Effect of Vitamin D Supplementation on Markers of Vascular Function: A Systematic Review and Individual Participant Meta- Analysis

Background-—Low 25-hydroxyvitamin D levels are associated with an increased risk of cardiovascular events, but the effect of vitamin D supplementation on markers of vascular function associated with major adverse cardiovascular events is unclear. Methods and Results-—We conducted a systematic review and individual participant meta-analysis to examine the effect of vitamin D supplementation on flow-mediated dilatation of the brachial artery, pulse wave velocity, augmentation index, central blood pressure, microvascular function, and reactive hyperemia index. MEDLINE, CINAHL, EMBASE, Cochrane Central Register of Controlled Trials, and http://www.ClinicalTrials.gov were searched until the end of 2016 without language restrictions. Placebo-controlled randomized trials of at least4 weeks duration were included. Individual participant data were sought from investigators on included trials. Trial-level metaanalysis was performed using random-effects models; individual participant meta-analyses used a 2-stage analytic strategy, examining effects in prespecified subgroups. 31trials (2751 participants) were included; 29 trials (2641participants) contributed data to trial-level meta-analysis, and24trials (2051 participants) contributed to individual-participant analyses. VitaminD3daily dose equivalents ranged from 900 to 5000 IU; duration was 4 weeks to12 months. Trial-level meta-analysis showed no significant effect of supplementation on macrovascularmeasures(flow-mediateddilatation,0.37%[95%confidenceinterval, 0.23to0.97]; carotid-femoralpulsewavevelocity, 0.00 m/s [95% confidence interval, 0.36 to 0.37]); similar results were obtained from individual participant data. Microvascular function showed a modest improvement in trial-level data only. No consistent benefit was observed in subgroup analyses or between different vitamin D analogues. Conclusions-—Vitamin D supplementation had no significant effect on most markers of vascular function in this analysis

Diabetes-Related Autoantibodies in Children With Acute Lymphoblastic Leukemia

[No abstract available

Beta-cell gene expression and functional characterisation of the human insulinoma cell line CM

Animal insulinoma cell lines are widely used to study physiological and pathophysiological mechanisms involved in glucose metabolism and to establish in vitro models for studies on β-cells. In contrast, human insulinoma cell lines are rarely used because of difficulties in obtaining and culturing them for long periods. The aim of our study was to investigate, under different experimental conditions, the capacity of the human insulinoma cell line CM to retain β-cell function, particularly the expression of constitutive β-cell genes (insulin, the glucose transporters GLUT1 and GLUT2, glucokinase), intracellular and secreted insulin, β-cell granules, and cAMP content. Results showed that CM cells from an early-passage express specific β-cell genes in response to glucose stimulation, in particular the insulin and GLUT genes. Such capacity is lost at later passages when cells are cultured at standard glucose concentrations. However, if cultured at lower glucose concentration (0.8 mM) for a longer time, CM cells re-acquire the capacity to respond to glucose stimulation, as shown by the increased expression of β- cell genes (insulin, GLUT2, glucokinase). Nonetheless, insulin secretion could not be restored under such experimental conditions despite the presence of intracellular insulin, although cAMP response to a potent activator of adenylate cyclase, forskolin, was present indicating a viable system. In conclusion, these data show that the human insulinoma cell line CM, at both early-passage and late-passage, possesses a functional glucose-signalling pathway and insulin mRNA expression similar to normal β-cells, representing, therefore, a good model for studies concerning the signalling and expression of β-cells. Furthermore, we have previously shown that it is also a good model for immunological studies. In this respect it is important to note that the CM cell line is one of the very few existing human β-cell lines in long- term culture

The G972R variant of the insulin receptor substrate-1 gene impairs insulin signaling and cell differentiation in 3T3L1 adipocytes; treatment with a PPAR gamma agonist restores normal cell signaling and differentiation

