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Lysophosphatidylcholine acyltransferase 2-mediated lipid droplet production supports colorectal cancer chemoresistance.
Cotte, AK, Aires, V, Fredon, M, Limagne, E, Derangère, V, Thibaudin, M, Humblin, E, Scagliarini, A, de Barros, JP, Hillon, P, et al
Nature communications. 2018;9(1):322
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Lipid droplet (LD) accumulation has been observed in an increasing number of cancer cell lines and is now a well-recognised hallmark of cancer. While the significance of LD accumulation remains unclear, recent studies have suggested it plays a role in tumour cell chemoresistance mechanisms. This study aims to fill in the gaps in the literature regarding LD formation and function under chemotherapy conditions in colorectal cancer cell models. For the first time, this study demonstrates a pertinent mechanism linking LD accumulation and resistance to conventional chemotherapies. The authors found that LD production is driven by the enzyme lysophosphatidylcholine acyltransferase 2 (LPCAT2), and that chemotherapy can trigger LD production, promoting chemoresistance. The authors conclude these findings could be useful for both prognostic factors as well as predictive factors for the patient’s responsiveness to conventional therapies.
Abstract
Lipid droplet (LD) accumulation is a now well-recognised hallmark of cancer. However, the significance of LD accumulation in colorectal cancer (CRC) biology is incompletely understood under chemotherapeutic conditions. Since drug resistance is a major obstacle to treatment success, we sought to determine the contribution of LD accumulation to chemotherapy resistance in CRC. Here we show that LD content of CRC cells positively correlates with the expression of lysophosphatidylcholine acyltransferase 2 (LPCAT2), an LD-localised enzyme supporting phosphatidylcholine synthesis. We also demonstrate that LD accumulation drives cell-death resistance to 5-fluorouracil and oxaliplatin treatments both in vitro and in vivo. Mechanistically, LD accumulation impairs caspase cascade activation and ER stress responses. Notably, droplet accumulation is associated with a reduction in immunogenic cell death and CD8+ T cell infiltration in mouse tumour grafts and metastatic tumours of CRC patients. Collectively our findings highlight LPCAT2-mediated LD accumulation as a druggable mechanism to restore CRC cell sensitivity.
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Functional variants in the sucrase-isomaltase gene associate with increased risk of irritable bowel syndrome.
Henström, M, Diekmann, L, Bonfiglio, F, Hadizadeh, F, Kuech, EM, von Köckritz-Blickwede, M, Thingholm, LB, Zheng, T, Assadi, G, Dierks, C, et al
Gut. 2018;67(2):263-270
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Congenital sucrase-isomaltase deficiency (CSID) is a genetic disorder which results in a lower ability to digest certain sugars, resulting in diarrhoea, abdominal pain and bloating, which are also common symptoms of Irritable Bowel Syndrome (IBS). The objective of this study was to test sucrase-isomaltase (SI) gene variants for their potential relevance in IBS. The researchers looked at genetics in several populations with and without IBS. The researchers found that genetic mutations are associated with a 35% reduction in the activity of the SI enzymes. CSID mutations were almost twice as common in IBS patients than healthy controls. The genetic variant 15Phe was associated with diarrhoea, stool frequency and changes in the gut bacteria. The authors concluded that people with SI gene variants associated with reduced enzyme activity are more at risk of IBS. Genetic screening could help to identify individuals at increased risk of IBS, and may lead to more targeted treatment for some people with IBS.
