CONCLUSIONS

According to our results, the low levels of serum 25(OH)D were common in women with PCOS, which was speculated to be associated with glucose homeostasis and the androgen level.

The Molecular Mechanisms by Which Vitamin D Prevents Insulin Resistance and Associated Disorders

Numerous studies have shown that vitamin D deficiency is very common in modern societies and is perceived as an important risk factor in the development of insulin resistance and related diseases such as obesity and type 2 diabetes (T2DM). While it is generally accepted that vitamin D is a regulator of bone homeostasis, its ability to counteract insulin resistance is subject to debate. The goal of this communication is to review the molecular mechanism by which vitamin D reduces insulin resistance and related complications. The university library, PUBMED, and Google Scholar were searched to find relevant studies to be summarized in this review article. Insulin resistance is accompanied by chronic hyperglycaemia and inflammation. Recent studies have shown that vitamin D exhibits indirect antioxidative properties and participates in the maintenance of normal resting ROS level. Appealingly, vitamin D reduces inflammation and regulates Ca²⁺ level in many cell types. Therefore, the beneficial actions of vitamin D include diminished insulin resistance which is observed as an improvement of glucose and lipid metabolism in insulin-sensitive tissues.

Vitamin D supplementation in obese Sri Lankan children: a randomized controlled trial

Background

Micronutrient deficiencies are identified among obese individuals. Vitamin D deficiency (VDD) is prevalent in obese children, and is hypothesized to cause insulin resistance and metabolic abnormalities. This study aimed to determine the effect of vitamin D supplementation on obesity and related metabolic abnormalities among obese Sri Lankan children with VDD.

Methods

A triple-blind randomized controlled trial was conducted among vitamin D deficient (< 20 ng/ml), obese children (n = 96), randomly allocated to three intervention arms - treatment arm receiving weekly vitamin D₂ 50,000 IU; supplementation arm receiving 2500 IU weekly and control arm, receiving placebo. Anthropometry, percentage fat mass (%FM) and blood pressure were assessed and fasting blood glucose, fasting insulin, lipid profile, aspartate transaminase (ALT), alanine transaminase (AST), vitamin D, parathyroid hormone (PTH) and hs-CRP and OGTT with 2-h random blood glucose and insulin was performed at baseline and after 24 weeks of treatment. Ethics Review Committee of Faculty of Medicine, University of Colombo approved the protocol.

Results

Waist circumference Z-score, %FM and serum calcium significantly improved across all three arms, ALT significantly improved in treatment and supplementation arms while, BMI Z-score, PTH and vitamin D significantly improved in the treatment arm. Biceps (p = 0.035) and subscapular (0.048) skin fold thickness, vitamin D (p = 0.004) and ALT (p = 0.012) significantly improved in the treatment arm.

Conclusions

A strict dietary and physical activity regimen could improve some of the anthropometric, body composition and metabolic profiles, but high dose vitamin D, enhances those improvements. Therefore high dose vitamin D seems to potentiate management outcomes of obese children with vitamin D deficiency.

Trial registration

The study was registered at the Sri Lanka Clinical Trials Registry (SLCTR/2015/017) on 12th September 2015 at https://slctr.lk/trials/slctr-2015-017.

Overview of dietary supplements on patients with type 2 diabetes

BACKGROUND AND AIMS

The primary approach for managing type 2 diabetes mellitus (T2DM) involves lifestyle modification and diet therapy along with pharmacologic interventions. Many patients are interested to identify nutritional supplements that may provide benefit in prevention and management of diabetes. However, the efficacy and safety of nutritional supplements such as chromium, n-3 polyunsaturated fatty acids (PUFAs), vitamin D, zinc and magnesium in disease treatment is a worrying and controversial matter. In this narrative review, patients and health care providers are introduced to the effects of mentioned dietary supplements that may help in choosing or not choosing these supplements in treatment of diabetes.

METHODS

This review was carried out using comprehensive and systematic literature reports on the dietary supplements in the management of diabetes. Empirical searches were conducted using Google Scholar, Science Direct and PubMed databases. Searches were also undertaken using keywords, in English, such as "chromium" OR "vitamin D" OR "omega-3 fatty acids" OR "zinc" OR "magnesium" in combination with "type 2 diabetes".

RESULTS

The available evidence is insufficient to create a definite conclusion that nutritional supplements including chromium, n-3 PUFAs, vitamin D, zinc and magnesium might be beneficial for the prevention and treatment of T2DM and therefore, the general recommendation to use these supplements in the management of diabetes cannot be justified. The results of most studies lack uniformity across multiple aspects, including different dose and formation of supplements, duration, and subjects under intervention.

CONCLUSIONS

There is a need for well-designed, high quality, large and long-term studies to strengthen the available evidence and ensure the safety and efficacy of products.

Interventions to prevent women from developing gestational diabetes mellitus: an overview of Cochrane Reviews

BACKGROUND

The prevalence of gestational diabetes mellitus (GDM) is increasing, with approximately 15% of pregnant women affected worldwide, varying by country, ethnicity and diagnostic thresholds. There are associated short- and long-term health risks for women and their babies.

OBJECTIVES

We aimed to summarise the evidence from Cochrane systematic reviews on the effects of interventions for preventing GDM.

METHODS

We searched the Cochrane Database of Systematic Reviews (6 August 2019) with key words 'gestational diabetes' OR 'GDM' to identify reviews pre-specifying GDM as an outcome. We included reviews of interventions in women who were pregnant or planning a pregnancy, irrespective of their GDM risk status. Two overview authors independently assessed eligibility, extracted data and assessed quality of evidence using ROBIS and GRADE tools. We assigned interventions to categories with graphic icons to classify the effectiveness of interventions as: clear evidence of benefit or harm (GRADE moderate- or high-quality evidence with a confidence interval (CI) that did not cross the line of no effect); clear evidence of no effect or equivalence (GRADE moderate- or high-quality evidence with a narrow CI crossing the line of no effect); possible benefit or harm (low-quality evidence with a CI that did not cross the line of no effect or GRADE moderate- or high-quality evidence with a wide CI); or unknown benefit or harm (GRADE low-quality evidence with a wide CI or very low-quality evidence).

