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1.
The Genetics of Pediatric Nonalcoholic Fatty Liver Disease.
Goyal, NP, Schwimmer, JB
Clinics in liver disease. 2018;(1):59-71
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Abstract
Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in children. Severe fibrosis and cirrhosis are potential consequences of pediatric NAFLD and can occur within a few years of diagnosis. Observations suggest that genetics may be a strong modifying factor in the presentation, severity, and natural history of the disease. There is increasing interest in determining at-risk populations based on genetics in the hope of finding genotypes that correlate to NAFLD phenotype. Ultimately, the hope is to be able to tailor therapeutics to genetic predispositions and decrease disease morbidity in children with NAFLD.
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Visceral adiposity and cancer survival: a review of imaging studies.
Xiao, J, Mazurak, VC, Olobatuyi, TA, Caan, BJ, Prado, CM
European journal of cancer care. 2018;(2):e12611
Abstract
Although obesity is a well-known risk factor for cancer, the association between obesity and cancer survival remains controversial. This is partially due to the inability of conventional obesity measures to directly assess adiposity or adipose tissue distribution. As a metabolic organ, visceral adipose tissue (VAT) secrets a variety of cytokines and cytokine-like factors, potentially affecting cancer survival. The objective of this review was to investigate the influence of imaging-assessed VAT on cancer survival. A total of 22 studies assessing the impact of visceral adiposity on survival were included. Negative associations between VAT and survival were more frequently observed among patients with colorectal (four of six studies) and pancreatic (three of five studies) cancers, compared to higher VAT predicting longer survival in most studies of renal cell carcinoma patients (four of five studies). Methodological limitations, including unstandardised VAT measurement methods, lack of other body composition measurement (i.e. muscle mass), small sample size and heterogeneous cohort characteristics, may explain controversial findings related to the impact of VAT on cancer survival.
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Visceral Adipose Tissue Accumulation and Residual Cardiovascular Risk.
Le Jemtel, TH, Samson, R, Milligan, G, Jaiswal, A, Oparil, S
Current hypertension reports. 2018;(9):77
Abstract
PURPOSE OF THE REVIEW Low-grade systemic inflammation increases residual cardiovascular risk. The pathogenesis of low-grade systemic inflammation is not well understood. RECENT FINDINGS Visceral adipose tissue accumulates when the subcutaneous adipose tissue can no longer store excess nutrients. Visceral adipose tissue inflammation initially facilitates storage of nutrients but with time become maladaptive and responsible for low-grade systemic inflammation. Control of low-grade systemic inflammation requires reversal of visceral adipose tissue accumulation with intense and sustained aerobic exercise or bariatric surgery. Alternatively, pharmacologic inhibition of the inflammatory signaling pathway may be considered. Reversal visceral adipose tissue accumulation lowers residual cardiovascular risk.
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Exercise and ectopic fat in type 2 diabetes: A systematic review and meta-analysis.
Sabag, A, Way, KL, Keating, SE, Sultana, RN, O'Connor, HT, Baker, MK, Chuter, VH, George, J, Johnson, NA
Diabetes & metabolism. 2017;(3):195-210
Abstract
Ectopic adipose tissue surrounding the intra-abdominal organs (visceral fat) and located in the liver, heart, pancreas and muscle, is linked to cardio-metabolic complications commonly experienced in type 2 diabetes. A systematic review and meta-analysis was performed to determine the effect of exercise on ectopic fat in adults with type 2 diabetes. Relevant databases were searched to February 2016. Included were randomised controlled studies, which implemented≥4 weeks of aerobic and/or resistance exercise and quantified ectopic fat via magnetic resonance imaging, computed tomography, proton magnetic resonance spectroscopy or muscle biopsy before and after intervention. Risk of bias and study quality was assessed using Egger's funnel plot test and modified Downs and Black checklist, respectively. Of the 10,750 studies retrieved, 24 were included involving 1383 participants. No studies were found assessing the interaction between exercise and cardiac or pancreas fat. One study assessed the effect of exercise on intramyocellular triglyceride concentration. There was a significant pooled effect size for the meta-analysis comparing exercise vs. control on visceral adiposity (ES=-0.21, 95% CI: -0.37 to -0.05; P=0.010) and a near-significant pooled effect size for liver steatosis reduction with exercise (ES=-0.28, 95% CI: -0.57 to 0.01; P=0.054). Aerobic exercise (ES=-0.23, 95% CI: -0.44 to -0.03; P=0.025) but not resistance training exercise (ES=-0.13, 95% CI: -0.37 to 0.12; P=0.307) was effective for reducing visceral fat in overweight/obese adults with type 2 diabetes. These data suggest that exercise effectively reduces visceral and perhaps liver adipose tissue and that aerobic exercise should be a key feature of exercise programs aimed at reducing visceral fat in obesity-related type 2 diabetes. Further studies are required to assess the relative efficacy of exercise modality on liver fat reduction and the effect of exercise on pancreas, heart, and intramyocellular fat in type 2 diabetes and to clarify the effect of exercise on ectopic fat independent of weight loss.