Abstract
OBJECTIVE IBS is a common gut disorder of uncertain pathogenesis. Among other factors, genetics and certain foods are proposed to contribute. Congenital sucrase-isomaltase deficiency (CSID) is a rare genetic form of disaccharide malabsorption characterised by diarrhoea, abdominal pain and bloating, which are features common to IBS. We tested sucrase-isomaltase (SI) gene variants for their potential relevance in IBS. DESIGN We sequenced SI exons in seven familial cases, and screened four CSID mutations (p.Val557Gly, p.Gly1073Asp, p.Arg1124Ter and p.Phe1745Cys) and a common SI coding polymorphism (p.Val15Phe) in a multicentre cohort of 1887 cases and controls. We studied the effect of the 15Val to 15Phe substitution on SI function in vitro. We analysed p.Val15Phe genotype in relation to IBS status, stool frequency and faecal microbiota composition in 250 individuals from the general population. RESULTS CSID mutations were more common in patients than asymptomatic controls (p=0.074; OR=1.84) and Exome Aggregation Consortium reference sequenced individuals (p=0.020; OR=1.57). 15Phe was detected in 6/7 sequenced familial cases, and increased IBS risk in case-control and population-based cohorts, with best evidence for diarrhoea phenotypes (combined p=0.00012; OR=1.36). In the population-based sample, 15Phe allele dosage correlated with stool frequency (p=0.026) and Parabacteroides faecal microbiota abundance (p=0.0024). The SI protein with 15Phe exhibited 35% reduced enzymatic activity in vitro compared with 15Val (p<0.05). CONCLUSIONS SI gene variants coding for disaccharidases with defective or reduced enzymatic activity predispose to IBS. This may help the identification of individuals at risk, and contribute to personalising treatment options in a subset of patients.
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Hypothesis and data-driven dietary patterns and colorectal Cancer survival: findings from Newfoundland and Labrador colorectal Cancer cohort.
Sharma, I, Roebothan, B, Zhu, Y, Woodrow, J, Parfrey, PS, Mclaughlin, JR, Wang, PP
Nutrition journal. 2018;17(1):55
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Diet and lifestyle play a role in the risk and outcome of chronic diseases including colorectal cancer (CRC). This prospective follow-up study looked at the association between different dietary patterns and the risk of death and cancer recurrence in people with CRC. Over 500 CRC patients diagnosed between 1999 and 2003 were followed-up until 2010. Participants completed a food frequency questionnaire based on their diet a year prior to diagnosis, and this was used to identify several dietary patterns. Diets that were high in processed meats (HR 1.82), meat and dairy products (HR 2.19), and total grains, sugar and soft drinks (HR 1.95) were associated with a higher risk of mortality, cancer recurrence or metastasis. Poor adherence to a Mediterranean-style diet increased the risk of overall mortality (HR 1.62). Prudent vegetable, high sugar pattern, Recommended Food Scores and Dietary Inflammatory Index had no significant association with either mortality or combined mortality, recurrence or metastasis. The authors concluded that the risk of mortality, recurrence and metastasis in patients with colorectal cancer varies with different dietary patterns.
Abstract
BACKGROUND Dietary patterns are commonly used in epidemiological research, yet there have been few studies assessing if and how research results may vary across dietary patterns. This study aimed to estimate the risk of mortality/recurrence/metastasis using different dietary patterns and comparison amongst the patterns. METHODS Dietary patterns were identified by Cluster Analysis (CA), Principal Component Analysis (PCA), Alternate Mediterranean Diet score (altMED), Recommended Food Score (RFS) and Dietary Inflammatory Index (DII) scores using a 169-item food frequency questionnaire. Five hundred thirty-two colorectal cancer patients diagnosed between 1999 and 2003 in Newfoundland were followed-up until 2010. Overall Mortality (OM) and combined Mortality, Recurrence or Metastasis (cMRM) were identified. Comparisons were made with adjusted Cox proportional Hazards Ratios (HRs), correlation coefficients and the distributions of individuals in defined clusters by quartiles of factor and index scores. RESULTS One hundred and seventy cases died from all causes and 29 had a cancer recurrence/metastasis during follow-up. Processed meats as classified by PCA (HR 1.82; 95% confidence interval (CI) 1.07-3.09), clusters characterized by meat and dairy products (HR 2.19; 95% CI 1.03-4.67) and total grains, sugar, soft drinks (HR 1.95; 95% CI 1.13-3.37) were associated with a higher risk of cMRM. Poor adherence to AltMED increased the risk of all-cause OM (HR 1.62; 95% CI 1.04-2.56). Prudent vegetable, high sugar pattern, RFS and DII had no significant association with both OM and cMRM. CONCLUSION Estimation of OM and cMRM varied across dietary patterns which is attributed to the differences in the foundation of each pattern.