MAIN RESULTS

We included 11 Cochrane Reviews (71 trials, 23,154 women) with data on GDM. Nine additional reviews pre-specified GDM as an outcome, but did not identify GDM data in included trials. Ten of the 11 reviews were judged to be at low risk of bias and one review at unclear risk of bias. Interventions assessed included diet, exercise, a combination of diet and exercise, dietary supplements, pharmaceuticals, and management of other health problems in pregnancy. The quality of evidence ranged from high to very low. Diet Unknown benefit or harm: there was unknown benefit or harm of dietary advice versus standard care, on the risk of GDM: risk ratio (RR) 0.60, 95% CI 0.35 to 1.04; 5 trials; 1279 women; very low-quality evidence. There was unknown benefit or harm of a low glycaemic index diet versus a moderate-high glycaemic index diet on the risk of GDM: RR 0.91, 95% CI 0.63 to 1.31; 4 trials; 912 women; low-quality evidence. Exercise Unknown benefit or harm: there was unknown benefit or harm for exercise interventions versus standard antenatal care on the risk of GDM: RR 1.10, 95% CI 0.66 to 1.84; 3 trials; 826 women; low-quality evidence. Diet and exercise combined Possible benefit: combined diet and exercise interventions during pregnancy versus standard care possibly reduced the risk of GDM: RR 0.85, 95% CI 0.71 to 1.01; 19 trials; 6633 women; moderate-quality evidence. Dietary supplements Clear evidence of no effect: omega-3 fatty acid supplementation versus none in pregnancy had no effect on the risk of GDM: RR 1.02, 95% CI 0.83 to 1.26; 12 trials; 5235 women; high-quality evidence. Possible benefit: myo-inositol supplementation during pregnancy versus control possibly reduced the risk of GDM: RR 0.43, 95% CI 0.29 to 0.64; 3 trials; 502 women; low-quality evidence. Possible benefit: vitamin D supplementation versus placebo or control in pregnancy possibly reduced the risk of GDM: RR 0.51, 95% CI 0.27 to 0.97; 4 trials; 446 women; low-quality evidence. Unknown benefit or harm: there was unknown benefit or harm of probiotic with dietary intervention versus placebo with dietary intervention (RR 0.37, 95% CI 0.15 to 0.89; 1 trial; 114 women; very low-quality evidence), or probiotic with dietary intervention versus control (RR 0.38, 95% CI 0.16 to 0.92; 1 trial; 111 women; very low-quality evidence) on the risk of GDM. There was unknown benefit or harm of vitamin D + calcium supplementation versus placebo (RR 0.33, 95% CI 0.01 to 7.84; 1 trial; 54 women; very low-quality evidence) or vitamin D + calcium + other minerals versus calcium + other minerals (RR 0.42, 95% CI 0.10 to 1.73; 1 trial; 1298 women; very low-quality evidence) on the risk of GDM. Pharmaceutical Possible benefit: metformin versus placebo given to obese pregnant women possibly reduced the risk of GDM: RR 0.85, 95% CI 0.61 to 1.19; 3 trials; 892 women; moderate-quality evidence. Unknown benefit or harm:eight small trials with low- to very low-quality evidence showed unknown benefit or harm for heparin, aspirin, leukocyte immunisation or IgG given to women with a previous stillbirth on the risk of GDM. Management of other health issues Clear evidence of no effect: universal versus risk based screening of pregnant women for thyroid dysfunction had no effect on the risk of GDM: RR 0.93, 95% CI 0.70 to 1.25; 1 trial; 4516 women; moderate-quality evidence. Unknown benefit or harm: there was unknown benefit or harm of using fractional exhaled nitrogen oxide versus a clinical algorithm to adjust asthma therapy on the risk of GDM: RR 0.74, 95% CI 0.31 to 1.77; 1 trial; 210 women; low-quality evidence. There was unknown benefit or harm of pharmacist led multidisciplinary approach to management of maternal asthma versus standard care on the risk of GDM: RR 5.00, 95% CI 0.25 to 99.82; 1 trial; 58 women; low-quality evidence.

AUTHORS' CONCLUSIONS

No interventions to prevent GDM in 11 systematic reviews were of clear benefit or harm. A combination of exercise and diet, supplementation with myo-inositol, supplementation with vitamin D and metformin were of possible benefit in reducing the risk of GDM, but further high-quality evidence is needed. Omega-3-fatty acid supplementation and universal screening for thyroid dysfunction did not alter the risk of GDM. There was insufficient high-quality evidence to establish the effect on the risk of GDM of diet or exercise alone, probiotics, vitamin D with calcium or other vitamins and minerals, interventions in pregnancy after a previous stillbirth, and different asthma management strategies in pregnancy. There is a lack of trials investigating the effect of interventions prior to or between pregnancies on risk of GDM.

Cytosolic Ca2+ Buffers Are Inherently Ca2+ Signal Modulators

For precisely regulating intracellular Ca²⁺ signals in a time- and space-dependent manner, cells make use of various components of the "Ca²⁺ signaling toolkit," including Ca²⁺ entry and Ca²⁺ extrusion systems. A class of cytosolic Ca²⁺-binding proteins termed Ca²⁺ buffers serves as modulators of such, mostly short-lived Ca²⁺ signals. Prototypical Ca²⁺ buffers include parvalbumins (α and β isoforms), calbindin-D9k, calbindin-D28k, and calretinin. Although initially considered to function as pure Ca²⁺ buffers, that is, as intracellular Ca²⁺ signal modulators controlling the shape (amplitude, decay, spread) of Ca²⁺ signals, evidence has accumulated that calbindin-D28k and calretinin have additional Ca²⁺ sensor functions. These other functions are brought about by direct interactions with target proteins, thereby modulating their targets' function/activity. Dysregulation of Ca²⁺ buffer expression is associated with several neurologic/neurodevelopmental disorders including autism spectrum disorder (ASD) and schizophrenia. In some cases, the presence of these proteins is presumed to confer a neuroprotective effect, as evidenced in animal models of Parkinson's or Alzheimer's disease.

Oncomodulin: The Enigmatic Parvalbumin Protein

EF-hand Ca²⁺-binding protein family members, α- and β-parvalbumins have been studied for decades. Yet, considerable information is lacking distinguishing functional differences between mammalian α-parvalbumin (PVALB) and oncomodulin (OCM), a branded β-parvalbumin. Herein, we provide an overview detailing the current body of work centered around OCM as an EF-Hand Ca²⁺-binding protein and describe potential mechanisms of OCM function within the inner ear and immune cells. Additionally, we posit that OCM is evolutionarily distinct from PVALB and most other β-parvalbumins. This review summarizes recent studies pertaining to the function of OCM and emphasizes OCM as a parvalbumin possessing a unique cell and tissue distribution, Ca²⁺ buffering capacity and phylogenetic origin.

Prevalence of vitamin D deficiency and its association with metabolic derangements among children with obesity

Background

It is known that obesity is associated with vitamin D deficiency and observational studies have shown vitamin D deficiency to be linked with the development of type 2 diabetes. There are no comprehensive data regarding vitamin D deficiency in children with obesity in Sri Lanka and the objective of the study was to assess the prevalence of Vitamin D deficiency and its association with metabolic derangements among children with obesity.

