Improvement in glucose tolerance and beta-cell function in a patient with vitamin D deficiency during treatment with vitamin D

The correlation of vitamin D with HOMA-IR and glycated hemoglobin in type 2 diabetes mellitus patients

Background and objective: Diabetes mellitus, the most common endocrine condition, is characterised by an elevated level of plasma glucose. Vitamin D's primary functions are homeostasis of calcium and metabolism of bone, but it also has a significant role in homeostasis of plasma glucose. This study sought to examine the relationship between vitamin D and glycated haemoglobin and insulin resistance in type 2 diabetes mellitus (T2DM) subjects by analysing vitamin D, homeostasis model assessment of insulin resistance (HOMA-IR), and haemoglobin A1c (HbA1c) levels. Methods: 150 patients with newly diagnosed T2DM participated in this case-control research. Additionally, 150 controls of the same age and gender were also recruited. Serum vitamin D and fasting insulin levels were estimated by the electrochemiluminescence immunoassay (ECLIA) method. High-performance liquid chromatography (HPLC) was used to analyse HbA1c. Pearson's correlation coefficient was used to determine the relationship of vitamin D with HbA1c and HOMA-IR. Results: Around 70.7% of diabetes subjects had low vitamin D levels, compared to 31.3% in the control group. Vitamin D-deficient T2DM subjects had significantly higher HOMA-IR and HbA1c levels. Both vitamin D and HOMA-IR (r = -0.75) and vitamin D and HbA1c (r = -0.73) showed a strong inverse connection in T2DM patients. Conclusions: Vitamin D deficiency is correlated with ineffective glycemic control, and the reason might be its potential role in the secretion and sensitivity of insulin. Therefore, vitamin D screening must be incorporated as a routine check-up for T2DM patients.

Associations of Serum Total 25OHD, 25OHD3, and epi-25OHD3 with Insulin Resistance: Cross-Sectional Analysis of the National Health and Nutrition Examination Survey, 2011–2016

Background: Vitamin D may have a role in insulin sensitivity. However, the data on the association between various metabolites of Vitamin D and insulin-related parameters have been limited. Methods: We identified 6026 adults aged 20–80 years who participated in the 2011–2016 National Health and Nutrition Examination Survey (NHANES). Serum total 25OHD, 25OHD3, and epi-25OHD3, fasting glucose, insulin, and HOMA2-IR were obtained from the NHANES data. The association between serum Vitamin D-related values and insulin resistance was analyzed using a generalized linear model. For risk analysis, multifactorial logistic regression was used. Results: The median total 25-hydroxyvitamin D level, 25-hydroxyvitamin D3 level, and 3-epi-25-hydroxyvitamin D3 level were 62.5 nmol/L, 58.8 nmol/L, and 3.3 nmol/L, respectively. After adjustment for sex, age, race, ethnicity, and education status, the ORs for the insulin resistance of participants of total 25-hydroxyvitamin D, 25-hydroxyvitamin D3, and 3-epi-25-hydroxyvitamin D3 were 0.32 (95% CI 0.24, 0.43), 0.34 (95% CI 0.26, 0.44), and 0.64 (95% CI 0.53, 0.77), respectively. After an adjustment for body mass index, diabetes, and drinking and smoking, the ORs for the insulin resistance of the participants for total 25-hydroxyvitamin D, 25-hydroxyvitamin D3, and 3-epi-25-hydroxyvitamin D3 were 0.56 (95% CI 0.40, 0.78), 0.63 (95% CI 0.46, 0.85), and 0.99 (95% CI 0.80, 1.24), respectively. Conclusions: Our study provides suggestive evidence for the association between Vitamin D concentrations and a lower risk of insulin resistance. Evidence from larger and more adequately powered cohort studies is needed to confirm our results.

Associations of Vitamin D Level and Glucoregulatory Parameters in Type 2 Diabetes Mellitus

Vitamin D is known to affect the functions of pancreatic beta cells, but the effects of vitamin D deficiency on glucoregulatory mechanisms are still inconclusive. The aim of this study was to link vitamin D levels with parameters of insulin resistance and insulin secretion. The study included 70 male and female participants, 40 newly diagnosed patients with type 2 diabetes mellitus (T2DM) and 30 healthy controls. All participants were tested for fasting glucose, hemoglobin A1c, fasting insulin, vitamin D levels, and the HOMA indexes were calculated using HOMA2 calculator. Fasting glucose levels, insulinemia, hemoglobin A1c levels and HOMA IR were all significantly higher in the diabetic group (p<0.001), while vitamin D levels and HOMA S index were significantly lower (p<0.001). HOMA-B values did not differ between the two groups (p=0.31). Vitamin D levels moderately correlated with HOMA S and HOMA B indexes (r=0.466, p<0.001; r=0.394, p<0.001, respectively), whereas a negative correlation was found between vitamin D levels and HOMA IR (r=−0.285; p<0.001). Multiple regression analysis showed that vitamin D levels significantly predicted the values of HOMA B index (p=0.001), but they had no predictive value on HOMA IR (p=0.26). In conclusion, the group of newly diagnosed patients with T2DM showed significantly lower vitamin D values compared to the healthy control group. The connection between vitamin D, glucose levels, hemoglobin A1c and insulin secretion index underlines the role of this vitamin in glucoregulation.

Bioactive Compounds and Diabetes Mellitus: Prospects and Future Challenges

Diabetes mellitus is a metabolic condition that influences the endocrine framework. Hyperglycemia and hyperlipidemia are two of the most widely recognized metabolic irregularities in diabetes, just as two of the most well-known reasons for diabetic intricacies. Diabetes mellitus is a persistent illness brought about by metabolic irregularities in hyperglycemic pancreatic cells. Hyperglycemia can be brought about by an absence of insulin-producing beta cells in the pancreas (Type 1 diabetes mellitus) or inadequate insulin creation that does not work effectively (Type 2 diabetes mellitus). Present diabetes medication is directed toward directing blood glucose levels in the systemic circulation to the typical levels. Numerous advanced prescription medicines have many negative results that can bring about unexpected severe issues during treatment of the bioactive compound from a different source that is beneficially affected by controlling, adjusting metabolic pathways or cycles. Moreover, a few new bioactive medications disengaged from plants have shown antidiabetic action with more noteworthy adequacy than the oral hypoglycemic agent that specialists have utilized in clinical treatment lately. Since bioactive mixtures are collected from familiar sources, they have a great activity in controlling diabetes mellitus. This study discusses bioactive compounds and their activity to manage diabetes mellitus and their prospects. Though bioactive compound has many health beneficial properties, adequate clinical studies still need to gain large acknowledge that they are effective in the management of diabetes mellitus.

Conundrum of vitamin D on glucose and fuel homeostasis

As an endocrine hormone, vitamin D plays an important role in bone health and calcium homeostasis. Over the past two decades, the non-calcemic effects of vitamin D were extensively examined. Although the effect of vitamin D on beta cell function were known for some time, the effect of vitamin D on glucose and fuel homeostasis has attracted new interest among researchers. Yet, to date, studies remain inconclusive and controversial, in part, due to a lack of understanding of the threshold effects of vitamin D. In this review, a critical examination of interventional trials of vitamin D in prevention of diabetes is provided. Like use of vitamin D for bone loss, the benefits of vitamin D supplementation in diabetes prevention were observed in vitamin D-deficient subjects with serum 25-hydroxyvitamin D < 50 nmol/L (20 ng/mL). The beneficial effect from vitamin D supplementation was not apparent in subjects with serum 25-hydroxyvitamin D > 75 nmol/L (30 ng/mL). Furthermore, no benefit was noted in subjects that achieved serum 25-hydroxyvitamin D > 100 nmol/L (40 ng/mL). Further studies are required to confirm these observations.

Vitamin D3 deficiency is associated with more severe insulin resistance and metformin use in patients with type 2 diabetes

BACKGROUND

Vitamin D3 (vit. D3) deficiency is considered as one of the main factors involved in the development of type 2 diabetes (T2D). We assessed insulin resistance (IR), β-cell functional activity and metabolic profile according to 25(OH) vit. D3 status in patients with T2D.