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Subcutaneous fat loss is greater than visceral fat loss with diet and exercise, weight-loss promoting drugs and bariatric surgery: a critical review and meta-analysis.
Merlotti, C, Ceriani, V, Morabito, A, Pontiroli, AE
International journal of obesity (2005). 2017;(5):672-682
Abstract
Aim of this review is to compare visceral and subcutaneous fat loss with all available strategies (diet and exercise, weight-loss promoting agents and bariatric surgery). Eighty-nine studies, all full papers, were analyzed to evaluate visceral and subcutaneous fat changes, measured through ultrasound, computerized tomography, magnetic resonance imaging and expressed as thickness, weight, area and volume. Studies were included in a meta-analysis (random-effects model). Intervention effect (absolute and percent changes of visceral and subcutaneous fat) was expressed as standardized mean differences, with 95% confidence intervals. Publication bias was formally assessed. The result was that subcutaneous fat was greater than visceral fat when measured as area, volume and weight, not as thickness; decrease of subcutaneous fat was greater than visceral fat when measured as area, volume and weight, not as thickness; percent decrease of visceral fat was always greater than percent decrease of subcutaneous fat, with no differences between different strategies. No intervention preferentially targets visceral fat. Basal visceral fat depots are smaller than basal subcutaneous fat depots. Visceral fat loss is linked to subcutaneous fat loss. With all strategies, percent decrease of visceral fat prevails on subcutaneous fat loss.
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Is epicardial fat depot associated with atrial fibrillation? A systematic review and meta-analysis.
Gaeta, M, Bandera, F, Tassinari, F, Capasso, L, Cargnelutti, M, Pelissero, G, Malavazos, AE, Ricci, C
Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology. 2017;(5):747-752
Abstract
AIMS: Atrial fibrillation (AF) is the leading rhythm disorder in western countries. A direct relationship between left atrium (LA) enlargement and electromechanical remodelling has been established. A causative link between epicardial fat (EF), visceral adipose tissue deposited around the heart, and AF has been hypothesized. Several reports suggested the association between EF and the presence of AF. The aim of this study was to verify the relationship between AF and EF depot, performing a meta-analysis of observational case series studies. METHODS AND RESULTS Studies were identified by searching electronic databases by two independent investigators using 'atrial fibrillation' and 'epicardial fat' as keywords. Comparisons between healthy participants and AF cases were performed using a random effect meta-analysis estimating standardized mean difference among comparison groups. Meta regression was used to address the effect given by potential biological and technical confounders. Through a search result of 502 articles, only 7 were selected to conduct the present study. The comparison between all AF with respect to healthy participants resulted in a 32.0 ml of EF difference (95% confidence interval (CI) = 21.5, 42.5) showing that EF volume is higher in AF cases. A statistical significant difference of EF was observed when comparing both persistent and paroxysmal AF subtypes with respect to healthy participants (EF difference 48.0 ml (95% CI = 25.2, 70.8) and 15.7 ml (95% CI = 10.1, 21.4) for persistent and paroxysmal, respectively). A significant EF difference resulted also when comparing persistent to paroxysmal AF subtypes (29.6 ml (95% CI = 12.7, 46.5)). CONCLUSIONS The present work expands the strength of previously reported association between EF amount and atrial arrhythmia.
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The Effect of Diet or Exercise on Visceral Adipose Tissue in Overweight Youth.
Vissers, D, Hens, W, Hansen, D, Taeymans, J
Medicine and science in sports and exercise. 2016;(7):1415-24
Abstract
OBJECTIVE Excess visceral adipose tissue (VAT) in children with obesity is associated with the development of cardiovascular and metabolic disease. This meta-analysis investigated if lifestyle interventions can reduce VAT in overweight and obese youth. METHODS Pubmed, Cochrane, and PEDro were searched for clinical trials that objectively assessed VAT and included study arms with supervised diet, exercise, or a combination of both. If there was a no-therapy control group, the data of the control group and the intervention groups were used to meta-analyze the data. In all other cases, the preintervention and the postintervention data were used to meta-analyze. Effect sizes were calculated as standardized mean differences or changes of VAT and expressed as Hedges' g. RESULTS The overall weighted mean effect size on VAT of all included interventions was -0.69 (95% confidence interval [CI] = -0.90 to -0.48) (P < 0.001). Subgroup analysis showed that the overall weighted mean effect size of diet-only interventions on VAT was 0.23 (95% CI = -0.22 to 0.68) (P = 0.311). Interventions that combined diet and exercise showed a pooled effect size on VAT of -0.55 (95% CI = -0.75 to -0.39) (P < 0.001). The pooled effect size of exercise-only interventions on VAT was -0.85 (95% CI = -1.20 to -0.57) (P < 0.001). CONCLUSIONS Supervised exercise-only or combined diet and exercise interventions can reduce VAT in overweight and obese children and adolescents. The strongest effect was found in exercise-only groups. However, high-quality randomized controlled trials describing the effect of supervised dietary interventions on VAT in children are lacking.
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Metabolically healthy obese individuals: Key protective factors.