Methodology

Two hundred and two children between 5 and 15 years of age attending the obesity clinic Lady Ridgeway Hospital (LRH) were recruited excluding those having possible secondary causes for obesity. Blood was drawn after 12-h overnight fast for fasting blood glucose(FBG), lipid profile, serum insulin, alanine aminotransferase (ALT),aspartate aminotransferase(AST), Vitamin D, parathyroid hormone(PTH),high sensitivity C reactive protein(hs-CRP). Oral glucose tolerance test (OGTT) was done with 2 h random blood glucose. Anthropometry, blood pressure were measured, and body fat mass was assessed using bio-impedance.

Results

Vitamin D deficiency (< 20 ng/ml) was seen in 152(75.2%) children and 43(21.3%) had insufficient (20-30 ng/ml) levels. Skin fold thickness, fasting and post-glucose insulin, HOMA-IR, PTH, LDL, Serum cholesterol and hs-CRP showed statistically significant negative correlations with Vitamin D levels.

Conclusions

Vitamin D deficiency was significantly high in Sri Lankan children with obesity and showed significant negative correlations with indicators of insulin resistance and adiposity.

Cardiovascular Risk Factors and Their Association with Vitamin D Deficiency in Mexican Women of Reproductive Age

Based on a nationally representative sample of young Mexican women aged 20 to 49 years (n = 3260), we sought to explore whether cardiovascular risk factors and acute myocardial infarction (AMI) were associated with vitamin D deficiency (VDD, defined as 25-OH-D <50 nmol/L). To this end, we obtained sociodemographic, serum and anthropometric data from the 2012 National Health and Nutrition Survey (ENSANUT 2012). Analyses were developed through logistic regression models adjusted for potential confounders. The prevalence of VDD was significantly higher in obese women (42.5%, 95% CI; 37.3–47.9) compared to women with a normal body mass index (29.9%, 95% CI; 23.5–37.1, p = 0.05), in those with high total cholesterol (TC) (45.6% 95% CI; 39.4–51.9) compared to those with normal TC levels (33.9%, 95% CI 30–38.1, p = 0.03), and in those with insulin resistance (IR) (44%, 95% CI; 36.9–51.7) or type 2 diabetes mellitus (T2DM) (58.6%, 95% CI 46.9–69.4) compared to those with normal glycemia (no insulin resistance: 34.7%, 95% CI; 30.9–38.8, p = 0.04 and no T2DM: 34.9%, 95% CI 31.4–38.6, p < 0.001). Utilizing individual models to estimate cardiovascular risk according to VDD, we found that the odds of being obese (odds ratio, OR: 1.53, 95% CI 1.02–2.32, p = 0.05), or having high TC levels (OR: 1.43, 95% CI; 1.05–2.01, p = 0.03), T2DM (OR: 2.64, 95% CI; 1.65–4.03, p < 0.001), or IR (OR: 1.48, 95% CI 1.04–2.10, p = 0.026) were significantly higher in women with VDD (p < 0.05). Odds were not statistically significant for overweight, high blood pressure, sedentarism, AMI, high serum concentration of triglycerides, homocysteine, or C-reactive protein models. In conclusion, our results indicate that young Mexican women with VDD show a higher prevalence of cardiovascular risk factors.

Interventions to prevent women developing gestational diabetes mellitus: an overview of Cochrane Reviews

This is a protocol for a Cochrane Review (Overview). The objectives are as follows:

To summarise the evidence from Cochrane systematic reviews regarding the effects of interventions to prevent women developing gestational diabetes mellitus (GDM).

Analysis of Association between Vitamin D Deficiency and Insulin Resistance

Recent evidence revealed extra skeleton activity of vitamin D, including prevention from cardiometabolic diseases and cancer development as well as anti-inflammatory properties. It is worth noting that vitamin D deficiency is very common and may be associated with the pathogenesis of insulin-resistance-related diseases, including obesity and diabetes. This review aims to provide molecular mechanisms showing how vitamin D deficiency may be involved in the insulin resistance formation. The PUBMED database and published reference lists were searched to find studies published between 1980 and 2019. It was identified that molecular action of vitamin D is involved in maintaining the normal resting levels of ROS and Ca2+, not only in pancreatic β-cells, but also in insulin responsive tissues. Both genomic and non-genomic action of vitamin D is directed towards insulin signaling. Thereby, vitamin D reduces the extent of pathologies associated with insulin resistance such as oxidative stress and inflammation. More recently, it was also shown that vitamin D prevents epigenetic alterations associated with insulin resistance and diabetes. In conclusion, vitamin D deficiency is one of the factors accelerating insulin resistance formation. The results of basic and clinical research support beneficial action of vitamin D in the reduction of insulin resistance and related pathologies.

Vitamin D Insufficiency in Overweight and Obese Children and Adolescents

Excessive body weight and obesity in childhood and adolescence are becoming more and more important unfavorable factors that entail extremely adverse consequences and require close attention of physicians of any specialty. Along with the high prevalence of obesity and metabolic syndrome in pediatric patients, children and adolescents in the majority of countries are diagnosed with vitamin D deficiency. Among the non-calcaemic effects of vitamin D, a significant role is played by its impact on the hormonal regulation of glucose metabolism and the synthesis of adipokines by fat tissue. The review presents literature data indicative of a close pathogenic relationship between vitamin D insufficiency and impaired tissue insulin sensitivity. It demonstrates the role of vitamin D insufficiency in immune reactions resulting in development of subclinical inflammation in fat tissue infiltrated with macrophages and lymphocytes. It also shows the role of adipokines, immune system cells and pro-inflammatory cytokines produced by them in the pathogenesis of obesity, as well as the function of vitamin D as an endocrine and paracrine regulator of the process of inflammation in adipose tissue. The relationships between the principal adipokines (leptin, adiponectin, resistin) are revealed in the presence of normal vitamin D content and in vitamin D deficiency. The carbohydrate and lipid metabolism parameters in overweight children and adolescents with vitamin D insufficiency are analyzed. A high prevalence of vitamin D insufficiency in overweight and obese children and adolescents (increasing along with the severity of obesity) is demonstrated. The review also presents the current recommendations for the correction of vitamin D insufficiency and underlines the need for higher cholecalciferol doses to achieve serum calcifediol targets in overweight and obese children and adolescents.

The X-ray structure of human calbindin-D28K: an improved model

Calbindin-D28K is a widely expressed calcium-buffering cytoplasmic protein that is involved in many physiological processes. It has been shown to interact with other proteins, suggesting a role as a calcium sensor. Many of the targets of calbindin-D28K are of therapeutic interest: for example, inositol monophosphatase, the putative target of lithium therapy in bipolar disorder. Presented here is the first crystal structure of human calbindin-D28K. There are significant deviations in the tertiary structure when compared with the NMR structure of rat calbindin-D28K (PDB entry 2g9b), despite 98% sequence identity. Small-angle X-ray scattering (SAXS) indicates that the crystal structure better predicts the properties of calbindin-D28K in solution compared with the NMR structure. Here, the first direct visualization of the calcium-binding properties of calbindin-D28K is presented. Four of the six EF-hands that make up the secondary structure of the protein contain a calcium-binding site. Two distinct conformations of the N-terminal EF-hand calcium-binding site were identified using long-wavelength calcium single-wavelength anomalous dispersion (SAD). This flexible region has previously been recognized as a protein-protein interaction interface. SAXS data collected in both the presence and absence of calcium indicate that there are no large structural differences in the globular structure of calbindin-D28K between the calcium-loaded and unloaded proteins.