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Disruption of maternal gut microbiota during gestation alters offspring microbiota and immunity.
Nyangahu, DD, Lennard, KS, Brown, BP, Darby, MG, Wendoh, JM, Havyarimana, E, Smith, P, Butcher, J, Stintzi, A, Mulder, N, et al
Microbiome. 2018;6(1):124
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The gut microbiota is key for immune development, especially during a critical window in infancy, and it has been shown that maternal diet before, during and after pregnancy influences infant metabolism and gut microbiota. The aim of this study was to assess the effects of maternal antibiotics administration during gestation and nursing on offspring gut microbiota and immunity. Pregnant mice, dams, received oral vancomycin in drinking water 5 days prior to give birth (gestation group), 14 days after delivery (nursing group) or 5 days prior to delivery and throughout nursing (gestation plus nursing group), while control mice received no vancomycin. Adaptive immunity and gut microbiota in dams and pups were analysed at various times after delivery. This study showed that antibiotic alteration of maternal gut microbiota during both pregnancy and nursing results in changes in the adaptive immunity in offspring. The authors conclude these findings are important as they provide insight into the mechanism by which maternal exposures during pregnancy may impact infant health, therefore identifying potential targets for intervention.
Abstract
BACKGROUND Early life microbiota is an important determinant of immune and metabolic development and may have lasting consequences. The maternal gut microbiota during pregnancy or breastfeeding is important for defining infant gut microbiota. We hypothesized that maternal gut microbiota during pregnancy and breastfeeding is a critical determinant of infant immunity. To test this, pregnant BALB/c dams were fed vancomycin for 5 days prior to delivery (gestation; Mg), 14 days postpartum during nursing (Mn), or during gestation and nursing (Mgn), or no vancomycin (Mc). We analyzed adaptive immunity and gut microbiota in dams and pups at various times after delivery. RESULTS In addition to direct alterations to maternal gut microbial composition, pup gut microbiota displayed lower α-diversity and distinct community clusters according to timing of maternal vancomycin. Vancomycin was undetectable in maternal and offspring sera, therefore the observed changes in the microbiota of stomach contents (as a proxy for breastmilk) and pup gut signify an indirect mechanism through which maternal intestinal microbiota influences extra-intestinal and neonatal commensal colonization. These effects on microbiota influenced both maternal and offspring immunity. Maternal immunity was altered, as demonstrated by significantly higher levels of both total IgG and IgM in Mgn and Mn breastmilk when compared to Mc. In pups, lymphocyte numbers in the spleens of Pg and Pn were significantly increased compared to Pc. This increase in cellularity was in part attributable to elevated numbers of both CD4+ T cells and B cells, most notable Follicular B cells. CONCLUSION Our results indicate that perturbations to maternal gut microbiota dictate neonatal adaptive immunity.
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A Pilot Study To Investigate the Immune-Modulatory Effects of Fasting in Steroid-Naive Mild Asthmatics.
Han, K, Nguyen, A, Traba, J, Yao, X, Kaler, M, Huffstutler, RD, Levine, SJ, Sack, MN
Journal of immunology (Baltimore, Md. : 1950). 2018;201(5):1382-1388
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Previous studies have shown that caloric restriction and fasting may modulate immune function and have positive effects in asthmatics. The aim of this pilot study was to evaluate the effects of fasting on specific inflammatory markers that might mediate such benefits. 18 mild asthmatics, 5 of whom were not on steroid inhalers, fasted for 24 hours. Lung function and immune parameters were evaluated at baseline and 2.5 hours after the first meal following the fast. There were significant differences between subjects who were and were not on steroid inhalers. Whilst one day of fasting did not affect lung function, a number of inflammatory parameters were improved by fasting in those not taking steroid inhalers, but not in those who were taking steroids. The authors conclude that caloric restriction might be considered as a strategy to improve systemic and pulmonary inflammation in asthma.