METHODS

The study included 109 patients with T2D, divided in 3 groups: group 1 (N.=11) with normal levels of vit. D3 (>30 ng/mL); group 2 (N.=38) with vit. D3 insufficiency (21-29 ng/mL); and group 3 (N.=60) with vit. D3 deficiency (<20 ng/mL). IR and β-cell functional activity were assessed as change in C-peptide concentration and homeostasis model assessment-estimated (HOMA) β-cell function which was calculated using HOMA2 calculator.

RESULTS

Patients with vit. D3 deficiency presented significantly higher C-peptide concentration compared to other groups. HOMA2 (3.29±1.89 vs. 2.12±0.71; P=0.049) and hemoglobin (H8b)A1c (9.11±1.63 vs. 7.75±1.06; P=0.016) levels changed significantly only in patients with vit. D3 deficiency compared to diabetics with normal vit. D3 levels. Furthermore, in univariate Pearson's correlation analysis, we observed significant association between vit. D3 levels and C-peptide, insulin sensitivity, HOMA2, triglyceride-glucose index, HbA1c and Body Mass Index, only in the vit. D3 deficiency group. In multivariate logistic regression analysis, poor glycemic control, as defined by HbA1c levels, was independent from metformin use while high density lipoprotein-cholesterol levels were associated with vit. D3 deficiency.

CONCLUSIONS

Our study demonstrated that vit. D3 deficiency in patients with T2D was associated with more severe IR, poor glycemic control and obesity compared to normal status or vit. D3 insufficiency.

Serum vitamin D levels in relation to type-2 diabetes and prediabetes in adults: a systematic review and dose-response meta-analysis of epidemiologic studies

BACKGROUND

Findings of observational studies that investigated the relationship between vitamin D deficiency and abnormal glucose homeostasis were contradictory. This meta-analysis of epidemiologic studies evaluated the association of vitamin D status and risk of type-2 diabetes (T2D) and prediabetes in adults.

METHODS

A systematic search was conducted on all published articles in five electronic databases (including MEDLINE/PubMed, EMBASE, Institute for Scientific Information, Scopus and Google scholar), up to August 2020. Twenty-eight prospective cohort and nested case-control studies and 83 cross-sectional and case-control investigations that reported relative risks (RRs) or odds ratios (ORs) with 95% confidence intervals (CIs) for abnormal glucose homeostasis in relation to serum vitamin D levels in adults were included in the analysis.

RESULTS

In prospective studies, high versus low level of vitamin D was respectively associated with significant 35%, 30% and 51% decrease in risk of T2D (RR:0.65; 95%CI: 0.55-0.76; 27 effect sizes), combined T2D and pre-diabetes (RR:0.70; 95%CI: 0.52-0.95; 9 effect sizes) and pre-diabetes (RR:0.49; 95%CI: 0.26-0.93; 2 effect sizes). These inverse associations were significant in almost all subgroups. Dose-response analysis in prospective studies showed that each 10 ng/ml increase in serum vitamin D levels resulted in 12% and 11% reduced risk of T2D (RR:0.88; 95%CI: 0.83-0.94) and combined T2D and prediabetes (RR:0.89; 95%CI: 0.87-0.92), respectively. In cross-sectional and case-control studies, highest versus lowest level of serum vitamin D was linked to reduced odds of T2D (OR:0.64; 95%CI: 0.57-0.72; 42 effect sizes) and combined T2D and pre-diabetes (OR:0.79; 95%CI: 0.74-0.85; 59 effect sizes); but not pre-diabetes (OR:0.64; 95%CI: 0.17-2.37; 11 effect sizes).

CONCLUSION

This meta-analysis of epidemiologic studies disclosed that serum vitamin D level was reversely associated with the risk of T2D and combined T2D and prediabetes in adults, in a dose-response manner. However, the association was not remarkable for pre-diabetes.

Early myocardial injury biomarkers in diabetic hyperlipidemic rats: Impact of 10-dehydrogingerdione and vitamin D3

IMPACT STATEMENT

Hyperlipidemia represents a major risk factor for cardiovascular diseases leading to myocardial injury (MI). The present study aimed to illustrate the pattern of myocardial injury induced in diabetic hyperlipidemic rat model and the effect of vitamin D3, 10-dehydrogingerdione (10-DHGD) intake either individually or in combination form.

25(OH)D Serum Level in Non-Diabetic and Type II Diabetic Patients: A Cross-Sectional Study

Background

Diabetes mellitus is a major disease worldwide. In Saudi Arabia, it is considered to be the most common disease in the country. Diabetes mellitus has been also found to be associated with 25(OH)D (vitamin D) deficiency. In Saudi Arabia, sunlight is considered a major source for vitamin D. Saudi Arabia is popular for sunny weather most of the year, in which people can get vitamin D from the sun. However, vitamin D deficiency is common in Saudi Arabia, and its deficiency can increase blood glucose levels. We conducted a study to determine the reason for vitamin D deficiency in Saudi Arabia and to assess the relationship of diabetes mellitus with vitamin D.

Aim of the work 

This study is aimed to assess the incidence of vitamin D deficiency in non-diabetic and type II diabetic patients in the King Faisal University (KFU) Health Center in the Al-Ahsa region.

Methods

Our study is a cross-sectional study that was carried out at the KFU Health Center in Saudi Arabia. Ethical approval was obtained from the Ethics and Research Committee at the College of Medicine at King Faisal University. The study period was from January 2016 to April 2016. We collected each patient's vitamin D serum level, glycosylated hemoglobin (HbA1c), and fasting blood glucose at the same time for each patient's particular visit to the hospital. Data were analyzed using the Statistical Package for Social Sciences (SPSS) (IBM SPSS Statistics, Armonk, NY). 

Results

Our results showed that 89.53% of the patients had a vitamin D level below the normal range. There was a higher incidence of vitamin D deficiency in females (81.67%) than in males (65.27%) (p-value = 0.001). The incidence of vitamin D deficiency was greater in Saudi (82.19%) than non-Saudi patients (68.40%) (p-value = 0.001), as well as in diabetics (89.68%) than non-diabetics (76.12%) patients (p-value = 0.001). Within each group, the incidence of vitamin D deficiency was higher in females than in males. The incidence of vitamin D deficiency was highest in the age group of 21 to 40 years old (86.19%) and lowest in the age group of one to 20 years old (66.1%). The results showed an inverse relationship between the vitamin D level and both fasting blood glucose and HbA1c (independent sample t-test) were used for correlation. The mean fasting glucose was higher in the deficiency group (165.55) as compared to the insufficiency group (118.67). Also, the mean HbA1c was higher in the deficiency group (8.06) as compared to the insufficiency group (7.23) (p-value = 0.030). 

Conclusions

There was a high incidence of vitamin D deficiency among KFU Health Center patients. The vitamin D level was inversely proportional to the level of fasting glucose and HbA1c. There is an evident role of vitamin D deficiency on glucose tolerance in diabetic patients.

Role of Hypovitaminosis D in the Pathogenesis of Obesity-Induced Insulin Resistance

Obesity and type 2 diabetes have both rapidly increased during the last decades and are continuing to increase at an alarming rate worldwide. Obesity and impaired glucose homeostasis are closely related, and during the last decades of investigation about vitamin D, several clinical and epidemiological studies documented an inverse correlation between circulating vitamin D levels, central adiposity and the development of insulin resistance and diabetes. The insufficient sun exposure and outdoor activities of obese individuals, the storage of vitamin D in adipose tissue, because of its lipophilic properties, and the vitamin D-mediated modulation of adipogenesis, insulin secretion, insulin sensitivity and the immune system, are the main reasons for the close relationship between obesity, glucose homeostasis and hypovitaminosis D. Then objective of this review is to explore the pathophysiological mechanism(s) by which vitamin D modulates glycemic control and insulin sensitivity in obese individuals.