Vitamin D: Effect on Haematopoiesis and Immune System and Clinical Applications

Vitamin D is a steroid-like hormone which acts by binding to vitamin D receptor (VDR). It plays a main role in the calcium homeostasis and metabolism. In addition, vitamin D display other important effects called “non-classical actions.” Among them, vitamin D regulates immune cells function and hematopoietic cells differentiation and proliferation. Based on these effects, it is currently being evaluated for the treatment of hematologic malignancies. In addition, vitamin D levels have been correlated with patients’ outcome after allogeneic stem cell transplantation, where it might regulate immune response and, accordingly, might influence the risk of graft-versus-host disease. Here, we present recent advances regarding its clinical applications both in the treatment of hematologic malignancies and in the transplant setting.

Isx9 Regulates Calbindin D28K Expression in Pancreatic β Cells and Promotes β Cell Survival and Function

Pancreatic β-cell dysfunction and death contribute to the onset of diabetes, and novel strategies of β-cell function and survival under diabetogenic conditions need to be explored. We previously demonstrated that Isx9, a small molecule based on the isoxazole scaffold, drives neuroendocrine phenotypes by increasing the expression of genes required for β-cell function and improves glycemia in a model of β cell regeneration. We further investigated the role of Isx9 in β-cell survival. We find that Isx9 drives the expression of Calbindin-D28K (D28K), a key regulator of calcium homeostasis, and plays a cytoprotective role through its calcium buffering capacity in β cells. Isx9 increased the activity of the calcineurin (CN)/cytoplasmic nuclear factor of the activated T-cells (NFAT) transcription factor, a key regulator of D28K, and improved the recruitment of NFATc1, cAMP response element-binding protein (CREB), and p300 to the D28K promoter. We found that nutrient stimulation increased D28K plasma membrane enrichment and modulated calcium channel activity in order to regulate glucose-induced insulin secretion. Isx9-mediated expression of D28K protected β cells against chronic stress induced by serum withdrawal or chronic inflammation by reducing caspase 3 activity. Consequently, Isx9 improved human islet function after transplantation in NOD-SCID mice in a streptozotocin-induced diabetes model. In summary, Isx9 significantly regulates expression of genes relevant to β cell survival and function, and may be an attractive therapy to treat diabetes and improve islet function post-transplantation.

Vitamin D and pancreas: The role of sunshine vitamin in the pathogenesis of diabetes mellitus and pancreatic cancer

Increasing evidence suggests that vitamin D exerts multiple effects beyond bone and calcium metabolism. Vitamin D seems to play a role in pancreatic disease, including type 1 and type 2 diabetes mellitus as well as pancreatic cancer. Vitamin D's immune-modulatory action suggests that it could help prevent type 1 diabetes. In type 2 diabetes, vitamin D may influence β-cell function, insulin sensitivity, and systematic inflammation-all characteristic pathways of that disease. Data from observational studies correlated vitamin D deficiency with risk of type 1 and type 2 diabetes. Prospective and ecological studies of pancreatic cancer incidence generally support a beneficial effect of higher 25-hydroxyvitamin D concentration as well as inverse correlations between UVB dose or exposure and incidence and/or mortality rate of pancreatic cancer. This review discusses the literature regarding vitamin D's role in risk of diabetes and pancreatic cancer. The results to date generally satisfy Hill's criteria for causality regarding vitamin D and incidence of these pancreatic diseases. However, large randomized, blinded, prospective studies are required to more fully evaluate the potential therapeutic role of vitamin D in preventing pancreatic diseases.

The association of vitamin D status and dietary calcium intake with individual components of the metabolic syndrome: a population-based study in Victoria, Australia

This study examined the associations between 25-hydroxyvitamin D (25-OHD), dietary calcium (Ca) intake, and individual components of the metabolic syndrome (MetS).

Methods

We analyzed a population-based sample of 18-75-year-old adults (n=3387) from the Victorian Health Monitor survey.

Results

After adjustment for sociodemographic, physical, and dietary factors, as well as other MetS components, every 10 nmol/l increment in 25-OHD was associated with reduced adjusted odds ratio (AOR) of elevated triglycerides (TG) [AOR: 0.79, 95% confidence interval (CI): 0.74-0.84, P<0.001], and higher fasting plasma glucose (AOR: 0.91, 95% CI: 0.86-0.96, P=0.002). After adjustment for confounders, every 500 mg/day increment in dietary Ca intake significantly reduced the odds of elevated diastolic blood pressure (AOR: 0.80, 95% CI: 0.66-0.99, P=0.038). When nine combinations of 25-OHD and Ca tertiles were examined, certain combinations were associated with reduced AOR for elevated TG (P<0.001), when referenced against the combination of low 25-OHD (median: 33 nmol/l) and low Ca (median: 579 mg/day). At low 25-OHD, increasing Ca intake decreased the AOR for low high-density lipoprotein cholesterol in a dose-dependent manner, but at high 25-OHD; such effects of Ca were blunted.

Conclusion

Higher vitamin D status and Ca intake or their combination were associated with reduced odds for a number of individual MetS components.

The Role of Vitamin D in the Prevention of Type 2 Diabetes: To D or Not to D?

Evidence on biological plausibility from mechanistic studies and highly consistent data from observational studies raise the possibility that optimizing vitamin D status may reduce the risk of type 2 diabetes. However, the observational nature of cohort studies precludes a definitive assessment of cause and effect because residual confounding or reverse causation cannot be excluded. Confounding is especially problematic with studies of vitamin D because blood 25-hydoxyvitamin D concentration is not only an excellent biomarker of vitamin D status, reflecting intake or biosynthesis, but also an excellent marker of good overall health. Results from underpowered trials and post hoc analyses of trials designed for nondiabetic outcomes do not support a role of vitamin D supplementation for prevention of type 2 diabetes among people with normal glucose tolerance. Whether vitamin D supplementation may have a role in the prevention of diabetes in high-risk populations remains to be seen. Adequately powered, randomized trials in well-defined populations (e.g., prediabetes) are ongoing and expected to establish whether vitamin D supplementation lowers risk of diabetes.