Abstract
A fasting mimetic diet blunts inflammation, and intermittent fasting has shown ameliorative effects in obese asthmatics. To examine whether canonical inflammatory pathways linked with asthma are modulated by fasting, we designed a pilot study in mild asthmatic subjects to assess the effect of fasting on the NLRP3 inflammasome, Th2 cell activation, and airway epithelial cell cytokine production. Subjects with documented reversible airway obstruction and stable mild asthma were recruited into this study in which pulmonary function testing (PFT) and PBMCextraction was performed 24 h after fasting, with repeated PFT testing and blood draw 2.5 h after refeeding. PFTs were not changed by a prolonged fast. However, steroid-naive mild asthmatics showed fasting-dependent blunting of the NLRP3 inflammasome. Furthermore, PBMCs from these fasted asthmatics cocultured with human epithelial cells resulted in blunting of house dust mite-induced epithelial cell cytokine production and reduced CD4+ T cell Th2 activation compared with refed samples. This pilot study shows that prolonged fasting blunts the NLRP3 inflammasome and Th2 cell activation in steroid-naive asthmatics as well as diminishes airway epithelial cell cytokine production. This identifies a potential role for nutrient level-dependent regulation of inflammation in asthma. Our findings support the evaluation of this concept in a larger study as well as the potential development of caloric restriction interventions for the treatment of asthma.
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Inflammatory bowel diseases: a burden in pediatrics: Case series and a review of the literature.
Mărginean, CO, Meliţ, LE, Mocanu, S, Mărginean, MO
Medicine. 2017;96(11):e6329
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Inflammatory bowel disease (IBD) is a disorder of the digestive tract and is of two types –Ulcerative colitis and Crohn’s disease. IBD can occur at any age but it seems, it's on increase in children especially in developed countries. The etiology of IBD is not fully understood, though the prognosis depends on the number of relapses. This study is a review based on four cases of IBD presenting in children under the age of 16. The authors found that emotional disorders and stress are often the common factors encountered in IBD patients. Also, a diet high in animal fat and low in fruit and vegetable seems to be associated with increased risk of IBD. The authors concluded that intervention of defined formula diet and supplementation of vitamin D showed positive outcomes in IBD sufferers. However, alongside medical approach for the treatment of IBD, educational intervention as well as addressing the emotional disorders may be helpful in the management of IBD.
Abstract
INTRODUCTION Inflammatory bowel disease is a chronic condition of the gastrointestinal tract, comprising mainly Crohn disease (CD) and ulcerative colitis (UC). Both of them are frequently encountered in children, being multifactorial conditions, with an unclear etiology. PATIENTS CONCERNS We present 4 cases of inflammatory bowel disease (IBD) in children in order to underline the variable evolution depending on the patient's particularities. DIAGNOSIS, INTERVENTIONS AND OUTCOMES The first case, a 13-year-old male patient, with a history of Henoch-Schonlein purpura, was admitted for rectal bleeding and weight loss, with normal laboratory parameters. The colonoscopy and the histopathological examination established the diagnosis of UC. The evolution was initially favorable under corticosteroids and sulfasalazine, but with 3 relapses in 2 years. The second case, a 16-year-old male patient, with a history of lactose intolerance and constipation, was admitted for bloody, diarrheic stools, the laboratory tests pointing out only leukocytosis with neutrophilia. The colonoscopy and histopathological examination established the diagnosis of UC. The patient's evolution was slowly favorable. The third case, a 9-year old male patient, with emotional disorders and babbling, admitted for semiconsistent, bloody stools, with increased inflammatory tests, whose colonoscopy pointed out diffuse edema and hemorrhages, the histopathological examination establishing the diagnosis of CD. The evolution was initially favorable, but with 5 relapses in 3 years. The last case, a 12-year-old male patient, was admitted with diarrheic, bloody stools, refractory to antibiotics, and weight loss, with increased inflammatory tests. The colonoscopy pointed out ulcerations, hemorrhages, and disseminated puss deposits. The histopathological examination established the diagnosis of CD. The patient's evolution was favorable, with only 1 relapse in 3 years. CONCLUSIONS The adequate management, especially the self-management can influence the prognosis of patients with IBD, even though it is unpredictable and burdened by the risk of malignant transformation.