Vitamin D levels and platelet reactivity in diabetic patients receiving dual antiplatelet therapy

BACKGROUND

Hypovitaminosis D represents an emerging cardiovascular risk factor, and especially among higher-risk subsets of patients, such as in those with diabetes mellitus. The anti-inflammatory and anti-thrombotic properties of vitamin D, in fact, could be even more beneficial among diabetics, where platelet hyperreactivity and suboptimal response to antiplatelet drugs has been associated with poorer outcomes. However, no study has so far evaluated the impact of vitamin D levels on platelet reactivity and high-on treatment platelet reactivity (HRPR) among diabetic patients receiving dial antiplatelet therapy (DAPT).

METHODS

Our population is represented by a consecutive cohort ofdiabetic patients treated with DAPT (ASA + clopidogrel or ticagrelor or dose-adjusted prasugrel) for an acute coronary syndrome or elective PCI, undergoing platelet reactivity assessment at 30-90 days post-discharge. Aggregation was assessed by multiple-electrode aggregometry. HRPR was defined for values above the lower limit of normality (in non-treated patients).

RESULTS

We included 440 patients, that were divided according to quartiles values of vitamin D (< 9.4; 9.4-15.59; 15.6-21.64; ≥ 21.65 ng/ml). Among them, 31 were excluded as chronically treated with vitamin D supplementation. Lower vitamin D quartiles were associated with more advanced age (p = 0.01), female gender (p = 0.04), renal failure (p = 0.005), history of previous MI (p = 0.01), CABG and use of diuretics (p = 0.003), severe coronary disease (p = 0.002), but lower ejection fraction (p = 0.001), treatment with statins (p = 0.04) and new ADP-antagonists (p = 0.002). Vitamin D levels related with higher HbA1c (p = 0.001), cholesterol (p = 0.02) and creatinine (p = 0.004) and lower hemoglobin (p = 0.004). The prevalence of HRPR with ASA was low and not related to vitamin D quartiles (3.4% vs 2.7% vs 1.8% vs 2.1%, p = 0.44; adjusted OR[95%CI] = 1.16[0.60-2.26], p = 0.67). The prevalence of HRPR for ADP antagonists was associated to hypovitaminosis D (40.2% vs 29.1% vs 29.4% vs 25.5%, p = 0.03; (adjusted OR[95%CI] = 1.76[1.04-2.98], p = 0.036for I vs II-IV quartile). The impact of vitamin D quartiles, was significant only in patients on new ADP antagonists (n = 225, of whom 81 on prasugrel 5 mg; p = 0.03; adjusted OR[95%CI] = 3.12[1.34-7.49], p = 0.009) but not with clopidogrel (p = 0.85, adjusted OR[95%CI] = 1.05[0.49-2.24], p = 0.89).

CONCLUSIONS

Among diabetic patients receiving dual antiplatelet therapy for an acute coronary syndrome or elective percutaneous coronary intervention, severe vitamin D deficiency is associated with a higher ADP-mediated platelet reactivity and rate of HRPR, and especially for new ADP-antagonists over clopidogrel.

Diabetic regulation of subjects with type 2 diabetes mellitus is associated with serum vitamin D levels

OBJECTIVE

Vitamin D deficiency is not only associated with bone metabolism but also with diabetes mellitus. We aimed to study the possible association between serum vitamin D concentration and HbA1c level in patients with type 2 diabetes mellitus (T2DM) in this retrospective report.

METHODS

Patients with T2DM were enrolled to the study either in regulated or non-regulated T2DM groups, according to HbA1c levels. An HbA1c level of <8% was considered as relatively controlled and others were considered as poorly controlled T2DM.

RESULTS

Serum vitamin D levels in poorly controlled T2DM subjects (9.4 (4.9-34) ng/ml) were significantly lower than that of the relatively well regulated T2DM patients (13.5 (3.4-36) ng/ml) (p=0.03). Vitamin D was strongly and inversely correlated with HbA1c levels (r= -0.295, p=0.005).

CONCLUSION

Whatever the cause or result of the diabetes mellitus, it is clear that lower vitamin D is strongly associated with worse diabetic regulation in T2DM subjects. Randomized controlled larger studies, which research the relation between diabetic regulation and vitamin D status, are needed to claim whether it could be a therapeutic target in future in diabetic subjects.

Nutrition Therapy in Managing Pregnant Women With Gestational Diabetes Mellitus: A Literature Review

Objective: Gestational diabetes mellitus is the most common metabolic and endocrine perinatal complication and is a growing health problem worldwide. Considering the fetal programming and its contribution as one of the evolutionary origins of human diseases, it is very important to improve the glucose metabolism in pregnant women, determination of other nutrients, preventing excessive accumulation of fetal fats, emphasis on weight loss measures before pregnancy, dietary intake with low-fat healthy food and prevention of abundant weight loss. In this paper, we have provided a brief review on dietary intake and dietary interventions in GDM from the perspective of nutrition science attending the physiopathology and etiology of the disease. Materials and methods: Electronic search for English and Persian articles has been perform in databases, including Google Scholar, PubMed ,Scopus, Cochrane central ,Science direct, ISC, SID, Magiran, Iran Medex, and Med Libby key words: gestational diabetes, gestational diabetes mellitus, nutrition, macronutrient, micronutrient, Diabetes. All available articles (cross-sectional, descriptive-analytic, and clinical studies with desirable design and review quality studies were used. Reference books including Krause's Food and the Nutrition Care, The Williams Obstetrics editions of the 14^th (2017) and the 24^th edition (2014) were also reviewed. Results: Nutrition therapy and physical activity are the initial treatment of GDM. Proper and flexible methods of nutrition therapy that successfully regulate maternal glycaemia while improving expected fetal growth have extensive concepts. Meanwhile, dietary supplements with proven beneficial effects can play an important role in improving deficiencies and improving the metabolic profile of patients. Conclusion: Nutritional management is the main treatment for gestational diabetes mellitus and overweight/obesity is the principal contest in patient counseling and interventions during pregnancy. Despite extensive researches carried out, this field is an active research area and requires more clinical research to minimize maternal and fetal complications.

Prevalence Pattern of Key Polymorphisms in the Vitamin D Receptor gene among Patients of Type 2 Diabetes Mellitus in Northeast India

AIMS

To investigate the association between Vitamin D receptor gene polymorphisms (BsmI, TaqI and FokI) and type 2 diabetes mellitus in patients in north eastern India.

SETTINGS AND DESIGN

This was a case control study with 40 cases of type 2 diabetes and 20 controls.

MATERIALS AND METHODS

Genomic DNA was extracted from blood and genotyped for the single nucleotide polymorphism (SNPs) of BsmI [rs1544410], TaqI [rs731236] and FokI [rs2228570] by polymerase chain reaction and gene sequencing. Genotype distribution and allelic frequencies were compared between patients and controls. Data was expressed as mean ±standard deviation. Chi square test and t test were used to compare groups. Statistical analysis was done using SAS version 9.3 software. P value of <0.05 was considered significant.

RESULTS

Body weight and BMI were significantly associated with VDR polymorphisms BsmI and TaqI while BsmI was significantly associated with HbA1C. Vitamin D deficiency was significantly greater in cases than controls. The frequency of the heterozygous genotype of the BsmI polymorphism was significantly greater in type 2 diabetics than in controls.

CONCLUSIONS

Vitamin D receptor polymorphisms are associated with type 2 diabetes in our population and require larger scale studies to be considered as possible risk factors or type 2 diabetes mellitus.