Gonçalves, CG, Glade, MJ, Meguid, MM
Nutrition (Burbank, Los Angeles County, Calif.). 2016;(1):14-20
Abstract
OBJECTIVES Obesity is a significant quality of life-impairing health problem affecting industrialized nations. However, despite carrying a large fat mass, some very obese individuals exhibit normal metabolic profiles (metabolically healthy obesity). The physiological factors underlying their protective and favorable metabolic profiles remain poorly defined. METHODS A search of the National Library of Medicine PubMed database was performed using the following keywords: Metabolically healthy obese, metabolically normal obese, insulin resistance, metabolically unhealthy normal weight, and uncomplicated obesity. RESULTS This article reviewed factors associated with severe obesity that lacks complications, and suggests putative activities by which these obese individuals avoid developing the clinical features of metabolic syndrome, or the metabolic complications associated with severe obesity. CONCLUSIONS Despite the knowledge that visceral fat deposition is the seminal factor that ultimately causes insulin resistance (IR) and the detrimental inflammatory and hormonal profile that contributes to increase risk for cardiovascular disease, it remains unknown whether metabolically healthy obesity (MHO) has genetic predisposing factors, and whether MHO ultimately succumbs to IR and the metabolic syndrome, indicating a need for prophylatic bariatric surgery.
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The effects of abdominal lipectomy in metabolic syndrome components and insulin sensitivity in females: A systematic review and meta-analysis.
Seretis, K, Goulis, DG, Koliakos, G, Demiri, E
Metabolism: clinical and experimental. 2015;(12):1640-9
Abstract
BACKGROUND Adipose tissue is an endocrine organ, which is implicated in the pathogenesis of obesity, metabolic syndrome and diabetes. Lipectomy offers a unique opportunity to permanently reduce the absolute number of fat cells, though its functional role remains unclear. This systematic and meta-analysis review aims to assess the effect of abdominal lipectomy on metabolic syndrome components and insulin sensitivity in women. METHODS A predetermined protocol, established according to the Cochrane Handbook's recommendations, was used. An electronic search in MEDLINE, Scopus, the Cochrane Library and CENTRAL electronic databases was conducted from inception to May 14, 2015. This search was supplemented by a review of reference lists of potentially eligible studies and a manual search of key journals in the field of plastic surgery. Eligible studies were prospective studies with ≥1month of follow-up that included females only who underwent abdominal lipectomy and reported on parameters of metabolic syndrome and insulin sensitivity. RESULTS The systematic review included 11 studies with a total of 271 individuals. Conflicting results were revealed, though most studies showed no significant metabolic effects after lipectomy. The meta-analysis included 4 studies with 140 subjects. No significant changes were revealed between lipectomy and control groups. CONCLUSIONS This meta-analysis provides evidence that abdominal lipectomy in females does not affect significantly the components of metabolic syndrome and insulin sensitivity. Further high quality studies are needed to elucidate the potential metabolic effects of abdominal lipectomy. Systematic review registration PROSPERO CRD42015017564 (www.crd.york.ac.uk/PROSPERO).
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Visceral adiposity and colorectal adenomas: dose-response meta-analysis of observational studies.
Keum, N, Lee, DH, Kim, R, Greenwood, DC, Giovannucci, EL
Annals of oncology : official journal of the European Society for Medical Oncology. 2015;(6):1101-1109
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Abstract
BACKGROUND Obesity-related hormonal and metabolic perturbations implicated in colorectal carcinogenesis are mainly driven by visceral adipose tissue (VAT) rather than subcutaneous adipose tissue (SAT). Yet, most epidemiologic studies have examined the relationship between excess adiposity and colorectal neoplasia using body mass index (BMI) and waist circumference (WC). Due to the inability of BMI and WC to distinguish VAT from SAT, they are likely to have underestimated the true association. PATIENTS AND METHODS We conducted a dose-response meta-analysis to summarize the relationships between VAT and colorectal adenomas and to examine the value of VAT as an independent risk factor beyond BMI, WC, and SAT. PubMed and Embase were searched through September 2014 to identify relevant observational studies. The summary odds ratio (OR) 95% confidence interval (CI) were estimated using a random-effects model. RESULTS In linear dose-response meta-analysis, the summary OR for each 25 cm(2) increase in VAT area was 1.13 (95% CI 1.05-1.21; I(2) = 62%; 6 studies; 2776 cases; range of VAT area = 30-228 cm(2)). The dose-response curve suggested no evidence of nonlinearity (Pnon-linearity = 0.37). In meta-analysis comparing the highest versus lowest category of VAT based on 12 studies, a positive association between VAT and adenomas remained statistically significant even after adjustment for BMI, WC, and SAT. In contrast, adjustment for VAT substantially attenuated associations of BMI, WC, and SAT with adenomas. Across the studies, VAT was more strongly associated with advanced adenomas than nonadvanced adenomas. CONCLUSIONS VAT may be the underlying mediator of the observed associations of BMI and WC with adenomas, increasing adenoma risk continuously over a wide range of VAT area. Considering that the joint use of BMI and WC better captures VAT than the use of either one, clinicians are recommended to use both BMI and WC to identify those at high risk for colorectal neoplasia.