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Presurgical weight loss affects tumour traits and circulating biomarkers in men with prostate cancer.
Demark-Wahnefried, W, Rais-Bahrami, S, Desmond, RA, Gordetsky, JB, Hunter, GR, Yang, ES, Azrad, M, Frugé, AD, Tsuruta, Y, Norian, LA, et al
British journal of cancer. 2017;117(9):1303-1313
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Obesity is a risk factor for 13 different cancers and a recent meta-analysis has shown increased weight to be associated with biochemical recurrence in men with prostate cancer. However, few studies have explored whether presurgical intentional weight loss results in improved prostate cancer outcomes. The aim of this trial was to explore the efficacy of weight loss among overweight and obese men with prostate cancer. Forty participants were randomised to either the presurgical weight loss intervention group or control arm, and changes in weight, body composition, quality of life, tumour biology and biomarkers were recorded. This study found that intentional weight loss caused mixed effects on tumour proliferation and gene expression. Based on these results, the authors recommend that more research is needed before effectively recommending presurgical weight loss among overweight men with prostate cancer.
Abstract
BACKGROUND Obesity is associated with aggressive prostate cancer. To explore whether weight loss favourably affects tumour biology and other outcomes, we undertook a presurgical trial among overweight and obese men with prostate cancer. METHODS This single-blinded, two-arm randomised controlled trial explored outcomes of a presurgical weight loss intervention (WLI) that promoted ∼1 kg per week loss via caloric restriction and increased physical activity (PA). Forty overweight/obese men with clinically confirmed prostate cancer were randomised to the WLI presurgery or to a control arm; changes in weight, body composition, quality-of-life, circulating biomarkers, gene expression, and immunohistochemical markers in tumour and benign prostatic tissue were evaluated. RESULTS The study period averaged 50 days. Mean (s.d.) change scores for the WLI vs control arms were as follows: weight: -4.7 (3.1) kg vs -2.2 (4.4) kg (P=0.0508); caloric intake: -500 (636) vs -159 (600) kcal per day (P=0.0034); PA: +0.9 (3.1) vs +1.7 (4.6) MET-hours per day (NS); vitality: +5.3 (7.l4) vs -1.8 (8.1) (P=0.0491); testosterone: +55.1 (86.0) vs -48.3 (203.7) ng dl-1 (P=0.0418); sex hormone-binding globulin: +14.0 (14.6) vs +1.8 (7.6) nmol l-1 (P=0.0023); and leptin: -2.16 (2.6) vs -0.03 (3.75) (P=0.0355). Follow-up Ki67 was significantly higher in WLI vs control arms; median (interquartile range): 5.0 (2.5,10.0) vs 0.0 (0.0,2.5) (P=0.0061) and several genes were upregulated, for example, CTSL, GSK3B, MED12, and LAMC2. CONCLUSIONS Intentional weight loss shows mixed effects on circulating biomarkers, tumour gene expression, and proliferative markers. More study is needed before recommending weight loss, in particular rapid weight loss, among men with prostate cancer.
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Adipose Tissue Meal-Derived Fatty Acid Uptake Before and After Diet-Induced Weight Loss in Adults with Overweight and Obesity.
Vink, RG, Roumans, NJ, van der Kolk, BW, Fazelzadeh, P, Boekschoten, MV, Mariman, EC, van Baak, MA
Obesity (Silver Spring, Md.). 2017;25(8):1391-1399
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Weight loss among the obese population is difficult to sustain and there is substantial evidence arising that biological and metabolic mechanisms are a crucial factor. In obese people, the ability of adipose tissue to remove fatty acids from circulation is impaired, and it is hypothesised that reducing the size of adipose cells through weight loss will increase the storage capacity in adipose tissue, leading to greater uptake for circulating fatty acids. Therefore the aim of this study was to investigate whether diet-induced weight loss alters fat uptake in adipose tissue. In this randomised controlled trial, 16 individuals were assigned to either a low-calorie diet for 12-weeks or very low calorie diet for 5-weeks, both followed by a 4-week weight stable period and a 9-month follow up. Blood samples, adipose tissue biopsies and anthropometric measurements were taken at baseline, after weight loss, after weight stable period and at follow-up. Contrary to hypothesis, this study found that fatty acid uptake dynamics and expression of genes involved in fat metabolism were not significantly changed during the intervention period. Based on these results, the authors did not detect dietary weight loss-induced changes in gene expression involved in fat metabolism.