Vitamin D receptor gene polymorphisms among Emirati patients with type 2 diabetes mellitus

At a prevalence rate close to 19.5%, the UAE has one of the highest rates of Type 2 Diabetes Mellitus (T2DM) in the world. Genome wide association studies (GWAS) have led to the identification of several genetic variants that are associated with T2DM. Recently, genes involved in vitamin D metabolism have gained interest because of the association between vitamin D deficiency (VDD) and increased risk for T2DM. Among these, the Vitamin D receptor (VDR) gene is a good candidate for T2DM susceptibility. The aim of this study was to investigate the association between VDR polymorphisms and T2DM among a representative sample of the Emirati population. In this cross sectional study, two hundred and sixty four patients with T2DM and ninety-one healthy controls were enrolled. The study population was genotyped for the three VDR gene mutations, TaqI (rs731236), FokI (rs2228570) and BsmI (rs1544410). VDR alleles and haplotypes were compared between patients and their healthy controls. The mean age of the T2DM cohort was 60±11.59years and 48.21±12.17years for the healthy controls. The G-allele and GG genotype of rs2228570 and T-allele and TT genotype of rs1544410 SNPs were associated with T2DM. In regards to T2DM-related metabolic complications, the AG and GG genotypes of rs731236 were significantly associated with higher total cholesterol (p=0.011) and LDL-cholesterol (p=0.009) levels in the patients with T2DM. In contrast, the CT genotype of rs1544410 was significantly associated with lower BMI (p=0.031) and the TT genotype was associated with lower LDL-cholesterol level (p=0.007). The frequency of AAT and GGC haplotypes was also different between groups (p=0.014; p=0.032, respectively), implying that these haplotypes of the VDR gene are associated with the susceptibility to T2DM in the Emirati population. To conclude, an association between SNPs in the VDR gene (except for rs731236) and T2DM per se was demonstrated. The rs731236 variant was shown to be associated with high cholesterol and LDL-cholesterol levels in T2DM patients, while rs1544410 was associated with lower BMI and lower LDL cholesterol levels. Our results imply that alleles and haploypes of the VDR gene are associated with the susceptibility to T2DM in the Emirati population.

Cholecalciferol improves glycemic control in type 2 diabetic patients: a 6-month prospective interventional study

Background and purpose

To investigate the effects of vitamin D supplementation on glucose homeostasis and lipid profile in type 2 diabetic patients who have vitamin D deficiency.

Patients and methods

One hundred twenty-five type 2 diabetic patients taking oral hypoglycemic agents as mono- or combination therapy were recruited from the diabetes and endocrinology clinic. Subject demographics, duration of diabetes, antidiabetic medication, body mass index (BMI), pulse, and blood pressure (BP) were assessed. Laboratory measurements of serum vitamin D3 level, hemoglobin A1c (HbA1c), fasting plasma glucose (FPG), and lipid profile were measured. Homeostatic model assessment-insulin resistance (HOMA-IR) was calculated whenever fasting insulin (FI) was available. Forty-one patients (27 males and 14 females) were started on cholecalciferol replacement–45,000 units once weekly for 8 weeks and then 22,500 units once weekly for 16 weeks. Calcium carbonate tablets 500 mg once daily were also prescribed for the initial 2 months of treatment. Measured variables were reassessed after 6 months of replacement therapy. During the trial, subjects were instructed not to change their diabetes drugs or lifestyle.

Results

No significant association was found between vitamin D3 level and any of the measured variables apart from a significant positive correlation with blood urea nitrogen. Vitamin D3 replacement was associated with a significant increase in its level (14.0±4.0 vs 31.0 vs 7.9 ng/mL, P<0.001). This was associated with a significant reduction of HbA1c (7.9±1.7 vs 7.4%±1.2%, P=0.001) and FPG (9.1±4.3 vs 7.9±2.4 mmol/L, P=0.034). Mean reduction of HbA1c was 0.54% and that of FPG was 1.22 mmol/L. FI, c-peptide and insulin resistance (IR) were reduced but this was statistically insignificant (P=0.069, 0.376, 0.058, respectively). FI decreased by 22%, HOMA-IR by 27.6%, and c-peptide by 1.83%. Total cholesterol, low-density lipoprotein cholesterol, parathyroid hormone, alkaline phosphatase, serum creatinine, and pulse rate significantly decreased (4.3±0.9 vs 4.0±0.9 mmol/L, P=0.036; 2.5±0.8 vs 2.2±0.8 mmol/L, P=0.018; 4.6±2.1 vs 3.5±1.8 pmol/L, P=0.001; 82.1±26.2 vs 66.2±19.5 U/L, P<0.001; 74.6±15.6 vs 70.7±14.7 μmol/L, P=0.047; and 81.6±11.9 vs 77.5±12.0 bpm, P=0.045, respectively). Triglycerides and high-density lipoprotein cholesterol, both systolic and diastolic BP, and BMI did not show significant change.

Conclusion

Cholecalciferol helps improve blood glucose control and cholesterol profile in vitamin D3-deficient type 2 diabetic patients.

Vitamin D3 intake as regulator of insulin degrading enzyme and insulin receptor phosphorylation in diabetic rats

Insulin-degrading enzyme (IDE, insulysin) is a rate-limiting enzyme in the insulin degradation process. It is an intracellular 110-kDa thiol zinc-metalloendopeptidase located in the cytosol, peroxisomes, endosomes and cell surface. IDE catalyzes degradation of several small proteins including insulin, amylin and β-amyloid protein. In addition, insulin clearance was expressed as a target in the treatment of type 2 diabetes given the role of hyperinsulinemia in the pathogenesis of insulin resistance. In this study, fourtyadult male Wistar albino rats were used, thirty rats received 20% fructose in drinking water (HFW) for six weeks to induce diabetes. Subsequently, these rats developed significantly higher body weights, dyslipidemia, hyperglycemia and insulin resistance compared to their controls. Significant increase in the levels of serum glucagon, IDE in liver tissue along with an inhibition of insulin receptor phosphorylation were also observed. Concurrent oral administration of vitamin D3 along with HFW resulted in significant decrease of serum glucose, total cholesterol, triacylglycerol and LDL-C levels. Vitamin D alleviated also insulin resistance, where both IDE, glucagon levels showed significant decrease along with activation of insulin receptor phosphorylation. Normal rats, received vitamin D3 only demonstrated non significant changes of the studied biomarkers. We concluded that vitamin D3 ameliorated insulin resistance and hyperinsulinemia in diabetic rat model received HFW through reduction of IDE and activation of insulin receptor phosphorylation.

Metabolic effects of vitamin D supplementation in vitamin D deficient patients (a double-blind clinical trial)

BACKGROUND

Vitamin D has recently been given a lot of attention for its role in controlling insulin secretion. Many studies have spoken of its role in weight management, blood sugar control and many other metabolic variables.

PATIENT AND METHODS

In a randomized double-blind clinical trial, 210 people with vitamin D deficiency were randomly allocated into two groups receiving vitamin D (50,000 units per week) or placebo for 8 weeks.

RESULTS

Vitamin D levels were significantly increased in the group receiving vitamin D supplementation (13.7±5.2 unit increase versus 0.8±2.8). The increased levels of vitamin D lead to significant changes in fasting insulin levels (6.8±8.1 unit reduction versus 2.3±3.7), a 2-h insulin (31.1±34.9 unit reduction versus 4.5±24.6) and Homeostasis Model Assessment (HOMA) indices.

CONCLUSION

Correction of vitamin D deficiency leads to increased insulin sensitivity that was significantly able to maintain glucose in the normal range with lower levels of insulin.

FokI polymorphism in vitamin D receptor gene: Differential expression of TNFα in peripheral mononuclear cells of type 2 diabetic subjects

INTRODUCTION

FokI polymorphism has been associated with obesity and type 2 diabetes (T2D) in some populations.

OBJECTIVE

To investigate the frequencies of a genetic polymorphism of Vitamin D receptor (FokI) in patients with T2D and control subjects and investigate the role of 1,25(OH)2D3 in the expression of pro-inflammatory markers in peripheral blood mononuclear cells (PBMCs).

METHODS

The case-control study was conducted in 160 patients with T2D and 160 control subjects, men and women (30-74 years old). The genotype and allele frequency of FokI polymorphisms were determined in these subjects. Subsequently a subgroup of 40 subjects was included from which PBMCs were removed. In vitro, the culture medium was supplemented with two different concentrations of 1,25(OH)2D3(10- 8 M and 10- 10 M). The expression profiles of TNFα and mRNA were analysed by qPCR, and GAPDH and β-actin were used as housekeeping genes.

