A systematic review protocol examining the effect of vitamin D supplementation on endothelial function.

INTRODUCTION: Vitamin D has potential benefits for extraskeletal health. These could include an anti-inflammatory effect as well as a reduction in endothelial dysfunction. We aim to provide quality evidence for the hypothesis that supplementation with vitamin D will improve endothelial function (EF), possibly through the abrogation of systemic inflammation. METHODS AND ANALYSIS: We will conduct a systematic review of all randomised controlled trials on vitamin D supplementation and EF lasting 12 weeks or more. The search will cover the period 2000-2015 and include studies that describe direct measures of EF, markers of endothelial cell (EC) activation and if concurrently reported, indicators of systemic inflammation. Study selection will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and study quality will be assessed by the Jadad score in addition to an evaluation of allocation concealment and data analysis. If sufficient data are available, a meta-analysis will be conducted. The effect sizes will be generated using Hedges' g score, for both fixed and random effect models. I(2) statistics and Galbraith plots will be used to assess heterogeneity and identify their potential sources. Potential publication and small sample size bias will be assessed by visual inspections of funnel plots and also Egger's test. Meta-regression analysis (if feasible) will be conducted with restricted maximum likelihood (REML) estimation method, controlling for potential confounders (demographics, study methods, location, etc). A backward elimination process will be applied in the regression modelling procedure. Subgroup analysis, conditional on number of studies retrieved and their sample size, will be stratified on participant disease category, total dose administered, degree of 25(OH)D change and type of supplement used. ETHICS AND DISSEMINATION: Formal ethical approval is not required as primary data will not be collected. The results will be disseminated through a peer-reviewed publication, conference presentation and the popular press. TRIAL REGISTRATION NUMBER: International Prospective Register for Systematic Reviews (PROSPERO) number CRD42014013523.

Vitamin D & endothelial function.

There is increasing interest in the extra-skeletal roles of vitamin D for health and well-being. Poor vitamin D status has been associated with obesity, cardiovascular disease, type 2 diabetes and mental health. Endothelial dysfunction may underscore insulin resistance and hence predispose to both cardiovascular disease (CVD) and type 2 diabetes. The objective of this review was to gain an appreciation of the recent causative evidence linking vitamin D and endothelial function. The PubMed database was searched from 2009 to date. Key words used were vitamin D, supplementation, systemic inflammation, endothelium, endothelial dysfunction and humans. Selected articles were restricted to the English language and to randomized control trials (RCTs) of vitamin D supplementation with direct measures of endothelial function. Final inclusion was based on a quality rating ≥ 3, based on the Jadad score. Ten RCTs met these criteria and were summarized for their outcomes. Only two studies showed an improvement in flow mediated dilatation with vitamin D. Three other studies reported decreases in C-reactive protein, platelet activation inhibitor-1, tissue plasminogen activator or B type natriuretic peptide. Recent evidence from good quality RCTs did not support a beneficial effect of vitamin D on vascular reactivity. Future intervention studies may need to target a higher vitamin D status and longer duration to determine whether the vitamin has a regulatory role in endothelial function.

Vitamin D and parathyroid hormone in insulin resistance of abdominal obesity: cause or effect?

The objective was to examine whether there were causal links between vitamin D status, parathyroid hormone, insulin resistance (IR)/insulin sensitivity (IS) and the metabolic syndrome (MS). A total of 72 Caucasian men and women, aged 55.7 ± 7.57 years, with body mass index 33.4 ± 4.02 kg/m(2) and abdominal obesity, were assessed for IR/IS based on three commonly used indices before and after 12 weeks of supervised weight loss. During weight stability, though both lower intact parathyroid hormone (iPTH) and higher vitamin D were independently associated with greater IS/lower IR, this was consistent for iPTH across the surrogate measures tested. Higher iPTH, but not lower vitamin D, increased the risk of MS after adjustment for IR/IS. Weight loss resulted in significant reductions in percent fat (-2.83 ± 2.20%), waist (-9.26 ± 5.11 cm), improvements in all IS indices, reductions in MS and iPTH (-0.28 ± 1.17 pmol/l), but no increase in vitamin D (+2.19 ± 12.17 nmol/l). Following weight loss, ΔiPTH either predicted change in IR/IS or contributed to their variance by 4.1-8.9%. On adjustment for IR/IS, higher ΔiPTH did not significantly predict MS after weight loss, though the odds ratios for the effect were sizeable. The data are suggestive of an intrinsic inverse relationship between iPTH and IS in abdominally obese individuals, independent of vitamin D. There remains the possibility of a direct relationship between iPTH and MS.