Abstract
OBJECTIVE This study investigated whether diet-induced weight loss alters indices of in vivo postprandial fat uptake in adipose tissue (AT) and whether these changes are associated with weight regain in adults with overweight and obesity. METHODS In this randomized controlled trial, 16 (6 male) individuals (BMI: 28-35 kg/m2 ) were randomized to either a low-calorie diet (1,250 kcal/d) for 12 weeks or a very-low-calorie diet (500 kcal/d) for 5 weeks (weight loss [WL] period) followed by a 4-week weight-stable (WS) period (together, the dietary intervention [DI] period) and a 9-month follow-up period. Arteriovenous difference measurements combined with stable isotope labeling ([U-13 C] palmitate) of a mixed meal were used to determine postprandial fatty acid uptake in AT. RESULTS Body weight was significantly reduced during the WL period (-8.2 ± 0.6 kg, P < 0.001), remained stable during the WS period (0.4 ± 0.3 kg, P = 0.150), and increased during follow-up (3.5 ± 0.8 kg, P = 0.001). Meal-derived in vivo fatty acid uptake dynamics across AT and expression of genes important for fatty acid uptake, storage, and release were not significantly changed during the DI period. CONCLUSIONS Subcutaneous AT does not appear prone to enhanced meal-derived fatty acid uptake after weight loss, nor were fatty acid uptake dynamics detected as related to weight regain.
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Spexin peptide is expressed in human endocrine and epithelial tissues and reduced after glucose load in type 2 diabetes.
Gu, L, Ma, Y, Gu, M, Zhang, Y, Yan, S, Li, N, Wang, Y, Ding, X, Yin, J, Fan, N, et al
Peptides. 2015;71:232-9
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Little is known about the functions of the peptide spexin. Recent studies have shown a relationship between spexin and body weight regulation. It is thought that spexin might be related to glucose control and fat metabolism in type 2 diabetes mellitus (T2DM). The aim of this study was to examine the location of spexin in human tissue and measure spexin levels after a glucose load in T2DM patients. First, the researchers examined human tissue samples. Blood samples were then collected from 121 adults with T2DM and 105 healthy individuals. Additionally, an oral glucose tolerance test (OGTT) was performed on 12 healthy volunteers. In human tissue samples, the levels of spexin were highest in the adrenal gland, skin, stomach, small intestine, liver, thyroid, pancreatic islets, visceral fat, lung, colon, and kidney, and lowest in muscle and connective tissue. Blood levels of spexin were significantly lower in T2DM patients compared to healthy controls. Spexin levels were found to be inversely related to fasting blood glucose and lipids. During the OGTT, spexin levels were also inversely correlated with blood glucose levels. The authors concluded that spexin is highly expressed among endocrine and epithelial tissues. Changes in the blood levels of spexin could represent an adaptation to the rise of glucose and lipids associated with T2DM. However, the exact role of spexin in endocrine diseases is still to be discovered.