RESULTS

The control subjects have an increased frequency of the FF genotype. In subjects with T2D, the ff genotype was associated with higher HOMA-IR values than individuals with genotype Ff (p = 0.021). In vitro study in PBMCs showed differential expression of TNFα mRNA by FokI genotype, with a lower expression of this marker of inflammation in FF genotype subjects at a concentration of 10- 8 M of 1,25(OH)2D3.

CONCLUSION

Our data suggest that VDR FokI polymorphism is associated with T2D, and the genotypes Ff and ff of this variant show a reduced response or resistance to the anti-inflammatory action of VitD, which could indicate a functional role of FokI polymorphism of VDR.

Causes of Vitamin D Deficiency and Effect of Vitamin D Supplementation on Metabolic Complications in Obesity: a Review

Obese subjects are often characterized by low plasma 25-hydroxy-vitamin D (25OHD) levels. Many explanations for this association have been proposed. Low plasma 25OHD is associated with obesity-related comorbidities such as insulin resistance, type 2 diabetes mellitus, and low-grade inflammation. In this review, we discuss the proposed mechanisms for low 25OHD in obesity and explore the results of recent RCTs on vitamin D (VD) supplementation on obesity and its metabolic complications such as insulin resistance and type 2 diabetes. Although the results from these clinical randomized controlled trials vary, the general picture is that VD treatment of obese individuals does not seem to be an effective treatment of obesity-related metabolic complications.

Vitamins and their derivatives in the prevention and treatment of metabolic syndrome diseases (diabetes),

A cluster of inter-related conditions such as central obesity, dyslipidemia, impaired glucose metabolism, and hypertension is referred to as Metabolic Syndrome, which is a risk factor for the development of type-2 diabetes. The micro- and macro-vascular complications of diabetes contribute to its morbidity and mortality. In addition to its calcitropic effect, vitamin D is a regulator of gene expression as well as cell proliferation and differentiation. Various cross-sectional and longitudinal cohort studies have indicated a beneficial effect from vitamin D supplementation on the development of type-2 diabetes. Binding of retinol-bound retinol-binding protein to a membrane-binding protein suppresses insulin signaling. All-trans retinoic acid, a derivative of vitamin A, reverses these effects, resulting in increased insulin sensitivity, suppression of the phosphoenolpyruvate carboxy kinase (PEPCK) gene, and the induction of the glucokinase gene. Glucokinase and PEPCK are also regulated in opposite directions by the vitamin biotin, acting at the transcriptional level. Biotin also regulates the synthesis of insulin by the islet of Langerhans cells of the pancreas. The increase in advanced glycation end products (AGEs) is implicated in the initiation and progression of diabetes-associated microvascular diseases. Benfotiamine, a derivative of thiamine, and pyridoxamine, a vitamer of vitamin B6, both have anti-AGE properties, making them valuable therapeutic adjuvants in the treatment of diabetic complications. Thus, various vitamins and their derivatives have profound therapeutic potential in the prevention and treatment of type-2 diabetes.

Effect of vitamin D supplementation on glycemic control in patients with type 2 diabetes: a systematic review of interventional studies

Background

Diabetes and vitamin D deficiency are global epidemics. Researchers have long been exploring the role of potentially modifiable factors to manage type 2 diabetes. We conducted a systematic review of prospective studies and randomized controlled trials that involved vitamin D supplementation and specifically intended to study glycemic outcomes related to type 2 diabetes.

Methods

Two authors independently searched Medline and PubMed for longitudinal studies that had assessed the effect of vitamin D supplements on glycemic control, insulin resistance and beta-cell dysfunction in patients with diabetes.

Results

Seventeen randomized control trials and seven longitudinal studies with a minimum follow-up of one month were included.

Results of the various short-term studies (follow up ≤ 3 months) suggested that vitamin D supplementation had a positive impact on glycemic control and metabolic parameters such as insulin resistance and beta cell dysfunction. However, the evidence was weak due to the low methodological quality of the studies. There was no significant effect on HbA1c, beta cell function and insulin resistance in the long-term studies (follow up > 3 months). There existed heterogeneity in the methodology of the studies, inclusion criteria, mode of supplementation of vitamin D and the duration of follow up.

Conclusions

Current evidence based on randomized controlled trials and longitudinal studies do not support the notion that vitamin D supplementation can improve hyperglycemia, beta cell secretion or insulin sensitivity in patients with type 2 diabetes. Large-scale trials with proper study design, optimal vitamin D supplementation and longer follow up need to be conducted.

Role of bioactive food components in diabetes prevention: effects on Beta-cell function and preservation

Bioactive compounds found in fruits and vegetables can have anti-oxidant, anti-inflammatory, and anti-carcinogenic effects and can be protective against various diseases and metabolic disorders. These beneficial effects make them good candidates for the development of new functional foods with potential protective and preventive properties for type 1 and type 2 diabetes. This review summarizes the most relevant results concerning the effects of various bioactive compounds such as flavonoids, vitamins, and carotenoids on several aspects of beta-cell functionality. Studies using animal models with induced diabetes and diabetic patients support the hypothesis that bioactive compounds could ameliorate diabetic phenotypes. Published data suggest that there might be direct effects of bioactive compounds on enhancing insulin secretion and preventing beta-cell apoptosis, and some compounds might modulate beta-cell proliferation. Further research is needed to establish any clinical effects of these compounds.

Does the intramuscular injection of vitamin D increase insulin resistance?

Objective:

Considering the physiologic roles of vitamin D on insulin regulation, the effects of vitamin D treatment on insulin sensitivity and resistance indexes and beta cell function in pre-diabetic vitamin D deficient patients were investigated.

Methods:

In a randomized open clinical trial, 61 pre-diabetic vitamin D deficient patients who were the first degree relatives of type 2 diabetic patients, were enrolled and randomized into three groups (A, B and C). Group A (n = 21) were treated with intramuscular injection of 300,000 units of vitamin D at the beginning of the study and one month later. In group B (n = 20), injection of vitamin D plus 500 mg/d calcium and in group C (n = 20), just calcium was administered for two months. At baseline and two months later, oral glucose tolerance test was done. Homeostasis Model of Assessment-Insulin Resistance (HOMA-IR), insulin resistance index, Homeostasis Model of Assessment-B (HOMA-B) which is a beta cell function index, and Matsuda index, an insulin sensitivity index, were calculated and compared before and after intervention and between three groups.

Findings:

In vitamin D treated groups (A + B), the mean (SD) of HOMA-IR increased from 2.46 (1.36) to 3.1 (2.3) (P = 0.02), and Matsuda index decreased from 11 (3) to 9.0 (2.3) (P = 0.001).

Conclusion:

Injection of vitamin D increased insulin resistance and decreased insulin sensitivity indexes.

Efficacy of supplementary vitamin D on improvement of glycemic parameters in patients with type 2 diabetes mellitus; a randomized double blind clinical trial

Introduction: Studies have revealed the association between vitamin D deficiency and changes in blood glucose and insulin levels as well as sensitivity of the target tissues to insulin.

Objective: In this study, we examined the effect of adding vitamin D (cholecalciferol ; 50,000 units) to therapeutic regimen of T2DM patients compared to placebo on regulating the blood glucose and glycemic parameters.

Patients and Methods: This study was a double blind clinical trial conducted on 60 type 2 diabetes mellitus (T2DM) patients. Exclusion criteria were taking calcium, vitamin D supplements or any drugs effecting calcium and vitamin D metabolism in the past 6 months. Serum 25-Hydroxy vitamin D [25(OH)D] level was measured with ELISA method. Patients were administered weekly vitamin D supplementation (50000 units) for 12 weeks.

Results: There was no significant relation between HbA1c and 25(OH)D level prior the study (p> 0.05). After intervention, 25(OH)D level in interventional group was significantly higher compared to that of control group. HbA1c in male interventional group was significantly less than that of control group (p= 0.0068).

Conclusion: Weekly vitamin D supplementation had beneficial effect on glycemic parameters in male type 2 diabetic patients.