Breastfeeding, body mass index, asthma and atopy in children.

The objective of this study was to determine the relationship between breastfeeding, asthma and atopy, and any influence of child body mass index (BMI). Prospective birth cohort data were used to model the association between breastfeeding duration, BMI, asthma and atopy in children at six years. After adjustment for BMI and associated covariates, breastfeeding (per additional month of feeding) was marginally associated with decreased BMI (p=0.083). BMI was significantly associated with current asthma (p=<0.0005) and atopy (p=0.055). Exclusive breastfeeding for less than four months was a risk for current asthma (p=0.033) and atopy (p=0.005). The early introduction of formula leads to an increase in child BMI and early asthma and atopy. Increased BMI is a risk factor for childhood asthma and atopy. These findings suggest that public health interventions to optimise breastfeeding duration and reduce overweight in children may help attenuate the community burden of wheezing illness early in life.

What do children with cystic fibrosis and their parents know about nutrition and pancreatic enzymes?

OBJECTIVE: To describe the development and validation of questionnaires designed to assess nutrition and pancreatic enzyme replacement therapy knowledge and cystic fibrosis self-management skills, and the results obtained when the questionnaires were used. DESIGN: A cross-sectional study using validated questionnaires to interview the respondents. The outcome measures were scores for knowledge, appropriate and inappropriate self-management, and Socioeconomic Index. SUBJECTS: Forty-two children with cystic fibrosis aged 6 to 11 years and 55 caregivers of 2 to 11-year-old patients of the Princess Margaret Hospital Cystic Fibrosis Clinic, Perth, Australia. STATISTICAL ANALYSES: Descriptive statistics and correlations between scores were used for statistical analyses. Associations between knowledge scores were examined using Pearson's correlation coefficient. Spearman's rank correlation was used to examine the associations between knowledge and self-management scores and socioeconomic index. RESULTS: Children's and caregivers' mean knowledge scores were 63% and 85%, respectively. Mean appropriate and inappropriate self-management scores for children were 55% and 21%, respectively, and for the caregivers were 74% and 32%, respectively. There was a statistically significant (P < .05) positive association between caregivers' and children's knowledge (r = 0.32), and children's knowledge and appropriate self-management scores (r = 0.41); and a statistically significant negative association between caregivers' knowledge and inappropriate self-management scores (r = -0.35); and no statistically significant associations between Socioeconomic Index and children's and caregivers' knowledge and self-management scores. APPLICATIONS: This study identified areas in which the nutrition knowledge of children with cystic fibrosis and their caregivers needs to be enhanced to increase the likelihood that optimum dietary and pancreatic enzyme therapy is achieved. The questionnaires that were developed for the study could be refined and used in the clinical setting to identify knowledge and self-management deficits. Alternatively, the questionnaires could become valuable research tools for assessing the type of intervention required and in planning and evaluating programs.

Homeostatic mechanisms that regulate lactation during energetic stress.

