131,526 research outputs found
2-D response mapping of Multi-Linear Silicon Drift Detectors
No full textMulti-linear silicon drift detectors (MLSDDs) are good candidates to fulfill simultaneous requirements for 2-D position-sensing and spectroscopy applications. The optimization of their design and performance as 2-D imagers requires a detailed study of timing properties of the charge cloud in the MLSDD architecture. In particular it is important to experimentally determine the dependence of the measured amplitude and time-of-arrival on the photon position of interaction so as to derive the 2D detector response. In this paper we will present a detailed experimental characterization aimed at measuring the detector amplitude response and its timing response. The dependence of charge cloud drift time on precise position of interaction has been measured as a function of detector biasing conditions
UNA GRAVE COMPLICAZIONE NEL MORBO DI HIRSCHSPRUNG: L'ENTEROCOLITE (ATTUALITà DI TRATTAMENTO)
No full textVitamin D deficiency: a new risk factor for type 2 diabetes?
No full textRecent 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
Mechanisms in endocrinology: vitamin D as a potential contributor in endocrine health and disease.
No full textAbstract
OBJECTIVE:
It has been suggested that vitamin D may play a role in the pathogenesis of several endocrine diseases, such as hyperparathyroidism, type 1 diabetes (T1DM), type 2 diabetes (T2DM), autoimmune thyroid diseases, Addison's disease and polycystic ovary syndrome (PCOS). In this review, we debate the role of vitamin D in the pathogenesis of endocrine diseases.
METHODS:
Narrative overview of the literature synthesizing the current evidence retrieved from searches of computerized databases, hand searches and authoritative texts.
RESULTS:
Evidence from basic science supports a role for vitamin D in many endocrine conditions. In humans, inverse relationships have been reported not only between blood 25-hydroxyvitamin D and parathyroid hormone concentrations but also with risk of T1DM, T2DM, and PCOS. There is less evidence for an association with Addison's disease or autoimmune thyroid disease. Vitamin D supplementation may have a role for prevention of T2DM, but the available evidence is not consistent.
CONCLUSIONS:
Although observational studies support a potential role of vitamin D in endocrine disease, high quality evidence from clinical trials does not exist to establish a place for vitamin D supplementation in optimizing endocrine health. Ongoing randomized controlled trials are expected to provide insights into the efficacy and safety of vitamin D in the management of endocrine disease.
© 2014 European Society of Endocrinology
Hypovitaminosis D Is Associated with Liver Insulin Resistance in Obese Subjects
No full textHypovitaminosis D is highly prevalent in obese subjects. Serum 25-hydroxy vitamin D3 [25(OH)D] concentration, the best marker of human vitamin D status, has been reported to be associated with glucose status, insulin resistance (IR) and beta cell function. To specifically investigate the relationship between 25(OH)D and liver IR we performed a comprehensive metabolic assessment (2-h OGTT, hyperinsulinemic euglycemic clamp [HEC], body composition by DXA) in 20 obese non-diabetic subjects (42.9±2.7 yrs; BMI 37.7±0.8 kg/m2) with 25(OH)D insufficiency (<30 ng/mL). Liver IR was estimated using the index by Vangipurapu et al. (-0.091 + [log insulin AUC 0-120 min x 0.400] + [log fat mass% x 0.346] - [log HDL cholesterol x 0.408] + [log BMI x 0.435]). There was a significant inverse correlation between 25(OH)D and the liver IR index (r = -0.514, p = 0.02). This correlation maintained its significance after adjusting for age, gender, total cholesterol, triglycerides and whole body insulin sensitivity (M value assessed by HEC) in multiple linear regression analysis. There was no significant correlation between 25(OH)D and beta cell function estimated by the Disposition Index. Our data suggest that, in obese subjects, low 25(OH)D levels are independently associated with liver insulin resistance, but not with beta cell function. Further studies are needed to clarify the relationship between glucose homeostasis and vitamin D levels
Vitamin D deficiency: A new risk factor for type 2 diabetes?
No full textRecent 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. © 2012 S. Karger AG, Basel
Hypovitaminosis D Is Associated with Liver Insulin Resistance in Obese Subjects
No full textHypovitaminosis D is highly prevalent in obese subjects. Serum 25-hydroxy vitamin D3 [25(OH)D] concentration, the best marker of human vitamin D status, has been reported to be associated with glucose status, insulin resistance (IR) and beta cell function. To specifically investigate the relationship between 25(OH)D and liver IR we performed a comprehensive metabolic assessment (2-h OGTT, hyperinsulinemic euglycemic clamp [HEC], body composition by DXA) in 20 obese non-diabetic subjects (42.9±2.7 yrs; BMI 37.7±0.8 kg/m2) with 25(OH)D insufficiency (<30 ng/mL). Liver IR was estimated using the index by Vangipurapu et al. (-0.091 + [log insulin AUC 0-120 min x 0.400] + [log fat mass% x 0.346] - [log HDL cholesterol x 0.408] + [log BMI x 0.435]). There was a significant inverse correlation between 25(OH)D and the liver IR index (r = -0.514, p = 0.02). This correlation maintained its significance after adjusting for age, gender, total cholesterol, triglycerides and whole body insulin sensitivity (M value assessed by HEC) in multiple linear regression analysis. There was no significant correlation between 25(OH)D and beta cell function estimated by the Disposition Index. Our data suggest that, in obese subjects, low 25(OH)D levels are independently associated with liver insulin resistance, but not with beta cell function. Further studies are needed to clarify the relationship between glucose homeostasis and vitamin D levels
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Can vitamin D deficiency cause diabetes and cardiovascular diseases? Present evidence and future perspectives
No full textSeveral studies have shown that vitamin D may play a role in many biochemical mechanisms in addition to bone and calcium metabolism. Recently, vitamin D has sparked widespread interest because of its involvement in the homeostasis of the cardiovascular system. Hypovitaminosis D has been associated with obesity, related to trapping in adipose tissue due to its lipophilic structure. In addition, vitamin D deficiency is associated with increased risk of cardiovascular disease (CVD) and this may be due to the relationship between low vitamin D levels and obesity, diabetes mellitus, dyslipidaemia, endothelial dysfunction and hypertension. However, although vitamin D has been identified as a potentially important marker of CVD, the mechanisms through which it might modulate cardiovascular risk are not fully understood. Given this background, in this work we summarise clinical retrospective and prospective observational studies linking vitamin D levels with cardio-metabolic risk factors and vascular outcome. Moreover, we review various randomised controlled trials (RCTs) investigating the effects of vitamin D supplementation on surrogate markers of cardiovascular risk. Considering the high prevalence of hypovitaminosis D among patients with high cardiovascular risk, vitamin D replacement therapy in this population may be warranted; however, further RCTs are urgently needed to establish when to begin vitamin D therapy, as well as to determine the dose and route and duration of administration
- …