Association of 25-hydroxyvitamin D with type 2 diabetes among patients undergoing coronary angiography: cross-sectional findings from the LUdwigshafen Risk and Cardiovascular Health (LURIC) Study

OBJECTIVE

Evidence suggests that vitamin D may protect against the onset of diabetes. However, the mechanisms underlying the role of vitamin D on glycaemic status are unclear and warrant further investigation. We sought to determine the relationship between serum 25-hydroxyvitamin D (25[OH]D) and glycaemic status among intermediate-to-high-risk patients scheduled for coronary angiography.

METHODS

Participants were 3316 male and female patients (mean ± SD age, 62·7 ± 10·6 years). Four categories were formed according to serum 25[OH]D levels. The association between serum 25[OH]D and diabetes was assessed using multivariable logistic regression.

RESULTS

Fasting and 2 h post-load glucose, HbA1c and the HOMA-IR indices diminished with increasing serum 25[OH]D levels (P < 0·001). However, no associations were observed between insulin, pro-insulin or C-peptide and serum 25[OH]D concentrations. The pro-inflammatory markers IL-6 and hs-CRP also decreased considerably with higher vitamin D levels (P < 0·001). After full adjustment, those with optimal serum 25[OH]D levels had a reduced odds for fasting diabetes (OR = 0·63; 95% CI, 0·46-0·86; Ptrend = 0·01), 2 h post-load diabetes (OR = 0·46; 95% CI, 0·29-0·74; Ptrend = 0·004), both fasting/2 h post-load diabetes (OR = 0·61; 95% CI, 0·42-0·87; Ptrend = 0·001) and all of the combined hyperglycaemic states (OR = 0·68; 95% CI, 0·52-0·80; Ptrend = 0·01).

CONCLUSIONS

Higher serum 25[OH]D levels were associated with better glycaemic status and lower inflammation. Should these observations be confirmed in future studies, vitamin D supplementation may prove a useful adjunct in attenuating the onset of diabetes.

Spinal deformity index in patients with type 2 diabetes

The objective of this study is to investigate bone metabolism, density, and quality in patients with diabetes type 2 using DEXA and spinal deformity index (SDI), a surrogate index of bone quality. Fifty-six patients with type 2 diabetes were studied; exclusion criteria were diseases and medications that affect bone and mineral metabolism. Mean age was 65 ± 7 years. Mean diabetes duration was 10 ± 7 years and mean HbA1C was 6.6 ± 0.5 %. BMI was 30 ± 4. Fifty-six sex, age, and BMI matched served as controls. All subjects underwent a clinical and biochemical examination. Spinal and femoral neck BMD were measured by DEXA, and a spine radiography was performed to assess vertebral fractures and to calculate SDI. Mean serum 25-OH vitamin D levels were 19.6 ± 3.7 ng/ml in patients and 30 ± 14 ng/ml in controls (p < 0.01). PTH serum levels were 47.9 ± 40 pg/ml in patients versus 37 ± 5.3 pg/ml in controls (p < 0.01). At lumbar spine there was a significant difference between patients and controls only for T-score (p = <0.01), while at femoral neck there was a difference in BMD (p < 0.01) and in T-score (p < 0.01). Radiological vertebral fractures were found in 46 % of patients and 17 % of controls (p < 0.05). SDI was higher in patients than in controls (p < 0.05). The percentage of fractures with T-score BMD greater than -2.5 was 69 % in patients and 10 % in controls (p < 0.05). As a conclusion, BMD was similar in patients and in controls, while SDI value was higher in patients; therefore, SDI was more specific than BMD for the diagnosis of osteoporosis due to metabolic diseases.

Diabetes and cancer: Could vitamin D provide the link?

Diabetes and cancer are common diseases that may co-exist in the same individual. There is significant evidence that patients with diabetes have increased risk of developing certain cancers, especially colorectal, pancreatic and primary hepatic cancer. There is also good evidence that low levels of vitamin D are associated with increased risk of diabetes and increased risk of colorectal, and possibly other, cancers. In this article we propose that low levels of vitamin D may increase the risk of cancer in people with diabetes and describe potential molecular pathways. We suggest that large scale randomised trials of vitamin D supplementation in patients at risk of diabetes, and in patients with established diabetes to examine the effect on cancer risk, are required.

The effects of oral vitamin D on insulin resistance in pre-diabetic patients

BACKGROUND

Some epidemiological and interventional studies have shown the role of vitamin D on insulin secretion and resistance. A previous study in our center showed that intramuscular vitamin D decreases insulin sensitivity in pre-diabetic patients. We investigated the role of oral vitamin D on the insulin sensitivity index and insulin resistance in pre-diabetic patients.

MATERIALS AND METHODS

In a randomized clinical trial, we divided 45 people with pre-diabetes aged 47.4 ± 6.6 (range 33-61) years into three groups: group A subjects treated with 50,000 IU oral vitamin D and 500 mg calcium carbonate (n = 21), group B subjects treated with a single 300,000 IU intramuscular vitamin D and 500 mg calcium carbonate (n = 9), and group C subjects treated with 500 mg calcium carbonate alone (n = 15). Serum 25-hydroxyvitamin D [25(OH) D] was measured at baseline. If it was less than 75 nmol/l, 50,000 IU vitamin D was given weekly, and if serum 25(OH) D was more than that, vitamin D was administered every 2 weeks. Before and after 12 weeks of treatment, a 75-g glucose tolerance test was performed. We used paired t-test and analysis of variance (ANOVA) to analyze the data. P values less than 0.05 were considered significant.

RESULTS

Mean (SD) of serum vitamin D increased from 77.5 ± 39.2 to 118.8 ± 56.3 nmol/l (P = 0.009) in group A and from 80 ± 36 to 102.8 ± 43.3 nmol/l (P = 0.053) in group B, and decreased from 44.8 ± 18.3 to 34.6 ± 13.9 nmol/l (P = 0.06) in group C. Insulin sensitivity index (Matsuda) decreased from 11.4 ± 3 to 9.9 ± 3.2 (P = 0.046) in group A, but in comparison with other groups, it was not significant.

CONCLUSION

Oral vitamin D had no effect on insulin sensitivity in pre-diabetes patients in 12 weeks treatment. A randomized double-blind study with a longer duration of treatment is suggested to investigate the effect of vitamin D on insulin resistance.

Vitamin D and type 2 diabetes mellitus

WHAT IS KNOWN AND OBJECTIVE

The deleterious effect of vitamin D deficiency on bone health has long been known. More recent studies suggest a deleterious effect of low vitamin D (hypovitaminosis D) on general health. And specific studies propose an association between hypovitaminosis D and the aetiology and progression of type 2 diabetes (T2DM). Given a commonly assumed lack of toxicity of vitamin D, routine measurement of plasma vitamin D and supplementation is rapidly becoming accepted general practice.

COMMENT

Authoritative practice guidelines have raised the level of vitamin D that is to be considered minimal for optimum health. This recommendation was based on a wealth of information and definitive evidence for skeletal benefits of vitamin D, but there was a lack of compelling evidence that hypovitaminosis D is causally related to extra-skeletal health outcomes such as diabetes. Hence, vitamin D supplementation for the purpose of achieving a level consistent with good health is evidence based, but measurement and supplementation for the purpose of preventing or treating T2DM is not.

WHAT IS NEW AND CONCLUSION

Although the maintenance of adequate vitamin D levels is desirable for all patients, we conclude that routine measurement of vitamin D level in every patient or initiating high-dose supplementation for the purpose of preventing or treating T2DM is not evidence based.

Vitamin D deficiency: a new risk factor for type 2 diabetes?