Vitamin D deficiency and anemia risk in children: a review of emerging evidence

There has been renewed scientific interest in the sequelae of vitamin D deficiency, given the emerging evidence on the diverse biologic functions of vitamin D, besides its fundamental role in bone and mineral metabolism. For the past decade, the evidence in the medical literature pointing to a relationship between anemia risk and vitamin D deficiency has been accumulating. This paper critically reviews the current evidence linking vitamin D deficiency to anemia risk in children. The synthesized evidence indicates that the studies, which were preponderantly conducted among the adult population, not only reported a bidirectional relationship between vitamin D deficiency and anemia but also showed a racial effect. In studies conducted among children, similar results were reported. Although the causal association of vitamin D deficiency with anemia risk (especially iron-deficiency anemia) remains debatable, the noncalcemic actions of the vitamin and its analogs hold prospects for several novel clinical applications. There is, however, unanimity in many reports suggesting that vitamin D deficiency is directly associated with anemia of chronic disease or inflammation. Despite the advances in unraveling the role of vitamin D in iron homeostasis, further research is still required to validate causality in the relationship between vitamin D deficiency and anemia, as well as to determine its optimal dosing, the ideal recipients for therapeutic intervention, and the preferred analogs to administer.

Vitamin D and Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) has become a significant global health care problem and its reported incidence is increasing at an alarming rate. Despite the improvement in therapy and development of new drugs, treatment still remains insufficient especially due to the associated side effects of most available drugs. Efforts are continuing toward disease prevention and search for safer drugs. Conflicting evidence is associating low levels of vitamin D in the body to T2DM and as such studies have been conducted to test the effect of vitamin D levels on incidence of diabetes, diabetic control as well as diabetic complications.Despite the conflicting evidence, vitamin D replacement seems to have some beneficial effect on the many aspects of diabetes: incidence, control and complications. Further long term and more convincing controlled trials are required in order to draw firmer conclusions on this beneficial role of vitamin D treatment on T2DM.

Relationship between Serum Vitamin D Status and Metabolic Risk Factors among Korean Adults with Prediabetes

Serum vitamin D status has been associated with prediabetes and metabolic syndrome. Evidence for the increased risk of metabolic disorders in individuals with prediabetes and a low vitamin D status is limited and uncertain. Furthermore, it has not been confirmed whether this possible relationship occurs in the Korean population. The aim of this study was to assess serum vitamin D status and to examine the relationship between serum vitamin D levels and metabolic risk factors in Korean adults with prediabetes. This cross-sectional study was conducted among 60 subjects aged 20-65 years. Participants had fasting glucose levels of 100 to 125 mg/dl. A questionnaire was used to assess vitamin D synthesis from sun exposure and a dietary intake examined using 3-days dietary records. Clinical and biochemical data were also collected. The 2009 harmonized definition of metabolic syndrome was used. Serum vitamin D levels were classified according to criteria from the 2011 Institute of Medicine report. The majority of subjects (75%) had a serum 25(OH)D level < 20 ng/ml, and among them, 31.1% were vitamin D deficiency (< 12 ng/ml). The proportion (42.9%) of subjects having low HDL-cholesterol was the highest among vitamin D deficiency (< 12 ng/ml) group (12 to < 20 ng/ml: 16.1%, ≥ 20 ng/ml: 6.7%). We observed an inverse relationship between 25(OH)D levels and TG, AI (β = -6.355, SE = 2.463; β = -0.020, SE = 0.008) after adjusted confounders. Korean adults with prediabetes were more likely to have low serum 25(OH)D levels. A sufficient 25(OH)D level may have possible beneficial effects on lipid profiles.

Interventions for preventing gestational diabetes mellitus: an overview of Cochrane Reviews

This is the protocol for a review and there is no abstract. The objectives are as follows:

To summarise the evidence from Cochrane systematic Reviews regarding the effects of interventions for preventing gestational diabetes mellitus.

Ways of calcium reabsorption in the kidney

The role of the kidney in calcium homeostasis has been reshaped from a classic view in which the kidney was regulated by systemic calcitropic hormones such as vitamin D3 or parathyroid hormone to an organ actively taking part in the regulation of calcium handling. With the identification of the intrinsic renal calcium-sensing receptor feedback system, the regulation of paracellular calcium transport involving claudins, and new paracrine regulators such as klotho, the kidney has emerged as a crucial modulator not only of calciuria but also of calcium homeostasis. This review summarizes recent molecular and endocrine contributors to renal calcium handling and highlights the tight link between calcium and sodium reabsorption in the kidney.

PTH and Vitamin D

PTH and Vitamin D are two major regulators of mineral metabolism. They play critical roles in the maintenance of calcium and phosphate homeostasis as well as the development and maintenance of bone health. PTH and Vitamin D form a tightly controlled feedback cycle, PTH being a major stimulator of vitamin D synthesis in the kidney while vitamin D exerts negative feedback on PTH secretion. The major function of PTH and major physiologic regulator is circulating ionized calcium. The effects of PTH on gut, kidney, and bone serve to maintain serum calcium within a tight range. PTH has a reciprocal effect on phosphate metabolism. In contrast, vitamin D has a stimulatory effect on both calcium and phosphate homeostasis, playing a key role in providing adequate mineral for normal bone formation. Both hormones act in concert with the more recently discovered FGF23 and klotho, hormones involved predominantly in phosphate metabolism, which also participate in this closely knit feedback circuit. Of great interest are recent studies demonstrating effects of both PTH and vitamin D on the cardiovascular system. Hyperparathyroidism and vitamin D deficiency have been implicated in a variety of cardiovascular disorders including hypertension, atherosclerosis, vascular calcification, and kidney failure. Both hormones have direct effects on the endothelium, heart, and other vascular structures. How these effects of PTH and vitamin D interface with the regulation of bone formation are the subject of intense investigation.

Identification of novel regulatory NFAT and TFII-I binding elements in the calbindin-D28k promoter in response to serum deprivation

Calbindin-D28k, a key regulator of calcium homeostasis plays a cytoprotective role in various tissues. We used serum free (SFM) and charcoal stripped serum (csFBS) culture media as models of cellular stress to modulate calbindin D28k expression and identify regulatory cis-elements and trans-acting factors in kidney and beta cells. The murine calbindin-D28k promoter activity was significantly upregulated under SFM or csFBS condition. Promoter analysis revealed evolutionary conserved regulatory cis-elements and deletion of 23 nt from +117/+139 as critical for basal transcription. Bioinformatics analysis of the promoter revealed conserved NFAT and TFII regulators elements. Forced expression of NFAT stimulated promoter activity. Inhibition of NFAT transcriptional activity by FK506 attenuated calbindin-D28k expression. TFII-I was shown to be necessary for basal promoter activity and to act cooperatively with NFAT. Using chromatin immunoprecipitation (ChIP) assays, NFAT was shown to bind to both proximal and distal promoter regions. ChIP assays also revealed recruitment of TFII to the -36/+139 region. Knockdown of TFII-I decreased promoter activity. In summary, calbindin-D28k expression during serum deprivation is partly regulated by NFAT and TF-II. This regulation may be important in vivo during ischemia and growth factor withdrawal to regulate cellular function and maintenance.