Abstract
Spexin mRNA and protein are widely expressed in rat tissues and associate with weight loss in rodents of diet-induced obesity. Its location in endocrine and epithelial cells has also been suggested. Spexin is a novel peptide that involves weight loss in rodents of diet-induced obesity. Therefore, we aimed to examine its expression in human tissues and test whether spexin could have a role in glucose and lipid metabolism in type 2 diabetes mellitus (T2DM). The expression of the spexin gene and immunoreactivity in the adrenal gland, skin, stomach, small intestine, liver, thyroid, pancreatic islets, visceral fat, lung, colon, and kidney was higher than that in the muscle and connective tissue. Immunoreactive serum spexin levels were reduced in T2DM patients and correlated with fasting blood glucose (FBG, r=-0.686, P<0.001), hemoglobin A1c (HbA1c, r=-0.632, P<0.001), triglyceride (TG, r=-0.236, P<0.001) and low density lipoprotein-cholesterol (LDL-C, r=-0.382, P<0.001). A negative correlation of blood glucose with spexin was observed during oral glucose tolerance test (OGTT). Spexin is intensely expressed in normal human endocrine and epithelial tissues, indicating that spexin may be involved in physiological functions of endocrine and in several other tissues. Circulating spexin levels are low in T2DM patients and negatively related to blood glucose and lipids suggesting that the peptide may play a role in glucose and lipid metabolism in T2DM.
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Vitamin D supplementation for the prevention of type 2 diabetes in overweight adults: study protocol for a randomized controlled trial.
de Courten, B, Mousa, A, Naderpoor, N, Teede, H, de Courten, MP, Scragg, R
Trials. 2015;16:335
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With the rising rates of vitamin D deficiency, identifying cost-effective, preventative strategies are imperative. Vitamin D plays a well-known role in bone mineralisation, however its protective role against chronic diseases is not very well understood. The aim of this trial is to investigate whether vitamin D supplementation will increase insulin sensitivity and secretion, as well as to determine whether vitamin D deficiency underlies the inflammatory properties associated with obesity. 50 overweight adults between 18 and 60 years old were recruited and assigned to receive either 4,000 IU vitamin D daily or identical placebo capsules for 16 weeks. This study elucidates the potential role vitamin D supplementation could have on preventing diabetes and its associated co-morbidities. It also provides comprehensive insight into the potential mechanisms of action. The authors conclude that this trial can corroborate existing knowledge while expanding the understanding on the role of vitamin D in the inflammatory response and subsequent development of disease.
Abstract
BACKGROUND Despite Australia's sunny climate, low vitamin D levels are increasingly prevalent. Sun exposure is limited by long working hours, an increase in time spent indoors, and sun protection practices, and there is limited dietary vitamin D fortification. While the importance of vitamin D for bone mineralization is well known, its role as a protective agent against chronic diseases, such as type 2 diabetes and cardiovascular disease, is less understood. Observational and limited intervention studies suggest that vitamin D might improve insulin sensitivity and secretion, mainly via its anti-inflammatory properties, thereby decreasing the risk of development and progression of type 2 diabetes. The primary aim of this trial is to investigate whether improved plasma concentrations of 25-hydroxyvitamin D (25(OH)D), obtained through vitamin D supplementation, will increase insulin sensitivity and insulin secretion. A secondary aim is to determine whether these relationships are mediated by a reduction in underlying subclinical inflammation associated with obesity. METHODS/DESIGN Fifty overweight but otherwise healthy nondiabetic adults between 18 and 60 years old, with low vitamin D levels (25(OH)D < 50 nmol/l), will be randomly assigned to intervention or placebo. At baseline, participants will undergo a medical review and anthropometric measurements, including dual X-ray absorptiometry, an intravenous glucose tolerance test, muscle and fat biopsies, a hyperinsulinemic euglycemic clamp, and questionnaires assessing diet, physical activity, sun exposure, back and knee pain, and depression. The intervention group will receive a first dose of 100,000 IU followed by 4,000 IU vitamin D (cholecalciferol) daily, while the placebo group will receive apparently identical capsules, both for a period of 16 weeks. All measurements will be repeated at follow-up, with the primary outcome measure expressed as a change from baseline in insulin sensitivity and secretion for the intervention group compared with the placebo group. Secondary outcome measures will compare changes in anthropometry, cardiovascular risk factors, and inflammatory markers. DISCUSSION The trial will provide much needed clinical evidence on the impact of vitamin D supplementation on insulin resistance and secretion and its underlying mechanisms, which are relevant for the prevention and management of type 2 diabetes. TRIAL REGISTRATION Clinicaltrials.gov ID: NCT02112721 .