Recent compelling evidence suggests a role of vitamin D deficiency in the pathogenesis of insulin resistance and insulin secretion derangements, with a consequent possible interference with type 2 diabetes mellitus. The mechanism of this link is incompletely understood. In fact, vitamin D deficiency is usually detected in obesity in which insulin resistance is also a common finding. The coexistence of insulin resistance and vitamin D deficiency has generated several hypotheses. Some cross-sectional and prospective studies have suggested that vitamin D deficiency may play a role in worsening insulin resistance; others have identified obesity as a risk factor predisposing individuals to exhibit both vitamin D deficiency and insulin resistance. The available data from intervention studies are largely confounded, and inadequate considerations of seasonal effects on 25(OH)D concentrations are also a common design flaw in many studies. On the contrary, there is strong evidence that obesity might cause both vitamin D deficiency and insulin resistance, leaving open the possibility that vitamin D and diabetes are not related at all. Although it might seem premature to draw firm conclusions on the role of vitamin D supplementation in reducing insulin resistance and preventing type 2 diabetes, this manuscript will review the circumstances leading to vitamin D deficiency and how such a deficiency can eventually independently affect insulin sensitivity.

Role of vitamin D in insulin resistance

Vitamin D is characterized as a regulator of homeostasis of bone and mineral metabolism, but it can also provide nonskeletal actions because vitamin D receptors have been found in various tissues including the brain, prostate, breast, colon, pancreas, and immune cells. Bone metabolism, modulation of the immune response, and regulation of cell proliferation and differentiation are all biological functions of vitamin D. Vitamin D may play an important role in modifying the risk of cardiometabolic outcomes, including diabetes mellitus (DM), hypertension, and cardiovascular disease. The incidence of type 2 DM is increasing worldwide and results from a lack of insulin or inadequate insulin secretion following increases in insulin resistance. Therefore, it has been proposed that vitamin D deficiency plays an important role in insulin resistance resulting in diabetes. The potential role of vitamin D deficiency in insulin resistance has been proposed to be associated with inherited gene polymorphisms including vitamin D-binding protein, vitamin D receptor, and vitamin D 1alpha-hydroxylase gene. Other roles have been proposed to involve immunoregulatory function by activating innate and adaptive immunity and cytokine release, activating inflammation by upregulation of nuclear factor κB and inducing tumor necrosis factor α, and other molecular actions to maintain glucose homeostasis and mediate insulin sensitivity by a low calcium status, obesity, or by elevating serum levels of parathyroid hormone. These effects of vitamin D deficiency, either acting in concert or alone, all serve to increase insulin resistance. Although there is evidence to support a relationship between vitamin D status and insulin resistance, the underlying mechanism requires further exploration. The purpose of this paper was to review the current information available concerning the role of vitamin D in insulin resistance.

Vitamin D and diabetes

There is no doubt that vitamin D deficiency is the cause of several metabolic bone diseases, but vitamin D status is also linked to many major human diseases including immune disorders. Mounting data strengthen the link between vitamin D and diabetes, in particular T1D and T2D. Despite some inconsistencies between studies that associate serum 25(OH)D levels with the risk of developing T1D or T2D, there seems to be an overall trend for an inverse correlation between levels of 25(OH)D and both disorders. There is also compelling evidence that 1,25(OH)2D regulates b-cell function by different mechanisms, such as influencing insulin secretion by regulating intracellular levels of Ca2+, increasing β-cell resistance to apoptosis, and perhaps also increasing β-cell replication. The capacity of vitamin D, more specifically 1,25(OH)2D, to modulate immune responses is of particular interest for both the therapy and prevention of diabetes. In the case of T1D, vitamin D supplementation in prediabetic individuals could help prevent or reduce the initiation of autoimmune processes possibly by regulating thymic selection of the T-cell repertoire, decreasing the numbers of autoreactive T cells, and inducing Treg cells. Although immune modulation is generally discussed for the treatment of T1D, it is also relevant for T2D. Indeed, recent studies have shown that T2D patients have increased systemic inflammation and that this state can induce β-cell dysfunction and death. Supplementation trials with regular vitamin D for the protection against the development of T1D and T2D have generated some contradictory data, but many weaknesses can be identified in these trials as most were underpowered or open-labeled. However, the overwhelming strength of preclinical data and of the observational studies make vitamin D or its analogues strong candidates for the prevention or treatment of diabetes or its complications. However, proof of causality needs well-designed clinical trials and if positive, adequate dosing, regimen, and compound studies are needed to define the contribution of vitamin D status and therapy in the global diabetes problem. There are many confounding factors that need to be taken into consideration when translating successful vitamin D therapies in animal models into humans, for example, gender, age, lifestyle, and genetic background. To come to solid conclusions on the potential of vitamin D or its analogues in the prevention of or therapy for all forms of diabetes, it is clear that large prospective trials with carefully selected populations and end points will be needed, but should also receive high priority.

Effects of a single post-partum injection of a high dose of vitamin D on glucose tolerance and insulin resistance in mothers with first-time gestational diabetes mellitus

AIM

This study was performed to determine the effect of a single, large, intramuscular injection of vitamin D post-partum on glucose tolerance and insulin resistance in women with gestational diabetes.

METHODS

Forty-five participants in a randomized controlled trial on gestational diabetes mellitus were divided into an intervention group and a control group. Only subjects in the intervention group received one intramuscular injection of 300,000 IU of vitamin D3. HbA(1c), serum 25-hydroxyvitamin D3, fasting insulin and blood glucose, C-peptide, homeostasis model assessment insulin resistance index (HOMA-IR), β-cell function, insulin sensitivity and the Quantitative Insulin Sensitivity Check Index (QUICKI) were measured at baseline and after 3 months of intervention.

RESULTS

Approximately 80% of the mothers had a degree of vitamin D deficiency. Post-intervention, this was found in 4.2 and 71.4% in the intervention and control groups, respectively. The medians of HOMA-IR indices before and after intervention were 0.6 and 0.5 (P = 0.7), respectively, in subjects in the intervention group, and 0.5 and 0.9 (P = 0.01) in subjects in the control group. The mean of the QUICKI fell only in the control group (P = 0.008). In the control group, β-cell function increased by ~8% (P = 0.01) and insulin sensitivity decreased after 3 months (P = 0.002). Post-intervention, the median C-peptide decreased in the intervention group and increased in the control group, but the change was significant only in the control group (P = 0.03).

CONCLUSIONS

A single injection of 300,000 IU of vitamin D3 achieves a 3-month serum 25-hydroxyvitamin D range of 50-80 nmol/l and is an efficient, effective and safe procedure for improving the vitamin status and indices of insulin resistance in mothers with gestational diabetes after delivery.

Vitamin D3 supplementation improves insulin sensitivity in subjects with impaired fasting glucose

Vitamin D has in vitro and in vivo effects on β cells and insulin sensitivity. Vitamin D deficiency (VDD) has been associated with the onset and progression of type 2 diabetes mellitus (DM-2). However, studies involving supplementation of vitamin D in subjects with previously established diabetes have demonstrated inconsistent effects on insulin sensitivity. The aim of this open-label study was to assess the effects of high-dose vitamin D3 supplementation on insulin sensitivity in subjects with VDD and impaired fasting glucose. We studied 8 subjects with VDD and prediabetes with the modified, frequently sampled intravenous glucose tolerance (mFSIGT) test before and after vitamin D supplementation. Vitamin D3 was administered as 10,000 IU daily for 4 weeks. The mFSIGT was analyzed with MinMod Millennium (purchased from Dr. Richard Bergman, Keck School of Medicine of USC, Los Angeles, Calif) to obtain estimates of acute insulin response to glucose (AIRg), insulin sensitivity (SI), and disposition index (DI). We found that AIRg decreased (P = 0.011) and SI increased (P = 0.012) after a intervention with vitamin D. If these findings are repeated in a randomized, double-blind study, the results indicate that orally administered high-dose vitamin D3 supplementation improves insulin sensitivity in subjects with impaired fasting glucose and suggests that high-dose vitamin D3 supplementation might provide an inexpensive public health measure in preventing, or at least delaying, the progression from impaired fasting glucose to diabetes.

Diabetes, pancreatic cancer and vitamin D. Is there a link?