Vitamin D Levels Decline with Rising Number of Cardiometabolic Risk Factors in Healthy Adults: Association with Adipokines, Inflammation, Oxidative Stress and Advanced Glycation Markers

INTRODUCTION

Hypovitaminosis D associates with obesity, insulin resistance, hypertension, and dyslipoproteinemia. We asked whether the presence of multiple cardiometabolic risk factors, and which particular combination, exerts additive negative effects on 25(OH)D3 levels; and whether 25(OH)D3 levels associate with markers of inflammation and oxidative stress.

SUBJECTS AND METHODS

In non-diabetic medication-free adults central obesity (waist-to-height ratio > 0.5); elevated blood pressure (systolic BP≥130 mm Hg and/or diastolic BP ≥85 mm Hg); increased atherogenic risk (log(TAG/HDL) ≥ 0.11); and insulin resistance (QUICKI < 0.322) were considered as cardiometabolic risk factors. 25(OH)D3 status was classified as deficiency (25(OH)D3 ≤20 ng/ml); insufficiency (levels between 20-to-30 ng/ml), or as satisfactory (>30 ng/ml). Plasma adipokines, inflammatory and oxidative stress markers, advanced glycation end-products, and their soluble receptor were determined.

RESULTS

162 subjects were cardiometabolic risk factors-free, 162 presented increased (i.e. 1 or 2), and 87 high number (i.e. 3 or 4) of cardiometabolic risk factors. Mean 25(OH)D3 decreased with rising number of manifested risk factors (36 ± 14 ng/ml, 33 ± 14 ng/ml, and 31 ± 15 ng/ml, respectively; pANOVA: 0.010), while prevalence of hypovitaminosis D did not differ significantly. Elevated blood pressure and insulin resistance appeared as significant determinants of hypovitaminosis D. Subjects presenting these risk factors concurrently displayed the lowest 25(OH)D3 levels (29 ± 15 ng/ml). Plasma adipokines, inflammatory and oxidative stress markers, advanced glycation end-products, and their soluble receptor generally differed significantly between the groups, but only advanced oxidation protein products and advanced glycation end-products associated fluorescence of plasma showed significant independent association with 25(OH)D3 levels.

CONCLUSION

In apparently healthy adults increasing number of cardiometabolic risk factors associates with poorer 25(OH)D3 status, while the association between 25(OH)D3 status and inflammatory or oxidative stress markers remains equivocal.

Bone morphogenetic protein 4 inhibits insulin secretion from rodent beta cells through regulation of calbindin1 expression and reduced voltage-dependent calcium currents

AIMS/HYPOTHESIS

Type 2 diabetes is characterised by progressive loss of pancreatic beta cell mass and function. Therefore, it is of therapeutic interest to identify factors with the potential to improve beta cell proliferation and insulin secretion. Bone morphogenetic protein 4 (BMP4) expression is increased in diabetic animals and BMP4 reduces glucose-stimulated insulin secretion (GSIS). Here, we investigate the molecular mechanism behind this inhibition.

METHODS

BMP4-mediated inhibition of GSIS was investigated in detail using single cell electrophysiological measurements and live cell Ca(2+) imaging. BMP4-mediated gene expression changes were investigated by microarray profiling, quantitative PCR and western blotting.

RESULTS

Prolonged exposure to BMP4 reduced GSIS from rodent pancreatic islets. This inhibition was associated with decreased exocytosis due to a reduced Ca(2+) current through voltage-dependent Ca(2+) channels. To identify proteins involved in the inhibition of GSIS, we investigated global gene expression changes induced by BMP4 in neonatal rat pancreatic islets. Expression of the Ca(2+)-binding protein calbindin1 was significantly induced by BMP4. Overexpression of calbindin1 in primary islet cells reduced GSIS, and the effect of BMP4 on GSIS was lost in islets from calbindin1 (Calb1) knockout mice.

CONCLUSIONS/INTERPRETATION

We found BMP4 treatment to markedly inhibit GSIS from rodent pancreatic islets in a calbindin1-dependent manner. Calbindin1 is suggested to mediate the effect of BMP4 by buffering Ca(2+) and decreasing Ca(2+) channel activity, resulting in diminished insulin exocytosis. Both BMP4 and calbindin1 are potential pharmacological targets for the treatment of beta cell dysfunction.

Early pregnancy maternal vitamin D concentrations and risk of gestational diabetes mellitus

BACKGROUND

While associations of vitamin D deficiency with type 2 diabetes have been well demonstrated, investigations of vitamin D and risk of gestational diabetes mellitus (GDM) reported inconsistent findings. We examined associations of vitamin D status with GDM.

METHODS

In a nested case-cohort study (135 GDM cases and 517 non-GDM controls), we measured maternal serum vitamin D status (total 25[OH]D and 25[OH]D3 ) in early pregnancy (16 weeks on average) using liquid chromatography-tandem mass spectroscopy. GDM was diagnosed according to the American Diabetes Association guidelines. We calculated adjusted odds ratios and 95% confidence intervals (CIs) using logistic regression models.

RESULTS

GDM cases had lower mean total 25[OH]D (27.3 vs. 29.3 ng/mL) and 25[OH]D3 (23.9 vs. 26.7 ng/mL) concentrations compared with women who did not develop GDM (both P-values < 0.05). Overall, 25[OH]D3 concentrations, but not total 25[OH]D concentrations, were significantly associated with GDM risk. A 5-ng/mL increase in 25[OH]D3 concentration was associated with a 14% decrease in GDM risk (P-value = 0.02). Women in the lowest quartile for 25[OH]D3 concentration had a twofold [95% CI 1.15, 3.58] higher risk of GDM compared with women in the highest quartile (P-value for trend < 0.05).

CONCLUSIONS

Early pregnancy vitamin D status, particularly 25[OH]D3 , is inversely associated with GDM risk.

Vitamin D and diabetes

There has been increasing evidence that vitamin D may have a role in modifying risk of diabetes. Vitamin D has both direct and indirect effects on various mechanisms related to the pathophysiology of type 2 diabetes, including pancreatic beta cell dysfunction, impaired insulin action and systemic inflammation. This article describes the biologic plausibility behind the potential association between vitamin D and type 2 diabetes and summarizes the current evidence from human studies that suggests but does not prove a relation between vitamin D and type 2 diabetes, and briefly reports on the potential association between vitamin D and type 1 diabetes.