The insulin receptor substrate-1 (IRS-1) plays a central role in insulin sensitivity, and association studies have shown that the IRS-1 G972R variant is a risk factor for insulin resistance. However, how this mutation may lead to impaired insulin sensitivity is still to be determined. Our study aimed to evaluate, after transfection of the IRS-1 G972R variant in 3T3L1 adipocytes, the effect of this mutation on insulin signaling and on cell differentiation. The 3T3L1 cells were transfected with pcDNA3 expression vector containing either the human wild-type IRS-1 or the G972R, variant. After induction of differentiation, the 3T3L1 transfected with wild-type IR-S-1 differentiated in 6-8 days, while the cells transfected with G972R variant did not differentiate. To determine whether the defect in IRS-1 was responsible for this, we analyzed the expression of several genes involved in the insulin signaling pathway. Results showed that PPAR gamma expression was significantly reduced in cells transfected with the mutated IRS-1, together with a significant decrease in binding of phosphatidylinositol-3 kinase (PI 3-kinase) to IR-S-1 G972R and in PI 3-kinase activity. In addition, we observed that the interaction between the insulin receptor (IR) and the IRS-1 G972R protein was increased and that the autophosphotylation of the 111, was significantly inhibited in 3T3Ll-G672R cells compared with 3T3L1-WT. Treatment of the 3T3L1-G972R cells with pioglitazone (PIO), a PPAR gamma agonist, restored differentiation with higher level of PRAR gamma expression and restoration of PI 3-kinase binding to IRS-1 G972k and PI3-kinase activity. IR autophosphorylation was also increased. Withdrawal of PIO in fully differentiated 3T3L1-G972R cells determined the reappearance Of the insulin signaling defect. Finally, we observed higher levels of IRS-2 expression, suggesting that IRS-2 may play a more important role in adipocyte insulin signalina. In conclusion. IRS-1 G972R variant impairs insulin signaling, and treatment with PPAR gamma agonist restores the normal phenotype of 3T3L1 cells

Metabolic and immune parameters at clinical onset of insulin-dependent diabetes: a population-based study. IMDIAB Study Group. Immunotherapy Diabetes.

The age at diagnosis of insulin-dependent diabetes mellitus (type I DM) varies between childhood and adulthood. The aim of this study was to define the immunologic and metabolic characteristics of the disease according to the age at which it is diagnosed. We evaluated the residual beta-cell function (basal and stimulated C-peptide) and frequency of two major islet cell-related autoantibodies, glutamic acid decarboxylase (GAD) and tyrosine phosphatase-like molecule (IA-2ic), at the onset of type I DM. A population-based study was performed with 235 consecutive cases of recent-onset (<4 weeks) type I DM (ages 5 to 45 years) diagnosed in the Lazio region of central Italy. Five age groups were considered: patients diagnosed between ages 5 and 7 years (n = 10), 7 and 10 years (n = 38), 10 and 17 years (n = 94), 17 and 20 years (n = 17), and 20 and 45 years (n = 76). Patients diagnosed before puberty had significantly reduced C-peptide secretion compared with patients diagnosed at a later age (P < .02). Glycosylated hemoglobin (HbA1c) did not differ at diagnosis between the different age groups. Patients diagnosed at puberty or after required significantly less insulin compared with younger patients (P < .04). GAD antibodies were found in 65% and IA-2ic antibodies in 59% of patients. GAD antibodies tended to be more frequent in patients diagnosed after age 17 compared with younger patients (P = .05), while IA-2ic antibodies were not age-related. These data suggest that (1) the extent of beta-cell damage differs between patients diagnosed before and after puberty, the process being more destructive in children less than 7 years of age, when C-peptide levels are the lowest; and (2) residual beta-cell function at diagnosis is not influenced by the presence or absence of islet cell-related antibodies. These findings have implications for trials in type I DM diagnosis aimed at protecting beta cells from end-stage destruction and in attempts to prevent the disease in susceptible individuals

Nitric oxide and type I diabetes: Low toxicity of NO towards human beta cells due to hsp 70 expression

[No abstract available