The role of vitamin D is not merely limited to maintaining skeletal health but also extends to maintaining glucose homeostasis by preserving insulin secretion and sensitivity and thus deficiency of vitamin D plays an important role in aetiopathogenesis of T2 diabetes. In addition to its many other roles, vitamin D has recently been found to have growth inhibiting affects on pancreatic cancer cells. Ecological studies have shown that there exists an inverse correlation between sun exposure and death rates for pancreatic cancer. Since vitamin D has promising role in both type 2 diabetes mellitus and pancreatic cancer, its deficiency may be associated to any or both of these chronic diseases. The present review thus aims to find correlation between diabetes and pancreatic cancer and if vitamin D is a common link between the two.

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.

A potential role for adjunctive vitamin D therapy in the management of weight gain and metabolic side effects of second-generation antipsychotics

Second-generation antipsychotic (SGA) medications introduced about 20 years ago are increasingly used to treat psychiatric illnesses in children and adolescents. There has been a five-fold increase in the use of these medications in U.S. children and adolescents in the past decade. However, there has also been a parallel rise in the incidence of side effects associated with these medications, such as obesity, dyslipidemia, insulin resistance, and diabetes mellitus. Despite the severity of these complications and their financial impact on the national healthcare budget, there is neither a clear understanding of the mechanisms contributing to these side effects nor the best ways to address them. Studies that examined lifestyle modification and pharmaceutical agents have yielded mixed results. Therefore, clinical studies using agents, such as vitamin D, which are inexpensive, readily available, with low side effects profile, and have mechanisms to counteract the metabolic side effects of SGA agents, are warranted. Vitamin D is a prohormone with skeletal and extraskeletal properties that could potentially reduce the severity of these metabolic side effects. Its role as an adjunctive therapy for the management of metabolic side effects of SGA agents has not been adequately studied. Effective strategies to curb these side effects will improve the overall health of youths with psychiatric illnesses who receive SGAs. Herein we present a pilot study on the use of vitamin D in patients on treatment with SGAs.

A systems approach to bone pathophysiology

With evolving interest in multiscalar biological systems one could assume that reductionist approaches may not fully describe biological complexity. Instead, tools such as mathematical modeling, network analysis, and other multiplexed clinical- and research-oriented tests enable rapid analyses of high-throughput data parsed at the genomic, proteomic, metabolomic, and physiomic levels. A physiomic-level approach allows for recursive horizontal and vertical integration of subsystem coupling across and within spatiotemporal scales. Additionally, this methodology recognizes previously ignored subsystems and the strong, nonintuitively obvious and indirect connections among physiological events that potentially account for the uncertainties in medicine. In this review, we flip the reductionist research paradigm and review the concept of systems biology and its applications to bone pathophysiology. Specifically, a bone-centric physiome model is presented that incorporates systemic-level processes with their respective therapeutic implications.

Pilot study to evaluate the effect of short-term improvement in vitamin D status on glucose tolerance in patients with type 2 diabetes mellitus

OBJECTIVE

To study the effect of improvement in vitamin D status on glucose tolerance in Asian Indian patients with moderately controlled type 2 diabetes mellitus (T2DM).

METHODS

This randomized, double-blind, placebo-controlled pilot study was conducted in 28 Asian Indian patients with T2DM. Study participants were randomly assigned to a vitamin D-treated group (group D) or a placebo group (group P). Serum 25-hydroxyvitamin D, hemoglobin A1c, and serum fructosamine levels were measured, and an oral glucose tolerance test (OGTT) was performed in all patients at baseline and 4 weeks after intervention. During the OGTT, plasma glucose and serum insulin levels were measured at 0, 30, 60, 90, and 120 minutes. The unpaired t test was used to compare the groups at baseline and to compare the differences in changes from baseline to 4 weeks between the 2 study groups.

RESULTS

Group D and group P were similar with respect to their fasting plasma glucose and serum insulin concentrations, post-OGTT plasma glucose and serum insulin levels, and hemoglobin A1c and fructosamine values at baseline. Serum 25-hydroxyvitamin D levels increased significantly in group D at 4 weeks. No significant differences were found between the groups at baseline and 4 weeks with respect to serum fructosamine, fasting plasma glucose and serum insulin, post-OGTT plasma glucose and serum insulin levels, and homeostasis model assessment of insulin resistance.

CONCLUSION

In this study, short-term improvement in vitamin D status was not associated with improvement in glucose tolerance, insulin secretion, or insulin sensitivity in Asian Indian patients with moderately controlled T2DM.

The skeletal subsystem as an integrative physiology paradigm

Homeostatic bone remodeling depends on precise regulation of osteoblast-osteoclast coupling through intricate endocrine, immune, neuronal, and mechanical factors. The osteoblast-osteoclast model of bone physiology with layers of regulatory complexity can be investigated as a component of a local skeletal subsystem or as a part of a complete whole-body system. In this review, we flip the traditional investigative paradigm of scientific experimentation ("bottom-top research") to a "top-bottom" approach using systems biology. We first establish the intricacies of the two-cell model at the molecular signaling level. We then provide, on a systems level, an integrative physiologic approach involving many recognized organ-level subsystems having direct and/or indirect effects on bone remodeling. Lastly, a hypothetical model of bone remodeling based on frequency and amplitude regulatory mechanisms is presented. It is hoped that by providing a thorough model of skeletal homeostasis, future progress can be made in researching and treating skeletal morbidities.

Effect of oral vitamin D and calcium replacement on glycaemic control in South Asian patients with type 2 diabetes

BACKGROUND

Vitamin D deficiency is associated with a greater risk of developing type 2 diabetes mellitus (T2DM). Studies looking at the effect of vitamin D replacement on glycaemic control in type 2 diabetics are few and conflicting. In addition, none have been published looking at the South Asian population despite both T2DM and vitamin D deficiency being gross burdens in this population. The aim of this study was to determine the effect of using vitamin D and calcium replacement therapy on glycaemic control in South Asian patients with T2DM and vitamin D inadequacy.

MATERIALS AND METHODS

Data were collected retrospectively from patients' records focusing on South Asians with established T2DM treated with combined oral vitamin D(3) and calcium supplementation. Vitamin D, parathyroid hormone (PTH), HbA1c and weight were recorded before and after 3 months on this therapy.

RESULTS

Post-treatment, all patients' (n = 52) vitamin D levels were normalised (> 50nmol/l). There was a mean decrease in HbA1c of 0.70 +/- 0.77% (p < 0.001) in the vitamin D deficient group (n = 29) and 0.21 +/- 0.28% (p = 0.001) in the vitamin D insufficient group (n = 23). The change in weight post-treatment was only significant in the vitamin D deficient group at -0.80 +/- 1.11 kg (p = 0.001). Overall, there were negative correlations between the changes in HbA1c and weight with the change in vitamin D (p < 0.05).

CONCLUSION

This study shows that vitamin D and calcium replacement therapy in South Asian patients with T2DM causes a significant decrease in both HbA1c and weight, which may be attributed to the increase in vitamin D levels post-treatment.

Vitamin D and diabetes

Type 1 (T1D) and type 2 (T2D) diabetes are considered multifactorial diseases in which both genetic predisposition and environmental factors participate in their development. Many cellular, preclinical, and observational studies support a role for vitamin D in the pathogenesis of both types of diabetes including: (1) T1D and T2D patients have a higher incidence of hypovitaminosis D; (2) pancreatic tissue (more specifically the insulin-producing beta-cells) as well as numerous cell types of the immune system express the vitamin D receptor (VDR) and vitamin D-binding protein (DBP); and (3) some allelic variations in genes involved in vitamin D metabolism and VDR are associated with glucose (in)tolerance, insulin secretion, and sensitivity, as well as inflammation. Moreover, pharmacologic doses of 1,25-dihydroxyvitamin D (1,25(OH)(2)D), the active form of vitamin D, prevent insulitis and T1D in nonobese diabetic (NOD) mice and other models of T1D, possibly by immune modulation as well as by direct effects on beta-cell function. In T2D, vitamin D supplementation can increase insulin sensitivity and decrease inflammation. This article reviews the role of vitamin D in the pathogenesis of T1D and T2D, focusing on the therapeutic potential for vitamin D in the prevention/intervention of T1D and T2D as well as its complications.