Inhibition of inositol monophosphatase (IMPase) at the calbindin-D28k binding site: molecular and behavioral aspects

Bipolar-disorder (manic-depressive illness) is a severe chronic illness affecting ∼1% of the adult population. It is treated with mood-stabilizers, the prototypic one being lithium-salts (lithium), but it has life threatening side-effects and a significant number of patients fail to respond. The lithium-inhibitable enzyme inositol-monophosphatase (IMPase) is one of the viable targets for lithium's mechanism of action. Calbindin-D28k (calbindin) up-regulates IMPase activity. The IMPase-calbindincomplex was modeled using the program MolFit. The in-silico model indicated that the 55-66 amino-acid segment of IMPase anchors calbindin via Lys59 and Lys61 with a glutamate in between (Lys-Glu-Lys motif) and that the motif interacts with residues Asp24 and Asp26 of calbindin. We found that differently from wildtype calbindin, IMPase was not activated by mutated calbindin in which Asp24 and Asp26 were replaced by alanine. Calbindin's effect was significantly reduced by a linear peptide with the sequence of amino acids 58-63 of IMPase (peptide 1) and by six amino-acid linear peptides including at least part of the Lys-Glu-Lys motif. The three amino-acid peptide Lys-Glu-Lys or five amino-acid linear peptides containing this motif were ineffective. Mice administered peptide 1 intracerebroventricularly exhibited a significant anti-depressant-like reduced immobility in the forced-swim test. Based on the sequence of peptide 1, and to potentially increase the peptide's stability, cyclic and linear pre-cyclic analog peptides were synthesized. One cyclic peptide and one linear pre-cyclic analog peptide inhibited calbindin-activated brain IMPase activity in-vitro. Our findings may lead to the development of molecules capable of inhibiting IMPase activity at an alternative site than that of lithium.

Unraveling the effects of 1,25OH2D3 on global gene expression in pancreatic islets

INTRODUCTION

Vitamin D deficiency has been linked to type 1 and 2 diabetes, whereas supplementation may prevent both diseases. However, the extent of the effects of vitamin D or its metabolites directly on pancreatic islets is still largely unknown. The aim of the present study was to investigate how active vitamin D, 1,25(OH)2D3, affects beta cells directly by establishing its effects on global gene expression in healthy murine islets.

MATERIALS AND METHODS

Pancreatic islets were isolated from 2 to 3 week old C57BL/6 mice and cultured in vitro with 1,25(OH)2D3 or vehicle for 6 and 24h. Total RNA was extracted from the islets and the effects on global gene expression were analyzed using Affymetrix microarrays.

RESULTS AND DISCUSSION

Exposure to 1,25(OH)2D3 compared to vehicle resulted in 306 and 151 differentially expressed genes after 6 and 24h, respectively (n=4, >1.3-fold, p<0.02). Of these 220 were up-regulated, whereas 86 displayed a decreased expression after 6h. Furthermore, expression levels were increased for 124 and decreased for 27 genes following 24h of exposure. Formation of intercellular junctions, cytoskeletal organization, and intracellular trafficking as well as lipid metabolism and ion transport were among the most affected gene classes. Effects on several genes already identified as being part of vitamin D signaling in other cell types were observed along with genes known to affect insulin release, although with our assay we were not able to detect any effects of 1,25(OH)2D3 on glucose-stimulated insulin release from healthy pancreatic islets.

CONCLUSION

The effects of 1,25(OH)2D3 on the expression of cytoskeletal and intracellular trafficking genes along with genes involved in ion transport may influence insulin exocytosis. However, an effect of 1,25(OH)2D3 on insulin release could not be detected for healthy islets in contrast to islets subjected to pathological conditions such as cytokine exposure and vitamin D deficiency as suggested by other studies. Thus, in addition to previously identified tolerogenic effects on the immune system, 1,25(OH)2D3 may affect basic functions of pancreatic beta cells, with the potential to render them more resistant to the detrimental conditions encountered during type 1 and 2 diabetes. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Analysis of Foxo1-regulated genes using Foxo1-deficient pancreatic β cells

Several reports have suggested that Foxo1, a key regulator in differentiation, growth and metabolism, is involved in pancreatic β-cell function. However, detailed analyses have been hampered by a lack of Foxo1-deficient β cells. To elucidate Foxo1's function in β cells, we produced a β-cell line with inducible Foxo1 deletion. We generated a conditional knockout mouse line, in which Cre recombinase deletes the Foxo1 gene. We then established a β-cell line from an insulinoma induced in this knockout mouse by the β-cell-specific expression of simian virus 40 T antigen. In this cell line, designated MIN6-Foxo1flox/flox, adenovirus-mediated Cre expression ablates the Foxo1 gene, generating MIN6-Foxo1-KO cells. Using these knockout and floxed cell lines, we found that Foxo1 ablation enhanced the glucose-stimulated insulin secretion (GSIS) at high glucose concentrations and enhanced β-cell proliferation. We also conducted DNA microarray analyses of MIN6-Foxo1-KO cells infected with either an adenovirus vector expressing a constitutively active FOXO1 or a control vector and identified several Foxo1-regulated genes, including some known to be related to β-cell function. These cells should be useful for further studies on Foxo1's roles in β-cells and may lead to novel strategies for treating the impaired insulin secretion in type 2 diabetes mellitus.

The Effects of Vitamin D Deficiency on Atrial Fibrillation

Background:

Vitamin D deficiency is associated with cardiovascular disease such as coronary artery disease, heart failure, and hypertension. Vitamin D deficiency activates the renin–angiotensin–aldosterone system, which affects the cardiovascular system. For this reason, it could be suggested that there is a relationship between vitamin D deficiency and atrial fibrillation (AF). In our study, we compared 25-hydroxyvitamin D (25-OHD) levels between nonvalvular AF, valvular AF, and control groups in sinus rhythm.

Method:

A total of 102 patients with nonvalvular chronic AF without any other cardiovascular disease (mean age 62.51 ± 5.88; group I) and 96 patients with AF, which is associated with mitral valve disease (mean age 61.51 ± 5; group II) were included in our study. Of all, 100 age-matched healthy people with sinus rhythm were accepted as control groups (mean age 61.35 ± 5.44). Routine biochemical parameters, 25-OHD and parathormone levels were performed.

Results:

Baseline characteristics of the study groups were comparable. Group I patients had a lower vitamin D level than group II and the control group (6.51 ± 4.89, 9.24 ± 7.39, and 11.18 ± 6.98 ng/mL, P < .001, respectively). In groups I and II, the patients’ left atrium diameter and systolic pulmonary artery pressure are higher than the control group.

Conclusion:

As a result, our study revealed a relationship between vitamin D deficiency and nonvalvular AF.

Vitamin D deficiency in obese children and its relationship to glucose homeostasis

OBJECTIVES

The aim of the study was to compare the prevalence of vitamin D deficiency in obese and non-overweight children in North Texas, to examine relationships between dietary habits and 25-hydroxyvitamin D [25(OH)D] level in obese children, and to examine the relationship between 25(OH)D level and markers of abnormal glucose metabolism and blood pressure.

PATIENTS AND METHODS

Using a cross-sectional design, systolic and diastolic blood pressure, dietary information, serum 25(OH)D, fasting glucose and insulin, 2-h glucose from oral glucose tolerance test, hemoglobin A1c, and homeostasis model assessment of insulin resistance were recorded for 411 obese subjects (6-16 yr old) at an obesity referral clinic. 25(OH)D was also obtained from 87 control non-overweight subjects (6-16 yr old).