Apart from the metabolic differences between species (ruminant vs. nonruminant), there are other important physiologic differences in both the energy requirements for lactation and in the control of milk production between dairy cows and women. Unlike dairy cows, the partitioning of nutrients for lactation in women therefore cannot be generalized to all lactating women but must be related to individual women, taking into account their particular metabolic circumstances. Homeorhetic models may be appropriate for women in developing countries, whereas in developed countries, the flexibility in both homeostatic and homeorhetic adaptations to the substrate demands for milk synthesis means that women can adopt a variety of strategies to support the metabolic demands of lactation. In these women, as in dairy cows, body reserves, dietary intake and milk production vary widely among individuals, and individual differences in capacity for homeorhetic regulation of nutrient partitioning under these conditions require further investigation.

Voluntary exercise and monounsaturated canola oil reduce fat gain in mice fed diets high in fat.

High fat diets increase body fat stores. The following experiment was undertaken to determine whether the type of dietary fat could influence fat storage and whether voluntary exercise could prevent diet-induced obesity in mice fed high fat diets. Sixty-nine 6-wk-old female mice were fed one of three diets: low fat (11.5% of energy from fat), beef fat (40.8% of energy from fat) or canola oil (40.8% of energy from fat). In each diet group, 13 mice had free access to activity wheels in their cages (exercising), and the remaining 10 mice were housed in standard mouse cages (nonexercising). Body weight and body composition were measured before and after 8 wk of treatment. The nonexercising mice fed beef fat weighed more and had significantly more body fat (23.2 +/- 2.5 g/100 g body wt) than mice fed the low fat or canola oil diet (13.9 +/- 1.7 and 16.8 +/- 1.9 g/100 g body wt, respectively). Voluntary exercise did not affect lean body mass but did result in significantly lower body fat in all diet groups (beef, 12.6 +/- 0.9; low fat, 7.4 +/- 0.6; canola oil, 9.6 +/- 1.4 g/100 g body wt). The amount of body fat of mice fed the monounsaturated canola oil was significantly less than that of mice fed the beef fat diet, suggesting that the type of fat as well as the amount of fat influences body fat stores. Furthermore, voluntary exercise decreased body fat in all mice and prevented diet-induced obesity in mice fed diets high in fat.

Diet-induced obesity in mice can be treated without energy restriction using exercise and/or a low fat diet.

Diet-induced obesity was treated with a high carbohydrate, low fat diet and/or increased voluntary exercise in mice. All mice had free access to food and water during the two stage experiment. In Stage 1, 20 female mice were fed a high carbohydrate diet and 50 were made obese by consumption of a diet providing 40.8% of energy from fat. At the end of Stage 1, obese mice had significantly greater body fat stores (22.9 +/- 0.9 g/100 g body wt) than mice fed the high carbohydrate diet (12.9 +/- 1.2) (P < 0.001), yet there was no significant difference in lean body mass. In Stage 2, half of the mice were given activity wheels to increase their voluntary activity and half of the obese mice were switched to a high carbohydrate diet resulting in six groups with treatment designations of obese or lean; exercise or nonexercise, and carbohydrate or fat diets. Body fat was significantly reduced by consumption of the high carbohydrate diet (P < 0.005) and by exercise (P < 0.001), but neither treatment affected lean body mass. Exercising mice consumed significantly more energy than nonexercising mice, yet experienced a decrease in body fat and energy stores.(ABSTRACT TRUNCATED AT 250 WORDS)

The isolation of glucose tolerance factors from brewer's yeast and their relationship to chromium.

Growth of brewer's yeast in the presence of Cr3+ led to increased yields of substances with GTF activity in assays performed with isolated adipocytes. The formation of these substances may be a means of diminishing the toxic effects of Cr on yeast. During fractionation of extracts of brewer's yeast the Cr was easily dissociated from any complexes that may have been present. The GTF activity for both yeast and adipocytes was isolated in cationic and anionic small amino-acid or peptide-like molecules. These substances caused increased glycolysis in yeast and increased glycolysis and fatty acid synthesis in adipocytes. No evidence was found that GTF aided the binding of insulin to its receptor. The GTF activity could only be demonstrated with adipocytes from rats fed a torula yeast-high sucrose diet, which may have caused the rats to have a decreased sensitivity to insulin.