RESULTS

Ninety-two percent of obese subjects had a 25(OH)D level below 75 nmol/liter, and 50% were below 50 nmol/liter. Among non-overweight subjects, these frequencies were 68 and 22%, respectively (both P < 0.01 compared with obese subjects). 25(OH)D was negatively associated with soda intake (P < 0.001), juice intake (P = 0.009), and skipping breakfast (P < 0.001). 25(OH)D was negatively correlated with homeostasis model assessment of insulin resistance (r = -0.19; P = 0.001) and 2-h glucose (r = -0.12; P = 0.04) after adjustment for body mass index and age but was not correlated with hemoglobin A1c, systolic blood pressure Z score, or diastolic blood pressure Z score.

CONCLUSIONS

Vitamin D deficiency is common in children in this southern United States location and is significantly more prevalent in obese children. Lower 25(OH)D level is associated with risk factors for type 2 diabetes in obese children.

Investigation of Archived Formalin-Fixed Paraffin-Embedded Pancreatic Tissue with Whole-Genome Gene Expression Microarray

The use of formalin-fixed, paraffin-embedded (FFPE) tissue overcomes the most prominent issues related to research on relatively rare diseases: limited sample size, availability of control tissue, and time frame. The use of FFPE pancreatic tissue in GEM may be especially challenging due to its very high amounts of ribonucleases compared to other tissues/organs. In choosing pancreatic tissue, we therefore indirectly address the applicability of other FFPE tissues to gene expression microarray (GEM). GEM was performed on archived, routinely fixed, FFPE pancreatic tissue from patients with congenital hyperinsulinism (CHI), insulinoma, and deceased age-appropriate neonates, using whole-genome arrays. Although ribonuclease-rich, we obtained biologically relevant and disease-specific, significant genes; cancer-related genes; genes involved in (a) the regulation of insulin secretion and synthesis, (b) amino acid metabolism, and (c) calcium ion homeostasis. These results should encourage future research and GEM studies on FFPE tissue from the invaluable biobanks available at the departments of pathology worldwide.

Vitamin D and diabetes: its importance for beta cell and immune function

Experimental evidence indicates that vitamin D may play a role in the defense against type 1 diabetes (T1D) as well as type 2 diabetes (T2D). Epidemiological data have established a link between vitamin D deficiency and an increased incidence of both T1D and T2D, whereas early and long-term vitamin D supplementation may decrease the risk of these disorders. The protective effects of vitamin D are mediated through the regulation of several components such as the immune system and calcium homeostasis. However, an increasing amount of evidence suggests that vitamin D also affects beta cells directly thereby rendering them more resistant to the types of cellular stress encountered during T1D and T2D. This review evaluates the role of vitamin D signaling in the pathogenesis of T1D and T2D with a special emphasis on the direct effects of vitamin D on pancreatic beta cells.

Novel roles of vitamin D in disease: what is new in 2011?

Vitamin D is a steroid molecule, mainly produced in the skin that regulates the expression of a large number of genes. Until recently its main known role was to control bone metabolism and calcium and phosphorus homeostasis. During the last 2 decades it has been realized that vitamin D deficiency, which is really common worldwide, could be a new risk factor for many chronic diseases, such as the metabolic syndrome and its components, the whole spectrum of cardiovascular diseases, several auto-immune conditions, and many types of cancer as well as all-cause mortality. Except for the great number of epidemiological studies that support the above presumptions, vitamin D receptors (VDRs) have been identified in many tissues and cells. The effect of vitamin D supplementation remains controversial and the need for more persuasive study outcomes is intense.

Vitamin D: an ancient hormone

Vitamin D has been produced by plants and animals almost from the time life began. The ability to transport and metabolize vitamin D to more active forms evolved as the structures of plants and animals became more complex, and the cells within these organisms took on more specialized functions. In higher-order animals, the vitamin D receptor (VDR) is found in nearly every cell, and the ability of the cell to produce the active hormone, 1,25(OH)2D, is also widely distributed. Furthermore, the physiological functions with which vitamin D signalling is now associated are as diverse as the tissues in which the VDR is located. Why is this, and is there a common theme? This viewpoint article argues that there is. All cells maintain a fairly constant and submicromolar concentration of free calcium. Calcium is an important regulator of many processes within the cell. The ebb and flow of calcium within cells is controlled by calcium pumps, antiporters and channels. Animals with calcified exo- or endoskeletons have an additional need for calcium, a need that changes during the life cycle of the organism. In this article, I make the case that vitamin D signalling evolved to enable the organism to effectively regulate calcium flux, storage and signalling and that such regulation is critical for the evolutionary process.

Vitamin D and cardiometabolic health: a review of the evidence

The cardiometabolic syndrome (MetS) is a clustering of related metabolic abnormalities including abdominal adiposity, insulin resistance, hypertension, dyslipidaemia and increased inflammatory and thrombotic markers, which is linked to increased risk of type 2 diabetes, CVD and overall mortality. Several cross-sectional and prospective studies have shown an association between low vitamin D status, as indicated by concentrations of serum 25-hydroxyvitamin D (s25(OH)D), and increased prevalence of the MetS and individual CVD risk factors. These epidemiological observations are supported by mechanistic studies but experimental data are limited. The available data from intervention studies are largely confounded as most vitamin D supplementation trials were mainly carried out to explore the role of Ca in CVD and include Ca in the treatment arms. Inadequate consideration of seasonal effects on s25(OH)D concentrations is also a common design flaw in most studies. Further complications arise from shared risk factors such as adiposity and ageing, which predispose individuals to exhibit both a more pronounced risk profile and relatively lower s25(OH)D concentrations. In conclusion, while epidemiological associations are promising and a rationale for low vitamin D status as a potentially modifiable risk factor for CVD is supported by mechanistic data, suitable experimental data from appropriately designed trials are just beginning to emerge. As yet, this body of literature is too immature to draw firm conclusions on the role of vitamin D in CVD prevention. Carefully controlled vitamin D trials in well-described population groups using intervention doses that are titrated against target s25(OH)D concentrations could yield potentially valuable outcomes that may have a positive impact on CVD risk modification.

Vitamin D status and supplementation in morbid obesity before and after bariatric surgery

Interest in vitamin D has increased recently because of its role on multiple biologic mechanisms and the high prevalence of deficits, particularly in obese individuals. The epidemic of morbid obesity has led to a growing number of bariatric surgical procedures, the only therapeutic modality with a reasonable chance of success on a long-term basis. Vitamin D status following bariatric surgery depends on several interacting factors and should be monitored carefully. We review vitamin D, calcium and parathyroid hormone dynamics following the main types of bariatric surgery and the guidelines for the postoperative periodic assessment and therapy.